Apparatus and method for processing a substrate

Abstract

An apparatus for electrochemically processing a semiconductor substrate includes a processing chamber of the type that is sealable to a peripheral portion of a semiconductor substrate so as to define a covered processing volume. The semiconductor substrate is supported by a substrate support. A magnetic arrangement is disposed outside of the processing chamber and produces a magnetic field. The magnetic field is changed using a controller for controlling the magnetic arrangement. An agitator is disposed within the processing chamber. The agitator comprises a magnetically responsive element which is responsive to changes in the magnetic field of the magnetic arrangement so as to provide a reciprocating motion to the agitator.

Claims

1. An apparatus for electrochemically processing a semiconductor substrate, the apparatus comprising: a processing chamber that is sealable to a peripheral portion of a semiconductor substrate so as to define a covered processing volume; a substrate support for supporting the semiconductor substrate; a magnetic arrangement disposed outside of the processing chamber, the magnetic arrangement producing a magnetic field; a controller for controlling the magnetic arrangement so as to change the magnetic field; and an agitator disposed within the processing chamber, the agitator comprising a magnetically responsive element which is responsive to changes in the magnetic field of the magnetic arrangement through a side wall of the processing chamber so as to provide a reciprocating motion to the agitator.

2. The apparatus according to claim 1, in which the magnetically responsive element comprises at least one permanent magnet.

3. The apparatus according to claim 1, in which the magnetically responsive element is responsive to changes in a position of the magnetic field of the magnetic arrangement.

4. The apparatus according to claim 1 in which the side wall through which the magnetically responsive element is responsive to changes in the magnetic field has a thickness of less than the thickness of another side wall of the processing chamber.

5. The apparatus according to claim 1 in which the side wall through which the magnetically responsive element is responsive to changes in the magnetic field has a thickness of 3-10 mm.

6. The apparatus according to claim 1, in which the magnetically responsive element and the magnetic arrangement have a separation of less than 30 mm, less than 25 mm, less than 20 mm, or less than 10 mm.

7. The apparatus according to claim 1, in which the agitator comprises two magnetically responsive elements arranged to be adjacent to opposing side walls of the processing chamber, wherein each magnetically responsive element is responsive to changes in the magnetic field of the magnetic arrangement so as to provide a reciprocating motion to the agitator.

8. The apparatus according to claim 1, in which the magnetic arrangement comprises a permanent magnet, an electromagnet, or a magnetic array.

9. The apparatus according to claim 1, in which the agitator further comprises at least one paddle.

10. The apparatus according to claim 9, in which the at least one paddle is a plurality of paddles, and adjacent paddles in the plurality of paddles are spaced apart by a regular spacing.

11. The apparatus according to claim 1, in which the agitator comprises a tab that is received by a complementary portion of the processing chamber to support the agitator.

12. The apparatus according to claim 11, in which the tab comprises the magnetically responsive element.

13. The apparatus according to claim 1, in which the agitator is made from a metallic material; a dielectric material; or a plastic material.

14. The apparatus according to claim 1, in which the substrate support supports the semiconductor substrate horizontally thereon, optionally with a front face of the semiconductor substrate to be processed facing upwards.

15. The apparatus according to claim 1, in which the processing chamber has a cross-sectional dimension of less than 300 mm or less than 200 mm.

16. A processing system comprising a vertical stack of a plurality of apparatuses according to claim 1.

17. The processing system of claim 16, in which the apparatuses that are adjacent in the vertical stack are spaced apart by a spacing of 200 mm or less, and optionally 150 mm or less.

Description

DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic cross-sectional view of a substrate processing system;

(3) FIG. 2 is a schematic cross-sectional view of a substrate processing apparatus according to a first embodiment of the invention;

(4) FIG. 3 is a partial cut-away view of a substrate processing apparatus according to the first embodiment without the substrate or substrate support shown; and

(5) FIG. 4 is a schematic plan view of an agitator according to the first embodiment.

DETAILED DESCRIPTION OF THE DISCLOSURE

(6) The present inventors have considered various problems that are relevant to practical commercialisation of electrochemical processing chambers in previous applications EP2652178 A2, EP2781630 A1, and EP3352206 A1. The entire contents of these are all hereby incorporated by reference. FIG. 1 shows a substrate processing system 100 of the present invention. The substrate processing system may be of the type described in EP3352206 A1 (SPTS Technologies Limited).

