Selective Etching of Silicon Dioxide Using Reactive Ion Etching with CF 4 ‐ H 2

Highly selective etching of silicon dioxide relative to both silicon and resist has been obtained by reactive ion etching substrates which are loaded onto an rf cathode and exposed to a low pressure discharge of a etching gas mixture. Silicon dioxide‐to‐silicon etch rate ratios as high as 35 to 1 have been measured and silicon dioxide‐to‐resist etch rate ratios have been found to exceed 10 to 1. The use of reactive ion etching is important in achieving these high etch ratios; the low operating pressure of between 2.7 and 5.3 Pa and the exposure of substrates to bombardment by energetic ions tend to inhibit polymerization on the substrates. As a result, it is possible to use the greater concentrations which are required for high etch rate ratios.