Formation of SiO2-like Thin Films under Atomospheric Pressure by Vacuum Ulraviolet CVD using Ultrasonic Assisted Vaporizer

Using ultrasonicwave, we have developed a technique to support the vaporization of TEOS which is hardly vaporized by only decompression in Vacuum ultraviolet chemical vapor deposition (VUV-CVD). Mist of TEOS with the averaged particle size of 4 μm was generated by an equipment combinating a double vessel system and an ultrasonic device of which freguency is 1.7 MHz. TEOS was successfully vaporized under the room temperature and atmospheric pressure by using this equipment, and flat SiO2-like films were deposited with the VUV-CVD method, using a Xe excimer lamp(λ=172 nm). Besides, by the observation with the scanning electron microscope it was found that a number of spherical particles of around 0.6 ~ 0.8 μm in diameter were observed on the film. We have also demonstrated that the spherical particles on the film surface can be reduced by reducing the mist particles from the introducing gas material.departmental bulletin pape

STM Observation of Au Particles Adsorbed on Si(111)-Clean Surface by PLD Method

To obtain important information for fabricating atomic-scale Au thin films that are used for biosensors, we have examined the flushing temperature for forming the Si(111) clean surface and observed the morphology of Au particles adsorbed by Pulsed Laser Deposition method on a Si(111)-7×7 surface by STM, which is supposed to be the initial stage of Au atomistic thin film formation. As the result of this study, it was found that flushing temperature must be controlled within 5℃ and we can fix the flushing requirement by STM images. Besides, we have estimated that Au particles are adsorbed on the position which is about 0.21 ± 0.03 nm away from the center of Si adatom.departmental bulletin pape

Flattening Treatment of Substrate for Optical Components Using the Vacuum Ultraviolet CVD

In order to shorten the processing period for polishing of substrates for optical components, we have developed a technique of flattening treatment of the substrate utilizing the vacuum ultraviolet method. The flattening property and the laser damage resistance of the treated substrate have been evaluated. Substrate with scratches in one direction was used for the flattening treatment. As a result, scratches with widths less than 0.5 μm were found to be covered smoothly after the 40 minute-deposition. Experiments to evaluate the laser damage resistance of the treated substrates were performed by the fourth harmonic and the second harmonic of Nd:YAG laser. The results indicated that the some of obtained values were high enough compared to the damage threshold of the dielectric multilayer films asuming to use for the high-reflactance mirrors. In the evaluation of laser damage resistance, it was found that a tendency of peeling of the film was due to differences in the absorption coefficient of the two laser wavelengths.departmental bulletin pape

Study for the Possibility of Utilization of Lower Volatility Material in Thin Film Deposition by the Vacuum Ultraviolet CVD

In mass production of electronic and optical devices, lower processing temperature is required for reducing cost and environmental load. We have developed a technique to support the vaporization of supplying raw materials for the vacuum ultraviolet-CVD without heating by using an ultrasonic mist generator. In this work, we used the TEOS of which vaporization rate is not enough at room temperature. We did not obtain any films in deposition experiments in which we introduced 150 Pa of the mixed gas which contained the saturated vapor of TEOS at atmospheric pressure into the chamber for CVD. However, we have successfully obtained dense and flat silica films when mist of TEOS is introduced together under the same total pressure of 150 Pa. Though silica films were a7lso obtained when the mixture of 0.1 MPa was introduced into the chamber, porous-structured films are obtained. This maybe due to interference caused by nitrogen which is the main component of the mixture. From these results, in order to obtain the films of good quality it is necessary to achieve both reduction of total pressure and increase of the partial pressure of TEOS. To achieve both the conditions consistently, it is considered that the mist of TEOS should be introduced under some reduced pressure, and then, vaporized `in the chamber.departmental bulletin pape

The development of the element process technology for the new type LSI of the product layer by VUV-CVD

平成15年―平成17年度科学研究費補助金(基盤(B))研究成果報告書research repor

Fabrication of Tilted Fiber Bragg Grating as a Sensor of Refractive Index of Liquids

We have developed a fabrication technique of tilted fiber Bragg gratings (TFBG) for refractive index sensor of liquids. We demonstrated that a simple technique using a combination of 266-nm laser and a phase mask with a period of 1.065 μm was quite effective for the fabrication of the TFBG. Using fabricated TFBGs which had the tilted angles of 3.3˚, 6.7˚, 7.3˚, 8.0˚, and 9.9˚, we tried to measure the refractive index of liquids which have different indices. Water, ethanol and glycerine solutions (12%, 24%, 35%, 46%, 66%, and 84%) were used as samples. For the measurement, a 10-mm long TFBGs were covered with a sample liquid droplet. The transmission spectra in the cladding mode and core mode were observed by an optical spectrum analyzer. We have directed our attention to the fact that wavelength of cladding mode shifts to be longer with the increase of refractive index of sample liquids. Utilizing this wavelength shift, we proposed a new measurement method. As a result, we could successfully measured the refractive index of liquids within a range from 1.00 to 1.41 with a maximum resolution of 3.0_x10^-3. In addition, we have found that a contact length of only 2.4 mm is necessary to obtain 90% of signal intensity of 10-mm long TFBG.departmental bulletin pape

