Patent Publication Number: US-2021183680-A1

Title: V-shape seal band for a semiconductor processing chamber

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims the benefit of U.S. patent application Ser. No. 15/361,365, filed Nov. 25, 2016, the contents of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     Examples described herein generally relate to a seal band that can be utilized in a substrate support assembly of a semiconductor processing chamber. 
     Description of the Related Art 
     Reliably producing nanometer and smaller features is one of the key technology challenges for next generation very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of VLSI and ULSI interconnect technology have placed additional demands on processing capabilities. Reliable formation of gate structures on the substrate is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die. 
     To drive down manufacturing cost, integrated chip (IC) manufactures demand higher throughput and better device yield and performance from every silicon substrate processed. Conventional electrostatic chucks (ESC) are typically bonded to a cooling plate in a substrate support assembly. The bond may be protected with a seal. However, the seals only provide a marginal protection due to a minimal surface contact between the ESC and the cooling plate. The electrostatic chuck may experience bonding problems within the substrate support assemblies due to fluorine radical penetration etching away the bonding layer once the seal has been compromised. Loss of bond material accelerates delamination of the ESC from the cooling plate. Additionally, a compromised seal may cause the bond material to outgas into the processing volume, thereby causing contamination in the chamber. The chamber may require down time to repair or replace the substrate support assembly, effecting costs, yield and performance. 
     Thus, there is a need for an improved substrate support assembly. 
     SUMMARY 
     Examples described herein provide a seal band for use in a substrate support assembly for semiconductor processing. The seal band has a ring shaped body. The ring shaped body has an inner surface, a top surface, and a bottom surface. Each of the top surface and the bottom surface extend from the inner surface at a first angle of more than 110° from the inner surface. The seal band also has an outer surface that has an indent formed therein. The outer surface connects the top surface to the bottom surface. A second angle is formed between an imaginary line normal to the inner surface and the bottom surface. The second angle is between about 10° and about 30°. The ring shaped body has a cross-sectional profile forming a V-shape. 
     In another example, an elastomer seal band has a ring shaped body that includes an inner surface, a top surface, and a bottom surface. Each of the top surface and the bottom surface extend from the inner surface at a first angle of more than 110° from the inner surface. The seal band includes an outer surface having an indent formed therein. The outer surface connects the top surface to the bottom surface. A second angle is formed between an imaginary line normal to the inner surface and the bottom surface. The second angle between about 10° and about 30°. The ring shaped body further includes a vertical height defined as a vertical distance between an intersection of the outer surface and the top surface, and an intersection of the outer surface and the bottom surface. The ring shaped body includes a horizontal length defined as a horizontal distance between the outer surface and the inner surface. The vertical height is greater than a horizontal length. The ring shaped body has a cross-sectional profile forming a V-shape. 
     In another example, an elastomer seal band has a ring shaped body with an outer diameter between about 306 mm and about 310 mm. The ring shaped body is formed from a perfluoroelastomer void of fillers having a Shore D hardness between about 60 and 80. The ring shaped body has a tensile strength between about 10 Mpa and about 15 Mpa. The ring shaped body includes an inner surface, a top surface, and a bottom surface. Each of the top surface and the bottom surface extend from the inner surface at an angle of more than 110° from the inner surface. The ring shaped body has an outer surface that has an indent formed therein. The outer surface connects the top surface to the bottom surface. The indent forms a profile in the elastomer seal band having a V-shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to implementations, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical implementations of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective implementations. 
         FIG. 1  is a cross-sectional schematic side view of a processing chamber having one embodiment of a substrate support assembly. 
         FIG. 2A  is a top plan view of a seal for the substrate support assembly. 
         FIG. 2B  is a cross sectional view of the seal taken across section line B-B in  FIG. 2A . 
         FIG. 3  is a partial cross-sectional schematic side view of the substrate support assembly detailing one embodiment of the seal disposed between an electrostatic substrate support and a cooling plate. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one implementation may be beneficially used in other implementations without specific recitation. 
