Electrochemical deposition chamber

Abstract

According to the invention a method of removing electrolyte from an electrochemical deposition or polishing chamber comprising the steps of: providing an electrochemical deposition or polishing chamber comprising a support for a substrate, the support having an in-use position; a housing having an interior surface and a fluid outlet pathway for removing electrolyte from the chamber, wherein the fluid outlet pathway includes one or more slots which extend into the housing from at least one slotted opening formed in the interior surface; a seal for sealing the housing to a peripheral portion of a surface of a substrate position on the support in its in-use position; and a tilting mechanism for tilting the chamber in order to assist in removing electrolyte from the housing through the fluid outlet pathway; using an electrolyte to perform an electrochemical deposition or polishing processing on a substrate positioned on the support in its in-use position; and tilting the chamber using the tilting mechanism in order to assist in removing electrolyte from the housing through the fluid outlet pathway.

Claims

1. A method of removing electrolyte from an electrochemical deposition or polishing chamber comprising the steps of: providing an electrochemical deposition or polishing chamber comprising a support for a substrate, the support having an in-use position; a housing having an interior surface and a fluid outlet pathway for removing electrolyte from the chamber, wherein the fluid outlet pathway includes one or more slots which extend into the housing from at least one slotted opening formed in the interior surface; a seal for sealing the housing to a peripheral portion of a surface of a substrate positioned on the support in its in-use position; and a tilting mechanism for tilting the chamber in order to assist in removing electrolyte from the housing through the fluid outlet pathway; using an electrolyte to perform an electrochemical deposition or polishing processing on a substrate positioned on the support in its in-use position; and tilting the chamber using the tilting mechanism in order to assist in removing electrolyte from the housing through the fluid outlet pathway.

2. A method according to claim 1 in which the chamber is tilted by less than 10.

3. A method according to claim 1 in which said one or more slots comprise a slot which is in communication with said at least one slotted opening and extends generally upwardly therefrom.

4. A method according to claim 1 in which the slotted opening is formed in the interior surface so as to face downwardly into the chamber.

5. A method according to claim 4 in which the interior surface comprises an overhanging section, and the slotted opening is formed in the overhanging section.

6. A method according to claim 1 in which the housing comprises a lower housing portion and an upper housing portion which are spaced apart to define at least one of said slots of the fluid outlet pathway and, optionally, said at least one slotted opening formed in the interior surface.

7. A method according to claim 6 in which the upper housing portion is a shroud member which is positioned over the lower housing portion.

8. A method according to claim 1 in which the seal is an annular seal having an outer surface which is downwardly inclined towards the interior of the chamber.

9. A method according to claim 8 in which the annular seal tapers to a sealing surface for sealing against the surface of the substrate.

10. A method according to claim 9 in which the sealing surface is an edge region formed at the intersection of two mutually inclined surfaces of the annular seal.

11. A method according to claim 8 in which the annular seal is funnel shaped.

12. A method according to claim 1 in which the seal contacts the substrate at a level, and the slotted opening is disposed less than 5 mm above said level.

13. A method according to claim 1 in which the seal is disposed so that, in-use, the seal contacts a peripheral portion of the surface of the substrate which is less than 3 mm from an edge of the substrate.

14. A method according to claim 1 including an electrode disposed within the chamber and an electrode contact for contacting the substrate when the support is in its in-use position.

15. A method according to claim 14 in which, when the support is in its in-use position, the separation between the substrate and the electrode is less than 40 mm.

16. A method according to claim 15 in which the separation between the substrate and the electrode is in the range 5 to 30 mm.

17. A method of removing electrolyte from an electrochemical deposition or polishing chamber comprising the steps of: providing an electrochemical deposition or polishing chamber comprising a support for a substrate, the support having an in-use position; a housing having an interior surface and a fluid outlet pathway for removing electrolyte from the chamber, wherein the fluid outlet pathway includes one or more slots which extend into the housing from at least one slotted opening formed in the interior surface; a seal for sealing the housing to a peripheral portion of a surface of a substrate positioned on the support in its in-use position; and a tilting mechanism for tilting the chamber in order to assist in removing electrolyte from the housing through the fluid outlet pathway; using an electrolyte to perform an electrochemical deposition or polishing processing on a substrate positioned on the support in its in-use position; and tilting the chamber using the tilting mechanism in order to assist in removing electrolyte from the housing through the fluid outlet pathway; in which the seal is an annular seal having an outer surface which is downwardly inclined towards the interior of the chamber.

