Abstract:
A new and improved, multi-phase pressure control valve for facilitating quick and accurate attainment and stabilization of gas pressure inside a semiconductor fabrication process chamber such as an etch chamber or CVD chamber. In one embodiment, the multi-phase pressure control valve is a butterfly-type valve which includes outer and inner vanes that independently control flow of gases from a process chamber to a vacuum pump. The larger-diameter outer vane stabilizes gas pressures within a large range, whereas the inner vane stabilizes pressure within a smaller range. In another embodiment, the multi-phase pressure control valve is a gate-type valve which may include a pivoting outer vane and an inner vane slidably disposed with respect to the outer vane for exposing a central gas flow opening in the outer vane.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to valves for regulating chamber pressures of process chambers used in the fabrication of semiconductor integrated circuits. More particularly, the present invention relates to multi-phase pressure control valves for the rapid and accurate attainment of interior chamber gas pressures of process chambers such as etch chambers and CVD chambers.  
         BACKGROUND OF THE INVENTION  
         [0002]    Integrated circuits are formed on a semiconductor substrate, which is typically composed of silicon. Such formation of integrated circuits involves sequentially forming or depositing multiple electrically conductive and insulative layers in or on the substrate. Chemical vapor deposition (CVD) processes are widely used to form layers of materials on a semiconductor wafer. CVD processes include thermal deposition processes, in which a gas is reacted with the heated surface of a semiconductor wafer substrate, as well as plasma-enhanced CVD processes, in which a gas is subjected to electromagnetic energy in order to transform the gas into a more reactive plasma. Forming a plasma can lower the temperature required to deposit a layer on the wafer substrate, to increase the rate of layer deposition, or both.  
           [0003]    After the material layers are formed on the wafer substrate, etching processes may be used to form geometric patterns in the layers or vias for electrical contact between the layers. Etching processes include “wet” etching, in which one or more chemical reagents are brought into direct contact with the substrate, and “dry” etching, such as plasma etching. Various types of plasma etching processes are known in the art, including plasma etching, reactive ion (RI) etching and reactive ion beam etching. In each of these plasma processes, a gas is first introduced into a reaction chamber and then plasma is generated from the gas. This is accomplished by dissociation of the gas into ions, free radicals and electrons by using an RF (radio frequency) generator, which includes one or more electrodes. The electrons are accelerated in an electric field generated by the electrodes, and the energized electrons strike gas molecules to form additional ions, free radicals and electrons, which strike additional gas molecules, and the plasma eventually becomes self-sustaining. The ions, free radicals and electrons in the plasma react chemically with the layer material on the semiconductor wafer to form residual products which leave the wafer surface and thus, etch the material from the wafer.  
           [0004]    Referring to the schematic of FIG. 1, a wafer processing system, such as an etcher or CVD chamber, is generally indicated by reference numeral  10 . The processing system  10  includes a reaction chamber  12  having a typically grounded chamber wall  14  closed by a chamber top  18 . Source gases for wafer processing are provided by a gas supply  20 . The gas supply  20  is coupled with the reaction chamber  12  through a gas control panel  22 , which selects and controls the flow of the source gases into the reaction chamber  12 . A semiconductor wafer  34  is supported on a wafer chuck  36  in the reaction chamber  12 . Volatile reaction products and unreacted plasma or gas species are removed from the reaction chamber  12  by a gas removal mechanism, such as a vacuum pump  24  through a throttle valve  26 .  
           [0005]    The reaction chamber  12  may be a plasma etching chamber, in which the plasma formed in the chamber  12  includes high-energy ions, free radicals and electrons which react chemically with the surface material of the semiconductor wafer  34  to form reaction products that leave the surface of the wafer  34 , thereby etching a geometrical pattern or a via in a wafer layer. The reaction chamber  12  may be a CVD chamber, in which gases are introduced into the reaction chamber  12  and a plasma may be formed from the gases in the reaction chamber  12 . In a heterogenous, or surface-catalyzed reaction, the gas or plasma deposits a solid film on the surface of the wafer  34 .  
