JP2008170371A - Pattern defect inspection method and pattern defect inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect a defect generated in a repetitive pattern having a unit pattern pitch of, for example, 50 μm to 1000 μm in a short time with high reliability.
A pattern defect inspection method for inspecting a defect generated in a repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged, wherein light is incident on the repetitive pattern at a predetermined incident angle. A step of irradiating and generating diffracted light, a step of receiving and diffracted light from the repetitive pattern, and a step of detecting defects generated in the repetitive pattern by observing the image formed by diffracted light In the step of receiving diffracted light and forming an image, the super high-order diffracted light having an absolute value of 45th to 1600th order is received from the diffracted light from the repetitive pattern.
[Selection] Figure 3

Description

  The present invention relates to a pattern defect inspection method and a pattern defect inspection apparatus for inspecting defects generated in a repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged.

  For example, the surface of a display device substrate used in a display device (Flat Panel Display; FPD) such as a liquid crystal display device, a plasma display device, an EL display device, an LED display device, or a DMD display device, and manufacture of the display device substrate A repetitive pattern in which unit patterns are periodically arranged may be formed on the surface of the photomask used in the process. The unit patterns are arranged according to a predetermined rule. However, for some reason in the manufacturing process, some unit patterns may include defects arranged according to a rule different from the predetermined rule. Such defects can also be referred to as mura defects.

  If the defect occurs in the display device substrate, it is manufactured by having a regular arrangement even if the defect has a minute size within an allowable range in the manufacturing process. There may be display unevenness that can be detected by the naked eye in the display device. In addition, if the defect occurs in the photomask used in the manufacturing process of the display device substrate, the defect may be transferred to the pattern formed on the display device substrate, which increases the influence of the problem. Therefore, the device substrate and the photomask used in the manufacturing process of the device substrate need to be inspected for defects generated in the repetitive pattern as an object to be inspected.

  However, since the defects are periodically arranged according to some rule, although they are defects, they are likely to appear normal at first glance and it is often difficult to detect their presence or absence. For example, even if an attempt is made to perform micro inspection for measuring the dimensions and coordinates of each unit pattern for the defect, the number of unit patterns is enormous, which is difficult from the viewpoint of time and cost. In addition, there are cases where the defect can be detected by oblique light inspection in which light is applied to the entire or partial area of the repetitive pattern and the area is visually observed from an oblique direction. There is a problem in terms of sex.

  On the other hand, a method for inspecting defects generated on the surface of a semiconductor device (IC, LSI, etc.) substrate provided with an integrated circuit and on the surface of a photomask used in the manufacturing process of the semiconductor device substrate is known.

Patent Document 1 discloses a method for inspecting defects generated on the surface of a photomask used in a manufacturing process of a semiconductor device substrate in a short time. In the method disclosed in Patent Document 1, an object to be inspected is illuminated so that diffracted light from the object is generated with a substantially uniform amount of light over the entire inspection area, and a predetermined order (for example, (11th order) An objective lens is disposed at a position where the higher-order diffracted light is selectively incident, the light intensity distribution of the object image by the objective lens is detected by a sensor, and the detection result by the sensor is analyzed by an analysis means. Thus, information on the fine structure of the object is acquired.
JP-A-2005-233869

  However, for example, the pitch of unit patterns in a photomask used in a manufacturing process of a liquid crystal display device generally includes about 50 μm to 1000 μm, and a substrate for a semiconductor device provided with an integrated circuit, or a substrate for the semiconductor device Compared with a unit pattern (for example, a unit pattern having a pitch of 0.1 μm to 0.4 μm described in patent literature) in a photomask used in the manufacturing process, the size is 500 times to 10,000 times. Therefore, when a photomask used in a manufacturing process of a liquid crystal display device or the like is an object to be inspected, it is difficult to inspect defects generated in a repetitive pattern even using the method disclosed in Patent Document 1. The inventors have found that there is.

  Accordingly, the present invention provides a pattern defect inspection method and a pattern defect inspection apparatus capable of inspecting defects generated in a repetitive pattern whose unit pattern pitch is, for example, 50 μm to 1000 μm in a short time with high reliability. The purpose is to provide.

According to one aspect of the invention,
A pattern defect inspection method for inspecting a defect generated in a repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged, wherein the repetitive pattern is irradiated with light at a predetermined incident angle. A step of generating diffracted light, a step of receiving and diffracting the diffracted light from the repetitive pattern, and detecting defects formed in the repetitive pattern by observing the image formed by forming the diffracted light. A pattern defect inspection method for receiving ultrahigh-order diffracted light having an absolute value of 45th to 1600th of the diffracted light from the repetitive pattern in the step of receiving and diffracting the diffracted light to form an image. Is provided.

  Preferably, the defect has regularity different from the period. The effect of the present invention is particularly advantageously obtained when the defect is a repetitive pattern having unit patterns arranged with a period different from the period.

  Preferably, in the step of forming an image by receiving the diffracted light, ultrahigh-order diffracted light having an absolute value of the 90th to 1600th order among the diffracted light from the repetitive pattern is received.

