COMPOSITE SHOWERHEAD ELECTRODE ASSEMBLY FOR A PLASMA PROCESSING APPARATUS

• US 20090163034A1
• Filed: 12/17/2008
• Published: 06/25/2009
• Est. Priority Date: 12/19/2007
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: LARSON, DEAN JAY, Stevenson, Tom, Wang, Victor
• Granted Patent: US 8,418,649 B2
• Time in Patent Office: Days
• US Class Current: 438/729
• CPC Class Codes: B29C 65/483 Reactive adhesives, e.g. chemically curing adhesives
• CPC Class Codes: B29C 65/4835 Heat curing adhesives
• CPC Class Codes: B29C 65/4855 characterised by their physical properties, e.g. being electrically-conductive
• CPC Class Codes: B29C 65/4865 containing additives C09J11/00 and subgroups take precedence
• CPC Class Codes: B29C 65/4875 being spherical, e.g. particles or powders
• CPC Class Codes: B29C 65/4885 characterised by their composition being non-plastics
• CPC Class Codes: B29C 65/5028 being textile in woven or non-woven form
• CPC Class Codes: B29C 65/5057 positioned between the surfaces to be joined B29C65/5035 takes precedence
• CPC Class Codes: B29C 65/5071 and being composed by one single element
• CPC Class Codes: B29C 66/73111 Thermal expansion coefficient
• CPC Class Codes: B29C 66/73112 of different thermal expansion coefficient, i.e. the thermal expansion coefficient of one of the parts to be joined being different from the thermal expansion coefficient of the other part
• CPC Class Codes: B29C 66/742 to metals or their alloys
• CPC Class Codes: B29K 2305/00 Use of metals, their alloys or their compounds, as reinforcement
• CPC Class Codes: B32B 2307/202 Conductive
• CPC Class Codes: B32B 2309/02 Temperature
• CPC Class Codes: B32B 2309/10 linear, e.g. length, distance, width
• CPC Class Codes: B32B 2309/105 Thickness
• CPC Class Codes: B32B 2457/00 Electrical equipment
• CPC Class Codes: B32B 37/025 Transfer laminating
• CPC Class Codes: B32B 37/1292 selectively, e.g. in stripes, in patterns B32B37/0076 takes precedence
• CPC Class Codes: B32B 38/145 : Printing
• CPC Class Codes: B32B 38/164 : Drying
• CPC Class Codes: C23C 16/45565 : Shower nozzles
• CPC Class Codes: H01J 37/32009 : Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/3244 : Gas supply means
• CPC Class Codes: H01J 37/32541 : Shape
• CPC Class Codes: H01J 37/3255 : Material
• CPC Class Codes: H01L 21/3065 : Plasma etching; Reactive-ion etching
• CPC Class Codes: H05K 13/00 : Apparatus or processes specially adapted for manufacturing or adjusting assemblages of electric components
• CPC Class Codes: Y10T 156/10 : Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 156/1062 : Prior to assembly
• CPC Class Codes: Y10T 29/49 : Method of mechanical manufacture
• CPC Class Codes: Y10T 29/49002 : Electrical device making
• CPC Class Codes: Y10T 29/5313 : Means to assemble electrical device
• CPC Class Codes: Y10T 29/532 : Conductor
• CPC Class Codes: Y10T 29/53204 : Electrode

Abstract

A showerhead electrode for a plasma processing apparatus includes an elastomeric sheet adhesive bond between mating surfaces of an electrode and a backing member to accommodate stresses generated during temperature cycling due to mismatch in coefficients of thermal expansion. The elastomeric sheet comprises a thermally conductive silicone adhesive able to withstand a high shear strain of ≧300% in a temperature range of room temperature to 300° C. such as heat curable high molecular weight dimethyl silicone with fillers. The sheet form adhesive has bond thickness control for parallelism of bonded surfaces over large areas. The sheet adhesive may be cast or die cut into pre-form shapes that can conform to irregularly shaped features, maximize surface contact area with mating electrode surfaces, and installed into cavities of the mating assembly. Installation can be manually, manually with installation tooling, or with automated machinery. Composite layers of sheet adhesive having different physical properties can be laminated or coplanar.

