U.S. patent application number 11/855935 was filed with the patent office on 2008-01-03 for system for detecting anomalies and/or features of a surface.
Invention is credited to Stanley Stokowski, Mehdi Vaez-Iravani, Guoheng Zhao.
Application Number | 20080002193 11/855935 |
Document ID | / |
Family ID | 25419930 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080002193 |
Kind Code |
A1 |
Zhao; Guoheng ; et
al. |
January 3, 2008 |
SYSTEM FOR DETECTING ANOMALIES AND/OR FEATURES OF A SURFACE
Abstract
A cylindrical mirror or lens is used to focus an input
collimated beam of light onto a line on the surface to be
inspected, where the line is substantially in the plane of
incidence of the focused beam. An image of the beam is projected
onto an array of charge-coupled devices parallel to the line for
detecting anomalies and/or features of the surface, where the array
is outside the plane of incidence of the focused beam.
Inventors: |
Zhao; Guoheng; (Milpitas,
CA) ; Stokowski; Stanley; (Danville, CA) ;
Vaez-Iravani; Mehdi; (Los Gatos, CA) |
Correspondence
Address: |
DAVIS WRIGHT TREMAINE LLP - KLA-TENCOR CORPORATION
505 MONTGOMERY STREET, SUITE 800
SAN FRANCISCO
CA
94111-6533
US
|
Family ID: |
25419930 |
Appl. No.: |
11/855935 |
Filed: |
September 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10949078 |
Sep 24, 2004 |
7280199 |
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11855935 |
Sep 14, 2007 |
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10452624 |
May 30, 2003 |
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10949078 |
Sep 24, 2004 |
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08904892 |
Aug 1, 1997 |
6608676 |
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10452624 |
May 30, 2003 |
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Current U.S.
Class: |
356/237.2 |
Current CPC
Class: |
G01N 21/9501
20130101 |
Class at
Publication: |
356/237.2 |
International
Class: |
G01N 21/00 20060101
G01N021/00 |
Claims
1. A method for detecting anomalies and/or features of a surface,
comprising: focusing a beam of radiation at an oblique incidence
angle to illuminate a line on the surface, said beam and a
direction through the beam and normal to the surface defining an
incidence plane of the beam, said line being substantially in the
plane of incidence of the beam; and imaging said line onto an array
of detectors, each detector in the array detecting light from a
corresponding portion of the line.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/949,078, filed on Sep. 24, 2004, which in turn is a continuation
of application Ser. No. 10/452,624, filed May 30, 2003, which is a
continuation of application Ser. No. 08/904,892, filed Aug. 1,
1997, now U.S. Pat. No. 6,608,676, which applications are
incorporated herein in their entirety by this reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates in general to surface inspection
systems, and in particular, to an improved system for detecting
anomalies and/or features of a surface.
[0003] The need to detect anomalies of a surface such as those on
the surface of a semiconductor wafer has been recognized since at
least the early 1980's. In the article "Automatic Microcircuit and
Wafer Inspection in Electronics Test," May 1981, pp. 60-70, for
example, Aaron D. Gara discloses a wafer inspection system for
detecting whether microcircuit chips are placed upside down or not
and for detecting flaws. In this system, a light beam from a laser
is passed through a beam expander and a cylindrical lens having a
rectangular aperture, where the lens focuses the beam to a narrow
line of laser light transverse to the incidence plane of the beam
to illuminate the wafer surface. It is stated in the article that
the smallest defect the system can reveal is less than 10 microns
wide.
[0004] The size of semiconductor devices fabricated on silicon
wafers has been continually reduced. The shrinking of semiconductor
devices to smaller and smaller sizes has imposed a much more
stringent requirement on the sensitivity of wafer inspection
instruments which are called upon to detect contaminant particles
and pattern defects as well as defects of the surfaces that are
small compared to the size of the semiconductor devices. At the
time of the filing of this application, design rule for devices of
down to 0.2 microns or below has been called for. At the same time,
it is desirable for wafer inspection systems to provide an adequate
throughput so that these systems can be used for in-line inspection
to detect wafer defects. One type of surface inspection system
employs an imaging device that illuminates a large area and images
of duplicate areas of surfaces, such as a target area and a
reference area used as a template, are compared to determine
differences therebetween. These differences may indicate surface
anomalies. Such system requires significant time to scan the entire
surface of a photomask or semiconductor wafer. For one example of
such system, see U.S. Pat. No. 4,579,455.
