A high-quality thin Si layer on epitaxial spinel(MgO·Al2O3) on Si substrate has been developed. It was obtained by the solid phase epitaxial (SPE) regrowth of amorphous Si with Si seed islands on the epitaxially grown spinel. The SPE-Si layer on the epitaxial spinel was superior to conventional Si on sapphire (SOS) in stacking-fault density, Hall mobility, and contamination from the insulating materials. The SPESi layer has low stacking-fault density of 10–50 cm-2, even for 0.4 μm thickness. This value is eight orders of magnitude less than that of Si on epitaxial spinel obtained by vapor phase epitaxial (VPE) growth with SiH4. The SPE-Si also has high electron Hall mobility of 880 cm2/V-s for n=5×l016 cm-3, for 1-μm-thick Si. This value is about 85% of that in bulk Si, and is higher than that in Si on spinel grown by VPE-growth and SOS. (100) spinel layer was grown on (100) Si substrate by a MgCI2-Al-HCI-CO2-H2 VPE growth system. After thermal oxidation, Si seed islands were grown on the spinel by the pyrolysis of SiH4. Amorphous Si was deposited on the Si seed islands by chemical vapor deposition (CVD) of SiH4. The SPE-Si layer was obtained by regrowth of the amorphous Si in a hydrogen atmosphere.

Epitaxial Si films have been grown on single crystalline CaF2 on (l00)Si substrates by molecular beam epitaxy(MBE) or combination of MBE and solid phase epitaxy(SPE) of deposited amorphous Si(a-Si). It has been found that Ca and F segregate at the surface of the Si grown by MBE. The high energy electron diffraction (RHEED) patterns from the Si surface show the superstructures which are caused by the existence of Ca and F at the Si surface. To reduce the segregation effect, SPE process has been successfully applied to Si epitaxy. The Si SPE performed on top of the MBE Si layer reduces the Ca concentration at the Si surface by an order of magnitude, although the segregation effect is not completely suppressed.

Rapid thermal annealing (RTA) has been shown to be a useful technique for improving the epitaxial quality of CaF2 films grown on Si(100) by molecular beam epitaxy. We have modified the annealing procedure to prevent crack formation, while still maintaining high film quality. Our work also shows RTA to be useful for improving the crystalline quality, chemical stability, and electrical characteristics of CaF2 films grown on Si(111). After RTA, the crystallinity of CaF2 films on Si(111), as measured by electron channeling, is indistinguishable from bulk single crystal CaF2, and the interface state density is reduced by nearly two orders of magnitude from that found in as-grown films.

This work outlines an optimized seed selection through ion channeling (SSIC) process for enhancing the grain size and {110} texture of polycrystalline Si films grown by LPCVD on SiO2. These films, 0.44 μm thick, were self-implanted at normal incidence to various doses (1×1014 - 20×l014 cm-2) and then recrystallized at 600°C. An enhanced average grain diameter resulted after implantation and annealing, ranging from 0.10 to 2.0 μm (vs. the as-deposited 0.080 μm) and increasing with the implant dose. The grain size vs. implant dose behavior may be explained by a previously proposed stochastic model. An enhanced {110} texture was also observed after processing for implant doscs in the range 6×1014 - 14×1014 cm-2. The optimal dose was 11×1014 cm-2, for which the <110> directions were confined to within ±4° (vs. the as-deposited ±20°) of the surface normal. The overall results suggest a strong potential of SSIC in growing large-grain, restricted fibertextured polycrystalline Si thin films on amorphous insulators.

We studied the selective epitaxial deposition of silicon in patterned oxide-free regions over silicon dioxide in a RF-heated, commercial, reduced-pressure epitaxial reactor, using SiH2Cl2/HCl/H2 gas system. We found that etching into silicon occurs at the high end of HCl content, and nucleation on the silicon dioxide at the low end of HCl content. The selective epitaxial growth of silicon islands is obtained in between.

Solid-phase epitaxial regrowth of polysilicon films. amorphized by a room-temperature silicon implant. has been achieved using a (low temperature) furnace anneal or a (high temperature) rapid thermal anneal. Lateral extension of the growth onto an oxide layer, 4 μm wide, has also been observed. The electrical properties of the films were examined by building MO2S devices in them. Average electron mobilities of 520 cm2/v-sec and 200 cm2/v-sec have been measured for films regrown on top of silicon and oxide respectively.

