Patent Publication Number: US-2023146837-A1

Title: Apparatus and methods for fine planar non-uniformity improvement

Description:
TECHNICAL FIELD 
     Embodiments of the disclosure generally relate to apparatus and methods for improving deposition non-uniformity. In particular, embodiments of the disclosure pertain to apparatus and methods to decrease the non-uniformity of deposited films due to temperature non-uniformity of the substrate. 
     BACKGROUND 
     In the field of semiconductor processing, flat-panel display processing or other electronic device processing, vapor deposition processes have played an important role in depositing materials on substrates. With smaller technology nodes, on-wafer process uniformity becomes more stringent, having a larger impact on the formation of usable devices. 
     Most of the chemical vapor deposition (CVD) and atomic layer deposition (ALD) chambers are thermally asymmetric due, at least in part, to having a slit valve at one side of the chamber and an exhaust at the other side. The slit valve area is typically colder than the exhaust area and thermal loss from the wafer are correlated with these temperature differences. 
     The overall deposition non-uniformity in a process chamber results from a combination of several sources; radial non-uniformity, planar non-uniformity and residual non-uniformity. Radial non-uniformity generally appears as a somewhat symmetric pattern with the center of the wafer having a different thickness than the edges of the wafer. Planar non-uniformity occurs in a pattern across the wafer surface with one edge of the wafer having a different thickness than the opposite edge. The temperature gradient over the wafer surface has a planar non-uniformity impact on thickness of the film being deposited. Planar non-uniformity, while not as significant as radial non-uniformity, becomes a substantial concern to the semiconductor chip making industries for the N3 or beyond node for upcoming next generation microprocessors. 
     Accordingly, there is a need in the art for apparatus and methods for improving the planar temperature uniformity. 
     SUMMARY 
     One or more embodiments of the disclosure are directed to pedestal heater radiators comprising a first radiator body and a second radiator body. The first radiator body comprises a central clamping portion and an outer peripheral portion. The first radiator body has a top surface and a bottom surface defining a thickness. The first radiator body comprises a first material having a first emissivity. The second radiator body is connected to a portion of the first radiator body by at least two connection points. The second radiator body has a top surface and a bottom surface defining a thickness. The second radiator body comprises a second material having a second emissivity different from the first emissivity. 
     Additional embodiments of the disclosure are directed to pedestal assemblies comprising a heater and a pedestal heater radiator. The heater is positioned on a top end of a pedestal shaft and has a support surface and a bottom surface defining a thickness of the heater. The pedestal heater radiator comprises a first radiator body and a second radiator body. The first radiator body comprises a central clamping portion and an outer peripheral portion. The first radiator body has a top surface and a bottom surface defining a thickness. The first radiator body comprises a first material having a first emissivity. The second radiator body is connected to a portion of the first radiator body by at least two connection points. The second radiator body has a top surface and a bottom surface defining a thickness. The second radiator body comprises a second material having a second emissivity different from the first emissivity. The pedestal heater radiator is positioned along the length of the pedestal shaft and spaced a distance from the bottom surface of the heater. 
     Further embodiments of the disclosure are directed to methods of decreasing film thickness non-uniformity. A size of a first radiator body having a first emissivity and a second radiator body having a second emissivity are determined. The first radiator body is assembled with the second radiator body by connecting at least one connection tab on the second radiator body to at least one connection hub on the first radiator body to form a single component radiator body. The single component radiator body is positioned adjacent a bottom surface of a heater positioned on a top end of the pedestal shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the disclosure are attained and can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG.  1    shows a view of a pedestal heater radiator in accordance with one or more embodiments of the disclosure; 
         FIG.  2    shows an expanded view of a portion of a pedestal heater radiator in accordance with one or more embodiment of the disclosure; 
         FIG.  3    shows a bottom view of a pedestal assembly including a pedestal heater radiator in accordance with one or more embodiment of the disclosure; 
         FIG.  4    shows a side view of a pedestal assembly including a pedestal heater radiator and clamp in accordance with one or more embodiment of the disclosure; and 
         FIG.  5    shows a partial cross-sectional view of a pedestal assembly including a heater radiator and clamp in accordance with one or more embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. 
