JP2006276756A - Foreign matter inspecting device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the constitution of a detection system and to improve detection precision for foreign matters. <P>SOLUTION: A detection system 7 detects an inspected surface 2a of an inspected body 2 with illumination light from a light source 101 and also detects the inspected surface 2a with illumination light from a light source 102 differing in wavelength from the light source 101, and respective detection results are compared with each other to decide the foreign matters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a foreign matter inspection apparatus and a foreign matter inspection method for inspecting foreign matter attached to a mask or the like used in a manufacturing process of a device such as a semiconductor element or a liquid crystal display element.

  In the manufacturing process of semiconductor elements, liquid crystal display elements, and other devices, a pattern formed on a photomask or reticle (hereinafter referred to as a mask when collectively referred to as a mask) is a wafer or glass plate (hereinafter referred to as a generic name). The process of transferring to a substrate is repeated. If foreign matter such as dust or dust adheres to the mask, the image of the foreign matter is transferred together with the pattern formed on the mask, and the same defect may occur in a plurality of substrates subjected to exposure processing.

  The mask is formed with a light shielding material such as chrome on one surface of a transparent glass substrate, and foreign matter such as dust or dust adheres to the surface on which this pattern is formed (hereinafter sometimes referred to as the pattern surface). In order to prevent this, there are cases where a pellicle is erected apart from the pattern surface. Such an exposed surface of the mask, that is, a surface opposite to the pattern surface of the glass substrate of the mask (hereinafter sometimes referred to as a non-pattern surface) and a surface outside the pellicle (hereinafter also referred to as a pellicle surface). It is necessary to inspect whether or not foreign matter is attached to the surface before performing the exposure process, and for this purpose, a foreign matter inspection apparatus is used.

  The foreign matter inspection apparatus irradiates illumination light with the non-patterned surface or pellicle surface of the mask as the test surface, and detects the scattered light generated by the foreign matter when the foreign matter is attached by a light detection element such as a photodetector. It is a device that inspects for the presence or absence.

  More specifically, the foreign substance inspection apparatus mounts an illumination device that illuminates a mask as a subject with an elongated, substantially rectangular illumination light having a longitudinal direction in a first direction (Y direction), and the mask. A table that moves in a second direction (X direction) orthogonal to the first direction, and a plurality of photodetectors and tables arranged along the first direction that detect scattered light generated by foreign matter on the surface to be detected And a detection system having an optical system provided between the mask placed on the light detection element and the mask placed on the mask while illuminating a part of the mask with illumination light. The presence or absence of foreign matter is inspected by moving the table and detecting the light scattered by the foreign matter on the surface to be examined by a light detection element.

  FIG. 12 is a diagram showing a configuration of a scattered light detection system in a conventional foreign matter inspection apparatus. In this figure, the light to be inspected (non-patterned surface) 2a of the mask (glass substrate) 2 is irradiated with the illumination light 3 from the light source 4, and the scattered light 3a scattered by the foreign matter G adhering to the surface to be tested 2a. Is imaged on the light receiving surface of the light detecting element 7.

  By the way, when the non-pattern surface 2a of the mask is inspected using the foreign substance inspection apparatus, as shown in FIG. 12, a part of the illumination light 3 irradiated to the test surface (non-pattern surface) 2a The light enters the mask 2 at an angle corresponding to the incident angle of the illumination light 3 and the refractive index of the mask (glass substrate) 2. Since a pattern P having various spatial frequency components is formed on the pattern surface of the mask 2, the observation direction (light detection) of the light diffracted by the pattern P and refracted by the non-pattern surface 2a. The light 3b traveling in the optical directivity direction with respect to the inspection region (illumination region) of the detection system including the element 7 (hereinafter the same applies) is in a very close positional relationship with the light 3a scattered by the foreign matter G. The light may enter the light detection element 7. In the foreign object detection, the light diffracted by the pattern P is merely noise, which adversely affects the detection result by the light detection element 7. As described above, when the light 3a from the foreign substance G and the light 3b from the pattern P are in a very close positional relationship, it is difficult to accurately distinguish these detection signals electrically, and the field of view of the light detection element 7 Even if a filter such as an aperture for limiting the above is provided, these may be incident on the light detection element 7 almost simultaneously, so that foreign matter may not be detected accurately.

