The influence of SiNx:H film properties on the electrical characteristics of metal-insulator-semiconductor devices

Abstract

SiNx:H thin films were deposited by the electron cyclotron resonance plasma method at low substrate temperature (200 degrees C) to fabricate metal-insulator-semiconductor devices. The effects of film properties on the electrical characteristics of two different devices, SiNx:H/Si and SiNx:H/InP, were analysed according to the C-V high-low frequency method. The results show that, in the devices based on Si, the presence of N-H bonds in the SiNx:H film increases the density of trapping centres at the insulator/semiconductor interface. This behaviour was analysed by the model recently proposed by Ying (1995 J. Vac. Sci. Technol. B 13 1613) for nitrided SiO2/Si interfaces. For the SiNx:H/InP capacitors, the electrical characteristics of the interface were strongly dependent on the SiNx:H composition. When the nitrogen to silicon ratio of the film was N/Si = 1.49, the minimum of the interface trap density was 2 x 10(12) cm(-2) eV(-1) This value was similar to the same data reported by other authors on devices where the InP surface was sulphur passivated. This suggests that nitrogen atoms of the insulator play some passivation role at the InP surface. The plasma exposure of the semiconductor surface during the deposition of the SiNx:H film promotes the formation of phosphorus vacancies at the InP surface. Nitrogen atoms may fill these vacancies and this gives rise to an insulator/semiconductor interface with few defects.