Search

The parasitic resistance of the FinFET is investigated by the measurement based analysis. The RS/D model suggests that careful optimization as to the NiSi incorporation is necessary for the effective Rp reduction. The Rext seriously increases the Rp for TfinLt25 nm and also causes the Rp variability due to the Tfin variation.

TiN gate FinFET SRAM half-cells with different s-ratios from 1-3 have successfully been fabricated by using the orientation dependent wet etching and conventional reactive sputtering, for the first time. It is experimentally found that static noise margin (SNM)at read condition increases with increasing s-ratio due to the strength of pull-down transistor. To overcome SRAM cell size increment with increasing s, a fin-height controlled pass-gate (PG) SRAM structure is proposed.

An independent-gate four-terminal FinFET SRAM have been successfully fabricated for drastic leakage current reduction. The new SRAM is consisted of a four-terminal (4T-) FinFET which has a flexible Vth controllability. The 4T-FinFET with a TiN metal gate is fabricated by a newly developed gate separation etching process. By appropriately controlling the Vth of the 4T-FinFET, we have successfully demonstrated the reduction of the leakage current and power consumption of the SRAM cell.

We propose a flexible-pass-gate (Flex-PG) FinFET SRAM to enhance both the read and write noise margins. The flip-flop in the Flex-PG SRAM cell consists of usual FinFETs while its pass gates consist of Vth-controllable four-terminal (4T) FinFETs with independent double-gates. We experimentally demonstrate that the proposed Flex-PG SRAM increases both the read and write margins by controlling the Vth of the pass gates.

Dual metal gate CMOS FinFETs have been integrated successfully by the Ta/Mo interdiffusion technology. For the first time, low- V t CMOS FinFETs representing on-current enhancement and high- V t CMOS FinFETs reducing stand-by power dramatically, namely multi- V t CMOS FinFETs, are demonstrated by selecting Ta/Mo gates for n or pMOS FinFETs with non-doped fin channels. The dual metal gate FinFET SRAM with a low- V t configuration is demonstrated with excellent noise margins at a reduced supply voltage.

As one of promising metal gate materials, PVD TiN has widely been studied for conventional bulk-planar CMOS devices due to its high purity [1, 2]. However, there have been no systematical studies regarding the PVD TiN gate work function (tin) control using the nitrogen gas flow ratio (Rfrac12 = N2/(Ar+N2)) in the sputtering. In this paper, we present the Rfrac12 controlled tunable work function PVD TiN gate technology and its application for FinFET CMOS.

By means of X-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC), this study set out to investigate the application of plasma immersion ion implantation (PIII) for the surface modification of ProTaper® NiTi rotary instruments. This study was undertaken because the PIII method was perceived to have the potential of developing into a standard surface modification technique that improves clinical quality and outcome. Specimens received nitrogen ion or nitrogen plus argon ion implantation. XPS analyses with and without argon ion etching were obtained for all specimens. In addition, DSC analysis was performed to investigate the phase transformation behavior of the bulk material. Results indicated that the surfaces of NiTi instruments were successfully modified by nitrogen PIII, whereby a light golden TiN layer was yielded. Moreover, the PIII technique did not alter the superelastic character of NiTi instruments because it was carried out at near-room temperature. We thus concluded that nitrogen PIII is a promising surface modification technique to improve the surface characteristics of NiTi rotary instruments.

One of the biggest challenges for the VLSI circuits with 32-nm-technology nodes and beyond is to overcome the issue of catastrophic increases in power consumption due to short-channel effects (SCEs). Fortunately, "independent" double-gate (DG) FinFETs (named "4-terminal-FinFET" because of its four terminals; source, drain, gate 1 and gate 2) have a promising potential to overcome this issue thanks to a post-fabrication flexible Vth controllability in addition to their superior SCE immunity. This paper presents novel 4T-FinFET device technology based on experimental demonstrations. Newly-developed DG separation processes for the 4T-FinFETs, successful fabrication of the optimum 4T-FinFET with asymmetric gate oxides, and dynamic power management demonstration using 4T-FinFET are presented.

A rigorous analytical thermal model has been formulated for the analysis of self-heating effects in FinFETs, under both steady-state and transient stress conditions. 3-D self-consistent electrothermal simulations, calibrated with experimentally measured electrical characteristics, were used to understand the nature of self- heating in FinFETs and calibrate the proposed model. The accuracy of the model has been demonstrated for a wide range of multi-fin devices, by comparing against finite element simulations. The model has been applied to carry out a detailed sensitivity analysis of self-heating with respect to various FinFET parameters and structures which are critical for improving circuit performance and EOS/ESD reliability. The transient model has been used to estimate the thermal time constants of these devices and predict the sensitivity of power-to-failure to various device parameters, for both long and short pulse ESD situations.

