JPH08167638A - Pattern inspection apparatus and method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a pattern inspection device capable of optically automatically classifying defects obtained by the pattern inspection device. An illuminating means for illuminating a target field of view substantially uniformly through an objective lens, an image detecting means for converting reflected light from the target object into an image by photoelectric conversion, the detected image and a reference image. Image comparing means, an illuminating means for illuminating an object from outside the numerical aperture of the objective lens, an image detecting means by photoelectric conversion of scattered light from the object, and a defect type from these two images A pattern inspection apparatus comprising a classifying means. [Effect] It is possible to provide a pattern inspection apparatus capable of simultaneously detecting a pattern defect and a foreign substance, and comparing these data to discriminate the pattern defect and the foreign substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus for inspecting a circuit pattern formed on a wafer,
In particular, the present invention relates to an image detection method optimal for highly sensitive detection of fine defects generated on a circuit pattern or highly accurate measurement of circuit pattern dimensions, and a pattern inspection apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in LSI manufacturing, a circuit pattern formed on a wafer has been miniaturized in response to the need for high integration. The detection of minute defects in the circuit pattern was very important in determining the quality of the circuit pattern formation. Further, the foreign matter adhered to the circuit pattern becomes a defect in the pattern manufactured in the next step, so that detection of the foreign matter was also important.

Therefore, various proposals have been made for the detection of minute defects in circuit patterns and foreign substances. For example, two images that have been formed to have the same pattern are detected, alignments are compared, and inconsistencies between these images are determined as defects in a pattern inspection. The amount of positional deviation of the image is detected, and the positional deviation correction of these images is made dependent on the positional deviation of the image up to the previous time.

The above method is an excellent method in which false detection of a normal portion as a defect, which occurs when there is a small circuit pattern density or a large pattern defect, is significantly reduced and the reliability of inspection is improved. Related to this,
There is a technique described in JP-A-5-6928.

On the other hand, in the foreign matter inspection, focusing on the fact that the shape of the foreign matter is complicated, it is illuminated obliquely, and the scattered light from the pattern of the scattered light from the wafer is removed using a spatial filter or the like. Some foreign substances are detected by detecting only scattered light generated from the foreign substances.

[0006]

The circuit pattern defect and foreign matter obtained by the above means have been measured by different devices. Further, since foreign matter may be included in the result of circuit pattern failure, it is necessary to discriminate between these in order to find out the cause of generation of the circuit pattern failure or foreign matter, but the inspection device is different in the conventional method. Since they cannot be detected at the same time, and the data obtained from the two devices have an error due to a difference in stage accuracy or the like, accurate discrimination cannot be performed. Further, there is a deep correlation between the circuit pattern defect and the foreign matter, but the conventional method could not check the accurate correlation due to the difference in the accuracy of the stage.

[0007]

In order to solve the above-mentioned problems, in the present invention, an illuminating means for illuminating the object almost uniformly in the detection visual field through an objective lens and a reflected light from the object are photoelectrically converted. An image detecting means for converting the image and a comparing means for comparing the detected image with the reference image, an illuminating means for illuminating an object from an angle larger than the numerical aperture of the objective lens, and a pupil position of the objective lens. A spatial filter is provided at a conjugate position, and a pupil visual field image detection means for photoelectrically converting scattered light from the object is provided. Further, the images obtained by these two detecting means are compared to discriminate the type of defect.

[0008]

According to the structure of the present invention, the pattern defect obtained by the image comparison means and the foreign matter obtained by the pupil visual field image detection means are measured at the same time. Foreign matter can be discriminated and further correlation is required.

[0009]

Embodiments of the pattern inspection apparatus and method according to the present invention will be described below.

