Teruaki Motooka

Growth of Si/3C–SiC/Si(100) heterostructures by pulsed supersonic free jets

We have investigated the epitaxial growth of multilayer structures of Si/3C–SiC/Si(100) by pulsed supersonic free jets of methylsilane (CH3SiH3) for SiC growth and trisilane (Si3H8) for Si growth. Epitaxial Si layers were obtained only on very thin (≈3 nm) 3C–SiC epitaxial layers, while polycrystalline Si was grown on thicker 3C–SiC layers. It was also found that the transition regions with a thickness of ≈1 nm existed at the interface between epitaxial 3C–SiC and Si layers by high-resolution transmission electron microscopy observation. These results suggest that the surface roughness and thickness of the 3C–SiC layer play an important role for epitaxial growth of Si.

Recrystallization of MeV Si implanted 6H‐SiC

Microstructures of recrystallized layers in 8 MeV Si3+ ion implanted 6‐H‐SiC (0001) wafers have been characterized by means of transmission electron microscopy. Epitaxial recrystallization of buried amorphous layers was observed at annealing temperature as low as 1000 °C. Layer‐by‐layer epitaxy of 6H‐SiC initially occurred and it was changed to columnar growth when layer‐by‐layer growth exceeded 100 nm in thickness. From the microdiffraction analysis, it was found that the columnar regions are defected 6H‐SiC with crystal orientations different from the substrate. In addition to 6H‐SiC, epitaxial 3C‐SiC was also confirmed in the recrystallized layer. Based on these results, we have proposed a structure model of the recrystallized layer in which stacking faults in the columnar regions are induced by mismatched connections between the columnar and layered 6H‐SiC regions.

Growth of Ultrathin Epitaxial 3C-SiC Films on Si(100) by Pulsed Supersonic Free Jets of CH3SiH3

We have developed a new method for epitaxial growth of ultrathin (~nm) 3C-SiC films on Si(100) by pulsed supersonic free jets of methylsilane (CH3SiH3). It was found that pit formation at the SiC/Si(100) interface was suppressed by increasing the pulse width and the surface roughness was decreased by decreasing the number of CH3SiH3 jet pulses. A linear relationship was observed between the film thickness and the pulse number in the thin film region of less than ≈40 nm, while the growth rate was decreased and the thickness was eventually saturated for further pulse irradiation.

Amorphization and solid phase epitaxy of high-energy ion implanted 6H-SiC

Abstract We have investigated microstructures of damaged and recrystallized layers in MeV-ion implanted 6H-SiC (0001) wafers by means of cross-sectional transmission electron microscopy. The substrate surfaces were implanted at 160°C with 1 × 1017/cm2 8 MeV Si3+ ions using a tandem accelerator. A buried amorphous layer was formed ranging from ∼ 1.6 μm to ∼ 3.4 μm in depth. The amorphous/crystalline transition regions consisted of many stacking faults perpendicular to the [0001] direction, and their density increased toward the amorphous region. The amorphous layer regrew epitaxially from the undamaged substrate at an annealing temperature of ∼ 1000°C. This epitaxial 6H-SiC layer changed to columnar 6H-SiC with crystal orientations different from the substrate. In addition to these crystalline 6H-SiC, the existence of polycrystalline 3C-SiC was confirmed in the middle part of the recrystallized layer.

Epitaxial Growth of a Low-Density Framework Form of Crystalline Silicon

Crystal growth processes of low-density framework forms of crystalline silicon, named Si clathrates ( Si34 and Si46), during solid phase epitaxy (SPE) have been successfully observed in molecular-dynamics simulations using the Tersoff potential. The activation energy of SPE for Si34 has been found to correspond with the experimental value ( approximately 2.7 eV) for the cubic diamond phase, while the SPE rates of Si46 are much lower than that of Si34. The structural transition from Si46 to Si34 can be also observed during the Si46-[001] SPE. The present results suggest that new wide-gap Si semiconductors with clathrate structures can be prepared using epitaxial growth techniques.

Epitaxial growth of 3C–SiC on Si(100) by pulsed supersonic free jets of Si(CH3)4 and Si3H8

Heteroepitaxial growth of 3C–SiC on Si(100) by pulsed supersonic free jets of Si(CH3)4 and Si3H8 with various mixture ratios has been investigated. The heteroepitaxy is achieved at the substrate temperature of 900 °C without any carbonization process. The films grown by pure Si(CH3)4 contain inverse pyramidal pits surrounded by the {111} planes of Si, while {311} faceted pits are formed by mixing Si(CH3)4 with a small amount of Si3H8. When the Si3H8/Si(CH3)4 ratio further increases, pit formation is suppressed and instead Si islands are epitaxially grown from the pit region.

Transmission electron microscopy studies of crystal-to-amorphous transition in ion implanted silicon

The microstructure of 5 MeV ion implanted silicon at room temperature has been investigated in detail by means of cross-sectional transmission electron microscopy. Buried amorphous layers were observed in the specimens obtained by ion doses of 1×1017 and 2×1017/cm2 with abrupt amorphous-to-crystal interfaces. Damaged layers adjacent to the amorphous layers included many dislocation loops and the concentration increased toward the amorphous region. Microdiffraction patterns and high-resolution images showed that this damaged region is defective crystalline silicon, suggesting that homogeneous amorphization occurs due to an accumulation of defects. The atomistic structure of the damaged regions was analyzed by comparing high-resolution electron microscopy images with those calculated on the basis of a model for amorphization processes proposed previously [T. Motooka, Phys. Rev. B 49, 16 367 (1994)].

Epitaxial growth of Si by ArF laser‐excited supersonic free jets of Si2H6

Epitaxial growth processes of Si from ArF laser‐excited Si2H6 supersonic free jets have been investigated using reflection high‐energy electron diffraction, growth rate, and atomic force microscopy measurements. Layer‐by‐layer epitaxial growth was observed at substrate temperature Ts=670 °C regardless of the laser excitation. However, it was found that island growth was predominant at Ts=550 °C without the laser excitation, while layer‐by‐layer growth occurred by using the ArF laser‐excited Si2H6 jet probably due to an enhancement of surface reactions induced by precursor species obtained from laser‐excited Si2H6 .

Sensitivity analysis of scanning microwave microscopy for nano-scale dopant measurements in Si

We analyzed the sensitivity of scanning microwave microscopy (SMM) for doping concentration measurements in n-type Si based on the conventional equivalent-circuit model combined with numerical simulations of carrier distributions in metal-oxide-semiconductor capacitors. The minimum detectable change in capacitance was estimated to be 0.26 aF for the amplitude of the applied 17 GHz microwave voltage of 0.3 V. Possible measurable range of electron concentrations in Si was found to be 1015–1020 cm−3 with ∼10%–1% accuracy by using nano-scale flat-shaped tips for SMM measurements.

Amorphization Processes in Ion Implanted Si: Temperature Dependence

Temperature dependence of amorphization processes in ion-implanted Si has been investigated using Raman spectroscopy together with cross-sectional transmission microscopy. The crystal Si Raman peak decreased and the amorphous Si (a-Si) peak became predominant as the substrate temperture was decreased from 23°C to -200°C during 200 keV Si+ ion implantation with a dose of 5×1014 cm-2. Based on the analysis of bond angle deviations derived from the a-Si peaks, we have proposed a model in which an accumulation of small defects induces amorphization at low temperatures, while at higher temperatures larger defect complexes are formed and an accumulation of them gives rise to defected amorphous Si.