JP2006163122A - Optical microscope, autofocus method and observing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical microscope capable of adjusting a focal position using a simple constitution. <P>SOLUTION: The optical microscope includes an observing light source 30; an objective lens 18 for condensing light to be made incident on a specimen; a light source 11 for emitting a light made incident on an area of the objective lens 18 corresponding to a half of the pupil; a beam splitter 14, by which light from the observing light source 30 is reflected, and the light from the power source 11 is transmitted and guided to the specimen 19; and an optical detector 22 for detecting a first reflection light ray reflected from the specimen 19 among the light rays made incident on the specimen 19 from the observing light source 30 via the objective lens 18, and a second reflection light ray, reflected from the specimen 19 among the light rays made incident on the specimen 19 from the second light source via the region of the objective lens 18, corresponding to the half of the pupil and passed through an area of the objective lens 18, corresponding to the opposite half of the pupil. Based upon the second reflection light ray detected by the optical detector 22, focal position is adjusted. Based on the first reflection light ray, the specimen is observed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical microscope, an autofocus method, and an observation method using the same, and particularly relates to an optical microscope having an autofocus function.

  In an optical microscope, an autofocus function (autofocus function) for automatically focusing on an object to be observed is used. As the autofocus function, for example, an optical lever system or an astigmatism system is known.

  For example, in the optical lever method, light is irradiated to a region on one half of the pupil of the objective lens. The reflected light reflected by the object passes through a half region on the opposite side of the pupil of the objective lens. Then, the reflected light that has passed through the objective lens is detected by a two-divided photodiode or the like. At this time, it arrange | positions so that reflected light may inject into the center of a 2 division | segmentation photodiode in the state which a target object has become a focus position. Therefore, when the object is deviated from the focal position of the objective lens, the position of the reflected light deviates from the center of the two-divided photodiode. The difference in the output of the two-divided photodiode based on the positional deviation of the reflected light indicates the amount of focal position deviation. Therefore, the focus can be adjusted by performing feedback control so that the outputs of the two-divided photodiodes are the same (see, for example, Patent Document 1). In addition, there is a type in which light from a light source is incident on a cylindrical lens and a target is irradiated with a linear spot (for example, see Patent Document 2). In addition, there is an apparatus that adjusts the position of the aperture stop (for example, see Patent Document 3).

JP-A-8-254650 JP-A-10-161195 JP 2003-29130 A

  When the AF function using the optical lever method is used for an optical microscope, it is necessary to use a light source and a detector (for example, a two-division photodiode) dedicated to the autofocus function. That is, it is necessary to separately provide an observation optical system and an autofocus optical system.

  A method for solving this problem is described in Patent Document 3. In the optical microscope disclosed in Patent Document 3, automatic focusing is performed by controlling the aperture stop and the field stop of the Koehler illumination optical system. That is, when focusing is performed, the aperture stop is moved to shield the lower half of the light beam. On the other hand, when performing microscopic observation, the center of the aperture stop aperture is made to coincide with the optical axis. Thereby, the light source and detector of the observation system and the autofocus system can be shared. That is, an optical microscope with an autofocus function can be configured with one light source and one detector.

  However, in the above-described optical microscope, the aperture stop is moved during autofocusing and microscopic observation. For this reason, the focal point of the objective lens may deviate from the sample surface due to mechanical vibration when the aperture stop is moved.

  The present invention has been made in view of the above problems, and an optical microscope capable of adjusting a focal position with a simple configuration, an autofocus method capable of easily adjusting a focal position, and the use thereof. The purpose is to provide an observation method.

  An optical microscope according to a first aspect of the present invention includes a first light source that emits illumination light for observing a sample, and an objective lens that collects the light from the first light source and makes the sample incident on the sample. A second light source that emits light incident on one half of the pupil of the objective lens, a beam splitter that mixes the light from the first light source and the second light source and guides the light to the sample, Of the light incident on the sample from the first light source through the objective lens, the first reflected light reflected by the sample and the region from one side half of the pupil of the objective lens from the second light source. A two-dimensional photodetector that detects second reflected light that has been reflected by the sample out of the light incident on the sample and passed through a half-region on the opposite side of the pupil of the objective lens, Based on the second reflected light detected by the two-dimensional photodetector To adjust the focal position, and is for observing the sample based on the first reflected light detected by the first two-dimensional photodetector. The focal position can be adjusted with a simple configuration.

