JP3329105B2 - Pattern inspection apparatus and method - Google Patents

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 most suitable for high-sensitivity detection of fine defects generated on a circuit pattern or high-accuracy measurement of circuit pattern dimensions, and a pattern inspection apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of LSIs, circuit patterns formed on wafers have been miniaturized in response to the need for high integration. Detection of minute defects in a circuit pattern is very important in determining the quality of circuit pattern formation. In addition, foreign matter adhering to the circuit pattern becomes a defect of a pattern manufactured in the next step, and therefore, detection of the foreign matter is also important.

For this reason, various proposals have been made for detecting minute defects and foreign matter in a circuit pattern. For example, in a pattern inspection in which two images formed to have the same pattern are detected, the alignment is compared, and a portion where these images are mismatched is determined as a defect, these images are determined at predetermined time intervals. Are detected, and the correction of the positional deviation of these images is made dependent on the amount of positional deviation of the image up to the previous time.

The above-described method is excellent in that erroneous detection of a normal portion as a defect when a circuit pattern density is low or a large pattern defect is present is greatly reduced, and inspection reliability is improved. Related to this,
There is a technique described in JP-A-5-6928.

On the other hand, regarding foreign matter inspection, illumination is performed obliquely, paying attention to the complicated shape of the foreign matter, and among the scattered light from the wafer, scattered light from the pattern is removed using a spatial filter or the like. Some devices detect foreign matter by detecting only scattered light generated from the foreign matter.

[0006]

The circuit pattern defects and foreign matters obtained by the above means have been measured by separate devices. In addition, since foreign matters may be included in the circuit pattern failure results, it is necessary to discriminate these in order to determine the cause of the occurrence of the circuit pattern failure or foreign matter. Since data cannot be detected at the same time and data obtained from the two devices has an error due to a difference in stage accuracy or the like, accurate discrimination cannot be performed. In addition, although there is a deep correlation between a circuit pattern defect and a foreign substance, the conventional method cannot examine an accurate correlation due to a difference in stage accuracy or the like.

[0007]

In order to solve the above-mentioned problems, according to the present invention, an illuminating means for illuminating a detection field of an object almost uniformly through an objective lens and a light reflected from the object are photoelectrically applied. An image detecting means for converting the image into an image, a comparing means for comparing the detected image as a reference, and an illuminating means for illuminating the object from an angle larger than the numerical aperture of the objective lens; and a pupil position of the objective lens. A pupil visual field image detecting means that includes a spatial filter at a conjugate position and converts scattered light from the object into an image by photoelectric conversion. Further, the images obtained by these two detection 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 comparing means and the foreign matter obtained by the pupil visual field image detecting means are measured at the same time. Can be discriminated, and a correlation is required.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a pattern inspection apparatus and method according to the present invention will be described.

FIG. 1 is a block diagram of a pattern inspection apparatus in a pattern inspection method using annular illumination according to an embodiment of the present invention. 1 is an LSI wafer for pattern inspection, 2 is an XYZ stage on which the LSI wafer is mounted,
3 is a lamp house for a light source, 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 an 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 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 object 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,
39 is a comparison circuit, 40 is a pattern defect output, 41 is a foreign matter defect output, and 42 is a pattern defect and foreign matter defect discrimination output.

In FIG. 1, light from a lamp house 3 is applied to an LSI wafer 1 mounted on an XYZ stage 2 (θ stage is not shown) by a collimator lens 4, an aperture stop 5, a field stop 6, a condenser Illumination is performed via a lens 7, a beam splitter 8, a dichroic mirror 9, and an 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 a so-called Koehler illumination without illumination unevenness. 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 mounted. In this case, the movement of the X stage may be 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, and a mismatch is detected as a defect. And pattern defect output 40
Is output.

In FIG. 1, an image sensor 21 is a pupil monitor for detecting, via the lens 11, information on a pupil surface 12a of the objective lens 11 during dark-field illumination. Note that the pupil plane 12a includes an image-side focal plane of an objective lens, a position of an aperture stop,
Alternatively, it is called a Fourier spectrum surface.
Light emitted from the illumination light source 13 for dark field illumination is transmitted through the collimator lens 14, mirrors 15 and 16, and the condensing lens 17 from an angle direction larger than the numerical aperture of the objective lens 11 to LS.
The I wafer 1 is illuminated. 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 subjected to A / D conversion by the A / D converter 30, and the image is captured by the CPU 38 for Fourier transform image analysis, edge density determination, and pupil plane condition control. .

The edge detector 36 is connected to the image sensor 28.
Converts the pattern edge of the image detected by the A / D converter 3
4 , and the detected edge information is taken into the CPU 38.

