JPH1130590A - Foreign matter and defect inspecting device, and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a foreign matter and a defect on a pattern, which is different in the quantity of scattered light with high sensitivity, by providing an adjusting means for the quantity of detection light of a photodetector corresponding to an inspection area of a body to be inspected. SOLUTION: The body to be inspected is irradiated by a lighting means 201 and the scattered light from the body to be inspected is imaged on a detection light quantity adjusting means 204 by an imaging optical system 203. At this time, the scattered light intensity distribution is modulated according to the scattered light intensity from the body to be inspected by using a nonlinear element, etc. This modulated light is re-imaged on the photodetecting means 206 by the imaging optical system 205 and a signal processing circuit 207 detects a foreign body and a defect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor substrate, a photomask, and a reticle in a semiconductor manufacturing process.
The present invention relates to an apparatus for inspecting defects with high sensitivity and a method for manufacturing a high-quality semiconductor using the apparatus.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing process, the presence of foreign matter on a semiconductor substrate (semiconductor wafer) causes defects such as poor insulation of a wiring, short circuit, or destruction of an insulating film and a gate oxide film of a capacitor. These contaminants are generated in various ways depending on the causes, such as those generated from the operating part of the transport device, those generated from the human body, those generated by reaction in the processing device by process gas, and those mixed in chemicals and materials. It is mixed in the state of. Also, when a layer of chromium or the like is formed on a transparent thin plate such as glass or quartz like a photomask or reticle, and this is etched to form a fine transparent or opaque circuit pattern, foreign substances may be present on the substrate surface. Then, the shadow of the foreign matter is also transferred at the time of exposure, and a defect occurs.

As one of the conventional techniques for detecting foreign matter on a semiconductor substrate of this type, as described in Japanese Patent Application Laid-Open No. 62-89336, a semiconductor substrate is irradiated with a laser beam so Detects scattered light from foreign matter generated when foreign matter is attached to the substrate and compares it with the inspection result of the same type of semiconductor substrate inspected immediately before, eliminating false alarms due to patterns, and ensuring high sensitivity and high reliability of foreign matter In addition, as disclosed in Japanese Patent Application Laid-Open No. 63-135848, a foreign substance generated when a semiconductor substrate is irradiated with a laser and a foreign substance adheres to the substrate as disclosed in JP-A-63-135848. There is a method in which scattered light from the object is detected, and the detected foreign matter is analyzed by an analysis technique such as laser photoluminescence or secondary X-ray analysis (XMR).

Conventionally, in an apparatus for inspecting foreign substances and defects on a substrate, the substrate to be inspected is irradiated with illumination light, and scattered light from the inspected object is detected by a photodetector. A method for detecting foreign matter and defects by comparing signals using the repeatability of an object, irradiating a semiconductor substrate with coherent light, removing light scattered from a repeat pattern on the substrate with a spatial filter, and improving repeatability. There is disclosed a method of emphasizing and detecting foreign substances / defects not having them.

Japanese Patent Application Laid-Open No. 63-210755 discloses a spatial filter utilizing the photoconductivity and Pockels effect of a spatial light modulator.
Japanese Patent Laid-Open Publication No. Hei 3-2546 discloses a means for solving the problem of damage to a photoelectric conversion unit due to excessive scattered light from a pellicle frame such as a reticle with a pellicle, and the detection of weak light from a foreign substance due to a malfunction of an amplifier due to the excessive signal. As
Techniques for changing the detection sensitivity have been disclosed.

[0006]

However, in the conventional inspection apparatus, since the entire inspection area is illuminated with the same illuminance, the amount of light detected by the photodetector is proportional to the amount of light scattered from the pattern on the inspection object. And eventually reaches the saturation level of the photodetector. In this case, a change in the amount of foreign matter or defect on the pattern that has reached the saturation level cannot be detected, and the foreign matter or defect is overlooked. Further, in order to detect the oversight, a method of reducing the amount of detected light over the entire inspection target area, for example, reducing the illuminance of illumination light is used. However, in this case, a minute amount of light from a foreign substance or a defect is also reduced, and the detection sensitivity is reduced.

