Pattern inspection device

Abstract

To provide a pattern inspection device that can move a substrate of an inspection object to a position away from a projection lens or objective lens, while suppressing an increase in size of a stage device.SOLUTION: A stage of a pattern inspection device has: a surface plate; a pair of a first fixed guide and a second fixed gude that extend in a first direction; first and second air sliders that are attached to the first fixed guide and the second fixed guide; a movement guide that has both ends coupled to the first and second air sliders, and extends in a second direction orthogonal to the first direction; a third air slider that is attached to the movement guide; a substrate holding part that has one end part in the first direction coupled to the third air slider, and has an air pad provided at the other end part; a guide plate that is fixed to the surface plate; and an objective lens that is positioned below the substrate holding part. When each of both ends in the first direction of a substrate and both ends in the second direction thereof is positioned above a center of the objective lens, the air pad is in a position where ejecting air hits the guide plate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pattern inspection apparatus.

Background Art

[0002] In recent years, with the increasing integration density and large capacity of large-scale integrated circuits (LSIs), the circuit line widths required for semiconductor elements have been becoming increasingly narrow. These semiconductor elements are manufactured by exposing and transferring a pattern onto a wafer using a reduction projection exposure apparatus called a stepper, so-called, using an original pattern (also referred to as a mask or reticle; hereinafter, collectively referred to as a mask) on which a circuit pattern is formed to form a circuit.

[0003] For the manufacture of LSIs that require a great deal of manufacturing cost, improvement in yield is essential. As one of the factors that reduce yield, there is a pattern defect of a mask used when exposing and transferring an ultrafine pattern onto a semiconductor wafer by photolithography technology. In recent years, with the miniaturization of LSI pattern dimensions formed on a semiconductor wafer, the dimensions that must be detected as pattern defects have also become extremely small. Therefore, higher precision of a pattern inspection apparatus for inspecting mask defects is required.

[0004] As inspection methods, for example, there are “die to die inspection” in which optical image data obtained by imaging the same pattern at different locations on the same mask are compared with each other, and “die to database inspection” in which drawing data (design data) converted into a device input format for input by a drawing apparatus when a pattern is drawn on a mask from CAD data designed with a pattern is input to an inspection apparatus, a reference image is generated based on this, and this is compared with an optical image that is measurement data obtained by imaging the pattern.

[0005] The pattern inspection apparatus places the mask to be inspected on a movable stage, irradiates it with a laser beam, positions the irradiation light projection lens and the inspection objective lens relative to each other, and acquires an optical image. By moving the stage between the projection lens and the objective lens, an optical image of the entire mask can be acquired.

[0006] An air slider is used for the stage that moves the mask. For example, as shown in FIG. 15, the stage 302 includes a pair of fixed guides 222 extending in the Y-axis direction fixed to the sliding surface 221 of the surface plate 220, a U-shaped cross-section Y slider 223 attached to each of the pair of fixed guides 222, a pair of moving guides 224a and 224b extending in the X-axis direction with both ends connected to the Y slider 223, a U-shaped cross-section X slider 225a attached to the moving guide 224a, an air pad 225b movable in the X-axis direction along the moving guide 224b, and a mask holding portion 226 with one end in the Y-axis direction connected to the X slider 225a and the other end connected to the air pad 225b. The objective lens 304 is erected and fixed on the sliding surface 221 of the surface plate 220, and the mask holding portion 226 is located above the objective lens 304. The upper end of the objective lens 304 is close to the mask holding portion 226.

[0007] By ejecting air from the Y slider 223 toward the fixed guide 222, the Y slider 223 slightly lifts from the surface of the fixed guide 222, and the Y slider 223 and the moving guides 224a and 224b can move in the Y-axis direction along the fixed guide 222. Also, by ejecting air from the X slider 225a and the air pad 225b toward the moving guides 224a and 224b, the X slider 225a and the air pad 225b slightly lift from the surface of the moving guides 224a and 224b, and the X slider 225a, the air pad 225b, and the mask holding portion 226 can move in the X-axis direction along the moving guides 224a and 224b. In this way, the mask 301 held by the mask holding portion 226 can move in the XY directions.