Local variation of photoluminescence (PL) spectra for MBE GaAs grown on an insulating substrate with Ge-islands interface layers, prepared by zone melting recrystallization, has been investigated. The GaAs layers on the single crystalline Ge islands emit PL, the intensity of which was almost comparable to that of the GaAs layers on bulk Ge, while by a factor of 50 lower PL intensity was observed for the GaAs layers on Si02. PL spectra were found to show peak shifts due to the band-gap variation near the interface layer of GaAs, which was in good agreement with the residual strain obtained by microprobe Raman scattering for underlying Ge islands.

Excimer laser annealing at 248 nm has resulted in the recrystallization of a-GaAs on (100) silicon. An AlAs encapsulation layer was found to be necessary to prevent the loss of arsenic during laser annealing. An energy density of 105 mJ/cm2 was the critical energy density which gave optimum results. Field effect transistors were fabricated on the regrown (100) GaAs utilizing ion implantation for the n-type channel, and resulted in a transconductance of 70–80 mS/mm.

100 μm-wide silicon-on-insulator (SOI) structures have been accomplished by utilizing silicon molecular beam epitaxial (Si-MBE) growth on porous silicon anid subsequent lateral-enhanced oxidation of porous silicon through pattern widows. A silicon beam method was used for insitu cleaning of Si surface at 750°C, and the effectiveness of this method was demonstrated by Auger electron spectroscopy and checked by the etch-pit density of the grown film. A two-step growth process of Si MBE was used to grow epitaxial layers of high quality. An electron mobility of 1300 cm2V-1s-1 was obtained by van der Pauw measurements.

We report results on the feasibility of forming buried conductors under single crystal silicon using low pressure chemical vapor deposition of tungsten on the internal surfaces of porous silicon. The infiltration of tungsten into the pores depends on the porous silicon porosity, and on tungsten deposition process parameters such as deposition duration, total deposition pressure, and carrier gas species. The resulting tungsten-porous silicon layers were characterized by transmission and scanning electron microscopy, by Rutherford backscattering and x-ray spectroscopy and by four-point probe resistivity measurements.

The synthesis of buried layers of SiO2 and Si3N4, by ion implantation is reviewed. This process, which may be used to form device worthy silicon-on-insulator (SOI) structures, involves (i) implantation of O+ or N+ ions and (ii) high temperature processing to achieve defect annealing and chemical segregation of the implanted species.

The top silicon layer in as-implanted SIMOX wafer is usually too thin to support device fabrication. Hence, an epitaxial layer is usually grown on a SIMOX wafer after oxygen ion implantation and anneal. Because this epitaxial layer is typically very thin,less than 500 nm) and because of the material structure of the S1MOX wafer, special care has to.be exercised in order to obtain desirable epitaxial growth. This paper describes the unique problems of epitaxial growth on SIMOX.

Ion beam synthesis of a buried SiO2 layer is an attractive silicon-on-insulator technology for high speed CMOS circuits and radiation hardened devices. We demonstrate here a new annealing procedure at 1405°C that produces silicon films of excellent quality, essentially free of oxygen precipitates and with sharp interfaces between the Si and the SiO2.

We have carried out a study to understand the mechanisms involved in the formation of buried SIO2 by high dose implantation of oxygen into Si targets. Oxygen ions were implanted at 150 keV with doses up to 2.5 X 1018 ions/cm2 and a current density of less than 10 μA/cm2 into Si 〈100〉 at room and liquid nitrogen temperatures. In-situ Rutherford backscattering (RBS) analysis clearly indicates the formation of uniform buried SIO2 for both room and liquid nitrogen temperatures for doses above 1.5 X 1018/cm2.

Oxygen ions were implanted at room temperature into crystalline quartz to doses of about 1018 ions cm2 at 150 keV, with a current density of 〈10〉10 μA/cm2. The RBS spectra of the oxygen implanted quartz cannot be distinguished from those of unimplanted ones. Furthermore, Si ions were implanted into crystalline quartz at 80 keV and dose of 1 X 1017 Si/cm2, and a current aensity of about 1 μA/cm2. However, no signal from Si in excess of the SiO2 ratio could be observed. Our results obtained by RBS show that implantation of either Si+ or O into SiO2 under conditions stated above does not create a layer whose Si:O ratio differs measurably from that of SiO2.

