JP2001056437A - Laser microscope and operating method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage given to an observation sample by an extreme ultraviolet laser beam. SOLUTION: By this operating method, an object to be observed on the sample is specified first by using the visible light beam of a normal optical system and observed with high resolution by using the extreme ultraviolet laser beam of a confocal optical system after it is specified when the sample is observed by a ultraviolet laser confocal microscope 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser microscope and a method of operating the same, and more particularly, to a laser microscope using an extreme ultraviolet laser, which is capable of reducing damage to an observation sample caused by the extreme ultraviolet laser. The present invention relates to a microscope and an operation method thereof.

[0002]

2. Description of the Related Art As microscopes used for observing a sample, for example, there are an optical microscope and an extreme ultraviolet laser confocal microscope. The optical microscope uses an i-line having an oscillation wavelength of 365 nm. On the other hand, an extreme ultraviolet laser confocal microscope uses an extreme ultraviolet laser having an oscillation wavelength of 266 nm. Since the resolution of the microscope is improved by shortening the oscillation wavelength of the light to be used, an extreme ultraviolet laser confocal microscope is used to observe the sample at a higher resolution. The resolution of an extreme ultraviolet laser confocal microscope is theoretically 1.37 times higher than the resolution of an optical microscope.

[0003]

However, since the extreme ultraviolet laser has larger light energy than long wavelength light such as i-line, when the extreme ultraviolet laser irradiates the sample with the same output as the i-line, the sample becomes larger. There was a problem of causing damage.

Here, the damage means, for example, that when a silicon wafer coated with a photoresist is observed using an extreme ultraviolet laser confocal microscope, the photoresist evaporates within the scanning range of the extreme ultraviolet laser. That is, when a thin metal film is observed, the outline remains thin within the scanning range of the extreme ultraviolet laser.

Further, when the damage to the sample is remarkable as in the above-mentioned example, there is a problem that not only the measurement and inspection results are adversely affected but also the sample itself cannot be reused.

Accordingly, an object of the present invention is to provide a laser microscope using an extreme ultraviolet laser, which is capable of reducing damage to an observation sample caused by the extreme ultraviolet laser, and a method of operating the laser microscope. is there.

[0007]

Means for Solving the Problems In order to achieve the above object, one aspect of the present invention is that, when observing a sample with an extreme ultraviolet laser confocal microscope, first, an object to be observed on the sample is usually optical system. After identifying the observation target using the visible light, the observation target is observed with higher resolution using the extreme ultraviolet laser of the confocal optical system.

Thus, the number of times of irradiation of the sample with the extreme ultraviolet laser can be minimized. as a result,
Damage to the observation sample caused by the extreme ultraviolet laser can be reduced.

[0009] To achieve the above object, the present invention provides:
In the operating method of the laser microscope, a specifying step of specifying the observation target on the sample using the normal optical system, and using the confocal optical system to specify the observation target on the sample specified in the specifying step And observing with higher resolution.

According to the present invention, it is possible to reduce the damage that the extreme ultraviolet laser causes to the observation sample.

In order to achieve the above object, another aspect of the present invention is to observe a sample composed of a plurality of layers with an extreme ultraviolet laser confocal microscope, first of all, an object to be observed on the sample is usually After specifying using the optical system and specifying the observation target, the stage is moved at a constant pitch in the height direction, and each time the observation target is observed using the confocal optical system.

Thus, when observing a sample composed of a plurality of layers, it is possible to avoid a difference between an image observed by a confocal optical system and an image observed by a normal optical system due to a difference in depth of focus. . Also,
Since the observation sample is irradiated with the extreme ultraviolet laser only a minimum number of times, damage to the observation sample caused by the extreme ultraviolet laser can be suppressed to a minimum.

[0013] To achieve the above object, the present invention provides:
In the operating method of the laser microscope, when the observation sample is composed of a plurality of layers, the stage is moved at a constant pitch in the height direction in the observation step, and the sample is observed each time. I do.

According to the present invention, when observing a sample composed of a plurality of layers, it is possible to avoid a difference between an image observed by a confocal optical system and an image observed by a normal optical system due to a difference in depth of focus. can do.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.

