Patent Publication Number: US-2018046206-A1

Title: Method and apparatus for controlling gas flow to a process chamber

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/374,833, filed with the United States Patent Office on Aug. 13, 2016, which is herein incorporated by reference in its entirety. 
    
    
     FIELD 
     Embodiments of the disclosure generally relate to method and apparatus for processing a substrate. 
     BACKGROUND 
     Processing systems having process chambers typically share processing resources such as, for example, a shared gas supply, a shared pump, etc. The shared resources reduce the cost of components of the processing system. However, the inventors have discovered that a variance exists in the gas conductance of the gas supply lines to each chamber and, thus, leads to mismatching of the chamber performance. As such, the inventors have developed an improved gas supply system to more accurately match the conductance, and thus, the process results of both chambers of the dual chamber processing system and improve uniformity of process results between substrates being processed in the different chambers. 
     Therefore, the inventors have provided an improved gas supply system. 
     SUMMARY 
     Methods and apparatus for controlling gas flow to a process chamber are disclosed herein. In some embodiments, a processing system includes a first process chamber having a first gas input; a first gas break disposed upstream of the first gas input; a first adjustable valve disposed upstream of the first gas break; and a first isolation valve disposed upstream of the first adjustable valve. In some embodiments, the processing system may further include: a second process chamber having a second gas input; a second gas break disposed upstream of the second gas input; a second adjustable valve disposed upstream of the second gas break; and a second isolation valve disposed upstream of the second adjustable valve. In some embodiments, a shared gas source is disposed upstream of the first isolation valve and the second isolation valve to provide one or more gases to the first process chamber and to the second process chamber. The first process chamber and the second process chamber may be part of a dual-chamber processing system having the first process chamber and the second process chamber as adjacent process chambers having a shared wall separating respective processing volumes of the first and second process chambers. 
     In some embodiments, a method of controlling gas flow to a process chamber includes adjusting a first adjustable valve fluidly coupled to the process chamber upstream of a gas break to achieve a predetermined first pressure corresponding to a first flow rate at the gas break, wherein the predetermined first pressure is substantially equivalent to a reference pressure corresponding to a reference flow rate at a gas break in a reference process chamber; and processing a substrate in the process chamber while providing one or more process gases to the process chamber via the first adjustable valve. 
     In some embodiments, a method of controlling gas flow to a pair of process chambers, includes closing a second isolation valve fluidly coupled to a second process chamber; opening a first isolation valve fluidly coupled to a first process chamber; adjusting a first adjustable valve fluidly coupled to the first process chamber upstream of a first gas break coupled to the first process chamber to achieve a first pressure corresponding to a first flow rate at the first gas break; repeating the adjusting of the first adjustable valve until an optimal first pressure is achieved at the first gas break; closing the first isolation valve; opening the second isolation valve; adjusting a second adjustable valve fluidly coupled to the second process chamber upstream of a second gas break coupled to the second process chamber to achieve a second pressure corresponding to a second flow rate at the second gas break; repeating the adjusting of the second adjustable valve until the second pressure is substantially similar to the first pressure; opening the first isolation valve; and processing a substrate in each of the first and second process chambers while providing one or more process gases to each of the first and second process chambers via respective ones of the first and second adjustable valves. 
     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. However, the appended drawings illustrate only typical embodiments of the disclosure and are therefore not to be considered limiting of scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  depicts a schematic cross-sectional view of a process chamber in accordance with some embodiments of the present disclosure. 
         FIG. 2  depicts a flowchart illustrating a method of controlling gas flow to a process chamber 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. 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 a gas supply system. Embodiments of the inventive gas supply system advantageously improve chamber matching and deposition uniformity between multiple process chambers. Although not limiting of scope, embodiments of the present disclosure may be particularly useful when implemented in connection with a tandem processing chamber (e.g., a dual chamber or twin chamber processing system). 
     Embodiments of the present disclosure relate to balancing the conductance between two process chambers, such as each chamber of a twin chamber processing system, to improve the chamber matching, or side-to-side chamber matching and uniformity between the two chambers. Embodiments of the present disclosure can be used on any process chambers which need conductance adjustment. In some embodiments, conductance control can be achieved by adding a valve, such as a needle valve, next to a gas break in each chamber to add a tuning knob for conductance of gas flow into the chamber. By adjusting the needle valve, the chamber gas line conductance can be tuned, for example, to match a predetermined conductance, such as a “golden” or standard conductance determined to be a desired conductance for the process chamber. 
     Embodiments of the present disclosure advantageously allow adjustment to reduce or eliminate any difference in the conductance between different process chambers. In addition, embodiments of the present disclosure allow for the loosening of tolerances in the pressure drop specification for the gas breaks, which advantageously reduces the cost of manufacturing of the gas breaks. 
