神田 一浩

Low-temperature crystallization of Si, Ge and Si_XGe_1−X films by SR-soft x-ray irradiation using short undulator light is examined. By setting the photon energy to that of the core electron orbital, the crystallization is examined experimentally and discussed theoretically from a view point of Ge diffusion. The temperature during the crystallization of Si, Ge or Si_0.5Ge_0.5 by soft x-ray was 80 to 140 degree C lower than that by the conventional rapid thermal annealing. The elementary process of the soft x-ray irradiation is thought to be the atom-diffusion following the localized excitation of the core-electrons and the generation of Coulomb repulsion. For the low-temperature crystallization, the quasi-nuclei are formed via the elementary process.<br>

The interaction mechanism of continuous soft X-rays with irradiated in vacuum diamond-like carbon (DLC) films, to simulate space environment conditions, was investigated using synchrotron radiation (SR). The thickness of the highly hydrogenated DLC film was found to decrease with increasing SR dose. The variation of local structure of DLC film was evaluated by measurements of the near edge X-ray absorption fine structure of carbon K-edge using SR. The characteristic peaks were observed in the spectrum of highly hydrogenated DLC film before irradiation, with these peaks disappearing from the spectrum after irradiation. These peaks are considered to be derived from the carbon bonding to hydrogen, which was desorbed by the soft X-ray irradiation. The sp2/(sp2 +sp3) ratio of DLC film was found to increase by the irradiation of soft X-ray.

The focusing characteristics of a ruthenium-coated cylindrical mirror were investigated on the basis of its ability to collect and focus broadband 5-17-nm soft X-rays emitted from a laser-produced plasma. Based on the plasmas spectral intensity distribution and the reflectivity function of the mirror, we defined the optimum position of the integrated cylindrical mirror at which the X-ray energy flux transported and focused through the mirror was maximum. A minimum spot diameter of 22 mm at a distance of approximately 200 mm from a soft X-ray source was confirmed. The maximum intensity of the collected soft X-rays was 1.3 mJ/cm2 at the center of the irradiation zone. Thus, the irradiation intensity was improved by approximately 27 times when compared to that of 47 μJ/cm2 without the mirror. The debris sputtering rate on the reflection surface of the mirror can be reduced to 1/110 by argon gas at 11 Pa, while the attenuation rate of the soft X-rays due to absorption by the buffer gas can be suppressed to less than 10% at the focal point. The focusing property of the mirror is expected to be maintained for 3000 h or longer without significant degradation for a 100 W/320 pps laser shot if the ruthenium layer is thicker than 10 μm. These results suggest that a stand-alone broadband soft X-ray processing system can be realized by using laser-produced plasma soft X-rays. © 2012 American Institute of Physics.

In this study, various kinds of diamond-like carbon (DLC) films were classified in terms of their biological responses (specifically the number of adhering cells). Forty three kinds of DLC samples that had been deposited on Si substrate by various physical vapor deposition (PVD) and chemical vapor deposition (CVD) system equipment were obtained at random from coating companies, universities, and public organizations in Japan. Mouth fibroblasts (NIH-3T3) were used to estimate the cellular responses on the DLC samples. During the cell culture, 12 of the DLC samples were peeled off from the Si substrates. As a result, the remaining 31 DLC samples with a wide range of properties were classified into four groups in terms of their number of adhering cells. Group 1 (high density, low sp 2 content, and low hydrogen contents) and Group 2 (low or medium density, high sp 2 content, and low hydrogen contents) had a low number of adhering cells. Group 3 (medium density, and medium sp 2 content, and relatively high hydrogen contents) and Group 4 (low sp 2 content, low density, and a wide range of hydrogen contents) had a wide range of number of adhering cells. Especially, 7 DLC samples in Group 4 had good cell growth. It was shown that this classification is one of the design criteria of DLC film deposition for biomaterials regardless of the various deposition system equipment. It is expected that ordinary DLC users can carefully select a DLC film for specific applications to medical devices using the classification. © 2012 Elsevier B.V.

Mitigation of fast debris and soft x-rays generated from laser-produced xenon plasmas were studied in an argon buffer gas in laser intensities of 10 910 11W cm 2using a cryogenic drum target. Considerable mitigation of debris was confirmed by measurements of material sputtering. From the experimental results, an attenuation parameter of sputtering by the debris and an absorption cross section of soft x-rays at 13.5 nm 2(13.5nm) were derived to be 2.2×10 20m 2and 1.8×10 22m 2, respectively. Moreover, is concluded to be equivalent to the effective collision cross section 1 of a debris particle at kinetic energy of 14 keV. Sufficient debris mitigation can be obtained together with low soft x-ray absorption (less than 10%). These parameters provide a useful design tool for realizing a practical soft x-ray source because they predict the effect of the buffer gas well. © 2012 IOP Publishing Ltd.

