KR0154686B1 - Method of and apparatus for inspecting reticle for defects - Google Patents

Abstract

A defect inspection device that detects defects such as foreign matters attached to circuit patterns such as reticles and photomasks, and it is possible to easily remove defects such as fine foreign matters attached to circuit patterns such as reticles from circuit patterns with a simple configuration. A method for detecting defects such as foreign matter adhering on a transparent or semitransparent substrate having a pattern formed with a light shielding film or a light semitransmissive film or a light transmissive film on one surface (surface), in order to detect the surface of the substrate. Irradiated with the illumination light, the light generated from the surface by the irradiation of the illumination light is detected on the surface side and photoelectric conversion to generate a first electrical signal, the light generated from the surface by the irradiation of the illumination light transmitted through the substrate on the back side Detects and photoelectrically converts to generate a second electrical signal, and detects defects such as foreign matter attached to the substrate using the first electrical signal and the second electrical signal. Shipments were configured.

By using such a method, it becomes possible to manufacture semiconductor elements such as LSI using photomasks such as reticles to which defects such as foreign matters do not adhere.

Description

Defective reticle inspection device and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a reticle or photomask (hereinafter referred to as a reticle) provided with a phase shifter made of a light transmitting film and a circuit pattern in order to detect defects such as foreign matters attached to the reticle. The present invention relates to a method for inspecting a reticle provided with a phase shifter for detecting defects such as foreign matters of submicron order size before transferring the reticle onto an image, and a reticle inspection apparatus for executing the reticle inspection method.

When manufacturing an LSI chip or a printed wiring board, defects of the reticle are inspected in the exposure process before transferring the reticle having the circuit pattern onto the wafer. If the reticle has defects such as small foreign matters of the submicron size, the reticle cannot be accurately transferred onto the wafer, and therefore, the LSI chip manufactured using such a wafer becomes defective. In particular, with the recent high integration of LSI, problems caused by defects such as minute foreign matters attached to the reticle become more prominent, and the presence of defects such as foreign matters of submicron size is not allowed on the reticle.

In order to prevent the transfer failure of the reticle, inspection of defects such as foreign matters of the reticle before the transfer of the reticle on the wafer is indispensable, and conventionally, various inspection techniques for detecting defects such as foreign matters of the reticle have been proposed. As a defect inspection method such as a foreign material of a reticle, a method of irradiating obliquely with a highly directional light beam such as a laser beam and detecting scattered light scattered by a defect such as a foreign material is widely used because of its high-speed and high sensitivity inspection. However, since the light beam is diffracted also at the edges of the pattern of the reticle, the scattered light and the diffracted light scattered by defects such as foreign matters must be discriminated from each other. Therefore, various technical means for discriminating diffracted light and scattered light have been proposed.

As a first proposed technical means, there is an inspection apparatus described in, for example, Japanese Patent Laid-Open No. 54-101390. The inspection apparatus includes a laser emitting a linearly polarized laser beam, irradiation means for irradiating the linearly polarized laser beam obliquely to the circuit pattern so that the linearly polarized laser beam is incident on the circuit pattern at a specific incidence angle, and a polarizing plate and a lens in all directions. (Inclined direction) It consists of a condensing optical system. When the linearly polarized laser beam is irradiated to the circuit pattern, the scattered light scattered by the diffraction light diffracted by the circuit pattern and defects such as foreign matters is different from the polarization plane, that is, the vibration plane, so that only scattered light scattered by defects such as foreign matters is used. It can be detected.

Secondly, as a technical means proposed, there is an inspection apparatus described in, for example, Japanese Patent Laid-Open Publication No. 59-65428, Japanese Patent Application No. 1-17024 or Japanese Patent Application Publication No. 1-153943. The inspection apparatus includes scanning means for scanning a sample by a laser beam projected obliquely onto the sample to be inspected, and condensed scattered laser light on the sample to be arranged so that the irradiation point of the laser beam substantially coincides with the focusing point. The scattered light obtained through the light shielding plate and scattered by defects such as a light shielding plate or a foreign material disposed on the Fourier transform image surface of the first lens and the circuit pattern of the sample to be inspected is scattered by the circuit pattern of the sample to be inspected. The slit of the slit plate is scattered by defects such as a slit plate and a foreign material, which are disposed at the second lens to be converted, the imaging point of the second lens, and shield the scattered light from a portion other than the irradiation point of the laser beam of the sample under test. It consists of a light-receiving device for receiving the scattered light passing through. This inspection apparatus focuses on the fact that the elements of the circuit pattern extend in one direction or two to three directions, and the diffraction light diffracted by the elements of the circuit pattern extending in a specific direction is transferred to a Fourier transform image plane. By shielding, only scattered light scattered by defects such as foreign matters is detected.

The third proposed technical means includes, for example, the structure described in JP-A-58-62543. This configuration discriminates foreign matters according to the logical product of the outputs of several obliquely arranged detectors, focusing on the fact that the diffracted light diffracted at the edge of the circuit pattern has no directivity and scattered light scattered by defects such as foreign matters. It is.

The fourth proposed technical means includes, for example, the structure described in Japanese Patent Application Laid-open No. 60-154634 or 60-154635. This configuration focuses on the fact that the diffracted light diffracted at the edge of the circuit pattern is focused only in a specific direction, and the scattered light scattered by defects such as foreign matter is scattered in all directions, thereby discriminating foreign matter from the outputs of several detectors. will be.

Apparatus and methods related to inspection of specimens for defects such as micro foreign matters include the Schlieren method, a phase difference microscope, and a technique related to a finite size diffraction image. For example, Kubota Hiroshi, Oyo Kogaku, Iwanami Zensho, pp. 129-136.

In the case of using an array-shaped detector such as a one-dimensional solid-state imaging device having an array of solid-state imaging sensors, when defects such as foreign matters are detected in several elements of the detector, output signals indicating defects of foreign matters are dispersed into several pixels. As a result, there is a possibility that the output of the detector is reduced, so that defects such as foreign matters cannot be detected by the detector. As a method for preventing this, Japanese Patent Laid-Open No. 61-104242 describes a method of arranging an array-shaped detector so as to be inclined with respect to the scanning operation direction of the inspection table. In addition, Japanese Patent Laid-Open Publication No. 61-104244 and Japanese Patent Application Laid-Open No. 61-104659 disclose an invention using an array-type detector provided with elements having a special shape and arranged in a special configuration.

Irregular irradiation and fluctuations in the irradiation adversely affect the precision and reproducibility of the detection. Japanese Patent Laid-Open No. 60-038827 discloses an invention for automatically adjusting the intensity of scattered light by using a standard sample having known characteristics.

Japanese Patent Application Laid-Open No. 56-132549 describes an invention for preventing a large amount of scattered light scattered by a defect such as a relatively large foreign material into a scattered light scattered by a defect such as several relatively small foreign matters. .

As described above, as the size of defects such as foreign matters to be detected becomes smaller and smaller, it becomes an important problem that it is impossible to detect defects such as foreign matters that adversely affect the quality of the LSI chip. Firstly, in the technical means proposed, for example, in Japanese Patent Laid-Open No. 54-101390, the polarization plane of scattered light scattered by defects such as micro foreign matter and the polarization plane of diffracted light diffracted at the edge of the circuit pattern Because of the small deviation, it is impossible to detect defects such as minute foreign matters.

Secondly, in the invention described in the technical means, for example, Japanese Patent Application Laid-Open No. 59-65428, 1-117024, and 1-153943, the light shielding plate and the slit plate are scattered due to defects such as foreign matter. The scattered light and the diffracted light diffracted by the circuit pattern are separated to detect only scattered light scattered by defects such as foreign matters. In these inventions, a structure for detecting defects such as foreign matters by a simple binary method uses a simple detector mechanism. However, the diffracted light diffracted at the intersection of the circuit pattern elements is oriented in one direction as the diffracted light diffracted at the straight edges of the circuit pattern. Since it does not move, it becomes impossible to completely shield the diffracted light diffracted at the intersection point of the circuit pattern element by the spatial filter. In addition, since diffracted light diffracted in a micron sized circuit pattern with high integration of LSI is similar to scattered light scattered by defects such as foreign matters, defects such as circuit patterns and foreign substances are detected by a simple binary method. Discrimination is practically difficult.

As the third proposed technical means, for example, the apparatus described in Japanese Patent Laid-Open No. 58-62543, and the fourth proposed technical means, for example, Japanese Laid-Open Patent Nos. 60-154634 and 60-154635 Since the apparatus described in the heading is difficult to use an optical system having a sufficiently high light condensing capability in their construction, it is practically difficult for these apparatuses to detect weak scattered light scattered by defects such as foreign matters.

The fifth proposed technique, for example, the apparatus described in Japanese Patent Laid-Open No. 61-104242 and No. 61-104244, requires a special detector and a special optical system in its construction, resulting in a cost increase. have.

The sixth proposed technical means, for example, the apparatus described in Japanese Patent Application Laid-Open No. 60-038827, has a high accuracy in construction accuracy for detecting defects such as application to an array detector suitable for high-speed detection or minute foreign matter. It has a drawback.

The seventh proposed technical means, for example, the apparatus described in Japanese Patent Laid-Open No. 56-132544, detects only one point of a large foreign material, and thus there is a problem in that it is impossible to accurately recognize the shape of an elongated foreign material.

Recently, a reticle developed to improve the transfer resolution of a circuit pattern formed on a reticle has a phase shifter formed so as to cover a space between the circuit pattern elements with a film thickness of 1/2 of the optical wavelength used for exposure. Or a transparent or semitransparent thin film called a phase shift film is provided. Although this thin film is transparent or translucent, the thickness of this thin film is several times the thickness of the circuit pattern of about 0.1 m. As a result, the intensity of the diffracted light diffracted at the edge of the thin film becomes several times to several tens of the intensity of the diffracted light diffracted at the edge of the circuit pattern, which significantly lowers the detection sensitivity of defects such as foreign matters.

Accordingly, an object of the present invention has been made to solve the above-described problems, and includes a submicron attached to a transparent or translucent substrate, particularly a circuit pattern such as a reticle having a phase shift film and a circuit pattern for improving the transfer resolution. The present invention provides a reticle inspection method capable of stably detecting defects of defects such as minute foreign matters of a magnitude and stably detecting a circuit pattern, and an apparatus for performing the method.

Another object of the present invention is to provide a circuit pattern formed on the mask by the reduced projection exposure apparatus in such a state that defects such as fine foreign matters do not exist on a mask such as a reticle having a phase shift film. The present invention provides a projection exposure method and apparatus capable of projecting exposure on an exposed substrate.

The present invention further refines the invention of US Application No. 08 / 192,036 to US Application No. 07 / 902,819 or Korean Application No. 94-3209 to Korea Application No. 92-11092.

1 is a schematic view showing a reticle inspection device of a first embodiment according to the present invention,

2 is a plan view illustrating a reticle scanning method according to the present invention;

3 is a schematic view of one of the symmetrically arranged irradiation systems included in the reticle inspection device of FIG.

4 (a) to (d) are views illustrating a reticle inspection method according to the present invention;

5 is a plan view illustrating an angle circuit pattern;

6 (a) to 6 (c) show the distribution of scattered light and diffracted light on the Fourier transform plane;

7A is a partial plan view of a corner portion of a circuit pattern,

7B is an enlarged view of the CO unit of FIG. 7A,

8 is a graph for explaining the relationship between the scattered light detection signal generated when detecting scattered light scattered by a defect such as a foreign material and the detection signal generated when detecting a circuit pattern;

9 is a plan view of a microcircuit pattern in which defects are inspected by the reticle inspection apparatus of the present invention;

10 is a graph showing the levels of detection signals generated when detecting defects such as foreign matters and corner portions of circuit patterns;

FIG. 11 is a graph showing the relationship between the theoretical intensity of scattered light scattered by fine particles and a dimensionless value π d / λ (where d is the size of the fine particles and λ is the wavelength of the illumination light beam);

12A and 12B are diagrams for explaining a method for detecting scattered light from defects such as foreign matter using the optical system having a high NA according to the present invention;

Fig. 13 is a schematic diagram showing the moving direction of diffracted light diffracted by defects such as foreign matters,

14 is a schematic diagram illustrating the definition of an NA of an optical system according to the present invention;

15 is a graph showing the relationship between the cross-sectional area of scattered light proportional to the intensity of scattered light scattered by defects such as foreign matters and the diameter d of defects such as foreign matters;

16 is a schematic diagram showing the configuration of a reticle inspection device of the prior art;

17 is a schematic diagram showing the configuration of a reticle inspection device embodying the present invention;

18 is a schematic diagram showing the relationship between the distribution of scattered light components scattered by the fine particles and d / λ (where d is the size of the fine particles and λ is the wavelength of the illumination light beam);

19 (a) and 19 (b) are schematic diagrams illustrating the configuration of a reticle inspection device and scattered light components detected by the device according to the present invention;

20 is a graph showing the relationship between the amount of change of the detection signal and the illumination light beam generated when detecting particles having a diameter of 0.5 µm on the chromium pattern in the surface irradiation method and when detecting the chromium pattern, respectively;

Fig. 21 is a graph showing the relationship between the amount of change in the detection signal and the illumination light beam generated when detecting particles having a size of 1.0 μm on a chromium pattern in the surface irradiation method and when detecting a phase shifter pattern, respectively.

Fig. 22 is a graph showing the relationship between the amount of change in the detection signal and the illumination light beam generated when detecting particles having a diameter of 0.5 μm on a glass substrate and when detecting a chromium pattern in the surface irradiation method;

Fig. 23 is a graph showing the relationship between the amount of change in the discrimination ratio (0.5 μm particle / chromium pattern on a chrome pattern) used in the surface irradiation method and the wavelength of the illumination light beam;

24 is a graph showing the relationship between the amount of change of the discrimination ratio (1.0 μm particle / phase shifter pattern on a chrome pattern) used in the surface irradiation method and the wavelength of the illumination light beam;

Fig. 25 is a graph showing the relationship between the amount of change in the discrimination ratio (0.5 μm particle / chromium pattern on a glass substrate) used in the surface irradiation method and the wavelength of the illumination light beam;

Fig. 26 is a schematic diagram for explaining detection of defects such as foreign matters by a process using 2 μm × 2 μm pixels instead of the 4 pixel addition process;

Fig. 27 is a schematic diagram for explaining detection of defects such as foreign matters by a 4-pixel addition process using 1 µm x 1 µm pixels;

28 is a block diagram of a four pixel addition circuit;

29 is a graph for explaining the shading effect in the detection of defects such as foreign matters;

Fig. 30 is a diagram for explaining the principle of shading, (a) is a drawing showing the measurement result (before correction) of shading, (b) is a drawing showing the result of calculating shading correction data, and (c) is shading. Shows the measurement result (after correction) of

31 is a block diagram of a shading correction circuit;

32 is a block diagram of a block processing circuit;

33 is a block diagram showing the functional relationship between a shading correction circuit, a four pixel addition circuit and a block processing circuit;

34 is a schematic view of a reticle inspection device of a second embodiment according to the present invention;

35 is a schematic diagram of a reticle inspection device of a third embodiment according to the present invention;

36 is a schematic diagram illustrating scattered light and diffracted light respectively scattered and diffracted by a reticle provided with a phase shifter film;

37 is a plan view showing a switching situation of the illumination system according to the present invention;

38 is a cross-sectional view showing a switching situation of an illumination system according to the present invention;

39 is a cross-sectional view showing a switching situation of an illumination system according to the present invention;

40 is a plan view showing a switching situation of the illumination system according to the present invention;

41 is a view showing an example of a block of a signal processing system according to the present invention;

42 is a view showing an example of a block of a signal processing system according to the present invention;

43 is a view showing an example of a block of a signal processing system according to the present invention;

44 is a diagram showing an example of a block of a signal processing system according to the present invention;

45 is a diagram showing an example of a block of a signal processing system according to the present invention;

46 is a view showing an example of a block of a signal processing system according to the present invention;

47 is a diagram showing an example of a block of a signal processing system according to the present invention;

48 is a diagram showing an example of a block of a signal processing system according to the present invention;

49 is a diagram showing an example of a block of a signal processing system according to the present invention;

50 is a diagram showing an example of a block of a signal processing system according to the present invention;

51 is a view showing an example of a block of a signal processing system according to the present invention;

52 is a diagram showing an example of a block of a signal processing system according to the present invention;

53 is a diagram showing an example of a block of a signal processing system according to the present invention;

54 is a schematic block diagram showing an example of a back lighting system according to the present invention;

55 is a schematic structural diagram showing an example of a back lighting system according to the present invention;

56 is a sectional view showing a problem of the back lighting system;

Fig. 57 is a sectional view for explaining a principle of solving a problem of a back light system;

58 is a schematic structural diagram showing an example of a back lighting system according to the present invention;

59 is a schematic block diagram showing an example of a back lighting system according to the present invention;

60 is a cross-sectional view illustrating a principle of solving a problem of a back lighting system;

61 is a schematic block diagram showing an example of a back lighting system according to the present invention;

62 is a schematic block diagram showing an example of an observation system according to the present invention;

63 is a plan view showing the situation of the spatial filter according to the present invention;

64 is a schematic block diagram showing an example of a situation of a spatial filter in the apparatus according to the present invention;

65 is a view showing a mask fabrication process and a stepper process according to the present invention;

66 is a view showing a reticle related process according to the present invention;

Fig. 67 is a diagram showing detection of defects such as foreign matters in 2 占 퐉 x 1 占 퐉 pixels by a two-pixel addition process;

Fig. 68 is a diagram showing the detection of defects such as foreign matters in 1 탆 x 1 탆 pixels by a 4-pixel maximum value process;

69 is a signal processing system according to the present invention, showing an example of a block for outputting a detection output from the result of a logical product operation;

70 is a signal processing system according to the present invention, showing an example of a block for outputting a detection output from a logical sum calculation result;

Fig. 71 is a diagram showing the occurrence of scattered light and its detection output in surface / rear logic product detection;

Fig. 72 is a diagram showing the occurrence status of scattered light and its detection output in surface / rear logic product detection;

73 shows the shape of scattered light from various circuit patterns and a spatial filter shape corresponding thereto;

Fig. 74 is a signal processing system according to the present invention, showing an example of a block for outputting a detection output from the result of a logical product operation.

