JPH1151616A - Defect inspecting instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an easier measurement of the dimension of a fine defect with a simple structure by estimating the dimension of the defect based on the quantity of light detected from scattered light generated from irradiation by an optical system and lighting systems which irradiate the defect on a substrate with light from a plurality of directions. SOLUTION: Power of light sources 13, 14 and 15 is turned on to open a shutter 16 by a signal of a signal processing circuit 26. Scattered light by the light source 13 is detected by a linear sensor 24. When a detect exists, the level of a signal and the intensity of light inputted increase. The shutter 16 is closed and a shutter 18 is opened to irradiate a substrate 7 with a laser light from the light source 14 and the scattered light is detected. The same is with the light source 15. The scattered light is detected by opening or closing a shutter 18. The characteristic of the scattered light is that the projection surface of the defect and the quantity of light detected is in a proportional relationship. Light condensed by an imaging lens 23 of a detection optical system 5 is detected by a linear sensor 24 of a signal processing system 6. The light detected is sent to an A/D converter 25 and the signal processing circuit 26 measures the size of the defect in the order of submicron on the substrate 7, based on the quantity of light detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for detecting a defect on a thin film substrate, and more particularly to a defect inspection method suitable for easily detecting a submicron-order minute defect with a simple structure. Related to the device.

[0002]

2. Description of the Related Art As a device for detecting the size of a defect on a thin film substrate, a prior art described in Japanese Patent Application Laid-Open No. 63-6924 discloses a method of judging the size of a defect from an output signal level of a detected light amount. .

[0003]

In the above-mentioned prior art JP-A-63-69244, the directivity of incident light with respect to a defect is not taken into consideration. Therefore, it was not possible to accurately calculate the size of the defect based on the amount of light detected from one direction.
Further, there is no patent that calculates the size and shape of a defect from the detected light amount.

[0004] The present invention solves the above-mentioned problems of the prior art.
It is an object of the present invention to provide a defect inspection apparatus capable of easily measuring the size of a fine defect on the order of submicron on a thin substrate with a simple configuration.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical system for irradiating light on a defect on a thin film substrate from a plurality of light sources, a scattered light generated by irradiation of each illumination system, and a detected light amount from diffracted light. Is solved by means for predicting the size of

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of one embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a defect inspection apparatus according to the present invention. The present apparatus includes an X stage 9 that can move the substrate 7 in the X direction by fixing the substrate 7 to the upper surface by the inspection stage unit 1 by the fixing means 8, and a Y stage 10 that moves the substrate 7 in the Y direction via the Y stage 10. X to move the substrate 7 in the X direction
It comprises a stage drive system 11 and a Y stage drive system 12 for moving the substrate 7 in the Y direction. Each stage is a substrate 7
During the inspection, the focus is always controlled to the required accuracy. The stage drive systems 11 and 12 may use an air micrometer or may detect the position by a laser interferometer. Note that X and Y are directions shown in the figure.

2 is a first illumination system, 3 is a second illumination system, 4
Is a third illumination system, each illumination system being independent and composed of the same components. 13, 14, and 15 are laser light sources, and each laser light source has the same wavelength, for example, 800 [nm].
And The illumination angles of the three light sources are the same. The laser light sources 13, 14, and 15 are irradiated on the substrate 7 at time intervals by shutters 16, 17, and 18. Reference numerals 19, 20, and 21 denote condensing lenses, which converge light beams emitted from the laser light sources 13, 14, and 15 and irradiate the substrate 7 with the light beams. In this case, care should be taken not to install the three light sources on the same straight line on the XY plane. The angle of each illumination system on the XY plane is not limited to 120 degrees.

Reference numeral 5 denotes a detection optical system.
And an image forming lens 23 provided near the image forming position of the objective lens 22 facing the image forming apparatus. Reference numeral 6 denotes a signal processing system which detects the light condensed by the imaging lens 23 with a linear sensor 24. The detected light is sent to the A / D converter 25, and the signal processing circuit 2
The defect size is measured from the detected light quantity by 6.

