Chemical vapour deposition coating of crystalline Si 3N 4 on a quartz crucible for nitrogen-doped Czochralski silicon crystal growth

Abstract

A dense crystalline α-Si 3N 4 layer was formed on a quartz substrate by chemical vapour deposition (CVD) from an SiCl 4NH 3H 2 gas mixture under the following reaction conditions: NH 3-to-SiCl 4 ratio, 0.7–0.9; temperature, 1310 °C; pressure, 5–9 Torr; the Si 3N 4 deposition rate is 30–40 μm h −1. A Si 3N 4-coated crucible remained almost intact after immersion in reactive molten silicon for 24 h; the rate of erosion of Si 3N 4 layer was as small as 5–6 μm day −1. On the basis of these test results an α-Si 3N 4 approximately 300 μm thick layer was formed by CVD on the inner surface of a 7 in quartz crucible. Czochralski silicon crystal pulling tests were carried out using the coated crucible. The result indicates that solution of α-Si 3N 4 from the coated crucible and precipitation of ß-Si 3N 4 whiskers disturbed single-crystal growth and led to polygonization of the grown crystal. The concentrations of nitrogen and oxygen in the Czochralski crystal were (5–12) × 10 15 cm −3 and (5–16) × 10 16 cm −3 respectively.