Characterization of laser-ablated boron nitride thin films on silicon

Abstract

The ability to grow heteroepitaxial cubic boron nitride (cBN) films is the first step in the development of a process to grow electronic-grade, doped cBN films. This will eventually facilitate the development of cBN-based, high speed integrated circuits. Such a capability is critical to the development of ultra fast and high power density devices. Recent work is reported here on the characterization of BN thin films grown on 1 cm2 (100)Si substrates using a newly developed reactive laser ablation technique. The exact nature of the resulting films is highly process dependent and can yield any of the common BN crystal structures, i.e. cubic, hexagonal or wBN. This paper presents the results of Fourier transform IR spectroscopy, channelling and thermal wave analysis on various BN films resulting from that reactive laser ablation process. The results presented from channelling experiments on the cBN films show the heteroepitaxy of the cBN films. In those films, the (100) plane of the resulting heteroepitaxial cBN layer is parallel to the (100) plane of Si, with the (011) plane of the film parallel to the (001) plane of the Si substrate, i.e. a 45° rotation of the cBN lattice relative to the Si lattice. It is believed that the thermal diffusivity value reported here for the cBN thin film is the highest value measured for such films to date.