Film-induced stress in substrate/film structure

Most all microelectronic devices have the basic material structure of a semiconductor substrate with thin films on it. The thin film layer and its discontinuity will give rise to stress fields in both the semiconductor substrate and the thin film. We investigate the stress in such film/substrate structures by using the photoelastic method. Compared with other stress measurement technologies, the photoelastic method is a distinctive method. It can offer the real-time qualitative observation as well as the quantitative determination of stress distribution in a sample. Under a polarized light field, birefringence patterns are obtained in a semiconductor substrate when it is stressed. By analyzing the polarization information added by the stressed crystal region, the stress distribution in the substrate may be extracted. According to the principle of static force balance, the stress introduced into the thin film can be estimated by investigating the stress integral of the substrate.