Silicon-carbide-base compound substrate and manufacturing method thereof

Abstract

The invention provides a silicon-carbide-base compound substrate and a manufacturing method thereof. The silicon-carbide-base compound substrate comprises a silicon-carbide-base monocrystal substrate, a compound stress covariant layer which is covered on the silicon-carbide-base monocrystal substrate and formed by alternatively stacking a titanium nitride monocrystal thin film material and a multi-layer aluminum nitride monocrystal thin film material, and a gallium nitride template layer which grows on the compound stress covariant layer and consists of a gallium nitride monocrystal thin filmmaterial. The invention also provides a method for manufacturing the silicon-carbide-base compound substrate. By the invention, the crystal lattice mismatch of the silicon-carbide-base gallium nitride material is relieved, and the heat dismatch of the silicon-carbide-base gallium nitride material is solved; therefore, the performance and the qualification rate of the gallium nitride light emitting diode (LED) epitaxial sheet prepared on the silicon-carbide-base compound substrate are enhanced greatly; and the silicon-carbide-base compound substrate is suitable for application and market popularization.

Description

technical field [0001] The invention relates to a substrate for epitaxial growth of semiconductor materials, and more particularly, to a silicon carbide-based composite substrate for preparing nitride semiconductor epitaxial materials. Background technique [0002] Nitride semiconductors, especially gallium nitride (GaN), are the core materials for preparing light-emitting diode (LED) devices used in semiconductor lighting and display backlighting. Due to the lack of homogeneous single crystal materials, device applications of GaN materials are usually carried out on heterogeneous substrates, more commonly used are sapphire (a-Al 2 o 3 ), silicon carbide (6H-SiC), silicon (Si), etc. With the advancement of SiC single crystal material preparation technology at home and abroad in recent years, the price of SiC single crystal substrates has gradually decreased, which has created conditions for reducing the production cost of GaN LED epitaxial wafer materials prepared on SiC s...

AI Technical Summary

Problems solved by technology

However, SiC substrates and GaN materials have large differences in lattice constants and thermal expansion coefficients, which will encounter two problems: (1) lattice mismatch: due to the lattice constant of GaN (a=0.3189nm, c=0.5185nm) and the lattice constant of 6H-SiC (a=0.3073nm, c=1.0053nm) are different, and the lattice mismatch of 3.77% will cause a very large lattice loss in the early stage of epitaxial growth of the GaN epitaxial layer. When the thickness of the grown GaN epitaxial layer exceeds a certain critical thickness (several nm to hundreds of nm thick, depending on the introduced intermediate layer), the large lattice distortion accumulated in the GaN epitaxial layer The matching stress will be released in the form of dislocations and defects at the interface, which will cause the deterioration of the crystallization quality of the GaN epitaxial layer and reduce the performance of the subsequent LED device structure; (2) thermal mismatch problem: due to the thermal expansion coefficient of GaN ( a: 5.59×10 -6 K) and thermal expansion coefficient of 6H-SiC (a: 3.54×10 -6 K) also has a large difference, which causes the GaN epitaxial layer or LED device structure to accumulate very large thermal stress during the process of dropping the GaN epitaxial layer or LED device structure from a very high growth temperature (such as 800-1100 ° C) to room temperature. For the epitaxial layer, it is a kind of tensile stress, which is easy to cause cracks or bending of the GaN epitaxial layer material

Existing stress covariant layers, such as low-temperature GaN buffer layers, AlN buffer layers, AlGaN composition graded buffer layers, thin InAlGaN flexible layers, etc., have good effects in transferring and coordinating the release of lattice mismatch stress, but in Limited role in transferring and coordinating release of thermal mismatch stress

However, the patterned substrate method requires masks and photolithographic patterns (nano- or micron-scale patterns) on the SiC substrate or GaN epitaxial layer. Because the dislocation density at the window is difficult to reduce, multiple masks and photolithographic patterns are required. It is complex and further increases the cost of material preparation, and it is also difficult to obtain large-scale GaN epitaxial layer materials with uniform crystal quality, such as GaN epitaxial layer materials with a diameter of more than 2 inches

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