CONTROL OF DISSOLVED GAS CONCENTRATION IN ELECTROPLATING BATHS

Abstract

A concentration of a dissolved gas can be controlled by following an electroplating solution through a contactor, controlling a pressure within the contactor, and thereby maintaining the concentration of the dissolved gas in the electroplating solution within a first concentration range. The first concentration range is non-zero and sub-saturation.

Claims

1. A method of controlling a concentration of a dissolved gas in an electroplating solution of an electroplating system having one or more electroplating cells, a contactor having a membrane with a shell side and a lumen side, and being fluidically connected to the one or more electroplating cells, a vacuum source connected to the contactor and configured to apply a vacuum to the contactor, the method comprising: flowing the electroplating solution through the contactor; and controlling a pressure within the contactor and thereby maintaining the concentration of the dissolved gas in the electroplating solution within a first concentration range that is non-zero and sub-saturation.

2. The method of claim 1, wherein: the controlling includes increasing the pressure in the contactor and thereby increasing the concentration, and the controlling includes decreasing the pressure in the contactor and thereby decreasing the concentration.

3. The method of claim 2, wherein: the electroplating system further includes a valve that is interposed between the vacuum source and the contactor, configured to stop the applying of the vacuum to the contactor when closed, and configured to enable application of the vacuum to the contactor when open, the increasing the pressure further includes closing the valve to stop applying the vacuum to the contactor, and the decreasing the pressure further includes opening the valve to apply the vacuum to the contactor.

4. The method of claim 3, further comprising detecting the pressure within the contactor using a pressure sensor, wherein: the controlling further includes opening the valve, in response to detecting a first pressure in the contactor, and thereby decreasing the pressure within the contactor, and the controlling further includes closing the valve, in response to detecting a second pressure in the contactor lower than the first pressure, and thereby increasing the pressure within the contactor.

5. The method of claim 3, further comprising detecting a gas concentration of the electroplating solution using a gas sensor, wherein: the controlling further includes opening the valve, in response to detecting a first gas concentration, and thereby decreasing the pressure within the contactor, and the controlling further includes closing the valve, in response to detecting a second gas concentration lower than the first gas concentration, and thereby increasing the pressure within the contactor.

6. The method of claim 5, wherein: the dissolved gas is oxygen, and the gas sensor is an oxygen sensor.

7. The method of claim 3, wherein the controlling further includes: opening and closing the valve at a first frequency when one or more of the electroplating cells have a wafer positioned therein, and opening and closing the valve at a second frequency greater than the first frequency when one or more of the electroplating cells do not have a wafer positioned therein.

8. The method of claim 3, wherein the controlling further includes: opening and closing the valve at a first frequency when electroplating is being performed on a wafer one of the electroplating cells, and opening and closing the valve at a second frequency different than the first frequency when one or more of the electroplating is not being performed in one of the electroplating cells.

9. The method of claim 1, wherein the concentration of the electroplating solution has a substantially positive correlation to the pressure in the contactor.

10. The method of claim 1, wherein: the controlling further includes repeatedly increasing and decreasing the pressure within the contactor and thereby maintaining the pressure within a first pressure range, and the first pressure range corresponds with the first concentration range.

11. The method of claim 1, wherein: the electroplating system further includes a pressure regulator connected to the contactor, the controlling further includes maintaining the pressure within a first pressure range that corresponds with the first concentration range.

12. The method of claim 1, wherein the first concentration range is between about 2 ppm and about 8 ppm.

13. The method of claim 1, wherein the controlling includes maintaining the pressure within a first pressure range between about 0.2 atmosphere and about 1 atmosphere.

14. The method of claim 1, wherein the dissolved gas is oxygen.

15. The method of claim 1, wherein the controlling further includes: maintaining, when one or more of the electroplating cells have a wafer positioned therein, the pressure within the contactor to a first pressure range and thereby causing the concentration to be maintained within the first concentration range, and maintaining, when one or more of the electroplating cells do not have a wafer positioned therein, the pressure within the contactor to a second pressure range and thereby causing the concentration to be maintained within a second concentration range that is non-zero, sub-saturation, and different than the first concentration range.

16. The method of claim 1, wherein the controlling further includes: maintaining, when electroplating is being performed on a wafer in one of electroplating cells, the pressure within the contactor to a first pressure range and thereby causing the concentration to be maintained within the first concentration range, and maintaining, when electroplating is being performed on a wafer in one of electroplating cells, the pressure within the contactor to a second pressure range and thereby causing the concentration to be maintained within a second concentration range that is non-zero, sub-saturation, and different than the first concentration range.

17. An electroplating system comprising: one or more electroplating cells; a contactor having a membrane with a shell side and a lumen side, and being fluidically connected to the one or more electroplating cells; an electroplating solution having a concentration of dissolved gas; a pump configured to pump the electroplating solution between the one or more electroplating cells and the contactor; a vacuum source connected to the contactor and configured to apply a vacuum to the contactor; and a controller with instructions that are configured to: cause the electroplating solution to flow through the contactor; and control a pressure within the contactor and thereby maintain the concentration of dissolved gas in the electroplating solution within a first concentration range that is non-zero and sub-saturation.

18. The electroplating system of claim 17, wherein the control of the pressure further includes: increasing the pressure in the contactor and thereby increasing the concentration, and decreasing the pressure in the contactor and thereby decreasing the concentration.

19. The electroplating system of claim 17, further comprising: a valve that is: interposed between the vacuum source and the contactor, configured to stop an application of the vacuum to the contactor when closed, and configured to enable the application of the vacuum to the contactor when open, wherein the control of the pressure further includes: closing the valve to stop the application of the vacuum to the contactor and thereby increase the pressure in the contactor, and opening the valve to apply the vacuum to the contactor and thereby decrease the pressure in the contactor.

20. The electroplating system of claim 19, further comprising a pressure sensor configured to detect the pressure within the contactor, wherein the controller further includes instructions configured to: detect a first pressure in the contactor, detect a second pressure in the contactor lower than the first pressure, and the control further includes: opening the valve, in response to detecting the first pressure, and thereby decrease the pressure within the contactor, and closing the valve, in response to detecting the second pressure, and thereby increase the pressure within the contactor.

21. The electroplating system of claim 19, further comprising a gas sensor configured to detect a gas concentration of the electroplating solution, wherein the controller further includes instructions configured to: detect a first concentration of the electroplating solution, detect a second concentration of the electroplating solution lower than the first concentration, and the control further includes: opening the valve, in response to detecting the first concentration, and thereby decrease the pressure within the contactor, and closing the valve, in response to detecting the second concentration, and thereby increase the pressure within the contactor.

22. The electroplating system of claim 21, wherein the gas sensor is positioned in one or more of: one of the electroplating cells, the contactor, or a reservoir of the electroplating system.

23. An electroplating system comprising: one or more electroplating cells; a contactor having a membrane with a shell side and a lumen side, and being fluidically connected to the one or more electroplating cells; an electroplating solution having a concentration of dissolved gas; a pump configured to pump the electroplating solution between the one or more electroplating cells and the contactor; a vacuum source connected to the contactor and configured to apply a vacuum to the contactor; and a pressure regulator connected to the contactor and configured to maintain a first pressure range that corresponds with a first concentration range of dissolved gas in the electroplating solution that is non-zero and sub-saturation.

24. An electroplating system comprising: one or more electroplating cells; an electroplating solution having a concentration of dissolved gas; a plating cell flow loop configured to flow electroplating solution within the electroplating system; a contactor having a membrane with a shell side and a lumen side, and being fluidically connected in parallel with the plating cell flow loop such that electroplating solution can simultaneously flow in the plating cell flow loop and the contactor; a pump configured to pump the electroplating solution within the plating cell flow loop and to the contactor; a vacuum source connected to the contactor and configured to apply a vacuum to the contactor; and a controller with instructions that are configured to: cause the electroplating solution to flow simultaneously through the plating cell flow loop and contactor, and apply the vacuum source to the contactor and thereby maintain a first dissolved gas removal rate in the contactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The various implementations disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements.

