DIRECT PHOTO CHEMICAL VAPOR-DEPOSITION OF SILICON-NITRIDE AND ITS APPLICATION TO MIS STRUCTURE

Silicon nitride (SiNx) films have been deposited at lower substrate temperatures (< 500-degrees-C) by direct (without mercury-sensitization) photo-chemical vapor deposition (photo-CVD) using SiH4 and NH3 with a low-pressure mercury lamp. Films deposited at around 350-degrees-C have a polymeric structure such as (Si(NH)2)n. Films deposited at 500-degrees-C were close to stoichiometric Si3N4 with a slight amount of hydrogen. The refractive index and the dielectric constant of films deposited at 500-degrees-C became almost equal to the values of thermally synthesized Si3N4. The resistivity was as high as 5 x 10(16) OMEGAcm. The minimum density of interface states in Al/SiNx/Si MIS (metal-insulator-semiconductor) diodes was estimated to be 9 x 10(10) cm-2eV-1 by a quasi-static capacitance-voltage measurement. For SiNx films deposited at 300-degrees-C, the density of interface states, which was in the order of 10(11) cm-2eV-1 as deposited, decreased by a rapid thermal anneal after the deposition. For Al/SiNx/InP MIS diodes, it was 3 x 10(11) cm-2eV-1 by high-frequency capacitance-voltage measurements. Direct photo-CVD for SiNx films is promising for low-temperature formation of a gate insulator.