  The optical microscope according to a second aspect of the present invention is the optical microscope described above, further comprising a drive stage on which the sample is placed and the placed sample is moved, and the sample is identified by the drive stage. The first reflected light detected by the two-dimensional photodetector after the sample has moved to a specific position after focusing on the second reflected light while moving to the position. Is used to observe the sample. Thereby, the substantial processing speed of an optical microscope can be improved.

  The optical microscope according to the third aspect of the present invention is the optical microscope described above, wherein the ratio of the light guided to the sample out of the light incident on the beam splitter from the second light source is from the first light source. The transmittance and reflectance of the beam splitter are set so as to be lower than the ratio of the light guided to the sample in the light incident on the beam splitter. Thereby, utilization efficiency can be improved for illumination light.

  An optical microscope according to a fourth aspect of the present invention is the above-described optical microscope, wherein the second light source is a laser light source.

  An optical microscope according to a fifth aspect of the present invention is the above-described optical microscope, further comprising a cylindrical lens that irradiates the sample with light from the second light source as line light, and the line light Is irradiated at an angle with the pattern provided on the sample. Thereby, it can focus correctly.

  An optical microscope according to a sixth aspect of the present invention is the integrating optical detector according to the above-described optical microscope, wherein the two-dimensional photodetector integrates received light for a predetermined time and outputs a signal. It is. Thereby, it can focus correctly.

  The autofocus method according to the seventh aspect of the present invention condenses the light from the first light source by the objective lens and irradiates the sample, and the first reflected light from the sample is irradiated by the two-dimensional photodetector. An automatic focusing method in an optical microscope for detecting and observing, the step of causing light from a second light source to enter a region on one half of the pupil of the objective lens; Making the light incident on the region incident on the sample, and out of the light from the second light source incident on the sample, the second reflected light reflected by the sample on the opposite side of the pupil of the objective lens Incident on one half region, detecting the second reflected light that has passed through the half region opposite to the pupil of the objective lens with the two-dimensional detector, and with the two-dimensional detector The second detected And performs focusing based on Shako. Thereby, automatic focusing can be performed simply.

  According to an eighth aspect of the present invention, there is provided an autofocus method according to the above autofocus method, wherein the light from the second light source is made into a line-shaped light and incident on the sample, and the line-shaped light is incident on the sample Irradiation is performed with an inclination with respect to the direction of the pattern provided on the substrate. Thereby, it can focus correctly.

  In the observation method according to the ninth aspect of the present invention, the light from the first light source is condensed by the objective lens and irradiated on the sample, and the reflected light from the sample is detected by the two-dimensional photodetector and observed. The step of causing the light from the second light source to enter the region on one half of the pupil of the objective lens, and the light incident on the region on one half of the pupil of the objective lens to the sample Making the light incident on the sample, the light reflected by the sample out of the light from the second light source made incident on the sample, and entering the half region on the opposite side of the pupil of the objective lens; and the objective lens Detecting the second reflected light that has passed through the half-region on the opposite side of the pupil with the two-dimensional detector, and the sample and the objective lens based on the light detected by the two-dimensional detector Focus by changing the distance between Performing the autofocusing, stopping the operation of the second light source, illuminating the sample with the first light source, and the two-dimensional photodetector And detecting the reflected light reflected by the sample and observing the sample. Thereby, observation can be performed in a state in which automatic focusing is simply performed.

  An observation method according to a tenth aspect of the present invention is the above-described observation method, wherein the two-dimensional photodetector is used while moving a relative position between the sample and light incident on the sample from the second light source. Focusing is performed based on the detected second reflected light, and the movement of the second light source is stopped in a state where movement of the relative position is stopped, and the first reflected light is converted into the two-dimensional light. It is detected by a detector and observed. Thereby, the time required for observation can be shortened.

  An observation method according to an eleventh aspect of the present invention is the observation method described above, wherein the sample is a sample in which a defect position is specified, and in the step of focusing, the second light source is placed at the defect position. In the step of performing the observation while moving the relative position so that the light from the light is irradiated and performing the observation, the defect position is observed. Thereby, the time required for observing defects can be shortened.

  An observation method according to a twelfth aspect of the present invention is the observation method described above, wherein the sample is a pattern substrate in which a pattern is formed on the substrate, and the light from the second light source is converted into a line-shaped light. The sample is incident on the sample, and the line-shaped light is tilted with respect to the direction in which the pattern is provided to irradiate the sample. Thereby, it can focus correctly.