Description

BRIEF DESCRIPTION

(1) Embodiments of chambers in accordance with the invention will now be described with reference to the accompanying drawings, in which:

(2) FIG. 1 is a semi-schematic cross section of a portion of a first embodiment of a chamber of the invention;

(3) FIG. 2 is a further semi-schematic cross section of a portion of the first embodiment (a) in a horizontal configuration and (b) in a tilted configuration; and

(4) FIG. 3 shows (a) a cross sectional view of a second embodiment of a chamber of the invention excluding the substrate support and (b) shows the circled portion of (a) in greater detail.

DETAILED DESCRIPTION

(5) FIG. 1 shows a first embodiment of a chamber of the invention, depicted generally at 10. The chamber 10 is an electrochemical deposition chamber for processing a substrate 5. The substrate 5 is placed on a platen 4 either by hand or by mechanical means. The platen 4 is raised to compress an elastomeric seal 2 on the upper surface of the substrate 5 to form a fluid seal. At the same time as the fluid seal is being made, electrical contact is made with a seed layer on the upper surface of the substrate 5 by means of conductive springs 3. The seal 2 and conductive springs 3 are retained in a lower chamber body 1. As explained in more detail below, an advantage of the present invention is that it is possible to make contact within 1-2 mm of the edge of the substrate 5.

(6) A soluble anode 7, which could be Cu or phosphorized Cu for Cu deposition, is located parallel with the wafer surface at or near to the top of the chamber 10. Electrical connections to the anode 7 and fluid connections to the chamber cavity are made through an upper chamber plate 10a. Additional fluid connections are made through the lower chamber body 1 as can be seen in FIG. 2. In certain configurations it is desirable to have a membrane/filter assembly 6 to assist fluid distribution and manage particulates between the substrate 5 and the anode 7. Representative but non-limiting separation distances from the substrate to the anode are 5-30 mm for a system configured for 300 mm wafers.

(7) As shown in FIG. 2a), the chamber 10 comprises a fluid outlet pathway 9 which includes an arrangement of slots. When evacuating the electrolyte 8 from the cell it is not possible to remove fluid which lies below the lowest point of the fluid outlet pathway 9 as can be seen in FIG. 2 a). Even if the outlet point can be maintained 2 mm above the elastomeric seal, about 140 mL of fluid for a 300 mm wafer remains in the cell (see Table 1). Upon opening the cell some of the electrolyte 8 will be lost over the edge of the wafer and contaminate the chamber hardware. It is likely that this fluid will be costly to be reclaimed/recycled and hence is likely to be lost.

(8) TABLE-US-00001 TABLE 1 Remaining fluid volume for 2 mm edge exclusion with 1 and 2 mm outlet height. Diameter of wafer Edge excl Height of outlet Fluid vol (cm) (cm) (cm) (cm3) 30 0.2 0.2 139.49 30 0.2 0.1 69.74

(9) By tilting the cell by 5 for a 300 mm wafer the amount of fluid remaining in the cell can be reduced to 2 mL even for the situation when the outlet lies 2 mm above the wafer plane. When the wafer is returned to the horizontal position the wafer can be removed with no fluid reaching the edge of the wafer. This approach works for fluids on hydrophobic and hydrophilic surfaces. Following the electrochemical deposition step when the DC field is removed and the electrolyte is removed from the cell the tilt procedure is employed to ensure that all but the last few mL of electrolyte can be reclaimed/recycled. Depending on the process sequence required the wafer can be either removed and cleaned at another station on the tool or potentially on another system or a post deposition cycle could be carried out in the cell such as a DI water rinse. If the rinse sequence is employed the small amount of electrolyte would be once again lost from the electrolyte reservoir.

