JP2008216151A - Apparatus and method for inspecting surface pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection apparatus and a surface inspection method capable of improving accuracy in detecting boundary lines of patterns formed in the surface of an object to be inspected. <P>SOLUTION: The surface inspection apparatus is provided with (a) a light-emitting part 14 for irradiating luminous flux 15a to a surface 2a of an object to be inspected 2 from a diagonal direction and making an irradiating location 15s of the luminous flux 15a move linearly; (b) a light-receiving part for detecting the regularly reflected light 15b, that is regularly reflected at the irradiating location 15s and outputting signals; and (c) a pattern detecting part, including an inverted filter having a cross-sectional intensity distribution of the luminous flux 15a for detecting the boundary lines of the patterns formed in the surface of the object to be inspected, on the basis of signals after the signals, outputted by the light-receiving part, have passed through the inverted filter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface pattern inspection apparatus and a surface pattern inspection method, and relates to a surface pattern inspection apparatus and a surface pattern inspection method for optically detecting a pattern formed on the surface of an inspection object.

2. Description of the Related Art Conventionally, a surface inspection apparatus that inspects a surface by irradiating the surface of an inspection object with a light beam from an oblique direction and receiving regular reflection light from the surface has been proposed (for example, see Patent Document 1).
Japanese Patent Application Laid-Open No. 2005-201782

  Such a surface inspection apparatus has a pattern formed on the surface of the object to be inspected by the level of specularly reflected light from the surface fluctuating due to the difference in reflectance depending on the presence or absence of the pattern formed on the surface of the object to be inspected. Can be detected.

  However, the detection accuracy of the pattern boundary line is limited by the spot diameter of the light beam applied to the surface of the inspection object. For example, as shown in FIG. 5, in the case of the pattern 100 in which the reflectance changes stepwise, the amount of reflected light gradually changes when the light beam crosses the stepped boundary of the pattern. The waveform 102 is rounded, and the waveform gently changes near the boundary of the pattern. For this reason, variations in the position detection of the boundary line of the pattern formed on the surface of the object to be inspected occur, and the minimum detectable size (decomposition capability) for the pattern width and the interval between patterns is practically the spot diameter of the light beam. It is difficult to make it smaller than about twice.

  In view of such circumstances, the present invention intends to provide a surface pattern inspection apparatus and a surface pattern inspection method capable of improving the detection accuracy of a boundary line of a pattern formed on the surface of an inspection object.

  In order to solve the above-described problems, the present invention provides a surface pattern inspection apparatus configured as follows.

  The surface pattern inspection apparatus includes: (a) a light emitting unit that irradiates a surface of an inspection object with a light beam from an oblique direction and moves the irradiation position of the light beam linearly; and (b) a regular reflection that is regularly reflected at the irradiation position. A light receiving unit that detects light and outputs a signal; and (c) an inverse filter corresponding to a cross-sectional intensity distribution of the light beam, and the signal output from the light receiving unit is based on the signal after passing through the inverse filter. And a pattern detection unit for detecting a boundary of a pattern formed on the surface of the inspection object.

  In the above configuration, the surface of the inspection object can be continuously inspected by moving the inspection object relative to the light emitting unit and the light receiving unit.

  According to the above configuration, when the light beam crosses the boundary line of the pattern formed on the surface of the object to be inspected, the intensity of the specularly reflected light received by the light receiving unit is gentle corresponding to the cross-sectional intensity distribution of the light beam. Change. Such a gentle change is caused by correcting the signal output from the light receiving section through an inverse filter corresponding to the cross-sectional intensity distribution (for example, Gaussian distribution) of the light beam, thereby correcting the actual reflectance of the surface of the object to be inspected. It is possible to follow changes more accurately. Thereby, the detection accuracy (resolution) of the boundary line of the pattern formed on the surface can be improved.

  Moreover, in order to solve the said subject, this invention provides the surface inspection method comprised as follows.

  The surface inspection method includes (1) a first step of irradiating the surface of the object to be inspected with a light beam from an oblique direction and moving the irradiation position of the light beam linearly, and (2) a positive reflection that is regularly reflected at the irradiation position. A second step of detecting the reflected light and outputting a signal; and (3) based on the signal after passing the signal output in the second step through an inverse filter corresponding to the cross-sectional intensity distribution of the luminous flux. And a third step of detecting a boundary of a pattern formed on the surface of the inspection object.

  In the above method, the surface of the inspection object can be continuously inspected by moving the inspection object relative to the light emitting unit and the light receiving unit.

  According to the above method, when the light beam crosses the boundary line of the pattern formed on the surface of the object to be inspected, the intensity of the specularly reflected light received by the light receiving unit is gentle corresponding to the cross-sectional intensity distribution of the light beam. Change. Such a gentle change is caused by correcting the signal output from the light receiving section through an inverse filter corresponding to the cross-sectional intensity distribution (for example, Gaussian distribution) of the light beam, thereby correcting the actual reflectance of the surface of the object to be inspected. It is possible to follow changes more accurately. Thereby, the detection accuracy (resolution) of the boundary line of the pattern formed on the surface can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the detection accuracy of the boundary line of the pattern formed in the surface of to-be-inspected object can be improved.

  Hereinafter, examples of the present invention will be described with reference to FIGS.

  As shown in the perspective view of FIG. 1, the surface inspection apparatus 10 irradiates the surface 2a of the inspection object 2 conveyed in the direction shown by the arrow 3 by the conveyance apparatus 4 with a laser beam 15a from the light emitting unit 14. The reflected light 15 b is incident on the light receiving unit main body 16.

  The light emitting unit 14 moves the laser beam 15a in a substantially fan shape as indicated by an arrow 15p. The irradiation position 15 s of the laser beam 15 a moves linearly on the surface 2 a of the inspection object 2. The light receiving unit main body 16 is arranged in parallel so as to face the linear irradiation position 15s.

