Plasma-enhanced chemical vapor deposition of silicon dioxide

Abstract

Silicon dioxide deposited by plasma-enhanced chemical vapor deposition (PECVD) is widely used as an intermetal dielectric (IMD) for multilevel interconnections in VLSI technology. The main motivation for using PECVD is the low deposition temperature, typically T ~300°C or lower making it compatible with aluminum metallization. PECVD is achieved by reacting source gases in a glow discharge (plasma). The plasma provides the energy for the reaction to occur unlike in thermal oxidation and conventional chemical vapor deposition where high temperature is used to drive the reaction. Silicon dioxide deposited by PECVD, often called as PECVD-oxide, is usually non-stoichiometric (SiO_x, x < 2). PECVD-oxide films are usually deposited using silane (SiH₄) and nitrous oxide (N₂O).
In device fabrication, precise control of the thickness of PECVD-oxide is very important. However, the deposition rate PECVD-oxide is strongly dependent on the deposition conditions and the equipment used. Hence, in-house study of the deposition rate of the PECVD-oxide is necessary.
In this paper, we report the characteristics of the PECVD-oxide we had deposited using the PECVD facility in CMPL. The thickness and composition of the PECVD-oxide (FTIR) films have been determined using ellipsometry and Fourier transform infrared spectroscopy respectively. Effects of RF power and temperature on the deposition rate have been studied. A graph of oxide thickness vs. time has been prepared for PECVD-oxide deposited at constant RF power (30 W) and temperature (300°C).