First, a method for irradiating a laser to a defect from three directions and calculating the defect size and shape from the detected light amounts will be described with reference to FIG. First, the light sources 13, 14, and 15 are turned on, and the shutter 16 is opened by a signal from the signal processing circuit. Shutters 17, 18 remain closed. The scattered light from the light source 13 is detected by the linear sensor 24. In this case, if a defect exists, the input signal level and light intensity increase. After detecting the scattered light from the light source 13 with the linear sensor 24, the shutter 16 is closed. Next, the shutter 17 is opened, and the substrate 7 is irradiated with a laser from the light source 14 to detect scattered light from the substrate in the same manner as the light source 13. Thereafter, the shutter 17 is closed by the signal of the signal processing circuit 26. For the scattered light of the light source 15, the shutter 18 is similarly opened and closed to detect the scattered light. As a characteristic of the scattered light, the projected area of the defect (the area of the object projected on a plane perpendicular to the optical axis of the illumination light) and the detected light amount are in a proportional relationship as shown in FIG. In FIG. 2, the X-axis is the projection area of the defect, and the Y-axis is the detected light amount. Even if the materials are the same, the refractive index differs depending on the wavelength of the incident light, so that the graph corresponding to the projected area and the detected light amount is different. Also, the graph of the correspondence between the projected area and the detected light amount differs depending on the illumination angle. That is, the material of the defect can be specified by the distribution of the defect, comparison with the conventional data, or the state of the process.
Of course, there are cases where it cannot be specified.

When the material of the defect is clear, the correspondence between the projected area of the defect and the detected light amount is clear as shown in FIG. Therefore, the projected area in each illumination direction can be calculated based on the detected light amounts from the light sources 13, 14, and 15. Further, the dimensions of the defect in the X, Y, and Z directions can be calculated based on the size of the projection area.

When the material of the defect is unknown, the correspondence between the detected light amount and the projected area is unknown. However, the ratio of the projected area of the defect can be calculated from the ratio of the detected light amount in each irradiation direction. This reveals the shape of the defect.

Referring to FIG. 3, a method of estimating a shape from a projected area of a defect will be described. As shown in FIG. 3, the defect shapes in (a) to (c) are predicted from the projection areas in the three orthogonal directions, for example, when the ratio of the projection areas in the three illumination directions is 4, 6, 1. In short, an elongated foreign object is specified. If the illumination direction is orthogonal to the component plane of the defect, it is clear that the feature amount is easily extracted by the detected light amount.

Next, a method of observing a defect from above with a monitor and then irradiating the defect with laser from two directions and measuring the defect size from the detected light quantity in each illumination direction will be described with reference to FIG. First, the configuration of FIG. 4 will be described. FIG. 4 shows a defect inspection apparatus according to the present invention. The apparatus includes an X stage 9 that can move the substrate 7 in the X direction by fixing the substrate 7 to the upper surface by the fixing means 8 by the inspection stage unit 1, a Y stage 10 that moves the substrate 7 in the Y direction, and An X stage drive system 11 moves the substrate 7 in the Y direction, and a Y stage drive system 12 moves the substrate 7 in the Y direction. During the inspection of the substrate 7, each stage is controlled so that it can always be focused with necessary accuracy.

The stage drive systems 11 and 12 may use an air micrometer or may detect the position by a laser interferometer. Note that X and Y are directions shown in the figure.

2 is a first illumination system, 3 is a second illumination system,
Each illumination system is independent and consists of the same components. Laser light sources 13 and 14 have the same wavelength, for example, 800 nm. The illumination angles of the two light sources are the same. The illumination light from the laser light sources 13 and 14 is applied to the substrate 7 at time intervals by shutters 16 and 17. Reference numerals 19 and 20 denote condensing lenses, which converge light beams emitted from the laser light sources 13 and 14, respectively, and irradiate the substrate 7 with the light beams. In this case, care must be taken not to install the two light sources on the same straight line on the XY plane. The angle of each illumination system on the XY plane is not limited to 90 degrees.

Reference numeral 5 denotes a detection optical system.
And an image forming lens 23 provided near the image forming position of the objective lens 22 facing the image forming apparatus. Reference numeral 6 denotes a signal processing system which detects the light condensed by the imaging lens 23 with a linear sensor 24. The detected light is sent to the A / D converter 25, and the signal processing circuit 2
According to 6, the defect size is measured from the detected light amount. 27 is an observation system. The defect is observed with the objective lens 28, and the image signal from the camera 29 is image-processed by the image processing device 33. Observation and positioning of the substrate are performed by the monitor 31. In order to illuminate the substrate 7, an illumination light 30 and a mirror 32 are provided. The captured image of the defect is observed from the camera 29 on the monitor 31.

