Abstract
Semiconductor devices will soon reach physical limitation and several new technologies have been proposed to overcome it. Among them are silicon-on-insulator (SOI) substrates, which are thought to be ideal substrates since they reduce the body effect and parasitic junction capacitance, which degrade device performance. Additionally, fabricating devices on SOI substrates less than several ten nanometers thick and operating them in the fully depleted mode offers further performance advantages. Several techniques have been proposed to fabricate SOI substrates, such as oxygen-ion implantation, wafer bonding with a thinning process or hydrogen-ion implantation. The remaining issue is how to improve the crystalline quality of SOI substrates using these techniques. Since the substrates are formed in the thermally equilibrium condition at high temperature, the difference of thermal expansion coefficients induces defects and interface strains during the cooling process. Grazing incidence x-ray diffraction (GIXD) is more sensitive to the internal strains of thin SOI since the penetration depths of x-rays can be controlled by changing incident angles. We have recently succeeded in observing the strain structures of various SOI substrates in real-time using the GIXD technique.
