Foreign matter measurement method, foreign matter measurement device and calibration substrate

Abstract

To provide a foreign matter measurement method that can highly accurately measure reflective a foreign matter and / or non-reflective foreign matter that may be contained in an object to be inspected.SOLUTION: A foreign matter measurement method according to the present invention is used to evaluate the cleanliness of an object to be inspected, and comprises: a foreign matter collection step in which foreign matter is captured from the object to be inspected onto a filter; an imaging preparation step in which the filter is placed on a stage within a dome-shaped reflective illumination part; a transmitted light imaging step in which light is emitted from a first light source arranged on the rear side of the filter, and transmitted light that has passed through the filter is imaged; a reflected light imaging step in which, on the front side of the filter, light is emitted from a second light source via the dome-shaped reflective illumination part to the filter, and reflected light from the filter is imaged; and a processing step in which the total number of foreign matters is counted on the basis of image information obtained in the transmitted light imaging step, and the number of reflective foreign matters and / or non-reflective foreign matters is counted on the basis of the image information obtained in the reflected light imaging step.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a foreign matter measurement method for examining the cleanliness of an object to be inspected such as a cleaning part, a foreign matter measurement device used therefor, and a calibration substrate.

Background Art

[0002] In addition to in-vehicle battery parts, high cleanliness is required for various automotive parts and the like. ISO16232 is a standard related to cleanliness measurement, which is used for the cleanliness inspection of automotive parts. Usually, foreign matter particles of 50 μm or more are the objects of cleanliness analysis.

[0003] Generally, the measurement of foreign matter consists of three steps: first, washing away foreign matter from the surface of the part, then filtering the extract containing foreign matter with a filter, and finally measuring the foreign matter captured by the filter. As foreign matter measurement systems, a scanner method using an existing scanner, an optical microscope method using an existing microscope, and a camera method using a CCD sensor are known.

[0004] Patent Document 1 describes a detection and discrimination device for detecting foreign matter on a substrate. This detection and discrimination device includes a detection system that detects foreign matter on the substrate with an imaging system to obtain position information and image information of the foreign matter, an irradiation system that irradiates the foreign matter detected by the detection system with laser light, and a discrimination unit that discriminates the type of foreign matter based on the image information of the region of the foreign matter before laser light irradiation obtained by the detection system and the image information of the corresponding region after laser light irradiation.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Foreign substances adhering to the surface of automotive parts and the like include reflective foreign substances such as metal powder and non-reflective foreign substances such as carbon. In inspections, in addition to the total number of foreign substances, it may be required to identify such reflective foreign substances and non-reflective foreign substances and count their respective numbers. Moreover, while high accuracy is required for detecting foreign particles, it is also desired that the foreign substance measuring device itself be relatively inexpensive. An object of the present invention is to provide a foreign substance measuring method capable of highly accurately measuring foreign substances including reflective foreign substances and / or non-reflective foreign substances that may adhere to an object to be inspected, a foreign substance measuring device that can be manufactured relatively inexpensively, and a calibration substrate used for calibrating the foreign substance measuring device implemented for performing highly accurate measurement.

Means for Solving the Problems

[0007] The foreign substance measuring method of the present invention is used to examine the cleanliness of an object to be inspected, a foreign substance sampling step of capturing foreign substances from the object to be inspected by a filter, an imaging preparation step of placing the filter on a stage within a dome-shaped reflection illumination unit, a transmitted light imaging step of irradiating light from a first light source disposed on the back side of the filter, and imaging the transmitted light transmitted through the filter with an imaging unit provided on the front side of the filter, a reflected light imaging step of irradiating light from a second light source to the filter through the dome-shaped reflection illumination unit on the front side of the filter, and imaging the reflected light reflected from the filter with the imaging unit, a processing step of counting the total number of foreign substances based on the image information obtained in the transmitted light imaging step, and counting the number of at least one of the reflective foreign substances and non-reflective foreign substances based on the image information obtained in the reflected light imaging step, and includes.

