JP5659507B2 - Pattern drawing apparatus state monitoring method and state monitoring apparatus - Google Patents

Description

The present invention relates to a state monitoring method and a state monitoring apparatus for a pattern drawing apparatus for monitoring a state of the pattern drawing apparatus, with a substrate on which a periodic pattern is formed by the pattern drawing apparatus as a state monitoring target.
The periodic pattern refers to an aggregate of patterns having a constant interval. For example, a periodic pattern of stripes in which patterns are arranged at a predetermined pitch, or a pattern of openings is two-dimensional with a predetermined period. For example, a matrix pattern or the like arranged in a regular manner is applicable. Examples of the substrate having a periodic pattern include a photomask that is used in an exposure process of photolithography when manufacturing a semiconductor device, an imaging device, a display device, and the like.

  Conventionally, as a photomask used in a manufacturing process of a semiconductor device, an imaging device, a display device and the like, a photomask that is configured by partially removing a light shielding film such as chromium on a transparent substrate such as glass in a certain pattern is used. Are known.

  Uneven defects in a periodic pattern such as a photomask are usually caused by a regular arrangement of fine pitch deviations and positional deviations, and are therefore difficult to find by individual pattern inspection. However, it is a defect recognized for the first time when the periodic pattern is observed in a wide area.

  For the purpose of providing a periodic pattern unevenness inspection apparatus capable of imaging and detecting periodic pattern irregularities such as CCD and CMOS device photomask unevenness stably and with high accuracy, illumination light is applied to the object to be inspected. An inspection apparatus that performs image inspection on transmitted diffracted light that is irradiated and generated by a periodic pattern is known (for example, see Patent Document 1).

  In the normal part of the periodic pattern, the shape and pitch of the openings are constant, so that they interfere with each other and generate diffracted light in a certain direction. On the other hand, since the shape and pitch of the opening are irregular in the uneven portion, diffracted light is generated with various intensities in various directions depending on the shape and pitch. This inspection apparatus adopts a method of detecting the uneven portion from the difference in diffracted light intensity contrast between the normal portion and the uneven portion.

  In the photomask for manufacturing a CCD or CMOS device as disclosed in Patent Document 1, the pattern pitch is about 5 μm to 30 μm, and there are many patterns in which diffracted light at each diffraction order is easily separated from each other. However, for example, photomasks for manufacturing LCDs have a wide range of pattern pitches from about 20 μm to about 1000 μm, and the ratio is often larger than that of photomasks for manufacturing CCD and CMOS devices. In a pattern where the pattern pitch exceeds 100 μm, it is difficult to separate diffracted light from each other, and it has been thought that it is difficult to detect a nonuniform portion from a difference in contrast between a normal portion and an abnormal portion.

  On the other hand, for example, with respect to the main pattern (pattern period is 80 to 2000 μm), an auxiliary pattern (pattern period is 1 to 50 μm) having a different period from the main pattern, Formed by drawing simultaneously, capturing the error occurrence position due to drawing by capturing the diffracted light contrast difference from this auxiliary pattern, even in the main pattern arranged on the same straight line as the auxiliary pattern in which the error has occurred An inspection method that assumes that a similar error has occurred is known (for example, see Patent Document 2).

  However, in an actual drawing process, there is a possibility that a pattern size shift or a position shift partially occurs due to a variation in beam intensity or a shift in scan position during one beam scan. Even if they are in the same straight line, the degree of uneven defect may be changed, so that the method of Patent Document 2 is hardly effective.

  Moreover, many LCD photomasks have a larger pattern pitch than CCD and CMOS device photomasks. Therefore, even when macro imaging is performed, the pattern is resolved in the image to be inspected at the in-focus position, making it difficult to discriminate from uneven defects on the image to be inspected, and there is a problem that inspection accuracy is reduced. . Defocusing can be mentioned as a technique for reducing the influence of pattern resolution.

  There is an example (for example, refer to Patent Document 3) in which a substrate to be inspected is captured and an image is acquired in a state in which the focal position is intentionally shifted by the unevenness inspection method in the shadow mask. This is not a method of capturing diffracted light by irradiating light on the inspection surface from an oblique direction.

  As also shown in Patent Document 1, in order to stably detect unevenness in the periodic pattern, the diffracted light generated in the pattern is captured and attention is paid to the difference in the amount of diffracted light generated in the normal portion and the defective portion. Has been known to be effective.

  By the way, the drawing method in the pattern drawing apparatus is classified into a vector method and a raster method. An EB (electron beam) drawing apparatus is used for pattern drawing on a photomask for manufacturing a CCD or CMOS device or a photomask for manufacturing a substrate for a semiconductor device, most of which is based on a vector method in which only the drawing portion performs beam scanning. . On the other hand, a laser drawing apparatus is used for pattern drawing on an LCD manufacturing photomask, and a raster method is used in which the entire region is scanned and the beam is turned on only in the drawing portion.

