High density plasma etching of wide bandgap semiconductor materials for fabricating novel devices

AlxGa1-xN and SiC are being projected as the key semiconductor materials for the new generation of high power and high frequency novel electronic devices capable of reliable operation under extremely harsh environment and elevated temperatures. Most of these devices would require convenient and reproducible etching procedures. Owing to their lack of reactivity to chemicals both AlxGa1-xN and SiC cannot be conveniently etched using wet chemistry. Therefore, they have to be etched using dry etching processes. In this thesis we extensively investigated the etching characteristics of AlxGa1-xN and SiC using inductively coupled plasma reactive ion etching (ICP-RIE).; A comprehensive study of ICP etching of AlxGa1-x N over its entire compositional range using Cl2/Ar gas mixtures was conducted. The etching results of AlxGa1-xN were successfully applied to form highly anisotropic and smooth facets for GaN/AlGaN laser heterostructures. SiC etching was also characterized using both fluorine-based and chlorine-based plasmas. The etching results were successfully used for through-via hole fabrication in SiC substrate, using masking processes compatible with microelectronic fabrication.; Dry etching processes rely on ion assisted removal which can cause significant damage to the substrate material being etched. This makes it imperative to do systematic studies to characterize the damage induced by various dry etching tools in order to optimize the device etching processes for AlxGa 1-xN and SiC. Therefore, the effect of plasma bias voltage, ICP coil power and the etch duration on the Schottky diode characteristics fabricated on AlxGa1-xN and SiC substrates were also analyzed. Inductively-coupled-plasma induced damage on two-dimensional electron gas (2DEG) in AlGaN/GaN High-electron-mobility-transistor (HEMT) structure was also investigated. It was shown that the post-etch anneal was able to remove any plasma induced damage resulting in a high gate-drain breakdown voltage and low gate leakage current. The measured values of gate-drain breakdown voltage of over -90 volts, fT of 48 GHz and fmax of 108 GHz are the highest ever reported data for recessed-gate AlGaN/GaN HEMTs.; We also demonstrated the fabrication of recessed 0.15 mum gate-length AlGaN/GaN HEMTs using ICP-RIE on sapphire substrate. These devices exhibited high DC and RF performance. The drain current density as high as 1.31 A/mm, a peak transconductance of 401 mS/mm, an fT of 107 GHz and an f max of 148 GHz were measured on these devices. To the best of the authors' knowledge, this is the highest ever-reported value of gm for AlGaN/GaN HEMTs. Also, an fT of 107 GHz is the highest data for similar gate-length devices.