| Abstract |
| We report on the electrical properties of silicon nitride (SiNX) films deposited at 150℃ from highly diluted SiH4 in N2 by a plasma enhanced chemical vapor deposition (PECVD) method. The films were also prepared below 200℃ for comparison. Although the N2 dilution gas acted as a source of nitrogen atoms inside the SiNX film, it was necessary to introduce NH3 to obtain good dielectric quality in the low-temperature films. An amount of NH3 equal to the net SiH4 in the gas mixture was found to be adequate, and further addition of NH3 resulted in little improvement. For SiNX films deposited at 150℃, the NH3 addition decreased the C-V hysteresis (△Vth) from 15 V to 3 V, and increased the resistivity and the breakdown field strength from 109 Ωcm and 4 MV/cm to 1013 Ωcm and 7 MV/cm, respectively. When these films were applied as a gate dielectric layer, the resulting TFT prepared at 150℃ showed an on/off current ratio higher than 105, a threshold voltage of 1.1 V, a subthreshold slope of 1.2 V/dec, and a field effect mobility of 0.04 cm2/Vsec. Under a dc bias stress of VD = VG = 25 V, the on-current of this TFT was stable over a period of 5000 seconds. |
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| Key Words |
| dielectrics, plasma deposition, electrical properties, electrical resistivity, highly-diluted gas |
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