For the crystals of the non-riche, it has an anisotropy-different direction to have different properties.
The space group of 4H-SiC and 6H-SiC is p63mc, and the population is 6mm, which belongs to the hexalectine, with anisotropy.
The spatial group of the 3C-SiC is F-43M, the point group is -43m, belongs to the cube, does not have an anisotropy.
The space group of 15R-SiC is R3M, and the point group is 3m, which belongs to the triple crystal system, with anisotropy.
Further, 6mm, 3m belongs to one of 10 polar points (1, 2, 3, 4, 6; m, 3M; mm2, 4 mm, 6 mm), so 4H-SiC, 6H-SiC, 15R-Sic It is a polar crystal. The polar crystal refers to the performance of at least one direction in a crystal having different performance in opposite directions, which may be electrical properties (thermoelectric properties, ferroelectric properties), growth performance, and the like. That is, the positive and negative of the same direction will have a performance difference. For anisotropic representation, it is directly reflected in different properties of different crystalline masks. In crystals, different crystals are expressed by the difference in crystal plane index. The crystal plane index is also called the Miller index, which is (HKL). The specific representation is: the coordinate system of the crystal is established. The interval of this crystal plane and the coordinate axis will be A, B, C, followed by the recruid distance 1 / a, 1 / b, 1 / c, and the simplest Simple integer ratio is (HKL). For three-party and hexagonal crystal, (HKL) = (HKIL), I = -H-k. However, according to the symmetry of the crystal, a series of crystal faces is the same. For example, (100) and (200) are only invisible to the simplest integer ratio. There are many applications for anisotropy. The growth properties of seed crystals in different directions have a great difference. The wafer deflected at a certain angle (step stream) is more susceptible to the growth of silicon carbide as a baseline based on the crystal surface (0001). There will be great differences in electrical properties. For example, SiC MOSFET is prepared using crystal faces (0-33-8), because due to its lower interface density and higher free electron ratio, the surface is highest in all doped concentrations at all doped concentrations. .
As shown, when the doping concentration of 10 ^ 18 / cm3 is employed, the high channel mobility of 60 cm2V-1S-1 can be achieved, and the threshold voltage of up to 4V - the voltage is sufficient to suppress the misoperation of the high temperature. The ratio (0001) is high.
Using this nature, Japanese Sumitomo Electrical Industry Co., Ltd. has developed a new structure for SiC MOSFET. It has a V-tank, using (0-33-8) crystal surface, thereby having a higher mobility performance.
The 4H-SiC (0-33-8) crystal plane and (0001) were surfaced into a 54.7 degree of an index.
The cell parameters of the tripartite and the hexagonal graft are A, C. The calculation method of the crystal face (H1K1L1) (H2K2L2) is as follows:
The key to producing the device is to use the chemical etching process to form a V-shaped groove. The use of silica as an etching mask and etched in a chlorine environment of about 900 ° C.
The surface of the non-etched surface is oxidized to silica;
Chlorine gas is chemically reacted with surface silicon carbide so that it is converted to carbon, then reacts with oxygen to form carbon dioxide;
The resulting silicon chloride and carbon dioxide were volatilized at high temperatures and exposed (0-33-8) crystal surface.
Note that ion etching cannot be used, although ion etching is a conventional method of forming a U-shaped trench, but will result in etch injury and subgitting.
By scanning an image of the electron microscope, it can be seen that the chemical etching has obtained high quality crystal plane.
Original title: Material | Different silicon carbide thickness brings new possibilities!
Article Source: [WeChat public number: Want Material Chip] Welcome to add attention! Please indicate the source of the article.
Editor: HAQ, read full article, original title: Material | Different silicon carbolic silicon wafers bring new possibilities!
Article Source: [Micro Signal: WC_YSJ, WeChat Public Number: Want Material Chip] Welcome to add attention! Please indicate the source of the article.
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