Northrop Grumman Systems Corporation

Ii-vi Incorporated

Westinghouse Electric Corporation

Donovan L Barrett

Richard H Hopkins

Ilya Zwieback

Avinash K Gupta

Hudson McDonald Hobgood

Raymond G Seidensticker, Deceased

James P McHugh

Edward Semenas

Richard N Thomas

Andrew E Souzis

Thomas E Anderson

Rowland C Clarke

Gary E Ruland

Ping Wu

Godfrey Augustine

Charles D Brandt

Albert A Burk, Jr

Graeme W Eldridge

Elizabeth Ann Halgas

In a method of forming polycrystalline SiC grain material, low-density, gas-permeable and vapor-permeable bulk carbon is positioned at a first location inside of a graphite crucible and a mixture of elemental silicon and elemental carbon is positioned at a second location inside of the graphite crucible. Thereafter, the mixture and the bulk carbon are heated to a first temperature below the melting point of the elemental Si to remove adsorbed gas, moisture and/or volatiles from the mixture and the bulk carbon. Next, the mixture and the bulk carbon are heated to a second temperature that causes the elemental Si and the elemental C to react forming as-synthesized SiC inside of the crucible. The as-synthesized SiC and the bulk carbon are then heated in a way to cause the as-synthesized SiC to sublime and produce vapors that migrate into, condense on and react with the bulk carbon forming polycrystalline SiC material.

Method for synthesizing ultrahigh-purity silicon carbide

In method of crystal growth, an interior of a crystal growth chamber () is heated to a first temperature in the presence of a first vacuum pressure whereupon at least one gas absorbed in a material () disposed inside the chamber is degassed therefrom. The interior of the chamber is then exposed to an inert gas at a second, higher temperature in the presence of a second vacuum pressure that is at a higher pressure than the first vacuum pressure. The inert gas pressure in the chamber is then reduced to a third vacuum pressure that is between the first and second vacuum pressures and the temperature inside the chamber is lowered to a third temperature that is between the first and second temperatures, whereupon source material () inside the chamber vaporizes and deposits on a seed crystal () inside the chamber.

Intra-cavity gettering of nitrogen in SiC crystal growth

A physical vapor transport system includes a growth chamber charged with source material and a seed crystal in spaced relation, and at least one capsule having at least one capillary extending between an interior thereof and an exterior thereof, wherein the interior of the capsule is charged with a dopant. Each capsule is installed in the growth chamber. Through a growth reaction carried out in the growth chamber following installation of each capsule therein, a crystal is formed on the seed crystal using the source material, wherein the formed crystal is doped with the dopant.

System for forming SiC crystals having spatially uniform doping impurities

In a physical vapor transport method and system, a growth chamber charged with source material and a seed crystal in spaced relation is provided. At least one capsule having at least one capillary extending between an interior thereof and an exterior thereof, wherein the interior of the capsule is charged with a dopant, is also provided. Each capsule is installed in the growth chamber. Through a growth reaction carried out in the growth chamber following installation of each capsule therein, a crystal is formed on the seed crystal using the source material, wherein the formed crystal is doped with the dopant.

Method of and system for forming SiC crystals having spatially uniform doping impurities

An apparatus for growing single-polytype, single crystals of silicon carbide utilizing physical vapor transport as the crystal growth technique. The apparatus has a furnace which has a carbon crucible with walls that border and define a crucible cavity. A silicon carbide source material provided at a first location of the crucible cavity, and a monocrystalline silicon carbide seed is provided at a second location of the crucible cavity. A heat path is also provided in the furnace above the crucible cavity. The crucible has a stepped surface that extends into the crucible cavity. The stepped surface has a mounting portion upon which the seed crystal is mounted. The mounting portion of the stepped surface is bordered at one side by the crucible cavity and is bordered at an opposite side by the furnace heat path. The stepped surface also has a sidewall that is bordered at one side by and surrounds the furnace heat path. The apparatus may also have a thermal insulating member, in which a side of the stepped surface sidewall opposite to the furnace heat path is bordered by the thermal insulating member.

