JP2012073040A - Particle detection optical device and particle detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle detection optical device capable of eliminating detection failure due to interference of inspection light.SOLUTION: In a particle detection optical device of a particle detection device, a substrate surface 4a of a substrate 4 is irradiated with inspection light L from an inspection light source unit, an imaging part 29 takes an image of scattered light of the inspection light L scattered by a particle P on the substrate surface 4a, and the particle P on the substrate 4 is detected based on obtained image data. The inspection light source unit comprises a light-emitting diode 41 as a light source, a convex lens 44 that converts divergent light emitted from the light-emitting diode 41 into convergent light, a scan mirror 432 that irradiates the convergent light emitted from the convex lens 44 as the inspection light L to a plane inspection region 24 as while scanning along the plane inspection region 24. The inspection light L is convergent light of incoherent light emitted from the light-emitting diode 41.

Description

  The present invention relates to an optical device for particle detection and a particle detection device for detecting particles adhering to a substrate surface.

  In the technical field of semiconductors and the technical field of liquid crystal devices, defects occur when particles adhere to a substrate, so the presence or absence of particles is inspected. In Patent Document 1, as an apparatus for detecting particles on the substrate surface, the substrate surface of the substrate to be inspected is irradiated with laser light as inspection light from the inspection light source unit, and the inspection is scattered by the particles on the substrate surface. There is described a foreign object detection device that captures scattered light of light with an image sensor and detects particles on a substrate based on the imaging result of the image sensor.

JP 2008-39444 A

  Since the laser light is coherent light, the inspection light from the inspection light source part directly irradiates this particle with respect to specific particles adhering to the substrate surface, and after reaching the substrate surface from the inspection light source part, the substrate If a situation occurs in which the particles bounce off the surface and irradiate these particles, they interfere. Here, when the interference of the inspection light occurs, the intensity of the scattered light changes due to the interference, which causes a problem that the particle size cannot be accurately detected from the imaging result.

  In view of such a problem, an object of the present invention is to provide an optical device for particle detection and a particle detection device capable of eliminating a detection failure caused by interference of inspection light.

In order to solve the above problems, the present invention provides:
An inspection light source unit that irradiates inspection light onto a planar inspection region where a substrate surface of a substrate to be inspected is arranged, and an imaging unit that acquires scattered light of the inspection light generated on the substrate surface as image data In the optical device for particle detection for detecting particles adhering to the substrate surface based on the image data,
The inspection light source unit is
A light emitting diode as a light source;
A converging lens that converts divergent light emitted from the light emitting diode into convergent light;
A scanning mirror that irradiates the planar inspection region with the convergent light emitted from the converging lens as the inspection light and scans along the planar inspection region;
It is characterized by having.

  According to the present invention, the inspection light source unit includes a light emitting diode as a light source, and uses incoherent light emitted from the light emitting diode as inspection light. Therefore, for the specific particles adhering to the substrate surface, the inspection light from the inspection light source unit directly irradiates the particles, and after reaching the substrate surface from the inspection light source unit, it rebounds on the substrate surface. Even if the situation of irradiating particles occurs, interference hardly occurs. As a result, the change in the intensity of the scattered light caused by the interference of the inspection light can be reduced, so that the particles on the substrate can be accurately detected based on the image data acquired by the imaging unit. In addition, when a semiconductor laser that emits laser light is used as the light source, the output change due to temperature change is large, so the amount of inspection light changes due to environmental temperature change or the semiconductor laser's own heat generation. In some cases, it may not be possible to accurately detect the particle size or the like from the imaging result. However, if a light emitting diode is used as the light source, the change in the amount of light caused by the change in temperature can be suppressed. Particles on the substrate can be accurately detected based on image data acquired by the imaging unit.

  Here, the inspection light emitted from the light emitting diode has a smaller amount of light compared to the case where the laser light is used as the inspection light, but since the inspection light is irradiated onto the planar inspection region in the state of convergent light, It is possible to secure the amount of inspection light irradiated to the irradiation area. In addition, when the inspection light is irradiated on the substrate in the divergent light state, the amount of light reaching the side on which the inspection light is incident (the side optically close to the light source) is large, but the inspection is performed on the substrate surface. Since the amount of light reaching the side far from the light incident side (the side optically far from the light source) decreases, the intensity of scattered light varies depending on the position on the substrate surface even for particles of the same size. Although the detection accuracy for detecting particles may be lowered, the intensity distribution of such inspection light can be relaxed by setting the inspection light to be irradiated onto the substrate in the state of convergent light. Furthermore, when a light-emitting diode is used as a light source, an illuminance distribution is generated in the planar inspection region due to the light distribution characteristic of the light-emitting diode, but it is emitted toward the planar inspection region while scanning the inspection light by the scanning mirror. Therefore, the illuminance distribution in the planar inspection region can be made almost uniform. Also, if the inspection light is emitted toward the plane inspection area while scanning with the scanning mirror, particles can be detected on the entire surface of the substrate while the substrate is stationary, so the configuration of the optical device for particle detection is simplified. Can be

  In the present invention, the substrate surface of the substrate is preferably mirror-polished. If such a substrate is used for particle detection, scattering on the substrate surface of the substrate itself can be prevented, and thus detection accuracy is high.

