Hisayoshi Ohshima

Study of shallow donor formation in hydrogen-implanted n-type silicon

Formation of shallow donors has been studied in 100 keV hydrogen-implanted n-type silicon with a dose of . Annealing experiments are made in the temperature range 100 to C for 30 min. Gold Schottky contacts are fabricated on these samples to obtain carrier profiles. The hydrogen profiles are measured by secondary-ion mass spectroscopy. The zero-bias depletion layer width measured at 90 K is below the pre-implantation value in the annealing temperature range 300 to C, indicating the introduction of shallow donors. Two kinds of shallow donor (HS1 and HS2) are found to be formed in this annealing temperature range from carrier profile measurements. The HS1 donor is observed at the annealing temperatures around C and shows a concentration peak at the depth around the mean projected range of implanted hydrogen. The HS2 donor is observed in the annealing temperature range 350 to C and spreads toward the surface with almost flat profiles. Comparison of carrier and hydrogen profiles indicates that the HS1 donor is hydrogen related. The possibility that the HS2 donor is also hydrogen related is discussed.

Hydrogen-implantation-induced activation in phosphorus-implanted silicon

A partial activation of phosphorus -implanted (100) silicon substrates was found to be induced by a subsequent hydrogen ion implantation at . The energy, dose and dose rate dependences of activation were studied using spreading resistance, secondary-ion mass spectroscopy and transmission electron microscopy. In the investigated range of 10 to 60 keV we found 30 keV to be the most suitable implantation energy for activation of -implanted samples at 80 keV without changing the phosphorus depth profile. The activation had a depth profile which was similar to the hydrogen depth profile immediately after implantation. The activation proceeded with increasing dose and decreasing dose rate. A reduction in the density of residual defects was observed with decreasing dose rate. Further electrical activation was achieved by annealing at with a sharper carrier concentration profile for -implanted samples than for just -implanted samples. The activation and annealing mechanism is discussed in view of the contribution of the elastic collision process between ions and substrate atoms.

Molecular Orientation and Photochemical Reaction of Organoaluminum Compounds Investigated by Buried Metal Layer Infrared Reflection Absorption Spectroscopy

The structure and synchrotron radiation (SR) irradiation effects of the low-temperature condensed layer of several organoaluminum compounds on the SiO2 surface were investigated by infrared reflection absorption spectroscopy using a buried metal layer substrate (BML-IRAS). Trimethylaluminum is a dimer at temperatures lower than 180 K, and a photoproduct having the methyl group is produced by SR irradiation. The condensed layer of dimethylethylamine alane (DMEAA) as-deposited at temperatures less than 140 K consists of randomly oriented dimer molecules, and changes to a more ordered orientation of monomer molecules at temperatures higher than 140 K. Concerning the SR irradiations, the results are different for the two different molecular orientations. Upon SR irradiations of the ordered orientation layer, a new broad vibration band, possibly assigned to the aggregation of inhomogeneous AlH stretching vibrations, appears. On the other hand, in the case of the random orientations of the dimer molecules, such a new broad band does not appear, and only an intensity decrease is observed for all bands.

Soft X-Ray Emission Spectroscopic Analysis of Pt Silicides (Pt2Si, PtSi).

We have studied the partial valence band density of states (VB-DOS) of Pt-silicides by using soft X-ray emission spectroscopy (SXES). Si Kβ emission spectra of Pt2Si and PtSi provide information on the Si p partial VB-DOS, showing the clear bonding and antibonding states. The contribution of Si s and/or d states to the upper part of VB-DOS has also been observed from the Si L2,3 emission spectra of Pt2Si and PtSi. Such a contribution of the Si s and/or d state to the upper part of the VB-DOS has not been predicted by previous theoretical studies.

High Sensitivity FT-IR-Ras for Silicon Surface Study

A novel configuration for Fourier-transform infrared reflection absorption spectroscopy (FT-IR-RAS) has been devised to study the nature of silicon wafer surfaces in the wide IR irradiation region (especially below 1300 cm −1 ) with high sensitivity. The configuration is basically similar to a conventional one of FT-IR-RAS except that a optical-flat mirror is placed on a silicon wafer surface and the IR beam is incident on the back side of the wafer with a grazing angle. The sensitivity of the novel technique was estimated by the observation of the stretching vibration absorption of the Si-H x bond (2070-2150 cm −1 ) on HF/NH 4 F-treated Si(111) surfaces and Si-O bond (1000-1250 cm −1 ) of chemically oxidized layer ( ∼0.7 nm ) on Si(111) surfaces. The dependence of Si-H x absorption peaks intensities on the composition of HF/NH 4. F solutions was clearly observed. Furthermore, Si-O bond peak corresponding to the longitudinal optical phonon was also detected.

Novel technique of infrared reflection absorption spectroscopy for Si surface study

It is demonstrated that Fourier-transform infrared reflection absorption spectroscopy with a novel arrangement is a powerful technique to study the nature of Si surfaces. The technique was applied to the observation of the Si-H bond absorption (2083 cm-1) on HF- or NH4F-treated Si(111) surfaces and the Si-O-Si bond absorption (1000-1300 cm-1) of oxides on the Si surface formed by native oxidation in air. Both absorptions were clearly observed.