Smooth, low rate, selective GaN/AlGaN etch

Abstract

The aluminum content is widely used in III-N semiconductors as a determiner of material etch characters. Applications consisting of thin GaN/AlGaN heterostructures can afford a maximum of 6 nm of a thin AlGaN layer over etch demand complex processes with precise low etch rates and low etched GaN surface roughness. In this paper, the effects of bias power and SF6 flow ratios on the chlorine chemistry etch rate, selectivity, and GaN surface roughness are investigated in a high-frequency bias generator and low power inductively coupled plasma configuration. Bias power and SF6 flow control the etch responses and are used to find the optimal spots for low etch rate, low GaN roughness, and high GaN:AlGaN selectivity for the fabrication of devices consisting of thin GaN/AlGaN heterostructures. The results are compared with the other selective gas chemistries and the more common 13.56 MHz frequency bias generator.

High Selectivity, Low Damage ICP Etching of p-GaN over AlGaN for Normally-off p-GaN HEMTs Application

“…The selectivity in this study is the highest value ever reported, which can be attributed to our systematic optimization and the lowest bias power of our designed etch tool. Additionally, as reported in reference [20], a high selectivity of 33:1 was realized by using a higher frequency bias generator of 40 MHz. The much higher plasma frequency produces lower-energy ions which tends to achieve higher selectivity but with much lower etch rate.…”