Study of dynamics and mechanism of metal-induced silicon growth

The present study addresses the mechanism of metal-induced growth of device-quality silicon thin films. Si deposition was performed by magnetron sputtering on a 25-nm-thick Ni prelayer at 525-625°C and yielded a continuous, highly crystalline film with a columnar structure. A Ni disilicide intermediate layer formed as a result of the Ni reaction with Si deposit provides a sufficient site for the Si epitaxial growth because lattice mismatch is small between the two materials. The reaction between Ni and Si was observed to progress in several stages. The Ni_xSi_y phase evolution in a Ni:Si layer was studied by x-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, transmission electron microscopy, and x-ray diffraction and found to be controlled by the Ni-to-Si concentration ratio at the growing front. After Ni is completely consumed in the suicide, continued Si deposition leads to the nucleation and growth of Si crystals on the surface of the NiSi₂ grains. The issues related to the nature of Ni_xSi_y, phase transformations and Si heteroepitaxy are discussed.