Abstract
The surface tension of molten silicon is measured to be almost unchanged in the range of oxygen partial pressure, PO2≤10−22 MPa with the sessile drop method under precisely controlled the oxygen partial pressure. Then, the effects of boron concentration (CB/mass%) and carbon concentration (CC/mass%) on the surface tension were investigated with the same method under PO2≤10−22 MPa. The results obtained are summarized as follows. The surface tension increases with increasing CB, and the maximum increase rate of the surface tension is about 30 mN·m−1·(mass%CB)−1 in the range of dilute boron concentration. The temperature coefficient of the surface tension, (∂σ⁄∂T)CB, increases with increasing CB. Since dissolved boron from the BN substrate into molten silicon is below 0.054 mass% and the associated increase of the surface tension is below 1.5 mN/m, the contamination from the BN substrate on the surface tension can be ignored. The relation between the surface tension and CB indicates negative adsorption and is well described with Szyszkowski’s equation. The surface tension remains almost constant even in carbon saturated silicon and CC has almost no influence on (∂σ⁄∂T)CC in the range of CC≤84 mass ppm (Cc,sat at 1693 K).
