Lithographic properties of SiN/sub x/ and Se/sub 75/Ge/sub 25/ thin films as the low-energy ion-beam resist

A low-energy focused-ion-beam lithography has been investigated, where low-pressure chemical-vapor-deposited (LPCVD) SiN/sub x/ and thermal-evaporated(TE) Se/sub 75/Ge/sub 25/ thin films are used as resists and exposure is by Ga/sup +/-ion sources below 30 keV. Ga/sup +/-implanted Se/sub 75/Ge/sub 25/ and SiN/sub x/ thin films act as positive-type and negative-type resists for the development conditions using HNO/sub 3/+HCl+H/sub 2/O wet-etching and CF/sub 4/ reactive-ion-etching (RIE), respectively. As exposing energy for Se/sub 75/Ge/sub 25/ resist increases from 10 to 30 keV, the threshold dose decreases from 4.0/spl times/10/sup 15/ to 1.4/spl times/10/sup 15/ ions/cm/sup 2/ and then the imaging contrasts appear to be approximately 0.5 and 2.5, respectively. Considering that threshold dose and contrasts in each type resists have a different energy dependence, a predominant factor in this lithography can be understood differently from each other.