Patent Publication Number: US-10312116-B2

Title: Methods and apparatus for rapidly cooling a substrate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. Pat. No. 9,779,971, issued on Oct. 3, 2017, which is herein incorporated by reference in its entirety. 
    
    
     FIELD 
     Embodiments of the present disclosure generally relate to substrate processing equipment. 
     BACKGROUND 
     Formation of some devices on substrates requires multiple processes in various chambers. For example, processes such as atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), etching, etc., may be performed to form or remove layers on a substrate. Many of these processes require the substrate to be heated to a high temperature and, therefore, subsequent cooling of the processed substrate is necessary. 
     Some processes require a cool down step before further process steps can be performed. The inventors have observed that many conventional cool down stations are operated in a high vacuum environment and, therefore, take a long period of time to cool a substrate. As such, these cooling stations are a bottleneck in a substrate transfer process in which the substrate is moved from one chamber to another. 
     Therefore, the inventors have provided improved cooling chambers for more rapidly cooling a substrate. 
     SUMMARY 
     Embodiments of methods and apparatus for rapidly cooling a substrate are provided herein. In some embodiments, a cooling chamber for cooling a substrate includes a chamber body having an inner volume; a substrate support disposed in the chamber and having a support surface to support a substrate; a plate disposed in the chamber body opposite the substrate support, wherein the substrate support and the plate are movable with respect to each other between a first position and a second position, wherein when in the first position the substrate support and the plate are disposed away from each other such that the support surface is exposed to a first volume within the inner volume, wherein when in the second position the substrate support and the plate are disposed adjacent to each other such that the support surface is exposed to a second volume within the inner volume, and wherein the second volume is smaller than the first volume; a plurality of flow channels disposed in one or more of the plate or the substrate support to flow a coolant; and a gas inlet to provide a gas into the second volume. 
     In some embodiments, a substrate processing system includes a central vacuum transfer chamber; at least one vacuum processing chamber coupled to the central vacuum transfer to perform a process on a substrate; and at least one cooling chamber coupled to the central vacuum transfer chamber to cool the substrate. The cooling chamber may include a chamber body having an inner volume; a substrate support disposed in the chamber and having a support surface to support a substrate; a plate disposed in the chamber body opposite the substrate support, wherein the substrate support and the plate are movable with respect to each other between a first position and a second position, wherein when in the first position the substrate support and the plate are disposed away from each other such that the support surface is exposed to a first volume within the inner volume, wherein when in the second position the substrate support and the plate are disposed adjacent to each other such that the support surface is exposed to a second volume within the inner volume, and wherein the second volume is smaller than the first volume; a plurality of flow channels disposed in one or more of the plate or the substrate support to flow a coolant; and a gas inlet to provide a gas into the second volume. 
     In some embodiments a method for cooling a substrate includes placing a substrate onto a support surface of a substrate support disposed within an inner volume of a cooling chamber; moving at least one of the substrate support or a plate disposed in the cooling chamber opposite the substrate support from a first position, in which the substrate is placed onto the support surface, to a second position, in which a second volume is created between the support surface and the plate, the second volume being smaller than and substantially sealed off from a remaining portion of the inner volume; flowing a gas into the second volume to increase a pressure within the second volume; and flowing a coolant through a plurality of channels disposed in at least one of the substrate support or the plate to cool the substrate. 
     Other and further embodiments of the present disclosure are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted 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  depicts a processing system suitable for use with the inventive cooling chamber in accordance with some embodiments of the present disclosure. 
         FIG. 2  depicts a cooling chamber in accordance with some embodiments of the present disclosure. 
         FIG. 3  depicts a partial view of the inventive cooling chamber in accordance with some embodiments of the present disclosure. 
         FIG. 4  depicts a partial view of the inventive cooling chamber in accordance with some embodiments of the present disclosure. 
         FIG. 5  depicts a top of a substrate support suitable for use with the inventive cooling chamber in accordance with some embodiments of the present disclosure. 
         FIG. 6  depicts a flow diagram illustrating a method for cooling a substrate in accordance with some embodiments of the present disclosure. 
       To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of methods and apparatus for rapidly cooling a substrate are provided herein. Embodiments of the inventive cooling chamber may advantageously increase throughput by decreasing the amount of time necessary to cool a substrate. Embodiments of the inventive processing chamber may advantageously be easily retrofitted to existing processing systems, thereby avoiding unnecessary and costly modification of existing processing systems. 