  In the case where foreign matter detection is performed using the surface (pellicle surface) 2c of the pellicle erected via a support member on the side where the pattern P of the mask 2 is formed, the subject 2 is turned over in the same manner. In this case, a similar problem may occur.

  As a conventional technique for alleviating such a problem, a plurality of illumination systems are provided, illumination lights are simultaneously irradiated from different directions, light beams are separated according to the illumination light directions, and each is provided corresponding to the illumination system. What is detected by a detection system is known (Japanese Patent Laid-Open No. 10-212267). Further, there is also known one in which a plurality of illumination lights are simultaneously irradiated from the same direction, light beams are separated for each illumination light, and each is detected by a detection system provided corresponding to the illumination system (Japanese Patent Laid-Open No. Hei. 11-194097).

  However, in such a conventional technique, it is necessary to separate the light that is simultaneously irradiated and scattered on the surface to be measured by the separating means, and to detect the light by the same number of light detection elements as the number of illumination lights, There is a problem that the configuration is complicated and the cost is increased.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to simplify the configuration of the detection system and increase the accuracy of foreign object detection.
JP-A-10-212267 Japanese Patent Laid-Open No. 11-194097

  Hereinafter, in the description shown in this section, the present invention will be described in association with the member codes shown in the drawings representing the embodiments. However, each constituent element of the present invention is limited to the members shown in the drawings attached with these member codes. Is not to be done.

  According to the first aspect of the present invention, in the foreign matter inspection apparatus (1) for inspecting the foreign matter attached to the test surface (2a) of the subject (2), the first illumination light having a predetermined wavelength and the first illumination An illumination system (4, 5, 101, 102) for selectively emitting second illumination light having a wavelength different from that of the light to illuminate the inspection area (IA) on the surface to be inspected, and observing the inspection area A detection system having a single light detection device (7) for the detection, the first detection result by the light detection device when illuminated with the first illumination light, and the light detection when illuminated with the second illumination light There is provided a foreign substance inspection apparatus including a processing device (35) for specifying a foreign substance on the surface to be detected based on a second detection result by the apparatus.

  In the present invention, since the wavelengths of the first illumination light and the second illumination light are different from each other, the light is incident on the subject and diffracted by a pattern or the like existing on the surface opposite to the subject surface ( Hereinafter, the noise light may have different properties when illuminated with the first illumination light and when illuminated with the second illumination light. By comparing the detection results of both, Among the scattered light, the light traveling in the direction of observation by the light detection device (hereinafter sometimes referred to as observation light) can be distinguished from the noise light, and the foreign object can be accurately detected. In addition, in the present invention, the first illumination light and the second illumination light are selectively irradiated, and each of them is detected by a detection system having a single photodetection device. A foreign substance on the surface to be measured can be accurately detected without providing a detection system having means or a plurality of light detection devices.

  According to the second aspect of the present invention, in the foreign matter inspection apparatus (1) for inspecting the foreign matter adhering to the test surface (2a) of the subject (2), illumination light is emitted on the test surface. The illumination system (4, 5, 101) for illuminating the examination area, the detection system having a light detection device (7) for observing the examination area, and the relative posture of the subject and the detection system are adjusted. The posture detection device (9) and a second posture different from the first posture and the first detection result by the light detection device when the subject is set to a predetermined first posture by the posture adjustment device. There is provided a foreign substance inspection apparatus including a processing device (35) for specifying a foreign substance on the surface to be detected based on the second detection result by the photodetection device at the time.

  In the present invention, the test surface is detected in the first posture and the second posture, which are different from each other, and the noise light has different properties in the case of the first posture and the case of the second posture. Thus, by comparing the detection results of both, the observation light and the noise light can be distinguished, and the foreign matter can be accurately detected. Therefore, it is not necessary to provide a plurality of illumination systems and a plurality of detection systems, and the configuration of the optical system can be simplified.

  According to the present invention, it is possible to simplify the configuration of the optical system and to accurately inspect the foreign matter. Therefore, for example, when foreign matter inspection of a mask used in exposure processing is performed using the present invention, it is possible to accurately inspect the presence or absence of adhesion, so that when performing exposure processing, a plurality of substrates have similar defects. This can be prevented and yield can be improved.

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

  FIG. 1 is a perspective view showing a schematic configuration of a foreign matter inspection apparatus according to the first embodiment of the present invention. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. In the XYZ orthogonal coordinate system, the X axis and the Y axis are set to a plane parallel to the surface of the mask 2 as a subject, and the Z axis is set to a direction orthogonal to the surface of the mask 2. In this embodiment, a foreign substance inspection apparatus that inspects foreign substances attached to a relatively small mask (for example, a 6-inch mask: □ 150 mm) will be described as an example.

