The dielectric breakdown strength of thermally grown silicon dioxide films was studied for MOS capacitors fabricated on silicon wafers that were intentionally contaminated with magnesium and zinc. Most of magnesium was detected in the oxide film after oxidation. Zinc, some of which evaporated from the surface of wafers, was detected only in the oxide film. The mechanism of the dielectric degradation is dominated by formation of metal silicates, such as Mg2SiO4 (Forsterite) and Zn2SiO4 (Wilemite). The formation of metal silicates has no influence on the generation lifetime of minority carriers, however, it provides the flat-band voltage shift less than 0.3 eV, and forces to increase the density of deep surface states with the zinc contamination.

This paper describes the formation of ultra-thin tantalum oxide capacitors, using rapid thermal nitridation (RTN) of the storage-node polycrystalline-silicon surface prior to low-pressure chemical vapor deposition of tantalum oxide, using penta-ethoxy-tantalum [(Ta(OC2H5)5) and oxygen gas mixture. The films are annealed at 600-900 in dry O2 atmosphere. Densification of the as-deposited film by annealing in dry O2 is indispensable to the formation of highly reliable ultra-thin tantalum oxide capacitors. The RTN treatment reduces the SiO2 equivalent thickness and leakage current of the tantalum oxide film, and improves the time dependent dielectric breakdown characteristics of the film.

Water desorption from interlayer dielectric, spin-on-glass and SiO2 film deposited with tetraethylorthosilicate and O3, was controlled in order to reduce MOSFET hot-carrier degradation by using plasma SiO2 film as a water blocking layer. Two kinds of plasma SiO2 film were used in this study: SiH4 plasma SiO2 film deposited with SiH4 and N2O, and TEOS plasma SiO2 film deposited with TEOS and O2. Thermal desorption spectroscopy was used to study water desorption. Reduction of water desorption was obtained using plasma SiO2 film with water blocking ability; this reduction of water desorption resulted in suppression of the MOSFET hot-carrier degradation. The water blocking ability was obtained by low pressure deposition for SiH4 plasma SiO2 and low flow rate ratio of TEOS to O2 deposition for TEOS plasma SiO2. Water absorption studies of plasma SiO2 film using Fourier transform infrared spectroscopy revealed that water blocking ability is associated with small amount of water absorption both in SiH4 plasma SiO2 film and in TEOS plasma SiO2 film. Consequently, it is considered that the water blocking ability, as well as water absorption, of plasma SiO2 film depends on porosity.

The dielectric breakdown characteristics of a thin gate oxide during high-current ion implantation with an electron shower have been investigated by controlling the energy distribution of the electrons. Degradation of the oxide has also been discussed with regard to the total charge injected into the oxide during ion implantation in comparison with that of the TDDB (time dependent dielectric breakdown). Experimental results show that the high-energy and high-density electrons which concentrated in the circumference of the ion beam due to the space charge effect cause the degradation of the thin oxide. It was confirmed that eliminating the high-energy electrons by applying magnetic and electric fields lowers the electron energy at the wafer surface, thereby effectively suppressing the negative charge-up.

Plasma damage to gate oxide is studied using the test structures with various length antennas. It is shown that the plasma damage to gate oxide can be monitored quantitatively by measuring charge to breakdown (QBD). From the QBD measurements, it is confirmed that the degradation occurs in the duration of over-etching but not in the duration of main etching. The breakdown spots in gate oxide are detected by a photon emission method. The breakdown are caused by plasma damage at the LOCOS edge. A LOCOS structure plays an important role for the degradation by the plasma damage.

The Cooper pairing interaction in high Tc oxide superconductor is discussed in terms of an empirical expression; TcDexp[1/g], gcωo which was derived in our previous investigation. The dual character of this expression consisting of the phonon Debye temperature D and electronic excitation ωo in the mid-infrared region can be interpreted on the basis of the phonon-assisted mechanism on carrier conduction and the electronic excitation. A tunneling spectrum here presented shows certain evidence of the phonon contribution. The characteristics of the long range superconductive proximity phenomena recently reported are also may be interpreted by this mechanism.

A new technique for evaluating gate oxide reliability using photon emission method has been developed. This method enables the measurements of the initial breakdown characteristics, reliability testing and failure analysis consistently. From the experimental results, followings are clarified for the first time using this technique. Failure modes in the initial characteristics have close correlation to TDDB characteristics and both characteristics correspond to the location of breakdown spot. The results suggest measures to improve the reliability of gate oxide and the existance of new failure mechanism.

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.

Among the many fabrication methods for oxide superconductor films, metal organic chemical vapor deposition (MOCVD) is particularly suitable for industrial application because of its mass productivity and the low growth temperature. Therefore we have studied this technique using the horizontal cold wall furnace type MOCVD method to obtain high quality superconducting films. As the result, we have succeeded in fabricating YBa2Cu3Oy films which have high critical temperatures (over 80 K) under substrate temperatures as low as 700 without post-annealing. But, in the course of our experiments, it was found that the thicknesses of YBa2Cu3Oy films fabricated by MOCVD were not uniform. The cause of this non-uniformity is believed to be that the deposition rate exponentially falls off along the flow direction because of the decrease of the source gas concentration through the reaction. In this paper, this non-uniformity is analytically studied. It is shown that the deposition rate decrease can be controlled with a tapered inner tube, and that these theoretical results are in good agreement with the results of experiment. In addition, it is indicated that the superconducting property of the films has less dependence on substrate position as a result of the tapered inner tube.