[0005] FIG. 1 depicts an example electroplating system.

[0006] FIG. 2A depicts a cross-sectional illustration of an example contactor.

[0007] FIG. 2B depicts a magnified cross-sectional portion of the contactor of FIG. 2A.

[0008] FIG. 3 depicts the example system of FIG. 1 with a diagrammatical cross-sectional view of an electroplating cell.

[0009] FIG. 4 depicts another electroplating system.

[0010] FIG. 5 depicts a chart of measured dissolved oxygen versus contactor pressure.

[0011] FIG. 6A depicts another example electroplating system.

[0012] FIG. 6B depicts another example electroplating system.

[0013] FIG. 7A depicts yet another example electroplating system.

[0014] FIG. 7B depicts yet another example electroplating system.

[0015] FIG. 7C depicts yet another example electroplating system.

[0016] FIG. 8 depicts a first technique for controlling a concentration of dissolved gas in an electroplating solution.

[0017] FIG. 9 depicts a graph of dissolved gas concentration and contactor pressure over time.

[0018] FIG. 10 which depicts a second example technique for controlling a concentration of dissolved gas in an electroplating solution.

[0019] FIG. 11 depicts a graph of dissolved gas concentration over time.

[0020] FIG. 12 depicts a third example technique for controlling a concentration of dissolved gas in an electroplating solution.

[0021] FIG. 13 depicts a fourth example technique for controlling a concentration of dissolved gas in an electroplating solution.

[0022] FIG. 14 depicts another example technique for controlling a concentration of dissolved gas in an electroplating solution.

[0023] FIG. 15 depicts yet another example technique for controlling a concentration of dissolved gas in an electroplating solution.

DETAILED DESCRIPTION

[0024] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail to not unnecessarily obscure the disclosed embodiments. While the disclosed embodiments will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the disclosed embodiments.

Definitions

[0025] The following terms are used intermittently throughout the instant disclosure:

[0026] SubstrateIn this application, the terms semiconductor wafer, wafer, substrate, wafer substrate and partially fabricated integrated circuit are used interchangeably. One of ordinary skill in the art would understand that the term partially fabricated integrated circuit can refer to a silicon wafer during any of many stages of integrated circuit fabrication thereon. A wafer or substrate used in the semiconductor device industry typically has a diameter of 200 mm, or 300 mm, or 450 mm. Further, the terms electrolyte, electroplating bath, plating bath, bath, electroplating solution, and plating solution are used interchangeably. The work piece may be of various shapes, sizes, and materials. In addition to semiconductor wafers, other work pieces that may take advantage of the disclosed embodiments include various articles such as printed circuit boards, magnetic recording media, magnetic recording sensors, mirrors, optical elements, micro-mechanical devices and the like.

[0027] Electroplating cella cell, typically configured to house an anode and a cathode, positioned opposite to each other. Electroplating, which takes place on the cathode in an electroplating cell, refers to a process that uses electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. In certain embodiments, an electroplating system has two compartments, one for housing the anode and the other for housing the cathode. In certain embodiments, an anode chamber and a cathode chamber are separated by a semi-permeable membrane that permits for the selective movement of concentrations of ionic species therethrough. The membrane may be an ion exchange membrane such as a cation exchange membrane. For some implementations, versions of Nafion? (e.g., Nafion 324) are suitable for use as such a membrane.

[0028] Anode chambera chamber within the electroplating cell designed to house an anode. The anode chamber may contain a support for holding an anode and/or providing one or more electrical connections to the anode. The anode chamber may be separated from the cathode chamber by a semi-permeable membrane. The electrolyte held in the anode chamber is sometimes referred to as anolyte.

[0029] Cathode chambera chamber within the electroplating cell designed to house a cathode. Often in the context of this disclosure, the cathode is a substrate such as a wafer, e.g., a silicon wafer, having multiple partially fabricated semiconductor devices. The electrolyte held in the cathode chamber is sometimes referred to as catholyte. In many implementations, the cathode may be removable from the cathode chamber in order to allow a wafer to be connected with the cathode; the cathode may then be reintroduced into the cathode chamber and immersed in the catholyte. It will be understood that the anode chamber and the cathode chamber may also refer to different portions of the same overall structure, e.g., the electroplating cell. If a membrane is used, the membrane may serve as a partition between the two chambers.

[0030] Electroplating solution (or electroplating bath, plating electrolyte, bath, electroplating solution, solution, or primary electrolyte)a liquid of dissociated metal ions, often in solution with a conductivity-enhancing solvent such as an acid or base. The dissolved cations and anions disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons.

[0031] Recirculation systema system that circulates the electroplating solution back into a central reservoir for subsequent re-use. A recirculation system may be configured to efficiently re-use electroplating solution and also to control and/or maintain concentration levels of metal ions within the solution as desired. A recirculation system may include pipes or other fluidic conduits together with a pump or other mechanism for driving recirculation.

Introduction and Context

[0032] Manufacturing of semiconductor devices commonly requires deposition of electrically conductive material on semiconductor wafers. The conductive material, such as copper, nickel, and cobalt, for instance, is often deposited by electroplating onto a seed layer of metal deposited onto the wafer surface by various methods, such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). Electroplating is generally used for depositing metal into the vias and trenches of the processed wafer during Damascene and dual Damascene processing.

[0033] Electroplating is typically performed in an electroplating bath, in which the semiconductor wafer is submerged in an electroplating solution. An electroplating solution (or solution, electrolyte solution, electroplating bath, plating electrolyte, or primary electrolyte) may be considered a liquid of dissociated metal ions, often in solution with a conductivity enhancing component such as an acid or base. The dissolved cations and anions disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons.

[0034] The composition of electroplating solution is selected so as to optimize the rates and uniformity of electroplating. During some copper plating processes, copper salt serves as the source of the copper cation, and also provides conductivity to the electroplating solution; in certain embodiments, sulfuric acid enhances electroplating solution conductivity by providing hydrogen ions as charge carriers. Also, organic additives, generally known in the art as accelerators, suppressors, or levelers, are capable of selectively enhancing or suppressing rate of copper (Cu) deposition on different surfaces and wafer features, for instance.

[0035] Some electroplating solutions use a dissolved gas, such as oxygen or nitrogen, to control the various constituents in the electroplating solution, including the additives as well as byproducts. For example, some copper electroplating processes produce copper one (Cu.sup.1+) as a byproduct which can adversely affect the electroplating process and resulting wafer performance. In some implementations, the Cu.sup.1+ is a highly reactive species that is the product of anode electrolysis and it reacts with one or more of the organic additives in the plating solution to form a reduced state of the one or more additives. The reduced state of certain organic additives has different reactivity than in the oxidized state which can change the performance of the electroplating solution and resulting electrodeposition. In the presence of the electroplating solution's dissolved gas, however, the presence and effect of the Cu.sup.1+ may be controlled. For instance, dissolved oxygen can oxidize the Cu.sup.1+ to a stable bath ionic species copper two (Cu.sup.2+) via the reaction of 2Cu.sup.1++2H.sup.++O.sub.2/2 which results in 2Cu.sup.2++H.sub.2O.