  In this case, in order to easily obtain the substrate, the substrate is preferably a silicon substrate.

  In this invention, it has the illumination intensity reference member arrange | positioned in the position remove | deviated from the said plane | planar inspection area | region, The said light source part for a test | inspection can irradiate the said illumination intensity reference member to the said imaging | photography part, Preferably, the scattered light of the inspection light generated by the illuminance reference member is imaged for intensity correction of the scattered light of the inspection light generated by particles on the substrate surface. In this way, even when the amount of inspection light varies, particles can be detected based on the intensity of light scattered by the illuminance reference member. Therefore, even if the emission intensity from the light source varies, the particle detection accuracy is high.

  In this case, it is desirable that the illuminance reference member is irradiated with the inspection light with an illuminance lower than that of the planar inspection region. In this way, the intensity of the scattered light generated by the illuminance reference member in the imaging result of the imaging unit can be made weaker than the intensity of the scattered light generated by the particles on the substrate surface. It becomes easy to correct the intensity of the scattered light of the inspection light generated by the surface particles.

  In the present invention, it is desirable that the surface of the illuminance reference member is at a position lower than the planar inspection region. When the surface of the illuminance reference member is positioned lower than the substrate surface, the configuration in which the distance between the illuminance reference member and the scanning mirror is increased when the illuminance reference member is irradiated with the illuminance lower than the substrate surface. Alternatively, the substrate and the illuminance reference member can be arranged in a narrow area as compared with a configuration in which a translucent member that reduces the light intensity is disposed between the scanning mirror and the illuminance reference member.

  In the present invention, it is desirable that the inspection light is focused at a position that is optically farthest from the light source in the planar inspection region. In this way, the amount of inspection light irradiated on the planar inspection region increases.

Next, the particle detector of the present invention is
The particle detection optical device;
An image processing unit that detects particles adhering to the substrate surface based on image data of a captured image of the substrate surface imaged by the imaging unit is provided.

  According to the present invention, the change in the intensity of scattered light due to the interference of the inspection light in the image data acquired by the imaging unit of the optical device for particle detection is reduced. Therefore, the image processing unit can accurately detect particles on the substrate based on the image data.

  According to the present invention, the inspection light source unit includes a light emitting diode as a light source, and uses incoherent light emitted from the light emitting diode as inspection light. Therefore, for the specific particles adhering to the substrate surface, the inspection light from the inspection light source unit directly irradiates the particles, and after reaching the substrate surface from the inspection light source unit, it rebounds on the substrate surface. Even if the situation of irradiating particles occurs, interference hardly occurs. As a result, the change in the intensity of the scattered light caused by the interference of the inspection light can be reduced, so that the particles on the substrate can be accurately detected based on the image data acquired by the imaging unit. In addition, when a semiconductor laser that emits laser light is used as the light source, the output change due to temperature changes is large, so the amount of inspection light changes due to changes in environmental temperature, and the size of the particles is determined from the imaging results. However, if a light emitting diode is used as the light source, the change in the amount of light due to the change in the environmental temperature can be suppressed, so the image acquired by the imaging unit regardless of the change in the environmental temperature. Particles on the substrate can be accurately detected based on the data.

It is explanatory drawing which shows the particle | grain detection apparatus and board | substrate to which this invention is applied. It is explanatory drawing for demonstrating the principal part of the optical apparatus for particle detection. It is explanatory drawing which shows the structure of the optical system etc. of the optical apparatus for particle detection. It is explanatory drawing which shows a mode that a reflective mirror (reflecting member) reflects test | inspection light. It is a block diagram which shows the structure of the data processing system of a particle detection apparatus. It is explanatory drawing which shows an example of image data. It is a flowchart which shows a particle detection method. It is explanatory drawing which shows another example of the optical part for a test | inspection.

  A particle detection optical apparatus and a particle detection apparatus to which the present invention is applied will be described below with reference to the drawings.

(overall structure)
FIG. 1A is an explanatory diagram showing the overall configuration of the particle detection apparatus, and FIG. 1B is a plan view of a substrate to be inspected for particles. FIG. 2 is an explanatory view showing a main part of the optical device for particle detection. As shown in FIG. 1A, the particle detection device 1 includes a particle detection optical device 2, and a computer 3 including a display unit 3a and an input unit 3b such as a keyboard and a mouse. The computer 3 is communicably connected to the particle detection optical device 2.

