Patents by Inventor Mohan Chandra

Mohan Chandra has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6491971
    Abstract: A method for preparing a release coating and applying it to crucibles used to contain molten material while it solidifies, by mixing a release coating power with a dry organic binder into a powder and binder dry mixture, mixing a defoamer with a liquid into a liquid and defoamer mixture, mixing the dry mixture with the liquid and defoamer mixture into a wet release coating, sieving to remove lumps and particles, checking the viscosity, wet-spraying onto a crucible, evaporating the liquid from the wet release coating so as to leave a dry release coating on the crucible, and separating the binder from the dry release coating by thermal decomposition.
    Type: Grant
    Filed: April 6, 2001
    Date of Patent: December 10, 2002
    Assignee: G.T. Equipment Technologies, Inc
    Inventors: Michael A Costantini, Mohan Chandra, Keith Matthei, Alleppey V. Hariharan
  • Publication number: 20020177962
    Abstract: An apparatus for the automated measurement and recording of the electrical resistivity of a semiconductor boule or ingot using the method of four probes. A four point boule support grid is provided adjacent to the home position of a four tip probe equipped with three axis linear mobility, rotational capability, and computer control, to enable automated mapping and testing of an “as grown” or ground semiconductor boule with cropped ends, for obtaining and recording all necessary resistivity data. The apparatus converts resistivity data to ASTM standards and reads over a wide resistivity range. The apparatus has all data logging capabilities and full computer control interfaces, and adapts readily to a production line setup with automated delivery and removal of boules under test.
    Type: Application
    Filed: May 3, 2002
    Publication date: November 28, 2002
    Inventors: Mohan Chandra, David M. Darling, L. Dolan Roman, Carl P. Chartier, Glen Alan Burgess
  • Patent number: 6479108
    Abstract: A thermodynamically stable, protective coating layer is applied by thermal spray technique to the inner and outer surfaces of a quartz crucible used for mono or polycrystalline silicon crystallization processing, inhibiting fusion between the silicon melt and the vitreous silica of the crucible, contamination of the silicon melt by contaminants released from the crucible by devitrification, and any chemical reaction occurring between the crucible and any supporting graphite structure. A powdered form of a suitable protective coating material compatible with high temperature plasma spray techniques, such as magnesium zirconate, barium zirconate, or stabilized zirconium oxide, is fed into a high temperature and high speed plasma jet directed at the crucible. The powder particles are softened or melted in the jet and deposited on the surfaces of the quartz crucible, and allowed to cool and harden into a protective coating.
    Type: Grant
    Filed: August 31, 2001
    Date of Patent: November 12, 2002
    Assignee: G.T. Equipment Technologies, Inc.
    Inventors: Alleppey V. Hariharan, Mohan Chandra, Michael Costantini, Yuepeng Wan
  • Publication number: 20020146510
    Abstract: A method for preparing a release coating and applying it to crucibles used to contain molten material while it solidifies, by mixing a release coating power with a dry organic binder into a powder and binder dry mixture, mixing a defoamer with a liquid into a liquid and defoamer mixture, mixing the dry mixture with the liquid and defoamer mixture into a wet release coating, sieving to remove lumps and particles, checking the viscosity, wet-spraying onto a crucible, evaporating the liquid from the wet release coating so as to leave a dry release coating on the crucible, and separating the binder from the dry release coating by thermal decomposition.
    Type: Application
    Filed: April 6, 2001
    Publication date: October 10, 2002
    Inventors: Michael A. Costantini, Mohan Chandra, Keith Matthei, Alleppey V. Hariharan
  • Publication number: 20020115273
    Abstract: A method for producing formed semiconductor articles with predefined shapes such as core tubes for CVD production of bulk polysilicon. The method is characterized by thermal spray deposition of the semiconductor material in a on a temperature controlled rotating mandrel that is shaped complementarily to the desired article shape, and by later separation of the formed semiconductor body from the mandrel by thermal contraction, melting, or chemical reduction of the mandrel size.
    Type: Application
    Filed: August 20, 2001
    Publication date: August 22, 2002
    Inventors: Mohan Chandra, Yuepeng Wan
  • Publication number: 20020086119
    Abstract: A thermodynamically stable, protective coating layer is applied by thermal spray technique to the inner and outer surfaces of a quartz crucible used for mono or polycrystalline silicon crystallization processing, inhibiting fusion between the silicon melt and the vitreous silica of the crucible, contamination of the silicon melt by contaminants released from the crucible by devitrification, and any chemical reaction occurring between the crucible and any supporting graphite structure. A powdered form of a suitable protective coating material compatible with high temperature plasma spray techniques, such as magnesium zirconate, barium zirconate, or stabilized zirconium oxide, is fed into a high temperature and high speed plasma jet directed at the crucible. The powder particles are softened or melted in the jet and deposited on the surfaces of the quartz crucible, and allowed to cool and harden into a protective coating.
