Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Reexamination Certificate
2002-11-07
2004-11-02
Lee, John R. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
Reexamination Certificate
active
06812461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to specimen inspection and review. More particularly, the present invention relates to e-beam inspection and systems.
2. Description of the Background Art
Automated inspection and review systems are important in process control and yield management for the semiconductor and related microelectronics industries.
An example of an electron beam (e-beam) tool for an inspection or review system is shown in
FIG. 1
for purposes of background explanation. The secondary electron emission microscope (SEEM) apparatus of
FIG. 1
is a projection type system, where a large spot of electrons rather than a small one is formed at the surface of the specimen, and the secondary electrons from this spot are imaged onto a two-dimensional detector. Typically, the specimen may comprise a semiconductor wafer having integrated circuit related structures formed on its surface. Alternatively, the specimen may be another type of sample.
The system of
FIG. 1
is described in U.S. Pat. No. 5,973,323, entitled “Apparatus and Method for Secondary Electron Emission Microscope,” inventors Adler et al., and assigned at issuance to KLA-Tencor Corporation of San Jose, Calif. The disclosure of U.S. Pat. No. 5,973,323 is hereby incorporated by reference. As described in that patent,
FIG. 1
shows the basic configuration for the Secondary Electron Emission Microscopy (SEEM) apparatus. An electron gun source
10
emits a beam
11
of primary electrons e
1
along path
12
. The electron beam
11
is collimated by electron lens
13
and continues along path
12
. Magnetic beam separator
14
then bends the collimated electron beam
11
to be incident along electron optical axis OA normal to the surface to be inspected. Objective electron lens
15
focuses the primary electrons, e
1
, into a beam having a spot size typically in the range 1-10 mm and an incident energy on the order of 1 keV on specimen
9
.
Primary electrons e
1
incident on the specimen
9
produce secondary electrons e
2
which travel back along the axis OA perpendicular to the inspection surface to objective electron lens
15
, where they are re-collimated. Magnetic beam separator
14
bends the electrons to travel along image path
16
. The electron beam along image path
16
is focused by projection electron lens
17
to image plane
18
, where there is an electron detector
19
, which is a camera or preferably a time delay integrating (TDI) electron detector. The operation of an analogous TDI optical detector is disclosed in U.S. Pat. No. 4,877,326, entitled “Method and Apparatus for Optical Inspection of Substrates,” inventors Chadwick et al., and assigned at issuance to KLA Instruments Corporation. The disclosure of U.S. Pat. No. 4,877,326 is incorporated herein by reference. The image information may be processed directly from a ‘back thin’ TDI electron detector
19
, or the electron beam may be converted into a light beam and detected with an optional optical system
20
and a TDI optical detector.
Despite advances in e-beam inspection and review, such as SEEM described above, further improvement may be made. For example, it is typically desirable to increase the resolution of an inspection or review system. Resolution may be defined as the smallest distance apart that two point may be distinguishable as separate points. Current e-beam inspection and review systems have resolutions of about 100 nanometers (0.1 micrometers). Generally, the higher the resolution, the smaller the defects that may be detected and characterized by the automated inspection and review systems. In other words, the resolution of an e-beam system limits the smallness of the features that may be detected and characterized. Hence, in order to detect and characterize smaller and smaller features on semiconductors and other specimens, it is desirable to increase the achievable resolution of the system.
REFERENCES:
patent: 4820927 (1989-04-01), Langner et al.
patent: 4877326 (1989-10-01), Chadwick et al.
patent: 4970392 (1990-11-01), Oettinger et al.
patent: 5041724 (1991-08-01), Feuerbaum et al.
patent: 5973323 (1999-10-01), Adler et al.
patent: 6038018 (2000-03-01), Yamazaki et al.
Michelato et al., “Optical Properties of Cesium Telluride” Proc. of EPAC 200, Paris France, pp 8110-1812.*
Trotz, S., et al. “High Power Operation of a 17 GHz Photocathode RF Gun”, Advanced Accelerator Concepts, edited by S. Chattopadhyay, 1997.
J.E. Clendenin, et al. “Reduction of Thermal Emittance of RF Guns”, SLAC-PUB-8284, Oct. 1999.
Adler David L.
Mankos Marian
KLA-Tencor Technologies Corporation
Lee John R.
Leybourne James J.
Okamoto & Benedticto LLP
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