FIG. 1 is a diagram showing a configuration of an embodiment of an extreme ultraviolet laser confocal microscope 1 to which the present invention is applied. The extreme ultraviolet laser confocal microscope 1 is equipped with an epi-illumination system (normal optical system) using a halogen lamp (not shown) as a light source. Visible light emitted from a halogen lamp (not shown) is applied to a sample (not shown) installed on the motorized XYZ stage 2, and the reflected light is reflected by the eyepiece 6 and a visible light color CCD (Charge Coupled Device).
e) The light enters the camera 14. The operator can observe the sample on the electric XYZ stage 2 using the eyepiece 6. Further, the confocal optical system having the extreme ultraviolet laser light source 7 is mounted on the extreme ultraviolet laser confocal microscope 1, and the sample is observed by appropriately switching these two optical systems.

The electric XYZ stage 2 is motorized,
It can be moved in the X direction (horizontal direction), the Y direction (vertical direction) and the Z direction (height direction) within a predetermined range. The electric rotating revolver 3 includes a visible light objective lens 4 (10 ×, 40 ×, and 100 ×) and an extreme ultraviolet objective lens 5 (100 ×
) Is mounted, and by rotating the electric rotary revolver 3 itself, switching to a desired objective lens is performed. Note that the XYZ stage 2 and the rotary revolver 3 do not necessarily need to be electrically driven, and may be manually operated.

The extreme ultraviolet laser emitted from the extreme ultraviolet laser light source 7 is introduced into the confocal unit 9 through the extreme ultraviolet laser light path 8. The confocal unit 9 is composed of components of a confocal optical system. The confocal unit 9 includes a cable 11
Is connected to the confocal unit controller 10 via the
It is controlled by 0. The confocal unit controller 10 is connected to a personal computer 16 via a cable 12, and is controlled by the personal computer 16.

The autofocus unit 13 is a unit for focusing by autofocus, and is mounted on the confocal unit 9. The visible light color CCD camera 14 is connected to a personal computer 16 via a cable 15. Color for visible light
The CCD camera 14 converts the incident visible light (reflected light) into an electric signal (image signal), supplies the image signal to the personal computer 16 via the cable 15, and displays the image on the display unit 29 on the personal computer 16. Is displayed.

Next, the configuration of the personal computer 16 will be described. FIG. 2 shows a personal computer 16.
Is shown. As shown in FIG.
1. CD-ROM (Compact Disk-Read Only Memory) drive 22, floppy disk drive 23, interface unit 24, CPU (Central Processing Unit) 25, hard disk 26, ROM (Read Only Memory) 27, VRAM (Vi
The deo random access memory 28 and the display unit 29 are connected via a bus 30.

When the power is turned on, the CPU 25 reads a boot program (starting program) stored in the ROM 27 in advance via the bus 30 and executes it. Next, CP
The U 25 reads out a system program (OS) stored in the hard disk 26 in advance via the bus 30 and executes it. Thereby, initialization necessary for system operation is completed, and the CPU 25 waits for an input signal (command) supplied from the input unit 21. When the operator operates the input unit 21 to input a command, the CPU 25 executes a process corresponding to the command.

The CD-ROM drive 22 has a CD-ROM 31 as appropriate.
Is inserted, and necessary data is read. In the floppy disk drive 23, a floppy disk 3
2 is inserted, and necessary data is read.

An image signal output from the visible light color CCD camera 14 is supplied to an interface unit 24 in a personal computer 16 via a cable 15.
The image signal supplied to the interface unit 24 is
0 to the VRAM 28 and stored. VRAM28
The image signal stored in the display section 29 is read out as appropriate.
Will be displayed.

Next, a method for reducing the damage caused by the extreme ultraviolet laser to the observation sample will be described with reference to the flowcharts of FIGS. FIG. 3 and FIG. 4 are flowcharts showing the operation procedure of the extreme ultraviolet laser confocal microscope 1.

When observing a sample using the extreme ultraviolet laser confocal microscope 1, the visible light of an optical system is usually used to specify the observation target on the sample. In this way, by using visible light to identify the observation target,
It is not necessary to irradiate the observation sample with an extreme ultraviolet laser more than necessary. As a result, damage to the observation sample caused by the extreme ultraviolet laser can be reduced.

First, the operator operates the electric XYZ stage 2
Set the sample on the top and use a visible light objective lens 4 (10x)
To observe the sample (step S1), and determine whether the observation target on the sample exists at the center of the visual field (step S1).
2). If it is determined in step S2 that the observation target on the sample is not located at the center of the visual field, the position of the electric XYZ stage 2 is adjusted so that the observation target on the sample is located at the center of the visual field.