  The optical device 2 for particle detection has an apparatus main body 21 provided with a switch 21a and a lamp 21b on the front side, and an optical system storage section 22 that stands on the rear side of the apparatus main body 21 and has an upper portion protruding forward. ing. On the upper surface of the apparatus main body 21, a sample stage 23 is provided one step higher. The sample table 23 is provided with a circular plane inspection region 24 on the upper end surface thereof, the substrate 4 to be inspected for particles P is disposed in the plane inspection region 24, and the substrate surface 4a of the substrate 4 is flat. It is located on the inspection area 24. An illuminance reference member 25 is provided on the side of the sample table 23 (see FIG. 2). In front of the sample stage 23 and the illuminance reference member 25, a reflecting mirror (reflective member) 26 that covers the front part of the sample stage 23 and the illuminance reference member 25 is attached. In front of the reflecting mirror 26, a double revolving door 27 is provided between the apparatus main body 21 and the optical system storage unit 22 so as to switch between a state in which the sample table 23 is enclosed and an open state. The revolving door 27 has a light shielding property, and the inside of the revolving door 27 with the revolving door 27 in a closed state is a measurement chamber 28 in which light is blocked from the outside. In this embodiment, the reflecting mirror 26 has a mirror surface as a reflecting surface. Instead of the reflecting mirror 26, the reflecting surface is composed of a glass plate having fine irregularities, and this reflecting surface is light-scattering. A reflective member having a property may be used.

  The planar shape of the substrate 4 is substantially circular. The substrate 4 is a silicon wafer and is polished until the substrate surface 4a becomes a mirror surface. A positioning mark 4b for specifying the position of the substrate 4 is engraved on the substrate surface 4a by laser processing or the like. The positioning mark 4 b is formed at a position off the center 4 c of the substrate 4 and has a rectangular shape that extends long in a direction perpendicular to the radial direction of the substrate 4.

  As shown in FIG. 2, the sample stage 23 includes a circular recess 231 in the center, and the substrate 4 is disposed in the circular recess 231. The circular recess 231 has an inner diameter corresponding to the outer diameter of the substrate 4. When the substrate 4 is arranged inside the circular recess 231, the substrate 4 is positioned in the radial direction, and the center 4 c of the substrate 4 and the planar inspection region 24 are arranged. The centers 24a coincide with each other. The circular recess 231 has a depth corresponding to the thickness of the substrate 4. When the substrate 4 is disposed inside the circular recess 231, the substrate surface 4 a and the upper end surface 23 a of the sample stage 23 are in the height direction. Match. The upper end opening of the circular recess 231 defines the plane inspection region 24.

  The optical system storage unit 22 includes an imaging unit 29 and an illumination device 30 above the sample stage 23. The imaging unit 29 includes a CCD camera in which a plurality of pixels are arranged in a matrix, and is arranged downward so as to face the center 24 a of the planar inspection region 24. The illumination device 30 is disposed downward so as to face the planar inspection region 24, and irradiates divergent light that can irradiate the entire planar inspection region 24. The optical system storage unit 22 includes an inspection light source unit 31 that irradiates the planar inspection region 24 and the illuminance reference member 25 with the inspection light L (see FIG. 3) behind the sample stage 23.

  When the particles P adhering to the substrate 4 are detected, the particle detection optical device 2 sets the substrate 4 on the sample stage 23 and closes the rotary door 27. Next, the inspection light L is irradiated from the inspection light source unit 31 to the planar inspection region 24, and the scattered light of the inspection light L scattered by the particles P adhering to the substrate surface 4a is imaged by the imaging unit 29. When the image data is acquired in this way, the particle detection optical device 2 transmits the image data to the computer 3. The computer 3 detects the number and size of the particles P on the substrate 4 based on the received image data. Further, the computer 3 displays the detection result of the particles P together with the received image data on the display unit 3a.

  When observing the particles P adhering to the substrate 4, in the particle detection optical device 2, the substrate 4 is set on the sample stage 23 and the rotary door 27 is opened. Next, the illumination device 30 illuminates the planar inspection region 24 and irradiates the planar inspection region 24 with the inspection light L from the inspection light source unit 31, and the scattered light of the inspection light L scattered by the particles P on the substrate surface 4a. Is imaged by the imaging unit 29. When the image data is acquired in this way, the particle detection optical device 2 transmits the image data to the computer 3. The computer 3 displays the received image data on the display unit 3a.

(Light source for inspection)
The inspection light source unit 31 of the particle detection optical device 2 will be described with reference to FIGS. 3A is a plan view showing a planar layout of the inspection light source section 31, and FIG. 3B is an explanatory diagram showing an optical layout of the inspection light source section 31, and FIG. ) Is an explanatory view showing a state in which the inspection light L is irradiated onto the substrate surface 4a. In FIG. 3, the reflecting mirror 26 is removed. The inspection light source unit 31 emits a light-emitting diode 41 as a light source, a holder 42 that holds the light-emitting diode 41, and inspection light L toward the planar inspection region 24 and scans along the planar inspection region 24. The scanning device 43 is provided.

  The light emitting diode 41 emits green divergent light. As shown in FIGS. 3B and 3C, the scanning device 43 includes a scanning mirror 432 and a drive device (not shown) that rotates the scanning mirror 432 around its central axis 431. The scanning mirror 432 is a regular octagonal polygonal mirror having a central axis 431 oriented in a direction perpendicular to the planar inspection region 24, and is slightly smaller than the planar inspection region 24 as shown in FIGS. Is located above.