     As used in this specification and the appended claims, the term “substrate” refers to a surface, or portion of a surface, upon which a process acts. It will also be understood by those skilled in the art that reference to a substrate can also refer to only a portion of the substrate, unless the context clearly indicates otherwise. Additionally, reference to depositing on a substrate can mean both a bare substrate and a substrate with one or more films or features deposited or formed thereon 
     A “substrate” as used herein, refers to any substrate or material surface formed on a substrate upon which film processing is performed during a fabrication process. For example, a substrate surface on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, without limitation, semiconductor wafers. Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure and/or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in the present disclosure, any of the film processing steps disclosed may also be performed on an underlayer formed on the substrate as disclosed in more detail below, and the term “substrate surface” is intended to include such underlayer as the context indicates. 
     Embodiments of the disclosure provide new techniques to improve film thickness non-uniformity on the wafer side-to-side. The side-to-side uniformity is referred to as planar uniformity. Some embodiments advantageously provide techniques with less dependence on the surface emissivity to achieve consistent uniformity for extended process times. Some embodiments advantageously provide low-cost solutions to planar non-uniformity issues with fine tunability. Some embodiments allow for tuning planar non-uniformity in multiple zones. 
     One or more embodiments of the disclosure provide techniques using a heater backside radiator as an indirect heat source to alter radiation loss from the heater backside. Based on types of materials, surface temperatures of the radiator will vary and radiation heat transfer from the pedestal to the radiator can be tuned. Process burn-in can minimize the non-uniformity drift over time at extended runs. Some embodiments prevent relative heat loss between the wafer sides, enabling improved control over the process film thickness and/or improve planar non-uniformity. Some embodiments of the disclosure address planar non-uniformity to improve film thickness uniformity at the atomic scale. 
     Referring to  FIG.  1   , one or more embodiments of the disclosure are directed to pedestal heater radiators  100 . The radiator  100  comprises a first radiator body  110  and a second radiator body  150 . While two radiator bodies are illustrated in the Figures, the skilled artisan will recognize that there can be more than two radiator bodies. 
     The first radiator body  110  has a top surface  112  and a bottom surface  114  that define a thickness T1 of the first radiator body  110 . The first radiator body  110   includes a central clamping portion  120  and an outer peripheral portion  122 . The central clamping portion  120  has in inner peripheral face  121  and the outer peripheral portion  120  of the first radiator body  110  has an outer peripheral face  123 . 
     The first radiator body  110  comprises a first material having a first emissivity. The skilled artisan will understand that emissivity refers to the amount of energy emitted from the material surface as thermal radiation. The first material can be any suitable material including, but not limited to, aluminum, stainless steel, aluminum nitride, quartz or aluminum oxide. 
     In the embodiment illustrated in  FIG.  1   , the central clamping portion  120  of the first radiator body  110  comprises a center ring  126  and the outer peripheral portion  122  comprises an outer ring  128 . The center ring  126  is connected to the outer ring  128  by a plurality of spokes  130 . In the embodiment illustrated, there are six spokes  130 . However, the skilled artisan will recognize that there can be more or less than six spokes  130 . In some embodiments, the first radiator body  110  has no spokes  130  so that a disc of the first material is formed without a separate center ring  126  and outer ring  128 . In a disc-shaped radiator body, the outer ring  128  refers to the portion of the disc-shaped body adjacent the outer peripheral edge  123 . 
     The center ring  126  of some embodiments comprises a plurality of openings  132 . The number of openings  132  can be any suitable number and is not limited to the number of openings  132  shown in the Figures. The plurality of openings  132  of some embodiments, are configured to allow a fastener  140 , shown in  FIG.  2   , to pass through the first radiator body  110 . The fastener  140  can be any suitable fastener known to the skilled artisan including, but not limited to, bolts and screws. 
     The outer ring  128  of some embodiments includes an inset portion  142 . The inset portion  142  forms an outer peripheral recess where the outer peripheral edge  123   a  is closer to the center ring  126  than the outer peripheral edge  123  outside of the inset portion  142 . The inset portion  142  has a length measured along the arc segment formed by the first end face  144  and second end face  146 . The length of the inset portion  142  can be any suitable length. In some embodiments, the length of the inset portion  142  is measured as an angle. For example, in some embodiments, the length of the inset portion  142  is less than or equal to 210°, 195°, 180°, 165°, 150°, 135°, 120°, 105°, 90° or 75°. The width of the inset portion  142 , measured from the outer peripheral face  123  to the outer peripheral edge  123   a , is in the range of 1 mm to 100 mm, or in the range of 5 mm to 75 mm, or in the range of 10 mm to 50 mm. 