[0008] When replacing the mask 301 to be inspected, the mask 301 is moved to a position away from the projection lens (not shown) and the objective lens 304. For example, the Y slider 223 moves the pair of movement guides 224a, 224b, the X sliders 225a, the air pads 225b, and the mask holding part 226 in the Y-axis direction to move the mask 301 to a position away from the projection lens and the objective lens 304.

[0009] In a conventional pattern inspection apparatus, the distance between the projection lens and the objective lens 304 is narrow. When the mask 301 is moved to a position away from the lenses such as the projection lens and the objective lens 304, there is a risk that the X slider 225a or the air pad 225b, or the movement guide 224a or 224b may interfere (contact) with the lens. In order to avoid interference between the X slider and the like and the lens, even if the mask 301 is moved to a position away from the lens, the Y-direction size of the mask holding part 226 is increased so that the X slider and the like do not reach the lens, that is, the distance between the pair of movement guides 224a, 224b is increased. However, there is a problem of increasing the size of the stage apparatus.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to provide a pattern inspection apparatus capable of moving a substrate to be inspected to a position away from a projection lens or an objective lens while suppressing an increase in the size of a stage apparatus.

Means for Solving the Problems

[0012] A pattern inspection apparatus according to an aspect of the present invention includes a movable stage on which a substrate to be inspected is placed, virtually divides the substrate into a plurality of stripes in a strip shape along a predetermined direction, and acquires an optical image for each stripe. An optical image acquisition unit, a reference image generation unit that generates a reference image corresponding to the acquired optical image, and a comparison unit that compares the optical image and the reference image. The stage includes a surface plate, a first fixed guide and a second fixed guide that are fixed on the surface plate and arranged parallel to each other along a first direction, a first air slider attached to the first fixed guide, and a second air slider attached to the second fixed guide. A moving guide having one end connected to the first air slider and the other end connected to the second air slider and extending in a second direction orthogonal to the first direction, a third air slider attached to the moving guide, and one end in the first direction being connected to the third air slider. An air pad that ejects air upward or downward is provided at the other end in the first direction, a substrate holding unit that holds the substrate, a guide plate fixed to the surface plate, and an objective lens fixed to the surface plate and located below the substrate holding unit. When each of both ends of the substrate in the first direction and both ends in the second direction are located above the center of the objective lens, the air pad is at a position where the ejected air hits the guide plate.

Effects of the Invention

[0013] According to the present invention, while suppressing the enlargement of the stage device, the substrate to be inspected can be moved to a position away from the projection lens or the objective lens, and the replacement and maintenance of the substrate can be easily performed.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0016] FIG. 1 shows the configuration of a pattern inspection apparatus according to an embodiment. In FIG. 1, an inspection apparatus 100 for inspecting defects in a pattern formed on an inspection target substrate, for example, a mask, includes an optical image acquisition mechanism 150 and a control system circuit 160. Although only the transmission illumination optical system of the pattern inspection apparatus in FIG. 1 is illustrated, the inspection apparatus may also have a reflection illumination optical system. In that case, a light source, a beam splitter, a collimator lens, an imaging sensor, etc. (not shown) may be further added and configured to capture an image for reflection illumination inspection.

[0017] The optical image acquisition mechanism 150 includes a light source 103, an illumination lens 170, a stage 102 arranged to be movable, an objective lens 104, a TDI (Time Delay Integration) sensor 105, a sensor circuit 106, a stripe pattern memory 123, a laser length measurement system 122, and an auto loader 130. On the stage 102, a substrate 101 conveyed from the auto loader 130 is arranged. The substrate 101 includes, for example, a photomask for exposure that transfers a pattern onto a semiconductor substrate such as a wafer. Further, a plurality of graphic patterns to be inspected are formed on this photomask. The substrate 101 is arranged on the stage 102 with, for example, the pattern formation surface facing downward.

[0018] In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 is connected via a bus 120 to a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, an auto loader control circuit 113, a stage control circuit 114, magnetic disk devices 109, 131, a memory 111, a pattern monitor 118, and a printer 119.

