The impact of the O 2 content in SF 6 -O 2 gas mixtures on the etch rate and sidewall profile of silicon (Si), germanium (Ge), and phosphorous doped germanium (Ge:P) in reactive ion etching has been studied. The characteristics of etch rate and sidewall profile are greatly affected by the O 2 content. Below 50% of O 2 content, a large variation in Ge etch rates is found compared to that of Si, but for O 2 content above 50% the etch rates follow relatively the same trend. Lightly doped Ge shows the highest etch rate at a O 2 concentration up to 20%. Sidewall angles range from a minimum of 80 to a maximum of 166 , with O 2 concentration of 20% yielding perfect anisotropic mesa etch. Also at this O 2 concentration, reasonable Si/Ge selectivity is possible. These observations indicate that by adjusting the O 2 concentration, precision plasma etching of Si, Ge, and Ge:P is possible.
The effect of reactive ion etching (RIE) of Silicon (Si), Germanium (Ge) and highly phosphorous doped Germanium (Ge:P) in an SF 6 -O 2 plasma has been studied. We find that the etch characteristics of etch rate and sidewall profile are greatly affected by the O 2 content. Etching rates of Ge and Ge:P depend on the O 2 content with a significant reduction up to 20% of O 2 . We also find that an anisotropic sidewall etching mechanism exists and is dependent on the percentage of O 2 (%O 2 ) in the plasma. Sidewall angles range from a minimum of 66° to a maximum of 166°, where a critical concentration for etching angle exists where the etching angle can alternate from below 90° to above 90°. In combination, both features allow for precision plasma etching of Si, Ge and P:Ge.
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