In order to achieve the above object, the present invention provides a defect inspection apparatus for detecting a defect such as a defect such as a foreign matter attached to a substrate having a circuit pattern such as a photomask or a reticle. Stage part which can move arbitrarily in each direction of Z, the illumination system of the side which opposes the said circuit pattern surface from the four sides of the said circuit pattern surface, and avoided the shading with the pericle holding frame turns on. An illumination system having first and second independent light sources having a wavelength of 780 nm, the circuit pattern surface facing each other through a substrate on the back side of the circuit pattern surface, and being turned on in the first and second illumination systems. An illumination system having third and fourth independent light sources having a wavelength of approximately 488 nm on which the illumination system on the side opposite the illumination system is located, located on the surface side of the circuit pattern surface of each illumination system The direct reflected light and the direct transmitted light by the yarn are not focused, but scattered light and diffracted light generated at the same position on the circuit pattern are collected and wavelength-separated for each irradiation direction, and the spatial filter provided on each Fourier transform plane after separation is used to Binarization of a high-numbered imaging optical system having a NA of 0.4 or more for shielding diffracted light from a straight line and imaging an illuminated inspection area on a detector, and a binarization circuit having a threshold value set at the output of each detector. The signal processing system is configured to calculate and display defect data such as foreign matter on the circuit pattern based on the result and the signal output by the logical product of each binarization result.

That is, according to the present invention, a transparent or semitransparent substrate having a pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film is irradiated with a surface illumination system to the surface of the substrate in an oblique direction by a surface illumination system, thereby providing a surface of the substrate. And condensed scattered reflected light scattered and reflected from the surface of the pattern formed on the substrate, and the back illumination light is irradiated to the rear surface of the substrate in an oblique direction by a backside illumination system to transmit the diffraction through the substrate and the pattern formed on the substrate. The diffracted light is condensed, and the reflected scattered light and transmitted diffracted light from the pattern are shielded by an spatial filter provided on the Fourier transform surface among the collected scattered reflected light and transmitted diffracted light to form an image on a detector. Defects such as foreign matter adhering to the substrate by comparing the output by the optical diffraction light with the output by A defect detecting method of the foreign matter and so on, characterized in that for detecting.

The present invention also relates to a transparent or semitransparent substrate having a pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film, by irradiating the surface illumination light to the surface of the substrate in an oblique direction by a surface illumination system, thereby providing a surface of the substrate and Transmitted diffraction diffracted by diffusing scattered reflected light scattered and reflected from the surface of the pattern formed on the substrate and irradiating backside illumination light to the rear surface of the substrate in an oblique direction by means of a backside illumination system Condenses the reflected scattered reflected light and the transmitted diffracted light, and then separates the reflected scattered light and the transmitted diffracted light from the pattern by each spatial filter provided on each Fourier transform plane, and then separates each of the first detector and An image is formed on each of the second detectors, and the outputs of the first and second detectors are compared and deposited on the substrate. A defect detection method, such as foreign bodies, characterized in that for detection of defects, such as foreign matter.

In addition, the present invention is characterized in that in the defect detection method such as the foreign material, the substrate is a reticle provided with a phase shifter. In addition, the present invention is characterized in that in the defect detection method such as the foreign material, the reflected scattered light and transmitted diffraction light are focused by an imaging optical system provided on the surface side of the substrate and having an optical axis substantially perpendicular to the substrate surface. It is done. Moreover, in this invention, the defect detection methods, such as a foreign material, WHEREIN: The said surface illumination light is irradiated to the same location on the surface of the said board | substrate in several directions, and the said back illumination light is applied to the same location on the back surface of the said board | substrate in several directions. It is characterized by investigating. In addition, the present invention is characterized in that in the defect detection method such as the foreign material, the surface illumination light and the back illumination light are switched and irradiated.

In addition, the present invention is characterized in that in the defect detection method such as the foreign material, the wavelength of the surface illumination light and the back illumination light are different and the wavelength of the surface illumination light is longer than the wavelength of the back illumination light. The present invention is also characterized in that in the defect detection method such as the foreign material, the wavelength of the surface illumination light is set to 600 to 800 nm, and the wavelength of the rear surface illumination light is set to 450 to 550 nm.

In addition, the present invention is equipped with a foreign matter adhesion prevention means formed by attaching a transparent thin film to the frame on both sides of the reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of the light shielding film and a pattern formed of the light semitransmissive film or the light transmissive film. On the other hand, the surface illumination system irradiates the surface illumination light through the transparent thin film to the surface of the substrate in an oblique direction, and scatters the scattering reflected from the surface of the substrate obtained through the transparent thin film and the surface of the pattern formed on the substrate. Transmissive diffraction light that collects reflected light and irradiates backside illumination light through the transparent thin film to the backside of the substrate in an oblique direction by a backside illumination system, and transmits and diffracts through a pattern formed on the substrate and the substrate obtained through the transparent thin film Condensing, and the focused scattered reflection light and transmission diffraction After the separation, the separated scattered light and the transmitted diffracted light from the pattern are shielded by each spatial filter provided on each Fourier transform plane to form an image on each of the first detector and the second detector, and the first detector And a defect detection step of detecting a defect such as a foreign material adhering on the substrate by comparing the output of the second detector, and a foreign matter adhesion preventing means in which the defect is not attached to the substrate in the defect detection step. An import process of bringing a reticle provided with a mounted phase shifter into the exposure position of a projection exposure apparatus, and irradiating the exposure light to a reticle provided with a phase shifter equipped with a foreign matter adhesion preventing means carried in by the import process, and performing an imaging optical system. The light shielding film is prevented by changing the phase of light from the light semitransmissive film or the light transmissive film adjacent to the substrate to be exposed. A projection exposure method which is characterized in that it includes an exposure step of transferring a circuit pattern is exposed.

The present invention also relates to a reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film. Irradiates in the oblique direction and collects the scattered reflection light reflected from the surface of the substrate and the surface of the pattern formed on the substrate, and irradiates the back illumination light to the back surface of the substrate in an oblique direction by means of a back illumination system on the substrate and the substrate. Condensing the transmitted diffraction light diffracted by passing through the formed pattern, separating the collected scattered reflection light and the transmission diffraction light, and after the separation, the reflected scattered light and the transmitted diffraction light from the pattern by each spatial filter provided on each Fourier transform plane Shading to form an image on each of the first detector and the second detector, respectively, and the first detector and the second detector Projection exposure of a reticle provided with a phase shifter which compares the output of the output and detects defects such as foreign matters deposited on the substrate, and in which the defects are not adhered on the substrate in the defect detection process. An import process for bringing into the exposure position of the apparatus, irradiating the exposure light to the reticle provided with the phase shifter imported by the import process, and by means of an imaging optical system, the light from the light semitransmissive film or the light transmissive film adjacent to the substrate to be exposed. And an exposure step of changing the phase to prevent interference and exposing and transferring the circuit pattern of the light shielding film.

The present invention also relates to a reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film. Irradiates in the oblique direction and collects the scattered reflection light reflected from the surface of the substrate and the surface of the pattern formed on the substrate, and irradiates the back illumination light to the back surface of the substrate in an oblique direction by means of a back illumination system on the substrate and the substrate. Condensing the transmitted diffraction light diffracted by passing through the formed pattern, separating the collected scattered reflection light and the transmission diffraction light, and after the separation, the reflected scattered light and the transmitted diffraction light from the pattern by each spatial filter provided on each Fourier transform plane Shading to form an image on each of the first detector and the second detector, respectively, and the first detector and the second detector The first defect detection step of comparing the output of the output and detecting a defect such as a foreign matter attached to the substrate, and the phase shifter in which the defect is not attached to the substrate in the first defect detection step is provided. For a reticle provided with a phase shifter equipped with a foreign matter adhesion preventing means for mounting a foreign matter adhesion preventing means for attaching a foreign matter adhesion preventing means constructed by attaching a transparent thin film to the frame on both sides of the reticle; The surface illumination system irradiates surface illumination light through the transparent thin film to the surface of the substrate in an oblique direction to collect scattered and reflected light scattered and reflected on the surface of the substrate obtained through the transparent thin film and the surface of the pattern formed on the substrate. And back illumination light by the back illumination system through the transparent thin film. Irradiating the surface in oblique direction to the substrate obtained through the transparent thin film and the pattern formed on the substrate to transmit the diffraction diffracted light is diffracted, the scattered reflected light and the transmitted diffraction light is separated, and after each separation Fourier change Each spatial filter provided on the surface shields the reflected scattered light and the transmitted diffracted light from the pattern, and forms an image on each of the first and second detectors, and compares the outputs of the first and second detectors. A second defect detection step of detecting defects such as foreign matters deposited on the substrate, and a phase shifter equipped with foreign matter adhesion preventing means for confirming that no defects are attached on the substrate in the second defect detection step. Carry-in step of bringing the prepared reticle into the exposure position of the projection exposure apparatus, and a phase equipped with foreign matter adhesion preventing means carried in by the carry-in step. Exposure to irradiate exposed light to a reticle provided with a printer, and to change the phase of light from an adjacent light semitransmissive film or light transmissive film on an exposed substrate by an imaging optical system to prevent interference and to expose and transfer the circuit pattern of the light shielding film. It is a projection exposure method characterized by including the process.

The present invention also relates to a surface illumination system for irradiating surface illumination light to the surface of the substrate in an oblique direction with respect to a transparent or semitransparent substrate having a pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film. Back lighting system for irradiating the back surface of the substrate in an oblique direction, scattered reflection light that is reflected from the surface of the substrate and the surface of the pattern formed on the substrate by irradiating surface illumination light by the surface lighting system and back surface by the back lighting system An imaging optical system for reflecting the illumination illumination light and condensing and diffracting the diffraction diffracted light transmitted through the substrate and the pattern formed on the substrate, the scattered reflection light and the diffraction diffracted light from the scattered reflection light and the transmissive diffraction light A spatial filter provided on a Fourier transform surface for shielding the light; A detector that receives scattered reflected light and transmitted diffraction light formed by a system and converts the output signal into an output signal, and a foreign material attached to the substrate by comparing the output signal from the reflected scattered light obtained from the detector with the output signal from the transmitted diffraction light Defect detection apparatus, such as a foreign material, characterized by including the detection means for detecting the defect of the.

The present invention also relates to a surface illumination system for irradiating surface illumination light to the surface of the substrate in an oblique direction with respect to a transparent or semitransparent substrate having a pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film. Back lighting system for irradiating the back surface of the substrate in an oblique direction, scattered reflection light reflected from the surface of the substrate and the surface of the pattern formed on the substrate by irradiating surface illumination light by the surface lighting system and back surface by the back lighting system An imaging optical system for condensing and diffracting diffraction diffracted light that is diffracted by passing through the substrate and a pattern formed on the substrate by irradiating the illumination light, and a separation optical system that separates scattered reflected light and transmitted diffraction light collected by the imaging optical system, and the separation optical system Each Puri shading each of the reflected scattered light and the transmitted diffracted light from the pattern separated by First and second spatial filters provided on the conversion surface and first and second spatial filters respectively receiving scattered reflection light and transmitted diffraction light formed by the imaging optical system and converting the light into an output signal; And a detecting means for detecting defects such as foreign matter attached to the substrate by comparing the output signal by the reflected scattered light and the output diffraction light obtained by each of the two detectors and the first and second detectors. It is a defect detection apparatus such as a foreign material.

In addition, the present invention is equipped with a foreign matter adhesion prevention means formed by attaching a transparent thin film to the frame on both sides of the reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of the light shielding film and a pattern formed of the light semitransmissive film or the light transmissive film. On the other hand, the surface illumination system irradiates the surface illumination light through the transparent thin film to the surface of the substrate in an oblique direction, and scatters the scattered reflections on the surface of the substrate obtained through the transparent thin film and the surface of the pattern formed on the substrate. Transmissive diffraction light that collects reflected light and illuminates the back illumination light through the transparent thin film on the back surface of the substrate in an oblique direction by the back illumination system, and transmits and diffracts through the substrate formed through the transparent thin film and the pattern formed on the substrate. Condensing and separating the focused scattered reflection light and transmitted diffraction light After separation, each of the spatial filters provided on the Fourier transform surfaces shields the scattered reflected light and the transmitted diffracted light from the pattern, and forms an image on each of the first and second detectors. A defect detection means for comparing the output of the two detectors and detecting a defect such as a foreign material adhering on the substrate, and a foreign matter adhesion preventing means for confirming that the defect is not attached to the substrate by the defect detection means. A reticle provided with a phase shifter equipped with a phase shifter carrying the reticle provided with the phase shifter into the exposure position of the projection exposure means and a foreign matter adhesion preventing means carried by the carrying means is irradiated with an exposure optical system and exposed by the imaging optical system. By changing the phase of the light from the light transmissive film or the light transmissive film adjacent to the substrate to prevent interference and the circuit pattern of the light shielding film A projection exposure apparatus characterized by having a projection exposure means for exposing the transfer.

The present invention also relates to a reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film. Irradiating in the oblique direction to collect scattered reflection light reflected from the surface of the substrate and the surface of the pattern formed on the substrate, and irradiating the back illumination light to the back surface of the substrate in an oblique direction by a back illumination system on the substrate and the substrate Condensing the transmitted diffraction light diffracted by passing through the formed pattern, separating the collected scattered reflection light and the transmission diffraction light, and after the separation, the reflected scattered light and the transmitted diffraction light from the pattern by each spatial filter provided on each Fourier transform plane Shaded to form an image on each of the first detector and the second detector, and the first detector and the second gum Projection exposure of a reticle provided with a defect detecting means for comparing the output of the output and detecting a defect such as a foreign matter attached to the substrate, and a phase shifter having confirmed that no defect is attached to the substrate by the defect detecting means. The exposure means for carrying in to the exposure position of the means, the reticle provided with the phase shifter carried by the carrying means is irradiated with the exposure light, and the imaging of the light from the light semitransmissive film or the light transmitting film adjacent to the exposed substrate by the imaging optical system. And a projection exposure means for changing the phase to prevent interference and exposing and transferring the circuit pattern of the light shielding film.

The present invention also relates to a reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film. Irradiates in the oblique direction and collects the scattered reflection light reflected from the surface of the substrate and the surface of the pattern formed on the substrate, and irradiates the back illumination light to the back surface of the substrate in an oblique direction by means of a back illumination system on the substrate and the substrate. Condensing the transmitted diffraction light diffracted by passing through the formed pattern, separating the collected scattered reflection light and the transmission diffraction light, and after the separation, the reflected scattered light and the transmitted diffraction light from the pattern by each spatial filter provided on each Fourier transform plane Shading to form an image on each of the first detector and the second detector, respectively, and the first detector and the second detector Projection exposure of a reticle provided with a defect detecting means for comparing the output of the output and detecting a defect such as a foreign matter attached to the substrate, and a phase shifter having confirmed that no defect is attached to the substrate by the defect detecting means. The exposure means for carrying in to the exposure position of the means, the reticle provided with the phase shifter carried by the carrying means is irradiated with the exposure light, and the imaging of the light from the light semitransmissive film or the light transmitting film adjacent to the exposed substrate by the imaging optical system. And a projection exposure means for changing the phase to prevent interference and exposing and transferring the circuit pattern of the light shielding film.

In addition, the present invention relates to a reticle provided with a phase shifter formed of a transparent or semitransparent substrate having a circuit pattern of a light shielding film and a pattern formed of a light semitransmissive film or a light transmissive film, by a surface illumination system before and after mounting the foreign matter adhesion preventing means. The surface illumination light is irradiated to the surface of the substrate in an oblique direction to collect scattered reflection light scattered and reflected on the surface of the substrate and the surface of the pattern formed on the substrate, and the rear illumination light is inclined by the backside illumination system. The diffraction diffracted light is diffracted by passing through the substrate and the pattern formed on the substrate and irradiated in a direction, and the scattered reflected light and the transmissive diffraction light are separated, and separated by a spatial filter provided on each Fourier transform plane after separation. Reflecting scattered light and transmitted diffracted light from Defect detection means for forming an image on the substrate and comparing outputs of the first detector and the second detector to detect a defect such as a foreign matter attached to the substrate, and the defect detection means does not adhere the defect on the substrate. Exposure means for carrying in the reticle provided with the phase shifter with the foreign matter attachment prevention means confirmed to the exposure position of the projection exposure means, and the reticle provided with the phase shifter with the foreign matter adhesion prevention means carried in by the said import means. And projection exposure means for irradiating the light and changing the phase of the light from the adjacent light semitransmissive film or the light transmissive film on the exposed substrate by an imaging optical system to prevent interference and to expose and transfer the circuit pattern of the light shielding film. Projection exposure apparatus.

By the way, in the exposure process of a reticle or the like used for manufacturing an LSI or a printed board, a circuit pattern such as a reticle is inspected before being printed on a wafer, but a fine size of, for example, micron size is applied to the circuit pattern. Even in the presence of water, the circuit pattern was not normally transferred to the wafer by the foreign matter, and thus the entire LSI chip had a problem.

This problem is due to the recent high integration of LSIs, which has not allowed the presence of foreign objects of more or less deep submicron size and more present.

As described above, as defects such as foreign matters to be detected become smaller, defect detection leakage of defects such as foreign matters affecting the production of the LSI must be increased. Recently, a transparent or semi-transparent thin film called a phase shift film or a phase shifter between circuit patterns on a reticle for the purpose of improving the transfer resolution of a circuit pattern on a reticle formed of a metal thin film such as chromium (approximately 1/2 of the wavelength of an exposed light source) A reticle has been developed. Although the film is transparent or translucent, it has a structure of several times the size of the circuit pattern (about 0.1 μm in thickness), so that the diffracted light from the edge portion of the film is many times that of the diffraction light from the conventional circuit pattern and edge portion. It becomes tens of times larger, and the detection sensitivity of defects such as foreign matters is significantly lowered, and this problem needs to be solved.

[1] surface / rear logic detection, processing circuitry, lighting switching

As described so far, it has been difficult in the prior art to detect only foreign substances by distinguishing between a foreign material and a circuit pattern of a reticle used for manufacturing after a phase shift reticle, for example, 64 M DRAM.

The present invention solves the above problems by the experimental fact found by the present inventors that the amount of scattered light from the circuit pattern of these reticles changes depending on the illumination direction.

