Kit for disposition in processing chamber

Abstract

The embodiments described herein relate to apparatus and techniques for reducing metal contamination in a processing chamber while processing a substrate using decoupled plasma formed in the processing chamber. The liner substantially prevents the plasma from contacting any aluminum or alumina (e.g., anodic aluminum oxide) within the processing chamber. In one embodiment, the liner is an integral device located within the processing chamber. In another embodiment, the liner is deposited on the inner wall of the chamber body via a deposition process.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to semiconductor device processing equipment, and more particularly, to liners for processing chambers and processing chambers including the liners. Prior Art

[0002] Various processes are used to deposit films on substrates. Film deposition is typically accomplished by introducing a process gas into a processing chamber containing the substrate. The process gas is activated within the chamber, for example, by applying radio frequency (RF) power. The activated gas forms a plasma within the chamber, which facilitates etching or deposition of the material.

[0003] An aluminum liner or a liner coated with aluminum oxide is often placed in the chamber to prevent damage to the chamber walls due to etching or ion bombardment. However, aluminum or aluminum oxide liners can cause metal contamination of films deposited on the substrate. For example, ions and radicals from the plasma can come into contact with the liner, causing particles from the liner (e.g., metal particles) to mix with the plasma and deposit on the substrate. Consequently, the liner particles can cause metal contamination of films deposited on the substrate.

[0004] Therefore, there is a need for an improved apparatus to reduce metal contamination in a processing chamber. Summary of the Invention

[0005] In one embodiment, an apparatus is provided that includes a processing chamber having one or more chamber walls, a bottom, and a lid defining a processing space within the processing chamber. A cathode assembly is disposed within the processing space. A sidewall shield is disposed within the processing chamber and surrounds the processing space. A cathode shield is disposed within the processing space and surrounds the cathode assembly. The sidewall shield and the cathode shield are made of a titanium-containing material.

[0006] In another embodiment, an apparatus is provided that includes a processing chamber having one or more chamber walls, a bottom, and a lid defining a processing volume within the processing chamber. A cathode assembly is disposed within the processing volume. A lower liner is disposed within the processing chamber and surrounds at least a portion of the cathode assembly. An upper liner is disposed within the processing chamber and surrounds at least a portion of the processing volume. A portion of the upper liner extends above the lower liner. A sidewall shield is disposed radially inward of the upper and lower liners. The sidewall shield surrounds at least the processing volume and at least a portion of the cathode assembly. A cathode shield is disposed within the processing volume and surrounds the cathode assembly. The sidewall shield and the cathode shield are made of a titanium-containing material.

[0007] In another embodiment, an apparatus is provided that includes a chamber shield made of a titanium-containing material. The chamber shield includes a first portion and a second portion generally perpendicular to the first portion. A rounded edge is formed between the first and second portions. A first port is formed through the first portion. A second port is formed through the first portion opposite the first port. A slit valve opening is formed through the first portion between the first and second ports. An exhaust port is formed in the first portion opposite the slit valve opening. Simple diagram description

[0008] Thus, the manner in which the above-described features of the present disclosure can be understood in detail, the present disclosure may be more particularly described by reference to embodiments, the specific description of which has been briefly summarized above, with some embodiments illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, as the present disclosure may admit to other equally effective embodiments.

[0009] FIG. 1 is a schematic cross-sectional view of a processing chamber according to one embodiment.

[0010] FIG. 2 is a schematic representation of a sidewall shield according to one embodiment.

[0011] 3 is a bottom view of a sidewall shield according to one embodiment.

[0012] 4 is a top view of a support tray according to one embodiment.

[0013] 5 is an enlarged schematic cross-sectional view of a portion of a processing chamber according to one embodiment.

[0014] 6 is an enlarged schematic cross-sectional view of another portion of a processing chamber according to one embodiment.

[0015] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. Implementation Method

[0016] Embodiments described herein relate to apparatus and techniques for reducing metal contamination in a processing chamber while processing a substrate using a plasma formed therein. A liner substantially prevents contact between the plasma and any metal (e.g., aluminum or aluminum oxide, such as anodized aluminum oxide) within the processing chamber, such as the chamber sidewalls. In one embodiment, the liner is an integral piece of equipment located within the processing chamber. In another embodiment, the liner is a coating deposited on the interior walls of the chamber body via a deposition process.

