Abstract:
A manufacturing apparatus for a semiconductor device, treating a SiN film formed on a wafer with phosphoric acid solution, including a processing bath to store phosphoric acid solution provided for treatment of the wafer, a control unit for calculating integrated SiN etching amount of the phosphoric acid solation, determining necessity of quality adjustment of the phosphoric acid solution, based on correlation between the integrated SiN etching amount calculated and etching selectivity to oxide film, and calculating a quality adjustment amount of the phosphoric acid solution as needed, and also including a mechanism to adjust the quality of the phosphoric acid solution based on the quality adjustment amount calculated.

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. 2007-149465 filed on Jun. 5, 2007, 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 manufacturing apparatus for a semiconductor device and a manufacturing method for a semiconductor device, used for etching treatment of a semiconductor substrate, for example, with phosphoric acid solution. 
         [0004]    2. Description of the Related Art 
         [0005]    In the manufacturing processes of semiconductor devices, there is a process of etching a silicon nitride (SiN) film formed on a wafer with phosphoric acid solution, hereinafter referred to as “H 3 PO 4  solution”. This process uses a batch processing bath subjected to etching treatment, for example, with a plurality of wafers as one lot. Usually, H 3 PO 4  solution is maintained at a temperature of approximately 160° C. next to boiling point in the processing bath, and is used while being circulated for treatment of a plurality of lots. 
         [0006]    When etching treatment of a SiN film formed on a wafer using H 3 PO 4  solution is performed in the batch processing bath, etching residue resulting from silica (SiO 2 ) generated by an etching reaction remains in the H 3 PO 4  solution. By circulating the H 3 PO 4  solution and repeatedly using the solution for H 3 PO 4  treatment, etching residue gathers in the H 3 PO 4  solution as the number of lots to be treated increases, and the amount of etching residue increases. 
         [0007]    The etching residue causes dust generation and fluctuates SiN etching rate and etching selectivity to oxide film with the amount of etching residue gathered in H 3 PO 4  solution. Accordingly, to restrain process fluctuations, there have been studied various methods for controlling the concentration of etching residue (Si concentration) dissolved in H 3 PO 4  solution. 
         [0008]    For example, U.S. Pat. No. 6,780,277 has disclosed a method for additionally supplying H 3 PO 4  solution by directly monitoring Si concentration in H 3 PO 4  solution and discarding a required amount of solution when the concentration has reached a predetermined concentration. For this method, a dedicated Si concentration measurement unit for measuring Si concentration in high-temperature H 3 PO 4  solution with the in-situ technique is essential. However, such a unit exists in reality, but is very expensive and has questionable reliability. 
         [0009]    There has been known a method for controlling Si concentration in H 3 PO 4  solution to have a desired concentration by adding an appropriate amount of hydrofluoric acid (HF) into H 3 PO 4  solution and vaporizing SiO 2 by reaction with HF. This method requires measurement of Si concentration in H 3 PO 4  solution. However, it is difficult to control H 3 PO 4  solution in real time, as described above. 
         [0010]    US2005/0263488 has disclosed a method for re-precipitating silicate by cooling H 3 PO 4  solution and removing the re-precipitated silicate by filtration. However, the method requires use of a dedicated cooling system. 
         [0011]    Japanese Patent Application Laid-Open No. 2004-288963 (paragraph numbers [0030] to [0033],  FIG. 3  and others) has proposed a method for determining a current etching rate of H 3 PO 4  solution based on the use history of H 3 PO 4  solution up to now and data showing a relationship between the use history and etching rate and correcting etching time in accordance with the etching rate. This method requires no actual measurement of Si concentration by the in-situ technique during etching treatment. 
         [0012]    However, this method allows completion of etching treatment of a desired depth, but requires long treatment time and therefore a desired aperture shape maybe difficult to obtain due to a relationship with etching selectivity to oxide film. 
