The assignee for this patent, patent number 8647433, is
Reporters obtained the following quote from the background information supplied by the inventors: "Systems and methods herein relate generally to monocrystalline germanium ingots/wafers and in particular to growth of such ingots/wafers with reduced micro-pit density (MPD).
"Electronic and opto-electronic device manufacturers routinely require commercially grown, large and uniform single semiconductor crystals which, when sliced and polished, provide substrates for microelectronic device production. The growth of a semiconductor crystal involves heating raw material to its melting point to create a crystalline raw material melt, bringing the melt into contact with a high quality seed crystal, and allowing the crystallization of the melt when in contact with the seed crystal. A number of different processes for accomplishing this are known. These include the Czochralski (Cz) process and its variant the Liquid Encapsulated Czochralski (LEC) process, the Horizontal Bridgman and Bridgman-Stockbarger processes (HB) and their vertical variants (VB), and the gradient freeze (GF) and its variant, the vertical gradient freeze (VGF) processes. See for example 'Bulk Crystal Growth of Electronic, Optical and Optoelectronic Materials'
"The crystallization of the melt forms an essentially cylindrical crystal (an ingot) along a vertical axis with the seed crystal below the crystalline raw material(s). The equipment necessary to form the semiconductor crystal includes a crystal growth furnace, an ampoule, a crucible, and sometimes a crucible support. The crucible may also have a lower, narrow portion, called a seed well.
"Drawbacks exist with the conventional crystal growth process and crystal growth equipment. For example, known crystal growth processes often create crystals that have excessive micro-pits or micro-cavities which result in imperfections, flawed devices and/or otherwise reduce the overall useful quantity of the crystal grown using such processes. Such issues and reduction in useful grown crystal quantity result in a lower yield. Accordingly, there is a need for a crystal growth systems and methods that reproducibly provide high quality ingots/wafers and otherwise overcome such drawbacks in existing systems."
In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "Systems and methods consistent with the invention are directed to growth of moncrystalline germanium.
"In one exemplary implementation, there is provided a method of inserting an ampoule with raw material into a furnace having a heating source, growing a crystal using, e.g., a vertical growth process wherein movement of a crystallizing temperature gradient relative to the raw material/crucible is achieved to melt the raw material and reform it in monocrystalline form, and growing, at a predetermined crystal growth length, the crystal using a vertical growth process to melt the material and reform it as a monocrystalline compound, wherein monocrystalline ingots having reduced micro-pit densities are reproducibly provided.
"It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as described. Further features and/or variations may be provided in addition to those set forth herein. For example, the present invention may be directed to various combinations and subcombinations of the disclosed features and/or combinations and subcombinations of several further features disclosed below in the detailed description."
For more information, see this patent: Liu, Weiguo; Li, Xiao. Germanium Ingots/Wafers Having Low Micro-Pit Density (MPD) as Well as Systems and Methods for Manufacturing Same. U.S. Patent Number 8647433, filed
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