CHEMICALLY VAPOR-DEPOSITED TUNGSTEN SILICIDE FILMS USING DICHLOROSILANE IN A SINGLE-WAFER REACTOR - GROWTH, PROPERTIES, AND THERMAL-STABILITY

Compositionally uniform (in depth and in lateral position) chemically vapor deposited WSichi films were deposited on 200 mm Si wafers in a s ingle-wafer reactor using SiH2Cl2/WF6 chemistry. A process window was found to produce highly uniform compositions in the range of 2.2 less than or equal to chi less than or equal to 2.6, regardless of the nucl eation surface, SiO2 or poly-Si. 900 degrees C annealing in N-2 of suc h films deposited on P-doped poly-Si resulted in a uniform reduction o f chi to a value of 2.1 to 2.2. In contrast, as deposited dichlorosila ne-WSichi films which are Si-poor at the interface, were found to deve lop a high concentration of Si in the middle layer of the annealed str ucture. The as-deposited resistivity was found to increase linearly wi th chi with a value of similar to 750 mu Omega . cm for chi approximat e to 2.5. Upon annealing, the resistivities decreased to values in the range of 80 to 110 mu Omega . cm. The as-deposited films were predomi nantly in the hexagonal. structure of WSi2, which transformed to the t etragonal structure upon annealing at temperatures higher than 600 deg rees C. As-deposited stresses were in the range of (1.3 to 1.6) . 10(1 0) dyne/cm(2), and upon annealing reduced to similar to 1 . 10(10) dyn e/cm(2). The films had a very good step coverage even at high aspect r atios and did not crack or peel off upon annealing. The films containe d relatively low levels of impurities: F similar to 6 . 10(16) to 2 . 10(17) and Cl similar to 5 . 10(17) to, 1 . 10(19) atom/cm(3). This sy stematic study reviews the correlations between the structural, compos itional, mechanical, and electrical properties of the as-deposited and the annealed silicide films.