1. Introduction Thinning of the fin channel is a key technology for CMOS FinFET scaling. For sub-14nm- node FinFETs, the fin channel becomes thinner than 10 nm. Furthermore, lowering of the sheet resistance (Rs) in the source/drain extension (SDE) is essential for performance improvement [1]. However, in the case of conventional I/I, it is difficult to reduce Rs because conventional I/I generally causes poly-crystallization and/or crystal defects to be formed in ultrathin fin region, even after activation annealing [2, 3]. This problem is particularly severe for SOI FinFETs. Recently, a novel I/I technology called heated I/I has been proposed. By using the heated I/I technology, the crystallinity of the implanted layer for Si is maintained during heated I/I, and defect-free crystal can be realized by activation annealing [4, 5]. Furthermore, it has been reported that the Ion-Ioffcharacteristics are improved in bulk Si-channel nMOS FinFETs by heated I/I [6]. In this paper, we report heated I/I technology for high-performance metal-gate/high-k CMOS SOI FinFETs. 2. Experimental Both nMOS and pMOS SOI FinFETs were fabricated. (110) fin channel was formed on (100) SOI substrate. Doped-poly-Si/TiN/HfO2/SiO2 gate stacks were formed, patterned, and etched. SDE was formed by room temperature (RT) or 500oC I/I. As+ or BF2 + was implanted at 5keV with total doses of 2x1015cm-2. RTA was performed at 915oC for 2s. Finally, the back-end process was carried out. 3. Results and Discussion To understand the crystal condition in the ultrathin fin region after heated I/I, we investigated the crystallinity of the SOI layer after RT and heated I/I by cross-sectional TEM observation (Figs. 1 and 2). The I/I was performed under the same conditions as those for the SDE formation in FinFETs (Figs. 1(a) and 2(a)). In the case of RT I/I, the SOI layer is fully amorphized by I/I (Fig. 1(b)), and polycrystals and twins are observed even after annealing (Fig. 1(c)). Since there are no seed crystals in the SOI layer after I/I, the implanted region cannot be crystallized by activation annealing. On the other hand, in the case of heated I/I, the crystallinity is maintained in the SOI layer after I/I (Fig. 2(b)). The crystal perfectly recovers by activation annealing (Fig. 2(c)). These results indicate that the defect-free SDE can be formed in ultrathin fin region by heated I/I. We investigated the impact of heated I/I on the SOI FinFET performance. Figures 3 (a) and (b) show the Ion distribution in the nMOS and pMOS FinFETs, respectively, processed by RT or heated ion implantation. For the nMOS FinFETs, the 50% Ion value of heated I/I is about 7% higher than that of RT I/I. Also, for the pMOS FinFETs, the 50% Ion value in the case of heated I/I is about 1.5% higher. The resistance (Rsd) of the SDE becomes lower in the case of heated I/I (Fig. 4), owing to perfect crystal recover [7]. This is the main reason for the improvement in Ionby heated I/I. Thus, by using heated I/I, the SOI FinFET performance is improved as compared with conventional RT I/I. 4. Conclusion Heated I/I contributes to the formation of the defect-free SDE in ultrathin fin region and is effective for improving the performance of ultrathin FinFETs. Thus, heated I/I technology is promising for SDE formation in future SOI FinFETs. References [1] C.-H. Jan et al., IEDM Tech. Dig., 2012, p. 44. [2] M. J. H. van Dal et al., 2007 Symp. on VLSI Tech. Dig. (2007) 110. [3] R. Duffy et al., ESSDERC (2008) 334. [4] H. Onoda et al., Ext. Abs. the 13th Int. Workshop on Junction Tech. (2013) 66. [5] H. Onoda et al., Ext. Abs. the 14th Int. Workshop on Junction Tech. (2014) 126. [6] M. Togo et al., Symp. on VLSI Tech. Dig. (2013) T196. [7] W. Mizubayashi et al., IEDM Tech. Dig. (2013) 538. Figure 1

The impact of work function variation (WFV) in a metal gate (MG) electrode on low-frequency noise (LFN) is revealed for fin field-effect transistors (FinFETs). The LFN level is compared between the FinFETs having polycrystalline TiN and amorphous TaSiN MGs. The amorphous TaSiN MG exhibits a marked suppression of flicker noise in comparison with the TiN MG. The difference in the LFN level is correlated with the threshold voltage variability reflecting the WFV of the MG. By modeling the WFV of the TiN MG in the FinFET structure by three-dimensional device simulation, we clearly reveal the mechanism of the LFN increase by the WFV.

