JP7561867B2 - High Temperature Microzone Electrostatic Chuck - Google Patents

Description

[0001] The embodiments described herein relate generally to semiconductor manufacturing, and more particularly to a high temperature substrate support assembly having multiple micro-zone heaters.

[0002] Reliable fabrication of sub-nanometer features is one of the key challenges for the next generation of very large scale integration (VLSI) and very large scale integration (ULSI) semiconductor devices. However, as circuit technology limits continue to be pushed, VLSI and ULSI interconnect technologies have required ever-increasing throughput. Reliable formation of gate structures on substrates is critical to the success of VLSI and ULSI, as well as the continuing effort to increase circuit density and quality on individual substrates and dies.

[0003] To reduce manufacturing costs, integrated chip (IC) manufacturing demands higher throughput and better device yield and performance for every silicon substrate processed. Some manufacturing techniques currently being explored for next generation devices under development require processing at temperatures exceeding 300 degrees Celsius and high bias power during processing of films on the substrate. High bias power improves film roughness and morphology on the substrate. However, high bias power also generates thermal energy that, if not managed, can undesirably limit the choice of materials or the choice of processes that can be performed during processing of the substrate.

[0004] Some of these high temperature and high power manufacturing techniques are performed in processing chambers that utilize electrostatic chucks to secure the substrate being processed in the chamber. A conventional electrostatic chuck (ESC) is part of a substrate support assembly that includes multiple heating zones to ensure processing uniformity across the surface of the ESC. However, thermal smear, i.e., outward heat dissipation, between adjacent heating zones often results in an undesirable thermal profile due to heat moving laterally between adjacent regions in an unplanned manner. As a result, it is difficult to obtain a desired ESC thermal profile and processing results.

[0005] Therefore, there is a need for an improved substrate support assembly having multiple heaters.

[0006] Implementations described herein provide a substrate support assembly. The substrate support assembly includes a first ceramic plate having a workpiece support surface and a lower surface. The first ceramic plate includes a plurality of secondary heaters each forming a plurality of microzones. The substrate support assembly includes a second ceramic plate having an upper surface and a lower surface. A first metallic bonding layer is disposed between the lower surface of the first ceramic plate and the upper surface of the second ceramic plate. A third ceramic plate has an upper portion and a lower portion. The third ceramic plate includes a primary heater. A second metallic bonding layer is disposed between the lower surface of the second ceramic plate and the upper portion of the third ceramic plate.

[0007] In order that the above-mentioned features of the invention may be understood in detail, a more detailed description of the invention briefly summarized above may be obtained by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the invention is open to other equally effective implementations, and that the accompanying drawings illustrate only typical implementations of the invention, and therefore should not be considered as limiting the scope of the invention.

1 is a cross-sectional schematic side view of a processing chamber having an embodiment of a substrate support assembly. FIG. 2 is a schematic cross-sectional view of an electrostatic chuck of a substrate support assembly showing multiple secondary heaters. 1 is a schematic partial side view of a substrate support assembly according to an embodiment; 2 is a schematic partial side view of a substrate support assembly according to another embodiment; 2 is a schematic partial side view of a substrate support assembly according to yet another embodiment;

[0013] For ease of understanding, wherever possible, identical reference numbers have been used to designate identical elements common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific recitation.

[0014] The embodiments described herein provide a substrate support assembly that enables high temperature operation of an electrostatic chuck (ESC) having multiple heaters that generate a microzone effect. Here, a microzone refers to a discrete temperature controllable region of the ESC, and in the embodiments disclosed below, there may be 50 to 150 or more microzones on the ESC. High temperature refers to a temperature above about 150 degrees Celsius, for example, above about 300 degrees Celsius. The embodiments of the substrate support assembly provided below include a cooling plate and an electrostatic chuck separated by a bonding layer and a thermal interface layer. The thermal interface layer is formed of a glass that can generate a temperature gradient across the thermal interface between about 150° C. and about 260° C. The arrangement of the thermal interface between the electrostatic chuck and the cooling base reduces temperature drain and thermal smearing between the microzones in the electrostatic chuck.

[0015] Although the substrate support assembly is described below in an etch processing chamber, the substrate support assembly may be utilized in other types of plasma processing chambers, such as physical vapor deposition chambers, chemical vapor deposition chambers, ion implantation chambers, among others, and other systems in which high temperature (i.e., temperatures greater than 150 degrees Celsius) processing occurs.

[0016] FIG. 1 is a schematic cross-sectional view of an exemplary plasma processing chamber 100 shown configured as an etch chamber having a substrate support assembly 126. The substrate support assembly 126 may be utilized in other types of processing plasma chambers, such as plasma processing chambers, annealing chambers, physical vapor deposition chambers, chemical vapor deposition chambers, and ion implantation chambers, among others, as well as other systems in which the ability to control the processing uniformity of a surface of a workpiece, such as a substrate, is desirable. Control of the dielectric properties tan(δ), i.e., dielectric loss, or ρ, i.e., volume resistivity, of the substrate support assembly 126 in the high temperature range beneficially enables azimuthal processing control, i.e., processing uniformity, of a substrate 124 disposed on the substrate support assembly 126 during processing.