[0036] Various implementations control the concentration of the dissolved gas in the electroplating solution because too much or too little of the dissolved gas may have detrimental effects. For instance, too much dissolved gas in the electroplating solution may result in forming gas bubbles, such as microbubbles, which can lead to wafer defects. Too much dissolved gas may also, in some implementations, adversely affect other aspects of the electroplating system, such as causing chemical corrosion of a consumable electrode, including a copper anode, for example. On the other hand, too little dissolved gas may not adequately control the target constituent in the electroplating solution. For example, too little dissolved oxygen in the electroplating solution may not reduce the Cu.sup.1+ to the desired levels. It is therefore desirable to control the dissolved gas concentration in the electroplating solution at a sub-saturation concentration, greater than zero, in the solution. A sub-saturation concentration is a concentration in which additional gas could be dissolved in the solution without generating gas bubbles. In some embodiments, a desired sub-saturation concentration is referred to as an intermediate concentration.

[0037] Described herein are methods, techniques, systems, and apparatuses for controlling dissolved gas concentrations in electroplating solutions. A degassing device, such as a contactor, fluidically connected to the electroplating system may be used to control the dissolved gas concentration in the electroplating solution. The pressure within the contactor controls the dissolved gas concentration of the electroplating solution flowed through the contactor and some implementations may therefore control and maintain a desired dissolved gas concentration by controlling the pressure within the contactor. This control may rely on feedback from pressure sensors in the degassing device and/or gas sensors that determine the dissolved gas concentration in the electroplating solution. The contactor pressure may be controlled in some embodiments by selectively applying a vacuum to the contactor and/or by using a pressure regulator. In some embodiments, the dissolved gas concentration may be controlled to account for the different states of the electroplating cells or system, such as whether a wafer is in, or out of, an electroplating cell, and whether electroplating is being performed or the system is at idle, for example.

[0038] While some the embodiments described herein concern copper electroplating systems and dissolved oxygen concentration in a copper electroplating solution, the disclosed embodiments are not limited to this system. The concepts generally apply to controlling the concentration of any dissolved gas in an electrolyte for electroplating any metal, where the concentration of dissolved gas has an impact on one or more aspects of the electroplating. The disclosed embodiments are not limited to controlling oxygen as the dissolved gas. The embodiments may extend to other dissolved gases such as nitrogen.

[0039] Various mechanisms may be employed to control the dissolved gas concentration to an intermediate or sub-saturation level within the electrolyte.

Electroplating Systems

[0040] The various systems and apparatuses described herein are able to control dissolved gas concentrations in electroplating solutions. FIG. 1 depicts an example electroplating system 100 having two electroplating cells 102, a reservoir 104 for containing electroplating solution, a plating cell flow loop 106 configured to flow electroplating solution between the electroplating cells 102 and the reservoir 104. Although the electroplating system 100 depicts two electroplating cells, some embodiments may have more than two electroplating cells or only one electroplating cell; similarly, some embodiments may not have a reservoir. The electroplating system 100 also includes a degassing device, which may be a contactor 108, fluidically connected to the electroplating system through the plating cell flow loop 106, such as in line with a line through which the electroplating solution flows. A vacuum source 110 is connected to the contactor 108 and configured to apply a vacuum to the contactor 108.

[0041] The degassing device, including the contactor 108, is configured to remove gas from the liquid flowed within the device. Some implementations of the contactor 108 may have a hydrophobic gas-liquid separation membrane through which gas, not liquid, can flow and by applying a vacuum to one side of the membrane while flowing the liquid on the other side of the membrane, the dissolved gas in the solution is forced through the membrane pores and carried away by the vacuum. The membrane may have hundreds or thousands of hollow fibers to create a large surface area for liquid-gas contact. By flowing liquid on the outside, or shell side, of the membrane's hollow fibers, and applying a vacuum to the inside, or lumen side, of the membrane's hollow fibers, the gas in the liquid is forced from the shell side to the lumen side through the membrane and drawn out of the contactor by the vacuum.

[0042] FIG. 2A depicts a cross-sectional illustration of an example contactor. The contactor 208 includes a housing 212 that forms the exterior of the contactor 208, a fluid inlet 214 and fluid outlet 216, a vacuum port 218 where a vacuum line or vacuum pump may be connected in order to apply a vacuum to the contactor 208, and a membrane 220. The membrane 220, illustrated with shading, may have a generally annular shape that extends around a central cylindrical or tubular channel, sometimes called a collection tube 222. Some implementations of the contactor 208, although not shown in FIG. 2A, may have one or more baffles that force liquid radially outwards into the membrane 220. When liquid 228 is flowed through the fluid inlet 214 and on the shell side of the membrane 220, indicated by dashed arrows 228, while a vacuum, indicated by arrow 232, is applied at the vacuum port and to the lumen side of the membrane 220, the contactor 208 may degas the liquid 228 flowed therein.

[0043] FIG. 2B depicts a magnified cross-sectional portion of the contactor of FIG. 2A. Here, a section 220A of the membrane 220 is seen in-between the shell side 224 and the lumen side 226. Liquid 228 having dissolved gas 230 is flowed on the shell side 224 while a vacuum is applied to the lumen side 226, as indicated by arrows 232. The hydrophobic membrane 220 is permeable to the gas 230, but not the liquid 228, thereby causing the gas 230 dissolved in the liquid 228 to flow from the shell side 224 through pores 234 in the membrane 220 and to the lumen side 226 when the vacuum is applied.

[0044] The vacuum source 110 may be a vacuum pump configured to provide a vacuum, such as a one or two stage mechanical dry pump and/or turbomolecular pump, that can draw gases out of the contactor. The vacuum source 110 may be configured to reduce the pressure in the contactor between, for example, 0 and 2 Atm, including between 0.1 Atm and 1 Atm. The vacuum source may also be a vacuum pump system that includes a first roughing pump, a second roughing pump, and a turbomolecular pump, the turbomolecular pump being in fluid communication with one or both of the first roughing pump and the second roughing pump. The vacuum source 110 may also be a gas line connected to a vacuum pump or pumps, such as a facility vacuum.

[0045] In some implementations, a roughing pump, such as a dry mechanical pump, may be used to draw down pressure in the contactor. Rotary claw pumps, blower pumps, and/or booster pumps may be used, sometimes in combination, to provide roughing pump functionality. In some implementations, as the pressure in the contactor decreases, the roughing pump may be disengaged and a high-vacuum pump may be engaged to further draw down the pressure in the contactor.

[0046] For example, a turbomolecular pump, or turbopump, may be used to evacuate molecular-flow regime gas that remains in the contactor. Turbomolecular pumps may include a number of concentric, stacked rotating turbine blades interleaved with concentric, stationary turbine blades. As the turbine blades rotate, they impact gas molecules travelling into the throat of the turbomolecular pump and are forced through the turbine blade stack. A turbomolecular pump may be connected in series with a roughing pump downstream to assist in the evacuation of gas from the contactor. In some implementations, the same roughing pump or pumps may be used as the roughing pump downstream from the turbomolecular pump and as the roughing pump used in the initial draw-down. In such implementations, the foreline of the roughing pump(s) may be configured to be switchable, for example, using valves, between being directly connected with the contactor and being indirectly connected with the contactor via the turbomolecular pump. The turbomolecular pump may be kept spinning even when not being used to draw a vacuum in the contactor, and the valving system used may be able to isolate the turbomolecular pump from gas in the viscous flow regime while in this state to prevent damage to the turbomolecular pump.

[0047] Another example of a high-vacuum pump that may be used, either by itself or in combination with other high-vacuum pumps, is a cryopump. Cryopumps are devices that can be cooled to very low temperatures so as to trap gases and vapors through condensation. A cryopump, for example, may include a large surface that is cooled using, for example, helium or liquid nitrogen (or other suitable cooling mechanism). Any gas within, for example, a chamber that is in contact with the surface may condense on the surface and then freeze, thus reducing the amount of free gas within the chamber (thus reducing the gas pressure in the chamber). Cryopumps may be particularly useful for trapping water vapor, although cryopumps may also be used to trap other gases as well.

