Effect of Introducing Free Gaseous Radicals of Trichlorosilane and Ammonia Precursors on Growth and Characteristics of LPCVD a-SiNx Ultra Thin Films

Abstract

Preparation and characteristics of amorphous silicon nitride (a-SiNx) thin films deposited by low pressure chemical vapor deposition (LPCVD) are investigated. Free gaseous radicals of trichlorosilane (TCS) and ammonia (NH3) are produced by passing each of the precursor gases separately over Pt-Ir/Al2O3 catalyst at the temperature of 600 C. Kinetics studies of the LPCVD are carried out in different total pressures, NH3/TCS flow rate ratios and temperatures. Surface topography, chemical concentrations, growth rate and thickness are studied by Ellipsometry, x-ray photo-electron spectroscopy (XPS), atomic force microscopy (AFM) and auger depth profiling (ADP). Analysis of experiments indicates that at the temperatures between 730 C and 830 C, the growth rate of thin films follows an Arrhenius behavior with activation energy of 166.3 KJ.mol-1. The measured hydrogen contamination in a-SiNx ultra thin films is 1.05 at% which is 17 times lower than the corresponding contamination in the films produced by (PECVD) and 3.4 times lower than the contamination in the LPCVD thin films with silane (SiH4) or dichlorosilane (DCS) and Ammonia. The surface topography of the prepared films is smooth and uniform and the thickness varies between 23 and 101 nanometers.