SiCrystal AG

Erlangen, Germany

SiCrystal AG

Erlangen, Germany

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Grant
Agency: European Commission | Branch: FP7 | Program: CP | Phase: SPA.2009.2.2.01 | Award Amount: 3.28M | Year: 2010

The project High Quality European GaN-Wafer on SiC Substrates for Space Applications (EuSiC) is aiming at establishing an independent, purely European sustainable supply chain for Gallium Nitride (GaN) based space technologies. The project will significantly reduce the dependence on critical technologies and capabilities from outside Europe for future space applications. An independent supply chain has to include countries of the European Community (EC): a supplier of high-quality semi-insulating Silicon Carbide (SiC) substrates, qualified sources to perform GaN epitaxial layers and as well manufacturers with leading knowledge in GaN device technology required e.g. for Monolithic Microwave Integrated Circuits (MMICs). At present, the missing link in this chain is a reliable source for high-quality 3 inch semi-insulating SiC substrates in Europe. The intention of this project is to improve the quality of semi-insulating SiC-substrates at SiCrystal AG, the leading manufacturer of SiC substrates in Europe. The provided substrates shall be analyzed and evaluated by epi-growth specialists IAF, III-V-Lab, and QinetiQ. Finally devices shall be built and verified on the created GaN epi-wafers by UMS. Continuous monitoring and several feedback loops to the quality of the substrates will enable an accelerated development at SiCrystal AG. Also impacts to improvement of the performance of GaN devices are expected. The project will complement activities already undertaken by European Space Agency ESA, who has assembled a consortium of competent partners under the: GaN Reliability Enhancement and Technology Transfer Initiative (GREAT2).


The present invention relates to a configuration and in particular a physical vapor transport growth system for simultaneously growing more than one silicon carbide (SiC) bulk crystal. Furthermore, the invention relates to a method for producing such a bulk SiC crystal. A physical vapor transport growth system for simultaneously growing more than one SiC single crystal boule comprises a crucible containing two growth compartments for arranging at least one SiC seed crystal in each of them, and a source material compartment for containing a SiC source material, wherein said source material compartment is arranged symmetrically between said growth compartments and is separated from each of the growth compartments by a gas permeable porous membrane.


The present invention relates to a configuration and in particular a physical vapor transport growth system for simultaneously growing more than one silicon carbide (SiC) bulk crystal. Furthermore, the invention relates to a method for producing such a bulk SiC crystal. A physical vapor transport growth system for simultaneously growing more than one SiC single crystal boule comprises according to the present invention comprises a crucible (102) containing two growth compartments (114A, 114B) comprising each at least one SiC seed crystal (106A, 106B) and a source material compartment (112) for containing a SiC source material (104). The source material compartment (112) is arranged symmetrically between said growth compartments (114A, 114B) and is separated from each of the growth compartments by a gas permeable porous membrane (116A, 116B; 116A, 116B).


A method is used for producing an SiC volume monocrystal by sublimation growth. Before the beginning of growth, an SiC seed crystal is arranged in a crystal growth region of a growth crucible and powdery SiC source material is introduced into an SiC storage region of the growth crucible. During the growth, by sublimation of the powdery SiC source material and by transport of the sublimated gaseous components into the crystal growth region, an SiC growth gas phase is produced there. The SiC volume monocrystal having a central center longitudinal axis grows by deposition from the SiC growth gas phase on the SiC seed crystal. The SiC seed crystal is heated substantially without bending during a heating phase before the beginning of growth, so that an SiC crystal structure with a substantially homogeneous course of lattice planes is provided in the SiC seed crystal.


A method is used for producing an SiC volume monocrystal by sublimation growth. During growth, by sublimation of a powdery SiC source material and by transport of the sublimated gaseous components into the crystal growth region, an SiC growth gas phase is produced there. The SiC volume monocrystal grows by deposition from the SiC growth gas phase on the SiC seed crystal. The SiC seed crystal is bent during a heating phase before such that an SiC crystal structure with a non-homogeneous course of lattice planes is adjusted, the lattice planes at each point have an angle of inclination relative to the direction of the center longitudinal axis and peripheral angles of inclination at a radial edge of the SiC seed crystal differ in terms of amount by at least 0.05 and at most by 0.2 from a central angle of inclination at the site of the center longitudinal axis.


