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In this paper, a physical mechanism for hot carrier injection (HCI) induced trap generation and degradation in bulk FinFETs is investigated and verified with both experiment and simulation evidence. HCI degradation is mainly caused by interface states generated by drain avalanche hot carrier injection. From this model, impact ionization intensity, location and trapping immunity are proposed as key parameters to modulate HCI degradation. HCI reliability in I/O FinFETs is severely degraded with respect to planar FETs because of the enhanced capability of the gate to control the channel potential profiles increasing the intensity of the lateral E-field in comparison with planar devices. Based on this FinFET HCI mechanism, we have successfully optimized source/drain junction process to achieve reliable HCI characteristics for 14nm and 10nm FinFET devices.

We have developed a simple technique for forming ultrahigh-density HfO2 nanodots with diameters of less than 3 nm and densities of 6 ×1012 cm-2. The advantage of our method is that density and diameter are controllable. The memory cell in which ultrahigh-density nanodots are used as charge trap nodes shows 2 bits/cell operation without lateral migration of trapped charges. We propose that the ultrahigh-density HfO2 nanodots are suitable as charge storage nodes in future 45 and 32 nm generations.

A direct tunneling memory (DTM) with ultra-thin tunnel oxide and depleted floating gate has been proposed for low power embedded RAM. To achieve excellent charge retention characteristics with ultra-thin tunnel oxide, floating gate depletion is adopted to utilize the band bending at the interface between floating gate and tunnel oxide in charge retention period. The depleted floating gate is also effective to suppress the degradation of program/erase speed caused by the gate re-oxidation pro cess. These effects were evaluated by the device and process simulations and confirmed by the experimental data. As a consequence, both fast programming time and superior retention time have been achieved, which is a promising performance as a low power embedded RAM for system-on-a-chip (SoC) applications.

A polymetal dual gate dynamic random access memory (DRAM) for application specific memory (ASM) with dual nitrogen concentrated oxynitrides was developed for the first time. This technology uses selective nitrogen implantation performed just after gate oxidation. The nitrogen concentration of p-type metal oxide semiconductor (PMOS) in gate dielectric combined with nitrogen implantation and NO (nitric oxide) annealing is sufficiently high to suppress boron penetration, whereas that of the cell array transistor (cell-Tr) and n-type metal oxide semiconductor (NMOS) is sufficiently low to maintain the threshold voltage (Vth) without increasing the channel dosage by using only NO annealing.

Applications of SiH-free silicon nitride (SiN) films, formed by tetrachlorosilane (TCS) and ammonia, have been proved to effectively suppress the SiN-induced boron penetration. The SiN-induced boron penetration has been investigated in detail by using boron-doped polysilicon gated capacitors with several kinds of thick SiN films. It was clarified for the first time that the SiN-induced boron penetration becomes worse with SiH content in SiN films and deposition technique of SiH-free TCS-SiN films is essential for realization of the high-performance PMOSFETs.

We have studied the structural evolution of the high density interfacial layer around 10 A thick in 40 A thermal oxide observed by difference X-ray reflectivity (DXR) techniques during thermal annealing. Effects of interfacial stress are evaluated by grazing incidence X-ray diffraction. As the annealing proceeds, density of the interfacial layer decreased and got close to the value of the upper SiO 2 layer after 2 h of annealing in Ar at 800°C. At the same time, a slight increase in the thickness of the interfacial layer and the flattening of the Si interface are observed. These results indicate that during annealing, both the structural relaxation of oxide in the direction normal to the interface and an atomic rearrangement at the Si interface proceeds. Elastic deformation by stress can not be the dominant origin of the density change. The observed decrease of the interface state density D it along annealing may be linked to the decrease of structural defects accompanied with the structural relaxation at the interface.