[0005] U.S. Pat. No. 4,898,471 to Stonestrom et al. illustrates
another approach. The area illuminated on a wafer surface by a
scanning beam is an ellipse which moves along a scan line called a
sweep. In one example, the ellipse has a width of 20 microns and a
length of 115 microns. Light scattered by anomalies of patterns in
such illuminated area is detected by photodetectors placed at
azimuthal angles in the range of 80 to 100.degree., where an
azimuthal angle of a photodetector is defined as the angle made by
the direction of light collected by the photodetector from the
illuminated area and the direction of the illumination beam when
viewed from the top. The signals detected by the photodetectors
from a region are used to construct templates. When the elliptical
spot is moved along the scan line to a neighboring region,
scattered light from structures within the spot is again detected
and the photodetector signal is then compared to the template to
ascertain the presence of contaminant particles or pattern defects.
While the scanning beam scans across the surface of the wafer, the
wafer is simultaneously moved by a mechanical stage in a direction
substantially perpendicular to the sweep direction. This operation
is repeated until the entire surface has been inspected.
[0006] While the system of Stonestrom et al. performs well for
inspecting wafers having semiconductor devices that are fabricated
with coarser resolution, with a continual shrinking of the size of
the devices fabricated, it is now desirable to provide an improved
inspection tool that can be used to detect very small anomalies
that can be difficult to detect using Stonestrom's system.
[0007] In the wafer inspection system where a light beam
illuminates a small area of the surface to be inspected, such as
those by Stonestrom et al. and Gara described above, the size of
the illuminated spot affects the sensitivity of the system. If the
spot is large relative to the size of the defects to be detected,
the system will have low sensitivity since the background or noise
signals may have significant amplitudes in relation to the
amplitudes of the signals indicating anomalies within the spot. In
order to detect smaller and smaller defects, it is, therefore,
desirable to reduce the size of the illuminated area on the wafer
surface.
[0008] However, as the size of the illuminated area is reduced,
throughput is usually also reduced. In addition, a smaller spot
size imposes a much more stringent requirement for alignment and
registration. As discussed above, in many wafer inspection systems,
it is common to perform a target image to a reference image
comparison for ascertaining the presence of anomalies. If the area
illuminated is not the intended target area but is shifted relative
to the target area, the comparison may yield false counts and may
become totally meaningless. Such shifting of the image relative to
the intended target area is known as misregistration.
[0009] Misregistration errors can be caused by misalignment of the
illumination optics due to many causes such as mechanical
vibrations, as well as by change in the position of the wafer such
as wafer warp or wafer tilt or other irregularities on the wafer
surface. For this reason, a wafer positioning system has been
proposed as in U.S. Pat. No. 5,530,550 to Nikoonahad et al. In this
patent, Nikoonahad et al. propose to use the specular reflection of
the scanning beam and a position sensitive detector for detecting
the change in height of the wafer and use such information to alter
the position of the wafer in order to compensate for a change in
height or tilting of the wafer surface.
[0010] While the above-described systems may be satisfactory for
some applications, they can be complicated and expensive for other
applications. It is, therefore, desirable to provide an improved
surface inspection system with improved sensitivity and performance
at a lower cost that can be used for a wider range of
applications.
SUMMARY OF THE INVENTION
[0011] One aspect of the invention is directed towards a method for
detecting anomalies and/or features of a surface, comprising
focusing a beam of radiation at an oblique incidence angle to
illuminate a line on a surface, said beam and a direction through
the beam and normal to the surface defining an incidence plane of
the beam, said line being substantially in the incidence plane of
the beam; and imaging said line onto an array of detectors, each
detector in the array detecting light from a corresponding portion
of the line.
[0012] Another aspect of the invention is directed towards a method
for detecting anomalies of a surface and/or a surface feature,
comprising focusing a beam of radiation at an oblique incidence
angle to illuminate a line on the surface, said beam and a
direction through the beam and normal to the surface defining an
incidence plane of the beam; and imaging said line onto an array of
detectors outside of the incidence plane, each detector in the
array detecting light from a corresponding portion of the line.
