Fluorinated-chlorinated SiO2 films prepared at low temperature by remote plasma-enhanced chemical-vapor deposition using mixtures of SiF4 and SiCl4

Fluorine-chlorine-doped silicon-dioxide films have been deposited at 200 de greesC by the remote plasma-enhanced chemical-vapor-deposition technique us ing SIF4 and SiCl4 as silicon precursors in combination with O-2/He/H-2 mix tures. The behavior of the deposition rate and structural properties of the films as a function of SiF4 ratio, R = SiF4/(SiF4+SiCl4), was studied for two O-2 how rates by means of ellipsometry, chemical etch rate measurements , and infrared (IR) spectroscopy. Due the higher reactivity of SiCl4 compar ed with that of SiF4, films deposited with R<0.8 have high deposition rates (400-1410 <Angstrom>/min), high refractive indices (1.46-1.59), and contai n more chlorine than fluorine, On the contrary, films prepared using high S iF4 ratios (R>0.8) are deposited at lower rates (38-400 Angstrom /min), hav e low refractive indices (1.43 - 1.46), and contain more fluorine. Etch rat e and LR measurements indicate that all fuorinated-chlorinated SiO2 films d eposited with an O-2 flow rate of 130 seem do not contain Si-OH or SI-H bon ds and are more resistant to being chemically attacked than films deposited with 40 seem of this gas. In this study, I-V and C-V measurements were use d to compare the dielectric properties of stable fluorinated-chlorinated fi lms prepared with an O-2 flow rate of 130 seem and the two highest SiF4 rat ios; R = 0.9 and R = 1. The fluorine content measured by resonant nuclear r eactions with the F-19(p, alpha gamma)O-16 nuclear reaction is 2.6 at.% for the film deposited with R = 0.9 and 5.9 at.% for that deposited with R = 1 . The dielectric constants are 3.8 and 3.7, respectively. Although the depo sition rate is higher for the former film (190 Angstrom /min) than for the latter (38 seem), both films have a leakage current density lower than I x 10(-7) Angstrom /cm(2) and their dielectric breakdown occurs at electric fi elds higher than 8.2 MV/cm. These results indicate that the use of SiCl4 in combination with SiF4 is a good approximation to prepare and to increase t he deposition rate of hydrogen-free fluorinated-chlorinated SiO2 films with low dielectric constants and good electrical integrity. (C) 2001 American Vacuum Society.