Electrical Properties of Silicon Nitride Films Prepared by Photo-Assisted Chemical Vapor Deposition under Controlled Decomposition of Ammonia

Abstract

Silicon nitride (SiN x ) films have been deposited at lower substrate temperatures (≤500°C) by direct (without Hg-sensitization) photo-chemical vapor deposition (photo-CVD) with a low-pressure Hg lamp using SiH 4 and NH 3 . The resistivity was as high as 5×10 16 Ωcm. The minimum value of interface-trap density in Al/SiN x /Si metal-nitride-semiconductor (MNS) diodes was estimated to be 9×10 10 cm -2 eV -1 by a quasi-static capacitance-voltage measurement. In contrast to conventional plasma CVD of SiN x , the formation of intermediate species is controlled by the decomposition of NH 3 which is decomposed to a lesser extent in a plasma process, based on analyses of film structures and transient mass spectroscopy. This effect causes the properties of SiN x to not change in a wide range of NH 3 /SiH 4 gas composition.