Diamond like carbon film containing tungsten (W-DLC) was fabricated by focused-ion-beam chemical-vapor deposition (FIB-CVD), and its thermal durability was investigated using near the carbon K-edge X-ray absorption fine structure (C-K NEXAFS) spectroscopy and a combination of Rutherford backscattering and elastic recoil detection analysis, in comparison with those of commercial DLC and W-DLC films. The concentration of W in the films did not decrease when the annealing temperature was increased, while the concentration of H did. The sp 2/(sp 2 + sp 3) ratio of carbon atoms in the films increased with annealing temperature. The W-DLC film fabricated by FIB-CVD unchanged after annealing for 32 h at 873 K in vacuum. Its thermal durability was comparable to that of commercially available films. © 2012 The Japan Society of Applied Physics.

The low-temperature activation and the suppression of anomalous diffused B by using SR soft X-ray were investigated for ultra shallow junction. The transient enhanced diffusion due to the interstitial B clusters can be suppressed by using soft X-ray.

We investigated a low-temperature crystallization of a-Si and a-Ge films by the synchrotron radiation soft X-ray irradiation at storage-ring current of 25-220 mA. It is found that the crystallization temperatures of a-Si and a-Ge were decreased from 680 to 580 degrees C and from 500 to 390 degrees C. These decreasements relate effects of enhancement atomic migration via electron excitation at valence band and core level.

We investigated crystallization mechanism of a-Si 0.5Ge 0.5 film by excimer-laser annealing (ELA) at energy density of 50-70mJ/cm 2 in comparison with a method of synchrotron radiation soft X-ray irradiation at storage ring current of 50-220 mA. The nucleation mechanism of Si 0.5Ge 0.5 via ELA will be discussed by considering the soft X-ray method. © 2012 IEEE.

Ultraviolet (UV) nanoimprinting is a useful technique to fabricate nanostructure devices with high throughput, high resolution, and low cost. To eliminate bubble defects, one of the main problems in UV nanoimprinting, UV nanoimprinting in an atmosphere of pentafluoropropane (PFP) gas, which is a condensable gas, is proposed. This process has been reported to reduce the demolding force. To examine the PFP gas effect in a nanometer-scale area, adhesion and frictional forces were measured by scanning probe microscopy in a PFP gas atmosphere. The results show that the adhesion and frictional forces measured by scanning probe microscopy in a PFP gas atmosphere were lower than those measured in air and a N2 gas atmosphere. Furthermore, the adhesion and frictional forces were found to depend on the PFP gas pressure. © 2012 American Vacuum Society.

Nanoscale imprinted pillars were fabricated with three resin systems and characterized by measuring the spring constant using a scanning probe microscopy cantilever manipulated with a three-axis actuator. The functional dependence of the spring constant on the height and diameter of the pillar was then used to determine the Young's modulus. Nanoindentation was used to determine the Young's modulus of the base film. Before high temperature annealing, the Young's modulus of the imprinted pillar was nearly the same as that of film. After the annealing, the Young's modulus of the imprinted pillar was lower than that of the film. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3657520]

The antisticking capabilities and durability of thin poly(dimethylsiloxane) (PDMS) were compared to a fluorinated antisticking layer (F-ASL) to assess its suitability for use in UV nanoimprint lithography (UV-NIL). Typically, UV-NIL is used to fabricate high-throughput, low-cost, high-resolution nanostructure devices. The nanoimprint mold is typically coated with an antisticking layer to ensure easy separation of the mold from the UV nanoimprint resins. This layer must be highly durable to meet the demands of a manufacturing environment, and F-ASL is the standard type used. In PS-b-PDMS block copolymer lithography, the template is coated with a thin layer of PDMS. In this study, we focused on using PDMS as the antisticking layer for nanoimprinting and examined its antisticking capabilities and durability by step and repeat (S&R) UV nanoimprinting. Experimental results showed that the thin PDMS layer functions comparably to the F-ASL as an antisticking layer. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3653226]

