Large-scale data analysis of PECVD amorphous silicon interface passivation layer via the optical emission spectra for parameterized PCA

Abstract

In this study, the process of hydrogenated amorphous silicon (a-Si:H) thin films is prepared by plasma enhanced chemical vapor deposition (PECVD) in conjunction with the in situ plasma diagnostic tool of optical emission spectrometer (OES). The passivation quality of a-Si:H thin films was measured, and the results show that the quality of the passivation layer was strongly influenced by chamber background environment via two different predeposition times. The minority lifetime can be greatly increased from approximately 300 to 777 μs for the predeposition time of 60 and 150 min, respectively, primarily attributed to the stabilization of the chamber environment and gas discharge during the predeposition process. Transmission electron microscopy photograph showed a compact a-Si:H layer (of approximately 10 nm) interface passivation layer with a void-free and crystallite-free interface after a predeposition time of 150 min. In addition, correlations between the plasma characteristics (OES spectra) and passivation quality (minority lifetime) of deposited a-Si:H thin films are explored by applying the techniques of principal component analysis (PCA). The PECVD process health condition was established as high lifetime at predeposition time of 150 min with the mean health value of 0.58 and the control limits of 0.28. The health value generated can be interpreted and reflected the PECVD process which will provide valuable information for passivation quality of higher lifetime.