[0017] According to some device formation processes, the front-side aluminum contamination of a substrate is specified to be less than approximately 5 x 10 9 at / cm 2. Using a conventional aluminum chamber liner, the front-side aluminum on the substrate can be between approximately 2 x 10 10 at / cm 2 and approximately 5 x 10 10 at / cm 2 at an RF power of 1000 W eff. If the RF power is increased to approximately 2000 W eff using a conventional aluminum liner, the front-side aluminum contamination on the substrate can be approximately 1 x 10 11 at / cm 2 or greater. A similar increase in front-side contamination occurs if the pressure in the processing chamber is reduced during processing.

[0018] The aspects discussed herein enable the use of increased RF power or reduced pressure without increasing aluminum contamination of the substrate.

[0019] FIG1 is a schematic cross-sectional view of a processing chamber 100 according to one embodiment. The processing chamber 100 includes sidewalls 102, a bottom 112, and a lid 104 coupled to the sidewalls 102. The lid 104, the sidewalls 102, and the bottom 112 define a processing volume 110 therein. A cathode assembly 114 is disposed within the processing volume 110. The cathode assembly 114 is coaxial with the lid 104. The cathode assembly 114 includes an electrostatic chuck 134 and a ring 132 disposed therearound. In one embodiment, the electrostatic chuck 134 is made of a ceramic material and includes one or more electrodes (not shown) disposed therein. A clamping voltage is applied to the electrodes to electrostatically secure a substrate to the electrostatic chuck 134. During processing, a substrate (not shown) is placed on the cathode assembly 114, and a layer is deposited on the substrate.

[0020] In one embodiment that may be combined with one or more of the above embodiments, ring 132 is made of a quartz-containing material. Ring 132 surrounds and circumscribes at least a portion of electrostatic chuck 134. Upper liner 106 is positioned adjacent to and extends along an upper portion of sidewall 102. Lower liner 108 is positioned adjacent to and extends along a lower portion of sidewall 102. In one embodiment that may be combined with one or more of the above embodiments, the inner radius of upper liner 106 is substantially the same as the inner radius of lower liner 108. The lower end of upper liner 106 extends radially inward above lower liner 108 to substantially prevent plasma from traveling behind (i.e., radially outward from) upper and lower liner 106, 108. In one embodiment that may be combined with one or more of the above embodiments, lower liner 108 extends from sidewall 102 along bottom 112 to cathode assembly 114.

[0021] In one embodiment, which may be combined with one or more of the above embodiments, the upper liner 106 and the lower liner 108 are made of a material comprising aluminum oxide (e.g., anodized aluminum oxide). A support plate 120 is disposed on the lower liner 108, adjacent to the bottom 112 of the processing chamber 100. The support plate 120 is disposed between the cathode assembly 114 and the sidewall 102 and includes an upper surface and a lower surface that are substantially parallel to the bottom 112 of the processing chamber 100. The support plate 120 is made of a ceramic material, such as aluminum oxide. A first recess 142 is formed on the upper surface of the support plate 120. A second recess 150 is also formed in the upper surface of the support plate 120, opposite the first recess 142. The second recess 150 is radially inward of the first recess 142. In one example, the support plate 120 is a cylindrical ring.

[0022] A sidewall shield 116 is disposed in the processing chamber 100 radially inward of the upper liner 106 and the lower liner 108. An upper ring 118 is disposed in the processing chamber 100 between the lid 104 and the sidewall shield 116. The upper ring 118 is supported by the sidewall shield 116 and surrounds an opening 152 formed through the lid 104. The upper ring 118 is spaced apart from the upper liner 106 to substantially prevent the upper ring 118 from locking with the upper liner 106. The spacing between the upper ring 118 and the upper liner 106 can be, for example, 1 mm to 10 mm, such as 1 mm to 5 mm, or 1 mm to 3 mm. However, other distances are also contemplated. The sidewall shield 116 is spaced apart from the upper liner by between 1 mm and 10 mm, such as 1 mm to 5 mm, or 1 mm to 3 mm, or 0.5 mm to about 6 mm. One or more process gases may flow from the lid 104 through the opening 152 and the upper ring 118 into the processing volume 110 to process the substrate disposed on the cathode assembly 114 .

