Silicon Carbide Sublimation Growth Research Articles

Impact of Varying Parameters on the Temperature Gradients in 100 mm Silicon Carbide Bulk Growth in a Computer Simulation Validated by Experimental Results

AbstractThe investigation of the interplay of experimental crystal growth runs and computer simulations of the physical vapor transport (PVT) growth process of silicon carbide (SiC) strongly supports the development of the growth technology toward larger crystalline diameters. To apply computer‐aided designs of the growth process, a material database is developed that enables quantitative calculations of the temperature distribution inside the growth setup. The model utilizing COMSOL Multiphysics is validated by experimental means using five 100 mm SiC crystal growth runs, two measurement runs in a 100 mm PVT setup, and one SiC crystal growth run in a 75 mm PVT setup, varying in power, pressure, coil position, and reactor geometry. Material data are varied and the impact on the thermal gradients is investigated to trace out critical and noncritical parameters for the accuracy of the simulation. The influence of ambient pressure on the isolation's performance is studied experimentally and this correlation is implemented into the model. Beyond the state of the art, this work presents a modeling approach and handling of material properties for a true scale up of the current 100 mm and 150 mm SiC sublimation growth technologies to 200 mm.

Study of the Growth Temperature Measurement and Control for Silicon Carbide Crystal

The heating temperature of the silicon carbide sublimation growth crucible is changed by adjusting the output power of the medium frequency induction coil, and the sintering experiments were carried out using NaCl and Al2O3 to observe the morphological changes after sintered under different output power, the corresponding temperature was determined, and the corresponding relationship between the output power and the heating temperature was obtained, the precise temperature control was realized. The results of temperature measurement were compared with that of the infrared photoelectric pyrometer. Based on this, the SiC grains were prepared according to the temperature measurement results. The Raman spectroscopy result shows that the SiC polytype was 6H, the SiC grains distributions are homogeneous, and the size of the SiC grains is uniform and dense.

Macroscopic Approach to the Nucleation and Propagation of Foreign Polytype Inclusions during Seeded Sublimation Growth of Silicon Carbide

The nucleation and propagation of foreign polytypes during seeded sublimation growth of silicon carbide is addressed on a macroscopic footing, using a coupled experimental and numerical simulation approach. Experiments are conducted in a contactless growth geometry for different seed substrates with varying polarity, miscut angle, polytype, and crystal shape (concave and convex). The interface shape evolution is tracked by periodic nitrogen marking, which also allows the measurement of lateral and normal growth rates at any time during growth. Classical 2D nucleation theory is included in modeling the full process, and this is compared to experiments. We demonstrate that the occurrence of a foreign polytype is linked to the combined effects of (i) the presence of the natural {0001} facets and (ii) the minimization of 2D nucleation energy. Areas with a high probability of foreign polytype nucleation can thus be predicted. Once formed, the progress or disappearance of foreign inclusions is directly related ...

Interaction between Vapor Species and Graphite Crucible during the Growth of SiC by PVT

Graphite crucible in seeded sublimation growth of Silicon Carbide (SiC) single crystal does not only act as a container but also as an additional carbon source. The modeling of the growth process integrated with the etching phenomenon caused by the interaction between vapor species and the graphite crucible is shown to be able to predict the shape of the crystal front during the growth. The additional fluxes produced at the graphite part are delivered to the growing crystal mainly at the crystal periphery. The results obtained from the modeling are in good agreement with the experimental ones.

Similarities and differences in sublimation growth of SiC and AlN

The similarities and differences in development of crystal growth of bulk silicon carbide (SiC) and aluminum nitride (AlN) are discussed. It is concluded that AlN is going to become the second crystal grown in production scale using PVT technique. The growth technology of AlN may take advantage of learning from SiC technology as the latter is based on significant advances achieved in the course of last 20 years. The main differences between two materials are in incongruent evaporation of SiC and in poor compatibility of AlN with regular high-temperature crucible materials.

