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High-performance three-dimensional (3-D) stacked poly-Si complementary metal-oxidesemiconductor (CMOS) inverters with a high-quality laser-crystallized channel were fabricated. Lowtemperature crystallization methods of an a-Si lm using excimer-laser annealing (ELA) and sequential lateral solidi cation (SLS) were performed. The n-channel metal-oxide-semiconductor (NMOS) thinlm transistors (TFT) at the lower CMOS layer were fabricated on an oxidized bulk Si substrate and p-channel metal-oxide semiconductor (PMOS) TFT at the upper CMOS layer were fabricated on an interlayer dielectric lm. Considerably uniform silicon grains were obtained by laser annealing. Sub-threshold swings of the fabricated NMOS TFTs at the lower layer and PMOS TFTs at the upper layer were 78 mV/dec. and 86 mV/dec., respectively. The eld e ect mobilities of the NMOS and the PMOS TFTs were 42.5 cm2/V s and 76 cm2/V s, respectively. The on/o current ratio of both TFTs was larger than 107. 3-D stacked poly-Si CMOS inverter showed excellent electrical characteristics and can be used the vertical integrated CMOS applications.

Ultra shallow and abrupt n+–p junctions were formed on a silicon-on-insulator (SOI) using solid phase diffusion from arsenic-doped spin-on dopant source with various rapid thermal annealing (RTA) conditions. Their doping profiles and electrical characteristics were investigated and compared with those of junctions prepared from phosphorous-doped spin-on-dopant. Analysis of arsenic doped n+–p junctions prepared at the drive-in temperature of 950 °C revealed that the junction depth and junction abruptness are 27 nm and 8.5 nm/dec., respectively, which are superior to phosphorus-doped junctions. Moreover, the SOI n-type metal-oxide-semiconductor field effect transistor (MOSFET) with the gate length of 90 nm which source and drain extensions were doped from arsenic spin-on-dopant had good short channel properties.

For Si nanocrystals, which are formed by Si ion implantation into a SiO2 layer, the effects of crystal size and interface states on the photoluminescence property are investigated. The Si-implanted SiO2 samples are annealed in an N2 ambience at different temperatures to obtain Si nanocrystals of different sizes. The sample annealed at 1100°C shows a strong and broad photoluminescence (PL) peak at 700 nm (1.77 eV). The observed PL spectrum redshifts when the annealing temperature increases, blue shifts when the samples are oxidized, and redshifts followed by blue shifts when the average size of the Si nanocrystals increases and then decreases with etch depth of the SiO2 layer. Low-temperature annealing in an H2 ambience increases the PL intensity but does not change the PL spectral distribution. Experimental observations indicate that the size of the Si nanocrystal determines the quantum state for carrier excitation and that the interface states at the Si nanocrystal/SiO2 interface provide the nonradiative recombination centers.

We have successfully used hydrophobic direct wafer bonding along with hydrogen-induced layer splitting of germanium to transfer 700 nm thick, single-crystal germanium (100) films to silicon (100) substrates without using a metallic bonding layer. The metal-free nature of the bond makes the bonded wafers suitable for subsequent epitaxial growth of layered solar cells at high temperatures without concern about metal contamination of the device active region. Contact mode atomic force microscopy images of the transferred germanium surface generated by the formation of micro-bubbles and micro-cracks along the hydrogen-induced layer-splitting interface reveals minimum rms surface roughness of between 10 nm and 23 nm. Electrical measurements indicated ohmic I-V characteristics for germanium layers bonded to silicon substrates with ∼400 Ω cm−2 resistance at the interface. Triple-junction solar cell structures grown on these Ge/Si heterostructure templates by metal-organic chemical vapor deposition show comparable photoluminescence intensity and minority carrier lifetime to a control structure grown on bulk Ge. The use of a molecular beam epitaxy Ge buffer layer to smooth the cleaved surface of the Ge heterostructure has been shown to smooth the rms surface roughness from ∼11 nm to as low as 1.5 nm with a mesa-like morphology that has a top surface roughness of under 1.0 nm giving a promising surface for improved solar cell growth on solar cell structures.

