Barrier characteristics of chemical vapor deposited amorphous-like tungsten silicide with in situ nitrogen plasma treatment

Abstract

Our team investigated the characteristics of inserting an 80 nm amorphous-like WSi1.6N0.5N/WSi1.6 barrier layer between aluminum film and a shallow diode to retard aluminum and silicon interdiffusion. In one chamber without breaking vacuum, we used a nitrogen plasma treatment to stuff nitrogen atoms into the grain boundaries of amorphous-like tungsten silicide film. The nitrogen atoms eliminated the fast diffusion paths of film, thus giving the amorphous-like tungsten silicide film a smaller diffusion coefficient. We then examined the failure of diodes with amorphous-like WSi1.6N0.5/WSi1.6 barriers which were annealed at 575 degrees C for 30 min and which had leakage currents of 10(7) and 10(8) nA/cm(2). These diodes failed due to the diffusion of aluminum along the sidewalls of the barriers and the field oxide interface. In the search for a solution to this problem we investigated the use of tetraethylorthosilicate, which is known for its thermal stability as a stress buffer. In this experiment we used tetraelhylorthosilicate to form a "contact array structure" which in turn prevented diode failure at 575 degrees C annealing for 30 min, and furthermore, the diodes in the contact array structure only began to show evidence of degradation at 600 degrees C. (C) 1999 The Electrochemical Society. S0013-4651(98)09-086-7. All rights reserved.