[0013] Yet another aspect of the invention is directed towards an
apparatus for detecting anomalies of a surface comprising means for
focusing a beam of radiation at an oblique incidence angle to
illuminate a line on the surface, said beam and a direction through
the beam and normal to the surface defining an incidence plane of
the beam, said line being substantially in the incidence plane of
the beam; at least one array of detectors; and a system imaging
said line onto the at least one array of detectors, each detector
in the at least one array detecting light from a corresponding
portion of the line.
[0014] One more aspect of the invention is directed towards an
apparatus for detecting anomalies of a surface and/or a surface
feature, comprising means for focusing a beam of radiation at an
oblique angle to illuminate a line on the surface, said beam and a
direction through the beam and normal to the surface defining an
incidence plane of the beam; at least one array of detectors
outside of the incidence plane; and a system imaging said line onto
the array of detectors, each detector in the array detecting light
from a corresponding portion of the line.
[0015] Yet another aspect of the invention is directed to an
apparatus for detecting anomalies and/or a surface feature on a
first and a second surface of an object, comprising means for
focusing a beam of radiation at an oblique incidence angle to
illuminate a line on the first surface, said beam and a direction
through the beam and normal to the first surface defining an
incidence plane of the beam, said line being substantially in the
plane of incidence of the beam; at least one array of detectors; a
system imaging said line onto the at least one array of detectors,
each detector in the at least one array detecting light from a
corresponding portion of the line; and means for detecting
anomalies and/or a surface feature of the second surface.
[0016] One more aspect of the invention is directed to an apparatus
for detecting anomalies and/or a surface feature on a first and a
second surface of an object, comprising means for focusing abeam of
radiation at an oblique angle to illuminate a line on the first
surface, said beam and a direction through the beam and normal to
the first surface defining an incidence plane of the beam; an array
of detectors outside of the plane of incidence; a system imaging
said line onto the array of detectors, each detector in the array
detecting light from a corresponding portion of the line; and means
for detecting anomalies and/or a surface feature of the second
surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a surface inspection system
to illustrate the preferred embodiment of the invention.
[0018] FIG. 2 is a top view of the system of FIG. 1.
[0019] FIG. 3 is a perspective view of the illumination portion of
a surface inspection system to illustrate an alternative embodiment
of the invention.
[0020] FIG. 4 is a graphical plot of a point spread function useful
for illustrating the operation of the systems of FIGS. 1 and 3.
[0021] FIG. 5 is a schematic view of a parallel array of charged
coupled devices (CCD) useful for illustrating the invention.
[0022] FIG. 6 is a schematic view of a light beam illuminating a
line on a surface and corresponding positions of detectors of an
array with respect to an imaging system along the line 6-6 in FIG.
2 to illustrate the operation of the system of FIGS. 1-3 in
response to height variation of the surface inspected.
[0023] FIG. 7 is a schematic view of the imaging optics, the CCD
detectors and a portion of the surface to be inspected of the
system of FIG. 1 taken along the line 7-7 in FIG. 2 to illustrate
the operation of the system of FIGS. 1-3 in response to height
variation of the surface to illustrate the invention.
[0024] FIG. 8 is a schematic view of the collection and imaging
optics in the system of FIG. 1.
[0025] FIG. 9 is a perspective view of a portion of a wafer
inspection system employing a cylindrical mirror for illustrating
another alternative embodiment of the invention.
[0026] FIG. 10 is a schematic view of a system for inspecting the
top and bottom surfaces of an object to illustrate another
embodiment of the invention.
[0027] FIG. 11 is a perspective view of the illumination portion of
a surface inspection system to illustrate still another alternative
embodiment of the invention.
[0028] For simplicity in description, identical components are
labeled by the same numerals in this application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] FIG. 1 is a perspective view of a surface inspection system
to illustrate the preferred embodiment of the invention. System 10
includes a cylindrical objective such as a cylindrical lens 12 for
focusing a preferably collimated light beam 14 to a focused beam 16
for illuminating, on surface 18 to be inspected, an area in the
shape of a line 20. Beam 14 and therefore also focused beam 16 are
directed at an oblique angle of incidence to the surface 18.
Different from the approach by Gara described above, line 20 is
substantially in the incidence plane or plane of incidence of
focused beam 16. In this context, the incidence plane of beam 16 is
defined by the common plane containing beam 16 and a normal
direction such as 22 to surface 18 and passing through beam 16. In
order for the illuminated line 20 to be in the focal plane of lens
12, cylindrical lens 12 is oriented so that its principal plane is
substantially parallel to surface 18. Image of the line is focused
by an imaging subsystem 30 to an array of detectors, such as a
linear array of CCDs 32. The linear array 32 is preferably parallel
to line 20.