           [0006]    By regulating the flow of gases from the interior of the reaction chamber  12  to the vacuum pump  24 , the throttle valve  26  of the system  10  is typically used to control the interior pressures of the reaction chamber  12 . A cross-sectional view of a conventional butterfly-type throttle valve  26  is shown in FIG. 2. The conventional butterfly-type throttle valve  26  includes a cylindrical valve wall  27 , in which is pivotally mounted a vane  28  at a pivot point  29 . Upon flow of gases  30  from the reaction chamber  12  to the vacuum pump  26 , the vane  28  pivots from the position indicated by the solid lines to the position indicated by the dashed lines, thereby regulating the flow rate of the gas from the reaction chamber  12 , and thus, the interior pressure of the reaction chamber  12 .  
           [0007]    As shown in FIG. 3, an alternative conventional gate-type throttle valve  38  includes a cylindrical valve wall  39  having a vane  40  slidably mounted through a slot (not shown) in the valve wall  39  and pivotally mounted to the valve wall  39  at a pivot point  41 . The vane  40  pivots to the open position shown in FIG. 3 from a closed position inside the valve interior  42  of the throttle valve  38  to establish flow of the gases from the reaction chamber  12  to the vacuum pump  24 . The vane  40  partially blocks the valve interior  42  to prevent unimpeded flow of the gases, thereby regulating the flow rate of the gases through the throttle valve  38 , and thus, the pressure of the gases in the reaction chamber  12 .  
           [0008]    One of the limitations inherent in the conventional single-unit throttle valves is that the valves are characterized by an inordinately long response time upon initial flow of gases into the reaction chamber in order to establish the desired pressure for the etching or CVD process. The valves are incapable of achieving both pressure accuracy and pressure stabilization at the desired value in a short period of time. Consequently, the gases flowing through the processing system from the time of initial gas flow onset until stabilization of the gas flow rate and interior chamber gas pressure, tend to be wasted. Accordingly, a new and improved, multi-phase pressure control valve, characterized by quick response or pressure stabilization time as well as pressure accuracy, is needed for semiconductor processing systems.  
           [0009]    An object of the present invention is to provide a new and improved, multi-phase pressure control valve for process chambers used in the fabrication of semiconductors.  
           [0010]    Another object of the present invention is to provide a new and improved, multi-phase pressure control valve for the quick and accurate stabilization of pressure in a process chamber.  
           [0011]    Still another object of the present invention is to provide a new and improved, multi-phase pressure control valve which may be used in a variety of process chambers for semiconductor fabrication.  
           [0012]    Yet another object of the present invention is to provide a new and improved, multi-phase pressure control valve which is particularly well-suited for use in etching chambers and CVD (chemical vapor deposition) chambers for semiconductor fabrication.  
           [0013]    A still further object of the present invention is to provide a multi-phase pressure control valve which includes at least two control units for the quick and accurate establishment and stabilization of a desired pressure in a process chamber.  
           [0014]    Yet another object of the present invention is to provide a multi-phase pressure control valve which may be readily installed in conventional semiconductor processing systems.  
           [0015]    A still further object of the present invention is to provide a butterfly-type, multi-phase pressure control valve which may include outer and inner vanes for independently controlling flow of gases from a process chamber to a vacuum pump in order to facilitate quick and accurate attainment and stabilization of a desired interior chamber pressure for a semiconductor fabrication process chamber.  
           [0016]    Another object of the present invention is to provide a gate-type multi-phase pressure control valve which may include a pivoting outer vane and an inner vane slidably disposed with respect to the outer vane for exposing a central gas flow opening in the outer vane, which outer and inner vanes independently facilitate flow of gases through the valve in order to quickly and precisely stabilize gas pressures in a semiconductor fabrication process chamber.  
           [0017]    Still another object of the present invention is to provide a process-oriented design for a multi-phase pressure control valve.  
