Novel fabrication technique for 0.1 μm T-shaped gate with i-line negative resist and poly(methylmethacrylate)

We report on a novel fabrication technique for 0.1 mu m T-shaped gates using electron beam and i-line lithography. This technique adopts a TLOR-N001:(i-line: negative resist)/950k poly(methylmethacrylate) (PMMA) bilayer system. From Fourier-transform infrared spectrum analysis, we found a 70 nm mixed layer of PMMA and TLOR was formed at the interface of these resists which offers suitable overcut resist profile for the T-shaped ate but also enhances the resistance of the PMMA against dry etching. By utilizing this process,we obtained a 0.12 mu m gate length T-shaped gate and applied it to the fabrication of an AlGaAs/InGaAs pseudomorphic high electron mobility transistor with a f(T) and f(max) as high as 66 and 190 GHz. (C) 1999 American Vacuum Society. [S0734-211X(99)00902-6].