Substrate support assembly with deposition surface features

Abstract

A method for manufacturing an electrostatic chuck includes polishing a surface of a ceramic body of the electrostatic chuck to produce a polished surface, and depositing a ceramic coating onto the polished surface of the ceramic body to produce a coated ceramic body. The method further includes placing a mask over the coated ceramic body, the mask including a plurality of elliptical apertures, and depositing a ceramic material through the plurality of elliptical apertures of the mask to form a plurality of elliptical mesas on the coated ceramic body, wherein the plurality of elliptical mesas have rounded edges. The mask is then removed from the coated ceramic body, and the plurality of elliptical mesas are polished.

Description

[0001] This application is a divisional application of the invention patent application with application number 201680067355.X filed on June 1, 2016 and the invention name being “Substrate support assembly with deposition surface feature structure”. Technical Field

[0002]

[0011] Embodiments of the present invention generally relate to a substrate support assembly, such as an electrostatic chuck, having a plasma resistant protective layer with deposited surface features. Background Art

[0003] In the semiconductor industry, devices are manufactured using a variety of fabrication processes that produce structures of ever-decreasing size. Some fabrication processes, such as plasma etching and plasma cleaning processes, expose a substrate support, such as an electrostatic chuck (ESC), to a high-speed plasma stream (e.g., exposing the edge of the ESC during wafer processing and the entire ESC during chamber cleaning) to etch or clean the substrate. Plasma can be highly corrosive and may corrode the processing chamber and other plasma-exposed surfaces.

[0004] An ESC typically has surface features formed by placing a positive mask on the surface of the ESC and then bead blasting the exposed portions of the ESC through the positive mask. A positive mask is a mask containing an exact replica of the pattern that will be retained on the wafer. The bead blasting process results in sharp edges and cracks in the ESC surface. Furthermore, the spaces between the formed surface features, known as valleys, have a high roughness that provides pits for particle trapping and spikes that can fracture during thermal expansion. Trapped particles and fractured spikes can cause particle contamination on the backside of the retained wafer during processing. Summary of the Invention

[0005] In one embodiment, an electrostatic chuck includes a thermally conductive base and a ceramic body bonded to the thermally conductive base, the ceramic body having an embedded electrode. A protective ceramic coating covers a surface of the ceramic body. A plurality of elliptical mesas are deposited on the surface of the ceramic body. Each of the elliptical mesas has a rounded edge.

[0006] In one embodiment, a method of manufacturing an electrostatic chuck includes polishing a surface of a ceramic body of the electrostatic chuck to produce a polished surface. The method further includes depositing a protective ceramic coating onto the polished surface of the ceramic body to produce a coated ceramic body. The method further includes placing a mask over the coated ceramic body, the mask including a plurality of elliptical holes (e.g., circular holes). The method further includes depositing a ceramic material through the plurality of elliptical holes of the mask to form a plurality of elliptical mesas on the coated ceramic body, wherein the plurality of elliptical mesas (e.g., circular mesas) have rounded edges. The mask is then removed, and the plurality of elliptical mesas are polished.

[0007] In one embodiment, a circular mask for depositing an elliptical mesa onto the surface of an electrostatic chuck includes a body having a first diameter that is smaller than a second diameter of the electrostatic chuck on which the mask is to be placed. The circular mask further includes a plurality of elliptical through-holes in the body, the elliptical through-holes having an aspect ratio of about 1:2 to about 2:1. At least one of the elliptical holes has a flared top and a flared bottom, wherein the flared top is used to inject particles through the elliptical hole onto the electrostatic chuck to form an elliptical mesa on the electrostatic chuck, and wherein the flared bottom prevents the elliptical mesa from contacting the mask. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals indicate similar elements. It should be noted that different references to "one" or "an" embodiment in this disclosure do not necessarily refer to the same embodiment, and such references mean at least one.

[0009] Figure 1 depicts a cross-sectional side view of one embodiment of a processing chamber;

[0010] Figure 2A A top view illustrating an example pattern of oval terraces on the surface of an electrostatic chuck;

[0011] Figure 2B Draw Figure 2A A vertical cross-sectional view of an electrostatic chuck;

[0012] Figure 3A -D illustrates a side profile of an example countertop according to an embodiment of the present invention;

[0013] Figure 4 depicts a cross-sectional side view of one embodiment of an electrostatic chuck;

[0014] Figure 5 One embodiment of a process for manufacturing an electrostatic chuck is illustrated;

[0015] Figure 6A -C illustrates depositing ceramic material on the surface of the electrostatic chuck through a mask to form a circular mesa with rounded edges; and

[0016] Figure 7 A top view of a mask used to form mesas and rings on a ceramic body of an electrostatic chuck is shown in accordance with one embodiment. DETAILED DESCRIPTION

[0017] Embodiments of the present invention provide a substrate support assembly (e.g., an electrostatic chuck) having a deposition table with rounded edges. Embodiments also provide a substrate support assembly having a protective ceramic coating formed on a ceramic body of the substrate support assembly. The protective ceramic coating can provide plasma corrosion resistance to protect the ceramic body. A table can be deposited on the protective ceramic coating and further be resistant to plasma corrosion.

[0018] In one embodiment, an electrostatic chuck includes a thermally conductive base (e.g., a metal or metal alloy base) and a ceramic body (e.g., an electrostatic puck) bonded to the thermally conductive base. A protective ceramic coating serving as a protective layer covers the surface of the ceramic body, and a plurality of oval (e.g., circular) mesas are provided on the protective ceramic coating. In one embodiment, the electrostatic chuck is manufactured by first depositing the protective ceramic coating on the ceramic body and then depositing the oval mesas onto the ceramic body through holes in a mask. The term mesa as used herein refers to a protrusion on a substrate having steep sides and a flat or gently sloping top surface.

