Patent Publication Number: US-2023154768-A1

Title: Multi-zone azimuthal heater

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/856,634 filed Apr. 23, 2020, which claims priority to and the benefit of U.S. Provisional Application No. 62/838,535 filed on Apr. 25, 2019. The disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to heater assemblies, and more specifically to heater assemblies having resistive heaters that provide directional thermal control and distribution along a heating target. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Pedestals are known in semiconductor processing to support and heat a wafer disposed thereon. A pedestal generally includes a substrate for supporting a wafer and a shaft member attached to a bottom side of the plate member. A heater may be embedded in the substrate, or otherwise attached to the substrate, to provide the required heating to the wafer. Other devices such as showerheads are also used in semiconductor processing, which distribute process gases (e.g. reactants) across the wafer during processing. 
     During various wafer processing steps such as plasma enhanced film deposition, or etching, the substrate needs to be uniformly heated or cooled to reduce processing variations within the wafer. However, maintaining uniform azimuthal heating of a perimeter of the substrate may be difficult due to non-uniform heat loss along the perimeter. 
     The present disclosure addresses the issues related to the uniform azimuthal heating of a substrate, in a variety of applications, among other issues related to heating of a substrate. 
     SUMMARY 
     This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form of the present disclosure, a heater assembly includes a substrate, a plurality of resistive heating elements disposed along a perimeter of the substrate, and a common ground electrical lead connected to at least some of the plurality of resistive heating elements and having a portion extending along the perimeter of the substrate. The plurality of resistive heating elements are independently controllable to provide azimuthal temperature control of the heater assembly. 
     In other features of the present disclosure, each of the resistive heating elements has opposing ends along the perimeter of the substrate. The common ground electrical lead is connected to one of the opposing ends of some or all of the plurality of resistive heating elements. The heater assembly further includes a plurality of electrical leads each connected to a corresponding one of the plurality of resistive heating elements. One of the opposing ends of each of the resistive heating elements is connected to the common ground electrical lead and the other one of the opposing ends of each of the resistive heating elements is connected to a corresponding one of the electrical leads. The plurality of electrical leads include portions extending along the perimeter of the substrate. The electrical leads extend from a central portion of the substrate in a radial direction toward a sidewall of the substrate and then extend along the perimeter of the substrate to be connected to the plurality of resistive heating elements. 
     In another features, the plurality of resistive heating elements include a first resistive heating element and a second resistive heating element extending in a physical series connection along the perimeter of the substrate, a first positive electrical lead in communication with a positive end of the first resistive heating element, a second positive electrical lead in communication with a positive end of the second resistive heating element, and a common electrical lead in communication with a negative end of the first resistive heating element and a negative end of the second resistive heating element. Each of the plurality of resistive heating elements are isolated from each other. The substrate defines an isolation region between adjacent two of the heating elements. The heater assembly further includes a 2-wire controller connected to the plurality of resistive heating elements and being operable to independently control the plurality of resistive heating elements. The resistive heating elements define a material that functions as a heater element and as a temperature sensor. The common ground electrical lead extends from a central portion of the substrate in a radial direction toward a sidewall of the substrate and then extends along the perimeter of the substrate to be connected to the plurality of resistive heating elements. The plurality of resistive heating elements comprises n resistive heating elements and n+1 electrical leads. The plurality of resistive heating elements are selected from a group consisting of a tubular heater, a layered heater and a foil heater. The heater assembly further includes a shaft extending from the substrate. The common ground electrical lead extend through the shaft. 
     In another form of the present disclosure, a thermal system includes a controller, a substrate, and a plurality of resistive heating elements disposed along a perimeter of the substrate, and a common ground electrical lead connected to at least some of the plurality of resistive heating elements and having a portion extending along the perimeter of the substrate. Each of the plurality of resistive heating elements has opposing ends along the perimeter of the substrate. The plurality of resistive heating elements are independently controllable to provide azimuthal temperature control of the heater assembly. 
