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Charge localization causes initial retention loss and memory window narrowing after write/erase cycling in a nonvolatile memory device using a metal–oxide–nitride–oxide–semiconductor (MONOS) structure. To overcome these problems, we propose the use of silicon-rich silicon nitride (SRN) thin film as a charge-trapping layer. It was found that most of the electrons injected from the substrate were trapped at the interface between the SRN film and the top oxide and the number of electrons captured by bulk traps of the nitride is negligible. When negative bias is applied to the gate electrode, the electrons trapped at the top interface move back to the bottom interface with SRN. The high effective mobility of the electrons is presumably due to donor-like traps at 0.8 eV below the conduction band bottom of SRN.

The X-ray imaging of materials with low atomic number elements is difficult through a conventional photoabsorption contrast method whereas much higher contrast can be achieved by phase-contrast imaging. We have constructed a compact size imaging system using a microfocus X-ray generator with a few µm spot size. We present here the evaluation of basic characteristics and sample results, as well as future prospects.

A new long-wavelength-photosensitive self-assembled-monolayer (SAM) was developed, and a process fabricating alignment-free printable electrodes for flexible organic thin-film transistors (OTFTs) with the SAM was proposed. The SAM was degraded and its wetability was changed from hydrophobic to hydrophilic by irradiating it with UV light (>350 nm). The irradiated areas of SAM became more hydrophilic with tetramethylammonium hydroxide (TMAH) solution, which is a commercially available photoresist developer. Using the SAM and a back substrate exposure technique with TMAH rinsing, we can induce the self-alignment of solution-processed source/drain electrodes with respect to a gate electrode. A 20-µm-gap pattern of PEDOT was successfully formed by spin-coating on a plastic substrate.

One of the major challenges in advanced complementary metal oxide semiconductor (CMOS) technology is to achieve an adequate dopant activation at the polycrystalline silicon (poly-Si) gate/gate oxide interface to minimize the poly-Si depletion effect. We investigated gate pre annealing by laser thermal process (LTP) in conjunction with laser spike annealing (LSA) source/drain (S/D) activation to effectively suppress poly-Si gate depletion while forming highly activated ultra shallow junctions for S/D. We found that carrier concentration at the poly-Si gate/gate oxide interface increases and, accordingly, electrical inversion oxide thickness (Tinv) decreases whereas dopant penetration into the Si substrate is suppressed to a level far below that in conventional rapid thermal annealing (RTA). We realized improved device performance characteristics such as a high drive current, a small threshold voltage (Vth) shift, and a reduced off current (Ioff).

Ultra-thin single crystal silicon with the (100) surface formed by the local-oxidation-of-silicon (LOCOS) on a silicon-on-insulator (SOI) substrate becomes a quasi-direct band-gap semiconductor due to the quantum mechanical confinement effect. The device is a simple pn diode in a planar structure. Electro-luminescence (EL) has been observed by the lateral carrier injections into the two-dimensional quantum well.

We have proposed an area-selective post-deposition annealing (PDA) process that involves a combination of flash lamp annealing and the use of a Si photoenergy absorber (Si-PEA) for metal/high-k gate last metal–insulator–semiconductor field-effect transistors (MISFETs) with NiSi on source/drain (S/D). The process makes it possible to suppress the increase in both the sheet resistance and junction leakage current of NiSi S/D regions. This PDA process also showed optimality for silicide gate electrode formation with silicidation of part of the Si-PEA. It was found that the flash lamp PDA with Si-PEA on nickel–silicide/HfAlOx/SiO2 gate-last MISFETs reduced electron trapping at the gate dielectric and resulted in better PBTI immunity than conventional rapid thermal PDA and flash lamp PDA without Si-PEA.

Changes in optical thickness and equivalent oxide thickness (EOT) during postdeposition annealing (PDA) and postnitridation annealing (PNA) were investigated to fabricate sub-1-nm-EOT nitrided hafnium silicate (HfSiON) gate dielectrics. In spite of optical thickness reductions by PDA, none of the PDA conditions could reduce the EOT and bring about the merit in leakage current reduction. On the other hand, high-temperature PNA without oxygen was found to be effective for reducing both optical thickness and EOT. Furthermore, leakage current reduction ratio and effective mobility were improved by applying high-temperature PNA. Consequently, the fabrication of 0.81-nm-EOT HfSiON gate dielectrics with a gate leakage current of 0.74 A/cm2 at 0.7 V and an electron mobility of 235 cm2/(V s) at 0.8 MV/cm (76% of SiO2) has been realized.