       SUMMARY OF THE INVENTION 
       [0013]    In accordance with a first aspect of the present invention, a manufacturing apparatus for a semiconductor device, treating a SiN film formed on a wafer with phosphoric acid solution, including a processing bath to store phosphoric acid solution provided for treatment of the wafer, a control unit for calculating integrated SiN etching amount of the phosphoric acid solution, determining necessity of quality adjustment of the phosphoric acid solution, based on correlation between the integrated SiN etching amount calculated and etching selectivity to oxide film, and calculating a quality adjustment amount of the phosphoric acid solution as needed, and also including a mechanism to adjust the quality of the phosphoric acid solution based on the quality adjustment amount calculated. 
         [0014]    In accordance with a second aspect of the present invention, A manufacturing method for a semiconductor device treating a SiN film formed on a wafer is treated with phosphoric acid solution, including calculating integrated SiN etching amount of phosphoric acid solution provided for treatment of the wafer, determining necessity of quality adjustment of the phosphoric acid solution based on correlations between the integrated SiN etching amount calculated and etching selectivity to oxide film, calculating a quality adjustment amount of the phosphoric acid solution determined to be necessary, adjusting quality of the phosphoric acid solution based on the quality adjustment amount calculated, and treating the wafer using the phosphoric acid solution, the quality of the phosphoric acid solution is adjusted. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]    The accompanying drawings, which is incorporated in and constitute a part of this specification, illustrates an embodiment of the invention and together with the description, serve to explain the principles of the invention. 
           [0017]      FIG. 1  is a schematic view showing configuration of a H 3 PO 4  treatment apparatus according to one embodiment of the present invention; 
           [0018]      FIG. 2  is a block diagram illustrating a configuration of a control unit; 
           [0019]      FIG. 3A  is a graph illustrating relationship data between integrated SiN etching amount and etching rate stored in a database; 
           [0020]      FIG. 3B  is a graph illustrating relationship data between integrated SiN etching amount and etching selectivity to oxide film stored in a database; 
           [0021]      FIG. 4  is a flowchart illustrating an example of treatment with a H 3 PO 4  treatment apparatus; and 
           [0022]      FIG. 5  is a flowchart illustrating another example of treatment with a H 3 PO 4  treatment apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0023]    Reference will now be made in detail to the present embodiment of the invention, an example of which is illustrated in the accompanying drawing. Wherever possible, the same reference numbers will be used throughout the drawing to refer to the same or like parts. 
         [0024]    Referring now to the drawings, embodiments of the present invention will be described in detail.  FIG. 1  is a schematic view showing configuration of a manufacturing apparatus for semiconductor device which allows wafers to be H 3 PO 4  treated, hereinafter referred to as a “H 3 PO 4  treatment apparatus”. 
         [0025]    A H 3 PO 4  treatment apparatus  100  is so-called a batch treatment apparatus and is installed with a processing bath  10  for H 3 PO 4  treatment of wafers with H 3 PO 4  solution and a circulation line  11  through which H 3 PO 4  solution circulates. The circulation line  11  is mounted with a circulation pump  12  for circulating H 3 PO 4  solution, a filter  13  for removing dust in H 3 PO 4  solution and a heater  14  for adjusting temperature of H 3 PO 4  solution. 
         [0026]    The H 3 PO 4  treatment apparatus  100  further has mechanisms for quality adjustment of H 3 PO 4  solution described below. The apparatus includes a new-solution supply mechanism  15  for supplying new H 3 PO 4  solution to H 3 PO 4  solution to be circulated, solution discharge mechanisms  16 ,  17  for discharging H 3 PO 4  solution to be circulated, and a Si component input mechanism  18  serving as a mechanism for supplying Si component to H 3 PO 4  solution to be circulated. 
         [0027]    Further, the H 3 PO 4  treatment apparatus  100  includes a wafer carrier mechanism  19  for carrying wafers to be subjected to H 3 PO 4  treatment or dummy wafers for supplying Si component into/from the processing bath and a control unit  20  for controlling the whole H 3 PO 4  treatment apparatus  100 . 
