JP2009250911A - Optical measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical measuring device, capable of measuring defects and distortions in the inside of a measuring object, such as, a sapphire ingot using a single device. <P>SOLUTION: The device comprises a scatterer observation part, including a single CCD camera 10, a laser light source 1, and a monochromatic light source 5 to observe a scatterer present within a measuring object 8, by having the measurement object irradiated with a laser light from the laser light source; and a distortion observation part for observing distortions present in the measuring object by irradiating the measuring object, with a monochromatic light from a monochromatic light source. A half-wave plate 2, a first galvano mirror 3 and a second galvano mirror 4 are disposed on the optical path between the laser light source and the measuring object, and a polarizer 6, the measuring object placed on a rotary table 7 and a displaceable optical analyzer 9 are disposed, in the order starting from the monochromatic light source side, on an optical path between the monochromatic light source and the CCD camera. Accordingly, the observation of scatterer resulting from a defect and observation of distortions within the measuring object can be performed in a short time, without the accompanying movement of the measurement object. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical measurement apparatus that optically measures defects and distortion inside a measurement object such as a sapphire crystal, and in particular, an improvement of an optical measurement apparatus that can measure defects and distortion inside the measurement object using a single apparatus. It is about.

  2. Description of the Related Art Conventionally, there are known scatterer observation methods and apparatuses for obtaining information on defects inside a measurement object by irradiating the measurement object with light such as laser light and obtaining the scattered light.

  An apparatus for observing such a defect is disclosed in Patent Document 1, for example. In this apparatus, light such as laser light is irradiated from the side surface of the object to be measured. Incident light is scattered by defects inside the object to be measured. This scattered light is observed with a video camera arranged at a position orthogonal to the optical axis of the incident light. Further, the focus of the video camera is focused on the upper or lower end surface of the object to be measured, and the stage on which the object is supported is moved in the vertical direction, thereby scanning the inside of the object to be measured at a predetermined distance interval. Each obtained image is stored in a video frame memory, and the three-dimensional distribution of defects inside the object to be measured can be known. Patent Document 2 discloses a measuring apparatus that uses laser light as a light source, scans with a two-dimensional galvanometer mirror, and captures the entire image of the object to be measured with a CCD camera in a short time.

  On the other hand, for example, a method disclosed in Patent Document 3 is known as a method of knowing the distortion inside the object to be measured. This method measures the two-dimensional distribution of birefringence induced in the object to be measured to detect strain inside the object to be measured. However, since monochromatic laser light is used as the light source, the range that can be known by one measurement is only the portion through which the laser light is transmitted. As a retardation measuring device based on this birefringence measurement, for example, an ABR series device is available from Uniopt (see Non-Patent Document 1).

Note that the present inventor has already proposed an internal strain observation apparatus in which the entire interior of the object to be measured is irradiated with light at the same time so that the strain distribution inside the object to be measured can be observed in a short time (Japanese Patent Application). 2007-277228).
JP-A 62-56400 JP 2007-192716 A JP-A-6-147986 UNIOPT catalog

  By the way, in the prior art, since a device capable of measuring the defect and distortion inside the object to be measured with a single device has not been developed yet, each dedicated measuring device is used to measure the defect and distortion inside the object to be measured. It was necessary to carry out using.

  For this reason, it is necessary to transfer an object to be measured to each measuring apparatus, and there is a problem that it takes time and effort for handling to measure the internal state.

  The present invention has been made paying attention to such problems, and the object of the present invention is to provide an optical measuring device capable of measuring defects and distortions inside the object to be measured with a single device. .