To investigate gettering of heavy metal impurities to the damaged regions surrounding an implanted buried oxide, the behavior of chrominum and copper on annealing has been investigated. Cr tends to segregate to the surface Si-SiO2 interface, although a small fraction moves to the damaged regions surrounding the buried oxide. Cu segregates to the damaged regions more readily; in addition, a large fraction of the implanted Cu moves to a location several micrometers beneath the buried oxide layer. The buried oxide does not appear to stop the movement of the Cu.

Enhanced electron conductivity is observed in silicon that has been implanted with oxygen ions to form a buried oxide layer. The conductivity is attributed to donors that are created in the silicon both above and below the oxide. Secondary ion mass spectrometry and Rutherford backscattering spectroscopy show that, during subsequent annealing, oxygen accumulates only in the silicon surface. This causes the donors in the silicon surface to be easily activated to high concentrations and, unlike donors beneath the oxide, to be extremely resistant to thermal annihilation.

The effects of post implantation annealing on the properties of buried oxide silicon-on-insulator (SOI) substrates in the temperature range of 1150°C to 1300°C have been studied. Microstructural analyses showed that the crystallinity of the top silicon layer was improved at higher annealing temperature. Lower thermal donor generation at 450°C was observed in SOI annealed at higher temperature. The improvement in microstructure and lower thermal donor generation were correlated to the lower oxygen concentration in the top silicon film.

Oxygen has been implanted into Si wafers at high doses and elevated temperatures to form a buried SiO2 layer for use in silicon-on-insulator (SOI) structures. Substrate heater temperatures have been varied (300, 400, 450 and 500°C) to determine the effect on the structure of the superficial Si layer through a processing cycle of implantation, annealing, and epitaxial growth. Transmission electron microscopy was used to characterize the structure of the superficial layer. The structure of the samples was examined after implantation, after annealing at 1150°C for 3 hours, and after growth of the epitaxial Si layer. There was a marked effect on the structure of the superficial Si layer due to varying substrate heater temperature during implantation. The single crystal structure of the superficial Si layer was preserved at all implantation temperatures from 300 to 500°C. At the highest heater temperature the superficial Si layer contained larger precipitates and fewer defects than did wafers implanted at lower temperatures. Annealing of the as-implanted wafers significantly reduced structural differences. All wafers had a region of large, amorphous 10 to 50 nm precipitates in the lower two-thirds of the superficial Si layer while in the upper third of the layer there were a few threading dislocations. In wafers implanted at lower temperatures the buried oxide grew at the top surface only. During epitaxial Si growth the buried oxide layer thinned and the precipitate region above and below the oxide layer thickened for all wafers. There were no significant structural differences of the epitaxial Si layer for wafers with different implantation temperatures. The epitaxial layer was high quality single crystal Si and contained a few threading dislocations. Overall, structural differences in the epitaxial Si layer due to differences in implantation temperature were minimal.

Silicon wafers, implanted with oxygen at 550°C to form a buried oxide layer have been examined with TEM and x-ray diffraction. Implantation damage increased with depth up to ~1500 Å where some amorphous regions were seen. The amorphous region extended for -4500 Å to a damaged crystalline region ~1000 Å thick. Double crystal x-ray rocking curves of the as-implanted and of annealed crystals were obtained and analyzed. The strain normal to the (100) surface in the as-implanted crystalline Si did not exceed +0.05%. After an argon anneal, the strain disappeared, leaving a crystal with a lower density of extended defects and no measureable misorientation of surface or deep layers. In marked contrast, an anneal in a hydrogen atmosphere exhibited no normal strain but contained regions above the oxide layer which differed in orientation from the substrate. The misorientation ranged up to ~0.1 degree.

Buried nitride silicon-on-insulator (SOI) structures have been fabricated using the technique of nitrogen ion implantation. The crystallinity of the top silicon film was found to be exceptionally good. The minimum channeling yield, Xmin' was better than 3%. This is comparable to the value observed for single crystal silicon. The buried insulator formed during the anneals has been identified as polycrystalline α-Si3 N4 with numerous silicon inclusions. This nitride, however, has been found to remain amorphous in regions at the center of the implant where the nitrogen concentration exceeds the stoichiometric level of Si3N4. Nitrogen donor formation in the top silicon layer has also been observed.