  According to the present invention, it is possible to provide an optical microscope capable of adjusting the focal position with a simple configuration, an autofocus method capable of easily adjusting the focal position, and an observation method using the same.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

  The configuration of the optical microscope according to the present invention will be described with reference to FIG. FIG. 1B is a diagram showing the configuration of the optical microscope 1 according to the present invention. Fig.1 (a) is the figure which looked at FIG.1 (b) from the side surface. The direction parallel to the sample is the XY direction, and the perpendicular direction is the Z direction. The optical microscope 1 according to the present invention includes an observation optical system for observing a sample and an autofocus optical system that adjusts the position of the sample in the Z direction and performs focusing. The optical microscope 1 according to the present embodiment is a bright field microscope with epi-illumination. In the optical microscope 1 according to the present invention, it is possible to switch between an observation mode for observing a sample using an observation optical system and an autofocus mode for adjusting a focal position using an autofocus optical system.

  11 is a light source, 12 is a lens, 13 is a cylindrical lens, 14 is a beam splitter, 15 is a lens, 16 is a beam splitter, 17 is a lens, 18 objective lens, 19 is a sample, 20 is a stage, 21 is a processing device, and 22 is An optical detector, 30 is a light source for observation, and 31 is a bundle fiber. Reference numeral 40 denotes a light beam incident on the light receiving surface of the photodetector 22 from the light source 11.

  First, an observation optical system for observing the sample 19 will be described. The observation optical system includes an observation light source 30, a bundle fiber 31, a beam splitter 14, a lens 15, a beam splitter 16, a lens 17, an objective lens 18, and a photodetector 22. The observation optical system constitutes a Koehler illumination optical system.

  The observation light source 30 is a light source such as a lamp light source, and emits illumination light for illuminating the sample 19. Illumination light from the observation light source 30 enters one end of the bundle fiber 31. The bundle fiber 31 is configured by bundling a plurality of optical fibers. The illumination light incident on one end of the bundle fiber 31 from the observation light source 30 is emitted from the other end. That is, in the bundle fiber 31, the observation light source 30 side is the incident end, and the beam splitter 14 side is the emission end. The bundle fiber 31 is bundled, for example, so that the cross section is circular at the emission end. Illumination light emitted from the optical fiber is emitted at an emission angle or less determined by the NA (numerical aperture) of each optical fiber. The illumination light incident on the bundle fiber 31 exits from the exit end with a certain spread from each fiber. The exit end of the bundle fiber 31 is disposed on the pupil plane. By using the bundle fiber 31, the observation light source 30 can be arranged away from the sample 19. That is, by making the bundle fiber 31 longer, the distance between the observation light source 30 and the other optical system can be increased. Furthermore, by bending and arranging such a bundle fiber 31, light from the observation light source 30 can be guided to the sample 19 with a simple configuration. In this case, it is also possible to arrange the observation light source 30 in a space separated from other optical systems. Therefore, stray light from the outside of the observation optical system can be prevented from entering the sample 19 from the observation light source 30.

  Part of the illumination light emitted from the bundle fiber 31 and incident on the beam splitter 14 is reflected in the direction of the sample 19. The illumination light reflected by the beam splitter 14 is refracted by the lens 15 and enters the beam splitter 16. A part of the illumination light incident on the beam splitter 16 passes through the beam splitter 16 and enters the lens 17. The illumination light incident on the lens 17 is refracted and enters the objective lens 18. The illumination light incident on the objective lens 18 is condensed to a spot diameter corresponding to the NA and enters the sample 19. Thereby, the sample 19 can be illuminated. At this time, illumination from the observation light source 30 is performed in a state in which the objective lens 18 is focused on the surface of the sample 10 by an autofocus optical system described later. Of the illumination light incident on the sample 19, the reflected light reflected by the sample is refracted by the objective lens 18 and the lens 17 and enters the beam splitter 16.

  A part of the reflected light incident on the beam splitter 16 enters the photodetector 22. The photodetector is a two-dimensional photodetector in which light receiving elements are provided in an array. Therefore, each of the light receiving elements provided in an array on the photodetector 22 is a pixel for detecting light. As the photodetector 22, for example, a CCD camera can be used. The photodetector 22 is arranged so that the reflected light reflected by the sample forms an image on its light receiving surface. Therefore, the sample 19 can be imaged by the photodetector 22. The photodetector 22 outputs a signal based on the detected luminance of the light to the processing device 21. The processing device 21 is a normal personal computer or the like, and includes a central processing unit (CPU) that performs predetermined processing and a storage device such as a memory and a hard disk that stores processing results and signal waveforms. Reference numeral 21 includes a display device for displaying the detection result of the light detector 22 on the screen and an input device for executing predetermined processing such as a mouse and a keyboard. Observation is performed by displaying an image of the sample 19 picked up by the photodetector 22 on the display device. The processing device 21 further includes an autofocus servo circuit in order to realize an autofocus function described later. The autofocus servo circuit can adjust the focus by moving the stage 20 in the Z direction according to the output from the photodetector 22. This will be described later. In addition, the processing apparatus 21 does not need to be a physically single processing apparatus, and may be comprised from several apparatus.