  In FIG. 1, a foreign substance inspection apparatus 1 is an apparatus for inspecting foreign substances attached to the surface of a pellicle-equipped mask 2 as a subject. Although not shown, the pellicle is a transparent thin plate for preventing foreign matter such as dust and dirt from adhering to the surface (pattern surface) on which the pattern of the mask 2 is formed. It is erected in a parallel state with a gap through a support member.

  In this embodiment, the non-pattern surface opposite to the pattern surface (the surface on which the pellicle is provided) of the mask 2 with pellicle is inspected as the test surface 2a, and the mask 2 faces the test surface 2a upward. , Held by the foreign matter inspection apparatus 1. The inspection of the foreign matter on the surface of the pellicle can be performed in the same manner as the inspection of the non-pattern surface by placing the mask 2 on the foreign matter inspection apparatus 1 with the top and bottom of the mask 2 reversed.

  On one side (+ Y side) of the mask 2, an illumination system including the illumination device 4 and the reflection mirror 5 is arranged. The illumination device 4 irradiates an elliptical illumination light 3 having a longitudinal direction in the Y direction downward (−Z direction). The reflecting mirror 5 is provided below the illuminating device 4, and the illumination light 3 from the illuminating device 4 is reflected by the reflecting mirror 5 so that a linear inspection area (illuminating area) IA on the surface 2a to be measured is predetermined. It is designed to illuminate with a width of.

  That is, as shown in detail in FIGS. 2 and 3, the illumination light 3 from the illumination device 4 is reflected by the reflection mirror 5, and the reflected illumination light (reflected light) is detected on the mask 2. By irradiating the test surface 2a with the surface 2a at an extremely small angle from the oblique lateral direction (an angle of 89 ° with respect to the Z direction in this embodiment), the entire Y direction of the test surface 2a of the mask 2 is irradiated. A long and narrow inspection area IA having a longitudinal direction in the Y direction is formed.

  The width (maximum dimension in the X direction) of the illumination light 3 is preferably set as small as possible, and is a dimension viewed from the observation direction by a detection system described later, and is practically set to about 0.5 mm to 2 mm. . In this embodiment, it is set to 1 mm. In this embodiment, the longitudinal dimension of the illumination light 3 before being emitted by the illumination device 4 and reflected by the reflection mirror 5 is set to about 4 mm. Since the incident angle of the illumination light 3 with respect to the test surface 2a is 89 °, the length of the illumination light on the test surface 2a in the longitudinal direction (Y direction) is the Y direction of the mask 2 as the subject. Although it is sufficiently larger than the dimension (about 150 mm in this embodiment), about 150 mm in the central portion that can be regarded as a substantially rectangular shape is used as effective illumination light.

  As shown in FIGS. 4 and 5, the illumination device 4 includes two light sources 101 and 102, a reflection mirror 103, a half mirror 104, and the like. The light source 101 and the light source 102 are made of laser diodes, for example, and their oscillation wavelengths are set to be different from each other. As an example, when the oscillation wavelength of the light source 101 is 780 nm, for example, the oscillation wavelength of the light source 102 can be set to 580 nm. Light from the light source 101 is reflected by the reflection mirror 103 and deflected in the −Z direction, passes through the half mirror 104, and is irradiated onto the test surface 2 a through the reflection mirror 5. Light from the light source 102 is reflected by the half mirror 104, deflected in the −Z direction, and irradiated onto the test surface 2 a through the reflection mirror 5. Oscillation by the light sources 101 and 102 is controlled by a control device (not shown).

  4 and 5, the reflection mirror 5 is not shown. In addition, the light sources 101 and 102 are not limited to laser diodes, and LED arrays in which laser diodes are evenly arranged in a one-dimensional manner with a predetermined interval may be used. Also, those using a cylindrical light source such as a cold cathode fluorescent tube, or light beams from a light source such as a halogen lamp are guided by an optical fiber, and the irradiated part of the optical fiber is expanded to match the width of the inspection area. May be used.