The authors have previously used two methods for nanoimprinting hydrogen silsesquioxane (HSQ) patterns. In the casting method, the HSQ pattern was replicated at a low imprinting pressure of less than 1 MPa, however, the imprinting produced an uneven residue. On the contrary, in the spin-coating method, an evenly distributed HSQ film was produced. However, the HSQ pattern required a high imprinting pressure of about 40 MPa. To achieve imprinting at a low pressure with the spin-coating method, we propose a new room temperature nanoimprinting method using spin-coated HSQ and a poly(dimethylsiloxane) mold. The authors used high boiling point solvent, with a boiling point of greater than 200 degrees C, in place of the previously used solvent that had a boiling point of 96 degrees C. This method produced an evenly coated film in the liquid-phase. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3653227]

The formation of bubble defects during UV-nanoimprinting can be prevented by carrying out the process in a 1,1,1,3,3-pentafluoropropane (PFP) gas environment. The authors therefore evaluated the curing time and the calorific value of UV-curable resins in a PFP gas environment by photo differential scanning calorimetry and their polymerization degree by Fourier transform infrared spectroscopy. The authors found that UV-curable resins polymerized more efficiently in PFP than in air because PFP dissolves in the resins. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3656022]

Soft X-ray conversion efficiencies in a 5-17nm wavelength range in xenon and tin plasmas produced by a 1.06 mu m Q-switched neodymium-doped yttrium aluminum garnet laser were investigated. They were measured to be 25 and 20% for the xenon and tin plasmas, respectively at a laser intensity of about 2 x 10(10) W/cm(2). These results indicate that a stand-alone soft X-ray source using a laser-produced xenon or tin plasma is useful for various applications that require intense, soft X-ray photons in a wide wavelength range. (C) 2011 The Japan Society of Applied Physics

The orientation of molecules in photoinduced liquid crystalline polymer film was studied by means of a thermal nanoimprinting technique using a SiO2/Si mold with a line-and-space (L&S) pattern. If nanoimprinting reorients molecules in photoinduced liquid crystalline polymer, unique characteristics may result from carrying out nanoimprinting and linearly polarized UV (LPUV) irradiation at the same time. We found that the imprinted photoinduced polymer was oriented parallel to the line pattern on the mold. Furthermore, we found that photoinduced liquid crystalline polymer films that were pre-aligned by LPUV irradiation and a heat treatment could be reoriented by thermal nanoimprinting. (C) 2011 Elsevier B.V. All rights reserved.

The effects of thermal annealing of W incorporated diamond-like carbon (W-DLC) films fabricated with focused ion beam chemical vapor deposition (FIB-CVD) were investigated using X-ray absorption fine structure near the carbon K-edge (C-K NEXAFS) and the combination of Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA). W-DLC films were annealed for 32 h at temperatures, T_{\text{a } }, between 673 and 1073 K. Comparing the T_{\text{a } } dependences of Ga and H contents obtained from RBS-ERDA and the \mathrm{sp}^{2}/(\mathrm{sp}^{2} + \mathrm{sp}^{3}) ratios from C-K NEXAFS, it was found that even a trace amount of W incorporation into DLC films fabricated by Ga+ FIB-CVD may cause a significant \mathrm{sp}^{3} \rightarrow \mathrm{sp}^{2} structural change.

The effect of soft X-ray irradiation of diamond-like carbon films in vacuum was investigated using synchrotron radiation (SR). Etching and the desorption of hydrogen upon SR exposure in vacuum occurred in highly hydrogenated diamond-like carbon (H-DLC) films; these processes were not observed in the irradiation of a low-hydrogenated DLC film. The extent of decrease in hydrogen content due to SR exposure was found to decrease with increasing the etching ratio of the H-DLC film. This indicates that hydrogen desorption from the H-DLC films competed with the etching process. Namely, the modified surface, in which hydrogen content was decreased by SR exposure, was immediately removed from the H-DLC film that had a high etching rate. (C) 2011 The Japan Society of Applied Physics

Surface modification of diamond-like carbon (DLC) film was performed using a hyperthermal atomic fluorine beam on the purpose of production of hydrophobic surface by maintaining the high hardness of DLC film. By the irradiation of atomic fluorine beam of a 1.0 x 10(20) atoms/cm(2), the contact angle of a water drop against the DLC surface increased from 73 degrees to 111 degrees. The formation of CF3, CF2 and CF bonding on the modified DLC surface was confirmed from the measurements of X-ray photoelectron spectra and near-edge X-ray absorption fine structure spectra. Irradiation of hyperthermal atomic fluorine beam was concluded to produce insulator fluorine-terminated DLC film, which has high F content on the surface. by the taking of the use of neutral atomic beam as a fluorine source. (C) 2011 Published by Elsevier B.V.

