The Effect of H2 Dilution On Thin Film SiN Deposited by Hot Wire Cvd Using SiH4 and NH3 Gas Mixtures

Abstract

ABSTRACTThe structure of thin film SiN, deposited by the hot wire chemical vapor deposition (HWCVD) technique using SiH4 and NH3 gas mixtures, has been examined as a function of the amount of H2 dilution of the gas mixture. For NH3/SiH4 gas ratios > 0.5/1, all films are a-SiN:H. While H2 dilution does not change the basic film structure, in that the films are amorphous with all dilutions, H2 dilution does increase the efficiency of NH3 dissociation in the gas phase, and causes a further reduction in the already small amount of N-H bonding in a-SiN:H films deposited by HWCVD. For NH3/SiH4 gas ratios typically <0.5/1 and with high H2 dilution, the first deposition of µc-SiN is demonstrated. X-ray diffraction (XRD) measurements demonstrate that the structure of these films consists of silicon crystallites embedded in an a-SiN:H matrix. An upper limit for N incorporation with the preservation of microcrystallinity was found, beyond which the films again became amorphous. The existence of this limit is explained in terms of structural disorder in the a-SiN:H tissue brought about by N incorporation.