[0030] In one embodiment particularly advantageous for detecting
small size anomalies, the imaging subsystem 30 has an optical axis
36 which is substantially normal to line 20 so that the center
portion of the linear CCD array 32 is in a plane substantially
normal to the incidence plane of beam 16. The optical axis 36 may
be oriented in any direction within such plane, including a
position directly above the line 20. In such event, array 32 would
also be directly above line 20. If desired, another array 32' shown
in dotted line in FIG. 2 may be placed in a position diametrically
opposite to array 32, where array 32' has optical axis 36' also
substantially normal to line 20. The two arrays together may be
useful to detect 45 degree line patterns.
[0031] The imaging subsystem 30 projects an image of a portion of
the line 20 onto a corresponding detector in the CCD array 32 so
that each detector in the array detects light from a corresponding
portion of the line 20. The length of the line 20 is limited only
by the size of the collimated input beam 14 and the physical
aperture of lens or lens combination 12. In order to control the
length of line 20, an optional expander 34 shown in dotted lines
may be used for controlling the diameter of beam 14 so as to
control the length of line 20.
[0032] FIG. 3 is a perspective view of an illumination portion of a
wafer inspection system to illustrate an alternative embodiment of
the invention. To simplify the diagram, the portion of the system
for collecting and projecting an image of the illuminated line onto
a detector array has been omitted. Instead of using a single
symmetrical lens, the embodiment in FIG. 3 employs two cylindrical
lenses 12' for tighter focusing, that is, focusing to a thinner
line. In FIG. 1, both the illumination and collection portions of
system 10 are stationary and surface 18 is rotated about a spindle
50 which is also moved along direction 52 so that line 20 scans
surface 18 in a spiral path to cover the entire surface. As shown
in FIG. 3, the surface 18' to be inspected can also be moved by an
XY stage 54 which moves the surface along the X and Y directions in
order for line 20 to scan the entire surface. Again, the
illumination and collection portions of system 10' of FIG. 3 remain
stationary. This is advantageous since it simplifies the optical
alignment in the system, due to the fact that there is
substantially no relative motion between the illumination portion
and the collection portion of the system.
[0033] FIG. 4 is a graphical illustration of the point spread
function of focused line 20 along the focused direction along any
point of the line. As shown in FIG. 4, the point spread function of
line 20 is Gaussian in shape, such as one which is produced if a
488 nm argon laser is used. Line 20 may also exhibit a varying
point spread function along line 20 with a peak at the center of
line 20. In order to avoid the variation of intensity along the
line, it may be desirable to expand the beam by means of expander
34 to a longer length such as 10 mm and only use the center or
central portion of the line, such as the central 5 mm of the line,
so that power variation along the imaged portion of the line is
insignificant. By means of an appropriate aperture in the imaging
subsystem described below, it is possible to control the portion of
the line imaged onto the array.
[0034] FIG. 5 is a schematic view of the linear CCD array 32. As
shown in FIG. 5, the array 32 has dimension d in a direction
parallel to the line 20, and W is the illumination line width. In
other words, the image of line 20 as projected onto array 32 by
subsystem 30 has a width of W. The pixel size of the inspection
system 10 is determined by the scan pitch p and the pixel size of
the detectors in the array 32 in a direction parallel to line 20,
or d. In other words, the pixel size is dp. Thus, assuming that the
useful portion of the illumination line projected onto the CCD
array 32 has a length of 5 mm, and the illumination line width W is
10 microns and array 32 has 500 elements with d equal to 10 microns
and the scan line pitch is 5 microns, the effective pixel size on
the wafer is 5 microns.times.10 microns, assuming that the image of
the line at the array has the same length as the line. In practice,
to avoid aliasing, at least two or three samples are taken in each
direction (along line 20 and normal to it) per effective optical
spot size on the sample surface. Preferably, reasonably high
quality lenses such as quality camera lenses are used, such as ones
having 5 mm field of view, giving a 30.degree. collection
angle.
