Fast, smooth, and anisotropic etching of SiC using SF6/Ar

Using magnetically enhanced reactive ion etching and an etch chemistry cont aining sulfur hexafluoride and argon we have dry etched silicon carbide (Si C) with etch rates as large as 1900 Angstrom/min and obtained smooth etched surfaces and good etch anisotropy. Such etch processes are useful for a va riety of SiC devices, including vertical UMOSFETs. Etch chemistry was found to greatly affect etch rate and final surface roughness. Etching in mixtur es of sulfur hexafluoride (SF6) and oxygen, for example, resulted in relati vely rough etched surfaces (typically 25 Angstrom rms) with a maximum etch rate near 800 Angstrom/min. Etching in SF6/Ar gave smoother surfaces and la rger etch rates, most likely because physical sputtering by Ar+ ions helps to remove nonvolatile or low-volatility fluorocarbon and carbon-rich etch p roducts. For example, using equal SF6 and Ar flow rates of 40 seem, a proce ss pressure of 10 mTorr, and a rf power density near 2.5 W/cm(2), etch rate s near 1000 Angstrom/min are obtained. Atomic force microscopy indicates th at the surface roughness of SIC etched under these conditions actually decr eased slightly (from 6.1 Angstrom to 4.4 Angstrom rms). Scanning electron m icroscopy indicates good etch anisotropy with slight trenching at feature e dges. Increasing the rf power density to 3.5 W/cm(2) increases the etch rat e to 1900 Angstrom/min with only slightly increased surface roughness. The combination of large etch rate, smooth etched surfaces, and good etch aniso tropy make magnetically enhanced reactive ion etching in SF6/Ar attractive for SIC device fabrication. (C) 1999 American Vacuum Society.