TWI413768B - Pattern inspection method, pattern inspection device, photomask manufacturing method, and pattern transfer method - Google Patents

Abstract

The invention relates to a pattern inspection method, a pattern inspection device, a photomask manufacturing method and a pattern transfer method. The invention provides the pattern inspection method for simply and rapidly inspecting if the photomask has uneven pattern. The technical scheme of the invention is that the pattern inspection method comprises the steps as follows: an irradiating step for irradiating repeated patterns by utilizing the preset light beams, a Fourier transform image testing step for testing the Fourier transform image which corresponds to the inflected lights generated by irradiating repeated patterns, and a pattern uneven judging step for judging if the photomask has uneven pattern according to the tested Fourier transform image, wherein in the Fourier transform image testing step, the Fourier transform image corresponding to the high inflected lights in the preset inflected lights is tested in the manner of separating the Fourier transform image corresponding to the photomask having uneven pattern from the Fourier transform image corresponding to the normal image.

Description

Pattern inspection method, pattern inspection device, mask manufacturing method, and pattern transfer method

The present invention relates to a pattern inspection method and a pattern inspection apparatus for inspecting pattern unevenness of a photomask for an image device, and a transparent pattern formed by periodically arranging unit patterns is formed on a transparent substrate of the mask. The present invention also relates to a reticle manufacturing method that implements the pattern inspection method to fabricate a reticle. The present invention is more related to a pattern transfer method for transferring a transfer pattern to a transfer object using a photomask manufactured by the photomask manufacturing method.

In the field of reticle technology using photolithography, a prescribed mask quality is known as a reference for judging whether a pattern transferred to a mask blank correctly reproduces a design pattern. Representative quality items include, for example, pattern shape accuracy, pattern size (CD: Critical Dimension) accuracy, and pattern position accuracy. In order to avoid malfunction of the mounted product, the correct circuit pattern is transferred to the device substrate. Therefore, each quality item must satisfy a predetermined quality, that is, it is necessary to manufacture a mask that is substantially free of defects. On the other hand, a pattern inspection method or pattern inspection apparatus for inspecting irregularities (or repetition errors) in which the above-described repeated pattern occurs is disclosed, for example, in documents Nos. 1 and 2 of the Patent Document.

The pattern inspection method and the pattern inspection device described in Patent Document 1 cause the diffracted light of a predetermined order or more caused by the photomask to selectively enter the imaging optical system. Next, the incident diffracted light is synthesized, and the image thus obtained is detected to check for CD defects and the like.

The pattern inspection method and the pattern inspection device described in Patent Document 2 remove components having a predetermined frequency or more in a spatial spectrum obtained by Fourier transforming the mask, and analyze the removed spatial spectrum for a repeated error pattern in the mask. Perform a quantitative evaluation (inspection).

Patent Document 1: Special Publication No. 2005-233869

Patent Document 2: JP-A-8-194305

In the field of manufacturing technology of a photomask, a shape inspection is performed on a transfer pattern formed on a photomask, and defects are corrected as necessary, and then shipped. Especially in the mass production of photomasks for video devices, it is important to determine not only the shape defects but also the unevenness of the patterns before shipment, so that quality assurance can be obtained quickly and easily.

In general, the standard of the mask defect is set according to a predetermined quality sample (a quality sample required to transfer the substrate for the device to the correct circuit pattern in order to avoid malfunction of the mounted product). Therefore, it is important that a general LSI (Large Scale Integration) photomask satisfies the above criteria. On the other hand, the photomask for the video device should also consider matters other than the quality of the above-mentioned defects. For example, consider the case where the correct pattern of the regular arrangement contains an error having a regularity different from this. This error does not necessarily have sufficient product performance even if it satisfies the quality of the above-mentioned defects. An image of the image device manufactured by ignoring such an error may cause display unevenness due to the error. For example, even if the unit pattern constituting the repeating pattern does not affect the error of the small line width or the positional deviation of the quality, in the case of the area, in some cases, if a certain number is arranged in a certain order or in a certain When a part is concentrated in a large number, in the final product of the above-mentioned display device, it is visually recognized as a color or a density different from the surroundings as if it is recognized as a defect. These display unevenness is the cause of degrading the image quality of the image device, so it is undesirable. In the present specification, even if it is a small error that is not judged to be a defect in a unit pattern, when evaluating a repeating pattern included in a certain area, an error causing a display unevenness is called "pattern unevenness". "."

In the pattern inspection method and the pattern inspection apparatus described in Patent Document 1, for example, a high-order diffraction image is obtained using a predetermined inspection object, and as a result, no defect is found, and even if it is not determined, it is impossible to determine whether or not the inspection object conforms to the quality assurance. This is because in this document, the imaging surface is placed at a predetermined position in order to observe the real image of the diffracted image, but in some cases, pattern unevenness cannot be detected on the imaging surface. That is, even if the same inspection object is different depending on the inspection conditions (for example, the focus (foucus condition)) that can be detected, the inspection condition must be changed to perform the inspection of the same inspection object, for example, the inspection condition is changed. The mask is spaced from the objective lens to adjust the focus. Therefore, even if there is a judgment defect, it is necessary to perform inspection according to a plurality of inspection conditions, and the inspection time becomes long, which is disadvantageous in terms of lead time. Furthermore, inspection data exists for each defect, so the processing load on the data analysis device side is also increased.