  As indicated by reference numerals 13 and 19, the control unit 12 is connected to the light emitting unit 14 and the photodetector 18, and the light emitting unit 14 irradiates the received light amount of the regular reflection light 15 a detected by the photodetector 18. By performing signal processing in association with the irradiation angle 15p of the laser beam 15a, the position of the defect is specified. The control unit 12 includes an inverse filter 19 (FIG. 3) described later, performs signal processing according to a predetermined program, and a pattern 2x (FIG. 3) formed on the surface 2a of the inspection object 2 based on the signal after blur correction. 2) and the quality of the pattern 2x, such as the width and shape, is determined.

  As schematically shown in FIG. 2, which is a cross-sectional view taken along the line AA in FIG. 1, the laser beam 15a is a parallel light flux having a cross-sectional intensity distribution 15p substantially equal to a Gaussian distribution, and a desired spot diameter. (For example, 20 μm). The cylindrical light receiving unit main body 16 is formed with a light receiving window 16a extending linearly so as to face the irradiation position 15s, and the laser beam 15a is regularly reflected by the irradiation position 15s of the surface 2a of the object 2 to be inspected. The light 15b passes through. A substantially columnar light guide 17 is disposed inside the light receiving unit main body 16 so that specularly reflected light 15b passing through the light receiving window 16a is incident thereon.

  A light detector 18 (see FIG. 1) is disposed opposite one end of the light guide 17 so that light incident on the light guide 17 is emitted from one end of the light guide 17 and light emitted from one end of the light guide 17. The intensity is detected by the photodetector 18.

  Although it is preferable to use a photomultiplier tube (photomal) having a very good S / N characteristic for the photodetector 18, it is not limited to this.

  A light detector may be provided at the other end of the light guide 17 so that the outputs of both light detectors are added together.

  The inspection object is, for example, a glass substrate before assembly of a liquid crystal panel or a plasma display, and is inspected in a state where a pattern 2x such as a circuit is formed on the surface 2a.

  Next, the principle of inspection by the surface inspection apparatus 10 will be described.

  The surface 2a of the object to be inspected 2 has a different reflectance between a portion where the pattern 2x is formed and a portion where the pattern 2x is not formed. Therefore, the level of the output signal from the photodetector 18 is also different between the portion where the pattern 2x is formed and the portion where the pattern 2x is not formed.

  As schematically shown in the block diagram of FIG. 3, when the laser beam scans the surface of the object to be inspected and crosses the pattern 2x, the reflectance 20 changes stepwise. However, the light-receiving signal 22 that enters the light-receiving unit main body 16 from the light-receiving window 16a and is output from the photodetector 18 (see FIG. 2) is not stepped, but has a slanted waveform near the boundary, and the boundary is blurred. (Blurred). This is because the laser beam spot has a certain area. By inputting the light reception signal 22 to the inverse filter 19, bleeding can be corrected.

  That is, as shown in the frequency characteristic graph of FIG. 4, the frequency characteristic 21 of the step-like pattern change is constant, but the gain of the frequency characteristic 23 of the received light signal decreases as the frequency increases. Therefore, when the received light signal is corrected (equalized), the corrected frequency characteristic 26 improves the gain on the high frequency side. At this time, it is preferable to correct using a Gaussian inverse filter that substantially corresponds to the cross-sectional intensity distribution of the laser beam.

  As shown in FIG. 3, the signal 24 corrected by the inverse filter 19 has a waveform with sharp rising and falling edges. If the blurring of the pattern boundary line is corrected using the inverse filter 19, the detection accuracy of the pattern boundary line can be improved. As a result, the detection limit of the pattern width or the interval between patterns can be improved, for example, to the same extent as the spot diameter of the laser beam or more.

  <Summary> In the surface inspection described above, it is possible to improve the detection accuracy of the boundary line of the pattern formed on the surface of the inspection object by correcting the blur of the received light signal using an inverse filter.

  In addition, this invention is not limited to the said embodiment, It is possible to implement in various aspects.

  For example, the present invention can also be applied to an opaque object if the reflectance of the pattern formed on the surface is different from that of other portions of the surface.

It is a perspective view of a surface inspection apparatus. (Example) It is a principal part expanded sectional view of a surface inspection apparatus. (Example) It is a block diagram of a surface inspection apparatus. (Example) It is a graph of a frequency characteristic. (Example) It is a graph of a frequency characteristic. (Conventional example)

Explanation of symbols

10 Surface inspection device 12 Control unit (determination unit)
14 Light Emitting Unit 15a Laser Beam (Flux)
15b Regular reflection light 16 Light-receiving part body (light-receiving part)
17 Light guide (light receiving part)
18 Light detector (light receiving part)

Claims (2)

A light emitting unit that irradiates the surface of the inspection object with a light beam from an oblique direction and moves the irradiation position of the light beam linearly;
A light receiving unit that detects the specularly reflected light regularly reflected at the irradiation position and outputs a signal;
A boundary of a pattern formed on the surface of the object to be inspected based on a signal after including the inverse filter corresponding to the cross-sectional intensity distribution of the light beam and passing the signal output from the light receiving unit through the inverse filter A pattern detection unit for detecting
A surface pattern inspection apparatus comprising: A first step of irradiating the surface of the inspection object with a light beam from an oblique direction and moving the irradiation position of the light beam linearly;
A second step of detecting the specularly reflected light specularly reflected at the irradiation position and outputting a signal;
The boundary of the pattern formed on the surface of the object to be inspected is detected based on the signal after passing the signal output in the second step through an inverse filter corresponding to the cross-sectional intensity distribution of the light beam. A third step;
A surface pattern inspection method comprising:

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