Changes in transient capacitances during application of step voltages to the gate electrode of metal-oxide-semiconductor (MOS) structures with stacked gate dielectrics were investigated. The behaviors of the changes in transient capacitance varied depending on the thickness of high dielectric films. The results indicate that negative charges were trapped near the gate electrodes during stress voltage application, while positive charges were trapped near the Si/SiO2 interface. These charges in gate films were released at different time constants during relaxation.

3–7-nm-thick HfAlOx (Hf/Hf+Al=29%) films were deposited on thermally grown ~0.9-nm-thick SiO2/Si(100) by atomic layer chemical vapor deposition (ALCVD) at 350°C. After postdeposition anneal (PDA) in 0.2% O2 ambience at 1050°C for 1 s, we evaluated the compositional profile of HfAlOx/SiO2 dielectric stack structures by X-ray photoelectron spectroscopy (XPS) in combination with oxide thinning in a dilute HF solution and observed Si diffusion and incorporation into the HfAlOx network by a few at.% through the pregrown SiO2 layer. The energy band alignment in the dielectric stack structure on Si(100) after the PDA was determined by the energy band gap of the ALCVD HfAlOx films and the valence band offset at the interfaces between HfAlOx and Si(100), which were measured by analyzing the energy loss spectra of O1s photoelectrons and the valence band spectra of the dielectric stack structures, respectively. Also, by the total photoelectron yield spectroscopy (PYS) of the dielectric stack structures, filled defect states as many as 1–3×1017 cm-3 eV-1 were estimated in the HfAlOx layer in the energy region of 0.4 to 0.8 eV from the energy position corresponding to the Si valence band top.

Thin Hf0.3Al0.7Ox films fabricated by an atomic-layer-deposition technique were characterized using monoenergetic positron beams. From the measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positrons for 3- and 7-nm-thick HfAlOx films deposited on SiON(0.9 nm)/Si, it was found that positrons in the HfAlOx films annihilate from the trapped state by open spaces that exist intrinsically in their amorphous structure. The line-shape parameter S and the positron lifetime corresponding to the HfAlOx films decreased with increasing oxygen content (0.004–1%) in the annealing atmosphere. This fact was attributed to the shrinkage of the open spaces due to the change in the matrix structure of amorphous HfAlOx. The increase in oxygen content was also found to decrease the transient current of n+-polycrystalline-Si/HfAlOx/SiON/Si. The decrease in the mean size of the open spaces and the resultant hardening of the matrix structure are considered to suppress the dielectric polarization of HfAlOx.

The effects of introducing NH3/Ar plasma pulses during the atomic layer deposition (ALD) of HfAlOx films and during the in situ nitridation of an interfacial layer (IL) on the properties of HfAlOx-FETs were investigated. The interaction between HfAlOx and IL and the dopant penetration were suppressed by the introduction of a NH3/Ar plasma pulse during ALD, because it increases the nitrogen content at the interface of HfAlOx/IL. Moreover, the nitrogen content in the IL could be controlled by adjusting the number of NH3/Ar plasma pulses used for in situ nitridation. No threshold voltage shift due to the nitridation of the Si substrate was observed, indicating that the nitrogen profile was well controlled when using a NH3/Ar plasma pulse for in-situ nitridation. It was found that in-situ nitridation with 5 cycles of NH3/Ar plasma pulses was optimum for reducing C–V hysteresis and improving carrier mobility.

We have examined the effects of phase separation on the inversion electron mobility of metal-insulator-semiconductor field-effect transistors with high-permittivity (high-κ) gate dielectrics. On the basis of experimental data of hafnium silicate films, we developed a phase separation model of a high-κ film that contains crystal grains of high permittivity in an amorphous film of low permittivity. Using this model, we calculated the electron mobility by applying a linear response theory and found that the phase separation results in a significant reduction of the electron mobility. We also discuss the differences in the calculated electron mobility between the phase-separated hafnium silicate and hafnium aluminate.

