Silicon on Sapphire of Single Crystal Quality Obtained by Double Solid Phase Epitaxial Regrowth

Abstract

AbstractA dual-implantation and annealing procedure has been refined which results in silicon films of single crystal perfection on sapphire substrates. This double solid phase epitaxy (DPSE) procedure consists of two self-implantation steps that serve to amorphize the defect structure of the parent silicon film with subsequent annealing steps employed to recrystallize the amorphized structure. High resolution cross-section transmission electron microscopy (HRXTEM) and ion channeling have been employed to study the microstructure of the silicon films, the sapphire substrates, and the interface. The resulting perfection of the silicon layer is shown to be a sensitive function of the first self-implant energy, dose, and silicon film thickness. Also, a correlation has been established between microtwin density and dechanneling profiles. HRXTEM of microtwins in silicon on sapphire (SOS) starting material demonstrates contrast features identified as rotational Moire' fringes between the microtwins and the matrix by means of optical diffractometry. Best results are achieved for the first implant energy of 170 keV 28Si+. Thus, the DSPE process is shown to give optimal results in defect reduction.