Chuck for plasma processing chamber

Abstract

To provide an electrostatic chuck system for a plasma processing chamber that can operate over a temperature range that can be cooled to temperatures below -60°C and heated to temperatures above 200°C.SOLUTION: An electrostatic chuck system 100 for a plasma processing chamber is provided with a base plate 108 including Al-SiC, a ceramic plate 104 is disposed on the top of the base plate, and a bonding layer 105 bonds the ceramic plate to the base plate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority to U.S. Application No. 62 / 815,876, filed March 8, 2019, which is incorporated herein by reference for all purposes.

[0002] The present disclosure relates to components of plasma processing chambers used in semiconductor processing, and more particularly, to electrostatic chucks used in plasma processing chambers. [Background technology]

[0003] In plasma processing chambers, electrostatic chucks are used to support a substrate during processing, which may be exposed to different temperatures. Summary of the Invention

[0004] To achieve the foregoing and in accordance with the objects of the present disclosure, an electrostatic chuck system for a plasma processing chamber is provided. A base plate is provided that includes Al-SiC. A ceramic plate is disposed on the base plate. A bonding layer bonds the ceramic plate to the base plate.

[0005] These and other features of the present disclosure are described in more detail below in the detailed description of the present disclosure and in conjunction with the following figures. [Brief description of the drawings]

[0006] The disclosed embodiments are illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which:

[0007] [Figure 1] FIG. 1 is a partial cross-sectional view of one embodiment of an electrostatic chuck.

[0008] [Diagram 2]FIG. 2 is a partial cross-sectional view of another embodiment.

[0009] [Diagram 3] FIG. 3 is a schematic diagram of an etching reactor that may be used in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The embodiments will now be described in detail with reference to some of its embodiments as illustrated in the accompanying drawings. In the following description, specific details are set forth to provide a thorough understanding of the present disclosure. However, the present disclosure may be practiced without some or all of these specific details, and the present disclosure encompasses modifications that may be made in accordance with knowledge commonly available within the technical field. Well-known process steps and / or structures have not been described in detail in order to not unnecessarily obscure the present disclosure.

[0011] Electrostatic chuck (ESC) system technology may require bonding a ceramic material / layer to a heat sink (cooling) base plate. A bonding layer is typically used to bond the ceramic layer to the base plate. The base plate is usually made from aluminum metal. Aluminum is chosen because it is cheap, easy to manufacture, has high thermal conductivity, and results in a uniform heat sink temperature at the bonding layer. However, aluminum has a coefficient of thermal expansion (CTE) of 23 (parts per million per degree Celsius) ppm / °C, which is significantly higher than the CTE of ceramics, which is typically closer to 7-10 ppm / °C.

[0012] The high CTE of aluminum and the mismatch of the CTE of the ceramic material used in the ESC are significant drawbacks in plasma etcher systems. The bonding layer undergoes large mechanical strains at very low temperatures. The base plate shrinks about three times as much as the ceramic layer, limiting the thermal operating window of the ESC. In addition, the design of the edge ring in a plasma etch chamber must consider a wide range of base plate sizes across the thermal operating window. This leaves a gap between the edge ring and the base plate at some temperatures. The gap can fill with gas and generate a parasitic plasma.

[0013] Titanium-based baseplates with low CTE have been used. However, titanium and titanium-based alloys have very poor thermal conductivity, which increases the risk of thermal non-uniformity on the top surface of the baseplate, which can affect temperature uniformity at the wafer level. In addition, the poor thermal conductivity of the baseplate limits the minimum operating temperature under plasma load by leaving a larger temperature drop between the coolant setpoint and the temperature at the top of the baseplate.

[0014] Various embodiments relate to ESCs, where the base plate is made from an aluminum-silicon carbide (Al-SiC) alloy. ESCs made using such base plates have significant advantages compared to previous base plate technologies. Al-SiC based alloys offer a balance of low CTE and high thermal conductivity. In various embodiments, the thermal operating range of such ESCs may be extended beyond that of ESCs with aluminum base plates, as bond strains are reduced due to the more closely matched CTE of the ceramic layer and base plate. In various embodiments, less movement occurs at the connection between the chamber hardware and the base plate compared to aluminum base plate ESCs, thereby reducing requirements for shim materials, electrical connection flexibility, and O-ring wear. In addition, the gap between the base plate and the edge ring may be reduced and designed tighter compared to aluminum base plate ESCs. The reduced gap reduces deposition of etch by-products, surface degradation, and plasma discharge in the area between the edge ring and the base plate. In various embodiments, the ESC has improved thermal uniformity over an ESC with a titanium alloy base plate due to improved thermal conductivity. The improved thermal uniformity improves processing uniformity across the wafer surface. Additionally, the improved thermal conductivity of the base plate may allow for lower plasma processing temperatures under heat loads due to reduced temperature drop between the top surface of the base plate and the coolant.

