Hafnium silicide formation on Si(001)

The solid-state reaction of thick (similar to50 nm) and thin (similar tomonolayer) films of Hf with cleaned and oxidized Si(001) substrates was investigated. Upon annealing to 1000 degreesC, films of HfSi2 were formed after reaction times that depended upon the surface condition of the substrate before deposition. The chemical state of the reacted surfaces was characterized using x-ray photoelectron spectroscopy, and the shifts in binding energy upon silicide formation were recorded. Even for thick films, low-energy electron diffraction (LEED) revealed that the (2x1) pattern of the Si substrate emerged, suggesting that three-dimensional islanding of the HfSi2 film had occurred. The islanding behavior was investigated for both thick and thin films using LEED, atomic force microscopy, and scanning electron microscopy. Streaking in the LEED patterns for the thick films suggest that the island morphology is influenced by the underlying Si substrate.