         [0028]    The processing bath  10  includes an inner tank  10   a  and an outer tank  10   b . The inner tank  10   a  is installed for storing a sufficient amount of H 3 PO 4  solution to immerse wafers for wafer immersion before H 3 PO 4  treatment. The outer tank  10   b  is installed adjacent to the inner tank  10   a  and is connected to the circulation line  11 . H 3 PO 4  solution is made to overflow, flowed into the outer tank  10   b  and introduced into the circulation line  11 . 
         [0029]    The circulation line  11  is installed with the circulation pump  12 , the filter  13  and the heater  14  and is connected to the bottom of the inner tank  10   a . The H 3 PO 4  solution introduced from the outer tank  10   b  is circulated by the circulation pump  12 . Dust such as particles in H 3 PO 4  solution is removed by the filter  13  and H 3 PO 4  solution is adjusted to a predetermined temperature by the heater  14 . The dust-removed and temperature-controlled H 3 PO 4  solution is introduced into the inner tank  10   a  again by the circulation line  11 . 
         [0030]    The new-solution supply mechanism  15  is a mechanism for supplying new H 3 PO 4  solution to circulating H 3 PO 4  solution in the outer tank  10   b  and is controlled by the control unit  20 . The new-solution supply mechanism  15  may be of such a structure as to supply H 3 PO 4  solution to the inner tank  10   a.    
         [0031]    The solution discharge mechanisms  16 ,  17  discharges circulating H 3 PO 4  solution and are controlled by the control unit  20 . The solution discharge mechanism  16  is branched from the circulation line  11  connected to the outer tank  10   b  and is used in discharging a relatively small amount of H 3 PO 4  solution. The solution discharge mechanism  17  is connected to the bottom of the inner tank  10   a  and is used in discharging a large amount of H 3 PO 4  solution. 
         [0032]    The Si component input mechanism  18   a  inputs Si component into circulating H 3 PO 4  solution in the outer tank  10   b  and is controlled by the control unit  20 . In the Si component input mechanism  18   a , silica which is an etching residue, SiN powder which is a material to be etched or H 3 PO 4  solution having a certain Si concentration is input as a Si-containing material, to adjust Si concentration in H 3 PO 4  solution, as needed. 
         [0033]    The wafer carrier mechanism  19  carries wafers w to be subjected to H 3 PO 4  treatment into/from the processing bath. It may also carry dummy wafers on which silicon-containing material or SiN having a known thickness is wholly formed as needed and is controlled by the control unit  20 . This mechanism also has a function for counting with the number of wafers to be subjected to H 3 PO 4  treatment when carrying wafers w into/from the processing bath. 
         [0034]    When the wafers w are treated in H 3 PO 4  solution, the number of product Lot of wafers is counted and used for calculating integrated SiN etching amount as described below. When the dummy wafers are installed into H 3 PO 4  solution, the number of the dummy wafers needed to be installed is counted. 
         [0035]    The control unit  20  is provided to control the whole H 3 PO 4  treatment apparatus  100  including these mechanisms.  FIG. 2  is a block diagram illustrating a configuration of the control unit  20 . 
         [0036]    The control unit  20  is provided with an input/display unit  20   a  for inputting operating conditions of the H 3 PO 4  treatment apparatus  100 , verifying the setting conditions thereof and for displaying operating states thereof. The input/display unit  20   a  uses, for example, a display having a touch panel function. Through the display, conditions of etching selectivity to oxide film required for etching treatment are input. In addition, determined treatment information is displayed. 
         [0037]    The control unit  20  has a database  31 , a recipe setting unit  32 , a count accumulation unit  33 , a treatment determination unit  34 , a supply/discharge solution amount calculation unit  35  and a Si component input amount calculation unit  36 . Each of these components exhibits functions implemented by a computer. 
         [0038]    The database  31  stores previously obtained data such as the etching selectivity to oxide film to integrated SiN etching amount. 
         [0039]    The recipe setting unit  32  is input with the etching selectivity to oxide film required for the next wafer to be treated, a wafer treatment recipe and the number of wafers to be treated. An icon for input or selection is displayed on the input/display unit  20   a . Based on the input information, control information of the respective mechanisms is determined. The following description uses treatment of substantially the same type of wafers (wafers having the same SiN film thickness and aperture ratio) for convenience. 