[0023] In some embodiments that may be combined with one or more of the above embodiments, the upper ring 118 is made of quartz or a material containing quartz. In some embodiments that may be combined with one or more of the above embodiments, the upper ring 118 is made of titanium or a material containing titanium. In some embodiments that may be combined with one or more of the above embodiments, the upper ring 118 is part of (e.g., integral with) the sidewall shield 116. That is, the sidewall shield 116 may extend into the opening 152 formed through the lid 104. In some embodiments that may be combined with one or more of the above embodiments, the maximum inner radius of the sidewall shield is between approximately 250 mm and approximately 400 mm, such as between approximately 270 mm and approximately 300 mm, such as approximately 275 mm.

[0024] During operation, one or more gases flow through the lid 104 and the opening 152 into the processing volume 110. An energy source (not shown) provides energy to the gases in the processing volume to generate plasma therein. In some embodiments, which may be combined with one or more of the above embodiments, the plasma may be generated in a remote plasma source and flowed to the processing chamber 100. In that case, the plasma flows through the lid 104 and the opening 152 into the processing chamber.

[0025] In one embodiment that may be combined with one or more of the above embodiments, the sidewall shield 116 is an integral device disposed between the sidewalls 102 of the processing chamber 100. In this case, the thickness of the sidewall shield 116 and the cathode shield 122 can be between about 1 mm and about 5 mm, for example, between about 2 mm and about 4 mm, such as about 3 mm. In some examples, to reduce manufacturing costs, the thickness of the sidewall shield 116 and the cathode shield 122 can be thinner than about 1 mm. For example, the thickness of the sidewall shield 116 and the cathode shield 122 can be between about 0.1 mm and about 0.8 mm, such as about 0.35 mm.

[0026] The sidewall shield 116 is cylindrical. The sidewall shield 116 is spaced apart from the upper liner 106 or the lower liner 108 and does not contact the upper liner 106 or the lower liner 108. The space between the upper liner 106 and the sidewall shield 116, and the space between the lower liner 108 and the sidewall shield 116, are discussed below with reference to FIG3 and FIG4 , respectively. However, in some examples, it is contemplated that the sidewall shield 116 may contact the upper liner 106 or the lower liner 108.

[0027] In some embodiments, which may be combined with one or more of the above embodiments, the upper liner 106 and the lower liner 108 may be omitted from the processing chamber 100. In that case, the sidewall shield 116 is disposed along the sidewall 102 of the processing chamber 100. Various dimensions of the sidewall shield 116 may be varied to reduce the space between the sidewall shield 116 and the sidewall 102 of the processing chamber 100. For example, the outer diameter of the sidewall shield 116 may be increased to reduce the space between the sidewall shield 116 and the sidewall 102 to reduce the likelihood of parasitic plasma formation.

[0028] A first portion 136 of the sidewall shield 116 extends vertically along and generally parallel to the sidewall 102, thereby defining a cylindrical shape. A second portion 138 of the sidewall shield 116 extends horizontally along the base 112 and is generally perpendicular to the first portion 136. The sidewall shield 116 has a rounded edge 140 connecting the first portion 136 and the second portion 138. The second portion 138 of the sidewall shield 116 is disposed in a first recess 142 of the support plate 120. In some embodiments that may be combined with one or more of the above embodiments, the second portion 138 of the sidewall shield 116 is secured to the support plate 120 via one or more fasteners (not shown). In some embodiments that may be combined with one or more of the above embodiments, the support plate 120 includes one or more alignment keys (described with respect to FIG. 4 ) corresponding to one or more alignment recesses (described with respect to FIG. 3 ) formed in the sidewall shield 116. The alignment keys and alignment notches enable alignment of the ports 126 , 128 formed through the shield with the ports 126 , 128 formed through the upper liner 106 and the sidewall 102 .

[0029] The cathode shield 122 is positioned around the cathode assembly 114. The cathode shield 122 circumscribes and surrounds at least a portion of the cathode assembly 114. The cathode shield 122 is spaced apart from the cathode assembly 114, for example, by about 1 mm to about 5 mm. A first portion 144 of the cathode shield 122 is generally parallel to the first portion 136 of the sidewall shield 116 and defines a cylindrical shape. A second portion 146 of the cathode shield 122 is generally perpendicular to the first portion 144. The second portion 146 of the cathode shield 122 is positioned within a second recess 150 of the support plate 120. The cathode shield 122 has a rounded edge 148 connecting the first portion 144 and the second portion 146. In some examples, two or more of the cathode shield 122, the support plate 120, and the sidewall shield 116 are formed as a single unit (e.g., integrally).