  In many of these drawing apparatuses, there are many examples in which unique drawing parameters are provided. For example, a laser drawing apparatus for a photomask for LCD manufacturing has a parameter called “scan length” indicating one beam scanning width. To do. In the case where the pattern pitch and the scan length are different, there is an example in which the pattern dimension changes when the pattern edge and the boundary portion of the scan length overlap each other.

  In the EB drawing apparatus, a drawing area having a square shape called a drawing field (FIELD) is set, and an example in which a dimensional variation or a position variation of a pattern occurs at the drawing area boundary has been confirmed. The nonuniformity defect caused by the above phenomenon has periodicity depending on the drawing parameter, and therefore, the relationship between the drawing parameter and the nonuniformity generation period in the drawing apparatus has been regarded as important.

  And it can be said that the prior art mentioned above has remained in the content which concerns on the product inspection in a manufacturing process. From the viewpoint of preventing product defects discovered in the inspection process in the upstream process, uneven defects in products with periodic patterns formed on substrates such as LCD photomasks are effective. The state of the drawing device is monitored by visualizing the occurrence period and the generation cycle is easily derived, and the result of the feedback to the drawing device is used to set the optimum drawing conditions. The establishment of a method to prevent this is desired.

JP 2006-275609 A Japanese Patent No. 3366802 Japanese Patent Application Laid-Open No. 2007-271591

  The present invention has been made in view of the above circumstances, and in a pattern having periodicity, in particular, a substrate such as a photomask for LCD production, a pattern variation occurrence location is accurately identified from the contrast due to the difference in the amount of diffracted light, And it aims at providing the state monitoring method and state monitoring apparatus of a pattern drawing apparatus which can implement the state monitoring of a pattern drawing apparatus by deriving the fluctuation occurrence period simply.

The state monitoring method of the pattern drawing apparatus according to claim 1 of the present invention is directed to a state monitoring target on a substrate on which a periodic pattern is formed by the pattern drawing device, and irradiates illumination light to the substrate from an oblique direction. A method of monitoring a state of a pattern drawing apparatus that performs image acquisition using diffracted light generated by the periodic pattern and performs processing determination, and product information such as a pitch and size of the periodic pattern, and on the substrate A pattern information input step for inputting drawing information such as a pattern drawing condition and a type of the pattern drawing device, a positioning step for positioning the substrate in the in-plane direction of the image pickup, and the period input in the pattern information input step Imaging magnification to determine the imaging magnification from the relationship between pattern pitch and imaging resolution based on information about the sex pattern A defocusing step in which a surface on which the periodic pattern of the substrate is formed is an imaging surface, and a focal position is shifted by a predetermined amount with respect to the imaging surface in a vertical manner; An imaging step of capturing a periodic pattern of the substrate and acquiring a processed image at a focused position, and a luminance contrast generated between a normal portion and a varying portion of the periodic pattern with respect to the processed image A non-uniformity evaluation value calculating step for calculating a non-uniformity evaluation value , a non-uniformity defect period calculating step for obtaining a generation cycle of nonuniformity defects occurring on the substrate confirmed on the processed image, and the nonuniformity evaluation It is inputted in uneven period and before Symbol pattern information input step of determined magnitude of the irregularity evaluation value set determination threshold determined at a value calculation step, and in the uneven defect cycle calculating step And comparing the similarity between the pattern drawing condition, when the irregularity evaluation value is large and the unevenness in period than the determination threshold is similar to the pattern drawing condition is occurring on said substrate If it is determined that the unevenness defect is caused by a pattern drawing apparatus, and the unevenness evaluation value is smaller than the determination threshold value even if the unevenness period is similar to the pattern drawing condition, the unevenness defect is pattern-drawn. And a determination step for determining that it is not caused by the apparatus .

  The pattern drawing apparatus state monitoring method according to claim 2 of the present invention is the pattern drawing apparatus according to claim 1, wherein the pattern information input step includes imaging conditions for illumination at an arbitrary horizontal angle with respect to the periodic pattern of the substrate. It is possible to input conditions related to the horizontal angle direction between the illumination and the substrate.

  A pattern drawing apparatus state monitoring method according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the pattern pitch of the periodic pattern of the substrate is 20 μm to 400 μm.

  The pattern drawing apparatus state monitoring method according to claim 4 of the present invention is characterized in that, in any one of claims 1 to 3, the illumination light is green light having a center wavelength of 540 nm.