[0035] From the above, it is seen that system 10 has high
sensitivity, since the effective "pixel" size is 5.times.10
microns, which is much smaller than that of Stonestrom et al. At
the same time, due to the fact that the whole line of pixels on the
surface 18 are illuminated and detected at the same time instead of
a single illuminated spot as in Stonestrom et al., system 10 also
has acceptable throughput. As noted above, the length of line 20 is
limited only by the size of the collimated beam 14 and the physical
aperture of lens or lens combination 12. Thus, assuming that the
stage 54 has a stage speed of 10 microns per 0.1 millisecond, for a
line scan rate of 10 kHz, the surface can be scanned at a speed of
100 mm per second. For a line 20 of 5 mm, the wafer surface is then
scanned at a speed of 5 cm.sup.2/sec.
[0036] System 10 is also robust and tolerant of height variations
and tilt of surface 18 and 18'. This is illustrated in reference to
FIGS. 1, 2, 5-7. FIG. 6 is a cross-sectional view of a portion of
the surface 18 along the line 6-6 in FIG. 2, focused beam 16 and
two images of the array 32 when the surface 18 is at two different
heights. FIG. 7 is a cross-sectional view of the CCD array 32,
imaging subsystem 30 and two positions of a portion of the surface
18 to be inspected along the line 7-7 in FIG. 2.
[0037] In reference to FIGS. 1, 2 and 6, the imaging subsystem 30
will also project an image of the CCD array 32 onto surface 18
overlapping that of line 20. This is illustrated in FIG. 6. Thus,
if surface 18 is in the position 18A, then imaging subsystem 30
will project an image 32A of the detector array on surface 18A, as
shown in FIG. 6. But if the height of the surface is higher so that
the surface is at 18B instead, then the imaging subsystem will
project an image of the detector array at position 32B. The longer
dimension of beam 16 is such that it illuminates both images 32A
and 32B of the array.
[0038] From FIG. 6, it will be evident that the image of a
particular detector in the array will be projected on the same
portion of the surface 18 irrespective of the height of the
surface. Thus, for example, the imaging subsystem 30 will project
the first detector in the array 32 to position 32A(1) on surface
18A, but to the position 32B(1) on position 18B of the surface as
shown in FIG. 6. The two images are one on top of the other so that
there is no lateral shift between them. In the reverse imaging
direction, an image of the same portion of surface 18 and,
therefore, of line 20 will be focused to two different positions on
the array 32, but the two positions will also be shifted only in
the vertical direction but not laterally. Hence, if the detectors
cover both positions, then the variation in height between 18A, 18B
of the surface will have no effect on the detection by array 32 and
the system 10, 10' is tolerant of vertical height variations of the
surface inspected.
[0039] One way to ensure that the array 32 covers the images of
line 20 on surface 18 at both positions 18A, 18B is to choose
detectors in array 32 so that the dimension of the detectors in the
vertical direction is long enough to cover such change in position
of the surface, so that different positions of a portion of the
line 20 will be focused by subsystem 30 onto the detector and not
outside of it. In other words, if the vertical dimension of the
detector is chosen so that it is greater than the expected height
variation of the image of the line caused by height variation of
the wafer surface, the change in wafer height will not affect
detection. This is illustrated in more detail in FIG. 7.
[0040] As shown in FIG. 7, the pixel height (dimension normal to
optical axis and line 20) of array 32 is greater than the change in
position of the image of line 20 caused by a change in wafer
surface height, so that the imaging optics of subsystem 30 will
project the same portion of the surface and line on the wafer
surface onto the same detector. Alternatively, if the pixel height
of the CCD array 32 is smaller than the expected change in position
of image of line 20 due to height variation in the wafer surface,
multiple rows of CCDs may be employed arranged one on top of
another in a two-dimensional array so that the total height of the
number of rows in the vertical direction is greater than the
expected height variation of the line 20 image. If this total
height is greater than the expected movement of the image of the
line in the vertical direction, then such two-dimensional array
will be adequate for detecting the line despite height variations
of the wafer surface. The signals recorded by the detectors in the
same vertical column can be simply added to give the signal for a
corresponding portion of the line 20.
[0041] Even if the height or vertical dimension of array 32 is
smaller than the expected height variation of the wafer surface,
the imaging optics of subsystem 30 may be designed so that the
change in height or vertical dimension of the projected image of
line 20 onto the CCD array is within the height of the CCD array.
Such and other variations are within the scope of the invention.
