JP4869129B2 - Pattern defect inspection method - Google Patents

Description

  The present invention relates to 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.

  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.

Patent Document 1 discloses that illumination is performed so that diffracted light is generated in an inspection region of a photomask, and high-order diffracted light having a predetermined order or higher among the diffracted light is selectively incident. In addition, it is described that the predetermined order is + 11th order or −11th order.
JP-A-2005-233869

  Even if the defect is within an allowable range as an individual pattern shape, the defect is likely to be detected when the display device is used because it is periodically arranged according to a certain rule. However, in order to detect these defects in advance, the number of unit patterns is enormous even if it is attempted to carry out a micro inspection that individually measures the dimensions and coordinates of each unit pattern. Have difficulty.

  According to Patent Document 1, since the high-order diffracted light contains fine information on the object structure, the image obtained by re-diffraction (synthesis) of the high-order diffracted light is only the low-order diffracted light. It is said that the reproducibility of a fine part is superior to an image obtained by re-diffraction. However, according to studies by the present inventors, it has been found that it is not sufficient to select high-order diffracted light in order to detect pattern defects with high accuracy. That is, in order to accurately determine the presence of a defect, when receiving and observing the diffracted light obtained by irradiating light to the repeated pattern, information resulting from the defect and the original repeated pattern without the defect It was found that a signal-to-noise ratio that can be clearly distinguished from the information resulting from is required.

  Accordingly, the present invention provides a pattern that can clearly distinguish information resulting from a defect from information originating from a repetitive pattern having no defect when inspecting the defect by observing diffracted light generated from the repetitive pattern. An object is to provide a defect inspection method and a pattern defect inspection apparatus.

A first aspect of the present invention is 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 light at a predetermined incident angle to generate diffracted light, receiving diffracted light from the repetitive pattern to form an image, and observing an image formed by diffracted light Detecting defects that occur in the repetitive pattern,
In this pattern defect inspection method, the arrangement pitch of the unit patterns is 1 μm to 8 μm.

  According to a second aspect of the present invention, in the step of receiving the diffracted light to form an image, the diffracted light from the repetitive pattern is selected and received from the diffracted light having an absolute value of the order of 1 to 10. It is a pattern defect inspection method as described in 1 aspect.

  A third aspect of the present invention is the pattern defect inspection method according to any one of the first and second aspects, wherein a wavelength of light applied to the repetitive pattern is 380 nm to 780 nm.

  The fourth aspect of the present invention is the pattern defect according to any one of the first to third aspects, wherein the diffracted light from the repetitive pattern is received at a light receiving angle of 90 ° with respect to the main surface of the repetitive pattern. Inspection method.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the light irradiation to the repetitive pattern is performed at an incident angle of 30 ° to 60 ° with respect to a main surface of the repetitive pattern. This is a pattern defect inspection method.

  In a sixth aspect of the present invention, the inspection object includes a transparent substrate, and the repetitive pattern is formed of a light-shielding material or a semi-light-shielding material on the main surface of the transparent substrate. To 5. The pattern defect inspection method according to any one of aspects 5 to 5.

  In a seventh aspect of the present invention, the repetitive pattern is a test pattern drawn simultaneously with a main pattern having a repetitive pattern arranged on the transparent substrate with a different period from the repetitive pattern. It is a pattern defect inspection method as described in the aspect.

  An eighth aspect of the present invention is a pattern defect inspection method for inspecting a defect generated in the repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged. Irradiating light at a predetermined incident angle to generate diffracted light, receiving diffracted light from the repetitive pattern to form an image, and observing an image formed by diffracted light A step of detecting defects generated in the repetitive pattern, and in the step of forming an image by receiving the diffracted light, among the diffracted light from the repetitive pattern, the diffracted light having an absolute value of the order of 1 to 10 This is a pattern defect inspection method for selecting and receiving light.

  A ninth aspect of the present invention is a pattern defect inspection method for inspecting a defect generated in the repetitive pattern of an object to be inspected having a repetitive pattern in which unit patterns are periodically arranged. Forming a test pattern in which test unit patterns are periodically arranged at different pitches by simultaneously drawing the test pattern in a region other than the repetitive pattern, and a predetermined incident angle on the test pattern. Irradiating with light to generate diffracted light, receiving diffracted light from the test pattern and forming an image, and observing the image formed with the diffracted light to form the repetitive pattern And a step of detecting the generated defect, and a pattern defect inspection method in which the pitch of the arrangement of the test unit patterns is 1 μm to 8 μm It is.