FIG. 10 is an explanatory diagram, in which (701) and (702) are scattered light detection output values from a defect 70 such as a fine foreign material of 0.5 μm or less, (864), (874), (865), (875), (866), (876), (867), and (877) are the detection output values of the scattered light from all corner portions 82 formed by circuit patterns of 0 °, 45 °, and 90 °, ( 861, 871, 862, 872, 863, and 873 respectively represent detection output values of scattered light from a microstructure circuit pattern having a dimension 84 of about 0.5 탆. Among them, 701, 861, 862, 863, 864, 865, 866, and 867 are the swords of the first illumination system 2 (or (3)). 702, 871, 872, 873, 874, 875, 876, 877 are output by the second illumination system 20 (or 30). Denoting the detection output value, for example, (861) ← → (871) is a detection output value for each illumination system at the same position of the circuit pattern, where 861 is the value by the first illumination system 2 (or (3)). , 871 denotes a value by the second illumination system 20 (or 30). In addition, as shown in the figure, the defect 70 such as the foreign matter has a smaller variation in the detection output value of the scattered light in the irradiation direction than in the circuit pattern. In addition, the dotted line 91 in a figure shows the threshold value of a detection output value.

It is found from Fig. 10 that the output of the scattered light varies greatly depending on the irradiated direction even with the same circuit pattern, and the illumination is provided in two opposite directions in a direction opposite to 180 ° on the plane of the reticle 6. In this case, it can be seen that the output value of the scattered light on either side is necessarily smaller than the output value from defects such as foreign matters of the size of the deep submicron as shown in the table in the figure.

For this reason, when illuminating simultaneously in two opposite directions from 180 degrees on the plane of the reticle 6 as shown in FIG. 1, the detection output of the particles and the circuit pattern is the sum of the detection outputs of the respective illuminations. Although it is only difficult to binarize to the threshold value, it is difficult to detect the scattered light by the opposing illumination with two separate detectors, respectively, and each of the threshold values 91 by a separate binarization determination circuit. In the case of binarization, the two determination results are both 1 in the case of a defect such as a foreign material or the like, and in the case of a circuit pattern, only one of the two determination results is 1 or both are 0. Thus, by taking the logical product of the determination result of the binarization determination circuit, it is possible to detect defects 70 such as foreign matters, including defects such as foreign matters having a size of about a deep submicron, from the circuit pattern.

[2] back lighting, coherent length, light intensity balance, optical path length correction, lighting position correction

As described so far, it has been difficult in the prior art to distinguish between foreign matter and circuit patterns of reticles used for manufacturing after phase shift reticles, for example, 64 M DRAM, and foreign matter.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back lighting detection method capable of detecting foreign matters without being affected by the edge of the phase shifter. The light condensing state according to the type of glass substrate thickness when the four sides lighting is performed on the back surface is performed. In order to prevent the illumination position from changing, when inspecting other glass substrates, a glass plate for giving the optical path length equal to the difference in thickness is inserted between the rear surface and the optical system on the back side of the reticle, and a photomask such as a reticle The optical path length to the surface (circuit pattern surface) is kept constant regardless of the thickness of photomasks such as reticles.

[3] spatial filters for observation, laser illumination for observation

In the case where the detected foreign material has a small size (for example, about 0.3 µm), even if an observation optical system is used for confirmation, observation may be difficult by normal fallout or transmission illumination alone. Moreover, in such an object, even if normal dark field illumination is performed, it is difficult to obtain sufficient light quantity (brightness) for observation.

For such an object, it is practical to observe scattered light by performing all-round illumination with a laser. In this case, the detection laser may be used as a combination, but when the detection laser is not visible light, it is inconvenient to intervene a TV camera or the like having sensitivity to the wavelength of the laser. Therefore, in addition to the detection, a visible light laser illumination system is provided and used for observation. To this end, the use of a laser diode having an oscillation wavelength in the recently developed visible light region can be used to construct a compact and simple system.

In addition, in all directions of illumination by laser, the circuit pattern scattered light can be removed by a spatial filter similarly to the detection system. For this reason, if the observation system is a mechanism capable of inserting the spatial filter as necessary, scattered light from defects such as foreign matters is emphasized, and defects such as foreign matters are more easily identified.

[4] transmittance measurements, pericle

In order to protect the circuit pattern surface of the reticle, the pellicle film (hereinafter referred to as the reticle) is a study to prevent the amount of light transmitted through the anti-reflection film or the like from the exposure light (mostly near-ultraviolet light to ultraviolet light) to be reduced. Has become. However, since these studies are optimized for exposure light, they are generally not optimized for light sources used for defect inspection such as foreign matters, resulting in a reduction in illumination light for inspection. In addition, the rate of decrease varies slightly depending on the individual pellicle. For this reason, there is a problem that changes in individual ferrules reduce the margin of the criterion for inspection.

In the case of the light passing through the pellicle vertically (in the present invention, the scattered light from the sample corresponds to this), the amount of change is small and does not become a problem. However, in the light transmitted obliquely (in the present invention, all-round illumination light illuminating the sample corresponds to this), the influence may be a big problem. Hereinafter, the measuring method of the transmittance | permeability in the case where the light permeate | transmits obliquely which becomes this problem is described.

As a method of measuring the permeability of the pericle of each reticle at each inspection and correcting the detection output, there is one example of the invention in Japanese Patent Application Laid-Open No. 4-151663. According to this, a laser beam is incident vertically through a ferricle, the amount of specular reflection from the chromium film on the reticle substrate is measured, and the transmittance of the pellicle film is determined from the ratio with the amount of light before incidence. In this prior art, since the measured value includes not only the pericle but also the reflectance of the reticle substrate, the change in the substrate reflectance affects the measurement accuracy. In addition, in the case where the illumination for detection is performed in all directions as in the present invention as in the present invention, this conventional example cannot be applied because the laser beam for measurement also needs to be incident from all directions at the same angle as in the inspection.

Therefore, in the present invention, the amount of reflected light from the pellicle film is measured by entering the pellicle from all directions at the same wavelength and the same illumination angle as the detection wavelength, and the reflectance of the pellicle film is measured at this and the output light amount of the illumination light source. Assuming there is no internal loss of the pellicle membrane,

(Transmitted Light) = (Incidence Light)-(Reflected Light)

(Transmittance) = (Transmitted light amount) / (Incidence light amount)

Because of,

(Transmittance) = ((Incidence amount)-(Reflection amount)) / (Incidence amount)

The transmittance can be obtained to correct the detection result.

[5] spatial filter width switching, polarizer: maximum detection of four pixels and OR

According to the present invention, in the case of a photomask such as a reticle, diffraction / scattered light (hereinafter referred to as diffraction light) generated by illumination from all directions in a circuit pattern formed on a photomask such as a reticle is Fourier on the Fourier transform plane of the circuit pattern surface. It was made in accordance with the discovery that the light is condensed in a straight line at a specific place on the conversion surface, especially in the center portion thereof. The picture in the left column of Figs. 73A to 73C shows the situation. This photo shows the diffracted light generated by the illumination from all directions in the circuit pattern formed on the photomask such as a reticle on the Fourier transform plane of the circuit pattern surface. 73 (a) to 73 (c) each show diffracted light from photomasks such as different types of reticles. According to the findings of the inventors, the diffracted light generated in a photomask such as a reticle has a diffraction pattern different according to its type, but most of the diffracted light is linearly focused at the center of the Fourier transform plane as shown in the photograph of FIG. do. Therefore, as shown in the drawing in the right column of Figs. 73A to 73C, two or three types of linear shapes having the parameters of the width of the light shielding portion shielding the central portion of the Fourier transform surface as a parameter are shown. When a spatial filter is prepared and used after switching for each photomask such as a reticle, it scatters diffracted light generated in most circuit patterns, and scattered light (defects such as foreign matter) generated through defects such as foreign matter through the light transmitting portion of the spatial filter. Scattered light from the light beam may not be focused on the central part).

There is also an exceptionally exceptional photomask such as a reticle with little light condensing to the center as shown in Fig. 73 (d). However, for such an object, the entire Fourier transform plane may be switched to a filter composed of a polarizing filter.

In an array type detector such as a CCD, when detection and determination of defects such as foreign matters are performed in units of pixels, under conditions in which defects such as foreign matters are detected between a plurality of pixels (2 to 4), Scattered light from defects is also dispersed into several pixels, and as a result, the detection output of one pixel is reduced to 1/2 to 1/4, resulting in deterioration of detection reproducibility. In the case of -2262, the detection pixel dimension is reduced by reducing the length of one side to 1/2 (the area is 1/4), electrically adding the detection outputs of four adjacent pixels of each pixel, and detecting the output by the target pixel. We have devised a four-pixel addition process that simulates.

By the way, in the above-described method, when the size of defects such as foreign matters to be detected is small (for example, 0.5 µm) as compared with the pixel dimension (for example, 2 µm x 2 µm) for detecting detection, the detector before the 4-pixel addition process As long as defects such as foreign matters are caught in one pixel of (for example, 1 μm × 1 μm), the detection output from defects such as foreign matters is the same before and after the four pixel addition process (because the four pixel addition method This is because it is a method for compensation in the case where it is not captured by one pixel and spans several pixels as described above). In this case, it is considered that the scattered light from the circuit pattern decreases the scattered light from the circuit pattern because the smaller the area (pixel dimension) of the pixel of the detector is, the smaller the number (or area) of the corner portion of the circuit pattern fits in the pixel. The smaller the pixel dimension itself is, the more preferable it is, and more sensitive defects such as foreign matter can be detected. Therefore, it can be said that the 4-pixel addition processing system sacrifices the detection sensitivity as opposed to the stability of the detection. If the detection sensitivity is sufficient after sacrifice, it is not necessary to implement a new design for this problem, but in order to follow the change of the process conditions or the change of the exposure method, the inspection technology with more flexible detection sensitivity should be considered. You need to do it.

In response to this problem, the detection method may be switched in accordance with the performance required by selecting the high-definition detection mode in which the four-pixel addition processing is performed and the high sensitivity detection mode in which the four-pixel addition processing is not performed.

Note that the two modes are operable at the same time by performing detection determination of defects such as foreign matters before and after the four pixel addition process. In the present invention, the operation is executed simultaneously to obtain a logical sum of the detection results of the two modes. In this way, a constitution has been devised that performs high stability detection and high sensitivity detection simultaneously.

In addition, when the two modes are operated synchronously, there is a problem that the data amount is four times different before and after the four-pixel addition process (since the data amount is 1/4 because the data is obtained once per four pixels after the process). If only the data of the pixel of the maximum value among the four adjacent pixels among the data before processing is output (the data amount is 1/4 because the data is obtained once per four pixels), the data amount is the same before and after the processing. Thus, the logical sum can be easily obtained.

[6] two-pixel addition

In an array type detector such as a CCD, when detection and determination of defects such as foreign matters are performed in units of pixels, under conditions in which defects such as foreign matters are detected between several (two to four) pixels, such as foreign matters, etc. Scattered light from defects is also dispersed into several pixels, and as a result, the detection output of one pixel is reduced to 1/2 to 1/4, resulting in deterioration of detection reproducibility. In the case of -2262, the detection pixel dimension is reduced by reducing the length of one side to 1/2 (the area is 1/4), electrically adding the detection outputs of four adjacent pixels of each pixel, and detecting the output by the target pixel. We have devised a four-pixel addition process that simulates.

In the above-described conventional example, the four-pixel addition process is a measure to prevent the output decrease of the detection result that spans the detection pixels, so that the processing pixel may be processed with more than four pixels, and as long as the effect can achieve the desired purpose. The process of two pixels or three pixels may be sufficient.

In the present invention, attention is paid to rectangular pixels that can be realized by making the transfer speed of the stage faster than the accumulation time of the detector. For example, if it is intended to form a pixel of 1 μm × 2 μm on a sample, a 1 μm × 2 μm pixel on the sample is transmitted by transferring a 2 μm stage during the accumulation time T by a detector having a size of 1 μm × 1 μm on the sample. Can be realized.

In this case, the output of the target pixel can be obtained by performing the process of adding two pixels. The two-pixel addition process reduces the effect of preventing the output deterioration of the foreign material over four pixels, but the inspection speed is improved because the transfer speed of the stage is faster than the four-pixel addition.

[7] glass and glass detectors

Since the technique used in the present invention uses a high resolution detector, it is difficult to speed up, and it is disadvantageous in terms of inspection time compared to the conventional method of low sensitivity. On the other hand, in foreign material inspection of photomasks such as reticles, in addition to the portion of the circuit pattern surface which requires high sensitivity detection, the detection on the back surface (also referred to as the glass surface because there is no circuit pattern) or the surface of the pellicle other than the surface where the circuit pattern is formed It is also required. In these respects, detection with much lower sensitivity than that of the circuit pattern surface is sufficient, so that applying a high resolution and high sensitivity detection method unnecessarily consumes detection time.

In Japanese Patent Laid-Open Publication No. 4-273008, the depth of focus may be reduced to focus on the depth of focus instead of high speed. I am devising to implement lighting.

In the case of high-NA detection as in the present invention, it is common to change the resolution by changing the magnification of the objective lens, but in a photomask such as a reticle, since the circuit pattern surface and the back surface of the pericle film exist on different planes, the focus is detected. The position must be moved in the range of several millimeters, and the burden on the Z stage (moving stage in the thickness direction of the photomask, such as a reticle), which requires high precision and high resolution for focusing when detecting the circuit pattern surface, becomes large.

In the present invention, the low-resolution, high-speed detection unit for the back surface of the ferrule film surface is devised to be provided independent of the circuit pattern surface.

[8] shading correction method: detection wavelength determination method: detection sensitivity determination method

The above and other objects and novel features of the present invention will become apparent from the description and the accompanying drawings.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Recently, in order to improve the transfer resolution of a circuit pattern of a metal thin film such as a chrome thin film (hereinafter referred to as a chrome pattern), a reticle as shown in FIG. 36 has been developed. This recently developed reticle is hereinafter referred to as phase shift reticle. The phase shift reticle is provided with a pattern of transparent or semi-transparent thin film (hereinafter referred to as a phase shift pattern) having a thickness of a half of the wavelength of light emitted by the exposure light source and called a phase shift film or phase shifter. The film forming the phase shift film is transparent or translucent and has a thickness several times that of the chromium pattern (about 0.1 m in thickness).

When the reticle is inspected by a conventional reticle inspection device, the surface of the reticle on which the chrome pattern is formed is irradiated and the scattered light generated is collected by a detection optical system arranged on the surface side (surface irradiation method, FIG. 16). In the case of inspecting defects such as foreign matters in the phase shift reticle, the scattered light scattered at the edge of the phase shifter pattern is detected several times to several orders of magnitude larger than the diffracted light diffracted at the edge portion of the conventional chromium pattern, thereby detecting the sensitivity of defects such as foreign matters. Problem occurs that is significantly reduced.

In order to solve this problem, in the present invention, attention has been paid to the edge portion of the phase shifter pattern extending onto the chrome pattern of the light shielding film. When the scattered light generated by emitting illumination light from the back side of the reticle is collected by a detection optical system disposed on the surface side of the reticle (backside irradiation method, FIG. 17), the illumination light directed toward the edge side of the phase shift pattern is the light shielding film of the phase shift reticle. It is blocked by the chrome pattern, and since illumination light is not scattered by a phase shift pattern, the detection sensitivity of defects, such as a foreign material, does not fall.

The backside irradiation method can detect only defects such as foreign matters in the light transmitting portion, that is, the portion where the chromium pattern element is not formed. In practice, defects such as foreign matter on the chrome pattern should also be detected. Therefore, it is preferable to irradiate a reticle using both the surface irradiation method and the backside irradiation method together. Hereinafter, the surface irradiation method and the backside irradiation method will be described with respect to defects such as foreign matters and luminance of scattered light scattered on the surface of the reticle.

According to the scattering theory of light, the scattered light scattered by the particles is in the same correspondence with respect to the relationship between the wavelength and the particle size. FIG. 18 is a graph showing the relationship between the distribution of scattered light scattered by particles and d / λ (d: particle size, λ: wavelength of light emitted from a light source). The light component scattered in the moving direction of the illumination light is called the front scattered light component, and the light component scattered in the direction opposite to the moving direction of the illumination light is called the back scattered light component.

In the case of irradiating the illumination light to particles of any size, the front scattered light component increases as the wavelength of the illumination light is shorter, the scattered light component becomes uniform as the wavelength of the illumination light is longer, and the ratio of the back scattered light component to all the scattered light components is Gets bigger

FIG. 19A shows the positional relationship between the moving direction of the illumination light and the detection optical system when the surface irradiation method is used, and FIG. 19B shows the moving direction of the illumination light and the detection optical system when the backside irradiation method is used. It shows the positional relationship of. The back scattering light component is detected by the surface irradiation method, and the forward scattering light component is detected by the backside irradiation method. As shown in Fig. 18, the front scattered light component is always larger than the back scattered light component. Therefore, in order to obtain a defect detection signal such as a high foreign material, it is effective to detect the forward scattered light component. That is, it is advantageous to detect the front scattered light component by the backside irradiation method in order to detect defects such as foreign matters in the light transmitting portion of the reticle regardless of the presence or absence of the phase shifter pattern of the reticle.

In a reticle inspection device that detects defects such as foreign matter attached to a transparent (translucent) substrate having a circuit pattern formed of a light shielding film such as a photomask or a reticle, defects such as foreign matters of the light shielding portion are detected by the surface irradiation method. By detecting defects such as foreign matters in the light transmitting portion by the irradiation method, defect detection signals such as foreign matters can be increased.

In each irradiation method, defect detection signals such as foreign matters can be maximized by using illumination light having an optimal wavelength. In order to find the optimal wavelength of illumination light which maximizes the defect detection signal such as a foreign material, the result of the experiment which calculated the change of detection performance according to the wavelength of illumination light is shown.

In the surface irradiation method, by increasing the wavelength of illumination light, defect detection signals such as backscattered light components and foreign matters increase.

