Electrostatic chuck with multi-splat dielectric coating applied to base plate

Abstract

An electrostatic chuck comprises a base plate and a dielectric coating. The base plate has a shoulder portion configured to support an edge ring. Applied to at least the shoulder portion of the base plate, the dielectric coating comprises a locally laminar composite structure of a plurality of splats of a first splat composition interspersed among a plurality of splats of a second splat composition. The first splat composition has natively a higher dielectric constant and a lower thermal conductivity than the second splat composition.

Description

Docket No. LRC24322PPCTELECTROSTATIC CHUCK WITHMULTI-SPLAT DIELECTRIC COATING APPLIED TO BASE PLATEBACKGROUND

[0001] An electrostatic chuck can be used in a fabrication processing tool to hold a substrate, such as a semiconductor wafer, during processing. For example, an electrostatic chuck can be used to hold a substrate during an etch process or a deposition process.SUMMARY

[0002] This Summary is provided to introduce in simplified form a selection of concepts that are further described in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] Some disclosed examples relate to an electrostatic chuck comprising a base plate with a dielectric coating. The base plate has a shoulder portion configured to support an edge ring. Applied to at least the shoulder portion of the base plate, the dielectric coating comprises a locally laminar composite structure of a plurality of splats of a zirconia component interspersed among a plurality of splats of a trivalent- aluminum component. The zirconia component has natively a higher dielectric constant and a lower thermal conductivity than the trivalent-aluminum component.In some such examples, the zirconia component comprises one or more of a tetragonally stabilized zirconia and a partially stabilized zirconia. Alternatively or additionally, in some such examples, the zirconia component comprises a partially stabilized zirconia stabilized by yttrium doping at a dopant level reduced relative to tetragonally stabilized, yttrium-doped zirconia. Alternatively or additionally, in some such examples, the zirconia component comprises cerium-doped zirconia. Alternatively or additionally, in some such examples, the cerium-doped zirconia comprises 20 ± 5Docket No. LRC24322PPCT molar percent ceria. Alternatively or additionally, in some such examples, the zirconia component comprises alumina-toughened zirconia. Alternatively or additionally, in some such examples, the zirconia component comprises one or more of cerium or yttrium at sufficient doping to impart a tetragonal or cubic structure to the zirconia component. Alternatively or additionally, in some such examples, the trivalent- aluminum component comprises alumina. Alternatively or additionally, in some such examples, the trivalent-aluminum component comprises zirconia-toughened alumina. Alternatively or additionally, in some such examples, the coating comprises 50 ± 5 molar percent partially stabilized zirconia.

[0004] Other disclosed examples relate to an electrostatic chuck comprising a base plate and a dielectric coating. The base plate has a shoulder portion configured to support an edge ring. Applied to at least the shoulder portion of the base plate, the dielectric coating comprises a locally laminar composite structure of a plurality of splats of a first splat composition interspersed among a plurality of splats of a second splat composition. The first splat composition has natively a higher dielectric constant and a lower thermal conductivity than the second splat composition.

[0005] In some such examples, the dielectric coating has a thickness of 50 to 650 micrometers. Alternatively or additionally, in some such examples, the plurality of splats of the first spat composition have a median length of 50 to 500 micrometers and comprise 0 to 100 molar percent zirconia; the plurality of splats of the second splat composition have a median length of 50 to 500 micrometers and comprise 0 to 100 molar percent of a trivalent aluminum compound. Alternatively or additionally, in some such examples, the locally laminar composite structure is a structure achievable by sequential or concurrent spray application of the first and second splat compositions. Alternatively or additionally, in some such examples, the locally laminar composite structure is a structure achievable by spray application of the first and second splat compositions to a heated base plate. Alternatively or additionally, in some such examples, the coating has an RF impedance at dielectric breakdown power and isothermal conditions which is lower than the RF impedance of an alumina coating of optimized thickness comprising no zirconia.

[0006] Still other disclosed examples relate to a processing tool that exposes a substrate to a plasma. The processing tool comprises an electrostatic chuck and a dielectric coating. Configured to hold the substrate, the electrostatic chuck comprises aDocket No. LRC24322PPCT base plate with a shoulder portion configured to support an edge ring. Applied to at least the shoulder portion of the base plate, the dielectric coating comprises a locally laminar composite structure of a plurality of splats of a first splat composition interspersed among a plurality of splats of a second splat composition. The first splat composition has natively a higher dielectric constant and a lower thermal conductivity than the second splat composition.

[0007] In some such examples, at least the base plate is configured for operation at a cryogenic temperature, and one or more of a flexural strength or fracture toughness are superior to that of alumina Alternatively or additionally, in some such examples, the base plate is configured for operation at a cryogenic temperature, and the coating is less hygroscopic than non-doped zirconia. Alternatively or additionally, in some such examples, the first splat composition comprises one or more of tetragonally stabilized zirconia, partially stabilized zirconia, cerium-doped zirconia, or alumina-toughened zirconia, and the second splat composition comprises a trivalent aluminum component.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIGS. 1 A and IB show aspects of an example substrate processing tool.

[0009] FIG. 2 shows aspects of an example electrostatic chuck, including a base plate, and an example dielectric coating arranged on the base plate.

[0010] FIG. 3 shows aspects of a portion of an example dielectric coating comprising two layers.

[0011] FIG. 4 shows aspects of a portion of an example dielectric coating comprising more than two layers.

[0012] FIG. 5 A shows, in cross section, aspects of an example inhomogeneous layer of a dielectric coating.

[0013] FIG. 5B shows, in a plan view, aspects of the example inhomogeneous layer of the dielectric coating of FIG. 5 A.

[0014] FIG. 6 shows aspects of an example method for forming a dielectric coating on at least one surface of base plate of an electrostatic chuck.Docket No. LRC24322PPCTDETAILED DESCRIPTION

[0015] This disclosure is presented by way of example and with reference to the drawing figures listed above. Components, process steps, and other elements that may be substantially the same in one or more of the figures are identified coordinately and described with minimal repetition. It will be noted, however, that elements identified coordinately may also differ to some degree. It will be further noted that the figures are schematic and generally not drawn to scale. Rather, the various drawing scales, aspect ratios, and numbers of components shown in the figures may be purposely distorted to make certain features or relationships easier to see.

