JP2012168303A - Microscope device - Google Patents

Abstract

To obtain an image by dark field illumination and bright field illumination independently and simultaneously, thereby shortening an inspection time and improving work efficiency.
An objective lens 41 includes an inner cylinder 41b that holds an optical system 41a that collects light from a sample 12, and a lens barrel 41c that surrounds an outer wall of the inner cylinder 41b and is concentrically provided. The illumination optical system 20 includes a polarizer 25 and a ring-shaped half-wave plate 27. The detection optical system 40 includes first and second analyzers 43 and 44, one of which satisfies a parallel Nicol condition with the polarizer 25 and the other of which satisfies a crossed Nicol condition with the polarizer 25. As an imaging device, the first imaging element 51 that images light from the sample 12 through the objective lens 41 and the first analyzer 43, and the objective lens 41 and second light from the sample 12 by dark field illumination. And a second image sensor 52 that images through the analyzer 44.
[Selection] Figure 1

Description

  The present invention relates to a microscope apparatus.

  In a post-process of semiconductor manufacturing, a microscope is frequently used in a process of inspecting the surface of a substrate such as a semiconductor wafer or a liquid crystal display panel substrate. In a microscope apparatus used for such inspection, the surface of the substrate (sample) is illuminated through an objective lens, and bright-field illumination observation is performed to receive the specularly reflected light. Dark field illumination observation in which light is scattered at a larger angle and receives scattered light from the substrate surface is used.

  Images obtained by bright-field illumination observation are suitable for observing the structure of the substrate, but are not suitable for inspection of defects such as minute defects and dust / scratches. Observation is used.

  Thus, bright field illumination observation and dark field illumination observation have their respective characteristics, and a microscope apparatus has been devised that realizes both illumination by switching between bright field illumination observation and dark field illumination observation (for example, patents). Reference 1).

JP 2009-1116030 A

  In this way, according to the observation method for switching between the bright field illumination observation and the dark field illumination observation, the illumination method is switched twice to obtain a bright field image and a dark field image at any one position of the sample. This operation is necessary.

  However, in recent years, the substrate size has been increased with the increase in size of liquid crystal televisions and the like. For example, a 10th generation liquid crystal blank called G10 has a substrate size of about 3 square meters. In this way, when the sample is enlarged and there are a plurality of positions to be observed on the sample, the observer moves the microscope (not the stage side as in the past) on the large stage on which the sample is placed, The above operation must be performed at each position on the sample, and there is a problem that inspection takes time and work efficiency is lowered.

  The present invention has been made in view of such problems, and by acquiring images by dark field illumination observation and bright field illumination observation independently and simultaneously, the inspection time can be shortened and work efficiency can be improved. An object of the present invention is to provide a microscope apparatus capable of performing

In order to achieve such an object, the present invention provides an illumination optical system that irradiates a sample with illumination light emitted from a light source, a detection optical system that collects light from the sample through an objective lens, and the detection optical system. In the microscope apparatus having an imaging device that captures an image of the sample collected by the system, the objective lens includes an inner cylinder that holds an optical system that collects light from the sample, and an outer wall of the inner cylinder And the illumination optical system includes a polarizer and a ring-shaped half-wave plate, and the polarizer and the half-wavelength. Of the illumination light through the plate, a bright field illumination optical path for condensing the central portion including the optical axis on the optical system held by the inner cylinder and irradiating the sample, and a peripheral portion of the inner cylinder Than the numerical aperture of the objective lens through between the outer wall and the lens barrel A dark field illumination optical path for irradiating the sample at a desired angle, and one of the detection optical systems satisfies a parallel Nicols condition with the polarizer, and the other satisfies a Nicols condition with the polarizer and an orthogonal Nicols condition. A first imaging element that has one analyzer and a second analyzer, and the imaging device images light from the sample by the bright field illumination via the objective lens and the first analyzer. And a second image sensor that images light from the sample by the dark field illumination via the objective lens and the second analyzer.

  In the present invention, the half-wave plate is preferably disposed in the dark field illumination optical path.

  In the present invention, it is preferable that the half-wave plate is disposed at or near the pupil position of the objective lens.

  In the present invention, the objective lens includes a plurality of objective lenses, a revolver capable of switching and arranging an arbitrary objective lens on the optical axis, and the half-wave plate common to each objective lens is provided in the revolver. It is preferable to be installed.

  In the present invention, it is preferable that the following conditional expressions are satisfied.

