Patent ID: 8049181

Claim:
A method of suppressing positional drift of a beam used in a charged-particle beam lithography system, wherein a wait time for convergence of the drift of the beam prior to lithographic operation or calibration of the system is reduced, said method comprising the steps of: setting the beam current to a higher value than the current used during lithographic operation or calibration of the system; repeatedly measuring the beam drift d m , and gradually reducing the beam current according to the following steps: determining a convergence value d c to which the amount of beam position drift produced during lithography or system calibration converges from a relation of beam current to amounts of beam position drift occurred in the past; finding a beam current i(t) as a function of the convergence value d c of the amount of beam position drift, a measured value d m of the amount of beam position drift, a gain constant g, and a convergence value c of the amount of beam position drift per unit beam current and using an equation given by i(t)={(1+g)·d c −g·d m (t)}/c; making a check regarding d m , and d c as to whether a relationship given by |d m −d c |<ε holds, where ε is a positive number providing a decision criterion under the condition where the gain constant g of the beam current i(t) satisfies a relationship given by g>0; and stopping control of the beam position drift after the relationship |d m −d c |<ε has been achieved and performing lithography or calibration.