Increase of SiC sublimation growth rate by optimizing of powder packaging

In this paper, a comprehensive model for silicon carbide (SiC) sublimation crystal growth considering powder packaging is presented. This model is based on heat and mass transfer of porous powder charge with different sizes of the particle and accounts for induction heating, powder charge sublimation, vapor transport, and porosity evolution in a SiC sublimation crystal growth system. The mechanism of vapor transport is proposed by introducing a driving force arising from temperature difference between powder charge and seed in the growth system. Powder porosity evolution and sublimation rate variations are predicted based on vapor transport mechanism. Effects of powder geometry, such as particle sizes, volume and size ratios of different particles, and driving forces on the sublimation rate are studied. In addition, simulation results for powder sublimation with and without a central hole are presented. The results indicate that the sublimation rate can be increased by optimizing the powder packaging, or by creating a hole in the center of packed powder.

Numerical simulation of temperature fields during the sublimation growth of SiC single crystals, using WIAS-HiTNIHS

We present numerical computations of the temperature fields in axisymmetric growth apparatus for sublimation growth of silicon carbide (SiC) bulk single crystals by physical vapor transport (PVT) (modified Lely method). The results are computed using our software WIAS-HiTNIHS, the WIAS High Temperature Numerical Induction Heating Simulator; pronunciation: ∼ hit-nice , by solving the energy balance in the entire growth apparatus, taking into account the heat conduction in the solid parts as well as in gas cavities, and also accounting for the radiative heat transfer between the surfaces of the gas cavities. The insulation in a PVT growth apparatus usually consists of graphite felt, where the fibers are aligned in one particular direction, resulting in an anisotropic thermal conductivity. We show that neglecting this anisotropy can overestimate the SiC crystal's temperature by 70 K or underestimate the required heating power by 800 W.

Effect of heat transfer on macroscopic and microscopic crystal quality in silicon carbide sublimation growth

Numerical simulation was applied to observe the phenomena inside a crucible in silicon carbide (SiC) sublimation growth. Numerical simulation results show that crystal quality as well as crystal shape strongly depends on the temperature distribution inside the crucible. Numerical simulation also suggested that it is important to reduce the residual stress in the crystal in order to avoid the generation of dislocations. From these results, SiC sublimation growth was controlled actively, and large and high quality SiC single crystal was grown.

Transient numerical study of temperature gradients during sublimation growth of SiC: Dependence on apparatus design

Using transient and stationary mathematical heat transfer models including heat conduction, radiation, and radio frequency (RF) induction heating, we numerically investigate the time evolution of temperature gradients in axisymmetric growth apparatus during the sublimation growth of silicon carbide (SiC) bulk single crystals by physical vapor transport (PVT) (modified Lely method). Temperature gradients in the bulk and on the surface of the growing crystal can cause defects. Here, the evolution of these gradients is studied numerically during the heating, growth, and cooling stages, varying the apparatus design, namely the amount of the source powder charge as well as the size of the upper blind hole used for cooling of the seed. Our results show that a smaller upper blind hole can reduce the temperature gradients both in the bulk and on the surface of the crystal without reducing the surface temperature itself.

Influence of Anisotropic Thermal Conductivity in the Apparatus Insulation for Sublimation Growth of SiC: Numerical Investigation of Heat Transfer

Using a mathematical heat transfer model including anisotropic heat conduction, radiation, and radio frequency (RF) heating, we perform numerical computations of the temperature field in an axisymmetric growth apparatus during sublimation growth of silicon carbide (SiC) bulk single crystals by physical vapor transport (PVT) (modified Lely method). Because it is not unusual for the thermal insulation of a PVT growth apparatus to possess an anisotropic thermal conductivity, we numerically study the influence that this anisotropic thermal conductivity has on the temperature field in the growth chamber. Moreover, we also study the influence of the thickness of the insulation. Our results show that, depending on the insulation's orientation, even a moderate anisotropy in the insulation can result in temperature variations of more than 100 K at the growing crystal's surface, which should be taken into account for the simulation as well as for the design of a PVT growth apparatus.