[0048] Additional features of the electroplating system are described in FIG. 3 which depicts the example system of FIG. 1 with a diagrammatical cross-sectional view of an electroplating cell. Often, an electroplating system includes one or more electroplating cells in which the wafers are processed. Only one electroplating cell is shown in FIG. 3 to preserve clarity. In FIG. 3, a plating bath 114 contains the electroplating solution (having, for example, a composition as provided herein), which is shown at a level 116. The catholyte portion of this vessel is adapted for receiving substrates in a catholyte. A wafer 118 is immersed into the electroplating solution and is held by, e.g., a clamshell substrate holder 120, mounted on a rotatable spindle 122, which allows rotation of clamshell substrate holder 120 together with the wafer 118.

[0049] An anode 124 is disposed below the wafer within the plating bath 114 and is separated from the wafer region by a plating membrane 125, preferably an ion selective membrane. For example, Nafion? cationic exchange membrane (CEM) may be used. The region below the anodic membrane is often referred to as an anode chamber. The ion-selective anode membrane 125 allows ionic communication between the anodic and cathodic regions of the plating cell, while preventing the particles generated at the anode from entering the proximity of the wafer and contaminating it. The anode membrane is also useful in redistributing current flow during the plating process and thereby improving the plating uniformity. Ion exchange membranes, such as cationic exchange membranes, are especially suitable for these applications. These membranes are typically made of ionomeric materials, such as perfluorinated co-polymers containing sulfonic groups (e.g. Nafion?), sulfonated polyimides, and other materials known to those of skill in the art to be suitable for cation exchange. Selected examples of suitable Nafion? membranes include N324 and N424 membranes available from Dupont de Nemours Co.

[0050] During plating, the ions from the electroplating solution are deposited on the substrate. The metal ions must diffuse through the diffusion boundary layer and into the via hole or other feature of the wafer. A typical way to assist the diffusion is through convection flow of the electroplating solution provided by a pump 126. Additionally, a vibration agitation or sonic agitation member may be used as well as wafer rotation which may be advantageous for uniform plating. For example, a vibration transducer 128 may be attached to the clamshell substrate holder 120.

[0051] During electroplating, the electroplating solution is continuously provided to the cell from the reservoir, and to the reservoir from the cell, by the plating cell flow loop which may operate as described herein. As illustrated in the example embodiment in FIG. 3, the electroplating solution flows, using the pump 126, from the reservoir 104 to the cell, enters the cell above the membrane on the cathode side and then flows upwards to the center of wafer 118, and then flows radially outward and across wafer 118. The electroplating solution then overflows plating bath 114 to an overflow reservoir 132. The electroplating solution is then flowed back to the reservoir 104, thereby completing the recirculation of the electroplating solution through the plating cell flow loop 106, which is partially indicated by dashed arrow 106.

[0052] Other features of the electroplating system 100 in FIG. 3 include a reference electrode 134 located on the outside of the plating bath 114 in a separate chamber 136, this chamber is replenished by overflow from the main plating bath 114. Alternatively, in some embodiments the reference electrode is positioned as close to the substrate surface as possible, and the reference electrode chamber is connected via a capillary tube or by another method, to the side of the wafer substrate or directly under the wafer substrate. In some of the preferred embodiments, the apparatus further includes contact sense leads that connect to the wafer periphery and which are configured to sense the potential of the metal seed layer at the periphery of the wafer but do not carry any current to the wafer. A reference electrode 134 is typically employed when electroplating at a controlled potential is desired. The reference electrode 134 may be one of a variety of commonly used types such as mercury/mercury sulfate, silver chloride, saturated calomel, or copper metal. A contact sense lead in direct contact with the wafer 118 may be used in some embodiments, in addition to the reference electrode, for more accurate potential measurement (not shown).

[0053] A DC power supply 138 can be used to control current flow to the wafer 118. The power supply 138 has a negative output lead 140 electrically connected to wafer 118 through one or more slip rings, brushes and contacts (not shown); alternatively, the negative output lead may be electrically connected with the substrate holder 120, which may, in turn, be connected with the substrate. The positive output lead 142 of power supply 138 is electrically connected to an anode 124 located in plating bath 114. The power supply 138, a reference electrode 134, and a contact sense lead (not shown) can be connected to a system controller 144, which allows, among other functions, modulation of current and potential provided to the elements of electroplating cell. For example, the controller may allow electroplating in potential-controlled and current-controlled regimes. The controller may include program instructions specifying current and voltage levels that need to be applied to various elements of the plating cell, as well as times at which these levels need to be changed. When forward current is applied, the power supply 138 biases the wafer 118 to have a negative potential relative to anode 124. This causes an electrical current to flow from anode 124 to the wafer 118, and an electrochemical reduction (e.g. Cu.sup.2++2e.sup.?=Cu.sup.0) occurs on the wafer surface (the cathode), which results in the deposition of the electrically conductive layer (e.g. copper) on the surfaces of the wafer.

[0054] The system may also include a heater 152 for maintaining the temperature of the electroplating solution at a specific level. The electroplating solution may be used to transfer the heat to the other elements of the plating bath. For example, when a wafer 118 is loaded into the plating bath, the heater 152 and the pump 126 may be turned on to circulate the electroplating solution through the electroplating system 100 until the temperature throughout the apparatus becomes substantially uniform. In one embodiment the heater is connected to the system controller 144. The system controller 144 may be connected to a thermocouple to receive feedback of the electroplating solution temperature within the electroplating apparatus and determine the need for additional heating.

[0055] The controller will typically include one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc. In certain embodiments, the controller controls all of the activities of the electroplating apparatus. Non-transitory machine-readable media containing instructions for controlling process operations in accordance with the present embodiments may be coupled to the system controller.

[0056] Typically there will be a user interface associated with controller 144. The user interface may include a display screen, graphical software displays of the apparatus and/or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc. The computer program code for controlling electroplating processes can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program. One example of a plating apparatus that may be used according to the embodiments herein is the Lam Research Sabre tool. Electrodeposition can be performed in components that form a larger electrodeposition apparatus.

[0057] The system 100 of FIG. 3 also includes the contactor 108 and the vacuum source 110. The contactor 108 is fluidically connected to the electroplating system 100 such that the electroplating solution can flow through the contactor 108. This may include positioning the contactor in line with the plating cell flow loop 106 as illustrated in FIG. 3, or in parallel with the recirculation loop as described below.

[0058] The electroplating systems described herein may be implemented in various manners in order to control the dissolved gas concentration in the electroplating solution. FIG. 4 depicts another electroplating system 400 which includes a plurality of electroplating cells 402, a reservoir 404, a plating cell flow loop 406, contactor 408, vacuum source 410, and controller 444. These features may be the same as those the electroplating cells 102, the reservoir 104, the plating cell flow loop 106, the contactor 108, the vacuum source 110, and the controller 144 of FIGS. 1 and 3 described above.

[0059] Here in system 400, a valve 460 is included between the contactor 408 and the vacuum source 410 and is configured to control the application of the vacuum to the contactor 408. In some implementations, the valve 460 may be configured to be fully open and thereby allow the maximum amount of flow through the valve, fully closed and thereby not allow any flow through the valve, or a plurality of partially open configurations to allow different amounts of flow through the valve. The valve 460 is also connected to the system controller 444 which is configured to control the operation of valve 460, such as causing it to be fully open, partially open, or closed. By controlling the operation of the valve 460, the controller 444 is able to control the application of the vacuum to the contactor 408, control the degassing of the contactor 408, and control the dissolved gas concentration in the electroplating solution.

