Multi charged particle beam writing method, and multi charged particle beam writing apparatus

A multi charged particle beam writing method comprising:

• assigning each divided shot of a plurality of divided shots, for each unit irradiation region of unit irradiation regions of a target object, the unit irradiation region being an unit region to he irradiated by one beam of multi-beams, the unit irradiation region being written by the plurality of divided shots each using a different one of a plurality of sub irradiation time periods obtained by dividing a maximum irradiation time, the plurality of divided shots continuously irradiating a same unit irradiation region in the unit irradiation regions, to at least one of a plurality of beams that can be switched by collective deflection of the multi-beams;
• calculating, for the each unit irradiation region, an irradiation time of a beam;
• determining, for the each unit irradiation region, whether to make the each divided shot of the plurality of divided shots beam “on” or beam “off” so that a total irradiation time for a plurality of corresponding divided shots to be beam “on” in the plurality of divided shots becomes equivalent to the irradiation time calculated;
• applying, to the each unit irradiation region in the unit irradiation regions, the plurality of corresponding divided shots to be beam “on” in the plurality of divided shots continuously irradiating the same unit irradiation region, while switching a beam for irradiating between the plurality of beams by collective deflection of the multi-beams;
• specifying, for the each unit irradiation region, a reference beam to irradiate the corresponding unit irradiation region in the unit irradiation regions;
• and
• specifying, for the each unit irradiation region, a beam that can be switched by collective deflection of the multi-beams, as a switch beam to irradiate the corresponding unit irradiation region.

A multi charged particle beam wring apparatus comprising:

• an assignment processing circuitry configured to assign each divided shot of a plurality of divided shots, for each unit irradiation region of unit irradiation regions of a target object, the unit irradiation region being a unit region to be irradiated by one beam of multi-beams configured by charged particle beams, the unit irradiation region being written by the plurality of divided shots each using a different one of a plurality of sub irradiation time periods obtained by dividing a maximum irradiation time, the plurality of divided shots continuously irradiating a same unit irradiation region, to at least one of a plurality of beams that can be switched by collective deflection of the multi-beams;
• an irradiation time calculation processing circuitry configured to calculate, for the each unit irradiation region, an irradiation time of a beam;
• a determination processing circuitry configured to determine, for the each unit irradiation region, whether to make the each divided shot of the plurality of divided shots beam “on” or beam “off” so that a total irradiation time for a plurality of corresponding divided shots to be beam “on” in the plurality of divided shots becomes equivalent to the irradiation time calculated;
• and
• a writing mechanism, including a charged particle source, a deflector and a stage on which a target object is placed, configured to write a pattern on the target object with the multi-beams, while applying, to the each unit irradiation region in the unit irradiation regions, the plurality of corresponding divided shots to be beam “on” in the plurality of divided shots continuously irradiating the same unit irradiation region, to switch a beam for irradiating shots between the plurality of beams by collective deflection of the multi-beams,
• wherein the plurality of corresponding divided shots to be beam “on” are determined so that a dose error of each beam resulting from an opening area error of a plurality of openings for forming the multi-beams is corrected.