Mikio Kadoi

Growth and Optical Properties of Li13Nd(GeO4)4 Single Crystal

In this paper, single crystals of Li13Nd(GeO4)4 are grown by the Czochralski method. The unit cell dimensions and the crystal system are determined by an X-ray diffraction method. The principal refractive indices, na, nb and nc and the temperature dependence of birefringences, nc-nb, nc-na and na-nb, over the temperature range from room temperature to 500degC are measured. A fluorescence spectrum at around 1.06 µm is observed, and strong fluorescence is detected.

The Phase Diagram of the YO1.5–BaO–CuO Ternary System and Growth of YBa2Cu3O7 Single Crystals

Phase equilibria relations in the YO1.5–BaO–CuO system at 900°C in air were investigated and the phase diagram of the subsystem YBa2Cu3O7–BaCuO2–CuO was determined by differential thermal analyses, quenching experiments, and X-ray diffraction measurements. Single crystals were grown by the slow cooling method and then characterized.

Study of proximity lithography simulations using measurements of dissolution rate and calculation of the light intensity distributions in the photoresist

This report describes the results of a study on resist profile simulation in proximity printing, using light intensity distribution and actually measured dissolution rate values, a method that takes the gap effect into consideration (the effect of the distance between mask and wafer on the aerial image and resist profiles). We calculate the light intensity distribution with the gap effect based on the Van Cittert-Zernike theory and on the Hopkins equation as a model of light intensity distribution of proximity printing in resist film. Dissolution rate values are obtained using an apparatus to measure resist film thickness during development. The resist profile simulation is carried out using the combined data thus obtained. To verify the validity of this simulation, we use an SEM to observe resist profiles obtained from a diazonaphthoquinone (DNQ)-novolak resin positive-type resist for thick films, varying the proximity gaps using the mask aligner, which uses light in the broadband wavelengths of 350 mm to 450 mm, and compare the results with the simulation. The results of simulation and those of the SEM observation are in agreement, proving the validity of our method.

Anomalous depth distributions of bulk microdefects in heat‐treated Czochralski silicon wafers due to nonequilibrium self‐interstitials

Anomalous depth distributions of bulk microdefects (BMDs) are observed in Czochralski silicon wafers subjected to two‐step annealing [(550–700 °C)×t1+(850–950 °C)×t2, where t1 and t2=1–100 h]. The number density of BMDs near the surface is smaller than that in the bulk when t1 is short, and is larger when t1 is long. The anomalous distribution extends deeper than 100 μm from wafer surfaces and cannot be explained by the behavior of interstitial oxygen atoms. Distributions are examined under various annealing conditions, such as annealing temperature, rate of temperature ramping, ambient atmosphere, and initial oxygen concentration. The anomalous distributions are found to be formed in the early stage of second‐step annealing only when the annealing starts with a rapid temperature rise. A formation model of anomalous distributions is proposed based on the following assumptions: (1) self‐interstitials exist in the thermal equilibrium state, (2) wafer surfaces are a permanent source and sink of self‐intersti...

Radial Distribution of Oxygen Precipitates in Czochralski Silicon Single Crystals

The effect of annealing conditions on the radial distribution of oxygen precipitates in Czochralski (CZ) silicon crystals was examined through two-step annealing. When the preannealing temperature was lower than 800°C, the oxygen precipitation depended on the initial oxygen concentration, and precipitation near the periphery of the crystal was often suppressed. When the preannealing temperature was higher than 900°C, the oxygen precipitation was enhanced near the periphery. This result indicates that extremely stable nuclei, whose density is low compared with the total amount of nuclei, exist near the periphery of the CZ crystals.

Development of Photochemical Analysis System for F2-Excimer Laser Lithography Processes.

A system for photochemical analysis of F2-excimer laser lithography processes has been developed. The system, VUVES-4500, consists of 3 units: (1) an exposure and bake unit that uses the F2-excimer laser to carry out a flood exposure and then post-exposure bake (PEB), (2) a unit for measurement of the development rate of photoresists, and (3) a simulation unit that utilizes PROLITH of profile simulation software to calculate the resist profiles and process latitude using the measured development rate data. With this system, preliminary evaluation of the performance of F2-Excimer laser lithography can be performed without the use of a lithography tool capable of imaging and alignment. Profiles for 150 nm lines are simulated for the PAR-101 resist (manufactured by Sumitomo Chemical) and the SAL-601 resist (manufactured by Shipley), a chemically amplified resist that has sensitivity at the F2-excimer laser wavelength. The simulation successfully predicts the resist behavior. Thus it is confirmed that the system enables efficient evaluation of the performance of F2-excimer laser lithography processes.

Development of analysis system for F2-excimer laser photochemical processes

A system for photochemical analysis of F2-excimer laser lithography processes has been developed. The system, VUVES- 4500, consists of 3 units: (1) an exposure and bake unit that uses the F2-excimer laser to carry out a flood exposure and then post-exposure bake (PEB) of a resist coated wafer, (2) a unit for the measurement of development rate of photoresists, and (3) a simulation unit that utilizes PROLITH to calculate the resist profiles and process latitude using the measured development rate data. With this system, preliminary evaluation of the performance of F2 excimer laser lithography can be performed without a lithography tool that is capable of imaging and alignment. Profiles for 100 nm lines are simulated for the PAR-101 resist (manufactured by Sumitomo Chemical) and the SAL-601 resist (manufactured by Shipley), a chemically amplified resist that has sensitivity at the F2 excimer laser wavelength. The simulation successfully predicts the resist behavior. Thus, it is confirmed that the system enables efficient evaluation of the performance of F2 excimer laser lithography processes.

In-situ measurement of outgassing generated from EUV resist including metal oxide nanoparticles during electron irradiation

In this study, we evaluated the outgassing generated from EUV resist which included metal oxide nanoparticles during electron irradiation. We prepared two types of samples including ZrO2 and TeO2, and a sample without including metal oxide, respectively. The outgassing species were measured from each sample during electron irradiation at the Eth exposure dose. The electron acceleration energy was 2 keV. In the outgassing measurement, we used original in-situ outgassing monitoring system in quadrupole mass spectrometry which we developed. From the results of mass spectrum, we observed CO2, H2O as typical mass peaks at each sample. And also we observed C4H4O2 and C4H6O2 peaks in spectrum of each sample. And these peaks are guessed 2(5H)-furanone and butyrolactone generated from base polymer. C6H6 peaks were observed in the mass spectrum of including ZrO2 and TeO2. We guessed that these peaks are from benzene generated from photo-acid generator (PAG). On the other hand, C6H6 peaks were not observed in the mass spectrum of without metal oxide. About this, we could not explain that mechanism by our knowledge of the present, but we can guess that metal oxide nanoparticles worked to generate benzene. About metal oxide peaks did not observe about mass spectrum of each sample. Each metal or metal oxide might not be evaporated during electron irradiation.