ABSTRACT Polysilicon thin films constitute a key functional layer in the fabrication of BiCMOS‐based microelectronic devices, directly influencing device electrical performance and long‐term operational stability. During the BiCMOS manufacturing flow, numerous thermal, chemical, and plasma‐based process steps induce deviations in polysilicon film properties relative to their as deposited state. In this study, the structural, chemical, and optical evolution of a polysilicon film advancing through a standard BiCMOS process sequence and re‐exposed at the final stage is systematically examined. The same polysilicon layer is comprehensively characterized at different fabrication stages using complementary techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), Raman spectroscopy, x‐ray photoelectron spectroscopy (XPS), profilometry, ellipsometry, and reflection spectroscopy. The results demonstrate that BiCMOS process steps concurrently affect the microstructural and chemical characteristics of the polysilicon film, and that the re‐exposed surface at the end of fabrication must be evaluated not solely in terms of its initial deposition conditions but within the framework of its complete process history.
Fatma Betül Akgül Taner (Wed,) studied this question.