A silicon-carbide volume monocrystal is produced with a specific electrical resistance of at least 10^(5 )cm. An SiC growth gas phase is generated in a crystal growing area of a crucible. The SiC volume monocrystal grows by deposition from the SiC growth gas phase. The growth material is transported from a supply area inside the growth crucible to a growth boundary surface of the growing monocrystal. Vanadium is added to the crystal growing area as a doping agent. A temperature at the growth boundary surface is set to at least 2250 C. and the SiC volume monocrystal grows doped with a vanadium doping agent concentration of more than 510^(17 )cm^(3). The transport of material from the SiC supply area to the growth boundary surface is additionally influenced. The growing temperature at the growth boundary surface and the material transport to the growth boundary surface are influenced largely independently of one another.


A bulk AlN single crystal is grown on a monocrystalline AlN seed crystal having a central longitudinal mid-axis and disposed in a crystal growth region of a growing crucible. The bulk AlN single crystal grows in a growth direction oriented parallel to the longitudinal mid-axis by deposition on the AlN seed crystal. The crucible has a lateral crucible inner wall extending in the growth direction, a free space being provided between the AlN seed crystal and the growing bulk AlN single crystal on the one hand, and the lateral crucible inner wall on the other hand. Bulk AlN single crystals and monocrystalline AlN substrates produced therefrom are therefore obtained with only few dislocations, which furthermore are substantially distributed homogeneously. The growing crucible, inside which the crystal growth region is located, is an inner growing crucible which is arranged in an outer growing crucible. The two growing crucibles are provided with a crucible lid with a gap formed between the inner growing crucible and the crucible lid through which some of the AlN growth gas phase generated inside the crystal growth region escapes and is deposited on a crucible bottom of the outer growing crucible which lies opposite the crucible lid.


A configuration for producing a bulk SiC crystal includes a growing crucible having an electrically conductive crucible wall, an inductive heating device disposed outside the growing crucible for inductively coupling an electric current, which heats the growing crucible, into the crucible wall, and an insulation layer disposed between the crucible wall and the inductive heating device. The insulation layer is formed of a graphite insulation material having short carbon fibers with a fiber length in a range of between 1 mm and 10 mm and a fiber diameter in a range of between 0.1 mm and 1 mm. A method for producing a bulk SiC crystal is also provided.


A silicon carbide bulk single crystal is produced at a growth temperature of up to 2200 C. by sublimation growth and is subjected to thermal aftertreatment after the sublimation growth. The bulk single crystal is brought to an aftertreatment temperature that is higher than a growth temperature. Very low-stress and low-dislocation SiC substrates can be produced from such a SiC bulk single crystal, the substrates additionally having a particularly low electrical resistivity. The SiC bulk single crystal is positioned within an SiC powder before the thermal aftertreatment and it is completely surrounded by the SiC powder during the thermal aftertreatment.


Patent
SiCrystal AG | Date: 2012-07-31

A bulk AlN single crystal is grown on a monocrystalline AlN seed crystal having a central longitudinal mid-axis and disposed in a crystal growth region of a growing crucible. The bulk AlN single crystal grows parallel to the longitudinal mid-axis by deposition on the AlN seed crystal. The crucible has a lateral crucible inner wall extending in the growth direction. A free space is formed between the AlN crystals and the lateral crucible inner wall. Bulk AlN single crystals and monocrystalline AlN substrates produced therefrom are obtained with only few dislocations, which are substantially distributed homogeneously. Growing crucibles are provided with a crucible lid with a gap formed between an inner growing crucible and the crucible lid through which some of the AlN growth gas phase generated inside the crystal growth region escapes and is deposited on a bottom of an outer growing crucible opposite the lid.

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