       FIG. 1  illustrates a cross-sectional view of an exemplary dual chamber processing system (e.g., process chambers  100 ,  101 ) having a gas supply system  180  in accordance with some embodiments of the present disclosure. Although illustratively described in connection with a dual chamber processing system, embodiments of the present disclosure may also be used in connection with standalone process chambers. Each of the respective first and second process chambers  100 ,  101  may include an upper portion  119  and a lower portion  131 , wherein the upper portion  119  generally includes processing regions  102 ,  103  and wherein the lower portion  131  generally includes a loading region  111  adjacent an aperture  109 . Each of the respective first and second process chambers  100 ,  101  include a chamber body having sidewalls  105 A,B, an interior wall  106 , a bottom  113 , and a lid  115  disposed on the first and second process chambers  100 ,  101 . In some embodiments, the lid  115  is a radio frequency (RF) cover. The sidewall  105 A, interior wall  106 , and portion of lid  115  disposed on the first process chamber  100  define a first processing region  102 . The sidewall  105 B, interior wall  106  and portion of lid  115  disposed on the second process chamber  101  define a second processing region  103 . The interior wall  106  is shared between the respective first and second process chambers  100 ,  101  and isolates the processing environment of the processing regions  102 ,  103  from each other. As such, the processing regions  102 ,  103  defined in the respective process chambers  100 ,  101  while process isolated, may share a common pressure, as the lower portion of interior wall  106  may allow the respective first and second process chambers  100 ,  101  to communicate with each other. The lower portion of interior wall  106  is defined by a central pumping plenum  117  described below. 
     The lid  115  may include one configuration of a gas distribution assembly  116  including a showerhead  122  configured to dispense a gas from a gas source  188  (such as a gas panel) into the respective processing regions  102 ,  103 . The lid  115  is coupled to the gas source  188  via respective gas feedthroughs  187 ,  189  corresponding to processing regions  102 ,  103 , respectively. In some embodiments, the showerhead  122  may be electrically floating. To ensure that the showerhead  122  remains electrically floating and is not grounded through the gas feedthroughs  187 ,  189  to the gas source  188 , the gas feedthroughs  187 ,  189  include corresponding gas breaks  181 ,  182 . The gas breaks  181 ,  182  are formed of an electrically insulative material to ensure that the showerhead  122  remains floating. The gas breaks  181 ,  182  may also include restrictors to substantially reduce or eliminate plasma from flowing back to the gas source  188 . As such, the pressure of gas flowing into the gas breaks  181 ,  182  from the gas source  188  is greater than the gas pressure at the outlets of the gas breaks  181 ,  182 . 
     A valve system  199  is disposed between the gas source  188  and the gas breaks  181 ,  182 . The valve system  199  improves chamber matching by facilitating independent adjustment of the pressure in each process chamber  100 ,  101  to obtain a predetermined desired pressure, for example, corresponding to a pressure at a known flow rate of a different process chamber. The desired pressure values are determined based on process uniformity and yield (e.g., to maximize uniformity and yield). In some embodiments, the valve system  199  includes isolation valves  185 ,  186  disposed in series with corresponding adjustable valves  183 ,  184 , respectively. Each set of valves is disposed in-line with a corresponding one of the gas breaks  181 ,  182  (e.g., isolation valve  186  is disposed upstream of adjustable valve  184 , which is in turn disposed upstream of the gas break  182 ). To reduce processing discrepancies between the process chambers  100 ,  101 , the gas breaks are designed to have substantially similar pressure drops. However, the inventors have discovered that due to manufacturing variance, no two gas breaks are identical and, even the allowable tolerance variation results in undesirable discrepancies in processing results between the process chambers  100 ,  101 . 
       FIG. 2  depicts a method  200  of controlling gas flow to a process chamber. The method  200  is used to determine the optimal pressure values at the gas breaks  181 ,  182  at which chamber matching is achieved, yield is maximized, and processing uniformity between the two process chambers is maximized. The method generally begins at  202 , where a second isolation valve  186  fluidly coupled to a second gas break  182  is closed and a first isolation valve  185  fluidly coupled to a first gas break  181  is opened. At  204 , a first adjustable valve  183  is adjusted to achieve a first pressure corresponding to a first flow rate at the first gas break  181 .  204  is optionally repeated until a desired, predetermined first pressure is achieved at the first gas break  181 . The predetermined first pressure and the first flow rate are values that provide a chamber yield and processing uniformity in the process chamber  101  that more closely match a reference process chamber (such as the companion process chamber  100 , or some other reference process chamber). 
     At  206 , the first isolation valve  185  is closed and the second isolation valve  186  is opened. At  208 , a second adjustable valve  184  is adjusted to achieve a second pressure corresponding to a second flow rate at the second gas break  182 .  208  is optionally repeated until a desired, predetermined second pressure is achieved at the second gas break  182 . The predetermined second pressure and the second flow rate are values that provide a chamber yield and processing uniformity in the process chamber  100  that more closely match a reference process chamber (such as the companion process chamber  101 , or some other reference process chamber). For example, the first pressure and the second pressure may be substantially equivalent. Alternatively or in combination, the first flow rate and the second flow rate may be substantially equivalent. At  210 , the first isolation valve  185  is opened and processes in both chambers  100 ,  101  are allowed to proceed. Although described in connection with a dual chamber processing system, the above method could also be carried out with a single process chamber in comparison to some reference process chamber to match or substantially match the pressure provided from the gas source (or another gas source) to the reference process chamber. 