  Returning to FIG. 1, the scattered light from the foreign matter existing in the inspection area IA of the test surface 2 a is detected by a detection system having a photodetection device (sensor 7 which is a one-dimensional line sensor in this embodiment). The detection system includes an imaging optical system having a plurality of lenses, reflection mirrors, etc. (all not shown), and the scattered light is transmitted through the imaging optical system at a predetermined reduction magnification (for example, 1/5). Are detected by a sensor 7 formed by arranging the photodetecting elements. In this embodiment, a MOS type one-dimensional sensor is used as the sensor 7. The sensor 7 may be a CCD (Charge Coupled Device) or the like in which light detection elements are arranged one-dimensionally or two-dimensionally. The imaging optical system includes, for example, a line-shaped microlens array, and reduces the image of the line-shaped inspection area IA to form an image on the sensor 7.

  As shown in FIG. 6, the sensor 7 is configured by arranging a plurality of light detection elements 7a in a line in the Y direction. In this embodiment, the total length of the sensor 7 in the Y direction is set to about 25 mm, and the length (dimension in the Y direction) of each photodetecting element 7a is set to about 500 μm and the width is about 50 μm. In the present embodiment, the electrical scanning direction in which the elements 7a of the sensor 7 are arranged one-dimensionally is set in the Y-axis direction, and the scanning direction of the mask table 8 by a mechanical drive device to be described later is set. It is set as the X-axis direction orthogonal to the Y-axis.

  Refer to FIG. 1 again. The pellicle-equipped mask 2 is placed and fixed on a mask table 8 via a holder 9, and the mask table 8 is moved in the X-axis direction by a driving device 10. The driving device 10 includes two linear guides 11a and 11b fixed to a base plate 11, a ball screw 12, and a driving motor 13. The mask table 8 is supported by the linear guides 11a and 11b so as to be linearly movable in the X-axis direction. Has been.

  The ball screw 12 is supported by support plates 11c and 11d fixed in the vicinity of both ends of the base plate 11 in the X-axis direction, and is rotatable about the center between the support plates 11c and 11d in parallel with the linear guides 11a and 11b. It is supported. A nut 12 a that meshes with the ball screw 12 is fixed to the mask table 8, and the ball screw 12 is rotated by a drive motor 13.

  As the drive motor 13, for example, a stepping motor or a servo motor provided with an encoder is used. The driving device 10 moves the mask 2 one-dimensionally in the X-axis direction with respect to the detection system including the sensor 7 and the imaging optical system. In FIG. 1, the configuration in which the mask 2 is moved and scanned with respect to the detection system including the sensor 7 and the imaging optical system is illustrated, but the illumination system including the illumination device 4 and the reflection mirror 5 with respect to the mask 2, and The detection system including the sensor 7 and the imaging optical system may be configured to move and scan one-dimensionally. Here, the drive motor 13 is provided with an encoder 14 for detecting the rotation amount of the drive motor 13.

  A gain correction plate 15 is attached to one end of the mask table 8. The gain correction plate 15 is used when correcting the gain (amplification factor) of the amplifier provided in each light detection element 7a of the sensor 7. The sensitivity characteristic of each cell is corrected by correcting the amplification factor of each amplifier. The gain correction plate 15 is formed of a material that scatters light emitted from the illumination device 4, for example, a white resin plate. The upper surface of the gain correction plate 15 is set to a height substantially equal to the surface height of the mask 2 placed on the mask table 8.

  Here, a signal processing circuit for processing the detection signal of the sensor 7 will be described. FIG. 7 is a block diagram showing a configuration of a signal processing circuit provided in the foreign matter inspection apparatus. In FIG. 7, the illumination system driver 31 selectively supplies power to the light sources 101 and 102 in the illumination device 4 to control the light emission of each of the light sources 101 and 102.

  The sensor driver 32 connected to the sensor 7 supplies the drive signal D1 including the clock signal to the sensor 7 to drive the sensor 7, and the detection signal D2 sequentially output from the sensor 7 by the supply of the drive signal D1. Receive. An output terminal of the sensor driver 32 is connected to an analog-digital converter (hereinafter referred to as ADC) 33.

  The Y coordinate counter 34 generates a sensor clock signal and an ADC clock signal and supplies them to the sensor driver 32 and the ADC 33, respectively. The Y coordinate counter 34 supplies the same clock signal as the sensor clock signal supplied to the sensor driver 32 to the signal processing unit 35 as Y coordinate data. The ADC 33 digitizes the detection signal D2 indicating the scattered light intensity output from the sensor 7 to, for example, 256 gradations, and outputs it to the signal processing unit 35 as scattered light intensity data.