FIG. 1 is a block diagram of a pattern inspection apparatus in a pattern inspection method using an annular illumination according to an embodiment of the present invention. 1 is an LSI wafer for pattern inspection, 2 is an XYZ stage for mounting the LSI wafer,
3 is a light source lamp house, 4 is a collimator lens, 5 is an aperture stop, 6 is a field stop, 7 is a condenser lens, 8 is a beam splitter, 9 is a dichroic mirror, 10 is an autofocus unit, and 11 is an objective. Lens, 12a
Is a pupil plane of the objective lens, 13 is a dark field illumination light source, 14 is a collimator lens, 15 and 16 are mirrors, 17 is a condenser lens, 18 is a beam splitter, 19 is a pupil imaging lens,
20 is a wavelength selection filter, 21 is an image sensor, 22
Is an imaging lens, 23 is a dichroic mirror, 24 is a pupil imaging lens, 12b is a spatial filter at a position conjugate with the pupil plane of the objective lens, 25 is an imaging lens, 26 is an image sensor, 27 is a zoom lens, 28 Is an image sensor,
29 is a stage driver, 30 is an A / D converter, 31 is a spatial filter moving mechanism, 32 is an A / D converter, 33 is a foreign matter detection circuit, 34 is an A / D converter, 35 is a delay memory,
36 is an edge detector, 37 is a comparison circuit, 38 is a CPU,
Reference numeral 39 is a comparison circuit, 40 is a pattern defect output, 41 is a particle defect output, and 42 is a pattern defect and particle defect discrimination output.

In FIG. 1, light from the lamp house 3 is generated by collimating the LSI wafer 1 mounted on an XYZ stage 2 (θ stage not shown), collimator lens 4, aperture stop 5, field stop 6, condenser. Illumination is performed via the lens 7, the beam splitter 8, the dichroic mirror 9, and the objective lens 11.

The reflected light of the illumination light from the LSI wafer 1 is detected by an image sensor 28 via a beam splitter 18, an imaging lens 22, a dichroic mirror 23, and a zoom lens 27.

The illumination is so-called Koehler illumination without uneven illumination. Although not shown, focusing is performed so that the image of the reflected light from the LSI wafer 1 is clearly formed on the image sensor 28.

A two-dimensional image is obtained by scanning with the image sensor 28 while moving the X stage on which the LSI wafer 1 is placed. In this case, the X stage may be moved by continuous feed, step feed, or repeat feed.

The output of the image sensor 28 is A / D converted by an A / D converter 34, and the obtained image signal is compared with a reference image by a comparison circuit 37 via a delay memory 35 to detect a mismatch as a defect. Pattern defect output 40
Is output.

In FIG. 1, the image sensor 21 is a pupil monitor for detecting information on the pupil plane 12a of the objective lens 11 through the lens 11 during dark field illumination. The pupil plane 12a is the image-side focal plane of the objective lens, the position of the aperture stop,
Alternatively, it is called the Fourier spectrum plane.
The light emitted from the illumination light source 13 for dark field illumination passes through the collimator lens 14, the mirrors 15 and 16, and the condenser lens 17 from the angle direction larger than the numerical aperture of the objective lens 11 to obtain the LS.
Illuminate the I-wafer 1. The light scattered by the LSI wafer 1 passes through an objective lens, a dichroic mirror 9, a beam splitter 8, a beam splitter 8, a pupil imaging lens 19, and a wavelength selection filter 20, and a pupil image is detected by an image sensor 21. The detected image of the pupil plane 12a on the image sensor 21 is A / D converted by the A / D converter 30, and the image is taken into the CPU 38 for Fourier transform image analysis, edge density determination, and pupil plane condition control. .

The edge detector 21 is an image sensor 21.
The pattern edge of the image detected by the A / D converter 3
The detected edge information is fetched by the CPU 38.

The image sensor 26 detects foreign matter information on the LSI wafer 1 during illumination of the pupil visual field.
Beam splitter 1 of scattered light from LSI wafer 1
The light passing through 8 passes through the imaging lens 22, the dichroic mirror 23, the pupil imaging lens 25, the spatial filter 12b, and the imaging lens 25, and the image sensor 21 detects the image of the LSI wafer 1.