(7) The substrate processing system 100 comprises a frame 102 which defines a handling environment 104; a loading/unloading port 106, and at least one vertical stack 108 of substrate processing modules 110a-d. FIG. 1 shows a single vertical stack 108. However, the substrate processing system 100 can have a plurality of vertical stacks. The vertical stack 108 shown in FIG. 1 comprises four processing modules 110a-d. The number of processing modules in each vertical stack 108 can be any number and is typically greater than three. The substrate processing modules 110a-d may each individually be suitable for one or more wet chemical processing steps, such as electrochemical deposition, electroless deposition, chemical etching, electrochemical polishing, and the like; and/or cleaning, rinsing, and/or drying processing steps.

(8) A transfer robot 112 comprising an end effector 114 is disposed in the handling environment 104. The transfer robot 112 can transfer a substrate 116 on the end effector 114 between the loading/unloading port 106 and any substrate processing module 110a-d, and/or can transfer the substrate 116 between individual substrate processing modules 110a-d. The handling environment 104 is maintained substantially free of particles, for example by using a filtered air supply from a fan/filtration system 118, to avoid contamination of the substrate 116.

(9) Fluid supplies, such as electrolyte supplies; and control equipment, such as pumps, filters and the like 120 are provided underneath or next to the substrate processing modules 110a-b.

(10) A substrate processing apparatus 200 suitable for electrochemically processing a semiconductor substrate will now be described with reference to FIGS. 2 and 3. The substrate processing apparatus 200 is adapted to be incorporated into the substrate processing system 100 as one of the substrate processing modules 110a-d.

(11) The apparatus 200 comprises a processing chamber 202 having one or more side walls 204. In the first embodiment, the processing chamber 202 is an electrochemical processing chamber. The processing chamber 202 is typically substantially cylindrical, for example, when processing circular substrates. However, the processing chamber 202 can have any other geometry. For example, for rectangular shaped substrates, such as panels, the chamber can be substantially cuboid or box shaped. The processing chamber 202 is of the type that is sealable to a peripheral portion of a substrate 208 in order to define a covered processing volume 218. In the first embodiment, the height of the processing chamber 202 is less than 300 mm. The apparatus 200 is made using materials that are compatible with the electrolyte and reagents being used in the processing steps. Suitable materials include (but are not limited to): dielectric materials, such as polypropylene, polyvinyl chloride (PVC), polyether ether ketone (PEEK); or fluorinated polymers, such as polytetrafluoroethylene (PTFE) or perfluoroalkoxy alkane (PFA).

(12) The apparatus 200 further comprises a substrate support 206, onto which a substrate to be processed 208 is positioned. The substrate support 206 supports the substrate substantially horizontally. The substrate 208 is a semiconductor substrate which acts as an electrode during electrochemical processing steps. For example, in an electrochemical deposition process, the substrate 208 acts as a cathode. The substrate 208 is typically present as a wafer, such as a silicon wafer. In the first embodiment, the front face of the substrate 208 faces upwards into the processing chamber. In an alternative embodiment, the front face of the substrate 208 faces downwards into the processing chamber 202.

(13) A second electrode 210 is positioned opposite the substrate 208. In an electrochemical deposition process, the second electrode 210 is an anode. The anode can be a consumable or inert electrode. A DC power supply 212 is connected between the substrate 208 and the second electrode 210 via an Ohmic connection. The DC power supply can apply a potential difference between the substrate 208 and the second electrode 210. The Ohmic connection to the substrate 208 is typically made by a series or ring of Ohmic contacts 214 made at the periphery of the substrate, for example at about 1-1.5 mm from the substrate edge. The Ohmic contacts 214 are typically made from titanium, or a platinum coated titanium.