  The stage 20 on which the sample 19 is placed is an XYZ stage and is driven in the X, Y, and Z directions based on the output signal of the processing device 21. Thereby, the illumination light from the observation light source 30 can be incident on an arbitrary position of the sample 19. That is, the entire sample 19 can be observed by driving the stage 20 and moving the sample 19 in the XY directions. Further, the distance between the objective lens 18 and the sample 19 can be changed by moving in the Z direction. Therefore, focusing can be performed. Note that the optical axis of the illumination light from the bundle fiber 31 coincides with the centers of the objective lens 18, the lens 17, and the lens 15. That is, the optical axis of the observation optical system coincides with the centers of the objective lens 18, the lens 17, and the lens 15.

  Next, the autofocus optical system will be described. The optical microscope 1 of the present invention constitutes an optical lever type autofocus optical system. The autofocus optical system includes a light source 11, a lens 12, a cylindrical lens 13, a beam splitter 14, a lens 15, a beam splitter 16, a lens 17, an objective lens 18, and a photodetector 22. A common detector is used for the observation optical system and the autofocus optical system. Therefore, only one detector is provided in the optical microscope with an autofocus function. Here, the surface of the sample 19 is focused by the autofocus function.

  The light source 11 is a point light source such as a laser diode, and is arranged with a deviation from the optical axis of the observation optical system. That is, in the optical microscope 1, the optical axis of the light source 11 does not coincide with the optical axis of the illumination light from the bundle fiber 31. The light beam emitted from the light source 11 enters the lens 12. The lens 12 collimates the light from the light source 11 and adjusts the beam from the light source 11 to a predetermined beam diameter. The light beam emitted from the lens 12 is a parallel light beam in both the XY directions. Then, the light beam having a predetermined beam diameter is converted into line-shaped light by the cylindrical lens 13. That is, the light beam is refracted and emitted from the cylindrical lens 13 in the X direction and is emitted as it is in the Y direction. The line-shaped light beam is incident on the beam splitter 14. A pupil plane is a position where the light emitted from the cylindrical lens 13 between the beam splitter 14 and the cylindrical lens 13 is converged in the X direction. A part of the light beam incident on the beam splitter 14 passes through the beam splitter 14 and enters the lens 15.

  The lens 15 refracts the light beam and emits it in the direction of the beam splitter 16. Here, the light beam is made parallel in the X direction by the lens 15 and condensed in the Y direction. A part of the light beam incident on the beam splitter 16 passes through the beam splitter 16 and enters the lens 17. The lens 17 refracts the incident light beam and emits it in the direction of the objective lens 18. Here, the light beam is condensed in the X direction by the lens 17 and becomes parallel in the Y direction. Therefore, at the pupil position A between the lens 17 and the objective lens 18, the incident light from the light source 11 is focused in the X direction and parallel in the Y direction. The light beam incident on the objective lens 18 is refracted and enters the sample 19. The light beam is irradiated as line-shaped light along the X direction on the surface of the sample 19.

  Here, the optical axis of the light source 11 is deviated from the optical axis of the illumination light. Therefore, the optical axis of the light beam from the light source 11 coincides with the centers of the lens 12 and the cylindrical lens 13, but deviates from the centers of the lens 15, the lens 17, and the objective lens 18. The light beam from the light source 11 passes through a region on one side half of the lens 15, the lens 17 and the objective lens 18. Specifically, in FIG. 1B, the light beam from the light source passes through the right side of the lens 15, the left side of the lens 17, and the left side of the objective lens 18. In this way, in order to realize the optical lever type autofocus function, the light source 11 is arranged so as to be shifted from the center of the lens 12 so that the light beam is incident on one half of the pupil of the objective lens 18.

  The light beam incident on one half of the pupil of the objective lens 18 is reflected by the sample 19. Then, the light beam specularly reflected by the sample 19 is incident on a half region on the opposite side of the pupil of the objective lens 18. That is, the light beam incident on the objective lens 18 from the light source 11 and the reflected light regularly reflected by the sample 19 pass through different regions with the center line of the objective lens 18 as a boundary. Specifically, in FIG. 1B, the light beam incident on the objective lens 18 from the light source 11 is in the left half area of the objective lens 18, and the reflected light reflected by the sample 19 is in the right half area of the objective lens 18. Pass through. Here, when the distance between the sample 19 and the objective lens 18 changes, the position where the light beam is incident on the surface of the sample 19 changes. Therefore, the position where the reflected light is incident on the objective lens 18 changes. Based on this change in position, focusing can be performed.