In the pattern inspection method and the pattern inspection device described in Patent Document 2, since the defect of the mask is detected with high sensitivity, the spatial filter is used to selectively remove information on the inside of the unit cell and the ideal repetition period. However, it is necessary to prepare a mask for a filter ring for each pattern shape of the reticle as the subject, and it is difficult to remove the noise of the low-order diffracted light with sufficient sensitivity. The test is performed, so the method and device cannot be easily adopted.

As described above, the conventional pattern inspection method and the pattern inspection device have problems such as lengthy inspection and difficulty in setting the device, and are not suitable for easily and quickly checking the presence or absence of pattern unevenness of the mask.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pattern inspection method and a pattern inspection apparatus which are suitable for easily and quickly checking the presence or absence of pattern unevenness of a photomask for an image device. The present invention also provides a photomask manufacturing method, which is implemented to fabricate a photomask. The present invention further provides a pattern transfer method for transferring a transfer pattern to a transfer object using a photomask manufactured by the photomask manufacturing method.

A pattern inspection method according to an aspect of the present invention for solving the above-mentioned problems relates to a method of inspecting a pattern unevenness in which a repeating pattern composed of a periodic arrangement of unit patterns is formed on a transparent substrate of the mask, and the pattern inspection method has the following Characteristics. That is, the pattern inspection method includes: an illuminating step of illuminating the repeating pattern by a predetermined beam; and a Fourier transform image detecting step of detecting a Fourier transform image corresponding to the diffracted light generated by irradiating the repeating pattern with the light beam; and pattern unevenness In the determining step, it is determined whether or not the pattern unevenness of the mask is based on the detected Fourier transform image. In the Fourier transform image detecting step, in order to spatially separate the Fourier transform image corresponding to the pattern unevenness of the mask and the Fourier transform image corresponding to the normal pattern, the Fourier transform corresponding to the predetermined high-order diffracted light in the diffracted light is detected. image.

In this way, by observing the Fourier transform image instead of the real image of the reticle, it is possible to easily and quickly determine the presence or absence of the pattern unevenness of the reticle, and to quickly obtain the quality assurance of the reticle, thereby improving the manufacturing efficiency of the reticle.

In the pattern inspection method of the present invention, in order to spatially separate the Fourier-converted image corresponding to the pattern unevenness of the mask and the Fourier-converted image corresponding to the normal pattern, it is preferable to use an absolute value of, for example, 20~. A high-order diffracted light of 700 is used to generate a Fourier transform image.

A pattern inspection method according to another aspect of the present invention, which solves the above problems, relates to a method of inspecting a pattern unevenness in which a repeating pattern composed of a periodic arrangement of unit patterns is formed on a transparent substrate of the mask, and the pattern inspection method has the following Characteristics. That is, the pattern inspection method has an irradiation step of irradiating a repeating pattern by a predetermined light beam, and a Fourier transform image detecting step of detecting a Fourier transform image corresponding to the diffracted light generated by irradiating the repeating pattern with the light beam; and pattern unevenness The determining step determines whether or not the pattern unevenness of the mask is based on the detected Fourier transform image. The wavelength of the light beam is defined as λ (unit: μm), the distance between unit patterns is defined as ω (unit: μm), and the distance between the unit patterns including pattern unevenness is defined as ω' (unit: μm), the focus of the optical system The distance defined as f (unit: mm), the decomposition energy of the Fourier transform surface detected by the Fourier transform image is defined as p (unit: mm), and the angle formed by the diffracted light of the 0th order and the diffracted light of the nth order is defined as θn (unit In the case of :deg), in the Fourier transform image detecting step, a Fourier transform image corresponding to the n-th order diffracted light satisfying the following conditions in the diffracted light is detected.

f(tan(Δθn))>p Δθn=sin ^-1 (nλ/ω)-sin ^-1 (nλ/ω')

Here, in the case where the angle between the normal of the Fourier transform surface of the Fourier transform image detected and the optical axis of the illumination optical system that illuminates the light beam in the illumination step is defined as θi, the pattern inspection method of the present invention is preferably satisfied. 0° < θi < 90°.

Since the Fourier transform image is to be generated, the beam illuminated in the illumination step is preferably a parallel beam that is at least spatially coherent and single wavelength.

In the pattern unevenness determining step, the Fourier transform image detected in the Fourier transform image detecting step is compared with a predetermined reference image, and the pattern unevenness of the mask is automatically determined based on the comparison result, and the pattern is uneven. The decision step is beneficial to improve inspection efficiency.

Preferably, the pattern inspection method of the present invention is such that when the inspection area that can be simultaneously inspected is narrower than the entire inspection object of the mask, the mask is moved and the inspection area is continuously scanned, and the irradiation step and the Fourier transform image are performed on the inspection area. The steps of the detecting step and the pattern unevenness determining step are performed to determine the presence or absence of the pattern unevenness of the mask.

Further, a method of manufacturing a mask according to an aspect of the present invention, which solves the above-described problems, is a method for producing a mask by forming a predetermined mask pattern on a mask blank, and the method includes the steps of: performing the pattern inspection method described above to determine The pattern of the mask formed with the mask pattern is uneven.

Moreover, the pattern transfer method according to one aspect of the present invention which solves the above-described problems is characterized in that the mask pattern is transferred to the transfer target substrate by using the photomask manufactured by the above-described photomask manufacturing method.