[0019] In particular, the electrostatic chucks and other substrate supports described in embodiments herein have mesas produced by depositing the mesas through a negative mask. A negative mask is a mask containing a pattern that is the exact opposite of the pattern to be formed on the electrostatic chuck. In other words, the negative mask has voids in which the features on the electrostatic chuck will be formed. In contrast, mesas are conventionally formed on the surface of an electrostatic chuck by sandblasting the surface of the electrostatic chuck through a positive mask (a mask containing an exact replica of the pattern to be transferred to the electrostatic chuck). Mesas formed by sandblasting processes have sharp edges that can chip and cause particle contamination on the backside of a wafer supported by the electrostatic chuck. However, mesas deposited according to embodiments described herein have rounded edges (e.g., a top-hat profile) that are less prone to chipping.

[0020] Furthermore, the sandblasting process traditionally used to create the mesas in electrostatic chucks results in high surface roughness in the areas (valleys) between the resulting mesas. This high surface roughness can act as pits that trap particles, which can then be released onto the backside of the support wafer during processing. Furthermore, localized peaks in the roughened surface of the valleys can break off and break off during thermal cycling. This can become another source of particle contamination. However, in the embodiments described herein, the surface of the electrostatic disc is polished prior to depositing the mesas. As a result, the valleys between the deposited mesas have a very low surface roughness (e.g., approximately 4-10 microinches), further reducing particle contamination on the backside.

[0021] The electrostatic chuck described in the embodiments herein also includes a blanket protective ceramic coating that acts as a protective layer for the electrostatic chuck. The protective ceramic coating covers the surface of the electrostatic chuck and is deposited on the electrostatic chuck after the surface of the electrostatic chuck is polished. The protective ceramic coating is very conformal and has a surface roughness that is approximately the same as that of the polished electrostatic chuck. The protective ceramic coating and the table deposited on the protective ceramic coating can each be a plasma-resistant material, such as yttrium aluminum garnet (YAG). Therefore, the electrostatic chuck (including the table formed on the electrostatic chuck) can be resistant to chlorine, fluorine, and hydrogen-based plasmas.

[0022] Figure 1 is a cross-sectional view of one embodiment of a semiconductor processing chamber 100 having disposed therein a substrate support assembly 148. According to embodiments described herein, the substrate support assembly 148 includes an electrostatic chuck 150 having an electrostatic puck 166 having a resting rounded edge table.

[0023] The processing chamber 100 includes a chamber body 102 and a lid 104 that enclose an interior volume 106. The chamber body 102 can be made of aluminum, stainless steel, or other suitable materials. The chamber body 102 generally includes sidewalls 108 and a bottom 110. An outer liner 116 can be positioned adjacent the sidewalls 108 to protect the chamber body 102. The outer liner 116 can be made of and / or coated with a material that is resistant to plasma or halogen-containing gases. In one embodiment, the outer liner 116 is made of aluminum oxide. In another embodiment, the outer liner 116 is made of and / or coated with yttrium oxide, a yttrium alloy, or oxides thereof.

[0024] An exhaust port 126 can be defined in the chamber body 102, and the interior volume 106 can be coupled to a pumping system 128. The pumping system 128 can include one or more pumps and throttle valves for pumping and regulating the pressure of the interior volume 106 of the processing chamber 100.

[0025] The lid 104 can be supported on a sidewall 108 of the chamber body 102. The lid 104 can be opened to allow access to the interior volume 106 of the processing chamber 100 and can provide a seal for the processing chamber 100 when closed. A gas panel 158 can be coupled to the processing chamber 100 to provide process and / or cleaning gases to the interior volume 106 via a gas distribution assembly 130, which is part of the lid 104. Examples of process gases that can be flowed into the processing chamber include halogen-containing gases such as C2F6, SF6, SiCl4, HBr, NF3, CF4, CHF3, CH2F3, Cl2, and SiF4, among others, as well as other gases such as O2 or N2O. Notably, the process gases can be used to generate highly corrosive chlorine-based plasmas, fluorine-based plasmas, and / or hydrogen-based plasmas. The gas distribution assembly 130 may have a plurality of apertures 132 on a downstream surface of the gas distribution assembly 130 to direct the gas flow to the surface of a substrate 144 (e.g., a wafer) supported by a substrate support assembly 148. Additionally or alternatively, the gas distribution assembly 130 may have a central hole into which gas is supplied via a ceramic gas nozzle.

[0026] A substrate support assembly 148 is disposed within the interior volume 106 of the processing chamber 100, below the gas distribution assembly 130. The substrate support assembly 148 holds the substrate 144 during processing. An inner liner 118 may be coated around the periphery of the substrate support assembly 148. The inner liner 118 may be a material resistant to halogen-containing gases, such as those discussed with reference to the outer liner 116. In one embodiment, the inner liner 118 may be made of the same material as the outer liner 116.

[0027] In one embodiment, the substrate support assembly 148 includes a mounting plate 162 that supports a base 152 and an electrostatic chuck 150. The mounting plate 162 can be coupled to the bottom 110 of the chamber body 102 and includes channels for routing utilities (e.g., fluids, power lines, sensor leads, etc.) to a thermally conductive base 164 and an electrostatic puck 166. In one embodiment, the electrostatic chuck 150 further includes a thermally conductive base 164 bonded to the electrostatic puck 166 by a silicone bond 138.