[0016] A ‘ceramic’, as used herein, refers to a non-molecular compound of at least one metallic element and at least one highly electronegative element, such as fluorine, oxygen or nitrogen; a ceramic may or may not be sintered. The ‘coefficient of thermal expansion’ (CTE) is the fractional change in a dimension of a material per degree Kelvin change in the temperature of the material, at constant pressure. The ‘dielectricbreakdown voltage’ is the minimum potential difference that, when applied across an electrical insulator, causes the insulator to become conductive; the ratio of the dielectric-breakdown voltage to the thickness of the insulator is the ‘dielectric strength’, an intrinsic property of the insulator. The ‘dielectric constant’, symbol k, is the ratio of the permittivity of a material to the permittivity of free space. As used herein, the terms ‘electrode’ and ‘electrical terminal’ refer to an electrical conductor that makes contact with a non-metallic part of an electrical circuit. The term ‘etch’ and variants thereof refer to removal of material from a substrate; ‘dielectric etching’ refers to a process whereby portions of dielectric material are removed from the surface of a substrate. The ‘etch rate’ is a metric of etch depth per unit of time. An ‘inductance-capacitance- resistance’ (LCR) meter is a device used to measure the electrical inductance, capacitance, and / or resistance of a circuit element, typically as a function of frequency. The terms ‘mesoscale’ and ‘mesoscopic’ are applied herein to dimensions greater than 0.1 millimeter (mm) The terms ‘microscale’ and ‘microscopic’ are applied herein to dimensions from 0.1 to 100 micrometers (pm). The terms ‘nanoscale’ and ‘nanoscopic’ are applied herein to dimensions from 0.1 to 100 nanometers (nm). The term ‘radio frequency’ (RF), as applied herein to electric current, refers to current alternating at one or more frequencies between 10 kilohertz (kHz) and 1 terahertz (THz). As used herein, a ‘ shoulder portion’ is a peripheral edge portion of a base plate of an electrostatic chuck,Docket No. LRC24322PPCT where the shoulder portion accommodates and supports an edge ring. In some examples the shoulder portion takes the form of a rabbet, which may be a generally right-angle shaped recess formed along the peripheral edge portion, replacing the peripheral edge by two corresponding edges separated by adjacent, generally orthogonal faces. The ‘thermal conductivity’ of a material is a measure of the flux of heat through a volume of the material relative to the temperature gradient across the volume. ‘Thermal spray coating’ refers to a process for coating an object with a solid coating derived from a heated feedstock, which is accelerated toward the object to be coated as a stream of particles in flowing carrier gas. Additional definitions are provided hereinafter.

[0017] Turning now to the drawings, FIGS. 1A and IB show aspects of an example processing tool 102 configured to enact a fabrication process on a substrate 104. In some examples the process enacted may comprise a plasma-etch process. In some examples, the plasma etch process may be a cryogenic-etch process in which cooling is applied to the substrate 104 during etching. The etch process may be configured to etch an electrically conductive material or a dielectric material. To those ends, processing tool 102 is configured to expose the substrate to a plasma. In some examples the substrate 104 exposed to the plasma may comprise a semiconductor (e.g., silicon) wafer. A semiconductor wafer cut from a boule is generally disc-shaped and may be 100, 150, 200, or 300 mm in diameter. Other shapes and sizes are also envisaged.

[0018] Processing tool 102 comprises a process chamber 106 and an electrostatic chuck 108 arranged within the process chamber. The electrostatic chuck 108 may be used during semiconductor manufacturing or other processing to support substrate 104. Subject to process control, the electrostatic chuck may be energized controllably to hold the substrate in place and de-energized controllably to release the substrate.

[0019] Electrostatic chuck 108 comprises a base plate 110. In some examples, the base plate 110 can be configured as an electrical terminal for RF plasma-generation. More specifically, RF current conducted through the base plate ignites, forms, and supports a capacitively coupled plasma within process chamber 106. In other examples, a substrate processing tool can be configured to form an inductively coupled plasma. In some examples, base plate 110 can be configured as a cathode. In some examples the base plate can be configured as a biasing electrode, to control the electric field through with which ions from the inductively coupled plasma are accelerated toward a substrate.Docket No. LRC24322PPCT

[0020] Electrostatic chuck 108 comprises a substrate support 112 disposed on base plate 110. In some examples the substrate support is made of an electrically insulating, ceramic material. One or more clamping electrodes (not shown in FIGS. 1 A or IB) can be embedded within the substrate support 112 to provide electrostatic clamping force to hold substrate 104 during processing.

[0021] Base plate 110 includes a shoulder portion 114, which is shown in greater detail in FIG. IB. The shoulder portion is configured to support an edge ring 116. One edge and at least one face (preferably two adjacent faces) of edge ring 116 are configured to match the geometry of the shoulder portion, such that the shoulder portion supports the edge ring. The edge ring surrounds substrate 104 when substrate 104 is positioned on substrate support 112. Edge ring 116 may have any suitable construction. In some examples, edge ring 116 is made of silicon carbide, which is an ohmic conductor. The electrically conductive edge ring undergoes capacitive RF coupling with base plate 110 during plasma operation. To that end, electrostatic chuck 108 comprises a dielectric coating 118 formed on the base plate. The dielectric coating covers at least the shoulder portion of the base plate. In the illustrated example the dielectric coating covers a substantial additional portion of the surface of the base plate, but that aspect may vary from one implementation to another. In some examples the areal coverage of the dielectric coating on the base plate may differ from the coverage shown in the drawings herein.

[0022] Substrate 104 also undergoes RF coupling with base plate 110 during plasma operation. Base plate 110, edge ring 116, and intervening dielectric coating 118 form a capacitor that supports the RF current. Due to the reactance of the capacitor a somewhat lower voltage may develop at edge ring 116 than at substrate 104 during plasma operation. Dielectric coating 118 also helps to electrically insulate base plate 110, which may prevent undesired arcing during plasma operation.

[0023] The thickness, composition, and structure of dielectric coating 118 may be engineered to provide a desired capacitance between shoulder portion 114 and edge ring 116. The capacitance can be selected to help avoid a lensing effect in the electric field at the edge region of substrate 104 during processing. This may help to achieve a suitably uniform etch or deposition rate at the edge region relative to interior regions. In some example the capacitance may lie within a range of 0.5 to 15 nanofarads (nF). In some examples the capacitance may lie within a range of 3 to 10 nF. Unless otherwiseDocket No. LRC24322PPCT noted, each and every capacitance recited herein is measured at 100 kHz using LCR meter. Some example capacitances lie within a range of 1 to 5 nF. More generally, in some examples, the dielectric coating can be selected to have a thickness d and dielectric constant k in a ratio k! d of between 10 and 350 per millimeter. The thickness, composition, and structure of dielectric coating 118 also can be engineered to provide a desired dielectric-breakdown voltage. Example dielectric-breakdown voltages include kilovolts (kV) or higher. Dielectric coating 118 is described in greater detail hereinafter.

[0024] Processing tool 102 comprises a gas inlet 120 and flow-control hardware 122. Flow-control hardware 122 is connected to an etchant source 124 and to an inert-gas source 126. Etchant source 124 may comprise any suitable etchant. Examples of etchants include halogen-based etchants such as hydrogen fluoride (HF), nitrogen trifluoride (NF3), perfluoroalkanes such as carbon tetrafluoride (CF4) and hexafluoroethane (C2F6), sulfur halides such as sulfur hexafluoride (SFe), phosphorus halides such as phosphorus trifluoride (PF3) and phosphorus pentafluoride (PFs). In some examples, chlorine-containing etchants can be used. Other examples of etchants include oxygen-based etchants and hydrogen-based etchants. Example oxygen-based etchants include molecular oxygen (O2), carbon dioxide (CO2), and nitrous oxide (N2O). Example hydrogen-based etchants include molecular hydrogen (H2) and ammonia (NH3). Inert-gas source 126 may comprise any suitable, substantially inert gas. Examples include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and, in some processing environments, nitrogen (N2). Flow-control hardware 122 can be controlled to flow gas from etchant source 124 and inert-gas source 126 into process chamber 106 via gas inlet 120. Flow-control hardware 122 may comprise one or more valves controllable to place a selected gas source in fluid communication with gas inlet 122.

