Methods and apparatus for preventing component cracking using stress relief layers

Abstract

Methods and apparatus for protecting parts of a process chamber from thermal cycling effects of deposited material. In some embodiments, a method of protecting parts of a process chamber includes the steps of wet etching the parts using a weak base or weak acid; cleaning the parts by sandblasting; coating at least a portion of a surface of the parts using a stress release layer. The stress release layer forms a continuous layer of about 50 microns to about 250 microns thick and is configured to maintain structural integrity of the parts from thermal cycling of aluminum deposited on the parts. The method also includes wet cleaning the parts after forming the stress release layer using a heated deionized water rinse.

Description

TECHNICAL FIELD

[0001] Embodiments of the present principles generally relate to semiconductor processing of semiconductor substrates. BACKGROUND

[0002] Large scale integrated circuits (LSIs) have long used aluminum as an interconnect material. When single layer wiring was used in LSIs, the film thickness was about 1 micron. Advancements in technology, such as the use of barrier metal layers, allowed the film thickness to be reduced to about 0.3 to 0.6 microns. However, recently, the semiconductor industry has shifted to require an increase in film thickness from about 1.5 microns to about 6 microns or more in order to support advanced packaging technology. As the film thickness increases, the target material is consumed more quickly and the life of the process kit is shortened, thereby reducing productivity. The inventors have observed that in aluminum deposition chambers that produce increased film thickness, the process kit components need to be serviced more frequently than the target material, resulting in additional downtime to replace the process kit components and then more downtime to replace the target material at the end of its life.

[0003] Accordingly, the inventors have provided improved life of process kit components that increase throughput while reducing maintenance costs. SUMMARY

[0004] Methods and apparatus for increasing the life of a part used in a process chamber are provided herein.

[0005] In some embodiments, a method of protecting a part of a process chamber includes the steps of wet etching the part using a weak base or weak acid; cleaning the part by bead blasting; coating at least a portion of a surface of the part using a stress release layer, wherein the stress release layer forms a continuous layer of about 50 microns to about 250 microns thick and is configured to maintain the structural integrity of the part from thermal cycling of aluminum deposited on the part; and wet cleaning the part using a heated deionized water rinse.

[0006] In some embodiments, the method can further include wherein the stress release layer is formed from an aluminum oxide (AI2O3) based material; wherein the at least a portion of the surface of the part is coated using a plasma spray process; wherein the at least a portion of the surface of the part is coated using a perhydropolysilazane (PHPS) process; wherein the part is a deposition ring formed from a ceramic material; wherein the stress release layer forms a continuous layer that is approximately 100 microns to approximately 150 microns thick; wherein the part is an electrostatic chuck formed from a ceramic material; wherein the thermal cycling is between approximately 200 degrees Celsius and approximately 400 degrees Celsius; wherein the stress release layer has a first adhesion threshold with aluminum deposited under vacuum, and a second adhesion threshold with the part when the part is formed from a ceramic material, and wherein the first adhesion threshold is greater than the second adhesion threshold; and / or wherein the aluminum deposited on the part exceeds a thickness of the part.

[0007] In some embodiments, a method of protecting a part of a process chamber can include the steps of: coating at least a portion of a surface of the part with a stress release layer, wherein the stress release layer forms a continuous layer that is approximately 50 microns to approximately 250 microns thick, wherein the stress release layer is configured to have an adhesion threshold to a material deposited on the stress release layer that is higher than an adhesion threshold with a base material, and wherein the stress release layer is configured to maintain structural integrity of the part from thermal cycling of aluminum deposited on the part between approximately 200 degrees Celsius and approximately 400 degrees Celsius.

[0008] In some embodiments, the method can further include the steps of: prior to coating the part, wet etching the part using a weak base or weak acid, and prior to coating the part, cleaning the part by sandblasting; wherein the stress release layer is formed from an aluminum oxide (AI2O3) based material; wherein a plasma spray process using powdered aluminum oxide is used to coat the at least a portion of the surface of the part; wherein the part is a deposition ring formed from a ceramic material; wherein the stress release layer forms a continuous layer that is approximately 100 microns to approximately 150 microns thick; wherein the part is an electrostatic chuck formed from a ceramic material; and / or wherein the stress release layer has a first adhesion threshold with aluminum deposited under vacuum, and a second adhesion threshold with the part when the part is formed from a ceramic material, and wherein the first adhesion threshold is greater than the second adhesion threshold.

