JP3512259B2 - Scanning probe microscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope, and more particularly to a scanning probe microscope suitable for combination with an auxiliary observation device.

[0002]

2. Description of the Related Art A scanning probe (probe) microscope has a measurement resolution of an atomic order and is used in various fields such as surface shape measurement. The scanning probe microscope includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), a magnetic force microscope (MFM), etc., depending on the physical quantity to be detected. Among them, the atomic force microscope is suitable for detecting the shape of the sample surface with high resolution, and is used for measuring the surface shape of semiconductors, optical disks, and the like. Below,
An atomic force microscope will be described as an example.

FIG. 8 shows the basic structure of a conventional atomic force microscope. The sample to be measured 12 is placed on the XYZ fine movement mechanism 11, the cantilever 13 having a fixed base end is arranged above the sample 12, and the probe 14 attached to the tip of the cantilever 13 faces the surface of the sample 12. I'm out. The XYZ fine movement mechanism 11 is a movement mechanism that can perform fine movements in each of the orthogonal X axis, Y axis, and Z axis directions. Above the cantilever 13, a laser light source 15 for irradiating the back surface of the cantilever 13 with a laser beam 16 and a photodetector 17 for receiving the reflected laser beam are arranged. The laser light source 15 and the photodetector 17 form a detection optical system. In this configuration, the probe 14 and the sample 12 are moved by a cantilever approach mechanism (not shown).
When the distance is approached to about 1 nm, an interatomic force acts between the two to cause the cantilever 13 to deform flexibly. The deflection angle is detected by utilizing the principle of lever using the laser light from the laser light source 15. XYZ fine movement mechanism 1
1, the sample 12 is scanned in the XY axis directions, and at that time, the sample 12 is moved in the Z axis direction so that the deflection angle of the cantilever 13 becomes constant. The shape of the surface of the sample 12 is measured by monitoring the amount of movement of the mechanical portion that moves the sample 12 in the Z-axis direction.

Although the atomic force microscope has a high resolution in principle,
There is a problem that the measurement range is very narrow, such as several μm and several hundred μm. Therefore, in order to specify the observation location of the sample 12, it is desired to be combined with an auxiliary observation device such as an optical microscope. For example, an atomic force microscope combined with an optical microscope as shown in FIG. 9 has been conventionally proposed. ing. The sample 21 measured by the atomic force microscope having this configuration is a large one such as a silicon wafer or an optical disk. In these samples 21, it is desired to identify a predetermined element or recording pit on the semiconductor circuit or recording surface and observe with an atomic force microscope, and such an atomic force microscope needs to be combined with an optical microscope or the like. It is essential. The atomic force microscope of FIG. 9 is provided with an XYZ fine movement mechanism 11 on the cantilever 13 side, and is configured to scan the cantilever 13 side. 9, elements that are substantially the same as the elements described in FIG. 8 are given the same reference numerals. The detection optical system is attached to the block 23 and coupled to the XYZ fine movement mechanism 11 side, and the XYZ fine movement mechanism 11 is attached to the cantilever approach mechanism 24. The optical microscope 25 is arranged laterally of the atomic force microscope with a distance D, and the sample 21 is arranged on an XY stage 26 for moving the sample.

The above-mentioned measurement by the atomic force microscope is performed by observing with the optical microscope 25 and determining the measurement point on the surface of the sample 21. The measurement point is moved by the distance D using the XY stage 26 to measure the atomic force. The steps of setting the position of the microscope, bringing the probe 14 closer to the surface of the sample 21 by the cantilever approach mechanism 24, and observing with the atomic force microscope are performed. In this measuring step, how accurately the distance D can be moved becomes a problem. In practice, it is difficult to know the distance D itself accurately, the distance D changes due to replacement of the cantilever and environmental factors such as temperature, and it is difficult to accurately move the distance D by the XY stage 26. Therefore, it is almost impossible to specify the place to be observed on the surface of the sample 21 with an accuracy of, for example, 1 μm or less.

Therefore, as shown in FIG. 10, the cantilever 13 and the probe 14 at the tip thereof are arranged so as to be located within the visual field of the optical microscope, and as shown in FIG.
A method of observing the sample 21 and the probe 14 at the tip of the cantilever 13 at the same time in the visual field 27 is proposed. According to this method, it is not necessary to move the XY stage 26 between the optical microscope and the atomic force microscope, and it becomes extremely easy to specify the measurement location. On the other hand, however, since the probe 14 is arranged in the visual field of the optical microscope, the following problem occurs.