[0025] Processing tool 102 further comprises an exhaust system 128. The exhaust system is configured to receive gas flowing out from process chamber 106. In some examples, exhaust system 128 is configured to actively remove gas from process chamber 106 and / or to apply a partial vacuum. Exhaust system 128 may comprise any suitable hardware, such as roughing pump, a high-vacuum pump, and suitable conduits and valves.Docket No. LRC24322PPCT

[0026] Processing tool 102 further comprises an RF power source 130, which is electrically connected to base plate 110 as a first electrical terminal for forming an RF plasma. Processing tool 102 also comprises a second electrical terminal 132. In the example illustrated in FIG. 1, second electrical terminal 132 takes the form of a ‘showerhead electrode’ that is also configured to dispense etchants and other process reagents. In other examples the second electrical terminal may take any other suitable form. Processing tool 102 includes matching network 134 for impedance matching of RF power source 130 to the plasma-forming circuit.

[0027] Processing tool 102 comprises a chiller 136 configured to circulate coolant through electrostatic chuck 108, to cool substrate 104 for reduced-temperature and / or cryogenic plasma operation. In some examples, substrate 104 is cooled to a temperature of 0 degrees Celsius (°C) or cooler. In some examples the substrate is cooled to a temperature between -60 and -10 °C. In other examples temperatures outside these ranges may be used. In other examples, a processing tool for etching can omit a chiller.

[0028] Electronic controller 138 is coupled operatively to flow-control hardware 122, exhaust system 128, RF power source 130, and chiller 136, among other processing tool components. The electronic controller is configured to control various functions of processing tool 102. Examples include operating chiller 136 to cool electrostatic chuck 108 to a desired temperature, operating flow-control hardware 122 to flow selected gases into process chamber 106, operating exhaust system 128, and / or operating RF power source 130 to form a plasma.

[0029] FIG. 2 shows additional aspects of an example electrostatic chuck 208. In some examples electrostatic chuck 208 can be the same as electrostatic chuck 108 of FIG. 1. Base plate 210 can be made of any suitable material that will function as an electrical terminal to form an RF plasma without contaminating the process-chamber environment. Aluminum and aluminum alloys are examples of suitable base-plate materials.

[0030] Base plate 210 supports dielectric coating 218. Again, the dielectric coating is located on at least on shoulder portion 214 of the base plate, and the shoulder portion is configured to support edge ring 216. In the example shown in FIG. 2, dielectric coating 218 covers a radially peripheral (e.g., circumferential) base plate surface 239. In some examples the dielectric coating may coat additional surfaces of the base plate —Docket No. LRC24322PPCT e.g., the surface that interfaces with substrate support 212, at least a portion of the bottom surface, and so on. As noted above, substrate support 212 may comprise one or more embedded electrodes (not shown in FIG. 2) for electrostatically clamping the substrate.

[0031] In some current electrostatic chucks, a dielectric coating of alumina (AI2O3) is applied to the base plate of an electrostatic chuck of a processing tool for semiconductor processing. Optimal thickness of an alumina coating on the base plate can be difficult to achieve, however. One issue is that the alumina coating, having a relatively low dielectric constant, offers commensurately low RF coupling between the base plate and the edge ring of the electrostatic chuck. Lower RF coupling degrades the uniformity of plasma exposure (e.g., etch or deposition rate), particularly in the edge regions of the substrate being processed. This may be due to the aforementioned lensing effect arising in the electric field, created by structures including the RF electrodes, the edge ring, and the substrate itself. A thinner alumina coating might help to improve the uniformity of plasma exposure, by providing stronger coupling. However, reducing the thickness of the alumina coating would necessarily reduce the dielectric-breakdown voltage, which is controlled by the dielectric strength of alumina. This increases the possibility of arcing at higher RF powers. A thicker alumina coating would provide a higher dielectric-breakdown voltage, but would also reduce the RF coupling.

[0032] Alumina coatings are also prone to cracking under some conditions, due to the difference between the coefficient of thermal expansion (CTE) of the coating relative to the aluminum or aluminum-alloy base-plate material. For instance, cryogenic etching involves cooling the substrate using a cryogenic fluid channeled through the base plate during the etch process. Heat generated by the cryogenic etching can cause a thermal gradient between the alumina dielectric coating and the cryogenic channels in the base plate sufficient to crack and / or delaminate the coating.

[0033] Accordingly, this disclosure presents electrostatic-chuck examples with base plates comprising dielectric coatings of different compositions, structures, and modes of application. Each dielectric coating includes at least one high-A material component. The term ‘high-A material component’ refers herein to a material component with a dielectric constant higher than that of alumina. This term is synonymous with ‘first material component’ herein. In some examples, a dielectric coating comprising a high- k material component can be thicker than a corresponding alumina coating but provideDocket No. LRC24322PPCT the same or greater RF coupling between the base plate and the edge ring. In some examples a thicker dielectric coating may offer increased resistance to dielectric breakdown. In some examples, a hi gh-Xr dielectric coating of the same thickness as a comparable alumina coating may be used, where the hi gh-Xr material component has a higher dielectric strength than alumina, thereby avoiding dielectric breakdown. In some examples the high-Xr material component may allow for the same or thinner coating thickness, relative to an alumina coating, to achieve a target dielectric-breakdown voltage and RF coupling between the base plate and edge ring. Furthermore, some high- k material components can have a CTE more closely matched to that of an aluminum or aluminum-alloy base plate, relative to alumina.

[0034] Various high-Xr material components may be used in a dielectric base-plate coating. Examples include tetragonal stabilized zirconia (TSZ) and partially stabilized zirconia (PSZ). Pure zirconia (zirconium dioxide, ZrCE) is monoclinic and relatively soft at room temperature but may be ‘stabilized’ by doping with other oxides to improve toughness and other properties. TSZ is zirconia which is stabilized to retain a tetragonal crystal structure at room temperature. The stabilization is achieved by doping with a small amount of a stabilizing oxide, such as yttria (yttrium oxide, Y2O3) or magnesium oxide (MgO). The doping prevents the zirconia from transforming into the monoclinic phase. The tetragonal phase of zirconia is desirable because it offers a combination of high strength and toughness. The tetragonal phase also allows for toughening mechanisms, such as transformation toughening, which helps improve resistance to crack propagation. PSZ also refers to zirconia which is stabilized with a small amount of a stabilizing oxide, typically at lower doping levels than TSZ. The stabilizing oxide changes the phase structure of the zirconia, creating a material that is partly stabilized against the phase transformations noted above.

[0035] Other examples of high-Xr material components include cerium oxide (ceria, CeO?), yttria-stabilized zirconia (e.g., (Y2O3)..(ZrO2)i-.v. where x is within a range of 0.02 to 0.20), zirconium oxide (zirconia, ZrO2), yttrium oxide (yttria, Y2O3), lanthanum oxide (La2Os), titanium oxide (TiO2), titanium-oxide doped alumina, lanthanum zirconium oxide (La2Zr2O?, LZO), hafnium oxide (HfO2), lanthanum lutetium oxide (LaLuO2), barium oxide (BaO), tantalum pentoxide (Ta20s), strontium oxide (SrO), calcium oxide (CaO), magnesium oxide (MgO), zirconium silicate (ZrSiO4), hafnium silicate (HfSiO4), molybdenum trioxide (MoOs), tungsten trioxide (WO3), andDocket No. LRC24322PPCT scandium oxide (SC2O3). The high-k material components enumerated above can also be called ‘high-k ceramic components’.