Further, in a pattern inspection apparatus according to an aspect of the present invention, which solves the above-described problems, a device for detecting a pattern unevenness is formed, and a transparent pattern formed by periodically arranging a unit pattern is formed on a transparent substrate of the mask, and the pattern inspection apparatus has The following features. That is, the pattern inspection device includes: an irradiation means for irradiating a repeating pattern by a predetermined light beam; and a Fourier transform image detecting means for detecting a Fourier transform image corresponding to the diffracted light generated when the repeating pattern is irradiated by the irradiation means; and the pattern is not The determination means determines whether or not the mask pattern is uneven based on the detected Fourier transform image. The Fourier transform image detecting means detects a Fourier transform image corresponding to the pattern unevenness of the mask and spatially separates the Fourier transform image corresponding to the normal pattern, and detects a Fourier transform image corresponding to the predetermined high order diffracted light in the diffracted light.

In the pattern inspection device of the present invention, in order to spatially separate the Fourier-converted image corresponding to the pattern unevenness of the mask and the Fourier-converted image corresponding to the normal pattern, it is preferable to use, for example, an absolute value of the order of 20~. A high-order diffracted light of 700 is used to generate a Fourier transform image.

Further, in a pattern inspection apparatus according to another aspect of the present invention, which solves the above-described problems, a device for inspecting a pattern unevenness is formed, and a transparent pattern formed by periodically arranging unit patterns is formed on a transparent substrate of the mask, and the pattern inspection apparatus has The following features. That is, the pattern inspection device includes: an irradiation means for irradiating a repeating pattern by a predetermined light beam; and a Fourier transform image detecting means for detecting a Fourier transform image corresponding to the diffracted light generated when the repeating pattern is irradiated by the irradiation means; and the pattern is not The determination means determines whether or not the mask pattern is uneven based on the detected Fourier transform image. The wavelength of the light beam is defined as λ (unit: μm), the distance between unit patterns is defined as ω (unit: μm), and the distance between the unit patterns including pattern unevenness is defined as ω' (unit: μm), the focus of the optical system The distance defined as f (unit: mm), the decomposition energy of the Fourier transform surface detected by the Fourier transform image is defined as p (unit: mm), and the angle formed by the diffracted light of the 0th order and the diffracted light of the nth order is defined as θn (unit In the case of :deg), the Fourier transform image detecting means detects a Fourier transform image corresponding to the n-th order diffracted light satisfying the following conditions in the diffracted light.

f(tan(Δθn))>p Δθn=sin ^-1 (nλ/ω)-sin ^-1 (nλ/ω')

Preferably, the pattern inspection apparatus of the present invention has an illumination optical system for irradiating a light beam, wherein an angle between a normal line of the Fourier transform surface on which the Fourier transform image is detected and an optical axis of the illumination optical system is defined as The case of θi satisfies 0° < θi < 90°.

Here, the light beam irradiated by the above-mentioned irradiation means is preferably a parallel light beam which is at least spatially substantially identical and which is a single wavelength.

Further, the above-described pattern unevenness determining means may compare the Fourier transform image detected by the Fourier transform image detecting means with a predetermined reference image, and automatically determine the presence or absence of the mask pattern unevenness based on the comparison result.

The pattern inspection device of the present invention further includes an inspection region scanning means for moving the mask and continuously scanning the inspection region when the inspection region that can be simultaneously inspected is narrower than the entire inspection target of the mask.

According to the pattern inspection method, the pattern inspection device, and the reticle manufacturing method of the present invention, it is possible to easily and quickly determine the presence or absence of pattern unevenness of the reticle and quickly obtain the quality assurance of the reticle, thereby improving the manufacturing efficiency of the reticle.

Hereinafter, a pattern inspection method, a pattern inspection device, a mask manufacturing method, and a pattern transfer method according to an embodiment of the present invention will be described with reference to the drawings. Further, in each of the drawings, for convenience of explanation, a partial depiction of a support portion for supporting various component parts is omitted.

In the present embodiment, the mask to be inspected is a mask for exposure, and is used to manufacture, for example, an FPD (Flat Panel Display, for example, a liquid crystal display device), a plasma display device, an EL (Electro Luminescence) display device, and an LED (Light). Emitting Diode) A substrate for an imaging device such as a display device or a DMD (Digital Mirror Device) display device. Such a mask is formed by forming a transfer pattern for one or a plurality of image devices on a large square substrate having a length of, for example, more than 1 m. Each of the transfer patterns includes a repeating pattern in which a plurality of identical patterns are repeatedly formed.

The first diagram schematically shows the overall configuration of the pattern inspection device 1 of the present embodiment. The pattern inspection device 1 is configured to inspect the pattern unevenness of the photomask 10, and a repeating pattern 12 is formed on the surface of the transparent substrate 11 of the photomask 10. In the present embodiment, light is irradiated from the back side (the side having no pattern) of the mask 10 as the subject, and light is received on the surface (pattern forming surface) side, and the details will be described later. In another embodiment, light may be irradiated from the surface side of the photomask 10 and received on the back side.

A method of manufacturing the mask 10 to be inspected in the present embodiment will be described. The photomask 10 is manufactured by each of a mask blank manufacturing program, a photoresist pattern forming program, a mask pattern forming program, and a pattern defect inspection program. Further, the inspection object may be an intermediate body of the photomask 10, that is, an object in which a photoresist pattern is formed or an object in which a photoresist pattern is formed as a mask pattern (object before peeling of the photoresist pattern). In the case where the substrate before the formation of the mask pattern is an inspection target, the device for observing the first image of the transmitted light can be changed, and the reflected light can be observed for inspection.

