Abstract
In this study, the change of mass distribution in a source material is tracked using an in situ computer tomography (CT) setup during the bulk growth of 4H- silicon carbide (SiC) via physical vapor depostion (PVT). The changing properties of the source material due to recrystallization and densification are evaluated. Laser flash measurement showed that the thermal properties of different regions of the source material change significantly before and after the growth run. The Si-depleted area at the bottom of the crucible is thermally insulating, while the residual SiC source showed increased thermal conductivity compared to the initially charged powder. Ex situ CT measurements revealed a needle-like structure with elongated pores causing anisotropic behavior for the heat conductivity. Models to assess the thermal conductivity are applied in order to calculate the changes in the temperature field in the crucible and the changes in growth kinetics are discussed.
Highlights
The physical vapor deposition (PVT) growth technique has matured to being the standard process for the production of 4H silicon carbide (SiC) crystals [1]
One approach is to set up a model in order to find how the source material evolves during growth and compare it with the experimental results afterwards [6].With our in situ Computer Tomography (CT) system [10], we are able to track the changes in the experiment, despite the very high process temperatures
Affect the the growth growth conditions. These findings indicate that the morphological changes strongly affect order to estimate the differences, a simulation of the temperature field of the growth start consisting of the isotropic powder in the bottom and the thin seed at the top is performed
Summary
The physical vapor deposition (PVT) growth technique has matured to being the standard process for the production of 4H silicon carbide (SiC) crystals [1]. One problem for the modeling of the growth conditions of bulk SiC is the lack of precise material data at elevated temperatures [9]. Another difficulty is accounting for the changes that happen inside the crucible during the growth process. One approach is to set up a model in order to find how the source material evolves during growth and compare it with the experimental results afterwards [6].With our in situ Computer Tomography (CT) system [10], we are able to track the changes in the experiment, despite the very high process temperatures.
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