Ion attachment mass spectrometry of nonequilibrium atmospheric-pressure pulsed remote plasma for SiO2 etching

An etching process for SiO2 that employs atmospheric-pressure pulsed remote plasma with a mixture gas (CF4∕Ar) has been demonstrated. The etch rate increased by increasing the pulse frequency and also increased rapidly with the addition of a small amount of O2 gas. A SiO2 etch rate of 400nm∕min was obtained without any bias supplied to the substrate, and more than 8μm∕min was obtained with H2O addition. The exhaust gas from the plasma source was investigated using ion attachment mass spectrometry (IAMS). With IAMS, the polymerized species were measured without the generation of fragment ions. The results suggest that HF molecules are generated by H2O addition to CF4 and that the etch rate of SiO2 depends on the density of HF molecules.