Search

The formability of deep drawn ultra-high strength steel sheets in dies coated with either titanium nitride (TiN) or Vanadium carbide (VC) at different drawing speeds and ironing ratios was investigated. TiN was deposited via chemical vapour deposition and physical vapour deposition (PVD) while thermal diffusion was used for VC deposition. In non-coated dies, seizure occurred on both surfaces of the die and the side wall of the drawn cup irrespective of the deep drawing conditions. The deep drawability is improved with coating of die. Whereas in coated dies, seizure became significant only during deep drawing extreme conditions of 120 mm/s for TiN-coated dies; and this was prevented in VC-coated dies across all drawing conditions. The VC-coated die was suitable for deep drawing of ultra-high strength steel sheets. The delayed fractured observed in the ultra-high strength steel cups occurred for a large amount of ironing ratio and drawing speeds; and this can be prevented by appropriate heat treatment.

Polycrystalline silicon thin films have been deposited on silicon oxide at 300°C by very high frequency (182.5 MHz) sputtering using an Ar and H 2 gas mixture and an arsenic-doped Si wafer target. Characteristics of films are affected by the hydrogen partial pressure, and polysilicon of lowest resistivity is obtained at 20 to 30% hydrogen partial pressure ratio. We found that as the hydrogen content of the film is reduced, resistivity decreases. This is attributed to reduction of amorphous grain boundary regions due to better crystallization. It is also found that the normalized ion flux incident on the growing surface varies with hydrogen partial pressure, an important parameter for determining the properties of as-deposited polysilicon.

The adhesion and removal behavior of metallic impurities on a PFA sheet surface was examined with TRXRF analysis. Metals such as Fe and Cu are strongly adhered, and they can be removed to some extent by SPM or FPM cleaning. The surface metallic concentration of PFA sheets did not increase when they were dipped into UPW or chemicals contaminated with metals, therefore it is assumed that metallic impurities do not adhere to the PFA surface from liquids. Moreover the metallic transfer tests showed that a cleaned PFA sheet did not contaminate Si wafers but an uncleaned sheet polluted the wafer strongly with metallic impurities. Therefore, when PFA molded parts such as wafer carriers and tubes are used in wet processing in semiconductor manufacturing, they must be cleaned by SPM or FPM cleaning

Thin polyoxide films grown at 400/spl deg/C on n/sup +/-poly-Si films, used as gate insulators in MOS capacitors, are shown to exhibit superior performance, with respect to conventional, thermally grown polyoxide films at 900/spl deg/C, i.e., they possess lower leakage currents and can sustain higher electrical fields. They are also shown to be superior to, either polyoxide films grown at 980/spl deg/C on substrates treated by chemical mechanical polishing (CMP) or polyoxide films grown by electron cyclotron resonance (ECR) nitrous oxide plasma at 400/spl deg/C. The present film growth techniques utilize oxygen radicals (O*), rather than oxygen molecules (O/sub 2/), which are used in conventional processing. The oxygen radicals are generated by microwave (2.45 GHz) excited high-density plasma of Kr/O/sub 2/ gas mixture.

In this paper, a new approach to reduce the 1/f noise levels in the MOSFETs on varied silicon orientations, such as Si(100) and (110) surfaces, has been carried out. We focus on the Accumulation‐mode (AM) FD‐SOI device structure and demonstrate that the 1/f noise levels in this AM FD‐SOI MOSFETs are obviously reduced on both the Si(100) and (110) surfaces.

Impurity back diffusion through a UHV pump in reduced-gas-processing chambers has been experimentally studied. A large throughput of process gases severely degrades the main UHV pump capability in dragging impurities, resulting in the back diffusion of impurities to the processing chamber. Such degradation is greatly influenced by the pumping speed of the backing pump. However, we have found for the first time that the impurity level in the chamber can be made even lower than that for the best performance under UHV when the gas flow rate is optimized for the system. The scenario to the gas pumping system optimization is presented.

The ultrastructure of Trichophyton mentagrophytes cells stained with neutral red was investigated using electron microscopy and X-ray microanalysis. Fixatives containing molybdenum and chromium were used to prevent the outflow of neutral red. Electron-dense particles composed of metals and dye were observed exclusively in the vacuoles, which were increased in number and size, but not near the cell wall. Results indicate that neutral red passes directly through the fungal cell wall and is incorporated into the vacuoles.

It is demonstrated that the dependence of the reverse breakdown voltage (V/sub B/) on the ambient temperature (T) of modern shallow and ultra-shallow Si pn junctions, required for future ULSI scaled down devices, is drastically changed, with respect to that of the deeper, conventional Si pn junctions reported so far. In this work it is shown that unlike the conventional junctions in which the dV/sub B//dT sign was determined by the dopant concentrations, in the present ultrashallow Si junctions, dVB/dT cm have positive, negative and zero slopes, in the same junction, almost independent of the dopant concentration.