FIG. 1 shows this state. In the figure,
(A) is a schematic diagram when the inspection object is viewed from above,
(B), (c), (d), and (e) show one-dimensional waveforms of the output signal of the photodetector. Reference numeral 101 denotes a pattern in which the amount of scattered light is relatively small in the inspection object, and reference numeral 102 denotes a pattern in which the amount of scattered light is large in the inspection object. Also, 103
Denotes a foreign substance existing on the inspection object 101, 104 denotes a foreign substance existing on the inspection object 102, and 105 denotes an output place of the one-dimensional waveform shown in (b) and (d). And reference numeral 106 denotes an output place of the one-dimensional waveform shown in (c) and (e). (B), (c), (d),
In (e), reference numeral 107 denotes a saturation level of the photodetector, and reference numeral 108 denotes a portion of the one-dimensional waveform of the photodetector due to scattered light from the inspection object 102. Similarly, in the one-dimensional waveform of the photodetector, reference numerals 109 and 111 denote signals of scattered light from the foreign substance 103, and 110 denotes a signal of scattered light from the foreign substance 104.

Conventionally, as shown in (b) and (c), the foreign matter 102, that is, the foreign matter 102 is hidden by the saturation level of the photodetector to set the illuminance of the illumination light source to detect the signal 109. Would. When the illuminance of the illumination light source is reduced to detect the foreign matter 102, (d),
As shown in (e), the foreign matter 102, ie, the signal 110
Is detectable, but the foreign matter 103, ie, the signal 11
No. 1 is difficult to detect, and one of them is likely to be overlooked. In addition, as described above, these missed foreign substances and defects also cause a malfunction of the semiconductor device in the semiconductor manufacturing process, which leads to a deterioration in the quality of the semiconductor device.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned drawbacks of the prior art, the present invention provides an illumination device for irradiating an object to be inspected with a conventional inspection apparatus, and an illumination device. Focusing and scattering structures from the illuminated inspection object
An apparatus having image forming means for forming an image, light detecting means for detecting an optical image by the image forming means, and signal processing means for detecting a foreign substance / defect based on a signal detected by the light detecting means; A light quantity adjusting means for adjusting the light quantity detected by the light detecting means and a detecting means for detecting in advance a change in the light quantity detected by the light detecting means are provided. That is, in the inspection object, the intensity of scattered light from the inspection object for each inspection area appropriately divided is detected in advance, and the light detection unit detects the intensity of scattered light from the inspection object for each inspection area in accordance with the intensity of scattered light from the inspection object. The point is to have a means for adjusting the amount of light.

Here, the object to be inspected is, for example, a semiconductor substrate, a reticle, or a photomask. As means for adjusting the amount of light detected by the light detecting means, for example, an illumination light source and an object to be inspected or an object to be inspected and light detection It is a means to install a filter whose light transmittance is changed locally or entirely in the optical path between the means, or by using a light spatial modulation element crystal having an electro-optic effect such as a photoconductive effect and a Pockels effect. Means for recording and modulating a light intensity distribution on the light spatial modulation element crystal. Alternatively, it is means for adjusting the voltage applied to the illumination means to change the illumination illuminance, or for adjusting the detection voltage of the detection means by adjusting the voltage applied to the detection means.

With these configurations, it is possible to appropriately adjust the light intensity detected by the light detecting means in accordance with each scattered light intensity for each pattern / inspection region having different scattered light intensity on the inspection object. It becomes possible. Therefore, conventionally, an inspection area in which a change due to scattered light from a foreign substance or a defect cannot be detected because it is on a pattern having a scattered light intensity equal to or higher than the saturation level of the detection output of the light detector. By using the present invention to reduce the detection output of the photodetector, it is possible to detect the signal of the pattern at a saturation level of the photodetector or less, and to detect a change in the signal of a foreign substance / defect on the pattern. This makes it possible to detect the foreign matter / defect.