[0019] The sensor circuit 106 is connected to the stripe pattern memory 123. The stripe pattern memory 123 is connected to the comparison circuit 108. The reference image creation circuit 112 is connected to the comparison circuit 108 by a dedicated cable 121.

[0020] A series of "~ circuits" such as the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the auto loader control circuit 113, and the stage control circuit 114 have a processing circuit. The processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device, etc.

[0021] For example, a series of "~ circuits" such as the position circuit 107, comparison circuit 108, reference image creation circuit 112, autoloader control circuit 113, and stage control circuit 114 may be configured and executed by the control computer 110. The input data or calculated results required for the position circuit 107, comparison circuit 108, reference image creation circuit 112, autoloader control circuit 113, and stage control circuit 114 are stored in a memory (not shown) within each circuit or in the memory 111 each time. A program for executing a processor or the like may be recorded on a recording medium such as a magnetic disk device 109 or a ROM (read-only memory).

[0022] In the inspection apparatus 100, a high-magnification inspection optical system is configured by a light source 103, a stage 102, an illumination lens 170, an objective lens 104, a TDI sensor 105, and a sensor circuit 106. The stage 102 is driven by a stage control circuit 114 under the control of the control computer 110. The stage 102 is movable by motors that drive in the X, Y, and Z directions. The moving position of the substrate 101 disposed on the stage 102 is measured by a laser length measurement system 122 and supplied to the position circuit 107.

[0023] The transfer process of the substrate 101 from the autoloader 130 to the stage 102 and the transfer process of the substrate 101 from the stage 102 to the autoloader 130 are controlled by the autoloader control circuit 113.

[0024] Drawing data (design data) serving as a basis for pattern formation of the substrate 101 to be inspected is input from outside the inspection apparatus 100 and stored in the magnetic disk device 109. A plurality of graphic patterns are defined in the drawing data, and each graphic pattern is usually composed of a combination of a plurality of element graphics. Note that there may be a graphic pattern composed of one graphic.

[0025] FIG. 2 is a conceptual diagram for explaining an inspection area. As shown in FIG. 2, the inspection area 10 (the entire inspection area) of the substrate 101 is virtually divided into a plurality of strip-shaped inspection stripes 12 having a scan width W of the TDI sensor 105 in, for example, the Y direction. And in the inspection apparatus 100, an image (strip area image) is acquired for each inspection stripe 12. For each of the inspection stripes 12, an image of a graphic pattern arranged in the inspection stripe 12 is captured in the longitudinal direction (X direction) of the stripe area using a laser beam (inspection light). In order to prevent omission of imaging, it is preferable that the plurality of inspection stripes 12 are set so that adjacent inspection stripes 12 overlap with each other with a predetermined margin width.

[0026] As the stage 102 moves, an optical image is acquired while the TDI sensor 105 moves continuously in the X direction relatively. The TDI sensor 105 continuously captures an optical image having a scan width W as shown in FIG. 2. In other words, the TDI sensor 105 captures an optical image on the surface of the substrate 101 on which a plurality of graphic patterns are formed while moving relatively in the integration direction of the TDI sensor 105. After capturing the optical image in one inspection stripe 12, it moves to the position of the next inspection stripe 12 in the Y direction and then moves in the reverse direction while continuously capturing an optical image having a scan width W in the same manner. That is, imaging is repeated in the forward (FWD)-backward (BWD) directions going in opposite directions for the forward and return paths.

[0027] Here, the imaging direction is not limited to the repetition of forward (FWD)-backward (BWD). Imaging may be performed from one direction. For example, repetition of FWD-FWD may be used. Alternatively, repetition of BWD-BWD may be used.

[0028] In the actual inspection, as shown in FIG. 2, the stripe area image of each inspection stripe 12 is divided into images of a plurality of rectangular frame areas 14. Then, inspections are carried out for each image of the frame area 14. For example, it is divided into sizes of 512×512 pixels. Therefore, the reference images to be compared with the frame images of the frame area 14 are also created for each frame area 14.

