Application of optical velocity measurements including a novel calibration technique for micron-resolution to investigate the gas flow in a model experiment for crystal growth. (December 2022)

• Record Type: Journal Article
• Authors: Bürkle, Florian; Förste, Maik; Dadzis, Kaspars; Tsiapkinis, Iason; Pätzold, Olf; Charitos, Alexandros; Dues, Michael; Czarske, Jürgen; Büttner, Lars
• Is Part Of: Flow measurement and instrumentation. Volume 88(2022)
• Publication Date: 2022-12
• Subjects: Optical flow measurement -- Crystal growth -- Reynolds similarity; Fluid dynamic measurements -- Periodicals; Flow meters -- Periodicals; Fluides, Dynamique des -- Mesure -- Périodiques; Débitmètres -- Périodiques; 681.2805
• DOI: 10.1016/j.flowmeasinst.2022.102258
• Languages: English
• ISSNs: 0955-5986

Abstract

Abstract: An important step in the fabrication of many modern semiconductor materials and devices is the crystal growth process. These processes take place in high-temperature furnaces using inert gas and other atmospheres. The flow in the gas phase influences the transport of crystal components, dopants and impurities and hence has a significant impact on the grown crystals. In this work, we study the flow in a simplified model of a crystal growth furnace. This model is made of PMMA filled with a Diesel mixture as a model fluid to match the refractive index of PMMA and to allow for measurements in the complex geometry. The comparability to the flow in a real furnace is ensured by matching the Reynolds number. Two optical measurement methods, Particle Image Velocimetry (PIV) and the Laser Doppler Velocity Profile Sensor (LDV-PS) are used to investigate the global flow field as well as the small-scale flow structures. A calibration model is developed for the LDV-PS to reduce systematic measurement errors caused by the refractive index of the model fluid from up to 1% to less than 0, 1%. The results obtained in this study improve the understanding of the gas flow behavior inside a crystal growth furnace and provide reference data for simulation. The first analysis shows a highly unsteady flow with unexpected flow direction along the crystal and melt surfaces. The near-surface flow patterns are of particular relevance in crystal growth because of their large influence on the local heat and mass transport during the crystallization process. Highlights: Silicon growth from Granulate Crucible is a new technique for crystal growth. A model experiment allows for investigation of the flow in the complex geometry. Optical measurement techniques are capable of measuring with high resolution. Errors induced by the refractive index are corrected with a new calibration model.