  In a tenth aspect of the present invention, in the step of receiving and diffracting the diffracted light, the diffracted light having an absolute value of the order of 1 to 10 is selected and received from the diffracted light from the test pattern. The pattern defect inspection method according to the ninth aspect.

  An eleventh aspect of the present invention is the pattern defect inspection method according to the ninth or tenth aspect, wherein a wavelength of light applied to the test pattern is 380 nm to 780 nm.

  In a twelfth aspect of the present invention, the diffracted light from the test pattern is received at a light receiving angle of 90 ° with respect to the main surface of the test pattern. This is a pattern defect inspection method.

  A thirteenth aspect of the present invention is the light emitting device according to any one of the ninth to twelfth aspects, wherein the light irradiation of the test pattern is performed at an incident angle of 30 ° to 60 ° with respect to the main surface of the test pattern. This is a pattern defect inspection method.

  In a fourteenth aspect of the present invention, the object to be inspected includes a transparent substrate, and the repeating pattern and the test pattern are formed of a light-shielding material or a semi-light-shielding material on a main surface of the transparent substrate. The pattern defect inspection method according to any one of the ninth to thirteenth aspects.

  A fifteenth aspect of the present invention is the pattern defect inspection method according to any one of the first to fourteenth aspects, wherein the diffracted light is diffracted light by reflected light of light irradiated on the repetitive pattern.

  A sixteenth aspect of the present invention is the pattern defect inspection according to any one of the first to fifteenth aspects, 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. Is the method.

  A seventeenth aspect of the present invention is the pattern defect inspection method according to the sixteenth aspect, wherein the photomask is a photomask for manufacturing a liquid crystal display device.

  An eighteenth aspect of the present invention is a photomask manufacturing method including a step of inspecting a defect using the pattern defect inspection method according to any one of the first to seventeenth aspects.

  According to a nineteenth aspect of the present invention, there is provided a drawing machine for inspecting a defect using the pattern defect inspection method according to any one of the first to seventeenth aspects and drawing the repetitive pattern based on the inspection result. It is a manufacturing method of a photomask which has a process of evaluating drawing accuracy.

  According to a twentieth aspect of the present invention, the photomask manufactured by the method for manufacturing a photomask according to the eighteenth to nineteenth aspects is exposed to light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm, and the photomask In this pattern transfer method, a pattern formed on a mask is transferred onto a transfer target.

  According to the pattern defect inspection method and the pattern defect inspection apparatus according to the present invention, it is possible to clearly distinguish information resulting from a defect from information resulting from an original repetitive pattern.

<A> One Embodiment of the Invention 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 pattern defect inspection apparatus (4) The pattern defect inspection method according to this embodiment will be described in order.

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

  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. For example, in the case of a photomask for a display device substrate, as illustrated in FIG. 1A, it is often configured as a substrate having sides L1 and L2. 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. In order to perform overall exposure using such a large photomask 50, the light quantity is given priority over the resolution. Therefore, as an exposure light source, light in a predetermined wavelength region including wavelengths of 365 nm to 436 nm is emitted. Such a light source is often used.

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

  As a material of the transparent substrate 57, for example, synthetic quartz glass or the like is used. Moreover, as a material of the thin film which comprises the repeating pattern 56, the material which has light-shielding properties, such as chromium, the material which has translucency, etc. are used, for example. 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. Hereinafter, the arrangement period of the unit patterns 53 is referred to as a pitch d of the unit patterns 53. The shape of the unit pattern 53 is not limited to the lattice shape, and may be configured as a repetitive pattern of other shapes such as a line and space shape.

(2) Defects generated in the photomask In the above, the unit patterns 53 should be arranged according to a predetermined rule. However, for some reason in the manufacturing process or the like, a defect (so-called uneven defect) in which some unit patterns are arranged according to a rule different from the above rule may occur. Below, the defect which arises in the repeating pattern 56 is demonstrated, using the manufacturing method of the photomask 50. FIG. As described above, line width anomalies and misalignments in line-and-space unit patterns are also included in the defects to be inspected in the present embodiment.

