Screwed wafer chuck thermal management system and method for wafer processing system

Abstract

A workpiece holder includes a puck, first and second heating devices in thermal communication with respective inner and outer portions of the puck, and a heat sink in thermal communication with the puck. The first and second heating devices are independently controllable and are in greater thermal communication with the puck than the heat sink is in thermal communication with the puck. A method of controlling a temperature profile of a workpiece includes flowing a heat exchange fluid through a heat sink to establish a reference temperature for a puck, raising temperatures of radially inner and outer portions of the puck to first and second temperatures greater than the reference temperature by activating respective first and second heating devices disposed in thermal communication with the radially inner and outer portions of the puck, and placing the workpiece on the puck.

Description

[0001] This application is a divisional application of 201680021497.2, filed August 4, 2016, entitled "Screw-on wafer clamp thermal management system and method for wafer processing system." TECHNICAL FIELD

[0002] The present disclosure has broad applicability in the field of processing equipment. More specifically, systems and methods for providing spatially tailored processing on a workpiece are disclosed. BACKGROUND

[0003] Integrated circuits and other semiconductor products are typically fabricated on the surface of a substrate, referred to as a "wafer." Sometimes processing is performed on groups of wafers held in carriers, while at other times processing and testing are performed on one wafer at a time. When performing a single wafer process or test, the wafer can be positioned on a wafer clamp. Other workpieces can also be processed on similar clamps. The clamps can be temperature controlled to control the temperature of the workpiece for processing. SUMMARY

[0004] In an embodiment, a workpiece holder positions a workpiece for processing. The workpiece holder includes a substantially cylindrical platen, a first heating device disposed in thermal communication with a radially inner portion of the platen, a second heating device disposed in thermal communication with a radially outer portion of the platen, and a heat sink disposed in thermal communication with the platen. The first and second heating devices are independently controllable relative to one another, and the first and second heating devices are in a greater respective degree of thermal communication with the platen than the heat sink is in thermal communication with the platen.

[0005] In an embodiment, a method of controlling a spatial temperature profile of a workpiece includes the steps of providing a reference temperature to a substantially cylindrical platen by flowing a heat exchange fluid through a channel in a heat sink in thermal communication with the platen at a controlled temperature, raising a temperature of a radially inner portion of the platen to a first temperature greater than the reference temperature by activating a first heating device disposed in thermal communication with the radially inner portion of the platen, raising a temperature of a radially outer portion of the platen to a second temperature greater than the reference temperature by activating a second heating device disposed in thermal communication with the radially outer portion of the platen, and placing the workpiece on the platen.

[0006] In an embodiment, a workpiece holder to position a workpiece for processing includes a substantially cylindrical puck characterized by a cylindrical axis and a substantially planar top surface. The puck defines two radial thermal breaks. A first thermal break is characterized as a radial notch that intersects a bottom surface of the puck at a first radius and extends through at least half of a thickness of the puck from the bottom surface. A second thermal break is characterized as a radial notch that intersects the top surface of the puck at a second radius that is greater than the first radius and extends through at least half of the thickness of the puck from the top surface. The first and second thermal breaks define a demarcation between a radially inner portion of the puck and a radially outer portion of the puck. The puck includes a first heating device embedded within the radially inner portion of the puck and a second heating device embedded within the radially outer portion of the puck. The workpiece holder also includes a heat sink that extends substantially below the bottom surface of the puck, the heat sink including a metal plate that flows a heat exchange fluid through channels defined in the metal plate to maintain a reference temperature for the puck. The heat sink is mechanically and thermally coupled with the puck at attachment points that provide a degree of thermal communication between the heat sink and the puck that is less than a degree of thermal communication between each of the first and second heating devices and the puck. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 The main elements of a processing system having a workpiece holder according to an embodiment are schematically illustrated.

[0008] Figure 2 An exemplary construction detail of a workpiece holder is illustrated, for illustrative cross-sectional view. Figure 1

[0009] Figure 3 A portion of a wafer chuck according to an embodiment is illustrated, for illustrative cross-sectional view, to illustrate features of a puck, resistive heaters, and a heat sink. Figure 1

[0010] Figure 4 A portion of a wafer chuck according to an embodiment is illustrated, for illustrative cross-sectional view, to illustrate features of a puck, resistive heaters, and a heat sink.

[0011] Figure 5 The underside of a puck having cable heaters mounted therein as inner and outer resistive heaters according to an embodiment is schematically illustrated.

[0012] Figure 6A A detailed view of a portion of a puck and optional heat sink of Figure 4 near a fixture.

[0013] ​​Figure 6B An embodiment of a wave washer in an uncompressed state is schematically illustrated in accordance with an embodiment.

[0014] Figure 6C Provided Figure 6A An upward looking plan view of the positioning disk and optional heat sink illustrated in the middle.

[0015] Figure 7 A lift pin mechanism disposed within a thermal break is schematically illustrated in accordance with an embodiment.

[0016] Figure 8 Three lift pin arrangements in a plan view are schematically illustrated in accordance with an embodiment, wherein the lift pins are disposed within a thermal break.

[0017] Figure 9 A flowchart for a method for processing a wafer or other workpiece in accordance with an embodiment.