  As shown in FIG. 3, a convex lens (convergence lens) 44 is accommodated in the holder 42, and divergent light emitted from the light emitting diode 41 is converted into convergent light by the convex lens 44. As shown in FIG. 3C, the convergent light proceeds as convergent light even after being reflected by the scanning mirror 432, and is irradiated as the inspection light L toward the planar inspection region 24. The inspection light L forms a focal point F at a position where the distance from the light source is optically farthest in the planar inspection region 24.

  Further, the inspection light L is reflected by the scanning mirror 432 rotating around the central axis 431, so that the surface of the substrate surface 4a along the planar inspection region 24 is indicated by an arrow S in FIG. Scanning is performed in the in-plane direction, and the entire substrate surface 4a is irradiated from an obliquely upward side.

(Illuminance reference member)
The illuminance reference member 25 is a glass plate or the like having fine irregularities on the surface 25a, and the surface 25a has light scattering properties. As shown in FIG. 2, the illuminance reference member 25 is disposed such that the surface of the illuminance reference member 25 is lower than the substrate surface 4 a disposed in the planar inspection region 24 at a position outside the planar inspection region 24. Yes. Accordingly, the inspection light L from the inspection light source unit 31 is applied to the illuminance reference member 25 with an illuminance lower than that of the planar inspection region 24.

(Reflector)
The reflecting mirror 26 will be described with reference to FIGS. FIG. 4 is an explanatory diagram showing a state in which the reflecting mirror 26 reflects the inspection light L. As shown in FIG. 2, the reflecting mirror 26 is disposed on the opposite side of the scanning mirror 432 across the center 24 a of the planar inspection region 24, and covers the front side portion of the planar inspection region 24 from obliquely upward from the front. . An inner reflection surface 26 a facing the flat inspection region 24 side in the reflecting mirror 26 is an arc surface defined with the center 24 a of the flat inspection region 24 as the center. As shown in FIG. 4, the reflecting mirror 26 reflects the reflected light of the inspection light L reflected by the substrate surface 4a of the substrate 4 arranged in the planar inspection region 24 to the substrate surface 4a side by the reflecting surface 26a. .

(Control system)
FIG. 5 is a block diagram showing a control system in the particle detection apparatus 1 to which the present invention is applied. FIG. 6 is an explanatory diagram showing an example of image data. The computer 3 operates based on a program stored in a memory in advance, and as shown in FIG. 5, an optical device control unit 51 that controls the particle detection optical device 2 based on a command from the input unit 3b, a particle A receiving unit 52 that receives image data transmitted from the detection optical device 2, an image processing unit 53 that detects particles P based on the image data, and detection of particles P detected based on the image data and image data The display control part 54 which displays a result on the display part 3a is provided.

  The optical device control unit 51 controls the imaging unit 29, the illumination device 30, and the inspection light source unit 31 based on the command input from the input unit 3b.

  In this example, when a “particle detection command” is input from the input unit 3b after the substrate 4 is set on the sample stage 23 and the rotating door 27 is closed, the inspection light source unit 31 and the imaging unit 29 are driven and controlled. Then, the inspection light L is irradiated from the inspection light source unit 31 to the planar inspection region 24, and the scattered light of the inspection light L scattered by the particles P on the substrate surface 4a is imaged by the imaging unit 29. Then, the acquired image data is transmitted from the imaging unit 29 to the computer 3. In the “particle detection command”, the illumination device 30 is not turned on, and the imaging by the imaging unit 29 is performed in the “dark field state”. The dark field state means a state in which light other than the inspection light L is not irradiated on the measurement chamber 28.

  When a “particle observation command” is input from the input unit 3 b after setting the substrate 4 on the sample stage 23 and closing the rotary door 27, the illumination device 30, the inspection light source unit 31, and the imaging unit 29 are input. , The illumination device 30 illuminates the planar inspection region 24, and the inspection light source 31 irradiates the planar inspection region 24 with the inspection light L and is scattered by the particles P on the substrate surface 4 a by the imaging unit 29. The scattered light of the inspection light L is photographed. Then, the acquired image data is transmitted from the imaging unit 29 to the computer 3. In the “particle observation command”, the illumination device 30 is turned on, and the imaging by the imaging unit 29 is performed in the “bright field state”. The bright field state means a state where light other than the inspection light L is irradiated on the planar inspection region 24. Note that, when a “particle observation command” is input, imaging may be performed without driving the inspection light source unit 31. That is, the inspection light L is not irradiated from the inspection light source unit 31 to the planar inspection region 24, and the scattered light of the diverging light of the illumination device 30 scattered by the particles P on the substrate surface 4a is captured by the imaging unit 29. May be.

