Defect inspection method and defect inspection device for transparent body

Abstract

The invention provides a defect inspection device and a defect inspection method, which can detect defects of a transparent body, especially a protective film, used in a photomask. A defect inspection device for detecting a defect of a transparent body according to the present invention includes a light source, an inspection pattern portion, an imaging device, and a detection circuit, and is configured so that light radiated from the light source can sequentially pass through the inspection pattern portion and the transparent body and is incident on the imaging device, and the imaging device outputs an image signal corresponding to the incident light to the detection circuit. The inspection pattern portion may have, for example, a line in which transmissive regions and light-shielding regions are alternately arranged, and an interval pattern. The detection circuit can obtain image data and judge whether the transparent body has defects or not.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for inspecting defects in a transparent body, particularly a transparent body for a photomask. Background Art

[0002] In a photolithography process of an electronic circuit for a flat panel display such as a liquid crystal panel, a photomask is used. On the photomask, a protective film assembly is mounted on the surface to prevent foreign matter from adhering.

[0003] The protective film assembly includes a frame and a protective film. The protective film is attached to the frame, and the frame is fixed to the photomask. When there is adhesion or unevenness of foreign matter on the protective film, depending on the situation, it is possible to cause defects due to foreign matter or unevenness on the transfer object in the exposure process of using the photomask.

[0004] To detect foreign matter attached to the protective film, there is known a foreign matter inspection apparatus that measures the optical characteristics, i.e., transmittance, of the protective film and detects foreign matter based on an abnormality in the transmittance (Patent Document 1).

[0005] Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Laid-Open No. 4-64041. Summary of the Invention

[0006] Problems to be Solved by the Invention However, in the existing foreign matter inspection apparatus, it is difficult to detect foreign matter or unevenness in a transparent body such as a protective film for a photomask with high sensitivity. Therefore, foreign matter is inspected using a microscope image, and unevenness of the protective film is inspected visually and manually.

[0007] In view of the above problems, an object of the present invention is to provide a defect inspection apparatus and a defect inspection method capable of detecting foreign matter or unevenness in a transparent body, particularly a protective film, used in a photomask.

[0008] Means for Solving the Problems The defect inspection apparatus of the present invention is a defect inspection apparatus for a transparent body, which includes a light source, an inspection pattern unit, an imaging device, and a detection circuit, and is configured to allow the light radiated from the light source to sequentially pass through the inspection pattern unit and the transparent body and enter the imaging device, and the imaging device outputs an image signal corresponding to the incident light to the detection circuit.

[0009] With such a defect inspection apparatus, it is possible to detect defects in a transparent body such as a protective film that affect the exposure process.

[0010] In addition, in the above structure, the inspection pattern portion may also have a line and space pattern formed by alternately arranging a transmissive region and a light-shielding region.

[0011] With such a defect inspection device, it is possible to effectively detect defects of a transparent body using a simple pattern.

[0012] In addition, in the above structure, the transparent body may also be a protective film.

[0013] With such a defect inspection device, it is possible to effectively detect defects of the protective film of the protective film assembly of a photomask.

[0014] In addition, in the above structure, an illumination lens may further be included, configured such that the position of the focus of the light can be located on the light source side of the transparent body through the illumination lens.

[0015] With such a defect inspection device, effective defect inspection can be performed.

[0016] In addition, in the above structure, the inspection pattern portion may be located between the illumination lens and the transparent body.

[0017] With such a defect inspection device, defect inspection can be performed with a structure close to the geometric conditions of the transparent body, particularly the protective film.

[0018] In addition, in the above structure, the inspection pattern portion may be located between the light source and the illumination lens.

[0019] With such a defect inspection device, the space for arranging the transparent body to be inspected is enlarged, improving the operability of the defect inspection device.

[0020] In addition, in the above structure, a viewing light source and a reflector may further be included. The reflector is disposed between the transparent body and the imaging device and is configured to guide the light irradiated from the viewing light source to the transparent body.

[0021] With such a defect inspection device, it becomes easier to observe the detected defects.

[0022] The defect inspection method of the present invention is a defect inspection method for a transparent body, which includes: a first step of irradiating light emitted from a light source to an inspection pattern portion and irradiating the transmitted light from the inspection pattern portion to the transparent body; a second step of an imaging device that receives the light transmitted through the transparent body outputs image data to a detection circuit; and a third step of the detection circuit acquires the image data and determines whether there are defects in the transparent body.

[0023] By such a defect inspection method, it is possible to detect defects such as those on a transparent body like a protective film that can affect the exposure process.