  The pattern drawing apparatus state monitoring method according to claim 5 of the present invention is any one of claims 1 to 4, wherein the imaging step uses diffracted light from the periodic pattern of the substrate using a photoelectric conversion element. The image pickup means is implemented by an image pickup means, and the image pickup means has an optical system that extracts only diffracted light perpendicular to the image pickup surface of the substrate out of the diffracted light generated by the periodic pattern of the substrate. It is characterized by that.

  According to a sixth aspect of the present invention, there is provided a state monitoring method for a pattern drawing apparatus according to any one of the first to fifth aspects, wherein the imaging magnification setting step uses an electric zoom lens to set the imaging magnification. It is characterized by.

  According to a seventh aspect of the present invention, there is provided the state monitoring method for a pattern drawing apparatus according to any one of the first to sixth aspects, wherein the defocusing step is such that the defocus amount from the in-focus position is greater than the focal depth of the optical system. It is large.

  The pattern drawing apparatus state monitoring method according to an eighth aspect of the present invention is the pattern drawing apparatus according to any one of the first to seventh aspects, wherein the defocusing step shifts the in-focus position in a direction away from the imaging surface vertically. It is characterized by that.

  The state monitoring method for a pattern drawing apparatus according to a ninth aspect of the present invention is the pattern monitoring device according to any one of the first to eighth aspects, wherein the uneven defect period calculating step is a two-dimensional operation on the processed image acquired by the imaging step. The period is calculated by using Fourier transform.

  The pattern drawing apparatus state monitoring method according to claim 10 of the present invention is the pattern drawing apparatus according to any one of claims 1 to 9, wherein the pattern drawing apparatus scans a pattern by scanning a krypton ion laser having a wavelength of 413 nm on the substrate. It is a raster pattern drawing device for drawing.

  According to claim 11 of the present invention, there is provided a state monitoring method for a pattern writing apparatus according to any one of claims 1 to 10, wherein the substrate is exposed to light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm. It is characterized by being a photomask.

  The pattern drawing apparatus state monitoring method according to claim 12 of the present invention is characterized in that in any one of claims 1 to 11, the substrate is a photomask for manufacturing a member for a liquid crystal display device.

A state monitoring device for a pattern drawing apparatus according to claim 13 of the present invention is directed to a state monitoring target on a substrate on which a periodic pattern is formed by the pattern drawing device, and irradiates illumination light to the substrate from an oblique direction. A state monitoring apparatus for a pattern drawing apparatus that performs image acquisition by using diffracted light generated by the periodic pattern and performs processing determination, and includes a mechanism for mounting the substrate and driving in the X-axis and Y-axis directions. And a positioning unit that performs predetermined image processing on an image obtained by irradiating a predetermined region of the substrate with light and imaging the predetermined region, and positioning the substrate in an in-plane direction of the imaged surface And an illumination head comprising a light source capable of generating visible light as illumination light, and an illumination that supports the illumination head and is substantially parallel to a certain area on the substrate placed on the transport means The illumination light irradiation angle φ with respect to the direction perpendicular to the surface to be imaged of the substrate can be controlled while the illumination head is driven, and the illumination head is driven in an angle θ direction horizontal to the surface to be inspected of the substrate. Illuminating head driving means capable of imaging, imaging means for imaging diffracted light caused by illumination light being applied to the periodic pattern of the substrate by the illumination head, and this imaging means for the surface to be inspected of the substrate An image pickup unit driving means that can be driven in the vertical direction (Z-axis direction), an image input means that uses a video output from the positioning means and a video output from the image pickup means as image information, and the periodic pattern Interpersonal operation means for inputting product information such as pitch, size, etc., pattern drawing conditions on the substrate, drawing information such as the type of the pattern drawing apparatus, and other operations Based on the information regarding the periodic pattern input by the interpersonal operation means, the imaging magnification determining means for determining the imaging magnification from the relationship between the pattern pitch and the imaging resolution, and the periodic pattern of the substrate are formed. A defocusing unit that shifts the in-focus position by a predetermined amount in a vertical direction with respect to the imaging surface, and a normal portion of the periodic pattern with respect to the processed image acquired by the imaging unit, Unevenness evaluation value calculating means for calculating unevenness evaluation values obtained by quantifying the brightness contrast generated between the fluctuation part and unevenness occurring on the substrate confirmed on the processed image acquired by the imaging means. and uneven defect period calculating means for calculating a generation period of a defect, the magnitude of the unevenness evaluation value set determination threshold determined in said unevenness evaluation value calculating means, and the unevenness defect periphery And uneven period calculated in calculation means before Symbol compares the similarity of the pattern drawn condition input in interpersonal operation means, large and the unevenness in period than the irregularity evaluation value is the threshold value for determining similarity between the pattern drawing condition and if that is uneven defect occurring on the substrate is determined to be a pattern writing apparatus caused the irregularity evaluation value even the uneven period similar to the pattern drawing conditions the A determination unit that determines that the unevenness defect is not caused by a pattern drawing device when the threshold value is smaller than a determination threshold ; the transport unit; the positioning unit; the illumination head; the illumination head drive unit; the imaging unit; A control unit for controlling the operation of the imaging unit driving unit, an image captured by the positioning unit and the imaging unit, and a process performed by the control unit. Display means for displaying the results.

