Patent Publication Number: US-2022223462-A1

Title: Using controlled gas pressure for backside wafer support

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims the benefit of pending U.S. Provisional Patent Application No. 63/136,046, filed Jan. 11, 2021, the contents of which are incorporated herein in their entirety. 
    
    
     BACKGROUND 
     Field 
     Embodiments of the present disclosure generally relate to substrate support assemblies. More specifically, embodiments of the present disclosure relate to substrate support assemblies for retaining a surface of a substrate and controlling a profile of the substrate. 
     Description of the Related Art 
     In the manufacture of optical devices, one or more devices having structures with sub-micron critical dimensions are disposed on two or more sides of a substrate, such as a front side and a backside of the substrate. To manufacture optical devices, such as waveguide combiners, a surface of the substrate having the one or more devices disposed on the surface must be retained on a substrate support assembly without contacting the one or more devices. Contacting the one or more devices may damage the devices. Furthermore, the substrate may include fragile materials, such as glass, and may have a thickness less than about 1 millimeter (mm). The combination of the fragile materials and the thickness may result in profile changes of the substrate, such as sagging of the substrate. Accordingly, what is needed in the art is substrate support assemblies which allow for profile control of the substrate and reduced contact on surfaces of the substrate. 
     SUMMARY 
     In one embodiment, a substrate support assembly is provided. The substrate support assembly includes a lower plate and an upper plate coupled to the lower plate. The upper plate is disposed on a top surface of the lower plate. The upper plate includes an upper surface and a retention surface disposed below the upper surface. The upper plate further includes a lip formed between the upper surface and the retention surface. The upper plate further includes a plurality of vacuum slots disposed through the retention surface. The substrate support assembly further includes at least two arcuate extensions disposed at a perimeter of the lower plate and the lower plate. The extensions are operable to move into a raised position and a lowered position. The substrate support assembly further includes a gas nozzle disposed through the upper plate. 
     In another embodiment, a substrate support assembly is provided. The substrate support assembly includes a lower plate and an upper plate coupled to the lower plate. The upper plate is disposed on a top surface of the lower plate. The upper plate includes an upper surface and a retention surface disposed below the upper surface. The upper plate further includes a lip formed between the upper surface and the retention surface. The upper plate further includes a plurality of vacuum slots disposed through the retention surface. The substrate support assembly further includes at least two extensions disposed at a perimeter of the lower plate and the lower plate. The extensions are operable to move into a raised position and a lowered position. The substrate support assembly further includes a gas nozzle disposed through the upper plate. The gas nozzle includes a top surface of the gas nozzle disposed below the substrate and the retention surface 
     In yet another embodiment, a method is provided. The method includes positioning a substrate onto at least two extensions disposed in a raised position of a substrate support assembly. The extensions are coupled to a body of the substrate support assembly. The method further includes lowering the extensions to a lowered positon. The lowered position includes the substrate sitting on a retention surface of the body. The retention surface includes a plurality of vacuum slots disposed therethrough. The method further includes providing a gas to active areas of the substrate through a gas nozzle disposed through the body of the substrate support assembly. The gas nozzle provides the gas at a direction perpendicular to a surface of the substrate. The method further includes providing a vacuum pressure to an exclusion zone of the substrate. The vacuum pressure is provided through the plurality of vacuum slots. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments. 
         FIG. 1  is a schematic, isometric view of a substrate support assembly in a raised position according to embodiments. 
         FIG. 2  is a schematic, cross-sectional view of a substrate support assembly in a raised position according to embodiments. 
         FIG. 3  is a flow diagram of a method for retaining a substrate with a substrate support assembly according to embodiments. 
         FIGS. 4A-4C  are schematic, cross-sectional views of the substrate support assembly during the method according to embodiments. 
