Elastomer bond method for electrostatic chuck assemblies with thermally activated fillers for adjustable low temperature debonding process

Abstract

A bonded assembly includes a first component, a second component, and a bond layer joining the first component to the second component. The bond layer includes a bonding composition that has a silicone elastomer and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer. The EG powder is in an amount of about 1.0 to about 5.0 wt.% of the bonding composition and has an average particle size of about 400 μm.

Description

ELASTOMER BOND METHOD FOR ELECTROSTATIC CHUCK ASSEMBLIESWITH THERMALLY ACTIVATED FILLERS FOR ADJUSTABLE LOW TEMPERATURE DEBONDING PROCESSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. provisional application number 63 / 654,557, filed May 31 , 2024. The disclosure of the above application is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to debonding components, and more specifically to materials and processes for debonding aluminum plates from ceramic plates.BACKGROUND

[0003] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0004] In the processing of wafers in semiconductor manufacturing, electrostatic chucks (ESCs) are often used, which generally include a heated ceramic plate that is bonded to a cooled aluminum baseplate. Over time, the heated ceramic plates of the ESCs become worn and either need to be replaced or refurbished. In some cases, the heated ceramic plate can be separated from the cooled aluminum baseplate, and a new heated ceramic plate can then be bonded to the preexisting cooled aluminum baseplate.

[0005] Various techniques have been attempted to debond the heated ceramic plate from the cooled aluminum baseplate, with a goal of both the heated ceramic plate and the cooled aluminum baseplate being fully recovered. For example, a typical debonding process includes high thermal heating for several days of both the aluminum base plate and the heated ceramic plate. The bonding material will decompose when the temperature goes above certain limits, but after thermal decomposition of the bonding material, the aluminum material of the cooled aluminum baseplate will be annealed, softened, and / or out of geometrical tolerances. Thermal shock may also cause stress to the heated ceramic plate, thus resulting in breaking or cracking.

[0006] These challenges related to the repair or refurbishment of ESCs, or other bonded assemblies of ceramics to aluminum, is addressed by the present disclosure.SUMMARY

[0007] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0008] In one form, a bonded assembly comprises a first component, a second component, and a bond layer joining the first component to the second component, wherein the bond layer comprises a bonding composition. The bonding composition comprises a silicone elastomer and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer. In one form, the EG powder is in an amount between about 1.0 to about 5.0 wt.% of the bonding composition and has an average particle size of about 400 pm.

[0009] In variations of this bonded assembly, which may be implemented individually or in any combination: the first component is an aluminum material and the second component is a ceramic material; the silicone elastomer is a liquid silicone rubber (LSR); the silicone elastomer is a high consistency rubber (HCR); the bond layer has a thickness between about 0.010 inches to about 0.012 inches; and the bond layer has thermal conductivity of about 1 .0 W / m*K.

[0010] In another form of the bonded assembly, a secondary bond layer is disposed between the bond layer and the first component, wherein the secondary bond layer does not include any EG. In variations of this bonded assembly, which may be implemented individually or in any combination: the secondary bond layer consists of a silicone elastomer; the first component is an anodized aluminum material; and the first component is an anodized aluminum material and the second component is a ceramic material.

[0011] In another form, a bonding composition is provided that comprises a silicone elastomer and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer, the EG powder being in an amount of about 1 .0 to about 5.0 wt.% of the bonding composition and having an average particle size of about 400 pm. In variations of this bonding composition, which may be implemented individually or in any combination: the silicone elastomer is a liquid silicone rubber (LSR) or the silicone elastomer is a high consistency rubber (HCR); and thermalconductivity of the bond layer is about 1.0 W / m*K.

[0012] In yet anotherform, a method of debonding a first component from a second component is provided. The first component is joined to the second component with a bond layer comprising a bonding composition, and the bonding composition comprises a silicone elastomer and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer, the EG powder being in an amount between about 1.0 to about 5.0 wt.% of the bonding composition and having an average particle size of about 400 pm. The method comprises placing the first component and the second component in an isothermal environment and heating the first component and the second component at a rate less than or equal to about 2°C per minute. The first component is debonded from the second component at a separation temperature without the use of mechanical force and the first component and the second component maintain their nominal geometrical shape and material properties after being debonded. In one form, the separation temperature is between about 180°C to about 230°C, and in another form, the separation temperature is about 230°C.

[0013] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.DRAWINGS

[0014] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

[0015] FIG. 1 is a schematic view of a bonded assembly constructed in accordance with the teachings of the present disclosure;

[0016] FIG. 2 is a detail view, taken from detail 2-2 of FIG. 1 ;

[0017] FIG. 3 is a flow diagram illustrating a method according to the teachings of the present disclosure;

[0018] FIG. 4 is a schematic view of another bonded assembly constructed in accordance with the teachings of the present disclosure; and

[0019] FIG. 5 is a detail view, taken from detail 5-5 of FIG. 4.