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. 5A and 5B are schematic views illustrating defects generated in a repetitive pattern. FIGS. 5A and 5B illustrate coordinate position variation type defects, and FIGS. 5C and 5D illustrate dimension variation type defects, respectively. is doing. In FIG. 5, a location where a defect has occurred is indicated by reference numeral 54.

  For example, FIG. 5A 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. 5B 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.

  Further, in FIGS. 5C and 5D, the size of the unit pattern 53 ′, that is, the width of the lattice frame 53a ′ fluctuates 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.

〔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, the light source device 12 and the imaging device 14 may be configured to be movable with respect to the stage 11. In this case, the light source device 12 and the imaging device can be moved relative to the object to be inspected. At this time, it is advantageous to arrange the light source device 12 and the imaging device 14 on the same side with respect to the object to be inspected and to integrally form the device, and to receive the reflected light from the object to be inspected. This is because it is easy to move the light source device 12 and the imaging device 14 synchronously while preventing the deviation of the optical axis.

[Light source device]
The light source device 12 as an illuminating unit is configured to irradiate light at a predetermined incident angle onto 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 °). It is preferable. The wavelength λ of the light from the light source device 12 is preferably set to a wavelength of 380 nm to 780 nm (visible light region) in order to obtain the above-described luminance at low cost and to realize the imaging device 14 described later at low cost. . 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 is configured to collimate 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. In addition, incident angle (theta) i here means the angle pinched | interposed into the normal line of the support surface of the stage 11, and the optical axis of irradiation light. In FIG. 1, the light source device 12 is disposed obliquely below the support surface of the stage 11, and the light receiving means described later receives transmitted light from the repetitive pattern, but on the support surface of the stage 11. It may be arranged diagonally upward. In that case, the light receiving means receives reflected light in which a repeated pattern is generated. In addition, according to the method using reflected light, what formed the pattern on the board | substrates other than transparency as a to-be-inspected object is applicable. Furthermore, as described above, the method using reflected light allows the irradiation optical system and the imaging device to be installed on the same side with respect to the object to be inspected. This is advantageous for maintaining stability. Furthermore, in the method using reflected light, the amount of received light is large compared to the case where transmitted light is received (it is not necessary to consider attenuation due to light absorption by the substrate), and the angle of the optical system can be easily controlled (substrate). There is no need to take into account the influence of refraction due to the thickness of the substrate), and there is an advantage in inspection accuracy.

  The incident angle θi is preferably 30 ° to 60 °. This is because if the incident angle θi is too large, the absolute value of the order of diffracted light received by the imaging device 14 described later increases, the amount of diffracted light decreases, and it becomes difficult to detect defects. Further, as described above, the repetitive pattern 56 is formed on the transparent substrate 57. However, if the incident angle θi is too large, it becomes difficult to irradiate light with a uniform illuminance in the region to be inspected. Absent. On the other hand, if the incident angle θi is too small, the transmitted light that has repeatedly transmitted through the pattern 56 is received by the imaging device 14, and the diffracted light including the defect signal is buried in the transmitted light with high intensity (zero-order light). This is because it becomes difficult to detect defects.

[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 repeated pattern 56 and forms an image on the light receiving surface of the area camera 14a. As shown in FIG. 4, the light receiving optical system 14b includes an objective lens 14c that condenses the diffracted light and a diaphragm 14d. The aperture NA of the objective lens 14c is configured to be smaller than the wavelength λ / pitch d by the objective aperture 14d. Note that the field of view of the imaging device 14 via the light receiving optical system 14b is configured to be, for example, a square or rectangle having a side of 10 mm to 50 mm.

  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. The light receiving angle θr is preferably substantially 90 °. When the imaging device 14 is arranged on the normal line of the support surface of the stage 11, distortion (area camera) is compared to the case where the imaging device 14 is arranged obliquely with respect to the support surface of the stage 11. This is because the image becomes smaller as it is farther from the light-receiving surface 14a, and the image becomes larger as it is closer, and distortion that makes the image trapezoidal is less likely to occur. That is, it is easy to obtain a uniform image within the same inspection field.

