Wafer carrier with independently isolated heater zones

Abstract

A wafer carrier with independently isolated heater zones is described. In one example, the carrier has: a puck for carrying a workpiece to facilitate a manufacturing process; a heater plate having a plurality of thermally isolated blocks, each thermally coupled to the puck and each having a heater to heat a corresponding block of the heater plate; and a cooling plate secured to and thermally coupled to the heater plate, the cooling plate having cooling channels to carry a heat transfer fluid to transfer heat from the cooling plate.

Description

[0001] This application is a divisional application of an application with a filing date of July 23, 2015, application number 201580049952.5 and titled “Wafer carrier with independently isolated heater areas”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Patent Application No. 14 / 614,199, filed on February 4, 2015, entitled “WAFER CARRIER WITH INDEPENDENT ISOLATED HEATER ZONES”, which claims priority to U.S. Provisional Patent Application No. 62 / 032,313, filed on August 1, 2014, entitled “WAFER CARRIER WITH INDEPENDENT ISOLATED HEATER ZONES” and is incorporated herein by reference in its entirety for all purposes. Technical Field

[0004] Embodiments of the present invention relate to the microelectronics manufacturing industry, and more particularly to a temperature controlled chuck for supporting a workpiece during plasma processing. Background Art

[0005] In the manufacture of semiconductor chips, silicon wafers or other substrates are exposed to various processes in various processing chambers. The chambers may expose the wafer to plasma, chemical vapor, metal, laser etching, and various deposition and acid etching processes to form circuits and other structures on the wafer. During these processes, a vacuum chuck or an electrostatic chuck (ESC) may be used to hold the silicon wafer in place. The chuck holds the wafer by generating an electrostatic field to clamp the back side of the wafer to a flat surface or a positioning plate surface of the chuck.

[0006] As the fabrication technology of plasma processing equipment (such as those designed to perform plasma etching of microelectronic devices and the like) advances, the temperature of the wafer during fabrication becomes increasingly important. Wafer chucks have been designed for thermal uniformity across the substrate surface (sometimes referred to as the workpiece). Wafer chucks are also designed for thermal non-uniformity across the wafer substrate surface. Liquid cooling is sometimes used to absorb and remove plasma power heat from the chuck. In some cases, independently controlled heaters are used in multiple zones. This allows for a wider process window under different process and plasma conditions.

[0007] In semiconductor etching processes, the temperature of the wafer during processing affects the rate at which structures on the wafer are etched. Other processes may also have temperature dependencies. For example, this temperature effect exists in conductor etching applications, where very accurate wafer temperature control helps to obtain a uniform etching rate. More accurate thermal performance allows for more accurately formed structures on the wafer. Controlled uniform and non-uniform etching rates across the wafer allow for smaller structures to be formed on the wafer. Thermal performance or temperature control is therefore a factor in reducing the size of transistors and other structures on silicon chips. Summary of the invention

[0008] A wafer carrier with independently isolated heater zones is described. In one example, the carrier has a puck for handling workpieces for a manufacturing process, a heater plate having a plurality of thermally isolated blocks, each of which is thermally coupled to the puck, each of which has a heater to heat a corresponding block of the heater plate, and a cooling plate secured to and thermally coupled to the heater plate, the cooling plate having cooling channels to carry a heat transfer fluid to transfer heat from the cooling plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments of the invention are depicted by way of example and not limitation in the figures of the accompanying drawings, in which:

[0010] Figure 1 A schematic diagram of a plasma etching system including a chuck assembly according to an embodiment of the present invention;

[0011] Figure 2 isometric and cross-sectional views of a portion of an electrostatic chuck for supporting a wafer according to an embodiment of the present invention;

[0012] Figure 3 isometric and cross-sectional views of a portion of an electrostatic chuck with a dielectric puck removed according to an embodiment of the present invention;

[0013] Figure 4 is an isometric bottom view of a heating plate of a susceptor according to an embodiment of the present invention;

[0014] Figure 5 is an isometric exploded and cross-sectional view from above of a susceptor for supporting a wafer according to an embodiment of the present invention;

[0015] Figure 6 According to an embodiment of the present invention Figure 5 An isometric assembled side view of the base;

[0016] Figure 7 is a bottom isometric view of a cooling plate of a susceptor according to an embodiment of the present invention; and

[0017] Figure 8 is a side cross-sectional view of an alternative susceptor for supporting a wafer in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In the following description, many details are set forth; however, it will be apparent to those skilled in the art that the present invention can be implemented without these specific details. In some examples, well-known methods and devices are shown in block diagram form (rather than in detail) to avoid obscuring the present invention. References to "embodiment" or "one embodiment" throughout the specification mean that the specific features, structures, functions or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. Therefore, the appearance of the term "in an embodiment" or "in an embodiment" in various locations throughout this specification does not necessarily refer to the same embodiment of the present invention. In addition, specific features, structures, functions or characteristics may be combined in one or more embodiments in any suitable manner. For example, the first embodiment may be combined with the second embodiment at any place where the specific features, structures, functions or characteristics associated with the two embodiments are not mutually exclusive.