[0024] In addition, in the above structure, in the third step, it may further include: a step in which the detection circuit compares the acquired image data with reference image data, and when a difference is confirmed, determines that there is a defect in the transparent body.

[0025] By such a defect inspection method, it is possible to determine whether there is a defect in a transparent body using a known pattern defect inspection method.

[0026] Advantages of the Invention According to the present invention, a defect inspection device and a defect inspection method can be obtained, which can detect foreign matters or unevenness in a transparent body, particularly a protective film, used in a photomask. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 In (A), it is a schematic diagram showing the main structure of the protective film assembly inspection device 100 of Embodiment 1. Figure 1 In (B), it is a top view schematically showing the inspection mask 7 used in the protective film assembly inspection device 100.

[0028] Figure 2 Schematically shows the scanning direction of the inspection area SA on which the pattern 7b is imaged on the protective film 8a as an inspection object. Figure 2 In (A), it illustrates a method of fixing the illumination device 1, the inspection mask 7, the objective lens 4, and the imaging device 5, and only moving the protective film 8a. Figure 2 In (B), it illustrates a method of fixing the protective film 8a and moving the illumination device 1, the inspection mask 7, the objective lens 4, and the imaging device 5 integrally.

[0029] Figure 3 In (A), it is a schematic diagram showing the main structure of the protective film assembly inspection device 100 of Embodiment 2. Figure 3 In (B), it is a top view schematically showing the projection pattern portion 11 used in the protective film assembly inspection device 100.

[0030] Figure 4 It is a schematic diagram illustrating the viewing function of the protective film assembly inspection device 100. Figure 4 In (A), it shows a structural example having a viewing function using coaxial epi-illumination. Figure 4 In (B), it shows a structural example having a viewing function using side illumination.

[0031] Figure 5 Shows an example of an image acquired by the imaging device 5. Figure 5In (A), it is a normal image of the inspection pattern. Figure 5 In (B) and (C), they are images judged to be abnormal. Figure 5 In (D) and (E), they are viewing images of the inspection area SA judged to be abnormal. Detailed implementation mode

[0032] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, none of the following embodiments shall give a restrictive interpretation in the determination of the gist of the present invention. In addition, sometimes the same reference numerals are assigned to the same or similar components, and the description thereof is omitted.

[0033] In addition, regarding terms such as "parallel", "orthogonal", "identical", etc. used in this specification to determine the conditions of shape or geometry and their degrees, and values of lengths, angles, etc., they are not limited to strict meanings, but are interpreted to include ranges to the extent that the same functions can be expected.

[0034] (Embodiment 1) Hereinafter, with reference to the accompanying drawings, a protective film component inspection device 100 (defect inspection device) for inspecting defects of a protective film component, particularly a protective film, will be described.

[0035] As described above, the protective film component is used to protect the photomask and is provided on the pattern formation side of the photomask.

[0036] In order not to affect the exposure process of the lithography process using the photomask, the protective film attached to the protective film component is a transparent body that is transmissive to the exposure light.

[0037] Since the protective film component is formed integrally with the photomask, it generally constitutes a part of the photomask.

[0038] Figure 1 In (A), it is a schematic diagram showing the main structure of the protective film component inspection device 100. Figure 1 In (B), it is a plan view schematically showing the inspection mask 7 (inspection pattern part) used in the protective film component inspection device 100.

[0039] As Figure 1 As shown in (A), the protective film component inspection device 100 includes: an illumination device 1, an objective lens 4, an imaging device 5 (camera), and an inspection circuit 6. In Figure 1 In (A), the Y direction represents the direction parallel to the optical axis, and the X direction represents the direction perpendicular to the optical axis.

[0040] The protective film component inspection device 100 has an inspection mask 7 between the illumination device 1 and the objective lens 4. The inspection mask 7 can be, for example, a binary photomask.

[0041] The lighting device 1 includes a light source 2 that emits light L and a lighting lens 3.

[0042] In addition, the light source 2 can use, for example, a lamp light source or a laser light source.

[0043] The wavelength of the light L emitted from the light source 2 is preferably the same as the wavelength of the exposure light used in the lithography process, but is not limited to this wavelength.

[0044] The lighting lens 3 is composed of, for example, a combination of a condenser lens, a focusing lens, and a projection lens without limitation.

[0045] The imaging device 5 has, for example, a two-dimensional imaging element such as a CCD image sensor without limitation.

