Wafer Temperature Dependence of the Vapor‐Phase  HF  Oxide Etch

Abstract

When HF/H₂O vapor derived from an azeotropic solution of HF/H₂O was used to etch various oxides of silicon, the etch rates were found to have qualitatively similar dependence on the wafer temperature. However, the sensitivites of the dependence were found to vary greatly among the different oxides. Consequently, the etch selectivities among different oxides could be controlled by changing the wafer temperature. In particular, the phosphosilicate glass to thermal oxide etch selectivity increased from about 18:1 to at least 2900:1, when the temperature was raised from around 25°C to around 50°C.