Abstract:
A semiconductor manufacturing apparatus that forms a carbon film on a wafer by plasma enhanced chemical vapor deposition includes a body having a top opening; a stage provided within the body for placement of the wafer; a showerhead that encloses the top opening and that introduces a deposition gas or an etch gas; and a gas delivery system including a central gas inlet that introduces gas toward a central portion of the wafer from a central portion of the showerhead, and a peripheral gas inlet that introduces gas toward a bevel of the wafer from an outer peripheral portion of the showerhead, wherein the gas delivery system, after activating the etch gas outside the body, delivers the activated etch gas toward the bevel of the wafer to selectively remove a portion of the carbon film formed on the bevel of the wafer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-215249, filed on, Aug. 25, 2008 the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The present disclosure relates to a semiconductor manufacturing apparatus and method of manufacturing a semiconductor device. 
       BACKGROUND 
       [0003]    Sidewall processing is known as a typical technology in forming smaller line and space patterns. Sidewall processing involves forming a core material, forming a spacer film comprising an amorphous silicon (a-Si) film, for example to perform a series of required processes, removing the core material, and processing the underlying features using the remaining spacer film as a mask. Core materials generally used in the above described sidewall processing are films such as TEOS film and SiN film formed by LPCVD (Low Pressure Chemical Vapor Deposition). Recent development has found carbon CVD film as a possible alternative to the conventional approach. Carbon CVD film is formed by PECVD (Plasma Enhance Chemical Vapor Deposition) and can be removed by dry etching such as O 2  ashing. 
         [0004]    Some of the disadvantages encountered in employing a core material comprising carbon CVD film were contamination within the fabrication equipment caused by delaminated or broken away fragments of spacer film overlying the carbon CVD film formed on the wafer bevel (outer peripheral edge) and wafer contamination by dust transferred onto the wafer which was produced by fragments of carbon CVD film delaminating from the wafer bevel when removing the core material by O 2  ashing. It is thus, desirable not to allow any carbon CVD film to remain on the wafer bevel after formation of the carbon CVD film. 
         [0005]    One possible solution to the above described problems may be dry etching the carbon CVD film by O 2  ashing, or the like, in the load lock chamber after formation of the carbon CVD film. The problem with such approach is contamination by dust blown up by large pressure variance caused by transfer of wafer in and out of the load lock chamber and significantly reduced throughput. Another problem is increased complexity of the fabrication equipment since exhaust from the load lock chamber need to be rendered dust-free by devices such as a filtering device. 
         [0006]    One example of a dedicated etching equipment for etching the wafer bevel is disclosed in 2006-120875 A. 
       SUMMARY 
       [0007]    In one aspect of the present invention, there is provided a semiconductor manufacturing apparatus that forms a carbon film on a wafer by plasma enhanced chemical vapor deposition including a body having a top opening; a stage provided within the body for placement of the wafer; a showerhead that encloses the top opening and that introduces a deposition gas or an etch gas; and a gas delivery system including a central gas inlet that introduces gas toward a central portion of the wafer from a central portion of the showerhead, and a peripheral gas inlet that introduces gas toward a bevel of the wafer from an outer peripheral portion of the showerhead, wherein the gas delivery system, after activating the etch gas outside the body, delivers the activated etch gas toward the bevel of the wafer to selectively remove a portion of the carbon film formed on the bevel of the wafer. 
         [0008]    In another aspect of the present invention, there is provided a method of manufacturing a semiconductor device in which a carbon film formation with plasma enhanced chemical vapor deposition is performed including forming the carbon film on a wafer by introducing a deposition gas from a central gas inlet positioned at a central portion of a showerhead and a peripheral gas inlet positioned at a peripheral portion of the showerhead, the showerhead enclosing an upper opening of a body of a plasma enhanced chemical vapor deposition apparatus, and etching away the carbon film formed on a bevel of the wafer by delivering a first etch gas activated outside the body toward the bevel of the wafer from the peripheral gas inlet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a vertical cross sectional view of a PECVD apparatus according to one exemplary embodiment of the present invention; 
           [0010]      FIG. 2  is a perspective view of an exhaust element; 
           [0011]      FIG. 3  is a descriptive view of a gas delivery system; 
           [0012]      FIGS. 4A to 4F  are cross sectional views describing film formation and etching performed at an outer peripheral edge of a wafer; 
           [0013]      FIGS. 5A to 5F  are comparative examples corresponding to  FIGS. 4A to 4F ; 
           [0014]      FIG. 6  is a chart indicating an ON/OFF state of a high-frequency power supply, an ON/OFF state of a reaction chamber, and an OPEN/CLOSE status of each valve; 
           [0015]      FIG. 7  corresponds to  FIG. 3  and depicts a second exemplary embodiment; and 
           [0016]      FIG. 8  corresponds to  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    A description will be given hereinafter on a first exemplary embodiment of the present invention with reference to  FIGS. 1 to 6 . References are made to the elements identified in the drawings hereinafter with identical or similar reference symbols when referring to identical or similar elements. 
