Composite showerhead electrode assembly for a plasma processing apparatus

• US 8,418,649 B2
• Filed: 12/17/2008
• Issued: 04/16/2013
• Est. Priority Date: 12/19/2007
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Stevenson, Tom, Wang, Victor, Larson, Dean Jay
• Primary Examiner(s): Zervigon, Rudy
• Application Number:
  US12/337,323
• Publication Number:
  US 20090163034A1
• Time in Patent Office: 1,581 Days
• Field of Search: 118/723.E, 118/723.ER, 156/345.43, 156/345.44, 156/345.45, 156/345.46, 156/345.47
• US Class Current: 118/723.E
• 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;

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; and

wherein the elastomeric sheet adhesive joint comprises a thermally conductive silicone adhesive sheet and 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.

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 at least one of the inner backing plate and 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 at least one of the inner showerhead electrode and 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 electrode plate and/or (b) the electrode plate is of single crystal silicon, polycrystalline silicon, graphite or silicon carbide;

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

7. The composite showerhead electrode assembly of claim 1, 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.

8. The composite showerhead electrode assembly of claim 1, 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.

9. The composite showerhead electrode assembly of claim 8, 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.

11. The composite showerhead electrode assembly of claim 1, 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.

4. 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;

wherein the elastomeric sheet adhesive joint comprises a thermally conductive silicone adhesive sheet; and

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.

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 300% shear strain from a shear stress of about 20 to 80 psi.

6. The composite showerhead electrode assembly of claim 4, 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.

10. 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;

wherein a gap distance between the mating surfaces varies by less than ±

25 μ

m (0.001 in).

12. 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; and

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.