Patent Number: 
Section: claims

1. A method of extracting characters comprising: a first step of preparing design data having a hierarchy with regard to figure cells, the design data being design data of a device pattern for exposure; and  a second step of extracting candidates for the figure cells corresponding to said characters from all levels of figure cells in said design pattern data by using the hierarchy with regard to the figure cells in said design pattern data, the candidates causing at least one of a number of kinds of characters and a number of shots of electron beams as a unit in performing an electron beam exposure of character projection system to be the smallest when said exposure is performed on at least a part of said device pattern. 2. The method of extracting characters according to  claim 1 , wherein said second step, with regard to the figure cells of all levels in said design data, further comprises finding, respectively, for the electron beam sizes which can be irradiated, the following values: the size of the figure cells, the number of kinds of characters, the number of shots of electron beams required in performing the exposure of character projection system, and the number of shots of electron beams required in performing the exposure of variable shaping beam system, and claim 1 wherein candidates for the figure cells corresponding to said characters are extracted based on these values found. 3. The method of extracting characters according to  claim 1 , wherein claim 1 said second step, candidates for the figure cells corresponding to said characters are extracted sequentially from the levels of a larger figure size to the levels of a smaller figure size based upon the magnitude of reduction of the number of shots of electron beams in comparison to the exposure of variable shaping beam system. 4. The method of extracting characters according to  claim 1 , wherein claim 1 said second step, candidates for the figure cells corresponding to said characters are extracted sequentially from the levels of a larger figure size to the levels of a smaller figure size on the criterion that the number of kinds of characters required in performing the exposure of character projection system is smaller. 5. The method of extracting characters according to  claim 1 , further comprising: claim 1 a first extracting step of extracting adjacent single-arranged figure cells together as one character when there are single-arranged figure cells among the candidates for the figure cells corresponding to said characters, the adjacent single-arranged figure cells causing more figure cells to be included in electron beam sizes; and  a second extracting step of extracting adjacent figure cells in one newly array-arranged figure cell together as one character when there are adjacent array-arranged figure cells which can be treated as said one newly array-arranged figure cell among the candidates for the figure cells corresponding to said characters, the adjacent figure cells in the newly array-arranged figure cell causing more figure cells to be included in the electron beam sizes. 6. The method of extracting characters according to  claim 5 , wherein claim 5 said first extracting step of extracting characters is performed using arrangement position coordinates of said adjacent single-arranged figure cells described in said design data and an external form size found by means of the calculations of the adjacent single-arranged figure cells grouped together into said one character; and  said second extracting step of extracting characters is performed using the arrangement position coordinates of said adjacent any-arranged figure cells described in said design data and the external form size found by means of the calculations of the figure cells grouped together into one character in said one newly array-arranged figure cell. 7. The method of extracting characters according to  claim 3 , wherein claim 3 said second step, from among the candidates for the figure cells corresponding to said characters, a candidate permitting a more effective exposure of character projection system is extracted preferentially one by one. 8. The method of extracting characters according to  claim 4 , wherein claim 4 said second step, from among the candidates for the figure cells corresponding to said characters, a candidate permitting a more effective exposure of character projection system is extracted preferentially one by one. 9. The method of extracting characters according to  claim 7 , wherein claim 7 said second step, from among the candidates for the figure cells corresponding to said characters, a candidate to be extracted preferentially is selected one by one on the criterion of the number of kinds of characters, the number of exposure shots required In performing the exposure of character projection system, and the magnitude of reduction of the number of exposure shots required in performing the exposure of variable shaping beam system using said extracted candidates for the figure cells. 10. The method of extracting characters according to  claim 8 , wherein claim 8 said second step, from among the candidates for the figure cells corresponding to said characters, a candidate to be extracted preferentially is selected one by one on the criterion of the number of kinds of characters, the number of exposure shots required in performing the exposure of character projection system, and the magnitude of reduction of the number of exposure shots required in performing an exposure of variable shaping beam system using said extracted candidates for the figure cells. 11. The method of extracting characters according to  claim 7 , wherein claim 7 said second step, for each of the candidates for the figure cells corresponding to said characters, a CP effectiveness defined by means of the equation of {(Number of VSB shots)xe2x88x92(Number of CP shots)}/{(Number of CP shots)xc3x97(Number of kinds of Characters)} is found, the number of kinds of characters and the number of exposure shots required in performing an exposure by means of the electron beam exposure of character projection system being the number of kinds of Characters and the number of CP shots respectively, and the number of exposure shots required in performing the exposure of variable shaping beam system using said extracted candidates for the figure cells being the number of VSB shots, and a candidate having a larger value of said CP effectiveness is extracted preferentially one by one. 12. The method of extracting characters according to  claim 8 , wherein claim 8 said second step, for each of the candidates for the figure cells corresponding to said characters, a CP effectiveness defined by means of the equation of {(Number of VSB shots)xe2x88x92(Number of CP shots)}/{(Number of CP shots)xc3x97(Number of kinds of Characters)} is found, the number of kinds of characters and the number of exposure shots required in performing an exposure by means of the electron beam exposure of character projection system being the number of kinds of Characters and the number of CP shots respectively, and the number of exposure shots required in performing the exposure of variable shaping beam system using said extracted candidates for the figure cells being the number of VSB shots, and a candidate having a larger value of said CP effectiveness is extracted preferentially one by one. 13. The method of extracting characters according to  claim 11 , wherein claim 11 from among the candidates for the figure cells corresponding to said characters, a candidate having a larger value of said CP effectiveness is extracted preferentially one by one when the number of the candidates for the figure cells corresponding to said characters is larger than the number of the available characters. 14. The method of extracting characters according to  claim 12 , wherein claim 12 from among the candidates for the figure cells corresponding to said characters, a candidate having a larger value of said CP effectiveness is extracted preferentially one by one when the number of the candidates for the figure cells corresponding to said characters is larger than the number of the available characters. 15. A program product for operating a computer, said computer program product comprising: a first program instruction means for causing a computer to read in the design data including a hierarchy with regard to figure cells, the design data being design data of a device pattern for exposure; and  a second program instruction means for extracting candidates for the figure cells corresponding to said characters from all levels of figure cells in said design pattern data by using the hierarchy with regard to the figure cells in said design pattern data, the candidates causing at least one of the number of kinds of characters and the number of shots of electron beams as a unit in performing an electron beam exposure of character projection system to be the smallest when said exposure is performed on at least a part of said device pattern.