  The motor driver 36 supplies a drive signal to the drive motor 13 that constitutes the drive device 10 that moves the mask table 8 in the X-axis direction to control the movement of the mask table 8. The encoder 14 connected to the output shaft of the drive motor 13 outputs a signal indicating the rotation amount of the drive motor 13 to the X coordinate counter 37. The X coordinate counter 37 calculates X coordinate data indicating coordinates in the X direction of the mask table 8 based on a signal indicating the rotation amount output from the encoder 14 and outputs the X coordinate data to the signal processing unit 35. The X coordinate counter 37 outputs a synchronization signal to the Y coordinate counter 34 in synchronization with the X coordinate. The Y coordinate counter 34 generates a scanning signal to the sensor driver 32 based on the synchronization signal output from the X coordinate counter 37. Further, a synchronization signal is also output to the ADC 33, and the signal from the sensor 7 is digitized.

  The signal processing unit 35 generates two-dimensional scattered light intensity data from the light intensity data output from the ADC 33, the Y coordinate data output from the Y coordinate counter 34, and the X coordinate data output from the X coordinate counter 37. To do.

  Here, in this embodiment, the test surface 2a is scanned twice to obtain the two scattered light intensity data described above. First, as illustrated in FIG. 4, the light source 101 of the illumination device 4 is driven via the illumination system driver 31, and illumination light having a wavelength of 780 nm is emitted as the first illumination light. At this time, the oscillation of the light source 102 is stopped. In this state, a first scan is performed, and scattered light intensity data as a first detection result is created and recorded in a memory (not shown) provided in the signal processing unit 35.

  Next, as shown in FIG. 5, the light source 102 of the illumination device 4 is driven via the illumination system driver 31, and illumination light having a wavelength of 580 nm as the second illumination light is emitted. At this time, the oscillation of the light source 102 is stopped. In this state, a second scan is performed, and scattered light intensity data as a second detection result is created and recorded in the memory. Of course, the first scan operation and the second scan operation may be performed in the same direction. However, from the viewpoint of improving the overall processing speed, for example, the first scan is in the + X direction, and the second scan is -X. It is preferable to carry out in a reciprocal direction.

  The signal processing unit 35 compares the first detection result and the second detection result respectively recorded in the memory for each pixel or a predetermined number of pixels as a group, and compares each of the two detection results with a foreign object. Is estimated as a foreign object. That is, those that are presumed to be foreign substances only in one of the detection results are excluded. Specifically, a logical product is calculated for each pixel or each group between the first detection result and the second detection result, and those that are equal to or greater than a predetermined threshold are finally determined as foreign matters. Based on the determination result, the signal processing unit 35 creates a distribution map relating to the foreign matter on the test surface 2a and displays it on a display device 38 such as a CRT or a liquid crystal display.

  As described above, each of the first detection result and the second detection result includes noise caused by diffracted light from a pattern or the like in addition to the scattered light from the actual foreign matter. It will be judged. However, the diffracted light from the pattern or the like changes its property including its direction if the wavelength of the illumination light is different. Therefore, as in this embodiment, the surface 2a is scanned with two types of illumination light having different wavelengths. Then, by obtaining two detection results and comparing them, it is possible to distinguish between scattered light and diffracted light, and the accuracy of foreign object detection can be increased.

  For example, as shown in FIG. 4, even when the diffracted light 3b in the pattern P by the illumination light 3 from the light source 101 enters the sensor 7, it is shown in FIG. As described above, when the illumination light 3 from the light source 102 having a wavelength different from that of the light source 101 is illuminated, the diffraction or refraction direction of the diffracted light 3b in the pattern P changes and the sensor 7 is prevented from entering. Thus, it is possible to distinguish between scattered light and diffracted light.

  As an example, FIG. 8 shows a detection result (distribution map MAP1) by irradiation of illumination light 3 from the light source 101, and FIG. 9 shows a detection result (distribution map MAP2) by irradiation of illumination light 3 from the light source 102. In FIG. 8, assuming that Ga is noise caused by diffracted light and the remaining part is scattered light from the foreign material in the portion (indicated by ○ in the figure) that is assumed to be foreign material, as shown in FIG. 9. As described above, the noise Ga due to the diffracted light disappears by changing the wavelength, so that the accuracy of foreign object detection can be improved by comparing these two detection results.