That is, the invention according to claim 1
In an optical measurement apparatus that irradiates light to the object to be measured and images the light emitted from the object to be measured with a CCD camera and observes the inside of the object to be measured.
A scatterer observing unit having a single CCD camera, a laser light source, and a monochromatic light source, irradiating the object to be measured with a laser beam from the laser light source and observing a scatterer existing in the object to be measured, and the monochromatic A distortion observation unit for irradiating the object to be measured with monochromatic light from the light source and observing the distortion existing in the object to be measured; and linearly polarized light on the optical path between the laser light source and the object to be measured. A half-wave plate whose direction is rotated, a first galvanometer mirror, and a second galvanometer mirror are arranged, and a laser beam transmitted through the half-wave plate at the time of scatterer observation is the first galvanometer mirror. Are reflected by the second galvanometer mirror and scanned two-dimensionally, and on the optical path between the monochromatic light source and the CCD camera from the monochromatic light source side, the polarizer is placed on the rotary stage. Measured object, displaceable analyzer When observing the scatterer, the analyzer waits at a position where it is out of the optical path, but when observing distortion, the analyzer is displaced and the analyzer is arranged on the optical path. The object to be measured is rotated on a rotary stage, and distortion at a position hidden in the isogyre in the conoscopic image is visualized.

The invention according to claim 2
In the optical measuring device according to the invention of claim 1,
The laser beam and monochromatic light emitted from the object to be measured are each photographed by a CCD camera disposed 90 degrees directly above the object to be measured,
The invention according to claim 3
In the optical measuring device according to the invention of claim 1 or 2,
The polarization of the laser beam applied to the object to be measured can be changed to horizontal polarization or vertical polarization by the half-wave plate.
The invention according to claim 4
In the optical measuring device according to the invention of claim 1, 2, or 3,
A laser beam and monochromatic light are irradiated in a state where the object to be measured is immersed in a refractive index matching liquid.

  According to the optical measurement apparatus of the present invention, the scatterer has a single CCD camera, a laser light source, and a monochromatic light source, and irradiates the object to be measured with the laser beam from the laser light source. The scatterer observation unit for observing the object and the distortion observation unit for irradiating the object to be measured with monochromatic light from the monochromatic light source and observing the distortion existing in the object to be measured. Thus, it is possible to observe the scatterer and the distortion in a short time without accompanying.

  Further, according to the optical measuring device of the present invention, the observing device waits at a position where the analyzer deviates from the optical path at the time of scatterer observation, and the laser beam transmitted through the half-wave plate is connected to the first galvanometer mirror and It is reflected by the two galvanometer mirrors and is two-dimensionally scanned. As a result, the entire object to be measured is irradiated, so that the scatterer distribution of the entire object to be measured can be measured.

  Furthermore, according to the optical measurement apparatus of the present invention, the analyzer is displaced and placed on the optical path during strain observation, and the object to be measured is rotated by rotating the rotary stage during strain observation. This allows you to visualize the distortion at the position hidden in the isogyre in the conoscopic image, so you can know the distribution of the distortion in the part that overlaps the isogyre, and the overall distortion distribution inside the object to be measured It becomes possible to observe in a short time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the optical measuring apparatus according to the present invention includes a laser light source 1 for a scatterer observation part, a monochromatic light source 5 for a distortion observation part, and scattered light and birefringent light generated from an object 8 to be measured. The measurement object 8 is placed on an automatic rotation stage 7.

  Further, as shown in FIG. 1, the laser light source 1 is disposed on the side surface of the object 8 to be measured, and linearly polarized light from the laser light source 1 side on the optical path between the laser light source 1 and the object 8 to be measured. A half-wave plate 2, a first galvanometer mirror 3, and a second galvanometer mirror 4 are arranged in order, and the laser light source is divided by one or two wavelengths when scatterers are observed. The plate 2, the first galvanometer mirror 3, the second galvanometer mirror 4, and the CCD camera 10 constitute a scatterer observing section of the object 8 to be measured.

  Further, as shown in FIG. 1, the monochromatic light source 5 is disposed below the object 8 to be measured, and on the optical path between the monochromatic light source 5 and the CCD camera 10, the polarizer 6 extends from the monochromatic light source 5 side. The object to be measured 8 placed on the automatic rotation stage 7 and the displaceable analyzer 9 are arranged in this order. When observing the distortion, these monochromatic light source 5, polarizer 6, automatic rotation stage 7, on the optical path The distortion observing portion of the object 8 to be measured is constituted by the analyzer 9 and the CCD camera 10 displaced in the above manner. Note that the object to be measured 8 is configured to be rotated by the automatic rotation stage 7 when observing the distortion.