  Preferably, in the step of receiving and diffracting the diffracted light, the diffracted light is received at a light receiving angle of 90 ° with respect to the main plane of the repetitive pattern.

  Preferably, in the step of irradiating the repetitive pattern with light at a predetermined incident angle to generate diffracted light, the repetitive pattern has an incident angle of 30 ° to 60 ° with respect to a main plane of the repetitive pattern, and receives the light. In the step of forming an image, light is irradiated at an incident angle at which the ultrahigh-order diffracted light can be received.

  Preferably, the unit pattern has a pitch of 50 μm to 1000 μm.

  Preferably, the inspection object is a photomask that exposes light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm.

  The photomask is for manufacturing a liquid crystal display device.

According to another aspect of the invention,
A pattern defect inspection apparatus for inspecting a defect generated in a repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged, and irradiating the repetitive pattern with light at a predetermined incident angle. Illuminating means for generating diffracted light, light receiving means for receiving and imaging diffracted light from the repetitive pattern, and defects generated in the repetitive pattern by observing an image formed by forming the diffracted light And a pattern defect inspection device that receives ultrahigh-order diffracted light having an absolute value of 45th to 1600th of the diffracted light from the repetitive pattern. .

  Preferably, the light receiving means receives ultrahigh-order diffracted light having an absolute value of 90th to 1600th of the diffracted light from the repetitive pattern.

  Preferably, the light receiving means receives the diffracted light at a light receiving angle of 90 ° with respect to the main plane of the repetitive pattern.

  Preferably, the illuminating unit irradiates light at an incident angle of 30 ° to 60 ° with respect to a main plane of the repetitive pattern, and the light receiving unit can receive the ultrahigh-order diffracted light.

  Preferably, the unit pattern has a pitch of 50 μm to 1000 μm.

  Preferably, the inspection object is a photomask that exposes light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm.

  Preferably, the photomask is for manufacturing a liquid crystal display device.

  ADVANTAGE OF THE INVENTION According to this invention, the pattern defect inspection method and pattern defect inspection apparatus which can test | inspect the defect which arose in the repetitive pattern whose unit pattern pitch is 50 micrometers-1000 micrometers, for example in a short time highly reliable. Can be obtained.

  As described above, in Patent Document 1, for example, a photomask or the like used in a manufacturing process of a semiconductor device substrate including an integrated circuit is used as an object to be inspected, and defects generated in a repetitive pattern provided in the photomask are detected in a short time. A method of inspection is disclosed. Here, the problems to be solved by the method disclosed in Patent Document 1 are as follows.

  Conventionally, when the size of a unit pattern of a semiconductor device substrate having an integrated circuit is 0.1 μm, the size variation of the unit pattern is about 10% of the size of the unit pattern (that is, 0.01 μm). It has been inspected whether it is within an acceptable range. Similarly, when the dimension of the unit pattern of the photomask used in the manufacturing process of the substrate for a semiconductor device is 0.4 μm (for example, in the case of a 1/4 exposure process), the size variation of the unit pattern is large. Has been inspected to determine whether or not is within an allowable range of about 0.04 μm. Such inspection has been performed by so-called “dimension measurement” in which the dimension of the unit pattern in the final inspection process is compared with the dimension of the unit pattern in the design stage.

  However, even if the result of the so-called “dimension measurement” is good, that is, even if the size variation of the unit pattern is within the allowable range, minute dimensional variations within the allowable range are found everywhere in the repeated pattern. When present, it has been regarded as a problem to have a serious adverse effect on the performance of a semiconductor device manufactured using a photomask. That is, it has been recognized that inspection is required even for minute dimensional variations that are difficult to detect due to insufficient resolution in so-called “dimension measurement”. In addition, it has been considered impractical to individually inspect such minute dimensional variations with an optical microscope using ultrashort ultraviolet rays.

As described above, the method disclosed in Patent Document 1 is intended to precisely inspect minute dimensional variations that are difficult to detect due to insufficient resolution in so-called “dimension measurement”. . That is, it is intended to inspect minute dimensional fluctuations that are less than 0.01 μm to 0.04 μm, which occur in a repetitive pattern in which the unit pattern dimension is, for example, about 0.1 μm to 0.4 μm. is there.

  On the other hand, for example, the unit pattern pitch in the photomask used in the manufacturing process of the liquid crystal display device has a pattern period larger than that of the photomask for manufacturing the semiconductor device, and is generally about 50 μm to 1000 μm. Including things. That is, compared with the pitch of the unit pattern in the photomask etc. used in the manufacturing process of the substrate for a semiconductor device, the size is 500 times to 10,000 times as described above. According to investigations by the inventors, the method disclosed in Patent Document 1 is effective for inspecting defects that occur in ultra-fine repetitive patterns having a unit pattern pitch of, for example, about 0.1 μm to 0.4 μm. Even so, it has been found that it is not always effective for inspecting defects that occur in a repetitive pattern having a relatively large unit pattern pitch. That is, according to investigations by the inventors, when a liquid crystal display device substrate or a photomask used in a manufacturing process of a liquid crystal display device substrate is used as an inspection object, the method disclosed in Patent Document 1 is used. It was found that it was difficult to inspect defects that occurred in repeated patterns.