Method for growing large silicon carbide single crystals

A nitrogen doped single crystal silicon carbide boule is grown by the physical vapor transport process by introducing nitrogen gas into the growth furnace. During the growth process the pressure within the furnace is maintained at a constant value, P.sub.o, where P.sub.o .ltoreq.100 Torr. This is accomplished by measuring the pressure within the furnace and providing the pressure measurement to a process controller which regulates the nitrogen introduction as nitrogen gas is incorporated into the crystal structure. The partial pressure of the nitrogen may be selected to be at a value between 1 and P.sub.o. If the desired partial pressure is less than P.sub.o, an inert gas is added to make up the difference.

Method of making a low resistivity silicon carbide boule

Silicon carbide wafers are prepared for semiconductor epitaxial growth by first lapping a silicon carbide wafer derived from a boule, by placing the wafer in a recess of a metal backed template and moving the wafer over and against a rotating plate. Two different diamond slurry mixtures of progressively smaller diamond grit sizes are sequentially used, along with a lubricant, for a predetermined period of time. The lapping operation is followed by a polishing operation which sequentially utilizes two different diamond slurry mixtures of progressively smaller diamond grit sizes, along with three different apertured pads sequentially applied to a rotatable plate, with the pads being of progressively softer composition. In a preferred embodiment the wafers are cleaned and the templates are changed after each new diamond slurry mixture used.

Method of preparing silicon carbide wafers for epitaxial growth

A silicon carbide feedstock charge for growing silicon carbide boules in a physical vapor transport system. The feedstock charge includes silicon carbide particles, as well as any dopant material, if required, in a structure which is rigid and self supportable. An elongated feedstock charge may be moved toward the seed crystal as the feedstock is depleted during boule growth. The feedstock charge may be tailored to provide a non-uniform flux for growing more planar boule faces.

Feedstock arrangement for silicon carbide boule growth

A method for producing crystals of silicon carbide in a furnace. The furnace has a crucible with a cavity in which the cavity has first and second spaced-apart regions. The crucible cavity of the furnace is capable of being heated, preferably by induction or resistance heating, with insulation placed around the crucible and crucible cavity. A source material of silicon carbide is provided at the first region of the crucible cavity, and a monocrystalline seed is placed at the second region of the crucible cavity. A first growth stage is then conducted in which the first region and the second region of the crucible cavity are heated to at least the sublimation temperature of silicon carbide under substantially isothermal conditions. Then, a second growth stage is conducted in which a temperature gradient is provided between the first and the second region of the crucible cavity, such that the seed in the second crucible region is kept at a temperature lower than a temperature of the first crucible region.

Method of producing large diameter silicon carbide crystals

Apparatus for growing large silicon carbide single crystals

A substrate for use in semiconductor devices, fabricated of silicon carbide and having a resistivity of greater than 1500 Ohm-cm. The substrate being characterized as having deep level impurities incorporated therein, wherein the deep level elemental impurity comprises one of a selected heavy metal, hydrogen, chlorine and fluorine. The selected heavy metal being a metal found in periodic groups IIIB, IVB, VB, VIB, VIIB, VIIIB, IB and IIB.

High resistivity silicon carbide substrates for high power microwave

A method for epitaxially growing a-axis .alpha.-SiC on an a-axis substrate is provided. A section is formed from the SiC crystal by making a pair of parallel cuts in the crystal. Each of these cuts is parallel to the c-axis of the crystal. The resulting section formed from the crystal has opposing a-face surfaces parallel to the c-axis of the crystal. A gas mixture having hydrocarbon and silane is passed over one of the a-face surfaces of the section. The hydrocarbon and silane react on this a-face surface to form an epitaxial layer of SiC. Preferably, the SiC is grown at a temperature of approximately 1450.degree. C.

Method for epitaxially growing .alpha.-silicon carbide on a-axis

A method of fabrication of low dislocation single crystal indium-doped gallium arsenide, and improved crystal structure. The method is an improved liquid encapsulant Czochralski process with an indium doping level of 5.times.10.sup.19 to 3.times.10.sup.20 indium atoms per cubic centimeter incorporated into the large diameter, long single crystal. The initial melt of elemental indium, gallium, and arsenic contain about 1 atom percent of indium, and inclusion of the indium permits high yield growth of crystals with desired near stoichiometric or slightly arsenic rich composition which exhibit the desired electrical characteristics.

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Port Orange, FL, United States of America

Donovan L Barrett