We investigated the effects of thin film interference during sub-millisecond annealing on junction activation and recrystallization using ultra-thin-body silicon-on-insulator (UTB-SOI) wafers. We showed that, in the wavelength range used by broadband heating sources in flash lamp annealing (FLA), thin film interference in the body Si and buried oxide layers of UTB-SOI wafers can change the light absorption. This in turn reduces the duration of the heat distribution, resulting in insufficient activation of junctions during sub-millisecond annealing. Further, we showed that laser spike annealing (LSA) can achieve full activation of junctions even in UTB-SOI wafers because using light waves in the far-infrared wavelength region can minimize thin film interference.

Microfocus X-ray generators have been extensively used for magnification radiography. In these applications, the sharpness of an image depends on the X-ray source size. Therefore, it is important to evaluate and optimize the X-ray spot quantitatively. Although several methods have been devised to date, some require complicated systems whereas others are not fully quantitative. Here, we introduce a simple, practical, and quantitative method that makes use of the penumbra of a knife edge. Because the method is very simple, it can be readily integrated as an auto focusing system of a focal spot.

A theoretical investigation has been made of the origin of substantial threshold voltage (Vth) shifts observed in p+poly-Si gate Hf-based metal insulator semiconductor field effect transistors (MISFETs), by focusing on the effect of oxygen vacancy (VO) formation in HfO2. It has been found that VO formation and subsequent electron transfer across the interface definitely causes substantial Vth shifts, especially in p+poly-Si gate MISFETs. Moreover, the theory also systematically reproduces recent experimental reports that large flat band (Vfb) shifts are observed, even in intrinsic poly-Si gates, and that the Vfb shifts exhibit a high dependence on HfSiOx thickness.

We have investigated the crystal structure of (1 − x)(Bi1/2Na1/2)TiO3–xBa(Mg1/3Nb2/3)O3 (BNT–BMN) by high-resolution neutron powder diffraction (NPD) analysis. Our NPD study combined with polarization hysteresis measurements for ceramics reveals that a boundary between rhombohedral R3c and tetragonal P4bm phases exists at x = 4–5%. The Rietveld analysis of the NPD data shows that the crystal structure with x = 10% has a single-phase tetragonal structure in space group P4bm, as has been reported for BNT–7%BaTiO3. The P4bm structure exhibits antiparallel displacements of A- and B-site cations, which results in a small spontaneous polarization (Ps) of 13.3 µC/cm2 (estimated from the refined structural parameters). The results obtained for BNT–10%BMN ceramics strongly suggest ferrielectric features; the application of electric fields induces a transition from the P4bm phase with a small Ps to other ferroelectric phases with a large Ps.

Tomohiro Shagawa, Hiroomi Torii, Fumihito Kato, Hirotsugu Ogi and Masahiko Hirao. Viscoelasticity evolution in protein layers during binding reactions evaluated using high-frequency wireless and electrodeless quartz crystal microbalance biosensor without dissipation. Japanese Journal of Applied Physics, 2015, 54(9), 096601. https://doi.org/10.7567/JJAP.54.096601., In this study, we demonstrate the effectiveness of a resonance acoustic microbalance with a naked embedded quartz (RAMNE-Q) biosensor for evaluating viscoelastic property changes in thin protein layers during protein deposition reactions without dissipation measurement. Quartz crystal microbalance (QCM) biosensors have conventionally been adopted for the viscoelasticity evaluation of adsorbed protein layers by measuring dissipation as well as resonance frequency. However, dissipation, or the vibrational energy loss, is easily affected by many factors and is rarely measured with sufficiently high accuracy. To evaluate viscoelasticity only from a reliable frequency response, one needs to perform an ultrahighfrequency measurement, which is here achieved using the RAMNE-Q biosensor. Simultaneous frequency measurement is performed for fundamental and overtone modes up to 406MHz of a 58MHz RAMNE-Q biosensor during various binding reactions, and evolutions of viscosity, shear modulus, and thickness of adsorbed protein layers are inversely evaluated. A marked difference is observed in the viscosity evolution between specific and nonspecific binding reactions. Furthermore, the reversed frequency response appears, which indicates the modification of the protein structure into a rigid structure.