         [0018]      FIG. 1  is a vertical cross sectional view of a PECVD apparatus  1  providing a schematic overview of the device. PECVD apparatus  1  comprises a body  2  shaped as a closed bottom cylinder, a showerhead  3  enclosing the top opening of body  2 , and a stage  4  provided inside body  2 . Stage  4 , being earthed, serves as a lower electrode and also as a placement for supporting a wafer  5 . 
         [0019]    Showerhead  3  has a projection  6  that protrudes into body  2  so as to confront stage  4 . Projection  6 , when viewed from the exterior of body  2 , defines a recess  7 . The interior of recess  7  is partitioned by a partition element  8  disposed so as to close the top opening of recess  7 . More specifically the interior of recess  7  is partitioned into a central gas inlet  9  and a peripheral gas inlet  10  by a cylindrical partition wall  8   a  extending from the underside of partition element  8 . 
         [0020]    Partition element  8  has in its central portion a gas delivery path  11  communicating with central gas inlet  9 . Gas delivered from a later described gas source is delivered into central gas inlet  9  through gas delivery path  11 . Gas supplied into central gas inlet  9  is introduced into body  2  through multiplicity of through holes (not shown) defined on a bottom wall  6   a  of projection  6 . Above bottom wall  6   a , a dispersion plate  12  in disc shape is disposed for gas dispersion. 
         [0021]    At the left end as viewed in  FIG. 1  of the outer periphery of partition element  8 , a gas delivery path  13  is provided so as to be in communication with peripheral gas inlet  10 . Gas delivered from a later described gas source flows into peripheral gas inlet  10  through gas delivery path  13 . Gas delivered into peripheral gas inlet  10  is introduced into body  2  through the multiplicity of through holes defined on bottom wall  6   a  of projection  6 . Above bottom wall  6   a , a dispersion plate  14  in ring shape is disposed for gas dispersion. 
         [0022]    Showerhead  3  functions as an upper electrode and is connected to one of the two terminals of a high-frequency power supply (RF power supply)  15 . The remaining other terminal of high-frequency power supply  15  is earthed. On a portion of the inner peripheral wall of body  2  confronting the outer periphery of stage  4 , a ring-shaped exhaust element  16  is disposed so as to rest upon a step provided on the inner peripheral wall of body  2 . As can be seen in  FIG. 2 , exhaust element  16  has multiplicity of exhaust holes  16   a  defined on its inner peripheral surface which communicates with an annular communication path  16   b  running inside exhaust element  16 . 
         [0023]    On the inner peripheral wall of body  2 , an exhaust port  17  is provided at a portion placed in abutment with the right end of exhaust element  16  as viewed in  FIG. 1 . Exhaust port  17  communicates with communication path  16   b  within exhaust element  16  through communication hole  16   c . Exhaust port  17  has an exhaust pump (vacuum pump) not shown connected to it that forces gas inside body  2  to be discharged through exhaust element  16  and exhaust port  17 . 
         [0024]    The spacing between exhaust holes  16   a  defined on exhaust element  16  is adjusted depending upon their distance from exhaust port  17  (communication hole  16   c ) such that as  FIG. 2  shows, the spacing becomes wider as exhaust holes  16   a  are located closer to exhaust port  17  and narrower as the exhaust holes  16   a  are located farther from exhaust port  17 . Such arrangement allows gas inside body  2  to be exhausted evenly. 