[0029] An air slider is used for the stage 102 that moves the substrate 101. For example, as shown in FIG. 3, the stage 102 has a surface plate 20, fixed guides 22, a Y slider 23, a moving guide 24, an X slider 25, a substrate holding portion 26, and an air holding portion 40. In FIG. 3, for convenience of explanation, a configuration for moving the substrate 101 in the XY directions is shown, and the illustration of the Z stage is omitted. Also, although the objective lens 104 located directly below the substrate holding portion 26 is shown, the illustration of the illumination lens 170 located directly above the substrate holding portion 26 is omitted.

[0030] On the sliding surface 21 of the surface plate 20, a pair of fixed guides 22, 22 (first fixed guide, second fixed guide) extending in the Y-axis direction are fixedly arranged. The pair of fixed guides 22, 22 are arranged in parallel.

[0031] To each of the pair of fixed guides 22, 22, Y sliders 23, 23 (first air slider, second air slider) which are air sliders having a U-shaped cross-sectional shape are attached. In the example shown in FIG. 3, the Y slider 23 is attached so as to face the upper surface and both side surfaces of the fixed guide 22.

[0032] The moving guide 24 extends in the X-axis direction orthogonal to the Y-axis direction, and both ends are connected to the pair of Y sliders 23, 23.

[0033] An X slider 25 (third air slider) which is an air slider having a U-shaped cross-sectional shape is attached to the moving guide 24. In the example shown in FIG. 3, the X slider 25 is attached so as to face the upper surface and both side surfaces of the moving guide 24.

[0034] The substrate holding part 26 is flat and holds the substrate 101 to be inspected. One end (rear end) of the substrate holding part 26 in the Y direction is connected to the X slider 25. An air pad 30 that ejects air in the vertical direction is provided at the other end (front end) of the substrate holding part 26 in the Y direction.

[0035] For example, as shown in FIGS. 4 and 5, the air pad 30 has pinholes 34 that penetrate the substrate holding part 26 in the thickness direction (vertical direction or Z direction). After the air supplied from the outside through the positive pressure tube 31 passes through the micro filter, it is ejected vertically from the pinholes 34. The positive pressure tube 31 is fixed to the Y slider 23, X slider 25, substrate holding part 26, etc. by a fixture 33. The micro filter 32 is fixed to the side surface of the substrate holding part 26.

[0036] The objective lens 104 is erected and fixed on the sliding surface 21 of the surface plate 20, and the substrate holding part 26 is located above the objective lens 104.

[0037] By ejecting air from the air outlet of the Y slider 23 toward the fixed guide 22, the Y slider 23 slightly lifts off from the surface of the fixed guide 22 and becomes movable along the fixed guide 22.

[0038] By ejecting air from the air outlet of the X slider 25 toward the moving guide 24, the X slider 25 slightly lifts off from the surface of the moving guide 24 and becomes movable along the moving guide 24.

[0039] As a result, the substrate holding part 26 can move above the objective lens 104 in the X direction and the Y direction.

[0040] The air holding part 40 has a columnar part 41 erected on the sliding surface 21 of the surface plate 20, and a pair of guide plates 42, 43 arranged at the upper end of the columnar part 41. The air holding part 40 is installed on the opposite side of the moving guide 24 and the X slider 25 with the objective lens 104 interposed therebetween. The columnar part 41 is fixed to the surface plate 20. The guide plate 42 is fixed to the upper end of the columnar part 41 and protrudes (extends) toward the X slider 25 side in the Y-axis direction from the columnar part 40. The guide plate 43 has dimensions similar to those of the guide plate 42 and is arranged such that its lower surface faces the upper surface of the guide plate 42.

[0041] The guide plate 42 is located lower than the substrate holding part 26. The guide plate 43 is located higher than the substrate holding part 26.

[0042] The end portions of the guide plates 42, 43 on the side opposite to the protruding direction are connected by a connecting part 44. The guide plates 42, 43 and the connecting part 44 may be formed as a member having a U-shaped cross-section.

[0043] The distance D (see FIG. 6) between the upper surface of the guide plate 42 and the lower surface of the guide plate 43 is slightly larger than the thickness of the substrate holding part 26, and the substrate holding part 26 can move between the guide plate 42 and the guide plate 43. For example, the distance D is about 1.01 times the thickness of the substrate holding part 26.