[0020] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.DETAILED DESCRIPTION

[0021] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0022] Referring to FIGS. 1 and 2, a bonded assembly is illustrated and generally indicated by reference numeral 20. The bonded assembly 20 in this example is in the form of an electrostatic chuck (ESC) for use in semiconductor processing, such as by way of example an interposer or susceptor. Further details of exemplary electrostatic chucks are illustrated and described in International Patent Publication WO 2023 / 158675, which is commonly owned with the present application and the contents of which are incorporated herein by reference in their entirety. It should be understood however that the teachings of the present disclosure are not limited to such electrostatic chuck or susceptors and may be used in a variety of applications.

[0023] As shown, the bonded assembly 20 comprises a first component 22, a second component 24, and a bond layer 26 joining the first component 22 to the second component 24. In one form, the first component 22 is an integrally cooled (e.g., internal cooling channels, not shown) aluminum material, such as by way of example alloy 6061 , while the second component 24 is a ceramic material, such as by way of example, AIN (aluminum nitride). It should be understood that other ceramic materials (e.g., AI2O3 (alumina)) or other materials such as sapphire may also be employed while remaining within the scope of the present disclosure.

[0024] The bond layer 26 includes a bonding composition that is generally comprised of a silicone elastomer and expandable graphite (EG) powder. This bonding composition is particularly effective when the first component 22 is an aluminum material and the second component 24 is a ceramic material, as described in greater detail below.

[0025] Generally, EG is a compound of graphite that expands or exfoliates when heated. More specifically, EG is made by intercalating graphite layers with certain chemicals. When heated, the chemicals decompose and release gases, creating pressure that forces the graphite layers apart, causing the EG to expand. Thisexpansion is employed by the teachings of the present disclosure to separate the first component 22 from the second component 24 for refurbishment or repair operations as set forth in greater detail below. The expansion creates a set of properties, including by way of example, excellent thermal and electrical conductivity, high temperature resistance, and chemical inertness. The EG powder as used herein is uniformly dispersed throughout the silicone elastomer and is in an amount between about 1 .0 to about 5.0 wt.% of the bonding composition. The EG powder in one form has an average particle size between about 75 pm and about 420 pm, and in another form, the particle size is targeted at 400 pm. The bond layer 26 may have a thermal conductivity between about 0.2 and 2.5 W / m*K, and in one specific form, the bond layer 26 has thermal conductivity of about 1.0 W / m*K. This thermal conductivity is particularly advantageous in semiconductor electrostatic chuck applications in order to inhibit heat loss from the second component 24 to the first component 22 during operation, or etching wafers. Further, the grade of EG used in this application has a "trigger temperature," or a temperature that causes the graphite to expand and intercalate it a porous structure, between about 180°C to about 230°C. In one specific form, the trigger temperature is about 230°C.

[0026] The thickness of the bond layer 26 in this particular application is between about 0.010 inches to about 0.012 inches with a first component 22 being an aluminum material and the second component 24 being a ceramic material. It should be understood, however, that various thicknesses may be employed as a function of the bonding composition and the materials and / or geometry of the second component 24 and the first component 22. Further, more than one bond layer 26 may be employed, such as by way of example with the presence of a third component (not shown), or with a secondary bond layer as set forth in greater detail below. Therefore, it should be understood that any number of components and bond layers may be employed while remaining within the scope of the present disclosure.

[0027] The silicone elastomer of the bonding composition may be provided in a variety of forms, including but not limited to a liquid silicone rubber (LSR) (generally pure dimethyl silicone elastomers) or a high consistency rubber (HCR), as set forth in greater detail below. LSRs are generally addition-cured through a “controlled” platinum-catalyzed hydrosilation reaction between a short crosslinker and longer oligomer chains resulting in a regular network with very few "dangling" chains.Platinum catalyzed HCRs have no by-products of the cure mechanism, unlike the peroxide-catalyzed systems. The HCR form results in a flat continuous sheet with a uniform thickness and can be die-cut prior to the bonding process.

[0028] It should be understood that the specific formulation of the bonding composition is critical to achieving performance during operation of the ESC (e.g., thermal cycling, corrosive environment) as well as debonding of the first component 22 from the second component 24 during a repair / refurbishment operation after use. Generally, the bonding composition has a low glass transition temperature (about -70°C to about -115°C), excellent thermal stability (stable between about -50°C to about 250°C), resistance to oxidation, the desired dielectric constant (> 400 V / mm), and high hydrophobicity.

[0029] Referring now to FIG. 3, along with FIGS. 1 and 2, a method for debonding the first component 22 from the second component 24 is illustrated and described in greater detail. As shown, the first component 22 and the second component 24 are placed in an isothermal environment. An isothermal environment is used so that the forces generated in the debonding process are as evenly distributed as possible, thereby inhibiting inadvertent cracking of the ceramic second component 24.

[0030] Next, the first component 22 and the second component 24 are heated at a rate less than or equal to about 2°C per minute, up to a separation temperature in one form of about 230°C, or until the first component 22 is debonded, or separated from, from the second component 24 without the use of an external mechanical force.

[0031] After the first component 22 is debonded from the second component 24, advantageously, the first component 22 and the second component 24 maintain their nominal geometrical shape and material properties. More specifically, the nominal geometrical shape is maintained within specified tolerances for overall dimensions and flatness, for example, and the material properties are maintained within specified limits, such as thermal conductivity and thermal resistivity, among others.