[0009] In some embodiments, an apparatus for installation into a process chamber can include: a deposition ring having at least a portion of an upper surface containing a stress release layer, wherein the stress release layer is an aluminum oxide layer having a thickness of approximately 50 microns to approximately 250 microns, and is configured to have an adhesion threshold with aluminum deposited in a vacuum that is higher than an adhesion threshold with a material of the deposition ring.

[0010] In some embodiments, the device may further include a stress relief layer configured to reduce stress generated by thermal cycling of aluminum deposited on the deposition ring between approximately 200 degrees Celsius and approximately 400 degrees Celsius.

[0011] Other and further embodiments are discussed below. Attached Figure Description

[0012] The embodiments of the principle briefly summarized above and discussed in more detail below can be understood by referring to the illustrative embodiments of the principle depicted in the accompanying drawings. However, the drawings only illustrate typical embodiments of the principle and should therefore not be considered as limiting the scope, as other equivalent embodiments of the principle are permissible.

[0013] Figure 1 Cross-sectional views of process chambers according to some embodiments of this principle are depicted.

[0014] Figure 2 A cross-sectional view of a substrate support assembly following an aluminum deposition process, according to some embodiments of this principle, is depicted.

[0015] Figure 3 Cross-sectional views of a deposition ring following aluminum deposition, according to some embodiments of this principle, are depicted.

[0016] Figure 4 Cross-sectional views of deposition rings according to some embodiments of this principle are depicted.

[0017] Figure 5 Cross-sectional views of a deposition ring with a stress-relief layer according to some embodiments of this principle are depicted.

[0018] Figure 6 A cross-sectional view of a deposition ring with a stress-relief layer following aluminum deposition, according to some embodiments of this principle, is depicted.

[0019] Figure 7 This is a method for applying a stress-relieving layer according to some embodiments of this principle.

[0020] For ease of understanding, the same reference numerals are used as much as possible to denote common elements in the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be advantageously incorporated into other embodiments without further description. Detailed Implementation

[0021] Methods and apparatus provide a low cost process for increasing the useful life of parts used in a process chamber. A stress relief layer is coated on the part surface to achieve improved structural strength and reduce part breakage to increase part useful life, reduce maintenance. Reduced downtime increases productivity and throughput. The coating can be applied to any number of parts in the process chamber and is process transparent (does not affect wafer performance). Using the methods and apparatus of the present principles, kit useful life can be increased by as much as 40% to 100%. The improvement can be from about 1800 kWh to about 2500 kWh or more in kilowatt hours.

[0022] The use case used herein involves a deposition ring of a process chamber as an example, but the use case is not meant to be limiting in any way, as the coating process can be used on any chamber part to maintain the structural integrity of the part within its useful life. In the case of the deposition ring, previous efforts included increasing the height of the electrostatic chuck (ESC) and reducing the thickness of the alumina ceramic deposition ring in response to the increase in aluminum deposition to make room for the additional aluminum deposition formed around the wafer to meet the target useful life. The inventors found that as the deposition ring thickness was reduced and the aluminum deposition increased, a break formed in the deposition ring when the aluminum deposition thickness on the deposition ring was greater than the deposition ring thickness (when the aluminum deposition thickness was about four to six times the deposition ring thickness).

[0023] The inventors also found that there were two reasons for the alumina deposition ring breakage: the difference in the coefficient of thermal expansion and adhesion of the aluminum (deposited material) and the alumina (underlying material), and the coefficient of thermal expansion of the volume of aluminum exceeded the tension of the alumina. The inventors found that by using an aluminum oxide coating on the alumina material of the deposition ring, the breakage of the deposition ring was prevented. The coating adhered more strongly to the deposited aluminum than the alumina of the deposition ring, allowing the aluminum to expand and contract independently of the alumina. In effect, the coating bonded with the aluminum deposit and unbonded from the alumina when the compressive and tensile forces due to heating expansion and cooling contraction overcame the small adhesion threshold between the coating and the alumina.