[0028] The electrostatic disc 166 can be a ceramic body including one or more clamping electrodes (also referred to as chucking electrodes) 180, which are controlled by a chucking power source 182. In one embodiment, the electrostatic disc 166 is composed of aluminum nitride (AlN) or aluminum oxide (Al2O3). The electrostatic disc 166 can alternatively be composed of titanium oxide (TiO), titanium nitride (TiN), silicon carbide (SiC), or the like. The chucking electrode 180 (or other electrodes located in the electrostatic disc 166) can be further coupled to one or more radio frequency (RF) power supplies 184, 186 via a matching circuit 188 to maintain a plasma formed from the process gas and / or other gases within the processing chamber 100. The one or more RF power supplies 184, 186 are typically capable of generating an RF signal having a frequency of about 50 kHz to about 3 GHz and a power of up to about 10,000 watts.

[0029] The upper surface of the electrostatic disc 166 is covered by a protective ceramic coating 136, which is deposited on the electrostatic disc 166. In one embodiment, the protective ceramic coating is Y3Al5O 12 (yttrium aluminum garnet, YAG) coating. Alternatively, the protective ceramic coating can be Al2O3, AlN, Y2O3 (yttrium oxide), or AlON (aluminum oxynitride). The upper surface of the electrostatic disc 166 further includes a plurality of mesas and / or other surface features deposited thereon. The mesas and / or other surface features can be deposited on the surface of the electrostatic disc 166 before or after the protective ceramic coating 136 is deposited thereon.

[0030] The electrostatic puck 166 also includes one or more gas channels (e.g., holes drilled in the electrostatic puck 166). In operation, a backside gas (e.g., He) can be provided under controlled pressure into the gas channels to enhance heat transfer between the electrostatic puck 166 and the substrate 144.

[0031] The thermally conductive base 164 can be a metal base composed of, for example, aluminum or an aluminum alloy. Alternatively, the thermally conductive base 164 can be made of a ceramic composite, such as an aluminum-silicon alloy infiltrated with SiC, to match the thermal expansion coefficient of the ceramic body. The thermally conductive base 164 should provide good strength and durability as well as heat transfer performance. In one embodiment, the thermally conductive base 164 has a thermal conductivity exceeding 200 watts per meter Kelvin (W / m K).

[0032] The thermally conductive base 164 and / or the electrostatic puck 166 may include one or more embedded heating elements 176, embedded thermal insulators 174, and / or conduits 168, 170 to control the lateral temperature profile of the substrate support assembly 148. The conduits 168, 170 may be fluidly coupled to a fluid source 172 that circulates a temperature-regulating fluid through the conduits 168, 170. In one embodiment, the embedded thermal insulator 174 may be positioned between the conduits 168, 170. The one or more embedded heating elements 176 may be regulated by a heater power source 178. The conduits 168, 170 and the one or more embedded heating elements 176 may be used to control the temperature of the thermally conductive base 164, thereby heating and / or cooling the electrostatic puck 166 and the substrate 144 being processed. The temperature of the electrostatic puck 166 and the thermally conductive base 164 may be monitored using a plurality of temperature sensors 190, 192, which may be monitored using a controller 195.

[0033] Figure 2A A top view depicting an exemplary pattern of oval mesas 202 on the surface 212 of an electrostatic disk 200. For illustrative purposes, only 16 mesas are shown. However, the surface of an electrostatic disk 200 may have hundreds or thousands of mesas formed thereon. Figure 2B Describe along Figure 2A A vertical cross-section of the electrostatic disc taken along the center line 3-3 of FIG. The electrostatic disc 200 includes one or more embedded electrodes 250. The electrostatic disc 200 may be the uppermost component of an electrostatic chuck, such as Figure 1 The electrostatic chuck 150 has a circular periphery and a disc-like shape that can substantially match the shape and size of the supported substrate 244 located on the electrostatic disc 200. In one embodiment, the electrostatic disc 200 corresponds to Figure 1 Electrostatic disc 166.

[0034] exist Figure 2A In the example shown, the elliptical mesas 202 are depicted as being positioned along concentric circles 204 and 206 on the surface 212 of the electrostatic disk 200. However, any pattern of elliptical mesas 202 distributed over the surface 212 of the electrostatic disk 200 is possible. In one embodiment, the elliptical mesas 202 are circular. Alternatively, the elliptical mesas 202 may be elliptical or have another elliptical shape.

[0035] The elliptical mesas 202 are formed into individual pads having a thickness between 2 microns and 200 microns (μm) and a dimension (e.g., diameter) in plan view between 0.5 mm and 5 mm. In one embodiment, the elliptical mesas 202 have a thickness between 2 microns and 20 microns and a diameter of approximately 0.5 mm to 3 mm. In one embodiment, the elliptical mesas 202 have a thickness between approximately 3 microns and 16 microns and a diameter of approximately 0.5 mm to 2 mm. In one embodiment, the mesas have a thickness of approximately 10 microns and a diameter of approximately 1 mm. In one embodiment, the mesas have a thickness of approximately 10 microns to 12 microns and a diameter of approximately 2 mm. In some embodiments, the mesas have a uniform shape and size. Alternatively, the various mesas may have different shapes and / or different sizes. The sidewalls of the elliptical mesas 202 may be vertical or inclined. Notably, each elliptical mesa 202 has rounded edges, where the elliptical mesas 202 will contact the substrate 244. This can minimize chipping of the oval mesa 202 and reduce particle contamination on the back side of the substrate 244. In addition, the rounded edges can reduce or eliminate scratching of the back side of the substrate 244 caused by clamping. Alternatively, the oval mesa 202 can have a chamfered edge.