[0017] The plasma processing chamber 100 includes a chamber body 102 having a sidewall 104, and a bottom and lid 108 that enclose an interior processing region 110. An injector 112 is coupled to the sidewall 104 and/or lid 108 of the chamber body 102. A gas panel 114 is coupled to the injector 112 to enable process gases to be provided into the processing region 110. The injector 112 may be one or more nozzles or inlet ports, or alternatively a showerhead. The process gases, along with any process by-products, are removed from the processing region 110 through an exhaust 128 formed in the sidewall 104 or bottom 106 of the chamber body 102. The exhaust 128 is coupled to a pumping system 132. The pumping system 132 includes a throttle valve and a pump that are utilized to control the reduced pressure level in the processing region 110.

[0018] The process gas may be energized to generate a plasma in the processing region 110. The process gas may be energized by capacitively or inductively coupling RF power to the process gas. In one embodiment depicted in FIG. 1, multiple coils 116 are positioned above the lid 108 of the plasma processing chamber 100 and are coupled to an RF power source 120 via a matching network 118. Power applied to the multiple coils 116 inductively couples power to the process gas to generate a plasma in the processing region 110.

[0019] The substrate support assembly 126 is disposed within the processing region 110 below the implanter 112. The substrate support assembly 126 includes an electrostatic chuck (ESC) 174 and a cooling base 130. The cooling base 130 may optionally be supported by a base plate 176. The base plate 176 is supported by one of the sidewalls 104 or the bottom 106 of the processing chamber 100. In addition, the substrate support assembly 126 may include a fixture plate 145 and/or an insulator plate (not shown) disposed between the cooling base 130 and the base plate 176 to facilitate electrical, cooling, and gas connections to the substrate support assembly 126.

[0020] The cooling base 130 is formed from a metallic material or other suitable material. For example, the cooling base 130 may be formed from aluminum (Al). The cooling base 130 includes a cooling channel 190 formed therein. The cooling channel 190 is connected to a heat transfer fluid source 122 by a transfer fluid conduit 192. The heat transfer fluid source 122 provides a heat transfer fluid, such as a liquid, a gas, or a combination thereof, that is circulated through the cooling channel 190 in the cooling base 130. In one embodiment, the heat transfer fluid circulating through the cooling channel 190 of the cooling base 130 maintains the cooling base 130 at a temperature between about 30 degrees Celsius and about 120 degrees Celsius, or at a temperature below 90 degrees Celsius.

The ESC 174 includes one or more chuck electrodes 186 disposed within a dielectric 175. The dielectric 175 has a workpiece support surface 137 and a lower surface 133 opposite the workpiece support surface _137. The dielectric 175 of the ESC 174 is fabricated from a ceramic material, such as alumina ( _Al2O3 ), aluminum nitride (AlN), or other suitable material. Alternatively, the dielectric 175 may be fabricated from a polymer, such as polyimide, polyetheretherketone, polyaryletherketone, or the like.

[0022] The dielectric 175 includes one or more primary resistive heaters 188 embedded therein. The primary resistive heaters 188 may alternatively be located in another portion of the substrate support assembly 126. The primary resistive heaters 188 are utilized to raise the temperature of the substrate support assembly 126 to a suitable temperature for processing a substrate 124 disposed on a workpiece support surface 137 of the substrate support assembly 126. The primary resistive heaters 188 are coupled to a heater power supply 189 through the fixture plate 145. The heater power supply 189 provides power to the primary resistive heaters 188. A controller is utilized to control operation of the heater power supply 189, the heater power supply 189 being generally configured to heat the substrate 124 to a predetermined temperature. In one embodiment, the primary resistive heaters 188 are arranged in a plurality of laterally separated heating zones, and the controller enables at least one zone of the primary resistive heaters 188 to be preferentially heated relative to primary resistive heaters 188 positioned in one or more of the other zones. For example, the primary resistive heaters 188 may be arranged concentrically in a plurality of radially separated primary heater zones (shown in FIG. 1A as items 181). In one embodiment, the primary resistive heaters 188 are arranged in four concentric primary heater zones 181: a first primary heater zone 181 ₁ , a second primary heater zone 181 ₂ , a third primary heater zone 181 ₃ , and a fourth primary heater zone 181 _4. The primary resistive heaters 188 may maintain the substrate 124 at a temperature suitable for processing, for example, between about 180 degrees Celsius and about 500 degrees Celsius, for example, above about 250 degrees Celsius, for example, between about 250 degrees Celsius and about 350 degrees Celsius, or greater.

[0023] The ESC 174 further includes a number of secondary heaters 140. The number of secondary heaters 140 may be an order of magnitude greater than the number of primary resistive heaters 188. The secondary heaters 140 serve to control the temperature of the ESC 174 at a micro level, such as plus or minus 5 degrees Celsius, while the primary resistive heaters 188 control the temperature of the ESC 174 at a macro level. The ESC 174 also has a number of microzones, e.g., 50 to 150 or more microzones, that are temperature controlled by the secondary heaters 140. The secondary heaters 140 generate temperature control within small discrete locations, i.e., microzones, on the ESC 174.

