Electron microscopy of defects in silicon-on-insulator structures formed by selective epitaxial growth

Abstract

In the interest of obtaining increased integrated circuit device density, a relatively new technology known as selective epitaxial growth (SEG) of silicon is being explored, especially for improved isolation of devices including possible three dimensional (vertical) integration. This technology involves the deposition and selective nucleation and growth of silicon from the vapor phase, seeded by the silicon substrate. The process is “selective” because nucleation and growth occurs on the silicon substrate but is prohibited on the oxide. The epitaxial silicon proceeds to grow upward and laterally over the oxide.Silicon deposition was performed in a horizontal hot-walled low pressure chemical vapor deposition (LPCVD) reactor. A dry thermal oxide was grown on the substrates, patterned, and etched to create seed windows. A 900 °C prebake was performed at a pressure of 6 torr in a hydrogen ambient for a period of 15 minutes, with in some cases, a small concentration (approximately 0.025%) of dichlorosilane (DCS) gas, and deposition was performed at 850 °C through the decomposition of DCS gas: SiH2Cl2 -> Si(s)+ 2HCl(g).