Enhanced thermal performances of silicon-on-diamond wafers incorporating ultrathin nanocrystalline diamond and silicon layers: Raman and micro-Raman analysis

Silicon-on-diamond (SOD) wafers potentially present thermal advantages over standard silicon-on-insulator (SOI) counterparts based on SiO2 as the buried insulating layer. This work reports the fabrication of high quality SOD wafers by the bond and etch back SOI process. One key parameter in the CVD diamond growth process is the substrate temperature. We focused here on two processes based on either high or low processing temperature to produce nanocrystalline diamond (NCD) on silicon. Both type of NCD films have been analyzed via Raman spectroscopy. Results have been correlated with scanning electron microscopy observations. In a second part, SOD wafers are fabricated and the crystalline quality of the active silicon layer is assessed via Raman measurements and high resolution transmission electron microscopy imaging. It is shown that the growth of diamond did not induce any structural defect or strain in the thin top silicon layer. Eventually, we demonstrate the efficiency of diamond integration thanks to micro-Raman spectroscopy, where the probing laser simultaneously generates Raman signal and controlled local heating. Our SOD wafers evidence a thermal resistance reduction of about 70% compared to conventional SOI materials, with heat source spatial extension in the micron range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3643006]