[0024] Briefly referring to FIG. 1A, FIG. 1A is a schematic cross-sectional view of an ESC 174 of a substrate support assembly 126 showing multiple secondary heaters 140. The ESC 174 shows one embodiment of multiple secondary heaters 140. The secondary heaters 140 may be arranged in a pattern to efficiently generate a thermal profile along a surface of the substrate support assembly 126. The pattern may be symmetrical about a midpoint while providing clearance in and around the holes 128 for lift pins or other mechanical, fluidic, or electrical connections. The secondary heaters 140 are arranged in multiple cells, or microzones 199. Each secondary heater 140 is considered to occupy a respective single microzone 199. A thermal choke 118 is disposed between each adjacent microzone 199. In addition, the thermal choke 118 may be disposed along the periphery of the ESC 174. The thermal chokes 118 limit heat transfer from adjacent microzones to prevent thermal smearing and true thermal control of each microzone 199 by its respective secondary heater 140.

The number of microzones 199 shown is for illustrative purposes only, and it is contemplated that the number of microzones 199 may be more than 50 zones, such as 150 or more. Thus, the number of secondary heaters 140 positioned throughout the substrate support assembly 126 may easily exceed several _hundred . Each microzone 199 of the secondary heater 140 occupies a single one of the primary heater zones 181. The boundaries or thermal chokes 118 of the microzones 199 coincide with the boundaries 182 of the respective primary heater zones 181, e.g., the first primary heater zone 181-1, such that the microzones 199 are contained entirely within only the first primary heater zone _181-1 and do not extend into the second primary heater zone _181-2 .

[0026] Each secondary heater 140 has a resistor 191 that terminates in a terminal. When current enters one terminal and exits the other, it travels through the resistor wire from terminal to terminal, generating heat. The amount of heat released by resistor 191 is proportional to the square of the current passing through it. The power design density may be between about 1 Watt/cell and about 100 Watts/cell, for example, 10 Watts/cell.

[0027] The resistors 191 may have a film thickness and wire thickness configured to efficiently provide heat when a current is passed along the resistors 191. Increasing the wire thickness of the resistors 191 may result in a decrease in the resistance R of the resistors 191. The wire thickness may range from about 0.05 mm to about 0.5 mm for tungsten wire and from about 0.5 mm to about 1 mm for nichrome wire. Recalling the formula R=ρ·l/A, it can be seen that the material, wire length, and wire thickness for the resistors 191 may be selected to control the cost, power consumption, and heat generated by each secondary heater 140. In one embodiment, the resistors 191 are constructed of tungsten with a wire thickness of about 0.08 mm and a resistance of about 90 ohms at 10 watts of power.

[0028] Referring back to FIG. 1, each secondary heater 140 may be controlled by a controller 142. The controller 142 may turn on a single secondary heater 140 or multiple secondary heaters grouped together. In this manner, temperature may be precisely controlled at independent locations along the microzones 199 formed within the ESC 174. Such independent locations are not limited to concentric rings as known in the art. Although the illustrated pattern is made up of smaller units, the pattern may alternatively have larger and/or smaller units, extend to the edges, or have other configurations to form 150 or more discrete microzones 199.

[0029] The ESC 174 generally includes a chuck electrode 186 embedded within a dielectric 175. The chuck electrode 186 may be configured as a unipolar or bipolar electrode, or other suitable arrangement. The chuck electrode 186 is coupled through an RF filter to a chuck power supply 187, which provides DC power for electrostatically clamping the substrate 124 to the workpiece support surface 137 of the ESC 174. The RF filter prevents RF power utilized to generate a plasma (not shown) in the plasma processing chamber 100 from damaging electrical equipment or causing electrical disturbances outside the chamber.

[0030] The workpiece support surface 137 of the ESC 174 includes gas passages (not shown) for providing a backside heat transfer gas to a gap space defined between the substrate 124 and the workpiece support surface 137 of the ESC 174. The ESC 174 also includes lift pin holes for receiving lift pins (not shown) for raising and lowering the substrate 124 above the workpiece support surface 137 of the ESC 174 to facilitate robotic transfer in and out of the plasma processing chamber 100.

[0031] A bonding layer 150 is disposed below the ESC 174 and secures the ESC 174 to the cooling base 130. In another embodiment, the bonding layer 150 is disposed between the ESC 174 and a lower plate disposed between the ESC 174 and the cooling base 130. The bonding layer 150 may include a glass material or may be formed from a glass plate. For example, the bonding layer 150 may include nickel gallium oxide (NGO), silicon oxide, polyimide, silicon, or other suitable material. The bonding layer 150 provides a thermal insulation layer between the ESC 174 and the cooling base 130 and improves the hot microzone effect by reducing heat loss from the microzone 199 to the cooling base 130. The bonding layer 150 may have a thermal conductivity between about 0.1 W/mK and about 5 W/mK. The composition of the bonding layer 150 is selected to compensate for differences in thermal expansion between the ESCs 174 and underlying portions of the substrate support assembly 126, such as the cooling base 130. The bonding layer 150 may be formed from a polymer instead of silicone for high temperature applications, such as substrate processing above 300 degrees Celsius. The bonding layer 150 is formed from a glass material with the same thermal expansion and thermal conductivity to reduce bowing due to mismatch or temperature gradients between the ESCs 174 and the cooling base 130.