[0019] Unless the content clearly indicates otherwise, the singular forms "a", "an" and "the" as used in the specification of the present invention and the appended claims are also intended to include the plural forms. It will also be understood that the term "and / or" as used herein means and includes any and all possible combinations of one or more of the associated listed items.

[0020] The terms "coupled" and "connected" and derivatives of these terms may be used herein to describe functional or structural relationships between components. It should be understood that these terms are not intended to be synonymous with each other. Instead, in a particular embodiment, "connected" may be used to indicate that two or more elements are in direct physical, optical, or electrical contact with each other. "Coupled" may be used to indicate that two or more elements (with other intermediate elements between the two or more elements) are in direct or indirect physical, optical, or electrical contact with each other, and / or that two or more elements cooperate or interact with each other (e.g., like a cause-and-effect relationship).

[0021] As used herein, the terms "over," "under," "between," and "on" refer to the relative position of a component or material layer with respect to other components or layers where such physical relationship is evident. For example, in the context of material layers, a layer disposed over or under another layer may directly contact the other layer or may have one or more intervening layers. Additionally, a layer disposed between two layers may directly contact the two layers or may have one or more intervening layers. In contrast, a first layer that is "over" a second layer directly contacts the second layer. Similar distinctions may be made in the context of component assemblies.

[0022] Improved cooling plates and improvements to the heater design and bonding of the cooling plates to the puck holding the workpiece have been used to improve temperature uniformity across the surface of the vacuum chuck. However, these designs and processes are still subject to manufacturing variations that can result in significant thermal non-uniformity. For some implementations, a spatial temperature variation of less than + / - 0.3°C across the wafer is desirable. For other embodiments, a difference of a few degrees from the center to the edge of the wafer is desirable.

[0023] In some embodiments, the critical dimensions of features on a wafer are controlled by controlling the temperature of a vacuum chuck. The temperature at the edge of a wafer in a plasma chamber may be much higher than the temperature near the center of the wafer. Additionally, the temperature around the periphery of the wafer may vary due to inconsistencies in the chamber.

[0024] As described herein, a multi-zone vacuum chuck or electrostatic chuck may have multiple independent heater zones. Each heater zone has a heater such as a resistive heater element and a temperature sensor such as a thermocouple or RTD (resistance temperature detector) to independently control the temperature of each heater zone based on active feedback from the sensor. Thermocouples in combination may provide any number of heating zones (from 12 to a higher number such as 64, 128, 256 or more and any number therebetween) using a simple combined heater.

[0025] As described herein, heating and cooling of each region (e.g., each pixel) can be achieved by heating an aluminum heater plate that applies heat to a wafer or other workpiece through a ceramic puck. The aluminum-ceramic interface connects adjacent pixels, but due to the low thermal conductivity of the ceramic puck, relatively little heat is transferred through the ceramic in a lateral or transverse direction between pixels.

[0026] Although the heat flow between pixels is reduced, the heat flux from each resistive heater to the workpiece passes through the bonding layer and the ceramic top plate of the chuck. The heat will be directed through the cylindrical portion of the drilled hole containing each heater, upward along the sidewall of each pixel, and perpendicular to the ceramic top plate. This allows the temperature of each pixel to be controlled independently and accurately. Therefore, the temperature of the workpiece carried by the chuck can be precisely controlled. The workpiece can be maintained at a consistent temperature across the surface of the workpiece, or any desired thermal pattern can be achieved with hotter pixels or cooler pixels as desired.

[0027] Figure 1 FIG. 1 is a schematic diagram of a plasma etching system 100 including a chuck assembly 142 according to an embodiment of the present invention. The plasma etching system 100 may be any type of high performance etching chamber known in the art, such as (but not limited to) the plasma etching chamber manufactured by Applied Materials, Inc., California, USA. DPS AdvantEdge TM G3, or Mesa TM Other commercially available etch chambers may similarly utilize the chuck assembly described herein. Although the exemplary embodiments are described in the context of a plasma etch system 100, the chuck assembly described herein can also be adapted for use with other processing systems used to perform any plasma manufacturing process (e.g., plasma deposition systems, etc.).