[0018] Figure 10 A flowchart for a method comprising, but not limited to Figure 9 A step of the method of

[0019] Figure 11 A flowchart for a method comprising, but not limited to Figure 9 Another step of the method of DETAILED DESCRIPTION

[0020] The present disclosure can be understood through the following detailed description in conjunction with the accompanying drawings in which like reference characters denote like elements throughout the several views, in which:

[0021] Figure 1The major components of a wafer processing system 100 are schematically illustrated. The system 100 is depicted as a single wafer, semiconductor wafer, plasma processing system, but it will be apparent to those skilled in the art that the techniques and principles herein can be applied to any type of wafer processing system (e.g., not necessarily processing wafers or semiconductors and not necessarily a system that utilizes plasma for processing). The processing system 100 includes a housing 110 for a wafer interface 115, a user interface 120, a plasma processing unit 130, a controller 140, and one or more power supplies 150. The processing system 100 is supported by various utilities, which can include gases (plural) 155, external power supplies 170, vacuum 160, and optionally other utilities. Internal plumbing and electrical connections within the processing system 100 are not shown for clarity of illustration.

[0022] The processing system 100 is shown as a so-called indirect plasma processing system, which generates plasma at a first location and directs the plasma and / or plasma products (e.g., ions, molecular fragments, excited species, etc.) to a second location where processing occurs. Thus, in Figure 1 The plasma processing unit 130 includes a plasma source 132 that supplies plasma and / or plasma products to a processing chamber 134. The processing chamber 134 includes one or more workpiece holders 135 on which the wafer interface 115 places a workpiece 50 (e.g., a semiconductor wafer, but can be a different type of workpiece) to be held for processing. When the workpiece 50 is a semiconductor wafer, the workpiece holder 135 is often referred to as a wafer chuck. In operation, the gases (plural) 155 are introduced into the plasma source 132, and a radio frequency generator (RF Gen) 165 supplies power to ignite a plasma within the plasma source 132. The plasma and / or plasma products pass from the plasma source 132 through a diffuser plate 137 to the processing chamber 134, where the workpiece 50 is processed. Instead of or in addition to plasma from the plasma source 132, a plasma can also be ignited within the processing chamber 134 for direct plasma processing of the workpiece 50.

[0023] The embodiments herein provide new and useful functionality for plasma processing systems. Notably in recent years, as feature sizes have decreased, semiconductor wafer sizes have increased so that more integrated circuits with better functionality can be harvested from each processed wafer. Processing smaller features while the wafer is growing larger requires significant improvements in processing uniformity. Because chemical reaction rates are generally temperature sensitive, temperature control across the wafer during processing is generally critical for uniform processing.

[0024] Furthermore, certain types of processing can exhibit radial effects (e.g., processing that varies from the center to the edge of the wafer). Some types of processing apparatus control these effects better than others; that is, some processing apparatuses achieve high radial process uniformity, while others do not. The embodiments described herein recognize that it is advantageous to control radial effects, and even more advantageous to provide radial processing that can be tailored to compensate for processes where such control cannot be achieved. For example, consider the following scenario: a layer is deposited on a wafer and then selectively etched away, as is common in semiconductor processing. If the deposition step is known to deposit a thicker layer at the edge of the wafer compared to the center, then a compensating etching step advantageously provides a higher etch rate at the edge of the wafer compared to the center, such that the deposited layer is etched simultaneously across all portions of the wafer. Similarly, if the etching process is known to have a center-to-edge variation, the compensating deposition prior to the etching process can be adjusted to provide a corresponding variation.

[0025] In many cases of treatments with radial effects, compensation can be provided by offering a definite center-to-edge temperature variation, since temperature typically substantially affects the reaction rate of the treatment.

[0026] Figure 2 For illustration Figure 1 A schematic cross-sectional view showing exemplary construction details of the workpiece holder 135. (See attached image.) Figure 2 As shown, the workpiece holder 135 includes a substantially cylindrical positioning disk 200, characterized by a positioning disk radius r1 in the radial direction R from the cylindrical axis Z. In use, a workpiece 50 (e.g., a wafer) can be placed on the positioning disk 200 for processing. The bottom surface 204 of the positioning disk 200 is taken as the central bottom surface height of the positioning disk 200; that is, excluding the plane that defines the general bottom surface height of the positioning disk 200 in the direction of the axis Z, which may be formed as an attachment point for other hardware (such as edge rings or other protrusions 206, or recesses 208). Similarly, the top surface 202 is taken as a flat surface configured to receive the workpiece 50, without regard to grooves (e.g., vacuum channels, see reference) that may be formed in the flat surface. Figure 4 And / or other features of the fixed workpiece 50. All such protrusions, indentations, grooves, rings, etc., do not diminish the "substantially cylindrical" characteristic of the positioning disk 200 in the context of this specification. The positioning disk 200 can also be characterized by having a thickness t between the bottom surface 204 and the top surface 202, as shown in the figure. In some embodiments, the positioning disk radius r1 is at least four times the positioning disk thickness t, but this is not required.