We propose a new type of photosensitive biosensor with a CMOS compatible Si photodiode integrated circuit, for the high-sensitive detection of small mycotoxin molecules requiring competitive assay approach. In this work, a photodiode is connected to the gate of a field effect transistor (FET) so that the open circuit voltage ( V OC ) of the illuminated photodiode is transferred into the drain/source current ( I DS ) of the FET. The sensing scheme employs competitive binding of toxin molecules (within the sample solution) and toxin–BSA conjugates (immobilized on the photodiode surface) with Au-nanoparticle-labeled antibodies, followed by silver enhancement to generate opaque structures on the photodiode surface. By utilizing the non-linear dependence of the V OC on the light intensity, we can maintain a sufficiently high signal resolution at low toxin concentrations (with most of the incident light blocked) for the competitive assay. By monitoring the I DS of the FET whose gate is driven by the V OC , quantitative detection of Aflatoxin B1 has been achieved in the range of 0–15 ppb.

The sensitivity of 'top-down' fabricated Si nanochannel field effect transistor (FET) biosensors has been analyzed quantitatively, as a function of the channel width and doping concentration. We have fabricated 130-, 150-, and 220 nm-wide Si FET channels with 40 nm-thick p-type silicon-on-insulator (SOI) layers doped at 8 x 10(17) and 2 x 10(18) cm(-3), and characterized their sensitivity in response to the variation of surface charges as hydrogen ion sensors within buffer solutions of various pH levels. Within the range of channel width and doping concentration investigated, the pH sensitivity of Si channels is enhanced much more effectively by decreasing the doping concentration than by reducing the channel width, which suggests a practical strategy for achieving high sensitivity with less effort than to reduce the channel width. Similar behavior has also been confirmed in the immunodetection of prostate specific antigen (PSA). Combined with excellent reproducibility and uniformity of the channel structure, high controllability of the doping concentration can make the 'top-down' fabrication a very useful approach for the massive fabrication of high-sensitivity sensor platforms in a cost-effective way.

We report the strong visible light emission from silicon (Si) nanocrystals (NCs) embedded in a Si carbide (SiC) film. Compared to Si NC light-emitting diode (LED) by employing the Si nitride (SiNx) film as a surrounding matrix, the turn-on voltage of the Si NC LED with the SiC film was significantly decreased by 4 V. This was attributed to a smaller barrier height for injecting the electrons into the Si NCs due to a smaller band gap of SiC film than a SiNx film. The electroluminescence spectra increases with increasing forward voltage, indicating that the electrons are efficiently injected into the Si NCs in the SiC film. The light output power shows a linear increase with increasing forward voltage. The light emission originated from the Si NCs in a SiC film was quite uniform. The power efficiency of the Si NC LED with the SiC film was 1.56 times larger than that of the Si NC LED with the SiNx film. The Si NCs in a SiC film show unique advantages and are a promising candidate for application in optical d...

The effect of rapid thermal annealing (RTA) and post-RTA annealing (PRA) on the electrical characteristics of both strained Si and conventional SOI n-MOSFETs was investigated. The authors demonstrated that post-RTA heat treatment rather than typical RTA is inevitable to obtain enhanced DC characteristics in strained Si n-MOSFET. This is attributed to the suppression of channel surface roughness owing to post-RTA

Real-time measurements of GexSi1 – x/Si(001) composition and segregation dynamics in Sn/Si(001) in molecular beam epitaxy are demonstrated using parallel detection reflection electron energy loss spectroscopy. Parallel detection enables quantitative acquisition of low-loss spectra in a time of < 500 µs and surface composition determination in GexSi1 – x/Si(001) via Ge L2,3 core loss analysis to a precision of approximately 2% in time of order 1 s. Segregation and trapping kinetics of monolayer thickness Sn films during Si epitaxy on Sn-covered Si(100) has also been studied using the Sn M4.5 core loss.

We designed and fabricated gravimetric sensors composed of silicon (Si) microbeams surrounded by silicon nitride (SiN) anchors. The oscillation properties of the fabricated devices show that a single oscillation mode originating from quasi-one-dimensional microbeams appears at an applied alternating electric field, which motion is well matched to the theoretical predictions and is much different from the dimensionally mixed oscillation modes in normal non-anchored devices. In addition, in order to elucidate the possibilities of the devices for mass sensing applications, we measured the frequency shift as a function of mass loading in a self-assembled monolayer of 3-aminopropyltrimethoxysilane and Au nanoparticles. The resulting limit of detection was 1.05 × 10−18 g/Hz, which is an extremely high value for micro electromechanical system gravimetric sensors relative to the normal ones.

