Self-aligned contact metallization to AlGaN/GaN heterostructures

Nitride device scaling and large scale integration requires the increased manufacturability of self-aligned processes. To date, excellent contacts to GaN heterostructures with 2DEG are achieved through lithographically-defined metallization [1], despite the so-called self-aligned regrowth processes used [2,3]. We have developed a novel self-aligned contact metallization process using Titanium to make ohmic contacts (R
_C
= 0.36 Ω-mm) to AlGaN/GaN hetero-structures. After metal selection experiments, the field dielectric, selective wet etch chemistry, surface pre-treatment and ohmic anneal are engineered to realize the salicide-like process. A CHF
₃
+O
₂
surface pre-treatment is found to be vital to implementation of the self-aligned contact. Gate-last transistor devices demonstrate the feasibility of the unique process module. These results demonstrate the first truly self-aligned contact module for AlGaN/GaN 2DEG devices.