REACTIONS WHICH FORM BOTH SILICIDE AND NITRIDE LAYERS

Reactions of Ti which form both a silicide and a nitride after rapid thermal annealing have been characterized using Auger depth profiling, X‐ray diffraction, and transmission electron microscopy. Reactions of Ti with Si annealed in a nitrogen ambient at temperatures above 700°C form a thin TiN layer on TiSi2 (C54). A similar structure is formed by annealing Ti deposited on thin Si3N4 films on Si in Ar at 1000°C. The reaction of nitrogen directly with TiSi2 begins at temperatures above 950°C, but at temperatures greater than 1050°C, TiSi2 completely reacts to form TiN. The reaction of Ti with thick Si3N4 films was studied in greater detail. At lower temperatures in Ar, mostly Ti5Si3 is formed at the interface, with some contaminant oxygen and nitrogen released from the reaction, uniformly dissolved throughout the unreacted Ti. Also, a very thin TiN layer exists at the Ti5Si3/Si3N4 interface. At higher temperatures, a three‐layered structure, TiN/TiSix/TiN/(unreacted Si3N4) develops, allowing a conducting layer to be formed on an insulator. A mechanism explaining the formation of the three‐layered structure is discussed. The important reactions are the fast dissolution of nitrogen into the unreacted Ti and the thermal instability of the Ti silicide/Si3N4 interface. Copyright © 1990, Wiley Blackwell. All rights reserved