Fig. 20 shows the variation in the chromium pattern detection signal generated at the time of chromium pattern detection in the surface irradiation method and the defect detection signal such as foreign matters generated at the time of 0.5 µm particle detection on the chromium pattern (light shielding part). It is a figure which shows about. Laser beams having wavelengths of 830 nm, 780 nm, 633 nm, 532 nm, 515 nm and 488 nm respectively were used as illumination light beams. In the wavelength range of 488 nm to 830 nm, the longer the wavelength, the larger the particle detection signal. When the wavelength is 780 nm, the particle detection signal reaches a peak. The chromium pattern detection signal changes with a relatively narrow range of wavelengths.

Fig. 21 shows the variation of the shifter pattern detection signal generated during the shifter pattern detection in the surface irradiation method and the variation of the particle detection signal generated when the 1.0 µm particle detection on the chromium pattern (light shielding part) occurs with respect to the wavelength of the illumination light. One drawing. Laser beams having wavelengths of 830 nm, 780 nm, 633 nm, 532 nm, 515 nm and 488 nm respectively were used as illumination light beams. In the wavelength range of 488 nm to 830 nm, the longer the wavelength, the larger the particle detection signal and the shifter pattern detection signal.

In the backside irradiation method, the shorter the wavelength of the illumination light, the more the front scattered light component increases and the larger the particle detection signal.

Fig. 22 shows the variation of the particle detection signal generated at the time of 0.5 µm particle detection on the glass plate (light transmitting part) in the backside irradiation method and the variation of the chromium pattern detection signal generated at the detection of the chromium pattern with respect to the wavelength of the irradiation light. The figure is shown. In the backside irradiation method, the shifter pattern does not scatter the illumination light at all. Laser beams having wavelengths of 780 nm, 633 nm, 532 nm, 515 nm and 488 nm respectively were used as illumination light beams. The shorter the wavelength, the larger the particle detection signal. The shorter the wavelength, the larger the chromium pattern detection signal, but the chromium pattern detection signal changes to a wavelength that is smoother than the particle detection signal.

When inspecting defects such as foreign matter on a sample provided with a circuit pattern, defect detection signals such as foreign matter generated at the time of scattered light scattered by defects such as foreign matter and pattern detection generated at the time of detecting scattered light scattered by the circuit pattern Consider the relationship of the signals. This relationship is based on the discrimination ratio defined by (discrimination ratio) = (output of the detector generated when the scattered light is detected by a defect such as foreign matter) / (output of the detector generated when the scattered light is detected by the pattern). It is represented by

If the discrimination ratio is larger than 1, defects such as foreign matter can be detected through comparison (binarization) of scattered light detection signals by a device having a simple configuration. In the actual apparatus, the detection signal is affected by electrical noise, optical noise, vibration of the mechanism part, variations in detection system sensitivity, and the like. Therefore, a sufficient distance must be provided between the level of the scattered light scattered by defects such as foreign matter and the level of the scattered light scattered by the chromium pattern. That is, the larger the discrimination ratio, the greater the ability to detect defects such as foreign matter.

The above experimental results were examined to determine the wavelength of the illumination light beam that maximizes the detection capability of the surface irradiation method and the backside irradiation method.

23 and 24 are diagrams showing variations in the discrimination ratio in the inspection of the surface irradiation method with respect to the wavelength of the illumination light beam.

[1] Figure 23: 0.5 µm standard particle / chromium pattern on chromium pattern (maximum value)

[2] Figure 24: 1.0 µm standard particle / shifter pattern (maximum value) on chrome pattern

In FIG. 23, it can be seen that when using an illumination light beam having a wavelength of about 780 nm, 0.5 µm standard particles on a reticle having no phase shift film can be detected most stably.

In FIG. 24, it can be seen that by using an illumination light beam in the wavelength range of 600 nm to 800 nm, 1.0 μm standard particles on the chromium pattern of the phase shift reticle can be detected.

23 and 24, it can be considered that the optimum illumination light beam in the surface irradiation method is an illumination light beam having a wavelength of about 780 nm.

As a light source capable of emitting an optimal illumination light beam having such a wavelength of about 780 nm, there is a semiconductor laser. As is clear from Fig. 23, the discrimination ratio obtained by using this optimal illumination light beam is higher than the discrimination ratio obtained by using a laser beam having a wavelength of 632.8 nm, which has been emitted by a red He-Ne laser which is generally used in the past. Therefore, defect detection, such as a foreign material, can be stably performed with an optimal illumination light beam.

Fig. 25 is a view showing variation of the discrimination ratio with respect to the wavelength of the illumination light beam during the inspection in the backside irradiation method.

[1] Figure 25: 0.5 µm standard particle / chrome pattern (maximum value) on glass substrate

In Fig. 25, it can be seen that the discrimination ratio reaches a maximum when using an illumination light beam having a wavelength of about 488 nm in the inspection in the backside irradiation method.

As a light source that emits light having a wavelength of about 488 nm, there is an Ar (argon) ion laser. An Ar ion laser having a large output capacity can be easily produced, and the output of the air-cooled Ar ion laser is several tens of kilowatts, and the output of the water-cooled Ar ion laser is several W. Therefore, the detection signal when using an Ar ion laser beam is larger than the detection signal when using a red He-Ne laser beam.

Therefore, as described above, in the present invention, in order to discriminate defects such as circuit patterns on a specimen having a phase shift film and foreign matters, the directional illumination and the wavelength of about 488 by an illumination light beam having a wavelength of about 780 nm in the surface irradiation method are used. Combination of both sides of the illumination with the light beam of illumination of nm is used.

The optimum wavelength is selected in consideration of the minimum dimension of defects such as foreign matter to be detected is 0.5 占 퐉. As the size of defects such as foreign matters increases, the amount of detection signals, i.e. scattered light, increases, so that the wavelength that maximizes the detection signal generated when detecting defects such as foreign matters having the smallest dimension is the optimum wavelength. The scattering phenomenon has a similar correspondence with the relationship d / λ (d: particle size, λ: wavelength of the illumination light beam). Therefore, according to the above experimental results, the optimum wavelength when the minimum size of defects such as foreign matters to be detected as d is about 1.6d in the surface irradiation method and about 1.0d in the backside irradiation method.

In the surface irradiation method, the use of an illumination light beam having a wavelength longer than the optimum wavelength increases the backscattered light component, but the total amount of the scattered light decreases in inverse proportion to the square of the wavelength of the illumination light beam (Reiley scattering area). Is reduced. When the illumination light beam having a wavelength shorter than the optimum wavelength in the backside irradiation method is used for the all-round illumination, the forward scattered light component is excessively increased, the amount of light incident on the detection optical system is reduced, and the particle detection signal is reduced. When the minimum dimension among defects, such as a foreign material to detect, is 0.5 micrometer, the wavelength in a surface irradiation system should be 600 nm-800 nm, and the wavelength in a back irradiation system should be 450 nm-550 nm.

In FIG. 1, the inspection stage 1 includes a Z stage 10 having a ferrule 7 and movable in the Z direction, a fixing device 18 for fixing the reticle 6 on the Z stage, and a reticle ( 6) an X stage 11 for moving the Z stage 10 supporting the X stage, a Y stage 12 for moving the Z stage 10 supporting the reticle 6 in the Y direction, Z for movement It consists of the stage drive system 13 which drives the stage 10, the X stage 11, the Y stage 12, and the focus position detection control system 14 which detects the position of the reticle 6 in the Z direction. The stages 10, 11 and 12 are controlled to the precision necessary for imaging during the inspection of the reticle 6.

As shown in Fig. 2, the X stage 11 and the Y stage 12 are controlled to move along the scanning line at an arbitrary moving speed. For example, the X stage has a constant acceleration of about 0.2 sec, a constant velocity of 4.0 sec, an equal deceleration of 0.2 sec, and a stop time of about 0.2 sec, with a maximum speed of about 25 mm / sec in 1/2 cycle. It is driven to perform periodic movement of 105mm in amplitude. The Y stage 12 is driven to move intermittently in the Y direction by 0.5 mm steps in synchronism with the constant acceleration motion and the constant deceleration motion of the X stage 11. When the Y stage 12 is moved 200 times in 0.5 mm steps, the reticle 6 can be moved 100 mm for about 960 sec, and the area of 100 mm 2 can be scanned for about 960 sec.

The stage drive system 13 may be provided with an apparatus using an air micrometer, a laser interferometer, or a stripe pattern to determine the focal position of the reticle 6. 1 and 2, the X, Y and Z directions are indicated by arrows X, Y and Z, respectively.

The reticle inspection apparatus includes a first surface illumination system 2, a second surface illumination system 20, a first backside illumination system 3 and a second backside illumination system 30, which are independent and have the same configuration. The surface illumination systems 2 and 20 are provided with laser light sources 21 and 201 for emitting a light beam having a wavelength of 780 nm, respectively. The back lighting systems 3 and 30 are provided with laser light sources 31 and 301 which emit light beams having a wavelength of 488 nm, respectively. The laser beams emitted from the laser light sources 21, 201, 31, and 301 are collected by the condenser lenses 22, 202, 32, and 302, respectively, to collect the reticle 6. Irradiate the circuit pattern formed on the surface. The incident angle i of each light beam emitted from the laser light sources 21, 201, 31 and 301 on the circuit pattern is about 30 to avoid collision of the light beam on the objective lens 41 of the detection optical system 4. It should be larger than ° and smaller than about 80 ° to avoid such collisions on the ferrule 7 mounted on the reticle 6. Thus, about 30 ° to about 80 °. Each optical system includes shutters 23, 203, 33, and 303, and transmits / shields light beams of the respective illumination systems. In addition, each shutter can operate independently as needed.

Since the first surface lighting system 2, the second surface lighting system 20, the first back lighting system 3, and the second back lighting system 30 have the same structure, only the first surface lighting system 2 will be described with reference to FIG. In the description, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals. The first surface illumination system 2 is provided with a condenser lens 22 composed of a convex lens 223, a cylindrical lens 224, a collimator lens 225, and a condenser lens 226.

The laser light sources 21 and 201 of the surface lighting systems 2 and 20 are linearly polarized beams having electric field vectors in which the light beams emitted from the laser light sources 21 and 201 maintain points in the X 'direction. S-polarized beam). The S-polarized beam is used at an incidence angle of about 60 ° and the reflectance of the S-polarized beam incident on the glass substrate is about 5 times larger than that of the P-polarized beam (linearly polarized beam having an electric field vector in the Y 'direction). This is because S-polarized beams are more suitable for detecting smaller particles than P-polarized beams.

The laser light sources 31 and 301 of the back lighting systems 3 and 30 are also arranged such that the light beams emitted from the laser light sources 31 and 301 become S-polarized beams, as shown in the experimental results. This is because the discrimination ratio in the case of using the S-polarized beam is larger than the discrimination ratio in the case of using the P-polarized beam. However, when considering the transmittance of the substrate, P-polarized beams are more suitable than S-polarized beams.

In the present invention, a spatial filter disposed on the Fourier transform plane of the detection optical system 4 is used to discriminate defects such as foreign matters and circuit patterns. In this case, the use of the parallel light beam can reduce the diffusion of the diffracted light diffracted by the circuit pattern, thereby increasing the discrimination ratio. However, the use of a high luminous intensity focused light can increase the output level of the detector and improve the SN ratio.

In order to increase the illuminance of the laser beam emitted from each illumination system (2), (20), (3) and (30), the NA of the condensing system is about 0.1 and the diameter of the laser beam is reduced to about 10 占 퐉. The depth is shortened to about 30 占 퐉, which is smaller than the size (500 占 퐉) of the entire area S of the inspection field (Fig. 3), so that the entire area S of the inspection field 15 cannot be focused. In this reticle inspection apparatus, the cylindrical lens 224 rotates around the X 'axis as shown in FIG. 3, and focuses on the entire area S of the inspection field 15 when the incident angle i is 60 °, for example. It becomes possible to match. Therefore, even if the detectors 51 and 551 of the signal processing system 5 are one-dimensional solid-state image pickup devices and the inspection area of the inspection field 15 is linear, the linear inspection area can be irradiated uniformly with high illuminance. Will be.

When the cylindrical lens 224 is rotated around the X'-axis and the Y'-axis (Fig. 3), even if a light beam is emitted in any direction so as to be incident on the reticle at an incident angle of 60 °, the entire area S of the inspection field 15 is It is possible to illuminate linearly with high illumination uniformly.

Shutters 23 and 203 are provided to shield light from light source 21 as necessary. Control of light by the shutter is required in the following cases. FIG. 38 shows the reticle 6 in FIG. 1, the pericle 7, the directional light 3802 by the illumination system 2, the directional light 3820 by the illumination system 20, and the directional light by the illumination system 3 ( 3803) shows the relationship between the all-round illumination light 3830 by the illumination system 30 and the inspection field of view (= illumination position) 15. When the stage moves in the positive Y-axis direction with the progress of the inspection in the state of FIG. 38 (b), the state becomes the state of FIG. 38 (a) after a while, and the four-sided illumination light 3820 from the illumination system 20 is a reticle ( It is to be shaded by the holding frame (3807) of the ferrule 7 provided in 6). Moreover, when a stage is sent to the negative direction of a Y-axis in the state of FIG. 38B, it will be in the state of FIG. 38C. In these states, the amount of light illuminating the inspection field 15 is reduced by shading, and the amount of decrease is changed every time by the change of the shading amount, so that stable illumination is not performed. In addition, part of the shaded light becomes stray light, which adversely affects detection. For this reason, it is necessary to shield the illumination system on the side shaded by the shutter 203 (or the shutter 23) before the shading occurs. Therefore, the area illuminated by the illumination system 2 or the illumination system 20 is determined by the relationship between the angle of all-round illumination and the ferric retaining frame. 37 shows an example of the illumination area. In the example of Fig. 37, the size of the ferrule holding frame is 102 mm x 102 mm, the height is 6.3 mm, and the angle between the optical axis of the illumination light and the reticle circuit pattern surface is 30 degrees. In (b), illumination of FIG. 38 (c) is performed in the area 3724, and illumination in FIG. 38 (a) is performed in the area 3704. In addition, it can be seen that the region 3704 where all the illumination can be executed and the detection is most stable covers all of the outline region 3701 of the 64M DRAM chip.

As mentioned above, although the illumination system 2 and 20 of the surface side were demonstrated, it can be said that it is the same about the reticle of the form in which the reticle is attached to the back surface of the illumination system of the back surface side.

In FIG. 1, the back lighting system 3 and the back lighting system 30 were comprised by two small power lasers. However, it is also possible to split the laser light emitted from one larger, higher power laser into two. The example is shown in FIG. Fig. 54 shows a part corresponding to the illumination system on the back side of Fig. 1. Since the laser beam emitted from one high-powered laser diverges, the optical path becomes long, and the light emitted from the light source 5401 is easily affected by disturbances in the optical path and also easily diffuses light. The beam extender 5402 increases the beam diameter. Thereafter, branching means 5403 is branched into two optical paths. One light path corresponds to the illumination system 3 of FIG. 1, controlled by the shutter mechanism 33, guided by the optical path mirrors 5406, 5407, 5408, and the like by the condenser lens 32. Is condensed on. Moreover, one optical path corresponds to the illumination system 30 of FIG. 1, controlled by the shutter mechanism 303, guided by optical path mirrors 5404, 5405, and the like, and focused on the specimen by the condenser lens 302. do. These are merely examples for carrying out two directions of illumination in one laser light source, and other configurations may be used as long as they can achieve the same purpose. When using a light source with linearly polarized light, it is necessary to consider the mirror in the optical path sufficiently so as not to adversely affect the polarization plane of the illumination light. In addition, the branching means 5403 divides the amount of light into two according to the transmittance, separates according to the polarization plane, or in the case of a laser light source capable of oscillating several wavelengths such as an argon laser, according to the wavelength. It does not matter. It is preferable that the light amounts of the two light paths are equally distributed. If it is difficult to distribute the light equally, the light quantity is controlled by using the variable-adjustable ND filters 5409 and 5410 on the light path after the branching as shown in FIG. You can do the same. In addition, in the case of separation by polarization, in order to prevent the polarization plane of the illumination light illuminated on the specimen from the illumination system 3 and the illumination system 30 from changing, 1/2 of the optical path after polarization separation as shown in FIG. The wavelength plates 5414 and 5412 may be provided to match the polarization planes, and the polarization elements 5415 and 5413 may increase the purity of the polarization.

In addition, when the optical paths of one laser light source are split and again illuminate the same field of view on each sample, interference occurs on the sample, and extreme unevenness is generated by the generation of interference stripes. In this case, it is good to provide an optical path difference to two branched optical paths more than the interference distance (for example, several mm-several m) of a laser oscillator. In addition, since the interference does not occur in the configuration in which wavelength separation is used for the wavelength branching means, the influence of the interference of the two optical paths does not need to be considered. In addition, when 488 nm and 515 nm of the oscillation wavelengths of the argon laser are used, the detection sensitivity is not significantly changed because the difference between the wavelengths is small, and the subtle wavelength difference occurs in the shape of defects such as foreign matters. The nonuniformity in detection sensitivity caused by the effect of difficult interference is eliminated. When the illumination is performed from the rear side, the change in the glass thickness of the reticle substrate affects the optical path difference of the illumination light, and even if the same illumination is performed as shown in FIG. 56, the thickness of FIG. If the illumination is configured to illuminate the field of view 15 in a reticle 5601 that is 0 (hereinafter referred to as thickness 0), the illumination is an optical path in a reticle 5602 that has a small thickness of the same drawing (2). Proceeding to 5612 and not passing through the optical path 5562 to illuminate the field of view 15, the result is that the illumination position is shifted by E2. Similarly, in the reticle 5603 of medium thickness of the same drawing 3, the illumination proceeds like the optical path 5613, and the optical path 5403 to illuminate the field of view 15 does not pass and consequently the illumination position is changed. It is shifted by E3. In the reticle 5604, which has a large thickness of the same drawing 4, the illumination proceeds like the optical path 5614 and does not pass through the optical path 5624 to illuminate the field of view 15, and consequently the illumination position is equal to E4. It is displaced. Photomasks, such as reticles, which are still in use today, are made of substrates of various thicknesses (for example, 2.3 mm, 4.6 mm, 6.3 mm, etc.), and therefore, countermeasures are required.