         [0025]    Dispersion plate  14  formed inside peripheral gas inlet  10  also has multiplicity of through holes (not shown) defined to it which are adjusted in spacing as was the case for exhaust holes  16   a  of exhaust element  16  such that spacing between the through holes become wider as the through holes are located closer to gas delivery path  13  and narrower as the through holes are located farther from gas delivery path  13 . Such arrangement allows gas delivered from gas delivery path  13  to flow evenly into body  2 . 
         [0026]    Next, with reference to  FIG. 3 , a description will be given on a gas delivery system that delivers various types of gas into central gas inlet  9  (gas delivery path  11 ) and peripheral gas inlet  10  (gas delivery path  13 ) within showerhead  3  of PECVD apparatus  1 . 
         [0027]    First, a description will be given on the gas delivery system responsible for supplying gas into gas delivery path  11  of central gas inlet  9 . Gas delivery path  11  is connected at the lower end of a central gas conduit  18  as viewed in  FIG. 3 , which is provided with a central main valve  19 . On the upper end of central gas conduit  18  as viewed in  FIG. 3 , five gas conduits  20  to  24  are connected in parallel. Gas conduit  20  is provided with a valve  25  and is connected to a gas source  260  of C 3 H 6  gas. Likewise, gas conduit  21  is provided with valve  27  and is connected to gas source  28  of He gas; gas conduit  22  has valve  29  and is connected to gas source  30  of O 2  gas; gas conduit  23  has valve  31  and is connected to gas source  32  of Ar gas; and gas conduit  24  has valve  33  and is connected to gas source  34  of N 2  gas. Each of gas sources  26 ,  28 ,  30 ,  32 , and  34  comprises an MFC (Mass Flow Controller) for controlling the supply of each type of gas, and a tank for storing each type of gas. In the above described configuration, by opening main valve  19  and opening/closing valves  25 ,  27 ,  29 ,  31 , and  33  as required, one or 2 or more of C 3 H 6  gas, He gas, O 2  gas, Ar gas, and N 2  gas can be supplied as required. 
         [0028]    Next, a description will be given on the gas delivery system responsible for delivering gas into gas delivery path  13  of peripheral gas inlet  10 . Gas delivery path  13  is connected to the lower end of a peripheral gas conduit  35  as viewed in  FIG. 3 , which is provided with a peripheral main valve  36 . On the upper end of peripheral gas conduit  35  as viewed in  FIG. 3 , three gas conduits  37  to  39  are connected in parallel. Gas conduit  37  is provided with a valve  40  and is connected to a gas source  41  of C 3 H 6  gas. Likewise, gas conduit  38  is provided with valve  42  and is connected to gas source  43  of He gas. 
         [0029]    Gas conduit  39  is provided with a reaction chamber  44  and two gas conduits  45  and  46  connected in parallel. Reaction chamber  44  activates oxygen (O 2 ) supplied into it by microwave discharge. Gas conduit  45  has a valve  47  and is connected to gas source  48  of O 2  gas, and gas conduit  46  has a valve  49  and is connected to gas source  50  of Ar gas. Each of gas sources  41 ,  43 ,  48  and  50  comprises an MFC (Mass Flow Controller) for controlling the supply of each type of gas, and a tank for storing each type of gas. In the above described configuration, by opening main valve  36  and opening/closing valves  40 ,  42 ,  47 , and  49  as required, one or 2 or more of C 3 H 6  gas, He gas, O 2  gas, and Ar gas can be supplied as required. 
         [0030]    PECVD apparatus  1  being configured as described above forms carbon CVD film  51  on wafer  5 . As indicated in the row labeled “film formation” in the table given in  FIG. 6 , high-frequency power supply  15  is turned on, main valve  19  opened, valves  25  and  27  opened, valves  29 ,  31 , and  33  closed, reaction chamber  44  turned off, main valve  36  opened, valves  40  and  42  opened and valves  47  and  49  are closed. As a result of the above operation, C 3 H 6  gas and He gas are introduced into body  2  via central gas inlet  9  and peripheral gas inlet  10  within showerhead  3  while high-frequency power supply  15  is turned on and discharge takes place between showerhead  3  and stage  4  to form carbon CVD film  51 .  FIG. 4A  shows the resulting carbon CVD film  51 . Of note is that carbon CVD film  51  is formed on a processing film  52  formed on wafer  5 . 