Claims

1. A composite showerhead electrode assembly for generating plasma in a plasma processing apparatus, comprising:

a backing plate comprising top and bottom surfaces with first gas passages therebetween, the bottom surface having bonded and unbonded regions, the first gas passages having outlets in unbonded regions to supply a process gas to an interior of the plasma processing apparatus;

an electrode plate having a top surface, a plasma exposed bottom surface, and second gas passages extending therebetween and in fluid communication with the first gas passages, wherein the second gas passages have inlets in unbonded regions of the top surface of the electrode plate; and

an elastomeric sheet adhesive joint disposed between mating surfaces at each of the bonded regions which allows movement in a lateral direction of the electrode plate relative to the backing plate during temperature cycling due to mismatch of coefficients of thermal expansion in the electrode plate and the backing plate.

2. The composite showerhead electrode assembly of claim 1, wherein

the backing plate comprises an inner backing plate and an outer backing ring, the outer backing ring surrounding the inner backing plate, wherein the first gas passages are in the inner backing plate and optionally in the outer backing ring,

the electrode plate comprises an inner showerhead electrode bonded to the inner backing plate and an outer ring electrode bonded to the outer backing ring, wherein the second gas passages are in the inner showerhead electrode and optionally in the outer ring electrode.

3. The composite showerhead electrode assembly of claim 2, wherein (a) the mating surface of the backing plate is parallel to the mating surface of the showerhead electrode and/or (b) the electrode is of single crystal silicon, polycrystalline silicon, graphite or silicon carbide;

and the backing member is of aluminum, graphite, or silicon carbide.

4. The composite showerhead electrode assembly of claim 1, wherein the elastomeric sheet adhesive joint comprises a thermally conductive silicone adhesive sheet.

5. The composite showerhead electrode assembly of claim 4, wherein the elastomeric sheet adhesive joint is elastically deformable in the lateral direction to at least 200% shear strain from a shear stress of about 20 to 340 psi in a temperature range of room temperature to 300°

C.

6. The composite showerhead electrode assembly of claim 5, wherein the elastomeric sheet adhesive joint is elastically deformable in the lateral direction to at least 300% shear strain from a shear stress of about 20 to 80 psi.

7. The composite showerhead electrode assembly of claim 5, wherein the electrode plate is a disk of single crystal silicon with a diameter of at least 200 mm and the elastomeric sheet adhesive joint is elastically deformable in the lateral direction to at least 200% shear strain from a shear stress of about 20 to 340 psi in a temperature range of room temperature to 300°

C. after 5000 temperature cycles of heating the showerhead electrode assembly from room temperature to 250°

C.

8. The composite showerhead electrode assembly of claim 4, wherein the thermally conductive silicone adhesive sheet comprises two or more laminated layers having different physical properties and/or the thermally conductive silicone adhesive sheet comprises two or more co-planar portions having different physical properties.

9. The composite showerhead electrode assembly of claim 4, wherein at least one portion of the conductive silicone adhesive sheet has a thermal conductivity of 0.5 W/mK to 0.8 W/mK, at least one portion of the conductive silicone adhesive sheet has a thermal conductivity of 0.8 W/mK to 1 W/mK and/or at least one portion of the conductive silicone adhesive sheet has a thermal conductivity of over 1 W/mK.

10. The composite showerhead electrode assembly of claim 4, wherein (a) the elastomeric sheet adhesive joint further comprises a primer on one or more of the mating surfaces of the backing member and/or the electrode backside;

and/or (b) the thermally conductive silicone adhesive sheet comprises a uniform distribution of thermally conductive filler.