In the mask blank manufacturing process, a film such as a light shielding film is formed on the surface of the transparent substrate 11. For example, a synthetic quartz glass substrate or the like is suitable as the material of the transparent substrate 11. Further, a material having a light-shielding property such as chrome or a semi-translucent material is suitable as a material constituting the film of the repeating pattern 12. A photoresist is formed on the film to form a photoresist film, thereby completing the mask blank. Next, in the photoresist pattern forming process, the laser beam generated by the drawing device is irradiated onto the photoresist film of the mask blank. The drawing process is performed by an arbitrary drawing method such as a raster drawing method, and a predetermined pattern is exposed to the resist film. After exposing the predetermined pattern, the photoresist pattern is formed by selectively removing the drawing portion or the non-drawing portion according to the photoresist (positive photoresist or negative photoresist) used for development. In the mask pattern forming process, the photoresist pattern is masked and the film is etched to form a repeating pattern (light-shielding film pattern) 12. Then, the residual photoresist is removed. In the photomask 10, after the residual photoresist is removed, a pattern defect inspection program is performed as one of the manufacturing procedures of the photomask 10. Further, the photomask 10 may be a so-called binary mask in which a single-layer light-shielding film is patterned, and the photomask 10 may be patterned by laminating a light-shielding film or a semi-transparent film, respectively. A multi-tone mask. In the case of patterning the laminated film, the above-described photolithography program from the mask blank manufacturing process to the mask pattern forming program is performed plural times.

In the pattern defect inspection program, shape defects can be inspected for each pattern. When the defect is found, the mask 10 can be subjected to flaw correction processing or white defect correction processing depending on the type of defect. Further, after the photoresist is removed or the correction process is performed by the pattern defect inspection, the mask 10 is inspected for pattern unevenness. In order to perform this inspection, the photomask 10 described above is placed on the pattern inspection device 1. A pellicle is attached to the reticle 10 which is inspected in the pattern defect inspection program.

The pattern transfer process is carried out using the photomask 10 equipped with a film. In the pattern transfer program, the transfer pattern including the repeat pattern 12 is transferred to the photoresist film of the substrate for the image device, and the pixel pattern based on the transfer pattern is formed on the surface of the substrate for the image device. The pixel pattern is, for example, a thin film transistor of a liquid crystal display panel or a repeating pattern of a counter substrate, a color filter, or the like.

Next, the configuration of the pattern inspection device 1 for checking the pattern unevenness of the reticle 10 in the pattern defect inspection program will be described.

The mask 10 is supported on the stage 20 as shown in the first figure after forming a mask pattern (or photoresist pattern). The stage 20 is, for example, an XY stage, and the reticle 10 is movably supported in the X direction or the Y direction. In the present specification, the first direction and the direction perpendicular to the paper plane are defined as the X direction, and the two directions orthogonal to the X direction and orthogonal to each other are defined as the Y direction and the Z direction. According to this definition, the stage 20 supports the mask 10 such that the surface of the mask 10 on which the repeating pattern 12 is formed (hereinafter referred to as "pattern forming surface 12a") is parallel to the XY plane. Further, the photographing device 40 is supported such that its optical axis AX is parallel to the Z axis.

In the pattern inspection device 1, it is necessary to capture an image of the reticle 10 that is irradiated with the illumination light from the illumination device 30 by the imaging device 40. In order to prevent the irradiation light from being impeded, the support body of the stage 20 is formed in a frame shape, for example, and supports only the outer peripheral portion of the mask 10.

The reticle 10 is moved in the X direction or the Y direction by the stage 20, thereby moving (scanning) the imaging range (inspection field of view) based on the imaging device 40. Further, in the case where the stage 20 is used as a fixed stage, the frame configuration is such that the illumination device 30 and the imaging device 40 can be moved in the X direction or the Y direction with respect to the stage 20 in order to scan the inspection field of view.

The second diagram schematically shows the structure of the main part of the pattern inspection device 1. As shown in the second figure, the illumination device 30 has a light source unit 31 and an illumination optical system 32. The light source suitable for the light source unit 31 is, for example, a light source that illuminates light that is at least spatially substantially coherent and that is a single wavelength. A laser such as a semiconductor laser can be used in such a light source.

The illumination optical system 32 is disposed between the photomask 10 and the light source unit 31. The illumination optical system 32 parallelizes the same dimming light from the light source unit 31 and enters the transparent substrate 11 at an incident angle θi (unit: deg). Further, in the second drawing, in order to clarify the drawing, the drawing of the light traveling inside the transparent substrate 11 is omitted.

The light source unit 31 and the illumination optical system 32 are arranged and arranged to constitute an incident angle θi (an angle formed by a normal line (optical axis AX) of a Fourier conversion surface to be described later and an optical axis of the illumination optical system 32), for example, according to another expression. The range of 0° < θi < 90° (more preferably 20° < θi < 80°). The illumination optical system 32 illuminates at least a portion of the pattern forming surface 12a (for example, an area of about φ60 to 70 mm), and the pattern forming surface 12a includes an inspection field of view based on the imaging device 40. By using a frame to illuminate the illuminating light into the reticle 10, it is possible to easily detect pattern unevenness occurring on a display device such as a liquid crystal display device, for example, by using a diffracted light of a desired order corresponding to an incident angle. .