Effects of cleaning by H2SO4: H2O2 on thin SiO2 film was investigated. The cleaning increases Fowler-Nordheim currents by about 14%, shifts the dielectric breakdown distribution to lower electric field intensity and degrades TDDB characteristics. These results are due to the oxidation and commensurate roughening of the silicon srface by the cleaning solution. When the cleaning is done at higher temperature and with higher concentration of hydroperoxide, microroughness of silicon surface increases. Therfore, the trade-off between the cleaning effect and the roughening effect of H2SO4: H2O2 should be found out.

Chemical structures of native oxides formed during wet chemical treatments of silicon surfaces were investigated using X-ray Photoelectron Spectroscopy (XPS) and Fourier Transformed Infrared. Attenuated Total Reflection (FT-IR-ATR). It was found that the amounts of Si-H bonds in native oxide and at native oxide/ silicon interface are negligibly small in the case of native oxides formed in H2SO4-H2O2 solution. Based on this discovery, it was found that native oxides can be characterized by the amount of Si-H bonds in the native oxide and the combination of various wet chemical treatments with the treatment in NH4OH-H2O2-H2O solution results in the drastic decrease in the amount of Si-H bonds in the native oxides.

The increase of surface microroughness on Si substrate degrades the electrical characteristics such as the dielectric breakdown field intensity (EBD) and charge to break-down (QBD) of thin oxide film. It has been found that the surface microroughness increases in the wet chemical process, particularly in NH4OH-H2O2-H2O cleaning (APM cleaning). It has been revealed that the surface microroughness does not increase at all if the NH4OH mixing ratio in NH4OH-H2O2-H2O solution is reduced from the conventional level of 1:1:5 to 0.05:1:5, and the room temperature ultrapure water rinsing is introduced right after the APM cleaning. At the same time, the APM cleaning with NH4OH-H2O2-H2O mixing ratio of 0.05:1:5 has been very effective to remove particles and metallic impurities from the Si surface. The surface microroughness dominating the electrical properties of very thin oxide films is strictly influenced by the wafer quality. The increase of surface microroughness due to the APM cleaning has varied among the wafer types such as Cz, FZ and epitaxial (EPI) wafers. The increase of surface microroughness in EPI wafer was very much limited, while the surface microroughness of FZ and Cz wafers gradually increase. As a result of investigating the amount of diffused phosphorus atoms into these wafers, the increase of the surface microroughness in APM cleaning has been confirmed to strongly depend on the silicon vacancy cluster concentration in wafer. The EPI wafer having low silicon vacancy concentration is essentially revealed superior for future sub-half-micron ULSI devices.

We have found out the effects of surfactant addition to developer on the developing characteristics: very uniform developing, scum-free developing, contact hole formation at lower exposure energy and substrate surfaces protection. Although these are excellent effects required for ULSI manufacturing, we have also discovered the problem that surfactant added to developer remains after the developing process. We has successfully established two effective methods for removing residual surfactant: the addition of 0.15 wt% hydrogen peroxide to surface-active developer, and 1-minute ozone-added ultrapure water rinsing at room temperature. We can therefore make best use of the developing characteristics of surface-active developer without any degradations.

In this paper, a "hydrodynamic" version of the three-dimensional code HFIELDS-3D is used to achieve a detailed knowledge on the distribution of the substrate current inside a recessed-oxide MOSFET. The physical model features a temperature-dependent formulation of the impact-ionization rate, allowing non-local effects to be accounted for. The discretization strategy relies on the Box Integration scheme and uses suitable generalizations of the Scharfetter-Gummel technique for the energy-balance equation. The simulation results show that the narrow-channel effect has a different impact on drain and substrate currents. Further three-dimensional effects, such as the extra heating of the carriers at the channel edge, are demonstrated.

The characteristics of a LiNbO3 light modulafor using the resonant YBa2Cu3Oy superconducting electrode were studied on the basis of the calculated results of surface resistances and transmission losses. The two-fluid model and the conventional transmission theory were used for the calculations. It was found that the modulation depth of this modulator using the YBCO electrode at 77 K was 7.5 times that using the Al electrode at room temperature. The drive voltage for the phase modulation of π radians was estimated to be a very low value of 2.3 V.

The characteristics of a LiNbO3 light modulator using the resonant YBa2Cu3Oy superconducting electrode were studied on the basis of the calculated results of surface resistances and transmission losses. The two-fluid model and the conventional transmission theory were used for the calculations. It was found that the modulation depth of this modulator using the YBCO electrode at 77 K was 7.5 times that using the Al electrode at room temperature. The drive voltage for the phase modulation of π radians was estimated to be a very low value of 2.3 V.