The image sensor 26 detects foreign substance information of the LSI wafer 1 at the time of pupil field illumination.
Beam splitter 1 of scattered light from LSI wafer 1
The light passing through 8 passes through an imaging lens 22, a dichroic mirror 23, a pupil imaging lens 24 , a spatial filter 12b, and an imaging lens 25, and an image of an LSI wafer 1 is detected by an image sensor 26 .

Here, the CPU 38 sets a spatial filter shape for blocking the diffracted light from the pattern in accordance with the pattern to be inspected, based on information detected by the image sensor 21 which is a pupil monitor of the objective lens 11. A desired filter is set by the filter moving mechanism.
Thereby, the scattered light from the pattern is removed to the image sensor 26, so that only the scattered light from the foreign substance reaches. Therefore, only the foreign matter is detected, the image is A / D converted by the A / D converter 32, and the foreign matter information output 41 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 the pattern defect information are sent from the foreign matter detection circuit 33 and the comparison circuit 37 to the comparison circuit 39. Here, the coordinates of the defect are collated to discriminate the type of the defect. Then, it is output as a pattern defect / foreign matter defect discrimination output 42. Further, a correlation can be obtained by comparing the foreign substance data in the previous step with the pattern defect data obtained in this step.

FIG. 2 shows the wavelength of light used for pattern defects, foreign matter, 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 substance inspection are independent of each other, for example, if the characteristics of the dichroic mirror 9 are as shown in FIG. Light is applied to the LSI wafer 1, but the image sensors 21, 26, 26
28, only the autofocus unit 10 is reached. Further, if the characteristics of the dichroic mirror 23 are as shown in FIG. 4, the light used for the foreign substance 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. 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 on the LSI wafer 1 can be changed arbitrarily, and the distance between the lens 17 and the LSI wafer 1 is changed to the focal length of the lens 17. The irradiation position does not change by adopting a configuration that is equal to. Also,
As shown in FIG. 7, the LSI wafer 1
Above, 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)

At this time, the light width 2w is determined by the beam waist (FIG. 8) of the irradiation light 53 represented by the following equation:

[0025]

(Equation 2)

It is equal to twice as large as 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.
If R is set to 0.57 mm, an oval illumination of 1 mm in length is realized.

[0027]

As described above, according to the structure of the present invention, a pattern defect and a foreign matter can be detected simultaneously, and by comparing these data, the pattern defect and the foreign matter can be discriminated. A pattern inspection device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a pattern inspection apparatus having a pattern defect inspection and a foreign substance 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 a dichroic mirror 9;

FIG. 4 is a diagram showing wavelength characteristics of a 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 on a wafer when a mirror is moved.

FIG. 7 is a schematic sectional view showing 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 on which SI wafer is mounted, 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 image forming lens 26 image sensor 27 zoom lens 28 image sensor 29 stage driver 30 ... A / D converter, 31 ... Spatial filter moving mechanism, 32 ... A
A / D converter, 33 Foreign object 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 discrimination output

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenji Oka 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Yokohama, Japan Examiner, Hitachi, Ltd. Production Research Laboratory Yoshinari Tashiro JP-A-6-148085 (JP, A) JP-A-4-366754 (JP, A)

Claims (10)

