Charging effect reduction in electron beam lithography with nA beam current

Charging effect becomes a more serious issue when performing electron beam lithography using high beam current. Here we studied the charging effect using PMMA, PMGI and ZEP-520A resist to pattern 200nm period hole array. It is found that charging effect can be reduced by simply re-arranging the exposure sequence such that subsequent writing elements are farther apart. It can also be decreased by using a more conductive substrate. Among the three resists, the charging effect is the least for the insensitive PMGI resist, though at the cost of longer writing time when using the same beam current. The opposite is true for the more sensitive ZEP-520A resist.