Behavior of Fe impurity at the Si-SiO 2 interface of a metal-oxide-semiconductor (MOS) made through HCl oxidation was studied with electrical measurements and transmission electron microscopy. Fe impurity was introduced in silicon wafers by ion implantation to the doses of 1.0 x 10 15 and 1.0 x 10 14 cm -2 . The wafers were then oxidized in HCl/O 2 ambient. The Fe impurity either nucleated (1.0 x 10 15 cm -2 ) to precipitates in the Si substrate near the Si-SiO 2 interface or scattered uniformly in the SiO 2 (1.0 x 10 15 and 1.0 x 10 14 cm -2 ). The precipitates were identified as metallic α-FeSi 2 or semimetallic FeSi. The precipitate is supposed to form a weak spot in the silicon oxide, where the electric field is strengthened ; however, the dielectric effect of uniformly scattered Fe impurity in the SiO 2 film is relatively small. Fe precipitates were gradually included into the SiO 2 film and finally dissolved during HCl oxidation. As a result, Fe impurity was scattered in the middle area of the SiO 2 film. The gettering ability of HCl oxidation is attributed to its enhancement of dissolution of Fe-silicides in the SiO 2 film.

We have investigated thin film transistors (TFTs) with ultra-thin polycrystalline silicon (poly-Si) of 77 A – 185 A. The TFT charge transfer characteristics such as ON current and effective mobility are dominated not by the thickness itself but by the grain size of poly-Si channel. When the poly-Si channel thickness is decreased with the same grain size, the sub-threshold TFT characteristics are improved without degradation of ON current and reliability properties. These results give us appropriate criteria to establish an excellent poly-Si channel in vertical NAND flash memory.

The x-ray interference technique has been applied to evaluate the structural changes of high temperature grown chemical vapor deposited (CVD) SiO2 film under several post annealing conditions. In annealing above 800 °C in O2 ambient, a thermal oxide growth has been found at the CVD SiO2/Si interface, and its precise thicknesses have been determined. The estimated diffusion coefficient of the oxidant in CVD film was about three times larger compared to that of thermal oxide. A threshold voltage shift in the oxide was found to strongly correlate to the thickness of the thermal oxide rather than to thermal modifications of the CVD SiO2 itself.

We demonstrated SONOS flash memory with a SiO/sub 2//High-k/SiO/sub 2/ structure based on a 2-bit/cell scheme. We evaluated three kinds of high-k dielectric films which were Si/sub 3/N/sub 4/, Al/sub 2/O/sub 3/ and HfO/sub 2/. Among these films, Al/sub 2/O/sub 3/ showed superior retention characteristics. The charge loss amount of Al/sub 2/O/sub 3/ at 150/spl deg/C is almost the same as that of Si/sub 3/N/sub 4/ at 25/spl deg/C. HfO/sub 2/ showed poor retention characteristics. In addition, we have found that each film has a different charge loss mechanism. We speculate that Si/sub 3/N/sub 4/ causes vertical charge migration, Al/sub 2/O/sub 3/ causes scarcely any leakage, and HfO/sub 2/ causes lateral charge migration. As a consequence, Al/sub 2/O/sub 3/ is very suitable for a charge trapping layer in multi-bit SONOS memory.

Direct Tunneling Memory (DTM) with ultra-thin tunnel oxide and novel depleted floating gate (FG) has been demonstrated for embedded RAM applications. Fast programming ( 10s) and large threshold voltage difference (>1.3V), has been achieved by utilizing the band bending at the FG/oxide interface in charge retention period. The depleted FG is also effective to suppress the degradation of program/erase speed caused by the gate re-oxidation process. As a consequence, newly proposed DTM is a promising candidate for cost-effective and scalable embedded RAM instead of a conventional embedded DRAM.

Using clean ozone in a new load-locked oxidation system, we made thin gate oxides with improved charge to breakdown characteristics (Q/sub bd/) and low surface state sensitise (D/sub it/). >

A significant improvement in ultra-thin (4 nm) gate oxide quality has been carried out using UV/O/sub 3/ pre-treatment of native oxide before thermal oxidation. UV/O/sub 3/ pre-treatment makes native oxide dense and close-packed without leaving any residue species. Ultra-thin gate oxide formed by UV/O/sub 3/ pre-treatment and O/sub 3/ oxidation has been found to have excellent behavior, low leakage current, low surface state density, and superior dielectric breakdown characteristics. UV/O/sub 3/ pre-treatment looks promising for using in ultra-thin gate oxidation necessary for 0.1 /spl mu/m ULSI fabrication.