[0032] Referring now to FIGS. 4 and 5, another form of the present disclosure includes a bonded assembly 100. The bonded assembly 100 in this form (also configured for the application of an electrostatic chuck (ESC) for use insemiconductor processing) is similar to the bonded assembly 20 set forth above, namely, with its inclusion of the first component 22, the second component 24, and the bond layer 26. The bond layer 26 functions as previously set forth, namely, to separate the first component 22 from the second component 24 at an elevated temperature without the use of an external mechanical force, via the EG material within the bond layer 26. In this form, a secondary bond layer 102 is disposed between the bond layer 26 and the second component 24.

[0033] In this form, the bond layer 26 is first cured, or joined, to the first component 22 as set forth above. Next, the secondary bond layer 102 is placed between the second component 24 and the bond layer 26, and the secondary bond layer 102 is secured to the bond layer 26 to join the first component 22 to the second component 24. The secondary bond layer 102 in one form is a silicone elastomer material but may comprise other elastomeric materials (without EG) while remaining within the scope of the present disclosure.

[0034] This form of the present disclosure is particularly beneficial when the first component 22 is an anodized aluminum material and the second component 24 is a ceramic material. Anodized aluminum materials are not typically able to withstand higher temperatures for an extended period of time, such as those set forth herein for the bonding / debonding processes using EG. In a variation of this form, the backside 104 of the first component 22 may optionally be cooled with a fluid (not shown) during the bonding and / or debonding processes. Further, the bonded assembly 100 may be similarly debonded according to the method set forth above, namely, with the use of EG within the bond layer 26.

[0035] It should be understood that the specific materials described herein are merely exemplary, and thus different formulations for the bonding composition may be employed, along with different configurations for the bond layer 26 (e.g., thickness, pattern), as a function of the components being bonded and debonded. For example, if a bond layer is greater than about 0.015 inches (15mils) mm, two bond layers may be required. In this case, one of the bond layers has the EG powder, while the other bond layer does not have any EG powder, e.g., silicone elastomer only, such as that illustrated and described relative to FIGS. 4 and 5.

[0036] Unless otherwise expressly indicated herein, all numerical values indicating mechanical / thermal properties, compositional percentages, dimensions and / or tolerances, or other characteristics are to be understood as modified by theword “about” or "approximately" in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

[0037] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0038] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.

Claims

CLAIMSWhat is claimed is:1 . A bonded assembly comprising: a first component; a second component; and a bond layer joining the first component to the second component, wherein the bond layer comprises a bonding composition, the bonding composition comprising: a silicone elastomer; and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer, the EG powder being in an amount of about 1.0 to about 5.0 wt.% of the bonding composition and having an average particle size of about 400 pm.

2. The bonded assembly according to Claim 1 , wherein the first component is an aluminum material and the second component is a ceramic material.

3. The bonded assembly according to Claim 1 , wherein the silicone elastomer is a liquid silicone rubber (LSR).

4. The bonded assembly according to Claim 1 , wherein the silicone elastomer is a high consistency rubber (HCR).

5. The bonded assembly according to Claim 1 , wherein the bond layer has a thickness between about 0.010 inches to about 0.012 inches.

6. The bonded assembly according to Claim 1 , wherein the bond layer has thermal conductivity between about 0.2 to about 2.5 W / m*K.

7. The bonded assembly according to Claim 6, wherein the bond layer has thermal conductivity of about 1 .0 W / m*K.

8. The bonded assembly according to Claim 1 , further comprising a secondary bond layer disposed between the bond layer and the first component,wherein the secondary bond layer does not include any EG.

9. The bonded assembly according to Claim 8, wherein the secondary bond layer consists of a silicone elastomer.

10. The bonded assembly according to Claim 8, wherein the first component is an anodized aluminum material.11 . The bonded assembly according to Claim 8, wherein the first component is an anodized aluminum material and the second component is a ceramic material.

12. A bonding composition comprising: a silicone elastomer; and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer, the EG powder being in an amount of about 1 .0 to about 5.0 wt.% of the bonding composition and having an average particle size of about 400 pm.

13. The bonding composition according to Claim 12, wherein the silicone elastomer is a liquid silicone rubber (LSR).

14. The bonding composition according to Claim 12, wherein the silicone elastomer is a high consistency rubber (HCR).

15. A method of debonding a first component from a second component, the first component being joined to the second component with a bond layer comprising a bonding composition, the bonding composition comprising: a silicone elastomer; and expandable graphite (EG) powder uniformly dispersed throughout the silicone elastomer, the EG powder being in an amount of about 1 .0 to about 5.0 wt.% of the bonding composition and having an average particle size of about 400 pm, wherein the method comprises placing the first component and the second component in an isothermal environment and heating the first component and the second component at a rate less than or equal to about 2°C per minute, andwherein the first component is debonded from the second component at a separation temperature without use of mechanical force.

16. The method according to Claim 15, wherein the separation temperature is between about 180°C to about 230°C.

17. The method according to Claim 15, wherein the separation temperature is about 230°C.

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