Abstract:
A processing tank stores heated sulfuric acid, and a semiconductor substrate having resist formed thereon and to be processed is immersed in the heated sulfuric acid. A first introduction unit introduces ozone gas into the sulfuric acid stored in the processing tank. A second introduction unit introduces hydrogen peroxide into the solution containing sulfuric acid and ozone at least before the processing of the semiconductor substrate is completed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-185896, filed Jul. 5, 2006, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of manufacturing a semiconductor device, and for example, relates to a semiconductor manufacturing apparatus for use in a cleaning process thereof, and a method of manufacturing the semiconductor device. 
         [0004]    2. Description of the Related Art 
         [0005]    In a process of manufacturing a semiconductor device, for example, resist is used as a mask material at the time of the formation of wiring patterns. The resist is used for etching the wiring patterns and for implanting impurities into the required part of the semiconductor device by use of an ion implantation apparatus. After these processes are completed, the resist which has become unnecessary is removed. 
         [0006]    A conventional resist removing method is generally carried out by using a combination of an asher and chemical, or the asher or chemical alone. The resist removal by the chemical is generally carried out by SPM cleaning in which sulfuric acid is mixed with hydrogen peroxide solution. Also, SOM cleaning exists, which introduces ozone gas into the sulfuric acid (refer to, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 2002-231683, 2002-231677 and 2004-327826). Furthermore, a cleaning method exists, which uses sulfuric acid chemical as a base, and combines the introduction or the like of hydrogen peroxide or ozone gas with the chemical (refer to, for example, JPn. Pat. Appln. KOKAI Publication Nos. 11-293288 and 2000-290693). 
         [0007]    Thus, the SOM cleaning which introduces the ozone gas into the sulfuric acid can enhance the peeling performance of the resist since the SOM cleaning has higher sulfuric acid concentration and can be carried out at higher temperatures as compared with the SPM cleaning in which the sulfuric acid is mixed with the hydrogen peroxide solution. However, when peroxodisulfuric acid (or hydrogen peroxide) is little and dissolution due to the substance is required, a problem exists in that resist residue exists in solution indefinitely. 
         [0008]    Examples of methods of enhancing the peeling performance of the resist include adding a peroxodisulfuric acid into a sulfuric acid-hydrogen peroxide mixture (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 11-293288). 
         [0009]    There has also been considered a method of adding the peroxodisulfuric acid or hydrogen peroxide capable of dissolving the resist into sulfuric acid/ozone capable of making it high temperature and having high sulfuric acid concentration by mixing to the sulfuric acid. However, as is well known, the hydrogen peroxide solution acts as a reducing agent to a stronger oxidizer than the hydrogen peroxide solution, and decomposes the ozone in the liquid. For this reason, when the hydrogen peroxide solution is merely added into the sulfuric acid/ozone, the concentration of the ozone or hydrogen peroxide is reduced, and the peeling performance of the resist is reduced. Therefore, it is not a good plan to simply mix an oxidizer into the sulfuric acid/ozone. 
         [0010]    Accordingly, there has been desired the provision of a semiconductor manufacturing apparatus which can dissolve the resist residue in the liquid efficiently by the introduction of the hydrogen peroxide solution without reducing the peeling performance of the resist due to the sulfuric acid/ozone (SOM) cleaning in which the ozone gas is introduced into the sulfuric acid, and a method of manufacturing a semiconductor device. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    According to a first aspect of the invention, there is provided a semiconductor manufacturing apparatus comprising: a processing tank in which heated sulfuric acid is stored and a semiconductor substrate having resist formed thereon and to be processed is immersed; a first introduction unit which introduces ozone gas into the sulfuric acid stored in the processing tank; and a second introduction unit which introduces hydrogen peroxide into the solution containing the sulfuric acid and ozone at least before the processing of the semiconductor substrate is completed. 
         [0012]    According to a second aspect of the invention, there is provided a semiconductor manufacturing apparatus comprising: a processing tank in which sulfuric acid is stored and a semiconductor substrate having resist formed thereon and to be processed is immersed; a first introduction unit which introduces ozone gas into the sulfuric acid stored in the processing tank; a mixing tank provided in an exterior of the processing tank, the mixing tank storing the solution containing sulfuric acid and ozone overflowed from the processing tank; a heating unit which heats the solution supplied from the mixing tank, the heating unit supplying the solution to the processing tank; and a second introduction unit which introduces hydrogen peroxide into the sulfuric acid at least before the processing of the semiconductor substrate is completed. 