  The reflected light that has passed through the right half of the objective lens 18 passes through the right half of the lens 17 and enters the beam splitter 16. The beam splitter 16 reflects a part of the incident reflected light toward the photodetector 22. The reflected light is lined on the light receiving surface of the photodetector 22. Since the photodetector 22 includes light receiving elements arranged in an array, this line-shaped light is detected in a partial region of the light receiving surface of the photodetector 22.

  Next, incident light and reflected light at the pupil position A will be described with reference to FIG. FIG. 2 is a diagram schematically showing the cross-sectional shape of the light beam at the position A of the pupil. In FIG. 2, incident light that enters the sample 19 from the light source 11 and reflected light that is specularly reflected by the sample 19 are projected. In FIG. 2, reference numeral 50 denotes the field of view at the position A of the pupil. In FIG. 2, the left half region of the visual field 50 at the pupil position A is defined as a first region 50a, and the right half region is defined as a second region 50b.

  Line-shaped incident light 51 along the Y direction enters the first region 50a. Here, the line-shaped incident light 51 has a spot in a direction perpendicular to a boundary line (a dotted line in FIG. 2) between the first region 50a and the second region 50b. That is, the line-shaped incident light 51 is perpendicular to the boundary line (dotted line in FIG. 2). When the incident light 51 enters the sample 22, it is regularly reflected on the sample surface. The specularly reflected light 52 is incident on a position symmetrical to the incident light 51 and the center point of the field of view. Therefore, the reflected light 52 specularly reflected on the sample surface is reflected only in the direction of the second region 50b. Therefore, the reflected light 52 does not enter the first region 50a but enters only the second region 50b at a normal location. Here, the reflected light 52 is a linear light beam along the Y direction as in the case of the incident light. The reflected light 52 incident on the second region 50 b is refracted and enters the beam splitter 16. Then, it is reflected by the beam splitter 16 and enters the photodetector 22. When the distance between the objective lens 18 and the sample 19 changes, the position of the reflected light 52 is displaced in the direction of the arrow (Y direction) shown in FIG. 2 according to the change in the distance.

  Next, the reflected light at the position B of the light receiving surface of the photodetector 22 will be described with reference to FIG. FIG. 3 is a diagram schematically showing the shape of the light beam on the light receiving surface of the photodetector 22. As shown in FIG. 3, a linear light beam 40 is incident on the light receiving surface 22a. The position of the line-shaped light beam 40 changes in the direction of the arrow in FIG. 3 according to the distance between the objective lens 18 and the sample 19. For example, the position of the light beam on the light receiving surface 22a moves to the right in FIG. 3 when the distance between the objective lens 18 and the sample 19 is away from the in-focus position, and to the left when the distance between the objective lens 18 and the sample 19 approaches. Move in the direction.

  Here, the position of the light beam on the light receiving surface 22a at the in-focus position is stored in the processing device 21. When the position of the actually detected light beam deviates from this position, feedback control is performed so that the focus position is reached. That is, the processing device 21 drives the stage 20 based on the signal from the photodetector 22 and moves the sample 19 in the Z direction. As a result, the distance between the objective lens 18 and the sample 19 changes and becomes the focal position. Of course, instead of the sample 19, the objective lens 18 may be moved by an actuator or the like.

  For example, when in the in-focus position, the light beam from the light source 11 is condensed at the position of the optical axis of the observation light source 30 in the Y direction as shown in FIG. However, when the objective lens 18 and the sample 19 are located away from the in-focus position, the light beam from the light source 11 is shifted to the right from the position of the optical axis of the observation light source 30 and enters the sample 19. On the other hand, when the objective lens 18 and the sample 19 are close to the in-focus position, the light beam from the light source 11 is shifted to the left from the position of the optical axis of the observation light source 30 and enters the sample 19. In this way, the light beam incident at different positions on the sample 19 propagates through the autofocus optical system through an optical path different from the optical path of the light beam at the in-focus position. Therefore, the reflected light incident on the light receiving surface 22a of the photodetector 22 is incident on different positions according to the deviation from the in-focus position. By detecting the positional deviation of the light beam 40 on the light receiving surface 22a by the photodetector 22, the deviation from the in-focus position can be obtained. Then, the stage 20 is driven in the Z direction so that the light beam is at a predetermined position on the light receiving surface 22a. Thereby, the focal position can be adjusted.