     In other features, the controller is a 2-wire controller controlling the resistive heating elements to operate as a heater to generate heat and as a sensor to measure a temperature of the resistive heating elements. The plurality of resistive heating elements comprise n resistive heating elements and n+1 electrical leads. 
     In yet another form of the present disclosure, a heater assembly includes a pedestal including a substrate and a shaft connected to a central portion of the substrate, a plurality of resistive heating elements disposed along a perimeter of the substrate, a common ground electrical lead connected to all of the resistive heating elements and extending through the shaft, and a plurality of electrical leads connected to the plurality of resistive heating elements and extending through the shaft. Each of the plurality of resistive heating elements has opposing ends along the perimeter of the substrate. The plurality of resistive heating elements are independently controllable to provide azimuthal temperature control of the heater assembly. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG.  1    is a perspective view of a heater assembly in accordance with the teachings of the present disclosure; 
         FIG.  2 A  is a sectional view of a heater assembly in accordance with the teachings of the present disclosure; 
         FIG.  2 B  is a cross-sectional view of section  2 B- 2 B in  FIG.  2 A ; 
         FIG.  3 A  is a perspective view of a heater assembly in accordance with the teachings of the present disclosure; and 
         FIG.  3 B  is a cross-sectional view of section  3 B- 3 B in  FIG.  3 A . 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Examples and variations are provided to fully convey the scope of the disclosure to those who are skilled in the art. Numerous specific details are set forth such as types of specific components, devices, and methods, to provide a thorough understanding of variations of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed and that the examples and variations provided herein, may include alternative forms and are not intended to limit the scope of the disclosure. In some examples, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     Referring now to  FIG.  1   , a heater assembly  10  according to the teachings of the present disclosure is schematically depicted. The heater assembly  10  includes a substrate  100  and at least one resistive heater  120  comprising a plurality of heating elements  122  and corresponding heating zones  124 . The substrate  100  has an upper surface  102  (+y-direction), a lower surface  104  (−y-direction), a sidewall  106 , and a perimeter  108  adjacent and/or proximate to the sidewall  106 . The substrate  100  has a thickness (y-direction) and the sidewall  106  extends between the upper surface  102  and the lower surface  104 . As used herein, the term “perimeter” refers to an area or region extending adjacent or proximate to an outer sidewall of a substrate. For example, the plurality of heating elements  122  schematically depicted in  FIG.  1    are disposed along the perimeter  108  of the substrate  100 . Also, the plurality of heating elements  122  are attached to the upper surface  102  of the substrate  100 . As schematically depicted in  FIG.  1   , the substrate  100  has a circular shape (i.e., a circular cross-section in the x-z plane). However, it should be understood that substrates with different shapes (e.g., rectangular, triangular, elliptical, etc.) are included within the teachings of the present disclosure. 
     In some variations of the present disclosure, the plurality of heating elements  122 , and thereby the plurality of heating zones  124 , are independently controllable. In such variations, azimuthal temperature control of the heater assembly  10  is provided. As used herein, the phrase “azimuthal temperature control” refers to temperature control of a substrate along a circumferential direction of the substrate (e.g., along a perimeter of a substrate) as opposed to temperature control along a radial direction of the substrate. As used herein, the phrase “radial direction” refers to a direction from a center of a substrate (e.g., center “C” of substrate  100 ) to a perimeter of the substrate (e.g., perimeter  108 ) as schematically depicted by arrow  2  in  FIG.  1   . 
     Still referring to  FIG.  1   , in some variations of the present disclosure, a controller  150 , e.g., a two-wire controller, is included and in communication with the heater assembly  10  such that independent control of the plurality of heating elements  122 , and thereby independent control of the plurality of heating zones  124 , is provided. In such variations, each of the plurality of heating elements  122  define a material that functions as a heater element and as a temperature sensor. Non-limiting examples of two-wire controllers and their materials are disclosed in U.S. Pat. No. 7,196,295 which is commonly assigned with the present application and the disclosure of which is incorporated by reference in their entirety. For example, in some variations of the present disclosure, a power source  155  is provided and configured to provide power to the plurality of heating elements  122 , and the controller  150  in the form of a two-wire controller determines the temperature(s) of the plurality of heating elements  122  based on a calculated resistance of the plurality of heating elements  122 . Also, the controller  150  sends signals to the power source  155  to control the temperature(s) of the plurality of heating elements  122 . In at least one variation of the present disclosure, the controller  150  independently controls power to and the temperature of each of the plurality of heating elements  122 . 
