The Growth of Thin Silicon Oxide and Silicon Nitride Films at Low Temperature (400 $^{\circ}{\hbox{C}}$) and High Growth Rates for Semiconductor Device Fabrication by an Advanced Low Electron Temperature Microwave-Excited High-Density Plasma System

Abstract

An advanced approach for the growth of thin and ultra-thin oxide and nitride films at low temperatures (400?C) for the fabrication of future scaled-down semiconductor electron devices is presented. This technique presents an alternative to the existing conventional thermal techniques currently employed in the IC industry, which utilize high-temperatures (800?C-1000?C) for the growth of both SiO2 and Si3N4 films. An alternative is needed since the high temperature range given above limits further down-scaling possibilities of semiconductor electronic devices. In this paper, the structure, operational principles, and performance of a microwave-excited high-density (> 1012 cm-3) plasma system, which utilizes low bombardment inert gas ion energies (<7 eV), low plasma potential (<10 V), and low electron temperature (<1 eV), is described, which yields high-integrity SiO2 and Si3N4 films grown at 400?C. The films grown by this technique were previously shown by us to demonstrate comparable or superior performance with respect to SiO2 films grown by the conventional thermal method at much higher temperatures (1000?C). The specific issue which this paper addresses is the problem of the growth rate of these films, which are grown at the above reduced temperature. This issue is important because it affects the compatibility of this fabrication approach with the need to obtain a high throughput in industrial electronic device processing. The results clearly demonstrate that both the SiO2 and Si3N4 films grown at these low temperatures (400?C) exhibited comparable growth rates to those of films thermally grown by conventional techniques at elevated temperatures (800?C-1000?C). Data is presented of Silicon Oxide (SiO2) films grown with various inert gases (He, Ar, Kr, Xe), mixed with O2. Silicon Nitride (Si3N4) films were grown by using Ar/N2, Ar/N2/H2, and Ar/NH3 gas mixtures. Both film types were grown in a vacuum chamber using different partial and total pressures of the above gases. Plasma excitation of these gases was achieved by irradiating them with microwave frequencies of 2.45 or 8.3 GHz. MOS transistors were fabricated using gate oxide grown by the above plasma system, in order to demonstrate the system's compatibility with electronic device fabrication.