  Here, the position of the light beam on the light receiving surface can be determined by, for example, the peak position or the center of gravity position of the light beam. Specifically, the line-shaped light beam has a profile as shown in FIG. Of these, the peak pixel position may be the position of the light beam, or the center of gravity may be the position of the light beam. For example, it is assumed that the peak or the center of gravity of the light beam 40 on the light receiving surface 22a is at the position C as shown in FIG. The processing device 21 stores this position C. When the peak or the center of gravity of the light beam 40 on the light receiving surface 22a is deviated from the position C in the autofocus mode for performing autofocus, the height of the sample 19 and the objective lens 18 is changed so as to move to the position C. Let Then, feedback control is performed until the position of the light beam reaches position C. Thereby, it can move to a focus position.

  Thus, in the optical microscope 1 according to the present invention, the photodetectors of the autofocus optical system and the observation optical system are shared. Thereby, an optical microscope with an autofocus function can be realized with a simple configuration. In the above description, the cylindrical lens 13 is used to irradiate the sample 19 with a linear light beam, but the present invention is not limited to this. That is, the focal point may be adjusted by irradiating the sample with a spot-like light beam without using the cylindrical lens 13. In addition, since different light sources are used for the observation optical system and the autofocus optical system, it is possible to use a light source suitable for each.

  Further, the optical system may be arranged so that the sample 19 is irradiated with the light beam that has passed through the beam splitter 14 from the observation light source 30 and the sample 19 is irradiated with the light beam reflected by the beam splitter 14 from the light source 11. . That is, in FIG. 1, by changing the arrangement of the light source 11, the lens 12, and the cylindrical lens 13 and the arrangement of the observation light source 30 and the bundle fiber 31, the light emitted from the bundle fiber 31 passes through the beam splitter 14 and passes through the sample. The light emitted from the light source 11 is reflected by the beam splitter 14 and enters the sample. Usually, an optical microscope without an autofocus function has such a configuration. Therefore, an autofocus function can be added to an existing optical microscope only by adding few optical components such as the light source 11 and the beam splitter 14. As described above, in the present invention, the light from the observation light source 30 and the light source 11 is mixed by the beam splitter 14 and guided to the sample 19. That is, when both the observation light source 30 and the light source 11 are turned on, one light is transmitted through the beam splitter 14 and the other light is reflected by the beam splitter 14. Thereby, the light from the observation light source 30 and the light source 11 can be mixed.

Here, the reflectance and transmittance of the beam splitter 14 can be adjusted according to the luminance of the light from the light source 11. For example, when a high-intensity light source such as a laser diode is used as the light source 11, the proportion of light incident on the sample 19 among the light emitted from the light source 11 can be reduced. Therefore, the reflectance of the beam splitter 14 can be increased. That is, the amount of light from the light source 11 only needs to be detected by the photodetector 22 and can be automatically focused. Therefore, the reflectance and transmittance of the beam splitter 14 are set to appropriate values. Thereby, the utilization efficiency of the light from the observation light source 30 can be improved. For example, in the configuration shown in FIG. 1B, the transmittance of the beam splitter 14 can be 1% and the reflectance can be 99%. Therefore, the utilization efficiency of light from the observation light source 30 can be improved.
Thus, the ratio of the light guided to the sample 19 out of the light incident on the beam splitter 14 from the light source 11 is lower than the ratio of the light guided to the sample 19 out of the light incident on the beam splitter 14 from the observation light source 30. Thus, the transmittance and reflectance of the beam splitter 14 can be set. Thereby, illumination light can be utilized efficiently.

  In the present invention, in the observation mode for observing the sample, the power source of the light source 11 is turned off and only the light from the observation light source 30 is irradiated onto the sample. On the other hand, in the autofocus mode in which automatic focusing is performed, the light from the observation light source 30 is blocked and only the light from the light source 11 is irradiated onto the sample. That is, when switching from the autofocus mode to the observation mode, the operation of the light source 11 is electrically stopped, and then the sample 19 is microscopically observed by the observation light source 30. On the other hand, when switching from the observation mode to the autofocus mode, the light from the observation light source 30 is blocked, and then the light source 11 is turned on to focus. In the optical microscope according to the present invention, the mode can be switched by switching on / off the power sources of the light source 11 and the observation light source 30. Therefore, it is possible to switch from the autofocus mode to the observation mode without causing mechanical vibration. Thereby, it can prevent shifting from a focus position at the time of observation. Switching between observing and irradiating light from the observation light source 30 is not limited to electrical OFF of the observation light source 30, and a mechanical shutter may be used. Here, since the bundle fiber 31 is used, the observation light source 30 can be arranged at a position away from the objective lens 18 and the sample 19. Therefore, even if a shutter is provided between the observation light source 30 and the bundle fiber 31 and this shutter is mechanically moved, there is almost no influence on the distance between the objective lens 18 and the sample 19.