[0015] FIG. 1 is a schematic cross-sectional view of one embodiment of an electrostatic chuck (ESC) 100. A ceramic plate / layer 104 may be bonded to a base plate 108 comprising Al-SiC by a bonding layer 105. Al-SiC is a metal matrix composite material comprising an aluminum matrix with silicon carbide (SiC) particles. In one embodiment, the bonding layer 105 may be a polymer adhesive, such as silicone, with filler particles to increase the thermal conductivity of the polymer adhesive. The base plate 108 may include channels 109 for the flow of gas or liquid. These channels 109 may be formed into complex distribution channels, for example, to cool or heat the ESC 100. In various embodiments, the channels 109 are temperature control channels. An edge ring 110 surrounds the electrostatic chuck 100. In this example, the edge ring 110 comprises quartz or silicon. In other embodiments, the edge ring 110 comprises ceramic or plasma erosion resistant glass. The edge ring 110 may comprise aluminum oxide or aluminum nitride. In this embodiment, the ceramic plate 104 comprises aluminum oxide or aluminum nitride.

[0016] 2 shows how, in one embodiment, the base plate 108 is formed. The base plate 108 includes a top plate 204 and a bottom plate 208. The top plate 204 has a channel 109 machined into the bottom of the top plate 204. The top plate 204 and the bottom plate 208 may be brazed together to form the base plate 108.

[0017] In one embodiment, the top plate 204 and bottom plate 208 are formed from Al-SiC that is about 20% SiC by weight. The channels 109 are machined into the top plate 204. It has been found that Al-SiC with about 20% SiC by weight is easy to machine and has a CTE that is closer to the CTE of the ceramic plate 104 compared to the CTE of aluminum versus the CTE of the ceramic plate 104.

[0018] In this embodiment, the ceramic plate 104 has a CTE of 7-8 ppm / °C and a thermal conductivity of 18 Watts per meter Kelvin (W / mK). The Al-SiC base plate 108 has a CTE of 13-15 ppm / °C and a thermal conductivity of over 170 W / mK. The edge ring 110 is made of quartz and has a CTE of 0.5 ppm / °C and a thermal conductivity of 2 W / mK. Thus, in this embodiment, the difference between the CTE of the Al-SiC base plate 108 and the CTE of the ceramic plate 104 is 5-8 ppm / °C. In addition, the difference between the CTE of the Al-SiC base plate 108 and the CTE of the edge ring 110 is 12.5-14.5 ppm / °C. In contrast, the base plate with aluminum has a CTE of 23 ppm / °C and a thermal conductivity of over 200 W / mK. Although the Al-SiC base plate 108 does not have a CTE exactly equal to the CTE of the ceramic plate 104 or the CTE of the edge ring 110, the Al-SiC nevertheless has a CTE that is closer to the CTE of the ceramic plate 104 and the CTE of the edge ring 110 compared to the CTE of aluminum versus the CTE of the ceramic plate 104 and the CTE of the edge ring 110.

[0019] In various embodiments, the base plate 108 is formed from Al-SiC having 18% to 65% SiC by weight. In various embodiments, the base plate 108 is formed from Al-SiC having 18% to 40% SiC by weight. In various embodiments, the base plate 108 is formed from Al-SiC having 18% to 30% SiC by weight. Al-SiC having 18% to 30% SiC by weight has been found to be easier to machine. Al-SiC having 40% to 65% SiC by weight may be more difficult to machine, but will have a lower CTE than Al-SiC with a lower percentage of SiC.

[0020] In other embodiments, the bonding layer 105 may include a less compliant material than may be used with an aluminum base plate, since with improved CTE match between the ceramic plate 104 and the base plate 108, the bond material does not need to withstand as much strain. For example, a silicon bond with higher thermal conductivity may be used in a system that experiences less strain in the same temperature window. Due to the increased filler content, a silicon bond with higher thermal conductivity tends to be harder than a silicon bond with lower thermal conductivity. In another embodiment, a bond material that requires a higher temperature to cure may be used in a system with a good CTE match (whereas in a system with mismatched CTEs, strains may be too high).

[0021] In another embodiment, an additive manufacturing process, such as an additive 3D printing process, is used in forming the base plate 108. Such an additive manufacturing process may provide a base plate 108 of Al-SiC that is about 40% SiC by weight. Al-SiC with a higher percentage of SiC is more difficult to machine. However, because an additive process is used to form the base plate 108, the complex shape of the base plate 108 may be formed without the need for machining. Such a process reduces or eliminates machining that removes material, thereby reducing waste material.

