Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
2000-06-19
2004-01-06
Mehta, Bhavesh M. (Department: 2625)
Image analysis
Applications
Manufacturing or product inspection
C382S147000, C382S173000, C348S130000
Reexamination Certificate
active
06674889
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pattern inspection method and a pattern inspection apparatus, and more particularly to pattern inspection method capable of performing a review and analysis without interrupting an inspection operation for fault information with regard to a prescribed pattern, and to an associated pattern inspection apparatus.
2. Description of the Related Art
In the past, in the process of manufacturing a semiconductor device, many processes have been used to form a pattern of a specific shape in a specific member.
In each of these processes, to ensure that the desired pattern satisfies pre-established conditions, it is necessary that a master pattern be precisely formed.
For this reason, whether or not the master pattern is precisely formed greatly affects the quality and performance of the final semiconductor product, and also influences an improvement in yield.
A general example of such a master pattern is in an electron beam exposure method, in which a reticule is used onto which are formed a plurality of patterns used when forming a desired pattern on a wafer, in which precision in the patterns formed on the reticule is important.
The problems involved in an example of a method of inspecting the patterns formed in a reticule are described below.
Specifically, in an LSI manufacturing process (patterning), a reticule is used to form a prescribed pattern on a semiconductor made of silicon or the like. If there is a pattern defect in the reticule itself, the defective pattern will be transferred to a large number of wafers, causing the manufacture of a large number of defective LSI devices, thereby making inspection of the reticule very important.
Visual inspection methods for a reticule used in LSI manufacturing include the die-to-die inspection method, in which the same pattern at different locations on a reticule are compared, and the die-to-database inspection method, in which a comparison is made between a reticule pattern and image data used to form the reticule pattern.
The term die used herein is used to indicate a pattern area including a certain number of patterns as a group used as an unit of a pattern comparison inspection or an a detected image thereof, while the term database used herein refers with respect to an actual pattern image data detected with an optical system, but rather to image data based on coordinate data, such as a reference image synthesized from CAD data or the like, for example.
A reticule inspection apparatus of the past was disclosed, for example, in the Japanese Unexamined Patent Publication (KOKAI) No. 10-185531, in Japanese Patent No. 2776416, and in the Japanese Unexamined Patent Publication (KOKAI) No. 4-365045.
Specifically, a reticule inspection apparatus of the past was generally formed by an XY stage for setting the reticule, an imaging optical system for forming a photoimage of the pattern of the reticule set on the XY stage to serve as a comparison image, an image input section for acquiring a photoimage that is the comparison image from the imaging optical system, a data conversion section that converts image data used in describing the reticule, such as CAD data, to a reference image, an image comparison section for comparing the comparison photoimage with the reference image so as to detect defects in the pattern, and a controller to perform overall control of the apparatus.
A reticule inspection apparatus of the past moved the stage onto which was set a reticule, and acquired one frame of pattern on the reticule using an imaging optical system and image input section, and sent the acquired image to the image comparison section.
The reference image is converted beforehand by the data conversion section to a reference image from, for example, CAD data, and is sent to the image comparison section in synchronization with the image.
At the image comparison section, a comparison is made between the image and the reference image, so as to detect defects.
A frame used in the above-noted prior art example is the unit of image that can be processed by the image comparison section at one time.
Compared to the time for acquisition of an image by the imaging optics system and image input section, the time for transfer from the image input section to the image comparison section, the time for conversion of the image data, and the time for image processing to detect defects are significantly long, so that in a reticule inspection apparatus of the past, even if the next frame of image is acquired by the image input section, unless the series of processing for defect detection in the previous frame is completed, it is not possible to transfer the next frame of image, thereby resulting in a waiting time.
For this reason, the stage movement speed is made slow, thereby delaying the image acquisition time so as to achieve adjustment of timing, but this results in the lengthening of the overall inspection time.
In the above-noted the Japanese Unexamined Patent Publication (KOKAI) No. 10-185531, in the above-noted technical constitution, in order to improve defect detection precision and shorten detection time, a method of dividing a laser beam is used. In the above-noted Japanese Patent No. 2776416, for the same purpose, a simulation means is adopted, and a comparison is made between the results of the simulation and an actually measured pattern image. In the Japanese Unexamined Patent Publication (KOKAI) No. 4-365045, the method adopted is that of using CAD data as reference data, and the above-noted problems remain basically unsolved.
Given the above, the inventors, in the Japanese Unexamined Patent Publication (KOKAI) No. 10-115049, proposed an improved technology as shown in FIG.
7
.
Specifically, when performing pattern inspection, inspection in each region is done by first moving an XY stage
3
, onto which is set a reticule
9
, to an inspection staring position.
Next, the XY stage
3
is fed in the X direction at a constant speed, as a laser scanning optical system scans in the Y direction each time a laser interferometer detects movement by a constant pitch, the transmitted light being detected by a transmitted light detection section
5
, and an optical image input distribution section
6
acquiring a two-dimensional image for each frame.
The acquired optical images are synthesized by image comparison sections
71
to
74
for each frame separately, a comparison is made with a reference image, and defect detection is performed. The term frame used herein refers to the image that can be processed at one time by the image comparison section.
In
FIG. 7
, the reference numeral 1 denotes a scanning controller, and 2 is an overall controller.
In a method of inspection employed with this type of inspection apparatus, division is made into a plurality of overlapping inspection regions with their long dimensions in the X direction, for example, as shown in
FIG. 3
, scanning being sequentially performed for each region, after which the defects for each region are combined so as to perform defect detection for the overall reticule.
In the above-noted method, although the problems with the prior art are significantly improved upon, there is still the problem in the case in which a large number of defects are detected in each inspection region, in which case a large amount of time is required by the controller in order to extract defect information from each channel, thereby causing a waiting time to occur before image acquisition for the next inspection region, which meant that the problem of the overall inspection requiring a long time remained not fully solved.
Additionally, in the case in which defects detected during inspection are reviewed in real time, it is necessary to interrupt inspection in order to search for defect images stored in the controller, thereby leaving the problem that the overall inspection time is long.
Accordingly, it is an object of the present invention, in order to improve on the above-noted drawbacks in the prior art, to provide a pattern inspec
Bayat Ali
Mehta Bhavesh M.
NEC Corporation
Sughrue & Mion, PLLC
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