Here, in the CPU 38, a spatial filter shape for blocking the diffracted light from the pattern is set according to the pattern to be inspected, based on the information detected by the image sensor 21 which is the pupil monitor of the objective lens 11, and the space is set. A desired filter is set by the filter moving mechanism.
As a result, the scattered light from the pattern is removed to the image sensor 26, so that only the confusion light from the foreign matter reaches the image sensor 26. Therefore, only the foreign matter is detected, this image is A / D converted by the A / D converter 32, and the foreign matter information output 40 is output by the foreign matter detection circuit 33.

The comparison circuit 39 discriminates the foreign matter of the pattern defect from the foreign matter detected by the foreign matter detection circuit 33 and the pattern defect information detected by the comparison circuit 37. The foreign matter and pattern defect information is sent from the foreign matter detection circuit 33 and the comparison circuit 37 to the comparison circuit 39. Here, the defect coordinates are collated to discriminate the defect type. Then, the pattern defect / foreign substance defect discrimination output 42 is output. Further, a correlation can be obtained by comparing the foreign matter data of the previous process with the pattern defect data obtained in this process.

FIG. 2 shows the wavelength of light used for pattern defects, foreign matters, and autofocus. Since the wavelength range 50 used for pattern defect inspection, the wavelength range 51 used for autofocus, and the wavelength range 52 used for foreign matter inspection are independent, for example, if the characteristics of the dichroic mirror 9 are as shown in FIG. The light is applied to the LSI wafer 1, but the image sensors 21, 26, 26
28, but only the autofocus unit 10 is reached. Further, if the characteristic of the dichroic mirror 23 is as shown in FIG. 4, the light used for the foreign matter inspection and the light used for the pattern defect inspection can be separated by the dichroic mirror 23.

FIG. 5 shows a dark field illumination system, in which the illumination light 53 is condensed on the LSI wafer 1 by the condenser lens 17. The mirror 16 can be moved up and down as shown in FIG. 6, whereby the irradiation angle of the illumination light 53 onto the LSI wafer 1 can be arbitrarily changed, and the distance between the lens 17 and the LSI wafer 1 is the focal length of the lens 17. The irradiation position does not change by making the structure equal to. Also,
As shown in FIG. 7, when irradiated from an angle θ, the LSI wafer 1
The irradiation light 53 becomes an ellipse like 54, and the length L at this time is represented by the following equation.

[0023]

[Equation 1]

The width 2w of the light at this time is defined by the beam waist of the irradiation light 53 (FIG. 8)

[0025]

[Equation 2]

Is equal to twice. For example, when the field of view of the objective lens is 1 mm, θ is 85 °, the focal length of the condenser lens 17 is 100 mm, and the wavelength of the irradiation light 53 is 780 nm.
Then, if R is set to 0.57 mm, oblong illumination with a length of 1 mm is realized.

[0027]

As described above, according to the configuration of the present invention, the pattern defect and the foreign substance can be detected at the same time, and the pattern defect and the foreign substance can be discriminated by comparing these data. A pattern inspection device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a pattern inspection apparatus equipped with a pattern defect inspection and a foreign matter inspection.

FIG. 2 is a diagram showing a wavelength range of light used for pattern defect inspection, foreign matter inspection, and autofocus.

FIG. 3 is a diagram showing wavelength characteristics of the dichroic mirror 9.

FIG. 4 is a diagram showing wavelength characteristics of the dichroic mirror 23.

FIG. 5 is a schematic sectional view showing a dark field illumination system.

FIG. 6 is a schematic cross-sectional view showing an irradiation angle of irradiation light onto a wafer when a mirror is moved.

FIG. 7 is a schematic sectional view showing the spread of irradiation light on a wafer.

FIG. 8 is a schematic sectional view showing a beam waist.