When illuminating a wide range including everything from the error E2 to E4, it can cope with the difference in the thickness of the substrate such as the reticle, but the problem of deterioration of the field of view causes a decrease in S / N. Therefore, it is one measure to be able to select the lighting position. Fig. 57 shows the principle of one example thereof. In FIG. 57, an illumination path 5712 for a reticle 5602 having a small thickness of the same drawing 2 according to the thickness of the reticle so that the position of the field of view 15 illuminated by the zero thickness reticle 5601 is illuminated. ), An illumination path 5713 for the reticle 5603 with a medium thickness of the same drawing 3, and an illumination path 5714 for a reticle 5604 with a large thickness of the same drawing 4. The state of changing the optical path position is shown. 58 shows an example of the configuration for realizing this principle. FIG. 58 shows a configuration in which the optical path positions are provided in the optical path of FIG. 55 by providing optical path moving means 5811 and 5801 and drive mechanisms 5802 and 5812 of the optical path moving means. In addition, in Fig. 59, the angles of the last illumination angle setting mirrors 5408 and 5405 of the back lighting system are defined by the illumination angle variable means 5401, 5911 and the drive mechanisms 5402 and 5912 of the illumination angle variable means. The configuration in which the illumination angle is changed by varying the illumination angle is shown.

The influence of the optical path due to the difference in the thickness of the reticle is caused by the difference in the refractive index of the reticle substrate and the illumination optical path (the effect can be eliminated by eliminating the difference in the refractive index). In addition, the difference in refractive index means that the optical path difference is generated in the condensing portion of the illumination system. That is, in the case of condensing light, the difference in the thickness of the reticle also affects condensing, and in the case of a condensing system that does not have sufficient depth of focus, it is necessary to adjust the focusing position by adjusting the focus, which causes complexity of the device. However, if the change in the optical path length due to the difference in the thickness of the reticle is corrected by any means, the moving means and the focus adjusting means as shown in Figs. 58 and 59 are unnecessary. The principle of one example thereof is shown in FIG. In FIG. 60 (1), an optical path length plate (optical path length compensating plate) corresponding to a thickness t4 of a large reticle is disposed under a zero reticle. In FIG. 60 (2), an optical path length correction plate corresponding to the thickness t4-t2 is disposed under the reticle having a thickness t2. In FIG. 60 (3), an optical path length correction plate corresponding to the thickness t4-t3 is disposed under the reticle having a thickness t3. In this way, in all cases of thicknesses 0, t2, t3, and t4, the optical path lengths are the same, and the illumination position and the focal position are also the same. Fig. 61 shows a state in which the optical path length correction units 6101 and 6111, which are integrated with these optical path length correction plates, are switched to the driving means 6102 and 6112 to correspond to reticles of various thicknesses. In addition, the optical path length correcting unit should be able to correct the optical path length. Therefore, the optical path length correcting unit may not only have a plate shape but also be capable of obtaining a continuous optical path length by deforming the liquid or by electro-optical means.

In addition, the detectors 51 and 551 are provided in FIG. 1 for the purpose of measuring the transmittance | permeability of a pellicle membrane. The permeable film changes its transmittance due to subtle differences such as its film thickness and antireflection film. In the case of light transmitted vertically (scattered light from the sample corresponds to this in the present invention), the amount of change thereof is small and does not become a problem. However, in the light transmitted obliquely (in the present invention, all-round illumination light illuminating the sample corresponds to this), its influence may be a big problem. This problem is good if the permeability of the pellicle membrane is measured for each specimen and the detection result is corrected. However, since the pellicle membrane is mounted on the reticle, the permeability cannot be measured directly. Therefore, the amount of reflected light from the pellicle film from the illumination system is measured by a detector, the reflectance of the pellicle film is measured from this and the output light amount of the illumination light source, and it is assumed that there is no internal loss of the pellicle film (transmittance) = 1- The transmittance is obtained by reflectance, and the detection result is corrected.

In addition, in FIG. 1, the detection optical system 4 includes the objective lens 41 disposed to face the surface of the reticle 6, the field lens 43 arranged near the imaging point of the objective lens 41, and the wavelength separation. It is comprised by the mirror 42. Light incident on the detection optical system 4 is separated into scattered light components and diffracted light components of the surface illumination systems 2 and 20, and scattered light components and diffracted light components of the back lighting systems 3 and 30. The separated light component is disposed on the Fourier transform plane with respect to the inspection field 15 on the reticle 6 and has a band-shaped light shielding part and a light transmitting part disposed on the opposite side of the band-shaped light shielding part, respectively. , (444) and through the imaging lens (45), (445) to move the image of the inspection field 15 on the reticle (6) detectors 51, 551 of the signal processing system (5) Each image is phased. The field lens 43 forms an image of the focal position 46 on the objective lens 41 on the spatial filters 44 and 444.

17 is a view showing a reticle inspection device of the back lighting system. The positions of the irradiation system 3 and the detection optical system 4 provided in the reticle inspection apparatus may be interchanged with respect to the reticle 6. FIG. 34 shows another reticle inspection device of the back lighting system, wherein the positions of the illumination system 31 and the detection optical system 40 with respect to the reticle 6 are shown in FIG. 17 and the illumination system 3 and the detection optical system of the reticle inspection device of FIG. The opposite of position (4). The reticle inspection apparatus of FIG. 17 detects scattered light scattered by defects such as foreign matters on the transparent substrate of the reticle 6, and the reticle inspection apparatus of FIG. 34 is transmitted through the transparent substrate of the reticle 6, and defects such as foreign matters are detected. Scattered light scattered by is detected. When the scattered light is transmitted through the transparent substrate of the reticle 6 as in the reticle inspection apparatus of FIG. 34, the resolution is lowered due to aberration generated by the substrate of the reticle 6, making it difficult to stably detect defects such as foreign matter. Done. Therefore, it is necessary to provide a lens in the imaging optical system of the reticle inspection device of FIG. 34 that can compensate for the aberration generated by the substrate of the reticle 6.

The reticle inspection device shown in FIG. 35 is similar to the configuration of the reticle inspection device shown in FIG. The reticle inspection device of FIG. 35 is suitable for the case of inspecting the entire surface of the reticle 6. The reticle inspection apparatus shown in FIG. 35 includes a first surface illumination system 21, a second surface illumination system 31, and a surface detection optical system 4 arranged on the surface side of the reticle 6 arranged on the surface side of the reticle 6. ) And a backside detection optical system 40 arranged on the backside side of the reticle 6. The surface detection optical system 4 detects scattered light, i.e., reflected light, scattered in the light shielding portion of the reticle 6, and the back detection optical system 40 detects scattered light, i.e., transmitted light, scattered in the light transmitting portion of the reticle 6. The surface detection optical system 4 and the back detection optical system 40 should be provided with appropriate wavelength filters so as to detect only the reflected light and the transmitted light, respectively.

Defects such as foreign matter on the chromium pattern, that is, the light shielding film, on the reticle are not directly the cause of the transfer failure during exposure, but defects such as the foreign matter on the exposed portion on the glass substrate cause the transfer failure. Therefore, it is necessary to detect defects such as foreign matters that may move from the chrome pattern to parts other than the chromium pattern, that is, defects such as mobile foreign matters.

In addition to detecting defects such as mobile foreign matters, it is considered that defects such as foreign matters on the chromium portion need to be detected in the following cases.

In a reticle having a phase shifter, defects such as foreign matter on the chromium portion may be a problem in the manufacturing process. The reticle provided with the phase shift film generally performs the formation of a circuit pattern by chromium (up to now the same process as a reticle without a shifter), and then deposits a film on the entire surface by applying or sputtering, and then etching process. As a result, a pattern (shifter pattern) formed by the shift film is formed. If defects such as foreign matters exist on the chromium portion before the film formation, defects such as bubbles and missing particles may be generated in the shift film, which may cause transfer failure. Therefore, in addition to defect inspection such as foreign matters after formation of the shifter pattern described above, inspection of the entire surface including the chromium portion before and after film formation (defects such as bubbles or missing in the method of the present invention can be detected in the same manner as defects such as foreign matters). Can be done).

Contrary to the above, when inspecting the transparent (translucent) substrate on which the light shielding film is not patterned, the entire surface inspection is possible in the configuration of FIG. 17 or 34. In this case, since the diffracted light from the circuit pattern does not exist, the spatial filter 44 may be omitted. By detecting forward scattered light in such a configuration, the detection output of defects such as foreign matters can be made larger than in the reflection lighting method. In addition, when there is no space filter 44, stage scanning at the time of inspection may use not only the X-Y scanning system but rotational scanning system.

Therefore, the spatial filter is preferably configured to be switched as necessary. In addition, the configuration may be such that various spatial filters, such as not only inserting or not inserting the spatial filter 44 but also changing the width of the linear spatial filter, can be switched. In Fig. 63, a conventional linear spatial filter 6301, a linear spatial filter and a polarizing plate are combined to simultaneously perform the spatial filter and the polarization detection to increase the ability of removing circuit pattern scattered light. It shows the situation where spare empty slots are arranged. 64 shows that the spatial filter groups 6401 and 6411 in FIG. 63 can be switched by the driving means 6402 and 6412 (the processing system is omitted in FIG. 64). have).

As described above, in the inspection target where the circuit pattern formation situation and the required detection sensitivity change from step to step, such as a reticle, the device specification that changes the required detection sensitivity for each step is considered, and the device configuration using the specification cleverly Is considered.

Reference numeral 5 denotes a signal processing system, and the signal processing system 5 includes shading correction circuits 113 and 123 for correcting the outputs of the detectors 51, 551, the detectors 51, 551. , 4-pixel addition circuits 114, 124, binarization determination circuits 52, 53, 552, 553, logic sum circuits 56, 556, AND logic circuit 57, Block processing circuits 58, 558, microcomputer 54, and display means 55. As shown in FIG.

The detectors 51 and 551 are, for example, charge transfer type one-dimensional solid-state image pickup devices. When a defect such as foreign matter is found in the inspection field 15 when scanning the circuit pattern of the reticle 6 while moving the X stage 10, the level of the optical signal representing the circuit pattern, that is, the intensity of incident light, becomes large. The outputs of the detectors 51 and 551 also increase. The one-dimensional solid-state image pickup device is advantageous because the inspection field 15 can be widened without degrading the resolution. The detectors 51 and 551 may be two-dimensional solid-state imaging devices or solid-state imaging sensors.

Binarization threshold values are set in the binarization circuits 52 and 552. When the output of the detectors 51 and 551 input to the binarization circuits 52 and 552 exceeds the level of the reflected light intensity corresponding to a defect such as a foreign material of a size to be detected, the binarization circuit 52 , 552 outputs a logic one.

The output of the detection value together with the logic level (the determination result) is because it is more convenient to estimate the size or to set the detection determination threshold value, since the detection value also remains in the final detection result of the defect such as foreign matter. .

The shading correction circuits 113 and 123 and the four pixel addition circuits 114 and 124 are described next. The block processing circuit 112 receives the output signals of the binarization circuits 52 and 552 and prevents double counting of the two signals, but this will be described later.

When the logic 1 is received from the block processing circuit 112, the microcomputer 54 determines that there is a defect, and the information on the respective positions of the X stage 10 and the Y stage 11 corresponding to the defect, The pixels of the detectors 51 and 551, that is, the defect data including the position information of the defects determined by the calculation according to the solid state imaging sensor and the output values of the detectors 51 and 551, are stored on the display means 55. Defect data is displayed on the screen.

In addition, the control of each part of the apparatus and the interface with the operator are also executed.

The inspection result is not only displayed but also formed so that the operator can confirm the detection position by calling the observation position according to the result. In samples such as reticles and photomasks, the LSI structure becomes a raw material, and therefore, even one defect such as a foreign material that affects the exposure transfer when the LSI structure is exposed is not allowed. For this reason, the function that the operator strictly checks whether or not a defect such as a detected foreign object affects the transcription is an important component. For this reason, the function of transmitting and observing a detection result to another station for observation is needed. FIG. 62 shows a configuration in which the optical path of the detection optical system is switched as an example of the observation function and the observation is made possible by the same apparatus as the inspection. As a result, other devices become unnecessary, and thus the observation accuracy can be improved and the work efficiency can be improved, and contamination while moving to other devices can be prevented. In FIG. 62, the inspection processing system and illumination system are omitted. The illumination system for the observation system includes a transmission illumination system 6201 with a shutter mechanism 6222, an illumination illumination system 6211 with a half mirror 6212 and its driving means 6213, and an omnidirectional illumination system 6321 by laser illumination means. It is. The omnidirectional illuminator 6321 should be provided when the inspection illuminometer from the surface (FIGS. 1 and 2) is not in the visible wavelength range, but the inspection illuminometer from the surface is visible wavelength. If you are in the realm, you can substitute it. The observation illumination is switched and used as necessary. The image of the detection position of a defect such as an illuminated foreign object is collected by the objective lens 41 and observed by means of observation means 6201 such as a TV camera or the naked eye via a mirror 6402 switched by the driving means 6203. . In the observation system, a space filter 6322 is inserted by the drive means 6303 as necessary, as in the inspection.

In FIG. 62, the inspection unit 6251 for a pellicle membrane was also shown. The inspection of the back surface (non-circuit pattern surface) such as a ferrule or reticle does not require the same high sensitivity as the circuit pattern surface. Therefore, by providing a low sensitivity, simple and high speed inspection unit, the inspection time can be shortened and the device structure It is simplified. In the inspection of the mirror-shaped reticle substrate (for example, a glass substrate or a substrate having a metal thin film formed thereon) before the circuit pattern is formed, there is no circuit pattern that prevents the detection of defects such as foreign matter. Therefore, since the detection unit with high sensitivity can be configured at a high speed with a simple configuration, a mirror-shaped reticle inspection unit may be provided separately in the apparatus.

The operation of the reticle inspection device will be described with reference to Figs. 4 to 10, and the same reference numerals are given to the same or corresponding parts as in Fig. 1. FIG. 4 is a view for explaining a reticle scanning method, FIG. 5 is a plan view for explaining an angle forming part of a circuit pattern, and FIGS. 6A to 6C show the distribution of diffracted light and scattered light on a Fourier transform plane. 7A is a partial cross-sectional view showing a corner portion of a circuit pattern, FIG. 7B is an enlarged view of a CO portion of FIG. 7A, and FIG. 8 is a scattered light detection signal generated when detecting scattered light caused by a defect such as a foreign material. 9 is a plan view illustrating the relationship between detection signals generated when a circuit pattern is detected, FIG. 9 is a plan view showing a micro circuit pattern, and FIG. 10 is a diagram illustrating a detection signal generated when detecting defects such as foreign matters and corner portions of a circuit pattern. A graph showing levels.

4A shows a defect 70 such as a foreign material on the reticle 6 fixed on the Z stage 10 by the fixing device 18, the straight portion 81 of the circuit pattern 80, and the circuit pattern. The corner portion 82 of 80 is shown.

The reticle 6 is irradiated obliquely in the illumination system 2 (or any one of the illumination systems 20, 3, and 30). Do not collect direct reflected light and direct transmitted light. Only scattered light and diffracted light are focused by the objective lens 41. Circuit pattern extending at an angle θ = 0 ° in a direction perpendicular to the horizontal component 60 in the traveling direction of the illumination light emitted from the illumination system 2 (or any one of the illumination systems 20, 3, and 30) Only diffracted light diffracted at the edge of 80 (hereinafter referred to as 0 degree edge) is focused in a band shape on the Fourier transform plane of the objective lens 41 as shown in FIG. The angle θ of the edge of the circuit pattern 80 is 0 °, 45 ° or 90 °. As shown in Fig. 4A, the diffracted light b diffracted at the edge of 45 ° and the diffracted light c diffracted at the edge of 90 ° are not incident on the objective lens 41, thus affecting the inspection of the reticle. Not crazy Scattered light scattered from the defect 70 such as a foreign material is scattered over the entire Fourier transform surface as shown in Fig. 6C. Thus, 0 ° shown in Fig. 4A by the spatial filters 44 and 444 respectively disposed on the Fourier transform surface and having a band-shaped light shielding portion and light transmitting portions disposed opposite to the light shielding portion, respectively. By shielding the diffracted light a diffracted in the pattern, the defect 70 such as a foreign material can be distinguished from the circuit pattern 80. In addition, since the Fourier transform surface is not only generated behind the objective lens as described herein, but also occurs on the incident pupil surface of the objective lens, the stencil filter can be disposed in front of the objective lens. In this case, since there is no aberration due to the wavelength of the detection light because it does not pass through the lens system, there is also an advantage that the Fourier transform planes of all wavelengths become coplanar.

In this case, the detection is not performed directly on the Fourier transform plane because the detection field is reduced on the plane of the inverse Fourier transform image to detect the Fourier transform image again, so that high sensitivity can be detected. to be. However, since the inverse Fourier transform is a mathematical operation, the magnitude of the amplitude and phase difference of the Fourier transform on the Fourier transform plane may be directly detected, and the inverse Fourier transform may be performed by a calculator. Further, in this case, because of the calculator processing, there is an advantage that the degree of freedom of spatial filtering is increased.

Thus, the detection optical system 4 has a high NA. NA = 0. If it is 5, the opening area of the detection optical system 4 is about 20 times the opening area of the detection optical system having the conventional low NA (NA = 0.1). Scattered light scattered at the corners of the circuit pattern 80 (FIG. 4D) cannot be completely blocked by the linear space filter. Therefore, when a detection pixel of 10 x 20 탆 ² is used for detection (Fig. 4 (b)), it becomes impossible to detect only a defect such as a foreign material in which scattered light scattered at several corner portions enters the pixel.

Therefore, in the present invention, the effect of scattered light and diffracted diffracted light scattered in the circuit pattern 80 is completely eliminated as much as possible using high resolution 2 x 2 탆 ² pixels (Fig. 4 (d)). The pixel size does not necessarily need to be 2 × 2 μm ² . The pixel size may be smaller than the size L of the smallest portion of the circuit pattern 80. When exposing the reticle with a stepper having a reduction ratio of 1/5 when fabricating a 0.8 μm process LSI, pixels of 0.8 × 5 = 4 μm ² or less are suitable, and a 0.5 μm process LSI may be produced. 0.5 x 5 = 2. Pixels of 5 μm ² or less are suitable.