[0044] During the inspection of the substrate 101, the tip of the substrate holding part 26 is located in the region between the guide plates 42, 43. The air jetted vertically from the pinhole 34 hits the lower surface of the guide plate 43 and the upper surface of the guide plate 42, generating a holding force due to static pressure rigidity and suppressing the occurrence of vibration in the Z direction (height direction) of the substrate holding part 26. Therefore, it is possible to suppress the occurrence of blurring in the optical image captured by the TDI sensor 105.

[0045] While the substrate 101 is being inspected, the pinhole 34 is located in the region between the guide plate 42 and the guide plate 43.

[0046] For example, as shown in FIG. 6, when the tip portion 101a of the substrate 101 in the Y direction is located above the center of the objective lens 104, the pinhole 34 is located in the region between the guide plate 42 and the guide plate 43.

[0047] Also, as shown in FIG. 7, until the rear end portion 101b of the substrate 101 in the Y direction is located above the center of the objective lens 104, the tip portion of the substrate holding portion 26 can enter the region between the guide plate 42 and the guide plate 43.

[0048] Also, although not shown, when both ends of the substrate 101 in the X direction are located above the center of the objective lens 104, the pinhole 34 is located in the region between the guide plate 42 and the guide plate 43.

[0049] That is, when each of both ends of the substrate 101 in the X direction and both ends in the Y direction are located above the center of the objective lens 104, the pinhole 34 is located in the region between the guide plate 42 and the guide plate 43.

[0050] When replacing the substrate 101 to be inspected, the Y slider 23 is controlled, and as shown in FIG. 8, the substrate holding portion 26 is retracted from the region between the guide plate 42 and the guide plate 43, and the substrate 101 is moved to a position away from the objective lens 104.

[0051] In the inspection apparatus 100, the objective lens 104 is disposed close to the substrate 101, and the upper end of the objective lens 104 is located higher than the lower surface of the guide plate 42. Here, when configured such that the air holding portion 40 (guide plate 42) moves together with the substrate holding portion 26, the guide plate 42 may interfere (contact) with the objective lens 104. In order to avoid interference between the guide plate 42 and the objective lens 104, it is necessary to increase the Y-direction size of the substrate holding portion 26 so that the guide plate 42 does not reach the objective lens 104 even when the substrate 101 is moved to a position away from the objective lens 104, but this leads to an increase in the size of the stage 102.

[0052] However, in the present embodiment, the air holding portion 40 is fixed to the surface plate 20, and the guide plate 42 does not move even when the substrate holding portion 26 is moved. Therefore, without increasing the size of the stage 102, the substrate 101 can be moved to a position away from the objective lens 104, and the replacement and maintenance of the substrate 101 can be easily performed.

[0053] In the above embodiment, when each of both ends in the X direction and both ends in the Y direction of the substrate 101 is located above the center of the objective lens 104, it has been described that the pinhole 34 is located in the region between the guide plate 42 and the guide plate 43. However, when each of both ends in the X direction and both ends in the Y direction of the pattern formation region, which is the inspection target region of the substrate 101 rather than the substrate 101, is located above the center of the objective lens 104, it is sufficient that the pinhole 34 is located in the region between the guide plate 42 and the guide plate 43.

[0054] As shown in FIG. 9, the guide plate 43 and the connecting portion 44 may be omitted, and the air pad 30 may have a positive pressure pinhole 35 and a negative pressure pinhole 36 provided on the lower surface side of the substrate holding portion 26. As shown in FIG. 10, after the air supplied from the outside through the positive pressure tube 31 passes through the microfilter 32, it is jetted downward from the positive pressure pinhole 35 toward the guide plate 42.

[0055] The negative pressure pinhole 36 is disposed in the vicinity of the positive pressure pinhole 35, and the gas is exhausted through the negative pressure tube 37.

[0056] When each of both ends in the X direction and both ends in the Y direction of the substrate 101 (or the pattern formation region) is located above the center of the objective lens 104, the positive pressure pinhole 35 and the negative pressure pinhole 36 are located above the guide plate 42 and face the upper surface of the guide plate 42.