Wurzite aluminum nitride is prepared on a c-plane sapphire substrate by electron cyclotron resonance plasma-enhanced sputtering deposition (ECR sputtering). Atomic force microscopy (AFM) showed flat AlN thin-film surfaces, and X-ray diffraction (XRD) analysis verified the epitaxial growth of AlN films with the full-width at half-maximum (FWHM) of the rocking curve of 0.025 deg on the film with the thickness of 100 nm. XRD analysis also verified the change in the peak position for the AlN film along both out-of-plane and in-plane directions. The effect of lattice constants on the energy gap was theoretically estimated by the first principles method.

Dynamic fluctuation in stress-induced leakage current, called V-SILC, which is one of the causes of erratic bits in flash memory, was investigated. This investigation showed that V-SILC is attributed to random telegraph noise, which is associated with a state transition of a single defect. To analyze the mechanism of the state transition, dependences of state-transition probabilities on gate current and temperature were investigated. These dependences indicate that the state transitions are caused by current injection, and the mechanism of the state transition causing V-SILC is a defect-structure transition caused by charge collision.

Dynamic fluctuation in stress-induced leakage current – called “variable stress-induced leakage current” – in a gate oxide of a metal–oxide–semiconductor structure was investigated. Variable stress-induced leakage current is attributed to random telegraph noise, which is associated with the state-transition of a single defect. To analyze the mechanism of the state-transition, dependence of state-transition probabilities on gate current and on temperature were investigated. These dependences indicate that the state-transition mechanism is a defect-structure transition by charge collision.

We have investigated the crystal structure of (Bi1/2Na1/2)TiO3–7%BaTiO3 (BNT–7%BT) by high-resolution neutron powder diffraction (NPD) and high-energy synchrotron radiation X-ray diffraction (SR-XRD) analyses. The NPD study revealed that the BNT–7%BT crystals have a single-phase tetragonal structure with P4b m symmetry. The crystal structure refined by the Rietveld method was found to be similar to the ferrielectric P4b m phase reported for BNT at a high temperature of 673 K. The SR-XRD analyses for single crystals of BNT–7%BT demonstrated that the P4b m phase remains as a stable phase in the crystals even after a high electric field is applied for poling, which is different from the structural analysis of ceramics by Ma et al. [Phys. Rev. Lett. 109 (2012) 107602].

We have reported the laser operation of a short-wavelength ultraviolet laser diode with multiple quantum wells composed of GaN well layers. The GaN well-width is estimated to be around 1–1.5 nm. We have simulated whole laser-diode structure, and calculated wave-function overlap integrals. It is provided the integral becomes the maximum value in the well-width of 1.5 nm. The laser operation has been achieved in 340-nm-band under the pulsed current mode at room temperature. The wavelength is far from the wavelength corresponding to band gap of GaN, and the shortest lasing wavelength ever reported for a semiconductor laser composed of binary compound well layer. Moreover, the device has been realized on an Al0.2Ga0.8N underlying layer with 0.1 lower AlN mole fraction margin than that of a previous reported 342 nm laser-diode with an Al0.3Ga0.7N underlying layer. These results provide a chance to the next stage for a shorter-wavelength ultraviolet laser diode.

It is clarified that suboxides and interface traps are closely linked to threshold-voltage variation (ΔV th) due to random telegraph noise (RTN) from an investigation of dependence of ΔV th on silicon-surface orientation: Si(100), (110), and (111). The amount of RTN traps increases with increasing amount of suboxides in the interfacial transition layer. With regard to the total amount of suboxides, the Si(110) surface orientation gives a larger amount than Si(100) and Si(111). Furthermore, we found that Si(110) has the potential to give fast RTNs with a larger ΔV th than Si(111). Accordingly, ΔV th for Si(110) is larger than those of Si(100) and Si(111). Attention should be paid to the possibility of the impact of RTN on Si(110) as the vertical plane of a three-dimensional device.

A new low-dielectric-constant spin-on glass (SOG) with a k value of 2.4 has been developed for a gap-filling process in advanced memory devices. The low-shrinkage characteristic of the SOG during thermal curing provides capabilities of gap filling and planarizing as high as those of conventional reflowable SOGs. The low-shrinkage SOG has thermal stability up to 800 °C and chemical stability against diluted hydrofluoric acid, sulfuric acid–hydrogen peroxide, and amine-based solutions, which makes it possible to be used as an interlevel dielectric of memory devices. Tungsten and aluminum interconnects fabricated using the low-shrinkage SOG showed a parasitic capacitance 30% lower than those fabricated using silicon dioxide and a sufficiently long line-to-line dielectric breakdown lifetime. Taking advantage of the high chemical stability of the SOG, an all-wet damageless via-formation process using an amine-based photoresist stripper has been developed. By using the process, the low-shrinkage SOG can be applied to multilevel metallization.