  Note that an image of diffracted light (hereinafter referred to as an area image) formed on the light receiving surface of the area camera 14a is configured to be output to the image analysis device 16 as image data.

[Image analyzer]
The image analysis device 16 as an analysis means observes the area image output from the imaging device 14 and detects the presence or absence of a defect that has occurred in the repeated pattern 56 by detecting a change in the light intensity distribution in the area image. It is configured to be able to. The reason why the defect can be detected by detecting the change in the light intensity distribution will be described later in the section of (4) Pattern defect inspection method.

  That is, the image analysis device 16 is configured to create numerical data obtained by digitizing the light intensity distribution in the area image after receiving the image data of the area image from the imaging device 14. Then, the image analysis device 16 objectively detects the change in the light intensity distribution by quantitatively comparing the numerical data and numerical data (reference data) based on the area image when there is no defect. It is configured.

  In addition, after receiving the image data of the area image, the image analysis device 16 differentiates the area image to create a differential image indicating the distribution of the light intensity change rate, and numerically represents the distribution of the light intensity change rate. Configured to create data. Then, the image analysis device 16 quantitatively compares the numerical data with numerical data (reference data) obtained by differentiating the area image when there is no defect, thereby detecting anomaly detection sensitivity of the light intensity distribution. It is configured to improve.

(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 light at an incident angle θi obliquely from below with respect to the main plane of the repeated pattern 56.

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

  FIG. 4 is a schematic view showing a state in which light is incident on the repetitive pattern 56 at an incident angle θi and diffracted light is received at a light receiving angle of 90 °. FIG. 4A shows a case where the unit pattern pitch d is 10 μm. (B) shows the relationship between the order of the diffracted light and the incident angle in this case. (C) shows the state of diffracted light when the unit pattern pitch d is 1 μm, and (d) shows the relationship between the order of the diffracted light and the incident angle in such a case. According to FIG. 4, it can be seen that the greater the pitch d of the unit patterns 53, the smaller the difference Δθ in diffraction angles between adjacent diffracted lights (that is, the difference between θn ± 1 and θn).

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

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 should have 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, when the incident angle .theta.i, diffraction angle theta _n are the same, the area image by the repeated pattern 56 'a defect occurs, the area image by repeating the pattern 56 is not defective, some differences occur It will be. Specifically, a change in the light intensity distribution due to the defect appears in the former area image. This anomaly in the light intensity distribution does not appear in the latter area image.

  Thereafter, the imaging device 14 outputs the image data of the area image to the image analysis device 16.

  In the above description, the case where light is radiated from diagonally below the repetitive pattern 56 and diffracted light is received by the transmission surface has been described as an example. Similar results can be obtained when diffracted light is received.

[Step of detecting presence or absence of defect (S3)]
As described above, in the area image from the repetitive pattern 56 ′ in which the defect has occurred, a change in the light intensity distribution indicating the presence of the defect appears. Therefore, the image analysis device 16 causes the area image to be observed and inspects for the presence or absence of a defect generated in the repeated pattern 56.

Specifically, the image analysis device 16 is caused to receive the image data of the area image output from the imaging device 14, and the differential light intensity distribution of the area image is differentiated to create a differential image in which the change is emphasized. The presence or absence of a defect is detected by observing a change (abnormality) in the intensity distribution.

As described above, it is preferable that the wavelength λ of the incident light is 380 nm to 780 nm, the incident angle θi is 30 ° to 60 °, and the light receiving angle θr is substantially 90 °. In this case, the pitch d of the unit patterns 53 is preferably 1 μm to 8 μm. At this time, when the area image or its differential image is observed, the signal caused by the defect is clearly higher than the signal caused by the original repetitive pattern (repetitive pattern having no defect) with an SN ratio of 1.2 or more. It is possible to distinguish. Further, according to the relational expression d (sin θ _n ± sin θi) = nλ described above, if the wavelength λ, the incident angle θi, the light receiving angle θr, and the pitch d are the above-described conditions, the imaging device 14 determines the absolute value of the order. It can receive 1st to 10th order diffracted light. The diffracted light having an absolute value of the order of 1 to 10 has a large amount of light and can obtain a bright area image, and it is possible to reliably detect a fluctuation (abnormality) in the light intensity distribution indicating the presence of a defect.

