A new channel stop design for submicton local oxidation of silicon (LOCOS) isolation was presented. The n-channel stop was designed with boron implanation after forming LOCOS, while the p-channel stop was constructed with high energy phosphorus or arsenic implantation before or after forming LOCOS. These optimized channel stop designs can extend an isolation spacing to the submicron region without a decrease in junction breakdown voltage and an increase in junction leakage current. Narrow channel effects were found to be effectively suppressed by optimum channel stop design issues.

A laser/microwave method using two lasers of different wavelengths for carrier excitation is proposed to evaluate Si surfaces. These constitute a He-Ne laser (wavelength=633 nm, penetration depth=3 µm) and a YAG laser (wavelength=1060 nm, penetration depth=500 µm). Using a microwave probe, the amount of excited carriers can be detected. The carrier concentration is mainly dependent on the condition of the surface when carriers are excited by the He-Ne laser, as well as on the condition of the bulk region when carriers are excited by the YAG laser. Microwave intensities detected under the He-Ne and the YAG lasers illumination are referred to as the surface-recombination-velocity-related microwave intensity (SRMI) and the bulk-related microwave intensity (BRMI), respectively. The difference between SRMI and BRMI is called relateve SRMI (R-SRMI), and is closely related to the condition of the surface and surface active region. We evaluate the surfaces of the samples after plasma and wet etching to remove the photoresist layer. And we evaluate the surfaces of the samples after heat or HF treatment which is done to recover the damage introduced by plasma etching. It was found that the R-SRMI method is better suited to surface evaluation than conventional lifetime measurements.

Isotope dilution secondary ion mass spectroscopy (ID-SIMS) using ³⁰Si as a spike is investigated as a quantitative analysis method for trace amounts of Si. For a standard solution of Si, the relateve standard deviation of results using this method is 5% for 0.2 µg Si, and the determination lower limit is 18 ng. Using this method, the amount of Si deposited on the Ge(100) surface by the self-limited adsorption of SiH₂Cl₂ is determined to be about 1.00.2 monolayer.

Surface damage to n-type silicon wafers induced by Reactive Ion Etching (RIE) with CF₄ gas was evaluated using X-ray photoelectron spectroscopy (XPS) and the current-voltage (I-V) characteristics of Au/n-Si Schottky diodes fabricated on the damaged surface. The reaction products (SiF, SiF₂, and SiF₃) in the damaged layer were detected by XPS. Assuming the surface damage on a silicon wafer induced by RIE acts as a donor, the donor density was found to be about 210¹⁹ cm^-3. The distribution of SiF₃ and the donor density in the depth direction were almost equal. The thickness of the damaged layer was about 15 nm. These findings suggest that the donor in the damaged layer on a silicon surface induced by RIE may be SiF₃.

Diffusion of phosphorus impurities from a polycrystalline silicon films into a silicon substrate was investigated as a function of the mean concentration of phosphorus in a polycrystalline silicon film at the first diffusion stage. We presented that good control of the redistribution of implanted phosphorus impurities was possible by optimizing the normalized dose, which is the value: [the total dose of phosphorus impurities]/[the polycrystalline silicon film thickness], in the case of samples both with and without an arsenic doped layers. In the range where the normalized dose was less than 1.52.510²⁰ cm^-3, deeper junctions were formed in samples with an arsenic doped layer. In the range where the normalized dose was more than 1.52.510²⁰ cm^-3, however, deeper junctions were formed in samples without any arsenic doped layer rather than in samples with an arsenic doped layer. These results mean that formation of the junction in the device structure where a high concentration phosphorus doped polysilicon layer is stacked on to the high concentration arsenic layer embeded at the surface of the substrate can be restricted by optimizing the normalized dose. Moreover, a trade-off relationship between suppressing phosphorus diffusion and maintaining low contact resistance against normalized doses was also observed.

Thin Si films grown on anodized porous silicon have been characterized using a high-energy ion scattering technique with related simulations of MeV ions in solids. It turned out that the simulations are necessary and very usuful for quantitative and nondestractive analysis of thin films with thicknesses less than 100 nm. In the case of the epitaxial Si films examined, it is often insufficient for the characterization of crystalline quality to measure only the channeling minimum yield, and therefore, it is emphasized that angular scans over the critical angle in the vicinity of a channeling direction must be performed for the analysis of possible imperfections in thin films. The possible imperfections observed in the epitaxial specimen are treated quantitatively.