[0036] Some example side profiles of the oval table 202 are shown in Figures 3A-3D As shown in the figure, Figures 3A-3D In each of the illustrated side profiles, the edges of the table top are rounded. Figure 3A The side profile of the -B is a variation of the top hat profile.

[0037] Return to reference Figures 2A-2B , the elliptical mesas 202 are deposition mesas that have been formed by a deposition process that forms a dense, conformal ceramic layer, such as ion assisted deposition (IAD). Figure 5 The deposition of the oval mesa 202 is discussed. In the illustrated embodiment, the oval mesa 202 has been deposited directly onto the surface 212 of the electrostatic disk 200 without first depositing a protective ceramic coating on the surface 212. However, the protective ceramic coating may be deposited before or after the oval mesa 202 is deposited. The oval mesa 202 may have an average surface roughness of approximately 2 microinches to 12 microinches. In one embodiment, the oval mesa 202 has an average surface roughness of approximately 4 microinches to 8 microinches.

[0038] In one embodiment, the oval table 202 is formed of YAG. In one embodiment, the table is composed of an amorphous ceramic comprising yttrium, aluminum, and oxygen (e.g., YAG in an amorphous form). The amorphous ceramic may include at least 8% by weight of yttrium. In one embodiment, the amorphous ceramic comprises approximately 8-20% by weight of yttrium, 20-32% by weight of aluminum, and 60-70% by weight of oxygen. In one embodiment, the amorphous ceramic comprises approximately 9-10% by weight of yttrium, approximately 25-26% by weight of aluminum, and approximately 65-66% by weight of oxygen. In alternative embodiments, the oval table 202 may be Al2O2, AlN, Y2O3, or AlON.

[0039] The surface 212 of the electrostatic disc 200 also includes a raised lip in the form of a ring 218 at the outer periphery 220 of the electrostatic disc 200. The ring 218 may have a thickness and material composition that is the same or substantially the same as the thickness and material composition of the oval mesa 202. The ring 218 may have been formed by deposition at the same time as the oval mesa 202 is formed. The ring 218 may also have rounded edges where the ring 218 contacts the substrate 244. Alternatively, the ring 218 may have chamfered edges or may have edges that are neither rounded nor chamfered. In one embodiment, the inner edge of the ring 218 is rounded, while the outer edge of the ring 218 is not rounded.

[0040] The top of the oval table 202 and the ring 218 contact the back side of the supported substrate 244. The oval table 202 minimizes the contact area between the back side of the substrate 244 and the surface 212 of the electrostatic puck 200 and facilitates chucking and dechucking operations. A gas, such as He, can also be pumped into the area between the substrate and the electrostatic chuck 200 to facilitate heat transfer between the substrate 244 and the electrostatic chuck 200. The ring 218 can act as a seal to prevent gas from escaping from the space between the electrostatic chuck 200 and the substrate 244.

[0041] Figure 4A cross-sectional side view of an electrostatic chuck 400 is shown according to one embodiment. The electrostatic chuck 400 includes a thermally conductive base 464 (e.g., a metal base) coupled to an electrostatic disc 402 via an adhesive 452, such as a silicone adhesive. Adhesive 452 can be, for example, a polydimethylsiloxane (PDMS) adhesive. The electrostatic disc 402 can be a generally disc-shaped dielectric ceramic body having one or more embedded electrodes. The electrostatic disc 402 can be a bulk sintered ceramic, such as aluminum oxide (Al2O3), aluminum nitride (AlN), titanium oxide (TiO), titanium nitride (TiN), silicon carbide (SiC), and the like. The electrostatic puck 402 may include one or more embedded electrodes 436 and / or resistive heating elements 438 (e.g., an inner resistive heating element and an outer resistive heating element). A quartz ring 446 or other protective ring may surround and cover portions of the electrostatic chuck 400. A substrate 444 may be lowered onto the electrostatic chuck 400 and held in place via electrostatic forces by providing a signal to one or more electrodes 436.

[0042] The thermally conductive base 464 is configured to provide physical support for the electrostatic disc 402. In some embodiments, the thermally conductive base 464 is also configured to provide temperature control. The thermally conductive base 464 can be made of a thermally conductive material, such as a metal, such as aluminum or stainless steel. The thermally conductive base 464 can include one or more heat exchangers, such as embedded heating elements, fluid channels that provide heat exchange by circulating cooling and heating fluids through the channels, or a combination thereof. Figure 1 , thermally conductive base 464 includes a plurality of fluid channels, also referred to as conduits 470 (e.g., inner and outer conduits), through which fluid can flow to heat or cool thermally conductive base 464, electrostatic chuck 400, and substrate 444 by exchanging heat energy between thermally conductive base 464 and other components of electrostatic chuck 400 and substrate 444. A temperature sensor 490 can be used to monitor the temperature of thermally conductive base 464.

[0043] In one embodiment, the electrostatic chuck 400 further includes a ceramic coating 496 that fills and / or covers imperfections in the surface of the electrostatic disc 402, such as microcracks, pores, pinholes, and the like. The ceramic coating 496 may be referred to as a cover ceramic coating or a blanket ceramic coating and may cover the entire surface of the electrostatic disc 402. Alternatively, the electrostatic chuck 400 may not include the ceramic coating 496. In one embodiment, the ceramic coating 496 is composed of the same ceramic as the electrostatic disc 402. Thus, if the electrostatic disc 402 is AlN, the cover ceramic coating 496 is also AlN. Alternatively, if the electrostatic disc 402 is Al2O3, the ceramic coating 496 is also Al2O3. Alternatively, the ceramic coating may be composed of the same material as the second ceramic coating 494 (discussed below). In one embodiment, the ceramic coating 496 has a thickness ranging from less than 1 micron to as much as tens of microns.