Next, a method for measuring the size of a defect by illuminating the defect from two directions and detecting scattered light after observing the defect on the monitor 31 will be described with reference to FIG. First, the X stage 9 and the Y stage 10 are moved to focus on the surface of the substrate 7 by an automatic focusing mechanism (not shown). After that, the defect is focused while observing with the television camera 29 and the monitor 31. The dimensions on the XY plane are detected by the image processing device 33 based on the imaging signal captured by the television camera 29.

Next, the light sources 13 and 14 are turned on, and the shutter
Open 16 and irradiate defects with laser. After detecting the amount of scattered light from the linear sensor 24, the shutter 16 is closed. Next, the shutter 17 is opened. Similarly, the defect is irradiated with a laser to detect the amount of scattered light, and then the shutter 17 is closed.

When the material of the defect is clear, the correspondence between the projected area of the defect and the detected light amount is clear as shown in FIG.
Therefore, the projection area can be calculated from the detected light amount. At this time, the projection area of the defect can be calculated even in one illumination direction. The dimension in the Z direction is calculated from the dimensions in the X and Y directions on the XY plane and the size of the projection area detected earlier. As a result, the size and shape of the defect in the X, Y, and Z directions can be detected.

If the material of the defect is unknown, the correspondence between the projected area of the defect and the detected light amount is unknown. However, from the detected light amounts from two directions and the dimensions in the X and Y directions on the XY plane detected earlier, the coefficients of the graph of the corresponding data of the detected light amount and the projected area as shown in FIG. 2 and the dimensions in the Z direction are calculated. it can. As a result, the size and shape of the defect in the X, Y, and Z directions can be detected.

With the above method, the feature amount of a defect, that is, the size and shape can be calculated. Needless to say, the range of defect sizes that can be calculated is limited by the characteristics of scattered light.

[0022]

As described above, according to the method and apparatus of the present invention, it is possible to easily inspect the size of defects on the order of submicrons on a circuit board, thereby improving the product yield and reducing the manufacturing cost. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a defect inspection apparatus according to a first embodiment.

FIG. 2 is a characteristic diagram showing correlation data between a detected light amount and a projection area of a defect.

FIG. 3 is a diagram showing a projection area and a defect shape of a defect.

FIG. 4 is a configuration diagram of a defect inspection apparatus according to a second embodiment.

[Explanation of symbols]

1. Inspection stage part 2. First illumination system 3.
2nd illumination system, 4 ... third illumination system, 5 ... detection optical system, 6 ... signal processing system, 7 ... substrate,
8: fixing means, 9: X stage, 10: Y stage, 11: X stage drive system, 12: Y stage drive system, 13: light source, 14: light source,
15 ... Light source, 16 ... Shutter, 17 ... Shutter, 18 ... Shutter, 19 ... Condenser lens,
20: condenser lens, 21: condenser lens, 22: objective lens, 23: imaging lens, 24: linear sensor, 25: A / D converter, 26: signal processing circuit,
27: Observation system, 28: Objective lens, 29: Camera,
30 ... lighting, 31 ... monitor, 32 ... mirror, 33 ... image processing device.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroaki Shishido 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref.

Claims (2)

[Claims] 1. A defect inspection apparatus for detecting a defect on a thin film substrate, an inspection stage comprising a stage on which the substrate can be arbitrarily moved and a drive control system thereof, and irradiating the thin film substrate from a plurality of directions. An illumination system having an independent light source, a detection optical system that causes a detector to detect scattered light and diffracted light generated by irradiation of each illumination system, and a feature amount of a defect from the detector output for each direction of illumination. 1. A defect inspection apparatus, comprising: a signal processing system for performing a calculation. 2. A defect inspection apparatus according to claim 1, wherein the material data of the defect on the substrate is compared with the material correspondence data of the defect projection area and the detected light amount for each material. Defect inspection device that calculates the feature value of