  According to the present invention, in a pattern having periodicity, in particular, a substrate such as a photomask for LCD manufacturing, a pattern fluctuation occurrence location can be accurately identified from the contrast due to the difference in the amount of diffracted light, and the fluctuation occurrence period can be easily determined. By deriving, it is possible to provide a state monitoring method and a state monitoring device for a pattern drawing device capable of monitoring the state of the pattern drawing device.

The schematic diagram which shows schematically the principal part of the state monitoring apparatus of the pattern drawing apparatus which concerns on embodiment of this invention. The characteristic view which shows the spectral transmittance of the optical filter incorporated in the light source of the illumination head. The flowchart explaining the state monitoring method of a pattern drawing apparatus. The figure which shows typically the correspondence of a board | substrate and the light projection direction (theta) axis | shaft. The figure which shows typically the definition method of the rectangular calculation area | region with respect to a to-be-processed image. The figure which shows typically the calculation method of integrated value (SIGMA) I and the comparison reference value (SIGMA) 0 from a to-be-processed image. The figure which shows typically the power spectrum image derivation method by the two-dimensional Fourier transform from a to-be-processed image. The figure which shows typically the shape of the periodic pattern in a 1st Example. The figure which shows the acquired image and power spectrum image in a 1st Example. The figure which shows typically the shape of the periodic pattern in a 2nd Example. The figure which shows the acquired image and power spectrum image in a 2nd Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows a main part of a state monitoring apparatus for a pattern drawing apparatus according to an embodiment of the present invention. FIG. 1 shows an apparatus configuration example for obtaining transmitted diffracted light. In addition, it is desirable that this state monitoring apparatus is operated in a dark environment where disturbance light and stray light are reduced as much as possible and in a clean environment that prevents foreign matter from adhering to the substrate.

  As shown in FIG. 1, the state monitoring apparatus includes a transmission illumination unit 10, an XY stage unit 20 capable of positioning and transporting a substrate 60, and an alignment imaging unit for performing positioning of the substrate 60. 30, an imaging unit 40 that captures a diffraction image from the substrate 60 and acquires a processed image, and a processing / control unit 100.

  In the transmitted illumination unit 10, the arc rail 11 is installed on the turntable 12. An illumination head 13 is provided on the arc rail 11, and light is guided from the light source 14 to the illumination head 13 using a light guide 15. By driving the illumination head 13 on the arc rail 11, it is possible to adjust the irradiation angle in the direction perpendicular to the imaging surface of the substrate 60 (this drive axis is defined as the φ axis).

  The illumination head 13 is adjusted so that it can irradiate illumination light to a predetermined position on the XY stage unit 20 at any position on the arc rail 11, and thereby the XY stage unit. Transmitted illumination from various irradiation angles can be performed on the imaging surface of the substrate 60 on the substrate 20.

  Further, the turntable 12 can rotate the arc rail 11 in the horizontal direction with respect to the surface to be imaged (this drive axis is defined as the θ axis), and illumination light can be irradiated from an arbitrary direction in the horizontal direction. It has become.

  The illumination head 13 is provided with a parallel optical system. The light source 14 is provided with a filter changer mechanism, and a plurality of wavelength selection filters can be used. In the present embodiment, the peak wavelength is 540 nm having the spectral transmittance shown in FIG. A bandpass filter is used.

  Further, it is desirable that the light source 14 has sufficient illuminance, and a metal halide light source is used as the light source 14 in the present embodiment. If the illuminance is insufficient, an apparatus configuration using a plurality of light sources may be used.

  The substrate 60 is fixed in the X and Y directions by the work stopper 21 in the XY stage unit 20. The work stopper 21 can be fixed at a fixed position according to the substrate size.

  The XY stage unit 20 has a function of translating the substrate 60 in the X-axis direction and the Y-axis direction of FIG. Accordingly, the substrate 60 is driven in the X-axis and Y-axis directions according to a preset operation procedure.

  The alignment imaging unit 30 includes a camera 31, a lens 32, an illumination lamp 33, and an illumination control device 34. Illumination light is radiated to the region including the alignment mark on the substrate 60 in a coaxial epi-illumination format, and the observation image is captured by the camera 31. The illumination lamp 33 can be controlled to be turned on / off and the intensity of illumination light can be adjusted by the illumination control device 34, and the actual control operation is performed by the processing / control unit 100.

