DEEP TRENCH PLASMA-ETCHING OF SINGLE-CRYSTAL SILICON USING SF6/O2 GAS-MIXTURES

A new magnetron ion etching (MIE) process has been developed to etch 50-mu-m deep trenches into single crystal silicon. The optimized SF6/O2 gas mixture results in a nearly vertical etch profile with a vertical to horizontal etch rate ratio of 9.4. Similar experiments were carried out on a Drytek reactive ion etching (RIE) system. Results indicate that although the sidewall angle, etch rate ratio, and etch rate of the RIE process for silicon is lower than that of the MIE process, the surfaces of the trench are smoother and more defect-free due to better substrate cooling. The effects of the processing parameters on the silicon etch rate and anisotropy were explored in order to optimize both the MIE and RIE processes. Both processes were used to fabricate single crystal silicon doughnuts of dimensions 25-50-mu-m thick, 50-mu-m inner diameter, and 100-200-mu-m outer diameter.