[0027] The puck 200 defines one or more radial thermal breaks 210, as shown. The thermal breaks 210 are radial notches defined in the puck 200 that intersect at least one of the top surface 202 or the bottom surface 204 of the puck 200. The thermal breaks 210, as the name implies, act to provide thermal resistance between the radially inner portion 212 and the radially outer portion 214 of the puck 200. This facilitates distinct radial (e.g., center-to-edge) thermal control of the inner and outer portions of the puck 200, which is advantageous in providing accurate thermal matching of the inner and outer portions or providing deliberate temperature variations across the inner and outer portions. The thermal breaks 210 can be characterized according to having a thermal break depth and a thermal break radius. The depth of the thermal breaks 210 can vary among embodiments, but the thermal break depth is typically more than one-half of the thickness t. The radial positioning of the thermal breaks 210 can also vary among embodiments, but the thermal break radius r2 is typically at least one-half of the puck radius r1, and in other embodiments, r2 can be three-quarters, five- quarters, six-fifths, or more of the puck radius r1. Certain embodiments can use a single thermal break 210, while other embodiments can use two thermal breaks 210 (as shown in Figure 2 FIG. 2) or more. The point of distinction between the radially inner portion 212 and the radially outer portion 214 is drawn as the radial average position between the two thermal breaks 210, but in embodiments having a single thermal break 210, such a point of distinction can be considered to be the radial midpoint of the single thermal break 210.

[0028] One way in which the thermal breaks (as drawn in Figure 2 ) can be advantageously used is to provide radially applied heating and / or cooling to the inner portion 212 and the outer portion 214 of the puck 200. Figure 3 To illustrate the integration of heaters and heat sinks with the inner and outer portions of the puck 200, a schematic cross-sectional view is drawn. Certain mechanical details of the puck 200 are not shown in Figure 3 for clarity of illustration. Figure 3 A central passage 201 defined by the puck 200 and an optional heat sink 230 is drawn. In conjunction with Figure 4A central channel 201 is described. Inner heaters 220-1 and outer heaters 220-2 are disposed in thermal communication with the puck 200; the heaters 220 are shown as embedded within the puck 200, but this is not required. It can be advantageous for the heaters 220 to be placed across a substantial portion of the puck 200, but the distribution of the heaters 220 across the surface 204 can vary in embodiments. The heat provided by the heaters 220 will substantially control the temperature of the inner portion 212 and the outer portion 214 of the puck 200; the thermal breaks 210 assist the portions 212 and 214 in being thermally isolated from one another to improve the accuracy of their thermal control. The heaters 220 are generally resistive heaters, but other types of heaters can be used (e.g., using forced gas or liquid).

[0029] An optional heat sink 230 can also be provided. The heat sink 230 can be controlled to present a lower temperature than the general operating temperature, for example by flowing a heat exchange liquid at a controlled temperature through the heat sink 230, or by using a cooling device such as a Peltier cooler. When present, the heat sink 230 provides several advantages. One such advantage is to provide a reference temperature to which all portions of the puck 200 tend to have, absent heat provided by the heaters 220. That is, although the heaters 220 can provide heat, such heat will generally propagate through the puck 200 in all directions. The heat sink 230 provides the ability to drive all portions of the puck 200 to a lower temperature, such that if a heater 220 is located at a particular portion of the puck 200, the heat generated by the heater does not simply diffuse throughout the puck 200 in every direction, and heat a portion of the puck 200 at which the heat from the heater 220 locally exceeds the tendency of the heat sink 230 to remove heat. When present, the heat sink 230 can be in thermal and / or mechanical communication with the puck 200 at a plurality of attachment points 222 (schematically illustrated in Figure 3 Figure 3 but the attachment points 222 can not be similar to those shown in Figure 6A , 6B and 6C), as described with reference to

[0030] ​A related advantage is that the heat sink 230 can provide a rapid heat sink capability, such that adjacent portions of the platen 200 respond with a relatively rapid temperature decrease when the temperature setting of the heater 220 (e.g., the current through the resistive wire) is decreased. This, for example, provides the benefit of being able to load a workpiece 50 onto the platen 200, provide heat through the heater 220, and achieve rapid stabilization of the temperature on the workpiece 50, such that processing can quickly begin to maximize the overall throughput of the system. Without the thermal communication that allows some heat dissipation to the heat sink 230, the temperature reached by portions of the platen 200 would decrease only as rapidly as other heat dissipation paths would allow.

[0031] The heater 220 and the heat sink 230 are generally disposed in different degrees of thermal communication with the platen 200; for example, the heater 220 can be said to be in direct thermal communication with the platen 200, while the heat sink is in indirect thermal communication with the platen 200. That is, the heater 220 is generally positioned for a high degree of thermal coupling with the platen 200, while the heat sink 230 is positioned for a lower degree of thermal coupling with the platen 200 (at least as compared to the lower degree of thermal coupling of the heater 220 with the platen 200). Also, the heater 220 has sufficient heat generation capability such that the heat applied by the heater 220 can overpower the thermal coupling of the platen 200 with the heat sink 230, such that the heater 220 can raise the temperature of the inner portion 212 and the outer portion 214 of the platen 200 even while some of the heat generated by the heater 220 is dissipated through the heat sink 230. Thus, the heat provided by the heater 220 can (but not immediately) be dissipated through the heat sink 230. In embodiments, the placement and degree of thermal coupling between the platen 200, the heater 220, and the heat sink 230 can be adjusted in accordance with the principles herein to balance considerations such as temperature uniformity within each of the inner portion 212 and the outer portion 214, rapidity of thermal stabilization, manufacturing complexity and cost, and overall energy consumption.