[0032] Figure 2 is a schematic partial side view of a substrate support assembly 200 according to one embodiment. The substrate support assembly 200 may be utilized in the processing chamber 100 described above in place of the substrate support assembly 126. The substrate support assembly 200 is formed from a stack of layers including a ceramic ESC 210, a metal bond 220, a ceramic plate 230, a thermal interface layer 240, and a cooling base 250. The cooling base 250 may be substantially similar to the cooling base 130 shown in Figure 1. The ceramic ESC 210 is configured to operate at temperatures up to and exceeding 300 degrees Celsius. The substrate support assembly 200 utilizes the thermal interface layer 240 to reduce heat transfer between the ESC 210 and the cooling base 250 while preventing warping, bowing, or other undesirable thermally induced movements in the stack of layers forming the substrate support assembly 200. The thermal interface layer 240 also inhibits the cooling base 250 from smearing the discrete temperature microzones 199 within the ESC 210. For example, the thermal interface layer 240 inhibits heat transfer from the secondary heater 140 to the cooling base 250 instead of the microzones 199 along the workpiece support surface 137.

[0033] The ceramic ESC 210 has a substrate support surface 212 and a lower surface 214. The ceramic ESC 210 has a body formed from a ceramic material, such as alumina, or other suitable material. The ceramic ESC 210 has a first coefficient of thermal expansion. The ceramic ESC 210 has one or more electrodes 202 and a plurality of heaters 204 disposed within the body. The electrode 202 is configured to chuck a substrate to the substrate support surface 212. The plurality of heaters 204 include secondary heaters for discretely heating the substrate support surface 212 and thus generating a plurality of microzones 199 for discretely heating a substrate supported on the substrate support surface 212.

[0034] The metal bond 220 has an upper surface 222 and a lower surface 224. The upper surface 222 is placed in contact with the lower surface 214 of the ESC 210. The lower surface 224 is placed in contact with the ceramic plate 230. The metal bond 220 may also act as an RF electrode to supplement or replace the electrode 202. The metal bond 220 may be in sheet form. The metal bond 220 may have one or more holes 225 formed therein. The material of the metal bond 220 may extend into one or more flaps 221 from which the holes 225 are formed. For example, the metal bond 220 may have one or more small openings in a circular pattern such that when the flaps 221 are extruded from the sheet of metal bond 220, e.g., orthogonally, out of a plane, the openings form the flaps 221 surrounding the holes 225. Connections that allow the metal bond 220 to act as an RF electrode are described below.

[0035] The ceramic plate 230 has an upper surface 232 and a lower surface 234. The upper surface 232 is in contact with the lower surface 224 of the metal bond 220. The lower surface 234 is in contact with the thermal interface layer 240. A cavity 235 having a sidewall 231 is formed in the ceramic plate 230 through the upper surface 232. A hole 238 extends from a bottom of the cavity 235 and exits the lower surface 224 of the ceramic plate 230. A flap 221 of the metal bond 220 extends below the sidewall 231 of the cavity 235. The ceramic plate 230 may be formed from alumina or other suitable material. The ceramic plate 230 has a second coefficient of thermal expansion, i.e., a coefficient of expansion that is greater along the thickness of the ceramic plate 230. The second coefficient of thermal expansion of the ceramic plate 230 is equal to or greater than the first coefficient of thermal expansion of the ESC 210.

Alternatively or additionally, the coefficient of thermal expansion increases from the ESCs 210 to the ceramic plate 230. The second coefficient of thermal expansion, which is higher than the first coefficient of thermal expansion, prevents the substrate support assembly 200 from bending when it is heated. In some embodiments, the secondary heater 140 may be disposed in the ceramic plate 230 instead of the ESCs 210. In another embodiment, the secondary heater 140 is disposed in the ESCs 210 and the primary resistive heater 188B is positioned in the ceramic plate 230. In yet another embodiment, the ceramic plate 230 is formed from a first ceramic plate 230A and a second ceramic plate 230B. The first ceramic plate 230A and the second ceramic plate 230B are formed from the same material selection as the ceramic plate 230, such as AlO or _Al2O3 . However, it should be understood that the first ceramic plate 230A and the second ceramic plate _230B do not have to be formed from the same material. In one embodiment, the first ceramic plate 230A and the second ceramic plate 230B have a thickness between about 5 mm and about 7 mm. The first ceramic plate 230A and the second ceramic plate 230B do not have to have the same thickness. For example, the first ceramic plate 230A may have a thickness of about 6 mm and the second ceramic plate 230B may have a thickness of about 6.5 mm. A second metal bond 220B bonds the first ceramic plate 230A and the second ceramic plate 230B. The second metal bond 220B is considered to be similar to the metal bond 220. However, the second metal bond 220B may comprise Al or other materials that are separate and different from the metal bond 220. The primary resistive heater 188B may have four zones and may be disposed within the first ceramic plate 230A or the second ceramic plate 230B. In one embodiment, the primary resistive heater 188B is disposed in the second ceramic plate 230B. In one such embodiment, the secondary heater is disposed in the ESC 210, the gas distribution is disposed in the first ceramic plate 230A, and the four zone primary heater 188 is disposed in the second ceramic plate 230B.