     DETAILED DESCRIPTION 
     Disclosed herein is a seal band for a substrate support assembly disposed within a semiconductor processing chamber. The seal band protects an adhesive layer that is disposed between an electrostatic chuck (ESC) and a cooling plate of the substrate support assembly. The seal band is particularly advantageous for ESC applications that are exposed to high temperature operation. High temperature is intended to refer to temperatures in excess of about 150 degrees Celsius, for example, temperatures in excess of about 250 degrees Celsius, such as temperatures of about 250 degrees Celsius to about 300 degrees Celsius. The seal band is disposed on the outer perimeter of the bonding layer to prevent the bonding material from outgassing or being attacked by the harsh chamber environment. The seal band is configured to have increased contact area for maintaining the integrity and longevity of the seal. Although the substrate support assembly is described below in an etch processing chamber, the substrate support assembly may be utilized in other types of plasma processing chambers, such as physical vapor deposition chambers, chemical vapor deposition chambers, ion implantation chambers, among others, and other systems where protection of the bonding layer is desirable. 
       FIG. 1  is a cross-sectional schematic view of an exemplary plasma processing chamber  100 , shown configured as an etch chamber, having a substrate support assembly  126 . The substrate support assembly  126  may be utilized in other types of processing plasma chambers, for example plasma treatment chambers, annealing chambers, physical vapor deposition chambers, chemical vapor deposition chambers, and ion implantation chambers, among others, as well as other systems where the ability to control processing uniformity for a surface or workpiece, such as a substrate, is desirable. Control of the dielectric properties tan(δ), i.e., dielectric loss, or ρ, i.e., the volume resistivity, for the substrate support at elevated temperature ranges and beneficially enables azimuthal processing uniformity for a substrate  124  thereon. 
     The plasma processing chamber  100  includes a chamber body  102  having sidewalls  104 , a bottom  106  and a lid  108  that enclose a processing region  110 . An injection apparatus  112  is coupled to the sidewalls  104  and/or lid  108  of the chamber body  102 . A gas panel  114  is coupled to the injection apparatus  112  to allow process gases to be provided into the processing region  110 . The injection apparatus  112  may be one or more nozzle or inlet ports, or alternatively a showerhead. Processing gas, along with any processing by-products, are removed from the processing region  110  through an exhaust port  128  formed in the sidewalls  104  or bottom  106  of the chamber body  102 . The exhaust port  128  is coupled to a pumping system  132 , which includes throttle valves and pumps utilized to control the vacuum levels within the processing region  110 . 
     The processing gas may be energized to form a plasma within the processing region  110 . The processing gas may be energized by capacitively or inductively coupling RF power to the processing gases. In the embodiment depicted in  FIG. 1 , a plurality of coils  116  are disposed above the lid  108  of the plasma processing chamber  100  and coupled through a matching circuit  118  to an RF power source  120 . 
     The substrate support assembly  126  is disposed in the processing region  110  below the injection apparatus  112 . The substrate support assembly  126  includes an electrostatic chuck  174  and a cooling plate  130 . The cooling plate  130  is supported by a base plate  176 . The base plate  176  is supported by one of the sidewalls  104  or bottom  106  of the processing chamber. The substrate support assembly  126  may additionally include a heater assembly (not shown). Additionally, the substrate support assembly  126  may include a facility plate  145  and/or an insulator plate (not shown) disposed between the cooling plate  130  and the base plate  176 . 
     The cooling plate  130  may be formed from a metal material or other suitable material. For example, the cooling plate  130  may be formed from aluminum (Al). The cooling plate  130  may include cooling channels  190  formed therein. The cooling channels  190  may be connected to a heat transfer fluid source  122 . The heat transfer fluid source  122  provides a heat transfer fluid, such as a liquid, gas or combination thereof, which is circulated through one or more cooling channels  190  disposed in the cooling plate  130 . The fluid flowing through neighboring cooling channels  190  may be isolated to enabling local control of the heat transfer between the electrostatic chuck  174  and different regions of the cooling plate  130 , which assists in controlling the lateral temperature profile of the substrate  124 . In one embodiment, the heat transfer fluid circulating through the cooling channels  190  of the cooling plate  130  maintains the cooling plate  130  at a temperature between about 90 degrees Celsius and about 80 degrees Celsius, or at a temperature lower than 90 degrees Celsius. 
