Reactive ion etching of quartz and glasses for microfabrication

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The reactive ion etching (RIE) of quartz and of silica-based glasses has been examined in CF<SUB>4</SUB>/CHF<SUB>3</SUB> plasmas. The etch rate was shown to reduce strongly with an increasing percentage of non-volatile elements in the glass. The etching of the quartz and the Suprasil 2 and Herasil 2 glasses was consistent with a process of ion-enhanced chemical reaction as identified by Steinbruchel. For these substrates, the etch rate was directly dependent on the square root of bias voltage in the RIE and increased with the ratio of CF<SUB>4</SUB>:CHF<SUB>3</SUB> in the gas mixture. The comparatively low etch rates of the LE, soda-lime and NA glasses were equivalent in both the CHF<SUB>3</SUB>/CF<SUB>4</SUB> and Ar plasmas, indicating a process of sputter etching. The BK7 glass has shown intermediate characteristics with a higher etch rate in CF<SUB>4</SUB>/CHF<SUB>3</SUB> than in Ar plasma, indicating ion enhanced chemical etching but with little dependence on the CF<SUB>4</SUB>:CHF<SUB>3</SUB> gas ratio. These results have been applied in the fabrication of grating patterns.