Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Reexamination Certificate
2000-03-21
2001-09-25
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
C356S237400
Reexamination Certificate
active
06295126
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inspection apparatus for foreign matter and pattern defects which is used in the process of manufacturing semiconductor devices.
2. Description of the Background Art
FIG. 12
is a perspective view of a prior art inspection apparatus for foreign matter and pattern defects which is disclosed in Japanese Patent Application Laid-Open No. P11-51622A (1999).
A foreign matter inspection apparatus
10
P comprises an inspection illumination device
20
P for directing inspection light (laser light)
21
P angularly toward a wafer
1
P, and a scattered light detector
34
P for detecting resultant scattered light
31
P from the wafer
1
P under dark field illumination, thereby determining the coordinate position of foreign matter
5
P. The foreign matter inspection apparatus
10
P further comprises a reflection type illumination device
40
P and an image pickup device
45
P. The image pickup device
45
P photographs the coordinate position of the foreign matter
5
P determined by a foreign matter judgement device
35
P based on the detection of the scattered light detector
34
P under bright field illumination provided by the reflection type illumination device
40
P. The foreign matter inspection apparatus
10
P extracts a foreign matter image, based on the photograph, and then specifies the size, shape, color, and property of the foreign matter, based on the extracted foreign matter image.
In
FIG. 12
, the reference character
2
P designates a first main surface;
3
P designates an orientation flat;
4
P designates a pellet;
11
P designates a stage device;
12
P designates an XY table;
13
P designates a &thgr; table;
14
P designates a controller;
22
P designates a laser light irradiating device;
23
P designates a condensing lens;
30
P designates a scattered light detecting device;
32
P designates an objective lens;
33
P designates a relay lens;
41
P designates white light;
42
P designates a white light irradiating device;
43
P designates a half mirror;
44
P designates a lens;
46
P designates an image processor;
47
P designates a comparator;
48
P designates a verifier; and
49
P designates a classifier.
Foreign matter and defects are of a variety of types. For example, some foreign matter affects yields, and some foreign matter does not affect yields. Some objects look like foreign matter or defects, but actually are, for example, grain patterns such as an elongated grain boundary of an aluminum film and scratches resulting from a chemical-mechanical polishing (CMP) process.
However, the use of the image pickup device
45
P for inspection for foreign matter and defects sometimes requires very long time. First, the image pickup device
45
P performs focusing and magnifying actions to photograph the surface of the wafer
1
P, thereby detecting surface information (a microscope image) from the wafer
1
P. Next, the foreign matter inspection apparatus
10
P extracts image information regarding foreign matter and defects from the microscope image photographed by the image pickup device
45
P to identify foreign matter and defects. If numerous, e.g. thousands of to tens of thousands of, pieces of foreign matter and defects are detected, the above described operations require quite long time and impractical, and it is very difficult to grasp an overview of all of the foreign matter and defects within a predetermined length of time. Additionally, the microscope image is an image of the wafer
1
P as viewed from above and shows only the plan configuration of the foreign matter and defects. This makes it difficult to judge whether or not the identified foreign matter and defects affect the yields.
Another method of identifying the foreign matter and defects on the wafer surface uses laser light. Laser light directed onto the wafer and scattered therefrom is detected for detection of surface information from the wafer. This method does not require the focusing and magnifying actions to detect the surface information from the wafer accordingly more quickly than the technique employing the image pickup device
45
P. This shortens the time required for inspection for the foreign matter and defects. However, this method is disadvantageous in that the light scattered from a pattern defect, a fine foreign particle and a scratch-type defect is low in intensity, resulting in decreased sensitivity of detection of these defects or, in some cases, failure to detect these defects.
As described above, the method employing the microscope and the method employing the laser light have both advantages and disadvantages and present great difficulties in effectively distinguishing the above-mentioned types of foreign matter and defects from each other, based on the wafer surface information.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, an apparatus for inspecting a semiconductor wafer surface for defects and foreign matter comprises: an optical portion including a microscope illumination optical system for acquiring an image of the semiconductor wafer surface by using microscope illumination to detect the semiconductor wafer surface in the form of a piece of first surface information, and a laser scattering type optical system for detecting scattered laser light from the semiconductor wafer surface by using laser light to detect the semiconductor wafer surface in the form of a piece of second surface information; and an analyzer for detecting a plurality of pieces of defect/foreign matter information from the piece of first surface information and the piece of second surface information to categorize the plurality of pieces of defect/foreign matter information into three modes comprised of a first mode containing pieces of defect/foreign matter information represented only in the piece of first surface information, a second mode containing pieces of defect/foreign matter information represented only in the piece of second surface information, and a third mode containing pieces of defect/foreign matter information represented in both the piece of first surface information and the piece of second surface information.
Preferably, according to a second aspect of the present invention, in the apparatus of the first aspect, the analyzer further categorizes the pieces of defect/foreign matter information contained in the third mode into three modes comprised of a fourth mode containing pieces of defect/foreign matter information in which a first defect/foreign matter size represented in the piece of second surface information is greater than a second defect/foreign matter size represented in the piece of first surface information, a fifth mode containing pieces of defect/foreign matter information in which the first defect/foreign matter size is approximately equal to the second defect/foreign matter size, and a sixth mode containing pieces of defect/foreign matter information in which the first defect/foreign matter size is smaller than the second defect/foreign matter size.
Preferably, according to a third aspect of the present invention, in the apparatus of the second aspect, the analyzer counts the number of pieces of defect/foreign matter information contained in the fourth mode.
According to a fourth aspect of the present invention, an apparatus for inspecting a semiconductor wafer surface for defects and foreign matter comprises: an optical portion for detecting the semiconductor wafer surface in the form of a piece of surface information; and an analyzer for detecting a plurality of pieces of defect/foreign matter information each including a horizontal dimension, a vertical dimension and the area of a defect/foreign matter from the piece of surface information to calculate a predetermined elongation factor indicating a degree to which each defect/foreign matter is elongate from the horizontal dimension, the vertical dimension and the area thereof.
Preferably, according to a fifth aspect of the present invention, in the apparatus of the fourth aspect, the elongation factor equal
Miyazaki Yoko
Mugibayashi Toshiaki
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pham Hoa Q.
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