Interactive effects in the reactive ion etching of SiGe alloys

rates of single;crystal Si and Gem are shown. The etch rates of the SiGe alloys increase with the Ge content for each etching gas which is qualitatively consistent with the greater etch rate of Ge as compared to Si. The dashed lines which connect the SiGe alloy nata with the elemental Ge etch rate data are intended to help in the comparison of SiGe and Ge-etch rates, but it is not implied that the actual etch rates would show a depen-m dence on Ge content given by the dashed lines. The SiGe etch rate shows the strong@ increase with Ge content for the CF, plasma. Analysis of profiles etched in photoresist- or oxidemasked SiGe films has shown that mask undercutting takes place for fluorine-rich discharges, e.g., SF,. No mask undercutting was observed with CF&& and HBr plasmas. These etch profile characteristics indicate that fijr Si, -t;GeX alloys F-based etching is ion assisted with a strong chemical etching component; but that Cl- and Brbased etching require ion bombardment. The behavior of Sil -XGeX alloys, xQl.20, is therefore in this respect the same as that of Si.’ A more detailed discussion of the processing parameters and-etch profile results will

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