         [0040]    The count accumulation unit  33  counts integrated SiN etching amount in etching treatment performed with current H 3 PO 4  solution. The integrated SiN etching amount is obtained by accumulating the product of an etching amount (depth) in one wafer (e.g. φ300 mm) and the number of treated wafers for each etching treatment. The number of treated wafers is input by the recipe setting unit or counted by the wafer carrier mechanism. Counting the integrated SiN etching amount starts when using new H 3 PO 4  solution. 
         [0041]    The treatment determination unit  34  determines whether input the etching selectivity to oxide film can be implemented by treatment with current H 3 PO 4  solution. In other words, the treatment determination unit determines whether solution quality adjustment is required. At this time, the determination can be implemented by comparing integrated SiN etching amount in the current H 3 PO 4  solution with data stored in the database  31 . 
         [0042]    The supply/discharge solution amount calculation unit  35  and the Si component input amount calculation unit  36  calculate a solution quality adjustment amount for Si concentration or the like based on determination by the treatment determination unit  34 . 
         [0043]    The supply/discharge solution amount calculation unit  35  calculates a discharge amount of H 3 PO 4  solution by the solution discharge mechanisms  16 ,  17  and a supply amount of new H 3 PO 4  solution by the new-solution supply mechanism  15  when a Si concentration in the current H 3 PO 4  solution is to be decreased, based on the determination of the treatment determination unit  34 . 
         [0044]    The Si component input amount calculation unit  36  calculates an amount of Si-containing material to be input into the current H 3 PO 4  solution or the number of dummy wafers to be supplied when Si concentration in the current H 3 PO 4  solution is to be increased, based on determination of the treatment determination unit  34 . The Si component input amount calculation unit  36  may have a selection function for selecting which of the Si component input mechanism  18  to use and the dummy wafer to supply. 
         [0045]    As hardware for implementing the functions of the respective units, the control unit  20  has a first storage unit including ROM and hard disk storing data such as programs and treatment recipes for performing various types of control to be performed in the H 3 PO 4  treatment apparatus  100  and database  31  thereof; a central processing unit (CPU) for executing such programs; an input device including input keys for inputting required data and a display; a second storage unit including such as a RAM for temporarily storing treatment data and a hard disk for storing treatment data. Mutual data exchange is performed between these components, and the functions of the respective units described above are implemented by cooperative operation between hardware and software. 
         [0046]      FIGS. 3A and 3B  illustrate graphed examples of data stored in the database  31 . The data illustrated in  FIGS. 3A and 3B  are, for example, in combination of [integrated SiN etching amount and etching rate] and [integrated SiN etching amount and etching selectivity to oxide film] and are stored as digital data for each given integrated SiN etching amount (e.g. 1 nm). 
         [0047]    These stored data are previously obtained for use in current H 3 PO 4  treatment. In obtaining such data, actual results of H 3 PO 4  treatment which was actually performed in the past using the H 3 PO 4  treatment apparatus  100 . 
         [0048]    Counting the integrated SiN etching amount starts when using new H 3 PO 4  solution. During the counting, H 3 PO 4  solution continues to be used without an input of new H 3 PO 4  solution into H 3 PO 4  solution in use nor the discharge of a part thereof on purpose. During this time, the etching rate can be determined, for example, by wafer observation with Photonic film thickness analyzer or cross-section SEM. 
         [0049]    As illustrated in  FIG. 3A , as integrated SiN etching amount increases, both SiN etching rate and SiO 2  etching rate decrease. The ratio of a decrease in SiO 2  etching rate to a decrease in SiN etching rate is large. Accordingly, as illustrated in  FIG. 3B , the etching selectivity to oxide film (=SiN etching rate/SiO 2  etching rate) increases as integrated SiN etching amount increases. In H 3 PO 4  treatment, control of the selectivity is important in addition to control of the etching rate. 