[0030] Advantageously, the sidewall shield 116 and cathode shield 122 are easily removed from the processing chamber 100 and easily replaced. For example, once the lid 104 is removed from the processing chamber 100, the sidewall shield 116 and / or cathode shield 122 can be lifted from the processing chamber 100 and replaced. To remove the sidewall shield 116 from the processing chamber 100, the upper liner 106 and upper ring 118 can also be removed. Compared to repairing the sidewall shield 116, the ease of replacing the sidewall shield 116 and cathode shield 122 reduces downtime for the processing chamber 100. In one embodiment, as shown, the sidewall shield 116 and cathode shield 122 are separate shields. However, in one embodiment, which may be combined with one or more of the above-described embodiments, the sidewall shield 116 and cathode shield 122 may be a single, integrated shield. Separating the sidewall shield 116 and cathode shield 122 into separate shields increases the ease of installation of the shields 116 and 122.

[0031] In some embodiments that may be combined with one or more of the above embodiments, the sidewall shield 116 and cathode shield 122 are coatings deposited on the inner surfaces of the upper liner 106 and the lower liner 108. For example, the sidewall shield 116 and cathode shield 122 are formed in the processing chamber 100 via a deposition process such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). In some embodiments that may be combined with one or more of the above embodiments, the coating is a titanium-containing material. For example, the coating may include titanium, a titanium alloy, titanium carbide, titanium oxide, titanium nitride, or a combination thereof. In some embodiments that may be combined with one or more of the above embodiments, the deposited coating is substantially titanium and then processed in the processing chamber 100 to form titanium carbide, titanium oxide, or titanium nitride. In one embodiment that may be combined with one or more of the above embodiments, the thickness of the sidewall shield 116 and cathode shield 122 coatings is between approximately 0.1 microns (e.g., microns) and approximately 5 microns, such as between approximately 1 micron and approximately 3 microns, such as approximately 2.5 microns.

[0032] In one embodiment that may be combined with one or more of the above embodiments, the sidewall shield 116 and the cathode shield 122 are made of a material having high density, high hardness, and high chemical inertness to the chemicals used to deposit the layer on the substrate. For example, the sidewall shield 116 and the cathode shield 122 can be made of a titanium-containing material, such as titanium, titanium alloys, titanium carbide, titanium oxide, titanium nitride, and combinations thereof.

[0033] While embodiments are described herein for sidewall shield 116 and cathode shield 122 comprising titanium, other materials are also contemplated. In some embodiments that may be combined with one or more of the above embodiments, sidewall shield 116 and cathode shield 122 are made of a tungsten-containing material, a molybdenum-containing material, or a platinum-containing material. Sidewall shield 116 and cathode shield 122 may be made of any combination of the above materials. In some embodiments that may be combined with one or more of the above embodiments, sidewall shield 116 and cathode shield 122 are made of different materials.

[0034] In some embodiments that may be combined with one or more of the above embodiments, outer surfaces of the sidewall shield 116 and the cathode shield 122 are made of the aforementioned material. That is, for example, the portion of the sidewall shield 116 and the cathode shield 122 exposed to the plasma formed in the processing volume 110 are made of the aforementioned material. In some embodiments that may be combined with one or more of the above embodiments, at least the surfaces of the sidewall shield 116 and the cathode shield comprise at least 99% titanium.

[0035] The sidewall shield 116, cathode shield 122, and support plate 120 substantially reduce the exposure of the sidewall 102, upper liner 106, and lower liner 108 to the plasma formed in the processing volume 110. Advantageously, the high density, hardness, and chemical inertness of the sidewall shield 116 and cathode shield 122 substantially reduce the occurrence of aluminum contamination of layers deposited on substrates disposed on the cathode assembly 114. Without the sidewall shield 116 and cathode shield 122 in the processing chamber 100, the amount of aluminum contamination on the substrate increases with increasing RF power. Due to the high density, high hardness, and chemical inertness of the titanium-containing material, the titanium-containing material used to fabricate the sidewall shield 116 and cathode shield 122 does not generate significant titanium contamination on the substrate.