       FIG. 1  is a schematic top-view diagram of an exemplary multi-chamber processing system  100  that may be suitable for use with the present inventive cooling chamber disclosed herein. Examples of suitable multi-chamber processing systems that may be suitably modified in accordance with the teachings provided herein include the ENDURA®, CENTURA®, and PRODUCER® processing systems or other suitable processing systems commercially available from Applied Materials, Inc., located in Santa Clara, Calif. Other processing systems (including those from other manufacturers) may be adapted to benefit from the embodiments disclosed in this application. 
     In some embodiments, the multi-chamber processing system  100  may generally comprise a vacuum-tight processing platform  102 , a factory interface  104 , and a system controller  140 . The processing platform  102  may include a plurality of process chambers  190 A-D, at least one cooling chamber  195 A-B (two shown in  FIG. 1 ) and at least one load-lock chamber (two shown)  184  that are coupled to a transfer chamber  188 . A transfer robot  106  is centrally disposed in the transfer chamber  188  to transfer substrates between the load lock chambers  184 , the process chambers  190 A-D, and the at least one cooling chamber  195 A-B. The process chambers  190 A-D may be configured to perform various functions including layer deposition including atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, de-gas, orientation and center-finding, annealing, and other substrate processes. Each of the process chambers  190 A-D may include a slit valve or other selectively sealable opening to selectively fluidly couple the respective inner volumes of the process chambers  190 A-D to the inner volume of the transfer chamber  188 . Similarly, each load lock chamber  184  may include a port to selectively fluidly couple the respective inner volumes of the load lock chambers  184  to the inner volume of the transfer chamber  188 . 
     The factory interface  104  is coupled to the transfer chamber  188  via the load lock chambers  184 . In some embodiments, each of the load lock chambers  184  may include a first port  123  coupled to the factory interface  104  and a second port  125  coupled to the transfer chamber  188 . The load lock chambers  184  may be coupled to a pressure control system which pumps down and vents the load lock chambers  184  to facilitate passing the substrate between the vacuum environment of the transfer chamber  188  and the substantially ambient (e.g., atmospheric) environment of the factory interface  104 . 
     In some embodiments, the factory interface  104  comprises at least one docking station  183  and at least one factory interface robot  185  (one shown) to facilitate transfer of substrates from the factory interface  104  to the processing platform  102  for processing through the load lock chambers  184 . The docking station  183  is configured to accept one or more (four shown) front opening unified pods (FOUPs)  187 A-D. Optionally, one or more metrology stations (not shown) may be coupled to the factory interface  104  to facilitate measurement of the substrate from the FOUPs  187 A-D. A substrate treatment apparatus  195  may also be coupled to the factory interface  104  to enable treatment of the substrates before they are moved to the load lock chambers  184 . The factory interface robot  185  disposed in the factory interface  104  is capable of linear and rotational movement (arrows  182 ) to shuttle cassettes of substrates between the load lock chambers  184  and the one or more FOUPs  187 A-D. Because current cooling apparatuses are in the same vacuum environment as the rest of the processing platform, the time it takes to cool a substrate is adversely affected. The inventors have designed a cooling chamber, which, although is disposed in the processing platform at vacuum, can cool the substrate in an environment with a pressure higher than vacuum, thereby reducing the time required to cool the substrate. 
       FIG. 2  depicts a cooling chamber  200  according to some embodiments of the present disclosure. The cooling chamber  200  may be used in the multi-chamber processing system  100  described above, or in other multi-chamber processing systems. The cooling chamber  200  generally comprises a chamber body  202  defining an inner volume  204 , a substrate support  208  disposed within the inner volume  204 , and a plate  214  disposed opposite the substrate support. 
     The substrate support  208  includes a support surface  210  to support a substrate  212  during cooling. The substrate  212  may rest directly upon the support surface or on other support elements. For example, as depicted in  FIG. 5 , in some embodiments, a plurality of support elements  506  may be provided to support the substrate  212  in a spaced apart relation to the support surface  210  to minimize potential contamination of the substrate  212  through contact with the substrate support  208 . The plurality of support elements  506  may be formed of any material whose properties prevent contamination (e.g., particle generation or undesirable material adhesion to the substrate) of the backside of the substrate  212 . For example, in some embodiments, the plurality of support elements  506  are sapphire balls. 
     The plate  214  is disposed opposite the support surface  210  of the substrate support  208 . In some embodiments, the plate  214  may be disposed in or proximate a lid or upper portion of the chamber body  202  (as shown in  FIG. 2 ). The substrate support  208  and the plate  214  are movable with respect to each other between a first position wherein the substrate support  208  and the plate  214  are disposed away from each other (e.g., as shown in  FIG. 2 ) and a second position wherein the substrate support  208  and the plate  214  are disposed adjacent to each other (e.g., as shown in  FIG. 3 ). 
