JP6633892B2 - Polarized image acquisition device, pattern inspection device, and polarized image acquisition method - Google Patents

Description

  The present invention relates to a polarization image acquisition device, a pattern inspection device, and a polarization image acquisition method. For example, the present invention relates to an apparatus and a method for acquiring a polarization image that can be used to generate an exposure image of an exposure mask substrate used in semiconductor manufacturing, and an apparatus and a method for inspecting a pattern defect of the exposure mask substrate.

  2. Description of the Related Art In recent years, circuit line widths required for semiconductor devices have become increasingly smaller with the increase in integration and capacity of large-scale integrated circuits (LSIs). These semiconductor elements are formed by exposing and transferring a pattern onto a wafer using a reduction projection exposure apparatus called a stepper, using an original pattern on which a circuit pattern is formed (also referred to as a mask or a reticle; hereinafter, collectively referred to as a mask). It is manufactured by forming a circuit. Therefore, in manufacturing a mask for transferring such a fine circuit pattern onto a wafer, a pattern drawing apparatus using an electron beam capable of drawing a fine circuit pattern is used. A pattern circuit may be directly drawn on a wafer using such a pattern drawing apparatus. Alternatively, development of a laser beam drawing apparatus that draws using a laser beam other than the electron beam has been attempted.

  In addition, for the production of LSIs that require a large production cost, improvement of the yield is indispensable. However, as represented by a 1 gigabit-class DRAM (random access memory), patterns constituting an LSI are on the order of submicrons to nanometers. One of the major factors that reduce the yield is a pattern defect of a mask used when exposing and transferring an ultrafine pattern on a semiconductor wafer by photolithography. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small. Therefore, it is necessary to improve the accuracy of a pattern inspection apparatus for inspecting a defect of a transfer mask used in LSI manufacturing.

  As an inspection method, an optical image obtained by imaging a pattern formed on a sample such as a lithography mask using a magnifying optical system at a predetermined magnification is compared with design data or an optical image obtained by imaging the same pattern on the sample. A method of performing an inspection by performing the inspection is known. For example, as a pattern inspection method, “die-to-die (die-to-die) inspection” in which optical image data obtained by imaging the same pattern at different locations on the same mask is compared, or a pattern is designed using CAD data designed as a mask. The drawing data (design pattern data) converted into the device input format for input by the drawing device when drawing is input to the inspection device, and a design image (reference image) is generated based on the data, and the pattern and the image are captured. There is a “die-to-database (die-database) inspection” for comparing the measured optical data with an optical image. In the inspection method in such an inspection apparatus, a sample is placed on a stage, and a light beam scans over the sample as the stage moves, thereby performing an inspection. The sample is irradiated with a light beam by a light source and an illumination optical system. Light transmitted or reflected by the sample is imaged on a sensor via an optical system. The image captured by the sensor is sent to a comparison circuit as measurement data. After the alignment of the images, the comparison circuit compares the measured data with the reference data according to an appropriate algorithm, and if they do not match, determines that there is a pattern defect.

  In a semiconductor product having a short product cycle, it is important to reduce the time required for manufacturing. When a mask pattern having a defect is exposed and transferred to a wafer, a semiconductor device made from the wafer becomes defective. Therefore, it is important to inspect the mask for pattern defects. Then, the defect found in the defect inspection is corrected by the defect correcting device. However, correcting all the defects found increases production time and reduces product value. With the development of the inspection apparatus, the inspection apparatus determines that there is a pattern defect even if a very small displacement occurs. However, when a mask pattern is transferred onto a wafer by an actual exposure apparatus, the circuit can be used as an integrated circuit as long as the disconnection and / or short circuit of the circuit is not caused by such a defect on the wafer. Therefore, it is desired to obtain an exposure image to be exposed on a wafer by an exposure apparatus. However, in an exposure apparatus, a mask pattern is reduced and formed on a wafer, whereas in an inspection apparatus, a mask pattern is enlarged and formed on a sensor. Therefore, the configuration of the optical system on the secondary side with respect to the mask substrate is different from the first. Therefore, it is difficult to reproduce a pattern image transferred by the exposure apparatus by the inspection apparatus as it is, no matter how the illumination light is adjusted to the exposure apparatus.

  Here, a dedicated machine for inspecting an exposure image exposed and transferred by an exposure device using an aerial image is disclosed (for example, see Patent Document 1).

JP 2001-235853 A

  Thus, one aspect of the present invention provides an apparatus and method for acquiring a polarization image that can be used to create an exposure image when transferred by an exposure apparatus. In addition, an inspection device using such a polarization image is provided.

A polarized light image acquisition device according to one embodiment of the present invention,
A movable stage on which a pattern-formed, mask substrate for exposure is mounted,
When the mask substrate is placed in the exposure apparatus, the same numerical aperture as in the case where the reduction optical system of the exposure apparatus that forms an image on the substrate to be exposed by transmitting the transmitted light from the mask substrate enters the transmitted light from the mask substrate An illumination lens illuminated on the mask substrate receives the transmitted light transmitted through the mask substrate, and an objective lens.
The mask substrate relative to the objective lens is disposed near the pupil position of the objective lens at a position opposite to the P-polarized light wave out of the P-polarized light wave and S-polarized light waves of the transmitted light after passing through the objective lens with each other A split-type half-wave plate that simultaneously aligns the S-polarized wave in one of the two orthogonal directions in the other of the two orthogonal directions ,
A limiting mechanism configured to pass one of a P-polarized wave and an S-polarized wave of transmitted light and to limit the other, and configured by one of a polarizer and a polarizing beam splitter;
A drive mechanism that rotates the limiting mechanism so that the limiting mechanism allows the other to pass, and restricts the above-described one to pass,
An imaging lens that forms an image of light having passed through the limiting mechanism with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus,
An image sensor that captures an image formed by the imaging lens;
It is characterized by having.

A polarization image acquisition device according to another aspect of the present invention includes:
A movable stage on which a pattern-formed, mask substrate for exposure is mounted,
When the mask substrate is placed in the exposure apparatus, the same numerical aperture as in the case where the reduction optical system of the exposure apparatus that forms an image on the substrate to be exposed by transmitting the transmitted light from the mask substrate enters the transmitted light from the mask substrate An illumination lens formed on the mask substrate, and an objective lens for transmitting the transmitted light transmitted through the mask substrate;
The mask substrate relative to the objective lens is disposed near the pupil position of the objective lens at a position opposite to the P-polarized light wave out of the P-polarized light wave and S-polarized light waves of the transmitted light after passing through the objective lens with each other A split-type half-wave plate that simultaneously aligns the S-polarized wave in one of the two orthogonal directions in the other of the two orthogonal directions ,
A limiting mechanism configured to pass one of a P-polarized wave and an S-polarized wave of transmitted light and to limit the other, and configured by one of a polarizer and a polarizing beam splitter;
A half-wave plate that rotates the polarization direction by 90 ° so that the restricting mechanism allows the other to pass, and restricts the other one;
A drive mechanism for rotating a half-wave plate for rotation,
An imaging lens that forms an image of light having passed through the limiting mechanism with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus,
An image sensor that captures an image formed by the imaging lens;
Equipped with a,
The amount of deviation ΔL of the position of the split type half-wave plate from the pupil position of the objective lens is determined using the pupil diameter D of the objective lens, the field diameter d of the objective lens, and the focal length f of the objective lens. Therefore , the following expression (1) is satisfied .
(1) ΔL <0.05 · D · f / d