         [0013]    According to a third aspect of the invention, there is provided a method of manufacturing a semiconductor device, comprising: introducing ozone gas into heated sulfuric acid and processing a semiconductor substrate having resist formed thereon using the solution containing sulfuric acid and ozone; and introducing hydrogen peroxide into the solution at least before the processing of the semiconductor substrate is completed to dissolve undissolved resist. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0014]      FIG. 1  is a diagram showing a configuration according to an embodiment of a semiconductor manufacturing apparatus; 
           [0015]      FIGS. 2A to 2E  are respectively timing charts showing processing sequences of a semiconductor device using the apparatus shown in  FIG. 1 ; 
           [0016]      FIG. 3  is a characteristic diagram showing an example showing a lifetime according to the temperature of hydrogen peroxide in a sulfuric acid solution; and 
           [0017]      FIG. 4  is a characteristic diagram showing an example showing a lifetime of hydrogen peroxide in a sulfuric acid solution in a different temperature from that of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
         [0019]    A semiconductor manufacturing apparatus according to an embodiment of  FIG. 1  will be schematically shown. In  FIG. 1 , highly concentrated sulfuric acid  12  is stored in a processing tank  11  cleaning a semiconductor substrate. The concentration of the sulfuric acid  12  is, for example, 85% or more. The sulfuric acid  12  overflowed from the upper part of the processing tank  11  is stored in an outer tank  13  as a mixing tank provided in the exterior of the processing tank  11 . That is, the outer tank  13  is provided at the periphery of the processing tank  11 . The sulfuric acid  12  stored in the outer tank  13  is guided to a heater  16  by a pipe  14  and a circulating pump  15 . The sulfuric acid  12  heated by the heater  16  is guided into the processing tank  11  via a filter  17  and a pipe  18 . Although the filter  17  for removing particles is contained in a circulating system, the filter  17  may be inserted in the system if necessary. A bubbler  19 , which is provided in the processing tank  11 , is connected to an ozone generator  21  via a pipe  20 . The ozone generator  21  generates ozone gas (O 3 )  22  from, for example, supplied oxygen O 2 . The generated ozone gas  22  is introduced into the sulfuric acid  12  of the processing tank  11  via the pipe  20  and the bubbler  19 . A mechanism for introducing the ozone gas is not limited to the bubbler  19 , and an ejector can be also used for the mechanism. Furthermore, hydrogen peroxide (H 2 O 2 )  24  is introduced into the outer tank  13  via a pipe  23 . A valve  25 , which is provided on the way of the pipe  23 , is controlled by a control unit  26 . As described later, the control unit  26  controls the supply timing and supply amount of hydrogen peroxide to a sulfuric acid solution. Furthermore, the control unit  26  may control the heater  16  to control the temperature of the sulfuric acid solution stored in the processing tank  11  and the operation of the ozone generator  21 . The hydrogen peroxide  24  is mixed with the sulfuric acid solution in the outer tank  13 , is heated by the heater  16 , and is guided into the processing tank  11 . The introduction position of the hydrogen peroxide to the sulfuric acid solution is not limited to the outer tank  13 . For example, the hydrogen peroxide may be introduced to the inner side of the processing tank  11 , the circulating pump  15 , the heater  16 , the filter  17  or the circulating system pipe  18  as shown by a dashed line in  FIG. 1 . 
         [0020]    In the above configuration, a method of cleaning a substrate will be described with reference to  FIG. 2 . 
         [0021]    The highly concentrated sulfuric acid  12  is stored in the processing tank  11  for cleaning the semiconductor substrate. The sulfuric acid  12  overflowed from the processing tank  11  is guided to the heater  16  by the circulating pump  15 , and is circulated to the processing tank  11  via the filter  17  while the sulfuric acid  12  is heated to a high temperature. The sulfuric acid  12 , which is heated to, for example,  130  to 180° C., is circulated. The ozone gas  22  generated by the ozone generator  21  is introduced into the processing tank  11  via the pipe  20  and the bubbler  19 . 