         [0050]    For example, in setting the etching selectivity to oxide film to 50 to 60, H 3 PO 4  solution having an actual result of 2,000 to 4,200 nm in integrated SiN etching amount is necessary. When the integrated SiN etching amount of H 3 PO 4  solution at present is in excess of 5,000 nm, wafer treatment cannot be performed using this H 3 PO 4  solution. Accordingly, there is need of returning the state of current H 3 PO 4  solution to a state of H 3 PO 4  solution having an actual result of approximately 2,000 to 4,200 nm in integrated SiN etching amount. 
         [0051]    Accordingly, a part of current H 3 PO 4  solution is discharged and new H 3 PO 4  solution is added. The addition of the new H 3 PO 4  solution allows the state of H 3 PO 4  solution to be returned to a state having small integrated SiN etching amount. The integrated SiN etching amount is a dissolved Si amount and therefore such an operation itself is the same as an operation for adjusting Si concentration of H 3 PO 4  solution. 
         [0052]    Specifically, in adjusting H 3 PO 4  solution having integrated SiN etching amount of 5,000 nm to H 3 PO 4  solution having integrated SiN etching amount of 2,000 nm, it is sufficient to discard 60% of H 3 PO 4  solution in use and then add new H 3 PO 4  solution by the same amount as the discharge amount. 
         [0053]    On the other hand, when it is necessary that the etching selectivity to oxide film is, for example, at least 50, solution having an actual result of 2,000 nm or more in integrated SiN etching amount is required. Accordingly, new H 3 PO 4  solution having no actual result cannot perform wafer treatment. 
         [0054]    To change a state of current H 3 PO 4  solution to a state of H 3 PO 4  solution having an actual result of approximately 2,000 nm in integrated SiN etching amount, a Si component needs to be supplied. Accordingly, Si-containing material is input or dummy wafer is supplied into current H 3 PO 4  solution. 
         [0055]    Supplying a Si component allows new H 3 PO 4  solution to have the same solution quality as the H 3 PO 4  solution which has treated a certain number of wafers. Addition amount of the Si-containing material or the number of dummy wafers to be treated can be obtained, based on the integrated SiN etching amount. 
         [0056]    Accordingly, the discharge amount from current H 3 PO 4  solution, the addition amount of new H 3 PO 4  solution, and the addition amount of Si component to be supplied can be determined from the integrated SiN etching amount without need of measurement of actual Si concentration in H 3 PO 4  solution. 
         [0057]    Referring next to a flowchart illustrated in  FIG. 4 , description will be made on a H 3 PO 4  treatment flow with the H 3 PO 4  treatment apparatus  100 . The time point when H 3 PO 4  treatment of a predetermined number of wafers is completed with new H 3 PO 4  solution is taken as a start point (ST 1 ). At this time, counted integrated SiN etching amount is taken as (N). No adjustment of H 3 PO 4  solution is made until ST 1  has been reached. 
         [0058]    A selectivity to oxide film (S 1 ) required for the next wafer to be treated are input from the input/display unit  20   a  (ST 2 ). 
         [0059]    The treatment determination unit  34  determines the selectivity to oxide film (S 2 ) when H 3 PO 4  treatment is performed with current H 3 PO 4  solution, using the database  31  (ST 3 ). 
         [0060]    The treatment determination unit  34  compares the selectivity to oxide film (S 1 ) and (S 2 ) with each other and determines whether the etching selectivity to oxide film (S 2 ) is within the allowable range of the etching selectivity to oxide film (S 1 ) (ST 4 ). 
         [0061]    If the determination is YES in ST 4 , wafer treatment can be implemented with current H 3 PO 4  solution and therefore H 3 PO 4  treatment (ST 5 ) is performed, without adjustment of H 3 PO 4  solution. The integrated SiN etching amount (N) is updated (ST 6 ) and then the process returns to ST 1 . 
         [0062]    If the determination is NO in ST 4 , the determination unit determines whether Si concentration in current H 3 PO 4  solution is to be lowered (ST 7 ). 