  Here, the image data transmitted from the particle detection optical device 2 to the computer 3 is two-dimensional image data, in which coordinates indicating pixel positions are associated with luminance values of the respective pixels. The position of each pixel is represented by, for example, coordinates (Xi, Yj) = coordinates (X1, Y1), (X1, Y2),... (Xn, Ym) as shown in FIG.

  The receiving unit 52 receives the image data from the particle detecting optical device 2 and stores it in the storage device 55. The image data is output to the image processing unit 53 and the display control unit 54.

  The image processing unit 53 specifies the size of the particle P based on the region extracted by the region extracting unit 531 and the region extracting unit 531 that extract the scattered light region from the image data received from the particle detection optical device 2. A particle identification unit 532 and a counting unit 533 that counts the number of particles P identified by the particle identification unit 532 are provided. Here, the region extraction unit 531, the particle identification unit 532, and the counting unit 533 operate when the “particle detection command” is input, and when the “particle observation command” is input, Do not work.

  The area extracting unit 531 includes various memories and stores a threshold value input in advance from the input unit 3b. The threshold value is a lower limit value for recognizing that the particle P exists in the intensity of the scattered light of the inspection light L irradiated to the particle P. Further, the region extraction unit 531 processes the image data using the image data input from the imaging unit 29 and the threshold value, and a group of pixels having luminance values equal to or higher than the threshold value are collected as shown in FIG. The obtained high-brightness pixel region R (high-brightness pixel regions R1, R2, R3) is obtained, and the position of the high-brightness pixel region R (high-brightness pixel regions R1, R2, R3) and the high-brightness pixel region R (high The number of pixels included in the luminance pixel regions R 1, R 2, R 3) and the luminance value of each pixel are extracted as high luminance pixel information and output to the particle specifying unit 532. The high luminance pixel region R extracted by the region extraction unit 531 corresponds to the particle P on a one-to-one basis.

  Here, the region extraction unit 531 corrects the luminance and threshold value of each pixel based on the intensity of the scattered light of the inspection light L irradiated on the illuminance reference member 25. That is, since the amount of light emitted from the light emitting diode 41 used as the light source may fluctuate and affect the luminance of each pixel, the luminance and threshold value of each pixel are corrected. In this example, the value obtained by dividing the actual luminance of each pixel by the detected value of scattered light from the illuminance reference member 25 is treated as the luminance of the pixel. For this reason, the threshold value is also set to a value corresponding to a value obtained by dividing the actual luminance of each pixel by the detected value of scattered light from the illuminance reference member 25.

  The particle specifying unit 532 is attached to the substrate surface 4a based on the position of the high luminance pixel region R, the total number of pixels of each pixel included in the high luminance pixel region R, and the luminance value included in the high luminance pixel information. The position and size of each particle P are specified. That is, if the size of the particle P is large, the number of pixels existing in the high luminance pixel region R is large and the luminance is high. Therefore, the size of the particle P is determined based on the number of pixels existing in the high luminance pixel region R and the luminance. Can be identified.

  In addition, the particle specifying unit 532 classifies each specified particle P by size. In this example, for example, it is classified into 30 μm or more and less than 60 μm, 60 μm or more, less than 90 μm, and 90 μm or more. Further, the particle identification unit 532 outputs the position and size of the particle P and the classification result to the counting unit 533 as the particle identification information.

  The counting unit 533 includes a plurality of counters, and counts the number of particles P by incrementing the counter value by 1 each time the particle identification information is received. Further, the number of particles P of each classification is counted based on the classification result included in the particle identification information. Further, the particle specifying information, the total number of counted particles P and the number of classified particles P are output to the display control unit 54.

  If the region extraction unit 531 cannot detect the high luminance pixel region R, the region extraction unit 531 outputs zero information indicating that the high luminance pixel region R does not exist to the particle specifying unit 532. In this case, since the particle identification information is not output from the particle identification unit 532, the counting unit 533 does not count the particles P.

  When the “particle detection command” is input, the display control unit 54 displays the image data from the reception unit 52 on the display unit 3a, and also includes the particle including the position and size of each particle P and the classification result. The specific information, the total number of particles P, and the number of particles P of each classification are displayed on the display unit 3a. Here, the image data displayed on the display unit 3a is acquired in the dark field state.

  Further, when the “particle observation command” is input, the display control unit 54 displays only the image data from the reception unit 52 on the display unit 3a. Here, the image data displayed on the display unit 3a is acquired in the bright field state.

(Particle detection operation)
FIG. 7 is a flowchart showing the particle detection operation. The particle detection apparatus 1 of this example is used for monitoring the particles P in the area where the substrate 4 has been arranged. In the latter case, the number of particles P present in the area where the substrate 4 was disposed is monitored by monitoring the particles P which are collected after being disposed in a predetermined area and then adhered to the substrate 4. Is required. In the case of continuously performing such monitoring, for example, the substrate 4 for which the particle P has been detected by the particle detection device 1 is again placed in the monitoring area, and after a predetermined time has elapsed, the substrate 4 is recovered again. The number and size of the particles P adhering to the substrate 4 are obtained and compared with the previous detection result. At this time, since it is necessary to align the position of the substrate 4, in this example, the position of the particle P on the substrate 4 is determined with the positioning mark 4b attached to the substrate 4 as the origin position.