[0008] The foreign substance measuring device of the present invention is for examining the cleanliness of an object to be inspected, a light-transmissive stage on which a filter capturing foreign substances from the object to be inspected is placed on the front, a first light source disposed on the back side of the stage and irradiating light from the back of the stage, On the front side of the stage, a second light source arranged around the stage, On the front side of the stage, a dome-shaped reflection illumination unit is arranged so as to cover the filter and the second light source placed on the stage, and irradiates the filter with light from the second light source from all directions, An imaging unit is arranged on the front side of the stage, and images transmitted light that has passed through the stage and the filter from the first light source, and reflected light that has been irradiated with light from the second light source to the filter via the dome-shaped reflection illumination unit and then reflected, A processing unit is connected to the imaging unit, counts the total number of foreign objects based on the image information obtained by imaging the transmitted light, and counts the number of at least one of the reflective foreign objects and non-reflective foreign objects based on the image information obtained by imaging the reflected light.

[0009] The calibration substrate of the present invention is used for calibrating the above foreign object measuring device, and a plurality of regions in which pseudo foreign objects are printed by photolithography are formed on the surface of the translucent substrate, and the pseudo foreign objects have different diameters or lengths for each region.

Advantages of the Invention

[0010] The foreign object measuring method of the present invention can perform high-precision measurement of foreign objects including reflective foreign objects and / or non-reflective foreign objects that may adhere to the object to be inspected. The foreign object measuring device of the present invention suitable for use in this foreign object measuring method includes a first light source that irradiates light from the back, a second light source arranged on the front side, and a dome-shaped reflection illumination unit that irradiates the filter with light from the second light source. Since the transmitted light from the first light source and the reflected light reflected by the dome-shaped reflection illumination unit from the second light source can be imaged by one imaging unit, it can be manufactured at a relatively low cost. In addition, the imaging unit using a camera is less expensive than the conventional scanner method and optical microscope method. Since the calibration substrate of the present invention can accurately print pseudo foreign objects with correct dimensions by photolithography, high-precision foreign object measurement becomes possible by using it for calibration of the foreign object measuring device.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a foreign object measuring method and a foreign object measuring device according to an embodiment of the present invention will be described with reference to the drawings. However, each of the drawings referred to below shows a simplified embodiment of the present invention for convenience of explanation. Therefore, the foreign object measuring device disclosed below may include any constituent members not shown in each of the drawings referred to. Also, the dimensions of the members in each drawing do not faithfully represent the dimensions of the actual constituent members and the dimensional ratios of the respective members.

[0013] FIG. 1 is a diagram showing an overview of a foreign object measuring device 1 according to the present embodiment. In FIG. 1, 2 is a membrane filter that holds foreign objects captured from the object to be inspected. The membrane filter 2 is held on the front surface of the pedestal 21, and the membrane filter 2 and the pedestal 21 are held on the front surface of the stage 3. The membrane filter 2 is used to be attached to a filtering device to capture foreign objects in a foreign object sampling process described later. The pedestal 21 supports the membrane filter 2 and is used to facilitate handling. The membrane filter 2 that has captured foreign objects and the pedestal 21 that supports it are placed on the front surface of the stage 3, but may be fixed using a fixture or the like. In this specification, the surface facing the imaging unit 10 shown in FIG. 1 is referred to as the back surface, and the back surface means the surface opposite to the front surface.

[0014] As the membrane filter 2, when capturing foreign matter with a particle size of 50 μm or more, a membrane filter with a pore diameter of 0.8 μm or more may be selected. The membrane filter 2 is made of, for example, a fluororesin such as polytetrafluoroethylene (PTFE). Examples of the pedestal 21 include porous glass having water permeability and light transmittance. Porous glass is generally used as a sintered filter. As the stage 3, for example, a diffusion plate made of an acrylic resin, a polycarbonate resin, etc., which has a function of scattering light, can be used, and a light-transmitting substrate such as porous glass or transparent glass can also be used. On the front surface of the stage 3, except for the portion where the pedestal 21 is held, a light-shielding sheet 9 is arranged to suppress light transmission and reflection.

