Beam energy effects in electron beam lithography: The range and intensity of backscattered exposure

The range and intensity of backscattered exposure from a silicon substrate were measured as a function of incident electron energy. The range is proportional to the energy to the 1.7 power. The integrated energy deposited at the silicon surface by backscattered electrons is about 0.8 of the energy deposited by the incident electrons and is nearly independent of the incident beam electron energy. These results show that the severity of the proximity effect, the exposure of regions not addressed by the beam, can be reduced by using high beam energy since the backscattered electrons are spread over a distance much larger than minimum feature sizes.