JPH0843017A - Scanning optical microscope - Google Patents

Abstract

PURPOSE:To perform the accurate measurement of a length by providing an objective lens, a photodetector, a two-dimensional scanning mechanism, a moving mechanism, which relatively moves the position of the focal point of the objective lens and the position of a sample, and a control means for the scanning mechanism and the moving mechanism. CONSTITUTION:The laser light emitted from a laser 1 is transmitted through a half mirror 2 and transmitted through an objective lens 4, and the minute spot is condensed on a sample 5 on a stage 6. The spot is moved in X and Y directions on the sample 5 by the same way in the raster scanning of a TV with a two-dimensional scanning mechanism 3. The light reflected from the sample 5 is returned in the reverse direction on the optical path of the incident light and reflected from the half mirror 2. The light is made to pass through a pinhole 7 and cast at a photodetector 8. The photodetector 8 converts the reflected light from the sample 5 into the electric signal. The electric signal undergoes signal processing in a signal processing unit 9. Then, the signal is preserved in the image memory of an image processing unit 12 as the image data. The setting of the measuring range, the setting of the moving amount of the stage 6 and the control of the system are performed with a monitor 14 of a computer 13.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to scanning optical microscopes.

[0002]

2. Description of the Related Art One of scanning optical microscopes is a confocal microscope. A confocal microscope illuminates an observation sample in a point-like manner with a point light source, re-images the transmitted light or reflected light from the illuminated sample into a point-like image, and uses a detector with a pinhole opening to detect image density information. It is a microscope to obtain. FIG. 4 is a schematic diagram thereof, in which the light emitted from the point light source 40 is a half mirror 41.
After passing through, the sample 43 is illuminated by being imaged as a point on the sample 43 by the objective lens 42 whose aberration is corrected well. The light reflected by the sample 43 passes through the objective lens 42 again and is reflected by the half mirror 41 to be condensed. A pinhole 44 is arranged at the condensing position, and the light passing therethrough is detected by the photodetector 45. Then, the two-dimensional image of the sample 43 is obtained by two-dimensionally scanning the sample 43 in the same manner as the raster scanning of the television.

By the way, the light of the dotted line shows the light from the position A deviated from the condensing position of the objective lens 42. This light is not condensed on the pinhole 44. Therefore, it cannot pass through the pinhole 44 and does not reach the photodetector 45.
That is, with such an optical system, it is possible to obtain an image only at the focusing position of the objective lens 42, that is, the focusing position.

Next, as shown in FIG. 5, samples 50 having different heights are used.
Consider the case of observing with a conventional optical microscope. Since the height of each surface is different, for example, when focusing on surface A, surface B or C
The surface is blurred. Therefore, it is impossible to obtain an image focused on all surfaces of A, B, and C. However, in the case of a microscope having a confocal optical system, an image focused on the A surface is stored, and B obtained in the same manner.
An image focused on the entire surface can be easily obtained by adding the images of the surfaces C and C. Actually, the maximum brightness value may be held for each pixel.

The surface shape of the sample can be measured by utilizing this optical characteristic. In this case, the amount of movement of the stage when the maximum intensity is obtained for each pixel is stored in the memory while moving the stage on which the sample is placed in the optical axis direction. Further, in order to detect the maximum intensity, the light intensity at the current stage position is compared with the intensity at the previous stage position. Here, when the light intensity at the current stage position is higher than the intensity at the previous stage position, the light intensity at the current stage position and the amount of movement of the stage are stored in the memory. If not, the strength and the movement amount of the stage at the previous stage position are continuously stored. By the method as described above, the height information of the sample can be obtained by detecting the maximum peak of the reflected light while moving the sample in the optical axis direction.