[0032] Yet another advantage of the heat sink 230 is to localize the heat generated by the heater 220 to the vicinity of the platen 200. That is, the heat sink 230 can provide an upper limit on heat for adjacent system components, to protect such components from the high temperatures generated at the platen 200. This can improve the mechanical stability of the system and / or prevent damage to temperature-sensitive components.

[0033] The heater 220 and heat sink 230 can be implemented in various ways. In an embodiment, the heater 220 is provided by cable-type heating elements that are integrated with the puck 200 and then (optionally) integrated with the heat sink 230 to form a wafer chuck assembly. Embodiments designed, assembled, and operated as disclosed herein allow for explicit control of the temperature of the edge region of a workpiece (e.g., a wafer) relative to the center region, and facilitate processing with explicit center-to-edge temperature control that generally cannot be achieved with prior art systems.

[0034] Figure 4 A schematic cross-sectional view of a portion of a wafer chuck is presented, illustrating features of the puck 200, a resistive heater serving as the heater 220-1, and the heat sink 230. Figure 4 To clarify the smaller features, a portion of the wafer chuck is presented near its cylindrical axis Z, and is not drawn to scale. The puck 200 is generally formed of an aluminum alloy, such as the well-known "6061" alloy type. The puck 200 is illustrated as defining surface grooves or channels 205 connected on an upper surface 202 of the puck 200, and having a central channel 201 centered about the axis Z. A vacuum can be supplied to the central channel 201, reducing the pressure within the channels 205, so that atmospheric pressure (or a relatively high pressure plasma or low pressure deposition system's gas pressure, such as about 10-20 Torr) will push the workpiece 50 against the puck 200 (refer to Figure 1 、 2 ), providing good thermal communication between the puck 200 and the workpiece 50.

[0035] An inner resistive heater 220-1 is illustrated in Figure 4 , but it should be understood that the description of the inner resistive heater 220-1 and the following description apply equally to the outer resistive heater 220-2. The resistive heater 220-1 includes a cable heater 264 that is wound in a spiral or other manner within the puck 200. The cable heater 264 is assembled into the puck 200 by placing it within a groove in the puck 200 and capping the groove (refer to Figure 5 ). After the cable heater 264 is assembled as the inner resistive heater 220-1 (and a second cable heater is assembled as the outer resistive heater 220-2), the puck 200 is assembled to the heat sink 230 by the fastener 270. Both the puck 200 and the heat sink 230 are arranged for the area of attachment points for the fastener 270 to manage the thermal transport characteristics between the puck 200 and the heat sink 230 around the fastener 270, as discussed in further detail below (refer to Figure 6A 、 6B 、6C).

[0036] Figure 5 The lower side of the positioning disk 200-1 is schematically illustrated, having cable heaters 264-1 and 264-2 mounted therein, serving as inner and outer resistance heaters respectively. The heat insulation element 210 is a recess defined in the bottom surface 204 of the positioning disk 200-1, forming a radial boundary between the inner portion 212 and the outer portion 214 of the positioning disk 200 (see reference). Figure 2 , 3). Cable heater 264-1 extends from connector 262-1 along a generally helical path arranged for uniform heat transfer to all areas of inner portion 212. Heater cover 266-1 is shown as a shaded portion of the helical path; heater cover 266-1 is coupled into place after cable heater 264-1 is put into place. In embodiments, heater cover 266-1 is a fillet pre-formed into a channel shape into which cable heater 264-1 is installed, and heater cover 266-1 is secured into place. Heater cover 266-1 can be welded into place, for example, using electron beam welding techniques, but can also be secured using adhesives or fillers (e.g., epoxy). The fillet is preferably welded into place at least along a portion of the arc length of the cable heater, but need not be welded along the entire arc length of the cable heater (e.g., portions can be left un-welded to avoid damage to overlying structures, such as cable heater 264-2). In embodiments, heater cover 266-1 is welded into place using electron beam welding techniques. Cold-to-heat transfer point 265-1 indicates where the wires in cable heater 264-1 (extending from connector 262-1 and hidden beneath heater cover 266-1) connect to the resistive material within cable heater 264-1. Thus, a small amount of heat is generated between connector 262-1 and transfer point 265-1, but uniform per-unit-length heat is generated in cable heater 264-1 past transfer point 265-1. Cable heater 264-2 extends from connector 262-2, first radially outward from the central region of positioning disk 200 (where the shaft through the wafer clamp is made), and then along a generally circular path arranged for uniform heat transfer to outer portion 214. Heater cover 266-2 is shown as a shaded portion of the helical path; heater cover 266-2 is coupled into place after cable heater 264-2 is put into place. In embodiments, heater cover 266-2 is a fillet pre-formed into a channel shape into which cable heater 264-2 is installed, and heater cover 266-2 is welded into place using electron beam welding techniques. Like heater cover 266-1, the fillet forming heater cover 266-2 is preferably welded into place at least along a portion of its arc length, but need not be welded along its entire arc length. Cold-to-heat transfer point 265-2 indicates where the wires in cable heater 264-2 (extending from connector 262-2 and hidden beneath heater cover 266-2) connect to the resistive material within cable heater 264-2. Thus, a small amount of heat is generated between connector 262-2 and transfer point 265-2, but uniform per-unit-length heat is generated in cable heater 264-2 past transfer point 265-2. A set of protrusions 268 is also shown in Figure 5 Figure 3 ​). The protrusion 268 forms a location for an attachment point 222, which cooperates with the fastener 270 Figure 4 ), and is linked below Figure 6A 、 6B are discussed in more detail.