         SUMMARY OF THE INVENTION  
         [0018]    In accordance with these and other objects and advantages, the present invention is generally directed to a new and improved, multi-phase pressure control valve for facilitating quick and accurate attainment and stabilization of gas pressure inside a semiconductor fabrication process chamber such as an etch chamber or CVD chamber. In one embodiment, the multi-phase pressure control valve is a butterfly-type valve which includes outer and inner vanes that independently control flow of gases from a process chamber to a vacuum pump. The larger-diameter outer vane stabilizes gas pressures within a large range, whereas the inner vane stabilizes pressure within a smaller range. In another embodiment, the multi-phase pressure control valve is a gate-type valve which includes a pivoting outer vane and an inner vane slidably disposed with respect to the outer vane for exposing a central gas flow opening in the outer vane. The outer and inner vanes independently facilitate flow of gases through the valve in order to quickly and precisely stabilize gas pressures in a semiconductor fabrication process chamber. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0020]    [0020]FIG. 1 is a schematic view of a typical conventional processing system for the fabrication of semiconductor integrated circuits;  
         [0021]    [0021]FIG. 2 is a longitudinal sectional view of a conventional throttle valve for a semiconductor fabrication process system;  
         [0022]    [0022]FIG. 3 is a cross-sectional view of another type of conventional throttle valve for a semiconductor fabrication process system;  
         [0023]    [0023]FIG. 4 is a top view of a butterfly-type multi-phase pressure control valve of the present invention, with the inner and outer vanes of the valve in the closed configuration;  
         [0024]    [0024]FIG. 4A is a top view of the valve of FIG. 4, with the inner vane of the valve in the open configuration;  
         [0025]    [0025]FIG. 4B is a longitudinal sectional view of the valve of FIGS. 4 and 4A, with the inner and outer vanes pivoted to the open configuration in operation of the valve;  
         [0026]    [0026]FIG. 5 is a top view of a gate-valve type multi-phase pressure control valve of the present invention, with the inner vane of the valve shown in the open configuration in operation of the valve;  
         [0027]    [0027]FIG. 5A is a sectional view, taken along section lines  5 A- 5 A in FIG. 5;  
         [0028]    [0028]FIG. 5B is a longitudinal sectional view of the valve of FIG. 5, with the outer vane of the valve pivoted to the open configuration in operation of the valve;  
         [0029]    [0029]FIG. 6 is a graph with chamber pressure plotted vs. time, illustrating enhanced stabilization of gas pressure in a process chamber in implementation of the present invention;  
         [0030]    [0030]FIG. 7 is a graph with chamber pressure plotted as a function of valve angle for various gas flow rates in implementation of the present invention;  
         [0031]    [0031]FIG. 8 is a side view, in section, of a valve piping system for another embodiment of the present invention;  
         [0032]    [0032]FIG. 9 is a sectional view of each of two multi-phase pressure control valves in the embodiment of the invention shown in FIG. 8; and  
         [0033]    [0033]FIG. 10 is a graph with process chamber pressure plotted vs. time, illustrating a typical operational schematic for a semiconductor fabrication process in implementation of the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    When used herein, the term, “valve unit” shall refer to a butterfly valve vane, a gate valve vane or any other valve element which is capable of regulating or modulating flow of a gas through a conduit.  
         [0035]    The present invention has particularly beneficial utility in the rapid establishment, stabilization and control of gas pressures inside a process chamber used in the fabrication of integrated circuits on semiconductor wafer substrates. However, the invention is not so limited in application, and while references may be made to such semiconductor fabrication process chambers, the present invention is more generally applicable to rapidly establishing, stabilizing and maintaining control of gas pressures inside process vessels in a variety of industrial and mechanical applications.  
         [0036]    Referring initially to FIGS.  4 - 4 B, a first illustrative embodiment of the pressure control valve of the present invention is generally indicated by reference numeral  45 . In typical application, the pressure control valve  45  connects an exhaust port on a process chamber  61  to a vacuum pump  62 . The pressure control valve  45  includes a valve housing  45   a  having a cylindrical valve wall  46  which defines a valve interior  47 . An annular outer vane  48 , having a central opening  49 , is mounted in the valve interior  47 . In a preferred embodiment, the outer vane  48  may have a diameter of about 3 inches, although the outer vane  48  may have other diameters. The edge of the outer vane  48  normally engages the interior surface of the valve wall  46 . A motor shaft  52  extends from operable engagement by an outer vane motor  51 , through a shaft opening (not shown) provided in the valve wall  46 , and is attached to or engages the outer vane  48 . Accordingly, by operation of the outer vane motor  51 , the motor shaft  52  is rotated and, in turn, rotates the outer vane  48  inside the valve interior  47 . This positions the outer vane  48  at a throttle angle “A” with respect to the normally closed position  53  of the outer vane  48 , as shown in FIG. 4B and hereinafter further described. A circular inner vane  54  is disposed in the central opening  49  of the outer vane  48 , and normally closes the central opening  49  as shown in FIG. 4. In a preferred embodiment, the inner vane  54  has a diameter of about  2  inches, although the inner vane  54  may have other diameters. A motor shaft  56  extends from operable engagement by an inner vane motor  55 , through a sheath  57  provided on the surface of the outer vane  48 , and is attached to or engages the inner vane  54 . Accordingly, by operation of the inner vane motor  55 , the motor shaft  56  is rotated and, in turn, rotates the inner vane  54 , independently of the outer vane  48 , inside the central opening  49 , as shown in FIG. 4A. This positions the inner vane  54  at a throttle angle “B” with respect to the normally closed position  58  of the inner vane  54 , as shown in FIG. 4B and hereinafter further described.  