       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 and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure generally relate to substrate support assemblies. More specifically, embodiments of the present disclosure relate to substrate support assemblies for retaining a surface of a substrate and controlling a profile of the substrate. In one embodiment, a substrate support assembly is provided. The substrate support assembly includes a lower plate and an upper plate coupled to the lower plate. The upper plate is disposed on a top surface of the lower plate. The upper plate includes an upper surface and a retention surface. The upper surface and the retention surface meet to form a lip therebetween. The upper plate further includes a plurality of vacuum slots disposed through the upper plate. The substrate support assembly further includes at least two extensions coupled to the lower plate and the upper plate. The extensions are operable to move into a raised position and a lowered position. The substrate support assembly further includes a gas nozzle disposed through the upper plate. In another embodiment, a method is provided. The method includes positioning a substrate onto at least two extensions disposed in a raised position of a substrate support assembly. The extensions are coupled to a body of the substrate support assembly. The method further includes lowering the extensions to a lowered positon. The lowered position includes the substrate sitting on a retention surface of the body. The retention surface includes a plurality of vacuum slots disposed therethrough. The method further includes providing a gas to active areas of the substrate through a gas nozzle disposed through the body of the substrate support assembly. The gas nozzle provides the gas at a direction perpendicular to a surface of the substrate. The method further includes providing a vacuum pressure to an exclusion zone of the substrate. The vacuum pressure is provided through the plurality of vacuum slots. 
       FIG. 1  is a schematic, isometric view of a substrate support assembly  100  in a raised position. The substrate support assembly  100  may be used with or modified to be used with different systems. For example, the substrate support assembly  100  may be utilized in chemical vapor deposition (CVD) systems, plasma-enhanced CVD (PECVD) systems, nano-imprint lithography systems, spin-on coating systems, angled etch systems, ink-jet systems, among others, as well as other systems utilized in manufacturing optical devices. 
     The substrate support assembly  100  is operable to retain a substrate  101 . The substrate  101  includes a second surface  103  (i.e., bottom surface) opposite a first surface  105 . In one embodiment, which can be combined with other embodiments described herein, the first surface  105  is a backside of the substrate  101 . In another embodiment, which can be combined with other embodiments described herein, the second surface  103  is a backside of the substrate  101  (as shown in  FIG. 1  and  FIG. 2 ). The substrate  101  may be glass, plastic, and polycarbonate, or any other suitable material. The substrate materials may have rollable and flexible properties. In one embodiment, which can be combined with other embodiments described herein, the substrate  101  has a thickness less than about 1 millimeter (mm). In some embodiments, the thickness is less than or equal to about 0.3 mm. 
     The substrate  101  is an optical device substrate. The substrate  101  includes one or more optical devices, such as waveguide combiners, disposed on the first surface  105  and/or the second surface  103  of the substrate  101 . The optical devices include structures having sub-micron critical dimensions, e.g., nano-sized critical dimensions. The optical devices are disposed on active areas of the substrate  101 . Touching, handling, and contacting the active areas of the substrate  101  can damage the one or more optical devices. The active zones also correspond to areas of the substrate  101  to be patterned with the optical devices. The substrate  101  further includes an exclusion zone. The exclusion zone does not include the one or more optical devices. In some embodiments, the exclusion zone is disposed along and around the perimeter of the substrate  101 . Supporting the exclusion zone allows for optical devices disposed on the first surface  105  and/or the second surface  103  of the substrate  101  to not be contacted. The active zones are interior to the exclusion zones. 
     Therefore, the substrate support assembly  100  can retain the substrate  101  by contacting and supporting the exclusion zone of the substrate  101  without contacting the active zones. Additionally, the substrate support assembly  100  is operable to control a profile of the substrate  101 , such as by compensating for sagging with pressurized gas as described by the method  300 . The substrate support assembly  100  is operable to control the profile of the substrate  101 . For example, the substrate support assembly  100  is operable to control the profile of the substrate  101  such that the substrate  101  is substantially planar, within +/− 0.1 mm. 
     The substrate support assembly  100  includes a body  102  and at least two extensions  108 . In one embodiment, which can be combined with other embodiments described herein, the body  102  is substantially circular in shape. The body  102  is not limited in shape and may support different shaped substrates. The extensions  108  are coupled to the body  102  and extend through apertures  109  in the body  102 . The extensions  108  are operable to move from a raised position (shown in  FIGS. 4A and 4B ) and a lowered position (shown in  FIG. 4C ). An actuator  120  is coupled to the extensions  108 . The actuator  120  is a mechanical actuator. The actuator  120  is operable to raise and lower the extensions  108  between the lowered position and the raised position. The extensions  108  are arcuate in shape. Each extension  108  has an angular range around the body  102 . The angular range is between about 10° and about 135° . More specifically, the angular range is between about 10° and about 135° , about 10° and about 100° , about 10° and about 90° , about 10° and about 80° , about 10° and about 70° , about 10° and about 60° , about 10° and about 50° , about 10° and about 40° , about 15° and about 90° , about 15° and about 45° , about 20° and about 90° , or about 20° and about 45° . 