     In operation, electrical current independently flows through each of the plurality of heating elements  122  and the controller  150  monitors the temperature or average temperature of each of the plurality of heating zones  124 , and based on temperature (or average temperature) of a given heating zone  124 , increases or decreases the electrical current through the corresponding heating element  122  such that the temperature of the given heating zone  124  is increased or decreased, respectively. 
     Non-limiting examples of resistive heater  120  and other resistive heaters disclosed herein, include a layered heater, a cable heater, a tubular heater, and a foil heater. A layered heater comprises layers of materials applied to a substrate and each layer, also referred to herein as a “heating element”, may be formed via laser-etching, thermal-spraying, or injection molding. 
     In some variations of the present disclosure, the plurality of heating elements  122  is a plurality of main heating elements, i.e., the plurality of heating elements  122  provide the main or primary heating of the substrate  100 . In at least one variation, the plurality of heating elements  122  are the only heating elements used for heating of the substrate  100 . In at least one other variation, the plurality of heating elements  122  provide the main or primary heating of the substrate  100  and secondary heating elements (not shown) provide secondary heating to a portion of the substrate  100  spaced inwardly from the plurality of heating elements  122  (i.e., in a direction from the perimeter  108  towards the shaft  126 ). 
     Referring now to  FIGS.  2 A and  2 B , a cross-section of a heater assembly  12  according to the teachings of the present disclosure is schematically depicted. Similar to the heater assembly  10  in  FIG.  1   , the heater assembly  12  includes the substrate  100  and at least one resistive heater  120 . The at least one resistive heater  120  schematically depicted in  FIGS.  2 A and  2 B  includes a plurality of heating elements  122 A- 122 C (also referred to herein as “first heating element  122 A”, “second heating element  122 B”, and “third heating element  122 C”) and corresponding heating zones  124 A- 124 C. Furthermore, the substrate  100  is in the form of a pedestal with a shaft  126  extending from the lower surface  104  of the substrate  100  encompassing electrical leads  128 A- 128 C,  130  (also referred to herein as “first electrical lead  128 A”, “second electrical lead  128 B”, “third electrical lead  128 C”, and “common ground electrical lead  130 ”). 
     Referring particularly to  FIG.  2 B , the plurality of heating elements  122 A- 122 C are arranged in series with the first electrical lead  128 A in communication with a first end (−x-direction) of the first heating element  122 A, the second electrical lead  128 B in communication with a first end (−x-direction) of the second heating element  122 B, the third electrical lead  128 C in communication with a first end (−x-direction) of the third heating element  122 C, and a common ground electrical lead  130  in communication with second ends (+x-direction) of the first, second, and third heating elements  122 A,  122 B,  122 C. Accordingly, electrical current is applied to or flows through the first heating element  122 A via electrical leads  128 A and  130 , electrical current is applied to the second heating element  122 B via electrical leads  128 B and  130 , and electrical current is applied to the third heating element  122 C via electrical leads  128 C and  130 . It should be understood that applying electrical current to the heating elements  122 A- 122 C in this manner provides independent control of the heating elements and the corresponding heating zones  124 A- 124 C. It should also be understood that applying electrical current to the heating elements  122 A- 122 C in this manner provides azimuthal temperature control of the substrate  100 . 