     The second radiator body  150  has a top surface  152  and a bottom surface  154  defining a thickness T2 of the second radiator body  150 . The second radiator body  150  comprises a second material having a second emissivity different from the first emissivity of the first material. The second material can be any suitable material known to the skilled artisan including, but not limited to, aluminum and stainless steel. The first material and second material can be selected to control the overall emissivity of the pedestal heater radiator  100 . In some embodiments, the first material of the radiator body  110  comprises aluminum and the second material of the second radiator body  150  comprises stainless steel. 
     The second radiator body  150  has a complementary shape to the inset portion  142  of the outer ring  128  of the first radiator body  110 . The inset portion  142  of some embodiments is an arcuate shaped cutout in the outer ring  128  and the second radiator body  150  is arcuate shaped to fit within the arcuate shaped cutout. 
     The second radiator body  150  has a length defined by a first end  156  and  158 . The length of the second radiator body  150  of some embodiments is equal to or slightly less than the length of the inset portion  142 . In some embodiments, the length of the second radiator body  150  is at least 0.1 mm less than the length of the inset portion  142 . The thickness T2 of the second radiator body  150  is measured along the middle portion of the second radiator body  150  away from any connection tab  160 , as described below. The length of the second radiator body  150  is measured between the faces of the second radiator body that fit within the inset portion  142  and do not include any length associated with a connection tab  160 , as described below. 
     The outer ring  128  of the first radiator body  110  of some embodiments includes at least one connection hub  115 . In the embodiment illustrated in  FIG.  1   , the first radiator body  110  includes two connection hubs  115  located at either end of the inset portion  142 . The second radiator body  150  comprises at least one connection tab  160  positioned to cooperatively interact with the at least one connection hub  115  of the first radiator body  110 . In the embodiment illustrated in  FIG.  1   , there are two connection tabs  160  positioned at opposite ends of the second radiator body  150 . The connection tabs  160  extend a distance (length L H2 ) from the first end  156  and second end  158  of the second radiator body  150 . 
     Referring to  FIGS.  1  and  2   , the connection tabs  160  include a top surface  162  configured to overlap at least a portion of the bottom surface  116  of the connection hub  115  of the first radiator body  110 . The size of the overlap Lo between the connection tab  160  and the connection hub  115  is variable to change contact resistance between the first radiator body  110  and the second radiator body  150 . Stated differently, the length L H1  of the connection hub  115  of the first radiator body  110  and the length L H2  of the connection tab  160  of the second radiator body  150  can be varied to change the amount of overlap Lo between the connection hubs and tabs, and change the thermal coupling between the first radiator body  110  and the second radiator body  150 . In some embodiments, the amount of overlap LO is less than or equal to 1.5 inches, 1.25 inches, 1 inch, 0.75 inches, 0.5 inches, 0.25 inches, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm or 5 mm. 
     In some embodiments, as shown in  FIG.  1   , an intermediate contact body  170  is positioned between the top surface  162  of the connection tab  160  of the second radiator body  150  and the bottom surface  116  of the connection hub  115  of the first radiator body  110 . The intermediate contact body  170  can be any suitable material of any suitable thickness. In some embodiments, the intermediate contact body  170  changes the contact resistance between the first radiator body and the second radiator body. In some embodiments, the intermediate contact body  170  is made of a third material having a third emissivity. The third emissivity of some embodiments is different than one or more of the first emissivity or second emissivity. In some embodiments, the third material cushions the contact between the first radiator body  110  and the second radiator body  150  to prevent formation of particulates as the radiator  100  is heated within the processing chamber. 
     In some embodiments, as shown in  FIG.  2   , the top surface  112  of the first radiator body  110  is substantially coplanar with the top surface  152  of the second radiator body  150 . As used in this manner, the term “substantially coplanar” means that the plane formed by the top surface  112  of the first radiator body  110  is within ±0.5 mm, ±0.2 mm or ±0.1 mm of coplanarity. In some embodiments, the top surface  112  of the first radiator body  110  and the top surface  152  of the second radiator body  150  are not coplanar. 