[0044] When deposited to fill pores up to a depth of about 5 microns or more, the ceramic coating 496 may initially have a thickness of at least 5 microns. However, the ceramic coating 496 may be polished to a thickness of 1 micron or less. In some cases, the ceramic coating 496 may be substantially polished away so that the ceramic coating 496 remains only in the filled pores of the electrostatic disc 402. The ceramic coating 496 may be polished to an average surface roughness (Ra) of 2 micro-inches to 12 micro-inches. In one embodiment, the ceramic coating 496 is polished to a surface roughness of about 4 micro-inches to 8 micro-inches. If a cover ceramic coating is not used, the surface of the electrostatic disc 402 may be polished to a surface roughness of 2 micro-inches to 12 micro-inches.

[0045] In one embodiment, the ceramic coating 496 (or electrostatic disc 402) is polished to an average surface roughness of approximately 4 microinches to 8 microinches. Lower surface roughness is ideal for minimizing particle contamination and sealing grain boundaries. Generally speaking, the lower the surface roughness, the less particle contamination will occur. In addition, by sealing the grain boundaries in the ceramic coating 496 and / or electrostatic disc 402, the ceramic coating 496 and / or electrostatic disc 402 becomes more corrosion resistant. However, the lower the surface roughness, the greater the number of nucleation sites that exist for the subsequent deposition of the second ceramic coating 494 and / or the mesa 492. In addition, reducing the surface roughness reduces the adhesion strength of subsequent coatings to the electrostatic disc 402. Therefore, it was unexpectedly discovered that performance degraded when the surface of the ceramic coating 496 and / or electrostatic disc 402 was polished to less than approximately 4 microinches.

[0046] Electrostatic chuck 400 also includes a second ceramic coating 494, which in embodiments is a protective ceramic coating. Second ceramic coating 494 can be disposed over ceramic coating 496 or, if no overlying ceramic coating is deposited, over electrostatic disc 402. Second ceramic coating 494 protects electrostatic disc 402 from corrosive chemicals, such as hydrogen-based plasma, chlorine-based plasma, and fluorine-based plasma. Second ceramic coating 494 can have a thickness ranging from several microns to several hundred microns.

[0047] In one embodiment, the second ceramic coating 494 has a thickness of about 5 microns to 30 microns. The second ceramic coating 494 can be a highly conformal coating and can have a surface roughness that substantially matches the surface roughness of the ceramic coating 496 and / or the electrostatic disc 402. If the ceramic coating 496 is deposited and polished, the second ceramic coating 494 can be substantially free of pores, pinholes, microcracks, etc. The second ceramic coating 494 can be Al2O3, AlN, Y2O3, Y3Al5O 12 (YAG), and AlON. In one embodiment, the second ceramic coating 494 is amorphous YAG having at least 8% by weight of yttrium. In one embodiment, the second ceramic coating 494 has a Vickers hardness (5Kgf) of about 9 gigapascals (GPA). Additionally, in one embodiment, the second ceramic coating 494 has a density of about 4.55 g / cm3, a flexural strength of about 280 MPa, a flexural strength of about 2.0 MPa·m 1 / 2 The fracture toughness, Young's modulus of about 160MPa, and the -6 / K thermal expansion coefficient (20 ~ 900 ℃), thermal conductivity of about 12.9W / mK, greater than 10 at room temperature 14 The volume resistivity is Ω·cm, and the friction coefficient is about 0.2-0.3.

[0048] As briefly mentioned above, the structure of the second ceramic coating 494 and the mesa 492 depends at least in part on the roughness of the electrostatic disc 402 and / or the ceramic coating 496 due to a number of roughness-related nucleation sites. When the surface roughness of the electrostatic disc 402 and / or the ceramic coating 496 is less than about 3 microinches, the surface on which the second ceramic coating 494 is deposited has a very high number of nucleation sites. This high number of nucleation sites produces a completely amorphous structure. However, by depositing the second ceramic coating 494 onto a surface having a surface roughness of about 4 microinches to 8 microinches, the second ceramic coating 494 grows or is deposited as an amorphous structure having many vertical fibers, rather than a purely amorphous structure.

[0049] In one embodiment, mesa 492 and ring 493 are deposited over second ceramic coating 494. In such an embodiment, mesa 492 can be composed of the same material as second ceramic coating 494. Alternatively, mesa 492 and ring 493 can be deposited before second ceramic coating 494 (and therefore below second ceramic coating 494). In such an embodiment, mesa 492 and ring 493 can be the same material as electrostatic disc 402 or the same material as second ceramic coating 494. The mesa can be approximately 3 microns to 15 microns high (in one embodiment, approximately 10 microns to 15 microns high) and, in some embodiments, have a diameter of approximately 0.5 mm to 3 mm.

[0050] If the electrostatic chuck 400 is refurbished after use, the thickness of the second ceramic coating 494 can be at least 20 microns in embodiments, and in one embodiment, between approximately 20 and 30 microns. To refurbish the electrostatic chuck 400, the mesas 492 can be removed by grinding, and a portion of the second ceramic coating 494 can also be removed by grinding. The amount of material removed during the grinding process can depend on the amount of curvature in the surface of the electrostatic chuck 400. For example, if the mesas are 8 microns thick and there is a 5 micron curvature in the electrostatic chuck 400, approximately 15 microns can be removed from the surface of the electrostatic chuck 400 to completely remove the mesas 492 and remove the 5 micron curvature. In embodiments, a thickness of at least 20 microns ensures that the underlying electrostatic disc 402 is not ground during the refurbishment process. Once the mesas and curvature are removed by grinding, a new ceramic coating can be applied to the remaining portion of the second ceramic coating 494, and a new mesa 492 and / or other surface features can be formed on the new ceramic coating as described herein.