(5) Effects in the present embodiment According to the present embodiment, the following effects [1] to [4] are obtained.

  [1] According to the present embodiment, fine defects generated in the repetitive pattern 56 clearly appear as a change in the light intensity distribution in the area image. Therefore, the defect of the repeated pattern 56 is inspected by observing the change in the light intensity distribution in the area image without performing the inspection (micro inspection) for individually measuring the dimensions and coordinates of each unit pattern 53. It becomes possible. If such an inspection is performed on a macro region including a plurality of unit patterns 53 (that is, an inspection field having a side or a square of 10 mm to 50 mm), the inspection time of the photomask 50 can be shortened, and productivity can be reduced. It becomes possible to improve.

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 this embodiment, 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 S1 to S3) If the execution time 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 the present embodiment, when the wavelength λ of incident light is 380 nm to 780 nm, the incident angle θi is 30 ° to 60 °, and the light receiving angle θr is substantially 90 °, the unit pattern By setting the pitch d of 53 to 1 μm to 8 μm, the imaging device 14 can clearly observe the change in the light intensity due to the defect. At this time, diffracted light having an absolute value of the order of 1 to 10 can be received, but the diffracted light having the absolute value of the order of 1 to 10 has a large amount of light, and a bright area image can be obtained. It becomes possible to detect the fluctuation (abnormality) of the light intensity distribution indicating the presence with high reliability.

  [3] According to this embodiment, the image analysis device 16 quantitatively compares the numerical data obtained by digitizing the light intensity distribution in the area image with the numerical data based on the area image when there is no defect. Detecting abnormalities (defects) in the light intensity distribution. That is, by numerically analyzing the light intensity distribution and quantitatively analyzing it, it is possible to objectively detect the presence or absence of a defect without relying on the visual impression of the worker. Thereby, it is possible to suppress the variation in the inspection result and improve the reliability of the inspection.

  [4] According to the present embodiment, the differential image in which the change in the light intensity distribution is emphasized by differentiating the area image is created, the numerical data obtained by quantifying the light intensity change distribution in the differential image, and there is no defect. By quantitatively comparing the numerical data obtained by differentiating the area image in this case, it is possible to further improve the detection sensitivity of the light intensity distribution anomaly (defect).

<B> Other Embodiments of the Present Invention Next, other embodiments of the present invention will be described.

  As described above, it is preferable that the wavelength λ of incident light is 380 nm to 780 nm, the incident angle θi is 30 ° to 60 °, and the light receiving angle θr is substantially 90 °. In this case, by setting the pitch d of the unit patterns 53 to 1 μm to 8 μm, it is possible to clearly distinguish information resulting from defects and information resulting from repeated patterns without defects. . However, the pitch d of the unit pattern 53 is determined according to the use and specifications of the object to be inspected, and in practice, the pitch d of the unit pattern 53 may exceed 8 μm.

  Here, when the pitch d of the unit patterns 53 is large, the difference Δθ in diffraction angles between adjacent diffracted lights becomes small. Therefore, when the wavelength λ, the incident angle θi, the light receiving angle θr, and the pitch d are the above-described conditions, the absolute value of the order of the diffracted light received by the imaging device 14 is much larger than 1-10. turn into. Since such high-order diffracted light has a small amount of light, the area image becomes dark, and it may be difficult to reliably detect fluctuation (abnormality) in the light intensity distribution indicating the presence of a defect.

However, when the pitch d of the unit pattern 53 exceeds 8 μm, the test pattern 56 t in which the test unit patterns are periodically arranged at a pitch different from the unit pattern 53 is repeated in an area other than the repeated pattern 56. The above-mentioned problem can be solved by forming the pattern 56 simultaneously with the pattern 56 and setting the pitch d of the test unit pattern 53t to 1 μm to 8 μm. The pitch of the test pattern of the present invention may be less than 1 μm. However, for the purpose of ensuring the drawing accuracy of the test pattern and preventing the drawing data from having an excessive capacity, the pitch of the test pattern is 1 μm or more. Is preferred. In particular, regarding the latter, the object to be inspected of the present invention is large in size with a side of 300 mm or more, and more effective with a side of 1 m or more. Therefore, it is significant to suppress the drawing capacity.