Here, the wavelength of the illumination light emitted from the light source 101 and the wavelength of the illumination light emitted from the light source 102 are selected using the following equations (1) and (2). By selecting the wavelengths of the two lights so as to satisfy these equations, erroneous detection can be prevented.
(Cos θb / cos θa) = (λb / λa) (1)
(Tan θb−tan θa) × h × cos θd> (t / β) (2)

  In equations (1) and (2), λa is the wavelength of the illumination light emitted from the light source 101, λb is the wavelength of the illumination light emitted from the light source 102, and θa is the diffracted light by the pattern P of the illumination light having the wavelength λa. Θb is the diffraction angle of the diffracted light by the illumination light pattern P of wavelength λb, θd is the detection angle (the angle formed by the pointing direction with respect to the inspection region of the detection system and the surface 2a to be detected), and t is The size of the light receiving part of the light detection device (sensor 7) (the width in the direction perpendicular to the pixel arrangement direction of the light receiving part, and the width when the aperture for limiting the field of view is provided in front of the light receiving part) H represents the thickness of the mask 2 (the dimension between the test surface 2a and the pattern surface 2b), and β represents the magnification of the imaging optical system included in the detection system.

  As an example, mask thickness h = 6.35 mm, light receiving element size t = 500 μm, imaging optical system magnification β = 0.12, detection angle θd = 85 degrees, one illumination light (illumination from light source 101) Wavelength λa = 780 nm, the wavelength λb of the other illumination light (assumed from the light source 102) is λb <590 nm or λb> 812 nm. By selecting the wavelength λb within this range, Thus, foreign matter can be detected without causing erroneous detection.

  The foreign matter inspection apparatus according to the first embodiment described above is configured to inspect only one side of the mask 2, but the configuration for holding the mask 2 in FIG. 1 is improved and the mask 2 is replaced. Without being able to inspect both sides at the same time. In this case, as shown in FIGS. 4 and 5, in order to inspect the pellicle surface 2c side of the mask 2, an illumination system including the illumination device 4 ′ and the reflection mirror (5) and the sensor 7 ′ and A detection system including an imaging optical system is also provided on the lower side. The illuminating device 4 ′ includes light sources 101 and 102, a reflecting mirror 103, and a half mirror 104 as in the illuminating device 4, and irradiates illumination light having different wavelengths from the light sources 101 and 102, and removes foreign substances from the two detection results. The determination is the same as in the above case.

  In the foreign substance inspection apparatus according to the first embodiment described above, a detection result by the first illumination light (illumination light by the light source 101) and a detection result by the second illumination light (illumination light by the light source 102) are obtained by two scans. I was getting. Accordingly, although the accuracy of foreign object detection is improved, the time required for inspection takes twice as long as that required for inspection in one scan. In order to improve this, one scan operation is performed by switching the irradiation of the first illumination light and the irradiation of the second illumination light in a very short cycle in relation to the scan speed, and separately processing the data for each. Thus, two detection results can be obtained. For example, when the scanning speed is set to 10 mm / second, the switching may be performed in about 1/10 second. In this embodiment, since semiconductor lasers are used as the light sources 101 and 102, such high-speed switching can be easily realized.

  During scanning, both the light source 101 and the light source 102 are in an oscillating state, and a shutter is provided on the optical path of the light source 101 and the light source 102, and the shutter is operated at high speed, thereby irradiating illumination light from the light source 101. You may make it switch irradiation of the illumination light from the light source 102. FIG. As the shutter, for example, a substantially disc-shaped member having a substantially semicircular arc-shaped light blocking portion and a light transmitting portion, one of the light blocking portion and the light transmitting portion is positioned on the optical path of the illumination light from the light source 101. It is possible to use a device in which the other is positioned on the optical path of the illumination light from the light source 102 and rotated at a high speed.

  Next, a second embodiment of the present invention will be described. In the first embodiment described above, the accuracy of foreign object detection is improved by irradiating the surface to be measured with two illumination lights having different wavelengths and performing determination based on the two detection results obtained by detecting each of the surfaces. I was letting. On the other hand, in the second embodiment, a single illumination light is irradiated onto a mask as a subject, and the postures of the mask with respect to the illumination system and the detection system are changed, and detection is performed in two different postures. By making a determination based on the two detection results, the accuracy of foreign object detection is similarly improved.