Substantially, the size of the pixel may be larger or smaller than the above size as long as it is a value capable of minimizing the influence of scattered light scattered at the corner portion of the circuit pattern. Specifically, the pixel size is preferably about the same as the size of the minimum circuit pattern portion. If the pixel size is about the size of the minimum circuit pattern portion, only less than two corner portions correspond to one pixel, and the pixel size is sufficiently small as is clear from the experimental results shown in FIG. In order to inspect the reticle for 64M DRAM manufacturing, a pixel size of about 1 μm ^{2 to 2} μm ² is suitable.

Since the corner portion 82 of the circuit pattern 80 shown in FIG. 7A is composed of continuous curved edges 820 as shown in FIG. 7B, the diffracted light d diffracted at the corner portion 82 is shown in FIG. 6. As shown in (b) of FIG. 2, scattering is performed on the Fourier transform plane, and the spatial filters 44 and 444 cannot completely shield the diffracted light d. For this reason, when the diffracted light diffracted at the several corner portions 82 enters the detector 51 or 551, as shown in FIG. 8, the output V of the detector 51 or 551 increases and the foreign material is increased. The defect 70 such as cannot be distinguished from the circuit pattern 80. As illustrated in FIG. 8, the output 822 of the detector 51 or 551 generated when detecting a plurality of corner portions 82 is an output of the detector generated when detecting one corner portion 82. It becomes higher than (821). When the output of the detector 51 or 551 is binarized using the binarized threshold value 90 indicated by a dotted line, the output of the detector 51 or 551 indicating a defect 70 such as a foreign material 701 cannot be distinguished at the output 812 of the detector 51 or 551 representing the multiple corner portions 82,

In order to solve the problem described in Fig. 8, in the present invention, the inspection field 15 is formed on the detector 51 or 551 by means of the objective lens 41 and the imaging lens 45, and the detector 51 By selectively determining the size and the image formation magnification of the () or (551), the size of the detection field 15 (for example, 2㎛ × 2㎛) is arbitrarily determined and diffracted at several corner portions 82 The diffracted light does not enter the detector 51 or 551 at the same time. However, this configuration is not very effective for discriminating defects such as foreign matters having a submicron size from the corner portion 82 of the circuit pattern 80. In addition, as shown in FIG. 9, the movement of the diffracted light diffracted by the size portion 84 of the submicron degree smaller than the size portion 83 of the normal structure portion of the circuit pattern 80 causes defects 70 such as foreign matters. Since it is the same as the scattered light scattered by, it is difficult to discriminate defects 70 such as foreign matters from minute circuit patterns.

The reticle inspection apparatus of the present invention can detect defects 70 such as foreign matter even in a minute circuit pattern having a size portion 84 of a submicron degree. In Fig. 10, reference numerals 701 and 702 denote detection signals 864, 874, and 865 which occur upon detection of scattered light scattered from a defect 70 such as a fine foreign material having a submicron size. ), (875), (866), (876), (867) and (877) are detection signals generated upon detection of scattered light scattered at all corner portions 82 at 0 °, 45 ° and 90 °, Reference numerals 861, 871, 862, 872, 863, and 873 are detection signals generated upon detection of scattered light scattered in the minute size portion 84 of submicron order. The detection signals 701, 861, 862, 863, 864, 865, 866, and 867 are provided with a first surface illumination system 2 (or a first backside illumination system 3). Is detected by the detector when detecting the illumination light beam projected by the beam and scattered by the microcircuit pattern, and is detected by the detection signals 702, 871, 872, 873, 874, 875, and (875). 876 and 877 are output from the detector when detecting the illumination light beam projected by the second surface illumination system 20 (or the second backside illumination system 30) and scattered by the microcircuit pattern. For example, the detection signal 861 → 871 is respectively projected by the first surface illumination system 2 (or the first backside illumination system 3) and detects the illumination light beam scattered in the microcircuit pattern portion. And an irradiation light beam projected by the second surface illumination system 20 (or the second backside illumination system 30) and scattered in the same microcircuit pattern portion, is output from the detector. As apparent from Fig. 10, the detection signal value generated upon detection of a defect 70 such as a foreign material has less dependence on the projection direction of the irradiation light beam than the detection signal value generated upon detection of the microcircuit pattern portion. In FIG. 10, the dotted line 91 represents the threshold value of binarization.

As is clear from Fig. 10, the detection signal value generated by the detector at the time of detection of the microcircuit pattern part is highly dependent on the projection direction of the illumination light beam, and is a path symmetrically perpendicular to the surface of the reticle 6 in the irradiation part. When the surface of the reticle 6 is irradiated obliquely by two illumination light beams moving along each other, one of the detection signals generated at the detection of the two illumination light beams scattered at the irradiation portion is indicated by Similarly, the detection signal is necessarily smaller than the detection signal generated at the time of the detection of the scattered light scattered by a defect such as a foreign matter having a submicron size. The first surface illumination system 2 and the second surface illumination system 20 arranged in the direction perpendicular to the surface of the reticle 6 in the irradiated portion or in the irradiation portion symmetrically in the vertical direction with respect to the surface of the reticle 6. When the illumination light beam is projected obliquely by the arranged first back lighting system 3 and the second back lighting system 30, the detection signal is projected by one of the two surface lighting systems and defects such as foreign matter or At the time of detection of defects such as foreign matters or scattered irradiation beams scattered in the same circuit pattern portion, projected by a surface (backside) illumination system different from the detection signal generated when the scattered irradiation beams scattered in the circuit pattern portion are detected. It is the sum of detection signals generated. Thereby, since defects, such as a foreign material, can be irradiated with illumination intensity higher than illumination intensity which irradiates a circuit pattern, the defect 70, such as a foreign material of the magnitude | size of a submicron grade, can be distinguished from the circuit pattern 80. FIG.

When detecting the scattered light scattered by the defect 70 such as the foreign material, the microcomputer 54 is the foreign material calculated according to the position information of each of the X stage 10 and the Y stage 11 and the position of the corresponding pixel. Defect data such as foreign matters including position information of defects 70 and the like and detection signals of the detectors 51 and 551 are stored in the storage device, and defect data such as foreign matters is displayed in the display unit 55 such as a CRT. Mark on.

That is, as described above, even in the same circuit pattern in FIG. 10, the output of the scattered light is significantly different depending on the irradiated direction, and the two directions of opposite directions are shifted by shifting the 180 ° direction on the plane of the reticle 6. In the case of illuminating in the above method, it can be seen that the output value of the scattered light on either side is necessarily smaller than the output value from defects such as foreign matters of the size of the deep submicron, as indicated by?

For this reason, as shown in FIG. 1, when 180 degree directions are shifted on the surface of the reticle 6, and simultaneously illuminated in two opposite directions, the detection output of a particle and a circuit pattern is the detection output by each illumination. It is difficult to binarize to the threshold value because it is only a sum of the sums, but the scattered light from the opposing illumination is detected by two separate detectors, and the threshold value is determined by the separate binarization determination circuit. In the case of binarization, the two judgment results are both 1 in the case of a defect such as a foreign material, and in the case of a circuit pattern, only one of the two judgment results is 1, or both are 0. do. Thus, by taking the logical product of the determination result of the binarization determination circuit, it is possible to detect defects 70 such as foreign matters, including defects such as foreign matters having a size of about a deep submicron, from the circuit pattern.

In order to realize the detection by the logical AND circuit, it is necessary to have a configuration for separating and detecting scattered light by opposing illumination. In the illumination system 2 and the illumination system 20 arranged on the surface side, a configuration such as performing wavelength separation (color separation) by changing the wavelength of the light source or performing polarization separation by changing the polarization characteristic of the light source is considered. However, the illumination system 2 and the illumination system 20 arranged on the surface side cannot execute illumination that opposes the front surface of the reticle because of the problem of shading by the above-described ferrule holding frame (area of FIG. 37). 3724 and region 3704, the illumination of the opposite cannot be executed due to the influence of the ferrule holding frame). Thus, in the present invention, attention has been paid to the following points. [1] The detection sensitivity is obtained by the light transmission portion (glass part) of the reticle having a small output of scattered light from defects such as foreign objects, and the like by the foreign material of the light shielding part (on the metal thin film part such as chromium) of the reticle. The defect is so large that the output of the scattered light does not require detection by the logical product. [2] The wavelength is different between the light source of the illumination system on the front side and the light source of the illumination system on the back side. [3] Illumination of the front and back surfaces can be used to illuminate the front surface, avoiding the influence of the ferrule holding frame (see below).

That is, the illumination system opposes defects such as foreign matter on the light transmitting portion of the reticle on the front side and the back side, specifically, illuminated by the illumination system 2 and the illumination system 30, or the illumination system 20 and the illumination system 3. It was set as the structure which performs the binarization determination of the scattered light detection value by each illumination system which opposes by wavelength separation.

71 and 72 are cross-sectional views for explaining the effect thereof. In the drawing, 6901 is a glass substrate of a photomask such as a reticle, 6904 is a four-sided illumination light having a wavelength? 1 that illuminates a circuit pattern surface from the surface side. 6905 is a four-sided illumination light of wavelength lambda 2 that illuminates the circuit pattern surface 180 ° relative to the four-sided illumination light at the back side, (6902), (7002) is the edge portion of the circuit pattern, (6942) is the four sides of the surface side Scattered light generated at the edge portion 6702 of the circuit pattern by the illumination light 6904, scattered light generated at the edge portion 6702 of the circuit pattern by the oblique illumination light 6905 from the back side 6704 Is scattered light generated at the edge portion 7002 of the circuit pattern by the oblique illumination light 6904 on the surface side, and 7042 is generated at the edge portion 7002 of the circuit pattern by the oblique illumination light 6905 from the back side. Scattered light, (6903), (7003) is a standard particle, which is a model of foreign matter of about 0.3 ㎛ Reference numeral 6943 denotes scattered light generated by the standard particle 6903 by the oblique illumination light 6904 on the surface side, and 6953 denotes scattered light generated by the standard particle 6903 by the oblique illumination light 6905 from the back side. 7043 denotes scattered light generated by the standard particle 7003 by the oblique illumination light 6904 on the surface side, and denoted by 7043 denotes scattered light generated by the standard particle 7003 by the oblique illumination light 6905 from the back side. .

In a circuit pattern having a small but cross-sectional structure (thickness), such as a circuit pattern of a photomask such as a reticle, the intensity of scattered light generated greatly in accordance with the direction of all directions of illumination changes. For example, in FIG. 71, the scattered light from the edge portion of the circuit pattern has a large scattered light generated by the illumination by the oblique illumination light 6905, while the scattered light generated by the illumination by the oblique illumination light 6904 is small. In addition, scattered light from an object, such as a foreign material, which does not exhibit clear anisotropy does not show a large change.

The state is similar to the graph showing the detection output (V) of the scattered light in FIG. 71. In the scattered light by the all-round illumination 6905, the scattered light 6952 from the circuit pattern is more than the scattered light 6953 from the standard particle. It is not possible to detect defects such as foreign matters only with this large binary threshold value Th2. However, in the scattered light by the all-round illumination light 6904, the scattered light 6943 from the standard particles is larger than the scattered light 6942 from the circuit pattern, so that only foreign matter can be detected with a simple binary threshold value Th1.

In the circuit pattern 6702 in the direction of FIG. 71, the scattered light by the four-sided illumination light 6904 may be detected, but there is one more direction of the edge of the circuit pattern, and FIG. 72 shows the state in that case.

In FIG. 72, the scattered light from the edge portion of the circuit pattern is large in scattered light generated by the illumination by the four-sided illumination light 6904, while scattered light generated in illumination by the four-sided illumination light 6905 is small. In addition, scattered light from an object, such as a foreign material, which does not exhibit clear anisotropy does not show a large change.

The state is as shown in the graph showing the detection output (V) of the scattered light in Fig. 72, the scattered light from the circuit pattern than the scattered light (7043) from the standard particle in the scattered light by the oblique illumination light (6904) The foreign material cannot be detected only by this large binary threshold value Th1. However, in the scattered light by the all-round illumination light 6905, the scattered light 7053 from the standard particle is larger than the scattered light 7052 from the circuit pattern, so that only defects such as foreign matters can be detected with a simple binary threshold value Th2. have.

In the circuit pattern 7002 in the direction of FIG. 72, the scattered light by the four-sided illumination light 6905 may be detected. However, in the case of FIGS. 71 and 72, since they appear arbitrarily during the inspection, either of them is selectively detected. Can not. Therefore, in the detection method devised in the present invention, in either case of Figs. 71 and 72, the foreign material threshold value Th1, in the detection results of both the four illumination lamps 6904 and 6905, as for the foreign matter. Scattered light is larger than both of Th2, and scattered light is not larger than both of the binarized threshold values Th1 and Th2 with respect to the circuit pattern. For this reason, when scattered light by the four sides illumination light 6904 and 6905 is respectively detected and binarized by the binarized threshold values Th1 and Th2, and the logical product is obtained, only the scattered light from the foreign material can be detected. .

In this operation, since the scattered light can be easily separated by a color separation filter or the like when the wavelengths of the light sources of the two illumination lights 6904 and 6905 are different, the two illumination lights 6906 and 6905 are used. Detection can be performed simultaneously, so that the detection plate can be executed in real time.

39 is similar to FIG. 38, the reticle 6 in FIG. 1, the pericle 7, the illumination light 3802 by the illumination system 2, the illumination light 3820 by the illumination system 20, and the illumination system 3 The relation between the four-sided illumination light 3803 and the four-sided illumination light 3830 by the illumination system 30 and the inspection field (= illumination position) 15 is shown. FIG. 39 (a) shows an illumination situation when the divided area 4024 is inspected with the border of the centerline 4001 of the ferrule holding frame shown in FIG. 40, and the pair facing each other on the front and back sides. The situation where the illumination by the all-round illumination light 3820 and the all-round illumination light 3803 is performed by the illumination system of FIG. When the stage is sent in the positive direction of the Y axis with the progress of the inspection, the area 4004 in Fig. 40 is in the state of Fig. 39 (b) after a while, and the illumination is performed by a pair of illumination systems facing each other on the front and back sides. Illumination is performed by the 3820 and the oblique illumination light 3830. The dividing of the area into two to switch the illumination pair is to avoid shading by the pericle holding frame 3808, so the timing of the switching must necessarily be executed on the centerline 4001 of the pericle holding frame. none.

Fig. 41 is a block diagram of signal processing of detection results for the above illumination method. FIG. 41 is a diagram showing a part of the signal processing system 5 in FIG. 1, in which the same numbers as those in FIG.

Scattered light from the backside illumination system 3 (omitted in FIG. 41) or the omnidirectional illumination system 30 (omitted in FIG. 41) passes through the wavelength separation mirror 42 (omitted in FIG. 41) to the detector 51. Is detected. Scattered light by the surface illuminometer 2 (omitted in FIG. 41) or the omnidirectional illuminator 20 (omitted in FIG. 41) is reflected by the wavelength separation mirror 42 (omitted in FIG. 41) to the detector 551. Is detected.

Binarization determination circuit which is the result of the binarization determination of the logic output 4103 of the binarization determination circuit 52 and the detection output 4111 of the detector 551 which are the binarization determination results of the detection output 4101 of the detector 51. The logical product output of the logic output 4113 of 552, that is, the output 4102 of the logical product circuit 57, is the result of detection determination of defects such as foreign matters. It is to be noted that the output 4102 preferably outputs not only the logic level determination result but also the detection value. It is also common to the following description that it is better to output not only the logic level judgment result but also the detection value to the final judgment result.

In this case, it becomes the structure as shown in FIG. In the binarization circuit 6701, a threshold value 6702 for detecting scattered light generated by the backside illumination (this is called "detection by the backside illumination" and the same in the case of the surfaceside illumination) is preset. do. In the binarization circuit 6711, a threshold value 6712 for detection by surface-side illumination is set in advance. The detection value 6703 by the backside illumination is input to the binarization circuit 6701, and the detection value 6713 by the surface-side illumination is input to the binarization circuit 6711 to determine the binarization. Each determination result is calculated by the logical product means 6721, and when the result is a logic level 1, the detection value 6732 by the surface side illumination is output as the detection result by the data selector 6731. In this case, the output of the detection result may be a detection value by backside illumination.

However, the above-described configuration is effective for defects such as foreign matter on the light transmissive portion of photomasks such as reticles, but the following problems occur in the detection of defects such as foreign matter on the light shielding portion. That is, since defects such as foreign matter on the light shielding portion do not reach from the backside side, scattered light does not occur due to illumination from the backside side. Therefore, defects such as foreign matter having a large dimension (that is, need to be detected) generate large scattered light by illumination from the surface side, and the output of the binarization circuit 6711 in FIG. At this point, the output of the binarization circuit 6701 does not become logic level 1, and therefore, it is not determined that the defect is a foreign material or the like.

Therefore, in order to prevent this, when the scattered light generated by the illumination on the front side is large, it is necessary to determine that it is a defect such as foreign matter even when there is no scattered light generated by the illumination from the back side. In this case, defects such as foreign matters on the light shielding part are not detected defects such as small foreign matters with small scattered light generated, but the reason described in the explanation of the operation of the present application (defects such as foreign matters on the light shielding part are exposed at the time of exposure). Only defects, such as a large foreign material, which are not transferred and may move to the light transmitting portion, may be detected).

74 shows a block of the processing circuit in this case. The difference in the block diagram of FIG. 69 is that a binary signal circuit 7201 and a logical sum calculation circuit 7201 of the decision result are added as a binarization circuit of the detection result by surface side illumination. In the binarization circuit 7201, a threshold value 7212 for detection by surface-side illumination is set in advance. The threshold value 7212 is larger than the other threshold value 6712, specifically, larger than the detected value of the scattered light from the circuit pattern. When a large detection value of a degree exceeding this threshold value is detected, the binarization circuit 7201 outputs a logic level 1. The output of the binarization circuit 7201 and the output of the logical product circuit 6721 are ORed by the OR operation circuit 7121, and the surface selector is illuminated by the data selector 6731 when the result is a logic level 1. Detected value 6732 is output as a detection result. In this case, what is output as a detection result is limited to the detection value by surface side illumination. This is because, in defects such as foreign matter on the light shielding portion, the detection result by the backside illumination is not obtained.