  The optical microscope 1 with an autofocus function according to the present invention is suitable when the coordinates to be observed next are known, such as a defect review station. This will be described. First, a defect inspection is performed on a sample, and a defect position on the sample is specified. Note that the defect position on the sample 19 may be specified by another inspection apparatus. In this case, inspection is performed with another inspection apparatus, the defect position is specified, and the sample is placed on the stage 20 of the optical microscope 1. Then, the stage 19 is driven to move the sample 19 to the defect position to be observed. While the sample 19 is moving, autofocus feedback control is continuously executed. Thereby, when the sample 19 moves to the defect position, it becomes the in-focus position. When the movement is completed, the light source 11 is turned off and the observation light source 30 is illuminated. This is repeated when the next defect position is observed. Thereby, it is substantially unnecessary to provide time for focusing. Therefore, when the movement is completed, observation can be performed immediately. Therefore, the substantial processing speed of the apparatus can be improved.

  In the optical microscope 1 shown in FIG. 1, a cylindrical lens 13 is used to illuminate the sample with line-shaped light in order to focus more accurately. For example, when the sample 19 is a pattern substrate, the reflectance differs between a portion with a pattern and a portion without a pattern. That is, regions having different reflectivities are formed on the pattern substrate. For example, in the case where a metal pattern is formed on a glass substrate, the reflectance is high at a location where the metal pattern is formed. On the other hand, the reflectivity is low at locations where the metal pattern is not formed and the glass is exposed. Therefore, when light is applied to the edge of the pattern, the intensity distribution of the reflected light is affected by the pattern. Therefore, the center of gravity of the light beam is shifted toward the light receiving surface 22a with higher reflectivity. Therefore, when autofocus is executed based on this position, the position of the sample 19 converges to a position that is shifted from the focal position.

  In order to avoid this, the sample 19 is irradiated with a linear light beam inclined with respect to the pattern of the sample 19. For example, consider the case where the metal pattern 61 is provided in three directions, that is, a direction perpendicular to each other and a direction therebetween as shown in FIG. In this case, it is assumed that the direction of the line-shaped light beam 62 is tilted from any of these directions. That is, the direction of the linear light beam 62 and the direction in which the metal pattern 61 is provided are not matched. Thereby, focusing can be performed accurately. When there is a pattern direction at a specific angle of the substrate like a pattern substrate used in a liquid crystal display, the direction of the line-shaped light beam is set so as to avoid the direction. This setting can be easily performed by inserting a cylindrical lens 134 from the light source 11 to the emission side. In addition, when there are a plurality of directions in which the pattern is provided, the light beam is irradiated with being inclined from any direction.

  On the other hand, even when spot illumination is performed without using the cylindrical lens 13, when the sample is continuously moving, the light beam is not always illuminated on the edge of the specific pattern. That is, since the relative position of the spot-like light beam and the sample 19 is constantly changing, even if the light beam is irradiated on the pattern edge at a certain time, the light beam is Is irradiated to other than the pattern edge. Therefore, the effect of the pattern edge can be ignored by looking at the average (integrated) over a certain time. For this, an integrating detector that integrates and outputs the light received at a certain time, such as a CCD camera, may be used as the photodetector 22. If the stage is moved at a speed higher than a certain level in the autofocus mode, the pattern can be substantially unaffected. By using the autofocus mode only while the stage is moving, not only the processing speed is improved, but also the influence of the pattern can be reduced. At this time, it is preferable to move the sample 19 in a direction inclined with respect to the direction in which the pattern is provided. Further, by using such an integration type detector, even if the sample has irregularities based on the pattern, it is possible to focus on the average height.

  Thus, in the optical microscope 1 according to the present invention, the focal position can be adjusted with a simple configuration. Therefore, the sample can be observed accurately.

It is a figure which shows the structure of the optical microscope concerning this invention. In the optical microscope of this invention, it is a figure which shows typically the shape of the light beam in the position A of a pupil. It is a figure which shows typically the shape of the light beam in the light-receiving surface of a photodetector in the optical microscope concerning this invention. It is a figure which shows the shape of the light beam on a sample in the optical microscope concerning this invention.