[0036] In some examples, a dielectric coating can include two or more hi gh-Xr material components. In some examples two or more high-Xr material components may be segregated into different microscopic or mesoscopic regions of the coating, as described hereinafter. In some examples, two or more high material components may be mixed intimately — i.e., co-located in at least some microscopic or mesoscopic regions of the coating. Segregated microscopic or mesoscopic regions, when included, may have any suitable volume and geometry. Examples include regions with an average size of 200 nm to 100 pm. In other examples, regions of the respective material components can have average sizes outside of this range.

[0037] Despite the advantages afforded by high-Xr material components, it will be noted that some high-& material components may have lower thermal conductivities than alumina. The overall thermal conductivity of the dielectric coating is relevant because it affects the rate at which the coating can discharge heat into the base-plate material (which then may flow to actively cooled portions of the electrostatic chuck). That rate sets and upper limit on the RF power that can be used for plasma operations. As the thermal conductivity decreases, the coating must support an increasing temperature gradient in order to discharge a given flux of heat, to support a given RF power. Because the dielectric strength of a material decreases with increasing temperature, the increasing temperature gradient will reduce the dielectric-breakdown voltage, which may lead to undesired arcing. Accordingly, one objective of this disclosure is to provide a dielectric coating having an RF impedance at dielectric breakdown power and isothermal conditions which is lower than an RF impedance of an alumina coating of optimized thickness comprising no zirconia.

[0038] In addition, decreased thermal conductivity of the coating will effectively increase, for a given RF power, the temperature of all of the components that discharge heat through the coating and to the baseplate — e.g., the edge ring and, in some examples, the substrate support and the substrate itself. Thus, a dielectric coating with relatively high thermal conductivity may mitigate overheating of one or more components.Docket No. LRC24322PPCT

[0039] To address these issues and provide further advantages, the disclosed dielectric coatings include at least one additional material component (in addition to the one or more high-& material components). ‘Additional material component’ is synonymous with ‘second material component’ herein. The additional material component can have a higher thermal conductivity than any, some, or all of the hi gh-Xr material components of the coating. By virtue of the high f and additional material components and the methods here disclosed, the thickness, composition, and structure of the dielectric coating on the base plate can be tailored to achieve a desired balance of physical properties. Such properties may include RF coupling strength, dielectric-breakdown voltage, thermal conductivity, and / or other properties discussed below — e.g., CTE, electrical resistivity, flexural strength, fracture toughness and / or hygroscopicity.

[0040] Example additional material components with relatively high thermal conductivities include trivalent-aluminum compounds, such as alumina (AI2O3), aluminum nitride (AIN), and aluminum oxynitride ((AlNffAkOs)!-.-.. where x is within a range of 0.30 to 0.37)). The additional material components enumerated above can also be called ‘additional ceramic components’.

[0041] In some examples, a dielectric coating can include two or more additional components. In some examples the two or more additional components may be segregated into different microscopic or mesoscopic regions of the coating, as described hereinafter. In some examples, two or more high material components may be mixed intimately — i.e., co-located in at least some microscopic or mesoscopic regions or colocated with any, some, or all of the ki gh-Xr material components.

[0042] The dielectric coatings presented herein can allow for increased base-plate coating thickness, relative to alumina coatings, without compromising RF coupling. The increased coating thickness can secure an increased dielectric-breakdown voltage at the base plate, depending upon the dielectric strength of the coating material. For example, a alumina may have a dielectric strength of 9.8 to 30 kV / mm on a flat surface, whereas yttrium-stabilized zirconia (YSZ) may have a dielectric strength of 9 to 35 kV / mm on a flat surface. It will be noted that YSZ is available in various compositions (e.g., 3%, 8%, or 14% yttria by mass). The 8% yttria composition (YSZ8) is commonly used. All compositions of YSZ, however, may have a dielectric strength substantially above that of alumina. A corresponding difference in the dielectric strength may also be observed on a base plate coating of a more complex geometry (due to the constraintsDocket No. LRC24322PPCT of thermal-spray processing). As another example, yttrium oxide (Y2O3) has a dielectric strength of 16.5 kV / mm. Dielectric-breakdown voltages achievable using these materials in place of alumina may be 10 kV or higher than that of an alumina coating of the same thickness.

[0043] In other examples a dielectric coating can be configured to allow for a greater degree of RF coupling than an alumina coating of equal thickness. In examples where the hi gh-Xr material component has a higher dielectric strength than alumina, the high f material component can be used in a coating as thin or thinner than an alumina coating, to secure a target dielectric-breakdown voltage.

[0044] The RF coupling between edge ring 216 and base plate 210, as well as the RF coupling between substrate 204 and base plate 210, can be tuned to be substantially equal to one another, or vary from one another, in dependence of the thickness, composition, and structure of dielectric coating 218. This feature enables the processing tool to achieve desired energy densities during substrate processing. For example, in some etch processes, it can be desirable for a substrate to be subjected to highly directional (e.g., vertical) ion flux uniformly across the (upward facing) surface of substrate 204 (opposite the base plate 210). However, RF coupling differences across the substrate 204 and edge ring 216 can influence energy densities and energy vectors in, for example, substrate edge region 240 between the substrate edge and the radially inward edge of the edge ring 216. The substrate edge region 240 between substrate 204 and edge ring 216 can comprise an area within which the etch rate can vary compared to the etch rates of other portions of the substrate. Whereas energy vectors across substrate 204 during substrate processing can be directed substantially vertically (downward) toward base plate 210, opposite substrate geometries associated with substrate edge region 240 may also allow for a lensing effect in substrate edge region 240. This feature may cause changes in the energy-vector direction and / or intensity, thereby potentially degrading the uniformity of etch rate near the radial outward edge of the substrate 204.

[0045] The RF coupling can be influenced by the capacitance between base plate 210 and substrate 204, as well as the capacitance between base plate 210 and edge ring 216. Dielectric coating 218 may be situated between base plate 210 and substrate 204, as well as between base plate 210 and edge ring 216. Accordingly, the dielectric coating can be configured (e.g., by varying composition and / or thickness) to achieve suitableDocket No. LRC24322PPCTRF coupling strength between edge ring 216 and base plate 210, and also between substrate 204 and base plate 210. This can help to negate the lensing effect in the electric field that accelerates plasma ions toward the substrate surface — e.g., in a semiconductor etching process.

[0046] In some examples the capacitance between base plate 210 and edge ring 216 is from 0.5 to 15 nF. In some such examples, the capacitance between the base plate and the edge ring is from 1 to 7.7 nF. In some examples the capacitance is from 3 to 10 nF. Such values can help to maintain a desired, targeted voltage at the edge ring. In some examples, the dielectric coating can be selected to have a thickness and a dielectric constant to provide a ratio of the dielectric constant k to the thickness d of between 10 and 350 per millimeter.

[0047] In some examples the desired voltage on edge ring 216, due to RF coupling at peak RF signal amplitude, can be controlled by the thickness, composition, and structure of the dielectric coating 218, to be 80% of the voltage at substrate 204 or greater. This voltage relationship can provide the desired plasma density at the edge of the substrate, so as to provide a more uniform etch rate.