  In the scatterer observation unit of the optical measurement apparatus according to the present invention, the laser beam emitted from the laser light source 1 is converted into p-polarized light or s-polarized light by the half-wave plate 2. In addition, the laser beam transmitted through the half-wave plate 2 and incident on the first galvanometer mirror 3 is scanned in the horizontal direction, and the laser beam incident on the second galvanometer mirror 4 is vertical in addition to the horizontal direction. Thus, the entire object to be measured 8 is randomly scanned by the laser beam.

  The first galvanometer mirror 3 and the second galvanometer mirror 4 can independently set the scanning frequency and the deflection angle of the laser beam by the control system. Further, when the scatterer is observed, the rotation of the automatic rotation stage 7 and the output of the monochromatic light source 5 are stopped.

  Then, the laser beam irradiated on the entire object to be measured 8 is emitted from the object to be measured 8 as scattered light by a scatterer inside the object to be measured 8, and the scattered light is photographed as a scattered image by the CCD camera 10. It becomes possible to know the scatterer distribution of the measurement object 8.

  Here, it is desirable that the laser beam emitted from the laser light source 1 is linearly polarized light. However, if it is not linearly polarized light, it may be converted into linearly polarized light by a polarizer. Then, by rotating the half-wave plate 2, it becomes possible to select p-polarized light and s-polarized light.

  By the way, when considering the polarization state of incident waves and scattered waves, the description method differs depending on the position of the observer, and hence the case where the electric field vector of the laser beam is horizontal with respect to the ground regardless of the position of the observer. This polarization state is called horizontal polarization, and the polarization state when the electric field vector of the laser beam is perpendicular to the ground is called vertical polarization.

  Then, when the scattered light when the horizontally polarized light is incident on an object to be measured such as single crystal sapphire is observed from directly above, it is possible to detect microbubbles existing in the object to be measured. In addition, when the scattered light when vertically polarized light is incident on the object to be measured is observed from directly above, it is possible to detect large bubbles present in the object to be measured and parts with large distortion due to edge dislocations. It becomes.

  Next, in the distortion observation unit of the optical measurement device according to the present invention, the monochromatic light emitted from the monochromatic light source 5 is converted into linearly polarized light by the polarizer 6 and is placed on the automatic rotation stage 7. The light passing through 8 and passing through the object 8 to be measured passes through the analyzer 9 displaced on the optical path and forms an image on the light receiving surface by the lens system of the CCD camera 10.

  In the distortion observation unit of the optical measurement apparatus according to the present invention, since the object to be measured 8 is rotated by the automatic rotation stage 7, the distortion at a position hidden in the isogyre in the conoscopic image is obtained. Is visualized and the distribution of distortion of the part that overlaps the isogyre can be known. Therefore, it is possible to observe the entire strain distribution inside the DUT 8 in a short time. Note that the output of the laser light source 1 is stopped during distortion observation.

  Here, the method for observing the conoscopic image is known as a method for measuring the birefringence of an anisotropic mineral in microscopic observation, and the observation method itself is known. The observation principle of conoscopic images is shown in FIG. In FIG. 3, it is assumed that the object to be measured is a uniaxial crystal and the c-axis is parallel to the horizontal direction in FIG. There is a change in the refractive index due to strain inside the object to be measured. In FIG. 3, the light from the monochromatic light source that has passed through the polarizer is separated into normal light and abnormal light inside the object to be measured.

If the refractive index of the c-axis is (ne), the refractive index in the plane perpendicular to the c-axis is (no), and the effective thickness of the object to be measured is d, the interference fringes appearing in the conoscopic image are
d · (no−ne) = k · λ (k = 0, 1, 2, 3,...)
It can be seen that this occurs when the following equation is satisfied. Note that λ is the wavelength of light, and the effective thickness d of the object to be measured is a function of the incident angle of light incident on the object to be measured.