     In some embodiments, a seal (not shown) is disposed on each of the extensions  108  to retain the substrate  101 . For example, the seal is an O-ring. The extensions  108  in the lowered position (as shown in  FIG. 4C ) are lowered such that the extensions  108  are in plane with the body  102 . Each extension  108  may also include an extension surface  111 . The extension surface  111  may correspond to a retention surface  210  (shown in  FIG. 2 ) such that when the extensions  108  are in the lowered position, the extension surface  111  is sufficiently the same as the retention surface  210 . For example, the substrate  101  is operable to sit on the extension surface  111  and the retention surface  210 . The extension surface,  111  is in plane with the retention surface  210  in the lowered position. The extension surface  111  is configured to support an exclusion zone of a substrate to be retained on the extensions  108 . 
     The body  102  includes a lower plate  104  and an upper plate  106 . The upper plate  106  is coupled to the lower plate  104 . The lower plate  104  includes an exterior surface  113 . In some embodiments, the upper plate  106  is coupled to the lower plate  104  via a plurality of fasteners (not shown) such as bolts or screws disposed through the upper plate  106  and the lower plate  104 . The extensions  108  are disposed around a perimeter of the upper plate  106  and the lower plate  104 . The upper plate  106  includes a plurality of vacuum slots  110 . The plurality of vacuum slots  110  are disposed through the upper plate  106 . The plurality of vacuum slots  110  are positioned underneath the substrate  101 . The plurality of vacuum slots  110  are in fluid communication with a vacuum source  114 . 
     A gas nozzle  118  is disposed through the upper plate  106 . The gas nozzle  118  is in fluid communication with a gas source  112 . The gas source  112  may include clean dry air (CDA), helium (He), argon (Ar), nitrogen gas (N 2 ), or combinations thereof. The substrate support assembly  100  further includes a controller  107 . The controller  107  is operable to control aspects of the substrate support assembly  100  during processing. A gas is provided through a top surface  122  of the gas nozzle  118 . 
     In one embodiment, which can be combined with other embodiments described herein, the body  102  is formed from a metallic material, such as aluminum, stainless steel, or alloys, combinations, or mixtures thereof. In another embodiment, which can be combined with other embodiments described herein, the body  102  is formed from a ceramic material, such as a silicon nitride material, an aluminum nitride material, an alumina material, or alloys, combinations, or mixtures thereof. 
       FIG. 2  is a schematic, cross-sectional view of a substrate support assembly  100  in a raised position. The lower plate  104  includes a vacuum channel  202 . The vacuum channel  202  is disposed through the lower plate  104 . The vacuum channel  202  is disposed around the perimeter of the body  102 . The vacuum channel  202  is in fluid communication with a vacuum source  114  via a vacuum line  205 . The lower plate  104  further includes a plurality of openings  204 . The plurality of openings  204  are disposed through a lower plate top surface  206  of the lower plate  104 . The upper plate  106  includes a recess  208 . The recess  208  is disposed through the upper plate  106 . The recess  208  is disposed around the perimeter of the body  102 . The vacuum source  114  provides a vacuum pressure to a plurality of vacuum slots  110 . The vacuum pressure is provided to the plurality of vacuum slots  110  from the vacuum source  114  via the vacuum channel  202 , the plurality of openings  204  and the recess  208 . 
     The substrate  101  is secured with the vacuum pressure when in a lowered position. The substrate  101  may sit on a retention surface  210  of the upper plate  106 . The vacuum source  114  is operable to provide vacuum pressure through the plurality of vacuum slots  110  to secure the substrate  101  to the retention surface  210 . The plurality of vacuum slots  110  are formed through the retention surface  210 . The retention surface  210  is recessed from an upper surface  212  of the upper plate  106 . The retention surface  210  is disposed below the upper surface  212 . The upper surface  212  and the retention surface  210  meet to form a lip  214  therebetween. The lip  214  extends between the retention surface  210  and the upper surface  212 . As such, the substrate  101  sits on the retention surface  210 . The retention surface  210  and the lip  214  are configured to support and define an exclusion zone of the substrate  101  to be retained on the retention surface  210 . The exclusion zone of the substrate  101  is supported by the extension surface  111  in the raised position. The exclusion zone of the substrate  101  is supported by the extension surface  111  and the retention surface  210  in the lowered position. 