[0037] The metal bond 220 does not extend the entire length of the ceramic plate 230 or the ceramic ESC 210. A first gap 270 extends between the outer edge of the metal bond 220 and the outer periphery of the ceramic ESC 210 and the ceramic plate 230. The first gap 270 is sized to receive a seal 292, or O-ring or the like. The seal 292 forms a hermetic seal between the ceramic ESC 210 and the ceramic plate 230. The seal 292 protects the metal bond 220 from exposure to plasma and chemicals present in the processing chamber environment, thereby extending the life of the metal bond 220.

[0038] In one embodiment, the thermal interface layer 240 may be formed from _SiO2 , NGO, or other suitable material. The thermal interface layer 240 may be similar to the metal bond layer 220 and may include an interface gasket 245. The interface gasket 245 is made of one or more of a flexible graphite sheet, such as GRAFOIL™, polyimide, or metal, or silicone, or fluoropolymer. The interface gasket 245 has a thickness ranging between about 0.1 mm and about 2 mm. The interface gasket 245 tolerates a temperature difference of up to 300 degrees Celsius between the ceramic plate 230 and the cooling base 250 without bowing or cracking in the ceramic plate 230.

[0039] The thermal interface layer 240 has an upper surface 242 and a lower surface 244. The upper surface 242 is in contact with the lower surface 234 of the ceramic plate 230. The lower surface 244 may include an interface gasket 245 and is sized similarly to the cooling base 250 and disposed on the cooling base 250. The thermal interface layer 240 has a thermal conductivity of about 0.2 W/mK to about 4 W/mK. Thus, the temperature differential across the thermal interface layer 240 may be between 100 degrees Celsius and 300 degrees Celsius, e.g., 200 degrees Celsius. The thermal interface layer 240 prevents smearing of the heater microzone effect in the ceramic ESC 210 by insulating heat loss from the microzone 199 to the cooling base 250. The thermal interface layer 240 includes a glass or insulating layer for high temperatures, such as 300 degrees Celsius or higher. The thermal interface layer 240 may have a thickness ranging between about 1/4 mm and about 2 1/2 mm.

[0040] The cooling base 250 has a plurality of cooling channels through which a cooling fluid is circulated during operation. The cooling base 250 has an upper surface 252 that contacts the lower surface 244 of the thermal interface layer 240. The cooling base 250 and the thermal interface layer 240 have an outer diameter 255. The outer diameter 255 is less than the outer periphery 201 of the ESC 210 by a distance 271. The cooling base 250 has a convection cooling cavity 950. The cooling base 250 has a plurality of cooling channels through which a cooling fluid flows to regulate the temperature of the cooling base 250. The cooling base 250 regulates the temperature of the substrate support assembly 200 by flowing a coolant therein to maintain the temperature of the cooling base 250 by removing heat with the cooling fluid. The convection cooling cavity 950 is maintained at a temperature similar to, such as about 60° C., by the coolant flowing through the cooling base 250. Additionally, the cooling base 250 prevents the high temperatures generated by the heater 204 in the ceramic ESC 210 from causing thermal damage to the equipment plate and lower components of the substrate support assembly 200.

[0041] Below the cooling base 250, an equipment plate 260 is disposed. The equipment plate 260 has an upper top surface 263, a lower top surface 265, and a lower surface 283. A protrusion 277 extends to the upper top surface 263. The upper top surface 263 is disposed in contact with the ceramic plate 230. The equipment plate 260 has a seal groove 269 disposed in the upper top surface 263. Alternatively, the seal groove 269 may be formed in the lower surface 234 of the ceramic plate 230. A gasket 294 is disposed in the seal groove 269 to provide an airtight seal between the ceramic plate 230 and the equipment plate 260. The protrusion 277 has an inner diameter 261. The inner diameter 261 extends from the lower top surface 265 to the upper top surface 263. The cooling base 250 is disposed on the lower upper surface 265 and has an outer diameter 261 that extends to the inner diameter 261 of the equipment plate 260.

[0042] The facilities plate 260 is formed from aluminum, an aluminum alloy, or other suitable material. Electrical connections that provide power to the electrodes, heaters, and various components of the substrate support assembly 200 extend through the facilities plate 260. The facilities plate 260 has through holes 268 extending therethrough. The through holes 268 align with the holes 238 in the ceramic plate 230. A recess 267 is formed in a lower surface 283 of the facilities plate 260 and is aligned with the through holes 268.

[0043] An insert 284 is provided in the cavity 235 of the ceramic plate 230. A fastener 281 has a head 282. The fastener 281 is configured to extend through the through hole 268 to the insert 284 in the cavity 235. The head 282 of the fastener 281 fits into the recess 267 of the equipment plate 260, adjacent the through hole 268, and does not extend into the through hole 268. The insert 284 is configured to receive the fastener 281 for securing the ceramic plate 230 to the equipment plate 260. The insert 284 may be formed from a conductive material such as molybdenum, stainless steel, aluminum, or other suitable material. The insert 284 is in contact with the flap 221 of the metal bond 220. In this manner, the fasteners 281 formed from a conductive material may provide an RF connection to the metal bond 220 when the metal bond 220 acts as an electrode. In other embodiments, the ceramic plate 230 is metallized by coating or other techniques. The metallized ceramic plate 230 may act as an electrode with the fasteners 281 forming an RF connection to provide power to the ceramic plate 230.

