COMPOSITION, STRUCTURE, AND FUNCTIONAL PROPERTIES OF THIN SILICON NITRIDE FILMS GROWN BY ATOMIC LAYER DEPOSITION FOR MICROELECTRONIC APPLICATIONS (REVIEW OF 25 YEARS OF RESEARCH)

Results of studies of compositions, structures, and main functional properties of thin silicon nitride (SiNx) films obtained by atomic layer deposition (ALD) are considered over the period of 25 years as applied to the problems of microelectronic technologies. Deposition rates of SiNx films of most processes studied in the temperature range of 200-600 °С correspond to 0.1 nm/cycle for two- and three-step processes involving precursors from chlorosilane, silane, aminosilane, silylamine, cyclosilazane groups and other secondary reagents (NH3, N2H4, H2, N2 and their combinations). XPS, RBS, FTIR, AES, AFM, etc. techniques are used to investigate SiNx films. The discussed schemes of growth processes imply the presence of surface NH and NH2 groups. Plasma activation of nitrogen-containing reagents is needed in preparing the surface of the growing SiNx film to begin precursor chemisorption in the subsequent cycle of deposition and allows a decrease in the precursor dose by several orders of magnitude. Plasma activation processes involving chlorosilanes can form unacceptable, thickness conformal films with heterogeneous properties on the side surfaces of complex stepped reliefs of microelectronic devices. The best characteristics in the stoichiometry, composition, and properties of SiNx films are observed at deposition temperatures above 500 °С for both thermal and plasma activation processes. The conclusion is drawn about the necessity of a deep systematic investigation of experimental publications on plasma-enhanced ALD thin films of silicon nitride as well as their composition, structure, and properties.