On the other hand, according to the means of the present invention, the detection output of the photodetector is not reduced for a pattern having a low scattered light intensity on the inspection object. Good detection is possible. Therefore, foreign substances and defects on patterns having different scattered light intensities on the inspection object can be detected with high sensitivity.
By reducing the number of defects and taking countermeasures against them, the quality of the semiconductor device can be improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

FIG. 2 shows an embodiment of the present invention.

In this embodiment, as shown in FIG.
01, imaging optical system 203, detected light amount adjusting means 204, imaging optical system 205, light detecting means 206, signal processing circuit 20
7. FIG. 3A shows the configuration of the detected light amount adjusting means 204 in this embodiment. As shown in the same figure, it is composed of a polarizer 305, a substrate glass 304, a transparent electrode 303, an insulating layer 302, a spatial light modulator crystal 301, and an analyzer 306.

Next, details of the detection light amount adjusting means 203 will be described.

In FIG. 3A, incident light 310 enters a polarizer 305, and polarized light in a certain direction is transmitted. When a sufficiently high voltage is applied to the transparent electrode 303 with respect to the transmitted light,
As shown in FIG. 3B, a charge distribution occurs in the spatial light modulator crystal 301. Here, the spatial light modulator crystal 3
01 is a crystal having an electro-optical effect such as the Pockesle effect, such as a single crystal of BSO (Bi ₁₂ SiO ₂₀ ). Here, the electro-optic effect means that when an electric field is applied to the crystal, the crystal is deformed due to the electrostriction effect. Further, the refractive index changes due to the photoelastic effect due to the deformation of the crystal.

Here, as shown in FIG. 3 (c), when the incident light 320 having a low light intensity and the incident light 321 having a high light intensity enter the detection light amount adjusting means, a light spatial modulation element is produced by a photoconductive effect. An electric charge is formed inside the crystal 301, drifts in the crystal due to the electric field imprinted on the transparent electrode 203, and is polarized on the crystal surface.

As a result, the portion of the incident light 320 has a small light intensity, so that the amount of movement of charges is small, and the electric field remains strong. However, the portion of the incident light 321 has a large light intensity, so that the amount of movement of charges is large. Is weakened, and the electric field distribution inside the spatial light modulator crystal 301 changes. Therefore, a birefringence index distribution is generated according to each electric field distribution, and phase modulation is performed according to the birefringence index distribution. Therefore, the incident light 3
10, the light transmitted through the polarizer 305 is input to the spatial light modulating element crystal 301, and the output light modulated by the spatial light modulating element crystal 301 blocks the output light from the portion where the incident light intensity is strong. By installing the analyzer 306, the output light intensity of the portion where the incident light intensity is high can be reduced.

The portion where the intensity of the incident light is weak is transmitted through the analyzer 306 because the amount modulated by the spatial light modulator crystal 301 is small. Here, the analyzer 306 is installed in a direction in which no voltage is applied to the transparent electrode, that is, the direction in which light transmitted through the polarizer 305 is most blocked in a state in which electric charges are moved by incident light. There is a way to do it.

Next, the operation of this embodiment will be described.

In the operation, the recording operation of the distribution of the scattered light amount to the detected light amount adjusting means 204 and the foreign matter / defect inspection operation are repeated.

First, the recording operation will be described. In FIG. 2, the illumination means 201 is, for example, an Ar laser having a wavelength of 488 nm, which can be recorded on the BSO, as described above.
The light emitted from the illumination means 201 is
Is irradiated. Of the illumination light, scattered light from the inspection object 202 is imaged by the imaging optical system 203 on the detected light amount adjusting means 204, and at this time, as described above according to the intensity distribution of the formed light amount. The voltage distribution is recorded.

FIG. 4 shows an example of this state. FIG. 4 (a)
Is a schematic diagram when the inspection object is viewed from above,
1 is a circuit pattern, 403 is a foreign substance, and 404 is an illumination area that can be illuminated at one time by the illumination means 201. FIG. 4B shows the X-ray intensity distribution of the light area formed by the imaging optical system 203 in FIG. 4A in the illumination area.
It shows a one-dimensional waveform in the direction.