For example, as shown in FIG. 46, when the periphery of the logical product processing circuit 57 or the logical product processing circuit 57 is formed, one of the inputs of the logical product operator 4157 is switched to the switching means 4133. By switching to the detection result 4103, the detection decision result by the logical product method is obtained in the output 4102, and the logic level 1 input is inputted by the switching means 4133 to one of the inputs of the logical product operator 4157. Switching to 4123, the detection results of the detection method not using the logical product method are obtained for the outputs 4102 and 4112, and the detection method of the inspection apparatus can be selected as necessary. In that case, the configuration shown in FIG. 41 is as shown in FIG. 47. In addition, since the detection apparatus can be selected by switching between the same apparatus, the objective of FIG. 46 may be any other configuration such as by software processing as long as the objective is achieved.

When it is determined that scattered light from a defect such as a foreign material is detected in the above configuration, when the detectors 51 and 551 are not single elements other than the position information of the X stage 10 and the Y stage 11 at the time of detection, The position information of defects 70 such as foreign matters calculated at the pixel position in the element and the detection output values 4101 and 4111 of the detectors 51 and 551 are the microcomputer 54 as defect data such as foreign matters. Is stored in a memory to be managed, and the stored contents are computed and displayed on display means 55 such as a CRT.

When detecting and determining defects such as foreign matters in accordance with the output of each pixel of the array detector, the following problems arise.

It is assumed that detection and determination of defects such as foreign matters are performed with a detector having a pixel of 2 x 2 탆 ² . At that time, when defects such as foreign matters are detected in four pixels as shown in FIG. 26, scattered light scattered by defects such as foreign matters is dispersed into several pixels, and the output of each pixel is foreign matters in one pixel. Is detected, the detection rate of defects such as foreign matters decreases as a result of about 1/2 to 1/4 (substantially about 1/3) of the crosstalk between pixels. In addition, the positional relationship between the pixels of the detector and defects such as minute foreign matters is subtle and very easily changed each time the inspection is executed, thereby degrading the reproducibility of the inspection. This problem occurs not only when a defect such as a foreign material is detected in four pixels but also when a foreign material is detected in three or two pixels.

In order to solve the above-mentioned problem, as shown in Fig. 27, 1 × 1 μm ² pixels are used, and the detected signals output from four adjacent 1 × 1 μm ² pixels are electrically added to each other to 2 ×. Simulate a detection signal of ² μm ² pixels. The sum of the detection signals of the adjacent four pixels of the four overlapping pixel groups a, b, c, and d is calculated, and the maximum sum of the outputs, that is, the sum of the pixel outputs of the pixel groups in FIG. 27, is 2x2. It is used as a defect detection signal, such as a foreign material, as a representative output of the output of a micrometer ² pixel. In such a defect detection method such as foreign matters, the detection signal indicating a defect such as foreign matters is within ± 10%, and the detection repeatability for defects such as all foreign matters is 80% or more.

Fig. 28 is a block diagram of a four pixel addition circuit. This four pixel addition circuit is used together with a one-dimensional image pickup device obtained by arranging 512 1 µm ² pixels, and the output 2503 of the odd-numbered pixel and the output 2502 of the even-numbered pixel are output separately. The output of four 1 × 1 μm ² pixels (2 × 2 pixels) shifted in four directions by one pixel is 256 stages of shift resist 2501, one stage of shift register 2504, and adder 2505. Is added by (2508), and the average value of the addition value of pixel output is measured by the dividers 2509-2512. The maximum value selecting circuit 2513 selects the maximum average value among the four average values as a defect detection signal 2514 such as foreign matter.

In this arrangement, since the determination result is output in units of 2 占 퐉 necessary for determination, and the data amount is 1/4, the speed of signal processing required in the subsequent processing circuit is reduced to 1/4, and the circuit design and Advantageous circuit operation. Such a configuration makes it possible to detect a defect such as a stable foreign material.

In the above example, the addition or averaging of four pixels is a measure to prevent the output degradation of the detection result between the detection pixels. Therefore, the processing pixels may be processed with more than four pixels, and as long as the effect can achieve the desired purpose, Alternatively, the processing of three pixels may be performed. 67 shows an example of the case of adding two pixels. In the same drawing, the shape of the pixel is not square but rectangular. This can be realized by making the transmission speed of a rectangular shaped detector or stage faster than the accumulation time of the detector (for example, if one is to form a pixel of 1 µm x 2 µm on a specimen, the size of the specimen is 1 µm). This can be achieved by sending a 2 μm stage during the accumulation time T by a detector of 1 μm). As shown in FIG. 67, the process may be performed by adding two pixels.

In the embodiment of the same drawing, at the timing b2 in the drawing,

(a1 + a2) / 2

(a2 + a3) / 2

(b1 + b2) / 2

(b2 + b3) / 2

(a1 + b1) / 2

(b1 + c1) / 2

(a2 + b2) / 2

(b2 + c2) / 2

Is calculated and the maximum value thereof is output as a detection result. That is, similarly to the case of four pixels, the maximum value of the average value of the added values is obtained. The two-pixel addition reduces the effect of preventing the output deterioration of the foreign material over four pixels, but the inspection speed is improved because the transfer speed of the stage is faster than the four-pixel addition.

By the way, in the said example, compared with the pixel dimension (2 micrometer x 2 micrometer) which performs detection determination, the dimension of defects, such as a foreign material, which should be detected is small (for example, 0.5 micrometer). In such a case, as long as defects such as foreign matters are captured in one pixel (1 μm × 1 μm in the above example) of the detector before the four-pixel addition process, the detection output from defects such as foreign matters before and after the four-pixel addition process. It is the same (because the four-pixel addition method is a method for compensation in the case where it is not captured in one pixel and spans a plurality of pixels as described above). In this case, the scattered light from the circuit pattern decreases the scattered light from the circuit pattern because the smaller the area (pixel dimension) of the pixel of the detector is, the smaller the number (or area) of the corner portion of the circuit pattern fits into the pixel. In consideration of this, the smaller the pixel dimension itself is, the more preferable it is possible to detect defects such as foreign matter with higher sensitivity. Therefore, it can be said that the 4-pixel addition processing system sacrifices the detection sensitivity as opposed to the stability of the detection. If the detection sensitivity is sufficient after sacrifice, it is not necessary to implement a new design for this problem, but in order to follow the change of the process conditions or the change of the exposure method, the inspection technology with more flexible detection sensitivity is considered. It is necessary.

For this problem, the detection method may be switched in accordance with the performance required by selecting the high-definition detection mode in which the four-pixel addition processing is performed and the high sensitivity detection mode in which the four-pixel addition processing is not performed.

Note that the two modes are operable at the same time by performing detection determination of defects such as foreign matters before and after the four-pixel addition process. In the present invention, high stability detection and high sensitivity detection have the configuration as shown in FIG. Designed to run the configuration.

In FIG. 42, the signal detected by the detector 51 or the detector 551 is detected by the four-pixel addition circuit 114 or the four-pixel addition circuit 124. The detection determination (binarization) circuit 52 of the result of the processing is executed. Or the detection judgment (binarization) circuit 533 or detection judgment (binarization) circuit 553 which is detected by the detection judgment (binarization) circuit 552 and does not execute the 4-pixel addition process. Detection is judged. The result is input to the computer 54, stored, and displayed on the display means 55.

In addition, in order to achieve the detection of defects such as foreign matters, the detection judgment of the result detected by the detection judgment (binarization) circuit 52 or the detection decision (binarization) circuit 552 or not performing the four pixel addition process is performed. Since it is sufficient to be detected by the (binarization) circuit 53 or the detection determination (binarization) circuit 553, each detection result is calculated by the logic sum circuit 56 or the logic sum circuit 556 as shown in FIG. By inputting and storing the result into the computer 54, the data amount of defect detection such as foreign matter on the circuit can be reduced. In this case, when the four-pixel addition result is obtained at the maximum value as in the four-pixel addition process of this embodiment, and the data amount is decreasing, it is difficult to simply calculate a logical sum with the result of not performing the four-pixel addition. In this case, as shown in Fig. 68, the processing for finding the maximum value of four pixels without the addition processing is performed, and if the data amount is reduced to 1/4, the logical sum can be easily calculated. Here, at the timing of b2 in the figure,

a 1

a 2

a 3

a 4

The largest one of them is output as a detection result.

In addition, it is better to output not only the logic level judgment result but also the detection value to the output of the detection result, as well as the logical product operation.

In this case, it becomes the structure as shown in FIG. In the binarization determination circuit 6801, a detection threshold value 6802 for not performing the four pixel addition process is set in advance. In the binarization determination circuit 6811, a threshold value 6812 for detecting the four-pixel addition process is set in advance. Then, the detection value 6803 that does not perform the four-pixel addition process is input to the binarization determination circuit 6801, and the detection value 6613 that performs the four-pixel addition process is input to the binarization determination circuit 6811. Evolution is determined. Each determination result is calculated by the logical sum means 6821, and when the result is the logic level 1, the detection value 6832 which has performed four pixel addition processing in the data selector 6831 is output as the detection result.

As shown in Fig. 42, when the logic sum circuit 56 or the logic sum circuit 556 is not provided, it is preferable to calculate the logic sum of defect detection data such as foreign matter by software before displaying on the display means 55.

When the detection using the logical product described above is not executed, the detection decision (binarization) circuit 52, the detection decision (binarization) circuit 552, and the detection decision (binarization) circuit 53 as shown in FIG. And a logic sum circuit 5556 for calculating the result of the detection determination (binarization) circuit 553 or for performing software calculation.

In addition, when performing the detection using the AND, the outputs of the OR circuit 56 and the OR circuit 556 may be calculated by the AND circuit 57 as shown in FIG. In this case, since the logical product operation is the final result of the detection of a defect such as a foreign material, it is preferable to be executed at the same time as the inspection proceeds, and the calculation by the circuit is more practical than the calculation by software.

The reticle inspection apparatus of the present invention detects and detects only defects such as foreign matter optically, and detects defects such as foreign matter by binarizing the detection signal when the detection signal is larger than the threshold value. However, the detection signal tends to change depending on the deviation (shading) of the sensitivity between the [1] pixels (about ± 15%) and the illuminance distribution on the reticle between the [2] pixels. Thus, as shown in Fig. 29, each pixel outputs different detection signals for defects such as foreign matters, and the level of the output signal depends on the position of the pixel in the Y-axis direction. Therefore, it is impossible to stably detect defects such as foreign matters by binarization of the detection signal exceeding the threshold value.

The present invention measures the shading effects of the above-mentioned [1] and [2] using the standard reticle 111 (FIG. 1) in advance ((a) in FIG. 30), and calculates the inverse of the measured shading effects. By determining the shading correction data ((b) in FIG. 30), by controlling the gain of the amplifier which amplifies the detection signal of the detector for each output of the pixel by removing the influence of the shading effect, A correction output is obtained ((c) in FIG. 30). The standard reticle 111 may be mounted on or near the Z stage 10 of the inspection stage 1, or may be mounted on the Z stage only when the shading effect is measured.

The standard reticle 111 has a small concave surface and uniform scattering characteristics. For example, the standard reticle 111 may be a glass plate having a fine concave convex formed on the surface by grinding, a glass plate having standard particles of a certain size uniformly attached to the surface, or an aluminum film formed by sputtering. The plate formed may be sufficient. However, it is substantially difficult to process the minute concave convex on the standard reticle 111 uniformly with respect to the pixel 1 × 1 μm ² . Therefore, the measurement of the shading effect is repeated several times, for example, 1000 times, and the correction data are determined according to the average value of the measured data.

Since light is scattered only at the surface portion of the standard reticle 111 having a small concave convex, and light is not scattered at the entire surface of the standard reticle 111, the addition of the measured value obtained by repeating the measurement 1000 times is a standard reticle It is much smaller than the addition of 1000 illuminance distributions over the entire irradiated area of the (111) surface. Therefore, a simple average value such as the average value of the measured data obtained by dividing the total of the measured data by the number of repetitions of the measurement is too small and the precision of the calculation decreases. Under these conditions, the average value may be determined by dividing the sum of the measured data by a divisor, for example, the measurement repetition number, for example, 200, which is 1000 pieces.

As is apparent from the comparative experiments of FIGS. 30A and 30C, about 50% of the shading (FIG. 30A) is lowered to 5% or less by correction. By determining and updating the correction data every time the inspection is performed, it is possible to eliminate the adverse effect of the optical component due to the correction data variable due to the time dependent variable according to the execution of the detection optical system and the irradiation system.

As shown in Fig. 31, the shading correction circuit for correcting shading uses the pixel values of the dark current portion in 8-bit values 3212 (256 stages) obtained by A / D conversion of the detection signal output by the one-dimensional imaging device. A subtraction circuit 3209 for subtracting data read from the memory 3206 controlled by the synchronization circuit 3205, and a shading correction factor for each pixel in the memory 3207 controlled by the synchronization circuit 3205. The multiplication circuit 3210 multiplied by the read data and the detection signal output by the one-dimensional imaging device are divided by twice the number of bits of the 8-bit value 3212 obtained by A / D conversion, that is, 16 bits which are twice the 8 bits. An intermediate bit signal output circuit 3211 returns the number of bits of the value to the number of initial bits, i.e., 8 bits. Although this shading correction circuit is a digital circuit which processes digital values, you may perform correction with analog data.

If pixels of 2 x 2 탆 ² are used to detect defects such as foreign matters having a size of 2 占 퐉 or more, the number of pixels for which defects such as foreign matters are detected differs from the number of defects such as foreign substances detected. To detect the fault A, such as a foreign body 10㎛ The pixels in the ² × 2㎛ 2, the pixel 25 ^{(2 10/22} = 25) of the detection signal can be output, and observing defects of the detected foreign object, etc. In order to do this, 25 detection signals must be examined.

The conventional reticle inspection method examines the positional relationship between pixels of defects such as foreign matters detected by software, and when pixels where defects such as foreign matters are detected are adjacent to each other, defects such as one foreign material by group processing are performed. In order to detect the error, it avoids the unreasonableness of investigating many detection signals. However, this conventional method requires software processing, and it takes about 10 minutes to process many detection signals, for example, 1000 detection signals.

The present invention is divided into a plurality of field of view blocks that can observe the entire inspection area at the same time, for example, a field of view blocks each 32 × 32 μm ² , and detect all defects such as foreign matters by detecting all detection signals corresponding to each field block. It is regarded as a detection signal obtained by This makes it possible to observe and confirm a defect such as a large foreign material in the field of view block regardless of its shape.

Block processing is functionally the same as group processing, but block processing can be achieved simply by hardware. The present invention shortens inspection time by performing block processing on hardware in real time, and improves throughput (manufacturing efficiency) of the reticle inspection apparatus. The reticle inspection apparatus of the present invention can inspect 1000 detection signals at a time two-thirds the time required by the conventional reticle inspection apparatus.

According to Fig. 32, the block processing circuit has three ranks according to the magnitude of the detection signal output from the detector, that is, a large rank (a defect detection signal such as a large foreign material) corresponding to a defect such as a large foreign material, and an intermediate foreign material. It is classified into detection signals of medium rank (defect detection signal such as a middle foreign matter) corresponding to a defect such as a small rank (defect detection signal such as a small foreign matter) corresponding to a defect such as a small foreign matter, The number of defect detection signals such as a large foreign material, a defect detection signal such as a middle foreign material, and a defect detection signal such as a small foreign material in each pixel block of 256 pixels (= 16 x 16 pixels) is counted, and the foreign material in each pixel block is counted. The number of defects such as large, medium, and small foreign matters included in each pixel block only when the number of defects such as one or more is larger than one, the maximum detection signal in the signals output from the pixels of each block, and the coordinates of each block in the storage device. Light it.

The CPU sets the maximum number of defects such as foreign matters in the latch 4201 as the upper limit number of defects such as foreign matters to be detected. If the number of defects such as foreign matters exceeds the maximum number, the inspection of the reticle having too many defects such as foreign matters is no longer meaningful, so the inspection is stopped. The counter counts the number of defects such as foreign matters detected, and the comparator 4211 compares the count of the counter 4201 with the maximum number set in the latch 4201. If the count of the counter 4201 is greater than the maximum number, the inspection is stopped.

The CPU sets a high threshold value in the latch 4202 to discriminate between a detection signal indicating a defect A such as a medium or small foreign material and a detection signal indicating a defect such as a large foreign material. When the level of the detection signal is higher than the high threshold value, it is determined that the detection signal indicates the detection of a defect such as a large foreign material. The comparator 4212 compares the detection signal with the threshold value, and if the detection signal is higher than the threshold value, the count of the counter 4202 that counts the number of defects such as a large foreign material is increased by one.

The CPU sets a middle threshold value in the latch 4203 to discriminate between a detection signal indicating a defect such as a small foreign material and a detection signal indicating a defect such as a middle foreign material. The comparator 4213 compares the detection signal with the intermediate threshold value and determines that the detection signal indicates a defect such as an intermediate foreign material when the detection signal is higher than the intermediate threshold value, and the count of the counter 4223 is increased by one. .

The CPU sets a low threshold value in the latch 4204 to discriminate between a detection signal indicating a substance other than a defect such as a foreign material and a detection signal indicating a defect such as a small foreign material. The comparator 4214 compares the detection signal with the low threshold value, and if the detection signal is higher than the low threshold value, determines that the detection signal indicates a defect such as a small foreign material, and the count of the counter 4224 increases by one. do.

In the above-described counting operation of defects such as foreign matters, the number of defects such as large foreign matters is determined by counting all the counters, namely, the counter 4422 for counting defects such as foreign matters, the counter 4223 for counting defects such as intermediate foreign matters, and the like. The counter 4224 counts defects such as foreign bodies, and the number of defects such as intermediate foreign bodies is counted by the counter 4223 for counting defects such as intermediate foreign bodies and the counter 4224 for counting defects such as small foreign bodies. Is counted by Therefore, the number of defects, such as a small foreign material, is determined by subtracting the number of defects, such as an intermediate foreign material, from the output of the counter 4224 which counts the defects, such as a small foreign material, and the number of defects, such as an intermediate foreign material, etc. It is determined by subtracting the number of defects such as a large foreign material from the output of the counter 4223 which counts the defects. The number of defects such as a large foreign material, a defect such as an intermediate foreign material, and a defect such as a small foreign material may be determined when displaying or outputting the inspection result. The detection signals may be compared with two comparators to discriminate detection signals indicating defects such as large, medium and small foreign matters. For example, only a detection signal between a high threshold value for defects such as a large foreign material and an intermediate threshold value for defects such as a medium foreign material is selected as a detection signal representing a defect such as an intermediate foreign material, and the intermediate threshold value is selected. Only the detection signal between the low threshold value indicating a defect such as and a small foreign matter is selected as a detection signal representing a defect such as a small foreign matter.