[0015] On the back side of the stage 3, a first light source 4 is arranged. The first light source 4 irradiates light from the back of the stage 3. The light irradiated from the first light source 4 passes through the stage 3, the pedestal 21, and the membrane filter 2, and is imaged by the imaging unit 5 above. Based on the image information of the transmitted light, the size of the foreign matter is actually measured, and it is determined whether it falls within a predetermined particle size range. If it falls within the range, it is counted. Thereby, for example, the total number of foreign matters with a diameter or length of 50 μm or more can be counted. The first light source 4 is configured in a flat shape and is arranged on the back of the stage 3. As the first light source 4, for example, a lighting device such as a white light-emitting diode (LED) can be used.

[0016] Also, on the front side of the stage 3, a second light source 6 is arranged around the stage 3. The second light source 6 is composed of, for example, light-emitting diodes (LEDs) arranged in a ring shape around the stage 3. As long as the second light source 6 is in a ring shape, it may be arranged in either a continuous or intermittent form. On the front side of the stage 3, a dome-shaped reflective illumination unit 7 is arranged. As shown in FIG. 2, this dome-shaped reflective illumination unit 7 is arranged to cover the membrane filter 2 and the second light source 6 held on the stage 3, and is configured to reflect the light from the second light source 6 and irradiate the membrane filter 2. The second light source 6 is preferably arranged at the bottom on the inner peripheral side of the dome-shaped reflective illumination unit 7. The irradiation of the membrane filter 2 is preferably from all directions.

[0017] The dome-shaped reflective illumination unit 7 is composed of, for example, a dome-shaped (hemispherical) substrate formed of plastic, metal, glass, etc. When the substrate itself does not have light reflection characteristics, a reflective film may be formed on the inner surface of the substrate. The reflective film is formed, for example, by a metal coating film such as silver, aluminum, gold, a coating film of a light-reflective paint, or pasting a light-reflective tape. The dome-shaped reflective illumination unit 7 is provided with an opening 8 at the top for photographing the membrane filter 2 from above.

[0018] The membrane filter 2 is preferably arranged such that its center coincides with the center of the radius of curvature of the dome-shaped reflective illumination unit 7. The opening 8 of the dome-shaped reflective illumination unit 7 is also preferably formed in a circular shape with its center coinciding with the center of the radius of curvature of the dome-shaped reflective illumination unit 7.

[0019] An imaging unit 10 is disposed in the opening 8. The imaging unit 10 is arranged so as to be able to photograph the surface (front surface) of the membrane filter 2 through the opening 8. The imaging unit 10 includes a condensing optical system 101 such as a telecentric lens and a camera 102. The camera 102 includes an image sensor that images by converting an optical image formed by the condensing optical system 101 into an electrical signal, and an image processing unit that generates an image of the optical image by performing predetermined processing on the output of the image sensor. As the image sensor, for example, a CCD (Charge-Coupled Devices) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, etc. can be used, and it is particularly preferable to use a CMOS image sensor in terms of being able to perform full-field observation (for example, field observation within a diameter of 25 mm). The CMOS image sensor to be used is preferably, for example, 20 million pixels or more.

[0020] The imaging unit 10 images the transmitted light that has passed through the stage 3, the pedestal 21, and the membrane filter 2 from the first light source 4, and the reflected light that has been irradiated onto the membrane filter 2 from the second light source 6 via the dome-shaped reflection illumination unit 7 and reflected, respectively. The imaging unit 10 outputs the captured image information to the processing unit 11. Note that the imaging unit 10 may output the output of the image sensor (for example, so-called RAW data) to the processing unit 11 without performing image processing or the like, and the processing unit 11 may perform image processing or the like to form an image.

[0021] The processing unit 11 is configured to detect the number of foreign objects held on the membrane filter 2. The processing unit 11 detects foreign objects having a predetermined diameter or length (hereinafter sometimes simply referred to as "size") from the captured image information. The predetermined size is, for example, a foreign object having a diameter or length of 50 μm or more. The foreign objects have various shapes such as granular and fibrous.

