In situ ellipsometry during plasma etching of silica films on Si

The etching of SiO2 films on a Si substrate in an rf plasma in CF4 has been studied with i n s i t uellipsometry. The etch rate was measured as a function of flow, rf power and pressure. An accurate analysis of the experimental data using numerical simulations based on multilayermodels has yielded information both on the refractive index of the etched SiO2 film and on the existence of a top layer. It could be established that a layer is present on top of the SiO2 during etching, which is probably caused by roughening of the SiO2 layer. Furthermore at high pressures (>8 Pa) it was demonstrated that after the complete removal of the SiO2 film a polymer layer starts growing on the Si substrate

Optical diagnostics for plasma etching

Several optical diagnostics were used to det. plasma properties and etch rates in an single wafer etch reactor. Results of UV-visible spectroscopy and IR absorption spectroscopy, indicating different mol. species and their densities are presented. The construction of an interferometer to det. the gas temp. and of an ellipsometer to det. the in situ each rate are also described