  As described above, the optical measuring apparatus according to the present invention has a single CCD camera 10, the laser light source 1, and the monochromatic light source 5, and irradiates the measurement object 8 with the laser beam from the laser light source 1. A scatterer observing unit for observing a scatterer present in the object 8; and a distortion observing unit for observing distortion existing in the object 8 by irradiating the object 8 with monochromatic light from the monochromatic light source 5. Therefore, observation of the scatterer and observation of distortion can be performed in a short time without the movement of the DUT 8.

  Hereinafter, the present invention will be described specifically by way of examples.

  First, in the scatterer observation unit of the optical measurement apparatus according to the present invention shown in FIG. 1, the laser beam emitted from the laser light source 1 passes through the half-wave plate 2 and is horizontally or vertically polarized. The first galvanometer mirror 3 scans in the horizontal direction at a frequency of 200 Hz, and the second galvanometer mirror 4 scans in the vertical direction at a frequency of 200 Hz. Note that the distance between the second galvanometer mirror 4 and the DUT 5 is 1 m.

  Here, a sapphire ingot having a diameter of 3 inches and a length of 70 mm is considered as the DUT 8. The sapphire single crystal is used as a substrate when epitaxially growing GaN which is a material of a blue LED. The sapphire substrate is cut out from the ingot and processed into a wafer, but if there are scatterers or defects in the crystal, they remain as protrusions or pits on the surface of the wafer. Is known to be transferred as a GaN defect. Therefore, in order to epitaxially grow good quality GaN, it is indispensable to use a sapphire wafer having no defects on the surface as a substrate. Since the cylindrical surface of the sapphire ingot of the object to be measured 8 and the upper and lower end surfaces are lapped, the internal scattering cannot be observed even when the laser beam is irradiated. If the cylindrical surface and the upper and lower end surfaces are subjected to optical polishing, scattering inside the ingot can be observed. However, since sapphire has the second highest hardness after diamond, optical polishing requires much time and cost. In order to solve this problem, a sapphire ingot is used by being immersed in methylene iodide for refractive index matching. Since the refractive index of sapphire in the visible range is about 1.76 and the refractive index of methylene iodide is 1.74, it is possible to remove the contribution of scattering and reflection on the surface of sapphire.

  The laser light source used for scatterer observation desirably has a higher output in order to detect minute defects. In addition, since a wavelength in the visible range where the light receiving sensitivity of the CCD camera 10 for taking a scattered image is high is desirable, a red semiconductor laser having an output of 300 mW and a wavelength of 630 nm was used. Further, since it is necessary to scan the entire ingot with the laser beam, the exposure time is required to be 1/200 second or more of one scanning period. In order to detect minute scattering, it is necessary to set the exposure time longer.

  The galvano is set so that the horizontal amplitude of the first galvanometer mirror 3 is 80 mm and the vertical amplitude of the second galvanometer mirror 3 is 70 mm so that the laser beam scans the entire sapphire ingot (object 8). Adjusted the mirror control system.

  FIG. 2 shows a light scattering measurement image of the sapphire ingot measured using this optical measuring device (a measurement image by horizontal polarization incidence and vertical polarization incidence) and a side view photograph of the sapphire ingot, respectively. By changing the placement of the sapphire ingot, it becomes possible to identify the position of a large scatterer, and when processing into a wafer, it is possible to select a part with few defects, thus reducing costs and processing time. The place that contributes to

  Next, the strain distribution of the sapphire ingot is observed in the strain observation unit of the optical measurement apparatus according to the present invention. In the optical measuring apparatus shown in FIG. 1, the monochromatic light source 5 is a green monochromatic lamp (wavelength 587.6 nm) manufactured by Edmund Optics Japan, and the polarizer 6 and the analyzer 9 are manufactured by Edmond Optics Japan. The polarizing film and the automatic rotation stage 7 use URS150 made by Newport Japan, and the CCD camera 10 uses D70 made by Nikon.

