In-situ detection of photoresist failures

In semiconductor manufacturing, the early detection of defects is one of the key factors to increase the yield. The qualitative inspection of the wafer during spin coating has remained limited due to the complexities of the measurement method in the lithography. In this paper, we introduce an optical method for the detection of photoresist failures which has been integrated into spin coating process tools. The detection technique is based on the measurement of light which is broadened at imperfections of the photoresist layer. In this paper, the light path has been analyzed based on geometrical and wave optics. The broadening of the light beam can be mainly attributed to diffraction at trench fields and scattering phenomena and reflection at resist edges, respectively. The analysis helped to reduce the false-detection-rate due to diffraction phenomena and facilitated the calibration of the detection system. The results of the analysis are compared with the output signal from sensor system. The new optical method is a promising technique for an in-situ wafer inspection during the spin coating process.