[0024] Figure 1is a cross-sectional view of a PVD chamber 100 according to some embodiments. The PVD chamber 100 represents an example chamber (not intended to be limiting) in which methods and apparatus of the present principles can be incorporated. The PVD chamber 100 can be used to deposit aluminum and other materials onto a wafer 110 that can include a semiconductor structure. The PVD chamber 100 includes a chamber body 102 and a source 190 that includes a magnetron assembly 104 and a target 112. The wafer 110 is supported on a substrate support assembly 192 that includes an electrostatic chuck (ESC) 108, which is supported by a substrate support pedestal 106. One or more gases can be supplied into a lower portion of the PVD chamber 100 from a gas source 184. A pump 182 is connected to the PVD chamber 100 for evacuating an interior of the PVD chamber 100 and facilitating maintenance of a desired pressure within the PVD chamber 100.

[0025] At a top of the processing volume 118 is the target 112 having a backing plate 114. In some embodiments, the target 112 can be aluminum or the like. A DC power source 128 provides DC power to the target 112 via the backing plate 114 to the target 112 during processing. The backing plate 114 can include a conductive material, such as copper-zinc, copper-chromium, or the same material as the target 112, such that the DC power can be coupled to the target 112 via the backing plate 114. Alternatively, the backing plate 114 can be non-conductive and can include a conductive element (not shown), such as an electrical feedthrough or the like. The backing plate 114 can be disk-shaped, rectangular, square, or any other shape that can be accommodated by the PVD chamber 100. The backing plate 114 is configured to support the target 112 such that a front surface of the target 112 is opposite the wafer 110 when present. The target 112 can be coupled to the backing plate 114 in any suitable manner. For example, in some embodiments, the target 112 can be diffusion bonded to the backing plate 114.

[0026] The magnetron assembly 104 can include a first magnet 136 that travels over the target 112 at a first radius about a central axis 154 and a second magnet that travels over the target 112 at a second radius about the central axis 154. The first radius can be referred to as an inner radius and the second radius can be referred to as an outer radius. A support apparatus 134 supports and enables rotation of the first and second magnets 136, 138 about the central axis 154. In some embodiments, the first magnet 136 can rotate about a first magnet axis 172 and / or the second magnet 138 can rotate about a second magnet axis 174. In some embodiments, the first and / or second magnets 136, 138 can include a plurality of individual magnets.

[0027] The RF bias power source 126 can be coupled to the substrate support assembly 192 in order to induce a bias on the wafer 110. Additionally, in some embodiments, a self-bias can be formed on the wafer 110 during processing. For example, the RF energy supplied by the RF bias power source 126 can be in a frequency range from about 2 MHz to about 60 MHz, for example, non-limiting frequencies such as 2 MHz, 13.56 MHz, or 60 MHz can be used. In some embodiments, the RF power can be supplied in a range from about 1 kW to about 20 kW. In some embodiments, the RF power supplied can be about 3 kW. In some embodiments, the RF power supplied can be about 1.9 kW. In some embodiments, the DC power source 128 can supply DC power to the target 112 in a range from about 38 kW to about 50 kW. In some embodiments, the DC power source 128 can provide DC power in a range from about 42 kW to about 50 kW. In some embodiments, the DC power source 128 can provide DC power in a range from about 42 kW to about 60 kW. In some embodiments, the DC power source 128 can provide DC power in a range from about 38 kW to about 60 kW. In other applications, the substrate support assembly 192 can be grounded or held electrically floating.

[0028] The PVD chamber 100 further includes a process kit shield or shield 152 to surround the processing volume 118 of the PVD chamber 100 and protect other chamber components from damage and / or contamination from processing. In some embodiments, the shield 152 can be grounded to the chamber body at a highest point 196 to provide an RF ground return path. The shield 152 extends downward and can include a generally tubular portion having a generally constant diameter to generally surround the processing volume 118. The shield 152 extends down the wall of the chamber body 102 below an uppermost surface 198 of the ESC 108 to the cover ring 122. The deposition ring 120 can be used to protect the edges of the substrate support assembly 192 including the substrate support pedestal and / or the ESC 108 from deposition around the edges of the wafer 110.