     The substrate  101  is retained laterally by the vacuum pressure from the plurality of vacuum slots  110  and the lip  214 . A vacuum pressure is provided through the plurality of vacuum slots  110  to sufficiently secure the substrate  101  to the retention surface  210  without shifting along the retention surface  210 . The vacuum pressure may be adjusted depending on size and thickness of the substrate  101 . The controller  107  is operable to provide instructions and facilitate the actuation of the vacuum source  114  to provide the vacuum pressure to the retention surface  210 . 
     A gas nozzle  118  is disposed through the upper plate  106 . The gas nozzle  118  is in fluid communication with a gas source  112  via a gas source line  216 . The gas source line  216  is disposed through the lower plate  104 . In some embodiments, the gas source line  216  is disposed from the exterior surface  113  of the lower plate  104  to the gas nozzle  118 . The gas source line  216  provides gas to the gas nozzle  118 . The gas nozzle  118  is positioned to release the gas in a direction perpendicular to the first surface  105  and the second surface  103  of the substrate  101 . The gas source  112  may be in communication with the controller  107 . The controller  107  is operable to provide instructions and facilitate the delivery of gas through the gas nozzle  118 . The controller  107  is operable to adjust a gas pressure of the gas delivered through the gas nozzle  118 . When in the lowered position (shown in  FIG. 4C ), the gas is operable to provide gas pressure to the substrate  101  to control the profile of the substrate  101  without contacting the second surface  103  of the substrate  101 . For example, the gas may provide pressure to control a profile of the substrate  101  and reduce contact on the substrate. For example, the gas may be utilized to maintain the substrate  101  substantially planar. The vacuum pressure will also vary according to the gas pressure to ensure the substrate  101  remains contacting the retention surface  210 . For example, increasing the gas pressure may require increasing the vacuum pressure accordingly. 
       FIG. 3  is a flow diagram of a method  300  for retaining a substrate  101  with a substrate support assembly  100 .  FIGS. 4A-4C  are schematic, cross-sectional views of the substrate support assembly  100  during the method  300 . It is to be noted that the method  300  may be utilized in optical device manufacturing systems. For example, the method  300  may be utilized in chemical vapor deposition (CVD) systems, plasma-enhanced CVD (PECVD) systems, nano-imprint lithography systems, spin-on coating systems, angled etch systems, ink-jet systems, among others, as well as other systems utilized in manufacturing optical devices. An end effector  402  is operable to interact with the substrate  101  during the method  300 . The end effector  402  is operable to position the substrate  101  on the substrate support assembly  100 . The end effector  402  may be coupled to a robot. 
     The method  300  described herein provides for the retention of the substrate  101  without contacting active areas of the substrate  101 . Additionally, the substrate support assembly  100  provides for control of the profile of the substrate. For example, the substrate  101  may be retained substantially planar within +/− 0.1 mm. It is undesirable for active areas of the substrate  101  to be handled or touched when retained by the substrate support assembly  100  as a second surface  103  (i.e., bottom surface) opposite a first surface  105  will be patterned with optical devices. 
     At operation  301 , an end effector  402  positions a substrate  101  onto extensions  108  of the substrate support assembly  100 . The extensions  108  are in a raised position. The raised position is defined by the extensions  108  being raised above an upper plate  106  of the substrate support assembly  100 . In the raised position, an extension top surface  404  of the extensions  108  are not planar with an upper surface  212  of the upper plate  106 . The end effector  402  contacts the substrate  101  on exclusion zones of the substrate  101  such that optical devices formed on a second surface  103  are not damaged due to direct contact from the end effectors  402 . The substrate  101  is positioned on an extension surface  11  of each of the extensions  108 . The extensions  108  contact the exclusion zone of the substrate  101 . 
     In one embodiment, which can be combined with other embodiments described herein, the exclusion zone of a first surface  105  of the substrate  101  is in contact with the extensions  108 . The first surface  105  is positioned such that active areas (i.e., portions of the substrate  101  including one or more optical devices or portions of one or more optical devices to be patterned thereon) of the substrate  101  are not contacted. In another embodiment, as shown herein, which can be combined with other embodiments described herein, the exclusion zone of a second surface  103  of the substrate  101  is in contact with the extensions  108 . The second surface  103  is positioned such that active areas (i.e., portions of the substrate  101  including one or more optical devices or potions for one or more optical devices to be patterned thereon) of the substrate  101  are not contacted. 