[0006]

Next, according to the method described above, as the sample 60, a substance 62 having a high reflectance and a substance 62 having a lower reflectance than the substance 61 as shown in FIG. Consider the case of obtaining the height information of the sample as described above. When the reflection intensity is measured while moving the sample 60 in the optical axis direction toward the objective lens 63, the result is as shown in FIG. First, the reflection intensity gradually increases as the surface of the substance 62 approaches the in-focus position of the objective lens 63. Then, it becomes maximum when the focus position is reached, and thereafter the reflection intensity gradually decreases. Here, the first peak 70 occurs. When the sample 60 is further moved, the substance 61 approaches the in-focus position of the objective lens 63, and the reflection intensity gradually increases again.
As a result, the second peak 7 is the same as when the substance 62 is used.
1 occurs. Here, the difference between the first-time peak 70 and the second-time peak 71 is that there is a difference in peak intensity due to the difference in reflectance between the substances 61 and 62. Naturally, the peak 71 of the substance 61 having a high reflectance is stronger than the peak 70. When the conventional peak detection is performed by such a method, the peak 71 having the maximum intensity is finally stored, so that the peak 70 which should be originally detected cannot be detected because of the peak 71.

As described above, although the conventional scanning optical microscope has a complicated circuit configuration such as a peak detection circuit and a Z movement amount memory, the peak of the portion to be measured cannot be detected depending on the sample. There was a problem that the height could not be measured accurately.

The scanning optical microscope of the present invention has been made in view of such a problem, and its object is to perform accurate height measurement without using a complicated circuit structure. It is to provide a scanning optical microscope capable of performing the above.

[0009]

In order to achieve the above object, the scanning optical microscope according to the first invention comprises:
An objective lens that collects the light emitted from the light source on the sample, a photodetector that detects the light from the sample, and a minute aperture that is arranged in front of the photodetector and at a position conjugate with the objective lens. And a scanning mechanism for two-dimensionally scanning the light focused on the sample in a first direction and a second direction, and a movement for relatively moving the focal position of the objective lens and the position of the sample in the third direction. Mechanism and start scanning in a first direction from a first position,
After the completion of this scanning, when scanning again in the first direction, the scanning should be started from the second position displaced from the first position in the second and third directions by a predetermined distance. And a control means for controlling the mechanism and the moving mechanism.

A scanning optical microscope according to a second aspect of the present invention is the scanning optical microscope according to the first aspect, in which a storage area for data obtained by scanning the sample is changed every time the scanning start position changes. Try to change.

A scanning optical microscope according to a third invention is the scanning optical microscope according to the first or second invention, wherein the first direction is the X direction and the second direction is the Y direction. Yes, and the third direction is the Z direction.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a confocal scanning optical microscope according to an embodiment. In the figure, the laser light emitted from the laser 1 passes through the half mirror 2, the objective lens 4, and is focused on the sample 5 on the stage 6 in a minute spot. The spot moves on the sample 5 in the X and Y directions by the two-dimensional scanning mechanism 3 as in the raster scanning of the TV. The light reflected from the sample 5 returns in the reverse direction of the incident optical path, is reflected by the half mirror 2, passes through the pinhole (small aperture) 7, and enters the photodetector 8. The photodetector 8 converts the reflected light of the sample into an electric signal. The electric signal is subjected to signal processing by the signal processing unit 9, and then the image processing unit 1
The image data is stored in the second image memory as image data. The image memory has, for example, 512 pixels × 512 pixels × 8 bits (2
56 gradations) are prepared, and the value of the electric signal of the reflected light is stored.

As for the movement of the stage 6 in the optical axis direction (Z direction), a command is issued from the computer (control means) 13 to the Z movement circuit 11. A command is issued from the computer 13 for each movement of the stage 6. The user sets the measurement range, the movement amount of the stage 6 in each measurement range, the image display, and the system control on the monitor 14 of the computer 13. In addition, the computer 13 outputs a command for two-dimensional scanning to the two-dimensional drive circuit 10. Since the two-dimensional drive circuit 10 and the Z movement circuit 11 are controlled by the computer 13, it is possible to drive in any combination in the XYZ directions.

The height measuring method according to this embodiment will be described below with reference to FIG.
And FIG. 3 will be described. In the present embodiment, as shown in FIG. 2, first, from the first position (point A) to the first direction (X
Scanning in the first direction), and after this scanning ends, when scanning again in the first direction (X direction), the first position (A
Two-dimensional drive circuit 10 and Z moving circuit to start scanning from a second position (point B) which is displaced from the point) in a second direction (Y direction) and a third direction (Z direction) by a predetermined distance. 1
Control 1

That is, in FIG. 2, the sample 20 has a substance 22 on a substrate 21 and a substance 23 covering the substance 22. The scanning start point starts from point A, which is slightly above the substance 23. The laser beam moves from point A in the X direction in a preset range. When the scanning in the X direction ends, the laser beam moves to the next scanning start position B.
This scanning start position B moves to a position slightly displaced from the point A in the Y direction, and also in the Z direction from the point A to the substance 2
The position is closer to 3. Here, the movement in the Y direction is performed by the two-dimensional scanning mechanism 3, and the movement in the Z direction is performed by the Z movement circuit 11 driving the stage 6.