  When detecting the particles P, first, the substrate 4 is set on the sample stage 23, that is, the substrate surface 4a of the substrate 4 is disposed on the planar inspection region 24, and the rotary door 27 is closed (step ST1). ). Thereafter, a “particle detection command” is input from the input unit 3b (step ST2). Thereby, irradiation of the inspection light L from the inspection light source unit 31 to the planar inspection region 24 is started, and imaging by the imaging unit 29 is started (step ST3). At that time, the illumination device 30 is turned off (dark field imaging step).

  In the dark field imaging step, when the imaging unit 29 acquires scattered light generated by the particles P as image data and transmits it to the computer 3, the receiving unit 52 stores the image data in the storage device 55. The receiving unit 52 outputs the image data to the display control unit 54 and also outputs the image data to the region extraction unit 531. The region extraction unit 531 obtains the high luminance pixel region R and extracts the position of the high luminance pixel region R, the number of pixels included in the high luminance pixel region and the luminance of each pixel as high luminance pixel information, and a particle specifying unit. It outputs to 532 (step ST4).

  In the particle specifying unit 532 to which the high luminance pixel information has been input, each particle attached to the substrate surface 4a based on the position of the high luminance pixel region R, the number of pixels included in the high luminance pixel region, and the luminance of each pixel. Specify the position and size of P. Moreover, each particle P is classified according to size. Then, the position and size of each particle P and the classification result are output as particle identification information to the measuring unit (step ST5).

  The counting unit 533 to which the particle identification information has been input counts the total number of particles P and the number of particles P of each classification (step ST6), and outputs them together with the particle identification information to the display control unit 54. Therefore, the display control unit 54 Along with the image data, the position and size of each particle P and the particle identification information including the classification result, the total number of particles P, and the number of particles P of each classification are displayed on the display unit 3a (step ST7).

  Next, when the user of the particle detection device 1 inputs a “particle observation command” to the input unit 3b of the computer 3 (step ST8), the illumination device 30 is turned on, and the imaging unit 29 scans the substrate surface 4a in the bright field state. An image is taken (step ST9). At that time, the inspection light L from the inspection light source unit 31 is in a state of scanning the planar inspection region 24. (Bright-field imaging process).

  In the bright field imaging step, when the imaging unit 29 acquires scattered light generated by the particles P as image data and transmits it to the computer 3, the reception unit 52 stores and holds this image data in the storage device 55. The receiving unit 52 outputs the image data to the display control unit 54, and the display control unit 54 displays the image data on the display unit 3a (step ST10). That is, since the particle P is not specified in the bright field imaging process, only the image data is displayed on the display unit 3a by the display control unit 54.

  Here, in the bright field imaging step, an image of the large-sized particle P is displayed on the display unit 3a, so that the outer shape of the large-sized particle P can be observed. Therefore, it is possible to determine what the large size particle P is derived from. Further, since the light emitting diode 41 continues to be lit during the bright field imaging process, the outer shape of the small particle P cannot be observed, but the scattered light from the small particle P is displayed on the display unit 3a. Is done.

  In such a particle detection operation, if the intensity of the inspection light L and the sensitivity of the imaging unit 29 are set corresponding to the particles P with low brightness of scattered light, the number of small particles P in the dark field imaging process is set. And size can be detected. In this case, the detection sensitivity is saturated at the brightness level of the scattered light from the large particles P, and the outer shape of the large particles P cannot be detected, but the outer shape of the large particles P can be detected in the bright field imaging process. . Accordingly, the particle P having a small size can be detected with a simple configuration, and the outer shape of the particle P having a large size can be detected.

(Function and effect)
According to this example, the inspection light source unit 31 includes the light emitting diode 41 as a light source, and uses the incoherent light emitted from the light emitting diode 41 as the inspection light L. Therefore, for the specific particles P adhering to the substrate surface 4a, the inspection light L from the inspection light source unit 31 directly irradiates the particles P and reaches the substrate surface 4a from the inspection light source unit 31. Even if a situation occurs in which the particle P is rebounded on the substrate surface 4a and irradiated with the particles P, interference does not easily occur. As a result, the change in the intensity of the scattered light caused by the interference of the inspection light L can be reduced, so that the particles P on the substrate 4 can be accurately detected based on the image data acquired by the imaging unit 29.

  Also, when a semiconductor laser that emits laser light is used as the light source, the output change due to temperature change is large, so the light quantity of the inspection light L changes due to changes in the environmental temperature or due to the heat generated by the semiconductor laser itself. In other words, the size of the particle P or the like cannot be accurately detected from the imaging result. However, since the light emitting diode 41 is used as the light source, it is possible to suppress a change in the amount of light due to a change in temperature. Therefore, the particles P on the substrate 4 can be accurately detected based on the image data acquired by the imaging unit 29 regardless of changes in temperature.

