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We investigate the effects of hydrogen radical treatment on piezoresistance coefficients of germanium under uniaxial stress up to ±500 μ strain over the temperature range −30 °C to 25 °C. Hydrogen radicals are produced by hydrogen gas (99.99%, 2.7 kPa) on a hot tungsten catalyst (1800 °C). The gauge factor and majority carrier on non-dope germanium dramatically changed from n- to p-type after the hydrogen radical treatment. The results suggest that the piezoresistance coefficients of germanium are seriously affected by vacancy-related levels around the midgap, which behave as donors or acceptors depending on the Fermi level and are passivated by the hydrogen radicals.

For fabricating semiconductor devices and for microelectromechanical systems, photoresists are important materials supporting photolithography processes. However, photoresists must be removed for subsequent processes. An earlier study demonstrated that adding a small amount of oxygen gas to the atmosphere in which hydrogen radicals are produced increased the decomposition rate of a positive-tone novolac photoresist. For this study, we prepared polymers with different side chain structures based on poly(vinyl phenol) (PVP). We examined the effects of added oxygen and the oxygen-added hydrogen radicals on the decomposition rates of PVP-based polymers. Hydroxyl groups of PVP are partly substituted with tert-butoxycarbonyl groups in order to use for base polymer of KrF photoresist. Results show that oxygen addition can be useful for KrF photoresist removal.

Photoresist removal method using hydrogen radicals produced by decomposing hydrogen on a hot-wire catalyst is one of an environmentally friendly methods. We examined the relationship between photoresist removal rate and its surface temperature and the surface element analysis for a tantalum catalyst. In this study, we considered an adaptability of the catalyst to the removal.

Learning by the actual experience of fabrication and evaluation of a p-n junction is a very effective way for students to obtain a deep meaningful understanding of the fundamentals of semiconductor physics. To achieve this requirement at a real-world classroom situation, a simplified fabrication process for making the silicon p-n junction as the educational application was studied. The process without using the lithography process, and in use of simple thermal diffusion furnace under the air environment for the impurity thermal diffusion process by using phosphorous silicate glass (PSG) thin film prepared by the Sol-Gel material as the phosphorus (P) diffusion source was proposed and tested. As the results, it was obtained that the impurity concentration and diffusion depth were controlled well by this method, and good rectification phenomenon of the p-n junction was successfully observed. The typical diode factor n of the p-n junction was approximately 2.3. The p-n junction also performed well as a solar cell. The FF is approximately 0.7. These results show that it is possible to use the p-n junction prepared by this simplified process as the educational device to help students’ understanding of the theory of the p-n junction.

It is well known that electron beam lithography is one of the potential candidates to fulfill of the demand of the miniaturization of the design rule of semiconductor integrated circuits beyond sub 100nm size with high reproducibility. It is also a fact that the resolution is recognized to depend on the various factors which are oriented to the machine and process conditions, for example, electron beam diameter, the intensity distribution of the beam itself, the resistance properties polymers, the development conditions, etc. Therefore, it is thought that it is impossible to be derivable directly and unambiguously from the resist material itself. In this study, the intrinsic resolution of the resist polymer was discussed based on the hypothesis that the resolution itself may be able to improve to the same size as the size of an electron beam profile, or less. The bi-layer structure ZEP520A/poly methyl glutar imide (PMGI) was proposed and tested. As for the results achieved, the contrast γ was improved constantly with a reduction in the development time and a decrease in the development temperature. The highest γ value, approximately 18, was obtained during development at the-20°C condition. An approximately 70nm with high aspect ratio pattern which is almost the same size of the beam pattern was obtained. This result provides an understanding how the intrinsic resolution of the resist material should be, and can be applied to other lithography methods. This process was applied to the actual electrode pattern making process. An approximately 100nm width of Copper nanowire as the gate electrode for the AlGaN/GaN HFET was successfully demonstrated. In addition, AlGaN/GaN HFET operated at about 73.5GHz, successfully.