  On the other hand, in photomasks used for manufacturing liquid crystal display panels and the like, structural defects (line width deviation, coordinate deviation, shape abnormality) may be latent in the pattern due to factors such as instability of the drawing apparatus. . In addition, photomasks for these applications are remarkably large (one side is 300 mm or more, and according to the recent trend toward larger size, one side is 1000 mm or more is not uncommon). Exposure. For this reason, unlike the photomask disclosed in Patent Document 1, it is necessary to prioritize the exposure light amount over the resolution. Therefore, the exposure light uses a light source having a predetermined wavelength range in the wavelength range of 365 to 436 nm. Therefore, in the inspection of the mask, the significance of performing the ultra-high resolution pattern shape inspection is low and the efficiency is low. In addition, since the pattern abnormality below the allowable range in the inspection of the resolution that reflects the exposure condition does not need to be handled as a defect, the above-described inspection method for errors that can be perceived by the naked eye by having a regular arrangement Was not established.

  Therefore, the inventors use a method using diffracted light to inspect a defect generated in a repetitive pattern such as a photomask used in a manufacturing process of a display device substrate in a short time with high reliability. And earnestly researched. As a result, it has been found out that it is necessary to increase the order of diffracted light received from a repetitive pattern when inspecting a defect generated in a repetitive pattern having a relatively large unit pattern pitch. That is, in order to inspect a defect generated in a repetitive pattern having a unit pattern pitch of about 50 μm to 1000 μm, it is effective to selectively receive 45th to 1600th order high-order diffracted light and inspect the defect. I found out. The present invention has been made based on the above knowledge obtained by the inventors.

  Hereinafter, as one embodiment of the present invention, (1) a configuration of a photomask as an object to be inspected, (2) a defect generated in the photomask, (3) a configuration of a pattern defect inspection apparatus, (4) A pattern defect inspection method according to an embodiment will be described in order.

(1) Configuration of Photomask In the pattern defect inspection apparatus and pattern inspection method according to an embodiment of the present invention, for example, it is used for a liquid crystal display device, a plasma display device, an EL display device, an LED display device, a DMD display device, and the like. The display device substrate to be used and the photomask used in the manufacturing process of the display device substrate can be used as the object to be inspected. In particular, the present invention is useful in a mask for manufacturing a liquid crystal display device.

  Below, the structure of the photomask 50 as a to-be-inspected object is demonstrated, referring drawings. In the drawings to be referred to, FIG. 1 is a schematic view illustrating the configuration of a photomask as an object to be inspected according to an embodiment of the present invention, (a) is a plan view of the photomask, and (b) is a photo. The cross-sectional views of the mask are schematically shown. FIG. 2 is a schematic view schematically illustrating the configuration of a repeating pattern provided in a photomask as an object to be inspected according to an embodiment of the present invention.

  The photomask 50 is an exposure mask used when a fine structure is manufactured using a photolithography technique, and is configured as a substrate having sides L1 and L2 as illustrated in FIG. There are many cases. As described above, the photomask 50 used in the manufacturing process of the display device substrate often has a side L1 or side L2 of more than 300 mm, and is sometimes configured as a large substrate of more than 1 m. And, in order to perform the whole surface batch exposure using such a large photomask 50, the light quantity has priority over the resolution, and therefore, as an exposure light source, light in a predetermined wavelength region including a wavelength of 365 nm to 436 nm is used. A light source that emits light is often used.

  As shown in FIG. 1B, the photomask 50 has a transparent substrate 57 as a transparent support and a repetitive pattern 56 made of a thin film (light-shielding film) formed on the main surface of the transparent substrate 57. is doing.

  As a material of the transparent substrate 57, for example, synthetic quartz glass or the like is used. Further, as a material of the thin film constituting the repeated pattern 56, for example, a light-shielding material such as chromium, a semi-translucent material, or the like is used. Note that the thin film is not limited to a single layer, and may be configured as a laminate. In that case, a semi-transparent film may be included in addition to the light-shielding film, and a functional film such as an etching stopper may be included. Also good. Furthermore, a resist film may be accompanied on the thin film.

  The shape of the repetitive pattern 56 of the display device photomask 50 is, for example, a shape in which lattice-shaped unit patterns 53 are periodically arranged as shown in FIG. The pitch d of the unit patterns 53 (that is, the arrangement period of the unit patterns 53) is configured to be 50 μm to 1000 μm, for example.