Measuring of Decomposition Process of Toxic Substances using Vacuum-Ultraviolet Irradiation

Vacuum-ultraviolet(VUV) radiation has high photon energy so, it has the feature which causes a strong photochemical reaction. Since it has high photon energy, various organic substances can be decomposed by the irradiation of VUV radiation. In this paper, we proposed decomposing toxic substances using vacuum-ultraviolet irradiation. We chose dioxins as a sample toxic substance. Dioxin such as Coplanar polychlorinated biphenyls(PCBs) are very poisonous and difficult to decompose by conventional chemical reactions to decompose. In this paper, Xe_2* lamp was used biphenyl which has a similar structure as PCB as a model substance. By irradiating with Xe_2* lamp, biphenyl was found to be disassembled and it decomposed. The resultants are 2(H_2), 12(C), 14(CH_2), 16(CH_4) and 28(CO), 32(CH_4O) and 44(CO_2) which are substances with less toxicity. In order to discuss a motion of the chlorine contained in PCBs, paradichlorobenzene was also tried to decompose with the Xe_2* lamp. The chlorine was found to disconnect easily and become hydrogen chloride (hydrochloric acid). It is thought that VUV lamp radiation is very effective in weakening the toxicity of dioxins.departmental bulletin pape

Observation of Au particle on Si clean surface by UHV-Scanning Tunneling Microscopy

In order to know growth process of atomic-level Au thin films, we have observed Au particles deposited by the pulsed laser deposition(PLD) method on Si clean surface by an ultra high vacuum scanning tunneling microscope(UHV-STM). As the result of examination for forming the Si(111) cleaned surface, it was found that temperature of flushing should be controlled within 5℃. Besides, we have successfully estimated that the strucuture of the film-like cluster of Au is almost monoatomic layer based on the face-centered cubic(fcc) sturucture.departmental bulletin pape

Development of Focusing and Irradiating System for Laser-stimulated Desorption Spectrometer

Vacuum ultraviolet (VUV) with a wavelength of 100-200 nm has a photon energy of about 6-12 eV, which is higher than the binding energy of many substances, and has the feature of being able to break chemical bonds. We have applied these features to develop an analyzer named the Photon-stimulated Desorption Spectrometer. Since the spatial and temporal resolutions of this system are low due to adaption of incoherent light source, it is expected to improve by replacing the light source with an ultrashort pulsed VUV laser. In the present study, we have developed a focusing and irradiating system that enables various laser irradiation modes by overlapping multiple beams spatially and temporally. High-precision position control of the focusing and irradiating system is necessary for this purpose. Here, we used a number of micrometers with encoder that can be computercontrolled with a resolution of 1 μm to develop a double beam focusing and irradiating system using currently available ultrashort pulsed lasers with wavelengths of 800 nm and 400 nm. As a results, we confirmed that the smaller spot diameter was obtained by using the shorter wavelength. The spatial superposition can be performed within an accuracy range of ±3 μm, and the temporal superposition can be performed with an accuracy of 33 fs. Besides, interference fringes were obtained by angled irradiation of two light beams which can be expected to induce desorption in finer areas.departmental bulletin pape

Analysis by the simulation of the character of reflection of the Fiber Bragg Grating sensor

Abstract Refractive indices of silica glass are well known to change when ultra violet light is irradiated. With the photo-refractive effect, regions with different refractive indices are generated in an optical fiber. Fiber Bragg Grating (FBG) that has a periodic structure of different refractive indices shows a sharp reflection spectrum at a wavelength. The center wavelength, width, depth and sub peaks of the reflection spectrum depend on the periodicity, index difference, and index distribution of the structure. However, it is considerably difficult to measure the indices of the structure, because the size is as small as an order of optical wavelength used. I simulate the reflection spectra by changing the length and intensity distribution within the laser beam and index change. By comparing the simulated spectra with there measured, I have found that the laser beam has Gaussian-type intensity distribution and that the spectra depend on the length and index change distribution. On the basis of the simulation, you can obtain the laser parameters for fabricating a desirable FGB.departmental bulletin pape