James J Hahn

US Patent:

6980011, Dec 27, 2005

Filed:

Jan 13, 2004

Appl. No.:

10/757694

Inventors:

Vijay Chowdhury - Fremont CA, US
James Hahn - Livermore CA, US

Assignee:

Altera Corporation - San Jose CA

International Classification:

G01R031/305
G01R031/302

US Classification:

324751, 324750, 324765

Abstract:

A method and apparatus for maximizing passive voltage contrast on the surface of a die and then using the maximized passive voltage contrast to identify electrical failures in the die. The method employs a primary electron beam to scan the surface of the die. In response, secondary electrons are emitted from the die and then captured by a secondary electron detector. The density of secondary electrons is further modulated by a passive voltage near the die surface. To enhance the passive voltage contrast on the die surface, the incident angle of the primary electron beam is adjusted with respect to the die, the passive voltage contrast reaching a maximum at an incident angle of about 75 or above. With such enhanced contrast, an image depicting the magnitude of the secondary electron current can be used to detect electrical failures in the die.