[0046] The objective lens 4 has an arbitrary magnification. For example, it has a field width of 100 μm to 2000 μm. The objective lens 4 can guide the light L to the imaging device 5 and image (project) the image of the inspection mask 7 onto the imaging element of the imaging device 5. The objective lens 4 can set the magnification in accordance with the imaging element. The imaging element of the imaging device 5 can generate two-dimensional image data corresponding to the imaged image (projected image). The image data can be composed of, for example, a combination of the brightness information of two-dimensional pixels and their coordinates. The imaging device 5 can convert the projected image into an electrical signal as image data and output it.

[0047] The protective film assembly inspection device 100 has a mask support portion 9 for supporting the inspection mask 7. The mask support portion 9 supports the inspection mask 7 in such a manner that the inspection mask 7 is located between the lighting device 1 and the objective lens 4.

[0048] As Figure 1 shown in (B) of , the inspection mask 7 is provided with a transmissive region and a light-shielding region. Specifically, the inspection mask 7 is configured as a mask in which a pattern 7b is formed on a light-transmissive substrate 7a as an inspection pattern. The pattern 7b is formed of, for example, a light-shielding film, and a plurality of patterns extending in the Z direction are formed in the drawing. The light-transmissive substrate 7a is exposed in the transmissive region, and a pattern composed of a light-shielding film is formed on the light-transmissive substrate 7a in the light-shielding region.

[0049] The pattern 7b preferably forms lines and intervals in which the light-shielding region and the transmissive region are alternately arranged. As the width of the pattern 7b (light-shielding region), it is preferably possible to set it to the resolution limit value of the expected exposure process. For example, it can be set to 1 μm to 5 μm, but is not limited thereto. In addition, the interval between the patterns 7b can be equal to the line width, for example. This is a simply repeated pattern, which is easy to manufacture and can effectively detect defects.

[0050] As the shape of the pattern 7b, for example, lines and intervals with a stable edge shape can be used, and it also becomes easy to perform defect inspection using the pattern inspection method.

[0051] In addition, the shape of the pattern 7b is not limited to a line and space pattern, and all patterns capable of detecting defects such as a dot pattern may be employed.

[0052] The size of the inspection mask 7 or the width of the pattern 7b can be determined according to the required detection sensitivity or the processing time of the inspection process of the protective film assembly 8.

[0053] The inspection mask 7 can be fabricated by a known method for manufacturing a photomask.

[0054] The protective film assembly inspection apparatus 100 includes a protective film assembly support portion 10 (inspected object support portion) for supporting the protective film assembly 8. The protective film assembly support portion 10 supports the protective film assembly 8 such that the protective film 8a of the protective film assembly 8, in particular, is located between the inspection mask 7 and the objective lens 4. The flat film-shaped protective film 8a is disposed in parallel with the inspection mask 7.

[0055] The relationship between the inspection mask 7 and the protective film 8a is configured to approximate the relationship between an actual photomask and the protective film 8a.

[0056] The protective film assembly 8 includes a protective film 8a and a frame 8b for fixing to a photomask, and the protective film 8a is fixed to the frame 8b. The protective film assembly support portion 10 supports the frame 8b.

[0057] The illumination lens 3 is configured to be adjustable such that the focal point F of the light L is located at the pattern 7b of the inspection mask 7. Accordingly, the focal point F of the light L is located closer to the light source 2 than the protective film 8a. By analogously reproducing the geometric positional relationship between the actual protective film 8a and the focal point F, the sensitivity of defect inspection can be improved, detection of excessive defects can be prevented, and effective defect inspection can be achieved.

[0058] The distance between the focal point F and the protective film 8a can be, for example, a distance of the same degree as the height of the frame 8b ( Figure 1 the length in the Y direction in (A) of

[0059] but is not limited thereto). The light L emitted from the light source 2 passes through the inspection mask 7 via the illumination lens 3 and is incident on the protective film 8a. Then, the light L transmitted through the protective film 8a is guided to the imaging device 5 through the objective lens 4, and the image of the pattern 7b is projected onto the imaging device 5. The imaging device 5 generates image data corresponding to the projected image of the light L (i.e., the image of the projected pattern 7b) and transmits (outputs) the image data as an image signal to the detection circuit 6.

[0060] The detection circuit 6 can store the image data obtained (input) based on the received image signal in the storage device. The image data can reproduce the image of the pattern 7b projected onto the imaging device 5.

[0061] In addition, the storage device can be built into the detection circuit 6 or can be external.

[0062] As described above, the image of the pattern 7b is formed on the imaging device 5 (especially on its imaging element). When there is an optical abnormality on the protective film 8a, abnormalities (such as abnormalities in size width or brightness) will occur in the imaged pattern due to defocusing of the exposure light or the like. By comparing the image of the imaged pattern 7b with the image of the normal pattern 7b, the abnormality of the protective film 8a can be detected.