The quality of polycrystalline silicon films and electrical characteristics of polycrystalline silicon gate metal-oxide-semiconductor (MOS) capacitors were investigated under various processing conditions, including phosphorus doping. The stresses observed in Si films deposited in the amorphous phase show complex behavior during thermal treatment. The stresses in as-deposited Si films are compressive. They change to tensile with annealing at 800, and to compressive after an additional annealing at 900. The kind of charges trapped in the SiO₂ film during the negative constant current stress in Polycrystalline silicon gate MOS capacitors differ with the maximum process temperature. The trapped charges of samples annealed at 800 were negative, while those of samples annealed at 900 were positive.

Reaction mechanisms in remote plasma CVD (in which plasma excitation of source meterials and film deposition are spatially separated) of SiO₂ using activated oxygen species and pure silane (SiH₄) were discussed in two destinct cases in a viewpoint of vapor phase reactions. Under high pressures of 50500 mTorr, activated oxygen species and SiH₄ could collide with each other many times in the vapor phase. SiH₄ was decomposed by chemical reactions due to the collisions generating chemically active precursors such as SiH_n (0n3) for film deposition. Nearly stoichiometric films with low hydrogen content were obtained at low temperatures of around 300. Under a pressure of 5 mTorr, the oxygen species and SiH₄ could scarcely collide with each other due to a long mean free path resulting no decomposition of SiH₄. Insufficient surface reactions between relatively stable SiH₄ and activated oxygen species yielded many O-H bonds in deposited films. Electrical properties of the films and the interfaces of SiO₂/Si were characterized.

Silicon nitride (SiN_x) films have been deposited at lower substrate temperatures (500) by direct (without mercury-sensitization) photo-chemical vapor deposition (photo-CVD) using SiH₄ and NH₃ with a low-pressure mercury lamp. Films deposited at around 350 have a polymeric structure such as (Si(NH)₂)_n. Films deposited at 500 were close to stoichiometric Si₃N₄ with a slight amount of hydrogen. The refractive index and the dielectric constant of films deposited at 500 became almost equal to the values of thermally synthesized Si₃N₄. The resistivity was as high as 510¹⁶ Ωcm. The minimum density of interface states in Al/SiN_x/Si MIS (metal-insulator-semiconductor) diodes was estimated to be 910¹⁰ cm^-2eV^-1 by a quasi-static capacitance-voltage measurement. For SiN_x films deposited at 300, the density of interface states, which was in the order of 10¹¹ cm^-2eV^-1 as deposited, decreased by a rapid thermal anneal after the deposition. For Al/SiN_x/InP MIS diodes, it was 310¹¹ cm^-2eV^-1 by high-frequency capacitance-voltage measurements. Direct photo-CVD for SiN_x films is promising for low-temperature formation of a gate insulator.

Microcrystalline silicon embedded in silicon oxide has been prepared by means of a wet oxidation of porous silicon (PS) anodically produced from degenerate Si wafers in a HF solution. As the oxidation proceeded, optical absorptions of the PS specimen in the visible light region shifted obviously to the higher energy side. Visible light emission from the oxidized specimen was observed at room temperature with photoexcitation by a He-Cd laser while the as-prepared specimen emitted no visible lights. These results are discussed in relation to the quantum size effect of the microcrystalline silicon confined in the oxide matrix as well as visible emissions from as-prepared specimens produced from non-degenerate Si wafers.

The a-Si films deposited on quartz substrates were crystallized by lateral sweep annealing in steep temperature gradient using a gas burner. Random nucleation in amorphous region was effectively suppressed in the temperature gradient, so lateral solid phase epitaxial growth from crystallites generated at the initial stage of lateral sweep annealing spread over 100 µm. Their crystallographic orientations were mostly (100).

After the intrinsic pulsed light illumination, a transient negative photoconductivity (TRANP) was observed in silicon doped with gold. The ambient temperature dependence of the TRANP-current was measured and compared with the simulated results obtained by solving rate equations. The temperature dependence of the peak value of the TRANP-current was in agreement with the simulated result. The activation energy of gold acceptor level obtained from the time constant in the recovery process was also consistent with the simulation. It was cleared from this result that the recovery process is dominated by the electron re-emission from gold acceptor level to the conduction band. It was concluded that the occurrence of the TRANP is well explained by using our model proposed before.