It is shown that not only the hole transfer between the decoupled two valence bands but also the stress-dependent hole effective mass is critical to the explanation of the origin of piezoresistance effects in p-type silicon. The difference between the density-of-state effective masses of heavy hole and light hole bands, which have been assumed equivalent in the decoupled two-band model reported previously, is shown to play an important role in the piezoresistance effects of p-type silicon at room temperature.

A simplification of the lithography process was studied. The simplification method of photolithography, named “alignment-less lithography” was proposed by omitting the photomask alignment process in photolithography process using mechanically aligned photomasks and substrate by using a simple jig on which countersinks were formed. Photomasks made of glass and the photomasks made of transparent plastic sheets were prepared for the process. As the result, approximately 5µm in the case of the glass mask, and 20µm in the case of the OHP mask were obtained with repetitive accuracies, respectively. It was confirmed that the alignment-less lithography method was successful. The possibility of the application to an educational program, such as a heuristic for solving problems was suggested using the method with the OHP mask. The nMOS FET fabrication process was successfully demonstrated using this method. The feasibility of this process was confirmed. It is expected that a totally simplified device fabrication process can be achievable when combined with other simplifications, such ass the simplified impurity diffusion processes using PSG and BSG thin film as diffusion source prepared by the Sol-Gel material under normal air environment.

The educational method which is including designing, making, and evaluating actual semiconductor devices with learning the theory is one of the best way to obtain the fundamental understanding of the device physics and to cultivate the ability to make unique ideas using the knowledge in the semiconductor device. In this paper, the simplified Boron thermal diffusion process using Sol-Gel material under normal air environment was proposed based on simple hypothesis and the feasibility of the reproducibility and reliability were investigated to simplify the diffusion process for making the educational devices, such as p-n junction, bipolar and pMOS devices. As the result, this method was successfully achieved making p+ region on the surface of the n-type silicon substrates with good reproducibility. And good rectification property of the p-n junctions was obtained successfully. This result indicates that there is a possibility to apply on the process making pMOS or bipolar transistors. It suggests that there is a variety of the possibility of the applications in the educational field to foster an imagination of new devices.

Volume production of 45nm node devices utilizing Nikon's S610C immersion lithography tool has started. Important to the success in achieving high-yields in volume production with immersion lithography has been defectivity reduction. In this study we evaluate several methods of defectivity reduction. The tools used in our defectivity analysis included a dedicated immersion cluster tools consisting of a Nikon S610C, a volume production immersion exposure tool with NA of 1.3, and a resist coater-developer LITHIUS i+ from TEL. In our initial procedure we evaluated defectivity behavior by comparing on a topcoat-less resist process to a conventional topcoat process. Because of its simplicity the topcoatless resist shows lower defect levels than the topcoat process. In a second study we evaluated the defect reduction by introducing the TEL bevel rinse and pre-immersion bevel cleaning techniques. This technique was shown to successfully reduce the defect levels by reducing the particles at the wafer bevel region. For the third defect reduction method, two types of tool cleaning processes are shown. Finally, we discuss the overall defectivity behavior at the 45nm node. To facilitate an understanding of the root cause of the defects, defect source analysis (DSA) was applied to separate the defects into three classes according to the source of defects. DSA analysis revealed that more than 99% of defects relate to material and process, and less than 1% of the defects relate to the exposure tool. Material and process optimization by collaborative work between exposure tool vendors, track vendors and material vendors is a key for success of 45nm node device manufacturing.

This paper describes the method for producing a nanobridge-type SQUID, the LsIo/ϕO ratio of which can be regulated to an optimal value at the liquid He temperature (4.2 K), and the properties of the SQUID. An epitaxial NbN film is produced by the reactive RF magnetron sputtering method for use as the electrode material, and an MgO film, which is thermally stable, is used as the insulating barrier. The Josephson nanobridges are formed in MgO film of the NbN/MgO (5-10 nm)/NbN junction of about 4 × 4 μm2 in area by field emission in the liquid He environment. The junction resistance before the application of electric field is very high, that is, 1 MΩ or higher. Needless to say, Josephson current is absent in the junction. The critical current can easily be regulated to a desired value by varying the applied voltage. The produced SQUID exhibits a high stability to the heat cycle test (300 K-4.2 K) which is carried out 50 to 60 times for about 2 years.

