The formation of tungsten disilicide from WSi and WCrSi structures

Abstract

Abstract The direct reaction between tungsten and silicon (or chromium and silicon) to obtain tungsten disilicide from a thin metallic layer deposited on a silicon wafer was investigated. The metallic layer (W, or WCr) was sputtered on As- or B-implanted silicon. The samples were annealed under neutral atmosphere or forming gas in an annealing furnace (AF) or by rapid thermal process (RTP), and then analysed by secondary ion mass spectrometry (SIMS) and X-ray diffraction. For a fixed annealing time (AF: 30 min; RTP: 20 s), the temperature above which the tungsten disilicide was detected is 800 °C for RTP and 700 °C for AF, irrespective of the dopant type; this temperature was considerably lower when an intermediate chromium layer was deposited between tungsten and silicon. In all cases, the growth kinetics, i.e. disilicide thickness proportional to the square root of the time, were consistent with the mechanism of silicon atom diffusion.