Multiple internal reflection IR spectroscopy of CVD SiO<inf>2</inf>, SiO<inf>x</inf>N<inf>y</inf>and SiO<inf>3</inf>N<inf>4</inf>films

Abstract

Thin 200-500 A films of chemically-vapor-deposited (CVD) SiO 2 , SiO x N y and Si 3 N 4 are technologically important dielectric materials in integrated circuits. Si 3 N 4 , for example, is used as a gate dielectric in non-volatile MNOS memory devices (1), and as an encapsulating layer for GaAs devices against surface damage during post-implant anneals (2). The processing and annealing conditions of CVD Si 3 N 4 can significantly alter the physical and chemical properties of the film which ultimately will have a pronounced effect on the performance of the device. A very sensitive tool for chemically analyzing these thin CVD films is by multiple internal reflection IR spectroscopy (MIR). The various active vibrational modes associated with Si, O, N and H can be detected. CVD Si 3 N 4 films have been characterized from MIR spectra, ellipsometry, etch rate, and conductivity. The influence of the Si 3 N 4 film properties on the performance of the MNOS memory devices will be discussed briefly.