Characteristics of Low Temperature SiN_x Films Deposited by Using Highly Diluted Silane in Nitrogen

摘要

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). Metal-insulator-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 l ×10~(13)? ? 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.