A polarization image acquisition device according to another aspect of the present invention includes:
A movable stage on which a pattern-formed, mask substrate for exposure is mounted,
When the mask substrate is placed in the exposure apparatus, the same numerical aperture as in the case where the reduction optical system of the exposure apparatus that forms an image on the substrate to be exposed by transmitting the transmitted light from the mask substrate enters the transmitted light from the mask substrate An illumination lens illuminated on the mask substrate receives the transmitted light transmitted through the mask substrate, and an objective lens.
It is located on the opposite side of the mask substrate with respect to the objective lens and near the pupil position of the objective lens, and simultaneously transmits the respective P-polarized wave and S-polarized wave images of the transmitted light after passing through the objective lens. In order to obtain the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens, the P-polarized wave in one of two directions orthogonal to each other, and the S-polarized wave in the two directions orthogonal to each other. A split-type half-wave plate that is simultaneously aligned in the other direction ;
A polarizing beam splitter that transmits one of a P-polarized wave and an S-polarized wave of transmitted light and reflects the other;
A first imaging lens that forms an image of light having passed through the polarizing beam splitter with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A first image sensor that captures an image formed by the first imaging lens;
A second imaging lens for imaging the light reflected by the polarization beam splitter with the above-described numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A second image sensor that captures an image formed by the second imaging lens;
It is characterized by having.

A pattern inspection apparatus according to one embodiment of the present invention includes:
The above-described polarization image acquisition device,
A combining unit that combines a first optical image formed by one of the P-polarized wave and the S-polarized wave and a second optical image formed by the other of the P-polarized wave and the S-polarized wave;
The first die image in which the first and second optical images in the first die are combined and the first and second optical images in the second die in which a pattern similar to that of the first die is formed. A comparing unit that compares the synthesized second die image corresponding to the first die image,
It is characterized by having.

According to one embodiment of the present invention, there is provided a polarization image acquiring method,
A step of illuminating the mask substrate for exposure with the illumination light, on which the pattern is formed,
When the mask substrate is placed in the exposure apparatus, the same numerical aperture as in the case where the reduction optical system of the exposure apparatus that forms an image on the substrate to be exposed by transmitting the transmitted light from the mask substrate enters the transmitted light from the mask substrate A step of irradiating the transmitted light transmitted through the mask substrate to the objective lens, and
Using a split-type half-wave plate located at a position opposite to the mask substrate with respect to the objective lens and near the pupil position of the objective lens, a P-polarized wave of the transmitted light after passing through the objective lens is used. Aligning the S-polarized waves in directions orthogonal to each other;
Passing one of the P-polarized wave and the S-polarized wave of the transmitted light and restricting the other,
Forming one of the passed P-polarized wave and S-polarized wave on the image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the image sensor described above, capturing a first image of one of the imaged P-polarized wave and the S-polarized wave,
Outputting an optical image of the first image;
Passing the other of the P-polarized wave and the S-polarized wave of the transmitted light as described above, and restricting the above-mentioned one passage;
Imaging the other of the P-polarized wave and the S-polarized wave that have passed through the image sensor with the numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus,
Using the image sensor described above, capturing a second image of the other of the formed P-polarized wave and the S-polarized wave,
Outputting an optical image of the second image;
It is characterized by having.

According to another aspect of the present invention, there is provided a polarization image acquiring method,
According to one embodiment of the present invention, there is provided a polarization image acquiring method,
A step of illuminating the exposure mask substrate with the pattern formed thereon, and
When the mask substrate is placed in the exposure apparatus, the same numerical aperture as in the case where the reduction optical system of the exposure apparatus that forms an image on the substrate to be exposed by transmitting the transmitted light from the mask substrate enters the transmitted light from the mask substrate A step of irradiating the transmitted light transmitted through the mask substrate to the objective lens, and
Using a split-type half-wave plate located at a position opposite to the mask substrate with respect to the objective lens and near the pupil position of the objective lens, a P-polarized wave of transmitted light after passing through the objective lens is used. Aligning the S-polarized waves in directions orthogonal to each other;
Passing one of the P-polarized wave and the S-polarized wave of the transmitted light and reflecting the other;
Forming an image of one of the P-polarized wave and the S-polarized wave that has passed on the first image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the first image sensor to capture a first image of the above-mentioned one of the formed P-polarized wave and S-polarized wave;
Outputting an optical image of the first image;
Forming an image of the other of the reflected P-polarized wave and the S-polarized wave of the transmitted light on the second image sensor at the numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the second image sensor to capture a second image of the other of the imaged P-polarized wave and S-polarized wave;
Outputting an optical image of the second image;
It is characterized by having.

  According to one embodiment of the present invention, it is possible to acquire a polarization image that is a source for creating an exposure image when transferred by an exposure apparatus.

1 is a configuration diagram illustrating a configuration of a pattern inspection device according to a first embodiment. FIG. 3 is a conceptual diagram for comparing a numerical aperture of an inspection device and a numerical aperture of an exposure device according to the first embodiment. FIG. 5 is a diagram for describing characteristics of an S-polarized wave and a P-polarized wave in a comparative example of the first embodiment. FIG. 9 is a diagram for comparing the relationship between the image-side numerical aperture and the S-polarized wave and the P-polarized wave in the first embodiment and the comparative example. FIG. 5 is a diagram for describing a method of separating and acquiring an image of a P-polarized component and an image of an S-polarized component in the first embodiment. FIG. 3 is a diagram illustrating an example of a configuration of a split type half-wave plate and a state of a polarization component according to the first embodiment. FIG. 3 is a diagram for explaining an arrangement position of a split-type half-wave plate according to the first embodiment. FIG. 3 is a conceptual diagram for describing an inspection area according to the first embodiment. FIG. 3 is a diagram illustrating an internal configuration of a comparison circuit according to the first embodiment. 13 is a diagram illustrating a part of a configuration of an optical image acquisition unit of the inspection device according to the second embodiment. 13 is a diagram illustrating a part of a configuration of an optical image acquisition unit of the inspection device according to the third embodiment.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a configuration of the pattern inspection apparatus according to the first embodiment. In FIG. 1, an inspection apparatus 100 for inspecting a defect of a pattern formed on a mask substrate 101 includes an optical image acquisition unit 150 and a control system circuit 160 (control unit).

  The optical image acquisition unit 150 (polarization image acquisition device) includes a light source 103, a transmission illumination optical system 170, an XYθ table 102 movably arranged, an enlargement optical system 104, a split-type half-wave plate 172, and a polarization beam splitter 174. It has two photodiode arrays 105 and 205 (an example of a sensor), two sensor circuits 106 and 206, two stripe pattern memories 123 and 223, and a laser length measurement system 122. The mask substrate 101 is placed on the XYθ table 102. The mask substrate 101 includes, for example, an exposure photomask for transferring a pattern to a semiconductor substrate such as a wafer. Further, a pattern constituted by a plurality of graphic patterns to be inspected is formed on the photomask. Here, the case where the same two patterns are formed on the left and right is shown. The mask substrate 101 is arranged on the XYθ table 102 with the pattern formation surface facing downward, for example.

  The transmitted illumination optical system 170 includes a projection lens 180, an illumination shape switching mechanism 181, and an imaging lens 182. In addition, the transmitted illumination optical system 170 may include other lenses, mirrors, and / or optical elements.

  The magnifying optical system 104 has an objective lens 171 and two imaging lenses 176 and 178. Further, the magnifying optical system 104 may include another lens and / or a mirror between the objective lens 171 and the imaging lens 176 and / or between the objective lens 171 and the imaging lens 178. .

