A Fundamental Study of the Electron Beam Lithography beyond Sub 100nm Process and its Application

Abstract

It is well known that electron beam lithography is one of the potential candidates to fulfill of the demand of the miniaturization of the design rule of semiconductor integrated circuits beyond sub 100nm size with high reproducibility. It is also a fact that the resolution is recognized to depend on the various factors which are oriented to the machine and process conditions, for example, electron beam diameter, the intensity distribution of the beam itself, the resistance properties polymers, the development conditions, etc. Therefore, it is thought that it is impossible to be derivable directly and unambiguously from the resist material itself. In this study, the intrinsic resolution of the resist polymer was discussed based on the hypothesis that the resolution itself may be able to improve to the same size as the size of an electron beam profile, or less. The bi-layer structure ZEP520A/poly methyl glutar imide (PMGI) was proposed and tested. As for the results achieved, the contrast γ was improved constantly with a reduction in the development time and a decrease in the development temperature. The highest γ value, approximately 18, was obtained during development at the-20°C condition. An approximately 70nm with high aspect ratio pattern which is almost the same size of the beam pattern was obtained. This result provides an understanding how the intrinsic resolution of the resist material should be, and can be applied to other lithography methods. This process was applied to the actual electrode pattern making process. An approximately 100nm width of Copper nanowire as the gate electrode for the AlGaN/GaN HFET was successfully demonstrated. In addition, AlGaN/GaN HFET operated at about 73.5GHz, successfully.