JPH08160306A - Optical microscope - Google Patents

Abstract

PURPOSE: To obtain the appearance of a sample and depth information with inexpensive constitution by one-dimentionally scanning the converging position on the sample only in the direction corresponding to the longitudinal direction of a one-dimensional image sensor arranged at the confocus. CONSTITUTION: A laser beam L1 from a laser beam source 10 becomes a point source by a fγ lens 13 and is converged on the front surface of a sample ωby an objective lens 18 through a beam splitter 14, a quarter wavelength plate 15, a half mirror 16 and an image forming lens 17 arranged on the optical axis. The laser beam reflected by the sample ω is transmitted through the objective lens 18 and the image forming lens 17, reflected by the half mirror 16 and the beam splitter 14 and converged on the surface of a one-dimensional image sensor 19 arranged on the focal position of the image forming lens 17. By rotary driving a galvano mirror 12 and deflecting the laser beam L1, the converging position on the sample ω is one-dimensionally scanned only in the direction Y corresponding to the longitudinal direction of a one-dimensional image sensor 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical microscope having a function of measuring the depth of a sample.

[0002]

2. Description of the Related Art Conventionally, an observing optical system for observing the appearance of a sample (subject), and a confocal optical system for measuring the intensity of reflected light of laser light and detecting information about the depth of the sample. Optical microscopes with are known (for example,
(See JP-A-1-123102 and JP-A-277812). This type of microscope can obtain not only a magnified image of the sample but also three-dimensional data including the depth of the sample, and is useful for knowing a fine structure such as a semiconductor integrated circuit.

[0003]

However, in order to obtain three-dimensional data, the laser beam or the sample is scanned two-dimensionally (planarly), while the sample stage is moved in the Z-axis direction (depth direction). Need to move to. Therefore, not only a driving device for the three-axis directions is required, but also synchronization for scanning and driving in the three-axis directions needs to be controlled, which complicates the mechanical and electrical structure. As a result, microscopes are inevitably expensive.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an optical microscope which enables observation of the appearance of a sample, obtains information on the depth, and is relatively inexpensive. It is to be.

[0005]

In order to achieve the above object, the present invention first collects laser light on a surface of a sample by an objective lens and collects reflected light on a surface of a detector. A confocal optical system that receives light and detects information related to the depth of the sample based on the intensity of the reflected light, a scanning mechanism that scans the condensing position of the confocal optical system with respect to the sample, and an observation device that is different from the laser light An observation optical system for observing the appearance of the sample with light from the light source is provided. A feature of the present invention is that a one-dimensional image sensor is provided as a detector of the confocal optical system, and the focusing position on the sample is primarily set only in a direction corresponding to the longitudinal direction of the one-dimensional image sensor as the scanning mechanism. That is, it has a one-dimensional scanning mechanism for original scanning.

[0006]

According to the present invention, the appearance of the sample can be observed by the observation optical system, and the information on the depth of the sample can be obtained by the confocal optical system. Here, according to the present invention, the focusing position on the sample is one-dimensionally scanned only in the direction corresponding to the longitudinal direction of the one-dimensional image sensor. Therefore,
For depth, only information about one cross section of the sample is available. However, in a semiconductor integrated circuit or the like, there are cases where it is sufficient to obtain sectional information in the direction orthogonal to the fine groove, and therefore the microscope of the present invention is useful. On the other hand, since the focusing position on the sample is scanned one-dimensionally, the mechanical and electrical structure becomes simpler than that of a microscope that performs two-dimensional scanning.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention. In FIG. 1, the optical microscope includes a confocal optical system 1 and an observation optical system 2.

First, the confocal optical system 1 will be described.
The confocal optical system 1 detects information about the depth (depth, film thickness) of the sample w, and for example, red laser light L1.
Is used as a light source. On the optical axis of the laser 10, a beam expander 11,
Galvanometer mirror (deflection means) 12 and fθ lens 13
Is provided. The laser light L1 becomes a point light source by the fθ lens 13, and a beam splitter 14, a quarter wavelength plate 15,
The first half mirror 16, the imaging lens 17, and the objective lens 18 are sequentially arranged. The objective lens 18
Can be switched by the revolver 71 (FIG. 7), and a plurality of types of magnifications can be selected.