Indium tin oxide (ITO) thin films were epitaxially grown on sapphire substrates by solid-source electron cyclotron resonance (ECR) plasma deposition. Compared with the other methods such as sputtering and evaporation methods, the ECR plasma method resulted in a flat surface and a low resistivity with a relatively low substrate temperature. The surface roughness was strongly dependent on the ratio of oxygen gas flow during deposition. With optimal deposition conditions, the ITO thin film epitaxially grew on a c-plane sapphire substrate with twelvefold symmetry. The surface roughness and resistivity were estimated to be 0.4 nm and 1.4×10-4 Ω·cm, respectively. The X-ray rocking curve revealed 0.025° of full width at half maximum (FWHM) on the epitaxial ITO thin film. The ITO film deposited on an epitaxial GaN(001) layer on a c-plane sapphire substrate showed sixfold in-plane symmetry, indicating the epitaxial growth of ITO(111) on the GaN(001)/c-plane sapphire substrate.

We report on a three-dimensional (3D) molding technique of fabricating bioceramic scaffolds. In this method, ceramic slurry is cast into a 3D polymer master mold, which is fabricated via microstereolithography, by a centrifugal casting method. The polymer master mold is thermally decomposed, so that a complex 3D bioceramic scaffold can be produced. In experiments, the decomposition process of the polymer model was optimized by the master decomposition curve theory to reduce harmful cracks in a green body. As a result, we could produce not only precise lattice models but also a sophisticated porous scaffold using beta-tricalcium phosphate (β-TCP) slurry. This bioceramic 3D molding technique based on microstereolithography will be useful for tailor-made tissue engineering and regeneration medicine.

This paper reports novel, non-epitaxial raised source/drain (S/D) approaches to decrease the parasitic external resistance in complementary metal–oxide–semiconductor field-effect transistors (CMOSFETs) fabricated on ultrathin silicon on insulator (UTSOI). This technique utilizes a metal Schottky S/D process with dopant segregation. Selectively formed NiSi2 with dopant segregation fabricated by laser-spike annealing (LSA) significantly lowered effective Shottky-barrier height and, thereby, lowered contact resistance (ρc). Satisfying the requirements of UTSOI MOSFETs in the 32-nm node for low stand-by power (LSTP) application, external parasitic resistance was reduced to 140 (NMOS) and 350 (PMOS) Ω µm. Our results show that ρc is an important component of parasitic resistance in terms of improving device performance of UTSOI MOSFETs.

One-dimensionally oriented poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) thin films with the thickness of approximately 50 nm were deposited by friction-transfer technique. Films were investigated using polarized optical spectroscopy. The dichroic ratio of absorption was estimated to be approximately eight. By means of transmission electron microscope (TEM), we revealed that the main-chains of F8T2 were aligned along the friction direction. Atomic force microscope (AFM) images of as-prepared films showed a roughened surface, whereas the film after subsequent thermal treatment showed remarkably smooth surface. Field-effect transistors utilizing the friction-transferred F8T2 films exhibited a field-effect mobility of 1.88×10-4 cm2 V-1 s-1 along the friction direction, which is about six times higher than that perpendicular to the friction direction.

The 0.875Pb(Mg1/3Nb2/3)O3–0.125Pb(Zr,Ti)O3 [0.125PMN–0.875PZT (50/50)] thin films, which have an extremely large piezoelectric coefficient d31 of -225 pm/V, have been successfully obtained on (100) Si substrates by RF-magnetron sputtering. These PMN–PZT thin films have a high (001) orientation. The dependences of the electrical and piezoelectric properties of these films on substrate heating temperature were evaluated. The er of PMN–PZT films prepared in the substrate heating temperature range of 540 to 620 °C was almost constant at 1400. The d31 was measured from the tip deflection of the cantilever beams. Even without a poling treatment, the d31of the PMN–PZT thin films at 580 °C was -225 pm/V. This d31 was 50% larger than that of PZT thin films deposited under the same conditions. These PMN–PZT thin films are attractive materials for micro actuator applications, especially for ink jet head actuators.