JP2008046362A - Optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device capable of rapidly switching an image obtained by an optical system to a confocal image and a transmitted image. <P>SOLUTION: The optical device 1 includes: an illuminating light source 21 to emit illuminating light; the optical system 3 to radiate the illuminating light to a specimen so as to obtain an image by reflected light from the specimen; a disk 40 provided on the optical path of the optical system and rotated on a plane orthogonal to an optical axis; and a switching controller 50. A pinhole area where the illuminating light is transmitted through a confocal pinhole and a transmission area where the illuminating light is transmitted as it is are formed to be divided in an angle direction on the disk 40. The switching controller 50 switches a mode to a transmission mode in which the transmitted image is obtained by transmitting the reflected light through the transmission area, and a confocal mode in which the confocal image is obtained through the confocal pinhole formed in the pinhole area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical apparatus for observing an image obtained by an optical system by switching between a confocal image through a confocal microscopic aperture and a bright field image not through the confocal microscopic aperture.

  As described above, as an optical apparatus for switching and observing an image obtained by an optical system, for example, a confocal microscope or an area height for inspecting surface properties of a semiconductor wafer substrate, an integrated device (IC), a liquid crystal display panel, or the like. There are inspection devices such as measuring machines. In these inspection devices, the bright field image is such that the target part of the object to be examined is searched for in the bright field image without using the confocal pinhole, and the height is measured with high accuracy by using the confocal image through the confocal pinhole. / Generally, the confocal image observation mode is switched. The switching of the observation mode is realized by a configuration in which a pinhole disc (also referred to as a “Nippou disc”) in which a confocal pinhole is formed is inserted into or extracted from the optical path, or a configuration in which a mirror that switches the optical path is inserted or extracted (for example, (See Patent Document 1).

JP 2005-337935 A

  However, since optical parts such as a pinhole disk and an optical path switching mirror have a certain degree of inertia, it takes time to move and position, resulting in a problem that the observation mode switching time becomes long. In addition, these methods have problems in terms of reproducibility and measurement accuracy because the pinhole disk and mirror are moved with respect to the optical axis.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical device capable of quickly switching an image obtained by an optical system between a confocal image and a bright field image. .

  In order to achieve the above object, an invention according to claim 1 is directed to an illumination light source that emits illumination light, an optical system that irradiates the object with illumination light and obtains an image by reflected light from the object, A disk provided in the optical path and rotated in a plane orthogonal to the optical axis, the disk having a micro aperture area that transmits the illumination light through the confocal micro aperture and a transmission area that transmits the illumination light uniformly. Are divided in the angular direction, and the reflected light is transmitted through the transmission region to obtain a bright field image, and the reflected light is transmitted through the confocal micro aperture formed in the micro aperture region. Thus, an optical device is configured with a switching control device that switches to a confocal mode for obtaining a confocal image.

  According to a second aspect of the present invention, in the optical device of the first aspect, the switching control device is configured to control the irradiation timing of the illumination light irradiated to the disk.

  According to a third aspect of the present invention, in the optical device of the first aspect, the illumination light source is a light emitting element, and the switching control device is configured to control the light emission timing of the light emitting element.

  According to the present invention, it is possible to provide an optical device that can quickly switch an image obtained by an optical system between a confocal image and a bright field image.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. As an example of an optical apparatus to which the present invention is applied, FIG. 1 shows a schematic configuration of an inspection apparatus 1 that observes the fine shape of the surface of an object. First, the configuration of the inspection apparatus 1 will be described.

  The inspection device 1 is positioned below the lens barrel unit 12, a base unit 11 serving as a base, a lens barrel unit 12 attached to the base unit 11 so as to be movable in the vertical direction (Z-axis direction). The stage 11 is attached to the base 11 and can move the table in two orthogonal directions (X-axis and Y-axis directions) in a horizontal plane, and the control device 5 that controls the operation of each part of the inspection apparatus 1. A linear scale 15 for detecting the height position of the lens barrel portion 12 in the Z-axis direction with respect to the base portion 11 is attached between the lens barrel portion 12 and the lens barrel portion 12. The base unit 11 is provided with a mode selector 16 that selects an observation mode.

  An illumination optical system 2 that emits illumination light inside the lens barrel 12, and a confocal optical system 3 that irradiates the test object 8 with illumination light and obtains an image of the test object 8 by reflected light from the test object 8. In addition, a disk unit 4 or the like that is provided on a surface including one confocal point in the optical path of the confocal optical system 3 and rotates the disk 40 is provided.