[0048] A dielectric coating as disclosed can take the form of a single region of mixed composition, or as two or more regions of different compositions. The composition, thickness, and structure of the dielectric coating can be engineered to achieve a desired dielectric constant and a desired dielectric-breakdown voltage. As examples, some compositions of YSZ can have a dielectric constant of 29. Yttria has a dielectric constant of 11.5; a alumina has a dielectric constant of 9.7 to 9.9. Thus, a dielectric coating comprising alumina for thermal conductivity and YSZ or yttria as a high-A material component can provide a coating with a higher dielectric constant than alumina. This can allow for an increased coating thickness without decreasing the RF coupling. Also, in view of the dielectric strengths of alumina versus YSZ, the increased coating thickness also can secure a higher dielectric-breakdown voltage. Other example high-A material components include zirconia (k = 10 to 23) and zirconia-toughened alumina (ZTA, k= 11). Alumina-toughened zirconia (ATZ), may also have a dielectric constants up to 30. This material may comprise 80% molar zirconia, for instance. In examples that include a high-A material component with a higher dielectric strength than alumina, a higher dielectric-breakdown voltage can be achieved at equal or lesser coating thickness, relative to alumina.Docket No. LRC24322PPCT

[0049] Furthermore, a dielectric coating comprising a mixture or segregated combination of, for example, alumina and YSZ, can provide a closer CTE match between the coating and the underlying aluminum or aluminum alloy of the electrostatic chuck base-plate material. Relative to an alumina coating, this type of dielectric coating may exhibit lower thermal stresses and improved adhesion to the base plate during plasma operation, such as when the base plate is cooled for cryogenic processing.

[0050] Returning now to FIG. 2, dielectric coating 218 includes one or more high-A material components and one or more additional material components selected and arranged to provide desired dielectric, thermal conductivity, and / or thermal-expansion properties.

[0051] The one or more high-A material components can be selected to give the dielectric coating any suitable dielectric constant higher than the dielectric constant of alumina. In some examples, the dielectric constant of any, some, or all of the high-A material components is from 11 to 60. In more specific examples, the dielectric constant of the high-A material component is greater than 15. In some such examples, the dielectric constant of the dielectric coating is greater than 11. YSZ may have a dielectric constant of 29 ± 3. In contrast, alumina may have a dielectric constant of 9.3 ± 1. Thus, dielectric coating 218 comprising, for example, YSZ as a high-A material component and alumina as an additional material component can provide a coating with a higher dielectric constant than an alumina coating. This can enable increased coating thickness without decreasing either the dielectric-breakdown voltage or the RF coupling between base plate 210 and edge ring 216.

[0052] Because some high-A material components may have lower thermal conductivity than alumina, the one or more additional material components of the dielectric coating may be selected to have a higher thermal conductivity than any, some, or all of the high-A material components. For example, a alumina may have a thermal conductivity of 25 to 45 Watts per meter-Kelvin (Wm 'l< '). YSZ may have a thermal conductivity of 2 to 2.5 Wm1K '. Thus, by using alumina as an additional material component, the thermal conductivity of the dielectric coating as a whole can be higher than that of an YSZ coating. Other examples of material components with higher thermal conductivities than YSZ include ZTA (25 Wm 'l< ') and yttria (15 Wm 'K ' ).Docket No. LRC24322PPCT

[0053] In some examples, one or more high- and one or more additional material components can be selected to produce a dielectric coating closer in CTE to the baseplate material (e.g. aluminum or an aluminum alloy) than alumina. This feature can help to prevent cracking and / or delamination of the dielectric coating when exposed to thermal cycling, such as in a cryogenic processing tool. In one example, YSZ has a CTE of 10.3 to 11x106per Kelvin (I< '). Alumina has a CTE of 7 to 8 * 106K ' . Aluminum alloy A16061 (an example base-plate material) has a CTE of 23.6 x | Q6K h Accordingly, YSZ is closer in CTE than alumina to A16061. A dielectric coating comprising a mixture of these material components provides a smaller CTE difference between the coating and the base-plate material, relative to alumina. In some examples comprising coatings with separate regions of alumina and YSZ, a YSZ layer may be positioned between an aluminum base plate and an alumina layer, to provide a smooth CTE gradation.

[0054] In some examples the one or more high- and the one or more additional material components of the dielectric coating may be selected to provide additional, desired physical properties. For example, the high-Xr and the additional material components can be selected to provide suitably high electrical resistivity, to achieve a desired voltage on the edge ring from RF coupling during a plasma process. Furthermore, the one or more high- and the one or more additional material components can be selected to be suitably resistant to processing chemistries employed in the processing tool.

[0055] Some of the high-Xr material components herein provide added benefits of increased flexural strength and fracture toughness relative to alumina. These features protect the dielectric coating from various mechanical stresses including, but not limited to, thermal-gradient stresses which occur during cryogenic process conditions. Material components that exhibit increased flexural strength and fracture toughness relative to alumina include the TSZ and PSZ materials discussed hereinabove. These materials are also substantially non-hygroscopic. One benefit of this feature is that virtually any type of processing at below-ambient temperatures is liable to condense adventitious water vapor onto the various surfaces of the electrostatic chuck, including the dielectric coating. Coatings that comprise hygroscopic material components are liable to undergo additional, stresses, accordingly, with repeated cryogenic-to-ambient temperature cycling. In addition to condensation inside the chamber, exposure to water-Docket No. LRC24322PPCT vapor condensate and cleaning solutions used in in-situ or ex-situ may degrade hygroscopic base plate coatings. Sorption of water from these and other exposures may cause additional stresses when the base plate is returned to the chamber, as the sorbed water may only be partly removed when the chamber is pumped down to vacuum. Under vacuum conditions the sorbed water may freeze and / or degrade plasma performance, for example. The use of non-hygroscopic material components in the coating, and especially on the exterior layer (vide infra), reduces these unwanted effects.

[0056] The one or more high- and the one or more additional material components of dielectric coating 218 can be mixed in any suitable molar ratio. Where a high-Zr material component is YSZ and an additional material component is alumina, example molar ratios (YSZ : AI2O3) include ratios within a range of 5 : 95 to 60 : 40. Further, the molar ratios of the one or more high-& and the one or more additional material components can be selected based upon a desired dielectric constant, dielectricbreakdown voltage, thermal conductivity, CTE, electrical resistivity, flexural strength, fracture toughness and / or hygroscopicity of the dielectric coating.

[0057] In some examples, the dielectric coating 218 has a thickness 244 within a range of 300 to 1000 pm. In other examples, the thickness may be outside of this range. The dielectric coating may have any suitable porosity consistent with the other properties set forth herein. In some examples, the dielectric coating can have a porosity of 10% or less. In more specific examples, the dielectric coating can have a porosity of 5% or less. A multi-layer dielectric coating may have a porosity within these ranges, in some examples.

[0058] In some examples dielectric coating 218 is a single layer comprising one or more high-& material components and one or more additional material components. In other examples, the dielectric coating may comprise two or more layers of different compositions and / or configurations. For example, a dielectric coating can comprise at least one layer comprising one or more hi gh-Xr material components, and, at least one layer comprising one or more additional material components. In various examples, a layer comprising one or more high- material components may either omit or include one or more additional material components. Likewise, a layer comprising one or more additional material components may either omit or include one or more high-& material components. In an example two-layer arrangement, a dielectric coating may have aDocket No. LRC24322PPCT layer of alumina at 200 to 300 m to increase thermal conductivity, and a layer of YSZ at 50 to 100 pm to increase the overall dielectric constant. In some examples, a layer with higher thermal conductivity material may be arranged over a high-A layer. This configuration provides a progressive change in CTE through the layers. In other examples, a high-A layer may be arranged over the higher-CTE layer. This configuration can be motivated by process considerations (e.g., particle generation, chemical compatibility) where process transparency can be achieved by having an alumina top layer, as opposed to one of the higher-dielectric layers.