If it is determined in step S2 that the object to be observed on the sample exists at the center of the visual field, the motor-driven rotary revolver 3 is rotated, and the sample is observed with the visible light objective lens 4 (40 ×) (step S3). Then, it is determined whether or not the observation target on the sample exists at the center of the visual field (step S4).
If it is determined in step S4 that the observation target on the sample is not located at the center of the visual field, the position of the electric XYZ stage 2 is adjusted so that the observation target on the sample is located at the center of the visual field.

In step S4, when it is determined that the observation target on the sample exists at the center of the visual field, the electric rotary revolver 3 is rotated, and the visible light objective lens 4 (100 ×)
To observe the sample (step S5), and determine whether the observation target on the sample exists at the center of the visual field (step S5).
6). As described above, the maximum magnification (100 times) of the objective lens 4 for visible light is changed to the maximum magnification (1 times) of the objective lens 5 for extreme ultraviolet.
00), it is possible to avoid a difference in the magnification of the acquired image (a difference in the field of view) when the objective lens 4 for visible light is switched to the objective lens 5 for extreme ultraviolet.

If it is determined in step S6 that the observation target on the sample is not at the center of the visual field, the position of the motorized XYZ stage 2 is adjusted so that the observation target on the sample is at the center of the visual field. If it is determined in step S6 that the observation target on the sample exists at the center of the visual field, one image of the observation target is acquired by the visible light color CCD camera 14 (step S7). The image signal obtained by the visible light color CCD camera 14 is supplied to the personal computer 16 via the cable 15 and displayed on the display unit 29.

Next, the operator determines whether or not to observe the observation target at a higher magnification (step S8). Here, when observing the observation target at a higher magnification, the galvano scanner zoom function of the confocal optical system is used. Therefore, when observing the observation target at a higher magnification, the operator operates the input unit 21 to turn on the galvano scanner zoom function (step S9).

When the galvano scanner zoom function is turned on, a frame 42 corresponding to the magnification as shown in FIG. 5, for example, is displayed on the screen of the display unit 29 (step S1).
0). A frame 42 indicates an image area corresponding to the magnification of the galvano scanner zoom, and can move within the screen of the display unit 29. The operator operates the input unit 21 to move the frame 42 to a desired position on the observation target of the sample 41 (step S11), and determines whether the position of the frame 42 is appropriate (step S12).

If it is determined in step S12 that the position of the frame 42 is not appropriate, the frame 42 is moved again,
So that it is in the desired position. In step S8,
If it is determined that the observation target is not observed at a higher magnification,
Steps S9 to S12 are skipped.

With the frame 42 set at a desired position on the observation object, observation with the confocal optical system is started. By rotating the electric rotary revolver 3, the objective lens for visible light 4 (100 times) is moved from the objective lens for extreme ultraviolet 5 (10 times).
(Step S13).

Incidentally, in performing the observation by the confocal optical system, a difference between the observation image by the normal optical system and the observation image by the confocal optical system may cause a problem. The difference between the observation image by the normal optical system and the observation image by the confocal optical system occurs because the focal depth of the normal optical system differs from the focal depth of the confocal optical system.

FIGS. 6 and 7 show the difference between the image observed by the ordinary optical system and the image observed by the confocal optical system.
This will be described with reference to FIG. FIG. 6B is a cross-sectional view of the sample 51, and FIG.
1 shows an example of one observation image. FIG. 7 (B) shows sample 5.
1 is a cross-sectional view, and FIG. 7A shows an example of an observation image of the sample 51 by the confocal optical system.
The sample 51 has a three-layer structure.

In an ordinary optical system, since the depth of focus is deep, FIG.
As shown in the figure, the first layer 51a to the third layer 51 of the sample 51
c All can be observed. On the other hand, in the confocal optical system, since the depth of focus is shallow, the second layer 51b located at the focal point of the sample 51 can be observed, but the first and third layers 51a and 51c above and below it are observed. Can not do.

As described above, when a sample having a structure of a plurality of layers in the Z direction (height direction) is observed with the ordinary optical system and the confocal optical system, different observation images are obtained due to the difference in the depth of focus. Here, in order to confirm the difference between the images obtained by the normal optical system and the confocal optical system,
If the stage 2 is moved many times in the Z direction (height direction) and image acquisition is repeated, the sample is unnecessarily irradiated with the extreme ultraviolet laser, and the damage by the extreme ultraviolet laser is promoted. .