  The illumination optical system 2 includes a condenser lens 22 and an illumination light source 21 on an optical axis that is located on the side of the confocal optical system 3 and extends laterally from the first half mirror 23. As the illumination light source 21, for example, a light emitting element capable of ON / OFF control of illumination light at a relatively high speed, such as a white or monochromatic light emitting diode (LED) or a laser diode (LD), is used. The light emission operation is controlled by the switching control unit 50 described below.

  The confocal optical system 3 is arranged on the optical axis extending upward from the test object 8, and the objective lens 32, the disk 40, the first half mirror 23, the imaging lens 33, the second half mirror 34, and the image sensor 35. And an eyepiece 38 on an optical axis extending laterally from the second half mirror 34. For example, a two-dimensional photoelectric element such as a CCD or a CMOS can be used as the imaging element 35 and is disposed on the image plane of the imaging lens 33. The test object 8 is placed on the stage 13, and the observation target region is introduced into the field of view by moving the stage 13 in the XY direction. The light beam emitted from the illumination light source 21 illuminates a range conjugate with the visual field range on the disk 40 via the condenser lens 22 and the first half mirror 23 (Keller illumination).

  The disk unit 4 includes a thin disk-shaped disk 40, a motor 45 having a motor shaft fixed to the center of the disk 40, a motor 45 that rotates the disk 40, and a rotation angle position of the motor shaft. The encoder 46 is configured to detect an angular position. The rotational angle position of the disk 40 may be directly detected by a photo interrupter or the like. The disk 40 is arranged orthogonal to the optical axis of the confocal optical system 3 so as to block the illumination light reflected by the first half mirror 23.

  Here, the disk 40 is basically a light-shielding disk surface that has been subjected to antireflection treatment, and a plurality of rows of light-transmitting confocal pinholes having a diameter that meets the conditions for obtaining the confocal effect. It is a disk having the same function as a pinhole disk called a “Nipknow-Disk” formed in a spiral. However, this disk 40 does not form a confocal pinhole on the entire disk surface like a conventional pinhole disk, but a pinhole region in which a confocal pinhole is formed on a light-shielding thin film, and a light-shielding film. A transmission region that transmits light as it is without forming a thin film is formed by being divided in the angular direction. The pinhole is not limited to a circle but may be an ellipse.

  FIGS. 2A and 2B are configuration examples illustrating the configuration of the disk 40, both of which include a pinhole region 42 in which a light shielding film and a number of confocal pinholes are formed on the disk surface. A transmission region 43 that does not have a light shielding film and transmits light as it is is formed by being divided in the angular direction. The transmissive region 43 only needs to transmit light uniformly, and a transparent material can be disposed. Moreover, it is good also as a space which does not arrange | position any member in the transmissive area | region 43.

  Of these, the disc 40 (A) having the configuration shown in FIG. 2A is a configuration example in which the division of the pinhole region 42 and the transmission region 43 is angularly divided into straight lines extending in the radial direction from the center of the disc. is there. According to such a configuration, angle division can be simplified. On the other hand, the disc 40 (B) having the configuration shown in FIG. 2B is a configuration example in which the division of the pinhole region 42 and the transmission region 43 is angularly divided in a spiral manner according to the confocal pinhole formation pattern. It is. Since this configuration divides the region along the array of confocal pinholes, it is possible to facilitate processing when generating a confocal image from image data captured by the image sensor 35. In any of the division forms, as the disk 40 rotates, the pinhole region 42 and the transmission region 43 are obtained at a constant ratio according to the division angle on the optical path of the confocal optical system 3, and are physically Significance is equivalent.

  An antireflection film is formed on the entire surface including the pinhole region 42 and the transmission region 43 on the upper surface of the disk 40 to suppress reflection on the upper surface of the disk and make it difficult for reflected light to reach the imaging lens 33. It has become. A polarizing beam splitter is used in place of the first half mirror 23, and a 1 / 4λ plate is provided in the optical path between the disk 40 and the test object 8, and the reflected light from the upper surface of the disk is reflected by the polarizing beam splitter. It may be configured as described above.

  The disk 40 is rotationally driven by a motor 45. The rotational speed of the motor 45 is such that the peripheral speed of the disk 40 on the optical path of the confocal optical system 3 is sufficiently faster than the response of the human pupil observing through the eyepiece 38, and the rotation speed of the image sensor 35 is shared. The rotation speed is set so as not to cause unevenness in the field of view of the focus pinhole. An aperture stop (not shown) having the same shape as that of the transmission region 43 is fixed in the vicinity of the disk 40, and the aperture stop does not move even when the disk rotates.

  Here, when the pinhole region 42 is located on the optical path of the confocal optical system 3, the confocal light out of the illumination light irradiated from the illumination light source 21 through the condenser lens 22 and the first half mirror 23 to the disk 40. The light that has passed through the pinhole is condensed and irradiated as an image of a confocal pinhole onto the test object 8 placed on the stage 13 via the objective lens 32.