[0057] As shown in FIG. 11, the air pad 30 may have a porous body 38. The porous body 38 is connected to the positive pressure tube 31 (see FIG. 4) and jets air in the vertical direction. As the porous body 38, a metal sintered body or a foamed resin can be used.

[0058] When both ends in the X direction and both ends in the Y direction of the substrate 101 (or the pattern formation region) are positioned above the center of the objective lens 104, the porous body 38 is located in the region between the guide plate 42 and the guide plate 43.

[0059] In the above embodiment, the configuration of ejecting air from the air pad 30 provided at the tip of the mask holding portion 26 has been described. However, as shown in FIG. 12, the air pad 30 may be omitted, and air may be ejected from the guide plates 42 and 43. Air is ejected upward from the upper surface of the guide plate 42 and downward from the lower surface of the guide plate 43. It is preferable that the air ejection holes of the guide plate 42 and the air ejection holes of the guide plate 43 face each other.

[0060] When both ends in the X direction and both ends in the Y direction of the substrate 101 (or the pattern formation region) are positioned above the center of the objective lens 104, at least a part of the substrate holding portion 26 is located between the air ejection holes of the guide plate 42 and the air ejection holes of the guide plate 43.

[0061] The guide plate 43 may be omitted, and the guide plate 42 may be provided with air ejection holes and air exhaust holes.

[0062] In the above embodiment, the rear end portion in the Y direction of the substrate holding portion 26 is attached to the X slider 25, while the front end portion is a free end that is not connected to anywhere. When the air pad 30 is not provided at the front end portion in the Y direction of the substrate holding portion 26, the substrate holding portion 26 vibrates in the Z direction (height direction) due to the influence of the disturbance moment applied to the X slider 25, and blurring may occur in the acquired optical image.

[0063] FIG. 13 is a schematic diagram showing the disturbance moment ΔM applied to the X slider 25 when the air pad 30 is not provided. The X slider 25 floating by air ejection can be modeled as a configuration in which an air spring is attached.

[0064] Let the air spring constants of the air gaps of the X slider 25 be K1 and K2, the distances from the center of gravity of the X slider 25 to the air ejection holes of the X slider 25 be L1 and L2, the distance from the center of gravity of the X slider 25 to the tip of the substrate 101 be L3, and the displacement angle of the substrate holding portion 26 be θ2. In this case, the disturbance moment ΔM is expressed by the following formula (1). ΔM = K1 × L1 × θ2 + K2 × L2 × θ2 ···(1)

[0065] From formula (1), the displacement angle θ2 is expressed by the following formula (2). θ2 = ΔM / (K1 × L1 + K2 × L2) ···(2)

[0066] Figure 14 is a schematic diagram showing the disturbance moment ΔM applied to the X slider 25 when the air pad 30 is provided. The air pad 30 can be modeled as a configuration in which an air spring is attached between the guide plates 42 and 43.

[0067] Let the air spring constant of the air pad 30 be K3, the distance from the center of gravity of the X slider 25 to the air pad 30 be L4, and the displacement angle of the substrate holding portion 26 be θ1. In this case, the disturbance moment ΔM is expressed by the following formula (3). ΔM = K1 × L1 × θ1 + K2 × L2 × θ1 + K3 × L4 × θ1 ···(3)

[0068] From formula (3), the displacement angle θ1 is expressed by the following formula (4). θ1 = ΔM / (K1 × L1 + K2 × L2 + K3 × L4) ···(4)

[0069] From formula (2) and formula (4), the ratio of the displacement angles when the air pad 30 is provided and when it is not provided is expressed by the following formula (5). θ1:θ2 = (K1 × L1 + K2 × L2):(K1 × L1 + K2 × L2 + K3 × L4) ···(5)

[0070] Here, as an example, when the stage is designed such that L1 = L2, L1:L4 = 1:4, K1 = K2, and K1:K3 = 3:1, θ1 / θ2 = 0.6. That is, when the same external disturbance moment is applied, by providing the air pad 30, an air spring is formed between the guide plates 42 and 43. As a result, the amplitude of the substrate 101 can be suppressed to 0.6 times, and blurring in the acquired optical image can be suppressed.