  In the control system circuit 160, a control computer 110, which is a computer, is connected via a bus 120 to a position circuit 107, a comparison circuit 108, an autoloader control circuit 113, a table control circuit 114, a magnetic disk device 109, a magnetic tape device 115, a flexible disk The device (FD) 116, CRT 117, pattern monitor 118, and printer 119 are connected. Further, the sensor circuit 106 is connected to the stripe pattern memory 123, and the stripe pattern memory 123 is connected to the comparison circuit 108. Similarly, the sensor circuit 206 is connected to the stripe pattern memory 223, and the stripe pattern memory 223 is connected to the comparison circuit 108. The XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor.

  In the inspection apparatus 100, a light source 103, an XYθ table 102, a transmission illumination optical system 170, a magnifying optical system 104, photodiode arrays 105 and 206, and sensor circuits 106 and 206 constitute a high-magnification inspection optical system. For example, an inspection optical system having a magnification of 400 to 500 times is configured. Table 102 is driven by table control circuit 114 under the control of control computer 110. It can be moved by a driving system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions. As these X motor, Y motor, and θ motor, for example, a linear motor can be used. The XYθ table 102 can be moved in the horizontal and rotational directions by motors for each axis of XYθ. Then, the focus position (optical axis direction: Z-axis direction) of the objective lens 171 is dynamically adjusted on the pattern formation surface of the mask substrate 101 by an autofocus (AF) control circuit (not shown) under the control of the control computer 110. You. The focal position of the objective lens 171 is adjusted, for example, by being moved in the optical axis direction (Z-axis direction) by a piezo element (not shown). The moving position of the mask substrate 101 arranged on the XYθ table 102 is measured by the laser length measuring system 122 and supplied to the position circuit 107.

  The design pattern data (drawing data) that is the basis for forming the pattern of the mask substrate 101 may be input from outside the inspection apparatus 100 and stored in the magnetic disk device 109.

  Here, FIG. 1 illustrates components necessary for describing the first embodiment. Needless to say, the inspection apparatus 100 may normally include other necessary components.

  FIG. 2 is a conceptual diagram for comparing the numerical aperture of the inspection apparatus and the numerical aperture of the exposure apparatus according to the first embodiment. FIG. 2A shows a part of an optical system of an exposure apparatus such as a stepper for exposing and transferring a pattern formed on a mask substrate onto a semiconductor substrate. In the exposure apparatus, illumination light (not shown) is illuminated on the mask substrate 300, transmitted light 301 from the mask substrate 300 is incident on the objective lens 302, and light 305 passing through the objective lens 302 is converted into a semiconductor substrate 304 (wafer: exposed light). Image on the substrate). Although FIG. 2A shows one objective lens 302 (reduction optical system), it goes without saying that a combination of a plurality of lenses may be used. Here, in the current exposure apparatus, the pattern formed on the mask substrate 300 is reduced to, for example, ４ and is exposed and transferred to the semiconductor substrate 304. At this time, the numerical aperture NAi (numerical aperture on the image i side) of the exposure apparatus with respect to the semiconductor substrate 304 is set to, for example, NAi = 1.4. In other words, the numerical aperture NAi (numerical aperture on the image i side) of the objective lens 302 that can pass through the objective lens 302 is set to, for example, NAi = 1.4. In the exposure apparatus, since the transmitted light image from the mask substrate 300 is reduced to ４, the sensitivity of the objective lens 302 to the mask substrate 300 is reduced to ４. In other words, the numerical aperture NAo (numerical aperture on the object o side) of the objective lens 302 that can enter when transmitted light enters the objective lens 302 from the mask substrate 300 is １ ／ of NAi, and NAo = 0.35 Becomes Therefore, in the exposure apparatus, the transmitted light image of the luminous flux having the numerical aperture NAo = 0.35 from the mask substrate 300 is exposed and transferred to the semiconductor substrate 304 as an image of the luminous flux having the very large numerical aperture NAi = 1.4. become.

  On the other hand, in the inspection apparatus 100 according to the first embodiment, as shown in a part of the inspection apparatus 100 in FIG. The light 190 enters the magnifying optical system 104 including the objective lens, and the light 192 passing through the magnifying optical system 104 forms an image on the photodiode array 105 (image sensor). At this time, when the transmitted light 190 is incident on the magnifying optical system 104 from the mask substrate 101, the numerical aperture NAo (numerical aperture on the object o side) of the objective lens which can be incident is made equal to the objective lens 302 of the exposure apparatus. For example, NAo = 0.35 is set. However, in the inspection apparatus 100, the transmitted light image from the mask substrate 300 is enlarged 200 to 500 times so that the inspection can be compared with the inspection. Therefore, the sensitivity of the magnifying optical system 104 to the mask substrate 101 is 200 to 500. Become. Therefore, the numerical aperture NAi (numerical aperture on the image i side) of the magnifying optical system 104 with respect to the photodiode array 105 cannot be set to a very large numerical aperture NAi = 1.4 like the objective lens 302 of the exposure apparatus, and NAo 1/500 to 1/200, for example, the numerical aperture NAi = 0.002. Thus, the numerical aperture NAi (numerical aperture on the image i side) of the magnifying optical system 104 with respect to the photodiode array 105 is sufficiently smaller than the numerical aperture NAi of the objective lens 302 (reducing optical system) of the exposure apparatus. Although FIG. 2B shows only the magnifying optical system 104, a plurality of lenses are arranged in the magnifying optical system 104. As described above, the magnifying optical system 104 includes at least the objective lens 171 and the imaging lens 176 (and the imaging lens 178).

  Therefore, when the mask substrate 101 is arranged in the exposure apparatus, the objective lens 171 of the exposure apparatus that receives the transmitted light from the mask substrate 101 and forms an image on the semiconductor substrate 304 is formed by the objective lens 171. At the same numerical aperture NAo (NAo = 0.35) as when the light 301 is incident, the transmitted light 190 transmitted through the mask substrate 101 is incident on the illumination light formed on the mask substrate 101. The imaging lens 176 (and the imaging lens 178) forms an image of the light that has passed through the magnifying optical system 104 with a numerical aperture NAi (NAi = 0.002) sufficiently smaller than that of the objective lens 302 of the exposure apparatus. .

  FIG. 3 is a diagram for explaining characteristics of an S-polarized wave and a P-polarized wave in a comparative example of the first embodiment. FIG. 3 shows an example of a state in which light 305 passing through an objective lens 302 of an exposure apparatus serving as a comparative example forms an image on a semiconductor substrate 304. The numerical aperture NAi (numerical aperture on the image i side) of the objective lens 302 with respect to the semiconductor substrate 304 is a very large numerical aperture NAi = 1.4. Decreases, disappears, or reverses.

  FIG. 4 is a diagram for comparing the relationship between the image-side numerical aperture and the S-polarized wave and the P-polarized wave in the first embodiment and the comparative example. As described above, in the exposure apparatus, since the numerical aperture NAi of the objective lens 302 on the side of the semiconductor substrate 304 is very large, that is, NAi = 1.4, the amplitude of the P-polarized light component is reduced or eliminated as shown in FIG. Or it will be inverted. Further, the same state of the amplitude of the S-polarized component is maintained regardless of the numerical aperture NAi of the objective lens 302 on the semiconductor substrate 304 side.