We report an enhancement in light emission and electrical efficiencies of a Si nanocrystal (NC) light-emitting diode (LED) by employing indium tin oxide (ITO) nanowires (NWs). The formed ITO NWs (diameter

The biosensor using a silicon nanochannel field effect transistor has been developed on the basis of a bulk silicon substrate instead of an expensive silicon-on-insulator material, for low cost applications. “Top-down” fabricated Si nanochannels for detecting prostate specific antigen (PSA) are electrically isolated from the bulk Si substrate only by a reverse-biased p-n junction with very low reverse leakage currents. The reverse leakage current flowing through the p-n junction is small enough to be ignored, when compared with the current flowing through the p-type Si channel; roughly 100 times lower. The surface immobilization of anti-PSA has been confirmed by the specific binding test of DNA stabilized Au nanoparticles (NPs), showing 1200 NPs/μm2 and atomic force microscopy surface analysis. The injection of 10 ng/ml PSA solutions leads to a clear increase in the conductance of Si nanochannels, indicating the specific binding of PSA with the immobilized anti-PSA. The similar signal changes were observe...

The electrical properties of the back interface between the thin silicon and buried-oxide layers of nano-silicon-on-insulator substrate were evaluated. The effects of rapid thermal annealing (RTA) process were investigated, and the distributions of interface states at the thin silicon/buried-oxide interface were estimated by using metal-point-contact field-effect-transistor method. The interface-states at the back interface were considerably increased by RTA process. The RTA higher than 800°C contributes to the increase of acceptor-type interface states. The increased interface states were effectively reduced by conventional furnace annealing at 500°C in nitrogen ambient.

The fin field-effect transistor (FET) silicon nanocrystal floating gate memory using the photochemical vapor deposition and the plasma doping processes was proposed. The silicon nanocrystals with a uniform size were formed on a vertical sidewall surface of the fin channel by the photochemical vapor deposition. The plasma doping was applied to form the junctions at the sidewall of the fin source-drain extension regions with a high aspect ratio. The FinFET silicon nanocrystal floating gate memory with a gate length of 100nm was successfully fabricated and it revealed a memory effect as well as a suppressed short-channel effect.

A process to form a self-aligned hard mask using hydrogen silsesquioxane (HSQ) was investigated. Application of the flowing property of HSQ to form a hard mask is the main concept underlying the proposed process. When HSQ is coated on a wafer, most of it remains beside the pattern. Using the thick remaining HSQ beside the pattern as a hard mask, we could reduce the height of the pattern exclusively without etching beside the pattern region by the dry etching process. The proposed mask process was successfully applied to fabricate a poly-Si elevated source drain ultrathin body silicon on insulator metal-oxide-semiconductor field effect transistor.

Si1–x–yGexCy/Si superlattices were grown by solid-source molecular beam epitaxy using silicon carbide as a source of C. Samples consisting of alternating layers of nominally 25 nm Si1–x–yGexCy and 35 nm Si for 10 periods were characterized by high-resolution x-ray diffraction, transmission electron microscopy (TEM), and Rutherford backscattering spectrometry to determine strain, thickness, and composition. C resonance backscattering and secondary ion mass spectrometries were used to measure the total C concentration in the Si1–x–yGexCy layers, allowing for an accurate determination of the substitutional C fraction to be made as a function of growth rate for fixed Ge and substitutional C compositions. For C concentrations close to 1%, high-quality layers were obtained without the use of Sb-surfactant mediation. These samples were found to be structurally perfect to a level consistent with cross-sectional TEM (< 10^7 defects/cm^2) and showed considerably improved homogeneity as compared with similar structures grown using graphite as the source for C. For higher Ge and C concentrations, Sb-surfactant mediation was found to be required to stabilize the surface morphology. The maximum value of substitutional C concentration, above which excessive generation of stacking fault defects caused polycrystalline and/or amorphous growth, was found to be approximately 2.4% in samples containing between 25 and 30% Ge. The fraction of substitutional C was found to decrease from roughly 60% by a factor of 0.86 as the Si1–x–yGexCy growth rate increased from 0.1 to 1.0 nm/s.