[0028] refer to Figure 1, the plasma etching system 100 includes a grounded chamber 105. Processing gas is supplied to the interior volume of the chamber 105 from a gas source 129 connected to the chamber via a mass flow controller 149. The chamber 105 is evacuated via an exhaust valve 151 connected to a high capacity vacuum pump stack 155. When plasma power is applied to the chamber 105, plasma is formed in the processing region above the workpiece 110. The plasma bias power 125 is coupled to the chuck assembly 142 to ignite the plasma. The plasma bias power 125 typically has a low frequency between about 2 MHz and 60 MHz, and the voltage bias power 125 can be, for example, in the 13.56 MHz frequency band. In an exemplary embodiment, the plasma etching system 100 includes a second plasma bias power 126, which operates at about a 2 MHz frequency band, and the 2 MHz frequency band is connected to the RF match 127. The plasma bias power 125 is also coupled to the RF match and also coupled to the lower electrode via a power conduit to supply a drive current 128. The plasma power supply 130 is coupled to the plasma generation element 135 through another match (not shown) to provide a high frequency power supply to inductively or capacitively excite the plasma. The plasma power supply 130 may have a higher frequency than the plasma bias power 125, such as between 100 MHz and 180 MHz, and the plasma power supply 130 may be in the 162 MHz band, for example.

[0029] A workpiece 110 is loaded through opening 115 and is clamped to a chuck assembly 142 inside the chamber. The workpiece 110, such as a semiconductor wafer, may be any wafer, substrate, or other workpiece disposed in semiconductor processing technology, and the present invention is not limited in this regard. The workpiece 110 is disposed on a dielectric layer or on the top surface of a positioning plate of a chuck assembly disposed on a cooling base assembly 144 of the chuck assembly. A clamping electrode (not shown) is embedded in the dielectric layer. In a particular embodiment, the chuck assembly 142 includes a plurality of different electric heater zones (not shown). Each zone may be independently controlled to the same or different temperature set points.

[0030] The system controller 170 is coupled to a variety of different systems to control the manufacturing process in the chamber. The controller 170 may include a temperature controller 175 to execute a temperature control algorithm (e.g., temperature feedback control), and the controller 170 may be software, hardware, or a combination of both. The temperature controller receives temperature information from the thermal sensor 143 in the chuck, and the temperature controller then adjusts the heater and heat exchanger. Although only one thermal sensor is shown, there may be more thermal sensors in a variety of different locations depending on the specific implementation. The system controller 170 also includes a central processing unit 172, a memory 173, and an input / output interface 174. The temperature controller 175 is to output a control signal or drive current 128 to affect the heating rate and therefore the rate of heat transfer between each heating zone of the chuck assembly 142 and the workpiece.

[0031] In an embodiment, there may be one or more coolant temperature zones in addition to different heaters. The coolant zones have heat transfer fluid circuits with flow control that are controlled based on a temperature feedback loop. In an exemplary embodiment, a temperature controller 175 is coupled to a heat exchanger (HTX) / cooler 177 (depending on the specific implementation) via control wiring 176. Control wiring may be used to allow the temperature controller to set the temperature, flow rate, and other parameters of the heat exchanger. The flow rate of the heat transfer fluid or coolant through the conduits in the chuck assembly 142 may alternatively or additionally be controlled by the heat exchanger.

[0032] One or more valves 185 (or other flow control devices) between the heat exchanger / cooler 177 and the fluid conduits in the chuck assembly 142 can be controlled by the temperature controller 175 to independently control the flow rate of the heat transfer fluid. The temperature controller can also control the temperature set point used by the heat exchanger to cool the heat transfer fluid.

[0033] The heat transfer fluid can be a liquid such as (but not limited to) deionized water / ethylene glycol, such as from 3M or from Solvay Solexis fluorinated coolant, or any other suitable dielectric fluid, such as those containing perfluorinated inert polyethers. Although the present specification describes the vacuum chuck in the context of a plasma processing chamber, the principles, structures, and techniques described herein may be used with a wide variety of different workpiece supports in a wide variety of different chambers and for a wide variety of different purposes.

[0034] Figure 2 For supporting a wafer in a chamber (e.g. Figure 1204 is a dielectric puck 204 that is atop the chuck to carry the wafer. The dielectric puck is supported by a top plate 206, which in turn is supported by a cooling plate 208 that is supported by a bottom plate 210. The bottom plate is carried by a shaft (shown in FIG. Figure 5 The chuck may be a vacuum chuck, a pedestal, a carrier, an ESC or a similar type device.