[0060] The system 400 may also include one or more sensors that are connected to the controller 444 and used to provide feedback for controlling operation of the contactor 408, such as operation of the valve 460 and the application of the vacuum source 410 to the contactor 408. In some implementations, the system 400 may include one or more gas sensors 462 configured to detect and/or determine the concentration of a gas within the electroplating solution. The gas sensors 462 may be positioned in various locations within the system 400, such as in one or more of the electroplating cells 402 including the plating bath of the cell (114 in FIG. 3), in the reservoir 404, in the overflow reservoir (132 in FIG. 3), and/or within a flow element of the system 400, such as a pipe, tube, or pump, for example. For some electroplating operations and/or states, it may be advantageous to measure the gas concentration in both the electroplating cells and the reservoir. This may include when an electroplating cell volume and bath volume are disproportionate and/or if there is a significant change in the dissolved gas concentration between the electroplating cell and the bath.

[0061] The gas sensors are configured to detect one or more gases in the electroplating, such as oxygen or nitrogen. Examples of some such gas sensors include a stainless-steel pressure sensor that is compatible with acid. As described in more detail below, directly detecting and measuring the gas concentration in the electroplating solution enables the control of the vacuum applied to contactor and the resulting degassing by the contactor in order to control the concentration of the dissolved gas in the electroplating solution.

[0062] The system may also include one or more pressure sensors 464 configured to measure the pressure within the contactor 408. The controller 444 is connected to the one or more pressure sensors 464 and configured to receive pressure data generated by the one or more pressure sensors 464. Detecting and measuring the pressure in contactor may be used as a proxy or surrogate for the dissolved gas concentration in the electroplating solution and enable the control the dissolved gas concentration in the electroplating solution. In some implementations, the pressure within the contactor has a positive correlation with the dissolved gas concentration such that increasing the contactor pressure increases the dissolved gas concentration and decreasing the contactor pressure decreases the dissolved gas concentration. In some instances, the contactor pressure and dissolved gas concentration may have a linear, or substantially linear (e.g., within 85% of linear), relationship as illustrated in FIG. 5 which depicts a chart of measured dissolved oxygen versus contactor pressure. The data for FIG. 5 was gathered in an experiment in which the contactor pressure and dissolved oxygen in electroplating solution were measured. As can be seen, increasing the contactor pressure increases the dissolved gas concentration and the relationship between the contactor pressure and dissolved gas concentration is close to, or substantially, linear and also follows a positive correlation.

[0063] Referring back to FIG. 4, the contactor 408 may be controlled by controlling the valve 460 operation. For instance, the contactor 408 pressure may be increased by closing the valve 460 and preventing the vacuum from being applied to the contactor 408, or by partially closing the valve 460 (which may also be considered a partially open state) and reducing its allowable flow therethrough. This may include transitioning the valve 460 from a fully open to a fully closed state, from a fully open position to a partially open state, from one partially open state to lower partially open state, or from a partially open state to fully closed. The contactor 408 pressure may be decreased by opening the valve 460 to fully open and applying the vacuum to the contactor 408, or increasing the valve 460's allowable flow therethrough and increasing the vacuum application to the contactor 408. This may include transitioning the valve 460 from a fully closed to a partially open state, from one partially open state to more partially open state, from a partially open state to fully open, or from a fully closed state to a fully open state.

[0064] In some implementations, the contactor pressure may be controlled with a pressure regulator. The pressure regulator is configured to maintain a constant pressure, or substantially constant pressure (e.g. within 15%), within the contactor by adjusting the amount of vacuum applied to the contactor and causing the contactor membrane to maintain an equilibrium between liquid inside on the shell side and the vacuum on the lumen side. Maintaining a constant, or substantially constant, contactor pressure results in a constant, or substantially constant, dissolved gas concentration of the liquid that flows out of the contactor. For instance, referring back to FIG. 5, maintaining the contactor pressure at one of the listed pressures, such as point A, results in maintaining a dissolved oxygen concentration in the electroplating solution at a particular corresponding value, such as point B in FIG. 5. This may hold true regardless of how high the dissolved gas concentration of the liquid entering the contactor is above the desired concentration because of the contactor's ability to maintain the equilibrium between the liquid inside on the shell side and the lumen side. The pressure at which the pressure regulator is fixed, i.e., the set pressure, may be determined and set before electroplating is performed.

[0065] Examples of electroplating systems with pressure regulators are shown in FIGS. 6A and 6B, each of which depicts another example electroplating system 600 that includes a plurality of electroplating cells 602, a reservoir 604, a plating cell flow loop 606, contactor 608, and vacuum source 610. These features may be the same as those the electroplating cells 102, the reservoir 104, the plating cell flow loop 106, the contactor 108, and the vacuum source 110 of FIGS. 1 and 3 described above. Here, a pressure regulator 666 is used to control the application of the vacuum to the contactor. In FIG. 6A, the liquid out of the electroplating cells 102 passes the contactor 108 before entering the reservoir 604. This is position is sometimes referred to as part of a return line. In FIG. 6B, the liquid out of the reservoir 604 enters the contactor 108 before entering the electroplating cells 102. This is position is sometimes referred to as part of a feed line. As provided above, using the pressure regulator to maintain the contactor at a constant, or substantially constant, pressure results in a constant, or substantially constant dissolved gas concentration in the liquid flowing out of the contactor.

[0066] In some implementations, the pressure regulator may be exposed to the electroplating solution which may result in metal salt and/or acid buildup in the regulator which can cause it to fail. This may occur because some of the electroplating solution may weep through the membrane and travel to the regulator. Many pressure regulators are unable to withstand the exposure to the corrosive electroplating solution. This exposure may be avoided by adding a liquid trap to protect the pressure regulator which may require, in some instances, hardware to sense trap levels, to drain the trap, and monitor the life of the regulator. These features may be included in some electroplating systems that use a pressure regulator.

[0067] Another implementation of the electroplating system may position a contactor in parallel with the plating cell flow loop such that fluid is simultaneously flowing through both the plating cell flow loop and the contactor. In some such implementations, the vacuum may be constantly applied to the contactor which results in a constant dissolved gas removal rate by the contactor. The flow rate through the contactor may therefore affect the resulting dissolved gas concentration of the electroplating solution flowed through the contactor. For example, the slower fluid flows through the contactor with the constant dissolved gas removal rate, the more dissolved gas will be removed from the fluid and the lower the resulting dissolved gas concentration of the electroplating fluid. Conversely, the faster fluid flows through the contactor with the constant dissolved gas removal rate, the less dissolved gas will be removed from the electroplating solution. Accordingly, during instances in which flow rates are high, such as during electroplating, less dissolved gas may be removed from the solution than during instances in which the flow rates are low, such as during system idle.

[0068] This is illustrated in FIGS. 7A and 7B, each of which depicts yet another example electroplating system 700 that includes a plurality of electroplating cells 702, a reservoir 704, a plating cell flow loop 706, contactor 708, and vacuum source 710. These features may be the same as those the electroplating cells 102, the reservoir 104, the plating cell flow loop 106, the contactor 108, and the vacuum source 110 of FIGS. 1 and 3 described above. Here, the contactor 708 is placed in parallel with the plating cell flow loop 706 such that fluid may flow simultaneously through both the contactor 708 and the plating cell flow loop 706. In FIG. 7A, contactor 708 is positioned in parallel with a return line, and in FIG. 7B, contactor 708 is positioned in parallel with feed line. In some implementations, the vacuum source 710 is fluidically connected to the contactor 708 and the application of the vacuum source 710 to the contactor 708 may be constant or optionally controlled by control valve 760 as described above. FIG. 7C depicts another example electroplating system 700 including features shown in FIGS. 7A and 7B. Here, the contactor 708 is not directly connected to the plating cell flow loop 706, via either a feed or return line. Instead, the contactor 708 is connected to only the reservoir 704 to control the oxygen concentration in the reservoir 704. In other words, both the inlet line and outline for to the contactor 708 connect to reservoir 704.