[0063] By moving the protective film 8a relative to the inspection mask 7 and the illumination device 1, image data of the entire protective film 8a can be acquired. The relative movement direction of the protective film 8a can be set to a direction perpendicular to the long side direction of the line pattern, that is, the pattern 7b (light-shielding area) ( Figure 1 the Z direction in (B) therein). By relatively moving the protective film 8a in a manner that crosses the line pattern, it is possible to avoid the line pattern from interfering with the detection of the abnormal part of the protective film 8a. Figure 1 the X direction in (B) therein).

[0064] Figure 2 Schematically shows the scanning direction of the inspection area SA where the pattern 7b is imaged on the inspection object, that is, the protective film 8a. The inspection area SA is an area for inspecting whether there is an abnormality in the protective film 8a. Figure 2 The dashed arrow in therein schematically shows the scanning direction of the inspection area SA.

[0065] By relatively moving the inspection area SA relative to the protective film 8a in a zigzag manner and turning back, the entire surface of the protective film 8a can be scanned.

[0066] The detection circuit 6 stores the image data acquired using the imaging device 5 in the inspection area SA in the storage device in association with the position (coordinates) of the inspection area SA.

[0067] As Figure 2 shown in (A) therein, the illumination device 1, the inspection mask 7, the objective lens 4, and the imaging device 5 are fixed, and only the protective film 8a is moved. In addition, in order to move the protective film 8a, the protective film assembly support portion 10 can be moved. The protective film assembly support portion 10 can be moved by a driving device (not shown). The position information (coordinates) of the inspection area SA is sent to the detection circuit 6. The detection circuit 6 can, for example, store the ID number for identifying the inspection area SA in association with its position information in the storage device. In addition, as the ID number, the time can also be used.

[0068] In addition, as Figure 2As shown in (B) in [reference number], conversely, the protective film 8a can be fixed, and the inspection area SA can be moved by moving the lighting device 1 or other components. In this case, the lighting device 1 or the like can also be moved by a driving device (not shown). The position information (coordinates) of the inspection area SA is sent to the detection circuit 6.

[0069] In any case, the positional relationship of the components other than the protective film assembly 8 to be inspected (the lighting device 1, the inspection mask 7, the objective lens 4, and the imaging device 5) is fixed.

[0070] While relatively moving the protective film 8a, image data can be continuously acquired by the imaging device 5, or the protective film 8a can be moved a predetermined distance and then stopped as in step-and-repeat, and image data can be acquired by the imaging device 5 in the stationary state.

[0071] In addition, in the case of adopting the movement based on step-and-repeat, if the above-mentioned predetermined distance is an integer multiple of the pitch in the line-and-space pattern, there may be a situation where foreign matters located in the pattern 7b (light-shielding area) cannot be detected. Therefore, the above-mentioned predetermined distance can be set to a value obtained by adding a distance equal to the width of the light-shielding area to an integer multiple of the pitch. In this way, at least all areas of the protective film 8a can be projected and inspected by the transmission area of the inspection pattern portion once.

[0072] In addition, the same applies when using other patterns such as dot patterns as the pattern 7b, and the above-mentioned predetermined distance can be determined based on the pitch of the pattern adopted.

[0073] By adopting a minute dot pattern, compared with the line-and-space pattern, minute defects can be further detected. There is a tendency that the influence of defocus is large at the corners of the dot pattern and the corners become rounded. There is a tendency that the difference in brightness is more pronounced at the corners, which can improve the detection sensitivity.

[0074] The detection circuit 6 compares the projected image of the inspection area SA obtained with the projected image of the optically normal protective film 8a. When a difference is confirmed between the two projected images, it can be determined that there is an optical abnormality in the protective film 8a of the inspection area SA.

[0075] In addition, sometimes the projected image (optically normal image) of the protective film 8a without defects (foreign matters, unevenness, etc.) is called a "reference image", and the image data generated based on the "reference image" is called "reference image data". The reference image data as optically normal image data can also be stored in the storage device as reference data.

[0076] In addition, for simplicity, sometimes the "optically normal image" is called a "normal image".

[0077] The detection circuit 6 can store the acquired image data in the storage device in association with the acquired time or position. Further, the detection circuit 6 includes, for example, differential detection circuits such as a simple comparison differential circuit and a detection circuit of a concentration difference system, and can compare the image data acquired several seconds ago or the image data at a position several mm ago. In addition, since there is a large amount of normal image data in general image data, it is easy to determine whether the acquired image data is normal image data.