A sample stage 30 is arranged near the focal position of the objective lens 18, and the objective lens 18 focuses the laser beam L1 on the surface of the sample w. Laser light L1
Is reflected by the sample w, and the objective lens 18 and the imaging lens 17
Through. A one-dimensional image sensor 19 such as a CCD line sensor is disposed at the focal position of the image forming lens 17, and the laser light L1 transmitted through the image forming lens 17 receives the first half mirror 16 and the beam. The light is reflected by the splitter 14 and condensed on the surface of the one-dimensional image sensor 19. The galvano mirror 12 is rotationally driven by a driving device (not shown) and deflects the laser beam L1 to scan the condensing position on the sample w one-dimensionally in the direction Y perpendicular to the paper surface. The longitudinal direction Y of the one-dimensional image sensor 19 is set in a direction corresponding to the scanning direction Y.

Next, the observation optical system 2 will be described. The observation optical system 2 is for enlarging and observing the external appearance of the sample w, and uses, for example, a lamp 20 that emits white light L2 as a light source (observation light source). On the optical axis of the lamp 20, the condenser lens 21 and the second half mirror 2
3 is arranged, and the observation optical system 2 is arranged so that the optical axis of the observation optical system 2 and the optical axis of the confocal optical system 1 coincide with each other in the second half mirror 23. .

The second half mirror 23 is on the optical axis of the objective lens 18, and the white light L2 is focused and irradiated on a predetermined area on the surface of the sample w. The white light L21 reflected by the sample w passes through the objective lens 18, the imaging lens 17, and the first half mirror 16 and is incident on the CCD camera (imaging device) 24. The image captured by the CCD camera 24 is output as an image signal e to the monitor 32 via the superimposer 31 of FIG. 2 and displayed.

Next, the drive circuit and the like of the confocal optical system 1 of FIG. 1 will be described. The synchronization circuit 40 includes a stage control circuit 41, a galvano drive circuit 42, and a CCD drive circuit 4.
The sync signal is output to 3. After receiving the synchronization signal, the CCD drive circuit 43 reads out the electric charge accumulated in each element of the one-dimensional image sensor 19 based on the read clock pulse, and passes through the gain control circuit 44 and the A / D converter 45 of FIG. Then, the light amount signal a is output to the microcomputer 50. The microcomputer 50 includes a CPU 51 and a memory 60, and as described later, the one-dimensional image sensor 19
Information regarding the depth (height) of the sample w is obtained based on the amount of received light. Reference numeral 52 is a keyboard.

The memory 60 includes a peak light amount storage unit 61 and a peak position storage unit 62 shown in FIG. Each of the storage units 61 and 62 has a storage element 61 ₀ corresponding to the number of elements of the one-dimensional image sensor 19.
And a to 61 _n and 62 ₀ through 62 _n.

Next, the principle of depth measurement will be briefly described. In the confocal optical system 1 of FIG. 1, the above-mentioned one-dimensional image sensor 19 is arranged at the focal position of the imaging lens 17, while each element of the one-dimensional image sensor 19 is extremely small, When the laser light L1 is focused on the sample w, the reflected light L1 is reflected by the one-dimensional image sensor 19
When the image is formed on the above, the amount of light received by one light receiving element of the one-dimensional image sensor 19 is remarkably increased, and conversely, when the laser light L1 is spread on the sample w, the reflected light L1 is also reflected. Since it spreads above, the amount of light received by the device is significantly reduced. Therefore, when the sample stage 30 is moved up and down, that is, in the Z-axis direction, the received light amount I changes as shown in FIG. 3B, and the Z-axis position is in focus, that is, at the peak position Zp. It will be the maximum. By obtaining the peak position Zp for each element of the one-dimensional image sensor 19, as shown in FIG. 3C, depth information in the direction Y (FIG. 1) perpendicular to the paper surface, that is, the cross-sectional shape is obtained. be able to. In addition,
The observation light L21 of the lamp 20 is incident on the one-dimensional image sensor 19 of FIG. 1, but in this embodiment, the CCD driving circuit 43 is one-dimensional for the time (5 msec) in which the one-dimensional image sensor 19 does not sense the observation light L21. By accumulating the electric charge in the image sensor 19, the noise due to the observation light L21 is removed.