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

(1) Configuration of Photomask As shown in FIG. 8, a photomask as an object to be inspected according to this embodiment was formed simultaneously with a repetitive pattern 56 on the main surface of a transparent substrate 57 as a transparent support. The difference from the above-described embodiment is that a test pattern 56t made of a thin film (light-shielding film) is provided. The test pattern 56 t is provided in a region other than the repeated pattern 56, for example, around the repeated pattern 56 on the main surface of the transparent substrate 57.

  The shape of the test pattern 56t is, for example, a shape in which lattice-shaped test unit patterns 53t are periodically arranged. Here, the pitch d of the test unit pattern 53t can be determined independently of the pitch d of the unit pattern 53, and is configured to be, for example, 1 μm to 8 μm. The shape of the test pattern 56t is not limited to the lattice shape, and may be configured as a repetitive pattern of other shapes such as a line and space shape.

  Here, the drawing of the test pattern 56 t is performed simultaneously with the drawing of the repeated pattern 56. That is, the test pattern 56t and the repeated pattern 56 are continuously drawn on the resist film formed on the transparent substrate 57 using the same drawing machine. Therefore, when a defect occurs repeatedly in the pattern 56 due to a scanning abnormality of the drawing machine, the same defect occurs in the test pattern 56t.

  Other configurations are the same as those of the photomask according to the above-described embodiment.

(2) Configuration of Pattern Defect Inspection Device Next, a configuration example of the pattern defect inspection device 10 according to another embodiment of the present invention will be described.

  The light source device 12 as an illuminating unit according to the present embodiment is configured to generate diffracted light by irradiating the test pattern 56t of the photomask 50 held on the stage 11 with light at a predetermined incident angle. This is different from the pattern defect inspection apparatus 10 according to the above-described embodiment. Further, the imaging device 14 as the light receiving means according to the present embodiment is configured to receive the diffracted light from the test pattern 56t and form an image thereof, which is the pattern defect inspection according to the above-described embodiment. Different from the device 10. Further, the image analysis device 16 as an analysis unit according to the present embodiment observes an image formed by diffracted light from the test pattern 56t (an area image formed by receiving the image by the image pickup device 14). Therefore, it is different from the pattern defect inspection apparatus 10 according to the above-described embodiment in that the presence / absence of a defect generated in the repeated pattern 56 can be indirectly detected.

  Other configurations are the same as those of the pattern defect inspection apparatus 10 according to the above-described embodiment.

(3) 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.

  First, the test pattern 56t described above is formed by drawing simultaneously with the repeating pattern 56 in an area other than the repeating pattern 56.

  Subsequently, the photomask 50 provided with the repeated pattern 56 and the test pattern 56t 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 test pattern 56t with an incident angle θi obliquely from below.

  Subsequently, using the imaging device 14, the diffracted light from the test pattern 56 t is received and imaged. That is, the diffracted light from the test pattern 56t is received by the light receiving optical system 14b and formed on the light receiving surface of the area camera 14a to obtain an area image.

  Subsequently, the image analysis device 16 receives the image data of the area image of the test pattern 56t, creates a differential image that differentiates the light intensity distribution of the area image and emphasizes the change, and changes the light intensity distribution. By observing (abnormality), the presence / absence of a defect in the repeated pattern 56 is detected.

  Other configurations are the same as those of the pattern defect inspection method according to the above-described embodiment.

(4) Effects in the present embodiment According to the present embodiment, in addition to the effects [1] to [4] in the embodiment of the present invention described above, the following effects are further exhibited.

  [5] According to the present embodiment, even when the pitch d of the unit patterns 53 exceeds 8 μm, it is possible to reliably detect defects generated in the repeated pattern 56 in a short time using diffracted light. . That is, according to the present embodiment, the test pattern 56 t in which the test unit patterns are periodically arranged at a pitch different from the unit pattern 53 is drawn simultaneously with the repetitive pattern 56 in an area other than the repetitive pattern 56. When a defect occurs in the repetitive pattern 56, a defect also occurs in the test pattern 56t drawn at the same time. Therefore, it is possible to inspect the repetitive pattern 56 indirectly by inspecting the test pattern 56t. is there.