  The confocal pinhole image focused and irradiated on the test object 8 is reflected by the surface of the test object 8 (hereinafter referred to as “object plane O”) and is incident on the objective lens 32 again. An image of the test object 8 is formed on the lower surface of the disk 40 by being condensed by the beam 32. At this time, when the object plane O is at the height position of the focal plane of the objective lens 32, the reflected light forms an image on the lower surface of the disk and almost all of the reflected light passes through the confocal pinhole. When O is not at the height of the focal plane of the objective lens 32, the reflected light does not form an image on the lower surface of the disk, and hardly passes through the confocal pinhole.

  Since the disk 40 is rotated by the motor 45, the illumination light that has passed through each confocal pinhole scans the surface of the test object 8 as spot light. Only the reflected light at the part where the object plane coincides with the object plane passes through the confocal pinhole and goes to the first half mirror. The reflected light that has passed through the confocal pinhole in the pinhole region 42 is hereinafter referred to as “passed light” for convenience.

  The passing light that has passed through the confocal pinhole reaches the image sensor 35 via the first half mirror 23, the imaging lens 33, and the second half mirror 34, and the pupil passes through the eyepiece 38 from the second half mirror 34. To obtain an image of the test object 8, that is, a confocal image.

  On the other hand, when the transmission region 43 is located on the optical path, the illumination light irradiated on the disk 40 passes through the transmission region 43 and is collected by the objective lens 32 and is applied to the test object 8 placed on the stage 13. Irradiated. The reflected light reflected by the test object 8 is collected by the objective lens 32 and forms an image of the test object 8 on the lower surface of the disk 40. At this time, the object plane O may or may not be at the height of the focal plane of the objective lens 32. However, since no confocal pinhole is formed in the transmission region 43, the entire reflected light is The light passes through the transmission region and travels toward the first half mirror 23. The reflected light transmitted through the transmission region 43 in this way is referred to as “transmitted light” in contrast to the “passed light”.

  The transmitted light that has passed through the transmission region 43 reaches the image sensor 35 via the first half mirror 23, the imaging lens 33, and the second half mirror 34, and reaches the pupil from the second half mirror 34 via the eyepiece 38. The images of the test object 8 are obtained respectively. The image obtained by the transmitted light in this way is hereinafter referred to as a “bright field image” for convenience.

  The switching control device 50 provided in the control device 5 combines the image obtained in the confocal optical system 3 with a transmission mode (BF) for obtaining a bright field image according to the observation mode selected in the mode selector 16. This is a control device for switching to a confocal mode (CF) for obtaining a focus image.

  FIG. 3 is a block diagram showing the configuration of the switching control device 50, and controls the operation of the area determination unit 52 that determines the area of the disk 40 located on the optical path of the confocal optical system 3 and the illumination optical system 2. It is comprised from the illumination control part 55. FIG. A signal of the rotational angle position of the disk 40 is input from the encoder 46 to the switching control device 50, and the region determination unit 52 is positioned on the optical path of the confocal optical system 3 from the input rotational angle position signal. It is determined whether the area is the pinhole area 42 or the transmission area 43.

  The switching control device 50 receives an observation mode selection signal from the mode selector 16 that switches the observation mode. The switching control device 50 receives the selection signal input from the mode selector 16 in the confocal optical system 3. The operation of the illumination light source 21 is controlled so that the obtained image becomes an image of the selected observation mode.

  For example, when the transmission mode BF is selected in the mode selector 16 and the selection signal is input, the region determination unit 52 determines that the transmission region 43 is confocal from the rotation angle position signal input from the encoder 46. An illumination command signal is output to the illumination control unit 55 only during an angle range on the optical path of the optical system 3. The illumination controller 55 supplies power to the illumination light source 21 to emit illumination light when an illumination command signal is input. That is, the illumination light is emitted from the illumination light source 21 and applied to the disk 40 only while the transmission region 43 is on the optical path of the confocal optical system 3. The disk 40 is rotated by a motor 45, and the light emission of the illumination light source 21 is synchronously controlled in accordance with the timing when the transmission region 43 passes on the optical path of the confocal optical system 3. Therefore, in the transmission mode BF, only the bright field image is intermittently obtained in the confocal optical system 3.