  Here, the inspection light L emitted from the light emitting diode 41 has a smaller amount of light compared to the case where the laser light is used as the inspection light L. However, since the inspection light L is convergent light, the irradiation area It is possible to secure the light quantity of the inspection light L irradiated on the surface. Furthermore, since the inspection light L is focused at a position where the distance from the light source is optically farthest in the planar inspection region 24, the amount of the inspection light L irradiated to the planar inspection region 24 increases.

  In addition, in this example, the reflection mirror 26 that reflects the reflected light of the inspection light L reflected by the substrate surface 4a of the substrate 4 to be inspected for the particles P to the substrate surface 4a side is provided. The amount of the inspection light L irradiated to the substrate surface 4a can be ensured. Further, since the inspection light L is incoherent light, even if the reflected light of the inspection light L reflected by the substrate surface 4a is reflected to the substrate surface 4a side using the reflecting mirror 26, interference occurs in the inspection light L. do not do. Therefore, even if the particle P is fine, it can be accurately detected.

  In addition, when the inspection light L is irradiated on the substrate 4 in a divergent light state, the amount of light reaching the side on which the inspection light L is incident (side optically close to the light source) on the substrate surface 4a is large. Since the amount of light reaching the side away from the side on which the inspection light L is incident on the substrate surface 4a (the side optically far from the light source) is reduced, even the particles P of the same size are on the substrate surface 4a. The intensity of the scattered light varies depending on the position, and the detection accuracy for detecting the particles P may be reduced. However, since the inspection light L is irradiated on the substrate 4 in the state of convergent light, the intensity of such inspection light L Distribution can be relaxed.

  Furthermore, in this example, in the image data obtained by the imaging unit 29, the luminance value of each pixel is compared with a threshold value to recognize the particle P. Therefore, if continuity of illuminance is not ensured, the size of the particle P The sheath number is falsely detected. However, in this example, since the inspection light L is irradiated toward the substrate 4 as convergent light, the intensity of the inspection light L continuously increases as the distance from the scanning mirror 432 increases, and the illuminance continues. It will be in the state. Therefore, the detection accuracy of the size and number of the particles P is high.

  When the light emitting diode 41 is used as the light source, an illuminance distribution is generated on the substrate surface 4a arranged in the planar inspection region 24 due to the light distribution characteristic of the light emitting diode 41. However, the reflecting mirror 26 causes the substrate surface 4a. Since the reflected light of the inspection light L reflected at the step 4 is reflected toward the substrate surface 4a, the illuminance distribution in the planar inspection region 24 can be made nearly uniform. Furthermore, since the inspection light L is emitted toward the planar inspection region 24 while being scanned by the scanning mirror 432, the illuminance distribution in the planar inspection region 24 can be made nearly uniform.

  Further, if the inspection light L is emitted toward the planar inspection region 24 while being scanned by the scanning mirror 432, the particles P can be detected on the entire substrate surface 4a while the substrate 4 is stationary. The configuration of the optical device 2 can be simplified.

  In this example, the substrate 4 is a silicon wafer, and the substrate surface 4a is mirror-polished. As a result, scattering on the substrate surface 4a of the substrate itself can be prevented, so that the detection accuracy is high. Further, if the substrate surface 4a is mirror-polished, the difference between the light amount of the inspection light L irradiated on the substrate surface 4a and the light amount of the reflected light of the inspection light L reflected by the substrate surface 4a becomes small. . Therefore, the reflected light of the inspection light L reflected by the substrate surface 4a is reflected by the reflecting mirror 26 toward the substrate surface 4a, so that the amount of the inspection light L applied to the substrate surface 4a is sufficient. it can.

  Further, since the positioning mark 4b is attached to the substrate surface 4a, the substrate 4 on which the particle P has been detected is again placed in an environment for monitoring the air cleanliness, and then the particle P on the substrate surface 4a. Is detected, it is possible to track the change in the amount of adhering particles P at each position on the substrate surface 4a with reference to the positioning mark 4b.

  Furthermore, in this example, since the illuminance reference member 25 to which the inspection light L is irradiated is provided, the imaging result in the imaging unit 29 can be corrected by the detection result for the illuminance reference member 25. For this reason, even when the light quantity of the inspection light L emitted from the light emitting diode 41 varies, the detection accuracy of the particles P is high.

  Further, the illuminance reference member 25 is disposed on the side of the planar inspection region 24, and the surface of the illuminance reference member 25 is at a position lower than the planar inspection region 24. As a result, since the inspection light L is irradiated with an illuminance lower than that of the substrate surface 4a, in the imaging result of the imaging unit 29, the intensity of the scattered light generated by the illuminance reference member 25 is scattered light generated by the particles P on the substrate surface 4a. Therefore, the intensity of the scattered light of the inspection light L generated by the particles on the substrate surface 4a can be easily corrected based on the scattered light. Moreover, since the surface of the illuminance reference member 25 is made lower than the planar inspection region 24 when the illuminance reference member 25 is irradiated with the illuminance reference member 25 at an illuminance lower than that of the substrate surface 4a, Compared to a configuration in which the distance from the scanning mirror 432 is increased or a configuration in which a translucent member for reducing the light intensity is disposed between the scanning mirror 432 and the illuminance reference member 25, the planar inspection region 24 is in a narrow region. And the illuminance reference member 25 can be disposed.