  FIGS. 4 and 5 show conoscopic images taken by rotating the sapphire ingot approximately every 15 °, and FIG. 6 shows a conoscopic image of a high-quality sapphire ingot. In the photographic diagram of FIG. 6, a cross represented by a white straight line is called an isogyre. 4 and FIG. 5, it can be seen that the strained portion rotates as the sapphire ingot is rotated. Further, the place where the interference fringes are distorted represents the place where the refractive index is non-uniform, that is, the presence of distortion inside. When the sapphire ingot of the DUT 8 rotates, the degree of deformation of the isogyr appearing in the shape of a dark line cross corresponds to the internal strain distribution.

  In this way, by rotating the sapphire ingot of the object to be measured 8 with the automatic rotation stage 7, the strain distribution of the entire sapphire ingot can be observed.

  Then, by using the optical measuring device according to the present invention, it is possible to sort out high quality sapphire ingots in a short time and non-destructively.

  According to the optical measurement apparatus according to the present invention, since the scatterer observation unit for observing the scatterer existing in the object to be measured and the distortion observation unit for observing the distortion existing in the object to be measured, It is possible to observe the scatterer and observe the distortion in a short time without moving the object to be measured. Therefore, it has industrial applicability used for the method of evaluating the quality of sapphire crystals and the like.

BRIEF DESCRIPTION OF THE DRAWINGS Configuration explanatory drawing of the optical measuring device which concerns on this invention. The measurement photograph figure of the light scattering of the sapphire ingot measured by horizontal polarization incidence and vertical polarization incidence respectively using the optical measuring device concerning the present invention, and the side photograph figure of the above-mentioned sapphire ingot. Explanatory drawing which shows the observation principle of the conventional conoscopic image. A photograph of a conoscopic image taken by rotating a sapphire ingot that is an object to be measured. A photograph of a conoscopic image taken by rotating a sapphire ingot that is an object to be measured. A photo of a conoscopic image of a sapphire ingot of good quality.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 1/2 wavelength plate 3 1st galvanometer mirror 4 2nd galvanometer mirror 5 Monochromatic light source 6 Polarizer 7 Automatic rotation stage 8 Object to be measured 9 Analyzer 10 CCD camera

Claims (4)

In an optical measurement apparatus that irradiates light to the object to be measured and images the light emitted from the object to be measured with a CCD camera and observes the inside of the object to be measured.
A scatterer observing unit having a single CCD camera, a laser light source, and a monochromatic light source, irradiating the object to be measured with a laser beam from the laser light source and observing a scatterer existing in the object to be measured, and the monochromatic A distortion observation unit for irradiating the object to be measured with monochromatic light from the light source and observing the distortion existing in the object to be measured; and linearly polarized light on the optical path between the laser light source and the object to be measured. A half-wave plate whose direction is rotated, a first galvanometer mirror, and a second galvanometer mirror are arranged, and a laser beam transmitted through the half-wave plate at the time of scatterer observation is the first galvanometer mirror. Are reflected by the second galvanometer mirror and scanned two-dimensionally, and on the optical path between the monochromatic light source and the CCD camera from the monochromatic light source side, the polarizer is placed on the rotary stage. Measured object, displaceable analyzer When observing the scatterer, the analyzer stands by at a position off the optical path, but when observing the distortion, the analyzer is displaced and the analyzer is arranged on the optical path. An optical measurement apparatus characterized in that a distortion is visualized by rotating a measurement object on a rotary stage and hiding in an isogyre in a conoscopic image.   2. The laser beam and monochromatic light emitted from the object to be measured are respectively photographed by a CCD camera disposed 90 degrees directly above the object to be measured. Optical measuring device.   The optical system according to claim 1 or 2, wherein the polarization of the laser beam irradiated to the object to be measured can be changed to horizontal polarization or vertical polarization by the half-wave plate. measuring device.   4. The optical measurement apparatus according to claim 1, wherein the measurement object is irradiated with a laser beam and monochromatic light in a state where the measurement object is immersed in a refractive index matching liquid.

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