Abstract：This paper investigates the drift of microcrystalline silicon (μc-Si∶H) thin film properties due to the chamber's long-time usage in plasma enhanced chemical vapor deposition (PECVD). The condition parameters were controlled to reach about 0.5 nm/s deposition rate for the samples to have a certain crystalline degree, 40%~80%, as detected and estimated by two different wavelength lasers in Raman scattering measurement. The samples under different silane concentrations (i.e. the flow rate ratio, [SiH4]/([SiH4]+[H2])) were compared carefully, and it is found that both their deposition rate and crystalline degree increase with the chamber usage time, which was used as an independent variable in this experiment. This phenomenon may be explained by the accumulated silicon remains such as powders and films, observed on the electrode plate and/or on the chamber wall in this experiment. These silicon remains probably take part in the reactions related to the film formation in plasma. It is found that this drift of μc-Si∶H structural and electronic properties can be adjusted by increasing the silane concentration, and with the deposition rate being kept at a high level.