[0022] In an exemplary embodiment, FIG. 3 is a schematic diagram of an etching reactor that may be used in an embodiment. In one or more embodiments, a plasma processing chamber 300 includes a gas distribution plate 306 that provides a gas inlet and an ESC 100 in an etching chamber 308 surrounded by a chamber wall 310. In the etching chamber 308, a stack 314 is positioned above the ESC 100. The ESC 100 includes a ceramic plate 104 that is bonded to a base plate 108. An edge ring 110 surrounds the ESC 100. An ESC temperature controller 350 is connected to a chiller 318. In this embodiment, the chiller 318 provides coolant to a channel 109 in the base plate 108 of the ESC 100. A radio frequency (RF) source 330 provides RF power to a lower electrode. In this embodiment, the lower electrode is a facility plate 320 below the base plate 108 and is separated from the base plate 108 by an O-ring 324. Conductive rods 326 provide electrical connections between the facility plate 320 and the base plate 108. As a result, the base plate 108 is electrically connected to an RF source 330. In an exemplary embodiment, a 400 kHz and 60 MHz power supply constitutes the RF source 330. In this embodiment, the upper electrode, the gas distribution plate 306, is grounded. In this embodiment, one generator is provided for each frequency. Other arrangements of RF sources and electrodes may be used in other embodiments. The gas distribution plate 306 is in fluid communication with a gas source 332. An exhaust pump 328 is provided to remove exhaust from the etching chamber 308. A controller 335 is controllably connected to the RF source 330, the exhaust pump 328, and the gas source 332. One example of such an etching chamber is the Flex® Etch System manufactured by Lam Research Corporation of Fremont, California. The process chamber may be a CCP (capacitively coupled plasma) reactor or an ICP (inductively coupled plasma) reactor.

[0023] Various embodiments are used in a plasma processing chamber 300 that can operate in a temperature range in which the ESC 100 is cooled to temperatures below −60° C. and heated to temperatures above 200° C. In various embodiments, the ESC temperature controller can cool the base plate 108 to temperatures below −40° C. and heat the base plate 108 to temperatures above 100° C.

[0024] Although the present disclosure has been described with respect to several preferred embodiments, there are modifications, permutations, and various substitute equivalents that are within the scope of the present disclosure. There are many alternative ways of implementing the methods and apparatuses disclosed herein. It is therefore intended that the following appended claims be interpreted to include all such modifications, permutations, and various substitute equivalents that are within the true spirit and scope of the present disclosure.

Claims

1. 1. An electrostatic chuck system for a plasma processing chamber, comprising: A base plate including Al-SiC; a ceramic plate disposed on the base plate; a bonding layer that bonds the ceramic plate to the base plate; An electrostatic chuck system comprising:

2. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system further comprising a channel in the base plate.

3. 3. The electrostatic chuck system of claim 2, The electrostatic chuck system, wherein the channel is a temperature controlled channel.

4. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system further comprises an edge ring surrounding the base plate.

5. 5. The electrostatic chuck system of claim 4, The difference between the CTE of the base plate and the CTE of the edge ring is between 12.5 and 14.5 ppm / °C.

6. 5. The electrostatic chuck system of claim 4, 11. An electrostatic chuck system, wherein the edge ring comprises at least one of quartz, ceramic, plasma erosion resistant glass, or silicon.

7. 2. The electrostatic chuck system of claim 1, The ceramic plate comprises at least one of aluminum oxide or aluminum nitride.

8. 2. The electrostatic chuck system of claim 1, The bonding layer comprises silicon.

9. 9. The electrostatic chuck system of claim 8, The bonding layer further comprises a thermally conductive filler material.

10. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system, wherein the base plate comprises Al-SiC having 18% to 65% SiC by weight.

11. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system, wherein the base plate comprises Al-SiC having 18% to 40% SiC by weight.

12. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system, wherein the base plate comprises Al-SiC having 18% to 30% SiC by weight.

13. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system further comprising an RF source electrically connected to the base plate.

14. 2. The electrostatic chuck system of claim 1, 11. An electrostatic chuck system, further comprising: a temperature controller connected to the base plate, the temperature controller configured to heat the base plate to a temperature greater than 90°C and to cool the base plate to a temperature less than −40°C.

15. 2. The electrostatic chuck system of claim 1, The base plate is a top plate, the channel being machined into a bottom of the top plate; a bottom plate connected to the top plate; An electrostatic chuck system comprising:

16. 2. The electrostatic chuck system of claim 1, The electrostatic chuck system, wherein the base plate is formed by an additive manufacturing process.

17. 2. The electrostatic chuck system of claim 1, The difference between the CTE of the base plate and the CTE of the ceramic plate is 5-8 ppm / °C.

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