Near-Room Temperature Deposition of W and WO 3 Thin Films by Hydrogen Atom Assisted Chemical Vapor Deposition
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NEAR-ROOM TEMPERATURE DEPOSITION OF W AND WO3 THIN FILMS BY HYDROGEN ATOM ASSISTED CHEMICAL VAPOR DEPOSITION Wei William Lee* and Robert R. Reeves** * IBM Research Division, Almaden Research Center, San Jose, CA 95120-6099 ** Department of Chemistry, Rensselaer Polytechnic Institute, Troy, NY 12180-3590 ABSTRACT A novel near-room temperature CVD process has been developed using H-atoms reaction with WF6 to produce tungsten and tungsten oxide films. The chemical, physical and electrical properties of these films were studied. Good adhesion and low resistivity of W films were measured. Conformal W03 films were obtained on columnar tungsten using a small amount of molecular oxygen in the gas stream. A reaction mechanism was evaluated on the basis of experimental results. The advantages of the method include deposition of adherent films in a plasma-free environment, near-room temperature, with a low level of impurity.
INTRODUCTION The development of chemical vapor deposition (CVD) has recently progressed to the point where low-temperature preparation of a wide variety of materials must be considered necessary. As microelectronic technology advances with device features in the submicron range, new metallization materials and processes are needed. For ultra large-scale integration (ULSI) metallization applications, these materials must have low resistivity, low contact resistance, high electromigration resistance, good adherence and step coverage and conformality. In order to satisfy these requirements, the refractory metals (tungsten in particular) as well as their disilicides are of interest [1-5]. Deposition of tungsten and other materials at relatively high temperature could result in undesirable diffusion and redistribution of materials to unwanted areas. Hence, there is a need for low-temperature deposition technology for UTLSI applications. In the present investigation, the deposition of tungsten and tungsten oxide have been studied using hydrogen atom reaction with tungsten hexafluoride. In this process, atomic hydrogen has been generated and reacted with tungsten hexafluoride to deposit W and W03 films at near-room temperature. The conventional W deposition process has used molecular hydrogen to react with WF6 in the temperature range of 300-600 °C. The objective of this research was to investigate the gas phase reaction between H-atom and WF6 and characterize the deposited films in order to optimize the deposition conditions. Atomic absorption spectroscopy was used for the in-situ measurement of W-atoms during deposition and results of these measurements provided a basis for the reaction mechanisms. Mat. Res. Soc. Symp. Proc. Vol. 250. @1992 Materials Research Society
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EXPERIMENTAL PROCEDURE Tungsten and tungsten oxide thin films were prepared in a horizontal atom-assisted CVD system. Apparatus for this work was described previously [6]. The pressure of the deposition was typically in the range of 0.01 to 1.0 mm Hg. Hydrogen atoms (10-20%) were produced upstream of the deposition chamber in a U-shaped di
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