[0078] Such a method of comparing image data can use the chip-to-chip comparison method employed by a known pattern inspection device.

[0079] The detection circuit 6 can register the inspection area SA where an abnormality is detected as an abnormal area in the storage device.

[0080] In addition, the detection circuit 6 may have a function of correcting the light intensity deviation. The correction function can, for example, reduce the influence of the deviation of the light intensity in the field of view, the temporal change of the illumination device 1 or the imaging device 5, etc. in a software manner. The protective film assembly inspection device 100 can be maintained in a more stable state.

[0081] In this way, by detecting the imaging image of the inspection pattern 7b that transmits through the protective film 8a and inspecting the image, defects of the protective film 8a that were difficult to detect in the past can be detected.

[0082] In the case of a conventional inspection device for detecting transmittance, if the detection sensitivity is increased to detect the non-uniformity of the protective film 8a, noise will be detected, or a change in minute optical characteristics that has no influence in the actual lithography process will be detected. Therefore, it is actually difficult to detect the non-uniformity of the protective film 8a.

[0083] However, in the present protective film assembly inspection device 100, by utilizing the optical characteristics of the light L that transmits through the inspection pattern portion, defects of the protective film 8a that can affect the exposure process can be detected with high sensitivity.

[0084] In addition, the present protective film assembly inspection device 100 is not limited to the protective film 8a, and can also be applied to the defect inspection of a light-transmissive substrate (quartz substrate, soda-lime glass, low-expansion glass, etc.) used for a photomask. On the protective film assembly support portion 10 (the object to be inspected support portion), a light-transmissive substrate to be inspected can be supported instead of the protective film 8a. The light-transmissive substrate is a flat transparent body that is transmissive to exposure light. By inspecting the image of the pattern 7b that is imaged through the light-transmissive substrate, optical non-uniformity, foreign matter, etc. of the light-transmissive substrate can be detected.

[0085] In short, the protective film assembly inspection device 100 is not limited to the protective film, and any transparent body that transmits light can be applicable.

[0086] (Embodiment 2) The protective film component inspection device 100 may also have an inspection pattern portion built in the illumination device 1.

[0087] Figure 3 In (A) is a schematic diagram showing the main structure of the protective film component inspection device 100 of Embodiment 2, Figure 3 In (B) is a top view schematically showing the projection pattern portion 11 (inspection pattern portion) used in the protective film component inspection device 100.

[0088] As Figure 3 shown in (A) in, the illumination device 1 has a light source 2 that emits light L, a projection pattern portion 11, and an illumination lens 12. The illumination lens 12 is composed of a combination of a condenser lens, a focusing lens, and a projection lens, for example.

[0089] The light source 2, the projection pattern portion 11, and the illumination lens 12 are housed in the housing of the illumination device 1. The projection pattern portion 11 is supported so as to be located between the light source 2 and the illumination lens 12. The projection pattern portion 11 can be appropriately replaced according to the sensitivity and productivity of defect inspection.

[0090] As Figure 3 shown in (B) in, the projection pattern portion 11 has a light-transmissive substrate 11a, and a pattern 11b that forms an inspection pattern for inspection is formed on the light-transmissive substrate 11a. The projection pattern portion 11 may have the same structure as the inspection mask 7 of Embodiment 1, and the structure of the pattern 11b may also be the same as the pattern 7b.

[0091] The illumination lens 12 is adjusted so that the focal point F of the light L irradiated from the light source 2 is located on the intermediate image projection plane MP. In addition, the intermediate image projection plane MP is an imaginary plane and does not actually exist.

[0092] The protective film 8a of the protective film component 8 is provided between the intermediate image projection plane MP and the objective lens 4, and the focal point F of the light L is located on the side closer to the light source 2 than the protective film 8a. The flat film-shaped protective film 8a is arranged parallel to the intermediate image projection plane MP.

[0093] The light L radiated from the illumination device 1 passes through the protective film 8a and forms an image of the pattern 11b on the imaging device 5 through the objective lens 4.

[0094] The imaging device 5 sends an image signal corresponding to the detected image data to the detection circuit 6, and the detection circuit 6 can investigate whether there are defects in the protective film 8a based on the acquired image data.

[0095] Since the illumination device 1 is internally provided with the projection pattern portion 11, it is not necessary to ensure an area for setting the inspection mask 7 between the illumination device 1 and the protective film 8a. Therefore, the distance between the illumination device 1 and the objective lens 4 can be set to be relatively long. The space for arranging the protective film assembly 8 between the illumination device 1 and the objective lens 4 becomes larger, improving the operability of the protective film assembly inspection device 100.

