A method for forming a power semiconductor device is provided. The method includes: providing a semiconductor wafer grown by a Czochralski process and having a first side; forming an n-type substrate doping layer in the semiconductor wafer at the first side, the substrate doping layer having a doping concentration of at least 10.sup.17/cm.sup.3; and forming an epitaxy layer on the first side of the semiconductor wafer after forming the n-type substrate doping layer.

A semiconductor wafer forms on a mold containing a dopant. The dopant dopes a melt region adjacent the mold. There, dopant concentration is higher than in the melt bulk. A wafer starts solidifying. Dopant diffuses poorly in solid semiconductor. After a wafer starts solidifying, dopant can not enter the melt. Afterwards, the concentration of dopant in the melt adjacent the wafer surface is less than what was present where the wafer began to form. New wafer regions grow from a melt region whose dopant concentration lessens over time. This establishes a dopant gradient in the wafer, with higher concentration adjacent the mold. The gradient can be tailored. A gradient gives rise to a field that can function as a drift or back surface field. Solar collectors can have open grid conductors and better optical reflectors on the back surface, made possible by the intrinsic back surface field.

A semiconductor wafer forms on a mold containing a dopant. The dopant dopes a melt region adjacent the mold. There, dopant concentration is higher than in the melt bulk. A wafer starts solidifying. Dopant diffuses poorly in solid semiconductor. After a wafer starts solidifying, dopant cannot enter the melt. Afterwards, the concentration of dopant in the melt adjacent the wafer surface is less than what was present where the wafer began to form. New wafer regions grow from a melt region whose dopant concentration lessens over time. This establishes a dopant gradient in the wafer, with higher concentration adjacent the mold. The gradient can be tailored. A gradient gives rise to a field that can function as a drift or back surface field. Solar collectors can have open grid conductors and better optical reflectors on the back surface, made possible by the intrinsic back surface field.

A semiconductor wafer forms on a mold containing a dopant. The dopant dopes a melt region adjacent the mold. There, dopant concentration is higher than in the melt bulk. A wafer starts solidifying. Dopant diffuses poorly in solid semiconductor. After a wafer starts solidifying, dopant cannot enter the melt. Afterwards, the concentration of dopant in the melt adjacent the wafer surface is less than what was present where the wafer began to form. New wafer regions grow from a melt region whose dopant concentration lessens over time. This establishes a dopant gradient in the wafer, with higher concentration adjacent the mold. The gradient can be tailored. A gradient gives rise to a field that can function as a drift or back surface field. Solar collectors can have open grid conductors and better optical reflectors on the back surface, made possible by the intrinsic back surface field.

[Object] An object of the present invention is to provide a method for manufacturing an oxide single crystal substrate having less dispersion in characteristics within the substrate surface. [Means to solve the Problems] In the manufacture method of the present invention, a powder containing a Li compound is dispersed in a medium to form a slurry, and heat is applied while the slurry is in contact with the surface of the oxide single crystal substrate, so as to diffuse Li into the substrate from the surface thereof to effect a modification of the substrate; or after the slurry is brought into contact with the surface of the oxide single crystal substrate, the oxide single crystal substrate is buried in a powder containing the Li compound, and heat is applied to effect the diffusion of Li in the substrate from the surface thereof whereby a modification of the substrate occurs.

[Object] An object of the present invention is to provide a method for manufacturing an oxide single crystal substrate having less dispersion in characteristics within the substrate surface. [Means to solve the Problems] In the manufacture method of the present invention, a powder containing a Li compound is dispersed in a medium to form a slurry, and heat is applied while the slurry is in contact with the surface of the oxide single crystal substrate, so as to diffuse Li into the substrate from the surface thereof to effect a modification of the substrate; or after the slurry is brought into contact with the surface of the oxide single crystal substrate, the oxide single crystal substrate is buried in a powder containing the Li compound, and heat is applied to effect the diffusion of Li in the substrate from the surface thereof whereby a modification of the substrate occurs.

A silicon epitaxial wafer including: a second intermediate epitaxial layer on a silicon substrate produced by being cut from a silicon single crystal ingot grown by the CZ method so as to have a carbon concentration ranging from 310.sup.16 to 210.sup.17 atoms/cm.sup.3, a first intermediate epitaxial layer doped with a dopant, and an epitaxial layer of a device forming region stacked on the first intermediate epitaxial layer, and to a method of producing this wafer. Also providing an industrially excellent silicon epitaxial wafer that is produced with a silicon substrate doped with carbon and used as a semiconductor device substrate such as a memory, a logic, or a solid-state image sensor, and a method of producing this silicon epitaxial wafer.

A silicon epitaxial wafer including: a second intermediate epitaxial layer on a silicon substrate produced by being cut from a silicon single crystal ingot grown by the CZ method so as to have a carbon concentration ranging from 310.sup.16 to 210.sup.17 atoms/cm.sup.3, a first intermediate epitaxial layer doped with a dopant, and an epitaxial layer of a device forming region stacked on the first intermediate epitaxial layer, and to a method of producing this wafer. Also providing an industrially excellent silicon epitaxial wafer that is produced with a silicon substrate doped with carbon and used as a semiconductor device substrate such as a memory, a logic, or a solid-state image sensor, and a method of producing this silicon epitaxial wafer.

The present disclosure generally relates to methods of preparing spherical salt particles for industrial, medical, and other uses. The methods can include combining the angular salt particles with a quantity of finishing media, for example, into a receptacle. Thereafter, the angular salt particles and the finishing media can be moved or agitated until the angular salt particles have a desired sphericity.

The present disclosure generally relates to methods of preparing spherical salt particles for industrial, medical, and other uses. The methods can include combining the angular salt particles with a quantity of finishing media, for example, into a receptacle. Thereafter, the angular salt particles and the finishing media can be moved or agitated until the angular salt particles have a desired sphericity.