[0037] Figure 6A is a detailed view of a portion of the puck 200, as shown in Figure 4 , and the optional heat sink 230, in the vicinity of the fastener 270. The puck 200 includes a cable heater 264 sealed into the puck 200 with a heater cover 266, as discussed above in connection with Figure 5 . As further noted above, the optional heat sink 230 can provide a reference temperature for the puck 200, however it is desirable that the heat sink 230 and the puck 200 are arranged for a lower degree of thermal communication between the puck 200 and the heater 220. Accordingly, the attachment points that allow thermal communication between the heat sink 230 and the puck 200 are preferably arranged to manage the thermal transport characteristics therebetween. For example, the puck 200 and the heat sink 230 can be manufactured such that a lateral gap 276 exists between the protrusion 268 and the heat sink 230, as shown. That is, the thickness of the heat sink 230 is reduced in a thinned region 235 in the vicinity of the protrusion 268, and the lateral extent of the thinned region 235 is greater than the lateral extent of the protrusion 268, thereby forming a lateral gap 276 between the protrusion 268 and the full thickness portion of the heat sink 230. The heat sink 230 forms an aperture for the fastener 270 to pass through, and the protrusion 268 defines an internal void 275, an interior portion of which can be threaded for the fastener 270 to couple to the void 275. However, the void 275 can be longer than the length of the fastener 270 (e.g., as shown in Figure 6A ), to limit thermal transport from the puck 200 through the protrusion 268. The physical attachment points of the puck 200 to the heat sink 230 include the protrusion 268, the fastener 270, and a pair of washers 272. The primary thermal transport path in the vicinity of the fastener 270 is illustrated as a solid, wavy arrow 278, while the secondary (e.g., radiative) thermal transport path is shown as a dashed, wavy arrow 279, in Figure 6A and 6B . The void 231 is discussed below in connection with Figure 6C .

[0038] Figure 6BAn embodiment of a wave washer 272 in an uncompressed state is schematically illustrated. While it is possible to utilize a flat washer in some embodiments, wave washers are advantageous in other embodiments. The advantageous form of the wave shape of the washer 272 is that the puck 200 can be coupled to the heat sink 230 at multiple points without unduly constraining the puck 200 or the heat sink 230 relative to one another. That is, assuming only three points form a mathematically planar surface, more than three attachment points between the puck 200 and the heat sink 230 form an over-constrained system that imposes very tight mechanical tolerances on the multiple attachment points between the heat sink 230 and the lugs 268 of the puck 200. The use of a wave washer 272 allows for looser planarity tolerances in such features, as the washer 272 will provide mechanical coupling over the entire compression range, rather than requiring the attachment points of the respective components to be positioned along a perfectly flat surface. Similarly, the compression range of the wave washer 272 allows for local thermal expansion effects in the puck 200 and / or the heat sink 230. In some embodiments, the wave washer 272 has an uncompressed thickness 273 that is at least twice the compressed thickness 274; in other embodiments, the wave washer 272 has an uncompressed thickness 273 that is at least five times the compressed thickness 274. While the washer 272 is shown in a flat cross-sectional profile in Figure 6A for clarity, it will be appreciated upon reading and understanding the present disclosure that the fixture 270 can not compress all the way to the point of flattening the wave washer 272, such that some of the waves will be present in many, if not all, instances of the wave washer 272 at installation. Also, in use, the wave washer 272 reduces thermal communication between the lugs 268 and the heat sink 230 by forcing heat from the lugs 268 through to the local peaks of the washer 272 that contact the lugs 268, then laterally within the washer 272 to the local through-holes of the washer 272 that contact the heat sink 230. The washer 272 can be formed, for example, of beryllium copper. Some embodiments utilize two washers 272, with one washer 272 on either side of the heat sink 230 (as shown), while other embodiments utilize only a single washer 272, which is generally between the lugs 268 and the heat sink 230.

[0039] Figure 6C An upward-looking bottom plan view of the vicinity of the fixture 270 is provided. In Figure 6C , the dashed line 6A-6A indicates the cross-sectional plane shown in Figure 6A The heat sink 230 forms one or more voids 231 within the thinned region 235 of the vicinity of the fixture 270. The voids 231 further reduce thermal communication between the puck 200 and the heat sink 230. The voids 231 are shown in Figure 6CThe number and arrangement of the gaps 231 in the heat sink 230 are not required; it will be understood upon reading and understanding this disclosure that the size, number, and arrangement of the gaps 231 can be changed to adjust the thermal coupling characteristics between the heat sink 230 and the positioning disk 200. For example, the thermal coupling between the heat sink 230 and the positioning disk 200 can be further reduced by providing a second set of gaps 231 (radially outward from the gaps 231, such as...) Figure 6C As shown in the diagram), and the arrangement of additional sets of structures interleaved relative to the shown gap 231, to lengthen the thermal path between the protrusion 268 and the heat sink 230 body. Furthermore, although... Figure 6C The outer edge of the thinned region 235 is shown to coincide with the outer edge of the gap 231, but this is not always the case. Some embodiments may have a gap 231 that is very close to the edge of the thinned region 235, or such gaps 231 may extend partially into the heat sink 230 outside the thinned region 235. Similarly, the number, placement, and wall thickness of the protrusions 268 may be changed to achieve higher or lower thermal conductivity between the positioning disk 200 and the heat sink 230.