[0029] A controller 144 can be provided and coupled to various components of the PVD chamber 100 to control its operation. The controller 144 includes a central processing unit (CPU) 146, a memory 148, and support circuits 150. The controller 144 can control the PVD chamber 100 directly or via computers (or controllers) associated with particular process chamber and / or support system components. The controller 144 can be one of any form of general-purpose computer processors that can be used in an industrial setting for controlling various chambers and sub-processors. The memory or computer readable medium 148 of the controller 144 can be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, optical storage media (e.g., compact disc or digital video disc), flash memory, or any other form of local or remote digital storage. The support circuits 150 are coupled to the CPU 146 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input / output circuitry and subsystems, and the like. Methods of controlling the PVD chamber 100 and / or processes can be stored as software routines in the memory 148, which can be executed by, or called by, the CPU 146 to control the operation of the PVD chamber 100 in the manner described herein. The software routines can also be stored and / or executed by a second CPU (not shown), that is remotely located from the hardware being controlled by the CPU 146.

[0030] Figure 2 A cross-sectional view of a substrate support assembly 200 after an aluminum deposition process is depicted in accordance with some embodiments. After a significant amount of aluminum deposition occurs, a buildup 202 of aluminum is formed on the deposition ring 120 after several deposition processes are performed. Figure 3 A cross-sectional view 300 of a portion of a deposition ring after aluminum deposition reaches a critical point is depicted, which can initiate cracking in the deposition ring. The inventors have discovered that when the aluminum deposition thickness 302 and the deposition ring thickness 304 reach a ratio of approximately 0.8 or higher, the deposition ring 120 can begin to crack in one or more locations due to the thermal cycling of the aluminum during the deposition process. The coefficient of thermal expansion (CTE) of aluminum (approximately 22 ppm) is much greater than the CTE of the ceramic material used to form the deposition ring 120 (approximately 7.8 ppm).

[0031] Figure 4A cross-sectional view 400 of the deposition ring 120 after the heating and cooling forces of the deposited aluminum buildup 202 have affected the structural integrity of the deposition ring 120 and formed a crack 406 is depicted. Aluminum generally tends to have a poor bond with oxides such as alumina or aluminum oxide under atmospheric conditions. In a vacuum, as is found in most deposition chambers, aluminum deposition bonds very well with the surfaces that the aluminum comes into contact with during processing. Under vacuum conditions, the deposited aluminum forms a strong bond with the ceramic material of the deposition ring 120. When the aluminum is heated, the aluminum expands 404 more than three times the rate of expansion of the ceramic material and causes internal stress in the deposition ring 120. As the aluminum cools, the aluminum shrinks 402 at a much greater rate than the ceramic material of the deposition ring 120. The temperature cycling eventually causes a failure in the structural integrity of the deposition ring 120, forming a crack.

[0032] The inventors have discovered that if a stress release layer is formed on the deposition ring 120 prior to depositing aluminum, the aluminum expansion and contraction forces of the aluminum can be prevented from destroying the structural integrity of the deposition ring 120. Figure 5 A cross-sectional view 500 of a deposition ring 120 having a stress release layer 502 is depicted in accordance with some embodiments. The stress release layer 502 is applied to at least a portion of the upper surface 504 of the deposition ring 120 that will come into contact with the deposited material during processing. In some embodiments, the stress release layer 502 is applied to the portions of the deposition ring 120 that can come into contact with the deposited aluminum or the like. In some embodiments, the stress release layer is formed of aluminum oxide (AI3O2). Aluminum oxide has a first adhesion threshold to the ceramic material of the deposition ring 120. When deposited in a vacuum, aluminum oxide has a second adhesion threshold to aluminum. The second adhesion threshold is significantly greater than the first adhesion threshold. In some embodiments, the ratio of the second adhesion threshold to the first adhesion threshold is 5: 1 or greater. For example, in some embodiments, the stress release layer has an adhesion threshold (first adhesion threshold) of about 3 MPa to about 6 MPa, and the stress release layer has an adhesion threshold (second adhesion threshold) of about 30 MPa to the deposited aluminum. The inventors have discovered that if the stress release layer is formed of any material that has an adhesion threshold to any underlying material that is higher than the adhesion threshold to the deposited material, the structural integrity of the part is maintained, significantly extending the useful life of the part.