[0069] In some embodiments, the flow rate through the contactor 708 may be controlled in various manners, such as using a static or adjustable control with a flow restrictor that could be inserted and adjusted, or actively controlled with a control valve 761 and feedback control based on the measured dissolved gas concentration in the system 700 using one or more of the sensors provided above, such as gas sensor 762. Although not shown in FIGS. 7A-7C, the feedback control may be implemented by a controller which may receive the sensor data, determine an adjusted flow rate through the contactor, and control the control valve 761 to change the flow, such as increase or decrease, through the contactor. For example, if the dissolved gas concentration was higher than desired, then the controller could cause the control valve to slow the flow of solution through the contactor and thereby remove move dissolved gas from the solution.

[0070] The contactor may be positioned in various locations within the electroplating system. This may include, for example, interposed between the electroplating cells and the reservoir as shown in FIGS. 1 and 3, 4, 6A, and 7A. The contactor may also be fluidically connected directly to the reservoir as shown in FIG. 7C, one or more of the cells, or within a different location of the plating cell flow loop, such as after the reservoir as shown in FIGS. 6B and 7B.

Techniques for Controlling Dissolved Gas Concentrations

[0071] Various techniques described herein are used to control and maintain dissolved gas concentrations in the electroplating solution, including some that rely on feedback while others do not rely on feedback. FIG. 8 depicts a first technique for controlling a concentration of dissolved gas in an electroplating solution. This embodiment may be implemented using the systems provided above, including system 400 of FIG. 4. In block 801 of the first technique, the electroplating solution is flowed into the contactor as described herein. This may include using one or more pumps, such as pump 126 in FIG. 3, to pull or push the solution through the contactor. In some instances, the electroplating solution is flowed into the contactor from the cells, while in some other embodiments that use a reservoir, the electroplating solution may be flowed into the contactor from the reservoir.

[0072] In block 803, the pressure is controlled in the contactor in order to cause the concentration of the dissolved gas in the electroplating solution to be maintained within a first range. In some implementations, this pressure control includes adjusting the contactor pressure by increasing and decreasing contactor pressure within a desired pressure range which in turn maintains the dissolved gas concentration within a desired concentration range. For example, as provided above and illustrated in FIG. 5, the pressure within the contactor may have a positive correlation with the dissolved gas concentration such that increasing the contactor pressure increases the dissolved gas concentration and decreasing the contactor pressure decreases the dissolved gas concentration. The controlling of block 803 may therefore include increasing the contactor pressure to increase the dissolved gas concentration and decreasing the contactor pressure to decrease the dissolved gas concentration. In some other implementations, the controlling may include using the pressure regulator to control the pressure in the contactor, such as with pressure regulator 666 of FIGS. 6A and 6B.

[0073] As provided herein, the contactor pressure may be decreased by applying the vacuum to the contactor and increased by stopping the application of the vacuum and continuing to flow electroplating solution through the contactor. In some implementations, the vacuum may be applied by connecting the vacuum source to the contactor by, for example, opening a valve between the contactor and the vacuum source, such as the control valve 460 of system 400 in FIG. 4, and/or turning on a vacuum pump of the vacuum source that is fluidically connected to the contactor. In some instances, the applied vacuum may be configured to reduce the pressure in the contactor to between, for example, 0 and 2 Atm, including between 0.2 Atm and 1 Atm.

[0074] In some embodiments, the contactor pressure may be repeatedly increased and decreased to maintain the contactor pressure within a desired pressure range, and therefore the dissolved gas concentration within a desired concentration range. For example, once the the dissolved gas concentration has been reduced by reducing the contactor pressure, the dissolved gas concentration may increase again due to the nature of electroplating systems, such as various operations performed in the system, whether a wafer is in or not in an electroplating cell, and dissolved gas uptake by the electroplating solution. The contactor is used to remove some of this dissolved gas concentration, but these various operations and states nevertheless result in gas being added back into the solution. Accordingly, the dissolved gas concentration of the electroplating solution may repeatedly, or cyclically, increase and decrease at one or more frequencies.

[0075] This concept is further illustrated with FIG. 9 which depicts a graph of dissolved gas concentration and contactor pressure over time. Here, an experiment was performed in which dissolved oxygen concentration and contactor pressure of an electroplating system were measured over a period of time. The dotted line represents contactor pressure and the solid line represents dissolved oxygen concentration. As can be seen, controlling (or maintaining) the contactor pressure within a particular pressure range, e.g., between about P1 Atm and about P2 Atm, resulted in maintaining the dissolved oxygen concentration within a particular concentration range, e.g., between about C1 ppm and about C2 ppm. The contactor pressure was controlled within this range by decreasing the contactor pressure when it reached an upper threshold, i.e., at about P1 Atm, by applying the vacuum to the contactor until the contactor pressure reached a lower threshold, i.e., about P2 Atm, and then stopping the application of the vacuum to the contactor at this lower threshold to allow the contactor pressure to increase. This may be repeated when the contactor pressure again reaches the upper limit.

[0076] More specifically in FIG. 9, at time zero the vacuum is not being applied to the contactor, so the contactor pressure is able to increase as fluid is flowed through the contactor and within the electroplating system. This may be enabled by closing control valve 460 in FIG. 4, for example. At time t1, the contactor pressure has reached an upper limit of a desirable pressure range. Because of this, at time t1 the vacuum is applied to the contactor and the pressure drops from about P1 Atm to about P2 Atm at time t2, which may be the lower threshold of the desired pressure range. This contactor pressure reduction may be accomplished by opening the control valve 460 in FIG. 4, for example, to apply the vacuum source 410 to the contactor 408. Once at time t2 and at the lower pressure threshold, the vacuum application is stopped, which may be done by closing the control valve 460. Between times t1 and t2 as the pressure decreases, the dissolved oxygen concentration also decreases from about C3 ppm to about C4 ppm. Between times t2 and t3, the vacuum is not applied to the contactor and the contactor pressure can increase as electroplating fluid flows through the contactor, which also causes the dissolved oxygen concentration in the electroplating solution to increase. At time t3, the pressure has again reached the upper limit like at time t1, and the vacuum source is applied to the contactor until time t4 at which point the vacuum application is stopped. This again causes the dissolved oxygen concentration to decrease. FIG. 9 illustrates that the dissolved gas concentration can be maintained within a desired concentration range by controlling the contactor pressure within a desired pressure range. In this example, repeatedly applying the vacuum and stopping the applying of the vacuum maintains the desired concentration and pressure ranges.

[0077] Controlling the contactor pressure by repeatedly increasing and decreasing the contactor pressure is further illustrated in FIG. 10 which depicts a second example technique for controlling a concentration of dissolved gas in an electroplating solution. Block 1001 is the same as 801. Block 1003 controls the contactor pressure by performing blocks 1003A and 1005B; these three blocks 1003, 1003A, and 1003B together may be considered controlling the contactor pressure. In block 1003A the vacuum is applied to the contactor which decreases the contactor pressure and decreases the dissolved gas concentration. As illustrated in FIG. 9, for instance, this pressure decrease may occur at time t1 when the pressure reaches an upper threshold and may continue until the contactor pressure reaches the lower threshold. The vacuum may be applied in any of the manners provided herein, including the FIG. 4 embodiment of opening the control valve 460 to apply the vacuum source 410 to the contactor 408. In block 1003B, the application of the vacuum to the contactor is stopped while fluid may continue flowing through the contactor, thereby allowing the pressure to increase and the further cause the dissolved gas concentration to increase. The application of the vacuum may be stopped in any of the manners provided herein, including the FIG. 4 embodiment of closing the control valve 460, or turning off the vacuum source 410.