     To achieve chamber matching, the first and second optimal pressures and flow rates are chosen to allow for substantially similar or equivalent chamber yield and processing uniformity between the process chambers  100 ,  101 . As a result, the discrepancies between the first and second gas breaks  181 ,  182  due to manufacturing are irrelevant due to the advantageous adjustability of the gas pressures and flow rates at the gas breaks. As such, gas breaks having high conductance (for example at least a higher conductance than that of the valve system  199 ) may be advantageously used so that the valve system  199  controls the conductance of the gas flow to the chambers  100 ,  101 . 
     Returning to  FIG. 1 , the lid  115  allows for convenient access to the chamber components such as the chamber liners  155  for example, for cleaning. In some embodiments, a cover  161  may be disposed on the lid  115  to protect components disposed in the lid  115 . To help decrease chamber servicing (i.e., cleaning) time, a removable chamber liner  155  may be disposed adjacent the sidewalls  105 A,B and interior wall  106 . The chamber liners  155  include an aperture  162  formed in the chamber liners  155  and in communication with the aperture  109 . The apertures  162  and  109  are positioned so as to enable substrates to be moved into and out of the respective process chambers  100 ,  101 . As such, each of the apertures  109 ,  162  may generally be in selective communication with, for example, a substrate transfer chamber (not shown). During servicing, the lid  115  is left open so that the interior of the process chambers  100 ,  101  may be accessed. 
     When the substrate supports  108  are in a processing position, the upper portion  119  of the respective first and second process chambers  100 ,  101  and substrate supports  108  generally define the respective isolated processing regions  102 ,  103  to provide process isolation between each of the respective process chambers  100 ,  101 . Therefore, in combination, the sidewalls  105 A,B, interior wall  106 , substrate support  108 , and the lid  115  provide process isolation between the processing regions  102 ,  103 . 
     The volume of the processing regions  102 ,  103  and loading regions  111  may vary with the position of the substrate support  108  relative to the lower boundary of the lid  115 . In one configuration, the substrate supports  108  may be lowered below the apertures  109 . In the lowered position, a substrate may be positioned on the substrate support  108  via the aperture  109 . More particularly, when the substrate support  108  is lowered, the lift pin assembly  112  may lift a substrate from the upper surface of the substrate support  108 . Subsequently, a robot blade (not shown) may enter into the loading region  111  and engage the substrate lifted by the lift pin assembly  112  for removal from the loading region  111 . Similarly, with the substrate support  108  in a lowered positioned, substrates may be placed on the substrate support  108  for processing. Subsequently, the substrate support  108  may be vertically moved into a processing position, i.e., a position where the upper surface of the substrate support  108  is positioned proximate to the respective processing region  102 ,  103 . 
     The lid  115  may have other plasma generation devices disposed adjacent to the lid  115 . The upper electrode assembly  118  may be configured with RF coils coupled to first and second RF power sources  150 ,  152  through respective matching networks  151 ,  153 , to inductively couple RF energy into the plasma processing regions  102 ,  103 . An RF power supply controller  149  may be coupled to both RF power sources  150 ,  152  to provide an output signal for controlling, for example, a power level, phase control, and/or frequency. 
     The lower portion  131  of the respective first and second process chambers  100 ,  101  may also include a commonly shared adjacent chamber region of each chamber defined by a central pumping plenum  117  that is in fluid communication with a vacuum source  120  through a pumping valve  121 . Generally, the central pumping plenum  117  includes two sections defined by the sidewalls  105 A,B that are combined with an output port  130  in fluid communication with the pumping valve  121 . The two sections may be formed as part of the lower portion  131  of each first and second process chambers  100 ,  101 . While the central pumping plenum  117  may be formed integral to the lower portion  131  of the first and second process chambers  100 ,  101 , the central pumping plenum  117  may alternatively be a separate body coupled to the lower portion  131 . In a gas purge or vacuum process, the pumping valve  121  couples the vacuum source  120  to the output port  130  through mounting flange  114 . Therefore, the central pumping plenum  117  is generally configured to maintain the respective process chambers  100 ,  101 , and more particularly, the respective processing regions  102 ,  103 , at a pressure desired for semiconductor processing while allowing for rapid removal of waste gases using the vacuum source  120 . 
     In some embodiments, the output port  130  is positioned at a distance from the processing regions  102 ,  103  such as to minimize RF energy in the processing regions  102 ,  103 , thus minimizing striking a plasma in the exhaust gases being flushed from the process chambers  100 ,  101 . For example, the output port  130  may be positioned at a distance from the substrate supports  108  and processing regions  102 ,  103  that is sufficiently far to minimize RF energy within the output port  130 . 
     In some embodiments, the upper electrode assembly  118  includes a first upper electrode assembly  118 A and a second electrode assembly  118 B disposed adjacent the processing regions and adapted to provide RF energy to respective processing regions  102 ,  103 . 
     Although the previous description has been made with regards to a process chamber, the valve system  199  may be utilized in any process chamber in which matching of multiple chambers is desirable. The valve system may also include any combination of various types of valve to achieve the above-discussed advantages. 
     While the foregoing is directed to some embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope of the disclosure.