This paper presents the copper oxidation and flowing out characteristics inside copper pipe line, which is a candidate for future cooling water pipe line, with various species of dissolved gases in cooling water. The result reveals that copper oxidation rate in air saturated ultrapure water is much faster than other conditions, whereas its rate in hydrogenated ultrapure water is not differentiated from that in de-aerated ultrapure water. However, the amount of copper flowed out from the pipe surface is drastically reduced by using hydrogenated ultrapure water. The data indicate that copper in neutral pH solution with the oxidation reduction potential (ORP) value of 400 mV such as hydrogenated ultrapure water is perfectly stable for surface oxidation. As a cooling water has many kinds of advantages: it is not necessary to use chemicals as anti-corrosive agents; there is no cooling efficiency degradation by oxidation inside pipe line surface, and a "maintenance-free system" can be realised. A newly developed cooling system using hydrogenated ultrapure water is applicable to other industry facilities as well as semiconductor fabrication with major benefits in terms of the "industrial cost" and "the environmental issues".

A room-temperature Cu metallization scheme has been established by a low kinetic-energy particle process, in which epitaxial growth of metal films on Si as well as the formation of ideal metal-silicon contacts without alloying heat cycles has been realized. Cu films deposited on SiO/sub 2/ showed excellent adhesion without an intervening glue layer. Ideal Schottky diode characteristics were obtained. The process is compatible with low-temperature high-throughput one-wafer processing. It is suggested that this process help to establish highly flexible metallization processes for custom VLSI circuit fabrication. >

Formation of hillock-free aluminum films has been realized by a low-kinetic-energy particle process. The process utilized the low-energy (a few tens of electron volts) Ar-ion bombardment of the growing film surface for modifying the thin-film properties. Completely

We have demonstrated that carbon contamination on a gate oxide surface induces the degradation of the gate oxide reliability. Highly-reliable ultra thin gate oxides can be obtained by a new oxide formation process: the thermal oxidation of a silicon surface in the strongly reductive ambient and/or the removal of hydro-carbon from the gate oxide surface with O/sub 3/ gas/IR lamp cleaning.

Highly selective SiO/sub 2/ over Si reactive ion etching has been achieved by utilizing carbon rich fluorocarbon plasma. The carbon rich plasma is very useful for deposition of a thick carbon rich fluorocarbon film that protects the Si surface from the etchant (Akimoto et al., 1993; Hayashi and Sekine, 1996; Goto and Hori, 1996). On the other hand, because the SiO/sub 2/ etching reactions occur under ion bombardment, implantation of a large amount of carbon to the Si substrate results from plasma exposure during the overetch period. This damage layer can degrade the contact resistance or increases the junction leakage current. Consequently, a great deal of research has been directed at removal or recovery of the damage layer. However, the damage formation has become a critical issue. As the projected ion implantation depth range for the MOS transistor source and drain may become shallower, contact hole etching demands low damage without removal of the damage layer. For further development of low damage SiO/sub 2/ etching, it is necessary to determine the cause of degradation of contact resistance in order to control the damage-inducing factor. In this study, damage layer properties were investigated by evaluation of implanted element profiles and carrier concentration profiles in the damage layer induced by reactive ion etching. Also, the relationship of the damage layer properties and contact resistance were investigated for various plasma sources or etching conditions.

We have developed an ultra-low contact resistance metallization process employing oxygen-contamination-free silicidation technology combined with ion beam mixing technique. Suppression of native-oxide layer formation on the metal surface by use of an in situ formed Si encapsulation layer has resulted in ultra-low metal-to-silicon contact resistances of 3.3/spl times/10/sup -9/ /spl Omega//spl middot/cm/sup 2/ and 7.5/spl times/10/sup -9/ /spl Omega//spl middot/cm/sup 2/ with Ta silicided contacts for n/sup +/-Si and p/sup +/-Si, respectively.

Copper films were epitaxially grown on (100)Si substrates at room temperatures utilizing low kinetic‐energy particle bombardment of growing copper film surfaces. The crystallographic structure of the film, such as (100) or (111) orientation, was selected by controlling the energy of incident particles. Low‐temperature, damage‐free substrate surface cleaning has also been realized by the low kinetic‐energy particle process, which has made it possible to form ideal metal‐semiconductor contacts without employing any alloying heat cycles.

Surface‐reaction film‐formation technology of epitaxial Si and polcrystalline silicon using free‐jet molecular flow is proposed. High‐rate (∼0.5 μm/min or higher) growth of homoepitaxial Si films with high crystallographic perfection has been achieved at temperatures as low as 600 °C without the chemical by‐product deposition on the inner surface of the reaction chamber. This result also implies that this system has the cleaning‐free function. The film‐formation mechanism appears to be dominated by the chemical reaction on the substrate surface without the vapor phase reaction.

Native silicon (Si) oxide growth on Si (100) wafers in air and in ultrapure water at room temperature requires coexistence of water and oxygen in the air and ultrapure water ambients. The growth rate data on n‐, n+‐, and p+‐Si (100) in air indicate layer‐by‐layer growth of an oxide. The growth rate on n‐Si (100) in ultrapure water may be governed by a parabolic law. For native oxide growth in ultrapure water, the number of Si atoms dissolved in ultrapure water is over one order of magnitude larger than the number of Si atoms contained in the grown native oxide film. The structural difference between the native oxide film in air and in ultrapure water is also discussed.