Next, the depth measuring method will be described. In FIG. 4, first, in step S1, the galvano mirror 12 is driven to scan the laser beam L1, and in step S2, the amount of light received by the one-dimensional image sensor 19 and the Z-axis position are stored in the storage units 61 of the memory 60. , 62
To memorize. Subsequently, in step S3, the sample stage 30 is raised by one step, then the process proceeds to step S4, the laser beam L1 is scanned again, and the process proceeds to step S5. In step S5, the CPU 51 determines for each element whether or not the amount of light measured this time is larger than the amount of light stored in each storage element 61 _i of the peak light amount storage unit 61. Rewrite the light quantity and Z-axis position. On the other hand, if it is smaller, the process proceeds to step S7. In step S7, it is determined whether or not the sample stage 30 has risen to a predetermined rising end, and if it is not the rising end, step S7.
Returning to 3, on the other hand, if it is the rising end, the measurement is ended.

In this way, the peak light amount I _i and the peak position Zp _i are stored in the storage units 61 and 62 of FIG. 3A, respectively. After that, the information of the peak position Zp _i is transferred to the image RAM of FIG. 2, and the microcomputer 50 outputs the image (FIG. 3C) to the superimposer 31. The superimposer 31 superimposes the image of the CCD camera 24 and the above-mentioned cross-sectional information, and outputs it to the monitor 32. Thereby, the operator can know the cross-sectional information in one cross-section together with the enlarged image of the sample w.

In the above structure, this optical microscope converts the laser beam L1 shown in FIG. 1 into, for example, one galvanometer mirror 1.
Since the scanning is performed only one-dimensionally by two, the conventional two-dimensional scanning with the laser beam L1 by the two galvano mirrors or the driving of the sample stage 30 in the X and Y directions (two-dimensional) is performed. The mechanical structure is simpler than that of a microscope. In particular, compared to the two-dimensional scanning, it is not necessary to synchronize in the X, Y, and Z directions, and only in the Y and Z directions, it is possible to remarkably simplify the electrical structure of the microscope. Therefore, the cost can be significantly reduced.

In the above embodiment, the galvanometer mirror 1 is used.
2 was driven to scan the laser beam L1, but in the present invention,
Deflection means such as a polygon mirror or an acousto-optic device that changes the direction of the laser beam L1 may be used, or the sample stage 30 may be driven in the Y direction to scan the focus position of the laser beam L1 on the sample w. May be.

By the way, in a general microscope of this kind, an optical filter is provided between the condenser lens 21 and the second half mirror 23 so that the component of the observation light L2 having the same wavelength as that of the laser light L1 is generated. Cut to prevent a decrease in depth measurement accuracy. However, in this case, the tint of the image of the sample w looks different from the actual one. On the other hand, if the noise is prevented by turning off the lamp 20 and performing depth measurement without providing an optical filter, the image becomes completely dark during the depth measurement. Therefore, in the second embodiment, in view of such a problem, an image having the same tint as the actual tint of the sample w can be obtained, and the image can be displayed on the monitor even during the depth measurement. I will provide a.

FIG. 5 shows a second embodiment. In the following embodiments, the same parts or corresponding parts as those in the first embodiment are designated by the same reference numerals, detailed description and illustration thereof will be omitted, and different parts will be mainly described. The microscope according to the second embodiment includes the frame memory 33, the selector 34 and the lamp control circuit 46 shown in FIG. In this embodiment, the appearance observation mode and the depth measurement mode are switched by the setting from the keyboard 52, and the lamp 20 (FIG. 1) is automatically turned off in the depth measurement mode. In the depth measurement mode, the frame memory 33 receives the trigger signal b from the microcomputer 50 and receives the CCD camera 2
The image signal e is stored by taking in the output before turning off from No. 4. In the appearance observation mode, the selector 34
As shown in FIG. 5A, while the output of the CCD camera 24 is output to the superimposer 31, in the depth measurement mode, the switching signal c from the microcomputer 50 is received and the image signal of the frame memory 33 is received. e is output to the superimposer 31. In the depth measurement mode, the lamp control circuit 46 receives the turn-off signal d from the microcomputer 50 and turns off the lamp 20 (FIG. 1).