We have investigated the impact of heated ion implantation (I/I) on the performance and reliability of silicon-on-insulator (SOI) complementary metal–oxide–silicon (CMOS) fin field-effect transistors (FinFETs). An implantation temperature equal to and higher than 400 °C is needed to maintain the crystallinity of the Si substrate during I/I within the experimental conditions of ion species, implantation energy, and ion dose in this study. By heated I/I at 500 °C, the 11-nm-thick SOI layer perfectly maintains the crystallinity even after I/I, and a defect-free crystal is obtained by activation annealing. It was clarified that the cap layer is essential for the suppression of the out-diffusion during heated I/I. Heated I/I on the source and drain improves the on-current–off-current (Ion–Ioff), threshold voltage (Vth) variability, and bias temperature instability (BTI) characteristics of nMOS and pMOS FinFETs as compared with those after room-temperature I/I.

Floating-gate (FG)-type three-dimensional (3D) fin channel flash memories with triangular fin (TF) and rectangular fin (RF) channels and different interpoly dielectric (IPD) materials have been successfully fabricated using (100)- and (110)-oriented silicon-on-insulator (SOI) wafers and orientation-dependent wet etching. The electrical characteristics of the fabricated FG-type 3D fin channel flash memories including threshold voltage (Vt) variability, program/erase (P/E) speed, memory window, endurance, and data retention at room temperature and 85 °C have been comparatively investigated. A higher P/E speed, a larger memory window, and a lower-voltage operation are experimentally obtained in the TF channel flash memories with an Al2O3–nitride–oxide (ANO) IPD layer (TF-ANO) than in the RF channel ones with the same ANO IPD layer (RF-ANO) and the TF channel ones with an oxide–nitride–oxide (ONO) IPD layer (TF-ONO). The larger memory window and lower-voltage operation of TF-ANO flash memories are due to the high-k effect of the Al2O3 layer and the electric field enhancement at the sharp foot edges of the TF channels. It was also found that data retention for all fabricated FG-type 3D fin channel flash memories shows a weak dependence on temperature.

A logic system consisting of four-terminal double-gate MSOFETs (4T-DGFETs) suppresses power consumption while it also improves processing efficiency by utilizing a flexible threshold-voltage control function by a second gate of 4T-DGFET. Based on the simulation calibrated with the fabricated device characteristics, it is shown that the 4T-DGFET logic is effective in low-standby-power applications below the half-pitch (hp) 32-nm technology node. A scaling strategy for the 4T-DG logic is also provided.

The purpose of this study was to provide a quantitative assessment of galvanic corrosion behavior of orthodontic archwire alloys coupled to orthodontic bracket alloys in 0.9% NaCl solution and to study the effect of surface area ratios. Two common bracket alloys, stainless steels and titanium, and four common wire alloys, nickel-titanium (NiTi) alloy, beta-titanium (beta-Ti) alloy, stainless steel, and cobalt-chromium-nickel alloy, were used. Three different area ratios, 1:1, 1:2.35, and 1:3.64, were used; two of them assumed that the multibracket appliances consists of 14 brackets and 0.016 inch of round archwire or 0.016 x 0.022 inch of rectangular archwire. The galvanic current was measured for 3 successive days using zero-impedance ammeter. When the NiTi alloy was coupled with Ti (1:1, 1:2.35, and 1:3.64 of the surface area ratio) or beta-Ti alloy was coupled with Ti (1:2.35 and 1:3.64 of the surface area ratio), Ti initially was the anode and corroded. However, the polarity reversed in 1 hour, resulting in corrosion of the NiTi or beta-Ti. The NiTi alloy coupled with SUS 304 or Ti exhibited a relatively large galvanic current density even after 72 hours. It is suggested that coupling SUS 304-NiTi and Ti-NiTi may remarkably accelerate the corrosion of NiTi alloy, which serves as the anode. The different anode-cathode area ratios used in this study had little effect on galvanic corrosion behavior.

Gold alloys with Cu contents of 10 mass%, 20%, and 30% were used for morphological observation of porous surface structures after heating at 800 degrees C in air followed by pickling with acid solution. With increasing Cu content in the gold alloy, the internal oxidation zone became well-developed in the alloy matrix. The mechanism by which a porous structure was formed on the surface of a gold alloy containing only Cu as a base metal was thought to be as follows: Cu2O which formed along the grain boundaries acted as a diffusion path, permitting the penetration of O2- into the inner alloy matrix, and thereby resulting in internal oxidation occurring predominantly along the grain boundaries.

