40nm In0.7GaAs HEMTs with Novel HSQ Based T-gate Process

We have successfully demonstrated the novel HSQ based T-gate process to transfer the negative nanoscale patterns to positive patterns. This process is based on electron beam (EB) lithography, O₂ plasma and BOE solution etching. Because O₂ plasma etching has the high selectivity between HSQ and ZEP, HSQ patterns were exposed over the ZEP layer without any loss of pattern dimension. HSQ was then selectively etched by BOE solution. Therefore it is very simple and reproducible process in achieving nanoscale pattern of positive tone and could be useful for the fabrication of nanoscale T-gate HEMTs. The fabricated 40 nm In_0.7GaAs HEMTs with the novel HSQ based T-gate process exhibit an extrinsic transconductance gm of 1.4 S/mm and a cut-off frequency f_T of 370 GHz