[0035] The shaft and base plate can be made of a variety of different materials, including ceramics, Aluminum and a variety of other materials. Although the present invention will be described in the context of a vacuum chuck 202, the chuck may alternatively use any of a variety of other techniques to hold the wafer against the dielectric puck 204, including electromagnetic forces, electrostatic forces, vacuum, and adhesives.

[0036] The cooling plate has one or more cooling channels 222 to carry cooling liquid through the cooling plate 208. The cooling liquid is supplied through the shaft 212 and is pumped from the shaft to the heat exchanger 177 to control the temperature of the cooling liquid before it is pumped back into the chuck 202. The cooling channels 222 are covered by a cover 224 at the bottom of the cooling plate. The cover 224 can also be used to seal the cooling plate against the base plate 210.

[0037] The cooling channels 222 are arranged in concentric paths that correspond to the concentric rings of the heater blocks 244. This provides for at least one cooling channel in the cooling plate below each heater block. As shown in this cross-sectional view, each heater block 244 has a heater 230 that extends down to a cooling plate with a cylindrical extension 262 with a hole to the cooling plate. The cooling plate has cooling channels on each side of the heater rod. The cooling plate and the heater plate are made of a thermally conductive material such as aluminum. This allows the cooling channels to remove any excess heat. The bottom plate 210 is made of a material with a lower thermal conductivity (such as titanium or ceramic) to prevent the bottom plate from conducting heat across the cooling plate or other components.

[0038] In operation, the heaters provide heat to each zone while the cooling plate removes heat. This prevents any heat buildup so that the temperature of each zone can be reduced simply by reducing the drive current to the heater. The combined effect of the cooling channels and heaters provides independent and accurate control over each heater zone.

[0039] The top sheet has a plurality of slots 228 to carry heaters. In the illustrated example, only one heater 230 is shown and two slots 228 are empty. However, a heater is typically placed in each of the slots 228. As described in detail below, the heaters are resistive heaters that generate heat in response to an applied electrical current. The heaters also include integrated temperature sensors (e.g., thermocouples) to sense heat of the top sheet in the vicinity of the resistive heaters. The heaters are coupled via a wire conduit 232 that is guided through the shaft 212 to receive signals from an external controller (e.g., Figure 1 A second temperature is also sent to the temperature controller via a wire conduit 232 below the shaft so that the temperature of each heater can be adjusted.

[0040] Figure 3 A portion of a vacuum chuck 202 with a dielectric positioning plate 204 removed is shown in cross section. The configuration of the upper surface of the top plate 206 can be easily seen. The top plate can be formed of aluminum or some other thermally conductive material. The top plate can be machined to have grooves and holes as shown in the figure. Because the top plate has multiple grooves 228 and each of the grooves 228 holds an independently controlled heater 230, the top plate acts as a heater plate. The top plate is machined with grooves 242 that form multiple isolated heater blocks 244. The grooves form a thermal isolation barrier between each block or pixel. The grooves can be filled with air, ambient gas in the chamber, or solid insulation or foam material. Each separate block forms a thermally independent island isolated from other blocks by the grooves 242.

[0041] Each block has its own independently controlled heater 230 that applies heat to the blocks. In addition to the independently heated blocks, the cooling plate may also include holes (not shown) for lift pins, purge and other gases, vacuum passages, and for other purposes.

[0042] Each heater 230 may be mounted to a corresponding slot 228 using a friction fit, thermal paste, or any other adhesive. The heater bar may have a cylindrical housing so that the walls of the housing touch the walls of the slot. To get the best control over the heat of each pixel, the heater bar is mounted so that it has good thermal conduction with the rest of the block. This allows the block to heat up quickly. In some cases, the heater bar may contain a temperature sensor, such as a thermocouple or thermal diode. Better thermal conduction between the heater bar and the block will provide a more accurate temperature measurement through the heater bar.

[0043] In another embodiment, the heater rod has no housing but is assembled and mounted to each respective slot. In this case, the heating element of the heater rod (such as a resistive copper winding) is mounted directly in the slot and held in place with a suitable thermally conductive paste or other adhesive. Attaching the heating element or winding directly to the slot provides better thermal conductivity to the respective heater block (but may be more difficult to assemble).

[0044] Each block 244 of the top plate 206 has a heat transfer surface 239 adjacent to the heater rod that directly contacts the cooling plate 208. As shown, the heater transfer surface is located at the bottom end of the heater block extension; however, the invention is not limited to this. The heat transfer surface can be placed in other locations. This surface allows heat transfer from the heating block to the cooling plate. The rest of the block is isolated from the cooling plate by the groove 242. By controlling the size and location of the heat transfer surface, the thermal characteristics of the component can be designed. The two components are joined together using technology on the heat transfer surface to maximize thermal conduction through the connection. In one example, thermal paste is used. In another example, the two surfaces are welded together.