As advanced FinFET technologies, we have developed the co-integration techniques of the TiN gated high-performance 3T- and flexible V/sub th/ 4T-FinFETs. By using the conventional reactive sputtering of TiN, the well symmetrical V/sub th/ N- and P-channel 3T-FinFETs and the high V/sub th/-controllable 4T-FinFETs using the resist etch-back process have been demonstrated. The developed technologies are attractive to materialize the high-performance and power-managed FinFET CMOS circuits.

Dual metal gate technology using a combination of Mo and a Ta/Mo stack suitable for fully depleted silicon-on-insulator (FD-SOI) and double-gate (DG) transistors applicable to a gate-first process has been investigated. The annealing of the Ta/Mo stack at 600–700 °C induces the diffusion of Ta into the Mo layer, and different work functions between the single Mo layer and Ta/Mo stack gates are successfully obtained. The sputtered Mo gate exhibits a higher thermal stability than the e-beam-evaporated Mo gate. The difference in flatband voltage (0.31 V) between the Mo and Ta/Mo gates is ensured even after annealing at 850 °C for 20 s, by which subsequent source/drain activation can be carried out.

We have successfully developed the advanced FinFET fabrication processes for materializing FinFET CMOS circuits. Using the developed technologies, we demonstrate the advanced TiN metal gate, fin-height controlled FinFET CMOS inverter with an excellent transfer performance, and the flexible threshold voltage, asymmetric gate insulator thickness four-terminal (4T) FinFET with a greatly improved subthreshold (S) slope, for the first time.

The effect on the thermal and dielectric properties of incorporating benzene rings in hydrogenated amorphous carbon (a-C:H) films was investigated. The benzene rings were introduced into a-C:H films by using plasma-enhanced chemical vapor deposition and aromatic source compounds. The a-C:H film that contained benzene rings had thermal stability up to 400 °C and a low-dielectric constant of 3.0. The difference in the dielectric constant and thermal stability of a-C:H films appeared to be due to the hydrogen concentration of the films.

By using the Ni-Ta alloys fabricated by interdiffusing stacks of Ni and Ta, we have experimentally investigated the work function (/spl phi//sub m/) controllability and thermal stability required for the advanced metal gate MOSFETs. The capacitance-voltage (C-V) measurement of the interdiffused Ni/Ta and Ta/Ni stacks revealed that the /spl phi//sub m/ of the Ni-Ta alloy was changed from that of pure Ni and Ta samples. The /spl phi//sub m/ uniformity of the interdiffused Ni-Ta alloy was found to be comparable to that of the pure Ni by observing the microscopic /spl phi//sub m/ by scanning Maxwell-stress microscopy. The excellent thermal stability of the interdiffused Ta/Ni stack was revealed up to 900/spl deg/C. From these experimental results, the Ni-Ta alloy is promising candidate for the metal-gate MOSFETs.

Summary form only given. The authors report the observation of a large stripe-direction dependence of threshold current density for AlGaInP laser diodes with CuPt-type natural superlattice (NSL) in a Ga/sub 0.5/In/sub 0.5/P active layer. The anisotropy is attributed to the existence of NSL in the active layer. Epitaxial wafers were grown on Si-doped exact

Perovskite-related layered multicomponent oxide films with strongly correlated electrons such as (La, Sr)MnO 3 and HTS are promissing candidates for advanced MRAM, Josephson devices and others. These devices have usually sandwich-type structure with an ultra-thin intermediate layer. Formation of the impurity-precipitates on the surface during the growth of the multicomponent oxide films is a fatal problem working against high-performance of devices. In this study, high quality and surface-clean thin films of multicomponent oxides have been grown by MOCVD on substrates with artificial steps of predefined height and width. The surface of the films grown on the steps having width equal to the 'double of the migration length' of the atomic species depositing on the substrate is totally free of precipitates: precipitates are gathered at the step edges where the free energy is lowest. The method has several advantages: it is simple, universal (it is independent of the materials, substrates, deposition technique or application) and allows control of precipitates segregates so that the quality and growth conditions of the films are the same as for the films grown on conventional substrates. The method is expected to result in new opportunities for the device fabrication, integration, design and performance. As an example we present successful fabrication of a mesa structure showing intrinsic Josephson effect. We have used completely precipitate-free thin films of Bi-2212/Bi-2223 superstructure grown on (001) SrTiO 3 single crystal substrates with artificial steps.