[0051] Figure 5 One embodiment of a process 500 for making an electrostatic chuck is shown. The process 500 may be performed to make any of the electrostatic chucks described in the embodiments herein, such as Figure 4 The electrostatic chuck 400 is provided. At block 505 of process 500, an initial ceramic coating (referred to as an overcoat ceramic coating) is deposited onto the ceramic body of the electrostatic chuck to fill pores, pinholes, microcracks, etc. in the ceramic body. The overcoat ceramic coating can be formed from the same material as the ceramic body. For example, both the ceramic body and the overcoat ceramic coating can be AlN or Al2O3. Alternatively, the overcoat ceramic coating can be formed from the same material as a subsequently deposited protective ceramic coating. For example, both the overcoat ceramic coating and the protective ceramic coating can be YAG, Y2O3, Al2O3, AlN, or AlON.

[0052] In one embodiment, the overlying ceramic coating is deposited via ion assisted deposition (IAD). Exemplary IAD methods include deposition processes that incorporate ion bombardment, such as evaporation (e.g., activated reactive evaporation (ARE)) and sputtering in the presence of ion bombardment, to form the coatings described herein. An exemplary IAD process is electron beam IAD (EB-IAD). Other conformal dense deposition processes that can be used to deposit the overlying ceramic coating include low pressure plasma spray (LPPS), plasma spray physical vapor deposition (PS-PVD), and plasma spray chemical vapor deposition (PS-CVD), chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, or a combination of the above processes. Other conformal deposition techniques may also be used.

[0053] If IAD is used to deposit a blanket ceramic coating, the blanket ceramic coating can be formed on the ceramic body by accumulating a deposition material in the presence of energetic particles, such as ions. The deposition material can include atoms, ions, radicals, and the like. The energetic particles can impact and compact the thin film protective layer as it is formed. A material source provides a stream of deposition material, while an energetic particle source provides a stream of energetic particles, both of which impact the ceramic body throughout the IAD process. The energetic particle source can be an oxygen or other ion source. The energetic particle source can also provide other types of energetic particles, such as inert radicals, neutron atoms, and nanometer-sized particles from a particle generation source (e.g., from a plasma, a reactive gas, or from a material source that provides the deposition material).

[0054] The source material (e.g., target body) used to provide the deposition material can be a sintered ceramic block corresponding to the same ceramic that constitutes the overlying ceramic coating. Other target materials can also be used, such as powders, calcined powders, preformed materials (e.g., materials formed by green compaction or hot pressing), or machined bodies (e.g., molten materials).

[0055] IAD can utilize one or more plasmas or beams (e.g., electron beams) to provide materials and high-energy ion sources. Reactive species can also be provided during the deposition of the plasma-resistant coating. In one embodiment, the high-energy particles include at least one of a non-reactive species (e.g., Ar) or a reactive species (e.g., O). In a further embodiment, reactive species such as CO and halogens (Cl, F, Br, etc.) can also be introduced during the formation of the plasma-resistant coating. When using the IAD process, the high-energy particles can be controlled by the high-energy ion (or other particle) source independently of other deposition parameters. The composition, structure, crystal orientation, and grain size of the ceramic coating can be manipulated according to the energy (e.g., velocity), density, and incident angle of the high-energy ion flow. Other parameters that can be adjusted are working distance and incident angle.

[0056] Post-coating heat treatment can be used to achieve improved coating properties. For example, a post-coating heat treatment can be used to convert an amorphous coating into a crystalline coating with higher corrosion resistance. Another example is to improve the adhesion strength of the coating to the substrate by forming a reactive region or transition layer.

[0057] The IAD-deposited overlay ceramic coating can have a relatively low film stress (e.g., compared to film stresses caused by plasma spraying or sputtering). The relatively low film stress can result in the ceramic body remaining very flat, with a curvature of less than about 50 microns across the entire ceramic body for a 12-inch diameter ceramic body. The IAD-deposited overlay ceramic coating can also have a porosity of less than 1%, and in some embodiments, less than about 0.1%. Thus, the IAD-deposited overlay ceramic coating is a dense structure. Furthermore, the IAD-deposited overlay ceramic coating can have a low crack density and high adhesion to the ceramic body.

[0058] The ceramic body may be the electrostatic disc described previously. The ceramic body may have undergone some processing, such as to form embedded electrodes and / or embedded heating elements. The lower surface of the ceramic body may be bonded to the thermally conductive base using a silicone adhesive. In an alternative embodiment, the operation of block 505 is not performed.

[0059] At block 510, the surface of the ceramic body is polished to produce a polished surface having a surface roughness of about 2 micro-inches to about 12 micro-inches. In one embodiment, the surface of the ceramic body is polished to an average surface roughness (Ra) of about 4 micro-inches to about 8 micro-inches. In addition to portions of the initial ceramic coating that fill pores, pinholes, etc., the polishing may reduce the initial ceramic coating and / or may substantially completely remove the initial ceramic coating.