[0033] Figure 6A cross-sectional view 600 of the deposition ring 120 with the stress release layer 502 after deposition of aluminum is depicted in accordance with some embodiments. As the aluminum buildup 202 is heated and cooled, the thermal cycling forces the stress release layer 502 to expand and contract due to the strong bond formed between the deposited aluminum and the stress release layer 502. The weaker bond formed between the stress release layer 502 and the ceramic material of the deposition ring 120 is broken and allows the stress release layer 502 to move independently of the ceramic material of the deposition ring 120, thereby preventing the formation of internal stresses and destroying the structural integrity of the deposition ring 120. Due to the weaker bond with the underlying material, the stress release layer 502 is allowed to expand 604 and contract 602 separately from the ceramic material of the deposition ring 120, thereby preventing the aluminum thermal cycling from damaging the deposition ring 120.

[0034] Figure 7 A method 700 of applying a stress release layer in accordance with some embodiments. In block 702, a weak base or weak acid is used to wet etch the surface of the part to be coated to ensure that any surface contaminants are removed. In block 704, the surface is cleaned and prepared by sandblasting. The sandblasting ensures that the surface will provide proper adhesion for the stress release layer to be subsequently applied. In block 706, the stress release layer is applied using any number of techniques such as, but not limited to, plasma spray techniques or perhydrolased polysilazane (PHPS) coating techniques, among others. The stress release layer is formed from any material that has a higher adhesion threshold to the material on which the stress release layer is applied than the adhesion threshold to the material deposited on the stress release layer, thereby allowing the stresses of the deposited material to be eliminated in the stress release layer, maintaining the structural integrity of the underlying part.

[0035] In plasma spray techniques, a plasma is used to spray a material in powder form using a strong plasma flame. The material is accelerated and impacts the part surface at high pressure and temperature. The spray is ejected from the plasma spray apparatus similar to a shockwave and the high pressure of the gas of the spray material powder adheres to the surface. In PHPS coating techniques, PHPS is used as a precursor to produce a coating that provides a high quality thin film on the surface. In some embodiments, the thickness of the stress release layer is approximately 50 microns to approximately 250 microns. In some embodiments, the thickness of the stress release layer is approximately 100 microns to approximately 150 microns. The stress release layer is applied such that the stress release layer is a continuous layer.

[0036] The stress release layer is configured to maintain the structural integrity of a part of a process chamber from thermal cycling of material deposited on the part, such as but not limited to aluminum and the like, during processing. In some embodiments, the stress release layer maintains the structural integrity of the part during thermal cycling between approximately 200 degrees Celsius and approximately 400 degrees Celsius. Aluminum deposition is typically performed at temperatures of approximately 200 degrees Celsius or higher to ensure reliability of aluminum interconnects formed on wafers. Aluminum, which has a melting point of approximately 600 degrees Celsius, begins to plastically deform at approximately 400 degrees Celsius. Since aluminum is in a plastically deformed state above 400 degrees Celsius, at higher temperatures, the aluminum does not add any additional stress to any underlying material. In some embodiments, the stress release layer is formed of an aluminum oxide (AI2O3) based material. In some embodiments, the part is a deposition ring or an electrostatic chuck or the like. The stress release layer is formed of any material that has a higher adhesion threshold to any underlying material than the adhesion threshold to the deposited material, maintaining the structural integrity of the part, significantly extending the useful life of the part. Environmental conditions in which the deposited material is formed can directly affect the adhesion threshold, such as in the case of aluminum deposition under vacuum. In some embodiments, the underlying material can include a ceramic based material or the like. In block 708, the stress release layer is wet cleaned using a heated deionized water rinse to remove any residual particles. The method can be used to apply a stress release layer on any part of a process chamber.