         [0031]    Next, after forming carbon CVD film  51  with PECVD apparatus  1  as described above, carbon CVD film  51  residing on the wafer bevel is etched away using PECVD apparatus  1 . As indicated in the row labeled “etching” in the table given in  FIG. 6 , high-frequency power supply  15  is turned off, main valve  19  opened, valves  25 ,  27  and  29  closed, valves  31  and  33  opened, reaction chamber  44  turned on, main valve  36  opened, valves  40  and  42  closed and valves  47  and  49  are opened. 
         [0032]    As a result of the above operation, Ar gas and N 2  gas (inert gas) are introduced into body  2  through central gas inlet  9  within showerhead  3  while Ar gas and O 2  gas activated by reaction chamber  44  are introduced into body  2  through peripheral gas inlet  10 . As a result, activated oxygen (O 2 ) gas flows onto the outer peripheral portion of wafer  5  to allow carbon CVD film  51  residing on wafer  5  bevel to be etched away within body  2 . Of note is that inert gas (Ar gas and N 2  gas) flown toward the central portion of wafer  5  keeps activated oxygen confined at wafer  5  bevel which is significantly advantageous in only etching away carbon CVD film  51  residing on wafer  5  bevel (refer to  FIG. 4B ). During etching, RF power of high-frequency power supply  15  is cut off from body  2  (that is, between showerhead  3  and stage  4 ) in order to prevent discharge between showerhead  3  and stage  4  from affecting carbon film  51  formed on the central portion of wafer  5 . 
         [0033]    Next, after forming an anti-reflection film (not shown) on the etched carbon CVD film  51 , a predetermined processing is performed on carbon CVD film  51  (refer to  FIG. 4C ). Then, as shown in  FIG. 4D , amorphous silicon film  53  serving as a spacer is formed on carbon CVD film  51 . Thereafter, using carbon CVD film  51  as a stopper, amorphous silicon film  53  is etched by RIE (Reactive Ion Etching) as shown in  FIG. 4E . Then, as shown in  FIG. 4F , carbon CVD film  51  is removed by dry etching such as O 2  ashing. Removing carbon CVD film  51  serving as a core material by dry etching allows successful formation of spacer  54  without surface tension collapse which was a problem encountered in wet etching. Of note is that amorphous silicon film  53  residing on wafer  5  bevel is not removed by the dry etching. 
         [0034]    A comparative example (conventional approach) will now be described with reference to  FIG. 5  which does not remove carbon CVD film  51  residing on wafer  5  bevel by etching. In the comparative example shown in  FIG. 5A , anti-reflection film  55  is formed on carbon CVD film  51  after forming carbon CVD film  51  on processing film  52 . Then, as shown in  FIG. 5B , predetermined processing is performed on carbon CVD film  51 . Next, as shown in  FIG. 5C , anti-reflection film  55  is removed. Then, as shown in  FIG. 5D , amorphous silicon film  53  serving as a spacer is formed on carbon CVD  51 . 
         [0035]    Thereafter, as shown in  FIG. 5E , amorphous silicon film  53  is etched by RIE using carbon CVD film  51  as a stopper. Then, as shown in  FIG. 5F , carbon CVD film  51  is removed to form spacer  54 . The problem in this approach is delamination of carbon CVD film  51  and amorphous silicon film  53  residing on wafer  5  bevel. 
         [0036]    In contrast, the present exemplary embodiment, as shown in  FIG. 4B , removes carbon CVD film  51  residing on wafer  5  bevel by etching and thus, delamination of amorphous silicon film  53  from wafer  5  bevel can be prevented as can be seen in  FIG. 4F . 
         [0037]    Next, a description will be given on cleaning, in other words, empty heating of body  2  interior of PECVD apparatus  1 . As indicated in the row labeled “cleaning” in the table given in  FIG. 6 , high-frequency power supply  15  is turned on, main valve  19  opened, valves  25 ,  27  and  33  closed, valves  29 ,  31  opened, reaction chamber  44  turned on, main valve  36  opened, valves  40  and  42  closed and valves  47  and  49  are opened. 
