Fabrication of 30 nm T gates using SiNx as a supporting and definition layer

A new process has been developed to fabricate 30 nm T gates for high performance metal–semiconductor field effect transistors and high electron mobility transistors. The fabrication of short gate length T gates becomes increasingly difficult as the footwidth of the gate is made smaller and this is particularly true when the footwidth is less than 50 nm. In this process a thin SiNx layer is deposited on the substrate prior to the application of a bilayer of poly(methylmethacrylate)/Shipley UVIII resist. After resist patterning by electron beam lithography the nitride layer is etched at a low bias voltage that causes negligible substrate damage. This process step helps to define the gate footwidth and improves mechanical stability of the gate. The measured gate resistance was 375 Ω/mm.