     The electrostatic chuck  174  includes a chucking electrode  186  disposed in a dielectric body  175 . The dielectric body  175  has a workpiece support surface  137  and a bottom surface  133  opposite the workpiece support surface  137 . The dielectric body  175  of the electrostatic chuck  174  may be fabricated from a ceramic material, such as alumina (Al 2 O 3 ), aluminum nitride (AlN) or other suitable material. Alternately, the dielectric body  175  may be fabricated from a polymer, such as polyimide, polyetheretherketone, polyaryletherketone and the like. 
     The dielectric body  175  may also include one or more resistive heaters  188  embedded therein. The resistive heaters  188  may be provided to elevate the temperature of the substrate support assembly  126  to a temperature suitable for processing a substrate  124  disposed on the workpiece support surface  137  of the substrate support assembly  126 . The resistive heaters  188  are coupled through the facility plate  145  to a heater power source  189 . The heater power source  189  may provide 900 watts or more power to the resistive heaters  188 . A controller (not shown) may control the operation of the heater power source  189 , which is generally set to heat the substrate  124  to a predefined temperature. In one embodiment, the resistive heaters  188  include a plurality of laterally separated heating zones, wherein the controller enables at least one zone of the resistive heaters  188  to be preferentially heated relative to the resistive heaters  188  located in one or more of the other zones. For example, the resistive heaters  188  may be arranged concentrically in a plurality of separated heating zones. The resistive heaters  188  may maintain the substrate  124  at a temperature suitable for processing. In some embodiments utilizing elevated processing temperatures, the resistive heaters  188  may maintain the substrate  124  at a temperature between about 180 degrees Celsius to about 500 degrees Celsius. 
     The electrostatic chuck  174  generally includes a chucking electrode  186  embedded in the dielectric body  175 . The chucking electrode  186  may be configured as a mono polar or bipolar electrode, or other suitable arrangement. The chucking electrode  186  is coupled through an RF filter to a chucking power source  187 , which provides a RF or DC power to electrostatically secure the substrate  124  to the workpiece support surface  137  of the electrostatic chuck  174 . The RF filter prevents RF power utilized to form a plasma (not shown) within the plasma processing chamber  100  from damaging electrical equipment or presenting an electrical hazard outside the chamber. 
     The workpiece support surface  137  of the electrostatic chuck  174  may include gas passages (not shown) for providing backside heat transfer gas to the interstitial space defined between the substrate  124  and the workpiece support surface  137  of the electrostatic chuck  174 . The electrostatic chuck  174  may also include lift pin holes for accommodating lift pins (not shown) for elevating the substrate  124  above the workpiece support surface  137  of the electrostatic chuck  174  to facilitate robotic transfer into and out of the plasma processing chamber  100 . 
     A bonding layer  150  is disposed between the electrostatic chuck  174  and the cooling plate  130 . The bonding layer  150  may be formed from several layers which provide for different thermal expansions of the electrostatic chuck  174  and the cooling plate  130 . The bonding layer  150  includes an adhesive layer (shown as  308  in  FIG. 3 ) and a seal band  140 . The seal band  140  is configured to protect the adhesive material forming the adhesive layer of bonding layer  150  disposed between the electrostatic chuck  174  and the cooling plate  130  from the gases and plasma present in the processing region  110 . 
       FIG. 2A  is a top plan view of the seal band  140 . The seal band  140  has a ring shaped body  201 . The ring shaped body  201  has a center  202  about which the seal band  140  is substantially congruent. The ring shaped body  201  has an inner surface  212  and an outer surface  210 . The outer surface  210  of the ring shaped body  201  has a diameter  208  that defines the outside diameter of the seal band  140 . In one embodiment, the diameter  208  may be between about 306 mm and about 310 mm, such as about 308 mm. In another embodiment, the diameter  208  may be between about 206 mm and about 210 mm, such as about 208 mm. In yet another embodiment, the diameter  208  may be between about 456 mm and about 460 mm, such as about 458 mm. 
     The seal band  140  may be formed from a soft elastomeric material, for example, having a Shore D hardness of between about 60 and about 80, such as about  72 . The seal band  140  may additionally have a tensile strength between about 10 Mpa and about 15 Mpa, such as about 11.1 Mpa. The elastomeric material forming the seal band  140  may be elongated to about 160% of its original size prior to breaking. The seal band  140  may be formed from a high performance elastomer such as a tetrafluoro ethylene/propylene, a perfluoroelastomer such as Fluoritz-TR® or Perlast G67P®, or other suitable material. In one embodiment, the seal band  140  is formed from Fluoritz-TR®. The material of the seal band  140  is void of fillers and is resistant to fluorine and oxygen chemistries for enhanced resistance to cracking and plasma radicals. The absence of filler material prevents premature crack formation that happens to conventional filled seals at the filler&#39;s material boundaries where the base elastomer has etched away. There may be an increase in the material erosion rate in absence of the filler material, but the larger contact and absence of cracks beneficially improves the service life of the seal band  140 . 
