Method and system for automated measurement of whole-wafer etch pit density in GaAs

US5008542A · kind A · utility

Assignee

• United States of America as represented by the Secretary of the Air Force · US

Inventors

• David C. Look · Dayton, US
• James S. Sewell · Kettering, US
• Millard G. Mier · Yellow Springs, US
• John R. Sizelove · Kettering, US
• Dennis Walters · Fairborn, US
• Scott C. Dudley · Woodland Park, US

Key dates

• Filing date: Dec 20, 1989
• Grant date: Apr 16, 1991
• Expiry date: Dec 20, 2009

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/8803
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method and system for measuring whole-wafer etch pit density (.rho..sub.D) is disclosed in which an etch GaAs wafer is tested for fractional transmission at a plurality of points over its surface. The fractional transmission (T) of light through the wafer is detected, amplified and fed to a computer where at least two points of transmission measurement are selected for calibration. From these measurements, together with an estimate of the average etch pit size (area), the values for fractional transmission in regions of low etch pit density T.sub.O and high etch pit density T.sub.E may be calculated, and used to convert transmission data directly to etch pit density (.rho..sub.D) according to the equation ##EQU1##