  In this embodiment, the camera 31 is an area CCD camera, the lens 32 is a coaxial incident type fixed magnification telecentric lens, and the illuminating lamp 33 is a high brightness spot type white LED.

  The imaging unit 40 includes a camera 41, a parallel optical system 42, and a Z stage 43. The camera 41 desirably includes a photoelectric conversion element having spectral sensitivity characteristics in the visible light range. In this embodiment, an area CCD camera is used as the camera 41, but a line CCD camera may be used.

  An electric telecentric zoom lens is used for the parallel optical system 42. At this time, it is desirable that the telecentricity of the lens satisfies 0.5 ° or less. Further, the camera 41 and the lens 42 can be moved in the vertical direction with respect to the imaging surface on the substrate 60 by the Z stage 43, and this operation enables fine adjustment of the focal position.

  The processing / control unit 100 includes an information processing unit 101, a signal input device 102, a signal input device 103, a display unit 104, and an interpersonal operation unit 105. The transmitted illumination unit 10, the XY stage unit 20, Operations management and control of the imaging unit for alignment 30 and the imaging unit 40 are performed, and outputs from the imaging unit for alignment 30 and the imaging unit 40 are input as image information or signals to perform arithmetic processing. Further, the processing result and the processed image are displayed on the display means 104.

  FIG. 3 is a flowchart for explaining a state monitoring method of the pattern drawing apparatus according to the embodiment of the present invention. This state monitoring method is performed by a series of steps of steps S1 to S12, and the contents of each step will be described below in order. Note that description of operation operations such as attachment / detachment of the substrate 60 is omitted.

  First, pattern drawing information such as the pattern pitch, size, panel layout, pattern drawing conditions, type of pattern drawing apparatus, etc. on the substrate 60 is input to the information processing unit 101 by the interpersonal operation unit 105 (step S1). At this stage, the type of the θ axis described above is also input. Here, FIG. 4 shows the correspondence between the substrate 60 and θ (in this case, three types of θ = 0 °, 45 °, and 90 ° are defined as an example).

  Next, an alignment operation for the substrate 60 is performed by the XY stage unit 20 and the alignment imaging unit 30 (step S2).

Next, the lens magnification in the parallel optical system 42 is set (step S3). In the present embodiment, the lens magnification is set such that the relationship between the imaging resolution r determined by the imaging element size and the lens magnification in the camera 41 and the pitch di on the substrate 60 satisfies the following formula (1). Note that h in the formula represents a relative ratio and is a positive integer.
r = h × di (1)
However, in the substrate 60, the apparent pitch value corresponding to the light irradiation direction changes in accordance with θ set in step S1, and therefore it is necessary to calculate the apparent pitch di value for each θ axis. .

When the pitch in the X direction is Δx and the pitch in the Y direction is Δy with respect to the vertical direction of the substrate 60,
When 0 ° ≦ θ ≦ 45 °,

When 45 ° <θ ≦ 90 °,

When 90 ° <θ ≦ 135 °,

When 135 ° <θ ≦ 180 °,

Respectively.

  Next, in the range of 10 ° ≦ φ ≦ 60 °, an illumination irradiation angle φ that is optimal for visualizing the uneven defect is set (step S4).

  Next, the XY stage unit 20 is driven to move the processing target panel to the imaging position (step S5). The illumination head 13 is moved to the φ position set in step S4.

  Next, fine adjustment in the Z-axis direction is performed by the Z stage 43 while capturing an image of the processing target panel with the camera 41, and defocusing from the focal position is performed (step S6).

  Next, while capturing an image with the camera 41, the output from the light source 14 is adjusted to adjust the captured image brightness level so that sufficient image brightness for image processing is secured. (Step S7).

  As described above, it is determined whether or not the processing from Steps S3 to S7 has been performed for all θ input in Step S1 (Step S8). If not, the processing returns to Step S3 and the same processing as above is performed. repeat.

  If it is determined in step S8 that the process has been performed for all θs, the processed image is captured in the processing target panel based on the conditions set in steps S3 to S7 (step S9).

  Next, the unevenness evaluation value C is calculated for the image to be processed obtained in step S9 (step S10). Here, the unevenness evaluation value C is a numerical value of the luminance contrast generated between the normal portion and the pattern variation portion in the unevenness defect image obtained in the present embodiment.

  Hereinafter, the unevenness evaluation value C calculation method in step S10 will be briefly described in the order of steps C1 to C3.

  As shown in FIG. 5, a rectangular calculation area is defined for the image to be processed obtained in step S9, and the luminance value in each pixel in the calculation area is separately integrated in the X and Y directions, and the integrated value ΣI Is calculated (step C1). The integrated value is an average value divided by the integrated number of pixels. Although FIG. 5 shows a state where the rectangular calculation area is inserted inside the processed image, the rectangular calculation area may be set on the entire processed image.