         [0037]    Referring again to FIGS.  4 - 4 B and to FIG. 10, in operation the multi-phase pressure control valve  45  facilitates prompt attainment and stabilization of a target gas pressure inside the process chamber  61  at the onset of a processing operation such as a plasma etching or plasma CVD operation carried out in the process chamber  61 . Accordingly, helium (He) gas  59  is typically used in the stabilization step prior to processing in order to attain and stabilize the desired target gas pressure inside the process chamber  61  for the processing operation. As the vacuum pump  62  draws the gas  59  from the process chamber  61  and through the valve interior  47 , at a gas flow rate of typically from about 500 sccm to about 15,000 sccm, the outer vane motor  51  is operated to rotate the outer vane  48  from the closed position  53  to the open position shown by the solid lines in FIG. 4B, until the throttle angle “A” shown in FIG. 4B is typically from about 5 to about 15 degrees. Simultaneously, the inner vane motor  55  is operated to rotate the inner vane  54  until the throttle angle “B” shown in FIG. 4B is from about 20 to about 35 degrees. This facilitates a gas pressure of from about 4 Torr to about 6 Torr in the process chamber  61 . As shown in FIG. 6, it will be appreciated by those skilled in the art that the inner vane  54 , the gas stabilization profile of which is indicated by the bottom graph in FIG. 6, stabilizes the gas pressure to the desired target gas pressure in the process chamber  61  within about 2 seconds. The outer vane  48 , the gas stabilization profile of which is indicated by the top graph in FIG. 6, stabilizes the gas pressure to the desired target gas pressure in the process chamber  61  within about 2.5 seconds. As shown in FIG. 6, processing recipes of semiconductor fabrication processes vary according to the time from onset of plasma inducement until the main processing step begins, typically from about 4.5 to about 5.5 seconds. Accordingly, the multi-phase pressure control valve  45  is capable of stabilizing the target gas pressure well within sufficient time before the main processing step begins. FIG. 7 illustrates interior chamber pressures at various flow rates of He gas as a function of various throttle angles of the outer vane  48  (bottom lines) and of the inner vane  54  (top lines), respectively. It will be appreciated from a consideration of FIG. 7 that the multi-phase pressure control valve  45  widens the safety-operation area of the process.  
         [0038]    Referring next to FIGS.  5 - 5 B, a second illustrative embodiment of the multi-phase pressure control valve of the present invention is generally indicated by reference numeral  65 . In typical application, the pressure control valve  65  connects an exhaust port on a process chamber  82  to a vacuum pump  83 . The multi-phase pressure control valve  65  includes a valve housing  65   a  having a cylindrical valve wall  66  which defines a valve interior  67 . An annular outer vane  68 , having a central opening  69 , is mounted in the valve interior  67 . As shown in FIG. 5A, the outer vane  68  may include a top panel  70  and a bottom panel  71 , between which is defined a pocket  72 , the purpose of which will be hereinafter described. In a preferred embodiment, the outer vane  68  may have a diameter of about 3 inches, although the outer vane  68  may have other diameters. The edge of the outer vane  68  normally engages the interior surface of the valve wall  66 , as shown in FIG. 5. A circular inner vane  77  is disposed in the central opening  69  of the outer vane  68 , and normally closes the central opening  69  as shown in FIG. 5. In a preferred embodiment, the inner vane  77  has a diameter of about 2 inches, although the inner vane  77  may have other diameters. A motor shaft  75  extends from operable engagement by an outer vane motor  74 , through a shaft opening (not shown) provided in the valve wall  66 , and is attached to or engages the outer vane  68 . By operation of the outer vane motor  74 , the motor shaft  75  is rotated, and the motor shaft  75 , in turn, rotates the outer vane  68  inside the valve interior  67 . This positions the outer vane  68 , as well as the inner vane  77 , at an angle “C” with respect to the normally closed position  80  of the outer vane  68 , as shown in FIG. 5B. A motor shaft  79  extends from operable engagement by an inner vane motor  78  and is attached to or engages the inner vane  77 . Accordingly, by operation of the inner vane motor  78 , the motor shaft  79  is retracted into the inner vane motor  78  to at least partially remove the inner vane  77  from the central opening  69  and retract the inner vane  77  at least partially into the pocket  72  of the outer vane  68 , as shown in FIGS. 5 and 5A.  
