FACTORS AFFECTING INTERFACE-STATE DENSITY AND STRESS OF SILICON-NITRIDE FILMS DEPOSITED ON SI BY ELECTRON-CYCLOTRON-RESONANCE CHEMICAL-VAPOR-DEPOSITION

The physical and electrical properties of nitrogen-rich silicon nitrid e films deposited by electron-cyclotron resonance chemical vapor depos ition with silane and molecular nitrogen have been investigated for pr essures below 0.4 Pa. No Si-Si bonding or oxygen has been observed in the nitride films by Auger spectroscopy, and no SIH or NH2 groups have been observed by Fourier transform infrared spectroscopy, showing tha t the films have the composition SiNy-z(NH)(z). As the pressure was de creased by lowering the nitrogen flow, the stress in the films became more compressive while the amount of N-H bonding in the films increase d. The electron temperature determined by Langmuir probe measurements increased at lower pressures as the plasma made a transition from over dense to underdense. Despite the increasing stress, electron temperatu re and NH concentration, capacitance-voltage (C-V) analysis of metal-n itride-Si(100) diodes showed that the SiN/Si interface improved with d ecreasing pressure. Using Al gates and 5 Omega cm p-type Si(100) subst rates an interface state density of 5 x 10(10) eV(-1) cm(-2) was deter mined by the high-low frequency C-V measurement method for 30 nm thick films deposited at a substrate temperature of 300 degrees C and the l owest pressure of 0.055 Pa. Bulk conduction by the Frenkel-Poole mecha nism dominated the current-voltage characteristics for negative gate p otentials and breakdown voltages >9 MV/cm were obtained at this pressu re. In situ single-wavelength ellipsometry showed that the interface i s formed predominantly by nitridation of the Si substrate, and thus it s high quality must be attributed to this nitridation rather than the chemical vapor deposition process. The results are discussed in terms of recent models for defects at the SiN/Si interface. (C) 1998 America n Vacuum Society. [S0734-2101(98)04305-X].