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.

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 (BMDs) are observed in Czochralski silicon wafers subjected to two-step annealing 'C)Xtz, where tI and t,= 1 -100 h]. The number density of BMDs near the surface is smaller than that in the bulk when tI is short, and is larger when tI is long. The anomalous distribution extends deeper than 100 pm 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-interstitial% (3) growing oxygen precipitates produce self-interstitials, and (4) self-interstitial undersaturation enhances stable growth of precipitate nuclei, and supersaturation suppresses stable growth. The nonequilibrium self-interstitial concentration induced in the bulk after the rapid temperature rise is responsible for the anomalous di&ributions. All the experimental characteristics are reasonably explained by the model. The formation process of the anomalous distributions is detected by three-step annealing experiments. Basic properties of self-interstitials in silicon are extracted from experimental results combined with the model. The activation energy for migration is about 2.5 eV. The diffusion coefficient is about 10m6 cm2 s-l at 900 "C. The thermal equilibrium concentration is estimated as about 10" cm-j at 1000 "C. These results are close to recent experimental estimates utilizing impurity diffusion in floating zone silicon. 0 1995 American Institute of Physics. 3710

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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.