Growth and characterization of silicon-nitride films by plasma-enhanced chemical vapor deposition

Abstract

Thin films of silicon nitride were deposited on Si wafers by plasma-enhanced chemical vapor deposition (PECVD). For deposition we designed and made hot wall capacitively coupled PECVD equipment which has a radial flow reactor. Using an RF generator of frequency 13.56 MHz and SiH 4 (5% SiH 4 in N 2) + NH 3 and N 2 as reactive gases and the carrier gas, respectively, we systematically varied the substrate temperature (240–360°C), the partial pressure of reactive gases (0.35 <P SiH 3 P SiH 4 <1.32, 5% of S iH 4 in N 2) and the RF power (20–160 W), as deposition parameters. The characteristics of the films such as composition, deposition rate, refractive index and hydrogen content were investigated by AES, ellipsometry, FTIR spectrometry, nanospec and spectroscopic ellipsometry. As a result of these measurements, well-known characteristics were observed as a function of the substrate temperature and the partial pressure of the reactive gases. However, in our investigation of the RF power dependence of the refractive index of the film, we found that the refractive index increases and then decreases as we increase the RF power. To explain this, we considered the RF power-dependent heating effect in the glow discharge process and the amount of NH radicals which increases with the RF power.