We consider nitrogen profiling in oxynitrides to be the key technology for next generation Flash Memories, because of its ability to suppress the generation of traps in tunnel oxides. We are trying to develop an oxynitriding technique for tunnel oxides that uses nitric monooxide. This time, we tried to control nitrogen profile in oxynitrides by using reoxidized oxynitride process. By using a three- step oxidationoxynitridation-reoxidation process, we attempted to systematically tune oxidation conditions, to obtain a satisfactory tunnel oxide/Si interface and SILC characteristics. Highly reliable tunnel oxide for flash memory has been achieved using recently developed reoxidized oxynitrides processing, which is characterized by wet oxidationoxynitridation-dry oxidation. This process yields excellent characteristics, such as low oxide trap formation, low leakage current, and high charge to breakdown (Qbd). This three-step oxynitride process is best suited for flash memories having superior Program/Erase (P/E) cycling endurance and data retention characteristics. In addition, I will propose the optimum conditions for the reoxidation process.

The UV-excited chlorine radical treatment effectively removed trace metal contaminants from Si ans SiO2 surfaces. We have found that this is predomonantly attributed to reactions between metal and chlorine, and metal oxides and silicon chloride, respectively. The former process was subjected to identify a breakdown spot on a thin gate dielectric film. After dielectric breakdown, a silicon crystallized filament as small as a few nanometers in diameter was formed and was selectively etched with chlorine radicals revealing a successively-etched region of the Si substrate. Nonuniformities of native exides on silicon were also detected using the same method. Gettering and etching wi:h a poly Si layer showed a possibility to make a gate dielectric film damage free and contamination free. Densification of native oxides formed after conventional wet cleaning of silicon was made with UV-excited oxygen radicals. Electrical characteristics of gate dielectrics treated with UV-excited chlorine and oxygen radicals showed high reliability.

Direct tunneling memory (DTM) is a floating-gate (FG) memory with ultra thin tunnel oxide. Using technology computer aided design (TCAD) to optimize the device parameters, we tried to prolong the retention time of DTM without degrading the operation speed. It has become clear that FG depletion, high substrate concentration, and source/drain offset from FG are essential techniques of improving the retention time. As a consequence, there is the prospect of simultaneously achieving fast program/erase time of 30 ns and long retention time of 10 s with an operation voltage of 3.3 V and tunnel oxide thickness of 1.2 nm.

We investigated the enhanced oxidation effect of using silicon (Si) implanted with fluorine (F), iodine (I), and xenon (Xe) before gate oxidation. I and Xe, which result in shallower implants because of their higher mass numbers, were expected to be less damaging to the Si substrate. The resultant increase in oxide thickness was found to be 20%, 80%, and 50% under F, I, and Xe implantations with a dose of 5×1014 cm-2, respectively. We found that F atoms outdiffuse to their ambient through SiO2, and that I implantation causes the greatest increase in oxide thickness. In addition, F implantation shows highly reliable dielectric characteristics, low contact resistance, and a low junction leakage current. Consequently, the F implantation process is capable of providing reliable dual-thickness gate oxide for embedded dynamic random access memories (DRAMs).

We demonstrated that the control of the nitrogen profile in the gate oxynitride for complementary metal oxide semiconductors (CMOSs) is very important. We grew NO or N2O nitrided gate oxide at 800°C or 900°C to prepare three kinds of oxynitrides with different nitrogen profiles, and investigated the atomic configuration and the chemical state of nitrogen using secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. Furthermore, we fabricated CMOS field effect transistors with gate oxide and oxynitride, and evaluated the interface state density and the hot carrier immunity. By systematical investigation of the relationship between the nitrogen profile and the electrical characteristics, we found that the nitrogen in the oxynitride should exist only at the interface for realizing the CMOS devices having high performance and high reliability.

We studied how the interaction between fluorine and chlorine in SiO2 influences oxide thickness change and metal oxide semiconductor (MOS) reliability. Anhydrous HF treatment on amorphous Si (a-Si) introduces a large quantity of fluorine into the gate oxide compared to HF solution treatment. When the oxide is formed in an HCl atmosphere, it contains a large quantity of chlorine. If the fluorine atoms diffuse into the chlorine-rich oxide, Si–Cl bonds are easily replaced by Si–F bonds and the equivalent thickness increases. This tendency is further enhanced as the oxide becomes thinner. Both fluorine and chlorine, introduced in excess during the fabrication process, degrade MOS reliability because Si–F and Si–Cl bonds are weaker than Si–O bonds.

