Crystal Systems Corporation

Gtat Corporation

Gt Crystal Systems, LLC

Gt Solar Incorporated

Ghemini Technologies

Chandra P Khattak

Frederick Schmid

Maynard B Smith

David B Joyce

Carl Chartier

Santhana Raghavan Parthasarathy

Yuepeng Wan

Dean C Skelton

Adrian Servini

Bernard D Jones

Bhuvaragasamy G Ravi

Dave Lackey

Vernon E White

Parthasarathy S Raghavan

Vladimir Gorbulev

John H Wohlgemuth

A method and process for the production of bulk polysilicon by chemical vapor deposition (CVD) where conventional silicon 'slim rods' commonly used in Siemens-type reactors are replaced with shaped silicon filaments of similar electrical properties but larger surface areas, such as silicon tubes, ribbons, and other shaped cross sections. Silicon containing gases, such as chlorosilane or silane, are decomposed and form a silicon deposit on the hot surfaces of the filaments The larger starting surface areas of these filaments ensures a higher production rate without changing the reactor size, and without increasing the number and length of the filaments. Existing reactors need only the adaptation or replacement of filament supports to use the new filaments. The filaments are grown from silicon melt by Edge-defined, Film-fed Growth (EFG) method. This also enables the doping of the filaments and simplification of power supplies for new reactors.

Increased polysilicon deposition in a CVD reactor

A method for preventing molten material breach in a crystal growth apparatus includes providing a chamber of the crystal growth apparatus which is coated with a ceramic material. The chamber can be coated on an interior surface to prevent damage to the chamber itself, which is made of steel, and to prevent steam explosions in the water-cooled chamber. Ceramic blanket layers also can be provided over the coated interior surface of the chamber. As a result, it is possible to produce high quality crystalline products while minimizing the hazards and costs in the event of a spill of molten material.

Crystal growth apparatus with ceramic coating and methods for preventing molten material breach in a crystal growth apparatus

A method for making a large surface area silicon filament for production of bulk polysilicon by chemical vapor deposition (CVD) includes melting silicon and growing the filament from the melted silicon by an EFG method using a shaping die. The cross sectional shape of the silicon filament is constant over its axial length to within a tolerance of 10%. In embodiments, a plurality of identical and/or dissimilar filaments are grown simultaneously using a plurality of shaping dies. The filaments can be tubular. Filament cross sections can be annular and/or can include outwardly extending fins, with wall and/or fin thicknesses constant to within 10%. Filaments can be doped with at least one element from groups 3 and 5 of the Periodic Table. The filament can have a length equal to a length of a specified slim rod filament, and a total impedance not greater than the slim rod impedance.

Method of making large surface area filaments for the production of polysilicon in a CVD reactor

To reduce the heat input to the bottom of the crucible and to control heat extraction independently of heat input, a shield can be raised between a heating element and a crucible at a controlled speed as the crystal grows. Other steps could include moving the crucible, but this process can avoid having to move the crucible. A temperature gradient is produced by shielding only a portion of the heating element; for example, the bottom portion of a cylindrical element can be shielded to cause heat transfer to be less in the bottom of the crucible than at the top, thereby causing a stabilizing temperature gradient in the crucible.

System and method for crystal growing

A method for using substantial quantities of silicon powders as charge and processing it to produce a high quality silicon ingots suitable for photovoltaic use is disclosed. In a fused silica crucible, silicon feedstock containing more than about 5% by weight silicon powder is charged. The crucible with the charged silicon feedstock is placed into a furnace chamber and a vacuum is drawn to remove air. The vacuum is applied slowly. Then, the furnace chamber is backfilled with argon gas and heated to form molten silicon. Afterward, the molten silicon is solidified and annealed to form a multicrystalline silicon ingot.

Processing of fine silicon powder to produce bulk silicon

A cutting machine has a blade mounted for reciprocating movement. A workpiece is rotated while the blade is reciprocated, and then the workpiece is rotated through smaller angles to complete the cut. A holder is attached to partially cut slices of the workpiece.

Method and apparatus for cutting workpieces

An apparatus for purifying metallurgical grade silicon to produce solar grade silicon has a container for holding molten silicon and one or more torches for providing oxygen and hydrogen gas to heat the molten silicon so that the reaction time is prolonged, to create turbulence, and to introduce silica powder and water vapor for reactions with molten silicon. The molten silicon is then directionally solidified.

Method and apparatus for purifying silicon

An apparatus for purifying metallurgical grade silicon to produce solar grade silicon has a container for holding molten silicon and one or more submergible torches for providing a flame surrounded by inert gas to heat the molten silicon so that the reaction time is prolonged, to create turbulence, and to introduce silica powder and water vapor for reactions with molten silicon. The molten silicon is then directionally solidified by providing the container in a coolant tank and controlling the coolant level with controllable valves so that further purification is achieved by segregating impurities.

Method for purifying silicon

A cutting blade the core of which is generally tear-drop shaped in cross-section. The sides of the tear-drop shaped core form an included angle of not less than about 5 degrees (and typically not less than about 9 degrees), and abrasive is provided essentially on only the wide bottom surface of the core.

Shaped blades

A high temperature heat exchanger is used with the Czochralski crystal growing method to control the heat extraction from crystal silicon ingots as they are grown. The high temperature heat exchanger also acts as a shaping die so that silicon bars, or ingots, of various shapes, including square, circular, rectangular or ribbon, can be produced by shaping during the growth stage.

Method and apparatus for growing shaped crystals

A process that, without doping of PBN crucibles, produces semi-insulating GaAs having low, or essentially no, dislocation density; and in which the crystal may be in situ annealed after growth. The process is a variant of the Heat Exchanger Method (HEM) disclosed in U.S. Pat. No. 3,898,051. Crack-free, semi-insulating GaAs crystals having low dislocation density are grown from presynthesized undoped GaAs meltstock in sealed quartz (vitreous silica) crucibles, without the need for an encapsulant. One aspect of the invention features seeded growth of &lt;100&gt; orientation crystals having a dislocation density 1-2 orders of magnitude less than that of the seed; in another aspect, crystals having fewer than 500 dislocations/cam.sup.2 in their center column are grown without a seed.

Gallium arsenide crystal growth

A wafering machine having a multiplicity of wire cutting blades supported by a bladehead reciprocally moving past a workpiece supported by a holder that rocks about an axis perpendicular to the wires at a frequency less than the reciprocation of the bladehead.

Growing community of inventors

Danvers, MA, United States of America

Chandra P Khattak