11. The composite showerhead electrode assembly of claim 10, wherein (a) the thermally conductive filler is one of boron nitride (BN), aluminum oxide (Al₂O₃), silicon, silicon carbide, and a combination thereof and/or (b) the thermally conductive silicone adhesive sheet is of (i) high molecular weight dimethyl silicone and the thermally conductive filler, (ii) high molecular weight dimethyl silicone and the thermally conductive filler matrixed around fiberglass screen (scrim), (iii) high molecular weight dimethyl silicone and the thermally conductive filler matrixed around metallic screen or (iv) high molecular weight dimethyl silicone and the thermally conductive filler mixed with glass microbeads, or nanobeads.

12. The composite showerhead electrode assembly of claim 1, wherein a gap distance between the mating surfaces varies by less than ±

25 μ

m (0.001 in).

13. The composite showerhead electrode assembly of claim 1, wherein (a) the elastomeric sheet adhesive joint comprises an elastomeric sheet adhesive cast or rolled into a pre-form shape;

(b) the elastomeric sheet adhesive joint comprises an elastomeric sheet adhesive of die cut pre-form shape;

(c) the elastomeric sheet adhesive joint comprises an elastomeric sheet adhesive laser cut, plotter cut and/or water jet cut pre-form shape; and

/or (d) one of the mating surfaces comprises a cavity.

14. The composite showerhead electrode assembly of claim 13, wherein (a) the cavity depth is in a range of 100 to 200 μ

m;

(b) the cavity depth is in a range of 200 to 500 μ

m;

(c) the cavity comprises an elevation jog sized to match a dimension of the sheet adhesive;

(d) the sheet adhesive bonds the top surface of the electrode to the bottom surface of the backing member with a spacing therebetween of 50 to 400 μ

m;

(e) the sheet adhesive joint comprises a silicone adhesive sheet in a form of a single sheet;

(f) the sheet adhesive joint comprises a silicone adhesive sheet in a form of one or more flat rings, flat rings with elevation jogs, cylinders, flat or columnar polygons, blocks or combination thereof; and

/or (g) the elastomeric sheet adhesive joint comprises a heat cured adhesive.

22. A method of processing a semiconductor substrate in a plasma processing apparatus, the method comprising:

placing a substrate on a substrate support in a reaction chamber of a plasma processing apparatus;

introducing a process gas into the reaction chamber with the composite showerhead electrode assembly of claim 1;

generating a plasma from the process gas in the reaction chamber between the composite showerhead electrode assembly and the substrate;

processing the substrate with the plasma.

23. The method of claim 22, wherein the processing comprises etching the substrate.

15. A method of joining components for a composite showerhead electrode assembly for a plasma processing apparatus, comprising:

applying a first surface of a sheet of uncured elastomeric adhesive in a predetermined pattern to a bottom surface of a backing member in a predetermined pattern of bonding regions which exclude regions to remain unbonded, the backing member having a top surface and a plurality of first gas passages extending between the top surface and the bottom surface and having outlets in unbonded regions;

applying a top surface of an electrode to a second surface of the sheet of uncured elastomeric adhesive in a predetermined pattern of bonding regions, the electrode having a plasma exposed bottom surface and a plurality of second gas passages extending between the top surface and bottom surface of the electrode wherein the second gas passages have inlets in unbonded regions of the top surface of the electrode; and

bonding the top surface of the electrode to the bottom surface of the backing member with the sheet of elastomeric adhesive therebetween wherein the second gas passages are in fluid communication with the first gas passages.

16. The method of joining components for a composite showerhead electrode assembly of claim 15, further comprising:

applying a primer to the bottom surface of the backing member in a predetermined pattern; and

applying a primer to the top surface of the electrode in a predetermined pattern.

17. The method of joining components for a composite showerhead electrode assembly of claim 16, wherein applying primer to the top surface of the electrode comprises:

rotating the electrode about its center point and depositing annular zones of the primer with a dispenser by contacting outlets of the dispenser with the rotating electrode at multiple radial positions relative to the center point;

or

covering the top surface with a mask having openings in a predetermined pattern and coating the primer on unmasked regions of the top surface.

18. The method of joining components for a composite showerhead electrode assembly of claim 17, wherein the predetermined pattern in the mask is a plurality of semi-annular zones.