     In some variations of the present disclosure, the controller  150  is included as schematically depicted in  FIG.  2 A . The controller  150  is in communication with the heater assembly  12  and is configured to independently control the plurality of heating elements  122 A- 122 C, and thereby independently control the plurality of heating zones  124 A- 124 C. Particularly, the controller  150  is configured to provide controlled heating of the resistive heater  120  by increasing or decreasing the electrical current through the heating elements  122 A- 122 C via electrical leads  128 A- 128 C as described above. In some variations of the present disclosure the controller  150  provides uniform heating of the perimeter  108  of the substrate  100 , i.e., the temperatures or average temperatures of the heating zones  124 A- 124 C are generally equal to each other (e.g., within +/−2° C.). In other variations of the present disclosure the controller  150  provides selective heating of the perimeter  108  of the substrate  100 , i.e., the temperatures or average temperatures of the heating zones  124 A- 124 C are intentionally not generally equal to each other. 
     Referring now to  FIGS.  3 A and  3 B , another heater assembly  14  according to the teachings of the present disclosure is schematically depicted. Similar to the heater assembly  12  in  FIGS.  2 A- 2 B , the heater assembly  14  includes the substrate  100  with the shaft  126  and at least one resistive heater  140  disposed within the substrate  100 . However, in contrast to the heater assembly  12 , the at least one resistive heater  140  comprises a plurality of heating elements  142  each having a ground electrical lead. Particularly, the at least one resistive heater  140  schematically depicted in  FIG.  3 A  includes a plurality of heating elements  142 A- 142 D with corresponding heating zones  144 A- 144 D. Also, and as best shown in  FIG.  3 B , each of the heating elements  142 A- 142 D (only heating elements  142 A and  142 B shown in  FIG.  3 B ) has a positive electrical lead  141 A- 141 D, connected to a first end (+y-direction) of the heating elements  142 A- 142 D, respectively, and a negative electrical lead  143 A- 143 D connected to a second end (−y-direction) of the heating elements  142 A- 142 D, respectively. Accordingly, electrical current is applied to or flows through the heating element  142 A via electrical leads  141 A and  143 A, electrical current is applied to the heating element  142 B via electrical leads  141 B and  143 B, electrical current is applied to the heating element  142 C via electrical leads  141 C and  143 C, and electrical current is applied to the heating element  142 D via electrical leads  141 D and  143 D. It should be understood that applying electrical current to the heating elements  142 A- 142 D via electrical leads  141 A- 141 D and  143 A- 143 D provides independent control of the heating elements  142 A- 142 D and the corresponding heating zones  144 A- 144 D. It should also be understood that applying electrical current to the heating elements  142 A- 142 D in this manner provides azimuthal temperature control of the substrate  100 . 
     In some variations of the present disclosure, a controller  160  and a power source  165  are included as schematically depicted in  FIG.  3 A . The controller  160  is in communication with the heater assembly  14  and is configured to independently control the plurality of heating elements  142 A- 142 D, and thereby independently control the plurality of heating zones  144 A- 144 D. Particularly, the controller  160  is configured to provide controlled heating (via the power source  165 ) of the resistive heater  140  by increasing or decreasing the electrical current through the heating elements  142 A- 142 D via electrical leads  141 A- 141 D and  143 A- 143 D, respectively, as described above. In some variations of the present disclosure, the controller  160  provides uniform heating of the perimeter  108  of the substrate  100 , i.e., the temperatures or average temperatures of the heating zones  144 A- 144 D are generally equal to each other (e.g., within +/−2° C.). In other variations of the present disclosure, the controller  160  provides selective heating of the perimeter  108  of the substrate  100 , i.e., the temperatures or average temperatures of the heating zones  144 A- 144 D are intentionally not generally equal to each other. 
     It should be understood that the controller  160  can be a two-wire controller as described above and in communication with the heater assembly  12  such that independent control of the plurality of heating elements  142 A- 142 D, and thereby independent control of the plurality of heating zones  144 A- 144 D, is provided. In such variations, each of the plurality of heating elements  142 A- 142 D define a material that functions as a heater element and as a temperature sensor. 
