Effects of Hydrogen Additive on Obtaining Residue‐Free Reactive Ion Etching of β ‐ SiC in Fluorinated Plasmas

In this paper we discuss the formation and prevention of residues during long‐term reactive ion etching (RIE) of β ‐ SiC thin films in a variety of fluorinated gas plasmas mixed with oxygen: CHF 3 , CF 4 , SF 6 , and NF 3 . Without the addition of H 2 , all fluorinated plasmas produced significant residue for mixtures with O 2 ranging from 0 to 90%. Only NF 3 and CHF 3 at 0% O 2 showed a low level, or the absence, of residues. The introduction of a relatively small amount of H 2 additive was observed to prevent residue formation in the etched region during the process. In CHF 3 etching, ∼10% H 2 was sufficient to prevent residues at all values of O 2 % . A significantly larger (>10%) amount of H 2 is required to prevent residue formation in CF 4 / O 2 , SF 6 / O 2 , and NF 3 / O 2 plasma. For these gases, the required H 2 additive concentration increases as the oxygen decreases, reaching a maximum for 10% O 2 . Optimum RIE conditions in different fluorinated gas plasmas are presented for SiC homojunction and heterojunction device fabrication. The effects of covering the powered electrode with graphite or Kapton sheets on residue formation and etch rates were investigated with a variety of fluorinated gas plasmas. The mechanisms of residue formation and prevention through the addition of H 2 are discussed.