0.8 <h × β / D ≦ 1.0
However,
h: the length of the diagonal of the light source,
β: Light source magnification of the illumination optical system,
D: pupil diameter of the objective lens.

  In the present invention, it is preferable that the polarizer, the first analyzer, and the second analyzer are configured to be rotatable about the optical axis.

  In the present invention, the detection optical system includes a light splitting member that guides the light from the sample collected by the objective lens to the first analyzer and the second analyzer, It is preferable that the polarizer is configured to be rotatable about an optical axis, and the first analyzer and the second analyzer are unitized together with the light splitting member.

  In the present invention, the light splitting member may be a beam splitter.

  In the present invention, the light splitting member may be a half mirror.

  ADVANTAGE OF THE INVENTION According to this invention, the microscope apparatus which can shorten test | inspection time and can improve work efficiency can be provided by acquiring the image by dark field illumination observation and bright field illumination observation independently and simultaneously.

It is a schematic sectional drawing of the microscope apparatus which concerns on this embodiment. It is a schematic diagram of the half-wave plate concerning this embodiment. It is the figure which looked at the axial direction of each optical element (a polarizer, a quarter wavelength plate, a 1st analyzer, a 2nd analyzer) from the upper part of the microscope apparatus. It is the figure which represented typically the optical path and polarization state at the time of acquisition of a bright field image. It is the figure which represented typically the optical path and polarization state at the time of acquisition of a dark field image.

  Hereinafter, the present embodiment will be described with reference to the drawings. A microscope apparatus 1 shown in FIG. 1 is an illumination optical system that irradiates a sample 12 (for example, a substrate such as a semiconductor wafer or a liquid crystal display panel substrate) placed on a stage 11 with illumination light emitted from a light source 21. 20, a detection optical system 40 that collects light from the sample 12, and first and second imaging elements 51 and 52 that capture an image of the sample 12 collected by the detection optical system 40. Configured.

  The illumination optical system 20 is converted by a light source 21 (for example, a white LED or a halogen lamp) arranged in order along the optical axis, a collimator lens 22 that converts light from the light source 21 into parallel light, and a collimator lens 22. A relay lens 23 that forms an image of the collimated light, a field stop S, a field lens 24 that again converts light partially blocked by the relay lens 23 and the field stop S, a polarizer 25, 1 half mirror (which may be a beam splitter) 26 and an objective lens 41 including a ring-shaped half-wave plate 27 as shown in FIG.

  The optical axis of the polarizer 25 is set to a predetermined direction (see FIG. 3), and incident light (in this embodiment, non-polarized light from the field lens 24) has an orientation corresponding to the optical axis. Use linearly polarized light. The first half mirror 26 reflects the illumination light from the light source 21 via the polarizer 25 to form a light beam parallel to the optical axis of the objective lens 41, and guides it into the objective lens 41, thereby bright field illumination and dark field illumination. While realizing illumination, the light from the sample 12 through the objective lens 41 is transmitted. The ring-shaped half-wave plate 27 has an angle θ (θ = 45 ° in the present embodiment) formed by the incident linearly polarized light with respect to the optical axis of the wave plate (see FIG. 3). The original linearly polarized light is changed to linearly polarized light rotated about the optical axis by 2θ (in this embodiment, θ = 90 °).

  The objective lens 41 includes an inner cylinder 41b that holds an optical system 41a that collects light from the sample 12, and a lens barrel 41c that surrounds the outer wall of the inner cylinder 41b and is concentric with the inner cylinder 41b. A half-wave plate 27 is disposed on the light source 21 side of a space (a dark field illumination optical path 29 described later) formed between the outer wall of the inner cylinder 41b and the lens barrel 41c. At this time, it is preferable that the half-wave plate 27 is disposed so as to coincide with the pupil position of the objective lens 41 in the space or in the vicinity of the pupil position.

  In the present embodiment, a plurality of objective lenses 41 having different magnifications are mounted, and 1/1 common to each objective lens 41 is provided in a revolver (not shown) in which an arbitrary objective lens can be switched and arranged on the optical axis. A configuration in which the two-wave plate 27 is installed is also possible. Also at this time, the half-wave plate 27 is preferably arranged so as to coincide with the pupil position of each objective lens 41 or the vicinity of the pupil position.