  Next, a comparison reference value Σ0 for the integrated value calculated in step C1 is calculated (step C2). The derivation of the comparison reference value from the integrated value is schematically shown in FIG. In this embodiment, moving average processing is used as a method for deriving a comparison reference value.

Next, the evaluation value C is calculated by the calculation of the following formula (6) (step C3).
C = | ΣI−Σ0 | (6)
In the present embodiment, when processing is performed for a plurality of panels, the one with the largest evaluation value C is treated as a representative value.
The steps C <b> 1 to C <b> 3 will be described regarding the method for calculating the unevenness evaluation value C.

Next, the uneven defect generation period F is calculated by the two-dimensional Fourier transform for the image to be processed obtained in step S9 (step S11).
Hereinafter, the uneven defect period calculation method using the two-dimensional Fourier transform in step S11 will be briefly described in the order of steps F1 to F3.

  As shown in FIG. 7, in the processed image obtained in step S9, a rectangular area of vertical R pixels and horizontal R pixels is defined with reference to the center of the image, and two-dimensional Fourier transform is executed in the rectangular area. Then, a power spectrum image is derived (step F1).

  As a pre-process for executing the two-dimensional Fourier transform, a binarization process is performed on the image in the rectangular area. Further, the value of the length R of one side of the rectangular area may be changed according to the size of the acquired processed image. However, since Fast Fourier Transform (FFT) is used for the calculation, it is necessary to define the value of R so as to be a numerical value represented by a power of 2, such as 128, 256, and 512.

  Next, a power spectrum distribution with respect to the spatial frequency f is obtained from the power spectrum image in each of the image X direction and the Y direction (step F2). Here, the spatial frequency f is a value defined as a frequency in the length of one side of the rectangular area defined in step F1.

Next, the spatial frequency f having the largest spectrum in the power spectrum distribution obtained in step F2 is obtained, and the spatial frequency f is converted into the nonuniform defect generation period F from the image resolution in the processed image (step F3).
The steps F <b> 1 to F <b> 3 will be described with respect to the method for calculating the uneven defect occurrence period by two-dimensional Fourier transform.

Next, based on the results obtained in steps S10 and S11, state determination is performed based on the following conditions, and the results are displayed on the display unit 104 (step S12). At this time, the determination threshold for the unevenness evaluation value C is defined as C_Th, and the determination value for the uneven defect occurrence period F is defined as F_Litho.
C> C_Th
And,
F = F_Lito
When the condition is satisfied, it is determined that a nonuniformity defect caused by the pattern drawing device to be monitored is generated.

  Note that the numerical value corresponding to F_Litho corresponds to a drawing scanning period in the normal pattern drawing apparatus or an integer multiple thereof. When there are a plurality of numerical values in the pattern drawing apparatus, it may be determined that an uneven defect caused by the pattern drawing apparatus is generated when the value of the uneven defect generation period F corresponds to any one of them.

  In addition, the uneven defect generation period F and the determination value F_Litho need not be completely coincident with each other under the above-described determination conditions, and an error of several μm may be allowed in some cases.

  As described above, according to the state monitoring method of the embodiment of the present invention, a pattern variation occurrence portion is detected from a contrast due to a diffracted light quantity difference in a periodic pattern, particularly a substrate such as a photomask for LCD manufacturing. Can be accurately identified, and the pattern generation apparatus can be monitored by simply deriving the fluctuation generation period.

Examples of the present invention will be described below.
The pattern drawing apparatus used in all the examples is the same, and the value of the drawing scanning period is 420 μm. Further, a determination threshold value C_Th = 100 for the unevenness evaluation value C is set, and 420 μm and 840 μm are input to the value of F_Litho in step S1. Note that the drawing scanning direction in the pattern drawing apparatus is all in the X direction in FIG. 4, and in this embodiment, the result when the relative light projection direction θ = 0 ° to the substrate 60 is shown.

  As a first example, a result is shown in which a substrate 60 on which an L / S-shaped pattern 51 having a pitch d = 20.5 μm is formed is a monitoring target substrate. A schematic diagram of the pattern 51 is shown in FIG. The substrate 60 on which the pattern 51 is formed is irradiated with illumination light from φ = 30 ° based on the processing in steps S1 to S9, the relative ratio h = 2.439, and the defocus amount is 15.0 mm. The image to be processed was acquired. Furthermore, as a result of calculating the unevenness evaluation value C and the uneven defect occurrence period F in steps S10 and S11, C = 18.0 and F = 426.7 μm. Note that R = 256.