We investigate the V/sub th/ controllability of the 4-terminal DG-MOSFET (4T-DGFET). We presented a simple and comprehensible model for the 4T-DGFET and made clear the V/sub th/ controllability in connection with the initial V/sub th/ in the DG-mode. These results discussed here are useful for the 4T-DGFET device and circuit design.

The quantitative comparison of the electron mobility (u/sub eff/) in the poly-Si gated n-channel multi-FinFETs fabricated by the orientation-dependent wet etching and conventional RIB processes has been carried out. A remarkable increment in u/sub eff/ has experimentally been confirmed in the Si-fin channels fabricated by the wet etching instead of the RIB. Therefore, it is concluded that the developed wet etching technique is very attractive for the fabrication process of the high quality and ultra-thin Si-fin channel FinFETs.

High quality thin films of HTS have been grown by MOCVD on substrates with artificial steps of predefined height and width. The surface of the films grown on the steps having width equal to the ‘double of the migration length' of the atomic species depositing on the substrate is totally free of precipitates: precipitates are gathered at the step edges where the free energy is lowest. The method has several advantages: it is simple, universal (it is independent of the materials, substrates, deposition technique or application) and allows control of precipitates segregates so that the quality and growth conditions of the films are the same as for the films grown on conventional substrates. The method is expected to result in new opportunities for the device fabrication, design and performance. As an example we present successful fabrication of a mesa structure showing intrinsic Josephson effect. We have used thin films of Bi-2212/Bi-2223 superstructure grown on (001) SrTiO3 single crystal substrates with artificial steps of 20 μm.

Nitrogen doped fluorinated amorphous carbon thin films for low dielectric constant interlayer dielectrics have been investigated. The films were deposited with a parallel‐plate plasma enhanced chemical vapor deposition. Source gases were CH4, CF4, and N2. The thermal stability of the films can be improved by the addition of N2. X‐ray photoelectron spectroscopy (XPS) measurement revealed that the C‐N bonds were formed in the films with the addition of N2. The dielectric constant of the films was increased from 2.1 to 2.4 at the nitrogen concentration of 10%.

Fluorinated amorphous carbon thin films (a‐C:F) for interlayer dielectrics are grown by helicon plasma enhanced chemical vapor deposition. The source gases are CH4, CF4, C2F 6 and their H2mixtures. a‐C:F films can be fabricated without adding hydrogen using the helicon reactor, while in the previously reported parallel‐plate reactor, no film grows unless a hydrogen source is added. The films grown in the helicon reactor have no hydrogen content. The growth rate of the films reaches 0.3 μm/min (C2F 6) and 0.15 μm/min (CF4). The thickness of the films deposited with C2F6 does not decrease on heating to 300 °C, while the films with CF4 shrink. The dielectric constants of the films deposited from C2F6 and CF4 are 2.4 and 2.3 respectively at 1 MHz. The dielectric loss tangent of these films is 0.01 at 1 MHz.

The anodic corrosion behavior of an experimental Ag-15Pd-18Cu-12Au alloy in 0.1% Na(2)S solution in relation to its microstructure was investigated using potentiodynamic and potentiostatic polarization techniques with analyses of corrosion products by X-ray diffractometry, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The role of Pd in improvement of the corrosion resistance was also investigated. In the potential/current density curve, three distinct current peaks, at -520 mV (peak I), -425 mV (peak II) and -175 mV (peak III), were observed. The Ag-rich alpha(2) matrix with coarse Cu and Pd-rich lamellae was the most corrosion-susceptible region, and this region was preferentially corroded at peak I with the formation of granular deposits of Ag(2)S. A small amount of Ag-Cu mixed sulfide deposited on the Cu and Pd-rich coarse particles and dissolution of Ag as AgO(-) might have occurred in parallel with Ag(2)S formation at peak II. Enrichment of Pd on the alloy surface occurred at peak III due to preferential dissolution of Ag and Cu. A high level of corrosion resistance was attained with the formation of a thin Pd-rich sulfide film, which enhanced the passivity of the alloy in an alkaline sulfide solution. It was found that passivity is an important phenomenon not only for base metal alloys but also for noble metal alloys to maintain high levels of resistance to corrosion and tarnishing in sulfide environments.