19. The method of joining components for a composite showerhead electrode assembly of claim 16, wherein applying primer to the bottom surface of the backing member comprises:

rotating the backing member about its center point and depositing annular zones of the primer with a dispenser by contacting outlets of the dispenser with the rotating backing member at multiple radial positions relative to the center point;

or

covering the bottom surface with a mask having openings in a predetermined pattern and coating the primer on unmasked regions of the bottom surface.

20. The method of joining components for a composite showerhead electrode assembly of claim 15, wherein

(a) applying the first surface of the sheet of elastomeric adhesive comprises precutting the sheet of elastomeric adhesive bonding material to the predetermined pattern using one of mechanical cutting, die-cutting, laser cutting, water jet cutting, plasma cutting, plotter cutting and combinations thereof;

(b) the top surface of the electrode and/or the bottom surface of the backing member comprise channels over at least a portion of the predetermined pattern;

(c) the sheet of elastomeric adhesive is a filled, uncured elastomeric silicone sheet; and

/or

(d) the filled, uncured elastomeric silicone sheet is filled with thermally conductive particles of aluminum, aluminum oxide, silicon, silicon carbide, boron nitride, or alloys thereof.

21. The method of joining components for a composite showerhead electrode assembly of claim 15, wherein

(a) bonding further comprises seating the sheet adhesive by pressing the top surface of the electrode and the bottom surface of the backing member together under compression, under a static weight or optionally by atmospheric pressure within a vacuum bag, wherein the sheet of elastomeric adhesive is heat curable;

(b) heating the composite showerhead electrode assembly to cure the bonding material after seating when the static weight or optional atmospheric pressure within a vacuum bag is removed;

(c) the electrode is of silicon, graphite, or silicon carbide; and

the backing member is of aluminum, graphite, or silicon carbide;

(d) applying the first surface of the sheet of elastomeric adhesive comprises removing a transfer sheet from the first surface before applying the first surface to the bottom surface of the backing member;

(e) applying the top surface of the electrode comprises removing a transfer sheet from the second surface of the sheet of elastomeric adhesive before applying the top surface of the electrode to the second surface of the sheet of elastomeric adhesive;

(f) applying the first surface of the sheet of elastomeric adhesive comprises applying a vacuum after applying the first surface to the bottom surface of the backing member to remove gaps therebetween;

(g) applying the top surface of the electrode comprises applying a vacuum after applying the top surface of the electrode to the second surface of the sheet of elastomeric adhesive to remove gaps therebetween; and

/or

(h) the electrode comprises an inner showerhead electrode and an outer ring electrode and the backing member comprises an inner backing plate and an outer backing ring.

24. A composite showerhead electrode assembly for a plasma processing apparatus, comprising:

a backing member having a bottom surface with regions to be bonded, excluding regions to remain unbonded, and a plurality of first gas passages extending between the bottom surface and a top surface of the backing member, wherein the first gas passages have outlets in regions to remain unbonded, to supply a process gas to an interior of a plasma processing apparatus;

an electrode to generate plasma in the plasma processing apparatus, the electrode having a top surface with regions to be bonded and a plurality of second gas passages in fluid communication with the first gas passages, the second gas passages have inlets in regions to remain unbonded, extending through the electrode from the top surface to a plasma-exposed bottom surface of the electrode; and

an uncured elastomeric sheet adhesive to be cured in a joint between mating surfaces of each of the regions to be bonded to allow movement in the lateral direction of the electrode relative to the backing member during temperature cycling due to mismatch of coefficients of thermal expansion of the backing member and electrode,

wherein the sheet of elastomeric adhesive is a filled, heat-curable, unvulcanized elastomeric silicone sheet.

25. The composite showerhead electrode assembly of claim 24, wherein the uncured elastomeric sheet adhesive is formulated with a peroxide as a heat activated component to perform a cross-linking reaction, the elastomeric sheet adhesive volume shrinkage is 3-5% during curing, or less than 3% during curing.