[0096] (Embodiment 3) The protective film assembly inspection device 100 may also have a viewing function.

[0097] Figure 4 FIG. is a schematic diagram for explaining the viewing function of the protective film assembly inspection device 100. Figure 4 In (A) of FIG., a structural example having a viewing function using coaxial epi-illumination is shown. Figure 4 In (B) of FIG., a structural example having a viewing function using side illumination is shown.

[0098] With the protective film assembly inspection device 100 having a viewing function, the detected defects can be easily observed.

[0099] In Figure 4 In the structure shown in (A) of FIG., the protective film assembly inspection device 100 has a first light source 13a for viewing (first viewing light source 13a), and also has a mirror 14 between the objective lens 4 and the imaging device 5. The mirror 14 can be, for example, a semi-reflective mirror.

[0100] The first light source 13a radiates light L perpendicularly to the optical axis of the objective lens 4.

[0101] When a semi-reflective mirror is used as the mirror 14, coaxial epi-illumination can be performed on the inspection area SA of the inspection object.

[0102] In addition, the light source 13 can use, for example, a lamp light source or a laser light source.

[0103] In addition, the protective film assembly inspection device 100 has a display device 15 for receiving the image signal of the imaging device 5.

[0104] The light L radiated from the first light source 13a is incident on the mirror 14, and at least a part (for example, 50%) of the light L is reflected by the mirror 14 and guided to the protective film 8a via the objective lens 4. The objective lens 4 can be adjusted so that the focus of the light L is located on the surface of the protective film 8a.

[0105] The detection circuit 6 relatively moves the protective film assembly 8 with respect to the objective lens 4, and moves the inspection area SA registered as an abnormal area in the storage device into the field of view of the objective lens 4.

[0106] The light L reflected in the inspection area SA is guided to the imaging device 5 through the objective lens 4, and the imaging device 5 sends an image signal to the display device 15. The display device 15 displays a surface image of the protective film 8a in the inspection area SA based on the image signal. Using the reflected light of the light L, unevenness of the protective film 8a can be detected as interference fringes, for example.

[0107] In Figure 4 the structure shown in (B) in, the protective film assembly inspection device 100 has a second light source 13b (second viewing light source 13b) for viewing.

[0108] The second light source 13b can emit light L having a predetermined angle with respect to the optical axis of the objective lens 4, and perform side illumination on the inspection area SA of the inspection object.

[0109] The light L reflected in the inspection area SA is guided to the imaging device 5 through the objective lens 4.

[0110] Through the display device 15 connected to the imaging device 5, the surface of the protective film 8a in the inspection area SA can be observed.

[0111] In addition, the second light source 13b may also be composed of a plurality of small light sources, for example, and arranged in a manner of drawing a circle around the optical axis of the objective lens 4. In this case, the second light source 13b constitutes annular illumination.

[0112] The protective film assembly inspection device 100 has a first light source 13a, a mirror 14, and a second light source 13b, and may include Figure 4 the structure shown in (A) in and Figure 4 both structures of the structure shown in (B) in. By adopting such a structure, the operator can appropriately select coaxial epi-illumination of the first light source 13a or side illumination of the second light source 13b according to the inspection object to observe defects of the inspection object.

[0113] In addition, even in the structure where the protective film assembly inspection device 100 includes the mirror 14, by setting the mirror 14 as a semi-reflecting mirror, a part (for example, 50%) of the reflected light of the light L of the second light source 13b from the inspection object is transmitted, so that an image of the inspection object can be detected by the imaging device 5.

[0114] As described above, the operator observes the abnormal part in detail through the image displayed on the display device 15, and thus can confirm the abnormal part of the protective film 8a.

[0115] In addition, the display device 15 may also be built into the imaging device 5.

[0116] (Defect inspection method) Hereinafter, the inspection process of the protective film assembly 8 using the protective film assembly inspection device 100 will be described.

[0117] Step 1: Optical system adjustment Irradiate the light L, and adjust the illumination lens 3 (or illumination lens 12) and the objective lens 4 so that the light L passing through the inspection pattern portion (inspection mask 7, projection pattern portion 11) is focused on the imaging device 5.

[0118] In addition, the in-plane deviation or temporal change of the intensity of the light L detected by the imaging device 5 can also be corrected by the correction function for detecting the light intensity deviation of the detection circuit 6.

