GUNARS INDARS
Broker in Littleton, MA
License number
Massachusetts 56685
Issued Date
Sep 1, 1967
Expiration Date
Mar 29, 1995
Type
Broker
Address
Address
Littleton, MA 01460
Organization information
See more information about GUNARS INDARS at bizstanding.comGunars Indars
119 King St, Littleton, MA 01460
Phone:
(978) 486-4758 (Phone), (978) 486-4163 (Phone), (978) 692-1971 (Phone)
SIC:
3491 - Industrial Valves
Professional information
Interferometers For The Measurement Of Large Diameter Thin Wafers
US Patent:
2007022, Oct 4, 2007
Filed:
Apr 3, 2006
Appl. No.:
11/278507
Inventors:
Gunars Indars - Littleton MA, US
Anatoliy E. Rzhanov - Westford MA, US
Anatoliy E. Rzhanov - Westford MA, US
Assignee:
Valley Design Corporation - Shirley MA
International Classification:
G01B 11/02
US Classification:
356515
Abstract:
An interferometer for measuring the flatness, variation of thickness and parallelism of large, thin transparent wafers held vertically and undistorted by gravitational forces. A sodium lamp provides monochromatic light that is diffusely reflected off a background screen towards the wafer. A reference flat surface is positioned sufficiently closely to the wafer that an interference fringe pattern is formed that is a measure of the air gap between the reference flat surface and the surface of the wafer being measured. The background screen is angled so that the fringe pattern, which is localized at the air gap can be viewed at an angle to a normal to the wafer. The background screen has trapezoidal markings that, when viewed at the angle required to see the fringes, appear as a grid. This allows counting of the number of fringes visible within a fixed distance to characterize the surface flatness.