     In the first position, the support surface  210  of the substrate support  208  is exposed to a first volume  206  within the inner volume  204 . The first volume  206  is essentially the entire inner volume  204 . For example, the first volume  206  may be predominantly bounded by the plate  214  and inner surfaces of the chamber body  202 . In the second position, the support surface  210  is exposed to a second volume (second volume  306  shown in  FIG. 3 ) within the inner volume  204 . The second volume  306  is smaller than the first volume  206 . For example, the second volume  306  may be predominantly bounded by the plate  214  and the support surface  210  of the substrate support  208 . The second volume  306  may be orders of magnitude smaller than the first volume  206 . For example, in some embodiments, the second volume  306  may be less than 10 percent, or less than five percent, or about 2 to about 3 percent of the first volume  206 . In one non-limiting example, the first volume may be about 9 liters and the second volume may be about 0.25 liters. 
     In some embodiments, the plate  214  is fixed and the substrate support  208  may be coupled to a lift mechanism  226  to control the position of the substrate support  208  between the first position (e.g., a lower position as shown in  FIG. 2 ) and the second position (e.g., an upper position as shown in  FIG. 3 ). Alternatively or in combination, the plate  214  may be movable with respect to the substrate support  208 . In the configuration shown in  FIG. 2 , the first, or lower position is suitable for transferring substrates into and out of the chamber via an opening  222  disposed in a wall of the chamber body  202 . The opening  222  may be selectively sealed via a slit valve  224 , or other mechanism for selectively providing access to the interior of the chamber through the opening  222 . The second, or upper position is suitable for more rapidly cooling the substrate. 
     A lift pin assembly  238  including a plurality of lift pins may be provided to raise the substrate  212  off of the support surface  210  to facilitate placement and removal of the substrate  212  onto and off of the substrate support  208 .  FIG. 5  depicts a top view of a substrate support in accordance with embodiments of the present disclosure. As depicted in  FIG. 5 , a plurality of lift pin holes  504  are shown extending through the substrate support  208  to facilitate movement of the lift pins of the lift pin assembly  238 . 
     Returning to  FIG. 2 , the cooling chamber  200  may include one or more mechanisms to enhance the rate of cooling of the substrate  212 . In some embodiments, a gas supply  228  may be coupled to the cooling chamber  200  via a gas inlet to provide one or more gases to the inner volume  204 . Although only one inlet is shown in  FIG. 2 , additional or alternative gas inlets may be provided in the plate  214  or in other locations suitable to provide the one or more gases to the second volume  306 . Examples of suitable gases for the one or more gases include inert gases, such as argon (Ar), helium (He), nitrogen (N 2 ), or the like, or reducing gases, such as hydrogen (H 2 ) or the like, or combinations of these gases 
     Specifically, the gas supply  228  supplies gas to the second volume  306  when the substrate support  208  and the plate  214  are disposed adjacent to each other. Providing the one or more gases to the second volume advantageously facilitates raising the pressure within the second volume  306 , which in turn enhances the rate of heat transfer from the substrate to surrounding components of the cooling chamber  200 , such as the substrate support  208  and the plate  214 . Moreover, by providing the one or more gases to the second volume  306 , which is much smaller than the first volume  206  or the inner volume  204  of the cooling chamber  200 , the pressure may be raised without significantly raising the pressure of the coolant chamber  200  as a whole, thereby reducing the time that would be required to pressurize and depressurize the entire coolant chamber or to rely upon a slower rate of cooling of the substrate in the lower pressure environment. 
     In some embodiments, the gas inlet may be provided through the plate  214  to provide the one or more gases to the second volume  306 . For example, as shown in greater detail in  FIG. 3 , in some embodiments, the gas supply  228  may be coupled to the second volume  306  through a central opening  304  (e.g., a gas inlet) disposed through the plate  214 . A cover  310  may be coupled to the plate  214  on a surface opposite the inner volume  204 . The cover  310  is coupled to a conduit  314  that leads ultimately to the gas supply  228 . A seal or gasket  312  may be disposed between the cover  310  and the plate  214  to minimize or prevent leakage of the one or more gases provided by the gas supply  228  during operation. Other configurations of providing the gas inlet in the plate  214  or other locations may also be used. 
     Returning to  FIG. 2 , in some embodiments, an annular seal  236  may be disposed between the substrate support  208  and the plate  214  such that the annular seal  236  contacts the plate  214  when in the substrate support  208  and the plate  214  are in the second position. The annular seal surrounds the support surface  210  of the substrate support  208 . The annular seal  236  serves to substantially seal off the second volume defined between the plate  214  and the support surface  210  when the substrate support  208  is in the upper position. Thus, the annular seal  236  facilitates controlling the amount of isolation between the second volume  306  and the remaining portion of the inner volume  204  such that the one or more gases provided to the second volume  306  flow into the remaining portion of the inner volume at a low, controlled rate. 