[0040] A further advantage of providing at least one thermal break 210 intersecting the top surface of the positioning disk 200 is that certain mechanical features can be at least partially housed within the thermal break, such that these mechanical features do not generate thermal anomalies on the surface of the positioning disk 200. For example, wafer jigs typically provide lifting pins that can be used to lift the wafer a short distance away from the jig to facilitate pickup by a wafer handling tool (generally using a wheel or other device inserted between the wafer and the jig after the wafer is lifted). However, the lifting pins generally retract into holes in the jig, and such holes and the lifting pin structure can locally affect the wafer temperature during processing. A location already exists where the thermal break intersects the top surface of the positioning disk 200, allowing for the placement of such a mechanism without causing thermal anomalies.

[0041] Figure 7 A portion of a wafer jig with a lifting pin mechanism 300 is schematically illustrated. This lifting pin mechanism controls a lifting pin 310, which is housed within a thermal insulation element 210. A portion of a heater 220 and an optional heat sink 230 are also shown. Figure 7 The cross-sectional plane shown passes through the center of mechanism 300, causing its components to reside within the lower portion of a thermal insulation element 210. Within and outside the plane shown, the positioning disc 200, thermal insulation element 210, and heat sink 230 may have similar characteristics. Figure 3 and 4 The contours shown are such that the thermal break 210 will extend through the positioning disk 200 along the arc length of the thermal break 210 (see reference). Figure 8 The mechanism 300 is housed within the heat insulation element 210. Furthermore, the lifting pin mechanism 300 is limited by a relatively small azimuth angle relative to the central axis of the positioning plate 200 (see again).Figure 8 ). That is, if a cross-sectional plane is taken at a distance into or out of the plane shown in Figure 7 , the bottom surface of the chuck 200 would be continuous along the same plane that indicates the bottom surface 204 in Figure 7 , and the heat sink 230 would be continuous underneath the chuck 200. The small size of the lift pin mechanism 300 limits thermal deviations of the chuck 200 in the area of the lift pin mechanism 300. Figure 7 The lift pin 310 is shown in a retracted position, where it will not create thermal anomalies on the surface of the chuck 200.

[0042] Figure 8 The three lift pin arrangements are schematically depicted in plan view, with the lift pin 310 disposed within the thermal break 210. Figure 8 Not drawn to scale, in particular, the thermal break 210 is exaggerated to clearly show the lift pin mechanism 300 and the lift pin 310. Because the lift pin 310 retracts well below the average surface of the chuck 200 into the thermal break 210, the lift pin 310 does not create spatial thermal anomalies during processing, such that the portion of the workpiece being processed at the location of the lift pin 310 (e.g., a particular integrated circuit at a corresponding location on a semiconductor wafer) experiences processing consistent with processing elsewhere on the workpiece.

[0043] Figure 9 A flowchart of a method 400 for processing wafers or other workpieces (hereinafter referred to as "product wafers" with the understanding that the concepts can be applied to workpieces other than wafers). The method 400 can be implemented uniquely by a thermal management apparatus as described in connection with Figures 2-8 The method 400 can be implemented uniquely by a thermal management apparatus as described in connection with Figure 10 , the bottom surface of the chuck 200 would be continuous along the same plane that indicates the bottom surface 204 in Figure 7 , and the heat sink 230 would be continuous underneath the chuck 200. The small size of the lift pin mechanism 300 limits thermal deviations of the chuck 200 in the area of the lift pin mechanism 300. Figure 7 The lift pin 310 is shown in a retracted position, where it will not create thermal anomalies on the surface of the chuck 200.

[0042] Figure 8 The three lift pin arrangements are schematically depicted in plan view, with the lift pin 310 disposed within the thermal break 210. Figure 8 Not drawn to scale, in particular, the thermal break 210 is exaggerated to clearly show the lift pin mechanism 300 and the lift pin 310. Because the lift pin 310 retracts well below the average surface of the chuck 200 into the thermal break 210, the lift pin 310 does not create spatial thermal anomalies during processing, such that the portion of the workpiece being processed at the location of the lift pin 310 (e.g., a particular integrated circuit at a corresponding location on a semiconductor wafer) experiences processing consistent with processing elsewhere on the workpiece.

[0043] Figure 9 A flowchart of a method 400 for processing wafers or other workpieces (hereinafter referred to as "product wafers" with the understanding that the concepts can be applied to workpieces other than wafers). The method 400 can be implemented uniquely by a thermal management apparatus as described in connection with Figures 2-8 The method 400 can be implemented uniquely by a thermal management apparatus as described in connection with Figure 10 , the bottom surface of the chuck 200 would be continuous along the same plane that indicates the bottom surface 204 in Figure 7 , and the heat sink 230 would be continuous underneath the chuck 200. The small size of the lift pin mechanism 300 limits thermal deviations of the chuck 200 in the area of the lift pin mechanism 300. Figure 7 The lift pin 310 is shown in a retracted position, where it will not create thermal anomalies on the surface of the chuck 200.