[0059] In the example illustrated in FIG. 2, dielectric coating 218 comprises a single layer. FIG. 3 shows aspects of a portion of example dielectric coating 318 on a base plate 210, which comprises layers 342A and 342B of differing composition. In some examples layer 342A may comprise one or more high-A material components, and layer 342B may comprise at least one additional material component with higher thermal conductivity than any, some, or all of the high-A material components of layer 342A. In other examples, the layer of the one or more high-A material components may be in direct contact with the base plate 210, and the layer of the at least one additional material component may be positioned over the layer of the one or more high-A material components.

[0060] Each layer 342A and 342B independently may comprise a single material component or mixture of material components as described hereinabove. More specifically, either or both of layers 342A and 342B may comprise one or more high-A material components and / or at least one additional material component with higher thermal conductivity than any, some, or all of the high-A material components. Although FIG. 3 shows two layers of different material composition, other dielectric coatings fully consonant with this disclosure may include three or more layers, with at least two of the layers having different material compositions.

[0061] Layers 342A and 342B may have any suitable thicknesses. In some examples, layers 342A and 342B have a combined thickness 344' between 300 and 1000 pm. In other examples, the combined thickness 344' may lie outside of this range. In some examples, where layer 342A comprises one or more high-A material components, the thickness 344A of layer 342A may be between 300 and 500 pm. In some such examples, where layer 342B comprises at least one additional material component with higher thermal conductivity than any, some, or all of the high-A material componentsDocket No. LRC24322PPCT of layer 342A, layer 342B may be between 50 and 300 m. In still other examples, the thicknesses of either or both of layers 342A and 342B may be outside of these ranges.

[0062] In some examples the capacitance between base plate 210 and edge ring 216, with dielectric coating 318 applied to shoulder portion of the base plate 210, is between 0.5 and 15 nF at 100 kHz. In some examples the capacitance is between 1 nF and 7.7 nF. In some examples the capacitance is between 3 and 10 nF. Furthermore, the voltage on edge ring 216 due to capacitive reactance at peak RF amplitude, can be tuned, via the thickness, composition, and structure of dielectric coating 318, to be 80% of the voltage at the substrate, or greater. In some examples the ratio of the dielectric constant k to the thickness d is between 10 and 350 per millimeter.

[0063] In a more specific example, first layer 342A of dielectric coating 318 comprises YSZ as a high-A material component, and has a thickness 344A of 500 ± 50 pm. The second layer 342B of the dielectric coating comprises alumina as an additional material component with a higher thermal conductivity than YSZ, and has a thickness 344B of 50 ± 5 pm. In one particular example configuration, the capacitance between base plate 210 and edge ring 216 is 8.5 ± 0.9 nF.

[0064] In another more specific example, first layer 342A of dielectric coating 318 comprises YSZ as a high-A material component, and has a thickness 344A of 500 ± 50 pm. The second layer 342B of the dielectric coating comprises alumina as an additional material component with a higher thermal conductivity than YSZ, and has a thickness 344B of 100 ± 10 pm. Here the capacitance between base plate 210 and edge ring 216 is 6.7 ± 0.7 nF.

[0065] In still another more specific example, first layer 342A of dielectric coating 318 comprises YSZ as a high-A material component, and has a thickness 344A of 300 ± 30 pm. The second layer 342B of the dielectric coating comprises alumina as a material component with a higher thermal conductivity than YSZ, and has a thickness 344B of 300 ± 30 pm. Here the capacitance between base plate 210 and edge ring 216 is 4.0 ± 0.4 nF.

[0066] FIG. 4 shows aspects of another example dielectric coating 418. Whereas the dielectric coating of FIG. 3 comprises two layers, dielectric coating 418 comprises a plurality of layers 442A, 442B, 442C, 442D, where adjacent layers may comprise different material components or proportions thereof. In some examples, layers 442A,Docket No. LRC24322PPCT442B, 442C and 442D include layers comprising one or more high- material components alternating with layers comprising at least one additional material component with higher thermal conductivity than any, some, or all of the high-& material components. In this manner, a dielectric coating can comprise layers of different material components of compositions and / or thicknesses selected to tune the properties of the dielectric coating for a desired plasma operation.

[0067] In the examples shown in FIG. 2, 3, and 4, the dielectric coatings are illustrated as one or more substantially homogeneous layers, even for variants in which a given layer may comprise a plurality of material components. Indeed the foregoing examples embrace dielectric coatings in which any microscale or mesoscale segregation of the material components is exclusively between layers, as opposed to within a given layer. For the class of material components used in the dielectric coatings (non-molecular compounds), however, some level of material segregation within layers is likely. This is because the materials are typically micro- or nanocrystalline solids, and because crystallites typically resist interpenetration by dissimilar materials. Accordingly, in any suitably prepared, multi-component layer of a dielectric coating, plural material components therein may be segregated at the crystallite level (i.e., on the nanoscale). In other examples a material component may comprise an amorphous glass, with roughly the same stoichiometric proportion as an oxide-nitride crystal. For the film chemistries discussed herein, that proportion will generally be greater than 5 volume %, but with some, more complex crystalline structures (e.g., YAG), the proportion can be upwards of 70 to 80 volume % amorphous material. This level of segregation may be observed in coatings applied via thermal spray coating, for instance, if all of the feedstocks contributing to a given layer were pre-mixed and flowed through the same spray jet.

[0068] In contrast, FIGS. 5A and 5B show aspects of an example inhomogeneous layer 542A of a dielectric coating 518. Layer 542A has additional, areal segregation of material components over a microscopic or mesoscopic length scale, which is larger than the scale of the crystallites of the material components. As evident from the cross- sectional view of FIG. 5A, inhomogeneous layer 542A is arranged in a multi-layer dielectric coating, as described in the context of FIGS. 3 and 4. That aspect is not strictly necessary, however, for inhomogeneous layer 542A may instead be the only layer of the coating. In either case, the inhomogeneous layer has a ‘local’ or ‘interrupted’Docket No. LRC24322PPCT lamellar structure, as opposed to the continuous lamellar structures represented in FIGS. 3 and 4. The term ‘splat structure’ may be used to describe this type of structure.

[0069] The plan view of FIG. 5B reveals that inhomogeneous layer 542A comprises a plurality of substantially homogeneous splats 544 of different splat compositions. The splats are formed by the impact against base plate 210 of the particles accelerated towards the base plate in the spray-coat process. Discrete homogeneous splats of the same splat composition are labeled using like alphabetic characters — viz., splats 544A1, 544A2, etc., have a first splat composition; splats 544B1, 544B2, etc., have a second splat composition. The shapes of the illustrated splats should not be construed as limiting in any way. Generally speaking, the shapes will vary based at least in part on the mode of application of the inhomogeneous layer. In some examples splats of the same splat composition may conform to a statistical size distribution. In some examples splats of the same splat composition may conform to a statistical shape distribution.