In FIG. 4B, reference numeral 410 denotes the foreign substance 4
Outputs 411 and 411 are obtained by arranging one-dimensional waveforms when the illumination area is scanned in a plurality of areas in the Y direction in FIG. 4A. Reference numeral 413 denotes a light amount distribution accumulated in the detected light amount adjusting means 204 when these areas are scanned. As the light intensity distribution recording operation, the light intensity distribution of a portion where no foreign matter exists in 411 in FIG. 4B is measured for an inspection object in which a pattern is formed at the same position over a plurality of inspection regions. Or record 41
A plurality of areas are scanned as shown in FIG. 3 and stored in the detected light amount adjusting means 204 by accumulating them.

Next, the operation at the time of inspection will be described. At the time of inspection, similarly to the recording operation described above, the illumination device 201 is used to inspect the inspection object 2
Illuminate 02. Of the illumination light, scattered light from the object to be inspected is incident on the detected light amount adjusting means 204 by the imaging optical system 203, and the light amount is adjusted according to the scattered light intensity distribution as described above. Further, the adjusted light is re-imaged by the image forming optical system 205, and the image forming optical system 205
Light detecting means 206 installed at the image forming position
It is detected by a CD linear sensor. The light detecting means 206
Is subjected to signal processing in a signal processing circuit 207 to detect foreign matter and defects.

FIG. 5 shows another embodiment of the present invention.

In this embodiment, as shown in the figure, an illumination light source 501, a half mirror 502, and an illumination light amount adjusting means 50 are provided.
3, a total reflection mirror 504, an imaging optical system 506, a light detecting means 507, a signal processing circuit 508, a scattered light intensity distribution detecting means 509, a voltage control system 510, and a power supply 511 of an illumination light amount adjusting means.

FIG. 6A shows the configuration of the illumination light amount adjusting means 503 in this embodiment. As shown in the figure,
It comprises a polarizer 605, a glass substrate 604, a transparent electrode 603, an alignment film 602, liquid crystal molecules 601 and an analyzer 606. FIG. 7A shows the configuration of the scattered light intensity distribution detecting means in this embodiment. As shown in the figure, an imaging optical system 701, a scattered light detector 702, a signal processing circuit 703
Consists of

Next, details of the illumination light amount adjusting means 503 will be described. In FIG. 6A, the incident light 610 is
05, and polarized light in a certain direction is transmitted. When no voltage is applied to the transparent electrode 603 for the transmitted light,
The deflection direction is twisted by 90 ° by the liquid crystal molecules 601, and the light passes through the polarizer 605 and the analyzer 606 that has been made into crossed Nicols. On the other hand, when a sufficiently high voltage is applied to the transparent electrode 603, the light transmitted through the polarizer 605 enters the analyzer 606 without being twisted by the liquid crystal molecules 601. Therefore, the light is blocked by the analyzer 606, and the amount of illumination is reduced. It is possible to reduce it. Further, in this embodiment, the polarizer 605, the glass substrate 604, the transparent electrode 603,
The alignment film 602, the liquid crystal molecules 601 and the analyzer 606 constitute one unit 611, and the units 611 are arranged in an array as shown in FIG. It is possible to do.

Next, details of the scattering intensity distribution detecting means 509 will be described. In FIG. 7A, illumination light 731 is irradiated on the inspection object 732, and scattered light from the inspection object 732 is formed on the photodetector 702 by the imaging optical system 701. Further, the output of the photodetector 702 is processed by a signal processing circuit 704 to calculate an adjustment amount of the illumination light amount.