Hydrogenated amorphous silicon carbide (a-SiCx:H) films were prepared by the decomposition of tetramethylsilane (TMS) with microwave discharge flow of Ar. When radio-frequency (RF) bias voltage (-V-RF) was applied to the substrate, the film hardness increased as (2.39 +/- 1.12)-(9.15 +/- 0.55) GPa for -V-RF = 0-100 V. The a-SiCx:H films prepared under various -V-RF conditions were analyzed by the carbon-K near edge X-ray absorption fine structure (NEXAFS), by the elastic recoil detection analysis (ERDA), and by the X-ray photoelectron spectroscopy (XPS). From a quantitative analysis of NEXAFS, the sp(2)/(sp(2)+sp(3)) ratios of C atoms were evaluated as 67.9 +/- 2.0, 55.4 +/- 2.7, and 51.7 +/- 0.7% for -V-RF = 0, 60, and 100 V. respectively. From ERDA, hydrogen content of the film prepared under the condition of - VRF = 100 V was found to decrease 28% comparing with that under -V-RF = 0 V. It is suggested that the cause of the increase of the film hardness when applying -V-RF is predominantly the growth of the sp(3)-hybridized structure of C atoms accompanied by the decrease of hydrogen terminations. (c) 2011 Elsevier B.V. All rights reserved.

An anti-fouling ability of diamond-like carbon (DLC) electrodes to biological macromolecules has been investigated from a decrease in the electrochemical redox current of Fe(CN)(6)(4-/3-), used as a redox marker. A DLC electrode and a glassy carbon (GC) electrode were immersed in a solution containing bovine serum albumin (BSA) or DNA. The GCs treated with biological macromolecules gave rise to a significant decrease in the currents, while there was no signal decreases from the treated DLCs. The signals from the DLCs remain essentially unchanged for at least 24 h at a 10 mg/mL concentration level of BSA.

Nanoimprint lithography (NIL) is a very useful technique for replicating planar nanostructures at low cost with high throughput, but an expansion from planar to nonplanar will probably be required to enhance the functional capabilities of nanodevices. On the other hand, focused-ion-beam chemical vapor deposition (FIB-CVD) is a promising technology for fabricating nonplanar nanostructures. In this study, the authors demonstrated a new nonplanar replication method using a combination of FIB-CVD and NIL to achieve nonplanar replication with submicrometer feature sizes. Furthermore, they replicated nonplanar nanostructures by using step and repeat NIL. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3524289]

We investigated a low-temperature crystallization of a- Si, a-Ge and a-Si1-xGex films by the synchrotron radiation (SR) soft X-ray irradiation at storage ring current of 25-220 mA. Crystallization of SiGe caused by the atomic migration during soft X-ray irradiation is effective as compared with the thermal annealing.

UV nanoimprint lithography is used to fabricate nanostructure devices with high throughput, low cost, and high resolution. UV-curable resins are one important factor in UV nanoimprinting and they are mainly categorized into two reaction types: radical and cationic curing systems. A drawback of the radical curing system is curing inhibition by oxygen. To evaluate the oxygen inhibition for UV-curable resins, the authors measured the force curve transition by scanning probe microscopy with an UV irradiation system. With this system, the authors are able to measure in situ the UV dose dependence of the force curve transition on the same UV-curable resin. Measurements showed that the curing speed of radical UV-curable resin in vacuum became 800 times higher than that in air due to oxygen inhibition. Furthermore, for a cationic UV-curable resin, although the curing reaction of a cationic UV-curable resin is not affected by oxygen, the authors observed that the curing speed in vacuum at about 15 Pa became 4.5 times higher compared to that in air. The curing reaction of a cationic UV-curable resin may be inhibited by alkali. (C) 2010 American Vacuum Society. [DOI:10.1116/1.3517511]

Surface structural changes of a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS), synchrotron radiation photoelectron spectroscopy (SR-PES), and near-edge X-ray absorption. ne structure (NEXAFS). It was confirmed that the DLC surface was oxidized and etched by high-energy collisions of atomic oxygen. RBS and real-time mass-loss data showed a linear relationship between etching and atomic oxygen fluence. SR-PES data suggested that the oxide layer was restricted to the topmost surface of the DLC film. NEXAFS data were interpreted to mean that the sp(2) structure at the DLC surface was selectively etched by collisions with hyperthermal atomic oxygen, and an sp(3)-rich region remained at the topmost DLC surface. The formation of an sp(3)-rich layer at the DLC surface led to surface roughening and a reduced erosion yield relative to the pristine DLC surface. (C) 2010 Elsevier B.V. All rights reserved.