[0070] Each splat in layer 542A has a length defined as the dimension parallel to the layer. If the splat is modeled as a circle or ellipse, then the length corresponds to a diameter. Each splat also has a thickness dimension perpendicular to the layer. In some examples the splat length is on the order of 4 to 6 times the diameter of the parent particle (under conditions of limiting low velocity where the parent particle can be modeled as a sphere). The splat thickness, then, can be computed geometrically, based on the volume of the parent particle. For instance, a 50 pm spherical parent particle may yield a splat which is 250 pm in length and 1.3 pm in thickness. In practice, however, the splat geometry may differ from the ideal, such that the splat length could be 1 to 10 times the diameter of the parent particle. Moreover, variation in thickness may be observed due to local quenching, or a quenched annular Tip’ may form at the expansion front of a parent particle in the state.

[0071] Metrics ‘dlO’, ‘d50’, and / or ‘d90’ may be used to characterize a feedstock powder corresponding to a splat composition used in thermal-spray application of layer 542A. A dx of y means that x% of the particles in the powder are smaller than y. In some examples the d50 of the powder feedstocks corresponding to the splat compositions herein range from 10 to 60 pm. For atmospheric plasma-spray application, however, d50 may range from 5 to 100 pm. Naturally the powder size itself admits of a distribution. An example powder may have dlO = 10 ± 1 pm, d50 = 50 ± 5 pm, and d90 = 90 ± 9 pm. Some distributions may exhibit cut tails due either to airDocket No. LRC24322PPCT powder classification or sieving; the tail cut-offs can either be one-sided or two-sided, in general. Furthermore, the variability of powder morphology (hollow-sphere versus agglomerated versus fused-and-crushed) means that the density of the parent particles may differ from that of the corresponding feedstock powders. Fused-and-crushed powders undergo the least densification on melting, while hollow-sphere morphologies undergo the greatest.

[0072] Typically the splat diameter depends also on the particle velocity, on the degree of overheating of the liquid droplet in the plasma plume, and on the degree to which the liquified particle wets the substrate upon impact. These quantities depend, in turn, on the heat capacities of the substrate and the particle, on the temperature of the substrate, and so on. In view of the considerations above, a reasonable estimate is that splat diameters are roughly 5 times the diameter of the average (d50) raw powder diameter. This estimate holds for zirconia- and alumina-based splat compositions to first order (e.g., 3 times smaller to 3 times larger, for a full order of magnitude), even where two different splat compositions are sprayed at the same time, with different sizes, morphologies, melting points, melt densities (and inertia).

[0073] A splat of a given splat composition must include at least one material component. More specifically, a splat of a given splat composition may include zero or more high-& material components and zero or more additional material components, such that at least one material component is included. Any, some, or all of the high-Xr material components of a given splat may be selected according to the logic presented above — e.g., to increase the dielectric constant or dielectric strength of the coating or layer, etc. Moreover, any, some, or all of the additional material components of the given splat may be selected according to the logic presented above — e.g., to increase the thermal conductivity of the coating or layer, etc.

[0074] Dielectric coating 518 comprises a locally laminar composite structure of a plurality of splats. The structure includes a plurality of splats 544A of a first splat composition interspersed among a plurality of splats 544B of a second splat composition. In some examples the first splat composition has natively a higher dielectric constant and a lower thermal conductivity than the second splat composition.

[0075] In some examples the first splat composition comprises a zirconia component. The zirconia component may comprise, for instance, one or more of tetragonallyDocket No. LRC24322PPCT stabilized zirconia, partially stabilized zirconia, cerium-doped zirconia, or alumina- toughened zirconia. In a more particular example the zirconia component may comprise a partially stabilized zirconia, which is stabilized by yttrium doping at a dopant level reduced relative to tetragonally stabilized, yttrium-doped zirconia. In another more particular example the zirconia component may comprise cerium-doped zirconia. The cerium-doped zirconia may comprise 20 ± 5 molar percent ceria, for instance. In some examples the zirconia component may comprise one or more of cerium or yttrium at sufficient doping to impart a tetragonal or cubic structure to the zirconia component.

[0076] In some examples the second splat composition comprises a trivalent- aluminum component, such as alumina and / or aluminum nitride. In some examples the trivalent-aluminum component may comprise zirconia-toughened alumina. In these and other examples the coating may overall comprise 50 ± 5 molar percent partially stabilized zirconia.

[0077] In some examples the dielectric coatings may span a range of thicknesses, starting from the top of the electrostatic chuck to around the edges. In one, non-limiting implementation the thickness may be 100 pm at the top to 300 pm at the minor radius of the sidewall, to 550 pm on the shoulder portion, to 400 pm at the major radius of the sidewall. More generally, the thickness may extend from 50 pm at minimum thickness to greater than 600 pm at maximum thickness. Moreover, the dielectric coating can have variable thickness in various places on the electrostatic chuck. In some examples, accordingly, the dielectric coating has a thickness of 50 to 650 pm. In some examples the plurality of splats of the first spat composition may have a median length of 50 to 500 pm and may comprise 0 to 100 molar percent zirconia. In these and other examples the plurality of splats of the second splat composition may have a median length of 50 to 500 pm and may comprise 0 to 100 molar percent of a trivalent aluminum compound.

[0078] The locally laminar composite structure is a structure achievable by alternating or concurrent spray application of first and second splat compositions. In some examples the locally laminar composite structure is a structure achievable by spray application of the first and second splat compositions to a heated base plate.

[0079] In some examples coating 518 has an RF impedance at dielectric breakdown power and isothermal conditions which is lower than an RF impedance of an alumina coating of optimized thickness comprising no zirconia. In examples wherein at least theDocket No. LRC24322PPCT base plate is configured for operation at a cryogenic temperature, one or more of a flexural strength or fracture toughness may be superior to that of alumina. In these and other examples the coating may be less hygroscopic than non-doped zirconia.

[0080] FIG. 6 shows aspects of an example method 600 for forming a dielectric coating on at least one surface of a base plate of an electrostatic chuck. Method 600 can be used to form a dielectric coating on a base plate of an electrostatic chuck, as described with reference to FIGS. 1 A through 5B, or to any portion thereof.

[0081] The mode of application of the dielectric coating in method 600 may vary from one implementation to the next. Some modes of application include thermal spray coating. Thermal spray coating uses a (typically solid) feedstock which is heated and conveyed into a stream of carrier gas to form particles of a corresponding material component or mixture of material components. The particles are accelerated with the carrier gas toward the object to be coated. The particles impinge on the object and adhere to the surface of the object, to form the coating. Example thermal spray-coating variants include plasma spraying, detonation spraying, wire-arc spraying, flame spraying, high-velocity oxy-fuel (HVOF) spraying, high-velocity air-fuel (HVAF) spraying, warm spraying, cold spraying, and spray-and-fuse spraying. These methods and others are envisaged herein.

[0082] At 646A of method 600, a spray-coat device having a plurality of substantially independent spray jets and corresponding feedstock reservoirs is provided, each feedstock reservoir communicating materially with one, corresponding spray jet. A plurality of feedstocks are also provided — viz., feedstocks corresponding to the splat compositions that will contribute to the dielectric coating. In some examples a feedstock has the same composition as its corresponding splat composition. In other examples a feedstock may differ compositionally from the corresponding splat composition. That approach may be taken in anticipation of a phase transition or chemical reaction that transforms a feedstock composition into the corresponding splat composition under spray-coat conditions or pursuant to post-treatment of the dielectric coating or base plate (vide infra). A feedstock of that kind is called a ‘precursor’. In some examples a feedstock may be a pure substance. In other examples a feedstock may comprise a mixture corresponding to all of the material components to be deposited in the same splat, in required proportions. Such a mixture may comprise zero or more high-ZrDocket No. LRC24322PPCT material components and / or corresponding precursors. Such a mixture may comprise zero or more additional material components and / or corresponding precursors.

