Silica, SiO2, is formed on silicon as an electrically insulating layer for micro

Question

Silica, SiO2, is formed on silicon as an electrically insulating layer for microelectronic devices. Silica is formed when silicon is exposed to O2 gas at an elevated temperature. At 900?C, it takes 95 minutes for the oxygen to diffuse from the surface to form a 0.06 micron thick layer of SiO2 on a very thick silicon plate. At this same temperature, how long (total time, in minutes) will it take for oxygen to diffuse to form a 0.05 micron thick layer of SiO2? Assume that the silicon can be treated as a semi-infinite solid with a constant concentration of oxygen at the surface. (Hint: What is true of the oxygen concentration at the Si/SiO2 interface?) Round your answer to the nearest minute.

Explanation / Answer

Silicon on insulator (SOI) technology refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance, thereby improving performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator, typically silicon dioxide or sapphire (these types of devices are called silicon on sapphire, or SOS). The choice of insulator depends largely on intended application, with sapphire being used for high-performance radio frequency (RF) and radiation-sensitive applications, and silicon dioxide for diminished short channel effects in microelectronics devices. The insulating layer and topmost silicon layer also vary widely with application. The first industrial implementation of SOI was announced by IBM in August 1998.

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