Patents by Inventor Sureshchandra M. Ojha

Sureshchandra M. Ojha 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).

  • Semiconductor etching process
    Patent number: 5419804
    Abstract: A process for plasma etching a compound semiconductor heterostructure, e.g. to fabricate a ridge laser on a wavelength demultiplexer comprises anisotropic etching of the semiconductor by exposure to a plasma incorporating methane, hydrogen and oxygen. The oxygen content of the plasma is derived from a gaseous precursor such as carbon dioxide or nitrous oxide.
    Type: Grant
    Filed: February 16, 1994
    Date of Patent: May 30, 1995
    Assignee: Northern Telecom Limited
    Inventors: Sureshchandra M. Ojha, Stephen J. Clements
  • Process for forming isolation trenches in silicon semiconductor bodies
    Patent number: 4957873
    Abstract: Isolation trenches are formed in a semiconductor, e.g. silicon, substrate by selectively doping the substrate and preferentially oxidizing the doped material. Typically the dopant is arsenic or phosphorus and preferably the substrate is doped to a level of at least 5.times.10.sup.19 cm.sup.-3.
    Type: Grant
    Filed: September 21, 1989
    Date of Patent: September 18, 1990
    Assignee: STC PLC
    Inventors: Sureshchandra M. Ojha, Paul J. Rosser, Philip B. Moynagh
  • Pulsed plasma apparatus and process
    Patent number: 4935661
    Abstract: An apparatus for pulsed plasma treatment of a substrate surface includes means for removing spent gas from a region adjacent the substrate for each pulse. The apparatus may also include means for sweeping an intense plasma region across a substrate surface. Rapid gas exchange is provided by pressure pulsing the gas admission. This facility also provides means for rapidly alternating different gases.
    Type: Grant
    Filed: June 26, 1986
    Date of Patent: June 19, 1990
    Assignee: STC plc
    Inventors: Rudolf A. Heinecke, Sureshchandra M. Ojha, Ian P. Llewellyn
  • Plasma etching process
    Patent number: 4886569
    Abstract: A polysilicon layer or a single crystal silicon substrate is plasma etched in a two staged process. The first stage was a non-selective anisotropic etch to define a desired pattern by etching part way through the polysilicon. The second stage was a selective etch to secure remaining polysilicon and expose the substrate.
    Type: Grant
    Filed: February 21, 1989
    Date of Patent: December 12, 1989
    Assignee: STC PLC
    Inventors: Sureshchandra M. Ojha, Stephen R. Jennings, Anthony D. Johnston
  • Method of surface treatment
    Patent number: 4749589
    Abstract: In a pulsed plasma process for surface treatment of a substrate the containing reactor vessel (11) has an inner cross-section conforming to the substrate geometry so as to confine the intense plasma region to the substrate surface (12). Preferably this region should be within 15 to 20 mm of the surface. Advantageously the inner surface is provided by a demountable insert (13).
    Type: Grant
    Filed: December 10, 1985
    Date of Patent: June 7, 1988
    Assignee: STC plc
    Inventors: Rudolf A. H. Heinecke, Sureshchandra M. Ojha, Ian P. Llewellyn
  • Optical fibre manufacture
    Patent number: 4568563
    Abstract: An optical fibre is provided with a moisture barrier layer by exposing a plastics coating on the fibre to a pulsed plasma in order to modify the surface, for instance by implantation of silicon and/or by the deposition on the plastics layer an inorganic layer such as a non-stoichiometric composition of silicon and carbon or silicon and nitrogen.
    Type: Grant
    Filed: June 21, 1985
    Date of Patent: February 4, 1986
    Assignee: Standard Telephones and Cables
    Inventors: Thomas M. Jackson, Rudolf A. H. Heinecke, Sureshchandra M. Ojha