[0045] Relative to the heater plate, the cooling plate 208 does not isolate each of the individual heating zones formed by the blocks of the top plate; however, the invention is not limited in this regard. Each heat zone has a cooling channel 222 of the cover 224 on each of the two opposing sides of the heater rod. In the illustrated embodiment, the coolant channels are approximately aligned with the grooves 242 between each heating zone. Therefore, each zone is heated at the center of each zone and cooled along the sides. This further thermally isolates each zone from each other by placing a cooling area between each zone. In addition, the temperature of each zone is allowed to be reduced so that a specific temperature can be controlled by the heater (rather than the cooling fluid).

[0046] Figure 4 A portion of the top plate 206 (which is the heating plate) is shown in an isometric view from the bottom side. Each of the slots 228 extends from its corresponding thermal isolation block 244 through a cylindrical extension 262, which acts like an axis. The cylindrical extension 262 has a central slot 228 for holding the heater 230. As described below, the cylinder fits inside the corresponding inner diameter of the cooling plate. The heat transfer surface 239 of the cylinder is circular. The heat transfer surface 239 of the cylinder is placed adjacent to the interior of the heater rod, and the heat transfer surface 239 of the cylinder surrounds the heater rod at one end. The heat transfer surface fits into a corresponding countersunk hole 270 in the cooling plate (as shown in FIG. 2A ). Figure 5 The support 263 (as shown in Figure 5As shown from the underside of the heater plate, the grooves 242 between the thermal isolation blocks extend all the way through the cooling plate.

[0047] Figure 5 for Figure 2 2 is an exploded view of a vacuum chuck of FIG. 2. As shown, a main support shaft 212 supports a base plate 210 with an isolator 216 (which is a thermal disconnect) between the support shaft and the base plate. The base plate supports a cooling plate 208. The cooling plate has cooling channels 222 that circulate a coolant fluid through the interior volume of the chuck. After the channels have been milled into the cooling plate, each cooling channel is covered with a cover 224. The cooling plate is typically made of aluminum and then covered with an elastomeric cover for each cooling channel.

[0048] The cooling plate absorbs heat from the embedded heater 230 via the heater plate and from the workpiece via the ceramic top plate or puck 204. Temperature uniformity depends on the quality of the elastomeric bond between the ceramic puck 204, the top surface 205 of the top plate and the puck 204, and the cooling plate channels. The temperature uniformity also depends on how well the heat is transferred from the workpiece to the ceramic puck. All of these factors are subject to variations in manufacturing and use.

[0049] The top surface 205 of the top plate 206 is bonded to the dielectric puck 204 using a high temperature adhesive such as silicone. The puck is typically ceramic; however, other materials may be used to make the puck instead. In the case of an electrostatic chuck, electrodes (not shown) are embedded within the puck to generate an electrostatic field that is used to clamp a workpiece such as a silicone substrate.

[0050] The base plate 210 provides structural reinforcement to the cooling plate 208. The base plate may be formed from a rigid material with poor thermal conductivity. This prevents heat flow between the cooling channels through the base plate. The base plate may be formed from titanium, aluminum, ceramic, stainless steel, nickel, and similar materials. The base plate may be formed from a single sheet or multiple parts welded together. Depending on the particular implementation, the base plate may be bolted, screwed, or riveted to the cooling plate.

[0051] The cooling plate has a cylindrical countersunk hole 270 for each of the cylindrical extensions 262. The cylindrical countersunk holes surround the slots 228, which each extend to a corresponding countersunk hole 270. A central hole extends through the countersunk hole all the way through the cooling plate to allow wires to be made through the cooling plate to the support shaft 212 for electrical connection. Wires for each heater and each thermal sensor pass through the holes of the corresponding countersunk hole 270 and gather around the bottom plate 210 to collect through the support shaft 212 to a conduit (not shown). The top heater plate fits into the coolant plate so that each cylinder passes through a corresponding countersunk hole.

[0052] The cylindrical extension 262 for each heater rod extends to each respective countersunk hole 270 so that the heat transfer surface 239 seats against each countersunk hole's respective protrusion or standoff 263. The surfaces are connected together to facilitate heat transfer between each heater plate block and the cooling plate.

[0053] The base plate 210 is carried on a shaft 212. The shaft is hollow inside and contains conduits for conductors, gases and other materials supplied to the top of the chuck. Isolators 216 are placed between the metal shaft and the metal base plate 210 to reduce heat conduction between the shaft and the base plate. This keeps the shaft cool and also shields heat from any processing mechanisms that may be attached to the shaft.

