Hideki Naruoka

Vacancy-type defects in strained-Si layers deposited on SiGe∕Si structures probed by using monoenergetic positron beams

Vacancy-type defects in strained-Si layers deposited on Si0.75Ge0.25∕graded-SiGe∕Si structures were probed by using monoenergetic positron beams. The Doppler broadening spectra of the annihilation radiation and the lifetime spectra of the positrons were measured for samples before and after annealing (800–1050 °C). For an as-received sample, the defects in the strained-Si layer were identified as vacancy-type defects coupled with Ge. The mean open size of these defects was estimated to be close to that of a divacancy. The line-shape parameter, S, corresponding to the positron annihilation in the strained-Si layers decreased with increasing annealing temperature, but no large change in the positron lifetime was observed. From a comparison between the Doppler broadening profiles for the strained-Si films and those calculated using the projector augmented-wave method, it was found that the number of Ge atoms forming a complex by coupling with a defect increased with increasing annealing temperature. The numb...

Preliminary study of a novel scanning charge-pumping method using extra gates for SOI wafer inspection

A novel scanning charge-pumping method using one or more extra contactless gates is proposed for silicon-on-insulator (SOI) wafer inspection. In the proposed method, a contactless; gate electrode is used as a measuring gate instead of the permanent gate electrode of normal metal-oxide-semiconductor transistors, allowing a wafer map of interface trap density to be obtained. A preliminary study is carried out using a sample device having two extra gate electrodes in the close vicinity of a measuring gate electrode, which are contacted on an oxidized SOI wafer. The results demonstrate that the proposed method is a promising technique for the characterization of interface trap density in SOI wafers.