The transparent substrate 11 is an optical substrate in which both surfaces are parallel planes. Therefore, the same dimming is emitted from the transparent substrate 11 at the emission angle θi (that is, the same angle as the incident angle θi). When the pattern forming surface 12a is irradiated with the same dimming light by the emission angle θi, the periodic structure (that is, the repeating pattern 12) formed on the pattern forming surface 12a causes diffracted light. Here, the dimming is at an angle to the optical axis AX of the imaging device 40. Therefore, the low-order diffracted light including the 0th order is diffracted in different directions in the direction in which the imaging device 40 is located. On the optical path parallel to the optical axis AX of the imaging device 40, there is a high-order diffracted light traveling in the vicinity of -n steps at an angle θn (unit: deg) with 0-order light. The imaging lens 41 included in the imaging device 40 has substantially only a predetermined order and diffracted light of a higher order (larger absolute value) than the predetermined order.

The typical pattern unevenness of the reticle 10 is fine with respect to the normal pattern. In order to perform defect inspection with high precision, it is preferable to use high-order diffracted light including information on the fine structure of the object. Therefore, the pattern inspection apparatus 1 is configured to exclude low-order diffracted light while checking the presence or absence of pattern unevenness of the reticle 10 by using high-order diffracted light.

The imaging device 40 is an area camera that captures diffracted light generated on the pattern forming surface 12a illuminated by the illumination optical system 32. The imaging device 40 is configured such that the object-side focal plane of the imaging lens 41 is located on the pattern forming surface 12a. Further, the imaging device 40 has a solid imaging element 42 (for example, a CCD (Charge Coupled Device)). The solid-state imaging element 42 is disposed such that the light receiving surface 42a is located on the image side focal plane of the imaging lens 41. Therefore, the same dimming of the penetrating pattern forming surface 12a is formed on the light receiving surface 42a by the Fourier transform image corresponding to the through image placed on the pattern forming surface 12a by the Fourier transform effect by the imaging lens 41. The solid-state imaging device 42 detects the Fourier-converted image on the light-receiving surface 42a as a light intensity distribution, and accumulates the obtained spatial spectrum as a charge corresponding to the detected light amount, and converts it into an image signal. The converted image signal is output to the material processing device 50.

Here, the third figure schematically shows an ideal reticle 10 without pattern unevenness. As shown in the third figure, a plurality of unit patterns 13 constituting the repeating pattern 12 are arranged in a matrix at a predetermined pitch ω (unit: μm) on the ideal pattern forming surface 12a. In the present embodiment, each of the imaginary unit patterns 13 has a pitch that falls within a range of 50 to 600 (unit: μm). The line width is preferably from 1 to 300 (unit: μm). Further, the number of unit patterns 13 shown in the third figure is merely illustrative. Actually, the number of unit patterns 13 formed on the pattern forming face 12a is larger.

Each of the fourth to fourth figures (A) to (D) shows an example of pattern unevenness formed on the pattern forming surface 12a. In each of the fourth (A) to fourth (D) drawings, the symbol 14 is attached to the defect region on the pattern forming surface 12a where the pattern unevenness exists. The fourth figure (A) shows pattern unevenness in which the distance between the specific unit pattern 13 groups and the pitch ω are different. The fourth figure (B) shows the pattern unevenness of the position of the specific unit pattern 13 group from the other unit pattern 13 group. The pattern unevenness shown in the fourth (A) and fourth (B) figures relates to the positional accuracy of the pattern, and the cause of the pattern shift is, for example, a positional shift occurring at the seam drawn by the laser beam. The fourth (C) and fourth (D) graphs show that the specific unit pattern 13 group is thinner or thicker than the other unit patterns 13 group. The pattern unevenness shown in the fourth (C) and fourth (D) figures relates to the CD accuracy, and the cause of the occurrence is, for example, the intensity variation of the laser beam at the time of drawing. In addition to the pattern unevenness illustrated in each of the fourth (A) to fourth (D) drawings, for example, when the specific unit pattern 13 group has the same shape defect, the image inspection apparatus 1 is also an object. The pattern is uneven.

The figures of the fifth (A) and fifth (B) diagrams show the spatial spectrum captured by the imaging device 40. In addition, each of the fifth (A) and fifth (B) diagrams shows the spatial spectrum upside down for the sake of clarity.

As shown in the third figure, in the case where the unit pattern 13 groups are regularly arranged without pattern unevenness, the diffraction light caused by the arrangement of the unit patterns 13 is regularly distributed to the Fourier conversion surface (light receiving surface 42a) in a certain cycle. In this case, on the light receiving surface 42, the spatial spectrum in which the cross pattern 100 is arranged at equal intervals is detected (refer to FIG. 5(A)).

On the other hand, as shown in each of the fourth to fourth figures (A) to (D), in the case where the pattern unevenness is formed on the pattern forming surface 12a, the distribution of the diffracted light on the Fourier transform surface is uneven due to the pattern. And out of shape. At this time, the alias appears as the spatial frequency component 110. The spatial frequency component 110 is an abnormal component having a high spatial frequency in which the pattern unevenness is generated in the shape of the normal unit pattern 13, and thus is distributed separately from the center of each of the cross-shaped patterns 100 as shown in FIG. 5(B). s position. In order to accurately detect the presence or absence of pattern unevenness, the spatial frequency component 110 and the cross pattern 100 must be separated and distributed. Here, the "separation" is, for example, a state in which the images of both sides are spatially separated by image analysis processing performed at the end of general information, and the degree of separation is sufficient to clearly distinguish the spatial frequency component 110 from the cross pattern 100.

Specifically, the absolute value of the diffraction order of the diffracted light generated by the periodic structure formed on the pattern forming surface 12a is defined as n, and the wavelength of the same dimming light irradiated by the light source unit 31 is defined as λ (unit: μm) The distance between the unit patterns 13 is defined as ω (unit: μm), and the n-th order diffracted light is emitted at an angle which is formed by the 0-order diffracted light and satisfies the following condition (1).

