Patent Number: 
Section: claims

1. A charged beam drawing apparatus which draws a desired pattern on a sample by use of a charged beam deflected in main/sub two stages, comprising:a main deflector which deflects a charged beam, the main deflector sequentially selecting a plurality of sub-deflection drawing regions obtained by dividing a main deflection drawing region of a sample,a main deflection driving unit which drives the main deflector,a sub deflector which deflects the charged beam in the selected sub deflection region, the sub deflector drawing a pattern in the selected sub deflection region, anda sub deflection driving unit which drives the sub deflector, the sub deflection driving unit including a sub deflection sensitivity correction circuit which corrects deflection sensitivity according to a shot position in the sub deflection region, a sub deflection astigmatic correction circuit which corrects a deflection astigmatic point according to a shot position in the sub deflection region, an adder circuit which superimposes an output of the sub deflection sensitivity correction circuit and an output of the sub deflection astigmatic correction circuit and a deflection amplifier which applies an output of the adder circuit to the sub deflector. 2. The charged beam drawing apparatus according to claim 1, wherein the sub deflection driving unit divides the main deflection drawing region into meshes and has a memory which stores a sub deflection sensitivity correction coefficient and sub deflection astigmatic correction coefficient for each mesh. 3. The charged beam drawing apparatus according to claim 2, wherein the mesh is not smaller than the sub deflection region. 4. The charged beam drawing apparatus according to claim 2, wherein the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit respectively read out a sub deflection sensitivity correction coefficient and sub deflection astigmatic correction coefficient corresponding to the position of the selected sub deflection region from the memory and perform correction operations according to a shot position in the selected sub deflection region based on the readout correction coefficients. 5. The charged beam drawing apparatus according to claim 2, wherein the sub deflection driving unit includes a sub deflection astigmatic correction value calculating unit which measures a preset inclination coefficient and a sub deflection astigmatic difference of a charged particle beam by scanning a preset mark in two perpendicularly intersecting directions by using the charged particle beam in which a sub deflection astigmatic point is corrected by use of an n-th sub deflection astigmatic correction value and calculates an (n+1)-th sub deflection astigmatic correction value in which no sub deflection astigmatic difference occurs based on the measured preset inclination coefficient and sub deflection astigmatic difference to derive the sub deflection astigmatic correction coefficient stored in the memory, and a sub deflection astigmatic correction coefficient calculating unit which repeatedly performs a calculating operation starting from the first correction value by the astigmatic correction value calculating unit until an absolute value of a difference between the n-th and (n+1)-th sub deflection astigmatic correction values becomes smaller than a preset value and calculates a sub deflection astigmatic correction coefficient which is a coefficient of a relational expression defining a sub deflection astigmatic correction amount by use of the (n+1)-th sub deflection astigmatic correction value which is finally obtained. 6. The charged beam drawing apparatus according to claim 1, wherein the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit are configured to perform an operation in a pipeline system. 7. The charged beam drawing apparatus according to claim 1, wherein the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit simultaneously and respectively perform a deflection sensitivity correcting process and deflection astigmatic correction process in parallel and the adder circuit adds outputs of the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit in adequately adjusted timing. 8. The charged beam drawing apparatus according to claim 1, wherein the sub deflector is an octopole deflector having eight electrodes. 9. A charged beam drawing apparatus which draws a desired pattern on a sample by use of a charged beam deflected in main/sub two stages, comprising:a sub deflection astigmatic correction value calculating unit which measures a preset inclination coefficient and a sub deflection astigmatic difference of the charged particle beam by scanning a preset mark in two perpendicularly intersecting directions by use of a charged particle beam in which a sub deflection astigmatic point is corrected by use of an n-th sub deflection astigmatic correction value and calculates an (n+1)-th sub deflection astigmatic correction value used to eliminate a sub deflection astigmatic difference based on the measured preset inclination coefficient and sub deflection astigmatic difference,a sub deflection astigmatic correction coefficient calculating unit which repeatedly performs an operation of calculating sub