(2) Defects in the photomask In the above, the unit patterns 53 are arranged according to a predetermined rule. In the present invention, not only those having a unit pattern arrangement of a fixed shape in a perpendicular direction as shown in FIG. 2, but also patterns having a constant line width and regularity such as a line and space are predetermined. It is included in the pattern arranged according to the rules. However, for some reason in the manufacturing process or the like, there may be a defect (so-called uneven defect) in which some unit patterns are arranged with regularity different from the regularity. Below, the defect which arises in the repeating pattern 56 is demonstrated, using the manufacturing method of the photomask 50. FIG. Note that, for example, a line width abnormality with a constant width and a positional deviation in a line pattern having a constant line width are also included in the defects arranged according to a rule different from the predetermined rule described above. That is, abnormal line width and misalignment in a line-and-space pattern are also defects that can be inspected by the method of the present invention described later.

In manufacturing the photomask 50, the following steps [1] to [5] are often performed. [1] First, a thin film (such as a light shielding film) is formed on the transparent substrate 57, and a resist film is further formed on the thin film. [2] Next, the formed resist film is irradiated with a laser beam or the like by a drawing method such as a raster drawing method using a drawing machine to expose a predetermined pattern.
[3] Next, development is performed to selectively remove the resist film in the drawing part or the non-drawing part, thereby forming a resist pattern on the thin film. [4] Thereafter, the thin film not covered with the resist pattern is selectively removed by etching to form a repeated pattern 56. [5] Subsequently, the remaining resist on the repeated pattern 56 is removed. In the case of a multilayer film, an additional step can be provided depending on the material of the film.

  Here, in the step [2] described above, the scanning pattern of the laser beam is suddenly deteriorated, the beam diameter is changed unexpectedly, or the environmental factor is changed. Defects may occur. FIGS. 6A and 6B are schematic views illustrating defects generated in a repetitive pattern. FIGS. 6A and 6B illustrate coordinate position variation defects, and FIGS. 6C and 6D illustrate dimension variation defects. is doing. In FIG. 6, a point where a defect has occurred is indicated by reference numeral 54.

  For example, FIG. 6A shows a defect in which the pitch d of the unit pattern 53 is partially widened due to the occurrence of a positional shift at the drawing joint by laser light. FIG. 6B shows a defect in which the position of the unit pattern 53 ′ is shifted relative to the other unit patterns 53 due to the occurrence of the position shift at the drawing joint by the laser beam. . These defects can be referred to as coordinate position variation system defects.

  6 (c) and 6 (d), the size of the unit pattern 53 ′, that is, the width of the lattice frame 53a ′ is changed due to changes in the beam intensity and beam diameter of the drawing machine. Indicates a defect. These defects can be referred to as dimension variation defects.

  Note that the cause of such defects is not necessarily limited to the above, and may be caused by various other causes.

(3) Configuration of Pattern Defect Inspection Device Next, a configuration example of the pattern defect inspection device 10 according to an embodiment of the present invention will be described with reference to FIG. The pattern defect inspection apparatus 10 includes a stage 11 as a holding means, a light source device 12 as an illumination means, an imaging device 14 as a light receiving means, and an image analysis device 16 as an analysis means. Each will be described below.

〔stage〕
The stage 11 as a holding means is configured to hold a photomask 50 as an object to be inspected.

  The stage 11 holds the photomask 50 so that light can be irradiated obliquely from below the main plane of the repeated pattern 56. For example, the stage 11 may be configured as a frame shape that holds the outer peripheral portion of the photomask 50, or may be configured by a member that is transparent to the light to be irradiated.

  The stage 11 is configured as an XY stage that can move in the X direction and the Y direction, for example. The inspection field of view can be moved by moving the photomask 50 held on the stage 11 relative to the light source device 12 and the imaging device 14 described later. When the stage 11 is not configured to be movable with respect to the light source device 12 and the imaging device 14, the light source device 12 and the imaging device 14 may be configured to be movable with respect to the stage 11.

[Light source device]
The light source device 12 as an illuminating unit is configured to irradiate light at a predetermined incident angle on the repetitive pattern 56 of the photomask 50 held on the stage 11 to generate diffracted light.

  The light source device 12 uses a light source 12a having sufficient luminance (for example, illuminance of 10,000 Lx to 600,000 Lx or more, preferably 300,000 Lx or more) and high parallelism (parallelism is within 2 °). ing. Examples of the light source 12a that can satisfy such conditions include an ultra-high pressure mercury lamp, a xenon lamp, and a metal halide lamp.

  The light source device 12 includes an irradiation optical system 12b including a lens. The irradiation optical system 12b is disposed between the support surface of the stage 11 (that is, the main plane of the repetitive pattern 56) and the light source 12a, and collimates the light from the light source 12a.

  The light collimated by the irradiation optical system 12b irradiates the main plane of the repetitive pattern 56 from obliquely below at an incident angle θi to generate diffracted light. Here, the incident angle θi is an angle between the normal line of the support surface of the stage 11 and the optical axis of the light irradiated to the repeated pattern 56. In FIG. 1, the light source device 12 is disposed obliquely below the support surface of the stage 11, but may alternatively be disposed obliquely above the support surface of the stage 11.

[Imaging device]
The imaging device 14 as a light receiving unit is configured to receive diffracted light from the repetitive pattern 56 and form an image.