FIG. 3A shows a state in which the above operation is continuously performed. FIG. 3B is an image of the information at that time. At point A, there is nothing that reflects the laser beam at the focus position of the laser beam, so the output of the photodetector 8 is almost zero during scanning in the X direction. Therefore, when imaged as shown in FIG. 3B, it is displayed as one dark line. The same is true at the next scanning start position B. In this embodiment, since the area for storing image information is changed every time the scanning start position is changed, the image information generated by the scanning from the point B is the image information obtained by the previous scanning from the point A. Will not be overwritten. Similar results are obtained for points D and F.

When the stage 6 is continuously moved, the scanning start point of the laser beam becomes the point C. At this time, the laser beam is reflected by the surface of the substance 23. Therefore, the photodetector 8
A laser beam is incident on the laser beam and a predetermined image signal is generated. Therefore, in this case, a bright line is drawn in the image as shown in FIG. Similarly, when the laser beam reaches the point E, it is reflected on the surface of the substance 22. Therefore, also in this case, a bright line is drawn in the image. The brightness of the bright lines at points C and E is
It is determined by the reflectance of the substance 22 and the substance 23. For example, substance 22
If the reflectivity of is higher than that of the substance 23, the bright line at the point E is displayed brighter than the bright line at the point C. Figure 3 (c)
Represents the luminance data in the Y direction of FIG. As described above, the point E is brighter than the point C.

According to the above-described embodiment, in the process of performing the Z drive in synchronization with the two-dimensional scanning to store the luminance information of the sample, the image data for each line (X scanning) is stored in different memory areas. All peaks can be detected without using a complicated structure such as a circuit for detecting peaks and a memory for storing the amount of movement in the Z direction.

[0019]

According to the present invention, accurate height measurement can be performed without using a complicated circuit structure.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a confocal scanning optical microscope according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a height measuring method according to the present embodiment.

FIG. 3 is a diagram showing a state in which data obtained by the height measuring method according to the present embodiment is imaged.

FIG. 4 is a diagram showing a configuration of a conventional confocal scanning optical microscope.

FIG. 5 is a diagram showing a sample having a non-uniform height.

FIG. 6 is a diagram for explaining a problem of a conventional method for measuring a surface shape of a sample.

FIG. 7 is a diagram showing two peaks obtained when a sample having a two-layer structure having different reflectances is measured.

[Explanation of symbols]

1 ... Laser, 2 ... Half mirror, 3 ... Two-dimensional scanning mechanism,
4 ... Objective lens, 5 ... Sample, 6 ... Stage, 7 ... Pinhole, 8 ... Photodetector, 9 ... Signal processing unit, 10 ... 2
Dimensional drive circuit, 11 ... Z moving circuit, 12 ... Image processing unit, 13 ... Computer, 14 ... Monitor.

Claims (3)

[Claims] 1. An objective lens for condensing light emitted from a light source onto a sample, a photodetector for detecting light from the sample, and a position in front of the photodetector and at a position conjugate with the objective lens. The minute aperture arranged and the light condensed on the sample are moved in the first direction and the second direction.
A scanning mechanism for three-dimensional scanning, and a focus position of the objective lens and a sample position relative to each other by a third
And a moving mechanism for moving the first direction from the first position to start scanning in the first direction, and after the scanning is finished, when scanning in the first direction again, And a control means for controlling the scanning mechanism and the moving mechanism to start scanning from a second position displaced in the third direction by a predetermined distance, and a scanning optical microscope. 2. The scanning optical microscope according to claim 1, wherein a storage area of data obtained by scanning the sample is changed every time the scanning start position changes. 3. The scanning optical microscope according to claim 1, wherein the first direction is the X direction, the second direction is the Y direction, and the third direction is the Z direction.