| The oxidation of electrochemically etched porous silicon (Si) has demonstrated success in the formation of device quality Localized Silicon on Insulator (L-SOI) for Complementary Metal Oxide Semiconductor (CMOS) applications [1, 2]. A primary advantage of L-SOI formation is the ability to integrate novel device structures and optoelectronics (i.e. optical switches, waveguides) with bulk silicon CMOS. The formation of porous Si can be selective by controlling the Fermi level in areas to be etched or not etched, which is typically done by adjusting the level of doping [1]. An alternative method is to introduce a reversible donor species such as protons [2] or fluorine (this work) for the selective formation of islands of crystalline silicon surrounded by porous silicon. Implanted fluorine in silicon has demonstrated a donor effect upon annealing at low temperature (600°C), which is reversible as the fluorine out diffuses during higher temperature annealing (1000°C). Crystalline silicon islands that were fabricated with this technique have a thickness of about 150nm and are completely surrounded by oxidized porous silicon. Further study to investigate the device quality of the L-SOI structures for microelectronic applications and optoelectronic applications has been done by building transistors for microelectronic application and waveguides for optoelectronic application. |