(57) [Claims] An apparatus for inspecting a defect of a pattern formed on a substrate, comprising: first irradiating means for irradiating the substrate with first light through an objective lens; First detecting means for detecting, via the objective lens, reflected light from the substrate due to irradiation of the irradiated first light, and second light from the outside of the objective lens of the first irradiating means, A second irradiating means for irradiating the area irradiated with the first light, and a second light irradiating by the second irradiating means, of the reflected light from the substrate, transmitted through the objective lens. Separating means for separating light from light reflected by the first light; and reflecting light reflected by the irradiation of the second light separated by the separating means from the pattern on the substrate in the reflected light.
Second detecting means for detecting the light by blocking the light with a spatial filter; and information on the defect obtained by the first detecting means and information on the defect obtained by the second detecting means. And a processing means for classifying and outputting the defect into a pattern defect on the substrate and a foreign matter defect on the substrate. 2. A first irradiation means for irradiating a sample on which a pattern is formed with a first light from a direction substantially perpendicular to a surface of the sample, and a first irradiation means for irradiating the sample with a first light. Second irradiating means for irradiating the region irradiated with the second light with a second light from a direction oblique to the surface of the substrate; first light by the first irradiating means; and the second irradiating means By the second
Condensing means for condensing the reflected light from the substrate due to the irradiation of the light; and, of the reflected light from the substrate condensed by the condensing means, the reflected light by the irradiation of the first light and the second light. Separation means for separating light reflected by the light irradiation of the first light, and first detection means for detecting light reflected from the substrate by the first light irradiation of the first illumination means separated by the separation means. , The second of the second illumination means separated by the separation means
The reflected light from the substrate due to the irradiation of the light
In addition, the reflected light component from the pattern on the substrate is spatially filled.
A second detecting means for detecting the light by shading the light , and processing the defect information detected by the first detecting means and the defect information detected by the second detecting means. A pattern inspection apparatus comprising: a processing unit that classifies and outputs the pattern defect on the substrate and the foreign matter defect on the substrate. 3. An apparatus for inspecting a defect of a pattern formed on a substrate, comprising: objective lens means; first irradiating means for irradiating the substrate with first light through the objective lens means; Detecting a reflected light from the substrate by irradiation of the first light by the first irradiation means through the objective lens means;
First detecting means, second irradiating means for irradiating the second light from the outside of the objective lens means to an area of the substrate which is irradiating the first light with the first irradiating means, Reflected light from the substrate due to irradiation of the second light by the second irradiation means
The substrate in one of the reflected light which has passed through the objective lens unit
A spatial filter for shielding a reflected light component from the pattern above, a second detector for detecting reflected light from the substrate due to irradiation of the second light passing through the spatial filter, The first signal detected by the detection means and the second signal detected by the second detection means are processed to detect a defect on the substrate and classify the type of the detected defect. A pattern inspection apparatus comprising: 4. The pattern inspection apparatus according to claim 1, wherein said first irradiation means illuminates the substrate with Koehler illumination. 5. A method for detecting information on a pupil plane of said objective lens means .
4. The pattern inspection apparatus according to claim 3, further comprising a pupil monitor . 6. A method for inspecting a defect of a pattern formed on a substrate, comprising irradiating the substrate with a first light through an objective lens, and reflecting the light from the substrate by the irradiation of the first light. Light is detected by a first detector via the objective lens, and second light is detected from outside the objective lens by the first detector on the substrate.
Light is irradiated to the region that is irradiated, the reflected light from the substrate Ru good <br/> the irradiation of the second light through the objective lens separated from the reflected light by the first light After the
The second detector detects the reflected light component from the turn through a spatial filter that blocks light, and the second detector detects the defect information obtained by the first detector. A pattern inspection method comprising: processing the obtained defect information to classify and output the information as a pattern defect on the substrate and a foreign particle defect on the substrate. 7. A pattern-formed sample is irradiated with first light from a direction substantially perpendicular to the surface of the sample, and a region of the sample irradiated with the first light is irradiated on the surface of the substrate. A second light is irradiated from an oblique direction with respect to the light, and the reflected light from the substrate caused by the irradiation of the first light and the second light is collected through an objective lens. From the reflected light due to the irradiation of the first light and the reflected light due to the irradiation of the second light, and the separated first light
Detecting the reflected light from the substrate due to the irradiation of light with a first detector, processing the signal obtained by detecting with the first detector to obtain information on the defect of the pattern on the substrate, The reflected light from the substrate due to the irradiation of the separated second light is
Of the reflected light, the reflected light component from the pattern on the substrate is
The light is shielded by a spatial filter and detected by a second detector.
The signal obtained by the detection of the detector is processed to obtain information of the defect on the substrate, and the information of the defect of the pattern on the substrate and the information of the defect on the substrate are processed to process the information on the substrate. A pattern inspection method, wherein a pattern defect and a foreign matter defect on the substrate are classified and output. 8. A method for inspecting a pattern formed on a substrate for defects, comprising irradiating the substrate with a first light through an objective lens, and reflecting the light from the substrate by the irradiation of the first light. Light is detected by a first detector via the objective lens, and second light is detected from outside the objective lens by the first detector on the substrate.
And irradiates the area irradiated with the second light with the reflected light from the substrate due to the irradiation of the second light, and reflects the reflected light that has passed through the objective lens out of the reflected light from the pattern on the substrate.
The emitted light component is shielded by a spatial filter , detected by a second detector, and a signal detected by the first detector and a signal detected by the second detector are processed to detect a defect on the substrate. A pattern inspection method characterized by detecting, categorizing and outputting the detected defects. 9. The pattern inspection method according to claim 6, wherein the illumination of the substrate by the irradiation of the first light is Koehler illumination. The method according to claim 10, wherein said spatial filter, switching using the moving means in accordance with the shape of the pattern formed on the substrate
Pattern inspection method according to claim 8, wherein the that.