[0042] Figure 8 The three lift pin arrangements are schematically depicted in plan view, with the lift pin 310 disposed within the thermal break 210. Figure 8 Not drawn to scale, in particular, the thermal break 210 is exaggerated to clearly show the lift pin mechanism 300 and the lift pin 310. Because the lift pin 310 retracts well below the average surface of the chuck 200 into the thermal break 210, the lift pin 310 does not create spatial thermal anomalies during processing, such that the portion of the workpiece being processed at the location of the lift pin 310 (e.g., a particular integrated circuit at a corresponding location on a semiconductor wafer) experiences processing consistent with processing elsewhere on the workpiece.

[0043] Figure 9 A flowchart of a method 400 for processing wafers or other workpieces (hereinafter referred to as "product wafers" with the understanding that the concepts can be applied to workpieces other than wafers). The method 400 can be implemented uniquely by a thermal management apparatus as described in connection with Figures 2-8 The method 400 can be implemented uniquely by a thermal management apparatus as described in connection with Figure 1011 Additional guidance is provided to those skilled in the art to allow for the useful exercise of method 400.

[0044] Figure 10 This is a flowchart of a method 401, which includes, but is not limited to, step 420 of method 400. Figure 10 All of 410-418 and 422 shown are considered optional when performing method 400 to achieve useful wafer processing results (but may be helpful in an embodiment).

[0045] Step 410 sets device characteristics for a first center-to-edge processing variation that will occur at 420. For example, when it is desired that 420 will cause a controlled change, 410 may involve providing device parameters, such as those set for a heater, that will provide a controlled center-to-edge temperature variation. As described herein Figures 2-8 The device described herein is useful in providing controlled center-to-edge temperature variations. Step 412 measures device characteristics with respect to the first center-to-edge processing variation. Processing knowledge can be acquired over time regarding which device settings (or measured device characteristics) are successful (or at least provide stable, albeit unintentional, processing variations) when producing known center-to-edge processing variations. If the device characteristics measured in 412 could be improved while taking this processing knowledge into account, method 401 may optionally return from 412 to 410 to adjust the device characteristics. Step 414 processes one or more test wafers that receive the first center-to-edge processing variation. Step 416 measures one or more characteristics of the first center-to-edge processing variation on the test wafers processed in step 414. Method 401 may optionally return from 416 to 410 to adjust the device characteristics based on the center-to-edge processing characteristics measured in 416. Any wafers processed in 414 may optionally be stored in 418 for testing in a second process (e.g., a process to be performed later in 440). Furthermore, 414 can be executed in parallel with 420. That is, when the processing equipment is properly configured, test wafers can be processed at the same time as product wafers (for example, if the first processing is a so-called "batch" processing, such as immersing wafer cassettes in a liquid bath, processing wafer sets together in ampoules, diffusion furnaces, or deposition chambers, etc.).

[0046] Step 420 processes the product wafer with a first center-to-edge processing variation. Step 422 measures one or more first center-to-edge characteristics on the product wafer to generate data for equipment processing control purposes, data for correlation with the yield or performance of the product wafer, and / or data for correlation with information surrounding step 440, as further described below.

[0047] Figure 11A flowchart of a method 402, which includes, but is not limited to, step 440 of method 400. Figure 11 All of 430-436 and 442 are considered optional (but can be helpful in embodiments) in performing method 400 to achieve a useful wafer processing result.

[0048] Step 430 sets up equipment characteristics with respect to a second center-to-edge processing variation that will result at step 440. For example, where 440 is expected to introduce a controlled variation, 430 can involve providing equipment parameters, e.g., heater settings, that will provide a controlled center-to-edge temperature variation. As discussed herein, equipment described in Figures 2-8 Equipment described in is useful in providing a controlled center-to-edge temperature variation. Step 432 measures equipment characteristics with respect to the second center-to-edge processing variation. In considering processing knowledge, as discussed above, method 402 can optionally go back from 432 to 430 to adjust equipment characteristics in dependence on equipment characteristics measured in 432. Step 434 processes one or more test wafers that receive the second center-to-edge processing variation; the test wafers processed in 434 can include one or more test wafers stored from the first processing step in 418. Step 436 measures one or more characteristics of the second center-to-edge processing variation on the test wafers processed in 434. In considering previously acquired processing knowledge, method 402 can optionally go back from 436 to 430 to adjust equipment characteristics in dependence on center-to-edge processing characteristics measured in 436.

[0049] Step 440 processes product wafers with the second center-to-edge processing variation. And, although not shown in method 402, of course additional test wafers can be processed in parallel with the product wafers. Step 442 measures one or more first center-to-edge characteristics on the product wafers to produce data for equipment processing control purposes, data for correlation to yield or performance of the product wafers, and / or data for correlation to information surrounding 420, as discussed above. Such measurements can also be performed on any test wafers, but in any case 442 will generally not further alter any conditions presented on the product wafers. That is, the results of 420 and 440 will be fixed in the product wafers at the end of 440, regardless of any further testing that is done.

[0050] Having described several embodiments, it will be recognized by those of skill that various modifications, alternative constructions, and equivalents can be used without departing from the spirit of the application. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present application. Accordingly, the above description should not be taken as limiting the present application.