Θn=sin ^-1 (nλ/ω)‧‧‧(1)

The difference (distance) between the position of the 0th-order diffracted light and the position of the n-th order diffracted light on the observation surface at a distance L (unit: mm) from the pattern forming surface 12a is defined as h (unit: mm), and the distance h satisfies the following Condition (2).

h=L(tanθn)‧‧‧(2)

Further, the distance between the unit patterns 13 in which the amount of error to be detected is defined as Δω (unit: μm) and the portion including the error is defined as ω' (= ω ± Δω, unit: μm), and the distance between the unit patterns 13 is ω In the case of ω', the difference (distance) between the positions of the n-th order diffracted lights on the observation plane is defined as Δh (unit: mm), and the distance Δh satisfies the following condition (3).

Δh=h-h'=L(tanθn-tanθ'n)=L{tan(sin ^-1 (nλ/ω))-tan(sin ^-1 (nλ/ω'))}‧‧‧(3)

The difference in the position of the n-th order diffracted light on the light receiving surface 42a when the focal length of the imaging device 40 (imaging lens 41) of the observation distance Δh is defined as f (unit: mm) and the distance between the unit patterns 13 is ω, ω' (Distance) is defined as Δh' (unit: mm), and the distance Δh' satisfies the following condition (4).

Δh'=f(tan(Δθn))‧‧‧(4)

Δθn=θn-θ'n=tan ^-1 (Δh'/f)=sin ^-1 (nλ/ω)-sin ^-1 (nλ/ω')

Further, the distance between the pixels arranged on the light receiving surface 42a of the solid-state imaging device 42 is defined as p (unit: mm). At this time, in order to separate the spatial frequency component 110 generated by the pattern unevenness from the cross pattern 100, the pattern inspection apparatus 1 frame configuration satisfies the following condition (5).

Δh’>p‧‧‧(5)

In order to inspect fine pattern unevenness with high precision, it is preferable to use high-order diffracted light as described above. The applicant changed his mind and did not stick to the technical common sense in the field of reticle technology (that is, viewing the real image of the reticle for defect inspection), and thus thought of viewing the Fourier transform image for defect inspection. Further, according to such a concept, in order to easily and quickly check the presence or absence of pattern unevenness, a method of separating and observing the spectrum (that is, the spatial frequency component 110) corresponding to the pattern unevenness from the cross pattern 100 is conceivable. The Applicant has found that the finer the pattern unevenness is than the normal pattern (unit pattern 13), and it is preferable to use a higher order diffracted light when separating the spatial frequency component 110 from the cross pattern 100.

In view of the relationship between the distance ω between the unit patterns 13 of the reticle 10 for the image device and the size of the typical pattern unevenness, the spatial frequency component 110 and the cross pattern are used in order to use the pattern inspection device 1 having the structure satisfying the condition (5). With 100 separation, it is desirable that the n-th order diffracted light incident on the imaging lens 41 satisfies the following condition (6).

20≦n‧‧‧(6)

When the n-th order diffracted light satisfies the condition (6), the spatial frequency component 110 can be separated from the cross-shaped pattern 100. On the other hand, when the n-th order diffracted light does not satisfy the condition (6), the spatial frequency component 110 cannot be separated from the cross-type pattern 100.

Here, the higher the order of the diffracted light, the less the amount of light diffracted. Therefore, the increase in noise, etc., may result in a decrease in inspection accuracy. Therefore, the n-th order diffracted light is more preferably satisfying the following condition (7).

20≦n≦700‧‧‧(7)

When the n-th order diffracted light satisfies the condition (7), the deterioration due to the noise of the spatial spectrum detected on the light-receiving surface 42a is suppressed, so that the inspection with high accuracy is ensured. When the n-th order diffracted light exceeds the upper limit of the condition (7), the noise of the spatial spectrum increases, which may deteriorate the inspection accuracy.

Further, in order to further improve the inspection accuracy, it is desirable to set the n-th order diffracted light to satisfy, for example, the following condition (8).

30<n<600‧‧‧(8)

The specific numerical combination of the pattern inspection device 1 is exemplified below. The solid-state imaging device 42 is, for example, a 1/3 type and is a VGA (Video Graphics Array). In this case, the pixel pitch p is 6.35 μm. Further, the wavelength λ of the same dimming light, the focal length f of the imaging lens 41, and the typical pattern unevenness Δω which can be inspected by the light source unit 31 are as follows.

λ: 0.532 μm

f: 50mm

Δω: 0.1 μm

When the distance ω between the unit patterns 13 is 100 μm, in order to separate the spatial frequency component 110 from the cross pattern 100, the pattern inspection apparatus 1 is configured to be -24 steps or more (the positional relationship between the mask 10 and the illumination device 30 is +24). The diffracted light of the order of the order or more is incident on the imaging lens 41. Further, when the distance ω between the unit patterns 13 is 200 μm or 300 μm, in order to separate the spatial frequency component 110 from the cross pattern 100, the pattern inspection apparatus 1 is configured to be -92 steps or more (in accordance with the above positional relationship, +92 steps or more). The diffracted light of the order of -200 steps or more (+200 steps or more according to the above positional relationship) is incident on the imaging lens 41.