       FIG. 2B  is a cross sectional view of the seal band  140  taken across section line B-B in  FIG. 2A . The seal band  140  has a top surface  254  and a bottom surface  252 . The top surface  254  and the bottom surface  252  are connected by the inner surface  212 . An imaginary normal line  253  may be disposed at 90° from the inner surface  212 . An angle  220  may be formed between the imaginary normal line  253  and the bottom surface  252 . The top surface  254  may be similarly angled with the imaginary normal line  253  as the bottom surface  252 . The angled  220  may be between about 10 degrees and about 30 degrees, such as about 20 degrees. Thus, the top surface  254  and the bottom surface  252  may have an angled  221  from the inner surface  212  of between about 100° and about 120°, such as more than about 110°. The top surface  254  and the bottom surface  252  may have a length  262  measured along the normal between the inner surface  212  and the outer surface  210 . The length  262  may be between about 1.55 mm and about 1.25 mm such as about 1.40 mm. 
     The outer surface  210  may have a height  264  extending between the top surface  254  to the bottom surface  252 . The height  264  may be between about  2 . 075  mm and about 2.125 mm such as about 2.100 mm. The outer surface  210  may have an indent  230  formed therein. The indent  230  may produce a V-shaped profile for the seal band  140 . The indent  230  may have a depth  232  between about 0.30 mm and about 0.50 mm such as about 0.40 mm. The indent  230  permits the seal band  140  to be easily compressed for ease of installation, and to orientate the top surface  254  and bottom surface  252  in a substantially parallel orientation that enhances the contact area with the electrostatic chuck  174  and the cooling plate  130  when making a seal therebetween when disposed in the substrate support assembly  127 . In one embodiment, the seal band  140  is symmetrical about an imaginary line bifurcating the indent  230  and inner surface  212 . 
     Use of the seal band  140  in the substrate support assembly  127  will now be discussed relative to  FIG. 3 .  FIG. 3  is a partial cross-sectional schematic side view of the substrate support assembly  126  detailing one embodiment of the seal band  140  disposed between an electrostatic chuck  174  and the cooling plate  130 . The bonding layer  150  disposed between the electrostatic chuck  174  and the cooling plate  130  may be formed from different materials. An electrical socket  360  may provide connections to the resistive heaters  188  and chucking electrode  186  embedded in the dielectric body  175 . The resistive heaters  188  may heat the bottom  133  of the electrostatic chuck  174  to temperatures above 250° Celsius. The bonding layer  150  may extend to about an outer diameter  352  of the electrostatic chuck  174  or the cooling plate  130 . The bonding layer  150  is flexible to account for thermal expansion between the electrostatic chuck  174  and the cooling plate  130 , to substantially prevent cracking, and to reduce the potential for the electrostatic chuck  174  delaminating from the cooling plate  130 . 
     The bonding layer  150  includes at least one adhesive layer  308 . The adhesive layer  308  may be formed from a perfluoro compound, silicone, porous graphite, an acrylic compound, perfluoromethyl vinyl ether, alkoxy vinyl ether, CIRLEX®, TEFZEL®, KAPTON®, VESPEL®, KERIMID®, polyethylene, or other suitable material. The adhesive layer  308  may have a thickness  302  of about 1 mm to about 5 mm, such as about 1.75 mm. The adhesive layer  308  may have a thermal conductivity between about 0.1 W/mK and about 1 W/mK, such as about 0.17 W/mK. 