  In the illumination optical system 20 having such a configuration, the central portion including the optical axis of the illumination light emitted from the light source 21 is condensed on the optical system 41 a held by the inner cylinder 41 b of the objective lens 41 to collect the sample 12. The bright field illumination optical path 28 (see FIG. 4) for irradiating the sample and a peripheral portion of the illumination light between the outer wall of the inner cylinder 41b of the objective lens 41 and the lens barrel 41c at a larger angle than the numerical aperture of the objective lens 41 12 is provided with a dark field illumination optical path 29 (see FIG. 5), and bright field illumination and dark field illumination can be performed simultaneously using these two illumination optical paths 28 and 29.

That is, according to the illumination optical system 20, the illumination light emitted from the light source 21 is collimated by the collimator lens 22, imaged by the relay lens 23, passes through the field stop S, and is again collimated by the field lens 24. The light is reflected by the first half mirror 26 through the polarizer 25 and guided to the objective lens 41. Of the illumination light guided to the objective lens 41,
A central portion including the optical axis is incident on the bright field illumination optical path 28 and a peripheral portion is incident on the dark field illumination optical path 29. As shown in FIG. 4, the illumination light incident on the bright field illumination optical path 28 as parallel light is condensed by an optical system 41a held by the inner cylinder 41b of the objective lens 41, and brightens the sample 12 on the stage 11. Illuminate the field of view. At the same time, as shown in FIG. 5, the illumination light incident on the dark field illumination optical path 29 as parallel light is incident between the outer wall of the inner cylinder 41b of the objective lens 41 and the lens barrel 41c, and the ring-shaped 1 After passing through the two-wavelength plate 27, the sample 12 on the stage 11 is irradiated at an angle larger than the numerical aperture of the objective lens 41 to illuminate the sample 12 with dark field.

  The illumination optical system 20 uses the light source 21 for both the bright field illumination and the dark field illumination as described above, but the dark field illumination is not too bright (too dazzling) when performing the bright field illumination. When performing the above, it is preferable to satisfy the following conditional expression in order to ensure sufficient brightness.

0.8 <h × β / D ≦ 1.0
However,
h: the length of the diagonal line of the light source 21;
β: light source magnification of the illumination optical system 20,
D: pupil diameter of the objective lens 41.

  The detection optical system 40 shares the first half mirror 26 and the objective lens 41 with the illumination optical system 20, and is arranged in order from the sample 12 side along the optical axis, the objective lens 41, the first half mirror 26, and the like. , A second half mirror (which may be a beam splitter) 42, a first analyzer 43, and a second analyzer 44.

  The second half mirror 42 transmits the light reflected by the sample 12 by the bright field illumination and guides it to the first analyzer 43, and the dark field illumination that passes through the half-wave plate 27. Is reflected and guided to the second analyzer 44. One of the first and second analyzers 43 and 44 passes polarized light having the same component as the polarized light component by the polarizer 25, and the other passes polarized light having a component different from the polarized light component by the polarizer 25 (this embodiment). The former is the first analyzer 43 and the latter is the second analyzer 44).

  According to the detection optical system 40, the reflected light from the sample 12 by the bright field illumination is condensed by the optical system 41a held by the inner cylinder 41b of the objective lens 41 as shown in FIG. The light passes through the mirror 26 and the second half mirror 42, and forms an image on the first image sensor 51 through the first analyzer 43. At the same time, the scattered light from the sample 12 by the dark field illumination is condensed by the optical system 41a held by the inner cylinder 41b of the objective lens 41 and transmitted through the first half mirror 26 as shown in FIG. Then, the light is reflected by the second half mirror 42 and imaged on the second image sensor 52 via the second analyzer 44.

  The first image sensor 51 receives light from the sample 12 by the bright field illumination condensed by the detection optical system 40 and captures a bright field image of the sample 12 (see FIG. 4). At the same time, the second image sensor 52 receives the light from the sample 12 by the dark field illumination collected by the detection optical system 40 and captures a dark field image of the sample 12 (see FIG. 5). As such 1st and 2nd image pick-up elements 51 and 52, it is possible to use CCD, CMOS, etc., for example.

  The image data of the bright field image and the dark field image acquired by the first and second imaging elements 51 and 52 can be displayed and observed on a display screen such as a display (not shown). At this time, the display or the like may be divided into left and right parts or vertically divided into two parts for simultaneous display.