The value of the drawing scanning period of the pattern drawing apparatus used for drawing the pattern 51 in this embodiment is 420 μm, which is very close to the value of the uneven defect generation period F obtained by two-dimensional Fourier transform. From the above results, it can be determined in step S12 that an uneven defect caused by the pattern drawing apparatus has occurred.
FIG. 9A shows an acquired image according to the first embodiment, and FIG. 9B shows a power spectrum image.

  Subsequently, as a second example, a result is shown in which a substrate 60 on which a lattice-like pattern 52 having a pitch d = 119.5 μm is formed is used as a monitoring target substrate. A schematic diagram of the pattern 52 is shown in FIG. The substrate 60 on which the pattern 52 is formed is irradiated with illumination light from φ = 30 ° based on the processing in steps S1 to S9, the relative ratio h = 0.895, and the defocus amount is 9.0 mm. The image to be processed was acquired. Furthermore, as a result of calculating the unevenness evaluation value C and the uneven defect generation period F in steps S10 and S11, C = 66.8 and F = 838.6 μm were obtained. Note that R = 256.

The value of the nonuniformity defect generation period F is a value close to 840 μm, which corresponds to twice the drawing scanning period of the pattern drawing apparatus used for drawing the pattern 52, but C <C_Th holds. In S12, the determination result is that no nonuniform defect due to the pattern drawing apparatus has occurred.
FIG. 11A shows an acquired image according to the second embodiment, and FIG. 11B shows a power spectrum image.

  DESCRIPTION OF SYMBOLS 10 ... Transmission illumination part, 11 ... Circular rail, 12 ... Turntable, 13 ... Illumination head, 14 ... Light source, 15 ... Light guide, 20 ... XY stage part, 21 ... Work stopper, 30 ... Imaging part for alignment, DESCRIPTION OF SYMBOLS 31 ... Camera, 32 ... Lens, 33 ... Illuminating lamp, 34 ... Illumination control device, 40 ... Imaging part, 41 ... Camera, 42 ... Parallel optical system, 43 ... Z stage, 51 ... Pattern, 52 ... Pattern, 60 ... Substrate DESCRIPTION OF SYMBOLS 100 ... Processing / control part 101 ... Information processing part 102 ... Signal input device 103 ... Signal input device 104 ... Display part 105 ... Interpersonal operation part

Claims (13)