[0071] The optical image acquisition mechanism 150 acquires optical images of a plurality of frame regions 14 of the substrate 101 on which patterns are formed. For this purpose, first, the optical image acquisition mechanism 150 scans the inspection stripe 12 with laser light (inspection light), and for each inspection stripe 12, the TDI sensor 105 captures an image of the stripe region. Specifically, it operates as follows. The stage 102 is moved to a position where the target inspection stripe 12 can be imaged. The pattern formed on the substrate 101 is irradiated with laser light (e.g., DUV light) having a wavelength in the ultraviolet region or below, which serves as inspection light, from an appropriate light source 103 via the illumination lens 170. The light transmitted through the substrate 101 forms an optical image on the TDI sensor 105 (an example of a sensor) via the objective lens 104 and enters.

[0072] The image of the pattern formed on the TDI sensor 105 is photoelectrically converted by each photodiode of the TDI sensor 105 and further A / D (analog - digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 12 to be measured is stored in the stripe pattern memory 123. When capturing this pixel data (stripe region image), the dynamic range of the TDI sensor 105 uses, for example, a dynamic range with the case where 60% of the light amount of the illumination light is incident as the maximum gradation. The measurement data (pixel data) is, for example, 8 - bit unsigned data, representing the gradation (light amount) of the brightness of each pixel. Thereafter, the stripe region image (stripe data) is sent to the comparison circuit 108 together with the data indicating the position of the substrate 101 on the stage output from the position circuit 107.

[0073] For each inspection stripe 12, the comparison circuit 108 reads stripe data from the stripe pattern memory 123 and creates a frame image for each frame area 14 shown in FIG. 2 for the area in charge. For example, a frame image of 512×512 pixels is created. A plurality of frame images are created such that adjacent frame images overlap with each other with a predetermined margin width. Through such processing, a plurality of frame images (optical images) corresponding to a plurality of frame areas are acquired. The plurality of frame images are stored in a storage unit such as the magnetic disk device 131. Thus, one of the images (measured image) data to be compared for inspection is generated.

[0074] The reference image creation circuit 112 (reference image creation unit) creates a plurality of reference images corresponding to the stripe images (optical images) of the plurality of inspection stripes 12. For example, as a reference image for each inspection stripe 12, a reference image is created for each frame area so as to correspond to the frame image. However, it is not limited thereto. It may be the case where a reference image is created for each inspection stripe 12. Specifically, it operates as follows. First, the reference image creation circuit 112 reads drawing data (design pattern data) from the magnetic disk device 109 through the control computer 110 and converts each graphic pattern defined in the read design pattern data into binary or multi-valued image data.

[0075] The graphics defined in the design pattern data are, for example, those based on basic graphics such as rectangles and triangles. For example, graphic data that defines the shape, size, position, etc. of each pattern graphic with information such as coordinates (x, y) at the reference position of the graphic, the side length, and a graphic code that is an identifier for distinguishing graphic types such as rectangles and triangles is stored.

[0076] When the design pattern data that becomes graphic data is input to the reference image creation circuit 112, it expands into data for each graphic, and interprets graphic codes, graphic dimensions, etc. indicating the graphic shape of the graphic data. Then, it expands and outputs into binary or multi-valued design pattern image data as a pattern arranged within a grid of a predetermined quantization dimension as a unit. In other words, it reads the design data, virtually divides the frame area into grids with a predetermined dimension as a unit, calculates the occupancy rate occupied by the graphics in the design pattern for each grid, and outputs n-bit occupancy rate data (design image data). For example, it is suitable to set one grid as one pixel. And if we assume that one pixel has a resolution of 1 / 2 8 (=1 / 256), we allocate a small area of 1 / 256 only for the area of the graphic arranged within the pixel and calculate the occupancy rate within the pixel. And it creates as 8-bit occupancy rate data. Such a grid (inspection pixel) may be matched to the pixel of the measurement data.

