| Summary: | 碩士 === 國立清華大學 === 工程與系統科學系 === 97 === Abstract
Plasma etching is an important etching process in the production of integrated circuits. In the plasma etching process, the ellipsometry can be used to monitor the etching process during the etching process. An in-situ ellipsometer using photo elastic modulator (PEM) was developed in our laboratory for monitoring the plasma etching of polysilicon. In this research, the in-situ ellipsometer was used in investigating the over-etching of silicon oxide thin film. The evolution of the surface roughness can also be monitored by the ellipsometer during the etching process. The etching of thin oxide film (about 30 nm on silicon wafer) was compared with the etching of bare silicon. It is found that the surface roughness begins to increase after the oxide layer is etched out. The surface roughness continues to increase rapidly as indicated by the ellipsometer signals. As for the etching of bare silicon, the surface remains smooth in the beginning of the etching for sometime, then it starts to become rough and the roughness also increases rapidly. Eventually the surface becomes needle-like as revealed by SEM. Although it is impossible to determine the magnitude of the surface roughness from the ellipsometry data, it is still very useful to use the ellipsometer to monitor the changes in the surface roughness during the over-etch of silicon oxides.
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