The corrosion characteristics of orthodontic alloy wires were investigated both in as-received and grinded conditions in 0.9% NaCl solution by atomic absorption spectrophotometry and potentiodynamic polarization measurements. The amount of each metal ion released from most alloys was larger for the grinded wires than for the as-received wires (p

Fluorinated amorphous carbon films were proposed as low dielectric constant interlayer dielectrics for ultralarge scale integration circuits. The films were deposited by plasma enhanced chemical vapor deposition with CH4 and CF4 in a parallel plate rf (13.56 MHz) reactor. The dielectric constant of the amorphous carbon films deposited with CH4 was increased with increases in rf power. The addition of CF4 to CH4 raised the deposition rate and reduced the dielectric constant. At an rf power of 200 W, and at a flow rate of 47 sccm for CF4 and 3 sccm for CH4, the dielectric constant of the fluorinated amorphous carbon films was 2.1.

We have developed a new interlayer technology that attains a 50% reduction in capacitance and keeps good process compatibility with current Chemical Mechanical Polishing (CMP) based multi-level metallization (MLM) processes. This technology uses fluorinated amorphous carbon (a-C:F) with a dielectric constant of 2.3, sandwiched between layers of SiO/sub 2/, which are formed sequentially by high density plasma-chemical vapor deposition (HDP-CVD). The top SiO/sub 2/ layer assures oxygen plasma resistance during via etching, metal etching, and resist removal.

Objective . The purpose of this study was to improve adhesion between dental adhesive resins and 14K gold alloy by creating a sponge-like structure on the alloy surface which enhanced mechanical bonding. Methods . The internal oxidation particles of Cu oxides precipitated on a 14K gold alloy surface after high-temperature oxidation at 800 °C in air were removed by pickling with an acid solution to create a sponge-like structure on the alloy surface. A PMMA resin containing 4-META as an adhesive monomer and a self-cured resin without 4-META were used to examine the effects of mechanical and chemical factors on bond strength. A thiophosphate-type metal primer (M-Primer II) was used in combination with 4-META resin to strengthen the chemical bonding of 4-META resin to the porous alloy surface. The surfaces of the alloy specimen treated by oxidation, pickling, and bonding with 4-META resin were analyzed using an electron probe X-ray micro-analyzer. Results . SEM observation showed many resin tags on the resin side of the bond structure after removal of the gold alloy matrix with aqua regia. The bond strength of 4-META resin to the porous alloy surface was 38±3 (mean±SD) MPa whereas that to a flat alloy surface with the same composition was 19±1 MPa. The bond strength of a self-cured resin without 4-META to the porous alloy surface was 24±2 MPa. Significance . A high bond strength was obtained when 4-META resin was bonded to the porous 14K gold alloy surface treated with M-Primer II.

The phase transformation behavior in three commercial nickel-titanium orthodontic wires having different transformation temperatures was studied by micro X-ray diffraction (micro-XRD). Micro-XRD spectra were obtained at three different included bending angles (135 degrees, 146 degrees and 157 degrees) and three different temperatures (25 degrees C, 37 degrees C and 60 degrees C). The regions analyzed by micro-XRD were within the separate areas of a given wire specimen that experienced only tensile or compressive strain. The intensity ratio (M002/A110) between the 002 peak for martensitic NiTi and the 110 peak for austenitic NiTi was employed as the index to the proportions of the martensite and austenite phases. The ratio of martensite to austenite increased in all three nickel-titanium wires with decreasing included bending angle (greater permanent bending deformation), and was lower within the compression area for all wires at all bending angles than within the tension area. Micro-XRD provides an effective method for quantitative evaluation of the proportions of these two phases in nickel-titanium orthodontic wires, even though considerable preferred crystallographic orientation exists because of the wire drawing process.

Fractographic analysis was conducted to evaluate the resin-dentin bond structures made under wet and dry conditions.Resin-dentin bonded specimens were prepared using two adhesive resin systems (Single Bond/SB; 3M and All Bond 2/AB2; Bisco Inc) under wet and dry conditions. The specimens were sectioned perpendicular to the adhesive interface to produce a square bar-shaped specimen (adhesive area: 0.9 mm(2)) by means of a diamond saw. The mean bond tensile test was then conducted at a crosshead speed of 1.0 mm/min. The mean bond strengths were statistically compared with two-way ANOVA and Fisher's PLSD test (p0.05). Subsequently, the fractured surfaces of all specimens were examined using SEM and the area fractions of failure modes (%) were measured using an image analyzer on SEM microphotographs.No significant differences in tensile-bond strength were observed between SB (60.1+/-16.4MPa) and AB2 (69.8+/-17.4MPa) (p0.05) under wet conditions. However, the bond strength either of SB or AB2 made under wet conditions was significantly greater than those made under dry conditions (SB: 26.2+/-12.5MPa and AB2: 6.8+/-3.3MPa) (p0.05). Under fractographic analysis, the major portion at the fractured surface was occupied by the cohesive failure of bonding resin and the resin composite for the wet conditions, and the top of the hybrid layer for the dry conditions in both systems.The interaction between the top of the hybrid layer and the bonding resin influenced the bond integrity.