Thus, in order for system 10 and 10' to be tolerant of wafer height
variation, the image of the line at the array 32 is longer than the
array, and the extent of the height variations of the image of the
line 20 on the detector array is such that the projected image
still falls on the detector array.
[0042] Where a two-dimensional array of detectors is employed in
array 32, time delayed integration may also be performed to improve
signal-to-noise or background ratio, where the shifting of the
signals between adjacent rows of detectors is synchronized with the
scanning of the line 20 across surface 18.
[0043] FIG. 8 is a schematic view illustrating in more detail the
imaging subsystem 30 of FIGS. 1 and 2. Subsystem 30 preferably
comprises two identical lenses: lens 102 for collecting light from
line 20 and to perform Fourier transform, and lens 104 for imaging
the line onto the array 32. The two lenses 102, 104 are preferably
identical to minimize aberration. A filter and polarizer may be
employed at position 106 where line 20, position 106 and array 32
appear at focal points of the two lenses 102, 104 each having a
focal length f. Arranged in this manner, subsystem 30 minimizes
aberration. As noted above, a variable aperture may also be applied
at a number of positions in subsystem 30 to control the portion of
the line 20 that is focused onto array 32 by controlling the size
of the aperture.
[0044] Instead of using a cylindrical lens 12 as shown in FIGS. 1
and 2, a cylindrical mirror may be used as shown in FIG. 9. In
order for line 20 to appear in the focal plane of cylindrical
mirror 112, the mirror should be oriented so that the plane 112'
defined by and connecting the edges 112a, 112b of the mirror is
substantially parallel to surface 18 inspected. In general, any
cylindrical objective that has the effect of focusing a beam 14
onto a focused line on surface 18 may be used, where the focusing
power is applied only in the direction substantially normal to the
incidence plane defined by focus beam 16 and a normal 22 to surface
18 through the beam.
[0045] An alternative method of generating a line focus on the
sample is to use a cylindrical lens in the convention way, i.e.
with its principal plane perpendicular to the propagation direction
of the light beam 14, and placing a diffraction grating 252
immediately following the lens. The grating period is such that
main diffraction angle matches the desired illumination angle
range. The lens and the grating are held parallel to each other,
and to the sample surface 18. The grating line structure (or
grooves) are perpendicular to the focused line direction. The
grating, therefore, will only have the effect of redirecting the
light along the desired incidence angle. Although a variety of
different grating types can be used, it is preferable to use a
holographic type grating for its enhanced efficiency.
[0046] By placing array 32 outside of the plane of incidence of
beam 16 in a double dark field configuration, signal-to-noise or
background ratio is improved over prior designs. A double dark
field collector configuration is one where the optical axis of the
collector in the subsystem is perpendicular to the optical axis of
illumination and the collector lies outside the incidence plane.
However, in some applications, it may be desirable to place the
array in the incidence plane. Preferably, beam 16 is at an angle in
the range of about 45 to 85 degrees from a normal direction to
surface 18. In addition to detection of anomalies, the invention
can also be used to detect other surface features such as
markers.
[0047] The invention as described above may be used to provide a
viable alternate mechanism to inspect rough films, patterned or
unpatterned semiconductor wafers and backsides of wafers, as well
as photomasks, reticles, liquid crystal displays or other flat
panel displays. The system of this invention is compact, has a
simple architecture, and provides a relatively low cost alternative
for inspecting patterned wafers. Furthermore, because of the low
cost of the system of this invention, it may also be advantageously
used in conjunction with another surface inspection system for
inspecting two different surfaces of an object, as illustrated in
FIG. 10. Thus, as shown in FIG. 10, a system 200 may include a
front side inspection system 202 for inspecting the front side 204a
of the semiconductor wafer 204, and a system 206 (which may be
similar to that in FIGS. 1, 2 or 3) for inspecting the backside
204b of the wafer. If, as in the invention described above, the
illumination and light collection portions of the system remain
stationary and the surface 204b is inspected by moving the surface,
the two systems 202, 206 may need to be synchronized. System 202
may include a system such as that described above in reference to
FIGS. 1-3, or may be one of many different kinds of anomaly and
surface feature inspection systems. All such variations are within
the scope of the invention.
[0048] While the invention has been described by reference to
various embodiments, it will be understood that modification
changes may be made without departing from the scope of the
invention which is to be defined only by the appended claims or
their equivalents.
* * * * *