Abstract:
A method of manufacturing a semiconductor device is disclosed, which comprises setting a stencil mask above a substrate to be processed in confronting to the substrate, the stencil mask having an opening, and irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a value of a current flowing between the substrate and the stencil mask.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of the priority from the prior Japanese Patent Application No. 2002-375979, filed Dec. 26, 2002, 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 using, for example, a stencil mask as a transfer mask and an apparatus for manufacturing the semiconductor device.  
         [0004]     2. Description of the Related Art  
         [0005]     There has been known a method in which in semiconductor device manufacturing process, a stencil mask having a predetermined pattern is set above a substrate to be processed at a predetermined distance and charged particles such as electrons or ions are projected onto the substrate through openings defining the pattern of the stencil mask. In the method, charged particles (ion beam) such as ions accelerated from a particle source by a predetermined energy pass through a scanner and a magnet to be formulated into a patterned ion beam. The patterned ion beam is projected onto the substrate through the openings formed in the stencil mask. The substrate to be processed mentioned here is a semiconductor substrate, on the surface of which a semiconductor device is to be formed or has been formed, not shown.  
         [0006]     There is a disadvantage that, when a substrate is processed using the charged particles, residue charges are accumulated on the substrate so that the semiconductor device formed on the substrate may be destroyed by being charged due to the accumulated charges. A conventional method is known to overcome this disadvantage (Jpn. Pat. Appln. KOKAI Publication No. 9-283411, see page 4). In this method, secondary electrons or plasma electrons are generated to neutralize the accumulated charges, thus preventing the destruction of a substrate due to the accumulated charges.  
         [0007]     Jpn. Pat. Appln. KOKAI Publication No. 2002-203806 (FIGS. 29 and 35) discloses a method of controlling the amount of charges accumulated on a substrate to be processed. In the method, a distance and a potential difference between a stencil mask and the substrate to control the amount of charges accumulated on the substrate. The controlling of the amount of charges is carried out by providing a power supply between the stencil mask and the substrate, or by providing a power supply between the stencil mask and the ground and also another power supply between the substrate and ground.  
         [0008]     However, neutralizing the accumulated charges by generating secondary electrons or plasma electrons is sensitive to the amount of charges on the substrate and the stencil mask, the amount of energy on charged particles, degree of vacuum in the apparatus, etc., and the amount of neutralized charges greatly changes depending on these factors. As a result, with the method of neutralizing the accumulated charges by generating secondary electrons or plasma electrons, the neutralized charge amount may be insufficient or an excessive amount of electrons may be supplied to cause negative charging, which possibly destroy the semiconductor devices. Further, the charge neutralizing mechanism, which generates the secondary electrons or plasma electrons, is complicated in structure.  
         [0009]     On the other hand, according to the method of controlling the amount of the charges accumulated on the substrate by changing a distance and a potential difference between the stencil mask and the substrate, yield is improved. However, it is necessary to set up the distance and the potential difference between the stencil and the substrate before an ion implantation process is carried out. There is no problem if the irradiation condition of the charged particles is stable and the state of the apparatus is stable during the processing. However, if the apparatus is unstable, and the irradiation amount (current amount) of the charged particles per unit time changes during the processing, the neutralized charge amount may be insufficient, or an excessive amount of electrons may be supplied to cause negative charging, which leas to a possible destruction of the semiconductor devices.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising:  
         [0011]     setting a stencil mask above a substrate to be processed in confronting to the substrate, the stencil mask having an opening; and  
         [0012]     irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a value of a current flowing between the substrate and the stencil mask.  
         [0013]     According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising:  
         [0014]     setting a stencil mask above a substrate to be processed in confronting with the substrate, the stencil mask having an opening; and  
         [0015]     irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a ratio between a value of a current flowing in the substrate and a value of a current flowing in the stencil mask.  