         [0038]    As a result of the above operation, O 2  gas and Ar gas are introduced into body  2  through central gas inlet  9  within showerhead  3  while introducing Ar gas and O 2  gas activated by reaction chamber  44  into body  2  through peripheral gas inlet  10  within showerhead  3 . Then, high-frequency power supply  15  is turned on and discharge takes place between showerhead  3  and stage  4  to activate O 2  gas introduced into body  2  and clean the interior of body  2  with the activated O 2  gas. 
         [0039]      FIGS. 7 and 8  depict a second exemplary embodiment of the present disclosure. Portions that are identical to the first exemplary embodiment are identified with identical reference symbols. In the second exemplary embodiment, as can be seen in  FIG. 7 , the portion of central gas conduit  18  connecting to gas delivery path  11  and the portion of gas conduit  39  connecting to peripheral gas conduit  35  are connected by a connecting gas conduit  56  which is provided with valve  57 . 
         [0040]    When forming carbon CVD film  51  on wafer  5  using PECVD apparatus  1  of the second exemplary embodiment, valve  57  of connecting gas conduit  56  is closed as indicated in the row labeled “film formation” in the table given in  FIG. 8 , and other on/off, open/close operations of valves etc., remain the same as the first exemplary embodiment (refer to  FIG. 6 ). 
         [0041]    Etching of carbon CVD film  51  residing on wafer  5  bevel performed using PECVD apparatus  1  after formation of carbon CVD film  51  in the above described manner is carried out by closing valve  57  of connecting gas conduit  56  as indicated in the row labeled “etching” in the table given in  FIG. 8 , and other on/off, open/close operations of valves etc., remain the same as the first exemplary embodiment (refer to  FIG. 6 ). 
         [0042]    Cleaning of the interior of body  2  using PECVD apparatus  1  is carried out by opening valve  57  of connecting gas conduit  56  as indicated in the row labeled “cleaning” in the table given in  FIG. 8 . This time, however, other on/off, open/close operations of valves etc., are different from the first exemplary embodiment. More specifically, as indicated in the row labeled “cleaning” in the table given in  FIG. 8 , high-frequency power supply  15  is turned off, main valve  19  closed, valves  25 ,  27 ,  29 ,  31  and  33  closed, reaction chamber  44  turned on, main valve  36  opened, valves  40  and  42  closed and valves  47 , 49 , and  57  are opened. 
         [0043]    As a result of the above operation, Ar gas and O 2  gas activated by reaction chamber  44  are introduced into body  2  through central gas inlet  9  as well as through peripheral gas inlet  10  within showerhead  3 . As a result, the interior of body  2  can be cleaned with activated O 2  without discharge taking place between showerhead  3  and stage  4  which is burdensome to body  2 . 
         [0044]    Other features not mentioned above remain the same from the first exemplary embodiment. Thus, the second exemplary embodiment obtains the same effects as the first exemplary embodiment. 
         [0045]    The present disclosure is not limited to the above described exemplary embodiments but may be modified or expanded as follows. 
         [0046]    Exhaust holes  16   a  formed on the inner peripheral surface of exhaust element  16  (refer to  FIG. 2 ) may be provided on other surfaces of exhaust element  16  such as on the upper surface of exhaust element  16  or on both the inner peripheral surface and the upper surface of exhaust element  16 . 
         [0047]    Further, a single gas delivery path  13  in communication with peripheral gas inlet  10  is provided at the left end of the outer periphery of partition element  8  as viewed in  FIG. 1  in the above exemplary embodiments. Alternatively, two or more gas delivery paths  13  in communication with peripheral gas inlet  10  may be provided at the outer periphery of partition element  8 , and gas may be delivered into peripheral gas inlet  10  from the two or more gas delivery paths  13 . 
         [0048]    Ar gas and N 2  gas are employed as inert gases directed to the central portion of wafer  5  to facilitate removing of carbon CVD film  51  residing on wafer  5  bevel in the present exemplary embodiment. Alternatively, at least one of Ar gas and N 2  gas as well as other combinations of gases may be employed and delivered toward the central portion of wafer  5 . 
         [0049]    The foregoing description and drawings are merely illustrative of the principles of the present disclosure and are not to be construed in a limited sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the disclosure as defined by the appended claims.