Explanation of symbols

1 optical microscope, 11 light source, 12 lens, 13 cylindrical lens,
14 beam splitter, 15 lens, 16 beam splitter, 17 lens,
18 objective lens, 19 sample, 20 stage, 21 processing device, 22 photodetector 40 light beam, 50 field of view, 50a first region, 50b second region,
51 incident light, 52 reflected light, 61 metal pattern, 62 light beam

Claims (12)

A first light source that emits illumination light for observing the sample;
An objective lens that collects the light from the first light source and enters the sample;
A second light source that emits light that is incident on one half of the pupil of the objective lens;
A beam splitter that mixes the light of the first light source and the second light source and guides the light to the sample;
Of the light incident on the sample from the first light source through the objective lens, the first reflected light reflected by the sample and the region from one side half of the pupil of the objective lens from the second light source. A two-dimensional photodetector that detects the second reflected light that has been reflected by the sample out of the light incident on the sample and has passed through one half region opposite to the pupil of the objective lens;
The focus position is adjusted based on the second reflected light detected by the two-dimensional photodetector, and the sample is adjusted based on the first reflected light detected by the second-dimensional photodetector. Optical microscope to observe. Further comprising a drive stage for placing the sample and moving the placed sample;
While the sample is moved to a specific position by the driving stage, focusing is performed based on the second reflected light,
The optical microscope according to claim 1, wherein the sample is observed by the first reflected light detected by the two-dimensional photodetector after the sample moves to a specific position.   The ratio of the light guided to the sample out of the light incident on the beam splitter from the second light source is larger than the ratio of the light guided to the sample out of the light incident on the beam splitter from the first light source. The optical microscope according to claim 1, wherein a transmittance and a reflectance of the beam splitter are set so as to be low.   The optical microscope according to claim 3, wherein the second light source is a laser light source. A cylindrical lens that irradiates the sample with light from the second light source as line-shaped light;
The optical microscope according to claim 1, wherein the line-shaped light is irradiated with being inclined with respect to a pattern provided on the sample.   The optical microscope according to any one of claims 1 to 5, wherein the two-dimensional photodetector is an integrating photodetector that integrates received light for a predetermined time and outputs a signal. An automatic focusing method in an optical microscope in which light from a first light source is collected by an objective lens and irradiated onto a sample, and the first reflected light from the sample is detected by a two-dimensional photodetector. There,
Allowing light from a second light source to enter a region on one half of the pupil of the objective lens;
Making the light incident on one half of the pupil of the objective lens enter the sample; and
Making the second reflected light reflected by the sample out of the light from the second light source incident on the sample incident on one half-region on the opposite side of the pupil of the objective lens;
Detecting the second reflected light that has passed through one half of the opposite side of the pupil of the objective lens with the two-dimensional detector;
An autofocus method for performing focusing based on the second reflected light detected by the two-dimensional detector. The light from the second light source is made into line-shaped light and incident on the sample,
The autofocus method according to claim 7, wherein the line-shaped light is irradiated with being inclined with respect to a direction of a pattern provided on the sample. An observation method in which light from a first light source is collected by an objective lens and irradiated onto a sample, and reflected light from the sample is detected by a two-dimensional photodetector to perform observation.
Allowing light from a second light source to enter a region on one half of the pupil of the objective lens;
Making the light incident on one half of the pupil of the objective lens enter the sample; and
Of the light from the second light source incident on the sample, the light reflected by the sample is incident on a half region on the opposite side of the pupil of the objective lens;
Detecting the second reflected light that has passed through one half of the opposite side of the pupil of the objective lens with the two-dimensional detector;
Focusing by changing the distance between the sample and the objective lens based on the light detected by the two-dimensional detector;
Stopping the operation of the second light source in a state where the automatic focusing is performed;
Illuminating the sample with the first light source;
Observing the sample by detecting the reflected light reflected by the sample with the two-dimensional photodetector. Focusing is performed based on the second reflected light detected by the two-dimensional photodetector while moving the relative position of the sample and the light incident on the sample from the second light source. The observation method according to claim 9, wherein the movement of the second light source is stopped, the operation of the second light source is stopped, and the first reflected light is detected by the two-dimensional photodetector. The sample is a sample in which a defect position is specified,
In the step of performing focusing, focusing is performed while moving the relative position so that light from the second light source is irradiated to the defect position,
The observation method according to claim 10, wherein in the step of performing the observation, the defect position is observed. The sample is a pattern substrate in which a pattern is formed on the substrate,
The light from the second light source is made into line-shaped light and incident on the sample,
The observation method according to claim 9, wherein the sample is irradiated with the line-shaped light inclined with respect to a direction in which the pattern is provided.

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