Daniel R Kerr

US Patent:

7074628, Jul 11, 2006

Filed:

Sep 22, 2004

Appl. No.:

10/947069

Inventors:

Bradley J. Albers - Dallas TX, US
Thomas Craig Esry - Orlando FL, US
Daniel Charles Kerr - Orlando FL, US
Edward Paul Martin, Jr. - Orlando FL, US
Oliver Desmond Patterson - Poughkeepsie NY, US

Assignee:

Agere Systems, Inc. - Allentown PA

International Classification:

H01L 31/26
H01L 21/66

US Classification:

438 14, 438 38, 438 60

Abstract:

A method and apparatus for identifying crystal defects in emitter-base junctions of NPN bipolar transistors uses a test structure having an NP junction that can be inspected using passive voltage contrast. The test structure eliminates the collector of the transistor and simulates only the emitter and base. Eliminating the collector removes an NP junction between collector and substrate of a wafer allowing charge to flow from the substrate to emitter if the emitter-base junction is defective since only one NP junction exists in the test structure. In one embodiment, the test structures are located between dies on a wafer and may be formed in groups of several thousand.