[0036] A slit valve opening 124, a first port 126, and a second port 128 are formed through the sidewall 102, the upper liner 106, and the sidewall shield 116. The second port 128 is disposed opposite the first port 126. As shown, the first port 126 and the second port 128 are circular. The diameter of the first port 126 is smaller than the diameter of the second port 128. For example, the diameter of the first port 126 may be from about 3 mm to about 13 mm. The diameter of the second port 128 may be from about 30 mm to about 40 mm. Other sizes for the first and second openings 126, 128 are also contemplated. During operation, substrates are transferred into and out of the processing chamber 100 through the slit valve opening 124. Sensors (not shown) may be disposed in the first port 126 (or have a visual channel therethrough) to measure properties of layers deposited on the substrates, properties of the plasma formed in the processing volume 110, or processing conditions such as temperature or pressure. In some embodiments that may be combined with one or more of the above embodiments, the optical emission spectroscopy system is positioned to use the first port 126. In one embodiment that may be combined with one or more of the above embodiments, the second port 128 may be used as an optical viewing window.

[0037] FIG2 is a schematic representation of the sidewall shield 116 according to one embodiment. A slit valve opening 124 is formed through the sidewall shield 116. An exhaust port 202 is formed through the sidewall shield 116 relative to the slit valve opening 124. The exhaust port may be circumscribed at an angle of approximately 100 degrees to approximately 160 degrees, for example, approximately 120 degrees to approximately 150 degrees. The slit valve opening 124 is formed in an upper portion 204 of the sidewall shield 116, while the exhaust port 202 is formed in a lower portion 206 of the sidewall shield 116. Thus, as shown, the exhaust port 202 and the slit valve opening 124 are disposed on different horizontal planes. However, in some embodiments that may be combined with one or more of the above-described embodiments, the exhaust port 202 and the slit valve opening 124 may be aligned such that the major axis of the exhaust port 202 is aligned with the major axis of the slit valve opening 124. In other embodiments, the exhaust port 202 and the slit valve opening 124 may be partially aligned such that a portion of the exhaust port 202 is aligned with the slit valve opening 124 .

[0038] The first port 126 and the second port 128 are formed through the upper portion 204 of the sidewall shield 116. As shown, the second port 128 is substantially coaxial with the first port 126. In some embodiments, which may be combined with one or more of the above embodiments, the first port 126 and the second port 128 may be vertically or horizontally misaligned.

[0039] FIG3 is a bottom view of the sidewall shield 116 according to one embodiment. FIG4 is a top view of the support plate 120 according to one embodiment. The second portion 138 of the sidewall shield 116 extends radially inward. An alignment slot 302 is formed through the second portion 138 of the sidewall shield 116. The alignment slot 302 is sized to accommodate an alignment key 402 formed on the support plate 120. The alignment key 402 is shown in FIG4 . The alignment key 402 is flush with the support plate 120 and protrudes into the first recess 142.

[0040] In one embodiment that may be combined with one or more of the above embodiments, during processing, the alignment slot 302 is aligned with the central vertical axis of the slit valve opening 124. The alignment slot 302 enables the sidewall shield 116 to be positioned in the processing chamber 100 so that the slit valve opening 124 and any other openings formed through the chamber and the sidewall shield (e.g., the exhaust port 202, the first opening 208, and the second opening 210) can be aligned.

[0041] FIG5 is an enlarged schematic cross-sectional view of a portion of the processing chamber 100 according to one embodiment. A first space 502 is formed between the upper liner 106 and the sidewall shield 116. A width 504 of the first space 502 is between approximately 2.5 mm and approximately 8 mm, such as between approximately 3.5 mm and approximately 6.4 mm, or approximately 4 mm. Other distances are also contemplated as described above. A channel 508 is formed in the surface of the upper ring 118 that contacts the sidewall shield 116. An O-ring 506 is disposed in the channel 508 to form a seal between the upper ring 118 and the sidewall shield 116. In one embodiment, which may be combined with one or more of the above embodiments, the width 504 of the first space 502 is less than 1 mm. For example, the width 504 may be between 0.6 mm and approximately 0.9 mm, such as between approximately 0.65 mm and approximately 0.8 mm. As described above, other distances are also contemplated.