For example, a case where the photomask 10 having a distance ω of 400 μm, 500 μm or 600 μm between the unit patterns 13 is examined is considered. When the pitch ω is 400 μm, 500 μm, or 600 μm, in order to separate the spatial frequency component 110 from the cross pattern 100, the pattern inspection apparatus 1 is configured to be -339 steps or more (+339 steps or more depending on the positional relationship), - The diffracted light of the order of 502 or more (+502 or more according to the above positional relationship) and -681 or more (+681 or more according to the above positional relationship) is incident on the imaging lens 41.

The data processing device 50 is, for example, a general desktop PC (Personal Computer), and is installed with an application for defect inspection for performing defect inspection of the reticle 10. The data processing device 50 activates an application for defect inspection, and generates an inspection image (for example, an image shown in FIG. 5(A) or FIG. 5(B)) based on an image signal output from the solid-state imaging device 42. Next, the generated inspection image is compared with a predetermined reference image (one image is a spatial spectrum of the ideal mask 10 in which pattern unevenness does not exist, and the spatial frequency component 110 does not substantially appear), and the difference is detected. The data processing device 50 determines the presence or absence of pattern unevenness of the photomask 10 based on the detected difference. Specifically, when the spatial frequency component 110 appears to be separated from the cross pattern 100, the data processing device 50 determines that the photomask 10 includes pattern unevenness. On the other hand, when the spatial frequency component 110 does not appear (when the spatial frequency component 110 is not separated from the cross pattern 100), it is determined that the mask 10 does not contain pattern unevenness. The result of the determination by the data processing device 50 is displayed on the display 60.

The operator surely grasps the presence or absence of pattern unevenness of the photomask 10 based on the determination result displayed on the display 60. The presence or absence of the pattern unevenness is determined for the mask 10, for example, when the scanning of the entire effective area of the mask 10 is completed, or when the pattern unevenness is detected.

According to the pattern inspection apparatus 1 of the present embodiment, it is not necessary to change the inspection condition (focus adjustment, etc.) of the defect type as usual, and repeat the inspection according to the defect type. Since the continuous scanning mask 10 can be inspected without changing the inspection conditions, the inspection time is greatly shortened. It is determined that there is no pattern unevenness after the entire effective area of the photomask 10 is scanned, and the quality assurance of the photomask 10 can be easily and quickly obtained. In this case, it is possible to proceed to the next procedure without checking the specific content of the pattern unevenness, which contributes to an improvement in manufacturing efficiency. Further, in order to examine and analyze the specific content of the pattern unevenness, for example, a structure may be attached to the pattern inspection device 1 which converts the Fourier converted image generated by the imaging lens 41 into a real image, and the converted real image is captured and analyzed. .

As described above, according to the pattern inspection device 1 of the present embodiment, the presence or absence of pattern unevenness can be easily and quickly checked. Therefore, the inspection time is greatly shortened, which is advantageous in terms of the lead time and the like. Further, the pattern inspection device 1 of the present embodiment has a simple configuration, and this configuration does not require a spatial filter for removing noise of low-order diffracted light, thereby reducing the burden on design development or manufacturing.

The above is the description of the embodiments of the present invention. The present invention is not limited to the above-described configuration, and various modifications can be made within the scope of the technical idea of the present invention.

1. . . Pattern inspection device

10. . . Mask

20. . . Loading platform

30. . . Lighting device

40. . . Camera

50. . . Data processing device

60. . . monitor

The first diagram schematically shows the overall configuration of a pattern inspection apparatus according to an embodiment of the present invention.

The second diagram schematically shows the configuration of the main part of the pattern inspection apparatus according to the embodiment of the present invention.

The third figure schematically shows an ideal mask without pattern unevenness.

The fourth figure shows an example of pattern unevenness formed on the mask pattern forming surface.

Fig. 5 is a view showing a spatial spectrum captured by an imaging device included in the pattern inspection device according to the embodiment of the present invention.

1. . . Pattern inspection device

10. . . Mask

11. . . Transparent substrate

12. . . Repeat pattern

12a. . . Pattern forming surface

13. . . Unit pattern

20. . . Loading platform

30. . . Lighting device

31. . . Light source department

32. . . Lighting optical system

40. . . Camera

41. . . Imaging lens

42. . . Solid imaging element

42a. . . Light receiving surface

AX. . . Optical axis of the camera

Claims (16)