[0051] Plasma processing of workpieces other than wafers can also benefit from improved process uniformity and are considered to be within the scope of the present disclosure. Thus, references herein to a "wafer clamp" having features for holding a "wafer" should be understood to be equivalent to a clamp for holding any kind of workpiece, and "wafer processing system" should be similarly understood to be equivalent to a processing system.

[0052] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and the endpoints are included in the range unless specifically excluded. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0053] As used in this document and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a process" includes a plurality of such processes, and reference to "the electrode" includes reference to one or more electrodes and equivalents thereof known to those skilled in the art, and so forth. Also, the terms "comprise," "comprising," "include," "including," and "includes" when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.

Claims

1. A workpiece holder comprising: a cylindrical puck; a first heating device disposed in thermal communication with a radially inner portion of the puck; a second heating device disposed in thermal communication with a radially outer portion of the puck, wherein the first and second heating devices are independently controllable relative to one another; and a heat sink disposed in thermal communication with the puck, wherein the first and second heating devices are in a greater respective degree of thermal communication with the puck than the heat sink is in thermal communication with the puck, wherein the puck is characterized by a cylindrical axis, a puck radius about the cylindrical axis, and a puck thickness, and wherein at least a top surface of the cylindrical puck is planar, wherein the puck is mechanically and thermally coupled with the heat sink at a plurality of attachment points, wherein for at least one of the attachment points: the puck forms a convexity facing the heat sink; the heat sink forms an aperture; and a fastener passes through the aperture and is coupled within the convexity; wherein at the at least one of the attachment points: the convexity defines a first lateral extent, and the heat sink defines a thinned portion that decreases in thickness about the aperture, the thinned portion having a second lateral extent that is greater than the first lateral extent, such that a lateral gap exists between the convexity and a full thickness portion of the heat sink.

2. The workpiece holder of claim 1, wherein at least one of the first heating device and the second heating device comprises a resistive heater disposed within a trench defined within a bottom surface of the puck.

3. The workpiece holder of claim 2, further comprising a heater cover placed within the trench to hold the resistive heater in place, the heater cover being secured to the puck along at least a portion of an arc length of the resistive heater.

4. The workpiece holder of claim 1, wherein the plurality of attachment points provide all of the thermal communication of the heat sink with the puck.

5. The workpiece holder of claim 1, wherein the puck is at least ten inches in diameter, and the plurality of attachment points comprises at least twenty attachment points.

6. The workpiece holder of claim 5, wherein the puck is at least twelve inches in diameter, and the plurality of attachment points comprises at least thirty attachment points.

7. The workpiece holder of claim 1, wherein the heat sink defines one or more voids near the aperture and within the thinned portion to limit thermal transport from the puck to the heat sink.

8. The workpiece holder of claim 1, further comprising a wave washer disposed about the fastener between the heat sink and the convexity, the wave washer having a net uncompressed thickness that is at least twice its compressed thickness.

9. The workpiece holder of claim 1, wherein the heat sink comprises a metal plate defining one or more fluid channels, and a heat exchange fluid flows through the fluid channels to define a reference temperature of the heat sink. ​ 10. The workpiece holder of claim 1, wherein the heat sink comprises a metal plate defining one or more fluid channels, and wherein a heat exchange fluid flows through the one or more fluid channels to define a reference temperature of the heat sink.

11. The workpiece holder of claim 1, wherein the cylindrical puck defines one or more radial thermal breaks between the radially inner portion and radially outer portion of the puck.

12. The workpiece holder of claim 11, wherein each thermal break is characterized as a radial notch intersecting at least one of the top and bottom faces of the cylindrical puck.

13. The workpiece holder of claim 12, wherein the radial notch is characterized by: a thermal break depth extending at least half the puck thickness from the top or bottom face of the puck, and a thermal break radius disposed symmetrically about the cylindrical axis and at least half the puck radius.

14. A workpiece holder, the workpiece holder comprising: a cylindrical puck characterized by a cylindrical axis and a planar top face, wherein the puck defines two radial thermal breaks, a first one of the thermal breaks is characterized as a radial notch intersecting the bottom face of the puck at a first radius, and a second one of the thermal breaks is characterized as a radial notch intersecting the top face of the puck at a second radius greater than the first radius, wherein the puck is mechanically and thermally coupled with a heat sink at a plurality of attachment points, wherein for at least one of the attachment points: the puck forms a ledge facing the heat sink; the heat sink forms an aperture; and a fastener passes through the aperture and is coupled within the ledge; wherein at the at least one of the attachment points: the ledge defines a first lateral extent, and the heat sink defines a thinned portion that decreases in thickness about the aperture, the thinned portion having a second lateral extent greater than the first lateral extent, such that a lateral gap exists between the ledge and a full thickness portion of the heat sink.

15. The workpiece holder of claim 14, wherein the first and second thermal breaks define a demarcation between a radially inner portion of the puck and a radially outer portion of the puck.

16. The workpiece holder of claim 15, wherein the puck comprises: a first heating device embedded within the radially inner portion of the puck, and a second heating device embedded within the radially outer portion of the puck.

17. The workpiece holder of claim 16, wherein the heat sink extends below the bottom surface of the puck, the heat sink comprising a metal plate that has a heat exchange fluid flowing through channels defined in the metal plate to maintain a reference temperature for the puck, and wherein the plurality of attachment points provide a degree of thermal communication between the heat sink and the puck that is less than a degree of thermal communication between each of the first and second heating devices and the puck.

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