(14) When a substrate 208 is being processed, the substrate 208 is brought into contact with a seal 216 situated at the base of the processing chamber 202. The seal 216 contacts a periphery of the substrate 208 to form a fluid seal between the substrate 208 and the processing chamber 202. The seal 216 contacts the substrate 208 within about 3 mm from the edge of the substrate 208. When the fluid seal is made, the walls 204 and the substrate 208 define a covered processing volume 218. During electrochemical processing, the covered processing volume 218 is filled with electrolyte. The fluid seal avoids electrolyte leaking from the covered processing volume 218 during processing. This helps to avoid contamination of the backside of the substrate 208 and other components of the apparatus 200. The seal 216 is made from an inert material, for example an inert elastomeric material, such as Viton™.

(15) The apparatus 200 further comprises a fluid agitation means, such as an agitator 220. An agitator is a device for stirring a fluid, such as a liquid, solution or electrolyte. In the first embodiment, the agitator is a paddle assembly. The agitator 220 is disposed inside the processing chamber 202. The agitator 220 comprises one or more paddles, fins or blades 222. A plurality of blades 222 are typically arranged parallel to each other with a pre-determined spacing between adjacent blades. The spacing between adjacent blades 222 is determined by the hydrodynamic requirements of the processing step. The blades 222 can be made from a metallic material or insulating material. The blades 222 are held in close proximity to (but spaced apart from) the substrate 208 being processed. Each blade 222 is supported on a frame 224 by a tab 226 at each end of the blade 222. Fixing the blade 222 to the frame 224 in this way allows the vertical spacing between the blades 222 and the substrate 208 during processing to be precisely controlled and maintained at a fixed, pre-determined spacing. The substrate 208 and the blades 222 can have a spacing of 1.5 mm-30 mm, 2 mm-20 mm, or 3 mm-10 mm. The substrate 208 and the blades 222 can be spaced apart at a pre-determined distance between any combinations of these ranges. The height of the blades (represented by the double headed arrow marked h on FIG. 2) can be about 10-50% the distance between the substrate 208 and the second electrode 210.

(16) The agitator 220 is configured to move with a reciprocating motion (i.e. oscillate backwards and forwards). A reciprocating motion has a forward stroke and a backward stroke, each having a stroke speed and stroke length. The agitator 220 reciprocates in a direction parallel to the substrate 208 and substrate support 206. The present inventors have found that a combination of the precise positioning of the agitator 220 and its reciprocating motion allow a low volume of electrolyte to be mixed efficiently. Additionally, the reciprocating motion of the agitator 220 helps to increase the rate of mass transport of electrolyte to the substrate 208 surface (i.e. the electrode surface). This decreases the diffusion boundary layer thickness and helps to increase the rate of a (mass transport limited) electrochemical reaction. For example, the reciprocating motion of the agitator 220 can help to increase the rate of deposition in an electrochemical deposition process. Additionally, the reciprocating motion of the agitator 220 helps to ensure the mass transport is uniform across the entire surface of the substrate (electrode). This results in a uniform coating being deposited during electrochemical deposition.

(17) The agitator comprises a magnetically responsive element 230. The magnetically responsive element 230 is disposed inside the processing chamber 202. The magnetically responsive element 230 can be a magnetic material, such as a magnetically susceptible metal; or a magnet, such as a permanent magnet, an electromagnet, or an array of magnets. Preferably, the magnetically responsive element 230 is a permanent magnet. Preferably, the apparatus 200 comprises a pair of magnetically responsive elements arranged so that each magnetically responsive element 230 is attached to an opposite side of the agitator 220. The magnetically responsive elements in the pair of magnetically responsive elements are typically diametrically opposed across the processing volume 218. The (or each) magnetically responsive element 230 typically has an associated magnetic field. In the first embodiment, the apparatus 200 comprises a pair of permanent magnets arranged at opposite ends of the blades 222 or tabs 226 and attached thereto, which function as a pair of magnetically responsive elements 230. Movement of the magnetically responsive element 230 causes movement of the agitator 220.