         [0063]    The case where the determination is YES in ST 7  is a case where SiN etching amount with the current H 3 PO 4  solution needs to be small amount. Therefore, the supply/discharge solution amount calculation unit  35  determines integrated SiN etching amount (n) of H 3 PO 4  solution to be adjusted, from the etching selectivity to oxide film (S 1 ), using the database  31  (ST 8 ). 
         [0064]    The supply/discharge solution amount calculation unit  35  further determines a discharge amount of current H 3 PO 4  solution and an input amount of new H 3 PO 4  solution from the integrated SiN etching amount (N) and the integrated SiN etching amount (n) of H 3 PO 4  solution to be adjusted. Based on the determined amounts, H 3 PO 4  solution is automatically adjusted by the new-solution supply mechanism  15  and the discharge solution mechanisms  16 ,  17  (ST 9 ). Preferably, circulation of H 3 PO 4  solution through the circulation line  11  is performed for a certain amount of time, so that the composition and temperature of the adjusted H 3 PO 4  solution are homogenized. 
         [0065]    The H 3 PO 4  solution adjusted in this way substantially becomes a H 3 PO 4  solution having an actual result of the integrated SiN etching amount (n). Accordingly, the previous integrated SiN etching amount (N) is replaced with integrated SiN etching amount (n) (ST 10 ). That is, “N” is substituted by “n”. Then H 3 PO 4  treatment is performed (ST 11 ). Further, integrated SiN etching amount (N) is updated (ST 12 ) and the process returns to ST 1 . 
         [0066]    The case where the determination is NO in ST 7  is a case where integrated SiN etching amount with current H 3 PO 4  solution needs to be larger amount. Therefore, the Si component input amount calculation unit  36  determines integrated SiN etching amount (n′) of H 3 PO 4  solution to be adjusted, from the etching selectivity to oxide film (S 1 ) using the database  31  (ST 13 ). 
         [0067]    The Si component input amount calculation unit  36  further calculates an Si amount to be input into current H 3 PO 4  solution from the integrated SiN etching amount (N), (n′). Next, Si input means (either one or both of Si component input mechanism  18  and dummy wafer) is determined as needed, and adjustment of H 3 PO 4  solution by the determined means is performed (ST 14 ). 
         [0068]    The H 3 PO 4  solution adjusted in this way substantially becomes a H 3 PO 4  solution having an actual result of the integrated SiN etching amount (n′). Accordingly, the previous integrated SiN etching amount (N) is replaced with integrated SiN etching amount (n′) (ST 15 ). That is, “N” is substituted by “n”. Then H 3 PO 4  treatment is performed (ST 16 ). Further, integrated SiN etching amount (N) is updated (ST 17 ) and the process returns to ST 1 . 
         [0069]    In the above description, H 3 PO 4 -treated wafers having the same SiN film thickness and aperture ratio are used for convenience, but in practice, various types of wafers, such as a wafer having different SiN film thickness, a wafer having different aperture ratio, a wafer having SiN on both faces or single face, a wafer formed with SiN film as a masking material in dry process, a wafer having different SiN volume and a wafer having different Si amount dissolved from the wafer, are treated as needed. 
         [0070]    In treating such wafers having different modes, current H 3 PO 4  solution is adjusted so that a desired the etching selectivity to oxide film are obtained. Accordingly, exact grasp of integrated SiN etching amount in current H 3 PO 4  solution is required. 
         [0071]    As comparison data stored in the database  31 , data describing a relationship between [integrated SiN etching amount per predetermined area and the etching selectivity to oxide film] are prepared. The integrated SiN etching amount per predetermined area refers to, specifically, the integrated SiN etching amount per predetermined area (nm/cm 2 ) or an integrated SiN etching amount (nm/wafer) per single area of one wafer (φ200 mm or φ300 mm). 
         [0072]    Such a data can be determined, for example, by correcting the integrated SiN etching amount of the data illustrated in  FIGS. 3A and 3B  in consideration of an aperture ratio in a wafer. Data obtained in advance by treating various types of wafers may also be used. 