  The imaging device 14 includes an area camera 14a that can capture a two-dimensional image, such as a CCD camera. The light receiving surface of the area camera 14a is provided to face the support surface of the stage 11 (that is, the main plane of the repeated pattern 56).

  The imaging device 14 further includes a light receiving optical system 14b having an objective lens. The light receiving optical system 14b receives a predetermined order of diffracted light from the repetitive pattern 56, and forms an image of the received diffracted light on the light receiving surface of the area camera 14a. The field of view of the imaging device 14 via the light receiving optical system 14b is set to be, for example, a square or a rectangle having a side of 10 mm to 50 mm.

  The diffracted light image formed on the light receiving surface of the area camera 14a can be output to the image analysis device 16 as image data.

  The imaging device 14 is disposed above the support surface of the stage 11 and receives diffracted light at a light receiving angle θr. Here, the light receiving angle θr is an angle between the support surface of the stage 11 (that is, the main plane of the repetitive pattern 56) and the optical axis of the light receiving optical system 14b. When the light receiving angle θr is substantially a right angle, that is, when the imaging device 14 is disposed on the normal line of the support surface of the stage 11, the imaging device 14 is inclined with respect to the support surface of the stage 11. The distance between the light receiving surface of the area camera 14a and the repetitive pattern 56 is uniform as compared with the case where they are arranged at the same position. In this case, it is easy to obtain a uniform image in the same inspection visual field, and it is easy to prevent defocusing in the same inspection visual field, which is preferable.

[Image analyzer]
The image analysis device 16 as an analysis unit can detect the presence or absence of a defect in the repetitive pattern 56 by observing an image formed by diffracted light, that is, image data output from the imaging device 14. It is configured as follows.

  When receiving the image data from the imaging device 14, the image analysis device 16 is configured to create numerical data by digitizing the light intensity of each part of the received image data, for example. The created numerical data is compared with the following reference data to automatically detect the presence or absence of a defect.

  As the reference data, for example, numerical data created based on an image formed by diffracted light from the repetitive pattern 56 having no defect can be used. In addition, as reference data, numerical data created based on an image obtained by moving an image formed by diffracted light in the arrangement direction of the unit patterns 53 can be used. In the latter case, when the reference data is subtracted from the numerical data, a pair of positive and negative peaks are formed corresponding to the defect, so that it may be easier to detect the defect.

(4) Pattern Defect Inspection Method Subsequently, a pattern defect inspection method according to an embodiment of the present invention will be described. This pattern defect inspection method is implemented by the pattern defect inspection apparatus described above.

  This pattern defect inspection method includes a step (S1) of irradiating light to the repetitive pattern 56 at a predetermined incident angle to generate diffracted light, and a step of receiving diffracted light from the repetitive pattern 56 and forming an image (S2). And observing an image formed by diffracted light to detect the presence or absence of defects generated in the repeated pattern 56 (S3). Hereinafter, each process is demonstrated in order.

[Step of generating diffracted light (S1)]
First, the photomask 50 provided with the repeated pattern 56 is held on the stage 11 of the pattern inspection apparatus. Then, the light source device 12 is used to irradiate the main plane of the repeated pattern 56 with an incident angle θi from obliquely below.

Then, diffracted light is generated on the transmitted light side and reflected light side of the repeated pattern 56. That is, when the pitch of the unit patterns 53 in the repetitive pattern 56 is d, the wavelength of light incident from the light source device 12 is λ, and the incident angle θi, the relationship d (sin θi ± sin θn) = nλ is satisfied. in the direction of Do diffraction angle theta _n, n th order diffracted light is observed.

  FIG. 4 is a schematic diagram showing the state of diffracted light from the repetitive pattern 56 when, for example, the incident angle θi is 0 ° (that is, when light is irradiated from vertically below the main plane of the repetitive pattern 56). (A) shows the state of diffracted light generated from the repetitive pattern 56 of the CCD photomask whose unit pattern 53 has a pitch d of 10 μm, and (b) shows a liquid crystal display in which the unit pattern 53 has a pitch d of 200 μm. The state of the diffracted light generated from the repeated pattern 56 of the apparatus photomask is shown. FIG. 5 shows diffraction angles θn when the incident angle θi is 0 ° and the pitch d of the unit patterns 53 is 10 μm, 100 μm, and 1000 μm.

  4 and 5, the larger the pitch d of the unit patterns 53, the smaller the difference dθ in diffraction angles between adjacent diffracted beams (that is, the difference between θn ± 1 and θn), and diffraction with different orders. It can be seen that the light is close.

[Step of receiving diffracted light and forming an image (S2)]
Subsequently, the diffracted light from the repeated pattern 56 is received and imaged using the imaging device 14. That is, the diffracted light from the repeated pattern 56 is received by the light receiving optical system 14b and imaged on the light receiving surface of the area camera 14a.