    Type: Application
    Filed: August 31, 2001
    Publication date: July 4, 2002
    Inventors: Allepey V. Hariharan, Mohan Chandra, Michael A. Costantini, Yuepeng Wan
  • Publication number: 20020076501
    Abstract: A method for preparing a release coating and applying it to crucibles used to contain molten material while it solidifies, such as in the directional solidification of polycrystalline silicon into ingots, by mixing a release coating power with a dry organic binder into a powder and binder dry mixture, mixing a defoamer with a liquid into a liquid and defoamer mixture, mixing the dry mixture with the liquid and defoamer mixture into a wet release coating, sieving to remove lumps and particles, checking the viscosity, wet-spraying onto a crucible at about room temperature, evaporating the liquid from the wet release coating so as to leave a dry release coating on the crucible, and separating the binder from the dry release coating by thermal decomposition.
    Type: Application
    Filed: November 15, 2001
    Publication date: June 20, 2002
    Inventors: Michael Costantini, Mohan Chandra, Keith Matthei, Alleppey V. Hariharan
  • Publication number: 20020056473
    Abstract: A method for fabricating multi-cell solar devices using thermal spray deposition techniques to spray metal powder directly on solar cells and on the backing upon which solar cells are assembled, to form collection grid lines, bus bars, electrodes and interconnections between solar cells.
    Type: Application
    Filed: November 16, 2001
    Publication date: May 16, 2002
    Inventors: Mohan Chandra, Yuepeng Wan, Alleppey V. Hariharan, Jonathan A. Talbott
  • Patent number: 6365225
    Abstract: A method and apparatus, and product by process, for the production of bulk polysilicon by a chemical vapor deposition process on a removable tube section. A quartz envelope and base plate form a CVD reactor enclosure, with external radiant heaters providing process heat through the wall of the reactor, and with process gas inlet and outlet ports located in the base plate. A tube section, preferably an EFG silicon tube-section, vertically emplaced on the base plate and capped to close the top is used as the reaction chamber. During the CVD process, deposition occurs on the inside surface of the chamber tube, the inner diameter of the deposit layer becoming increasingly smaller as the yield accumulates. In a two tube reactor, a smaller diameter, vertical middle tube is uniformly spaced and supported inside the chamber tube for fall flow of process gas over and under the middle tube so that deposition occurs on the three exposed tube surfaces.
    Type: Grant
    Filed: August 17, 2000
    Date of Patent: April 2, 2002
    Assignee: G.T. Equipment Technologies, Inc.
    Inventors: Mohan Chandra, Kedar P. Gupta, Jonathan A. Talbott, Ijaz Jafri, Vishwanath Prasad
  • Publication number: 20020014257
    Abstract: A dry process for the cleaning of precision surfaces such as of semiconductor wafers, by using process materials such as carbon dioxide and useful additives such as cosolvents and surfactants, where the process materials are applied exclusively in gaseous and supercritical states. Soak and agitation steps are applied to the wafer, including a rapid decompression of the process chamber after a soak period at higher supercritical pressure, to mechanically weaken break up the polymers and other materials sought to be removed, combined with a supercritical fluid flush to carry away the loose debris.
    Type: Application
    Filed: May 18, 2001
    Publication date: February 7, 2002
    Inventors: Mohan Chandra, David J. Mount, Michael A. Costantini, Heiko D. Moritz, Ijaz H. Jafri, Jim Boyd, Rick M. Heathwaite
  • Patent number: 6334266
    Abstract: A method and apparatus for fabricating and drying wafers, including micro-electro-mechanical system (MEMS) structures, in a second, supercritical processing fluid environment. The apparatus utilizes an inverted pressure vessel connected to a supercritical processing fluid supply and recover system, with an internal heat exchanger connected to external heating and cooling sources, which is closed with a vertically movable base plate. A wafer cassette configured for supporting multiple wafers is submerged in a first processing fluid within a container, which is installed on the base plate for insertion into the pressure vessel. Vessel inlet and outlet tubes extend vertically downward from the ceiling of the pressure vessel to nearly the base plate. Container inlet and outlet tubes extend vertically downward from the ceiling of the pressure vessel to inside the container and nearly to the bottom of the container.
    Type: Grant
    Filed: September 20, 2000
    Date of Patent: January 1, 2002
    Assignee: S.C. Fluids, Inc.
    Inventors: Heiko D Moritz, Jonathan A. Talbott, Mohan Chandra, James A. Tseronis, Ijaz Jafri
  • Publication number: 20010050096
    Abstract: A continuous flow, steady state fluid delivery and recovery system for a process chamber and processes requiring supercritical fluid and desired additives including co-solvents, for conducting repetitive batch processing operations in an automated environment, for such processes as supercritical carbon dioxide cleaning and processing of semiconductor wafers. The system provides for steady-state operation of fluid flow and byproducts recovery while the process chamber is brought rapidly and repeatedly on and off line as in batch operations and for various process steps.