         [0073]    The integrated SiN etching amount in current H 3 PO 4  solution is grasped as integrated SiN etching amount per predetermined area. As one of the methods, there is proposed a method of providing a function for including the SiN film amount practically etched in a treatment recipe as information. Specifically, parameters for automatically calculating SiN etching amount per predetermined area, such as film thickness, aperture ratio (mask area in the case of etching mask) and presence of back film are provided. Hence, SiN etching amount per predetermined area in one wafer is exactly grasped, depending upon a selected recipe. 
         [0074]    Further, as parameters, information of the number of wafers to be treated is used. This information can be obtained by inputting the number of wafers to be treated or counted result by a wafer carrier mechanism  19 . By using the parameters, integrated SiN etching amount per predetermined area can be obtained. Such a function may be provided in the recipe setting unit  32  and the count accumulation unit  33 . 
         [0075]    There may occur a case where a part of parameters for automatically calculating SiN etching amount per predetermined area included in a selected treatment recipe are different from actual parameters of wafers to be treated. Such treatment recipe parameters can be corrected through the input/display unit  20   a.    
         [0076]    Referring to a flowchart in  FIG. 5 , brief description will be made on actual wafer treatment when such integrated SiN etching amount per predetermined area is used. 
         [0077]    To sequentially perform a plurality of H 3 PO 4  treatments a recipe is preselected according to the sequence made and the content thereof is stored. Each recipe includes a required etching selectivity to oxide film. 
         [0078]    In  FIG. 5 , a state in which predetermined H 3 PO 4  treatments have been performed and adjustment of H 3 PO 4  solution has been completed as needed is taken as a start point. It is verified through a display of the input/display unit  20   a  that the number of wafers to be actually treated meets the previously input number of wafers (ST 101 ). When any changes need to be made, the number of wafers to be actually treated is input, and a treatment recipe is verified (ST 102 ). Hence, the integrated SiN etching amount per predetermined area is updated (ST 103 ) and H 3 PO 4  treatment is started (ST 104 ). 
         [0079]    In the treatment according to the flowchart in  FIG. 4 , integrated SiN etching amount with H 3 PO 4  solution at that point in time is updated after completion of predetermined batch treatment. The integrated SiN etching amount per predetermined area may be updated before actual batch treatment in the sane way as the treatment according to the flowchart in  FIG. 5 . 
         [0080]    After completion of the batch treatment in ST 104 , it is determined whether or not the etching selectivity to oxide film included in a recipe for the next batch treatment can be obtained with H 3 PO 4  solution after completion of the batch treatment in ST 104 . Specifically, it is determined whether or not the quality adjustment of H 3 PO 4  solution (H 3 PO 4  solution discharge/additional supply of new H 3 PO 4  solution or Si component addition) is necessary (ST 105 ). 
         [0081]    When the quality adjustment of H 3 PO 4  solution is necessary, the adjustment (ST 106 ) is automatically performed, thus leading to a next batch treatment standby state (ST 107 ). On the other hand, when H 3 PO 4  solution adjustment is not necessary, the process goes into a next batch treatment standby state without adjustment. Then, the process returns to ST 101 . 
         [0082]    The embodiment of the present invention has been described above, but the present invention is not limited thereto. For example, H 3 PO 4  solution adjustment to a substantially same state before starting respective H 3 PO 4  treatments allows continuous H 3 PO 4  treatment under the same conditions. 
         [0083]    For quality adjustment of H 3 PO 4  solution, Si component has been added, but adjustment by HF addition is also applicable. 
         [0084]    As described above in detail, the present embodiment enables easy adjustment, by in-situ technique, of H 3 PO 4  solution capable of obtaining a required etching selectivity to oxide film for H 3 PO 4  treatment without need of an expensive system. Accordingly, stable and etching selectivity to oxide film can be obtained in H 3 PO 4  treatment. Variations in characteristics of wafers subjected to H 3 PO 4  treatment and semiconductor devices formed therewith can be suppressed, so that the yield thereof can be boosted. 
         [0085]    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.