Selective Area Deposition of Hot Filament CVD Diamond on 100 mm MOCVD Grown AlGaN/GaN Wafers

Abstract

A new technique is reported for selective growth of polycrystalline diamond by hot filament chemical vapor deposition (HFCVD) on AlGaN/GaN-on-Si (111) wafers without degradation of the underlying layers. Selective diamond seeding is accomplished by dispersing nanodiamond seeds in photoresist and patterned lithographically prior to HFCVD growth. A thin layer of plasma enhanced CVD SiNx, deposited prior to seeding and diamond deposition, was found to be essential to protect the AlGaN/GaN wafer. A methane concentration of 3.0% was used to achieve an increased diamond growth rate and faster surface coverage. Excellent selectivity and minimal AlGaN surface damage were achieved with increased methane concentration. Damage mitigation was confirmed by comparison of atomic force microscopy, X-ray diffraction, and Raman spectroscopy, each conducted before and after diamond deposition, and by SEM images of the final structures.