We have developed a high-accuracy difference X-ray reflectivity (DXR) method using intense synchrotron radiation for the evaluation of ultrathin thermal oxides on Si(100). By carefully analyzing DXR data for gate oxides with thicknesses of 40 Å and 70 Å grown at 800° C to 1000° C, the existence of a dense ( ∼2.4 g/cm3), thin (∼10 Å) layer at the S i O 2/S i interface has been revealed. The thickness of the interfacial layer decreases with increasing oxidation temperature. Oxides grown in O3 or HCl/O2 have a thinner interfacial layer compared to those grown in O2.

High-accuracy X-ray reflectivity measurements using synchrotron radiation have been carried out to study native oxides formed during various chemical-cleaning processes on Si wafer. Clear differences in the density of native oxides between various chemical treatments were obtained from the normalized reflectivity for the first time. Native oxides formed by HCl and NH4OH solutions have a low density, in contrast to the oxides formed by H2SO4 solution and UV/O3 whose densities are close to that of thermal oxide. These results are closely related to the results of chemical studies and the etching characterization of native oxides.

Effects of a number of 3-hydroxyisoxazole derivatives substituted at 4 and/or 5 position of isoxazole ring on cucumber Fusarium wilt (Fusarium oxysporum f. cucumerinum) and cucumber seedling damping-off (Corticium rolfsii, Pythium aphanidermatum), and their antimicrobial activities on potato-sucrose-agar (PSA) medium and in soil were studied.Greenhouse evaluation (in vivo)-Compounds substituted with alkyl groups or hydrogen atom at 5-position of isoxazole ring were generally more effective than the derivatives substituted with aryl groups under greenhouse conditions. The effectiveness decreased in the following order:methyl>ethyl>propyl>butyl>hydrogen.Replacement of hydrogen atom at 4-position of isoxazole ring by nitro or methyl group or by chlorine or bromine atom reduced effectiveness against Fusarium wilt or seedling damping-off.Laboratory evaluation (in vitro)-Inhibitory effects of these derivatives on PSA medium against R. solani, C. rolfsii and P. debaryanum were generally strengthened in proportion to increase in the number of carbon atoms of alkyl groups at 5-position with the exception of activities against F. oxysporum. The growth inhibition of C. rolfsii by these derivatives in soil was not proportional to increase in the number of carbon atoms of alkyl groups at 5-position, and 3-hydroxy-5-methylisoxazole (hymexazol) showed the highest activity in soil. On the other hand, replacement of alkyl groups at 5-position by phenyl group enhanced inhibitory effect on PSA medium, but reduced it in soil. Effect of hymexazol thus selected as the most effective soil-fungicide in this series of compounds was studied extensively by large scale tests in a greenhouse.

The mode of action of hymexazol against Pellicularia sasakii was studied. When the living mycelium of P. sasakii was incubated in aqueous solution of hymexazol for 24hr, a decrease in dry mycelial weight caused. Measurable decrease occurred at 50ppm, with progressively greater weight losses as the concentration increased. On the other hand, a decrease in the dry weight of heat-treated mycelium was negligible even at 1000ppm of hymexazol. The decrease in the dry mycelial weight was found to be closely correlated to a leakage of protein from the mycelium. At 250ppm of hymexazol, the protein leakage increased in almost linear fashion during 8hr incubation period, and then leveled off. When the mycelium was immersed in hymexazol solution for 1hr and subsequently incubated in distilled water for 23hr, a large amouut of protein leaked out from the mycelium during the 23hr incubation period in distilled water, which was in proportion to the concentration of hymexazol. While only a small amount of protein leaked out during the 1hr incubation period in hymexazol solution. Hymexazol inhibited the uptake of glucose by P. sasakii. Hymexazol was readily absorbed by the mycelium from the ambient solution within the first 1hr, and then the absorption reached to equilibrium. On potato-sucrose agar containing hymexazol at 100ppm or 10ppm, the growth of P. sasakii was reduced to some extent. At growth-inhibitory concentration of hymexazol, the hyphae appeared swollen parts as the hyphal tips and at various points along the sides of hyphae, and in certain cases the hyphae burst with loss of protoplasm.

