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 μm 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 gate but also enhances the resistance of the PMMA against dry etching. By utilizing this process, we obtained a 0.12 μm gate length T-shaped gate and applied it to the fabrication of an AlGaAs/InGaAs pseudomorphic high electron mobility transistor with a fT and fmax as high as 66 and 190 GHz.