A pattern inspection method for inspecting a pattern unevenness of a reticle, wherein a transparent pattern formed by periodically arranging a unit pattern is formed on a transparent substrate of the reticle, wherein the pattern inspection method includes: an illuminating step, by specifying a light beam illuminating the repeating pattern; a Fourier transform image detecting step of detecting a Fourier transform image corresponding to the diffracted light generated by irradiating the repeating pattern with the light beam; and a pattern unevenness determining step, according to the detected Fourier transform image Determining whether or not the pattern unevenness of the mask is present; in the Fourier transform image detecting step, in order to spatially separate the Fourier transform image corresponding to the pattern unevenness of the mask and the Fourier transform image corresponding to the normal pattern a Fourier-converted image corresponding to the high-order diffracted light specified in the diffracted light. For example, in the pattern inspection method of the first aspect of the patent application, the absolute value of the order of the high-order diffracted light is 20 to 700. A pattern inspection method for inspecting a pattern unevenness of a reticle, wherein a transparent pattern formed by periodically arranging a unit pattern is formed on a transparent substrate of the reticle, wherein the pattern inspection method includes: an illuminating step, by specifying a light beam illuminating the repeating pattern; a Fourier transform image detecting step of detecting a Fourier transform image corresponding to the diffracted light generated by irradiating the repeating pattern with the light beam through a predetermined optical system; and a pattern unevenness determining step, detecting according to the foregoing The Fourier transform image is used to determine the presence or absence of pattern unevenness of the photomask; the wavelength of the light beam is defined as λ μm, the distance between the unit patterns is defined as ω μm, and the distance between the unit patterns including the pattern unevenness is defined as ω 'μm, the focal length of the aforementioned optical system is defined as f mm, the decomposition energy of the Fourier transform image detected by the aforementioned Fourier transform image is defined as p mm, and the angle between the aforementioned diffracted light of 0th order and the aforementioned diffracted light of nth order is defined as In the case of θn deg, in the aforementioned Fourier transform image detecting step, the detection of the above-mentioned diffracted light satisfies the following The n-th order diffracted light of the corresponding element of the Fourier transform image; f (tan (△ θn) )> p △ θn = sin -1 (nλ / ω) -sin -1 (nλ / ω '). The pattern inspection method according to any one of claims 1 to 3, wherein a normal line of the Fourier transform surface detected by the Fourier transform image and an optical axis of the illumination optical system that irradiates the light beam in the irradiating step are used The case where the angle is defined as θi satisfies 0° < θi < 90°. The pattern inspection method according to any one of claims 1 to 3, wherein the beam of light irradiated in the irradiation step is at least spatially substantially coherent and is a single wavelength parallel beam. The pattern inspection method according to any one of claims 1 to 3, wherein in the pattern unevenness determining step, the Fourier transform image detected in the Fourier transform image detecting step is compared with a predetermined reference image, according to The comparison result determines the presence or absence of the pattern unevenness of the photomask. The pattern inspection method according to any one of claims 1 to 3, wherein in the case where the inspection area which can be simultaneously inspected is narrower than the entire inspection object of the reticle, the reticle is moved and the inspection area is continuously scanned At the same time, the irradiation step, the Fourier transform image detecting step, and the pattern unevenness determining step are performed on the inspection region to determine the presence or absence of the pattern unevenness of the mask. A reticle manufacturing method for forming a mask pattern to form a reticle in a mask blank, comprising the steps of: performing a pattern inspection method according to any one of claims 1 to 3 to determine formation The pattern of the mask of the mask pattern is uneven. A pattern transfer method characterized in that the mask pattern is transferred to a transfer target substrate by using a photomask manufactured by the reticle manufacturing method of claim 8 of the patent application. A pattern inspection device for inspecting a pattern unevenness of a mask, wherein a transparent pattern formed by periodically arranging a unit pattern is formed on a transparent substrate of the mask, wherein the pattern inspection device has an illumination means, a light beam illuminating the repeating pattern; a Fourier transform image detecting means for detecting a Fourier transform image corresponding to the diffracted light generated when the repeating pattern is irradiated by the irradiation means; and a pattern unevenness determining means for detecting the Fourier transform image according to the The presence or absence of the pattern unevenness of the photomask is determined. The Fourier transform image detecting means detects the Fourier transform image corresponding to the pattern unevenness of the mask and spatially separates the Fourier transform image corresponding to the normal pattern. A Fourier transform image corresponding to the high-order diffracted light specified in the diffracted light. The pattern inspection device of claim 10, wherein the absolute value of the order of the high-order diffracted light is 20 to 700. A pattern inspection device for inspecting a pattern unevenness of a mask, wherein a transparent pattern formed by periodically arranging a unit pattern is formed on a transparent substrate of the mask, wherein the pattern inspection device has an illumination means, a light beam illuminating the repeating pattern; a Fourier transform image detecting means for detecting a Fourier transform image corresponding to the diffracted light generated when the repeating pattern is irradiated by the irradiation means; and a pattern unevenness determining means for detecting the Fourier transform image according to the Determining whether or not the pattern of the reticle is uneven; the wavelength of the light beam is defined as λ μm, the distance between the unit patterns is defined as ω μm, and the distance between the unit patterns including the pattern unevenness is defined as ω′ μm, the foregoing The focal length of the optical system is defined as f mm, the decomposition energy of the Fourier transform image detected by the Fourier transform image is defined as p mm, and the angle between the diffracted light of the 0th order and the diffracted light of the nth order is defined as θn deg. The aforementioned Fourier transform image detecting means detects the aforementioned diffraction of the nth order satisfying the following conditions in the diffracted light The Fourier transform image corresponding to the light; f(tan(Δθn))>p Δθn=sin ^-1 (nλ/ω)-sin ^-1 (nλ/ω'). The pattern inspection device according to any one of claims 10 to 12, wherein the illumination means has an illumination optical system for illuminating the light beam, a normal line of the Fourier conversion surface on which the Fourier conversion image is detected, and the foregoing The angle formed by the optical axis of the illumination optical system is defined as θi, which satisfies 0° < θi < 90°. The pattern inspection device of any one of claims 10 to 12, wherein the beam of light is at least spatially substantially coherent and is a single wavelength parallel beam. The pattern inspection device according to any one of claims 10 to 12, wherein the pattern unevenness determining means compares the Fourier converted image detected by the Fourier transform image detecting means with a predetermined reference image, according to the comparison result It is determined whether or not the pattern of the reticle is uneven. The pattern inspection apparatus according to any one of claims 10 to 12, further comprising an inspection area scanning means for narrowing the inspection area that can be simultaneously inspected to be narrower than the inspection object of the mask. The reticle is moved and the aforementioned inspection area is continuously scanned.