Abstract:
A manufacturing method for a semiconductor device includes: forming a first deposition film on a surface of a member in a chamber configured to perform plasma etching of a wafer, by introducing a first seasoning gas into the chamber; forming a second deposition film on the first deposition film to coat the first deposition film by introducing a second seasoning gas into the chamber; loading the wafer into the chamber; and performing plasma etching of the wafer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-160360 filed on Jun. 19, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a manufacturing method for semiconductor device in which seasoning is performed, for example, in a plasma etching process. 
         [0003]    In a manufacturing process of a semiconductor device using Cu wiring, generally, plasma etching is performed after formation of Cu wiring on a wafer. In such a process, seasoning is performed after cleaning of a chamber by previous use of a dummy wafer in order to ensure stable etching characteristics, as described in Japanese Patent No. 3568749 (e.g., claim 1). 
         [0004]    After completion of seasoning, plasma etching is performed. At this time, Cu deriving from Cu wiring of a previously processed wafer is adherent to a member such as a chamber innerwall. The adhering Cu repeats oxidation, reduction and fluoridation behaviors with fluorine based etching gas introduced into a chamber. Hence, the etchant is deactivated and thus etching characteristics vary. 
         [0005]    While, with further miniaturization of a semiconductor device, higher processing precision is required even for plasma etching, such variations in etching characteristics causes degradation in product performance, reliability and yield due to dimensional variations. However, since it is difficult to remove Cu particles adhering to an inside of the chamber by use of etching gas or the like, seasoning is essential to ensure as stable a process as possible even under such a state where Cu particles are adherent to the inside of the chamber. 
         [0006]    Generally, as a method for suppressing an effect of surface deposits by use of seasoning, for example, Japanese Patent Application Laid-Open No. 11-67746 (e.g., claim 1, paragraphs [00010], [0011]) proposes a technique of introducing a film-forming gas such as silane gas and forming a silicon oxide based seasoning layer in a chamber to coat fluorine absorbed and captured in an inner surface of the chamber. 
         [0007]    On the other hand, to suppress plasma damage of a plasma processing chamber, there is used a technique of covering a surface of a member, such as a chamber inner wall or a part, formed of an alumina base material with Y 2 O 3  film, as disclosed, for example, in Japanese Patent Application Laid-Open No. 2005-225745 (e.g., claim 1). However, in use of such a Y 2 O 3  film, when a silicon oxide based or carbon hydride based seasoning layer as described above is formed, the Y 2 O 3  film is reduced by hydrogen contained in the layer and hence a reduction-oxidation reaction of Y 2 O 3  is induced, which causes a problem that Y dust is generated. 
       SUMMARY 
       [0008]    According to an aspect of the present invention, there is provided a manufacturing method for a semiconductor device comprising; forming a first deposition film on a surface of a member in a chamber configured to perform plasma etching of a wafer, by introducing a first seasoning gas into the chamber; forming a second deposition film on the first deposition film to coat the first deposition film by introducing a second seasoning gas into the chamber; loading the wafer into the chamber; and performing plasma etching of the wafer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a sectional view of a plasma etching apparatus according to an aspect of the present invention; 
           [0010]      FIGS. 2  is a partially enlarged sectional view of a chamber inner wall of a plasma etching apparatus according to an aspect of the present invention. 
           [0011]      FIG. 3  is a flow chart illustrating a plasma etching process according to an aspect of the present invention; and 
           [0012]      FIGS. 4 and 5  are partially enlarged sectional views of a chamber inner wall of a plasma etching apparatus according to an aspect of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Reference will now be made in detail to the present embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawing to refer to the same or like parts. 
         [0014]      FIG. 1  is a sectional view of a plasma etching apparatus used in the present embodiment. A chamber  11  in which a wafer w is subjected to plasma etching is provided with an upper electrode  12  and a lower electrode  13  disposed to face the upper electrode  12 . The lower electrode  13  is supported by a lower portion of the chamber  11  by means of a column  14 . There is also provided a susceptor  15  for placing a wafer w on a top face thereof. High-frequency power supplies  16 ,  17  are connected to the upper electrode  12  and the lower electrode  13  to apply a high-frequency voltage to the upper electrode  12  and the lower electrode  13 , respectively. 
         [0015]    At the upper portion of the chamber  11 , there is provided a gas inlet  18  for introducing an etching gas or the like of predetermined gas type and flow rate. On the other hand, at the lower portion of the chamber  11 , there is provided a gas outlet  19  connected with a vacuum pump or the like for gas exhaust. A displacement regulating valve (not illustrated) is connected to the gas outlet  19 , which enables control of the inside of the chamber  11  at a predetermined pressure. 