  On the other hand, as described above, in the inspection apparatus 100, the numerical aperture NAi of the magnifying optical system 104 on the photodiode array 105 side is NAi = 0.0008, which is very (sufficiently) smaller than that of the objective lens 302 of the exposure apparatus. Therefore, the amplitude of the P-polarized light component does not decrease. The same state is maintained for the amplitude of the S-polarized component.

  Both the light of the mask pattern image formed on the semiconductor substrate 304 in the exposure apparatus and the light of the mask pattern image formed on the photodiode array 105 in the inspection apparatus 100 are both combined light of the P-polarized component and the S-polarized component. , P-polarized light components, the obtained optical images will not be the same image.

  Therefore, in the first embodiment, in consideration of such a phenomenon, the inspection apparatus 100 separates and acquires a mask pattern image formed on the photodiode array 105 into a P-polarized component image and an S-polarized component image. . Thus, by adjusting the manner (ratio) of combining the P-polarized component and the S-polarized component, an exposure image can be generated from the two types of images captured by the photodiode array 105.

  FIG. 5 is a diagram for explaining a method of acquiring a P-polarized component image and an S-polarized component image separately according to the first embodiment. FIG. 5 shows a part of the configuration of FIG. In FIG. 5, a dotted line indicates a pupil position from each lens. It should be noted that the scales and the like of the positions of the components in FIGS. 1 and 5 are not matched. Laser light (for example, DUV light) having a wavelength equal to or less than the ultraviolet range, which is inspection light, is generated from the light source 103. The generated light is illuminated on the illumination shape switching mechanism 181 by the projection lens 180, and the illumination shape switching mechanism 181 changes the shape of the illumination light (inspection light) to the same illumination shape as the illumination shape used in the exposure apparatus. You. Illumination light having the same illumination shape as used in such an exposure apparatus is imaged by the imaging lens 182 on the pattern formation surface of the mask substrate 101 from the back surface opposite to the pattern formation surface of the mask substrate 101. The transmitted light (mask pattern image) transmitted through the mask substrate 101 has the same numerical aperture NAo (NAo = 0.35) as when the objective lens 302 (reducing optical system) of the exposure apparatus receives the transmitted light from the mask substrate 101. 2) is incident on the objective lens 171 and is projected on the split type half-wave plate 172 by the objective lens 171 in parallel. Therefore, the optical conditions up to this point of the inspection apparatus 100 can be the same as those of the exposure apparatus.

  The split-type half-wave plate 172 is disposed on the opposite side of the objective lens 171 from the mask substrate 101 and near the pupil position of the objective lens 171. Then, the split-type half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, a pre-environment can be prepared so that the P-polarized wave can be separated and left from others. Alternatively, a pre-environment can be prepared so that the S-polarized wave can be separated and left.

  FIG. 6 is a diagram illustrating an example of a configuration of a split half-wave plate and a state of a polarization component according to the first embodiment. In the example of FIG. 6, an eight-segmented half-wave plate is shown as an example of the split half-wave plate 172. As shown in FIG. 6A, the eight-segment half-wave plate 172 is divided into eight regions, and the direction of the fast axis indicated by a dotted line differs in each region. As shown in FIG. 6A, the S-polarized light component is oriented in the circumferential direction of the transmitted light, and is, for example, aligned in the x-direction by passing through an 8-split type half-wave plate. On the other hand, as shown in FIG. 6B, the P-polarized light component is directed in the radial direction of the transmitted light, and is orthogonal to the S-polarized light component by passing through an 8-divided half-wave plate. For example, they are aligned in the y direction. In the example of FIG. 6, the eight-segment type is shown, but the invention is not limited to this. It may be a four-split type, a sixteen-split type, or another split type. It is only necessary that the P-polarized light component and the S-polarized light component of the transmitted light (mask pattern image) can be aligned in directions orthogonal to each other.

FIG. 7 is a diagram for explaining an arrangement position of the split-type half-wave plate in the first embodiment. The split-type half-wave plate 172 is disposed at a position opposite to the mask substrate 101 with respect to the objective lens 171 and near a pupil position of the objective lens 171. The spread of the light beam at the position of the split type half-wave plate 172 is desirably 5% or less of the pupil diameter D of the objective lens 171 (the maximum diameter of the on-axis parallel light beam passing through the objective lens 171). Therefore, the amount of deviation ΔL of the arrangement position of the split type half-wave plate 172 from the pupil position of the objective lens 171 is determined by the pupil diameter D of the objective lens 171, the field diameter d of the objective lens 171, and the focal length f of the objective lens 171. It is preferable that the following formula (1) is satisfied using
(1) ΔL <0.05 · D · f / d

  Therefore, it is preferable that the split-type half-wave plate 172 is disposed within a shift amount ΔL of the pupil position from the pupil position of the objective lens 171.

  The transmitted light transmitted through the split type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 transmits one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other. I do. In the example of FIG. 5, a P-polarized wave of transmitted light is transmitted, and an S-polarized wave is reflected. The relationship between the transmitted polarization component and the reflected polarization component may be reversed. Since the directions of the same polarized waves are aligned by the split type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174.

  The light (for example, a P-polarized wave) that has passed through the polarizing beam splitter 174 enters the imaging lens 176, and the imaging lens 176 (first imaging lens) converts the incident light into the objective lens 302 (reducing optics) of the exposure apparatus. An image is formed on the photodiode array 105 with a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the (system).

  The photodiode array 105 (first image sensor) captures an image (for example, an image of a P-polarized component) (first image) formed by the imaging lens 176.

  The light (for example, an S-polarized wave) reflected by the polarization beam splitter 174 enters the imaging lens 178, and the imaging lens 178 (the second imaging lens) converts the incident light into the objective lens 302 (reducing optics) of the exposure apparatus. An image is formed on the photodiode array 205 with a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture of the system (NAi = 1.4).

  The photodiode array 205 (second image sensor) captures an image (for example, an image of an S-polarized component) (second image) formed by the imaging lens 178.

  It is preferable to use, for example, a TDI (time delay integration) sensor or the like as the photodiode arrays 105 and 205. The photodiode arrays 105 and 205 (image sensors) capture an optical image of a polarization component corresponding to the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is mounted is moving. .

  FIG. 8 is a conceptual diagram for describing an inspection area according to the first embodiment. As shown in FIG. 8, the inspection region 10 (entire inspection region) of the mask substrate 101 is virtually divided into a plurality of strip-shaped inspection stripes 20 having a scan width W, for example, in the y direction. Then, the inspection apparatus 100 acquires an image (stripe region image) for each inspection stripe 20. For each of the inspection stripes 20, an image of a graphic pattern arranged in the stripe region is taken in the longitudinal direction (x direction) of the stripe region using laser light. Movement of the XYθ table 102 moves the mask substrate 101 in the x direction. As a result, an optical image is acquired while the photodiode arrays 105 and 205 relatively continuously move in the −x direction. The photodiode arrays 105 and 205 continuously capture an optical image having a scan width W as shown in FIG. In other words, the photodiode arrays 105 and 205, which are examples of the sensor, capture an optical image of the pattern formed on the mask substrate 101 using the inspection light while relatively moving with the XYθ table 102. In the first embodiment, after capturing an optical image of one inspection stripe 20, the optical image having the scan width W is similarly moved while moving in the y direction to the position of the next inspection stripe 20 and in the opposite direction. Image continuously. That is, imaging is repeated in the forward (FWD) -back forward (BWD) direction heading in the opposite direction on the outward path and the return path.

  Here, the imaging direction is not limited to repetition of forward (FWD) -backforward (BWD). The image may be taken from one direction. For example, repetition of FWD-FWD may be used. Alternatively, BWD-BWD may be repeated.

  The image of the pattern of the P-polarized light formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (striped region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range that maximizes the gradation when the amount of illumination light is 60% incident.

  On the other hand, the image of the pattern of the S-polarized light formed on the photodiode array 205 is photoelectrically converted by each light receiving element of the photodiode array 205, and further A / D (analog / digital) converted by the sensor circuit 206. . Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 223. When capturing such pixel data (striped region image), the dynamic range of the photodiode array 205 is preferably, for example, a dynamic range with the maximum gradation when the amount of illumination light is 60% incident.

  When acquiring the optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (arithmetic unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of the P-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of the P-polarized light is, for example, 8-bit unsigned data, and expresses the brightness gradation (light amount) of each pixel. The stripe region image of the P-polarized light output to the comparison circuit 108 is stored in a storage device described later.

  Similarly, the stripe region image of the S-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of the S-polarized light is, for example, 8-bit unsigned data, and expresses the brightness gradation (light amount) of each pixel. The stripe region image of the S-polarized light output to the comparison circuit 108 is stored in a storage device described later.

  As described above, according to the first embodiment, it is possible to simultaneously acquire the respective polarized images of the S-polarized wave and the P-polarized wave that are the basis for creating the exposure image when transferred by the exposure apparatus. Then, the polarization image of the acquired P-polarized wave is adjusted to the state of the P-polarized component whose amplitude is reduced, eliminated, or inverted by the objective lens 302 (reducing optical system) of the exposure apparatus, and then the S-polarized wave is By combining with the polarization image, an exposure image image can be created. According to the first embodiment, since imaging is performed in a state where the S-polarized wave and the P-polarized wave are separated, it is possible to adjust one of the polarization component images.

  The inspection apparatus 100 according to the first embodiment further performs a pattern inspection of the mask substrate 101 using the respective polarized images of the S-polarized wave and the P-polarized wave.

  FIG. 9 is a diagram illustrating an internal configuration of the comparison circuit according to the first embodiment. 9, the comparison circuit 108 includes storage devices 50, 52, 58, 60, 66, 68 such as magnetic disk devices, frame division units 54 and 56, a correction unit 62, a synthesis unit 64, a positioning unit 70, And a comparison unit 72.

  In the comparison circuit 108, the stripe region image (optical image) of the P-polarized wave of the inspection stripe 20 is stored in the storage device 50. Then, the frame dividing unit 54 reads the stripe region image of the P-polarized wave, and divides the stripe region image of the P-polarized wave in the x direction by a predetermined size (for example, the same width as the scan width W). For example, the image is divided into frame images of 512 × 512 pixels. Thus, for the plurality of frame regions 30 (FIG. 8) in which the inspection stripe 20 is divided by the same width as the scan width W, for example, a frame image of the P-polarized wave of each frame region 30 can be acquired. The frame image of the P-polarized wave is stored in the storage device 58.

  Similarly, a stripe region image (optical image) of the S-polarized wave of the inspection stripe 20 is stored in the storage device 52. Then, the frame dividing unit 56 reads the stripe region image of the S-polarized wave, and divides the stripe region image of the S-polarized wave in the x direction by a predetermined size (for example, the same width as the scan width W). For example, the image is divided into frame images of 512 × 512 pixels. Thereby, a frame image of the S-polarized wave in each frame region 30 can be obtained. The frame image of the S-polarized wave is stored in the storage device 60.

  Next, the correction unit 62 reduces the gradation value of the P-polarized wave frame image at a predetermined ratio so as to match the exposure image. The reduction rate may be adjusted to the amplitude (ratio) of the P-polarized light component that is reduced, eliminated, or inverted by the objective lens 302 (reducing optical system) of the exposure apparatus.

  The synthesizing unit 64 synthesizes a frame image (first optical image) based on the corrected P-polarized wave and a frame image based on the uncorrected S-polarized wave (second optical image). As a result, a combined frame image (first die image) in which the frame image of the P-polarized wave and the frame image of the S-polarized wave on the die (1) (first die) to be inspected are generated. The composite frame image of the die (1) is stored in the storage device 66.

  In the first embodiment, a “die-to-die (die-to-die) inspection” for comparing optical image data obtained by imaging the same pattern at different locations on the same mask is performed. For example, the above-described stripe region image includes images of two dies on which the same pattern is formed. Therefore, a composite frame image (second die image) of the frame region 30 of the die (2) (second die) corresponding to the frame region 30 of the composite frame image of the die (1) is similarly generated. The composite frame image of the die (2) is stored in the storage device 68.

  The positioning unit 70 performs positioning of the composite frame image (optical image) of the die (1) to be compared and the composite frame image (reference image) of the die (2) to be compared by a predetermined algorithm. Do. For example, alignment is performed using the least squares method.

  The comparing unit 72 is a composite frame in which the frame image (first optical image) of the corrected P-polarized wave in the die (1) and the frame image (second optical image) of the uncorrected S-polarized wave are synthesized. The image (first die image), the frame image (first optical image) of the corrected P-polarized wave in the die (2) on which the same pattern as the die (1) is formed, and the uncorrected S-polarized light A synthesized frame image (second die image) corresponding to the synthesized frame image (first die image) obtained by synthesizing the wave frame image (second optical image) is compared.

  Here, in the synthetic frame image generated according to the first embodiment, the numerical aperture NAo of the objective lens 171 is set according to the same conditions as those of the exposure apparatus. Therefore, the numerical aperture NAo of the objective lens 171 is smaller than the numerical aperture NAo of the objective lens used in the conventional high-resolution pattern defect inspection device. Therefore, since the light beam incident on the objective lens 171 is small, the image resolution is lower than that of the conventional high-resolution pattern defect inspection apparatus. On the other hand, when a mask pattern is transferred onto a wafer by an actual exposure apparatus, such a pattern can be used as an integrated circuit as long as no disconnection or short circuit of the circuit occurs on the wafer due to defects. Since the synthesized frame image generated according to the first embodiment is intentionally created in accordance with the exposure image to be exposed on the wafer by the exposure apparatus, whether or not a circuit disconnection and / or a short circuit is caused on the wafer. Should be inspected. Therefore, the comparing unit 72 does not inspect individual shape defects of individual graphic patterns, but inspects a distance between adjacent patterns. In such a case, the comparing unit 72 measures the inter-pattern distance of each pattern in the composite frame image (first die image), and similarly calculates the inter-pattern distance of each pattern in the composite frame image (second die image). Measure the distance. Then, it is determined whether or not the difference obtained by subtracting the corresponding inter-pattern distance of the combined frame image (second die image) from the inter-pattern distance of the combined frame image (first die image) is larger than a determination threshold. Is determined to be defective. Then, the comparison result is output. The comparison result may be output from the magnetic disk device 109, magnetic tape device 115, flexible disk device (FD) 116, CRT 117, pattern monitor 118, or printer 119.

  As described above, according to the first embodiment, the respective polarized images of the S-polarized wave and the P-polarized wave can be obtained. Can inspect the pattern of the mask substrate 101.

Embodiment 2 FIG.
In the first embodiment, the configuration in which the polarization image of the S-polarized wave and the polarization image of the P-polarized wave are simultaneously imaged using two sensors has been described, but the present invention is not limited to this. In the second embodiment, a configuration will be described in which a single sensor is used to image while switching between a polarization image of an S-polarized wave and a polarized image of a P-polarized wave.

  FIG. 10 is a diagram illustrating a part of a configuration of an optical image acquisition unit of the inspection device according to the second embodiment. FIG. 10 shows a part of the configuration of FIG. 1 that is necessary to describe the configuration of the optical image acquisition unit 150 (polarized image acquisition device) according to the second embodiment. The optical image acquisition unit 150 according to the second embodiment does not require the photodiode array 205 (an example of a sensor), the sensor circuit 106, and the stripe pattern memory 123 in the configuration in FIG. Instead, a drive mechanism 175 for rotating the incident surface of the polarization beam splitter 174 (restriction mechanism) is provided. Other points of the inspection apparatus according to Embodiment 2 are the same as those in FIG.

  The configuration and the situation until the laser light (for example, DUV light) having a wavelength equal to or less than the ultraviolet region serving as inspection light from the light source 103 is generated and the transmitted light of the mask substrate 101 is transmitted through the split type half-wave plate 172 are implemented. This is the same as in the first embodiment. Therefore, the split-type half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, a pre-environment can be prepared so that the P-polarized wave can be separated and left from others. Alternatively, it is the same as the first embodiment in that the advance environment can be adjusted so that the S-polarized wave can be left separately from the others.

  The transmitted light transmitted through the split type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 transmits one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other. I do. In other words, the polarization beam splitter 174 (an example of a limiting mechanism) allows one of the P-polarized wave and the S-polarized wave of the transmitted light to pass and restricts the other. Which polarized light is transmitted or restricted is determined by the position of the polarization beam splitter 174 rotated by the driving mechanism 175. That is, the driving mechanism 175 rotates the beam splitter 174 so that the polarization beam splitter 174 allows one of the P-polarized wave and the S-polarized wave of the transmitted light to pass and reflects the other. For example, when capturing a polarization image of the P-polarized wave of the transmitted light, the driving mechanism 175 controls the S-polarized wave so that the polarization beam splitter 174 allows the transmitted P-polarized wave to pass through and reflects the S-polarized wave. Is rotated by 90 ° (or −90 °). Conversely, when capturing a polarization image of an S-polarized wave of transmitted light, the driving mechanism 175 controls the P-polarized light so that the polarization beam splitter 174 allows the transmitted S-polarized wave to pass through and reflects the P-polarized wave. The direction of the beam splitter 174 in the state of the wave is rotated by −90 ° (or 90 °).

  In the example of FIG. 10, the polarization beam splitter 174 is used, but the invention is not limited to this. Instead of the polarization beam splitter 174, for example, a polarizer (another example of the limiting mechanism) may be used. As for the polarizer, similarly to the polarization beam splitter 174, the driving mechanism 175 adjusts the direction of the polarizer so that one of the P-polarized wave and the S-polarized wave can be passed and the other can be reflected. .

  As described above, since the directions of the same polarized waves are aligned by the split type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or the polarizer).

  When the direction of the polarization beam splitter 174 is set by the driving mechanism 175 so that the P polarization wave can pass, the light (P polarization wave) passing through the polarization beam splitter 174 enters the imaging lens 176 and forms an image. The lens 176 (first imaging lens) converts the incident light into a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reducing optical system) of the exposure apparatus. To form an image on the photodiode array 105.

  The photodiode array 105 (image sensor) captures an image (an image of a P-polarized component) (first image) formed by the imaging lens 176.

  Note that, for example, a TDI sensor or the like is preferably used as the photodiode array 105 as in the first embodiment. The photodiode array 105 (image sensor) captures an optical image of a polarization component corresponding to the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is mounted is moving. The imaging of the optical image may be performed for each inspection stripe 20 as described above.

  The image of the pattern of the P-polarized light formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (striped region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range that maximizes the gradation when the amount of illumination light is 60% incident.

  When acquiring the optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (arithmetic unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of the P-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of the P-polarized light is, for example, 8-bit unsigned data, and expresses the brightness gradation (light amount) of each pixel. The stripe region image of the P-polarized light output to the comparison circuit 108 is stored in the storage device 50.

  Next, the direction of the polarization beam splitter 174 is changed by the driving mechanism 175 so that the S-polarized wave can pass therethrough. Then, imaging of the S-polarized wave is performed for the same inspection stripe 20 that has performed the imaging of the P-polarized wave.

  The configuration and the situation until the laser light (for example, DUV light) having a wavelength equal to or less than the ultraviolet region serving as inspection light from the light source 103 is generated and the transmitted light of the mask substrate 101 is transmitted through the split type half-wave plate 172 are implemented. This is the same as in the first embodiment. Therefore, the split-type half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, a pre-environment can be prepared so that the P-polarized wave can be separated and left from others. Alternatively, it is the same as the first embodiment in that the advance environment can be adjusted so that the S-polarized wave can be left separately from the others.

  The transmitted light transmitted through the split type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 transmits the S-polarized wave of the transmitted light and reflects the P-polarized wave.

  As described above, since the directions of the same polarized waves are aligned by the split type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or the polarizer).

  Since the direction of the polarization beam splitter 174 is set by the driving mechanism 175 so that the S-polarized wave can pass, the light (S-polarized wave) passing through the polarization beam splitter 174 enters the imaging lens 176 and forms an image. The lens 176 (image forming lens) converts the incident light into a photodiode with a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reducing optical system) of the exposure apparatus. An image is formed on the array 105.

  The photodiode array 105 (image sensor) captures an image (an S-polarized component image) (second image) formed by the imaging lens 176.

  The photodiode array 105 (image sensor) captures an optical image of a polarization component corresponding to the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is mounted is moving. The imaging of the optical image may be performed for each inspection stripe 20 as described above.

  The image of the S-polarized light pattern formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (striped region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range that maximizes the gradation when the amount of illumination light is 60% incident.

  When acquiring the optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (arithmetic unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of the S-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of the S-polarized light is, for example, 8-bit unsigned data, and expresses the brightness gradation (light amount) of each pixel. The stripe region image of the S-polarized light output to the comparison circuit 108 is stored in the storage device 52.

  As described above, according to the second embodiment, the respective polarized images of the S-polarized wave and the P-polarized wave that are the basis for creating the exposure image when transferred by the exposure device are acquired at different times. it can. Then, the polarization image of the acquired P-polarized wave is adjusted to the state of the P-polarized component whose amplitude is reduced, eliminated, or inverted by the objective lens 302 (reducing optical system) of the exposure apparatus, and then the S-polarized wave is By combining with the polarization image, an exposure image image can be created. According to the second embodiment, since imaging is performed in a state where the S-polarized wave and the P-polarized wave are separated, it is possible to adjust one of the polarization component images.

  The inspection apparatus 100 according to the second embodiment further performs a pattern inspection of the mask substrate 101 using the respective polarized images of the S-polarized wave and the P-polarized wave. The inspection method may be the same as in the first embodiment.

Embodiment 3 FIG.
In the first embodiment, the configuration in which the polarization image of the S-polarized wave and the polarization image of the P-polarized wave are simultaneously imaged using two sensors has been described, but the present invention is not limited to this. In the second embodiment, a configuration will be described in which a single sensor is used to image while switching between a polarization image of an S-polarized wave and a polarized image of a P-polarized wave.

  FIG. 11 is a diagram illustrating a part of the configuration of the optical image acquisition unit of the inspection device according to the third embodiment. FIG. 11 shows a part of the configuration in FIG. 1 which is necessary to describe the configuration of the optical image acquisition unit 150 (polarized image acquisition device) in the second embodiment. The optical image acquisition unit 150 according to the third embodiment does not require the photodiode array 205 (an example of a sensor), the sensor circuit 106, and the stripe pattern memory 123 in the configuration of FIG. Instead, a half-wave plate 177 (a half-wave plate for rotation) and a drive mechanism 175 for rotating the half-wave plate for rotation are provided on the incident side of the polarization beam splitter 174 (restriction mechanism). Be placed. Other points of the inspection apparatus according to the third embodiment are the same as those in FIG.

  The configuration and the situation until the laser light (for example, DUV light) having a wavelength equal to or less than the ultraviolet region serving as inspection light from the light source 103 is generated and the transmitted light of the mask substrate 101 is transmitted through the split type half-wave plate 172 are implemented. This is the same as in the first embodiment. Therefore, the split-type half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, a pre-environment can be prepared so that the P-polarized wave can be separated and left from others. Alternatively, it is the same as the first embodiment in that the advance environment can be adjusted so that the S-polarized wave can be left separately from the others.

  The transmitted light transmitted through the split-type half-wave plate 172 is incident on the polarization beam splitter 174 after passing through the half-wave plate 177. The polarization beam splitter 174 generates a P-polarized wave and an S-polarized wave of the transmitted light. Pass one and reflect the other. In other words, the polarization beam splitter 174 (an example of a limiting mechanism) allows one of the P-polarized wave and the S-polarized wave of the transmitted light to pass and restricts the other. Which polarized light is allowed to pass or the passage is restricted depends on the arrangement position of the half-wave plate 177 rotated by the driving mechanism 175. That is, the driving mechanism 175 rotates the half-wave plate 177 so that the polarization beam splitter 174 allows one of the P-polarized wave and the S-polarized wave of the transmitted light to pass and reflects the other. For example, when capturing a polarization image of the P-polarized wave of the transmitted light, the driving mechanism 175 controls the S-polarized wave so that the polarization beam splitter 174 allows the transmitted P-polarized wave to pass through and reflects the S-polarized wave. Is rotated by 45 ° (or −45 °). Conversely, when capturing a polarization image of an S-polarized wave of transmitted light, the driving mechanism 175 controls the P-polarized light so that the polarization beam splitter 174 allows the transmitted S-polarized wave to pass through and reflects the P-polarized wave. The direction of the half-wave plate 177 in the state of the wave is rotated by −45 ° (or 45 °).

  In the example of FIG. 11, the polarization beam splitter 174 is used, but the invention is not limited to this. Instead of the polarization beam splitter 174, for example, a polarizer (another example of the limiting mechanism) may be used. As for the polarizer, similarly to the polarization beam splitter 174, the direction of the half-wave plate is adjusted by the driving mechanism 175 so that one of the P-polarized wave and the S-polarized wave is transmitted and the other is reflected. be able to.

  As described above, since the directions of the same polarized waves are aligned by the split type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or the polarizer).

  When the direction of the polarization beam splitter 174 is set by the driving mechanism 175 so that the P polarization wave can pass, the light (P polarization wave) passing through the polarization beam splitter 174 enters the imaging lens 176 and forms an image. The lens 176 (first imaging lens) converts the incident light into a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reducing optical system) of the exposure apparatus. To form an image on the photodiode array 105.

  The photodiode array 105 (image sensor) captures an image (an image of a P-polarized component) (first image) formed by the imaging lens 176.

  Note that, for example, a TDI sensor or the like is preferably used as the photodiode array 105 as in the first embodiment. The photodiode array 105 (image sensor) captures an optical image of a polarization component corresponding to the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is mounted is moving. The imaging of the optical image may be performed for each inspection stripe 20 as described above.

  The image of the pattern of the P-polarized light formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (striped region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range that maximizes the gradation when the amount of illumination light is 60% incident.

  When acquiring the optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (arithmetic unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of the P-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of the P-polarized light is, for example, 8-bit unsigned data, and expresses the brightness gradation (light amount) of each pixel. The stripe region image of the P-polarized light output to the comparison circuit 108 is stored in the storage device 50.

  Next, the direction of the half-wave plate 177 is changed by the driving mechanism 175 so that the S-polarized wave can pass therethrough. Then, imaging of the S-polarized wave is performed for the same inspection stripe 20 that has performed the imaging of the P-polarized wave.

  The configuration and the situation until the laser light (for example, DUV light) having a wavelength equal to or less than the ultraviolet region serving as inspection light from the light source 103 is generated and the transmitted light of the mask substrate 101 is transmitted through the split type half-wave plate 172 are implemented. This is the same as in the first embodiment. Therefore, the split-type half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, a pre-environment can be prepared so that the P-polarized wave can be separated and left from others. Alternatively, it is the same as the first embodiment in that the advance environment can be adjusted so that the S-polarized wave can be left separately from the others.

  The transmitted light transmitted through the split type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 transmits the S-polarized wave of the transmitted light and reflects the P-polarized wave.

  As described above, since the directions of the same polarized waves are aligned by the split type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or the polarizer).

  Since the direction of the half-wave plate 177 is set by the driving mechanism 175 so that the S-polarized wave can pass, the light (S-polarized wave) passing through the polarization beam splitter 174 enters the imaging lens 176, The imaging lens 176 (imaging lens) converts the incident light to a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reducing optical system) of the exposure apparatus. An image is formed on the photodiode array 105.

  The photodiode array 105 (image sensor) captures an image (an S-polarized component image) (second image) formed by the imaging lens 176.

  The photodiode array 105 (image sensor) captures an optical image of a polarization component corresponding to the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is mounted is moving. The imaging of the optical image may be performed for each inspection stripe 20 as described above.

  The image of the S-polarized light pattern formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (striped region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range that maximizes the gradation when the amount of illumination light is 60% incident.

  When acquiring the optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (arithmetic unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of the S-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of the S-polarized light is, for example, 8-bit unsigned data, and expresses the brightness gradation (light amount) of each pixel. The stripe region image of the S-polarized light output to the comparison circuit 108 is stored in the storage device 52.

  As described above, according to the third embodiment, the respective polarization images of the S-polarized wave and the P-polarized wave that are the basis for creating the exposure image when transferred by the exposure device are acquired at different times. it can. Then, the polarization image of the acquired P-polarized wave is adjusted to the state of the P-polarized component whose amplitude is reduced, eliminated, or inverted by the objective lens 302 (reducing optical system) of the exposure apparatus, and then the S-polarized wave is By combining with the polarization image, an exposure image image can be created. According to the third embodiment, since imaging is performed in a state where the S-polarized wave and the P-polarized wave are separated, it is possible to adjust one polarized component image.

  The inspection apparatus 100 according to the third embodiment further performs a pattern inspection of the mask substrate 101 by using the respective polarized images of the S-polarized wave and the P-polarized wave. The inspection method may be the same as in the first embodiment.

  In the above description, each “-circuit” or each “-unit” includes one arithmetic circuit, and the arithmetic circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, or the like. Is included. In addition, a common circuit (the same circuit) may be used as an arithmetic circuit included in each “-circuit” or each “-unit”. Alternatively, different circuits (separate circuits) may be used. The program that causes the processor or the like to execute may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (read only memory). For example, the position circuit 107, the comparison circuit 108, the autoloader control circuit 113, the table control circuit 114, and the like may be configured by at least one circuit described above. Similarly, the frame division units 54 and 56, the correction unit 62, the synthesis unit 64, the positioning unit 70, and the comparison unit 72 may be configured by at least one circuit described above.