FIGS. 7B and 7C show an example of a calculation method. Here, FIG. 7B is a schematic diagram of a pattern when the inspection object is viewed from above. In FIG. 7, reference numerals 710 and 711 denote patterns, reference numeral 713 denotes an inspection target area for one scan, and a one-dimensional waveform 712 is shown in FIG. 7C. 7 In FIG.
Reference numeral 720 denotes a one-dimensional waveform of several lines in the inspection target area 713. The sum of these waveforms is 721, and the highest level portion of the added waveform 721 is 725. As a calculation method, in the added waveform 721, an average value of an area corresponding to one unit of the illumination light amount adjusting means was obtained, the value of the high level portion 725 was divided by the average value, and an appropriate coefficient was multiplied. The transparent electrode 6 in the illumination light amount adjusting means 503
03 is a method of setting a voltage to be applied. Although a one-dimensional waveform in the X direction in FIG. 7B has been described here, a one-dimensional waveform in the Y direction is also performed in the present embodiment, and the voltage applied to the transparent electrode 603 is determined based on these results. Shall be determined.

Next, the operation of this embodiment will be described.

As shown in FIG. 5, the light emitted from the illumination light source 501 divides the optical path into two by a half mirror 502. First, the light 5 reflected by the half mirror 502
20 is illumination light of the scattered light intensity distribution detecting means 509,
The object to be inspected 505 is irradiated. Of the illumination light, the scattered light from the object to be inspected is detected by the scattered light intensity distribution detecting means 509 as described above, and is fed back to the voltage control system 510 according to the detected content.

On the other hand, the light 52 transmitted through the half mirror 402
1 is incident on the illumination light amount adjusting means 503. After adjusting the amount of illumination by the adjusting means 509, the total reflection mirror 50 is adjusted.
The light reflected by 4 is applied to the inspection target area on the inspection object 505. Of the irradiation light, the scattered light from the inspection object 505 is condensed and imaged by the imaging optical system 506, and the light detecting means 50 installed at the image forming position of the imaging optical system 506.
7 is detected. The output of the light detection means 507 is input to a signal processing circuit 508 and subjected to signal processing to detect foreign matter. By repeating these operations while moving the inspection object stage in the Y direction in FIG. 5, the inspection object 505 is inspected.

The scattered light from the inspection object in this specification may be reflected light of the inspection object or transmitted light of the inspection object. As the means for adjusting the amount of illumination light and the means for adjusting the amount of detected light, those which partially change the light transmittance, such as an ND filter, may be used. The device that adjusts the intensity of the illumination light from the illumination light source and that is installed between the object to be inspected and the light detection device and that adjusts the amount of scattered light is called the detection light intensity adjustment device. However, in both cases, the light amount incident on the photodetector is locally or entirely adjusted, and has the same function.

As means for adjusting the amount of illumination light from the illumination light source, the voltage applied to the illumination light source may be changed.
Further, in order to adjust the amount of light detected by the light detecting means, the sensitivity of the light detecting means may be adjusted by changing the printing voltage to the light detecting means. Here, the light detection means refers to a CCD linear sensor, a TDI, a TV camera, and a photomultiplier tube. Further, as a means for detecting the distribution of the scattering intensity from the inspection object, a method of recording on the spatial light modulation material as in the above-described embodiment, the detection is performed at a timing earlier than the inspection timing, and feedback is performed in real time. Alternatively, the scattered light intensity distribution may be sequentially read out from those in which it is stored in advance, and fed back to the light amount adjusting means. Further, the imaging optical system may be configured to use a spatial modulation material such as a spatial filter in the optical path.

[0038]

Since the present invention is configured as described above, foreign substances and defects on a pattern having a large amount of light detected on a substrate in a semiconductor manufacturing process can be detected without overlooking, and the detection result is used in the semiconductor manufacturing process. By providing feedback and taking measures, a high-quality semiconductor device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional problem.