We have successfully achieved an ALD like deposition of ZrO2 or HfO2 by using a MO precursor. The MO precursor used in this study was zirconium tetra-tert-butoxide (ZTB) Zr(t-OC(CH3)3)4 and hafnium tetra-tert-butoxide (HTB) Hf(t-OC(CH3)3)4. Because MO precursors are very sensitive to H2O, we used oxygen plasma as an oxidizer instead of H2O in order to reduce background H2O pressure and suppress the background reaction. As a result, we successfully achieved an ALD-like deposition proved by a self-limiting adsorption of MO precursor. The carbon content in the films was suppressed due to highly reactive oxygen plasma. The leakage current of the film with plasma oxidation is much lower than that of film with H2O oxidation. Thus, MO-ALD using a plasma oxidation is a promising candidate for the high-k gate deposition process.

Because dental implant abutments are located at transmucosal sites, their surface should inhibit bacterial accumulation to prevent peri-implantitis. The authors examined the effects of human lactoferrin (LF), an antibacterial protein present in saliva, as an antibacterial coating on the titanium surface and evaluated its effects before and after mucin-containing artificial saliva (AS) incubation. In the control group, titanium disks were soaked in distilled water, whereas in the LF group, titanium disks were soaked in LF solution to coat the disks. In the control-AS and LF-AS groups, half of the control and LF disks were incubated with AS. To confirm LF adsorption, the fluorescence intensity of fluorescein isothiocyanate-labeled LF was measured. The LF and LF-AS groups showed significantly higher intensity than the control and control-AS groups (P0.01). There was no significant difference between the LF and LF-AS groups (P0.05). The amount of adhered Streptococcus gordonii significantly increased by incubation with AS (P0.01) and significantly decreased by adsorption of LF (P0.01). There was no interaction between the two factors, LF adsorption and AS incubation (P = 0.561). These results suggest that the adsorbed LF inhibited bacterial adhesion following AS incubation. According to qualitative LIVE/DEAD analysis, viable bacteria appeared to be decreased in the presence of LF and SEM observation indicated that altered morphologies increased in LF and LF-AS groups. These results suggest that the adsorbed LF remained on the titanium surface after incubation with AS, and the remaining LF inhibited bacterial adhesion and exhibited bactericidal effects. Therefore, the adsorption of LF on the abutment material appears to be effective in preventing peri-implantitis.

Three-dimensional (3D) fin-channel charge trapping (CT) flash memories with different gate materials of physical-vapor-deposited (PVD) titanium nitride (TiN) and n+-polycrystalline silicon (poly-Si) have successfully been fabricated by using (100)-oriented silicon-on-insulator (SOI) wafers and orientation-dependent wet etching. Electrical characteristics of the fabricated flash memories including statistical threshold voltage (V t) variability, endurance, and data retention have been comparatively investigated. It was experimentally found that a larger memory window and a deeper erase are obtained in PVD-TiN-gated metal–oxide–nitride–oxide–silicon (MONOS)-type flash memories than in poly-Si-gated poly-Si–oxide–nitride–oxide–silicon (SONOS)-type memories. The larger memory window and deeper erase of MONOS-type flash memories are contributed by the higher work function of the PVD-TiN metal gate than of the n+-poly-Si gate, which is effective for suppressing electron back tunneling during erase operation. It was also found that the initial V t roll-off due to the short-channel effect (SCE) is directly related to the memory window roll-off when the gate length (L g) is scaled down to 46 nm or less.

Influence of work function variation (WFV) in metal gates (MGs) on fluctuation of sub-threshold drain current is investigated in detail by analyzing fluctuation of current–onset voltage (COV) for fin field-effect transistors (FinFETs) with polycrystalline TiN and amorphous TaSiN MGs. The polycrystalline TiN MG exhibits anomalously increased COV fluctuation of the nMOS FinFETs in comparison to the pMOS case, while the amorphous MG exhibits well suppressed COV fluctuation both for the n- and pMOS FinFETs. Through the discussion with regard to the WFV due to the polycrystalline TiN grains, it is concluded that the sub-dominant grains of TiN with lower work function (WF) in TiN form localized potential valleys in the channel of the nMOS FinFETs resulting in the anomalous leak current in the sub-threshold condition. In the pMOS FinFETs, in contrast, the lower WF grains in TiN form localized potential peaks for holes, which have less impact on the sub-threshold leakage.

