A novel PMMA-swelling technique to fabricate deep sub-micron T-shaped gate MODFETs

We report a novel PMMA-swelling technique to fabricate deep sub-micron T-shaped gate MODFETs with narrower gate length and raised T-head. The technique employs chemical formation of intermixed layer over PMMA film that makes uniform 0.1-μm thickness reproducibly. The technique provides narrowed gate length by 0.2pm with desirable round shape resist profile which avoids separation of the T-foot and 0.1-μm-raised T-head. An AlGaAs/InGaAs pseudomorphic MODFET with a f_T and f_max as high as 119 GFIz and 218 GHz was fabricated by utilising this technique.