Cerebral angiographic findings in 315 cases of postapoplectic hemiplegia were analysed with reference to their rehabilitation effects and the following conclusions were obtained.(1) Of 315 cases of postapoplectic hemiplegia, 41 were due to the occlusion of cerebral artery, of which 13 (4.1%) were attributed to the occlusion of the internal carotid artery; this is about 1/3 to 1/4 of the frequency reported in Europe and America. There were 23 cases (7.3%) of the middle cerebral artery (trunk) occlusion and 5 cases of anterior cerebral artery occlusion, of which 4 were the occlusion of its branches, both of which were of lower frequency than in Europe and America.Arteriosclerotic findings were clearly found in 101 (32.1%) and the angiograms were approximately normal in 95 (30.0%).(2) In the cases of cerebral artery occlusion, the improvements of ADL (Activity of Daily Living) were extremely poor. Of 41 cases of cerebral artery occlusion, 22 (53.6%) were dependent or partially independent and only 2 (4.9%) were independent in the ADL.Of 101 cases with advanced arteriosclerotic findings, 45 (45.0%) were poor in the ADL. Of 95 cases with normal angiograms, on the contrary, 68 (71.6%) became independent in the ADL.(3) In the cases of cerebral artery occlusion, the functions of the upper extr emities were usually very poor, resulting in nonfunctioning hands in most cases. This was also true in the functions of the lower extremities, that is, in ambulation; of 41 cases, 20 (48.8%) remained in abasia and there was not a single case of independent gait. Also in the cases with advanced arteriosclerotic findings, the rehabilitation effect of ambulation was poor. On the contrary, all the cases without pathological angiographic findingss reached the stage of either complete or incomplete independent gait.(4) The lowering of muscle strength on the unaffected side, incontinence and the absence of motivation which hinders the rehabilitation effect were hardly observed in the cases with normal angiograms, but were often observed in the cases with advanced arteriosclerotic findings, particularly in the cases with complication of cerebral artery occlution and arteriosclerosis.(5) Most cases with cerebral artery occlusion or with advanced arteriosclerotic findings were found to have abnormal mentality, such as neurasthenia, depression, mania, paranoia and character deterioration, and a low intelligence quotient of under 79.(6) The quantitative analysis of cerebral blood flow and metabolism in postapoplectic patients revealed that those with findings of angiographic cerebral artery occlusion were generally lower than those with no angiographic findings, and that it was still lower in those with findings of arteriosclerosis.(7) The location and the extent of the focus in the brain is the most important factor for the evaluation of rehabilitation potential in the postapoplectic patients.

A 26-year-old male with Marfan's syndrome complicated by renovascular hypertension was reported. Stenosis of the main renal artery among the left multiple renal arteries was proved. In the present case, a high incidence in cerebrovascular disturbance was found on the paternal side. The patient expired on account of malignant nephrosclerosis following an attack of cerebral apoplexy. The causative relationship between Marfan's syndrome and reno-vascular hypertension was discussed.

The aim of this investigation is to achieve high transition temperature, low resistivity films under conditions suitable for use in all-NbN Josephson junction fabrication. For this purpose, the heteroepitaxy of NbN on MgO films is investigated. For substrate temperature of 200°C or thereabouts, polycrystalline MgO films of (200) orientation were formed on (100) silicon, (11̄02) α-Al2O3, and fused silica. Based on XTEM, HEED and X-ray data, heteroepitaxial growth ((100)NbN//(100)MgO) was obtained in NbN films and NbN/MgO/NbN trilayers deposited on (200) oriented MgO films. The epitaxial NbN films of 10 nm thickness had high transition temperatures of about 14 K, and relatively low residual resistivities of less than 200 µΩ·cm. Using the GL relationships, we calculated the Ginzburg-Landau parameters, λ(0) and ξ, of our NbN films in the dirty limit. The calculated ξ(4.2 K) and λ(0) are ∼4.5 nm and ∼300 nm, respectively.