[0060] At block 515, a ceramic coating (e.g., a protective ceramic coating) is deposited or grown on the polished surface of the ceramic body (e.g., over the initial ceramic coating). In one embodiment, the ceramic coating is YAG, Y2O3, Al2O3, AlN, or AlON. The ceramic coating can be a conformal coating that can be deposited by any deposition technique discussed with reference to block 505. For example, the ceramic coating can be deposited by performing IAD such as EB-IAD. The ceramic coating can be deposited to a thickness of up to several hundred microns. In one embodiment, the ceramic coating is deposited to a thickness of approximately 5 microns to 30 microns. In one embodiment, the ceramic coating is deposited to a thickness of approximately 5 microns to 10 microns. In one embodiment, the ceramic coating is deposited to a thickness of approximately 20 microns to 30 microns.

[0061] At block 520, a negative mask is placed over the coated ceramic body. The negative mask may be a circular mask having a disk-like shape. The negative mask may have a diameter slightly smaller than the diameter of the ceramic body. The negative mask may further include a plurality of through holes, each of which is a negative image of a mesa to be formed on the ceramic body. Figure 6A -C and Figure 7 The negative mask is discussed in more detail. In one embodiment, the negative mask is bonded to the ceramic body (e.g., glued to the ceramic body) by an adhesive. Alternatively, the negative mask can be held in place on the ceramic body by a mechanical holder.

[0062] At block 525, ceramic material is deposited through the apertures of the negative mask to form a mesa having rounded edges. Additionally, ceramic material can be deposited on exposed portions of the ceramic body at the periphery of the ceramic body to form a ring on the ceramic body. The ring can be formed at the same time as the mesa. The mesa and ring can be conformal and dense and can be deposited using any of the deposition techniques discussed above with reference to block 505. For example, the mesa and ring can be deposited using IAD, such as EB-IAD.

[0063] In one embodiment, the hole in the mask has a flared top and a flared bottom. The flared top acts as a funnel to inject material into the hole and increase the deposition rate. The flared bottom, combined with the aspect ratio of the hole (e.g., an aspect ratio of 1:2 to 2:1), can function to control the shape of the deposition mesa and / or deposition ring. For example, the aspect ratio combined with the flared bottom can result in the deposited mesa having rounded edges and / or a top hat profile. In addition, the flared bottom prevents the mesa from contacting the wall of the hole. This can prevent the mesa from adhering to the mask and the mask from adhering to the ceramic body.

[0064] In one embodiment, the inner edge of the ring is rounded, but the outer edge of the ring is not. This may be because the shape of the negative mask may cause the inner edge of the ring to be rounded during deposition, but there may be no mask portion on the outer edge of the ring to control the shape of the deposit. Alternatively, the edge of the ring may not be rounded.

[0065] At block 530, the mask is removed from the ceramic body. At block 535, the mesa and the ring are polished. A soft polishing process may be performed to polish the mesa. The soft polishing may at least partially polish the walls of the mesa and the top of the mesa.

[0066] In method 500, the protective ceramic coating is deposited first, followed by the mesa and ring. However, in alternative embodiments, the mesa and ring can be deposited before the protective ceramic coating, and the protective ceramic coating can be deposited over the mesa. The protective ceramic coating can be highly conformal, so the shape of the mesa and ring can remain unchanged after the protective ceramic coating is deposited over the mesa and ring.

[0067] Figure 6A -C illustrates the deposition of ceramic material through a mask 610 to form circular mesas with rounded edges on the surface of an electrostatic chuck 640. Mask 610 includes a plurality of holes 615. In one embodiment, the mask is approximately 1 mm to 3 mm thick. In one embodiment, the mask is approximately 2 mm thick. In one embodiment, the holes are circular holes with a diameter of approximately 0.5 mm to 3 mm. In one embodiment, the holes have a diameter of approximately 0.5 mm to 2 mm. In one embodiment, the holes have a diameter of approximately 1 mm. In one embodiment, the holes are of equal size. Alternatively, the holes can have different diameters. In one embodiment, the holes have an aspect ratio of 1:2 to 2:1 width to height.

[0068] As shown, in some embodiments, the aperture has a flared top end 620 and a flared bottom end 625. The flared end may have a diameter that is approximately 30%-70% larger than the aperture diameter at the narrowest region of the aperture (e.g., the region vertically centered within the aperture). In one embodiment, the flared end has a diameter that is approximately 50% larger than the aperture diameter at the narrowest region. The top and bottom ends may have flares of the same shape and size. Alternatively, the flared portion at the top may have a different size and / or shape than the flared portion at the bottom end.

[0069] The mask 610 is placed over an electrostatic chuck 640 that includes a protective ceramic layer 635 that has been deposited onto the surface of the electrostatic chuck 640. Figure 6A In , small mesas 630 with rounded edges have been deposited. Figure 6B In , deposition has continued and the small mesa 630 has become a larger mesa 631 with rounded edges. Figure 6C In the embodiment of the present invention, the deposition continues until it is completed and the mesa 632 has reached its final size. It is worth noting that due to the flared bottom end 625, the mesa 632 does not contact the wall of the hole 615.

[0070] Figure 7A top view of a mask 710 used to form mesas and rings on a ceramic body 705 of an electrostatic chuck is shown, according to one embodiment. As shown, mask 710 is a negative mask having a first diameter that is smaller than a second diameter of ceramic body 705. Thus, the deposition process can cause the rings to form at the periphery of the ceramic body that is not covered by mask 710. Mask 710 also includes a plurality of holes 715. The deposition process causes mesas to form at each of holes 715.