[0054] Figure 6 for Figure 5 2 is an isometric view of an assembled ESC. A support shaft 212 supports a bottom plate 210 via an isolator 216. A cooling plate 208 and a top plate 206 (which is a heater plate) are carried by the bottom plate. The top plate 206 (which is a heater plate) carries a puck 204 above the top surface 205 of the heater plate. A workpiece (not shown) is in turn carried above the puck and the workpiece may be electrostatically (or otherwise) attached.

[0055] The vacuum chuck as shown and described can independently control the temperature of each of the isolated zones of the heating plate. This allows control of the local area above the top dielectric puck 204; thereby allowing precise control of the temperature of the wafer in each of these small heating zones of the wafer. Heat is controlled primarily by activating the corresponding heater elements in the appropriate heating zone. Each of the zones are thermally isolated from each other by grooves machined into the top heater plate. The individual zones are cooled using coolant and coolant channels that are part of the coolant plate.

[0056] Figure 7208 is a bottom isometric view of a cooling plate 208 to show an example configuration of cooling channels. The cooling channel in use will have a cover 224 (not shown) to seal the channel for the flow of cooling liquid through the cooling plate. The cooling plate is composed of a material with high thermal conductivity so that the heat absorbed by the heater block is conducted and absorbed by the cooling liquid flowing through the channel. In this example, there is an inlet 274 and an outlet 276 to the cooling liquid channel. The inlet and outlet are placed near the middle of the cooling plate to easily enter from the central support shaft through which the cooling liquid fluid is supplied. Other positions can be used for other types of supply configurations. As shown, the cooling liquid flows radially outward from the inlet to the first circular channel 280-1. The countersunk holes 270 for at least some heater elements are visible, and the circular path of the first circular channel 280-1 can be seen to flow between the holes in the first and second rows of the heater block. The path of the channel passes radially outward to the second concentric circular path 280-2 later in the radial section 290-1.

[0057] The second circular path is concentric with the first circular path and the second circular path is between the third and fourth circular rows of thermally isolated blocks. The path runs between blocks on the third and fourth rows for the outermost route of the path and then comes to a second radial section 290-2 that leads the cooling channel to the middle path. A third concentric circle 280-3 runs concentrically around the cooling plate between the second and third rows. The third radial section leads the cooling channel radially inward to the center of the cooling plate to run between the second and third rows of cooling plates. This concentric path 280-3 runs around the cooling plate and has another arm 290-3 that leads the channel to the outlet 276 of the concentric path 280-3. The coolant flows from the outlet down to the central support shaft.

[0058] The type of flow path depicted takes into account that the coolant fluid is cooler when it first enters the cooling plate from the inlet 274 than when it reaches the outlet 276. As the coolant fluid passes through the coolant channels, the coolant fluid absorbs heat from the cooling plate that has been heated by the heater plate above, causing the fluid passing through the path of the coolant fluid to warm. The circular channels alternate between rows so that each individual heater block has coolant channels that flow outward on one side and coolant channels that flow inward on the other side. In other words, coolant fluid flowing along one edge of the block will be cooler than fluid passing along the other edges of the block. It is true that for each coolant block, the overall cooling effect is balanced due to heat conduction through the plates that span each of the blocks.

[0059] A variety of other configurations may be used to facilitate more uniform cooling for all heater zones. The heater zones may be arranged linearly, in curves of different shapes, and in a grid, etc. The heater zones may be rectangular as shown or another shape such as triangular, hexagonal, or a shape with some other number of sides. The heater zones may have curved sides or straight sides. Different configurations may be adapted for different configurations of zones and different coolant configurations. Alternatively (or in addition), there may be a plurality of independent cooling channels, each of which is connected to a different heat exchanger via a support shaft.

[0060] The coolant plate against the heater plate does not necessarily isolate each of the independent heating zones formed by the blocks of the top plate. Figure 7 As shown, the coolant channels may be formed in the shape of concentric rings. Figure 2 As shown, each heater block has a coolant channel on each of two opposing sides. In the depicted embodiment, the coolant channels are substantially aligned with the grooves 242 between each heating area. Thus, each block is heated in its center and cooled along both sides. This further thermally isolates each block from each other by placing cooling areas between each block. Additionally, it allows the temperature of each block to be lowered so that a specific temperature can be controlled by the heater (rather than by the coolant fluid).