  Since the configuration of the foreign object detection device according to the second embodiment is substantially the same as that of the foreign object detection device according to the first embodiment shown in FIGS. 1 to 7, only different parts will be described. That is, the illuminating device 4 of the foreign object detection device of the first embodiment includes the two light sources 101 and 102. However, as shown in FIGS. 10 and 11, the foreign object detection device of the second embodiment is a single unit. Only the light source 101 is provided. Further, in this embodiment, the holder 9 that holds the mask 2 in FIG. 1 includes an attitude adjustment table (not shown) so that it can be slightly rotated around the X axis, the Y axis, and the Z axis, A holding unit for holding the mask 2 is installed on the stage 8 via the posture adjustment table. With this posture adjustment table, the posture of the held mask 2 can be arbitrarily adjusted based on control by a control device (not shown).

  As shown in FIG. 10, the posture adjustment stage is controlled to perform the first scan in a state where the posture of the mask 2 is set to the predetermined first posture, and the scattered light intensity as the first detection result. Create data. Next, as shown in FIG. 11, the second scan is performed in a state where the posture of the mask 2 is set to a second posture different from the first posture, and the scattered light intensity data as the second detection result. Create Of course, the first scan operation and the second scan operation may be performed in the same direction. However, from the viewpoint of improving the overall processing speed, for example, the first scan is in the + X direction, and the second scan is -X. It is preferable to carry out in a reciprocal direction. The posture adjustment is performed around the X axis, around the Y axis, around the Z axis, or a combination of two or more thereof.

  Then, as in the first embodiment described above, a logical product is obtained for each pixel or group between the first detection result and the second detection result, and those having a predetermined threshold value or more are finally regarded as foreign matters. Based on the determination result, a distribution map relating to the foreign matter on the surface to be examined is created.

  Even in this case, the first detection result and the second detection result include noise caused by diffracted light from the pattern or the like in addition to the scattered light from the actual foreign matter. It will be determined as a foreign object. However, the diffracted light from the pattern or the like changes its property including the direction if the relative posture with respect to the illumination light is different. Therefore, as in the present embodiment, the surface 2a is scanned in two different postures. By obtaining two detection results and comparing them, it is possible to distinguish between scattered light and diffracted light, and the accuracy of foreign object detection can be increased.

  For example, as shown in FIG. 10, even when the diffracted light 3b in the pattern P by the illumination light 3 from the light source 101 enters the sensor 7, it is shown in FIG. As described above, if the relative postures are different, the diffraction or refraction direction of the diffracted light 3b in the pattern P changes and it can be prevented from entering the sensor 7, so that it is discriminated whether it is scattered light or diffracted light. It can be done.

  For convenience of illustration, FIG. 11 shows a state rotated around the Y axis as an example, and the rotation amount is shown in a considerably exaggerated manner. The rotation amount (posture adjustment amount) θy is actually very small. As the reference axis for posture adjustment, since the adjustment amount is small, it may of course be performed around the X axis or the Y axis, but here the illumination method as shown in FIGS. Since the shape of the illumination area on the surface 2a to be measured changes when the posture is adjusted around the X axis or the Y axis, the movement is performed around the Z axis.

  The appropriate posture adjustment amount θz around the Z-axis depends on the state of the pattern (pattern pitch, shape, pattern density, etc.) formed on the reticle to be inspected, and the structure (detection angle θd and light reception) on the foreign substance inspection apparatus side. Part size t). In other words, while using the reticle pattern distribution state and the structure of the foreign matter inspection apparatus as input parameters, the appropriate rotation amount θz varies depending on the values of these parameters.

  As an example, the proper rotation amount θz when using a foreign matter inspection apparatus having a detection angle θd = 85 degrees of the foreign matter inspection apparatus and a light receiving portion size t = 500 μm depends on the reticle pattern formed on the reticle to be inspected. Is generally in the range of several mrad to several hundred mrad.

