A simple electrical method to determine the Si and oxidethicknesses in SOI materials

It is shown that the thickness of the silicon and oxide layers of a silicon-on-insulator (SOI) structure can be determined from high-frequency capacitance-voltage measurements. The test device consists of a Schottky diode in series with a Si-oxide-Si capacitor. The Si film and the substrate are n-type. The operation of this device is explained for n-type Si with the help of the energy-band diagrams. It is demonstrated that this simple test device can be implemented as a process monitor for silicon thickness control