Dry etching of silicon using a radio frequency glow discharge in SF6 + N20 and SF6 + O2 gas mixtures have been studied. Both N2O and O2 additives can significantly enhance the silicon etch rate. For low RF power, the same amount of N20 enhances silicon etch rate more than 02 does. When the RF power level is increased beyond a value, O2 becomes more efficient in enhancing the silicon etch rate. The chemisorption model based on the competition between atomic fluorine and oxygen species for active silicon etching sites is applied to explain these etching characteristics. Optical emission spectroscopy is used to measure the relative concentrations of atomic oxygen and fluorine, which are subsequently applied to correlate the silicon etch rates. According to XPS characterization, there is no detectable sulfur contamination on silicon surface after being etched by either plasma.
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