[0078] After block 1003B, blocks 1003A and 1003B may again be repeated. Repeatedly increasing and decreasing the pressure in the contactor by repeatedly applying the vacuum to the contactor and stopping the applying of the vacuum to the contactor, thereby controls and maintains the concentration of the dissolved gas within a first range. This may result in adjusting the contactor pressure between two pressures. For instance, at a first contactor pressure, the vacuum is applied to the contactor to lower the contactor pressure to a second contactor pressure, at which point the vacuum application will be stopped and the contactor pressure will rise again to the first contactor pressure. This cycle may be repeated and may result, given the correlations between pressure and dissolved gas described herein, in the dissolved gas concentration also increasing and decreasing within the range.

[0079] Blocks 1003A and 1003B may be repeated at different frequencies based on various factors and considerations. For example, the dissolved gas concentration of the electroplating solution may be affected by a wafer being positioned within a cell because each cell has a large surface area of electroplating solution within the cell that is covered by the wafer when it is positioned in the cell, and that is exposed to the environment when a wafer is not positioned therein. The more surface area of the electroplating solution is exposed to the environment, the higher and faster the resulting gas uptake by the electroplating solution and the higher the resulting dissolved gas concentration. Conversely, the less surface area exposed to the environment, the less gas uptake occurs. Because of this, the dissolved gas concertation may increase at a greater rate when a wafer is not positioned in a cell than when a wafer is positioned in the cell.

[0080] The techniques provided herein may be configured to account for differing gas uptake rates, including those based on whether a wafer is or is not in an electroplating cell. In some embodiments, the frequency at which the vacuum is and is not applied may be at one frequency when a wafer is positioned within a cell, and at a different frequency when a wafer is not positioned within the cell. When the gas uptake is at a greater rate when a wafer is not positioned in a cell, as compared to when a wafer is in the cell, the application of the vacuum and the stopping of the vacuum application may be performed at a higher frequency when the wafer is not in the cell, than when the wafer is in the cell.

[0081] FIG. 11 depicts a graph of dissolved gas concentration over time. An experiment was performed in which dissolved oxygen concentration was measured over a period of time as the contactor pressure was controlled. In a first section of the graph labeled wafer in, a wafer was positioned within the cell, and in a second section of the graph labeled wafer out, a wafer was not positioned within the cell. As can be seen, the dissolved gas concentration increases at a faster rate when the wafer is out of the cell than when in the wafer is in the cell. The results in the wafer in section having a slower frequency of applying and stopping applying the vacuum to the contactor than the wafer out frequency.

[0082] For example, at time t1 the vacuum is applied, at time t2 the vacuum is stopped being applied, at time t3 the vacuum is applied, at time t4 the vacuum is stopped being applied, and at time t5 the vacuum is applied again. In the wafer in section, the time between ti and t3 is greater than the wafer out section between t3 and t5, indicating that the frequency of applying and stopping applying the vacuum to the contactor is greater when the wafer is out of the cell. In FIG. 11, the wafer in section has a first frequency f1 between times t1 and t3 and the wafer out section has a second frequency f2 between times t3 and t5 that is greater than the first frequency f1.

[0083] Controlling the contactor pressure similar to FIG. 11 is not limited to wafer in and wafer out embodiments, but applicable to any implementation that as different dissolved gas concentrations. In some such embodiments, the frequency at which the two operations of the vacuum being applied and the vacuum application being stopped are repeated, e.g., the referring back to FIG. 10, the frequency at which blocks 1003A and 1003B are repeated, may be at a higher frequency when the gas uptake is at a greater rate and/or amount than when the gas uptake is at a relatively lower rate and/or amount. For example, when an electroplating system is at idle, the gas uptake by the electroplating solution, and thus the dissolved gas concentration of the electroplating solution, may be less than when the electroplating system is performing electroplating operations. In this example, referring back to FIG. 10, the frequency at which blocks 1003A and 1003B are repeated may be at one frequency during idle and at a higher frequency during plating operations.

[0084] As mentioned above, some embodiments may use feedback from one or more sensors to control the contactor pressure. This may include detecting the contactor pressure and controlling the contactor pressure based on this pressure detection, and/or detecting the dissolved gas concentration and controlling the contactor pressure based on this concentration detection. FIG. 12 depicts a third example technique for controlling a concentration of dissolved gas in an electroplating solution. Here, the contactor pressure is detected and controlled, e.g., increased or decreased, based on that detection in order to maintain the dissolved gas concentration within the desired range. In block 1201, as with block 801, an electroplating solution having a concentration is flowed through the contactor. In block 1205, the contactor pressure is detected by any of the pressure sensors provided above, such as pressure sensor 464 of FIG. 4. The contactor pressure may be continuously detected or determined. Based on this detection, the contactor pressure is controlled in blocks 1203, 1203A, and 1203B.

[0085] If it is detected or determined that the contactor pressure has reached a first contactor pressure, such as an upper threshold, then the contactor pressure may be decreased by performing block 1203A and applying the vacuum to the contactor as described herein, such as block 1003A above. Referring back to FIG. 9, for example, if the detection is made that the contactor pressure reached the upper threshold of about P1 Atm at time t1 or t3, then block 1203A may be performed. If it is detected or determined that the contactor pressure has reached a second contactor pressure lower than the first contactor pressure, such as a lower threshold, then the contactor pressure may be increased by performing block 1203B and stopping the application of the vacuum to the contactor as described herein, such as in block 1003B. Again referring back to FIG. 9 for example, if the detection is made that contactor pressure reached the lower threshold of about P2 Atm at time t2, for example, then block 1203B may be performed and continued to be performed until the contactor pressure again reaches the upper limit, such as at time t3. In some embodiments, the pressure may be detected as a measured value or an analog signal, while in some other embodiments, the pressure may be a value determined, calculated, and/or interpreted by a controller or other logic device that receives a signal from the pressure sensor. In any of these embodiments, the data generated by the pressure sensor is used for controlling the contactor pressure.

[0086] Similar to described above, blocks 1203A and 1203B may also be repeated at various frequencies based on the detected contactor pressure. For example, referring back to FIG. 11, the contactor pressure may be controlled in a similar manner as shown in FIG. 11 with different frequencies based on whether a wafer is in or out of an electroplating cell.

[0087] In some feedback-based embodiments, the contactor pressure control may be based on detecting the dissolved gas concentration and controlling the contactor pressure based on this concentration detection. FIG. 13 depicts a fourth example technique for controlling a concentration of dissolved gas in an electroplating solution. Here, the gas concentration is directly measured, and the contactor pressure is controlled, e.g., increased or decreased, based on that detection in order to maintain the dissolved gas concentration within the desired range. In block 1301, as with block 801, an electroplating solution having a concentration is flowed through the contactor. In block 1305, the gas concentration is measured by any of the gas sensors provided above, such as gas sensors 462 of FIG. 4, placed in one or more locations within the system as described above. Based on this detection, the contactor pressure is controlled in blocks 1303, 1303A, and 1303B.

[0088] If it is determined that the dissolved gas concentration has reached a first concentration level, such as an upper threshold, then the contactor pressure may be decreased by performing block 1303A and applying the vacuum to the contactor as described herein, such as block 1003A. For example, referring back to FIG. 9, if the detection is made that the concentration level reached the upper threshold of about C3 ppm at about time t1, then block 1303A may be performed to lower the contactor pressure. If it is detected or determined that the dissolved gas concentration has reached a second concentration level lower than the first concentration level, such as a lower threshold, then the contactor pressure may be increased by performing block 1303B and stopping the application of the vacuum to the contactor as described herein, such as block 1003B. Again referring back to FIG. 9, for instance, if the detection is made that dissolved gas concentration reached the lower threshold of about C4 ppm, then block 1303B may be performed and continued to be performed until time t3. In some embodiments, the gas concentration may be detected as a measured value or an analog signal, while in some other embodiments, the concentration may be a value determined, calculated, and/or interpreted by a controller or other logic device that receives a signal from the gas sensor. In any of these embodiments, the data generated by the gas sensor is used for controlling the contactor pressure. In some embodiments, the dissolved gas may be dissolved oxygen and the one or more gas sensors may be oxygen sensors.

