AUTOMATIC CONTROL OF STOICHIOMETRY IN CVD OF METAL SILICATES BY ALTERNATING SURFACE REACTIONS

摘要

Metal silicates, such as zirconium silicate, have recently been deposited by surface reactions between metal amide vapors and tris(tert-butoxy)silanol vapor. When the vapors are brought to a heated surface either simultaneously (CVD conditions) or alternately (ALD conditions), metal silicate films form with compositions that are very uniform even over large areas of deposit. The ALD conditions also produce excellent thickness uniformity and conformal step coverage. This paper proposes a mechanism by which the films are formed by reactions on the surface of the growing film. The mechanism explains why the surface reactions are self-limiting and lead automatically to uniform stoichiometry and thickness. It also explains how the carbon and nitrogen in the precursors is eliminated, leaving pure films. The mechanism also rationalizes how the remarkably high growth rate, over 0.3 nm per cycle, is achieved from rather bulky precursors that by conventional arguments would be expected to produce a low growth rate.