[0119] Step 2: Preparation of the object to be inspected Set the protective film 8a (transparent body) to be inspected.

[0120] The protective film 8a is arranged at a specified position (between the illumination device 1 and the objective lens 4 and closer to the objective lens 4 side than the focal point F) by fixing the protective film assembly 8 to the protective film assembly support portion 10 (object to be inspected support portion).

[0121] Step 3: Light irradiation Irradiate the light L emitted from the light source 2 onto the inspection pattern portion, and irradiate the transmitted light (or the transmitted image of the inspection pattern) from the inspection pattern portion, specifically from its inspection pattern, onto the inspection area SA of the protective film 8a.

[0122] Step 4: Image data generation Image the light L (or the image formed by the light L) transmitted from the inspection area SA of the protective film 8a onto the imaging device 5.

[0123] The imaging device 5 generates image data corresponding to the received light (or the imaged image), converts it into an image signal, and sends (outputs) it to the detection circuit 6.

[0124] The detection circuit 6 receives the image signal, acquires (inputs) the image data of the inspection area SA. The detection circuit 6 can store the acquired image data.

[0125] Step 5: Detection of abnormality (defect determination) The detection circuit 6 determines whether there are defects in the protective film 8a in the inspection area SA based on the received image signal. Specifically, the inspection circuit 6 reproduces the image data according to the image signal, compares the image data of each coordinate in the inspection area SA, and determines the abnormal part.

[0126] In addition, the determination method can adopt a well-known pattern inspection determination method used in the manufacturing process of photomasks or semiconductor manufacturing processes.

[0127] For example, the image data of the newly acquired inspection area SA is compared with the image data of the inspection area SA acquired before a specified time (or before a specified distance). The specified time is, for example, several seconds, and the specified distance is several millimeters, but it can be set according to the size of the inspection pattern and the scanning speed of the inspection area SA.

[0128] The acquired image data of the inspection area SA is compared with each other. When there is no difference between the image data of the object to be judged and the normal image data (reference image data), it is judged that the protective film 8a of the inspection area SA is normal (without defects). When there is a difference between the image data of the object to be judged and the normal image data, it is judged that the protective film 8a of the inspection area SA is abnormal (with defects).

[0129] The position coordinates of the inspection area SA judged to be abnormal are registered and stored in the storage device as abnormal parts, in association with the image data.

[0130] Step 6: Check Observe the part judged to be abnormal as needed. By observing the protective film 8a of the inspection area SA at the coordinates registered as the abnormal part, classification or analysis of the abnormal part can be performed.

[0131] Move the inspection area SA on the protective film 8a of the inspection object, and repeatedly execute Steps 2 to 5.

[0132] The inspection area SA is scanned in such a way that it moves over the entire surface of the inspection object to acquire image data.

[0133] In addition, the detection circuit 6 can also scan the entire surface of the inspection object, store the image data of the inspection area SA at each scanning position in the storage device, and finally determine whether there are defects in the inspection area SA at each scanning position through Step 5.

[0134] Necessary processing such as remanufacturing is performed on the protective film assembly 8 having the protective film 8a confirmed to be abnormal, while the protective film assembly 8 having the protective film 8a judged to be normal is fixed to the photomask.

[0135] In addition, as the optical system of the illumination lens 3 of the protective film assembly inspection device 100, an optical system of reduced projection or magnified projection can be adopted, and a corresponding inspection pattern 7 can also be adopted. In this case, the image of the inspection pattern 7 can be directly projected onto the imaging device 5, and the objective lens 4 can be dispensed with. As a result, the space for setting the inspection object (protective film 8a) can be expanded, and the operability of the protective film assembly inspection device 100 can be improved.

[0136] In addition, in the case of magnified projection, the spatial resolution of the imaging device 5 can be optically improved.

[0137] (Defect examples of the protective film) Figure 5 An example of an image acquired by the imaging device 5 is shown. Figure 5 In (A), it is a normal image of the inspection pattern (pattern 7b). Figure 5 In (B) and (C), they are images of the inspection pattern (pattern 7b) judged to be abnormal. Figure 5 In (D) and (E), they are viewing images of the protective film 8a of the inspection area SA judged to be abnormal.

[0138] Figure 5 The viewing image of (D) corresponds to Figure 5 the inspection area SA shown in (B). Figure 5 The viewing image of (E) corresponds to Figure 5 the inspection area SA shown in (C).