Next, the flow of the depth measurement mode will be described. When the frame memory 33 receives the trigger signal b in step S11 of FIG.
The image just before disappears is memorized. Then, step S
12, the selector 34 is switched by the switching signal c, and the image stored in the frame memory 33 is displayed on the monitor 32. After that, it advances to step S13,
The lamp 20 (FIG. 1) is turned off by the turn-off signal d, and the depth is measured (steps S1 to S7 in FIG. 4) in step S14.

Here, since the lamp 20 in FIG. 1 is extinguished, there is no fear that the accuracy of the depth measurement by the laser beam L1 will be deteriorated even without the optical filter. On the other hand, FIG.
Since the image stored in the frame memory 33 is displayed on the monitor 32, there is no inconvenience that the image becomes completely dark during the measurement.

FIG. 6 shows a third embodiment. In FIG. 6A, the optical microscope of the third embodiment has an autofocus device 51a. Auto focus device 51
a is built in the microcomputer 50, and in the autofocus mode, moves the sample stage 30 up and down to capture the output from the one-dimensional image sensor 19 to determine the height of the sample stage 30 when the amount of received light is maximized. It is something to choose.

The operation of the autofocus mode will be described. When the keyboard 52 is operated to turn on the switch of the microscope, the auto focus mode is set, and in step S21 of FIG. 6 (b), the received light amount of the central light receiving element in the one-dimensional image sensor 19 is stored. Succeedingly, in a step S22, the sample stage 30 is raised by one stage by the stage control circuit 41, and it is judged in a step S23 whether or not the received light amount of the central element is decreased. Returning to this, the sample stage 30 is again raised by one step, and if the sample stage 30 is decreasing, the process proceeds to step S24 and the sample stage 30 is raised by one step. Succeedingly, in a step S25, it is determined whether or not the received light amount of the central element is continuously reduced. Here, as can be seen from FIG. 3B, it is considered that the light beam has passed through the peak position (the in-focus position) if the received light amount is continuously reduced, and therefore, the process proceeds to step S26 in FIG. 6B. By advancing and lowering the sample stage 30 by two steps, the sample stage 30 can be automatically set at a peak position, that is, a focused position. On the other hand, if the amount of received light does not decrease continuously in step S25, step S25
Return to 22.

In the above embodiment, whether or not the focus is achieved is determined based on the amount of light received by one light-receiving element in the center of the one-dimensional image sensor 19, but the amount of light received by several light-receiving elements in the center is determined. Alternatively, the determination may be made based on the average value of 1 or the received light amount of all the light receiving elements of the one-dimensional image sensor 19. Further, in the depth measurement and the autofocus mode, the sample stage 30 is raised one step at a time, but may be lowered one step at a time.

Next, the appearance of the optical microscope will be described. In FIG. 7 (a), 50A is a controller main body incorporating the microcomputer 50 and the like, 70 is a microscope main body, and 72 is a manual operation unit for operating focus adjustment, field stop, aperture stop and the like. As shown in this figure, if the keyboard 52 is separated from the controller main body 50A, the keyboard 5
Since 2 can be arranged at any position, the hand is not obstructed when the keyboard 52 is operated, the monitor 32 is easy to see, and the controller body 50A is arranged under the table 80, so that space efficiency is improved.

FIG. 7B shows another example. In this figure, the manual operation unit 72 is provided on the lower portion of the front surface of the microscope 70. Here, since this optical microscope uses laser light, the manual operation unit 72 is operated while observing the monitor 32 after placing the sample w on the sample stage 30. Therefore, while sitting in front of the monitor 32, the manual operation unit 72
It would be convenient if you could operate. On the other hand, in this embodiment, since the manual operation part 72 is arranged on the front surface of the microscope 70, it becomes easy to operate the manual operation part 72 while watching the monitor 32, and the operability is improved.