[0071] The foregoing description sets forth numerous specific details, such as examples of specific systems, components, methods, and the like, to provide a good understanding of several embodiments of the present invention. However, it will be apparent to those skilled in the art that at least some embodiments of the present invention can be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented only in simple block diagram form to avoid unnecessarily obscuring the present invention. Therefore, the specific details set forth are merely exemplary. Specific embodiments may differ from these exemplary details and still be considered within the scope of the present invention.

[0072] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the phrase "in one embodiment" or "in an embodiment" appearing in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the term "or" is intended to be inclusive rather than exclusive. When the term "about" or "approximately" is used herein, this is intended to indicate that the nominal value presented is accurate to within ±10%.

[0073] Although the operations of the methods herein are illustrated and described in a particular order, the order of the operations of each method may be altered such that certain operations may be performed in a reverse order, or such that certain operations may be performed at least partially simultaneously with other operations. In another embodiment, instructions or sub-operations of different operations may be performed in an intermittent and / or alternating manner. In one embodiment, multiple metal bonding operations are performed as a single step.

[0074] It should be understood that the above description is intended to be illustrative rather than restrictive. After reading and understanding the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the present invention should be determined with reference to the appended claims together with the full scope of equivalents to which these claims are entitled.

Claims

1. An electrostatic chuck comprising: a ceramic body including an embedded electrode; a first ceramic coating on a surface of the ceramic body, wherein the first ceramic coating fills pores in the ceramic body; a second ceramic coating on the first ceramic coating; and A plurality of mesas are provided on the second ceramic coating, the plurality of mesas having rounded edges.

2. The electrostatic chuck of claim 1 , wherein the ceramic body comprises a material from the group consisting of AlN, TiO, TiN, SiC, and Al 2 O 3 .

3. The electrostatic chuck of claim 1 , wherein the second ceramic coating comprises a material selected from the group consisting of Al 2 O 3 , AlN, Y 2 O 3 , Y 3 Al 5 O 12 (YAG), and AlON.

4. The electrostatic chuck of claim 1 , wherein the second ceramic coating comprises an amorphous ceramic comprising yttrium, aluminum, and oxygen, wherein at least 8% of the amorphous ceramic is yttrium.

5. The electrostatic chuck of claim 1, wherein the second ceramic coating comprises a rare earth oxide, the rare earth oxide comprising Y2O3.

6. The electrostatic chuck of claim 1, wherein the plurality of lands have an average surface roughness of 2 microinches to 12 microinches.

7. The electrostatic chuck of claim 1 , wherein each of the plurality of mesas comprises a material selected from the group consisting of Al 2 O 3 , AlN, Y 2 O 3 , Y 3 Al 5 O 12 (YAG), and AlON.

8. The electrostatic chuck of claim 1, wherein the second ceramic coating has an average surface roughness of 2 microinches to 12 microinches.

9. The electrostatic chuck of claim 1, wherein the second ceramic coating has a thickness of 5 microns to 30 microns.

10. The electrostatic chuck of claim 1, wherein the first ceramic coating comprises AlN or Al2O3.

11. The electrostatic chuck of claim 1 , wherein the first ceramic coating has an average surface roughness of 4 microinches to 10 microinches.

12. The electrostatic chuck of claim 1, wherein the plurality of mesas are deposition mesas without sharp edges.

13. The electrostatic chuck of claim 1 , further comprising: A deposition ring on the second ceramic coating at the periphery of the ceramic body, wherein the deposition ring comprises a material selected from the group consisting of Al2O3, AlN, Y2O3, Y3Al5O 12 (YAG), and AlON.

14. An electrostatic chuck comprising: a ceramic body including an embedded electrode; a first ceramic coating on a surface of the ceramic body, wherein the first ceramic coating fills pores in the ceramic body; a plurality of mesas on the first ceramic coating, the plurality of mesas having rounded edges; and A second ceramic coating layer covers the first ceramic coating layer and the plurality of mesas.

15. The electrostatic chuck of claim 14, wherein the first ceramic coating comprises a first material selected from the group consisting of AlN and Al2O3.

16. The electrostatic chuck of claim 15, wherein the second ceramic coating comprises a coating selected from the group consisting of Al2O3, AlN, Y2O3, Y3Al5O 12 The second material of the group consisting of (YAG), and AlON.

17. The electrostatic chuck of claim 16, wherein each of the plurality of mesas comprises the first material or the second material.

18. The electrostatic chuck of claim 14, wherein the plurality of mesas comprises a plurality of oval-shaped mesas.

19. A circular mask comprising: main body; and A plurality of through holes in the body, the plurality of through holes having an aspect ratio of 1:2 to 2:1, wherein at least one hole of the plurality of through holes includes a flared top end and a flared bottom end, wherein the flared top end is used to inject particles through the at least one hole and onto the electrostatic chuck to form a mesa on the electrostatic chuck, and wherein the flared bottom end prevents the mesa from contacting the circular mask.

20. The circular mask of claim 19, wherein the circular mask has a thickness of 1 mm to 3 mm.

21. The circular mask of claim 19, wherein the flared top end and the flared bottom end each have a first diameter that is 20%-70% larger than a narrowest area of ​​the at least one aperture.

22. The circular mask of claim 19, wherein the body has a first diameter that is smaller than a second diameter of an electrostatic chuck on which the circular mask is to be placed.

23. The circular mask of claim 19, wherein the plurality of through-holes comprises a plurality of elliptical through-holes, and wherein the at least one hole comprises at least one elliptical through-hole, the at least one elliptical through-hole causing an elliptical mesa to be formed on the electrostatic chuck.

24. The circular mask of claim 19, wherein the at least one hole is a circular hole having a diameter of 0.5 mm to 2.0 mm and a thickness of 1 mm to 3 mm.

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