     It should also be understood that the heating elements  142 A- 142 D are isolated from each other. In some variations of the present disclosure, the heating elements  142 A- 142 D are isolated from each by an isolation region  110  of the substrate  100 . That is, an isolation region  110  is positioned between each of the heating elements  142 A- 142 D. While four heating elements  142  are shown in  FIG.  3 A , it should be understood that less than four heating elements  142  or more than four heating elements  142  are within the scope of the present disclosure. 
     In some variations of the present disclosure, the plurality of heating elements  142 A- 142 D is a plurality of main heating elements, i.e., the plurality of heating elements  142 A- 142 D provide the main or primary heating of the substrate  100 . In at least one variation, the plurality of heating elements  142 A- 142 D are the only heating elements used for heating of the substrate  100 . In at least one other variation, the plurality of heating elements  142 A- 142 D provide the main or primary heating of the substrate  100  and secondary heating elements (not shown) provide secondary heating to a portion of the substrate  100  spaced inwardly from the plurality of heating elements  142 A- 142 D (i.e., in a direction from the perimeter  108  towards the shaft  126 ). Such secondary heating elements may include, by way of example, those illustrated and described in U.S. Publication No. 2019/0159291, which is commonly owned with the present application and incorporated herein by reference in its entirety. 
     It should be understood from the teachings of the present disclosure that a heater assembly for azimuthal heating of a substrate is provided. The heater assembly includes at least one resistive heater comprising a plurality of heating elements disposed along a perimeter of the substrate. Also, the plurality of heating elements are attached to an outer surface of the substrate, disposed within the substrate, or a combination thereof. Applying current to each of the plurality of heating elements provides multiple zone tuning of the heating elements and allows for heat transfer along an azimuthal direction of the substrate. The heat transfer along the azimuthal direction may be either from a center of the at least one resistive heater toward a peripheral end of the at least one resistive heater, or from a peripheral end or the at least one resistive heater toward a center of the at least one resistive heater. The center of the substrate spaced apart from the perimeter of the substrate may have a temperature higher or lower than the temperature of the perimeter. 
     The heater can be of various types of resistive heaters and is not limited to only resistive heaters such as layered heaters, cable heaters, tubular heaters, and foil heaters. Also, the substrate may include but is not limited to ceramic or metal material and may include one piece or multiple pieces. 
     The plurality of heating elements may be electrically connected in series such that all of the heating elements have a common ground electrical lead and n heating elements are independently controlled with electrical current flowing through the n heating elements and n+1 electrical leads. In the alternative, the plurality of heating elements may have a positive electrical lead and a negative electrical lead and n heating elements are independently controlled with electrical current flowing through the n heating elements and 2n electrical leads. 
     A controller may be included and be operable to independently control the plurality of heating zones. The controller may comprise a power source, a voltage and current measurement component, a power regulator component, and a processor in communication with the at least one resistive heater. The processor is also in communication with a communications component, where certain output from the heater assembly (e.g., temperature readings) is delivered and also where input (e.g., updated TCR values, calibration data, temperature set points, resistance set points) may be provided to the heater system. One example of the controller may be a two-wire controller where the resistive heater defines a material that functions as a heater element and as a temperature sensor. 
     While not shown in the drawings, it should be understood that other components included with pedestals, showerheads, etc., used in semiconductor processing can be included as part of the heater assemblies disclosed herein. Non-limiting examples of such components include routing layers, cooling channels, conductive vias and the like. 
     Although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections, should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer and/or section, from another element, component, region, layer and/or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section, could be termed a second element, component, region, layer or section without departing from the teachings of the example forms. Furthermore, an element, component, region, layer or section may be termed a “second” element, component, region, layer or section, without the need for an element, component, region, layer or section termed a “first” element, component, region, layer or section. 
     Specially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above or below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C. 
     The terminology used herein is for the purpose of describing particular example forms only and is not intended to be limiting. The singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     The description of the disclosure is merely exemplary in nature and, thus, examples and variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such examples and variations are not to be regarded as a departure from the spirit and scope of the disclosure. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples and variations, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims.