JP7036574B2 - Pattern inspection device and pattern inspection method - Google Patents

Description

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

In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line width required for semiconductor devices has become narrower and narrower. These semiconductor elements use an original image pattern (also referred to as a mask or reticle, hereinafter collectively referred to as a mask) on which a circuit pattern is formed, and the pattern is exposed and transferred onto a wafer by a reduction projection exposure device called a so-called stepper. Manufactured by forming a circuit. Therefore, in manufacturing a mask for transferring such a fine circuit pattern to a wafer, a pattern drawing apparatus using an electron beam capable of drawing the fine circuit pattern is used. A pattern circuit may be drawn directly on the wafer using such a pattern drawing device. Alternatively, an attempt is being made to develop a laser beam drawing apparatus that draws using a laser beam in addition to the electron beam.

Further, improvement of the yield is indispensable for manufacturing LSI, which requires a large manufacturing cost. However, as typified by 1-gigabit class DRAM (random access memory), the patterns constituting the LSI are on the order of submicrons to nanometers. One of the major factors that reduce the yield is the pattern defect of the mask used when exposing and transferring an ultrafine pattern on a semiconductor wafer by photolithography technology. 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 the pattern inspection device for inspecting defects of the transfer mask used in LSI manufacturing.

As an inspection method, an optical image obtained by capturing a pattern formed on a sample such as a lithography mask using a magnifying optical system at a predetermined magnification is compared with a design data or an optical image obtained by capturing the same pattern on the sample. There is a known method of inspecting by doing so. For example, as a pattern inspection method, "die to die inspection" in which optical image data obtained by capturing the same pattern in different places on the same mask are compared with each other, or a pattern is used as a mask using CAD data with a pattern design. The drawing data (design pattern data) converted into the device input format for input by the drawing device at the time of drawing is input to the inspection device, a design image (reference image) is generated based on this, and the pattern is imaged. There is a "die to database inspection" that compares the measured optical image with the measured data. In the inspection method in such an inspection device, the sample is placed on the stage, and the moving of the stage causes the luminous flux to scan the sample, and the inspection is performed. The sample is irradiated with a luminous flux by a light source and an illumination optical system. The light transmitted or reflected from the sample is imaged on the sensor via the optical system. The image captured by the sensor is sent to the comparison circuit as measurement data. In the comparison circuit, after the images are aligned with each other, the measurement data and the reference data are compared according to an appropriate algorithm, and if they do not match, it is determined that there is a pattern defect.

For semiconductor products with short product cycles, shortening the manufacturing time is an important item. When a defective mask pattern is exposed and transferred to a wafer, the 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 correction device. However, fixing all the defects found will increase the manufacturing time and reduce the product value. Here, as the development of the inspection device progresses, the inspection device determines that there is a pattern defect even if a very small deviation occurs. However, when the mask pattern is transferred onto the wafer by an actual exposure apparatus, it can be used as an integrated circuit as long as it is not caused by a defect such as disconnection or / or short circuit of the circuit on the wafer. Therefore, it is desired to acquire an exposure image to be exposed on the wafer by the exposure apparatus. However, in the exposure device, the mask pattern is reduced and imaged on the wafer, whereas in the inspection device, the mask pattern is enlarged and imaged on the sensor. Therefore, the configuration of the optical system on the secondary side is different from that of the mask substrate. Therefore, no matter how much the state of the illumination light is adjusted to the exposure apparatus, it is difficult for the inspection apparatus to reproduce the pattern image transferred by the exposure apparatus as it is.

Therefore, on the user side performing mask inspection with the inspection device, for example, a dedicated machine manufactured by Carl Zeiss Co., Ltd. (for example, a patent document) that generates and inspects an image called a spatial image as an exposure image to be exposed and transferred by the exposure device. (Refer to 1) is put into the production site as a standard device, and inspection is performed with an exposure image.

Special Table 2013-504774A

The standard device using the above-mentioned spatial image takes time to measure. Therefore, instead of creating a spatial image of the entire surface of the mask, a spatial image is created for the portion determined to be a defect by the inspection device, and the inspection is performed on the exposed image. However, as described above, as the development of the inspection device progresses, the inspection device determines that there is a pattern defect even if a very small deviation occurs, so that a large number of defect locations occur. If spatial images were created for all of these and the exposure image inspection was performed, the throughput in mask manufacturing would be extremely poor. Therefore, it is required that the inspection device also reproduces the pattern image when transferred by the exposure device and suppresses the number of defective parts in advance in the inspection device. Therefore, in the inspection device, in addition to the usual pattern defect inspection, the development of a system capable of capturing such an exposure image is underway.

When the pattern dimensions, etc. are inspected using the exposure image reproduced by the inspection device developed as described above, the obtained inspection result may be different from the inspection result by the above-mentioned standard device. .. This is because the device configurations are different in the first place, and the results obtained are also different. However, since all of them evaluate the pattern dimensions on the nanometer order, it is difficult to determine which result is correct. If nothing is done, the user must determine whether the mask substrate to be inspected can be used for semiconductor manufacturing while wondering whether the result of any of the devices is correct. Currently, the standard is to inspect an exposed image using a spatial image, so it is desirable that the inspection device can obtain the same results as the inspection results of the standard device.

Therefore, in one aspect of the present invention, it is possible to obtain the same measurement result as, for example, an external image acquisition device as a standard device from an exposure transfer simulated image simulating a transfer pattern image when transferred by an exposure device. An inspection device and a method thereof are provided.

The pattern inspection device of one aspect of the present invention is
With the first optical image acquisition mechanism that irradiates the mask substrate for exposure on which the pattern is formed with illumination light and acquires the first optical image of the pattern by using the transmitted light or the reflected light obtained from the mask substrate. ,
A comparison unit that determines the presence or absence of defects in the first optical image by comparing the first reference image corresponding to the acquired first optical image with the first optical image.
Second optics for acquiring a second optical image that is an exposure transfer simulated image that simulates the transfer pattern image formed on the sample when the pattern is exposed and transferred to the sample for the defect portion determined to be a defect by the determination. Image acquisition mechanism and
The dimensions of the pattern in the second optical image are measured based on the data obtained by an external image acquisition device different from the second optical image acquisition mechanism that acquires the exposure transfer simulated image that simulates the transfer pattern image. A storage device that stores a correction table in which the correction threshold for which the measurement threshold is corrected is defined, and
Corresponds to the measurement pattern dimensions of the defect pattern measured from the second optical image using the correction threshold defined in the correction table and the defect location obtained from the second reference image corresponding to the second optical image. The dimension change rate calculation unit that calculates the dimension change rate using the reference pattern dimension of the pattern to be used, and
It is characterized by being equipped with.

Further, the correction table is set by using an optical image obtained from a reference mask substrate as a reference using the second optical image acquisition mechanism and an optical image obtained from the reference mask substrate using an image acquisition device. It is preferable that the corrected correction threshold is defined.

Further, it is preferable that the reference mask substrate is formed with a plurality of types of patterns each composed of a plurality of patterns of the same type having different pattern sizes, arrangement pitches, defect types, and defect sizes.

Further, in the correction table, the dimensional change rate of the pattern in the optical image obtained from the reference mask substrate using the second optical image acquisition mechanism is in the optical image obtained from the reference mask substrate using the image acquisition device. It is preferable that a correction threshold is defined in which the measurement threshold is corrected so as to match the dimensional change rate of the pattern.

The pattern inspection method of one aspect of the present invention is
A step of irradiating an exposure mask substrate on which a pattern is formed with a pattern inspection device with illumination light and acquiring a first optical image of the pattern using the transmitted light or the reflected light obtained from the mask substrate.
A step of determining the presence or absence of defects in the first optical image by comparing the first reference image corresponding to the acquired first optical image with the first optical image in the pattern inspection device.
A second optical image, which is an exposure transfer simulated image that imitates the transfer pattern image formed on the sample when the pattern is exposed and transferred to the sample, is obtained for the defect portion determined to be a defect by the pattern inspection device. The process to acquire and
The measurement threshold for measuring the dimensions of the pattern in the second optical image is based on the data obtained by an external image acquisition device different from the pattern inspection device that acquires the exposure transfer simulated image that simulates the transfer pattern image. The process of creating a correction table in which the corrected correction threshold is defined, and
Corresponds to the measurement pattern dimensions of the defect pattern measured from the second optical image using the correction threshold defined in the correction table and the defect location obtained from the second reference image corresponding to the second optical image. The process of calculating and outputting the dimensional change rate using the reference pattern dimension of the pattern to be used, and
It is characterized by being equipped with.

According to one aspect of the present invention, it is possible to obtain the same measurement result as, for example, an external image acquisition device as a standard device from an exposure transfer simulated image simulating a transfer pattern image when transferred by an exposure device. Therefore, in the inspection device, it is possible to exclude the parts that can be used as an integrated circuit when the exposure is transferred from the plurality of parts where the defect is determined.

It is a block diagram which shows the structure of the pattern inspection apparatus in Embodiment 1. FIG. It is a conceptual diagram which shows a part of the optical system of the exposure apparatus which becomes the comparative example in Embodiment 1. FIG. It is a conceptual diagram which shows a part of the optical system of the inspection apparatus in Embodiment 1. FIG. It is a flowchart which shows the main part process of the pattern inspection method in Embodiment 1. FIG. It is a figure which shows an example of the evaluation pattern formed on the reference mask substrate in Embodiment 1. FIG. It is a figure which shows an example of the pattern type which constitutes the evaluation pattern in Embodiment 1. FIG. It is a figure which shows another example of the pattern type which constitutes the evaluation pattern in Embodiment 1. FIG. It is a figure which shows an example of the defect type and defect size of the evaluation pattern in Embodiment 1. FIG. It is a figure which shows another example of the defect type and defect size of the evaluation pattern in Embodiment 1. FIG. It is a figure which shows another example of the defect type and defect size of the evaluation pattern in Embodiment 1. FIG. It is a figure which shows another example of the defect type and defect size of the evaluation pattern in Embodiment 1. FIG. It is a figure which shows another example of the defect type and defect size of the evaluation pattern in Embodiment 1. FIG. It is a figure which shows the internal structure of the correction table making circuit in Embodiment 1. FIG. It is a figure for demonstrating the measuring method of a line width dimension in Embodiment 1. FIG. It is a figure which shows an example of the format of the correction table in Embodiment 1. FIG. It is a figure which shows an example of the structure of the optical system for normal inspection and an example of the structure of the optical system for exposure image inspection in Embodiment 1. FIG. It is a conceptual diagram for demonstrating the inspection area in Embodiment 1. FIG. It is a figure which shows an example of the internal structure of the comparison circuit in Embodiment 1. FIG. It is a figure for demonstrating the flow of the pattern inspection of Embodiment 1 and the comparative example.

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

The optical image acquisition mechanism 150 includes a light source 103, a transmission inspection illumination optical system 170 (transmission illumination optical system), a reflection inspection illumination optical system 175 (reflection illumination optical system), a movablely arranged XYθ table 102, an aperture 173, and an enlargement. It has an optical system 104, a photodiode array 105 (an example of a sensor), a sensor circuit 106, a stripe pattern memory 123, and a laser length measuring system 122. The substrate 101 is placed on the XYθ table 102. The substrate 101 includes, for example, an exposure photomask (exposure mask substrate) that transfers a pattern onto a semiconductor substrate such as a wafer. Further, in this photomask, a pattern composed of a plurality of graphic patterns to be inspected is formed. The substrate 101 is arranged on the XYθ table 102, for example, with the pattern forming surface facing downward.

The transmission inspection illumination optical system 170 includes a projection lens 180, an illumination shape switching mechanism 181 and an imaging lens 182. Further, the transmission inspection illumination optical system 170 may have other lenses, mirrors, and / or optical elements. The reflection inspection illumination optical system 175 has at least one lens that illuminates the reflection inspection illumination light separated from the transmission inspection illumination light from the light source 103. The reflection inspection illumination optical system 175 may have other lenses, mirrors, and / or optical elements.

The magnifying optical system 104 includes an objective lens 171 and a projection lens 172, and an imaging lens 176. The objective lens 171 and the projection lens 172, and the imaging lens 176 are each composed of at least one lens. Further, another lens and / or a mirror may be provided between the objective lens 171 and the projection lens 172 and / or between the projection lens 172 and the imaging lens 176.

As the photodiode array 105, for example, it is preferable to use a TDI (time delay integration) sensor or the like. The photodiode array 105 (image sensor) captures a corresponding optical image of a pattern formed on the substrate 101 while the XYθ table 102 on which the substrate 101 is placed is moving.

In the control system circuit 160, the control computer 110 that controls the entire inspection device 100 uses the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the autoloader control circuit 113, the table control circuit 114, and the mode switching via the bus 120. It is connected to a control circuit 140, an exposure simulation reference image creation circuit 142, a correction table creation circuit 144, a magnetic disk device 109, a magnetic tape device 115, a flexible disk device (FD) 116, a CRT 117, a pattern monitor 118, and a printer 119. .. 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. Further, the XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor.

In the first embodiment, a high-magnification pattern image is imaged, an inspection for inspecting the pattern image (normal inspection mode (1)) and an exposure image are acquired, and an inspection using the exposure image (exposure image inspection). Mode (2)) and can be switched. In the normal inspection mode (1), in the optical image acquisition mechanism 150 of the inspection device 100, the light source 103, the transmission inspection illumination optical system 170, the reflection inspection illumination optical system 175, the XYθ table 102, the magnifying optical system 104, the photodiode array 105, And the sensor circuit 106 constitutes a high-magnification normal inspection optical system (inspection optical image acquisition mechanism: first optical image acquisition mechanism). For example, an inspection optical system having a magnification of 400 to 500 times is configured. In the exposure image inspection mode (2), in the optical image acquisition mechanism 150 of the inspection apparatus 100, the light source 103, the transmission inspection illumination optical system 170, the XYθ table 102, the aperture 173, the magnifying optical system 104, the photodiode array 105, and the sensor circuit. The 106 constitutes an optical system for inspection of an exposure image (optical image acquisition mechanism for exposure image: second optical image acquisition mechanism). The optical system for normal inspection and the optical system for exposure image inspection are configured in common with most of the optical equipment. In other words, a part of the configuration is configured by diverting the same optical equipment. This makes it possible to suppress an increase in the number of parts.

Further, the XYθ table 102 is driven by the table control circuit 114 under the control of the control computer 110. It can be moved by a drive system such as a 3-axis (XY−θ) motor that drives in the X direction, the Y direction, and the θ direction. As these X motors, Y motors, and θ motors, for example, linear motors can be used. The XYθ table 102 can be moved in the horizontal direction and the rotational direction by the motor of each axis of XYθ. Then, by fixing the position of the objective lens 171 and dynamically moving the XYθ table 102 in the optical axis direction (Z-axis direction) by an autofocus (AF) control circuit (not shown) under the control of the control computer 110. The focal position of the objective lens 171 is adjusted to the pattern forming surface of the mask substrate 101. In such a case, the focal position of the XYθ table 102 is adjusted by moving the XYθ table 102 in the optical axis direction (Z-axis direction) by, for example, a piezo element (not shown). Alternatively, the objective lens 171 is dynamically adjusted to the focal position (optical axis direction: Z-axis direction) on the pattern forming surface of the mask substrate 101 by an autofocus (AF) control circuit (not shown) under the control of the control computer 110. It is also suitable to do so. In such a case, the focal position of the objective lens 171 is adjusted by moving the objective lens 171 in the optical axis direction (Z-axis direction) by, for example, 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 position circuit 107 calculates the irradiation position of the inspection light relative to the position of the measured XYθ table 102.

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

Here, FIG. 1 describes the components necessary for explaining the first embodiment. It goes without saying that the inspection device 100 may usually include other necessary configurations.

FIG. 2 is a conceptual diagram showing a part of the optical system of the exposure apparatus as a comparative example in the first embodiment. A part of an optical system of an exposure apparatus such as a stepper that exposes and transfers a pattern formed on a mask substrate 300 to a semiconductor substrate is shown. In the exposure apparatus, illumination light (not shown) is illuminated on the mask substrate 300, the transmitted light 301 from the mask substrate 300 is incident on the objective lens 302, and the light 305 passing through the objective lens 302 is the semiconductor substrate 304 (wafer: exposed). An image is formed on the substrate). Although one objective lens 302 (reduced optical system) is shown in FIG. 2, 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, 1/4 and exposed and transferred to the semiconductor substrate 304. The numerical aperture NAi (numerical aperture on the image i side) of the exposure apparatus with respect to the semiconductor substrate 304 at that time 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, the transmitted light image from the mask substrate 300 is reduced to 1/4, so that the sensitivity of the objective lens 302 to the mask substrate 300 is 1/4. In other words, the numerical aperture NAo (numerical aperture on the object o side) of the objective lens 302 that can be incident when the transmitted light is incident from the mask substrate 300 to the objective lens 302 is 1/4 of NAi, and NAo = 0.35. It becomes. Therefore, in the exposure apparatus, the transmitted light image from the mask substrate 300 having a luminous flux with a numerical aperture of NAo = 0.35 is exposed and transferred to the semiconductor substrate 304 as an image of a luminous flux having a numerical aperture of NAi = 1.4. become.

FIG. 3 is a conceptual diagram showing a part of the optical system of the inspection device according to the first embodiment. Here, the numerical aperture of the inspection device according to the first embodiment and the numerical aperture of the exposure device shown in FIG. 2 are compared. In the inspection device 100 according to the first embodiment, as shown in FIG. 3, illumination light (not shown) is illuminated on the mask substrate 101, and the transmitted light 11 from the mask substrate 101 is incident on the magnifying optical system 104 including the objective lens. The light 12 that has passed through the magnifying optical system 104 forms an image on the photodiode array 105 (image sensor). At that time, the numerical aperture NAo (numerical aperture on the object o side) of the objective lens that can be incident when the transmitted light 11 is incident from the mask substrate 101 to the magnifying optical system 104 is set to, for example, NAo = 0.9. In the inspection device 100, the transmitted light image from the mask substrate 300 is magnified 200 to 500 times in order to make it comparable in the inspection, so that the sensitivity of the magnifying optical system 104 to the mask substrate 101 is 200 to 500. 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 is 1/500 to 1/200 of NAo, and for example, the numerical aperture NAi = 0.004.

As described above, the amount of light information obtained by the objective lens 302 of the exposure device having NAo = 0.35 and the amount of light information obtained by the objective lens of the inspection device 100 having NAo = 0.9, for example, are in the first place. It's different. Therefore, it is difficult to obtain the same image on the semiconductor substrate 304 because the number of luminous fluxes itself is different from the image on the light receiving surface of the photodiode array 105. Therefore, in order to make it equal to the objective lens 302 of the exposure device, the NAo of the objective lens of the inspection device 100 is set to, for example, NAo = 0.35 by reducing the luminous flux with the diaphragm 173. This makes it possible to match the number of luminous fluxes. Although only the magnifying optical system 104 is shown in FIG. 3, a plurality of lenses are arranged in the magnifying optical system 104. As described above, the magnifying optical system 104 includes at least an objective lens 171, a projection lens 172, and an imaging lens 176.

Therefore, in the objective lens 171, when the mask substrate 101 is arranged in the exposure apparatus, the objective lens 302 of the exposure apparatus that incidents the transmitted light from the mask substrate 101 and forms an image on the semiconductor substrate 304 transmits from the mask substrate 101. With the same numerical aperture NAo (NAo = 0.35) as in the case of incident light 301, the illumination light imaged on the mask substrate 101 incidents the transmitted light 11 transmitted through the mask substrate 101. The imaging lens 176 forms an image of the light passing through the magnifying optical system 104 with a numerical aperture NAi (NAi = 0.001) sufficiently smaller than that of the objective lens 302 of the exposure apparatus. The amount of information of light that passes through 101 and reaches the photodiode array 105 can be adjusted to the exposure device.

FIG. 4 is a flowchart showing a main process of the pattern inspection method according to the first embodiment. In FIG. 4, the pattern inspection method according to the first embodiment is a reference mask measurement step (S90), a correction threshold search step (S92), a correction table creation step (S94), a mode selection step (S102), and a squeeze. A release step (S104), an inspection illumination optical system placement step (S106), a scan step (S108), a reference image creation step (S110), a frame division step (S112), a comparison step (S114), and the like. The aperture step (S204), the illumination optical system arrangement step for exposure (S206), the defect candidate information input step (S208), the scan step (S210), the reference image creation step (S212), and the correction threshold calculation step (S212). S214), a CD measurement step (S216), a CD measurement step (S218), a dimensional change rate calculation step (S220), and a determination step (S222) are carried out.

Here, when the inspection of the pattern dimensions and the like using the exposure image reproduced by the inspection device 100 is performed, the obtained inspection result may be different from the inspection result of the external standard device. This is because the device configurations are different in the first place, and the results obtained are also different. However, since all of them evaluate the pattern dimensions on the nanometer order, it is difficult to determine which result is correct. Therefore, in the first embodiment, the inspection device 100 corrects the measurement threshold value so that the same result as the inspection result of the standard device can be obtained. In order to obtain such a corrected correction threshold value, first, the same reference mask substrate is measured by the inspection device 100 and an external standard device (not shown), and the measurement result of the inspection device 100 and the external standard device (not shown) are used. Compare with the measurement result of.

As the reference mask measuring step (S90), the inspection device 100 is used to image a graphic pattern formed on the reference mask substrate, and the line width dimension CD of the graphic pattern is measured. Further, an external standard device (for example, a dedicated machine manufactured by Carl Zeiss) (for example, a dedicated machine manufactured by Carl Zeiss), which is not shown, also separately measures the line width dimension CD of the graphic pattern formed on the reference mask substrate.

Here, the inspection device 100 captures an image of the reference mask substrate as an exposure image. Therefore, the light source 103, the transmission inspection illumination optical system 170, the XYθ table 102, the aperture 173, the magnifying optical system 104, the photodiode array 105, and the inspection optical system by the sensor circuit 106 (optical image acquisition mechanism for exposure image: second optical). Image acquisition mechanism). Specifically, as will be described later, the diameter of the opening of the aperture 173 is narrowed down, and the NAo of the objective lens 171 is made equal to the objective lens 302 of the exposure apparatus. For example, the NAo of the objective lens of the inspection device 100 is set to, for example, NAo = 0.35. Further, the illumination shape switching mechanism 181 switches optical elements including a lens, a mirror, and the like so that the shape of the illumination light (inspection light) for transmission inspection has the same illumination shape as the illumination shape used in the exposure apparatus.

FIG. 5 is a diagram showing an example of an evaluation pattern formed on the reference mask substrate according to the first embodiment. In FIG. 5, the reference mask substrate 300 is formed with a plurality of types of pattern groups each composed of a plurality of patterns of the same type having different pattern sizes, arrangement pitches, defect types, and defect sizes. As a plurality of types of patterns, for example, a hole pattern (A), a pillar pattern (B) that is black-and-white inverted with the hole pattern (A), a line and space (L / S) pattern (C) arranged in the x direction, and / or A line and space (L / S) pattern (D) arranged in the y direction can be mentioned.

FIG. 6 is a diagram showing an example of pattern types constituting the evaluation pattern in the first embodiment. FIG. 6A shows an example of a hole pattern (A) in which rectangular patterns having a width size dx in the x direction and a width size dy in the y direction are arranged at a pitch Px in the x direction and a pitch Py in the y direction. There is. FIG. 6B shows an example of a pillar pattern (B) in which rectangular space patterns having a width size dx in the x direction and a width size dy in the y direction are arranged at a pitch Px in the x direction and a pitch Py in the y direction. ing.

FIG. 7 is a diagram showing another example of the pattern types constituting the evaluation pattern in the first embodiment. FIG. 7A shows an example of a line and space (L / S) pattern (C) in which line patterns having a width size dx in the x direction are arranged in the x direction at a pitch Px in the x direction. FIG. 7B shows an example of a line and space (L / S) pattern (D) arranged in the y direction in which line patterns are arranged in the y direction at a pitch Py with a width size dy in the y direction.

FIG. 8 is a diagram showing an example of a defect type and a defect size of the evaluation pattern in the first embodiment. FIG. 8A shows a defect type (1) in which, for example, both ends of the pattern in the x direction are both reduced by the defect size Δx. FIG. 8B shows a defect type (2) in which, for example, the right end portion of both ends of the pattern in the x direction is reduced by the defect size Δx. FIG. 8C shows a defect type (3) in which the left end portion of both ends of the pattern, for example, in the x direction, is reduced by the defect size Δx. Although the x-direction end is shown here, there may be a similar defect type for the y-direction end.

FIG. 9 is a diagram showing another example of the defect type and the defect size of the evaluation pattern in the first embodiment. FIG. 9A shows a defect type (4) in which, for example, both ends of the pattern in the x direction are both increased by the defect size Δx. FIG. 9B shows a defect type (5) in which, for example, the right end of both ends of the pattern in the x direction is increased by the defect size Δx. FIG. 9C shows a defect type (6) in which, for example, the left end portion of both ends of the pattern in the x direction is increased by the defect size Δx. Although the x-direction end is shown here, there may be a similar defect type for the y-direction end.

FIG. 10 is a diagram showing another example of the defect type and the defect size of the evaluation pattern in the first embodiment. In FIG. 10A, a defect type (7) in which a recess (notch) having a defect size Δx in the x direction and a defect size Δy in the y direction is formed in a part of the left end portion of both ends of the pattern, for example, in the x direction. Is shown. In FIG. 10B, a defect type (8) in which a convex portion (protrusion) having a defect size Δx in the x direction and a defect size Δy in the y direction is formed in a part of the left end portion of both ends of the pattern, for example, in the x direction. Is shown. Although the x-direction end is shown here, there may be a similar defect type for the y-direction end. Further, although only one end of both ends is shown, there may be a similar defect type for the other end.

FIG. 11 is a diagram showing another example of the defect type and the defect size of the evaluation pattern in the first embodiment. FIG. 11A shows a defect type (9) in which a rectangular pattern having a defect size Δx in the x direction and a defect size Δy in the y direction is connected to, for example, an upper corner portion of the pattern in the x direction. FIG. 11B shows a defect type (10) in which a recess (notch) having a defect size Δx in the x direction and a defect size Δy in the y direction is formed at the upper corner portion of the pattern, for example, in the x direction. Although one corner of the four corners of the pattern is shown here, the same defect type may be present for the remaining other corners.

FIG. 12 is a diagram showing another example of the defect type and the defect size of the evaluation pattern in the first embodiment. FIG. 12A shows a defect type (11) in which, for example, a recess (cutout) having a defect size Δx in the x direction and a defect size Δy in the y direction is formed in the central portion of the pattern. FIG. 12B shows a defect type (12) in which a rectangular pattern having a defect size Δx in the x direction and a defect size Δy in the y direction is arranged in the vicinity of the periphery of the pattern with a gap.

A pattern group of each pattern type having a variable pattern size, arrangement pitch, defect type, and defect size as described above is formed on the reference mask substrate 300. In the example of FIG. 5, for example, with respect to the hole pattern (A), a plurality of hole pattern groups in which the defect types are sequentially changed in the x direction and the defect sizes are sequentially increased in the y direction are further formed in the x direction. The arrangement pitch is increased in order, and the pattern size is increased in order in the y direction. Similarly, for the pillar pattern (B), a plurality of pillar pattern groups in which the defect type is sequentially changed in the x direction and the defect size is increased in order in the y direction are further arranged and pitched in the x direction. The patterns are arranged so as to increase in order and increase the pattern size in order toward the y direction. Similarly, for the line and space (L / S) pattern (C) arranged in the x direction, a plurality of L / S patterns in which the defect type is sequentially changed in the x direction and the defect size is increased in order in the y direction. The group is further arranged so that the arrangement pitch is increased in order toward the x direction and the pattern size is increased in order toward the y direction. Similarly, for the L / S patterns (D) arranged in the y direction, a plurality of L / S pattern groups in which the defect types are sequentially changed in the x direction and the defect sizes are sequentially increased in the y direction are further formed. The arrangement pitch is increased in order toward the x direction, and the pattern size is increased in order toward the y direction.

The evaluation pattern formed on the reference mask substrate 300 as described above is imaged with an optical image by the optical image acquisition mechanism 150 set in the exposure image inspection mode (2) in the inspection apparatus 100. Further, the pattern data of the design evaluation pattern that is the basis for forming the evaluation pattern on the reference mask substrate 300 is input from the outside of the inspection device 100 and stored in the storage device 109. Then, the reference image of the evaluation pattern is created by the reference image creation circuit 112.

On the other hand, on the standard device side (not shown) to be compared with the inspection device 100, the width dimension CD of the pattern is measured for each pattern of the evaluation pattern, and the dimensional change rate is calculated for each pattern of the evaluation pattern. The dimensional change rate is defined by, for example, a value obtained by dividing the difference obtained by subtracting the design CD dimension from the CD dimension of the measured image (spatial image) by the design CD dimension (or a% value obtained by multiplying such a value by 100). To. When calculating the dimensional change rate on the inspection device 100 side, for example, the difference obtained by subtracting the CD dimension of the reference image from the CD dimension of the optical image is divided by the CD dimension of the reference image (or 100 is added to the value). It can be defined by multiplying by% value).

FIG. 13 is a diagram showing an internal configuration of the correction table creation circuit according to the first embodiment. In FIG. 13, a storage device 40, 42, 44 such as a magnetic disk device, a correction threshold value search unit 46, and a correction table creation unit 48 are arranged in the correction table creation circuit 144 according to the first embodiment. Each "-unit" such as the correction threshold value search unit 46 and the correction table creation unit 48 has a processing circuit. Such processing circuits include, for example, electrical circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices. For each "-part", a common processing circuit (same processing circuit) may be used, or different processing circuits (separate processing circuits) may be used. The information input / output to the correction threshold value search unit 46 and the correction table creation unit 48 and the information being calculated are stored in a memory (not shown) each time.

FIG. 14 is a diagram for explaining a method for measuring the line width dimension in the first embodiment. In FIG. 14, the obtained optical image is obtained as a gradation value (pixel value: image intensity) for each pixel. Therefore, as shown in FIG. 14, the vertical axis shows the gradation value (pixel value: image intensity) and the horizontal axis. It is acquired as gradation profile data indicating the position on the axis. By measuring the inter-AB dimension from the gradation value profile of the pattern in the optical image at the measurement threshold Th, where the inter-EF dimension in FIG. 14 becomes the desired design width dimension in the gradation value profile of the pattern in the reference image. , The width dimension CD of the pattern in the optical image can be obtained.

As described above, the standard device and the inspection device 100 in the first embodiment may not match the obtained dimensional change rates even though the same pattern is measured. Therefore, in the first embodiment, in the gradation value profile of the pattern in the reference image, each pattern of the evaluation pattern is used instead of the preset measurement threshold Th of the dimension between the EFs in FIG. 14 to be the desired design width dimension. , Search for a measurement threshold Th'that gives a dimensional change rate that matches the dimensional change rate obtained with the standard device.

Therefore, first, the optical image data of each pattern of the evaluation patterns acquired by the optical image acquisition mechanism 150 set in the exposure image inspection mode (2) is output to the correction table creation circuit 144, and the position circuit 107. It is stored in the storage device 40 together with the position information calculated by. Further, the data of the reference image of each pattern of the created evaluation pattern is output to the correction table creation circuit 144, and is stored in the storage device 42 together with the position information on the design data. Further, the dimensional change rate data of each pattern of the evaluation pattern obtained by the standard device is input from the outside of the inspection device 100 and stored in the storage device 44.

As the correction threshold search step (S92), first, the correction threshold search unit 46 uses the optical image data, the reference image data, and the dimensional change rate data obtained by the standard device for each pattern of the evaluation pattern. Read from the corresponding storage device and search for the measurement threshold Th'that is the CD dimension of the optical image and the CD dimension of the reference image that have a dimensional change rate that matches the dimensional change rate obtained by the standard device.

As the correction table creation step (S94), the correction table creation unit 48 creates a correction table 32 in which the correction threshold value corrected by the measurement threshold value Th for measuring the dimensions of the pattern is defined.

FIG. 15 is a diagram showing an example of the format of the correction table in the first embodiment. On the correction table 32, an optical image obtained from a reference mask substrate 300 as a reference by using the exposure image inspection optical system (exposure image optical image acquisition mechanism: second optical image acquisition mechanism) of the inspection device 100 is used. And an optical image obtained from the same reference mask substrate 300 using a standard device as an external image acquisition device, and a correction threshold set by using are defined. Specifically, as shown in FIG. 15, the correction table creation unit 48 is related to a pattern type, a pattern size, an arrangement pitch, a defect type, a defect size, a dimensional change rate obtained by a standard device, and a correction threshold value. As described above, the correction table 32 is created. As the correction threshold value, the searched measurement threshold value Th'itself may be used, or the measurement threshold value Th in which the inter-EF dimension of FIG. 14 preset by the inspection device 100 becomes the desired design width dimension is searched for. It may be the amount of change (for example, a difference value or an added value) for achieving the measurement threshold Th', or the rate of change. In other words, the correction table 32 is in an optical image obtained from the reference mask substrate 300 using the exposure image inspection optical system (exposure image optical image acquisition mechanism: second optical image acquisition mechanism) of the inspection device 100. Correction in which the measurement threshold Th is corrected so that the dimensional change rate of the pattern matches the dimensional change rate of the pattern in the optical image obtained from the same reference mask substrate 300 using a standard device as an external image acquisition device. A threshold is defined. In other words, the correction table 32 is obtained by a standard device which is an external image acquisition device different from the exposure image inspection optical system (exposure image optical image acquisition mechanism: second optical image acquisition mechanism) of the inspection device 100. Based on the obtained data, the dimensions of the pattern in the exposure transfer simulated image (exposure image image: second optical image) simulating the transfer pattern image acquired by the exposure image inspection optical system of the inspection device 100 are measured. A correction threshold in which the measurement threshold Th is corrected is defined. The created correction table 32 is output to the comparison circuit 108.

After the above pre-inspection process is completed, the substrate 101 to be actually inspected is inspected.

When the normal inspection mode (1) in which a high-magnification pattern image is imaged and the pattern image is inspected is selected in the mode selection step (S102), in the normal inspection mode (1), each step of FIG. 4 is performed. Of these, the squeeze release step (S104), the inspection illumination optical system placement step (S106), the scan step (S108), the reference image creation step (S110), the frame division step (S112), and the comparison step (S114). ) And each process.

When the exposure image inspection mode (2) is selected in the mode selection step (S102), in the exposure image inspection mode (2), among the steps of FIG. 4, the aperture step (S204) and the illumination optical system for exposure are selected. The placement process (S206), the defect candidate information input process (S208), the scanning process (S210), the reference image creation process (S212), the correction threshold calculation process (S214), the CD measurement process (S216), and the process. Each step of the CD measurement step (S218), the dimensional change rate calculation step (S220), and the determination step (S222) is carried out.

Therefore, first, in the mode selection step (S102), one of the normal inspection mode (1) and the exposure image inspection mode (2) is selected. For example, one of the inspection modes (1) and (2) may be selected from a keyboard, mouse, touch panel, etc. (not shown). Then, the information of the selected inspection mode is output to the mode switching control circuit 140 under the control of the control computer 110. The mode switching control circuit 140 switches the arrangement of the inspection optical system and the like according to the input inspection mode information. In the first embodiment, the normal inspection mode (1) is first selected.

As a squeezing release step (S104), the mode switching control circuit 140 increases the diameter of the opening of the aperture 173 and increases the light flux that can pass through, so that the NAo of the objective lens 171 is inspected at a normal high resolution. Make it equal. For example, the NAo of the objective lens of the inspection device 100 is set to, for example, NAo = 0.9. Alternatively, the opening of the aperture 173 may be completely opened. If the diameter of the opening of the diaphragm 173 has already been increased (or completely opened), such a step may be omitted.

As an inspection illumination optical system arrangement step (S106), under the control of the mode switching control circuit 140, the illumination shape switching mechanism 181 uses the shape of the illumination light (inspection light) for transmission inspection during normal inspection. The optical element for illumination of the exposure apparatus is moved from the optical path to the outside of the optical path so as to have an illumination shape. Alternatively, the optical element including a lens, a mirror, etc. is switched for normal inspection. If the lighting shape is already used for normal inspection, this step may be omitted.

FIG. 16 is a diagram showing an example of the configuration of the normal inspection optical system and the configuration of the exposure image inspection optical system according to the first embodiment. FIG. 16 shows a part of the configuration of FIG. It should be noted that the scales and the like of the positions of the configurations of FIGS. 1 and 16 do not match. FIG. 16A shows an example of the configuration of a normal inspection optical system. In the normal inspection optical system (inspection optical image acquisition mechanism: first optical image acquisition mechanism), the illumination shape of the transmission inspection illumination optical system 170 is controlled by the illumination shape switching mechanism 181 to the illumination shape used during normal inspection. ing. Then, the squeezing is released so that the numerical aperture NAo (numerical aperture on the object o side) of the objective lens 171 that can be incident when the transmitted light is incident from the substrate 101 to the magnifying optical system 104 is, for example, NAo = 0.9. ing. An example of the configuration of the exposure image inspection optical system shown in FIG. 16B will be described later.

As the scanning step (S108), an optical image configured in a normal inspection optical system (inspection optical image acquisition mechanism: first optical image acquisition mechanism) by each step of the above-mentioned squeezing release and inspection illumination optical system arrangement. The acquisition mechanism 150 irradiates the substrate 101 (exposure mask substrate) on which the pattern is formed with illumination light, and uses the transmitted light or the reflected light obtained from the substrate 101 to obtain an optical image of the pattern (first optical image). ). Specifically, it operates as follows.

In FIGS. 1 and 16 (a), a laser beam having a wavelength below the ultraviolet region (for example, DUV light) to be inspection light is generated from the light source 103. The generated light is illuminated by the illumination shape switching mechanism 181 by the projection lens 180, and the illumination light (first illumination light) having the illumination shape used at the time of normal inspection by the illumination shape switching mechanism 181 is the imaging lens. By 182, an image is formed on the pattern forming surface of the substrate 101 from the back surface side opposite to the pattern forming surface of the substrate 101. The transmitted light (mask pattern image) transmitted through the substrate 101 is incident on the objective lens 171 and advances to the imaging lens 176 via the projection lens 172 by the objective lens 171. Then, the imaging lens 176 forms an image of transmitted light (mask pattern image) on the light receiving surface of the photodiode array 105. Then, the photodiode array 105 captures the image formed. During such a scanning operation, the XYθ table 102 is continuously moving.

It should be noted that a reflection test may be used instead of the transmission test. For that purpose, the light generated from the light source 103 is divided into two light rays having different orbits by a half mirror (not shown), and one light ray is incident on the reflection inspection illumination optical system 175 (reflection illumination optical system). The other light beam may proceed to the transmission inspection illumination optical system 170 (transmission illumination optical system) described above. Alternatively, it may be blocked. The reflection inspection illumination optical system 175 (reflection illumination optical system) illuminates a beam splitter (not shown) with a light beam, and the beam splitter reflects the light beam and enters the objective lens 171. The objective lens 171 forms an image of the incident light rays on the pattern forming surface of the substrate 101. Then, the reflected light (mask pattern image) reflected from the substrate 101 is incident on the objective lens 171 and advances to the imaging lens 176 via the projection lens 172 by the objective lens 171. Then, the imaging lens 176 forms an image of transmitted light (mask pattern image) on the light receiving surface of the photodiode array 105. Then, the photodiode array 105 captures the image formed. Alternatively, simultaneous inspection of transmission and reflection may be performed. In such a case, two photodiode arrays may be prepared so that one receives the transmitted light from the substrate 101 and the other receives the reflected light from the substrate 101 at the same time. By slightly shifting the irradiation position of the substrate 101 between the transmission inspection light and the reflection inspection light, the trajectories of the transmitted light and the reflected light may be shifted. This makes it possible to simultaneously capture both the transmitted image and the reflected image of the pattern.

FIG. 17 is a conceptual diagram for explaining the inspection area in the first embodiment. As shown in FIG. 17, the inspection region 10 (entire inspection region) of the 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 device 100 acquires an image (stripe region image) for each inspection stripe 20. For each of the inspection stripes 20, a laser beam is used to capture an image of a graphic pattern arranged in the stripe region in the longitudinal direction (x direction) of the stripe region. By moving the XYθ table 102, the substrate 101 is moved in the x direction, and as a result, an optical image is acquired while the photodiode array 105 moves continuously in the −x direction. The photodiode array 105 continuously captures an optical image having a scan width W as shown in FIG. In other words, the photodiode array 105, which is an example of the sensor, captures an optical image of the pattern formed on the substrate 101 using the inspection light while moving relative to the XYθ table 102. In the first embodiment, after the optical image of one inspection stripe 20 is captured, the optical image of the scan width W is similarly moved to the position of the next inspection stripe 20 in the y direction and this time in the opposite direction. Images are taken continuously. That is, the imaging is repeated in the forward (FWD) -back forward (BWD) directions in the opposite directions on the outward and return paths.

Here, the direction of imaging is not limited to the repetition of forward (FWD) -back forward (BWD). You may take an image from one direction. For example, FWD-FWD may be repeated. Alternatively, BWD-BWD may be repeated.

The image of the 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), it is preferable to use, for example, a dynamic range in which the maximum gradation is when the amount of illumination light is 60% incident on the dynamic range of the photodiode array 105.

Further, when acquiring the optical image of the inspection stripe 20, the laser length measuring 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 (calculation unit) calculates the irradiation position of the illumination light of the substrate 101 by using the measured position information.

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

As the reference image creation step (S110), in the reference image creation circuit 112, the inspection stripe 20 is, for example, based on the pattern data defined in the design data (drawing data) that is the basis for forming the pattern on the substrate 101. A reference image is created for each frame area 30 of a plurality of frame areas 30 divided by the same width as the scan width W. Specifically, it operates as follows. First, the pattern data defined in the design data (drawing data) is read from the storage device 109 through the control computer 110, and each graphic pattern defined in the read design pattern data is converted into binary or multi-valued image data. do.

Here, the figure defined in the design pattern data is, for example, a figure having a rectangle or a triangle as a basic figure, for example, a figure such as a coordinate (x, y), a side length, a rectangle or a triangle at a reference position of the figure. Graphical data that defines the shape, size, position, etc. of each pattern graphic is stored with information such as a graphic code that serves as an identifier for distinguishing species.

When the design pattern data to be the graphic data is input to the reference image creation circuit 112, the data is expanded to the data for each graphic, and the graphic code indicating the graphic shape of the graphic data, the graphic dimension, and the like are interpreted. Then, it is developed into binary or multi-valued design pattern image data as a pattern arranged in the squares having a grid of predetermined quantized dimensions as a unit and output. In other words, the design data is read, the occupancy rate of the figure in the design pattern is calculated for each cell created by virtually dividing the inspection area into cells with a predetermined dimension as a unit, and the n-bit occupancy rate data is obtained. Output. For example, it is preferable to set one square as one pixel. Then, assuming that one pixel has a resolution of 1/28 ⁽ = 1/256), a small area of 1/256 is allocated to the area of the figure arranged in the pixel to determine the occupancy rate in the pixel. Calculate. Then, it is output to the reference circuit 112 as 8-bit occupancy rate data. Such squares (inspection pixels) may be matched with the pixels of the measurement data.

Next, the reference image creation circuit 112 applies an appropriate filter process to the design image data of the design pattern, which is the image data of the figure. Since the optical image data as a measurement image is in a state in which a filter is acted by the optical system, in other words, in an analog state in which the image intensity (shade value) changes continuously, the image intensity (shade value) becomes the design image data on the design side of the digital value. By applying a filtering process, it can be adjusted to the measured data. The image data of the created reference image is output to the comparison circuit 108 together with the position information on the design data, and is stored in a memory (not shown).

FIG. 18 is a diagram showing an example of the internal configuration of the comparison circuit according to the first embodiment. In FIG. 18, in the comparison circuit 108, a storage device such as a magnetic disk device 50, 52, 56, 57, 60, 61, 62, 68, a frame division unit 54, an alignment unit 58, a comparison processing unit 59, and a defect. The information interpretation unit 64, the measurement threshold calculation unit 66, the CD measurement units 70 and 72, the dimensional change rate calculation unit 74, and the comparison processing unit 76 are arranged. Each "... The unit has a processing circuit. Such processing circuits include, for example, electrical circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices. For each "-part", a common processing circuit (same processing circuit) may be used, or different processing circuits (separate processing circuits) may be used. Input / output to the frame division unit 54, alignment unit 58, comparison processing unit 59, defect information interpretation unit 64, measurement threshold calculation unit 66, CD measurement units 70 and 72, dimensional change rate calculation unit 74, and comparison processing unit 76. Information and information being calculated are stored in a memory (not shown) each time.

The data of the reference image sent to the comparison circuit 108 is stored in the storage device 50. Further, the data of the stripe area image sent to the comparison circuit 108 is stored in the storage device 52. Further, the correction table 32 sent to the comparison circuit 108 is stored in the storage device 68.

As the frame division step (S112), the frame division unit 54 reads out the stripe area image and divides the stripe area image in the x direction by a predetermined size (for example, the same width as the scan width W). For example, it is divided into a frame image of 512 × 512 pixels. As a result, the inspection stripe 20 can acquire a frame image of each frame area 30 for a plurality of frame areas 30 divided by the same width as the scan width W, for example. The frame image is stored in the storage device 56.

As a comparison step (S114), first, the alignment unit 58 uses a predetermined algorithm for a frame image (first optical image) to be compared and a reference image (first reference image) to be compared. Perform alignment. For example, alignment is performed using the method of least squares.

The comparison processing unit 59 (comparison unit) compares the reference image (first reference image) corresponding to the acquired frame image (first optical image) with the frame image (first optical image). Thereby, the presence or absence of defects in the frame image (first optical image) is determined. Specifically, the comparison processing unit 59 compares the aligned frame image (first optical image) and the reference image to be compared (first reference image) pixel by pixel. Using a predetermined determination threshold value, the two are compared for each pixel according to a predetermined determination condition, and the presence or absence of a defect such as a shape defect is determined. For example, if the gradation value difference for each pixel is larger than the preset determination threshold value, it is determined as a defect candidate. Then, the comparison result is output. The comparison result may be output to the storage device 57, the monitor 117, and the memory 118. Alternatively, it may be output from the printer 119.

In the above-mentioned example, the "die to database (die-database) inspection" for comparing the reference image and the optical image created from the design data (drawing data) on which the pattern is formed on the substrate 101 has been described. It is not limited to this. You may perform "die to die (die-die) inspection" comparing optical image data which imaged the same pattern in different places on the same substrate 101.

For example, the striped area image described above may include images of two dies with the same pattern formed. Therefore, in the case of the die-die inspection, the frame image of the frame area 30 of the die (2) corresponding to the frame image of the frame area 30 of the die (1) is similarly generated. Here, for example, the frame image of the frame area 30 of the die (2) becomes a reference image (first reference image) corresponding to the frame image of the frame area 30 of the die (1). Then, the alignment unit 58 aligns between the frame image of the die (1) and the frame image of the die (2). Then, the comparison processing unit 59 compares the frame image of the die (1) and the frame image of the die (2) for each pixel. The comparison result may be output to the storage device 57, the monitor 117, and the memory 118. Alternatively, it may be output from the printer 119.

As described above, the inspection device 100 inspects the presence or absence of defects in the pattern formed on the substrate 101, and acquires the defective portion. However, as described above, it can be used as an integrated circuit as long as it is not caused by a defect such as a circuit disconnection or / or a short circuit on the wafer when the mask pattern is transferred onto the wafer by an actual exposure apparatus. Is. However, even if there is no disconnection or / or short circuit at the stage of the mask substrate, it is necessary to exclude those in a state where there is a high possibility that the disconnection / / and short circuit will occur by using the mask substrate. Therefore, the above-mentioned dimensional change rate is used as a parameter for such determination. Therefore, in the inspection device 100 of the first embodiment, following the normal inspection in the normal inspection mode (1), the exposure image inspection in the exposure image inspection mode (2) is performed on the defective portion.

Therefore, the process returns to the mode selection step (S102), and this time, the exposure image inspection mode (2) is selected. The information of the selected inspection mode is output to the mode switching control circuit 140 under the control of the control computer 110. The mode switching control circuit 140 switches the arrangement of the inspection optical system and the like according to the input inspection mode information.

As a diaphragm step (S204), the mode switching control circuit 140 narrows the diameter of the opening of the diaphragm 173 and narrows the light flux that can pass through to make the NAo of the objective lens 171 equal to the objective lens 302 of the exposure device. For example, the NAo of the objective lens of the inspection device 100 is set to, for example, NAo = 0.35.

As an exposure illumination optical system arrangement step (S206), under the control of the mode switching control circuit 140, the illumination shape switching mechanism 181 has an illumination shape used in the exposure apparatus for the shape of the illumination light (inspection light) for transmission inspection. The optical elements including the lens, the mirror, and the like are switched so as to have the same illumination shape as the above. Such optical elements may be arranged in advance so as to be switchable according to the illumination conditions of the exposure apparatus.

FIG. 16B described above shows an example of the configuration of the optical system for exposure image inspection. As shown in FIG. 16B, in the exposure image inspection optical system (exposure image optical image acquisition mechanism: second optical image acquisition mechanism), the illumination shape of the transmission inspection illumination optical system 170 is used in the exposure apparatus. The optical element is controlled by the illumination shape switching mechanism 181 so as to have an illumination shape similar to the illumination shape. Then, the luminous flux is squeezed so that the numerical aperture NAo (numerical aperture on the object o side) of the objective lens 171 that can be incident when the transmitted light is incident from the substrate 101 to the magnifying optical system 104 is, for example, NAo = 0.35. ing.

As the defect candidate information input step (S208), the control computer 110 reads out the inspection result data of the normal defect inspection from the storage device 57, and inputs the information of the defect (currently, the defect candidate) determined to be a defect. The information on the defective portion includes the position (coordinates) of the defective portion, the design data of the pattern of the defective portion, and the data of the frame image including the defective portion. The information on the defective portion is output to the comparison circuit 108, the exposure simulation reference image creation circuit 142, and the table control circuit 114. For example, the defect location information output to the comparison circuit 108 is stored in the storage device 61.

Then, the table control circuit 114 sets the illumination position of the inspection light to be the imaging start position of the region including the defective portion (for example, the frame region 30), or to be near the front of the defective portion with respect to the imaging direction. The XYθ table 102 is moved. Alternatively, the table control circuit 114 moves the XYθ table 102 to the imaging start position of the inspection stripe 20 including the defective portion. Here, as an example, the XYθ table 102 is moved so that the illumination position of the inspection light becomes the imaging start position of the frame region 30 including the defective portion.

As the scanning step (S210), the optics configured in the exposure image inspection optical system (exposure image optical image acquisition mechanism: second optical image acquisition mechanism) by each step of the above-mentioned squeezing and exposure illumination optical system arrangement. The image acquisition mechanism 150 is an exposure transfer simulated image simulating a transfer pattern image formed on a sample when a pattern is exposed and transferred to a sample (for example, a semiconductor wafer) for a defect portion determined to be a defect by inspection. An optical image (second optical image) is acquired. Specifically, the image is taken as follows.

In FIGS. 1 and 16B, the laser beam having a wavelength below the ultraviolet region (for example, DUV light), which is the inspection light generated from the light source 103, is illuminated by the projection lens 180 on the illumination shape switching mechanism 181 to illuminate. Illumination light (second illumination light) having an illumination shape similar to that used in the exposure apparatus by the shape switching mechanism 181 is emitted from the back surface side opposite to the pattern forming surface of the substrate 101 by the imaging lens 182. An image is formed on the pattern forming surface of the substrate 101. The transmitted light (mask pattern image) transmitted through the substrate 101 is focused by the squeezing 173, then enters the objective lens 171 and advances to the imaging lens 176 via the projection lens 172 by the objective lens 171. Then, the imaging lens 176 forms a transmitted light (exposure image image) on the light receiving surface of the photodiode array 105. Then, the photodiode array 105 captures the image formed. During such a scanning operation, the XYθ table 102 is continuously moving.

Further, when acquiring an optical image (exposure image image: second optical image) as an exposure transfer simulated image of a defect region (for example, a frame region 30 or an inspection stripe 20) including a defect portion, the laser length measuring system 122 , XYθ Measure the position of the table 102. The measured position information is output to the position circuit 107. The position circuit 107 calculates the irradiation position of the illumination light of the substrate 101 by using the measured position information.

After that, the exposure image image (exposure transfer simulated image: second optical image) of the defect region including the defect portion is sent to the comparison circuit 108 together with the data indicating the position on the substrate 101 output from the position circuit 107. The measurement data (pixel data) is, for example, 8-bit unsigned data, and represents the gradation (light amount) of the brightness of each pixel. The exposure image image output in the comparison circuit 108 is stored in the storage device 62.

As the reference image creation step (S212), the exposure simulation reference image creation circuit 142 is obtained when the pattern at the defective portion is exposed and transferred by the exposure apparatus based on the pattern data defined in the design data (drawing data). The expected exposure simulation reference image (second reference image) is created. The exposure simulation reference image is created with the same size as the exposure image image, for example, a size suitable for the frame area 30. First, the pattern data defined in the design data (drawing data) is read from the storage device 109 through the control computer 110, and each graphic pattern defined in the read design pattern data is converted into binary or multi-valued image data. do. In such a case, it is preferable to set a conversion function for generating an image in advance by simulation or the like so as to obtain a shape obtained by exposure transfer. The image data of the created exposure simulation reference image is output to the comparison circuit 108 together with the position information on the design data and stored in the memory 60.

As the correction threshold calculation step (S214), first, the defect information interpretation unit 64 reads the information (defect information) of the defect location from the storage device 61 and interprets the defect information. Here, the pattern type, pattern size, placement pitch, defect type, and defect size of the pattern that is regarded as a defect are interpreted. For example, the pattern type, pattern size, and placement pitch of the pattern are interpreted from the design data of the pattern at the defect location. Then, the defect type and the defect size of the defect generated in the pattern are interpreted from the data of the frame image including the defect location.

The measurement threshold value calculation unit 66 reads the correction table 32 from the storage device 68, and the correction threshold value corresponding to (or closest to) the pattern type, pattern size, arrangement pitch, defect type, and defect size interpreted from the information of the defect location. Is calculated (or searched). When it corresponds to between two correction threshold values, it is also preferable to obtain the correction threshold value linearly interpolated by calculation. The obtained correction threshold value is output to the CD measuring units 70 and 72.

In the CD measurement step (S216), the CD measurement unit 70 uses the calculated correction threshold value to measure the measurement pattern dimension of the pattern at the defect portion from the optical image (exposure image image: second optical image) which is an exposure transfer simulated image. (CD size of optical image) is measured. When the correction threshold value is defined as the measurement threshold value Th'itself, the CD measurement unit 70 is cut between A'B'cut by the measurement threshold value Th'in the gradation profile of the optical image to be the exposure transfer simulated image shown in FIG. Measure the dimensions. When the correction threshold value is defined as a change amount (for example, a difference value or an addition value) from the measurement threshold value Th preset in the inspection device 100, the CD measurement unit 70 uses the measurement threshold value preset in the inspection device 100. With the measurement threshold value Th'in which the correction threshold value is added to Th or the measurement threshold value is subtracted from the measurement threshold value Th, the dimension between A'B'cut out in the gradation profile of the optical image to be the exposure transfer simulated image shown in FIG. 14 is measured. When the correction threshold value is defined as the rate of change from the measurement threshold value Th preset in the inspection device 100, the CD measurement unit 70 obtains the measurement threshold value Th preset in the inspection device 100 by multiplying the correction threshold value. With the measured threshold value Th', the dimension between A'B'that is cut out in the gradation profile of the optical image that is the exposure transfer simulated image shown in FIG. 14 is measured.

In the CD measurement step (S218), the CD measurement unit 72 uses the calculated correction threshold value to display the reference pattern dimension (CD dimension of the reference image) of the pattern corresponding to the defect portion from the exposure simulated reference image (second reference image). ) Is measured. When the correction threshold value is defined as the measurement threshold value Th'itself, the CD measurement unit 72 measures the E'F'interval dimension cut out at the measurement threshold value Th'in the gradation profile of the exposure simulation reference image shown in FIG. .. When the correction threshold value is defined as a change amount (for example, a difference value or an addition value) from the measurement threshold value Th preset in the inspection device 100, the CD measurement unit 72 uses the measurement threshold value preset in the inspection device 100. With the measurement threshold value Th'in which the correction threshold value is added to Th or the measurement threshold value is subtracted from the measurement threshold value Th, the E'F'interval dimension cut out in the gradation profile of the exposure simulation reference image shown in FIG. 14 is measured. When the correction threshold value is defined as the rate of change from the measurement threshold value Th preset in the inspection device 100, the CD measurement unit 70 obtains the measurement threshold value Th preset in the inspection device 100 by multiplying the correction threshold value. With the measured threshold value Th', the E'F' dimension cut out in the gradation profile of the exposure simulation reference image shown in FIG. 14 is measured.

In the dimensional change rate calculation step (S220), the dimensional change rate calculation unit 74 uses an optical image (exposure image image: second optical image) to be an exposure transfer simulated image using the correction threshold defined in the correction table 32. Using the measurement pattern size of the measured defect location pattern and the reference pattern dimension of the pattern corresponding to the defect location obtained from the exposure simulation reference image (second reference image) corresponding to the exposure transfer simulation image. , Calculate the dimensional change rate. The dimensional change rate is obtained by dividing the difference obtained by subtracting the reference pattern dimension (CD dimension) of the exposure simulation reference image from the measurement pattern dimension (CD dimension) of the exposure simulation reference image by the reference pattern dimension (CD dimension) of the exposure simulation reference image. It can be defined as a value (or a% value obtained by multiplying such a value by 100). The calculated dimensional change rate is output to the comparison processing unit 76. Alternatively, it may be further output to the storage device 109, the monitor 117, and the memory 118. Alternatively, it may be output from the printer 119.

As a determination step (S222), the comparison processing unit 76 compares and determines whether or not the calculated dimensional change rate is larger than the preset determination threshold value for each defect location. When the calculated dimensional change rate is larger than the preset determination threshold value, the defective portion is output to the storage device 109, the monitor 117, and the memory 118 as a true defective portion. Alternatively, it may be output from the printer 119. If the calculated dimensional change rate is not larger than the preset determination threshold value, it is excluded from the defect group determined as a defect as a pseudo defect.

FIG. 19 is a diagram for explaining the flow of pattern inspection between the first embodiment and the comparative example. FIG. 19A shows, as a comparative example, the flow of inspection when an inspection device that performs defect inspection without performing exposure image inspection is used. FIG. 19B shows an inspection flow when an exposure image inspection is performed by the inspection apparatus 100 of the first embodiment. In FIG. 19A, the substrate 101 such as an exposure mask is inspected for defects by a conventional inspection device. In the inspection device, even if a very small deviation occurs, it is determined that there is a pattern defect, so that many defect locations occur. Information on the defective portion of such a large number of mask patterns is output to an external standard device 400 that inspects the exposure image using the spatial image. Then, the dimensional change rate is calculated for each of these many defective parts of the mask pattern. As a result, if all the locations are OK, the mask pattern is exposed and transferred to a sample such as a wafer by the exposure apparatus 500. On the contrary, if there is even one place where NG occurs, the mask will be repaired or discarded. A standard device using a spatial image takes time to measure. Therefore, if a spatial image is created for all the defective parts of a large number of mask patterns and an exposure image inspection is performed, the throughput in mask manufacturing becomes very poor.

On the other hand, as shown in FIG. 19B, in the first embodiment, even in the inspection device 100, the defect portion of the mask pattern determined to be a defect in the normal defect inspection is transferred by the exposure apparatus 500. The pattern image is reproduced and the dimensional change rate is calculated for each. As a result, the number of defective parts can be reduced in advance in the inspection device 100. Further, in the first embodiment, the measurement threshold value used for the dimensional measurement when calculating the dimensional change rate is corrected so as to match the dimensional change rate when measured by the external standard device 400. Therefore, the number of defective parts output to the external standard device 400 can be suppressed to a small number under the same determination conditions as that of the external standard device 400. Therefore, the time required for the defect confirmation work in the standard device 400 can be significantly reduced, and the throughput in mask manufacturing can be improved. Alternatively, the defect confirmation work in the standard device 400 may be omitted. Thereby, the throughput can be further improved.

As described above, according to the first embodiment, from the exposure transfer simulated image simulating the transfer pattern image when transferred by the exposure apparatus 500, the measurement result similar to that of the external image acquisition apparatus which is, for example, the standard apparatus 400. Can be obtained. Therefore, in the inspection device 100, it is possible to exclude the parts that can be used as an integrated circuit when the exposure is transferred from the plurality of parts where the defect is determined.

In the above description, each "-circuit" has a processing circuit, and as the processing circuit, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, or the like can be used. Further, a common processing circuit (same processing circuit) may be used for each "-circuit". Alternatively, different processing circuits (separate processing circuits) may be used. The program for executing the processor or the like 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 reference image creation circuit 112, the mode switching control circuit 140, the exposure simulation reference image creation circuit 142, the correction table creation circuit 144, and the like may be configured by at least one circuit described above. good.

The embodiment has been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, as the pattern dimension for obtaining the dimensional change rate, it is preferable to measure not only the dimension of the pattern portion such as a rectangle but also the space dimension between the pattern portions such as a plurality of rectangles. As a result, since the dimensional change rate of the distance between patterns can be obtained, a failure preliminary group such as a short circuit can be obtained by inspection.

Further, when an exposure image image is imaged, the transmitted light of the substrate 101 may be separated into a plurality of polarized waves, imaged for each deflection wave, and then combined while being weighted by a predetermined model function.

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

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

10 Inspection area 11 Transmitted light 12 Light 20 Inspection stripe 30 Frame area 32 Correction table 40, 42, 44 Storage device 46 Correction threshold search unit 48 Correction table creation unit 50, 52, 56, 57, 60, 61, 62, 68 Storage Device 54 Frame division unit 58 Alignment unit 59 Comparison processing unit 64 Defect information interpretation unit 66 Measurement threshold calculation unit 70, 72 CD measurement unit 74 Dimension change rate calculation unit 76 Comparison processing unit 100 Inspection device 101 Board 102 XYθ table 103 Light source 104 Magnifying optical system 105 Photodiode array 106 Sensor circuit 107 Position circuit 108 Comparison circuit 109 Magnetic disk device 110 Control computer 112 Reference image creation circuit 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 length measurement system 123 Stripe pattern memory 140 Mode switching control circuit 142 Exposure simulation reference image creation circuit 144 Correction table creation circuit 150 Optical image acquisition mechanism 160 Control system circuit 170 Transmission inspection Illumination optical system 171 Objective Lens 172 Projection lens 173 Aperture 175 Reflection inspection Illumination optical system 176 Imaging lens 180 Projection lens 181 Illumination shape switching mechanism 182 Imaging lens 300 Mask substrate 301 Transmitted light 302 Objective lens 304 Semiconductor substrate 305 Light 400 Standard device 500 Exposure device

Claims (5)

A first optical image acquisition that irradiates an exposure mask substrate on which a pattern is formed with illumination light and acquires a first optical image of the pattern by using the transmitted light or the reflected light obtained from the mask substrate. Mechanism and
A comparison unit for determining the presence or absence of defects in the first optical image by comparing the first reference image corresponding to the acquired first optical image with the first optical image.
A second optical image, which is an exposure transfer simulated image simulating a transfer pattern image formed on the sample when the pattern is exposed and transferred to the sample, is acquired for the defect portion determined to be a defect by the determination . 2 optical image acquisition mechanism and
The pattern in the second optical image is based on the data obtained by an external image acquisition device different from the second optical image acquisition mechanism that acquires the exposure transfer simulated image simulating the transfer pattern image. A storage device that stores a correction table in which a correction threshold is defined, in which the measurement threshold for measuring dimensions is corrected.
Obtained from the measurement pattern dimensions of the pattern of the defect portion measured from the second optical image using the correction threshold defined in the correction table, and the second reference image corresponding to the second optical image. A dimensional change rate calculation unit that calculates a dimensional change rate using a reference pattern dimension of a pattern corresponding to the defect location, and a dimensional change rate calculation unit.
A pattern inspection device characterized by being equipped with. The correction table uses an optical image obtained from a reference mask substrate using the second optical image acquisition mechanism and an optical image obtained from the reference mask substrate using the image acquisition device. The pattern inspection apparatus according to claim 1, wherein the correction threshold set is defined. The pattern according to claim 2, wherein a plurality of types of pattern groups composed of a plurality of patterns of the same type having different pattern sizes, arrangement pitches, defect types, and defect sizes are formed on the reference mask substrate. Inspection equipment. In the correction table, the dimensional change rate of the pattern in the optical image obtained from the reference mask substrate using the second optical image acquisition mechanism is obtained from the reference mask substrate using the image acquisition device. The pattern inspection apparatus according to claim 2, wherein the correction threshold is defined in which the measurement threshold is corrected so as to match the dimensional change rate of the pattern in the optical image. A step of irradiating an exposure mask substrate on which a pattern is formed with a pattern inspection device with illumination light and acquiring a first optical image of the pattern using the transmitted light or the reflected light obtained from the mask substrate. When,
By comparing the first reference image corresponding to the acquired first optical image with the first optical image by the pattern inspection apparatus, it is determined whether or not there is a defect in the first optical image. And the process to do
A second exposure transfer simulated image simulating a transfer pattern image formed on a sample when the pattern is exposed and transferred to a sample for a defect portion determined to be a defect by the pattern inspection device. And the process of acquiring an optical image of
The dimensions of the pattern in the second optical image are measured based on the data obtained by an external image acquisition device different from the pattern inspection device that acquires the exposure transfer simulated image simulating the transfer pattern image. The process of creating a correction table in which the correction threshold is corrected and the correction threshold is defined,
Obtained from the measurement pattern dimensions of the pattern of the defect portion measured from the second optical image using the correction threshold defined in the correction table, and the second reference image corresponding to the second optical image. A process of calculating and outputting a dimensional change rate using a reference pattern dimension of a pattern corresponding to the defect location, and a process of calculating and outputting the dimensional change rate.
A pattern inspection method characterized by being equipped with.

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