Formation technology of through metallized holes to sources of high-power GaN/SiC high electron mobility transistors

The technology of through metallized holes to sources of high-power GaN/SiC high electron mobility transistors is studied. The dependences of the reactive ion etch rate of SiC in the inductively coupled plasma discharge on the pressure of the SF$_6$/O$_2$/Ar gas mixture (5–40 mTorr), the high-frequency power applied to the bottom electrode (200–300 W), the working gas flow ratio (5 : 1 : (0–10)), and the bottom electrode temperatures (5–50$^\circ$C) are studied. Based on these dependences, the hole etching process on 76-mm-diameter SiC substrates 50 and 100 $\mu$m thick is developed. The process features smooth etched-surface morphology, a high rate (1 $\mu$m/min), and low high-frequency power deposited into the inductively coupled plasma discharge (1000 W). The developed process of hole etching in SiC substrates is characterized by the selectivity coefficient $S$ = 12 and the anisotropy coefficient $A$ = 13. Films based on NiB are recommended as masks for etching through holes into SiC substrates. The processes of through-hole metallization by the electrochemical deposition of Ni and Au layers are developed.