     In some embodiments, the annular seal  236  is disposed in the substrate support  208 . In some embodiments, the substrate support  208  may include an outer ring  232  surrounding the support surface  210 . The outer ring  232  includes an annular groove  234  which retains the annular seal  236 . For example, as illustrated in  FIG. 3 , when the substrate support  208  is in the second position, the annular seal  236  substantially seals the second volume  306  from the remaining portion of the inner volume  204  of the cooling chamber  200 . 
     In some embodiments, a second annular seal  302  may be disposed between the outer ring  232  and the substrate support  205  to ensure that the pressurized one or more gases in the second volume  306  do not flow into the remaining portion of the inner volume  204  from beneath the outer ring  232 . For example, the second annular seal  302  may be disposed in a second annular groove  308  in a bottom surface of the outer ring  232 . Alternatively, the second annular seal  302  may be disposed partially or completely within a groove formed in the substrate support  208 . 
       FIG. 4  depicts a close-up of area around the outer ring  232  while the substrate support is in the second position shown in  FIG. 3  to more clearly show features for controlling the flow of the one or more gases from the second volume  306  into the remaining portion of the inner volume  204 . As illustrated in  FIG. 4 , an annular channel  402  is disposed between the outer ring  232  and the substrate support  208 . For example, the annular channel  402  may be defined between an inner diameter of a portion of the outer ring  232  adjacent the support surface  210  and an outer diameter of the support surface  210  of the substrate support  208 . The annular channel  402  extends in a direction opposite the plate  214 . 
     At least one through hole  404  may be disposed through the outer ring  232  from a peripheral surface of the outer ring  232  to the annular channel  402 . The at least one through hole  404  and the annular channel  402  fluidly couple the second volume  306  to the remaining portion of the inner volume  204 . For example,  FIG. 5  depicts a top view of a substrate support in accordance with embodiments of the present disclosure. As depicted in  FIG. 5 , three through holes  404  are shown extending from the annular channel  402  to the peripheral edge of the outer ring  232 . Although three through holes  404  are illustrated in  FIG. 5 , it should be noted that any number of through holes (e.g., one or more) may be provided to control the flow of gas from the second volume  306  to the remaining portion of the inner volume  204 . 
     Returning to  FIG. 4 , in some embodiments, the annular channel  402  is substantially vertical and the at least one through hole  404  is substantially horizontal (e.g., the annular channel  402  and the at least one through hole  404  may be perpendicular to each other). The at least one through hole  404  may include an outer section  406  with a diameter larger than that of the through hole  404 . The arrows depicted in  FIG. 4  illustrate a gas flow path according to some embodiments of the present disclosure wherein the inner volume  204  of the coolant chamber is maintained at a first pressure and the second volume  306  is maintained at a second pressure that is greater than the first pressure. As illustrated in  FIG. 4 , the resultant flow path provides a choked flow of gas from the second volume  306  to the remaining portion of the inner volume  204 . 
     Returning to  FIG. 2 , in some embodiments, an inner volume facing surface of the plate  214  may be contoured to facilitate providing a smooth, laminar, and more uniform flow of gas within the second volume  306 . For example, the surface of the plate  214  facing the second volume may be concave, to form a shallow bowl or funnel that provides a greater thickness across the second volume  306  near a central axis of the substrate support  208  (and the plate  214 ) and a lesser reducing thickness across the second volume  306  at positions radially outward of the central axis. In some embodiments, a thickness of the plate  214  increases outwardly from the central opening  304  to provide the concave shape of the second volume facing surface of the plate  214 . 
     In some embodiments, at least one of the plate  214  or the substrate support  208  may include one or more flow channels to flow a coolant to increase the rate of cooling of the substrate  212 . For example, as shown in  FIG. 2 , the substrate support  208  may include one or more flow channels  218  disposed in the substrate support  208 , for example, beneath the support surface  210 . A coolant supply  216  may be coupled to the one or more flow channels  218  to supply a coolant to the flow channels  218 . Alternatively or in combination, the plate  214  may include one or more flow channels  230 , which may be coupled to the coolant supply  216 , or to a second coolant supply  231  (as depicted in  FIG. 2 ). 