(10) It should be noted that conventional O ring seals are not well suited for this arrangement. Even with a 1 mm cross section O ring, due to the fact that the O ring must be retained in position laterally and maintain its contact with the chamber wall it is very difficult to meet the desired edge exclusion goal of 2 mm from the wafer edge. The edge electrical contact cannot interfere with the fluid seal. Without some form of active retention it is unlikely that an O ring could be expected to remain attached to the chamber. It is for this reason that a generally frustro-conical elastomeric seal 2 is used. Due to its shape, a seal of this kind will not fall out of the chamber due to gravity or surface tension with the surface of the wetted wafer. Also it provides simpler access for the electrical contacts and the exhaust fluid channel. The seal 2 is not a true frustro-conical shape, principally due to the presence of two mutually inclined surfaces which intersect to form a sealing edge. The seal 2 can fit into a slot. Conveniently, the slot can be formed by milling. Alternatively, the seal 2 can be retained in place by a washer.

(11) A preferred embodiment of a chamber 14 is shown in FIGS. 3 (a) and (b). A cross section of a chamber cavity is shown in FIG. 3(a) where an anode 17 is situated above a membrane assembly 16 and a wafer 15 is situated within the chamber 14. The detail in FIG. 3(b) shows a fluid inlet/outlet path formed between a shroud 19 and features in the lower portion of the chamber 14. A slot 20 is cut into a lower chamber wall 18 and the shroud 19 brings the opening down close to the wafer surface. By judicious choice of slot width, cross section and depth (height above wafer surface) a high conductance flow path can be achieved without interfering with the edge exclusion uniformity constraints. The use of one or more slots is much more preferable to the use of a tube or tubes as the slot can cover a large fraction of the perimeter of the chamber wall while minimizing potential screening at the edge of the wafer.

(12) As can be seen in FIG. 3(b) the wafer contact springs 13 are situated concentrically with the fluid seal 12 and the wafer 15. The seal 12 may be identical to the seal 2 described in relation to FIGS. 1 and 2. A recess 11 is formed in the lower chamber wall 10 to meet the slot 20. The recess 11 may itself be a further slot formed in the lower chamber wall 19. A lower opening of the recess is in communication with a fluid exhaust channel (not shown).

(13) Typical materials used for the chamber construction are PEEK (polyetheretherketone), HDPE (high density polyethylene), PVC (polyvinyl chloride) or similar dielectric materials that can provide the necessary mechanical properties while being compatible with the electrolyte.

(14) The present invention can provide a number of significant advantages. For example, the invention can be implemented as a low volume chamber. Also a very high proportion of the fluid can be re-cycled due to the fact that a very small amount of residual fluid is left in the chamber. Due to the low volume of the cell and the close proximity of the fluid path to the wafer surface a small amount of tilt of about 5 is sufficient to ensure effective removal of the electrolyte. The small amount of fluid remaining on the wafer either forms droplets on a hydrophobic surface or a uniform thin coating on a hydrophilic surface. In both cases the fluid does not extend to the edge of the wafer if the optimized process is followed. This avoids the need to protect the chamber and the transport system from stray fluid. As the remaining fluid stays on the wafer the chamber design can be greatly simplified and as a consequence be more cost effective to manufacture. Film uniformity can be maintained even with an edge exclusion of about 2 mm by minimizing shadowing of the electric field close to the wafer surface. Through the use of a conical shaped seal a reliable fluid seal can be achieved as the seal will not fall out. Furthermore, with chambers of the invention the volume of space required to contain the chamber can be kept close to the volume of the cell. A shallow tilt of around 5 maintains a low volume whereas a 90 tilt would result in a chamber volume defined by a cube with greater than 300 mm sides when processing 300 mm wafers, which would offset some of the advantages associated with low volume changes.

(15) Electrochemical deposition of metals or alloys other than copper, such as nickel, gold, indium, SnAg or SnPb, is possible using the present invention. Electrochemical polishing of suitable metals and alloys is also possible.