[0061] If Figure 7 As suggested by the countersunk holes 270 of FIG. 2 , the isolated blocks 244 are arranged in a concentric pattern around the top sheet. In this example, there are four concentric rings formed by the concentric pattern of blocks. The inner ring of blocks and each outer concentric ring are divided by radial lines separating the blocks from each other. After the first ring of blocks there are more than three circular rings of blocks surrounding each previous ring in a continuous concentric ring manner. Because the diameter of the ring increases towards the edge or perimeter of the sheet, each ring of the block has more blocks than the adjacent more central ring.

[0062] The number of separate and independent heating zones can be configured to suit any particular application and to provide any desired degree of precision. The size and number of these zones can also be adjusted to suit the size of different workpieces. A typical 300 mm wafer in a typical plasma process may have different requirements than another wafer. More zones may be used for more precise thermal control or to allow more heaters to apply more combined total heat to the wafer. Alternatively, fewer zones may be used where less precise control or less overall heating power is desired.

[0063] Figure 8 An alternative configuration for a vacuum chuck assembly is shown. Figure 8In the example of FIG. 1 , a top dielectric positioning plate 904 is carried on top of a top plate 906, which rests on top of a cooling plate 908. The top plate 906 is secured to a bottom plate 910. An edge ring 912 may be used around the edges of all substrates to hold the chuck assembly together. As in the previous example, the heater plate is shown with a plurality of slots 914, seven of which are visible to support heater elements 916. Although only four slots carry heater elements and three do not; as shown, after final assembly, each of the slots will have a heater element that can be independently controlled.

[0064] In this example, the slots are not carried by round holes extending into the cooling plate, but rather by the heater elements resting directly over the cooling plate and the heater elements are not extended into countersunk holes in the cooling plate. Additionally, there are grooves 920 to isolate the heating blocks from each other. The grooves extend two-thirds to three-quarters of the way through the top heater plate (rather than all the way to the end) to the cooling plate. This allows for a higher level of structural rigidity for the heater plate and still provides a significant amount of isolation between each heater block. Coolant channels 922 are provided in a manner similar to the top heater plate. Figure 3 In a similar manner, cooling plate 908 extends around each of heater blocks 924.

[0065] Figure 8 It is shown that the specific proportions, sizes, and shapes of the various elements described herein may be modified to meet different needs for strength, thermal isolation, and thermal control.

[0066] When a workpiece is heated in a plasma chamber, heat from the dielectric puck will be absorbed by the heater plate and cooling plate. The heater plate and cooling plate can be made of a metal with high thermal conductivity, such as aluminum or some other metal. This allows heat to be transferred from the aluminum heating block to the cooling plate and coolant fluid in the cooling channels. The air gap between each portion of the heater plate inhibits heat transfer between each block of the heater plate. Due to this air gap, and because the dielectric puck is a poor thermal conductor, the temperature of the dielectric puck can be divided among all zones.

[0067] Any other low thermal conductivity partition, such as silicone or ceramic, may be used as an alternative between each block. The grooves of the heater plate may be filled with thermally insulating material. This isolates the temperature of each block from each other. The air gap or other thermal barrier layer in the groove reduces thermal interference between the blocks to allow more precise and isolated control of the temperature of each block. Although this article describes an aluminum plate with an air gap between each block, the heater plate can be made of a variety of different materials with high thermal conductivity. The interface between each of the blocks can be an air gap as described, or the gap can be filled with a material with low thermal conductivity such as an adhesive, ceramic, or some other part.

[0068] It should be understood that the above description is also intended to be illustrative; not limiting. For example, although the flowcharts in the figures show a specific order of operations performed by certain embodiments of the present invention, it should be understood that such order is not required (e.g., alternative embodiments may perform operations in a different order, combine certain operations, overlap certain operations, etc.). In addition, numerous other embodiments will immediately become apparent to those skilled in the art once the above description is read and understood. Although the present invention has been described with reference to specific exemplary embodiments, it will be appreciated that the present invention is not limited to the described embodiments and may be implemented with modifications or alternatives within the spirit and scope of the appended claims. Therefore, the scope of the present invention should be determined with reference to the appended claims and the full scope of equivalents to which such claims are assigned.

Claims

1. A plasma processing system, include: a plasma chamber; a plasma source electrically coupled to a showerhead included in the plasma chamber; a workpiece holder in a processing region of the plasma chamber, the workpiece holder having a positioning disk for holding a workpiece, wherein the workpiece holder includes a heater plate having a plurality of separate thermally isolated blocks, each of the plurality of separate thermally isolated blocks being thermally coupled to the positioning disk, wherein each block includes a heater to heat a respective block of the heater plate, and wherein the workpiece holder includes a cooling plate secured to and thermally coupled to the heater plate, the cooling plate including cooling channels configured to distribute a heat transfer fluid to transfer heat from the cooling plate, wherein the heater extends downwardly into the cooling plate and the cooling channels are laterally adjacent to the heater plate; as well as Temperature controller for controlling each heater independently.