[0044] A micro-zone connector 910 is coupled to the secondary heater 140 in the ESC 210. The micro-zone connector 910 provides power and control to each individual secondary heater 140 to control the heat output at each micro-zone 199. The micro-zone connector 910 extends from the secondary heater 140 at a first end 911 to a convection cooling cavity 950 at a second end 912 of the micro-zone connector 910. The temperature of the convection cooling cavity 950 may be maintained at approximately 60° C. to provide cooling to components disposed therein. The temperature of the first end 911 of the micro-zone connector 910 may be 300° C. or higher. The temperature of the second end 912 of the micro-zone connector 910 may be approximately 60° C. Thus, the micro-zone connector 910 may experience a temperature drop, temperature difference of more than 200° C. from the first end 911 to the second end 912 of the micro-zone connector 910.

[0045] FIG. 3 is a schematic partial side view of a substrate support assembly 300 according to another embodiment. The substrate support assembly 300 may be utilized in the processing chamber 100 described above in place of the substrate support assembly 126. The substrate support assembly 300 is formed from a stack of layers including a ceramic ESC 310, an insulating bond 320, a bonding layer 340, and a cooling base 350. Here, in FIG. 3, the substrate support assembly 300 is shown exploded, i.e., the insulating bond 320 is shown separated from the bonding layer 340, but it should be understood that the insulating bond 320 and the bonding layer 340 are actually in contact with each other. The embodiment of FIG. 3 provides a simple stack design capable of operating at high temperatures.

[0046] The ceramic ESC 310 is configured to operate at temperatures up to and beyond 300 degrees Celsius. The substrate support assembly 300 utilizes insulating bonds 320 to reduce the temperature profile between the ceramic ESC 310 and the cooling base 350 while preventing warping, bowing, or other undesirable thermally induced movements in the stack of layers forming the substrate support assembly 300.

[0047] The ceramic ESC 310 has a substrate support surface 312 and a lower surface 314. The ceramic ESC 310 has a body formed from a ceramic material, such as alumina, or other suitable material. The ceramic ESC 310 has one or more electrodes 302 and a number of heaters 304 disposed within the body. The electrode 302 is configured to chuck a substrate to the substrate support surface 312. The number of heaters 304 may include primary and secondary heaters to generate a number of zones for discretely heating the substrate support surface 312, and thus a substrate supported on the substrate support surface 312.

[0048] The insulating bond 320 has an upper surface 322 and a lower surface 324. The upper surface 322 is disposed in contact with the lower surface 314 of the ESC 310. The lower surface 324 is disposed in contact with the bonding layer 340. The insulating bond 320 may include a metal on the top or bottom having a thermal conductivity of about 0.2 W/mK to about 4 W/mK. Thus, the temperature differential across the insulating bond 320 may be between about 150 degrees Celsius and about 260 degrees Celsius, for example, about 200 degrees Celsius. The insulating bond 420 includes a glass or insulating layer for high temperatures, such as 300 degrees Celsius or higher. The insulating bond 320 may be formed of _SiO2 , NGO, or other suitable material. The insulating bond 320 may have a thickness ranging between about ¼ mm to about 2½ mm.

[0049] The bonding layer 340 has an upper surface 342 and a lower surface 344. The upper surface 342 is in contact with the lower surface 324 of the insulating bond 320. The lower surface 344 is disposed on a cooling base 350. The bonding layer 340 may be formed of silicone or other suitable material suitable for operation at a temperature of about 200 degrees Celsius. The bonding layer 340 has a thermal conductivity of about 0.2 W/mK to about 1.5 W/mK, for example, about 0.9 W/mK. The bonding layer 340 may have a temperature drop from the upper surface 342 to the lower surface 344 of about 200 degrees Celsius. The bonding layer 340 is a low temperature bond having a thickness between about 0.1 mm and about 1.0 mm, for example, about 0.3 mm. The bonding layer 340 additionally insulates the secondary heater 140 from the cooling base 350, for example, to help prevent smearing of the heater microzone effect in the ceramic ESC 310.

[0050] The cooling base 350 has a plurality of cooling channels through which a cooling fluid flows. The cooling base 350 is formed from aluminum or other suitable metal or metal alloy. The cooling base 350 has an upper surface 352 and a lower surface. The upper surface 352 of the cooling base 350 is in contact with the bonding layer 340. The cooling base 350 is provided to regulate the temperature of the substrate support assembly 300. In addition, the cooling base 350 prevents high temperatures generated from the heater 304 in the ceramic ESC 310 from causing thermal damage to the equipment plate and lower components of the substrate support assembly 300. Additionally, in some embodiments, the cooling base 350 acts as an RF electrode and may be coupled to a power source to energize the RF electrode.