  The embodiment has been described with reference to the specific examples. However, the present invention is not limited to these specific examples. In the above-described example, after correcting the gradation value of the P-polarized wave frame image so as to match the exposure image, the corrected P-polarized wave frame image (first optical image) is not corrected. Although the case of synthesizing a frame image (second optical image) using polarized waves has been described, the present invention is not limited to this. Since it is a die-to-die inspection, it does not have to match the exposure image as long as the image is similarly synthesized. Therefore, the images may be synthesized at a different ratio from the exposure image. Further, the first optical image and the second optical image may be independently used for inspection without being combined. In the above-described example, the case where the distance between adjacent patterns is inspected has been described, but the present invention is not limited to this. For example, the gradation value of the combined frame image (first die image) and the combined frame image (second die image) may be compared for each pixel by a predetermined algorithm. For example, a defect may be determined when the difference obtained by subtracting the gradation value of the combined frame image (second die image) from the gradation value of the combined frame image (first die image) is larger than a threshold value.

  In addition, although description is omitted for parts that are not directly necessary for the description of the present invention, such as the device configuration and the control method, the required device configuration and control method can be appropriately selected and used.

  In addition, all polarization image acquisition apparatuses, pattern inspection apparatuses, and polarization image acquisition methods that include the elements of the present invention and that can be appropriately designed and modified by those skilled in the art are included in the scope of the present invention.

Reference Signs List 10 inspection area 20 inspection stripe 30 frame area 50, 52, 58, 60, 66, 68 storage device 54, 56 frame division unit 62 correction unit 64 synthesizing unit 70 positioning unit 72 comparing unit 100 inspection device 101 mask substrate 102 XYθ table 103 light source 104 magnifying optical system 105, 205 photodiode array 106, 206 sensor circuit 107 position circuit 108 comparison circuit 109 magnetic disk device 110 control computer 113 autoloader control circuit 114 table control circuit 115 magnetic tape device 116 FD
117 CRT
118 Pattern Monitor 119 Printer 120 Bus 122 Laser Measurement System 123, 223 Stripe Pattern Memory 150 Optical Image Acquisition Unit 160 Control System Circuit 170 Transmission Illumination Optical System 171 Objective Lens 172 Divided 1/2 Wavelength Plate 174 Polarizing Beam Splitter 176, 178 Imaging lens 177 Half-wave plate 180 Projection lens 181 Illumination shape switching mechanism 182 Imaging lens 190 Transmitted light 192 Light 300 Mask substrate 301 Transmitted light 302 Objective lens 304 Semiconductor substrate 305 Light

Claims (5)

A movable stage on which a pattern-formed, mask substrate for exposure is mounted,
A case where the reduction optical system of the exposure apparatus, which transmits light from the mask substrate and forms an image on a substrate to be exposed when the mask substrate is disposed in the exposure apparatus, receives the transmitted light from the mask substrate; At the same numerical aperture, the illumination lens formed on the mask substrate, the objective lens to enter the transmitted light transmitted through the mask substrate,
Of the P-polarized wave and the S-polarized wave of the transmitted light that has been disposed near the pupil position of the objective lens at a position opposite to the mask substrate with respect to the objective lens and that has passed through the objective lens. A split-type half-wave plate for simultaneously aligning a P-polarized wave in one of two directions orthogonal to each other and an S-polarized wave in the other of the two directions orthogonal to each other ;
A restricting mechanism configured to pass one of the P-polarized wave and the S-polarized wave of the transmitted light and restrict the other, and configured by one of a polarizer and a polarizing beam splitter;
A drive mechanism that rotates the restriction mechanism so that the restriction mechanism passes the other, and restricts the passage of the one;
An imaging lens that forms an image of the light having passed through the limiting mechanism with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus,
An image sensor that captures an image formed by the imaging lens;
A polarization image acquisition device, comprising: A movable stage on which a pattern-formed, mask substrate for exposure is mounted,
A case where the reduction optical system of the exposure apparatus, which transmits light from the mask substrate and forms an image on a substrate to be exposed when the mask substrate is disposed in the exposure apparatus, receives the transmitted light from the mask substrate; At the same numerical aperture, the illumination lens formed on the mask substrate, the objective lens to enter the transmitted light transmitted through the mask substrate,
Of the P-polarized wave and the S-polarized wave of the transmitted light that has been disposed near the pupil position of the objective lens at a position opposite to the mask substrate with respect to the objective lens and that has passed through the objective lens. A split-type half-wave plate for simultaneously aligning a P-polarized wave in one of two directions orthogonal to each other and an S-polarized wave in the other of the two directions orthogonal to each other ;
A restricting mechanism configured to pass one of the P-polarized wave and the S-polarized wave of the transmitted light and restrict the other, and configured by one of a polarizer and a polarizing beam splitter;
A half-wave plate that rotates the polarization direction by 90 ° so that the restriction mechanism allows the other to pass, and restricts the one to pass;
A driving mechanism for rotating the half-wave plate for rotation,
An imaging lens that forms an image of the light having passed through the limiting mechanism with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus,
An image sensor that captures an image formed by the imaging lens;
Equipped with a,
The amount of deviation ΔL of the position of the split type half-wave plate from the pupil position of the objective lens is determined using the pupil diameter D of the objective lens, the field diameter d of the objective lens, and the focal length f of the objective lens. A polarization image acquisition device characterized by satisfying the following expression (1) .
(1) ΔL <0.05 · D · f / d A movable stage on which a pattern-formed, mask substrate for exposure is mounted,
A case where the reduction optical system of the exposure apparatus, which transmits light from the mask substrate and forms an image on a substrate to be exposed when the mask substrate is disposed in the exposure apparatus, receives the transmitted light from the mask substrate; At the same numerical aperture, the illumination lens formed on the mask substrate, the objective lens to enter the transmitted light transmitted through the mask substrate,
The P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens are disposed at positions opposite to the mask substrate with respect to the objective lens and near the pupil position of the objective lens. In order to simultaneously acquire images, the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens, the S-polarized wave is orthogonal to the S-polarized wave in one of two directions orthogonal to each other. A split-type half-wave plate that is simultaneously aligned in the other of the two directions ;
A polarizing beam splitter that passes one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other;
A first imaging lens that forms an image of light that has passed through the polarizing beam splitter with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A first image sensor that captures an image formed by the first imaging lens;
A second imaging lens for imaging the light reflected by the polarization beam splitter with the numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A second image sensor that captures an image formed by the second imaging lens;
A polarization image acquisition device, comprising: A polarization image acquisition device according to any one of claims 1 to 3,
A first optical image based on the one of the P-polarized wave and the S-polarized wave, and a combining unit configured to combine a second optical image based on the other of the P-polarized wave and the S-polarized wave;
A first die image in which the first and second optical images in the first die are combined; and a first and second optical image in the second die in which a pattern similar to that of the first die is formed. A comparing unit that compares an optical image synthesized with a second die image corresponding to the first die image;
A pattern inspection apparatus comprising: The amount of deviation ΔL of the position of the split type half-wave plate from the pupil position of the objective lens is determined using the pupil diameter D of the objective lens, the field diameter d of the objective lens, and the focal length f of the objective lens. The polarization image acquisition device according to claim 1, wherein the following expression (1) is satisfied.
(1) ΔL <0.05 · D · f / d

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