Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Reexamination Certificate
1998-11-18
2001-04-03
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
C250S251000, C250S307000
Reexamination Certificate
active
06211518
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to enhanced feature measurement in scanning electron microscopy, and more specifically to a system and methods for controlling electron exposure on image specimens in scanning electron metrology, particularly in the inspection of features of micro-circuits. It may also apply to critical dimension measurement in similar instruments.
BACKGROUND OF THE INVENTION
In scanning electron microscopy, a beam of electrons is scanned over a specimen, and the resulting electrons that are returned from the specimen surface are used to create an image of the specimen surface. In some systems, the beam is arbitrarily controllable to make multiple scan passes over specific areas or portions of areas at different sample frequencies to magnify the image of the surface.
On a specimen made of a substantially insulative material (e.g., a semiconductor material), performing multiple scans over the same small area may cause the specimen to accumulate an excess positive charge in that small area relative to the rest of the scanned area. That excess charge causes an image of that small area to appear dark, thus obscuring image features in that small area.
SUMMARY OF THE PRESENT INVENTION
One embodiment of the present invention is a system and method for imaging a specimen that acquires a charge when scanned with a scanning electron microscope comprising an electron source and apparatus for forming, accelerating, focusing, and scanning an electron beam across a portion of said specimen. That imaging being performed by raster scanning a selected small area of the specimen for a single frame cycle, and then raster scanning a substantially larger area of the specimen that includes the small area to brighten the image of the small area of said specimen by flooding the substantially larger area with electrons.
A second embodiment of the present invention is a system and method of a scanning electron microscope to image a specimen that acquires a charge when scanned with a scanning electron microscope by injecting an inert gas at the point where the electron beam impinges on the surface of the specimen. That inert gas being ionized by the electron beam and thus neutralizing the charge as it builds up on the specimen.
REFERENCES:
patent: 4578279 (1986-03-01), Zingher
patent: 4842679 (1989-06-01), Kudo et al.
patent: 4992661 (1991-02-01), Tamura et al.
patent: 5055696 (1991-10-01), Haraichi et al.
patent: 5869833 (1999-02-01), Richardson et al.
Adler David L.
Askary Farid
Concina Stefano E.
Monahan Kevin M.
Richardson Neil
Jones Allston L.
Kla-Tencor Corporation
Nguyen Kiet T.
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