CHARACTERIZATION OF SILANE-REDUCED TUNGSTEN FILMS GROWN BY CVD AS A FUNCTION OF SI CONTENT

Tungsten (W) films grown by low-pressure chemical vapor deposition using tungsten hexafluoride (WF6) and silane (SiH4) are characterized as a function of the Si content ([Si]) in the films. The electrical resistance, stress, and composition of as-deposited films showed a strong dependence on [Si] and could be classified into three groups: [Si] ≤ 2 atom percent (a/o), 2 ≤ [Si] < 20–40 a/o, and [Si] > 40 a/o. When [Si] ≤2 a/o, the electrical resistance is approximately proportional to [Si], and is mainly determined by impurity scattering of Si. In this [Si] region, W can be selectively deposited on Si. When 2 ≤ [Si] < 20–40 a/o, the temperature dependence of electrical resistance is characteristic of semiconductors, and a substantial increase in superconducting transition temperature (Tc = 4.4 K) is observed. When [Si] > 40 a/o, microcrystals of WSi2 begin to form. These results are discussed in terms of a model based on the solubility of Si in W. © 1990, The Electrochemical Society, Inc. All rights reserved.