Apparatus for detecting the defect of pattern

• US 4,479,145 A
• Filed: 07/22/1982
• Issued: 10/23/1984
• Est. Priority Date: 07/29/1981
• Status: Expired due to Fees

• Current Assignee: Nippon Kotsu Kabushiki Kaisha (Nikon Corporation)
• Original Assignee: Nippon Kotsu Kabushiki Kaisha (Nikon Corporation)
• Inventors: Kawahara, Atsushi, Fujii, Norio, Azuma, Toru, Hazama, Junji, Hada, Kazunari
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US06/400,681
• Time in Patent Office: 824 Days
• Field of Search: 358/106, 358/107, 358/101, 382/8, 382/48
• US Class Current: 382/199
• CPC Class Codes: G01N 21/88 Investigating the presence of flaws or contamination
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

A pattern examining in which a pattern on an examined object such as reticle or mask is scanned to produce image binary signals of picture elements; binary information corresponding to a local area on the examined object is serially extracted from the image binary signals; and shape detection is effected for detecting by means of the binary information whether or not the pattern in the local area possesses a determined geometric shape or characteristics. The result of the shape detection is compared with the information on design relating to the geometric shape or characteristics which the pattern on the examined object should possess.

Claims

1. Apparatus for examining a pattern consisting of bright parts and dark parts formed on an examined object based upon design data, said apparatus comprising:

scanning means for scanning said pattern and producing binary signals according to the pattern;

first extracting means for serially extracting binary information corresponding to a determined area on said examined object from said binary signals;

first detection means for detecting a geometrical shape of the pattern in said determined area based on said binary information;

second detection means for detecting the edge portion between the bright part and the dark part of the pattern in said determined area;

second extracting means for extracting from said design data information relating to the geometrical shape which said pattern should have; and

examination means for producing defect information indicative of the presence or absence of any defect in the pattern in said determined area in response to said second detection means when the information extracted by said second extracting means and the information detected by said first detection means agree with each other.

6. Apparatus according to claim 1, wherein said first detection means includes means which detects a substantially corner shape from the pattern of said determined area.

2. Apparatus for examining a pattern on an examined object through the steps of scanning a geometric pattern formed on said object to obtain image signals corresponding to the pattern, detecting a geometrical shape of the pattern in a determined area on said object based on the image signals to produce detection information, and comparing said detection information with design data, said apparatus having improvements comprising:

means for forming said detection information, said means being adapted to detect a determined corner from the pattern in said determined area; and

encoding means for encoding said detected corner in such manner that one of two corners having the same angle and being point-symmetric to each other is given a first code and the other corner is given a second code.

7. Apparatus according to claim 2, wherein said forming means includes means detecting a corner having an angle of about 90 degrees and means detecting a corner having an angle of about 135 degrees.

3. In an apparatus for examining a pattern formed on an examined object having means for scanning said pattern to produce image binary information for transforming the image of said pattern into picture elements and means for producing design binary information for forming a binary image of the design of said pattern based on design data and wherein the characteristics of said pattern and the characteristics of said design that said pattern should possess are compared with each other based on said image binary information and said design binary information, the improvements comprising:

means for detecting, based on said design binary information, said characteristics of the design of said pattern which should appear on a scanning line of said scanning means and giving a determined binary code to the detected characteristics; and

memory means adapted to keep said binary code in memory every time the image of the pattern is transformed into a predetermined number of picture elements by said scanning means.

10. Apparatus according to claim 3, wherein said scanning means scans along plural scanning lines to cover a determined area of said pattern and said memory means includes at least one register means having a number of memory bits equal to the number of picture elements corresponding to one of said plural scanning lines divided by said predetermined number.

4. Apparatus for examining a geometrical pattern formed on an examined object comprising:

scanning means for scanning the original image of said pattern to produce image binary information of the picture elements of said original image;

memory means having memory units each corresponding to each picture element of said original image and able to store binary information in every memory unit, said memory means being capable of developing said stored binary images;

means for forming a design binary image which said original should have on design based on said design data;

means for forming an inhibition binary image for setting an examination inhibition area in said original image;

control means for selectively developing said design binary image and said inhibition binary image;

accumulation means for detecting predetermined characteristics of said pattern to be examined from said design binary image of said memory and accumulating the detected information; and

examination means for examining the defect of said pattern based on said image binary information and above detected information by said accumulation means and inhibiting said examination with reference to the inhibition binary image of said memory means.

5. Apparatus for examining a geometric pattern formed on an examined object said apparatus comprising:

scanning means for scanning the pattern in a determined area on said object to produce an image binary signal for converting the image of said pattern into picture elements;

image memory means provided with memory bits corresponding to the individual picture elements of said pattern image and for memorizing a bit pattern corresponding to said pattern image depending on the input of said image binary signal;

means for providing design data corresponding to the geometric pattern in said determined area;

moving means for moving said scanning means and said examined object relative to each other to set said determined area at any optional positon on said object; and

means for computing from said design data the position of the pattern which should be within said determined area, thereby detecting the deviation of said pattern position from the position of said bit pattern in said image memory means, and for controlling said moving means according to the deviation in such manner as to reduce the magnitude of the deviation to a value under a determined value.

8. Apparatus for examining a pattern on an examined object through the steps of scanning a geometric pattern formed on said object to obtain image signals corresponding to the pattern, detecting a geometrical shape of the pattern in a determined area on said object based on the image signals to produce detection information and comparing said detection information with design data, said apparatus having improvements comprising:

means for forming said detection information, said means being adapted to detect a determined corner from the pattern in said determined area; and

means which encodes said detected corner so that different binary codes may be provided between corners having different angles.

9. Apparatus according to claim 8, wherein said pattern consists of relatively bright parts and dark parts and wherein said encoding means provides the same binary codes if a corner formed by a portion of said bright parts and a corner formed by a portion of said dark parts are formed at the same position and at corresponding angles with respect to said determined area.