Here, in the repetitive pattern 56 is not defective, the pitch d of each of the unit patterns 53 are uniform, the wavelength lambda, the incident angle .theta.i, unless the diffraction angle theta _n are identical, forming a diffracted light of a particular order The image made has a certain regularity.

On the other hand, the pitch d ′ of the repeated pattern 56 ′ in which the defect has occurred is different from the pitch d of the repeated pattern 56 without the defect. Therefore, the wavelength lambda, diffraction angle of incidence .theta.i, even the diffraction angle theta _n is the same, the image obtained by imaging the diffracted light from the repetitive pattern 56 'in which the defect has occurred, there is no defect repetitive patterns 56 There is some difference from the image formed by the light. Specifically, in the former image, an abnormal change of the light intensity distribution appears due to a defect generated in the repeated pattern 56. Such a change in the light intensity distribution does not appear in an image formed by diffracted light from the repetitive pattern 56 having no defect.

  Here, a change in the light intensity distribution that suggests the presence of a defect can be remarkably observed by appropriately selecting the order of the diffracted light. For example, the fine defects of 50 nm to 100 nm generated in the repeated pattern 56 in which the pitch d of the unit pattern 53 is 50 μm to 1000 μm are 45th order or more, more preferably 90th order or more (or −45th order or less, more preferably It is possible to detect an abnormal change in the light intensity distribution in an image obtained by forming ultrahigh-order diffracted light of −90th order or less). On the other hand, in the image formed by diffracted light having a smaller absolute value than the above, it is difficult to detect the change in the light intensity distribution that suggests the existence of the defect.

  The intensity of the diffracted light decreases as the order increases, but if the image is formed by receiving diffracted light of 1600th order or lower (or -1600th order or higher), a light source with sufficient illuminance, Research by the inventors has revealed that it is possible to detect anomalies in the light intensity distribution that suggest the presence of the above-described defects by using a highly sensitive image sensor.

  According to the relational expression d (sin θi ± sin θn) = nλ described above, the pitch d of the unit patterns 53 formed in the repetitive pattern 56 is 50 μm to 1000 μm, and the wavelength λ of light from the light source device 12 is 0. When the light receiving angle θr of the imaging device 14 is 90 °, the incident angle θi of the light from the light source device 12 is set to 30 ° to 60 °, whereby the 45th to 1600th in the imaging device 14 is obtained. Next (or -50th to -1600th) ultrahigh order diffracted light can be received.

  Thereafter, the imaging device 14 outputs an image formed on the light receiving surface of the area camera 14a to the image analysis device 16 as image data.

  In the above description, the case where the imaging device 14 receives the diffracted light on the transmitted light side of the repeated pattern 56 has been described as an example. However, the imaging device 14 receives the diffracted light on the reflected light side of the repeated pattern 56. Similar results can be obtained for cases.

[Step of detecting presence or absence of defect (S3)]
As described above, a change in the light intensity distribution suggesting the existence of defects appears in an image formed by imaging the 45th to 1600th (or −45th to −1600th) ultrahigh-order diffracted light. Accordingly, by observing such an image, it is possible to inspect for the presence or absence of a defect that has occurred in the repeated pattern 56.

  Specifically, the image analysis device 16 receives the image data output from the imaging device 14, digitizes the light intensity of each part of the received image data, creates numerical data, And comparing with the reference data. In this way, by numerically comparing the light intensity and comparing it with the comparison data, it is possible to quantitatively detect abnormalities in the light intensity distribution caused by defects (that is, the presence or absence of defects) rather than visual impression of the worker. Is possible.

(5) Effects in one embodiment of the present invention According to one embodiment of the present invention, the following effects [1] to [3] are obtained.

  [1] According to one embodiment of the present invention, fine defects of 50 nm to 100 nm generated in the repetitive pattern 56 in which the pitch d of the unit pattern 53 is 50 μm to 1000 μm are, for example, 45th to 1600th (or −45). In the image formed with the ultrahigh-order diffracted light of the (1st to -1600th order), it appears as an anomaly of the light intensity distribution. Therefore, whether or not there is a change in the light intensity distribution in the image formed with the ultrahigh-order diffracted light without performing an inspection (so-called microscopic expansion inspection) for measuring the dimensions and coordinates of each unit pattern 53 individually. By observing the above, it is possible to inspect for the presence or absence of defects generated in the repeated pattern 56. Since such inspection is performed on a macro region including a plurality of unit patterns 53 (that is, an inspection visual field having a side or a square of 10 mm to 50 mm), the inspection time of the photomask 50 can be greatly shortened. Thus, productivity can be greatly improved.

For example, a photomask 50 used for manufacturing a display device substrate (42V type, area of about 0.5 m ² ) for a high-definition TV has 1920 (vertical) × 1080 (horizontal) = 2,073,600 unit patterns. 53. Here, if the size and coordinates of all the unit patterns 53 are to be micro-inspected using a laser length measuring instrument, a microscope, or the like, when the time required for measurement per unit pattern is about 10 seconds, 240 days are required. On the other hand, according to one embodiment of the present invention, for example, the field of view of the macro inspection is 25 mm ^{2 on a} side (however, 10% of overlap with the adjacent field of view is expected), and the inspection time in one field of view (that is, the above-mentioned If the execution time from S1 to S3 is about 2.5 seconds, the inspection can be completed in an inspection time of just over 40 minutes. That is, the inspection time of the photomask 50 can be greatly shortened, and the productivity of the photomask 50 can be greatly improved.