     Referring to  FIGS.  3  and  4   , one or more embodiments of the disclosure are directed to pedestal assemblies  200 . The pedestal assemblies  200  comprise a heater  210  on a top  204  of a pedestal shaft  202 . The heater  210  has a support surface  212  and a bottom surface  214  that define the thickness of the heater  210 . The pedestal heater radiator  100  is positioned along the length of pedestal shaft  202  and is spaced a distance D from the bottom surface  214  of the heater  210 . The distance D between the pedestal heater radiator  100  and the bottom surface  214  of the heater  210  can be tuned to allow for a decrease in temperature non-uniformity. In some embodiments, the distance D is in the range of 0.5 mm to 2.5 mm, or in the range of 0.75 mm to 2.25 mm, or in the range of 1 mm to 2 mm, or in the range of 1.25 mm to 1.75 mm. 
     The pedestal heater radiator  100  is maintained at a fixed position along the length of the shaft  202  using a clamp  220 . The clamp  220  is positioned around the pedestal shaft  202  and configured to cooperatively interact with the central clamping portion  120  of the pedestal heater radiator  100  at the distance D from the bottom surface  214  of the heater  210 . 
     In some embodiments, as shown in  FIG.  3   , the first radiator body  110  is split into a first radiator body part  110   a  and a second radiator body part  110   b  that can be positioned around the shaft  202  below the heater  210 . In embodiments of this sort, the first radiator body part  110   a  and second radiator body part  110   b  are connected together using a suitable fastener. The split body pedestal heater radiator  100  can be positioned on a pedestal without removing the heater, making it easier to retrofit to existing systems. 
     The clamp  220  of some embodiments is a split body that can be positioned around the shaft  202 . As shown in  FIG.  4   , the split body of the clamp  220  is separated into a first clamp body  220   a  and a second clamp body  220   b  that combine to form the clamp  220 . The clamp  220  can be connected to the pedestal heater radiator  100  through openings  230  using fasteners  232 . The fasteners  232  can be any suitable fasteners known to the skilled artisan. In some embodiments, at least some of the openings  230  are aligned to allow the first clamp body  220   a  and the second clamp body  220   b  to be connected together using a suitable fastener. 
       FIG.  5    shows a partial cross-sectional view of an embodiment of a pedestal assembly  200  including the pedestal heater radiator  100  and clamp  220 . In the illustrated embodiment, the clamp  220  includes a protrusion  222  that cooperatively interacts with a complementary recess  224  in the shaft  202 . In embodiments of this sort, the position of the clamp  220  is fixed and control of the distance D between the pedestal heater radiator  100  and the bottom surface  214  of the heater  210  is based on the thickness of the first radiator body  110  and second radiator body  150 . 
     Referring back to  FIG.  1   , in some embodiments, the second radiator body  150  is connected to the first radiator body  110  using a suitable fastener through openings  166 . In some embodiments, the second radiator body  150  is removable from the first radiator body  110  and can be replaced with a different second radiator body  150  with a different thickness and/or emissivity. 
     Additional embodiments of the disclosure are directed to methods of decreasing film thickness non-uniformity. A size of a first radiator body  110  and second radiator body  150  is determined. The sizes of the first radiator body  110  and second radiator body  150  include the radius and/or thicknesses of the materials where the first radiator body  110  has a first emissivity and the second radiator body  150  has a second emissivity. 
     The first radiator body  110  is assembled with the second radiator body  150  by connecting at least one connection tab  160  on the second radiator body  150  to at least one connection hub  115  on the first radiator body  100  to form a single component radiator body  100 . The single component radiator body is positioned adjacent a bottom surface of a heater  214  positioned at a top end  204  of a pedestal shaft  202 . In some embodiments, the single component radiator body is clamped into positioned at a fixed distance from the bottom surface of the heater  210  using a clamp  220  configured to interact with the central clamping portion  120  of the first radiator body  110 . 
     Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Although the disclosure herein has been described with reference to particular embodiments, those skilled in the art will understand that the embodiments described are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present disclosure without departing from the spirit and scope of the disclosure. Thus, the present disclosure can include modifications and variations that are within the scope of the appended claims and their equivalents.