PROCESSING OF WSi2 FILMS BY LOW PRESSURE CHEMICAL VAPOR DEPOSITION FROM IN SITU CHLORINATION OF METAL

Abstract

An experimental investigation of WSi2 thin films by LPCVD from in situ elaborated metal chlorides is presented. The films composition and properties are studied as a function of input gas phase composition. Preliminary results show that WSi2 films can selectively grow on silicon. An attempt has been made to understand the results in terms of deposition conditions. As the feature of VLSl circuits continues to shrink below one micron, unmet requirements have driven industry to find alternative methods to achieve acceptable RC delay due to interconnection paths and to manage wafer topography issues. Because CVD tungsten and tungsten disilicide, WSi2, meet these requirements and offer diffusion barriers and improved electromigration resistance, the level of interest in this technology has mushroomed. At present the CVD WSi2 films are mainly processed by fluorine based reactive gases. However, additionally to the technical problems due to the high reactive nature of these gases, this process is rather delicate to optimize. An alternative solution may be the use of chlorides instead of fluorides as tungsten precursors. We have already illustrated the advantages of the chlorides by doing a comparative thermodynamic study of the two processes 111. We have proposed a controlled and reproducible way of production and transport of the tungsten chlorides. It consists of an in situ chlorination of a thermoregulated tungsten bed situated just above the substrate. We simulated and thermodynamically optimized the chlorination conditions and also analysed the resulting gaseous phase by mass spectrometry 121. Based on these two works we presented a first experimental study of the CVD of WSi2 at atmosperic pressure 131. This study showed the feasibility of the deposition from the chlorides and the qualitative agreement between the calculated and the