         [0022]    As shown in  FIG. 2A , for example, simultaneously with immersing the semiconductor substrate (lot) on which the resist is formed in the processing tank  11 , as shown in  FIG. 2B , the ozone gas is introduced into the sulfuric acid  12  of the processing tank  11 . However, the introduction timing of the ozone gas can be also set earlier or later to some degree than the immersion of the semiconductor substrate into the processing tank  11 . Fundamentally, the processing of the semiconductor substrate in a mixed state of sulfuric acid/ozone may be the same timing as the resist removing process. 
         [0023]    Although the resist formed on the semiconductor substrate can be effectively peeled by the sulfuric acid and ozone processes, the solution rate of the resist may be reduced according to the increase in the amount of the resist peeled in the sulfuric acid solution to cause the existence of the resist residue in the sulfuric acid solution. In this case, when the resist is newly peeled in the next processing of the semiconductor substrate, the resist residue may remain in the sulfuric acid solution. Or when the semiconductor substrate is taken out from a cleaning fluid after the peeling of the resist is completed, the undissolved resist residue may be adhered to the semiconductor substrate. 
         [0024]    So, in the embodiment, in order to dissolve the undissolved resist using the mixed solution of the sulfuric acid having a rapid solution rate of the resist and hydrogen peroxide, hydrogen peroxide solution is added at least before taking out the semiconductor substrate. That is, as shown in  FIG. 2C , the hydrogen peroxide solution is added into the sulfuric acid solution of the processing tank  11  for a short interval of time before the processing of the semiconductor substrate is completed. The dissolved ozone in the sulfuric acid develops a redox reaction with the hydrogen peroxide, and is decomposed. Therefore, at least the amount of the hydrogen peroxide to be added need only be the sum of the amount required for the decomposition of the ozone and amount required for the dissolution of the resist residue. The concentration of the hydrogen peroxide to be added is, for example, 0.01 to 2 wt %. As shown in  FIG. 2D , the ozone concentration is reduced by the addition of the hydrogen peroxide, and as shown in  FIG. 2E , the concentration of the hydrogen peroxide is reduced with time. 
         [0025]    Thus, the undissolved resist can be dissolved by adding the hydrogen peroxide into the sulfuric acid/ozone solution before the processing of the semiconductor substrate is completed. Thereby, the undissolved resist in the solution can be efficiently dissolved. In addition, since the addition time of the hydrogen peroxide is a short period before the processing is completed, the addition has an advantage that the peeling performance of the resist due to the sulfuric acid solution is not reduced. 
         [0026]    When, after the semiconductor substrate processing (SOM cleaning), the hydrogen peroxide exists in the processing tank  11  in the case of the next semiconductor substrate processing (SOM cleaning), the introduced ozone is decomposed. For this reason, as shown in  FIG. 2E , the hydrogen peroxide must be fully decomposed, for example, for tens of minutes till the next processing of the semiconductor substrate. The decomposition rate of the hydrogen peroxide in the high-temperature sulfuric acid solution also depends on temperature. As shown in  FIG. 3 , the hydrogen peroxide exists at 120° C. for several hours, and by contrast, the hydrogen peroxide does not exist at 140° C. for 1 hour. In the manufacturing process of the semiconductor, the practical temperature of the sulfuric acid solution is 130° C. or more. The concentration of the hydrogen peroxide to be added is desirably about 0.01 to about 2 wt % in view of the experimental results. 
         [0027]    In the above description, the hydrogen peroxide is introduced once in order to dissolve the residue of the resist in liquid at the end of the processing of the semiconductor substrate. However, the processing is not limited thereto. 
         [0028]    For example, if the hydrogen peroxide is decomposed in several minutes, and the ozone concentration is immediately recovered during the processing, the hydrogen peroxide may be added several times during the processing, as shown by a dashed line in  FIG. 2C . By doing this, the resist residue in the sulfuric acid solution can be suitably dissolved. 
         [0029]    Furthermore, if required, the temperature of the sulfuric acid solution may be increased, and the temperature may be returned to the processing temperature after decomposing the hydrogen peroxide in order to increase the decomposition rate of the hydrogen peroxide between the processes of the semiconductor substrate. 
         [0030]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.