Development and Control of a 0.25µm Gate Process Module for AlGaN/GaN HEMT Production

A variety of process modules where developed on 4” GaN on SiC substrates to support a 0.25µm HEMT technology based on i-line photolithographic tools. The technological developments to be discussed pertain to a bi-layer photo-resist shrink on top of Silicon Nitride stress-optimized films; a low-damage inductively-coupled plasma etch, to tailor the dielectric sidewall profile yet tightly control the critical gate foot dimension; a re-patterned metal gate to form a T-gate profile; and the formation of an optimized field-plate structure overtop the T-gate structure. The developmental challenges will be elucidated followed by data showing the stability and control of the critical process modules for high-volume production purposes