SiO2/Si3N4 bilayer sloped etching for 20nm InAlAs/InGaAs metamorphic HEMTs

We developed a 20 nm gate process using SiO2/Si3N4 bilayer sloped etching. Selective and sloped etching of bilayer makes this technology realizable. A HEMT with this technology has merits of fine length definition beyond the limit of electron beam (E-beam) lithography system. Using this technology, we experimentally demonstrated that a 20 nm gate length from initial 50 nm line pattern. The fabricated InAlAs/InGaAs metamorphic HEMTs (MHEMTs) with 20 nm T-gate pattern have high DC and RF performance characteristics, a transconductance of 1.67 S/mm, a cutoff frequency ft of 460 GHz.