     In some embodiments, a gas supply  220  may be coupled to the substrate support  208  to supply a backside gas through an opening (shown in  FIG. 5 ) in the support surface  210 , which may include a plurality of grooves (not shown) to improve the backside gas circulation. Providing a backside gas can further enhance the rate of cooling of the substrate  212  by improving heat conduction between the substrate and the substrate support  208 . For example,  FIG. 5  depicts a top view of the substrate support in accordance with embodiments of the present disclosure. As illustrated in  FIG. 5 , the substrate support  208  may include a central opening  502  to flow a backside gas to a region disposed between the support surface  210  and a backside of the substrate  212  when disposed on the substrate support  208 . The central opening  502  is in fluid communication with the gas supply  220  to flow a backside gas into a space between the support surface  210  and a backside of the substrate  212  to improve the cooling of the substrate. 
     Returning to  FIG. 2 , in some embodiments, a controller  250  may be provided for controlling operation of the cooling chamber  200 . The controller  250  may be one of any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory, or computer-readable medium,  256  of the CPU  252  may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits  254  are coupled to the CPU  252  for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. 
     The methods disclosed herein may generally be stored in the memory  256  as a software routine  258  that, when executed by the CPU  252 , causes the cooling chamber  200  to perform processes of the present disclosure. The software routine  258  may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU  252 . Some or all of the method of the present disclosure may also be performed in hardware. As such, embodiments of the present disclosure may be implemented in software and executed using a computer system, in hardware as, e.g., an application specific integrated circuit or other type of hardware implementation, or as a combination of software and hardware. The software routine  258  may be executed after the substrate  212  is positioned on the substrate support  208 . The software routine  258 , when executed by the CPU  252 , transforms the general purpose computer into a specific purpose computer (controller)  250  that controls the chamber operation such that the methods disclosed herein are performed. 
       FIG. 6  depicts a flow diagram illustrating a method  600  in accordance with some embodiments of the present disclosure. The method  600  may be implemented via the controller  250  as discussed above. The method  600  generally begins at  605 , where the substrate  212  is placed on the support surface  210  of the substrate support  208 . During this process, the lift pin assembly  238  extends through the plurality of lift pin holes  504  to receive the substrate  212  and is subsequently lowered to allow the substrate  212  to rest on the support surface (e.g., directly or on the plurality of support elements). 
     At  610 , the relative position of the substrate support  208  and the plate  214  is moved from a first position (e.g.,  FIG. 2 ), which facilitates placement and removal of the substrate  212  onto the substrate support  208 , to a second position (e.g.,  FIGS. 3 and 4 ), in which the annular seal  236  disposed in the outer ring  232  contacts a periphery of the plate  214  to substantially seal off a second volume  306  from the remaining portion of the inner volume  204  of the cooling chamber  200 . In some embodiments, the substrate support  208  is moved and the plate  214  is fixed. In some embodiments, the plate  214  may be moved in addition to or instead of the substrate support  208 . 
     At  615 , a gas is flowed from the gas supply  228  through the central opening  304  of the plate  214  and into the second volume  306 . The flow of gas into the second volume  306  increases the pressure inside of the second volume  306  to a pressure higher than that of the inner volume  204 . The gas then flows from the second volume  306  through the annular channel  402  and through the at least one through hole  404  into the remaining portion of the inner volume  204 . In order to more easily maintain the increased pressure inside of the second volume  306  without raising the pressure within the inner volume  204  by too great an amount, the annular channel  402  and the at least one through hole  404  are sized and shaped to create a choked flow. The increased pressure improves the contact area between the substrate  212  and the support surface  210 , which results in improved conduction between the substrate  212  and the support surface  210 . Moreover, the increased pressure improves conduction through the gas from the substrate to the plate  214 , further enhancing the rate of cooling of the substrate. 
     At  620 , coolant may be flowed through the one or more flow channels  218  in the substrate support  208 , the one or more flow channels  230  in the plate  214 , or both, to more rapidly cool the substrate  212 . The coolant may include any known coolant such as, for example, water, such as deionized (DI) water, a suitable perfluoropolyether (PFPE) fluid, such as GALDEN®, or the like. 
     At  625 , the flow of the gas from the gas supply  228  and the gas supply  220  are stopped and the substrate support  208  is moved back to the first position to facilitate removal of the substrate  212  from the substrate support. In this position, the lift pin assembly  238  extends through the plurality of lift pin holes  504  to lift the substrate  212  off of the support surface  210  to facilitate removal of the substrate  212 . 
     Although described above with respect to rapid cooling of a substrate in a chamber coupled to a vacuum processing tool, the apparatus as described herein could instead be used for rapid heating of the substrate by providing a heater or flowing a heat transfer fluid at a desired temperature through the flow channels  218 ,  230 . 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.