FIG. 2 is a diagram showing a configuration of one embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a detection light amount adjusting unit in FIG. 2;

FIG. 4 is a view for explaining a method of a detected light amount adjusting means in FIG. 2;

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an illumination light amount adjusting unit in FIG. 5;

FIG. 7 is a view for explaining a method of the illumination light amount adjusting means of FIG. 5;

[Explanation of symbols]

101, 102: pattern, 103, 104: foreign matter, 1
05, 106: Waveform output location, 107: Saturation level of photodetector, 108, 109, 110, 111: Scattered light signal from the test object, 201: Illumination means, 202: Test object, 203: Imaging optics System, 204: detection light amount adjusting means,
205: imaging optical system, 206: light detection means, 207: signal processing circuit, 301: light spatial modulation element crystal, 302: insulating layer, 303: transparent electrode, 304: substrate glass, 305
... polarizer, 306 ... analyzer, 310,320,321 ...
Incident light, 401: pattern on inspection object, 402: waveform output location, 403: foreign matter, 404: illumination area, 410:
Scattered light signal from the inspection object, 411 ... one-dimensional waveform group, 4
13: light quantity distribution in the inspection area, 501: illumination light source, 502
... half mirror, 503 ... illumination light amount adjusting means, 504 ...
Total reflection mirror, 506: imaging optical system, 507: light detecting means, 508: signal processing circuit, 509: scattered light intensity distribution detecting means, 510: voltage control system, 511: power supply of illumination light amount adjusting means, 601: liquid crystal Molecule, 602... Alignment film, 603
... Transparent electrode, 604 ... Glass substrate, 605 ... Polarizer, 6
06: analyzer, 610: incident light, 611: light amount adjusting means, 701: imaging optical system, 702: scattered light detector, 70
3: Signal processing circuit, 710, 711: Pattern on inspection object, 712: Waveform output location, 713: Inspection target area,
720: one-dimensional waveform group, 721: added waveform, 725: maximum value in the added waveform, 731: illumination light, 732: inspection object.

Continued on the front page (72) Inventor Yukio Mibo 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture, Hitachi, Ltd.

Claims (10)

[Claims] 1. A foreign matter defect inspection apparatus characterized by inspecting foreign matter and defects on a semiconductor substrate with high sensitivity and obtaining a high quality semiconductor device by quality control based on a detected object of the inspection. And a semiconductor device manufacturing method. 2. An apparatus for inspecting foreign matter and defects on a semiconductor substrate, comprising: an illuminating means for irradiating the object with light; and a scattered light image from the object illuminated by the illuminating means. Imaging means for imaging, light detection means for detecting an optical image by the imaging means, signal processing means for detecting foreign matter / defects based on a signal detected by the light detection means, and the light detection means 2. The foreign matter defect according to claim 1, wherein the inspection is performed with high sensitivity by providing a detection light amount unit for adjusting a detected light amount and a detection unit for detecting a change in the light amount detected by the light detection unit in advance. Inspection equipment. 3. The detected light amount adjusting means adjusts the detected light amount such that the total detected light amount becomes the same level in each of the inspection regions appropriately divided. The foreign matter defect inspection device according to the above. 4. The detection light quantity adjusting means includes a storage means for storing in advance a distribution of a change in the intensity of scattered light from the inspection object, and adjusts the detection light quantity based on the contents of the storage means. The foreign matter defect inspection device according to claim 2 or 3, wherein 5. The detected light amount adjusting means detects a distribution of a change in the intensity of scattered light from the inspection object in real time, and adjusts the detected light amount in real time based on the detected content. Item 3. A foreign matter defect inspection device according to Item 2 or 3. 6. A foreign matter defect inspection apparatus according to claim 4, wherein said detected light amount adjusting means adjusts the amount of light irradiated on the inspection object based on the detected light amount. 7. The foreign matter defect inspection apparatus according to claim 4, wherein the detected light amount adjusting means adjusts a detectable amount of the scattered light amount from the inspection object based on the detected light amount. . 8. The detecting light amount adjusting means, wherein a filter having a changed light transmittance is used as a part of the illuminating means or the image forming means to adjust the detected light amount. The foreign matter defect inspection device according to the above. 9. A foreign matter defect inspection apparatus according to claim 6, wherein said detection light amount adjusting means adjusts an applied voltage to an illumination light source to adjust the amount of light applied to the inspection object. 10. The foreign matter defect inspection apparatus according to claim 7, wherein said detecting light amount adjusting means adjusts an applied voltage to said light detecting means to adjust the detected light amount.