The water durability at adhesion interfaces between 4-META resin and Au-In or Au-Si alloys was investigated by the peeling test and by surface analysis using X-ray photoelectron spectroscopy (XPS) as well as theoretical consideration based on Bolger's acid-base theory. XPS spectra demonstrated that several-nm thick layers of In2O3 and SiO2 were formed on the Au-In and Au-Si alloys. The water durability of the Au-In alloys increased with increases in In content. The Au-Si alloy and quartz glass specimens showed a total absence of water durability. Bolger's theory suggested that the interaction of 4-MET with In2O3 was considered to be ionic and stable in the presence of water while that of 4-MET with SiO2 was due to hydrogen bonds, which can easily be dissociated in the presence of water. These findings suggest that Bolger's theory is useful for evaluating chemical interactions between an adhesive monomer and oxides on a precious metal alloy.

The corrosion behaviors of four ferric stainless steels and two austenitic stainless steels were examined in a simulated physiological environment (0.9% NaCl solution) to obtain basic data for evaluating the appropriate composition of stainless steels for dental magnetic attachments. The corrosion resistance was evaluated by electrochemical techniques and the analysis of released metal ions by atomic absorption spectrophotometry. The surface of the stainless steels was analyzed by X-ray photoelectron spectroscopy (XPS). The breakdown potential of ferric stainless steels increased and the total amount of released metal ions decreased linearly with increases in the sum of the Cr and Mo contents. The corrosion rate of the ferric stainless steels increased 2 to 6 times when they were galvanically coupled with noble metal alloys but decreased when coupled with commercially pure Ti. For austenitic stainless steels, the breakdown potential of high N-bearing stainless steel was approximately 500 mV higher than that of SUS316L, which is currently used as a component in dental magnetic attachments. The enriched nitrogen at the alloy/passive film interface may be effective in improving the localized corrosion resistance.

We report on the successful preparation of intrinsic Josephson junctions on high-quality BSCCO-2212/2223 superlattice thin films grown by MOCVD. The surface of as-grown films was very smooth with the roughness of the order of a half unit cell. Mesas were effectively structured on the film by the liquid-nitrogen-cooled dry etching method. A typical I-V characteristic in the c-axis direction of a BSCCO film shows the hysteresis and multiple resistive branches. The number of branches is consistent with that of junctions calculated from the height of a mesa structure. This indicates that BSCCO-2212/2223 superlattice films consist of a series array of S(CuO2 bilayer) / I(SrO, BiO layers) / S(CuO2 trilayer) junction. The formation of stacked Josephson junctions was also confirmed by the temperature dependence and the magnetic field dependence of Ic.

The preparation of non c-axis oriented HTS films with longer coherence length is one of key technologies toward realisation of viable Josephson devices. We reports on the successful growth of (119)Bi-2223 films by MOCVD using a two-step growth temperature procedure and on AFM observation of the film surface. This temperature procedure was found to be effective for orientation control and phase control in comparison with a fixed growth temperature procedure. As a result, superconducting properties were much improved. The surface morphology observed by AFM showed a mountain-range-shaped one, which strongly reflects the epitaxial relationship between the (119)Bi-2223 film and (110) SrTiO3 substrate.

The purpose of this study was to evaluate the correlation between hybrid layer thickness and bond strength using specimens acid-conditioned for varying lengths of time.The dentin surfaces of human premolars, sectioned to remove the enamel from the labial surface, were conditioned with 35.0% phosphoric acid of an adhesive resin system (Scotchbond Multi-Purpose; 3M) for 15 (as directed by the manufacturer), 60, 120, or 180 s (experimental acid-conditioning times). The bonded specimens were then sectioned perpendicular to the adhesive interface to measure the hybrid layer thickness by SEM. The specimens for the micro-tensile test were sectioned perpendicular to the adhesive interface and trimmed to an hourglass-shape. Then, the micro-tensile test was performed at a crosshead speed of 1.0 mm/min. The bond strengths and hybrid layer thickness were statistically compared with Student's t-test (p0.05). All fractured surfaces were also observed by SEM.Significant differences between the groups exposed to acid for 15 and 60 s, and those exposed for 120 and 180 s were observed in hybrid layer thickness and bond strength (p0.05). SEM observation of the fractured surfaces revealed that a demineralized dentin zone without resin impregnation remained within the hybrid layer.A demineralized dentin zone was formed in the bond structures after prolonged acid-conditioning, resulting in low bond strength. The shrinkage of the hybrid layer due to desiccation during the SEM examination process provided evidence of the presence of the demineralized dentin zone within the hybrid layer.