Note that the timing of capturing image data of each observation image of bright field illumination and dark field illumination is, for example, the stage 11 or the stage 11 (when the sample 11 is configured to be movable when the sample 12 is relatively small). A sensor (not shown) for detecting the movement of the microscope apparatus 1 is provided (when the sample 12 is large, the microscope apparatus 1 is configured to be movable on the stage 11), and a detection signal output from this sensor From this, it is detected that the stage 11 and the microscope apparatus 1 are stopped, and in synchronism with the detection timing of the stop, the first and second imaging elements 51 and 52 are imaged to capture the image data. .

  Further, the presence or absence of movement of the sample 12 is detected from the images acquired by the imaging of the first and second imaging elements 51, 52, and the first and second imaging elements 51, 51 are synchronized with the detection timing of this stop. 52 may be configured to perform an imaging operation and capture the image data.

  Next, the polarization state of the microscope apparatus 1 having the above configuration will be described.

  As shown in FIG. 3, the half-wave plate 27 is arranged so that its optical axis forms 45 degrees with respect to the axis of the polarizer 25. Further, one of the first and second analyzers 43 and 44 satisfies the parallel Nicol condition with the polarizer 25 (in this embodiment, the axis of the first analyzer 43 is relative to the axis of the polarizer 25). So that the other satisfies the orthogonal Nicols condition with the polarizer 25 (in this embodiment, the axis of the second analyzer 44 is orthogonal to the axis of the polarizer 25). ) Is arranged. Note that the axial direction of the half-wave plate may be directed to the left or right with respect to the axis of the polarizer 25.

  The polarizer 25, the half-wave plate 27, and the first and second analyzers 43 and 44 can be finely adjusted by being rotatable around the optical axis so that the above-described conditions can be maintained. It is preferable that it is comprised.

  Further, only the polarizer 25 can be rotated around the optical axis so that it can be finely adjusted. The half-wave plate 27 is the objective lens 41, and the first and second analyzers 43 and 44 are the second half. The mirror 42 may be unitized. According to this configuration, when adjustment is necessary so that the state satisfying the above condition can be maintained, it is only necessary to rotate the polarizer 25, so that the burden on the observer can be reduced.

  4 and 5 schematically show the polarization state at the time of acquiring a bright-field image and at the time of acquiring a dark-field image. The solid line circle indicates the axial direction of each optical element, and the broken line circle P11. P13 indicates a polarization state viewed from the light receiving side. As shown in FIGS. 4 and 5, in the microscope apparatus 1, the illumination light (polarized state P11) from the light source 1 that is non-polarized light sequentially passes through the collimator lens 22, the relay lens 23, the field stop S, and the field lens 24. pass. Up to this point, the polarization direction of the illumination light is not particularly converted, and the illumination light remains unpolarized (that is, the polarization state P11). Subsequently, the illumination light is incident on the polarizer 25 and converted into linearly polarized light (polarization state P12), and then reflected by the first half mirror 26, and enters the bright field illumination optical path 28 and the dark field illumination optical path 29. Led.

  As shown in FIG. 4, the illumination light incident on the bright-field illumination optical path 28 is condensed by the optical system 41a held by the inner cylinder 41b of the objective lens 41, and is irradiated on the sample 12 with the polarization state P12. At the same time, the illumination light incident on the dark field illumination optical path 29 is applied to the half-wave plate 27 provided between the outer wall of the inner cylinder 41b of the objective lens 41 and the lens barrel 41c, as shown in FIG. Incident light is converted from the original linearly polarized light (polarized state P12) into linearly polarized light rotated about the optical axis by 90 degrees (polarized state P13), and irradiated on the sample 12 at an angle larger than the numerical aperture of the objective lens 41. The

The reflected light from the sample 12 by the bright field illumination is condensed by the optical system 41a held by the inner cylinder 41b of the objective lens 41 in the polarization state P12 as shown in FIG. And is guided to the first analyzer 43 and the second analyzer 44 by the second half mirror 42. The reflected light from the sample 12 guided to the first and second analyzers 43 and 44 has the polarization state P12 as described above, which is the same (parallel) as the polarization direction of the first analyzer 43. For this reason, the light passes through the first analyzer 43 as it is and is imaged by the first image sensor 51. On the other hand, since it is orthogonal to the polarization direction of the second analyzer 44, it is blocked by the second analyzer 44 and is not incident on (captured by) the second image sensor 52.