In order to avoid the above operation, the operation is performed in the following procedure. Returning to the flowchart of FIG. 4, the operator determines whether to change the focal position and acquire a plurality of images (step S14). If it is determined that a plurality of images are to be acquired by changing the focal position, the operator first fixes the in-focus position to the uppermost or lowermost part of the observation target by autofocusing, and then moves the electric XYZ stage 2 in the Z direction. The camera is moved at a constant pitch (in the height direction), one image is acquired each time, and the acquired image is supplied to the personal computer 16 and stored in the VRAM 28 (step S15).

Thus, even when observing a sample having a structure of a plurality of layers with a confocal optical system, the image is acquired only a minimum number of times, so that the damage caused by the extreme ultraviolet laser to the sample is minimized. Can be suppressed.

Further, each image stored in the VRAM 28 is read out to display only the second layer 51b and the third layer 51c (FIG. 8A), as shown in FIG. It is also possible to display only the first layer 51a and the second layer 51b (FIG. 8B). Further, as shown in FIG. 8C, by superimposing and displaying the first to third layers 51a to 51c, it is possible to obtain the same image as the image observed by the normal optical system.

If it is determined in step S14 that a plurality of images are not to be acquired by changing the focal position, one image is acquired at the focal position determined by the auto focus (step S16), and the operation is terminated.

[0042]

As described above, according to the present invention, when observing a sample with an extreme ultraviolet laser confocal microscope, first, an observation target on the sample is specified by using visible light of an ordinary optical system, and the observation is performed. After identifying the target, the observation target is observed at a higher resolution using the extreme ultraviolet laser of the confocal optical system, so that the number of irradiation of the sample with the extreme ultraviolet laser can be minimized. it can. As a result, damage to the observation sample caused by the extreme ultraviolet laser can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an extreme ultraviolet laser confocal microscope 1 according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a personal computer 16 in FIG.

FIG. 3 is a flowchart illustrating an operation procedure for reducing damage to a sample.

FIG. 4 is a flowchart following FIG. 3;

FIG. 5 is a diagram for explaining a frame displayed when a galvano scanner zoom function is turned on.

FIG. 6 is a diagram showing an example of an observation image obtained by a normal optical system.

FIG. 7 is a diagram illustrating an example of an image observed by a confocal optical system.

FIG. 8 is a diagram for explaining a method of displaying an observation image.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extreme ultraviolet laser confocal microscope 2 Electric XYZ stage 3 Electric rotating revolver 4 Objective lens for visible light 5 Objective lens for extreme ultraviolet 6 Eyepiece 7 Extreme ultraviolet laser light source 8 Optical path for extreme ultraviolet laser 9 Confocal unit 10 Confocal unit controller 13 Auto Focus Unit 14 Color CCD Camera for Visible Light 16 Personal Computer

Claims (6)

[Claims] 1. A stage on which an observation sample is placed, a normal optical system used for specifying an observation target on the sample, and an observation target specified by the normal optical system are observed with higher resolution. And a confocal optical system that is sometimes used. 2. The normal optical system includes a visible light source that emits visible light, and the visible light objective lens. The confocal optical system includes an extreme ultraviolet laser light source that emits an extreme ultraviolet laser, The laser microscope according to claim 1, further comprising the extreme ultraviolet laser objective lens. 3. The laser microscope according to claim 2, wherein the maximum magnification of the objective lens for visible light and the maximum magnification of the objective lens for extreme ultraviolet laser are the same. 4. A conversion means for detecting the visible light or the reflected light of the extreme ultraviolet laser applied to the sample and converting the detected light into an image signal; and a display means for displaying the image signal generated by the conversion means. The laser microscope according to claim 2, further comprising: 5. The method for operating a laser microscope according to claim 1, wherein a specifying step of specifying an observation target on the sample using the normal optical system, and the sample specified in the specifying step An observation step of observing the observation object at a higher resolution using the confocal optical system. 6. When the observation sample is composed of a plurality of layers, the stage is moved at a constant pitch in the height direction in the observation step, and the sample is observed each time. 6. The operation method of the laser microscope according to 5.