  [2] According to one embodiment of the present invention, the defect generated in the repetitive pattern 56 appears as an abnormal change in the light intensity distribution in the image formed with the ultrahigh-order diffracted light. Then, the image analysis device 16 generates numerical data by digitizing the light intensity of each part of the image data, and compares the generated numerical data with the reference data to thereby distribute the light intensity distribution caused by the defect. It is possible to detect anomalies (that is, the presence or absence of defects). That is, by digitizing the light intensity and comparing it with the comparison data, it is possible to quantitatively detect the presence or absence of a defect rather than the visual impression of the operator. As a result, it is possible to suppress variations in the inspection results and improve the reliability of the inspection results.

  [3] According to one embodiment of the present invention, in the display device manufactured using the display device substrate by performing the pattern defect inspection method described above in the manufacturing process of the display device substrate, Occurrence can be suppressed. Similarly, by performing the above-described pattern defect inspection method in the manufacturing process of the photomask 50 used in the manufacturing process of the display device substrate, the occurrence of display unevenness in the display device manufactured using the photomask 50 is suppressed. It becomes possible.

  Hereinafter, examples of the present invention will be described with reference to comparative examples.

First, as Example 1, a photo is provided with a repetitive pattern 56 ′ in which a pitch d of a lattice unit pattern 53 is 200 μm, and a defect having a large line width of about 100 nm is intentionally generated in one row of the array. A mask 50 was prepared as an object to be inspected. Then, the light source device 12 irradiates light having a wavelength λ of 0.55 μm to the repetitive pattern 56 ′ with an incident angle θi of 45 °. Then, the imaging device 14 installed in the direction where the light receiving angle θr is 90 ° received and imaged ultrahigh-order diffracted light having an absolute value corresponding to the 257th order, and image data of the image was created. Then, the image analysis device 16 analyzed the image data.

  FIG. 7 shows image data according to the first embodiment. According to FIG. 7, an abnormal change (vertical streak) in the light intensity distribution suggesting the presence of a defect was observed in the image formed with the ultrahigh-order diffracted light.

  In the image shown in FIG. 7, a stripe pattern appears in the horizontal direction, but this stripe pattern is considered to be caused by a normal repetitive pattern. According to the present invention, ultrahigh-order diffracted light from the repetitive pattern 56 ′ in which a defect has occurred is identified as an abnormality in the light intensity distribution that suggests the presence of a defect in the interference fringes resulting from such a normal pattern. This example has revealed that it is possible to inspect for the presence or absence of defects in the repeated pattern 56.

  Subsequently, in Example 2, the pitch d of the unit patterns 53 was set to 100 μm. Then, the imaging device 14 received ultrahigh-order diffracted light having an absolute value corresponding to the 130th order to form an image. Other conditions are the same as in the first embodiment. As a result, similar to FIG. 7 described above, abnormalities (vertical streaks) in the light intensity distribution suggesting the presence of defects were observed.

  Next, in Example 3, a lattice pattern as shown in FIG. 4 in which the pitch d of the unit patterns 53 is 50 μm was used, and a pattern in which a line width abnormality of 50 nm occurred in one column was used as a subject. Then, ultrahigh-order diffracted light corresponding to the 46th absolute value was received and imaged. Other conditions are the same as in the first embodiment. As a result, disturbance in the light intensity distribution indicating the presence of defects was recognized in the image data.

  Furthermore, in Example 4, the same lattice pattern as in Example 3 in which the pitch of the unit patterns 53 was 1000 μm was used, and a pattern in which a line width abnormality of 500 nm occurred in one column was used as the subject. Then, light was incident with an incident angle of 60 °, and light corresponding to diffracted light having an absolute value of 1587th order was received and imaged. Other conditions are the same as in the first embodiment. As a result, disturbance in the light intensity distribution indicating the presence of defects was recognized in the image data.

  On the other hand, in the comparative example, light was irradiated from the light source device 12 with an incident angle θi of 6.3 ° to generate diffracted light. The imaging device 14 received high-order diffracted light having an absolute value of the 40th order to form an image. Other conditions are the same as in the first embodiment.

  However, even when observing an image formed with high-order diffracted light having an absolute value of the 40th order, it was not possible to detect a change in the light intensity distribution indicating the presence of a defect. That is, for the repetitive pattern 56 having a large pitch d of the unit patterns 53, for example, even if high-order diffracted light having an absolute value of the 40th order is imaged, the image is an image formed by forming transmitted illumination (that is, the repetitive pattern 56), the light intensity distribution anomaly suggesting the presence of defects could not be detected.