  Furthermore, when the inspection light L is irradiated from one direction onto the planar inspection region 24, other particles P enter the shadow of the particle P formed by the inspection light L, and this shadow In some cases, the entering particle P cannot be detected, but in this example, the inspection light L is applied to the substrate surface 4a from a direction different from the inspection light L from the inspection light source unit 31 due to reflection by the reflecting mirror 26. it can. Accordingly, it is possible to detect particles P that are in the shadow of other particles P.

(Other embodiments)
FIG. 8 is an explanatory diagram showing an optical layout of another example of the inspection light source unit. The inspection light source unit 31 includes the convex lens 44 between the light emitting diode 41 and the scanning mirror 432. However, the inspection light source unit 61 of this example replaces the convex lens 44 with a collimating lens 62 and a convex lens. A lens system 64 including a (converging lens) 63 is provided. Since the inspection light source unit 61 of this example has a configuration corresponding to that of the inspection light source unit 31, the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  In the inspection light source unit 61 of this example, divergent light is emitted from the light emitting diode 41. This divergent light is converted into a parallel light beam by the collimator lens 62 in the lens system 64 and then converged by the convex lens 63. This becomes inspection light L1. Here, since the inspection light L1 only needs to be convergent light in the scanning direction by the scanning mirror 432, a cylindrical lens having a positive power in the horizontal direction (scanning direction) is used as the convex lens 63. Yes.

  In this way, since the light emitted from the collimating lens 62 is collimated light, the incident light quantity to the convex lens 63 and the convex lens 63 are emitted regardless of the position of the convex lens 63 in the optical axis direction. The convergence angle of the inspection light L does not change. Therefore, the position adjustment of the convex lens 63 is easy.

1. Particle detection device, 2. Optical device for particle detection, 3. Computer, 3a, Display unit, 3b, Input unit, 4. Substrate, 4a, Substrate surface, 4b, Position mark, 4c, Center, 21. Device Main body, 21a / switch, 21b / lamp, 22 / optical system storage unit, 23 / sample stage, 23a / upper end surface, 24 / planar inspection area, 24a / center, 25 / illuminance reference member, 25a / surface, 26 / reflection Mirror (reflective member), 26a / reflective surface, 27 / revolving door, 28 / measuring room, 29 / imaging unit, 30 / illuminating device, 31 / light source for inspection, 41 / light emitting diode, 42 / holder, 43 / scanning Mirror device, 44 / convex lens (convergence lens), 51 / optical device control unit, 52 / reception unit, 53 / image processing unit, 54 / display control unit, 55 / storage device, 61 / light source unit for inspection, 62 / collimator 63, convex lens (converging lens), 64, lens system, 71, inspection light source unit, 72, convex lens, 231, circular concave part, 431, central axis, 432, scanning mirror, 531, region extraction unit, 532, particle Specific part, 533 / counter, L / L1 / L2 / inspection light, P / particle, R / high brightness pixel area

Claims (8)

An inspection light source unit that irradiates inspection light onto a planar inspection region where a substrate surface of a substrate to be inspected is arranged, and an imaging unit that acquires scattered light of the inspection light generated on the substrate surface as image data In the optical device for particle detection for detecting particles adhering to the substrate surface based on the image data,
The inspection light source unit is
A light emitting diode as a light source;
A converging lens that converts divergent light emitted from the light emitting diode into convergent light;
A scanning mirror that irradiates the planar inspection region with the convergent light emitted from the converging lens as the inspection light and scans along the planar inspection region;
An optical device for particle detection, comprising: In claim 1,
An optical device for particle detection, wherein the substrate surface of the substrate is mirror-polished. In claim 2,
An optical device for particle detection, wherein the substrate is a silicon substrate. In any one of claims 1 to 3,
Having an illuminance reference member arranged at a position deviating from the plane inspection area;
The inspection light source unit can irradiate the illuminance reference member with the inspection light,
The imaging unit picks up the scattered light of the inspection light generated by the illuminance reference member for correcting the intensity of the scattered light of the inspection light generated by particles on the substrate surface. apparatus. In claim 4,
The optical device for particle detection, wherein the illuminance reference member is irradiated with the inspection light at an illuminance lower than that of the planar inspection region. In claim 5,
The surface of the illuminance reference member is at a position lower than the planar inspection region. In any one of claims 1 to 6,
The optical apparatus for particle detection according to claim 1, wherein the inspection light is focused at a position farthest from the light source optically in the planar inspection region. The optical device for particle detection according to any one of claims 1 to 7,
A particle detection apparatus comprising: an image processing unit that detects particles adhering to the substrate surface based on image data of a captured image of the substrate surface imaged by the imaging unit.

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