[0051] The insulating bond 320 does not extend the entire length of the cooling base 350. A first gap 370 extends between an outer edge of the insulating bond 320 and the outer periphery of the ceramic ESC 310. Similarly, the bonding layer 340 does not extend the entire length of the cooling base 350. A second gap 372 extends between an outer edge of the bonding layer 340 and the outer periphery of the cooling base 350. The first gap 370 and the second gap 372 may be substantially similar in size such that a seal 392, such as an O-ring, may fit therein when the bonding layer 340 and the insulating bond 320 are placed together in forming the substrate support assembly 300. The seal 392 disposed between the ceramic ESC 310 and the cooling base 350 protects the bonding layer 340 and the insulating bond 320 from exposure to plasma and chemicals present in the processing chamber environment, thus extending the life of the bonding layer 340 and the insulating bond 320.

[0052] Figure 4 is a schematic partial side view of a substrate support assembly 400 according to yet another embodiment. The substrate support assembly 400 may be utilized in the processing chamber 100 described above in place of the substrate support assembly 126. The substrate support assembly 400 is formed from a stack of layers including the ceramic ESC 210, the metal bond 220, the ceramic plate 230, the thermal interface layer 440, the cooling base 450, and the fixture plate 460. The ceramic ESC 210, the metal bond 220, and the ceramic plate 230 may be substantially similar to those described above with respect to Figure 2. In addition, a heater configuration in an embodiment in which the ceramic plate 230 is divided into a first ceramic plate 230A and a second ceramic plate 230B is additionally considered. The thermal interface layer 440 may include the interface gasket 245 described above with respect to the thermal interface layer 240. The substrate support assembly 400 utilizes a thermal interface layer 440 to reduce heat transfer between the ESC 210 and the cooling base 450 while preventing warping, bowing, or other undesirable thermally induced movements in the stack of layers forming the substrate support assembly 400. The thermal interface layer 440 further inhibits the cooling base 450 from smearing discrete temperature microzones 199 within the ESC 210.

[0053] The thermal interface layer 440 has an upper surface 442 and a lower surface 444. The upper surface 442 is in contact with the lower surface 234 of the ceramic plate 230. The lower surface 444 is sized similarly to the cooling base 450 and is disposed on the cooling base 450. The thermal interface layer 440 may be formed from a high temperature polymer such as polyimide or other suitable material. The thermal interface layer 440 prevents smearing of the heater microzone effect in the ceramic ESC 210 by insulating heat loss from the microzone 199 to the cooling base 450. The thermal interface layer 440 may have a thickness ranging between about ¼ mm and about 2½ mm.

[0054] The thermal interface layer 440 does not extend the entire length of the ceramic plate 230 or the cooling base 450. The outer edge of the thermal interface layer 440 is spaced from the outer periphery of the ceramic plate 230 and the cooling base 450, as is the gap 270. The gap 470 is sized to receive a gasket 494, or an O-ring or the like. The seal 494 forms an airtight seal between the ceramic plate 230 and the cooling base 450. The gasket 494 protects the thermal interface layer 440 from exposure to plasma and chemicals present in the processing chamber environment.

[0055] The cooling base 450 has a plurality of cooling channels through which a cooling fluid is circulated during operation. The cooling base 450 has an upper surface 452 in contact with the lower surface 444 of the thermal interface layer 440. The cooling base 450 has a plurality of cooling channels through which a cooling fluid flows to regulate the temperature of the cooling base 450. The cooling base 450 regulates the temperature of the substrate support assembly 400 by flowing a coolant therein to maintain the temperature of the cooling base 450 by removing heat with the cooling fluid. Additionally, the cooling base 450 prevents high temperatures generated from the heater 204 in the ceramic ESC 210 from causing thermal damage to the equipment plate 460 and lower components of the substrate support assembly 400.

[0056] The cooling base 450 has a hole 458 and a first through hole 451. The hole 458 may be a blind threaded hole, a nut, or other type of hole with a fastener disposed therein. The through hole 451 aligns with the hole 238 of the ceramic plate 230. The fastener 498 is configured to extend through the first through hole 451 to the insert 284 in the cavity 235 of the ceramic plate 230. The fastener 498 secures the ceramic plate 230 to the cooling base 450. The insert 284 is formed from a conductive material such as molybdenum, aluminum, or other suitable material, and is in contact with the flap 221 of the metal bond 220. The fastener 498 provides a conductive RF connection from a power lead 479 disposed through the equipment plate 460 to the metal bond 220 when the metal bond 220 is an electrode.

[0057] The cooling base 450 further includes a convection cooling cavity 956 as described above with respect to the cooling base 250. The micro-zone connector 910 coupled to the secondary heater 140 in the ESC 210 extends to the convection cooling cavity 956 in the same manner as described above and has a temperature drop of approximately 200° C. from the first end to the second end.

[0058] Below the cooling base 450 is disposed a facility plate 460. The facility plate 460 has an upper surface 462 and a lower surface 464. The upper surface 462 is disposed in contact with the cooling base 450. The facility plate 460 has a seal groove 469 disposed in the upper surface 462. Alternatively, the seal groove 469 may be formed in the lower surface 454 of the cooling base 450. A gasket 496 is disposed in the seal groove 469 to provide an airtight seal between the cooling base 450 and the facility plate 460. The facility plate 460 is formed from aluminum, an aluminum alloy, or other suitable material. Electrical connections that provide power to the electrodes, heaters, and various components of the substrate support assembly 400 extend through the facility plate 460.