    Type: Application
    Filed: April 18, 2001
    Publication date: December 13, 2001
    Inventors: Michael A. Costantini, Mohan Chandra, Heiko D. Moritz, Ijaz H. Jafri, David J. Mount, Rick M. Heathwaite
  • Publication number: 20010035129
    Abstract: A method and apparatus for the production of solar cells by directly spraying metal powder for both lines and layers on the front and back sides of a silicon wafer using focused plasma spray technique for making contacts on solar cells.
    Type: Application
    Filed: March 8, 2001
    Publication date: November 1, 2001
    Inventors: Mohan Chandra, Yuepeng Wan, Alleppey V. Hariharan, Jonathan A. Talbott
  • Publication number: 20010029971
    Abstract: An inverted pressure vessel system for conducting automated industrial processes requiring elevated pressure and temperatures has a vertically movable pedestal for opening and closing the underside loading port, with pedestal drive system and locking mechanism located below the pedestal top and isolated from the chamber opening. The chamber is connectible to a pressure control and process fluid supply system, and has heat exchangers connected to an external source for temperature control. Process fluids are distributed across a central process cavity through divergent inflow and convergent outflow process fluid channels.
    Type: Application
    Filed: February 5, 2001
    Publication date: October 18, 2001
    Inventors: Robert B. Farmer, Jonathan A. Talbott, Mohan Chandra, James A. Tseronis, Heiko D. Moritz
  • Patent number: 6284312
    Abstract: A method and apparatus, and product by process, for the production of bulk polysilicon by broad area chemical vapor deposition, consisting of a quartz envelope and base plate forming a reactor enclosure, with external radiant heaters providing the heat source. A thin wall, edge-defined film fed growth (EFG) silicon tube section is used as the deposition casing and reaction chamber wall. The tube is capped at the top and sealed to the base plate to form the reaction chamber. External heaters radiate heat through the quartz enclosure to heat the tube wall to deposition temperature. A through flow of process gas is introduced to initiate the deposition. A uniform wide surface area deposit occurs on the inside surface of the tube, causing the diameter to become increasingly smaller as the yield accumulates.
    Type: Grant
    Filed: February 18, 2000
    Date of Patent: September 4, 2001
    Assignee: GT Equipment Technologies INC
    Inventors: Mohan Chandra, Ijaz Hussain Jafri, Kedar Prasad Gupta, Vishwanath Prasad, Jonathan A. Talbott
  • Patent number: 6113473
    Abstract: A slurry recycle process for use in free-abrasive machining operations such as for wire saws used in wafer slicing of ingots, where the used slurry is separated into kerf-rich and abrasive-rich components, and the abrasive-rich component is reconstituted into a makeup slurry. During the process, the average particle size of the makeup slurry is controlled by monitoring the condition of the kerf and abrasive components and making necessary adjustments to the separating force and dwell time of the separator apparatus. Related pre-separator and post separator treatments, and feedback of one or the other separator slurry output components for mixing with incoming used slurry and recirculation through the separator, provide further effectiveness and additional control points in the process.
    Type: Grant
    Filed: April 24, 1998
    Date of Patent: September 5, 2000
    Assignee: G.T. Equipment Technologies Inc.
    Inventors: Michael A. Costantini, Jonathan A. Talbott, Mohan Chandra, Vishwanath Prasad, Allison Caster, Kedar P. Gupta, Philippe Leyvraz
  • Patent number: 6019841
    Abstract: The invention is an improved method and apparatus for growing crystals that incorporates an isolation valve between the growth and injection chambers to allow the growth chamber to be maintained at operating temperature and pressure while decoupling the injector chamber in order to make changes necessary to restart or advance the process. Separate heating elements in the injector assembly or chamber provide related heating control. Upper and lower load cells and programmable signal amplifiers are configured to weigh and output the dynamic weight range of the loss or gain of process materials of the growth chamber crucible and the injector assembly, and are connected by electrical slip rings or wireless means to a computer control system.
    Type: Grant
    Filed: March 24, 1998
    Date of Patent: February 1, 2000
    Assignee: G.T. Equuipment Technologies Inc.
    Inventors: Ijaz H. Jafri, Mohan Chandra, Rick C. White, Kedar P. Gupta, Robert B. Farmer, Bernard D. Jones, David F. Bliss
  • Patent number: 5580171
    Abstract: There is disclosed a static mixer for intimate mixing of granular solids, a solids flow controller and a solids transfer tube which are useful to mix polycrystalline material with dopant solids, and to feed the resultant mixture continuously and accurately into a modified Czochralski-type furnace for growing single crystal material. The static mixer is a series of conical funnel plates interspaced by thieving divider plates that are formed by a plurality of triangular V-shaped, radial sectors. Contiguous to the static mixer is a storage hopper which has sufficient storage capacity for all the polycrystalline feed material required in a single run of the furnace. Located beneath the hopper is a solids flow controller that is a V-shaped trough which is vibrated along its longitudinal axis. At one end, the trough has a transverse baffle located with a gap between its bottom edge and the bottom of the trough that controls the rate of flow of the solids.
    Type: Grant
    Filed: July 24, 1995
    Date of Patent: December 3, 1996
    Inventors: John C. Lim, William A. Koch, Mohan Chandra