The formation of an amorphous silicide by thermal reaction of sputter-deposited Ti and Si layers

The initial reaction in amorphous Si-Ti-amorphous Si trilayers was investigated with Auger electron spectroscopy, transmission electron microscopy, and x-ray diffraction. It was clearly demonstrated that at temperatures not exceeding 450 °C an amorphous Ti-Si alloy is formed. At temperatures of 500 °C and higher, crystalline TiSi2 with the ZrSi2 (C49) structure was found. The growth kinetics of the amorphous silicide could not be described by a simple diffusion controlled process. It was shown that at 400 °C the thickness of the amorphous silicide is limited to approximately 18 nm. Since it was found that the growth of the amorphous phase is accompanied by excessive Kirkendall void formation, it is proposed that these voids eventually suppress the growth of amorphous silicide. The composition of the amorphous phase was determined to be between TiSi0.9 and TiSi1.2, i.e., close to the composition of the monosilicide.