[0042] FIG6 is an enlarged schematic cross-sectional view of another portion of the processing chamber 100 according to one embodiment. A second space 608 is formed between the sidewall shield 116 and the lower liner 108. A third space 606 is formed between the cathode assembly 114 and the cathode shield 122. A width 610 of the second space 608 is between approximately 5 mm and approximately 12 mm, for example, between approximately 7 mm and approximately 10 mm. In one embodiment that may be combined with one or more of the above embodiments, the width 610 of the second space 608 is less than 1 mm. For example, the width 504 of the second space 608 may be between 0.1 mm and approximately 0.9 mm, for example, between approximately 0.6 mm and approximately 0.8 mm. As described above, other distances are also contemplated.

[0043] The first space 502 and the second space 608 described with respect to FIG. 5 are sufficiently small to substantially reduce the generation of plasma therein. In some embodiments that can be combined with one or more of the above embodiments, the width 504 of the first space 502 and the width 610 of the second space 608 are substantially the same. In some embodiments that can be combined with one or more of the above embodiments, the width 504 of the first space 502 and the width 610 of the second space 608 are different.

[0044] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is to be determined by the appended claims.

[0045] 100: Processing chamber 102: Sidewall 104: Cover 106: Upper pad 108: Lower pad 110: Processing Space 112: bottom 114: cathode assembly 116: Side wall shielding 118: Sheung Wan 120: Support plate 122: Cathode shield 124: Slit valve opening 126: First port 128: Second port 132: Ring 134: Electrostatic chuck 136: Part 1 138: Part 2 140:Rounded edges 142: First notch 144: Part 1 146: Part 2 148:Rounded edges 150: Second notch 152: Opening 202: Exhaust port 204: Upper part 206:lower part 302: Alignment groove 402: Alignment key 502: First Space 504: Width 506:O-ring 508: Channel 606: The Third Space 608: Second Space 610: Width

[0046] Domestic storage information (please note the order of storage institution, date, and number) none

[0047] Overseas deposit information (please note the order of deposit country, institution, date, and number) none

Claims

1. A kit for placement in a processing chamber, the kit comprising: a support disk; a cathode shield, sized and shaped for placement on the support disk, the cathode shield comprising titanium; and a sidewall shield, sized and shaped for placement on the support disk to surround at least a portion of the cathode shield, the sidewall shield comprising titanium.

2. The kit as claimed in claim 1, wherein the thickness of the sidewall shield is between 1 mm and 5 mm.

3. The kit as claimed in claim 1, wherein the sidewall shield is a coating deposited on an inner surface of one or more chamber walls, and the cathode shield is a coating on an outer surface of a cathode assembly.

4. The kit as claimed in claim 1, further comprising: one or more alignment keys formed in the support plate; and one or more alignment slots formed in the sidewall shield, and sized and shaped to at least partially accommodate the one or more alignment keys.

5. The kit as claimed in claim 1, wherein the support disk includes: a first recess formed in an outer surface of the support disk; and a second recess formed in the outer surface of the support disk.

6. The kit as claimed in claim 5, wherein the second notch is disposed radially inside the first notch, the first notch being adjusted in size and shape to at least partially accommodate the sidewall shield, and the second notch being adjusted in size and shape to at least partially accommodate the cathode shield.

7. The kit as described in claim 6, wherein the support disc is a cylindrical ring.

8. The kit as claimed in claim 6, wherein the sidewall shield comprises a first portion, a second portion extending relative to the first portion, and an edge connecting the first portion and the second portion.

9. The kit as claimed in claim 8, wherein the sidewall shield further comprises: a third portion extending radially inward relative to the first portion and spaced apart from the second portion; and a second edge between the first portion and the third portion, wherein the first portion is cylindrical, the second portion extending radially inward relative to the first portion, the second portion being sized and shaped to be disposed in the first recess of the support plate, and the sidewall shield layer containing at least 99% titanium.

10. The kit as claimed in claim 8, wherein the cathode shield comprises a first portion, a second portion and an edge, the first portion being sized and shaped to be parallel to the first portion of the sidewall shield, the second portion extending relative to the first portion of the cathode shield, and the edge connecting the first portion and the second portion of the cathode shield.

11. The kit as claimed in claim 10, wherein the first portion of the cathode shield is cylindrical, and the second portion of the cathode shield is sized and shaped to be disposed in the second recess of the support plate.

12. The kit as claimed in claim 1, wherein two or more of the sidewall shield, the cathode shield, or the support disk are integrally formed.

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