[Explanation of symbols]

1 ... LSI wafer for pattern inspection, 2 ... L
XYZ stage for mounting SI wafer, 3 ... Lamp house for light source, 4 ... Collimator lens, 5 ... Aperture stop, 6 ... Field stop, 7 ... Condenser lens, 8 ... Beam splitter, 9 ... Dichroic mirror, 10 ... Autofocus unit, 1
1 ... objective lens, 12a ... pupil plane of objective lens,
13 ... Dark field illumination light source, 14 ... Collimator lens, 15 ... Mirror, 16 ... Mirror, 17 ...
Condensing lens, 18 ... Beam splitter, 19 ...
Pupil imaging lens, 20 ... Wavelength selection filter, 21 ...
… Image sensor, 22 …… Imaging lens, 23 ……
Dichroic mirror, 24 ... Pupil imaging lens, 12
b ... Spatial filter at a position conjugate with the pupil plane of the objective lens, 25 ... Imaging lens, 26 ... Image sensor, 27 ... Zoom lens, 28 ... Image sensor, 29 ... Stage driver, 30 ... ... A / D converter, 31 ... spatial filter moving mechanism, 32 ... A
/ D converter, 33 ... Foreign matter detection circuit, 34 ... A / D
Converter, 35 ... Delay memory, 36 ... Edge detector, 37 ... Comparison circuit, 38 ... CPU, 39 ...
Comparison circuit, 40 ... Pattern defect output, 41 ... Foreign matter defect output, 42 ... Pattern defect, foreign matter defect discrimination output

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Kubota, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock, Institute of Industrial Science, Hitachi, Ltd. (72) Kenji Oka, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Production Engineering Research Laboratory, Hitachi, Ltd.

Claims (12)

[Claims] 1. An illuminating means for illuminating a target field of view substantially uniformly through an objective lens, and an image detecting means for converting reflected light from the target object into an image by photoelectric conversion.
An image comparing means for comparing the detected image and the reference image, an illuminating means for illuminating the object from outside the numerical aperture of the objective lens, and a spatial filter at a position conjugate with the pupil position of the objective lens are provided. 2. A pattern inspection apparatus comprising: a pupil field-of-view image detection means for converting scattered light of the above into an image by photoelectric conversion. 2. The pattern inspection apparatus according to claim 1, wherein a pupil image detecting means for detecting a pupil image via a lens which forms an image at a pupil position of the objective lens, and information detection for detecting information of the pupil image. And a spatial filter control unit that controls a spatial filter using the detected information. 3. The pattern inspection apparatus according to claim 2, wherein the information detecting means is configured to detect either or both of distribution and intensity of diffraction from the pattern. 4. The pattern inspection device according to claim 3, wherein the spatial filter filters the diffracted light by the intensity of the detected diffracted light. 5. The pattern inspection apparatus according to claim 1, wherein a polarizing plate is used for the spatial filter. 6. The pattern inspection apparatus according to claim 1, wherein the spatial filter is configured by combining at least one of the polarizing plate and the spatial filter according to claim 4. 7. The pattern inspection apparatus according to claim 1, wherein a wavelength used for the detected image and a wavelength used for the dark field image are different. 8. A pattern inspection method characterized by automatically discriminating a defect by comparing at least two images obtained by image detecting means using different optical means. 9. The optical means of claim 8 is a bright field illumination detector,
A pattern inspection method characterized by dark-field illumination detection. 10. A pattern inspection method, wherein the optical means according to claim 8 uses light having different wavelengths. 11. A pattern inspection method, wherein the optical means of claim 8 is a bright-field illumination detection and a dark-field illumination detection, and lights of different wavelengths are used. 12. Illumination means for illuminating a target field of view substantially uniformly through an objective lens, image detection means for converting reflected light from the target object into an image by photoelectric conversion, and the detected image. The image comparing means with the reference image, the illuminating means for illuminating the object from outside the numerical aperture of the objective lens, the image detecting means by photoelectric conversion of the scattered light from the object, and the type of the defect from these two images. A pattern inspection apparatus comprising means for automatically classifying patterns.