  On the other hand, when the confocal mode CF is selected in the mode selector 16 and the selection signal is input, the area determination unit 52 determines the pinhole area 42 from the rotation angle position signal input from the encoder 46. Outputs an illumination command signal to the illumination controller 55 only during an angular range on the optical path of the confocal optical system 3, and the illumination controller 55 supplies power to the illumination light source 21 when the illumination command signal is input. Supply and emit illumination light. That is, illumination light is emitted from the illumination light source 21 and irradiated onto the disk 40 only while the pinhole region 43 is on the optical path of the confocal optical system 3, and the optical path of the confocal optical system 3 is pinned by the rotation of the disk 40. The light emission of the illumination light source 21 is synchronously controlled in accordance with the timing when the hole area 43 passes. Therefore, only the confocal image is intermittently obtained in the confocal optical system 3 in the confocal mode CF.

  Here, as described above, the rotational speed of the motor 45 is such that the peripheral speed of the disk 40 on the optical path is faster than the accumulation time of the image sensor 35 and the response speed of the human pupil, and the blinking speed of the illumination light source 21 is the same. Is fast. For this reason, the image recognized by the image sensor 35 or the human pupil is not an intermittent image that repeatedly blinks but an image illuminated by a certain amount, and is a bright field image or a confocal image corresponding to the mode selected by the mode selector 16. .

  Therefore, a bright field image or a confocal image can be obtained by the confocal optical system 3 by switching the observation mode according to the purpose. In the confocal mode CF, the lens barrel portion 12 is moved up and down relative to the base portion 11 to move the focal position of the confocal optical system 3 with respect to the test object 8, and image data ( By processing the height information, the height and three-dimensional shape of each part of the test object 8 can be measured. In addition, about the process and measurement in such a confocal mode, since a well-known various method can be applied, description is abbreviate | omitted in this specification.

  Thus, according to the inspection apparatus 1, the image obtained in the confocal optical system 3 can be obtained by switching between the bright field image and the confocal image. Then, the selection setting of the bright field image or the confocal image can be switched instantaneously because of the configuration for controlling the light emission timing of the illumination light source 21, and the rapid switching of the observation mode can be realized.

  Further, in the disk 40 in which the pinhole region 42 and the transmission region 43 are formed, time division is performed while rotating the transmission region 43 without stopping the transmission region 43 in the optical path of the confocal optical system 3 in order to obtain a bright field image. The speed of observation mode switching can be ensured by the acquired configuration. Further, since the transmissive region 43 moves across the optical path, the angular width of the transmissive region 43 can be made narrower than that of the visual field region, and the area of the pinhole region can be enlarged to improve the confocal image acquisition sensitivity. . In addition, since the transmissive region 43 moves, even if a flaw or a foreign substance adheres to a part of the transmissive region 43, the influence can be mitigated and the observation is not disabled.

  In the above, a light emitting element capable of ON / OFF control at high speed, such as a light emitting diode or a laser diode, is used as the illumination light source 21, and the rotation angle position of the disk 40 in the switching control device 50 (illumination control unit 55). The embodiment configured to control the light emission timing of the illumination light source 21 according to the above is illustrated. However, the present invention only needs to be able to control the irradiation timing of the illumination light applied to the disk 40. For example, a shutter that opens and closes an optical path in the illumination optical system 2 between the light source 21 and the first half mirror 23, For example, a liquid crystal shutter, an optical path switching shutter using an acousto-optic modulator (AOM), an electrical engineering modulator (EOM), or the like is provided, and this shutter is controlled by the illumination control unit 55 according to the rotational angle position of the disk 40. You may comprise as follows. According to such a configuration, a continuous light source with high brightness such as a halogen lamp or a metal halide lamp can be used, and an inspection apparatus that obtains a clear image at high speed can be obtained.

It is a schematic block diagram of the test | inspection apparatus shown as an example of the optical apparatus of this invention. It is explanatory drawing which illustrates the structure form of the disk used for the said test | inspection apparatus. It is a block diagram of the switching control device in the inspection device.

Explanation of symbols

1 Inspection device (optical device) 3 Confocal optical system (optical system)
8 Test object 40 Disc 42 Pinhole area 43 Transmission area 50 Switching control device

Claims (3)

An illumination light source that emits illumination light;
An optical system that irradiates the object with the illumination light and obtains an image by reflected light from the object;
A disk provided in the optical path of the optical system and rotated in a plane perpendicular to the optical axis,
The disk is formed by dividing a minute aperture region that transmits the illumination light through the confocal minute aperture and a transmission region that uniformly transmits the illumination light in the angular direction,
A transmission mode in which the reflected light is transmitted through the transmission region to obtain a bright-field image, and a confocal image in which the reflected light is transmitted through the confocal micro aperture formed in the micro aperture region. An optical apparatus comprising a switching control device for switching to a focus mode.   The optical device according to claim 1, wherein the switching control device is configured to control an irradiation timing of the illumination light applied to the disk.   The optical apparatus according to claim 1, wherein the illumination light source is a solid light emitting element, and the switching control device is configured to control a light emission timing of the light emitting diode.

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