[0089] In some embodiments, the contactor pressure may be controlled based on both detected contactor pressure and measured dissolved gas concentration.

[0090] In some implementations, it may be advantageous to have different dissolved gas concentrations based on different states of the electroplating system, such as during electroplating, at idle, wafer in, and/or wafer out. For example, the contactor pressure may be controlled to cause a first dissolved gas concentration when a cell has a wafer positioned therein, and a different, second dissolved gas concentration when the cell does not have a wafer positioned therein. In another example, the contactor pressure may be controlled to cause a first dissolved gas concentration when electroplating is occurring and a different, second dissolved gas concentration when electroplating is not occurring. Similarly, the contactor pressure may be controlled to cause different dissolved gas concentrations during different stages of an electroplating process. This may advantageously be used to adjust for different byproduct levels during different the processing and/or to cause different bath and deposited material properties during the electroplating.

[0091] As provided above, the electroplating system may include a pressure regulator connected to the contactor as described above in FIGS. 6A and 6B. In some of these embodiments, the pressure regulator is set at a particular value and controls the contactor pressure and vacuum application to maintain the contactor at that particular value and therefore maintain the dissolved gas concentration at a set value. FIG. 14 depicts another example technique for controlling a concentration of dissolved gas in an electroplating solution. Here a pressure regulator for a contactor is set to a set pressure. The pressure regulator may be fluidically interposed, as shown in FIGS. 6A and 6B, between the vacuum source and the contactor; the regulator is configured to maintain the set pressure in the contactor. In block 1403, the electroplating solution is flowed through the contactor, as described herein, and in block 1405 the vacuum is applied to the contactor through the regulator which adjusts the vacuum application and maintains the set pressure in the contactor. As stated in block 1407, maintaining the set pressure causes the concentration of the dissolved gas in the solution to be maintained within a first value, at a set value, or substantially at a set value (e.g., within 15% of the value).

[0092] In some embodiments, the electroplating system may include a contactor in parallel with the electroplating flow loop as described above and shown in FIGS. 7A and 7B. In some such embodiments, the vacuum may be constantly applied to the contactor to cause a constant, or substantially constant (e.g., within 10% of the value), gas concentration removal rate. FIG. 15 depicts yet another example technique for controlling a concentration of dissolved gas in an electroplating solution. In block 1501, electroplating fluid is simultaneously flowed through both the electroplating flow loop, such as loop 706, and the contactor 708 in parallel with the loop 706. In block 1503, the vacuum is applied to the contactor to cause a substantially constant gas concentration removal rate of the electroplating solution flowed through the contactor.

[0093] As described above, the flow rate of fluid through the contactor affects the actual amount of gas removed from the fluid. The faster the flow rate, the lower the actual gas removed, for instance. Accordingly, in some embodiments, the technique of FIG. 15 may also include an optional step of adjusting the flow rate of fluid through the contactor to thereby increase, decrease, or maintain the gas concentration within a range or at a set level. In some embodiments, this flow rate adjustment may be based on a gas sensor determination, such as sensor 762 in FIGS. 7A, 7B, and 7C. For example, the flow rate may be decreased through the contactor if the gas sensor determines a gas concentration at or higher than a desired gas concentration level in order to remove more dissolved gas from the liquid and therefore lower the overall gas concentration level of the solution.

[0094] As provided above, some techniques account for different states of the electroplating cells or systems. These states may include whether a wafer is positioned in the bath/solution or out of the bath solution. In some such embodiments, the dissolved gas concentration, such as the dissolved oxygen concentration, may be at a relatively lower concentration when a wafer is positioned in the bath and at a relatively higher concentration when the wafer is out of the bath. These states may also include a wafer in a cell while electroplating occurs and while electroplating does not occur. Again, the dissolved gas concentration may be higher during one of these states than the other and the techniques may control the contactor pressure in order to account for these states.

[0095] For instance, when the concentration is at a relatively higher concentration during one of these states as compared to another state, the contactor pressure may be increased and decreased, as described above, at a higher frequency. The range at which the contactor pressure is maintained may also be higher when the concentration is higher during one of these states. Referring to FIG. 10 for example, the frequency at which blocks 1003A and 1003B are repeated may be higher when the concentration is higher. Also, the pressure range of blocks 1003A and 1003B may be at a higher range when the concentration is lower than when the concentration is lower.

Electrolyte Parameters

[0096] In various embodiments, the dissolved gas may be dissolved oxygen, and this dissolved oxygen concentration in a copper electroplating solution may be maintained between about 1 ppm and 10 ppm, or between about 2 ppm and about 8 ppm. In some embodiments, the dissolved oxygen concentration in a copper electroplating solution is maintained between about 3 ppm and 6 ppm. In further embodiments, the dissolved oxygen concentration in a copper electroplating solution is maintained between about 4.5 ppm and 6 ppm.

[0097] In various embodiments, the contactor pressures used to control dissolved oxygen concentrations are between about 0.2 Atm and 2 Atm. In certain embodiments, the contactor pressures used to control dissolved oxygen concentrations are between about 0.2 Amt and about 1 Atm, about 0.3 and about 0.7 Atm. In further embodiments, the contactor pressures used to control dissolved oxygen concentrations are between about 0.4 Atm and about 0.6 Atm. In certain implementations, the contractor pressures are applied to flowing or quiescent electroplating solution under conditions that reach an equilibrium concentration of the dissolved oxygen in the electroplating solution.

[0098] While controlling the dissolved oxygen concentration in the electroplating solution may be a goal of certain disclosed embodiments, various other parameters may impact the dissolved oxygen concentration. These other parameters may include the temperature of the electroplating solution and/or the composition of the electrolyte.

[0099] The systems provided herein are configured to perform any of the techniques described herein. This may include a system controller employed to control process conditions and hardware states of the electroplating systems described herein, including controllers 144 and 444, for example. The system controller may include one or more memory devices, one or more mass storage devices, and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc.

[0100] In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a processing tool or tools, chamber or chambers, electroplating cells, a platform or platforms for processing, and/or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the controller, which may control various components or subparts of the system or systems. The controller, depending on the processing requirements and/or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases and fluids, the vacuum source, pumps, electroplating, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and/or load locks connected to or interfaced with a specific system.

[0101] Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and/or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer.

[0102] The controller, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the cloud or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0103] Without limitation, example systems may include a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and/or manufacturing of semiconductor wafers.

[0104] As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and/or load ports in a semiconductor manufacturing factory.

[0105] It is to be understood that the use of ordinal indicators, e.g., (a), (b), (c), . . . , herein is for organizational purposes only, and is not intended to convey any particular sequence or importance to the items associated with each ordinal indicator. For example, (a) obtain information regarding velocity and (b) obtain information regarding position would be inclusive of obtaining information regarding position before obtaining information regarding velocity, obtaining information regarding velocity before obtaining information regarding position, and obtaining information regarding position simultaneously with obtaining information regarding velocity. There may nonetheless be instances in which some items associated with ordinal indicators may inherently require a particular sequence, e.g., (a) obtain information regarding velocity, (b) determine a first acceleration based on the information regarding velocity, and (c) obtain information regarding position; in this example, (a) would need to be performed (b) since (b) relies on information obtained in (a)-(c), however, could be performed before or after either of (a) or (b).

[0106] Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0107] Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.