[0083] In still other examples it may be possible to mix multiple powders in the same feedstock, which could be partially alumina and partially YSZ. There are some downsides to this (e.g., density driven separation), but it is a standard industry practice.

[0084] At 646B a base plate of an electrostatic chuck is positioned relative to the spray-coat device. At this step the base plate optionally may be masked to protect areas of the surface where no dielectric coating is desired. The positioning and / or masking is such that at least the shoulder portion of the base plate will be sprayed according to the subsequent steps of the method. In some examples the base plate may be heated to above-ambient temperature at this step of the method.

[0085] At 646C the spray-coat device is adjusted for application of the layer of the dielectric coating to be deposited next (which, initially is the first layer). Here the spraycoat device is charged with a plurality of feedstocks corresponding to the plurality of splat compositions of the layer. Each feedstock is received in a respective feedstock reservoir of the spray-coat device. In some examples one or more operating parameters of the spray-coat device are adjusted based on the properties of each feedstock to be sprayed into the layer.

[0086] At 646D the spray-coat device is operated to spray the feedstock corresponding to the splat composition to be added next to the layer. As shown in FIG. 6 method 600 iterates through each splat composition of a given layer multiple (N) times, thereby alternating the spray operation among the different feedstocks until the desired layer thickness is achieved. The value of N is not particularly limited, but may depend on the layer thickness and feedstock properties. Example values of Ainclude 5, 10, 50, 100, etc. Naturally, step 646D need only be executed once for homogeneous layers. Equally envisaged is an alternative mode of application where two or more spray jets are operated concurrently at carefully controlled flow rates until the desired layer thickness is achieved. Once a given layer is deposited to the desired thickness, the method proceeds to the next layer of the dielectric coating, or terminates for single-layer coatings.Docket No. LRC24322PPCT

[0087] At optional step 646E the base plate may be taken elsewhere and subjected to post-processing, which may include heat treatment, sintering, application of a coating, etc.

[0088] No aspect of the foregoing drawings or description should be interpreted in a limiting manner, because numerous variations, extensions, and omissions are also envisaged. For instance, although processing tool 102 of FIG. 1 is a cryogenic, dielectric-etch processing tool, other processing tools that use an electrostatic chuck with a multi-splat dielectric coating include non-cryogenic etch processing tools and various deposition processing tools.

[0089] It will be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and / or described may be performed in the sequence illustrated and / or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed. In that spirit, the phrase ‘based at least partly on’ is intended to remind the reader that the functional and / or conditional logic illustrated herein neither requires nor excludes suitable additional logic, executing in combination with the illustrated logic, to provide additional benefits.

[0090] The subj ect matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

Docket No. LRC24322PPCTCLAIMS:

1. An electrostatic chuck comprising: a base plate with a shoulder portion configured to support an edge ring; and a dielectric coating applied to at least the shoulder portion of the base plate, the dielectric coating comprising a locally laminar composite structure of a plurality of splats of a zirconia component interspersed among a plurality of splats of a trivalent- aluminum component, wherein the zirconia component has natively a higher dielectric constant and a lower thermal conductivity than the trivalent-aluminum component.

2. The electrostatic chuck of claim 1 wherein the zirconia component comprises one or more of a tetragonally stabilized zirconia and a partially stabilized zirconia.

3. The electrostatic chuck of claim 1 wherein the zirconia component comprises a partially stabilized zirconia stabilized by yttrium doping at a dopant level reduced relative to tetragonally stabilized, yttrium-doped zirconia.

4. The electrostatic chuck of claim 1 wherein the zirconia component comprises cerium-doped zirconia.

5. The electrostatic chuck of claim 4 wherein the cerium-doped zirconia comprises 20 ± 5 molar percent ceria.

6. The electrostatic chuck of claim 1 wherein the zirconia component comprises alumina-toughened zirconia.

7. The electrostatic chuck of claim 1 wherein the zirconia component comprises one or more of cerium or yttrium at sufficient doping to impart a tetragonal or cubic structure to the zirconia component.

8. The electrostatic chuck of claim 1 wherein the trivalent-aluminum component comprises one or more of alumina or zirconia-toughened alumina.Docket No. LRC24322PPCT9. The electrostatic chuck of claim 1 wherein the trivalent-aluminum component comprises zirconia-toughened alumina.

10. The electrostatic chuck of claim 1 wherein the coating comprises 50 ± 5 molar percent partially stabilized zirconia.

11. An electrostatic chuck comprising: a base plate with a shoulder portion configured to support an edge ring; and a dielectric coating applied to at least the shoulder portion of the base plate, the dielectric coating comprising a locally laminar composite structure of a plurality of splats of a first splat composition interspersed among a plurality of splats of a second splat composition, wherein the first splat composition has natively a higher dielectric constant and a lower thermal conductivity than the second splat composition.

12. The electrostatic chuck of claim 11 wherein the dielectric coating has a thickness of 50 to 650 micrometers.

13. The electrostatic chuck of claim 11 wherein the plurality of splats of the first spat composition have a median length of 50 to 500 micrometers and comprise 0 to 100 molar percent zirconia, and wherein the plurality of splats of the second splat composition have a median length of 50 to 500 micrometers and comprise 0 to 100 molar percent of a trivalent aluminum compound.

14. The electrostatic chuck of claim 11 wherein the locally laminar composite structure is a structure achievable by sequential or concurrent spray application of the first and second splat compositions.

15. The electrostatic chuck of claim 11 wherein the locally laminar composite structure is a structure achievable by spray application of the first and second splat compositions to a heated base plate.Docket No. LRC24322PPCT16. The electrostatic chuck of claim 11 wherein the coating has an RF impedance at dielectric breakdown power and isothermal conditions which is lower than an RF impedance of an alumina coating of optimized thickness comprising no zirconia.

17. A processing tool which exposes a substrate to a plasma, the processing tool comprising: an electrostatic chuck configured to hold the substrate, the electrostatic chuck comprising a base plate with a shoulder portion configured to support an edge ring; and a dielectric coating applied to at least the shoulder portion of the base plate, the dielectric coating comprising a locally laminar composite structure of a plurality of splats of a first splat composition interspersed among a plurality of splats of a second splat composition, wherein the first splat composition has natively a higher dielectric constant and a lower thermal conductivity than the second splat composition.

18. The processing tool of claim 17 wherein at least the base plate is configured for operation at a cryogenic temperature, and wherein one or more of a flexural strength or fracture toughness are superior to that of alumina.

19. The processing tool of claim 17 wherein at least the base plate is configured for operation at a cryogenic temperature, and wherein the coating is less hygroscopic than non-doped zirconia.

20. The processing tool of claim 19 wherein the first splat composition comprises one or more of tetragonally stabilized zirconia, partially stabilized zirconia, cerium- doped zirconia, or alumina-toughened zirconia, and wherein the second splat composition comprises a trivalent aluminum component.

Images