A substrate on which a periodic pattern is formed by a pattern drawing apparatus is an object to be monitored, and by illuminating the substrate with illumination light from an oblique direction, image acquisition is performed using diffracted light generated by the periodic pattern, and processing is performed. A method for monitoring a state of a pattern drawing apparatus for performing a determination,
A pattern information input step for inputting product information such as pitch and size of the periodic pattern, pattern drawing conditions on the substrate, and drawing information such as the type of the pattern drawing device;
A positioning step for positioning the substrate in the in-plane direction to be imaged;
An imaging magnification setting step for determining an imaging magnification from a relationship between a pattern pitch and an imaging resolution based on information on the periodic pattern input in the pattern information input step;
A defocusing step in which a surface on which the periodic pattern of the substrate is formed is an imaging surface, and a focal point is shifted by a predetermined amount in a vertical method with respect to the imaging surface;
An imaging step of capturing a periodic pattern of the substrate and acquiring a processed image at a position defocused by a predetermined amount from the in-focus position; and
A non-uniformity evaluation value calculating step for calculating a non-uniformity evaluation value obtained by quantifying the luminance contrast generated between the normal part and the fluctuation part of the periodic pattern for the processing image;
An uneven defect period calculating step for obtaining an occurrence period of uneven defects occurring on the substrate to be confirmed on the processed image;
Similar unevenness evaluation value set magnitude of the determination threshold value, and pattern drawing condition input in uneven period and before Symbol pattern information input step obtained in the uneven defect period calculation step determined in the unevenness evaluation value calculating step comparing sex, when the irregularity evaluation value is the determination large and the unevenness period than threshold is similar to the pattern drawing conditions, unevenness defects that are occurring on the substrate a pattern drawing device attributed If the unevenness evaluation value is smaller than the determination threshold even if the unevenness period is similar to the pattern drawing condition, it is determined that the unevenness defect is not caused by a pattern drawing apparatus. A determination step to
A state monitoring method for a pattern drawing apparatus.   In the pattern information input step, it is possible to input conditions regarding the horizontal angle direction between the illumination and the substrate so that an imaging condition can be set for illumination at an arbitrary horizontal angle with respect to the periodic pattern of the substrate. 2. The state monitoring method for a pattern drawing apparatus according to claim 1, wherein:   The pattern monitoring apparatus according to claim 1 or 2, wherein a pattern pitch of the periodic pattern of the substrate is 20 µm to 400 µm.   The state monitoring method for a pattern writing apparatus according to claim 1, wherein the illumination light is green light having a center wavelength of 540 nm.   In the imaging step, the diffracted light from the periodic pattern of the substrate is implemented by an imaging unit using a photoelectric conversion element, and the imaging unit is configured to detect diffracted light generated by the periodic pattern of the substrate. 5. The pattern drawing apparatus state monitoring method according to claim 1, further comprising an optical system that extracts only diffracted light perpendicular to the imaging surface of the substrate.   The pattern drawing apparatus state monitoring method according to claim 1, wherein the imaging magnification setting step uses an electric zoom lens to set the imaging magnification.   The pattern defocusing apparatus state monitoring method according to claim 1, wherein in the defocusing step, a defocus amount from the in-focus position is larger than a focal depth of the optical system.   The state monitoring method for a pattern drawing apparatus according to claim 1, wherein the defocusing step shifts the in-focus position in a direction away from the imaging target surface vertically.   The said nonuniformity defect period calculation process calculates a period by utilizing a two-dimensional Fourier transform with respect to the to-be-processed image acquired by the said imaging process, The one of Claims 1-8 characterized by the above-mentioned. A state monitoring method for a pattern drawing apparatus.   The pattern drawing apparatus according to claim 1, wherein the pattern drawing apparatus is a raster pattern drawing apparatus that draws a pattern by scanning a krypton ion laser having a wavelength of 413 nm on the substrate. Device status monitoring method.   The state monitoring of the pattern writing apparatus according to claim 1, wherein the substrate is a photomask for exposing light in a predetermined wavelength range within a wavelength range of 365 nm to 436 nm. Method.   The state monitoring method for a pattern drawing apparatus according to claim 1, wherein the substrate is a photomask for manufacturing a member for a liquid crystal display device. A substrate on which a periodic pattern is formed by a pattern drawing apparatus is an object to be monitored, and by illuminating the substrate with illumination light from an oblique direction, image acquisition is performed using diffracted light generated by the periodic pattern, and processing is performed. A state monitoring device for a pattern drawing device that performs determination,
A transport means for mounting the substrate and having a mechanism for driving in the X-axis and Y-axis directions;
Positioning means for performing predetermined image processing on an image obtained by irradiating light on a predetermined area of the substrate and imaging the predetermined area, and positioning the substrate in the in-plane direction of the image pickup;
An illumination head including a light source capable of generating visible light as illumination light;
The illumination light irradiation angle φ with respect to the direction perpendicular to the imaging surface of the substrate is set while irradiating illumination light substantially parallel to a predetermined region on the substrate placed on the transport means and supporting the illumination head. An illumination head driving means that is controllable, and further capable of driving the illumination head in an angle θ direction horizontal to the surface to be inspected of the substrate;
Imaging means for imaging diffracted light generated by illuminating illumination light onto the periodic pattern of the substrate by the illumination head;
An imaging unit driving unit capable of driving the imaging unit in a vertical direction (Z-axis direction) with respect to the surface to be inspected of the substrate;
Image input means for using the video output from the positioning means and the video output from the imaging means as image information;
Interpersonal operation means for inputting product information such as pitch and size of the periodic pattern, pattern drawing conditions on the substrate, drawing information such as the type of the pattern drawing device, and other operations;
Based on the information on the periodic pattern input by the interpersonal operation means, the imaging magnification determining means for determining the imaging magnification from the relationship between the pattern pitch and the imaging resolution;
A surface on which the periodic pattern of the substrate is formed as an imaging surface, and a defocusing unit that shifts a focal point by a predetermined amount in a vertical method with respect to the imaging surface;
A non-uniformity evaluation value calculation unit that calculates a non-uniformity evaluation value obtained by quantifying the luminance contrast generated between the normal part and the fluctuation part of the periodic pattern with respect to the processing image acquired by the imaging unit;
An uneven defect period calculating means for obtaining an occurrence period of uneven defects occurring on the substrate to be confirmed on the processed image acquired by the imaging means;
The magnitude of the unevenness evaluation value set determination threshold determined in said unevenness evaluation value calculating means, and similarity to pattern drawing condition input in uneven period and before Symbol interpersonal operating means determined in the uneven defect period calculating means If the unevenness evaluation value is larger than the determination threshold value and the unevenness period is similar to the pattern drawing condition, the unevenness defect occurring on the substrate is caused by the pattern drawing apparatus. If the unevenness evaluation value is smaller than the determination threshold even if the unevenness period is similar to the pattern drawing condition, it is determined that the unevenness defect is not caused by a pattern drawing apparatus. A determination means;
Control means for controlling the operation of the conveying means, the positioning means, the illumination head, the illumination head driving means, the imaging means, and the imaging unit driving means;
Display means for displaying an image picked up by the positioning means and the image pickup means and a processing result by the control means;
A state monitoring device for a pattern drawing device.

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