Thickness and optical constants measurement of thin film growth with circular heterodyne interferometry

In this article, we report an alternative method for in situ monitoring of the thickness and refractive index of thin film during the growth process. We design a special structure with a thickness-controlled air film to simulate the process of thin film growth. The phase term of the reflected light coming from this multi-layer structure is modulated and has a strong correlation with the thickness and optical constant of the thin air film within this structure. Based on the phase demodulated technique and the multiple beam reflection theory under the specific oblique incident angle, the thickness and refractive index of thin film can be measured with a single configuration. According to the theoretical prediction, the resolution of the thickness determination of the thin film should be better than 0.05 nm.