We have used admittance spectroscopy and deep-level transient spectroscopy to characterize electronic properties of Si/Si1–x–yGexCy heterostructures. Band offsets measured by admittance spectroscopy for compressively strained Si/Si1–x–yGexCy heterojunctions indicate that incorporation of C into Si1–x–yGexCy lowers both the valence- and conduction-band edges compared to those in Si1–xGex by an average of 107 ± 6 meV/% C and 75 ± 6 meV/% C, respectively. Combining these measurements indicates that the band alignment is type I for the compositions we have studied, and that these results are consistent with previously reported results on the energy band gap of Si1–x–yGexCy and with measurements of conduction band offsets in Si/Si1–yCy heterojunctions. Several electron traps were observed using deep-level transient spectroscopy on two n-type heterostructures. Despite the presence of a significant amount of nonsubstitutional C (0.29–1.6 at. %), none of the peaks appear attributable to previously reported interstitial C levels. Possible sources for these levels are discussed.

Realization of group IV heterostructure devices requires the accurate measurement of the energy band offsets in Si/Si1–xGex and Si/Si1–x–yGexCy heterojunctions. Using admittance spectroscopy, we have measured valence-band offsets in Si/Si1–xGex heterostructures and conduction-band and valence-band offsets in Si/Si1–x–yGexCy heterostructures grown by solid-source molecular-beam epitaxy. Measured Si/Si1–xGex valence-band offsets were in excellent agreement with previously reported values. For Si/Si1–x–yGexCy our measurements yielded a conduction-band offset of 100 ± 11 meV for a n-type Si/Si0.82Ge0.169C0.011 heterojunction and valence-band offsets of 118 ± 12 meV for a p-type Si/Si0.79Ge0.206C0.004 heterojunction and 223 ± 20 meV for a p-type Si/Si0.595Ge0.394C0.011 heterojunction. Comparison of our measured band offsets with previously reported measurements of energy band gaps in Si1–x–yGexCy and Si1–yCy alloy layers indicates that the band alignment is type I for the compositions we have studied and that our measured band offsets are in quantitative agreement with these previously reported results.

N-channel and p-channel metal-oxide-semiconductor (MOS) thin-film transistors (TFT's) have been fabricated on rapid thermal chemical vapor deposition (RTCVD) polycrystalline silicon-germanium (poly- Si0.88Ge0.12) films by a low temperature (≤550° C) process. These devices employ in-situ n+ doped poly- Si0.65Ge0.35 films as gate electrodes to reduce the process time and temperature, dual-offset spacers to reduce the electric field in the drain junction region, and silicon capping layers to protect the poly-Si1-x Ge x films against oxygen. The I d-V g characteristics in n-channel TFT's, as well as in p-channel TFT's, exhibit good behavior after remote-PECVD hydrogenation. Further improvements on electrical properties in n-channel TFT's are limited by trap-inducing G e behaviors in poly-Si1-x Ge x films.

Si/Si_(0.97)C_(0.03) superlattices grown on Si(001) substrates by Sb surfactant assisted molecular beam epitaxy are characterized by in situ reflection high energy electron diffraction (RHEED), atomic force microscopy, transmission electron microscopy (TEM), and high resolution x‐ray diffraction. The RHEED shows that, in the absence of Sb, the growth front roughens during Si_(0.97)C_(0.03) growth and smooths during subsequent Si growth. In contrast, when Sb is present, the growth front remains smooth throughout the growth. This observation is confirmed by cross‐sectional TEM, which reveals that for samples grown without the use of Sb, the Si/Si_(0.97)C_(0.03) interfaces (Si_(0.97)C_(0.03) on Si) are much more abrupt than the Si_(0.97)C_(0.03)/Si interfaces. In the case of Sb assisted growth, there is no observable difference in abruptness between the two types of interfaces. Atomic force microscopy micrographs of the Si_(0.97)C_(0.03) surface reveal features that could be the source of the roughness observed by RHEED and TEM.

We have studied the formation of buried oxide in MeV oxygen implanted Si. A continuous oxide layer is formed in the samples implanted with 2x1018/cm2 oxygen and annealed at 1300° C. The microstructures are studied by cross-sectional transmission electron microscopy and high resolution electron microscopy. Chemical information was obtained by electron energy loss spectroscopy. The effects of implantation temperature are studied. Implantation at a low substrate temperature leads to a well-defined buried SiO2 layer, inhibits the formation of oxide precipitates in the silicon, and reduces silicon inclusions in the SiO2.