(18) A magnetic arrangement 232, which produces a magnetic field, is positioned outside of the processing chamber 202. The magnetic arrangement 232 can be a permanent magnet, an electromagnet, or an array of magnets. Preferably, the apparatus 200 comprises a pair of magnets 232 disposed at opposite sides of and outside the processing chamber 202. The position of the magnetic arrangement 232 outside of the processing chamber 202 typically corresponds to the arrangement of magnetically responsive elements disposed within the process chamber 202. The magnetic field of the magnetic arrangement 232 couples to the magnetically responsive element 230. Minimising the distance between the magnetic arrangement 232 and the magnetically responsive element 230 can increase the strength of the magnetic coupling between them. The polarity of the magnetic field is tuned so that the magnetic coupling between the magnetic arrangement 232 and the magnetically responsive element 230 is maintained. In some embodiments the polarity of the magnetically responsive element 230 and the polarity of the magnetic arrangement 232 are tuned to maintain tight magnetic coupling. For example, the polarity of the magnetic arrangement can be the opposite to the polarity of the magnetically responsive element. Consequently, a change in the magnetic field of the magnetic arrangement 232 can cause the magnetically responsive element 230 to move. For example, a change in the position of the magnetic arrangement 232 can cause the position of the magnetically responsive element 230 to change, thereby moving the agitator 220. In another embodiment, the change in the magnetic field can be a change in the magnitude of the magnetic field.

(19) In the first embodiment, a pair of permanent magnets 232 are positioned adjacent an exterior of opposing chamber side walls 204. The magnets 232 magnetically couple to the pair of magnetically responsive elements 230 through the chamber side walls 204. However, the magnet arrangement 232 can be positioned above or below the processing chamber 202 so that the magnetic arrangement 232 magnetically couples to the magnetically responsive element 230 through a top or bottom of the processing chamber 202. Using a pair of magnets 232 and a pair of magnetically responsive elements 230 in this way enables a stronger magnetic coupling, and hence a greater force, to drive the movement of the agitator 220. The thickness of the chamber walls through which magnetic coupling occurs can be thinned relative to the remainder of the chamber walls to increase the strength of the magnetic coupling between the magnetic arrangement 232 and the magnetically responsive element 230. For example, the thinned chamber wall (through which magnetic coupling occurs) is typically about 3-10 mm, and optionally about 5 mm. The magnetic arrangement 232 and the magnetically responsive element 230 are positioned close to the thinned chamber wall. Preferably, the distance between the magnetic arrangement 232 and the magnetically responsive element 230 is minimised.

(20) In the first embodiment, a motion producing controller 234 is used to drive the movement of the magnetic arrangement 232 in the reciprocating motion. The controller 234 can be a pneumatic actuator, or an electronic motor.

(21) In operation, the controller 234 moves the magnetic arrangement 232 backwards and forward in a reciprocating motion. The reciprocating motion of the magnetic arrangement 232 causes the magnetically responsive element 230 to move in synchrony. In turn, this causes the agitator 220 to move in a reciprocating motion thereby mixing electrolyte within the processing chamber 202.

(22) Driving the movement of the agitator 220 in this way provides excellent agitation of electrolyte within the processing chamber 202. Using magnetic coupling also allows the processing space 212 to be sealed and enclosed without the need to have moving parts extending through a chamber wall. The benefits here are twofold. Firstly, this allows the processing chamber 202 to be isolated from the surroundings, which helps to avoid contamination. Secondly, it is very difficult to maintain a reliable fluid seal where a moving part extends through a chamber wall, and therefore the risk of leaks (which also lead to contamination) is further reduced.

(23) The length of the forward and backward strokes of the agitator is typically determined by the separation between adjacent blades 222. The stroke length is preferably the same as or greater than the separation between adjacent blades 222. Preferably, the reciprocating motion is asymmetric to avoid resonance effects occurring. For example, the speed of the forward stroke can be faster (or slower) than the speed of the backwards stroke. In operation, the agitator has a velocity of about 5-30 cm s.sup.−1.

(24) A Hall sensor (not shown) can be used to monitor the position of a magnet embedded in the agitator 220. A Hall sensor can provide real-time monitoring of the position of the agitator 220. A Hall sensor is a transducer that varies its output in response to a magnetic field, and can be used to measure the magnitude of a magnetic field. By monitoring the position of the agitator 220 in real-time, it is possible to accurately control the agitator 220 motion, such as agitator frequency and velocity. This helps to improve the uniformity and rate of mass transport of fluid, such as electrolyte, to the surface of the substrate being processed.