         [0016]    As illustrated in a partially enlarged sectional view of  FIG. 2 , a member of an inner wall of the chamber  11  is formed of a housing  11   a  made of alumina and a Y 2 O 3  film  11   b  formed on a surface thereof to suppress plasma damage. In addition to the inner wall, other members, such as the susceptor  15 , mounted inside the chamber  11  are also formed of alumina and Y 2 O 3  film in the same way. 
         [0017]    Using such a plasma etching apparatus, a wafer w is subjected to plasma etching as described below. 
         [0018]      FIG. 3  is a flow chart illustrating a plasma etching process. First, disassembly and wet cleaning are performed and then etching gas is introduced into the chamber  11  having no Cu particles on an inner surface from the gas inlet  18  for initial seasoning (Step  1 ). 
         [0019]    A first wafer w on which lower-layer Cu damascene interconnect is previously formed by a plating method or the like and on which an interlayer insulation film such as SiCOH film and a predetermined resist pattern are formed is loaded into the chamber  11  and placed on the susceptor  15 . Then, CF 4 , for example, as the etching gas is introduced from the gas inlet  18  and high-frequency voltage is applied to the upper electrode  12  by a high-frequency power supply  16  to generate plasma. The wafer w is subjected to plasma etching, using the generated plasma to form a predetermined pattern (opening) in an interlayer insulation film and the like. Next, the first wafer w is unloaded (Step  2 ). 
         [0020]    Since the lower-layer Cu damascene interconnect is exposed at the opening, Cu particles dropped off the exposed portion are adherent to the member such as the inner wall of the chamber  11 . 
         [0021]    An etching gas such as O 2  is introduced from the gas inlet  18  for dry cleaning to remove reaction by-product accumulated in the chamber  11  during previous plasma etching (Step  3 ). The Cu particles adhering to a member of the chamber  11 , such as the inner wall thereof, still remain without being removed by the cleaning. 
         [0022]    Subsequently, seasoning of a first stage is performed (Step  4 ). A dummy wafer is loaded into the chamber  11  and placed on the susceptor  15 . A gas including CF 4 /CH 2 F 2 , for example, as a seasoning gas is introduced from the gas inlet  18 . Further, a high-frequency voltage is applied to the upper electrode  12  by the high-frequency power supply  16  to generate plasma, thereby forming a fluorocarbon based deposition film on a surface of a member such as an inner wall of the chamber  11 . In this process, for example, by setting a ratio of CH 2 F 2  at a relatively large value such as CH 2 F 2  at 20 scm or more with respect to CF 4  at 150 scm, deposition can be positively accelerated. 
         [0023]      FIG. 4  illustrates a partially enlarged sectional view of an inner wall of the chamber  11  at this point. Cu particles  20  adhering to a surface of the Y 2 O 3  film  11   b  covering the casing  11   a  made of alumina of the chamber  11  are covered with a deposition film  21 . 
         [0024]    After forming the deposition film  21 , a formation state of the deposition film  21  is checked as needed. For example, it is checked whether the deposition film  21  has a sufficient film thickness of, for example, at least 0.5 μm by OES (Optical Emission System) or the like used in dry cleaning. 
         [0025]    Subsequent to the seasoning of the first stage, seasoning of a second stage is performed (Step  5 ). A gas including CH 4 /O 2 , for example, as a seasoning gas is introduced from the gas inlet  18  in the same way as the seasoning of the previous stage. Similarly, a high-frequency voltage is applied to the upper electrode  12  by the high-frequency power supply  16  to generate plasma, thereby forming a hydrocarbon based deposition film on a surface of the fluorocarbon based deposition film. In this process, for example, by setting a ratio of C (carbon) at a large value such as O 2  at 70 scm with respect to CH 4 : 250 scm, deposition can be positively accelerated. 
         [0026]      FIG. 5  is a partially enlarged sectional view of an inner wall of the chamber  11  at this point. Cu particles  20  adhering to a surface of the Y 2 O 3  film  11   b  covering the housing  11   a  made of alumina of the chamber  11  are coated with a deposition film  22 . 
         [0027]    After forming the deposition film  22 , a film formation state of the deposition film  22 , for example, whether the deposition film  22  is formed to have a sufficient film thickness of at least 0.5 μm is checked, as needed, in the same way as seasoning of the previous stage. 
