Inspection system for array of microcircuit dies having redundant circuit patterns
USRE33956E · kind E · reissue
Assignee
Inventors
Key dates
| Filing date | Nov 14, 1990 |
| Grant date | Jun 9, 1992 |
| Priority date | — |
| Expiry date | Nov 14, 2010 |
Classification
- Technology area (CPC —)General
Abstract
An inspection system (10, 100) employs a Fourier transform lens (34, 120) and an inverse Fourier transform lens (54, 142) positioned along an optic axis (48, 144) to produce from an illuminated area of a patterned specimen wafer (12) a spatial frequency spectrum whose frequency components can be selectively filtered to produce an image pattern of defects in the illuminated area of the wafer. Depending on the optical component configuration of the inspection system, the filtering can be accomplished by a spatial filter of either the transmissive (50) or reflective (102) type. The lenses collect light diffracted by a wafer die (14) aligned with the optic axis and light diffracted by other wafer dies proximately located to such die. The inspection system is useful for inspecting only dies having many redundant circuit patterns. The filtered image strikes the surface of a two-dimensional photodetector array (58) which detects the presence of light corresponding to defects in only the illuminated on-axis wafer die. Inspection of all possible defects in the portions of the wafer surface having many redundant circuit patterns is accomplished by mounting the wafer onto a two-dimensional tr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.