Characteristics of low temperature SiN _x films deposited by using highly diluted silane in nitrogen

We report on electrical and mechanical properties of silicon nitride (SiN _x) films deposited by a plasma enhanced chemical vapor deposition (PECVD) method at 200°C from SiH ₄ highly diluted in N ₂. The films were also prepared from SiH ₄ diluted in He for comparison. The N ₂ dilution was also effective in improving adhesion of the SiN _x films, fascilitating construction of thin film transistors (TFTs). Metalinsulator- semiconductor (MIS) and Metal-insulator- Metal (MIM) structures were used for capacitance-voltage (C-V) and current-voltage (I-V) measurements, respectively. The resistivity and breakdown field strength of the SiN _x films from N ₂-diluted SiH ₄ were estimated to be 1×10 ¹³ω · cm, 7.4 MV/cm, respectively. The MIS device showed a hysteresis window and a flat band voltage shift of 3 V and 0.5 V, respectively. The TFTs fabricated by using these films showed a field-effect mobility of 0.16 cm ²/Vs, a threshold voltage of 3 V, a subthreshold slope of 1.2 V/dec, and an on/off ratio of >10 ⁶.