The Raman spectra of amorphous fluorinated silicon films prepared by the reactive sputtering of Si in a gaseous mixture of SiF4-Ar have been measured. The calculations of the normal vibration frequencies of SiFn bonds using the valency force field model and the central force field model were also made. Comparing the experimental results with these calculations, the SiFn vibrational modes were assigned and the existence of SiF4 molecules was confirmed.

4種類の土壌(田無土壌,岩手土壌,三上-I土壌,野洲土壌)を用いてイネを箱育苗した際,出芽時に低温にあうと出芽前後の幼芽,幼根が腐敗あるいは褐変して枯死に至る苗立枯病が発生した。罹病苗からはPythium属菌が高頻度に分離され,それらはP. spinosum, P. irregulareおよびP. sylvaticumと同定された。これら3種のPythium属菌を種々の方法でイネに接種した結果,イネの幼芽,幼根に対しては強い病原性を示したが,1葉期のイネ苗に対しては病原性を示さなかった。これら3種の菌による苗立枯病の発生は,出芽揃い期までの低温と土壌pH 6の土壌で助長され,それ以後低温に遭遇しても発病が増加する傾向は認められなかった。上記の結果と比較するために,イネ以外の作物から分離されたPythium属菌(P. aphanidermatum, P. myriotylum, P. splendens, P. sylvaticum, P. ultimum, P. vexans)のイネに対する病原性を,接種実験で検討したところ,供試した全ての菌株は出芽時のイネに対して病原性を示した。

N-アリール環上に種々の置換基を有する4-カルボキシおよび4-ヒドロキシフタルイミド誘導体65種を合成し, アブラナ科野菜根こぶ病防除活性を検討した. 2, 6両位にアルキル基を導入した化合物群には高い活性が認められたが, これらの活性は両アルキル基の炭素原子数とα-branching 効果とに支配されていた. 高い活性発現に必要と考えられる条件として, 1) 両オルソ位にアルキル基のような疎水基が存在すること, 2) 両アルキル基中の炭素原子の合計数が4～6個であること, 3) 少なくとも一方のアルキル基にα-分岐が存在すること, 4) 2, 6両アルキル置換体のメタおよび, またはパラ位への置換基の導入は望ましくないことの四つの構造的特徴を提示した.

Eleven hands of Dupuytren's contracture in 9 male patients were surgically treated by limited fasciectomy with “open technique” over a period of 6 years. The average age from onset to operation was 2 years and 9 months. The lesions were evaluated according to Meyerding's classification; Grade 0 (2 hands); Grade 1 (2 hands); Grade 2 (6 hands), Grade 3 (1 hand) and Grade 4 (0 hand).We followed up these 11 hands of 9 patients for an average of 3 years and 7 months (minimum period, 2 years; maximum period, 6 years and 1 month).Postoperative results were classified according to Tubiana's method of evaluation: very good 5, good 5, fair 1 and poor 0. Six cases of good and fair results became recurrence and extension cases, but after surgical re-operation, became very good cases.The wounds were closed on an average of 25 days (range, from 17 days to 38 days) after operation.On follow-up, it was seen that the defective skin had become covered by soft skin with reproducted epidermal ridges.

3種類の土壌(田無土壌,岩手土壌,三上-II土壌)を用いてイネを箱育苗した際,特に育苗中・後期に低温にあうと,2∼3葉期のイネ苗が急に萎凋して枯死する症状の苗立枯病が発生した。これらの苗立枯病罹病苗からP. graminicolaが高頻度に分離された。P. graminicola分離菌株を種々の方法でイネに接種したところ,少量の菌糸を接種した土壌にイネ種子を播種するか,あるいは2葉期のイネ苗に遊走子を接種する方法では,2∼3葉期に萎凋症状を伴う苗立枯病が発生し,箱育苗で発生した萎凋・立枯型の病徴が再現された。一方,多量の菌糸を接種した土壌にイネ種子を播種するか,あるいは催芽種子に遊走子を接種する方法では,発病が出芽前後から始まり,出芽阻害となる例も多く観察された。以上の結果から,P. graminicolaは育苗中・後期に発生する苗立枯病に関与していることが明らかとなり,また出芽前後の苗立枯病にも関与している可能性が示唆された。