[0077] Next, the reference image creation circuit 112 performs a filtering process on the design pattern image data, which is the image data of the graphic, using a filter function to create a reference image closer to the optical image. Thereby, the design image data, which is the image data on the design side where the image intensity (shading value) is a digital value, can be matched to the image generation characteristics of the measurement data (optical image). As described above, the optical image (stripe data) of the target inspection stripe 12 is acquired, and the reference image is generated.

[0078] The comparison circuit 108 aligns the frame image (optical image) to be compared and the reference image with a predetermined algorithm. For example, alignment is performed using the least squares method.

[0079] The comparison circuit 108 compares the frame image with the reference image for each frame area (inspection unit area). For example, the frame image and the reference image are compared pixel by pixel to inspect for pattern defects. The comparison circuit 108 compares the two pixel by pixel according to a predetermined determination condition, and determines the presence or absence of a defect such as a shape defect. As the determination condition, for example, the two are compared pixel by pixel according to a predetermined algorithm to determine the presence or absence of a defect. For example, a difference value obtained by subtracting the pixel value of the frame image from the pixel value of the reference image for each pixel is calculated, and if the difference value is greater than a predetermined threshold value, it is determined as a defect. Then, the comparison result is output.

[0080] The comparison result may be stored in the magnetic disk device 109, or may be output using the pattern monitor 118 or the printer 119.

[0081] In the above embodiment, an example of performing die-database inspection processing for comparing optical image data with reference image data created from design pattern data has been described. However, die-die inspection processing for comparing optical image data using optical images acquired in the past from a substrate on which the same pattern is formed may be performed.

[0082] Note that the present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined.

Explanation of Reference Numerals

[0083] 10 Inspection area 12 Inspection stripe 14 Frame area 26 Substrate holding part 30 Air pad 40 Air holding part 100 Inspection device 101 Substrate 102 Stage 103 Light source 104 Objective lens 105 TDI sensor 114 Stage control circuit 150 Optical image acquisition mechanism 160 Control system circuit 170 Illumination lens

Claims

1. An optical image acquisition unit having a movable stage on which a substrate to be inspected is placed, virtually dividing the substrate into a plurality of stripes in a strip shape along a predetermined direction, and acquiring an optical image for each stripe; A reference image generation unit that generates a reference image corresponding to the acquired optical image; A comparison unit that compares the optical image and the reference image; comprising: The stage is a surface plate, a first fixed guide and a second fixed guide that are fixed on the surface plate and arranged parallel to each other along a first direction; a first air slider attached to the first fixed guide; a second air slider attached to the second fixed guide; a moving guide having one end connected to the first air slider and the other end connected to the second air slider, and extending in a second direction orthogonal to the first direction; a third air slider attached to the moving guide; a substrate holding part having one end in the first direction connected to the third air slider, and an air pad that jets air upward or downward provided at the other end in the first direction, for holding the substrate; a guide plate fixed to the surface plate; an objective lens fixed to the surface plate and positioned below the substrate holding part; having When each of both ends in the first direction and both ends in the second direction of the substrate are positioned above the center of the objective lens, the air pad is at a position where the ejected air hits the guide plate, a pattern inspection device.

2. The guide plate has a first guide plate positioned lower than the substrate holding part and a second guide plate positioned higher than the substrate holding part, The air pad jets air upward and downward when positioned in a region between the first guide plate and the second guide plate, the pattern inspection device according to claim 1.

3. The pattern inspection apparatus according to claim 2, wherein the air pad has a pinhole that penetrates the substrate holding portion in the vertical direction.

4. The guide plate is located lower than the substrate holding portion, The pattern inspection apparatus according to claim 1, wherein the air pad is provided on the lower surface side of the substrate holding portion and has a positive pressure pinhole for ejecting air and a negative pressure pinhole for exhausting air.

5. When each of both ends of the pattern formation region of the substrate in the first direction and both ends in the second direction are located above the center of the objective lens, the air pad is at a position where the ejected air hits the guide plate. The pattern inspection apparatus according to claim 1.

6. The pattern inspection apparatus according to claim 1, wherein the upper end of the objective lens is located higher than the lower surface of the guide plate.

Images