A novel method of preparation of silicon-on-diamond materials

Silicon-On-Diamond (SOD) technology has been proposed as a possible improvement of the widely used Silicon-On-Insulator (SOI) system. In the SOD concept thermally insulating SiO2 is replaced by extremely thermally conductive diamond. SOI technology is also involved in the implementation of monolithic pixel sensors (MAPS.) A similar approach could be possible with a SOD structure where diamond could also play the role of the bulk sensor. In this framework, we have implemented a technology which allows the bonding of independently chosen diamond and Si and can be used both for polycrystalline and single-crystal chemical vapour deposited diamond. The bonding between Si and diamond has been obtained by exposing the silicon-diamond interface to UV laser short pulses from the diamond side. The polished silicon and polycrystalline) diamond surfaces have been previously characterized by optical interferometry in order to evaluate the pressure needed to obtain the highest proximity of the two materials , which is critical to the outcome of the process. The formed silicon-diamond interface has been tested for thermal and mechanical stress, and for uniformity by electron and atomic force microscopy, yielding uniform and continuous bonding between the two materials. Micro-Raman and FTIR spectroscopy show evidence of interface layers of SiC and amorphous silicon, whose thicknesses do not exceed 100nm, and absence of graphite-like carbon phases. The characterization of the obtained SOD samples is presented and dicussed in detail.