The metabolism of hymexazol (3-hydroxy-5-methylisoxazole) in soil was studied by using 14C-labeled chemical (14C-labeled at the 3 position on the isoxazole ring) to obtain fundamental information on its persistence in disease controlling activity and on residue analysis. Radioactive hymexazol was degraded in the unsterilized soil, and three radioactive metabolites were identified with carbon dioxide, acetoacetamide, and 5-methyl-2(3H)-oxazolone. The amount of 14CO2 evolved from radioactive hymexazoltreated soil increased with time, whereas those of the other metabolites decreased. The breakdown of hymexazol in unsterilized soil is biological, since only a trace of 14CO2 was evolved from the sterilized soil. Production of 14CO2 was remarkable in submerged condition compared to that in moist one. The amount of 14CO2 evolved from radioactive hymexazol treated soil increased with increasing temperature levels from 15C to 35C. Hymexazol was also degraded to CO2, acetoacetamide, and 5-methyl-2(3H)-oxazolone in the soil infested with Bacillus subtilis, Streptomyces griseus, Aspergillus niger, Arthrinium sp., or Penicillium sp. A certain portion of hymexazol and/or its metabolites were so tightly adsorbed by the soil that it could not be removed by extraction with 1N HCl and subsequent elution with 1N NaOH or methanol. Since acetoacetamide and 5-methyl-2(3H)-oxazolone were found to be less effective than hymexazol against Fusarium wilt of cucumber, the metabolism of hymexazol in soil can be considered as a detoxication step.

The mechanism and the nature of selective toxicity of pentachloronitrobenzene (PCNB) were studied from the view-point of absorption, metabolism and accumulation of the compound by plant pathogenic fungi.PCNB inhibited strongly the growth of Rhizoctonia solani and an isolate of Botrytis cinerea, but slightly the growth of the other isolate of B. cinerea, Fusarium oxysporum f. lycopersici, F. oxysporum f. niveum, and so on.The inhibitory action of PCNB against R. solani was fungistatic. That is, the mycelium inhibited by PCNB grow well when transfered to the PCNB-free medium.When R. solani was successively cultured on the PCNB-containing medium for a long time, the mycelium which was inhibited in growth at an early stage began to grow gradually. The sensitive fungi took up two or three times more PCNB than did the resistant ones. The PCNB-metabolizing ability (detoxifying ability) of the resistant fungi was stronger than that of the sensitive fungi. A large amount of PCNB accumulated within the mycelium of sensitive fungi, whereas only slight amount within the resistant fungal mycelium. The balance between the speed of absorption of PCNB and the detoxication within the fungus may play the first important role on its selective toxicity.

Recently, we experienced a solitary bone cyst of the hamatum. Our case was a nineteen-year-old female. Her chief complaint was pain of the left wrist joint due to fracture of the end of the left radius. Upon examination, we discovered a cystic lesion in her left hamatum. During surgery, this cystic lesion was separated into two parts through the septum. One had liquid and connective tissue, the other was empty. This cystic lesion was diagnosed as a solitary bone cyst by histological examination. No recurrence has been found two years after operation.

A reliable method of controlling iron impurities on the silicon wafer surface at low levels has been developed by using an iron‐contaminated HNO3 solution. Iron ions are thought to react with the silicon native oxide to form an Fe(III)‐O complex in proportion to the iron concentration in the solution. Using this method, we have quantitatively investigated the influence of iron impurities on metal‐oxide‐semiconductor device characteristics. The drastic degradation of generation lifetime, surface generation velocity, and dielectric breakdown strength of SiO2 have been observed above the surface iron concentration of 1×1012, 5×1012, and 1×1013 cm−2, respectively.

We have developed a wafer cleaning technique called the slight etch (SE) using an HNO3 and trace HF mixture. A 30 nm surface removal by the SE reduces the surface Fe concentration by one tenth, compared to conventional RCA and all measured elements below a concentration of 1010 cm-2, without roughness degradation. The ultraclean surface results in a significant improvement in the C-t retention time and defect density of SiO2. Since the etch selectivity of silicon for the oxide is more than 10, this cleaning is also ideal for wafers with patterned oxides.