Etch rate monitoring with optical emission spectra in dry etching process

Summary form only given. This study focused on the monitoring method of dry etching chambers using optical emission spectroscopy(OES). A novel normalization method was suggested for the quantitative analysis of plasma emission spectra in dry etching process. The spectral signal was simplified into peaks and valleys, and then the peak intensity was divided with the average intensity of adjacent valleys. The normalized intensity indicated the relative proportion of the chemical species relevant to the wavelength of the peak. This type of calculation was inspired by the conventional actinometry but applicable to the various plasma conditions with most gas combinations. By using this technique, the window clouding effect, the unpredictable broadband attenuation from the accumulated deposition on OES window could be eliminated without any change in hardware. The etch rate changes of a plasma chamber after wet cleaning were calculated as an example of the practical applications. The linear correlation coefficient between the emission intensity and the measured etch rate jumped from 0.62 to 0.94 after normalization. The proposed technique enabled to analyze the complicated plasma emission spectra implying enormous information on actual manufacturing process. It can be also useful to control the plasma conditions for the products of narrow processing margin.