  On the other hand, the scattered light from the sample 12 by the dark field illumination is condensed by the optical system 41a held by the inner cylinder 41b of the objective lens 41 in the polarization state P13 as shown in FIG. The light passes through the mirror 26 and is guided to the first analyzer 43 and the second analyzer 44 by the second half mirror 42. The scattered light from the sample 12 guided to the first and second analyzers 43 and 44 has the polarization state P13 as described above, which is the same (parallel) as the polarization direction of the second analyzer 44. For this reason, the light passes through the second analyzer 44 as it is and is imaged by the second image sensor 52. On the other hand, since it is orthogonal to the polarization direction of the first analyzer 43, it is blocked by the first analyzer 43 and is not incident on (captured by) the first image sensor 51.

  According to the microscope apparatus according to the present embodiment having the above-described configuration, images by dark field illumination and bright field illumination can be acquired independently and simultaneously. As a result, the inspection time can be significantly shortened and the working efficiency can be improved as compared with the conventional method of imaging each time switching between bright field illumination and dark field illumination.

  Furthermore, according to the microscope apparatus of the present embodiment, a bright-field illumination / dark-field illumination switching mechanism including a diaphragm and a driving member such as a mirror becomes unnecessary, so that not only high speed but also dust generation can be suppressed. This leads to prevention of contamination due to dust generation, which is a great advantage particularly for a microscope apparatus for substrate inspection.

  In addition, in order to make this invention intelligible, although demonstrated with the component requirement of embodiment, it cannot be overemphasized that this invention is not limited to this.

  For example, in the above-described embodiment, the case where epi-illumination is adopted as an illumination method has been described as an example. It is.

DESCRIPTION OF SYMBOLS 1 Microscope apparatus 11 Stage 12 Sample 20 Illumination optical system 21 Light source 25 Polarizer 26 First half mirror 27 1/2 wavelength plate 28 Bright field illumination optical path 29 Dark field illumination optical path 40 Detection optical system 41 Objective lens 41a Optical system 41b In Tube 41c Lens tube 42 Second half mirror (light splitting member)
43 1st analyzer 44 2nd analyzer 51 1st image sensor 52 2nd image sensor

Claims (9)

An illumination optical system that irradiates the sample with illumination light emitted from a light source, a detection optical system that collects light from the sample through an objective lens, and an image of the sample that is collected by the detection optical system In a microscope apparatus having an imaging device,
The objective lens includes an inner cylinder that holds an optical system that collects light from the sample, and a lens barrel that surrounds an outer wall of the inner cylinder and is concentric with the inner cylinder.
The illumination optical system includes a polarizer and a ring-shaped half-wave plate, and a central portion including an optical axis is included in the illumination light that passes through the polarizer and the half-wave plate. A bright field illumination optical path for condensing the optical system held by a cylinder to irradiate the sample, and an angle larger than the numerical aperture of the objective lens through a peripheral portion between the outer wall of the inner cylinder and the lens barrel A dark field illumination optical path for irradiating the sample with
The detection optical system includes a first analyzer and a second analyzer, one of which satisfies a parallel Nicol condition with the polarizer and the other of which satisfies a crossed Nicol condition with the polarizer.
The imaging apparatus includes: a first imaging element that images light from the sample by the bright field illumination through the objective lens and the first analyzer; and light from the sample by the dark field illumination. A microscope apparatus, comprising: an objective lens; and a second imaging element that images through the second analyzer.   The microscope apparatus according to claim 1, wherein the half-wave plate is disposed in the dark field illumination optical path.   The microscope apparatus according to claim 1, wherein the half-wave plate is disposed at or near a pupil position of the objective lens. A plurality of the objective lenses are mounted, and a revolver capable of switching and arranging an arbitrary objective lens on the optical axis,
The microscope apparatus according to claim 1, wherein the half-wave plate common to each objective lens is installed in the revolver. The microscope apparatus according to claim 1, wherein the following conditional expression is satisfied.
0.8 <h × β / D ≦ 1.0
However,
h: the length of the diagonal of the light source,
β: Light source magnification of the illumination optical system,
D: pupil diameter of the objective lens.   6. The polarizer according to claim 1, wherein the polarizer, the first analyzer, and the second analyzer are configured to be rotatable about the optical axis. Microscope equipment. The detection optical system includes a light splitting member that guides light from the sample collected by the objective lens to the first analyzer and the second analyzer,
The polarizer is configured to be rotatable around an optical axis,
The microscope apparatus according to any one of claims 1 to 5, wherein the first analyzer and the second analyzer are unitized together with the light splitting member.   The microscope apparatus according to claim 1, wherein the light splitting member is a beam splitter.   The microscope apparatus according to claim 1, wherein the light splitting member is a half mirror.