FIG. 7C shows another example. In this figure, the monitor 32 is a liquid crystal monitor, and is provided on the front surface of the upper frame 70a of the microscope 70. On the other hand, the manual operation unit 72 is provided on the side surface of the microscope 70. In this example, the operator sits in front of the microscope 70 and can operate the manual operation unit 72 while looking at the monitor 32, and can perform the same operation as a normal optical microscope.
Operability is improved.

By the way, in each of the above-mentioned embodiments, the confocal optical system 1 and the observing optical system 2 of FIG. 1 are provided with the imaging lens 17 to adopt the infinite correction system. A correction system may be adopted. Further, in the present invention, a bandpass optical filter that transmits only a wavelength different from the wavelength of the laser light L1 may be provided between the condenser lens 21 and the second half mirror 23.

[0030]

As described above, according to the present invention,
Since the condensing position on the sample is scanned one-dimensionally only in the direction corresponding to the longitudinal direction of the one-dimensional image sensor arranged at the confocal point, mechanical and mechanical scanning is possible as compared with the conventional two-dimensional scanning. Since the electrical structure is simplified, the cost can be reduced, and a sufficiently useful optical microscope can be provided even with the information on the depth of one cross section.

If a frame memory and a selector are provided so that the image immediately before the observation light source is turned off is displayed on the monitor, the depth can be measured with the observation light source turned off. It is not necessary to provide an optical filter. Therefore, the tint of the image on the monitor does not change much from the actual one, and when measuring the depth with the laser beam, the image just before is displayed even if the observation light source is turned off, so the monitor It never becomes pitch black.

Further, since the in-focus position can be detected from the peak position where the amount of received light is maximum, it is possible to add the autofocus function only by changing the software.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an optical system of an optical microscope according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing the measurement circuit and the like.

FIG. 3 is a conceptual diagram for explaining the principle of depth measurement.

FIG. 4 is a flowchart showing a measuring method.

5A is a schematic configuration diagram of a measurement circuit and the like showing a second embodiment, and FIG. 5B is a flowchart showing a depth measurement mode.

6A is a schematic configuration diagram of a measurement circuit and the like showing a third embodiment, and FIG. 6B is a flowchart showing a depth measurement mode.

FIG. 7 is a perspective view showing the appearance of an optical microscope.

[Explanation of symbols]

 1: Confocal optical system 12: Galvano mirror (one-dimensional scanning device (structure)) 19: One-dimensional image sensor 2: Observation optical system 20: Observation light source 24: CCD camera (imaging device) 32: Monitor 33: Frame Memory 34: Selector 41: Stage control circuit 51a: Autofocus device L1: Laser light L2: White light

Claims (4)

[Claims] 1. A laser beam is focused on the surface of a sample by an objective lens, and the reflected light is focused on a detector surface to be received, and information on the depth of the sample is obtained based on the intensity of the reflected light. A confocal optical system for detecting, a scanning mechanism for scanning a condensing position with respect to the sample in the confocal optical system, and an observation optical for observing the appearance of the sample with light from an observation light source different from the laser light. In the optical microscope equipped with a system, a one-dimensional image sensor is provided as a detector of the confocal optical system, and as the scanning mechanism, light is focused on the sample only in a direction corresponding to the longitudinal direction of the one-dimensional image sensor. An optical microscope comprising a one-dimensional scanning mechanism for scanning a position one-dimensionally. 2. The stage control circuit according to claim 1, further comprising a stage control circuit for driving the sample stage on which the sample is mounted only in the depth direction, wherein the one-dimensional scanning mechanism deflects a laser beam toward the sample to generate a one-dimensional image. An optical microscope composed of deflecting means for scanning to. 3. The image pickup device according to claim 1, which is provided in the observation optical system to pick up an image of a sample, a frame memory for storing an image signal from the image pickup device, an image signal of the frame memory or the image pickup device. An optical microscope equipped with a selector that selectively switches the output from the monitor and outputs it to the monitor. 4. The height of the sample stage when the amount of received light is maximized by moving the sample stage on which the sample is placed up and down in the autofocus mode and capturing the output from the one-dimensional image sensor. Optical microscope equipped with an autofocus device that selects the size.