         [0016]     According to a further aspect of the present invention, there is provided a manufacturing apparatus of a semiconductor device, comprising:  
         [0017]     a stencil mask set above a substrate to be processed in confronting to the substrate, the stencil mask having an opening;  
         [0018]     a particle source which irradiates the substrate to be processed with charged particles through the opening of the stencil mask;  
         [0019]     a first power supply which is connected to the stencil mask and changes a potential of the stencil mask; and  
         [0020]     a first ammeter connected to the substrate to be processed. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0021]      FIG. 1  is a diagram showing part of a semiconductor device manufacturing apparatus according to a first embodiment of the present invention;  
         [0022]      FIG. 2  is a diagram showing part of a semiconductor device manufacturing apparatus according to a second embodiment of the present invention; and  
         [0023]      FIG. 3  is a diagram showing part of a semiconductor device manufacturing apparatus according to a third embodiment of the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.  
       First Embodiment  
       [0025]      FIG. 1  shows a semiconductor manufacturing apparatus according to a first embodiment of the present invention.  
         [0026]     In a semiconductor manufacturing process, a stencil mask  11  having a predetermined pattern formed by openings formed in the stencil mask is set above a substrate  12  to be processed at a distance. Charged particles  13  (ion beam) such as ion accelerated by an energy pass through a scanner and a magnet are formulated into a pattern of charged particles. The patterned ion beam  13  is irradiated onto the substrate  12  through the openings formed in the stencil mask. The substrate  12  to be processed mentioned here is a semiconductor substrate, in which a semiconductor device is to be formed or has been formed, not shown.  
         [0027]     The stencil mask  11  is connected to a power supply  14  which is also connected to ground. Thus, a potential of the stencil mask  11  can be controlled, with an outer wall of the apparatus or ground as a reference potential. The substrate  12  is connected to the outer wall of the apparatus or ground through an ammeter  15 . Thus, current flowing from the substrate can be measured by the ammeter  15 .  
         [0028]     When the irradiation amount of the ion beam  13  is not changed in a semiconductor manufacturing process such as an ion implantation process, that is, when the quantity of the charged particles applied to the substrate  12  is constant, a current I 1  measured by the ammeter  15  is also constant. That is, an appropriate current value for processing condition of processing the substrate  12  exists and the appropriate current value is usually constant. Although most preferably, the constant value of the current I 1  is 0(A), it is not restricted to this value but may be other constant value than 0(A).  
         [0029]     If electrical balance between the stencil mask  11  and the substrate  12  is get out due to factor variations of the apparatus so that the neutralizing effect is lowered, excessive positive charges may begin to be accumulated on the surface of the substrate  12 . The excessive positive charges accumulated on the surface of the substrate  12  flow to the outer wall of the apparatus so that the current I 1  increases. Thus, according to this embodiment, the current I 1  flowing to the substrate  12  is measured and if the current I 1  becomes larger than the appropriate current value for some reason during ion implantation, the positive charges which begin to be accumulated on the substrate  12  can be neutralized by lowering a potential of the stencil mask  11  by the power supply  14 . If the potential of the stencil mask  11  is lowered too much when the potential of the stencil mask  11  is adjusted, negative charges are then accumulated on the surface of the substrate  12 , and a current I 2  becomes smaller than an appropriate current value. The current I 2  is a current flowing through the power supply  14 . In this case, the negative charges which begin to be accumulated on the substrate  12  can be neutralized by increasing the potential of the stencil mask  11  by the power supply  14 .  
         [0030]     Thus, according to this embodiment, even if the neutralizing condition changes due to an instable state of the apparatus, in the semiconductor manufacturing process using the charged particles such as ion implantation process, the potential of the stencil mask can be changed following the state of the apparatus. Consequently, the possibility that the semiconductor device may be destroyed due to the charges accumulated on the substrate is reduced, thus yield is improved.  
       Second Embodiment  
       [0031]      FIG. 2  shows a semiconductor manufacturing apparatus according to a second embodiment of the present invention. Reference numerals corresponding to those used in  FIG. 1  are attached to the corresponding components, and description thereof is omitted.  
