Patent ID: 7923699

Claim:
A tracking control method comprising the steps of: reading positional data that specifies a position to be irradiated with an electron beam, said position being located in a subfield on a mask blank placed on a stage of an electron beam writing system, data on the number of all beam shots to be performed onto said subfield, and data on the time required for all the beam shots; reading stage data that specifies a position of said stage at which tracking control needs to be performed for deflecting by a main deflector an electron beam shot toward said subfield on said mask blank while said stage is moved continuously, the deflection being such that said electron beam is deflected onto a desired position in said subfield on said mask blank placed said continuously moving stage; calculating control data for said main deflector based on said positional data and said stage data when said mask blank reaches a region in which a shot operation can be performed; calculating the number of divided subfield sections by dividing said time required for all the beam shots by a time unit during which a shot operation can actually be performed in said subfield and the number of divided beam shots by dividing said number of all the beam shots by said number of divided subfield sections; and performing a tracking operation in which after voltage settlement for said main deflector, the number of beam shots is counted with the commencement of a shot operation for a divided subfield section and in which said shot operation is shifted to a next divided subfield section in accordance with the movement of said stage after said counted number of beam shots reaches said number of divided beam shots, wherein until the entire shot operations are performed for all the divided subfield sections, said steps of reading said stage data, calculating said control data, calculating said number of divided beam shots, and performing said tracking operation after voltage settlement for said main deflector are repeatedly performed in the mentioned order.