[0059] The facility plate 460 has a through hole 468 extending therethrough. The through hole 468 aligns with a hole 458 in the cooling base 450. A recess 467 is formed in the lower surface 464 of the facility plate 460 and aligns with the through hole 468. A fastener 496 has a head 482. The head 482 of the fastener 496 fits within and abuts the facility plate 460. The hole 458 in the cooling base 450 is configured to receive the fastener 496. For example, the hole 458 may be threaded. The fastener 496 secures the cooling base 450 to the facility plate 460.

[0060] In various embodiments described above, the substrate support assembly has an electrostatic chuck with 150 or more heating zones (microzones). The ESC is disposed on a cooling base with one or more layers between them to prevent the ESC from being firmly bonded to the cooling base without flexing. The one or more layers include an insulating layer that prevents heat dissipation from the ESC to the cooling base. Additionally, the insulating layer allows high temperature operation, such as temperatures greater than about 300 degrees Celsius. The insulating layer prevents multiple heater microzones, such as 150 or more microzones on the ESC, from smearing between microzones, thus allowing discrete control of the temperature at each microzone.

[0061] While the above is directed to implementations of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, the scope of which is determined by the claims which follow.

Claims (19)

a first ceramic plate having a workpiece support surface and a lower surface, the first ceramic plate having a plurality of secondary heaters each forming a plurality of microzones;
a second ceramic plate having an upper surface and a lower surface;
a first metallic bonding layer disposed between the lower surface of the first ceramic plate and the upper surface of the second ceramic plate;
a third ceramic plate having an upper portion and a lower portion, the third ceramic plate having a primary heater; and a second metallic bonding layer disposed between the lower surface of the second ceramic plate and the upper portion of the third ceramic plate. The substrate support assembly of claim 1, wherein the primary heater has four individually controlled zones. The second ceramic plate comprises:
The substrate support assembly of claim 2 , further comprising a cavity having an insert disposed therein, the insert configured to receive a fastener. 2. The substrate support assembly of claim 1, further comprising: a cooling base having an upper portion, the upper portion of the cooling base being disposed below the third ceramic plate; and an interface gasket disposed between the third ceramic plate and the cooling base, the interface gasket allowing a temperature differential of up to 300 degrees Celsius between the third ceramic plate and the cooling base without bending or cracking the third ceramic plate. The substrate support assembly of claim 4, wherein the substrate support assembly is configured to have a temperature differential of up to about 300°C between the third ceramic plate and the cooling base. The substrate support assembly of claim 4, wherein the cooling base is an RF electrode. The substrate support assembly of claim 4, wherein the interface gasket is made of one or more of a graphite sheet, a polyimide, a metal, a silicone, or a fluoropolymer. The substrate support assembly of claim 4, wherein the interface gasket has a thickness in the range of between about 0.1 mm and about 2 mm. The substrate support assembly of claim 1 , wherein the first metal bonding layer is an RF electrode, the first metal bonding layer being coupled to an RF power source. The substrate support assembly of claim 1, wherein the first metal bonding layer has a thickness in the range of between about 0.025 mm and about 2 mm. The substrate support assembly of claim 9, wherein the first metal bonding layer and the second metal bonding layer each have a thickness between about 0.1 mm and about 0.6 mm. The substrate support assembly of claim 1, wherein there are at least 150 individual secondary heaters, the secondary heaters being up to about 2 mm from an outer edge of the first ceramic plate. The substrate support assembly of claim 1, wherein the secondary heater in the first ceramic plate is less than about 3 mm from the workpiece support surface. A processing chamber comprising:
a body having a wall and a lid defining an internal processing region;
a substrate support assembly disposed within the internal processing region, the substrate support assembly comprising:
a first ceramic plate having a workpiece support surface and a lower surface, the first ceramic plate having a plurality of secondary heaters each forming a plurality of microzones;
a second ceramic plate having an upper surface and a lower surface;
a first metallic bonding layer disposed between the lower surface of the first ceramic plate and the upper surface of the second ceramic plate;
a third ceramic plate having an upper portion and a lower portion, the third ceramic plate having a primary heater; and a second metallic bonding layer disposed between the lower surface of the second ceramic plate and the upper portion of the third ceramic plate. The processing chamber of claim 14 , wherein the primary heater has four individually controlled zones. 15. The processing chamber of claim 14, further comprising: a cooling base having an upper portion, the upper portion of the cooling base being disposed below the third ceramic plate; and an interface gasket disposed between the third ceramic plate and the cooling base, the interface gasket allowing a temperature differential of up to 300 degrees Celsius between the third ceramic plate and the cooling base without bending or cracking the third ceramic plate. 17. The processing chamber of claim 16 , wherein the substrate support assembly is configured to have a temperature differential of up to about 300°C between the third ceramic plate and the cooling base. 17. The processing chamber of claim 16 , wherein the secondary heater in the first ceramic plate is less than about 3 mm from the workpiece support surface. 17. The processing chamber of claim 16 , wherein the secondary heater within the first ceramic plate is less than about 2 mm from an outer edge of the first ceramic plate.

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