Patent Number: 
Section: claims

1. A charged particle beam lithography system in which a pattern area to be drawn is divided into a plurality of frames, a main deflection positions a charged particle beam to a subfield within the frame, and an auxiliary deflection draws a pattern in units of the subfield, the lithography system comprising:a beam optical system including a deflector deflecting the beam;a driver driving the deflector; anda deflection control portion controlling the driver according to drawing data indicating a pattern to be drawn,the deflection control portion controlling the driver according to a settling time that is determined so that an offset of an irradiation position of the charged particle beam has a constant value irrespective of any changes in deflection amount of the auxiliary deflection in the subfield. 2. The charged particle beam lithography system according to claim 1, whereinthe constant value of the offset of the irradiation position is set to be between 1/24 and 1/12 of a maximum value of the offset of the irradiation position that may occur in the subfield. 3. The charged particle beam lithography system according to claim 1, further comprisinga stage holding a sample thereon, the stage being continuously movable in a first direction and being stepwise movable in a second direction perpendicular to the first direction,wherein the deflector comprises a main deflector positioning the beam to one of the subfields when the stage moves in the first direction, and an auxiliary deflector positioning the beam in the subfield. 4. The charged particle beam lithography system according to claim 3, whereinthe frame is a strip-like area defined by a deflection width of the main deflector and the subfield is an area defined by a deflection width of the auxiliary deflector. 5. The charged particle beam lithography system according to claim 4, whereinthe constant value of the offset of the irradiation position is set to be between 1/24 and 1/12 of a maximum value of the offset of the irradiation position that may occur in the subfield. 6. The charged particle beam lithography system according to claim 1, further comprising:a sub-field deflection calculation portion computing a deflection amount of the auxiliary deflection in the subfield; anda settling time setup unit determining, according to the deflection amount of the auxiliary deflection, the settling time so that the offset of the irradiation position of the charged particle beam has a certain value irrespective of any changes in the deflection amount of the auxiliary deflection. 7. A charged particle beam lithography system in which a pattern area to be drawn is divided into a plurality of frames, a main deflection positions a charged particle beam to a subfield within the frame, and an auxiliary deflection draws a pattern in units of the subfield, the lithography system comprising:a beam optical system including a deflector deflecting the beam;a driver driving the deflector;a deflection control portion controlling the driver according to drawing data indicating a pattern to be drawn;a sub-field deflection calculation portion computing a deflection amount of the auxiliary deflection in the subfield;a settling time setup unit determining, according to the deflection amount of the auxiliary deflection, a settling time of the charged particle beam in the auxiliary deflection so that an offset of an irradiation position of the charged particle beam has a constant value irrespective of any changes in the deflection amount of the auxiliary deflection in the subfield. 8. The charged particle beam lithography system according to claim 7, whereinthe constant value of the offset of the irradiation position is set to be between 1/24 and 1/12 of a maximum value of the offset of the irradiation position that may occur in the subfield. 9. The charged particle beam lithography system according to claim 7, further comprising:a stage holding a sample thereon, the stage being continuously movable in a first direction and being stepwise movable in a second direction perpendicular to the first direction,wherein the deflector comprises a main deflector positioning the beam to one of the subfields when the stage moves in the first direction, and an auxiliary deflector positioning the beam in the subfield. 10. The charged particle beam lithography system according to claim 9, whereinthe frame is a strip-like area defined by a deflection width of the main deflector and the subfield is an area defined by a deflection width of the auxiliary deflector. 11. The charged particle beam lithography system according to claim 10, whereinthe constant value of the offset of the irradiation position is set to be between 1/24 and 1/12 of a maximum value of the offset of the irradiation position that may occur in the subfield. 12. A method for evaluating a charged particle beam lithography system in which a pattern area to be drawn is divided into a plurality of frames, a main deflection positions a charged particle beam to a subfield within the frame, and an auxiliary deflection draws a pattern in units of the subfield,an irradiation pattern of the charged particle beam used for the evaluation being arranged on a first line and a second line including an intersection therebetween, the first and second lines being substantially perpendicular to each other,the method comprising:first irradiating the charged particle beam to a first irradiation position at an intersection of the first and second lines, moving the charged particle beam from the first irradiation position to a second irradiation position in the first line, and irradiating the beam thereto;second moving, after the first irradiation, the charged particle beam from the second irradiation position to a third irradiation position in the second line, and irradiating the beam thereto;repeating, after the second irradiation, moving the irradiation position along the first or second line and irradiating the charged particle beam thereto, and moving the irradiation position between the first and second lines and irradiating the charged particle beam thereto; andmeasuring an error between the irradiation pattern and an actual irradiation position of the charged particle beam to measure an offset of the deflection position in the subfield. 13. The method for evaluating a charged particle beam lithography system according to claim 12, whereina moving distance of the deflection amount of the charged particle beam in the first irradiation is less than a moving distance of the deflection amount of the charged particle beam in the second moving and irradiation. 14. A method for evaluating a charged particle beam lithography system comprising:dividing a pattern area to be drawn into a plurality of frames,positioning by a main deflection a charged particle beam to a subfield within the frame, anddrawing by an auxiliary deflection a pattern in units of the subfield,irradiating a plurality of shots of the charged particle beams to the pattern, the shots including odd shots and even shots of the charged particle beams, the odd shot beams having less deflection amount than the even shot beams or the even shot beams having less deflection amount than the odd shot beams.