         [0032]     In a semiconductor manufacturing process, a stencil mask  21  having a predetermined pattern formed by openings formed in the stencil mask is set above a substrate  22  to be processed at a distance. Charged particles  23  (ion beam) such as ion accelerated by an energy pass through a scanner and a magnet are formulated into a pattern of charged particles. The patterned ion beam  23  is irradiated onto the substrate  22  through the openings formed in the stencil mask. The substrate  22  to be processed mentioned here is a semiconductor substrate, in which a semiconductor device has been formed, not shown.  
         [0033]     The stencil mask  21  is connected to a power supply  24  which is also is connected to ground (i.e. an outer wall of the apparatus) through an ammeter  25 . Thus, a potential of the stencil mask  21  can be controlled, with the outer wall of the apparatus or ground as a reference potential. Further, a current flowing from the stencil mask  21  can be measured by the ammeter  25 . The substrate  22  is connected to ground (i.e. an outer wall of the apparatus.) through an ammeter  26 . Thus, a current flowing from the substrate can be measured by the ammeter  26 .  
         [0034]     When the irradiation amount of the ion beam  23  is not changed in a semiconductor manufacturing process such as an ion implantation process, that is, when the quantity of the charged particles applied to the substrate  22  is constant, a current I 1  measured by the ammeter  25  is also constant. That is, an appropriate current value for processing condition of processing the substrate  22  exists and that the appropriate current value is usually constant. Although most preferably, the constant value of the current I 1  is 0(A), it is not restricted to this value but may be other constant value than 0(A).  
         [0035]     However, if the irradiation amount of the ion beam  23  per unit time changes with time in the semiconductor manufacturing process such as an ion implantation process, the quantity of the charged particles applied to the substrate  22  per unit time also changes, so that the current I 1  measured with the ammeter  26  also changes. On the other hand, the ratio of the current I 1  flowing from the substrate  22  with respect to the current I 2  flowing from the stencil mask  21 , that is, a current ratio I 1 /I 2 , is constant, since the neutralizing effect is maintained if the electrical balance between a stencil mask  21  and the substrate  22  is stabilized. That is, an appropriate current ratio depending on the processing condition of processing the substrate  22  exists, and usually that value is constant.  
         [0036]     If electrical balance between the stencil mask  21  and the substrate  22  is get out due to factor variations of the apparatus so that the neutralizing effect is lowered, excessive positive charges may begin to be accumulated on the surface of the substrate  22 . If excessive positive charges begin to be accumulated on the surface of the substrate  22 , the ratio of the current I 1  flowing from the substrate  22  with respect to the current I 2  flowing from the stencil mask  21 , that is, the current ratio I 1 /I 2  is increased. Then, according to this embodiment, the current ratio I 1 /I 2  is measured and if the current ratio I 1 /I 2  becomes larger than its appropriate current ratio for some reason in the ion implantation process, the positive charges which begin to be accumulated on the substrate  22  can be neutralized by lowering the potential of the stencil mask  21  through a power supply  24 . If the potential is lowered too much when the potential of the stencil mask  21  is adjusted, negative charges are accumulated on the surface of the substrate  22 , and the current ratio I 1 /I 2  becomes smaller than the appropriate current ratio. In this case, the negative charges which begin to be accumulated on the substrate  22  can be neutralized by lowering the potential of the stencil mask  21  by the power supply  24 .  
         [0037]     Thus, according to this embodiment, even if the irradiation amount of the ion beam changes with time in the semiconductor manufacturing process using the charged particles such as an ion implantation process, yield can be improved by reducing the possibility that the semiconductor device may be destroyed due to the charges accumulated on the substrate.  
       Third Embodiment  
       [0038]      FIG. 3  shows a semiconductor manufacturing apparatus according to a third embodiment of the present invention. Reference numerals corresponding to those used in  FIG. 1  are attached to the corresponding components, and description thereof is omitted.  
         [0039]     In a semiconductor manufacturing process, a stencil mask  31  having a predetermined pattern formed by openings formed in the stencil mask is set above a substrate  32  to be processed at a distance. Charged particles  33  (ion beam) such as ion accelerated by an energy pass through a scanner and a magnet are formulated into a pattern of charged particles. The patterned ion beam  33  is irradiated onto the substrate  32  through the openings formed in the stencil mask. The substrate  32  to be processed mentioned here is a semiconductor substrate, in which a semiconductor device has been formed, not shown.  