Control of the Supersaturation in the CF−PVT Process for the Growth of Silicon Carbide Crystals: Research and Applications

In the classical sublimation growth of silicon carbide (SiC) single crystals, the supersaturation in the surrounding of the seed is mainly controlled by pressure and temperature distributions within the growth cavity. Precise control of the supersaturation is difficult, especially if it needs to be adjusted during the process. In the first part of the paper, an experimental study performed in a continuous feed−physical vapor transport reactor (CF−PVT) is shown. This process combines CVD for the feeding of the SiC source and PVT for the growth of the single crystal. It is shown that the feeding gas flow rate (TMS diluted in argon) and/or the temperature allow precise control of the supersaturation close to the seed, much more easily than in the classical sublimation process. In the second part of the paper, the application of the supersaturation control to SiC polytype engineering is demonstrated.

Modeling and simulation of sublimation growth of SiC bulk single crystals

We present a transient mathematical model for the sublimation growth of silicon carbide (SiC) single crystals by the physical vapor transport (PVT) method. The model of the gas phase consists of balance equations for mass, momentum, and energy, as well as reaction-diffusion equations. Due to physical and chemical reactions, the gas phase is encompassed by free boundaries. Nonlinear heat transport equations are considered in the various solid components of the growth system. Discontinuous and nonlocal interface conditions are formulated to account for temperature steps between gas and solid as well as for diffuse-gray radiative heat transfer between cavity surfaces. An axisymmetric induction heating model is devised using a magnetic scalar potential. For a nonlinear evolution problem arising from the model, a finite volume scheme is stated, followed by a discrete existence and uniqueness result. We conclude by presenting and analyzing results of transient numerical experiments relevant to the physical growth process.

Evolution of thermoelastic strain and dislocation density during sublimation growth of silicon carbide

Abstract The evolution of crystallization front and growth conditions during sublimation growth of SiC bulk crystal is studied using a coupled heat and mass transport two-dimensional model. It is shown, in particular, that movement of the inductor coil used for heating of the growth crucible modifies the temperature profile at the growth surface but can have no remarkable effect on the growth rate. Anisotropic elasticity theory and a semi-empirical model of dislocation generation are applied for a detailed analysis of thermoelastic strain and dislocation density evolution during SiC bulk crystal growth. An important effect of a method of SiC seed attachment to the holder is revealed by modeling. It is shown that under optimal attachment, the maximum dislocation density is concentrated near the crystallization front at the periphery of the crystal. The region of high dislocation density expands with enlargement of the crystal.

The analysis of mass transfer in system β-SiC–α-SiC under silicon carbide sublimation growth

The aim of the present paper is to discuss our results of the investigation (both theoretical and experimental) of mass transfer in the β-SiC–α-SiC system in conditions of about zero temperature gradient. Growth temperature was in the range 1800–2300°C. Modeling of growth of silicon carbide crystals have been carried out both for vacuum (10 −3 Pa) and for a gas (nitrogen, argon or their mixture) atmosphere. The gas pressure was in the range 10 2–10 5 Pa. Growth rate in the range from 0.01 to 1.5 mm/h for growth in vacuum and 0.001–0.15 mm/h for growth in gas have been calculated. Experimental results obtained are in a good agreement with theoretically predicted ones.

Thermodynamic Considerations of the Role of Hydrogen in Sublimation Growth of Silicon Carbide

The purpose of this study was to investigate the thermodynamic consequences of added hydrogen to the sublimation growth process of silicon carbide crystals. The results show that at each temperature there exists a level of hydrogen that leads to a silicon‐to‐carbon ratio of unity. At typical growth temperatures the added hydrogen does not significantly affect the supersaturation ratio.