1A and 1B are schematic views illustrating the configuration of a photomask as an object to be inspected according to an embodiment of the present invention, where FIG. 1A is a plan view of the photomask and FIG. 1B is a cross-sectional view of the photomask. Yes. It is the schematic which illustrates the structure of the repeating pattern with which the photomask as a to-be-inspected object concerning one Embodiment of this invention is provided. It is the schematic which shows the structure of the pattern defect inspection apparatus concerning one Embodiment of this invention. It is the schematic which shows the mode of the diffracted light which arises from the repetitive pattern when incident angle (theta) i is 0 degree, (a) is the diffraction light which arises from the repetitive pattern of the photomask for CCD whose unit pattern pitch d is 10 micrometers. (B) shows the state of diffracted light generated from the repetitive pattern of the photomask for display device in which the unit pattern pitch d is 200 μm. It is a table | surface figure which respectively shows diffraction angle (theta) n when incident angle (theta) i is 0 degree and the pitch d of a unit pattern is 10 micrometers, 100 micrometers, and 1000 micrometers. It is the schematic which illustrates the defect which generate | occur | produced in the repeating pattern arranged with the fixed regularity in the orthogonal direction, respectively, (a) and (b) are the defects of a coordinate position variation system, (c) and (d) are dimensions. Examples of fluctuating flaws are illustrated. FIG. 3 is an imaging diagram showing image data according to Example 1;

Explanation of symbols

10 pattern defect inspection equipment 11 stage (holding means)
12 Light source device (illumination means)
12a Light source 12b Irradiation optical system 14 Imaging device (light receiving means)
14a area camera 14b light receiving optical system 16 image analysis device (analysis means)
50 Photomask (inspection object)
53 Unit pattern 56 Repeat pattern d Pitch θi Incident angle θr Receiving angle θn Diffraction angle dθ Difference in diffraction angle

Claims (15)

A pattern defect inspection method for inspecting a defect generated in a repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged,
Irradiating the repeating pattern with light at a predetermined incident angle to generate diffracted light; and
Receiving diffracted light from the repetitive pattern and forming an image;
Observing an image formed by diffracted light to detect defects generated in the repetitive pattern,
In the step of receiving and diffracting the diffracted light to form an image, the pattern defect inspection method characterized by receiving ultrahigh-order diffracted light having an absolute value of 45th to 1600th of the diffracted light from the repetitive pattern.   The pattern defect inspection method according to claim 1, wherein the defect has regularity different from the period. 2. The step of receiving and diffracting the diffracted light receives ultra high-order diffracted light having an absolute value of 90th to 1600th of the diffracted light from the repetitive pattern. 2. The pattern defect inspection method according to 2. 4. The method according to claim 1, wherein in the step of receiving the diffracted light to form an image, the diffracted light is received at a light receiving angle of 90 ° with respect to a main plane of the repetitive pattern. 5. The pattern defect inspection method as described. In the step of irradiating the repeating pattern with light at a predetermined incident angle to generate diffracted light, the incident angle is 30 ° to 60 ° with respect to the main plane of the repeating pattern, and the light is received and imaged. 5. The pattern defect inspection method according to claim 1, wherein in the step, light is irradiated at an incident angle at which the ultrahigh-order diffracted light can be received. 6. The pattern defect inspection method according to claim 1, wherein a pitch of the unit pattern is 50 μm to 1000 μm. The pattern defect inspection method according to claim 1, wherein the object to be inspected is a photomask that exposes light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm.   The pattern defect inspection method according to claim 1, wherein the photomask is a photomask for manufacturing a liquid crystal display device. A pattern defect inspection apparatus for inspecting a defect generated in a repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged,
Illumination means for irradiating the repetitive pattern with light at a predetermined incident angle to generate diffracted light;
A light receiving means for receiving and diffracted light from the repetitive pattern to form an image;
An analysis means for detecting defects generated in the repetitive pattern by observing an image formed by imaging the diffracted light, and
The light receiving means receives a very high order diffracted light having an absolute value of 45th to 1600th of the diffracted light from the repetitive pattern. 10. The pattern defect inspection apparatus according to claim 9, wherein the light receiving unit receives ultrahigh-order diffracted light having an absolute value of 90th to 1600th out of diffracted light from the repetitive pattern. The pattern defect inspection apparatus according to claim 9, wherein the light receiving unit receives the diffracted light at a light receiving angle of 90 ° with respect to a main plane of the repetitive pattern. The illumination means irradiates light at an incident angle of 30 ° to 60 ° with respect to the main plane of the repetitive pattern, and the light receiving means can receive the ultrahigh-order diffracted light. The pattern defect inspection apparatus according to any one of claims 7 to 11. The pattern defect inspection apparatus according to claim 9, wherein a pitch of the unit patterns is 50 μm to 1000 μm. The pattern defect inspection apparatus according to claim 9, wherein the object to be inspected is a photomask that exposes light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm.   The pattern defect inspection apparatus according to claim 9, wherein the photomask is a photomask for manufacturing a liquid crystal display device.