  In the second embodiment described above, the illumination light is single, and the posture of the mask as the subject is changed to obtain two detection results. However, two detection results are obtained as in the first embodiment described above. The illumination device 4 having the light sources 101 and 102 is provided, and the change of the wavelength and the change of the posture are combined to obtain two or three or more detection results, and the foreign matter is determined from the comparison. good.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is a perspective view which shows schematic structure of the foreign material inspection apparatus which concerns on 1st Embodiment of this invention. It is a side view for demonstrating the illumination method by the illuminating device of 1st Embodiment of this invention. It is a top view for demonstrating the illumination method by the illuminating device of 1st Embodiment of this invention. It is the figure which represented typically the structure of the illuminating device of 1st Embodiment of this invention, and the case where a diffracted light injects into a sensor. It is the figure which represented typically the structure of the illuminating device of 1st Embodiment of this invention, and the case where a diffracted light does not inject into a sensor. It is a perspective view which shows the structure of the sensor of 1st Embodiment of this invention. It is a block diagram which shows the structure of the signal processing circuit with which the foreign material inspection apparatus which concerns on 1st Embodiment of this invention is provided. It is a figure which shows the test result at the time of illuminating with the 1st illumination light of 1st Embodiment of this invention. It is a figure which shows the test result at the time of illuminating with the 2nd illumination light of 1st Embodiment of this invention. It is the figure which represented typically the case where diffracted light injects into a sensor in the 1st attitude | position of 2nd Embodiment of this invention. It is the figure which represented typically the case where a diffracted light does not inject into a sensor in the 2nd attitude | position of 1st Embodiment of this invention. It is a figure for demonstrating the schematic structure and problem of the conventional foreign material inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Foreign substance inspection apparatus 2 ... Mask 2a ... Non-pattern surface 2b ... Pattern surface 3 ... Illumination light 3a ... Observation light 3b ... Noise light 4 ... Illumination device 5 ... Reflection mirror 6 ... Lens 7 ... Sensor 8 ... Mask table 9 ... Holder (Attitude adjustment device)
DESCRIPTION OF SYMBOLS 10 ... Drive device P ... Pattern G ... Foreign material 101,102 ... Light source

Claims (8)

In a foreign matter inspection apparatus that inspects foreign matter adhering to the test surface of a subject,
An illumination system that selectively emits first illumination light having a predetermined wavelength and second illumination light having a wavelength different from that of the first illumination light to illuminate the inspection region on the surface to be examined;
A detection system having a single light detection device for observing the inspection region;
Based on the first detection result by the light detection device when illuminated with the first illumination light and the second detection result by the light detection device when illuminated with the second illumination light, A foreign matter inspection apparatus comprising: a processing device that identifies foreign matter.   The first detection light and the second detection result are obtained by performing scanning detection on the surface to be measured while alternately switching illumination with the first illumination light and the second illumination light. The foreign matter inspection apparatus according to claim 1. In the foreign matter inspection method for inspecting the foreign matter attached on the test surface of the subject,
A first step of obtaining a first detection result by a light detection device that illuminates an inspection area on the surface to be inspected with first illumination light of a predetermined wavelength and observes the inspection area;
A second step of illuminating the inspection region on the test surface with second illumination light having a wavelength different from that of the first illumination light to obtain a second detection result by the light detection device;
A foreign matter inspection method comprising: a third step of identifying a foreign matter on the test surface based on the first detection result and the second detection result.   The first surface and the second step are performed by performing scanning detection on the surface to be measured while alternately switching the illumination by the first illumination light and the second illumination light. The foreign matter inspection method according to claim 3. In a foreign matter inspection apparatus that inspects foreign matter adhering to the test surface of a subject,
An illumination system that emits illumination light to illuminate the inspection area on the surface to be examined;
A detection system having a light detection device for observing the inspection region;
A posture adjusting device for adjusting a relative posture between the subject and the detection system;
A first detection result by the light detection device when the subject is set to a predetermined first posture by the posture adjustment device and a second detection by the light detection device when set to a second posture different from the first posture. 2. A foreign matter inspection device comprising: a processing device that identifies foreign matter on the surface to be examined based on a detection result.   The foreign object inspection apparatus according to claim 5, wherein the posture adjustment of the subject by the posture adjustment device is performed around an axis substantially orthogonal to the test surface. In the foreign matter inspection method for inspecting the foreign matter attached on the test surface of the subject,
A first step of emitting illumination light to an examination area on the examination surface of the subject set in a predetermined first posture, observing the examination area and obtaining a first detection result;
Illumination light is emitted to the examination area on the examination surface of the subject set to a second attitude different from the first attitude, and the examination area is observed to obtain a second detection result. Process,
A foreign matter inspection method comprising: a third step of identifying a foreign matter on the test surface based on the first detection result and the second detection result.   The foreign object inspection method according to claim 7, wherein the first posture and the second posture are different postures about an axis substantially orthogonal to the surface to be examined.

Images