We have previously reported the residue‐free reactive ion etching (RIE) of 3 C ‐ SiC in CHF 3 / O 2 , SF 6 / O 2 , CF 4 / O 2 , and NF 3 / O 2 mixtures with H 2 additive. The minimum H 2 concentration for residue prevention was found to vary with the O 2 content of each gas plasma and from gas to gas. In this paper, we report on the reactive ion etching of 6 H ‐ SiC in the same gas plasmas. The 6 H ‐ SiC etch rate and etched surface morphology under different etching conditions are presented. A similar pattern of minimum H 2 concentrations for the residue‐free RIE of 6 H ‐ SiC is obtained. This indicates that the process involving H 2 additive in the fluorinated plasma could be applied to other SiC polytypes. A residue‐free etching surface can be obtained without the H 2 additive only in pure CHF 3 plasma. Other plasma conditions do need various levels of H 2 concentration in the plasma to obtain a clean etched surface. In both 3C‐ and 6 H ‐ SiC the etch rate decreases as the H 2 concentration increases. No etching undercut was found for 6 H ‐ SiC with Al as etching mask. A graphite sheet covering the powered electrode also produced residue‐free RIE but suffers from undesirable side effects. A comparison of minimum H 2 levels for residue‐free etching of 3C‐ and 6 H ‐ SiC in different plasmas is discussed.
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Yih et al. (1995) studied this question.