     A notch  342  is formed between an outer periphery  350  of the adhesive layer  308  and the outer diameter  352  of the electrostatic chuck  174 . The diameter  208  of the seal band  140  is less than the outer diameter  352  of the electrostatic chuck  174 . Additionally, the diameter  208  of the seal band  140  is less than the outer diameter of the cooling plate  130 . The seal band  140  disposed about, i.e., circumscribes, the outer periphery  350  of the adhesive layer  308 . The notch  342  may be sized to permit the seal band  140  to sealingly engage the electrostatic chuck  174  and cooling plate  130 . Although the seal band  140  may optionally form a vacuum tight seal between the electrostatic chuck  174  and the cooling plate  130 , the primary function of the seal is to protect the exposed outer periphery  350  of the adhesive layer  308  from the environment within the processing region  110 . 
     In one embodiment, the seal band  140  prevents the process gas exposure to the bond material (adhesive layer  308 ) of the substrate support assembly  126 . That is, the seal band  140  protects the inner portions of the substrate support assembly  126  from exposure to the plasma environment. The seal band  140  prevents volatized gases from the adhesive layer  308  from contaminating the plasma environment. The seal band  140  protects the adhesive layer  308  and other internal structures of the substrate support assembly  127  from the plasma environment. 
     The seal band  140  may be V-shaped. The shape of the seal band  140  provides a contact surface  310  for sealing which is substantially larger than conventional O-ring seals. Additionally, the V-shaped provides for easier installation of the seal band  140 . For example, the force required to install the seal band  140 , having the V-shaped, is decreased by about 40% compared to the force required to install a conventional O-ring. For example, at 0° Celsius, the seal band  140  has an installation force of about 0.63 N/mm whereas conventional O-rings have an installation force of about 1.00 N/mm. The contact surface  310  of the seal band  140 , having the V-shaped, is substantially larger (in width) compared to the contact area of traditional O-rings. For example, the contact surface  310  of the seal band  140  is about 30% greater than the contact area of conventional O-rings. As the temperature increases from 0 degrees Celsius to 50 degrees Celsius, the contact surface  310  of the seal band  140  increases from about 0.62 mm to about 0.74 mm. 
     After installation, a compression load on the seal band  140  varies with the temperature of the seal band  140 . In operation, the seal band  140  may be compressed as much as 20%. The increase in compression of the seal band  140  at the higher temperature improves the seal-ability even after some erosion. The erosion profile of the seal band  140  may be indicative of the longevity for the seal band  140 . The erosion profile at 800 RF hours and 1700 RF hours have shown little wear requiring replacement of the seal band  140 . The compression load is not linear as thermal expansion of the seal band  140  leads to an increase squeeze of the seal band  140  resulting in an increase compression load. At the same time, the material of the seal band  140  is softened by the heat and results in a decrease in the compression load. For example, at 0 degrees Celsius, the compression load on the seal band  140  is about 0.23 N/mm; at 25 degrees Celsius, the compression load on the seal band  140  increases to about 0.26 N/mm; and at 50 degrees Celsius, the compression load on the seal band  140  decreases to about 0.15 N/mm. 
     The resistance of the seal band  140  to initial cracking was tested on a metallic drum. The seal band  140  was stretched 28% on the metallic drum. The seal band  140  was exposed to plasma having O 2  and CF 4  flowing at a 196:4 ratio by weight. The seal band  140  formed from Fluoritz-TR demonstrated a greater than 100% increase in longevity from cracking compared to seal bands  140  formed from Fluoritz-T20, transparent perfluoro-elastomers (FFKM) B or D, white FFKM F, K or L, and POR. Additionally, the weight loss due to erosion was less than all the aforementioned materials except for Fuoritz-T20. Advantageously, the compression load and material of the seal band  140  significantly reduced cracking which may compromise the seal. For example, after 320 RF hours and 600 RF hours, the seal band  140  formed from Fluoritz-TR had no visible signs of erosion or cracking. 
     Advantageously, the seal band  140  having a V-shaped substantially prevents cracking or degradation of the seal from harsh radical chemistries in the processing chamber, such as fluorine radicals penetrating and etching away the seal protecting the bonding layer. The seal band  140  having a V-shaped substantially minimizes the degradation of the bond between the ESC and the cooling plate while substantially preventing volatiles outgassing from the bonding layer from entering the processing environment. Thus, the seal band  140  having a V-shaped prevents contamination in the chamber and reduces chamber downtime which may affect process yields and costs of operations. 
     Examples described herein generally relate to a seal band that can be utilized in a substrate support assembly of a semiconductor processing chamber. While the foregoing is directed to implementations of the present invention, other and further implementations of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.