         [0028]    After performing two-stage seasoning in this way, the wafer won which lower-layer Cu damascene interconnect is previously formed by a plating method and on which an interlayer insulation film such as SiCOH film and a predetermined resist pattern are formed is carried into the chamber  11  and placed on the susceptor  15 , in the same way as after the initial seasoning. Then, CF 4 , for example, as an etching gas is introduced from the gas inlet  18  and a high-frequency voltage is applied to the upper electrode  12  by the high-frequency power supply  16  to generate plasma, thereby performing plasma etching on the wafer w. After forming a predetermined pattern (opening) in an interlayer insulation film and the like of the wafer w, the wafer w is unloaded (Step  6 ). 
         [0029]    Subsequently, the next wafer is subjected to plasma etching. In the previous plasma etching, a part of the hydrocarbon based deposition film  22  formed on a surface of the member such as the inner wall of the chamber  11  is removed by the introduced etching gas. Similarly, by performing plasma etching on the wafer, the lower-layer Cu damascene interconnect is exposed at the opening and therefore Cu particles newly dropped off the exposed portion are adherent to the member such as the inner wall of the chamber  11 . 
         [0030]    Accordingly, dry cleaning (Step  3 ), seasoning of the first stage (Step  4 ) and seasoning of the second stage (Step  5 ) are performed in the chamber  11  again in the same way. Similarly, the next wafer is loaded into the chamber  11  and, after completion of plasma etching, the wafer w is unloaded (Step  6 ). As described above, a plurality of wafers are subjected to plasma etching while two-stage seasoning is being performed for each processing of a wafer. 
         [0031]    Then, it is determined whether Cu particles need to be removed (Step  7 ). When it is determined that Cu particles adhering to the chamber  11  need to be removed, the chamber  11  is disassembled and wet-cleaned (Step  8 ). 
         [0032]    In the present embodiment, the two-stage seasoning is performed for each plasma etching of one wafer, but the two-stage seasoning may be performed on a plurality of wafers, depending upon a pollution condition of the chamber  11 . 
         [0033]    In the present embodiment, CF 4 /CH 2 F 2  which is gas including fluorocarbon gas is used as seasoning gas of the first stage, but the present invention is not limited thereto. The seasoning gas maybe any gas which is inactive against a member in the chamber and capable of forming a deposition film which re-dissociates to work as an etchant. 
         [0034]    Since the first deposition film to be formed does not need to be totally inactive against a member in the chamber and it is sufficient if the member in the chamber is not reduced which causes dust to be generated, the first deposition film preferably contains fluorine. Such a deposition film containing fluorine is re-dissociated by high-frequency discharge to generate F radical and work as etchant. 
         [0035]    As the gas for generating such a deposition film containing fluorine, a gas including at least one type of fluorocarbon gas may be used. As such a gas including at least one type of fluorocarbon gas, CH 3 F/N 2 , CF 4 /H 2  may be used in addition to CF 4 /CH 2 F 2 . 
         [0036]    As the seasoning gas for the second stage, CH 4 /O 2  which is a gas including hydrocarbon gas is used, but the seasoning gas for the second stage may be any gas which forms a deposition film active against a member in the chamber. Further, other gases such as a gas including at least one type of hydrocarbon based gas such as C 2 H 4  and a gas including at least one type of silane based gas such as SiH 4 , SiH 2 Cl 2  (dichlorosilane). 
         [0037]    In this process, by including O 2  gas at a predetermined flow rate, generation of dust is suppressed, which enables more stable formation of a hydrocarbon based or silicon based deposition film. Such a second deposition film allows a process to be stable without working as etchant during plasma processing of the wafer w although a part thereof re-dissociates. 
         [0038]    In any seasoning gas, preferably, the ratio of C (carbon) is high from the viewpoint of the film formation efficiency of a deposition film. Also in view of film formation efficiency of the deposition film, the temperature is preferably low. Where there is a cooling function in the susceptor  15  or the like, it is preferable to cool inside the chamber by driving the cooling function in the same way as for plasma etching. 
         [0039]    In the present embodiment, the film thickness of each of the deposition films  21 ,  22  is checked by OES or the like, but a film formation state can also be checked by exposing the inside of the chamber  11  to the atmosphere once, disassembling the chamber  11  and measuring the film thickness of each of the actual deposition films  21 ,  22 , thereby determining the film formation conditions of the deposition films  21 ,  22 . 
         [0040]    Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.