The deposition yield and physical properties of carbon films fabricated by focused-ion-beam (FIB) chemical vapor deposition were examined using several ion beam species of hydrogen, helium, xenon, and gallium. A gas-FIB was generated using an inductively coupled plasma ion source. It was found that the deposition yield is proportional to the total stopping power of the beam that penetrates into the carbon film. The physical properties of the carbon films deposited using gas-FIB are similar to those of films deposited using Ga-FIB, except for the Young's modulus.

A new room-temperature imprinting method was developed using liquid-phase hydrogen silsesquioxane (HSQ) with a hard poly(dimethylsiloxane) (h-PDMS) mold. The simultaneous imprinting of arbitrary patterns including both submicron and greater than 100 μm patterns on a 4-in. wafer were replicated at room-temperature and a low pressure with high throughput, because the solvent in HSQ gradually evaporated through the pores of the h-PDMS mold. A bilayer structure was successfully fabricated using as HSQ pattern as an etching mask without removing the residual layer.

The direct patterning of low-dielectric constant (low-$k$) materials via nanoimprint lithography (NIL) has the potential to simplify fabrication processes and significantly reduce the manufacturing costs of semiconductor devices. It is known that a low $k$ is realized by introducing a large number of nanoscale pores into a material. We demonstrated nanoimprinting on a sol–gel low-$k$ material ($k\sim 2.0$) formed using methyl silicate as a siloxane oligomer source and surfactants as a pore template. As a result, 200-nm-linewidth mold patterns were successfully transferred onto the sol–gel low-$k$ material by thermal nanoimprinting at 200 °C. However, pattern shrinkage was observed. The imprinted pattern linewidth was 180 nm. We assumed from the Fourier transform infrared spectroscopy (FT-IR) spectra of the sol–gel film before and after baking that the pattern shrinkage was induced by the condensation reaction.

The mechanical characteristics of iron-containing nanosprings (Fe-containing nanosprings) fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) using a ferrocene (C10H10Fe) source gas were investigated. The shear and Young's moduli were 34 and 92 GPa, respectively. We also evaluated the annealing effect of Fe-containing nanosprings and observed a droplet containing Fe and Ga on the nanospring after annealing at 600 °C. The spring constant rapidly decreased after annealing at 600 °C. By scanning electron microscopy energy–dispersive X-ray spectroscopy (SEM–EDX) and transmission electron microscopy energy–dispersive X-ray spectroscopy (TEM–EDX) line analysis, it was confirmed that the decrease in the spring constant was due to Ga removal.

The desorption processes of H and Ga from diamond-like carbon (DLC) film synthesized by focused-ion-beam chemical vapor deposition (FIB-CVD) were investigated by elementary analysis and local structure analysis after heat treatment under various conditions. The elementary composition of FIB-CVD DLC film was determined using a combination of Rutherford backscattering spectra and elastic recoil detection analysis spectra. Local structure analysis was performed by the measurement of near-edge X-ray absorption fine structure using synchrotron radiation. Desorption of H from FIB-CVD DLC film by heat treatment was found to comprise two types of process. One is the local graphitization along paths, where residual Ga atoms move by annealing. In this process, Ga acts as a catalyst for the graphitization of DLC. The other process is derived from the graphitization of the whole DLC film by heat, regardless of Ga. In this process, the sp2 content increases considerably.

Nanoimprint lithography (NIL) is a simple process for fabricating nanostructure devices. There are many factors in nanoimprinting such as nanoimprint pressure, an antisticking layer, temperature, and the viscosity of resin. Although these factors affect the imprinted pattern, the nanoimprint mechanism has not been resolved. The flow behavior during nanoimprinting is important for investigating the nanoimprint mechanism. We propose a cross-sectional observation method for filling a nm-scale pattern with nanoimprint resins after nanoimprinting using scanning electron microscopy (SEM). A polyvinyl alcohol (PVA), which is soluble in water, was used in this observation. We demonstrated the cross-sectional observation of UV-, thermal-, and room temperature-nanoimprint resins using the proposed method. (C) 2009 Elsevier B.V. All rights reserved.