[0139] It can be understood that Figure 5 compared with the inspection pattern shown in (A), the edge part of the image shown in (B) is not clear, and the brightness of the edge part increases. As Figure 5 shown in the viewing image of (D), in the area corresponding to the image shown in (B), streaky unevenness of the protective film 8a is observed, and it is considered that there is an abnormality in the optical characteristics in this uneven part. Figure 5 Figure 5 The edge part of the image shown in (C) is clear. Compared with the inspection pattern shown in (A), it is considered that the brightness difference of the edge part is small, but it can be understood that there is a part where the area between the inspection patterns is darker and the brightness decreases. As

[0140] Figure 5 Figure 5 shown in the viewing image of (E), in the area corresponding to the image shown in (C), foreign matter is observed on the protective film 8a. Figure 5 Figure 5

[0141]

[0142] Figure 5 Figure 5 According to the existing inspection devices, it is particularly difficult to detect unevenness caused by a small difference in transmittance of the protective film 8a. However, by inspecting the image of the pattern 7b formed by transmitting through the protective film 8a, it is considered that the optical effects such as unevenness of the protective film 8a can be emphasized and it becomes possible to automatically detect.

[0142] In addition, since the image with an abnormality caused by the unevenness of the protective film 8a ( Figure 5 in (D)) and the image with an abnormality caused by foreign matter ( Figure 5 in (E)) will appear different, the abnormal parts can also be classified according to the detected images.

[0143] Industrial Applicability According to the present invention, an inspection method and an inspection apparatus can be obtained, which can detect defects in a protective film that have been difficult to detect in the past. This inspection apparatus can contribute to the quality control of the protective film assembly, and as a result, it can also contribute to the quality control of the photomask.

[0144] In addition, the present inspection method and inspection apparatus are not limited to the protective film, and can also be applied to the transparent substrate used for the photomask. The present invention has high industrial applicability.

[0145] Explanation of Reference Numerals 100: Protective Film Assembly Inspection Apparatus (Defect Inspection Apparatus) 1: Lighting Device 2: Light Source 3: Illumination Lens (First Illumination Lens) 4: Objective Lens 5: Imaging Device (Camera) 6: Detection Circuit 7: Inspection Mask (Inspection Pattern Section) 7a: Light-Transmissive Substrate 7b: Pattern 8: Protective Film Assembly 8a: Protective Film 8b: Frame 9: Mask Support Section 10: Protective Film Assembly Support Section (Inspection Object Support Section) 11: Projection Pattern Section (Inspection Pattern Section) 11a: Light-Transmissive Substrate 11b: Pattern 12: Illumination Lens (Second Illumination Lens) 13a: First Light Source (First Viewing Light Source) 13b: Second Light Source (Second Viewing Light Source) 14: Mirror 15: Display Device F: Focus L: Light MP: Intermediate Image Projection Plane SA: Inspection Area.

Claims

1. A defect inspection device, which is a defect inspection device for a transparent body, characterized in that: It includes a light source, a pattern inspection unit, a camera device and a detection circuit. The light radiated from the light source is configured to sequentially transmit the inspection pattern portion and the transparent body and enter the imaging device. The imaging device outputs an image signal corresponding to the incident light to the detection circuit.

2. The defect inspection device according to claim 1, characterized in that: The inspection pattern portion has a line and space pattern in which transmissive regions and light shielding regions are alternately arranged.

3. The defect inspection device according to claim 1 or 2, characterized in that: The transparent body is a protective film.

4. The defect inspection device according to claim 1 or 2, characterized in that: Also includes lighting lens, The illumination lens is configured so that the focal point of the light can be located closer to the light source than the transparent body.

5. The defect inspection device according to claim 4, characterized in that: The inspection pattern portion is located between the illumination lens and the transparent body.

6. The defect inspection device according to claim 4, characterized in that: The inspection pattern portion is located between the light source and the illumination lens.

7. The defect inspection device according to claim 1, characterized in that: Also includes viewing light sources and reflectors, The reflector is disposed between the transparent body and the imaging device, and is configured to be able to guide the light irradiated from the inspection light source to the transparent body.

8. A defect inspection method, which is a defect inspection method for a transparent body, characterized in that: Include: In a first step, light emitted from a light source is irradiated onto the inspection pattern portion, and transmitted light from the inspection pattern portion is irradiated onto the transparent body; In a second step, the camera device receiving the light transmitted through the transparent body outputs image data to a detection circuit; and In the third step, the detection circuit acquires the image data and determines whether the transparent body has defects.

9. The defect inspection method according to claim 8, characterized in that: The third step includes a step in which the detection circuit compares the acquired image data with reference image data and, when a difference is found, determines that the transparent body has a defect.

Images