deflection astigmatic correction values starting from the first sub deflection astigmatic correction value by use of the astigmatic correction value calculating unit until an absolute value of a difference between the n-th and the (n+1)-th sub deflection astigmatic correction values becomes smaller than a preset value and calculates a sub deflection astigmatic correction coefficient which is a coefficient of a relational expression defining a sub deflection astigmatic correction amount by use of the (n+1)-th sub deflection astigmatic correction value which is finally obtained, anda drawing unit which draws a preset pattern on the sample by use of charged particle beam in which the sub deflection astigmatic point is corrected according to the relational expression containing the calculated sub deflection astigmatic correction coefficient. 10. The charged beam drawing apparatus according to claim 9, wherein the operation of calculating the sub deflection astigmatic correction coefficient is performed in a plurality of positions of the drawing region. 11. The charged beam drawing apparatus according to claim 9, wherein the operations of calculating the sub deflection astigmatic correction value and calculating the sub deflection astigmatic correction coefficient are performed in two perpendicularly intersecting directions different from the above two directions in addition to the above two directions. 12. The charged beam drawing apparatus according to claim 9, wherein the preset inclination coefficient is an inclination value of a variation amount of the sub deflection astigmatic difference when sub deflection astigmatic correction amounts in the two perpendicularly intersecting directions are used as variables. 13. A charged beam drawing method for drawing a desired pattern on a sample by use of a charged beam deflected in main/sub two stages, comprising:measuring sub deflection astigmatic differences in two perpendicularly intersecting directions of a charged particle beam by scanning a preset mark in the two perpendicularly intersecting directions by use of the charged particle beam in which a sub deflection astigmatic point is corrected by use of an n-th sub deflection astigmatic correction value,calculating an (n+1)-th sub deflection astigmatic correction value used to eliminate a sub deflection astigmatic difference based on the n-th sub deflection astigmatic correction value, measured sub deflection astigmatic difference and preset inclination coefficient,determining whether an absolute value of a difference between the (n+1)-th sub deflection astigmatic correction value calculated and the n-th sub deflection astigmatic correction value used for calculation is smaller than a preset value,repeatedly performing operations of measuring the sub deflection astigmatic difference, calculating the sub deflection astigmatic correction value and determining whether the absolute value of the difference is smaller than the preset value starting from the first sub deflection astigmatic correction value and terminating the above operations when the absolute value of the difference between the (n+1)-th and n-th sub deflection astigmatic correction values becomes smaller than the preset value, anddrawing a desired pattern on the sample by use of the charged particle beam subjected to astigmatic correction by use of an (n+1)-th sub deflection astigmatic correction value obtained when the difference becomes smaller than the preset value. 14. The charged particle beam drawing method according to claim 13, wherein (n+1)-th sub deflection astigmatic correction amounts in which the difference becomes smaller than a preset value are respectively calculated in a plurality of positions of the drawing region and a sub deflection astigmatic correction coefficient which is a coefficient of a relational equation defining the sub deflection astigmatic correction amount in each position of the drawing region is calculated by use of the (n+1)-th sub deflection astigmatic correction value calculated in each position. 15. The charged particle beam drawing method according to claim 13, wherein an inclination value of a variation amount of the sub deflection astigmatic difference is used as the preset inclination coefficient when sub deflection astigmatic correction amounts in the two perpendicularly intersecting directions are used as variables. 16. The charged particle beam drawing method according to claim 13, wherein an operation of measuring the sub deflection astigmatic difference in two perpendicularly intersecting directions different from the above two directions, calculating the sub deflection astigmatic correction value and determining whether the absolute value of the difference is smaller than the preset value is repeatedly performed from the first sub deflection astigmatic correction value and terminated when an absolute value of a difference between the (n+1)-th and n-th sub deflection astigmatic correction values becomes smaller than a preset value and the charged particle beam subjected to astigmatic correction by use of the (n+1)-th sub deflection astigmatic correction value obtained when the difference becomes smaller than the preset value is used to draw a pattern on a sample.