Adders 4232, 4233 and 4234, and shift registers 4242, 4243 and 4244 form arrays of one-dimensional detectors, such as CCD detectors, in two-dimensional blocks, for example 16x16 = 256. Block each block of pixels. The number of stages of the shift register is equal to (the number of pixels in the CCD array) / (the number of pixels in one block). In this case, since the number of pixels of the CCD array is 256 and the number of blocks on one side is 16, the number of stages of the shift register is 256/16 = 16. In this example, the number of stages of the shift register is the same as the number of one block-processed pixels, but it is a coincidence that these numbers coincide, and the number of stages of the register and the number of pixels of the one-blocked process are not necessarily the same. However, when the value of (Number of pixels of CCD array) / (Number of one block processed) is not an integer, a block processing circuit having a complicated configuration is required. Therefore, it is preferable to determine the number of pixels in the CCD array and the number of blocks in one block so that the value of (Number of pixels in the CCD array) / (Number of blocks in one block) becomes an integer.

The contents of the counter 4202 for counting the number of defects such as a large foreign material are cleared (reset to 0) each time one pixel (16 pixels) of each block is counted and a detection signal is output. The clear signal is obtained by dividing the clock outputted for each pixel arranged along the Y-axis of the detector by a divider (counter) 4421. In this case, the CCD array transfer clock may be used as the clock of each pixel arranged along the Y axis. The count of the counter 4422 immediately before being cleared, that is, the count of the detection signals for 16 pixels arranged along the Y-axis, is output by the adder 4232 from the output terminal of the 16-stage shift register 4242 for defects such as large foreign objects. The output signal of the adder 4232 is input to the input terminal of the defect 16-stage shift register 4242 for defects such as large foreign objects. As a result, the contents of the 16-stage shift register 4242 are shifted by one stage by the clear signal obtained by dividing the clock output for each of the 16 pixels arranged along the Y axis. Therefore, the contents of the sixteen-stage shift register 4242 are shifted by one stage for every 16 pixels arranged along the Y axis. The contents of the sixteen-stage shift register 4242 appear at the output terminal every time the contents are shifted by sixteen stages. At this time, the CCD array is shifted by a distance corresponding to one pixel along the X-axis, and the number of defects such as a large foreign material detected in 16 pixels arranged along the Y-axis is added to the 16-step shift register 4242 by the adder 4422. It is added to the contents of. The contents of the 16-stage shift register 4242 are cleared by a signal obtained by dividing the pulse of the encoder output by the divider (counter) 4422 every time the CCD array is shifted by a distance corresponding to one pixel along the X axis. do. That is, the contents of the 16-stage shift register 4242 are cleared each time the CCD array is shifted by a distance corresponding to 16 pixels arranged along the X axis. Therefore, the number of defects, such as a large foreign material detected by 16x16 = 256 pixels, accumulate | stores in the content of the 16-stage shift register 4242 for defects, such as a large foreign material. When it is determined by the comparator 4215 that the number of defects such as a large foreign material is not zero, a signal indicating the number of defects such as a foreign material and the coordinates of the block is outputted to the processing and memory means 4271, where The number of defects is a count of the counter 4224 equal to the sum of the respective numbers of defects such as large, medium, and small foreign matters. The operation mode of the block processing circuit for defects such as small foreign matters such as the defect of intermediate foreign matters and the like is the same as the block processing circuit for defects such as defects such as large foreign matters described above.

The circuit which selects the maximum detection signal among the detection signals contained in each block processes 16 x 16 = 256 pixels according to the maximum detection signal selection procedure, which is performed by latches 4201, 4202, 4203, and counters. Instead of using (4222), (4223), (4224), using a latch (4205) to hold the maximum detection signal output from one of the 16 pixels arranged along the Y axis, and adders (4232), (4233), ( The number of defects such as foreign matter detected using the 16-stage clear signal and the 16-stage shift register 4245 arranged along the Y-axis except for using the comparator 4217 and the selector 4251 instead of 4234). It is the same as the above-described defect counting procedure such as the foreign material for counting

In this manner, the number of detection signals (the number of defects such as large foreign objects) exceeding the defect determination threshold value of [1] large foreign objects or the like of the block in which it is determined that foreign objects exist in the memory in which foreign material data is accumulated. ] Number of detection signals exceeding defect determination threshold values such as intermediate foreign materials (defects such as intermediate foreign materials), [3] Number of detection signals exceeding defect determination threshold values such as small foreign objects (small foreign objects) Number of defects, etc.), [4] the maximum value in the detection signal, and [5] the coordinates of the block.

At the time of display, these data are displayed, and it confirms by an observation system by calling sequentially for confirmation according to said [5], but it may not be desirable to display all these data in some cases.

In the apparatus for detecting defects such as foreign matters in the binarization process as in the present invention, the setting of the binarization threshold value (particularly, the defect determination threshold value such as small foreign matters) greatly affects the detection sensitivity. That is, when the threshold value is set larger than necessary, defects such as small foreign matters that actually exist may be missed (missed) without being judged as defects such as foreign matters. Depending on the application, omission may not be a major problem (for example, the purpose of confirming the integrity of the process by monitoring the increase or decrease of defects such as foreign matter in the process). However, in the case of a photomask such as a reticle, defects such as foreign matters lost affect the result of exposure transfer of all products, so it is necessary to aim at zero (zero). For this reason, the determination threshold value is set as low as possible (small). In this case, when the threshold value is set smaller than necessary, the correct circuit pattern may be incorrectly judged as a defect such as foreign matter. Of course, in the present invention, if a worker calls a position considered to be a defect such as a detected foreign material and judges whether it is a defect such as a foreign material or a normal circuit pattern, or if the false detection result is erased in the memory according to the determination result, false detection is performed. Even if it exists, the detection result only of defects, such as a foreign material, can be obtained. However, if the number of incorrectly detected normal patterns is too large (it is common for the number of normal patterns existing in the LSI to be more than millions), the checking operation takes time and is not practical. For this reason, when the number of detection signals determined that the foreign material or the like is defective is too large (in this case, most of the normal circuit patterns are incorrectly detected), the threshold value is further reset and retested. This means that it will take longer to retest. Therefore, until the threshold value is established, the inspection area is limited to small (hence, the inspection time is also shortened), and the inspection for setting the threshold value is repeated, and the inspection area necessary after the threshold value is established. Inspection method that inspects the whole, or when the number of detection signals determined to be a defect such as foreign matter is larger than the set value, the inspection method that stops the inspection because the threshold value setting is inappropriate, or the threshold after the interruption Check and set the number of detection signals (increase rate of detection signals determined as defects such as foreign matters) determined by the inspection method that automatically increases the value by the set value, and automatically starts the re-inspection or the defects such as foreign matters in a certain section. If the value is higher than the value, the test method stops the test, or after the interruption, the threshold value is increased by the set value to automatically retest the test. When you add a design of such tests it is a more practical way. The latch 4201 in Fig. 32 is an important component for realizing their design.

Unlike the above-described grouping process, all the detection signals determined as defects such as detection signals or foreign matters are accumulated in the memory, and the threshold value is set again after completion of the inspection so that only foreign detection signals having a threshold value or more are foreign matters. A configuration that considers the detection signal from a defect such as this is also considered. In this configuration, however, "the large foreign object is incorrectly recognized as several small foreign objects, and it takes time to confirm the call of the inspection result," which the grouping processing circuit described above attempts to solve, or "after inspection by the software to avoid the problem." Grouping takes unnecessary time for processing ”.

Thus, in the present invention, display and call of detection results of defects such as foreign matters are executed in units of blocks, and as a result of the operation of the block processing circuit shown in FIG. 1] The number of detection signals exceeding the defect determination threshold value such as a large foreign material (the number of defects such as a large foreign object), [2] The number of the detection signals exceeding the defect determination threshold value such as a medium foreign material (large (3) Number of defects such as foreign matters and intermediate foreign matters), [3] Defects such as small foreign matters, etc. Number of detection signals exceeding the threshold value (defects such as large foreign matters, defects such as intermediate foreign matters and small foreign matters) The number of defects), [4] the maximum value in the detection signals, and [5] the positional coordinates of the block are accumulated.

That is, when performing display and call, not all detection signals of detection signals exceeding the defect determination threshold values such as small foreign objects are the targets of display and call, but defect determination thresholds of defects such as intermediate foreign objects. If only a block including a signal exceeding a value exceeding a value, or a signal exceeding a defect determination threshold value such as a large foreign object, is subjected to a reduction in the number of target blocks, high efficiency can be realized. This may be calculated for the above [1] to [3], but judging from the content of the above [4] is achieved in the shortest time.

In addition, if it judges by said [4], determination of a display or a call may be judged not only by 3 ranks of large, medium, and small, but also compared with arbitrary setting values. In other words, the arbitrary setting value is changed (increased) little by little at the time of display, and changed (decreased) until the number of detection blocks becomes the number of blocks suitable for call confirmation, and then the call is executed or the predetermined value after decrement is changed. The retest may be performed as the detection determination threshold value of the new defect, or the operation may be performed in an automatic sequence.

33 shows an example of the relationship between the detector output 3301, the shading correction circuit 3303, the four pixel addition circuit 3304, the block processing circuit 3305, and the defect detection circuit 3306 such as foreign matter.

FIG. 48 shows an embodiment in which the shading correction circuits 113, 123, the four pixel addition circuits 114, 124, and the block processing circuit 58 are applied to FIG. FIG. 49 shows an embodiment in which the shading correction circuits 113, 123, four pixel addition circuits 114, 124, block processing circuits 58, 558 are applied to FIG. FIG. 50 shows an embodiment in which the shading correction circuits 113, 123, four pixel addition circuits 114, 124, block processing circuits 58, 558 are applied to FIG. FIG. 51 shows an embodiment in which the shading correction circuits 113, 123, the four pixel addition circuits 114, 124, the block processing circuits 58, and 558 are applied to FIG. FIG. 52 shows an embodiment in which the shading correction circuits 113, 123, the four pixel addition circuits 114, 124, and the block processing circuit 58 are applied to FIG. FIG. 53 shows an embodiment in which the shading correction circuits 113, 123, block processing circuits 58, 558 are applied to FIG.

According to the present invention, the illumination is performed on the sample surface side (approximately wavelength 780 nm) and the sample back surface side (approximately wavelength 488 nm), and the scattered light generated by an optical system of NA 0.4 or more on the sample surface side is collected and illuminated. A detection optical system that shields diffracted light from the circuit pattern by using a spatial filter provided on a Fourier transform plane by separating the wavelength for each direction, and a circuit for correcting the detection value of the detector for uneven illumination and a 2 × 2 circuit. The board | substrate with which the circuit pattern, such as a photomask, was provided by comprised by the circuit which calculates the addition value of the detection value of a pixel, and the circuit which calculates the maximum value of the four addition values shifted by one pixel in the surrounding 4 directions, etc., In particular, defects such as defects such as fine foreign matter of a submicron size attached to a reticle having a phase shift film for the purpose of improving the transfer resolution are mainly optical. Facilitate a simple configuration and remove it from the circuit pattern to be stabilized to obtain a remarkable effect can be detected.

A photomask such as a reticle is formed by a metal thin film or a phase shifter by circuit pattern formation 651 in a photomask manufacturing process such as a reticle as shown in FIG. 65A and then cleaned by 652. Strictly cleaned. Subsequently, defects such as foreign matters are inspected by a foreign matter inspection 653 by a defect inspection apparatus such as foreign matters according to the present invention. Here, when the adhesion of defects such as foreign matters or the attachment of defects such as foreign matters that are substantially harmful is detected, the defects such as foreign matters are removed again by washing or the like until the attachment of defects such as foreign matters disappears. Is repeated.

A photomask, such as a reticle, from which defects such as foreign matters have been removed, is equipped with a pellicle for preventing adhesion of defects, such as foreign matters, by the pericle attachment 654. Here, by the foreign material inspection 655, defects such as foreign matters are inspected by a defect inspection apparatus such as foreign matters according to the present invention. If the adhesion of defects such as foreign matters is detected in this step, the ferrule is removed and the defects such as foreign matters are removed again by washing or the like, and the process is repeated until the adhesion of defects such as foreign matters is eliminated.

Photomasks, such as a reticle from which defects, such as a foreign material, were removed, are sent out by the exposure process by a stepper.

On the other hand, as shown in Fig. 65B, in a stepper step in which a photomask such as a reticle is received, a photomask such as a reticle is stored by a stocker 656 in a storage of a photomask such as a reticle when not used immediately. Then, the defect inspection such as the foreign matter is performed by the defect inspection apparatus such as the foreign matter according to the present invention by the foreign matter inspection 657 immediately before use or during storage. If adhesion of defects such as foreign matters is detected at this stage, photomasks such as reticles are returned to the manufacturing process of photomasks such as reticles, and the work of removing defects such as foreign matters is executed. If no defects such as foreign matters are detected on the photomask, dummy exposure 658 is performed on the stepper, and resist pattern inspection (reticle error check 659) is performed on the exposed substrate such as a wafer. In the case of OK, the product will start to be exposed. These processes are also shown in FIG. 66.

As described above, a defect inspection apparatus such as a foreign material according to the present invention is regularly used in close connection with a manufacturing process or an exposure process of a photomask such as a reticle, and a strict inspection is executed, so that defects such as foreign matters are finally performed. It is possible to manufacture a semiconductor device such as an LSI using a photomask such as a reticle having no adhesion.

Claims (15)

As a method for detecting defects such as foreign matter attached on a transparent or semitransparent substrate having a pattern formed by a light shielding film or a light semitransmissive film or a light transmissive film on one surface (surface), Irradiating illumination light onto the surface of the substrate on the surface side of the substrate, detecting light generated on the surface by the irradiation of the illumination light on the surface side and photoelectrically converting to generate a first electric signal, and irradiating the illumination light Detects and photoelectrically converts light generated on the surface and transmitted through the substrate to generate a second electrical signal, and is attached onto the substrate using the first electrical signal and the second electrical signal. A defect detection method such as a foreign material, characterized by detecting a defect such as a foreign material. The method of claim 1, And irradiating the illumination light on the surface side of the substrate while performing auto focusing on the surface of the substrate. The method of claim 1, The optical path of the light generated on the surface and transmitted through the substrate by the irradiation of the illumination light is corrected according to the thickness of the substrate, and the light on which the optical path is corrected is detected on the back side and photoelectrically converted to generate a second electric signal. Defect detection method, such as foreign matter, characterized in that. An apparatus for detecting a defect such as a foreign matter attached to a transparent or semitransparent substrate having a pattern formed by a light shielding film, a light semitransmissive film, or a light transmissive film on one surface (surface), Irradiation means (21, 22, 31, 32) for irradiating illumination light onto the surface of the substrate from the surface side of the substrate; First condensing optical system means (41, 43, 44, 45), which are irradiated by the irradiating means and condenses light generated on the surface of the substrate on the surface side of the substrate; First detection means (51) for detecting the light collected by said first light converging optical system means and outputting a first electric signal; Second condensing optical system means (401, 403, 404, 405) for condensing the light emitted from the surface by the irradiation means and transmitted to the surface (back side) side opposite to the surface on the back side; Second detection means 551 for detecting light collected by the second light converging optical system means and outputting a second electric signal; And a detecting means (5) for detecting a defect such as a foreign matter adhering on the substrate by using the first electric signal and the second electric signal. The method of claim 4, wherein And the optical axis of the first light converging optical system means is substantially perpendicular to the surface of the substrate. The method of claim 4, wherein And the optical axis of the second light converging optical system means is substantially perpendicular to the surface of the substrate. The method of claim 4, wherein The irradiating means includes a laser (21, 31) as a light source, defect detection apparatus such as foreign matter. The method of claim 7, wherein The defect detection apparatus such as a foreign material, characterized in that the laser (21, 31) is an argon gas laser. The method of claim 4, wherein Between the substrate 6 and the second condensing optical system means 401, 403, 404, 405 an optical path correction plate 6102 for correcting the optical path of the light passing through the substrate is provided. Fault detection device. The method of claim 4, wherein A defect detection apparatus such as a foreign material, wherein an NA of the first light converging optical system means is 0.4 or more. The method of claim 4, wherein And an automatic focusing means for aligning the focal position of the irradiating means with the surface of the substrate. The method of claim 4, wherein The substrate has a pattern protection transparent film supported by a holding frame for maintaining a gap with respect to the surface, and the pattern protection film defect detection means for detecting the foreign matter adhering to the surface of the pattern protection film by the defect detection device ( 6251), the defect detection apparatus such as foreign matter. A pattern is formed on one surface (surface) with a light shielding film 80 or a light semitransmissive film or a light transmissive film 1003 and has a transparent film for pattern protection supported by a holding frame for maintaining a gap with respect to the surface on which the pattern is formed. As a device for detecting defects such as foreign matter attached to a substrate, Means (5) for detecting defects such as foreign matter adhering to the surface of the substrate by irradiating the surface of the substrate with first illumination light and detecting light generated on the surface of the substrate; And a means (6251) for detecting defects such as foreign matter adhering to the surface of the pattern protection transparent film by detecting the light generated from the pattern protection transparent film by irradiating a second illumination light to the pattern protection transparent film. Defect detection apparatus such as foreign matter. The method of claim 13, The means 5 for detecting defects such as foreign matters adhered to the surface of the substrate and the means 6221 for detecting defects such as foreign matters attached to the surface of the pattern protection transparent film have different optical magnifications. Defect detection apparatuses. An apparatus for detecting defects such as foreign matters attached to a substrate formed with a pattern by a light shielding film 80 or a light semitransmissive film or a light transmissive film 1003 on one surface (surface), Means (5) for detecting defects such as foreign matter adhering to the surface of the substrate by irradiating the surface of the substrate with first illumination light and detecting light generated on the surface of the substrate; Luminaire (6231) for illuminating the substrate in a direction inclined with respect to the substrate; Observation means (6201) for observing the surface of the substrate inspected by the means for detecting the defect, characterized in that the defect detection apparatus such as foreign matter.