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

Abstract

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 number was estimated to be three or four after annealing at 1050 °C. Since the defect complexes were stable even after annealing at such a high temperature, the defects detected by the positrons could be part of chainlike vacancy clusters.

Positron annihilation studies of defects in Si1‐xGex/SOI heterostructures

“…As pointed out by Uedono et al [6], positrons can effectively characterize point defects in thin strained overlayers. Point defects are connected, for example, to dislocation motion, dopant diffusion and Si-Ge interdiffusion and are produced by semiconductor deformation [7].…”

Open volumes in SiN films for strained Si transistors probed using monoenergetic positron beams

“…6,10,11 For the samples in which positrons are fully trapped by defects ͑ion implanted semiconductors, amorphous materials, etc.͒, the L d value is below 5 nm. 3,6,8,12 Thus, for sintered Si 3 N 4 , the fraction of positrons trapped by vacancy-type defects is unlikely to be high. The lifetime spectrum of positrons for Si 3 N 4 was measured and then decomposed into two components, for which the derived lifetimes of positrons ͑ i , i = 1 and 2͒ and the second intensity ͑I 2 ͒ were 1 = 236± 2 ps and 2 = 470± 6 ps ͑I 2 =17% ±1%͒, respectively.…”

Local Bonding Structure of High-Stress Silicon Nitride Film Modified by UV Curing for Strained Silicon Technology beyond 45 nm Node SoC Devices

“…The S parameter correlates closely with the size of the vacancies in the film. 8,9) UV-modified HS-SiN has a reduced S parameter compared with the as-deposited p-SiN film with 0.3 GPa tensile stress. This result indicates that the vacancy in the p-SiN film shrinks during UV curing.…”