Effects of growth parameters on the performance of mu c-Si thin film transistors deposited using SiF_4

摘要

Top-gate microcrystalline silcion ( mu c-Si) thin film transistors (TFTs) were made, to study the effects of growth parameters of mu c-Si channel on the TFT performance. The mu c-Si layers were deposited by PE-CVD from mixtures of SiH_4, SiF_4, and H_2. The growth parameters were varied in the following range: Substrate temperature from 280 to 360 deg C; gas flow rate, SiF_4 from 10 to 35 sccm, H_2 from 50 to 200 sccm, SiH_4 constant at 1 sccm; deposition pressure from 500 to 900 m STorr; and plasma power from 18 W to 54 W (power density 80 mW/cm~2 to 240 mW/cm~2). We observed the following trends in TFT performance: The electron mobility rises with rising substrate temperature, deposition pressure and H_2 flow rate. The OFF current decreases drastically with deposition power and rises rapidly with SiF_4 flow rate above 20 sccm. We identified as set of best deposition parameters.