In this study, we evaluate the electrical characteristics of the SOI layer made by the wafer bonding method using a laser/microwave method. We use a He-Ne laser pulse for the photoconductivity modulation method and a semiconductor laser diode for the photoconductivity decay method as the carrier injection light source. The detected signal intensity at the void area decreases as compared with that at the center area of the SOI layer where there are no voids. The positions of the voids revealed by the proposed method are in good agreement with those by X-ray topography. We also measure the lifetime by the photoconductivity decay method using a laser diode. The lifetime at the void area is much shorter than that at the center area. It is considered that the decrease in the detected signal intensity at the void area is due to reduction in the minority carrier lifetime.

Silicon-on-insulator (SOI) films fabricated by the wafer bonding technique were studies with capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS) measurements. For our expereiments, two kinds of SOI wafers were prepared. Many voids were present in one sample (void sample), but few voids were in the other sample (no void sample). Before annealing, two DLTS peaks (E_c-0.48 eV and E_c-0.38 eV) were observed in the SOI layer of the void sample. For the no void sample, different two DLTS peaks (E_c-0.16 eV and E_c-0.12 eV) were observed. The trap with an activation energy of 0.48 eV was annealed out after 450 annealing for 24 h. On the other hand, other traps were annealed out after 450 annealing for several hours. During annealing at 450, thermal donors (TDs) were formed simultaneously. In usual CZ silicon, a DLTS peak of TD was observed around 60 K. In the no void sample, however, a TD peak was observed at a temperature lower than 30 K. This TD was annihilated by rapid thermal annealing. This suggests that the TD with a shallower level was formed in the no void sample after annealing at 450.

A Ge/Si structure grown by chemical vapor deposition (CVD) is angle-lapped and characterized by the micro-Raman spectroscopy. Near the interface, the phonon mode due to the Si-Ge bond is clearly observed, which indicates that a SiGe alloy is formed by the solid-phase interdiffusion at the interface. The thickness of the interfacial alloy layer is about 0.2 µm. Amount of residual strain is estimated by comparing the measured phonon frequencies with those predicted from the composition profie, but the shift due to the residual strain is not appreciable. Both the interdiffusion at the interface and the nearly complete relaxation of the lattice mismatch are attributed to the high growth temperature of the CVD sample.

Operation of a newly proposed semiconductor optical modulator based on absorption control by electron depletion around a p-n junction is demonstrated, forming preliminary structures of waveguide-type as well as panel-type (or surface-illuminated type) devices. The optical absorption is occurred at the intrinsic energy levels in the band structure not at the extended state into the band-gap. Performance of 35 dB on-off extinction ratio for 4 V variation of the applied voltage was obtained in a waveguide type device. Validity of the proposed mechanism were confirmed by getting large change of the absorption coefficient of around 5000 cm^-1 over wide wavelength range of 30 nm.

An accurate numerical solution is presented for the electromagnetic scattering from infinite strip gratings attached to both sides of a dielectric slab. This structure is a model of polarization discriminating devices. The period of the strips is common to both planes, but the widths and the axes may be different. The direction of propagation and the polarization of an incident plane wave are arbitray. We derive a set of singular integral equations and solve it by the moment method, where the Chebyshev polynomials are successfully used as the basis and the testing functions. This method is accurate and effective owing to the incorporation of the edge condition and the decomposition of the kernel functions into the singular and the regular parts. Numerical calculations are carried out for the purpose of designing polarization discriminators, and it is shown that the band width is widened by decreasing the permittivity of the slab. The cross-polarization characteristics at skew incidence are also discussed.

Recently most of the singularities of the equivalent edge currents for flat plates were eliminated by the authors using the paths of most rapid phase variation. A unique direction on the plate was determined for given incidence and observer. This paper extends this method for arbitrary angle wedges and presents the new expressions of the equivalent edge currents. The resultant expressions are valid for any incidence and observation aspects and have no false singularities. Diffraction patterns and radar cross sections of 3-D objects composed of wedges are calculated by using these currents. They show good agreements with experimental data or the results by the other methods.

This letter proposes an improvement of the equivalent source method in order to give an accurate solution for the scattering of an electromagnetic plane wave by a conducting cylinder with edges.

Analysis of the propagation of circularly symmetric fields is made using the finite-difference beam-propagation method. After testing the accuracy of this method, we analyze the guided-mode transmission of connected fibers whose core radii are different. The propagation behavior of the unguided-mode field generated at the junction is revealed using a transparent boundary condition.