     At operation  302 , as shown in  FIG. 4B , the end effectors  402  are retracted and cleared from the substrate support assembly  100 . At operation  303 , as shown in  FIG. 4C , the extensions are moved to a lowered position. The lowered position is defined by the extension top surface  404  of the extensions  108  being planar with the upper surface  212  of the upper plate  106 . The extensions  108  lower such that the substrate  101  will sit on the upper plate  106  (e.g., on a retention surface  210 , shown in  FIG. 2 ). A plurality of vacuum slots  110  (shown in  FIGS. 1 and 2 ) are disposed through the retention surface of the upper plate  106 . 
     At operation  304 , a gas is provided from a gas nozzle  118 . The gas nozzle  118  is positioned such that the gas is projected to the second surface  103  of the substrate  101 . The gas is provided from a gas source  112  in communication with the gas nozzle  118 . The controller  107  is operable to actuate the gas source  112  and to instruct the gas source  112  to increase and decrease a gas pressure of the gas, as desired. Therefore, the pressure applied to the substrate  101  may be static (i.e., constant gas pressure) or dynamic (i.e., gas pressure varies over time). In some embodiments, which can be combined with other embodiments described herein, the gas may be provided through the gas nozzle  118  prior to the operation  304 . For example, the gas may be provided concurrently as the substrate  101  is being lowered to the upper plate  106 . In other embodiments, which can be combined with other embodiments described herein, the operation  304  may be performed after the operation  305 . The gas may be provided when the extensions  108  are in the raised position or the lowered position. 
     The gas nozzle  118  does not contact the either the first surface  105  or the second surface  103  of the substrate  101 . As such, a top surface  122  of the gas nozzle  118  is below both the first surface  105  and the second surface  103  of the substrate  101 . The top surface  122  of the gas nozzle is also positioned below the retention surface to allow for a space between the top surface  122  and the substrate  101  on the retention surface  210 . The gas is provided from the gas nozzle  118  to contact the substrate  101  and control the profile of the substrate  101 . For example, gravitational forces can induce profile changes on the substrate  101  and the gas pressure may be utilized to counter the profile changes. The gas is operable to apply gas pressure to either the first surface  105  or the second surface  103  without contacting the active areas of the substrate  101 . Therefore, the substrate  101  may be flat or substantially flat. 
     At operation  305 , a vacuum pressure is provided to the substrate  101 . The vacuum pressure is provided from a vacuum source  114  in communication with the plurality of vacuum slots  110  (shown in  FIG. 2 ). The substrate  101  is positioned on the retention surface  210  and the vacuum pressure is activated to retain the substrate  101  on the upper plate  106 . The vacuum pressure prevents lateral movement of the substrate  101 . The vacuum pressure prevents rotation of the substrate  101 . The vacuum pressure counters the pressure provided from the gas nozzle  118  to chuck the substrate  101  to the substrate support assembly  100 . Therefore, the substrate maintains orientation and positon for processing. Maintaining the orientation and position improves the accuracy and quality during processing operations. 
     The combination of the gas from the gas source  112  provided to the substrate  101  and the vacuum pressure applied from the vacuum source  114  allows for the substrate to control the profile of the substrate  101  such that the substrate  101  is substantially planar, within +/− 0.1 mm. The controller  107 , in communication with the gas source  112  and the vacuum source  114 , can facilitate adjustments of gas pressure and vacuum pressure applied to the substrate  101 . The adjustments may be dynamic (i.e., gas pressure changes over time). The substrate support assembly  100  allows for retention of the substrate  101 . The substrate  101  is ready for processing of the first surface  105  and/or the second surface  103 . 
     In summation, substrate support assemblies for retaining a surface of a substrate and controlling a profile of the substrate are described herein. The substrate support assembly described herein provides for the retention of a substrate without contacting the one or more devices formed on a first surface or a second surface of the substrate. Additionally, the substrate support assembly compensates for changes in profile of the substrate. Gas is provided to a surface of the substrate to ensure the substrate is substantially planar. The gas nozzle does not contact active areas of the substrate while maintaining the desired profile of the substrate with pressure from the gas. A vacuum pressure is provided around the perimeter of the substrate to prevent lateral movement and rotation. The vacuum pressure also ensures the substrate remains chucked to the substrate support assembly. 
     While the foregoing is directed to examples of the present disclosure, other and further examples of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.