  [6] According to the present embodiment, the pitch d of the test unit pattern 53t can be determined independently of the pitch d of the unit pattern 53, and can be set to 1 μm to 8 μm. Therefore, in the case where the wavelength λ of the incident light is 380 nm to 780 nm, the incident angle θi is 30 ° to 60 °, and the light receiving angle θr is substantially 90 °, the absolute value of the order is 1 to 10th order diffracted light. Can be received by the imaging device 14. Therefore, a bright area image can be obtained, and a fluctuation (abnormality) in the light intensity distribution indicating the presence of a defect can be clearly and reliably detected.

  Hereinafter, examples of the present invention will be described with reference to comparative examples. In the drawings to be referred to, FIG. 7A is a graph summarizing the defect detection capability according to the example of the present invention and the comparative example, and FIG. 7B shows the case where the pitch d is 4 μm (Example 1). (C) shows a case where the pitch d is 8 μm (Example 2), (d) shows a case where the pitch d is 12 μm (Comparative Example 1), and (e) shows a case where the pitch d is 20 μm (Comparison) It is a graph which shows the distribution of the light intensity change rate in Example 2), respectively.

  First, as Example 1, a photomask 50 having a unit pattern 53 having a pitch d of 4 μm and a repetitive pattern 56 ′ in which a defect having a large line width of about 10 nm is intentionally generated in one row of the array. Prepared as a test object. Then, the light source device 12 irradiates light having a wavelength λ of 546 nm to the repetitive pattern 56 ′ with an incident angle θi of 45 °. And after obtaining the area image of the diffracted light corresponding to the absolute value of the order 5 by the imaging device 14 installed in the direction where the light receiving angle θr is 90 °, a differential image is created and the light intensity change distribution is obtained. It was digitized and shown in the graph. As a result, as shown in FIG. 7B, an abnormal change (pulse-like peak) in the light intensity distribution indicating the presence of defects was observed with a high S / N ratio (1.7 or more).

  Next, as Example 2, the pitch d of the unit patterns 53 was 8 μm. The repetitive pattern 56 ′ was irradiated with an incident angle θi of 45 °. Then, after obtaining an area image of diffracted light corresponding to an absolute value of order 10 by the imaging device 14, a differential image was created, and the light intensity change distribution was digitized and shown in the graph. As a result, as shown in FIG. 7C, an abnormal change (pulse-like peak) in the light intensity distribution indicating the presence of defects was observed with a high S / N ratio (1.5 or more).

  Next, as Comparative Example 1, the pitch d of the unit patterns 53 was set to 12 μm. The repetitive pattern 56 ′ was irradiated with an incident angle θi of 45 °. Then, after obtaining an area image of diffracted light corresponding to the absolute value of the order of 15 by the imaging device 14, a differential image was created, and the light intensity change distribution was digitized and shown in the graph. As a result, as shown in FIG. 7 (d), it was difficult to recognize a change in the light intensity distribution indicating the presence of a defect (pulse-like peak) with a good S / N ratio (less than 1.1 S / N ratio). ).

  Next, as Comparative Example 2, the pitch d of the unit patterns 53 was set to 20 μm. The repetitive pattern 56 ′ was irradiated with an incident angle θi of 45 °. Then, after obtaining an area image of the diffracted light corresponding to the absolute value of the order 25 by the imaging device 14, a differential image was created, and the light intensity change distribution was digitized and shown in the graph. . As a result, as shown in FIG. 7 (e), it was difficult to recognize abnormalities (pulse-like peaks) in the light intensity distribution indicating the presence of defects (S / N ratio less than 0.01).