[0037] Embodiments consistent with the present principles can be implemented in hardware, firmware, software, or any combination of these. Embodiments can also be implemented as instructions stored using one or more computer-readable media, which can be read and executed by one or more processors. A computer-readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform or "virtual machine" running on one or more computing platforms). For example, a computer-readable medium can include any suitable form of volatile or non-volatile memory. In some embodiments, a computer-readable medium can include a non-transitory computer-readable medium.

[0038] While the foregoing is directed to embodiments of the present principles, other and further embodiments of the present principles can be devised without departing from the basic scope thereof.

Claims

1. A method of protecting a part of a process chamber, comprising the steps of: wet etching the part using a weak base or weak acid; cleaning the part by sandblasting; coating at least a portion of a surface of the part with a stress release layer, wherein the stress release layer forms a continuous layer that is 50 microns to 250 microns thick and is configured to maintain structural integrity of the part from a thermal cycle of aluminum deposited on the part; and wet cleaning the part using a heated deionized water rinse; wherein the stress release layer has a first adhesion threshold to aluminum deposited under vacuum, and a second adhesion threshold to the part when the part is formed of a ceramic material, and wherein a ratio of the first adhesion threshold to the second adhesion threshold is at least 5:

1.

2. The method of claim 1, wherein the stress release layer is formed of an aluminum oxide (AI2O3) based material.

3. The method of claim 1, wherein the at least a portion of the surface of the part is coated using a plasma spray process.

4. The method of claim 1, wherein the at least a portion of the surface of the part is coated using a perhydropolysilazane (PHPS) process.

5. The method of claim 1, wherein the part is a deposition ring formed of a ceramic material.

6. The method of claim 1, wherein the stress release layer forms a continuous layer that is 100 microns to 150 microns thick.

7. The method of claim 1, wherein the part is an electrostatic chuck formed of a ceramic material.

8. The method of claim 1, wherein the thermal cycle is between 200 degrees Celsius and 400 degrees Celsius.

9. The method of claim 1, wherein the aluminum deposited on the part exceeds a thickness of the part.

10. A method of protecting a part of a process chamber, comprising the steps of: coating at least a portion of a surface of the part with a stress release layer, wherein the stress release layer forms a continuous layer that is 50 microns to 250 microns thick, wherein the stress release layer is configured to have a first adhesion threshold to aluminum deposited under vacuum, and a second adhesion threshold to the part when the part is formed of a ceramic material, and wherein a ratio of the first adhesion threshold to the second adhesion threshold is at least 5: 1, and wherein the stress release layer is configured to maintain structural integrity of the part from a thermal cycle of aluminum deposited on the part that is between 200 degrees Celsius and 400 degrees Celsius.

11. The method of claim 10, further comprising the steps of: wet etching the part using a weak base or weak acid prior to coating the part; and cleaning the part by sandblasting prior to coating the part.

12. The method of claim 10, wherein the stress release layer is formed of an aluminum oxide (AI2O3) based material.

13. The method of claim 10, wherein a plasma spray process using powdered aluminum oxide is used to coat the at least a portion of the surface of the part.

14. The method of claim 10, wherein the part is a deposition ring formed of a ceramic material.

15. The method of claim 10, wherein the stress release layer forms a continuous layer that is 100 microns to 150 microns thick.

16. The method of claim 10, wherein the part is an electrostatic chuck formed of a ceramic material.

17. An apparatus for installation into a process chamber, the apparatus comprising: a deposition ring having at least a portion of an upper surface containing a stress release layer, wherein the stress release layer is an aluminum oxide layer having a thickness of 50 microns to 250 microns and is configured to have a first adhesion threshold with aluminum deposited under vacuum, and a second adhesion threshold with the deposition ring when the deposition ring is formed of a ceramic material, and wherein a ratio of the first adhesion threshold to the second adhesion threshold is at least 5:

1.

18. The apparatus of claim 17, wherein the stress release layer is configured to reduce stress generated by a thermal cycle between 200 degrees Celsius and 400 degrees Celsius of aluminum deposited on the deposition ring.

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