         [0039]    Referring again to FIGS.  5 - 5 B, in operation helium (He) gas  81  is typically used in the stabilization step prior to processing in order to attain and stabilize the desired target gas pressure inside the process chamber  82  for the processing operation. As the vacuum pump  83  draws the gas  81  from the process chamber  82  and through the valve interior  67 , at a gas flow rate of typically from about 500 sccm to about 15,000 sccm, the outer vane motor  74  is operated to rotate the outer vane  68  from the closed position  80  to the open position shown by the solid lines in FIG. 5B, until the throttle angle “C” shown in FIG. 5B is typically from about 5 to about 15 degrees. Simultaneously, the inner vane motor  78  is operated to withdraw the inner vane  77  from the central opening  69  and retract the inner vane  77  into the pocket  72  of the outer vane  68 . This facilitates a gas pressure of from about 4 Torr to about 6 Torr in the process chamber  82 . Accordingly, the multi-phase pressure control valve  65  is capable of stabilizing the target gas pressure in the process chamber  82  well within sufficient time before the main processing step begins.  
         [0040]    Referring next to FIGS. 8 and 9, still another embodiment the invention includes a multi-phase valve conduit  89 , by which the reaction chamber  84  is connected to the vacuum pump  88  through a main conduit  85 . A diversion conduit  86  branches from the main conduit  85 , and a connecting conduit  87  connects the downstream end of the diversion conduit  86  to the downstream end of the main conduit  85 . A first multi-phase valve  90  is provided in the main conduit  85  between the entry point of the diversion conduit  86  and the re-entry point of the connecting conduit  87 , and a second multi-phase valve  90  is provided in the diversion conduit  86 , in parallel with the first multi-phase valve  90 .  
         [0041]    As shown in FIG. 9, each multi-phase valve  90  typically includes a valve housing  91  having a housing interior  92 , in which is pivotally mounted a butterfly valve vane  93 . A motor  98  engages the butterfly valve vane  93  through a motor shaft  99  which extends through a shaft opening (not shown) in the valve housing  91 . The motor  98  is operable to partially rotate or pivot the butterfly valve vane  93  in the valve interior  92 , between the closed position indicated by the dashed lines and the open position indicated by the solid lines. A gate valve vane  94  is mounted in the housing interior  92  downstream of the butterfly valve vane  93 . Alternatively, the gate valve vane  94  may be mounted upstream of the butterfly valve vane  93 . A motor  95  engages the gate valve vane  94  through a motor shaft  96 . The motor  95  is capable of moving the gate valve vane  94  between a closed position in which the vane  94  closes the housing interior  92 , as shown by the dashed lines, and an open position in which the vane  94  disengages the interior surface of the valve housing  91  and is partially retracted into a pocket  97  provided in the valve housing  91  to open the housing interior  92 , as shown by the solid lines.  
         [0042]    In operation of the multi-phase valve conduit  89 , gas  100 , such as helium, is drawn by operation of the pump  88  from the reaction chamber  84 , through the multi-phase valve conduit  89 , which establishes and stabilizes a target gas pressure inside the reaction chamber  84  as hereinafter described. Some of the gas  100  flows through the main conduit  85 , while a portion of the gas  100  flows through the diversion conduit and connecting conduit  87  and re-enters the downstream end portion of the main conduit  85 . As the gas  100  flows through the multi-phase pressure control valve  90  of the main conduit  85  and of the diversion conduit  86 , respectively, the motor  98  rotates the butterfly valve vane  93  to a throttle angle of typically about 5 to about 15 degrees with respect to the closed position of the vane  93 , indicated by the dashed lines in FIG. 9. Simultaneously, the motor  95  retracts the gate valve vane  94  from the closed position indicated by the dashed lines to the open position indicated by the solid lines in FIG. 9, into the pocket  97 . Accordingly, it will be appreciated by those skilled in the art that each multi-phase pressure control valve  90  is capable of stabilizing the target gas pressure in the process chamber  84  well within sufficient time before the main processing step of the etching, CVD or other process begins.  
         [0043]    While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.