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 a mode that irradiates light with incident angle (theta) i, and receives a diffracted light with a light-receiving angle of 90 degrees, (a) is a mode of the diffracted light in case the unit pattern pitch is 10 micrometers. (B) shows the relationship between the order of the diffracted light and the incident angle when the pitch is 10 μm, (c) shows the state of the diffracted light when the unit pattern pitch is 1 μm, and (d) shows the case when the pitch is 1 μm. The relationship between the order of the diffracted light and the incident angle is shown respectively. It is the schematic which illustrates the defect which arose in the repetitive pattern, (a) and (b) illustrate the defect of a coordinate position variation system, (c) and (d) illustrate the defect of a dimension variation system, respectively. (A) shows a repetitive pattern in which a defect occurs, (b) shows an area image formed by receiving diffracted light generated from this repetitive pattern, and (c) differentiates the light intensity of this area image. The differential image which emphasized the fluctuation | variation of light intensity distribution is shown, and the graph figure which shows the fluctuation | variation of the light intensity change is shown. (A) is the graph which summarized the defect detection capability concerning the Example and comparative example of this invention, (b) is a case where the pitch d is 4 micrometers (Example 1), (c) is the pitch d. Is a case where the pitch d is 12 μm (Comparative Example 1), and (e) is a change in light intensity when the pitch d is 20 μm (Comparative Example 2). It is a graph which shows distribution of a rate, respectively. It is the schematic which illustrates the structure of the photomask as a to-be-inspected object concerning other embodiment of this invention, (a) shows the top view of a photomask, (b) shows the cross-sectional view of a photomask, respectively. ing.

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 53t test unit pattern 56 repetitive pattern 56t test pattern d pitch θi incident angle θr light receiving angle θn diffraction angle Δθ difference in diffraction angle

Claims (13)

A pattern defect inspection method for inspecting defects generated in a repetitive pattern of a photomask for manufacturing a display device , comprising a repetitive pattern in which unit patterns are periodically arranged,
The photomask has a repetitive pattern in which the unit patterns are arranged at a pitch exceeding 8 μm, and a test pattern formed in a region other than the repetitive pattern by drawing simultaneously with the repetitive pattern,
The test pattern includes a test unit pattern arranged at a pitch of 1 to 8 μm, and
Irradiating the test pattern with light at a predetermined incident angle to generate diffracted light;
Receiving diffracted light from the test pattern and forming an image;
Pattern defect inspection method characterized by chromatic and a step of detecting a defect generated in the repeated pattern by observing the image obtained by imaging the diffracted light. In the step of forming an image by receiving the diffracted light, among diffracted light from the test pattern, to claim 1, wherein the absolute value of the order is received by selecting diffracted light 10 The pattern defect inspection method as described. Pattern defect inspection method according to claim 1 or 2, characterized in that the wavelength of the light irradiated to the test pattern, and 780nm from 380 nm. Said light receiving diffracted light from the test pattern, the pattern defect inspection method according to any one of claims 1 to 3, characterized in that the light-receiving angle of 90 ° to the principal surface of the test pattern. The irradiation of the light of the test pattern, the pattern defect inspection method according to any one of claims 1 to 4, characterized in that at an incident angle of 30 ° to 60 ° to the main surface of the test pattern . The photomask includes a transparent substrate,
The repeated pattern and the test pattern, the pattern according to the main surface of the transparent substrate, to claim 1, wherein the 5 to be composed of a light shielding material or semi-shielding material Defect inspection method. The diffracted light pattern defect inspection method according to any of claims 1 to 6, characterized in that said a diffracted light by the reflected light of light irradiated to the repeating pattern. The photomask pattern defect inspection method according to any one of claims 1 to 7, characterized in that a photomask for exposing light in a predetermined wavelength range in the wavelength range of 365Nm～436nm. The pattern defect inspection method according to claim 8 , wherein the photomask is a photomask for manufacturing a liquid crystal display device. Manufacturing method of a photomask, characterized by comprising a step of inspecting the defects using the pattern defect inspection method as claimed in any one of claims 9. Claims 1 using the pattern defect inspection method according to any one of claims 9 inspects the defects, further comprising the step of evaluating the drawing accuracy of the drawing machine for drawing the repeated pattern based on the result of the test A photomask manufacturing method characterized by the above. The photomask manufactured by the photomask manufacturing method according to claim 10 or 11 is exposed to light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm, and a pattern formed on the photomask is exposed. A pattern transfer method comprising transferring onto a transfer body. Repetitive patterns for manufacturing display devices in which unit patterns are periodically arranged at a pitch exceeding 8 μm;
A display device manufacturing photomask having a test pattern formed in a region other than the repetitive pattern by drawing simultaneously with the repetitive pattern,
The said test pattern is a photomask for display device manufacture for exposure by the wavelength of 365-436 nm provided with the unit pattern for a test arranged with the pitch of an array of 1-8 micrometers .