2. The plasma processing system of claim 1, It is characterized in that The heater includes a longitudinal resistive heater rod oriented with a longitudinal axis of the longitudinal resistive heater rod perpendicular to a top surface of the puck.

3. The plasma processing system of claim 1, It is characterized in that The sections of the heater plate are thermally isolated from each other by gaps between each section.

4. The plasma processing system of claim 3, It is characterized in that The gap is filled with an insulating material.

5. The plasma processing system of claim 1, It is characterized in that The blocks are arranged in concentric rings across the surface of the heater plate, and wherein the blocks are rectangular, triangular, or hexagonal with straight or curved sides.

6. The plasma processing system of claim 1, It is characterized in that The heater blocks have heat transfer surfaces that are in physical contact with the cooling plate to transfer heat from each respective heater block to the cooling plate.

7. The plasma processing system of claim 6, It is characterized in that The heater block and the cooling plate are formed of aluminum, and the heat transfer surface is welded to the cooling plate.

8. The plasma processing system of claim 6, It is characterized in that The heat transfer surface is adjacent to and surrounds the heater.

9. The plasma processing system of claim 1, further comprising: include: A base plate is fixed to the cooling plate opposite the positioning plate, and wherein the cooling channel is open to the base plate, and the workpiece holder also includes a plurality of seals to seal the cooling channel against the base plate.

10. The plasma processing system of claim 9, It is characterized in that The bottom plate is formed of a material having a lower thermal conductivity than that of the cooling plate.

11. The plasma processing system of claim 10, It is characterized in that The material is selected from titanium, stainless steel, alumina, ceramic and nickel.

12. A plasma processing chamber, include: a chamber housing defining a plasma processing region of the plasma processing chamber; an inlet defined in a top portion of the plasma processing chamber, wherein the inlet is configured to receive a precursor into the chamber; A substrate support comprising: Positioning plate, a heater plate having a plurality of separate thermally isolated blocks, each of which is thermally coupled to the puck, wherein each block includes a heater to heat a corresponding block of the heater plate, and a cooling plate secured to and thermally coupled to the heater plate, the cooling plate defining cooling channels configured to distribute a heat transfer fluid to transfer heat from the cooling plate, wherein the heater extends downwardly into the cooling plate and the cooling channels are laterally adjacent to the heater plate; as well as Temperature controller for controlling each heater independently.

13. The plasma processing chamber of claim 12, It is characterized in that The heater includes a longitudinal resistive heater rod oriented with a longitudinal axis of the longitudinal resistive heater rod perpendicular to a top surface of the puck.

14. The plasma processing chamber of claim 12, It is characterized in that The sections of the heater plate are thermally isolated from each other by gaps between each section.

15. The plasma processing chamber of claim 14, It is characterized in that The gap is filled with an insulating material.

16. The plasma processing chamber of claim 12, It is characterized in that The blocks are arranged in concentric rings across the surface of the heater plate, and wherein the blocks are rectangular, triangular, or hexagonal with straight or curved sides.

17. The plasma processing chamber of claim 12, It is characterized in that The heater blocks have heat transfer surfaces that are in physical contact with the cooling plate to transfer heat from each respective heater block to the cooling plate.

18. The plasma processing chamber of claim 17, It is characterized in that The heater block and the cooling plate are formed of aluminum, and the heat transfer surface is welded to the cooling plate.

19. The plasma processing chamber of claim 17, It is characterized in that The heat transfer surface is adjacent to and surrounds the heater.

20. A processing chamber, include: a chamber housing defining a plasma processing region of the processing chamber; an inlet defined at a top of the processing chamber, wherein the inlet is configured to receive a precursor into the chamber; A substrate support comprising: Positioning plate, a heater plate having a plurality of separate thermally isolated blocks, each of which is thermally coupled to the puck, wherein each block includes a heater to heat a corresponding block of the heater plate, and a cooling plate thermally coupled to the heater plate, the cooling plate defining cooling channels configured to distribute a heat transfer fluid to transfer heat from the cooling plate, wherein the heater extends downwardly into the cooling plate and the cooling channels are laterally adjacent to the heater plate; a temperature controller for independently controlling each heater; and A showerhead is positioned within the chamber housing, wherein the showerhead is electrically coupled to a plasma source configured to generate plasma within the processing chamber.

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