         [0040]     The stencil mask  31  is connected to a power supply  34  which is also is connected to ground (i.e. an outer wall of the apparatus) through an ammeter  35 . Thus, a potential of the stencil mask  31  can be controlled, with the outer wall of the apparatus or ground as a reference potential. Further, a current flowing from the stencil mask  31  can be measured by the ammeter  35 . The substrate  32  is connected to a power supply  36  which is also is connected to ground (i.e. an outer wall of the apparatus) through an ammeter  37 . Thus, a potential of the substrate  32  can be controlled, with the outer wall of the apparatus or ground as a reference potential. Further, a current flowing from the substrate  32  can be measured by the ammeter  37 .  
         [0041]     When the irradiation amount of the ion beam  33  is not changed in a semiconductor manufacturing process such as an ion implantation process, that is, when the quantity of the charged particles applied to the substrate  32  is constant, a current I 1  measured by the ammeter  35  is also constant. That is, an appropriate current value for processing condition of processing the substrate  32  exists and the appropriate current value is usually constant. Although most preferably, the constant value of the current I 1  is 0(A), it is not restricted to this value but may be other constant value than 0(A).  
         [0042]     However, if the irradiation amount of the ion beam  33  per unit time changes with time in the semiconductor manufacturing process such as an ion implantation process, the quantity of the charged particles applied to the substrate  32  per unit time also changes, so that the current I 1  measured with the ammeter  36  also changes. On the other hand, the ratio of the current I 1  flowing from the substrate  32  with respect to the current I 2  flowing from the stencil mask  31 , that is, a current ratio I 1 /I 2  is constant, since the neutralizing effect is maintained if the electrical balance between a stencil mask  31  and the substrate  32  is stabilized. That is, an appropriate current ratio depending on the processing condition of processing the substrate  32  exists, and usually that value is constant.  
         [0043]     If electrical balance between the stencil mask  31  and the substrate  32  is get out due to factor variations of the apparatus so that the neutralizing effect is lowered, excessive positive charges may begin to be accumulated on the surface of the substrate  32 . If excessive positive charges begin to be accumulated on the surface of the substrate  32 , the ratio of the current I 1  flowing from the substrate  32  with respect to the current I 2  flowing from the stencil mask  31 , that is, the current ratio I 1 /I 2  is increased. Then, according to this embodiment, the current ratio I 1 /I 2  is measured and if the current ratio I 1 /I 2  becomes larger than its appropriate current ratio for some reason in the ion implantation process, the positive charges which begin to be accumulated on the substrate  32  can be neutralized by decreasing the potential difference between the stencil mask  31  and the substrate  32  through power supplies  34 ,  36 . If the potential difference is lowered too much when the potential difference between the stencil mask  31  and the substrate  32  is adjusted, negative charges are then accumulated on the surface of the substrate  32 , and the current ratio I 1 /I 2  becomes smaller than the appropriate current ratio.  
         [0044]     According to the present embodiment, the negative charges which begin to be accumulated on the substrate  32  can be neutralized by adjusting the power supplies  34 ,  36  to thereby increase the potential difference between the stencil mask  31  and the substrate  32 . At this time, considering an influence upon the semiconductor device, it is preferable that the power supply  36  connected to the substrate  32  is used as a supplement of the power supply  34 . An optimum neutralization can be attained since the potentials of the stencil mask  31  and the substrate  32  can be independently adjusted by using the power supplies  34 ,  36  connected to the stencil mask  31  and the substrate  32 . Thus, according to the present embodiment also, the possibility that the semiconductor device may be destroyed due to the charges accumulated on the substrate is lowered and thus yield can be improved, even if the irradiation amount of the ion beam changes with time in the semiconductor manufacturing process using the charged particles such as ion implantation process.  
         [0045]     As described in detail above, according to the embodiments of the present invention, the possibility that the semiconductor device may be destroyed by the charges accumulated on the substrate in the semiconductor manufacturing process using the charged particles such as the ion implantation process can be decreased, thereby improving the yield.  
         [0046]     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.