Effect of Radiation in Solid during SiC Sublimation Growth
- PDF / 128,317 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 12 Downloads / 222 Views
0911-B01-02
Effect of Radiation in Solid during SiC Sublimation Growth Shin-ichi Nishizawa, Shin-ichi Nakashima, and Tomohisa Kato National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8568, Japan
ABSTRACT The effect of infrared absorption on SiC sublimation growth was numerically investigated. At first, absorption coefficient was estimated as function of doping concentration. Then temperature distribution inside a crucible was numerically analyzed with taking account of absorption in growing crystal. It was pointed out that temperature distribution in a growing crystal strongly depends on absorption coefficient, i.e. doping concentration. As increasing the absorption coefficient, the growth front temperature and temperature gradient inside a growing crystal increase. It might cause large thermal stress and affect the grown crystal quality. This agrees well with growth features in experiment. The growth condition should be determined with taking account of absorption coefficient, i.e. doping concentration. INTRODUCTION Sublimation is the most commonly used technique to grow SiC bulk single crystal. Recently, 4 inch both in diameter and length ingot was grown by this technique [1]. In this process, source powder and seed crystal are set inside a closed carbon crucible, and heated up over 2000 K. It is well known that radiative heat transfer is very important under such high temperature condition. So, the radiative heat transfer in gas phase is usually considered in the modeling of SiC sublimation. Since silicon carbide single crystal is semi-transparent, radiative heat transfer not only in gas phases but also in a growing crystal might be very important. And it is supposed that stress field which affect on grown crystal quality [2-6], depends on the radiative heat transfer in growing crystal [6]. From this point of view, in this study, the effect of infrared absorption of growing crystal on temperature field during SiC sublimation growth was numerically investigated. NUMERICAL ANALYSIS Figure 1 shows the schematic model used in this study. The conventional RF induction heating furnace with cylindrical crucible in 50mm inner diameter has been simplified in the 2D model. In order to consider the effect of crystal length, two cases of 1mm seed and 15mm growth length were analyzed. Electromagnetic and thermal fields were analyzed by using CFDACE+ commercially available software [7]. Since convective heat transfer could be neglected in the standard sublimation process, the equation for momentum transfer was not analyzed.
1. SiC source powder 2. Ar 3. SiC growing crystal 4. Graphite crucible 5. Insulator 6. RF coil
Figure 1 Schematic model of SiC sublimation growth. With respect to the heat transfer, radiative and conductive heat transfers were considered by the Discrete Ordinates Method. Silicon carbide is a semi-transparent crystal. In order to consider the effect of internal radiation in growing crystal, absorption coefficient of SiC crystal was estimated as follows. The dielectric
Data Loading...
