3D imprint technology using substrate voltage change

Spin-on-glass (SOG) is used as an electron beam (EB) resist whose depth is controlled by changing the EB acceleration voltage. Exposed SOG area and depth were developed with only 1 EB exposure using buffered hydrofluoric acid (BHF), yielding a three-dimensional (3D) SOG mold. Two acceleration voltage changes were used, i.e., changing the EB gun bias and changing the substrate voltage. When the EB gun bias was changed, patterned depth increased linearly by increasing with acceleration voltages and depth deviations of each acceleration voltages were within ±3%. The width resolution was 125nm on SOG using a 100nm EB diameter and the depth resolution was 10nm per 100V of acceleration voltage change. When the substrate voltage was changed, the relationship between the apparent acceleration voltage and pattern depth almost coincided with the change in EB gun bias, and the deviation in acceleration voltage was within ±4.4%. The depth gradation resolution limit was less than 10nm changing the substrate voltage. Imprinted patterns were transferred by pressing the fabricated 3D SOG mold onto photocurable resin at 0.5MPa and curing with a 1J/cm ² ultraviolet dose. Transferred patterns of photocurable resin were faithful and multigradational, corresponding to the mold pattern and attaining both 10nm mold depth resolution and 10nm transfer resolution.