[0022] The processing unit 11 has a function of processing two pieces of image information. One is the image information obtained by imaging the transmitted light that has passed through the membrane filter 2, and based on this image information, the total number of foreign matters of a predetermined size or more is counted. The second is the image information obtained by imaging the reflected light, and based on this image information, the number of at least one of the reflective foreign matters and non-reflective foreign matters of a predetermined size or more is counted. Further, the processing unit 11 may also have an arithmetic function of subtracting the number of one of the reflective foreign matters and non-reflective foreign matters from the total number of foreign matters, and thereby also have a function of outputting the number of the other. These processing results are output to the image display unit 12 connected to the processing unit 11. Also, a printing device such as a printer can be connected to the processing unit 11, and the processing results can be output to the printing device. These processing unit 11 and image display unit 12 can be realized by, for example, a personal computer or the like.

[0023] Next, the foreign matter measurement method of the present invention will be described. <Foreign matter collection step> As shown in FIG. 3, foreign matters are captured from the inspection object 14 by the membrane filter 2. Specifically, the foreign matters are washed away from the surface of the inspection object 14, and the extract containing the foreign matters is filtered by the membrane filter 2.

[0024] FIG. 3 is a schematic cross-sectional view showing an example of an automatic filtration device used in the foreign matter collection step. As shown in FIG. 3, this filtration device has a washing tank 13, and the foreign matters are washed away from the surface of the inspection object 14 in the washing tank 13. That is, a washing table 15 is installed in the washing tank 13, and the washing table 15 can be rotated by a rotation mechanism 20 such as a motor provided on the upper part. In the washing tank 13, a shower device 17 for the extract 16 is provided, and the extract 16 is sprayed from the shower device 17 onto the inspection object 14 from above, below, and horizontally to wash away the foreign matters. Thereby, the foreign matters can be washed away from the entire inspection object 14. The upper part of the washing tank 13 is sealed with a lid 22. As the extract 16 for washing away the foreign matters, for example, water (preferably pure water), an alcohol-based solvent, a hydrocarbon-based solvent, etc. can be used.

[0025] The extract 16 from which foreign matter has been washed away flows down into a storage tank 18 located below the washing tank 13. The extract 16 in the storage tank 18 is sent by a shower pump 23 through a filter 24 to a shower device 17 and sprayed again onto the object 14 to be inspected in the washing tank 13, forming a circulation path. Further, a suction pump 25 is connected to the storage tank 18 to suck the air in the storage tank 18, thereby improving the filtration efficiency of the extract 16.

[0026] A membrane filter 2 is attached to a passage 19 connecting the washing tank 13 and the storage tank 18. The membrane filter 2 is placed on a pedestal 21. The membrane filter 2 and the pedestal 21 are detachably attached to the passage 19. The membrane filter 2 has, for example, a foreign matter capture region where the diameter ranges from 20 to 30 mm.

[0027] FIG. 4 is a schematic cross-sectional view showing an example of a simple manual filtration device. As shown in FIG. 4, this filtration device includes a funnel 131 and a suction bottle 181 disposed below the funnel 131. A suction pump 25 is connected to the suction bottle 181. The membrane filter 2 is disposed between the funnel 131 and the suction bottle 181 together with the pedestal 21 and is clamped by a clamp (not shown). The extract 16 from which foreign matter has been washed away in advance is poured into the funnel 131, and the washed foreign matter is captured by the membrane filter 2 in the process of the extract 16 falling into the suction bottle 181. Since the rest is the same as the filtration device shown in FIG. 3, detailed description is omitted.

[0028] <Calibration process> The membrane filter 2 that has captured foreign matter is set in the foreign matter measuring device 1 to perform a cleanliness inspection of the object to be inspected. Calibration of the foreign matter measuring device 1 is important for accurately performing the cleanliness inspection. If the calibration of the foreign matter measuring device 1 is insufficient, there is a risk that foreign matter with a size of 50 μm or more, for example, cannot be reliably detected. For calibration of the foreign matter measuring device 1, it is preferable to use a calibration substrate 26 as shown in FIG. 5, for example.

[0029] The calibration substrate 26 shown in Fig. 5 has a circular region 30 (for example, a circular region with a diameter D of 25 μm) same as the measurement region (the foreign object capture region described above) provided on the surface of a translucent sheet 27 such as a plastic sheet or a glass plate. This circular region 30 is divided into four equal parts to form four regions 29A, 29B, 29C, and 29D. Pseudo foreign objects 28a, 28b, 28c, and 28d with different sizes are printed in each of the regions 29A, ··· 29D. The pseudo foreign objects 28a, ··· 28d may correspond to any of the above-described reflective foreign objects and non-reflective foreign objects. Examples of the pseudo foreign objects 28a, ··· 28d include printed images made of metal oxides such as chromium oxide.

[0030] The shapes of the pseudo foreign objects 28a, ··· 28d are not particularly limited, and shapes such as ●, ■, ▲ as illustrated in Fig. 5 can be adopted. The pseudo foreign objects 28a, ··· 28d have different diameters or lengths for each of the regions 29A, ··· 29D. For example, when detecting foreign objects of 50 μm or more, the dimensions of each of the pseudo foreign objects 28a, ··· 28d are set as shown in Table 1.

Table 1

[0031] In Fig. 5, pseudo foreign objects 28a, ··· 28d with different diameters or lengths are printed in the four regions 29A, ··· 29D, but it is not limited to the four regions 29A, ··· 29D, and it is sufficient to have two or more regions printed with pseudo foreign objects having different diameters or lengths. Also, at least, a calibration substrate having a pseudo foreign object having the same diameter or length as the foreign object having the minimum diameter or length (50 μm in the above example) to be counted by the foreign object measuring device 1 may be used.

[0032] To calibrate the foreign object measuring device 1 using the calibration substrate 26, instead of the membrane filter 2, the calibration substrate 26 is placed on the stage 3 together with the pedestal 21. At this time, it is arranged so that the circular region 30 of the calibration substrate 26 coincides with the measurement region. In this state, using the first light source 4 or the second light source 6, the pseudo foreign objects 28a, ··· 28d are counted. Table 2 shows the results of counting the total number of the pseudo foreign objects 28a, ··· 28d using the first light source 4 and software that can capture foreign objects with a size of 50 μm or more.

Table 2

[0033] As is clear from Table 2, it can be seen that the boundary between 40 μm and 50 μm can be distinguished. On the other hand, when there are pseudo foreign objects 28c, 28d that are not detected in the 50 μm region 29C or the 60 μm region 29D, it is advisable to adjust the illumination intensity, the height of the light source, etc., so that all the pseudo foreign objects 28c, 28d are detected in the 50 μm region 29C and the 60 μm region 29D. Calibration is preferably performed every time foreign objects are measured, but it may also be performed at regular intervals.

[0034] The pseudo foreign objects 28a ··· 28d of the calibration substrate 26 require high dimensional accuracy for performing calibration with high precision. In this embodiment, it is preferable to print the pseudo foreign objects 28a ··· 28d by photolithography. Figs. 6(a) to (e) show a method for manufacturing the calibration substrate 26 by photolithography. First, as shown in Fig. 6(a), a thin film 32 to be patterned is coated on the surface of the light-transmissive sheet 27. Examples of the thin film 32 include metal oxides such as chromium oxide. For coating, a sputtering method can be used. Next, a photoresist 33 (photosensitive material) is applied on the thin film 32 and dried. Here, a positive-type photoresist 33 is used.

[0035] Next, as shown in FIG. 6(b), the photoresist 33 is irradiated with light (ultraviolet rays) as indicated by the arrow to form a pattern. In this embodiment, a so-called maskless exposure apparatus is used to perform light irradiation according to design data, but a pattern may also be formed using a photomask (not shown). After exposure, the translucent sheet 27 is immersed in a known developer and developed (FIG. 6(c)).

[0036] Next, the thin film 32 is removed according to the pattern by etching (FIG. 6(d)). For etching, wet etching using chemicals and dry etching using plasma are known, and either may be used. At this time, at the edge portion indicated by the arrow E, so-called side edges are generated, and the dimensions of the pseudo foreign matters 28a... 28d are smaller than the design. Therefore, the design dimensions of the pseudo foreign matters 28a... 28d should be made slightly larger than the target value in consideration of being etched by etching. Specifically, for example, when obtaining the pseudo foreign matter 28c with a dimension of 50 μm, the design value should be selected within the range of 51 to 53 μm so that an appropriate value can be obtained.

[0037] Finally, as shown in FIG. 6(e), the unnecessary photoresist 33 is removed to obtain the calibration substrate 26. In this way, when the pseudo foreign matters 28a... 28d of the calibration substrate 26 are produced by photolithography, highly reliable and high-precision calibration becomes possible, and the adjustment of the foreign matter measuring device 1 to be used can be accurately performed. Thereby, the foreign matter measurement described below can be performed with high precision.

[0038] <Imaging Preparation Step and Transmitted Light Imaging Step> The membrane filter 2 that has captured the foreign matter is placed and fixed at a predetermined position on the stage 3 while being held on the surface of the pedestal 21 as shown in FIG. 1. In this state, light is irradiated from the first light source 4 disposed on the back side of the membrane filter 2, and the transmitted light that has passed through the membrane filter 2 is imaged. The image information obtained in the transmitted light imaging step is sent to the processing unit 11.

[0039] <Reflected Light Imaging Step> Separate from the transmitted light imaging process, a reflected light imaging process is performed. On the front side of the membrane filter 2, light is irradiated from the second light source 6 to the membrane filter 2 through the dome-shaped reflection illumination unit 7, and the reflected light reflected from the membrane filter 2 is imaged. The image information obtained in the reflected light imaging process is also sent to the processing unit 11. In the reflected light imaging process, the number of both or either of the reflective foreign matter and the non-reflective foreign matter can be counted. That is, in the case of reflective foreign matter, due to the reflected light reflected from the reflective foreign matter by the light irradiation from all directions of the dome-shaped reflection illumination unit 7, the black region decreases (the area of the black part decreases) compared to the foreign matter image taken with the transmitted light described above. Therefore, the number of reflective foreign matter can be counted from the area of the decreased black region.

[0040] On the other hand, non-reflective foreign matter appears black due to the light irradiation from all directions of the dome-shaped reflection illumination unit 7. Therefore, the counted foreign matter can be determined as non-reflective foreign matter. Note that after counting the number of either the reflective foreign matter or the non-reflective foreign matter in the reflected light imaging process, if the number of either the reflective foreign matter or the non-reflective foreign matter is subtracted from the total number of foreign matter counted in the transmitted light imaging process, the number of the other foreign matter can be calculated.

[0041] <Processing step> In the processing unit 11, the total number of the foreign matter is counted based on the image information obtained in the transmitted light imaging process. The information on the total number of the obtained foreign matter is stored in the processing unit 11. Also, in the processing unit 11, the number of at least either the reflective foreign matter or the non-reflective foreign matter is counted based on the image information obtained in the reflected light imaging process. The information on the number of the obtained reflective foreign matter and non-reflective foreign matter is stored in the processing unit 11.

[0042] The total number of these foreign substances, the number of radioactive foreign substances, and the number of non-radioactive foreign substances are output to the image display unit 12. In this way, since the total number of foreign substances having a predetermined size or more can be known, the cleanliness of the inspection object 14 can be accurately measured. Further, since the types of foreign substances, that is, radioactive foreign substances and non-radioactive foreign substances, can be identified with high precision, it can be used for inspection and the like in the manufacturing process of the inspection object 14.

[0043] In the above embodiment, the foreign substance measurement is performed in the order of the transmitted light imaging process and the reflected light imaging process. However, conversely, the foreign substance measurement may be performed in the order of the reflected light imaging process and the transmitted light imaging process.

[0044] As described above, the embodiments of the present invention have been described. However, the foreign substance measurement method, the foreign substance measurement device 1, and the calibration substrate 26 of the present invention are not limited to the above embodiments, and various changes and improvements are possible.

Explanation of Reference Numerals

[0045] 1 Foreign Substance Measurement Device 2 Membrane Filter 3 Stage 4 First Light Source 5 Imaging Unit 6 Second Light Source 7 Dome-Type Reflection Illumination Unit 8 Aperture 9 Light-Shielding Sheet 10 Imaging Unit 101 Condensing Optical System Lens 102 Camera 11 Processing Unit 12 Image Display Unit 13 Cleaning Tank 131 Funnel 14 Inspection Object 15 Cleaning Stand 16 Extract 17 Shower Device 18 Storage Tank 181 Suction Bottle 19 Passage 20 Rotation Mechanism 21 Pedestal 22 Lid 23 Shower pump 24 Filter 25 Suction pump 26 Calibration substrate 27 Translucent sheet (translucent substrate) 28a, 28b, 28c, 28d Pseudo foreign matter 29A, 29B, 29C, 29D Regions 30 Circular region 32 Thin film 33 Photoresist E Edge part

Claims

1. A foreign matter measurement method for examining the cleanliness of an object to be inspected, comprising the steps of: a foreign matter collection step of capturing foreign matter from the test object on a filter; an imaging preparation step of placing the filter on a stage in a dome-shaped reflective illumination unit; a transmitted light imaging step of irradiating light from a first light source disposed on the rear side of the filter and imaging the transmitted light transmitted through the filter with an imaging unit disposed on the front side of the filter; a reflected light imaging step of irradiating the filter with light from a second light source via the dome-shaped reflective illumination unit on the front side of the filter, and imaging the reflected light from the filter with the imaging unit; a processing step of counting the total number of the foreign objects based on the image information obtained in the transmitted light imaging step, and counting the number of at least one of the reflective foreign objects and the non-reflective foreign objects based on the image information obtained in the reflected light imaging step; A foreign object measuring method comprising:

2. a step of adjusting the transmitted light and / or the reflected light in advance so that the foreign matter having a diameter or length to be counted can be imaged on a calibration substrate, 2. The foreign particle measuring method according to claim 1, wherein a pseudo foreign particle equivalent to the foreign particle having the diameter or length is printed on the calibration substrate.

3. 3. The foreign matter measuring method according to claim 1, wherein the foreign matter to be counted has a diameter or length of 50 μm or more.

4. 3. The foreign matter measuring method according to claim 1 or 2, wherein in the foreign matter sampling step, the filter is held on a base and an extract obtained by washing the foreign matter from the test object is filtered to capture the foreign matter, and then the filter is placed on the stage while still held on the base.

5. A foreign matter measuring device for checking the cleanliness of an object to be inspected, comprising: a light-transmitting stage on which the filter that has captured the foreign matter from the object to be inspected is placed; a first light source that is disposed on a rear side of the stage and that irradiates light from the rear side of the stage; a second light source disposed around the stage on the front side of the stage; a dome-shaped reflective illumination unit that is disposed on the front side of the stage so as to cover the filter and the second light source placed on the stage, and that irradiates the light from the second light source onto the filter from all directions; an imaging unit that is disposed on a front side of the stage and captures transmitted light from the first light source that has been transmitted through the stage and the filter, and reflected light that is emitted from the second light source through the dome-shaped reflective illumination unit to the filter and reflected by the filter; a processing unit connected to the imaging unit for counting the total number of the foreign objects based on image information obtained by capturing the transmitted light, and for counting the number of at least one of the reflective foreign objects and the non-reflective foreign objects based on image information obtained by capturing the reflected light; A foreign object measuring device comprising:

6. A calibration substrate for use in calibrating the foreign matter measuring device according to claim 5, comprising: A calibration substrate having a pseudo foreign object printed on a surface of a light-transmitting substrate by photolithography, the pseudo foreign object having at least the same diameter or length as a foreign object having a minimum diameter or length to be counted by the foreign object measuring device.

7. A plurality of areas in which the pseudo foreign matter is printed are formed on a surface of the light-transmitting substrate, and the plurality of areas include a printing area of ​​a pseudo foreign object having a diameter or length equal to or greater than a foreign object having a minimum diameter or length to be counted by the foreign object measuring device; A printed area of ​​a pseudo foreign object having a diameter or length smaller than the minimum diameter or length of a foreign object to be counted; The calibration substrate of claim 6 , comprising:

8. 7. The calibration substrate according to claim 6, wherein the foreign matter having a minimum diameter or length to be counted has a diameter or length of 50 μm.

Images