シリコン融液の基本特性

抄録

Basic pmperties of molten silicon are examined experimentally. The temperature dependence of the density was determined in the range from solidification point of about 1,415℃ to 1,650℃ using an improved Archimedian method. An anomalous value in the thermal volume expansion coefficient of about 8×10^<-4>℃^<-1> was observed just above the solidification point. The time dependence of the density has also been recognized. The detailed temperature dependence of the surface tension of molten silicon was measured using an accurate ring method. The surface tension data showed an approximately linear temperature dependence from 1,430℃ to 1,650℃. The temperature coefficient of the surface tesion becomes positive at about 1,425℃ and returns to a negative value just above the solidification point. The viscosity of molten silicon was measured in the temperature range from the solidification point to about 1,600℃ using an oscillating cup made of SiC. The activation energy estimated from the data was 0.20eV. An anoomalous increase in viscosity with decreasing temperature was observed for temperatures lower than about 1,430℃. The temperature dependence of the electrical resistivity of molten silicon was measured based on the dirct-current four-probe method in the range from the solidification point to 1,630℃. The temperature coefficient of the resistivity varied slowly with temperature, being negative near the solidification point and positive above 1,500℃. The resistivity of molten silicon was calculated based on Ziman's formula. The temperature dependence of the measured resistivity was not reproduced when the structure factor S (Q) calculated by a simple hard-sphere model was substituted into Ziman's formula, but was reproduced by using the experimental data of S(Q) measured by Waseda which shows the first peak of asymmetric shape. These results indicate that the anomalous behavior of different properties occurs similtaneously, reflecting a kind of essential variation in the melt. The specific melt structure of molten silicon may have a significant effect on the anomaly in the temperature range near the solidncation point.