Investigation of gas bubble growth in fused silica crucibles for silicon Czochralski crystal growth

• Published in: Journal of crystal growth 2020-03, Vol.533, p.125470, Article 125470
• Main Authors: Hirsch, Antje, Trempa, Matthias, Kupka, Iven, Schmidtner, Lea, Kranert, Christian, Reimann, Christian, Friedrich, Jochen
• Format: Article
• Language: English
• Subjects: A1. Characterization; A1. Optical microscopy; A2. Czochralski method; B1. Fused quartz crucible; B2. Semiconducting silicon; Bubbles; Cost analysis; Crucibles; Crystal growth; Fused silica; Silicon dioxide; Single crystals
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2019.125470

•Vacuum bake-out tests can predict the bubble behavior in Cz crucibles.•Increased hold time and temperature, and decreased pressure increase bubble growth.•During the VBT, only existing bubbles grow, no new bubbles form. Gas bubbles in crucibles for Czochralski (Cz) silicon growth are both necessary and detrimental: In the outer, bubble-containing (BC) layer of the crucible, they are required for mechanical stability, while in the inner, bubble-free (BF) layer, bubbles can cause the release of particles from the crucible into the melt which may disrupt the single-crystalline growth. In this work, a vacuum bake-out test (VBT) procedure was set up for unused crucible parts and a microscopic characterization routine was developed to systematically investigate bubble formation and growth. Longer process time, higher temperature, and lower atmospheric pressure lead to an increased bubble growth in both, the BC and BF layer. During the VBT, no new bubbles form in the BF layer, while existing bubbles grow. The comparison to experimental data from crucibles used in an industrial Cz process indicates that VBTs can simulate this process. This allows the prediction of the gas-bubble formation in Cz crucibles using a cost-effective and less time-consuming analyzation method.