The first problem is that the servo characteristics are deteriorated with respect to the position control of the probe in the Z-axis direction, and the second problem is that interference occurs with the optical lever detecting optical system. Especially the first
The above problem becomes a big problem when the sample is large. The control of the servo in the Z-axis direction is an important factor that influences the measurement performance in the measurement by the atomic force microscope. The Z fine movement mechanism is operated so that the deflection angle of the cantilever is constant with respect to the unevenness of the sample surface, but if the servo control in the Z-axis direction is not fast, the unevenness of the sample surface can be accurately traced. Can not. If the Z fine movement mechanism is provided on the sample side when the sample is large, the mass of the mechanism such as the sample table increases due to the larger sample and the high speed is impaired. Therefore, provide the Z fine movement mechanism on the lightweight cantilever side. Will be required.

Therefore, FIG. 10 shows a configuration in which the XYZ fine movement mechanism 11 is provided on the cantilever 13 side. The XYZ fine movement mechanism 11 is attached to the fixed cantilever approach mechanism 24, and the beak-shaped member 31 for attaching the cantilever 13 is attached to the XYZ fine movement mechanism 11. The beak-shaped member 31 is a member for disposing the cantilever 13 in the visual field of the optical microscope 25, and has a beak portion extending in the direction of the visual field. The cantilever 13 is attached to the tip of the beak portion. Although the concrete shape and configuration of the beak portion has a considerable degree of freedom, a length longer than the radius R of the objective lens of the optical microscope 25 is required. With such a configuration, when the position of the probe 14 of the cantilever 13 is accurately controlled by the Z fine movement mechanism, mechanical rigidity becomes a problem, and it is not easy to obtain high speed. In order to obtain high speed, it is required that the mechanism has a high natural frequency. The natural frequency is generally expressed by the following equation, where f is the natural frequency (Hz), k is the rigidity, and m is the mass (inertia moment in the case of rotational movement).

[0009]

## EQU1 ## f = (1 / 2π) (k / m) ^1/2

According to the above equation, the higher the rigidity k in translational motion and rotational motion and the smaller the mass or moment of inertia, the higher the natural frequency. The band in servo control (the maximum frequency that servo control can follow) is basically set lower than the natural frequency of the mechanism. This is because, if the band is near the natural frequency, the mechanism resonates and becomes uncontrollable. Therefore, from the viewpoint of the band of servo control, it is desirable that the natural frequency of the mechanism is high, and that the mass is small in order to increase the natural frequency of the mechanism.

[0011]

The atomic force microscope shown in FIG. 10 has the following problems. X as shown in FIG.
A tube-type piezoelectric ceramic 41 is specifically used as the YZ fine movement mechanism, and a beak-shaped member 31 is provided at the lower end thereof. The piezoelectric ceramics 41 includes an X-axis drive electrode 41a,
It is provided with a Y-axis drive electrode 41b and a Z-axis drive electrode 41c. When a predetermined voltage is applied to each electrode, X-axis, Y-axis,
Displacement can be generated in each direction of the Z axis. A typical vibration mode is as shown by the broken line. In this motion, the beak-shaped member 31 has a required mass m and an inertia moment based on the length R1 of the beak portion, and there is a problem that the natural frequency of the mechanism decreases due to the increase of these masses and inertia moments. is doing.

The above-mentioned problems generally occur not only in atomic force microscopes but also in scanning probe microscopes combined with auxiliary observation devices such as optical microscopes.

An object of the present invention is to solve the above problems, and in a structure provided with an auxiliary observation device such as an optical microscope and arranging a cantilever using a beak member within the field of view of the auxiliary observation device, An object of the present invention is to provide a scanning probe microscope with improved servo performance of control in the Z-axis direction and improved measurement performance.

[0014]

A scanning probe microscope according to the present invention comprises a cantilever provided with a probe facing a sample at its tip, and an auxiliary observation device capable of observing the surface of the sample and the back surface of the cantilever. A beak-shaped member for arranging a cantilever in the field of view of this auxiliary observation device, a displacement detection device for detecting displacement of the cantilever, an XY fine movement mechanism and a Z fine movement mechanism for displacing the relative position of the probe and the sample, This is a device that controls the deflection amount of the cantilever based on the physical quantity acting between the probe and the sample by the Z fine movement mechanism and scans the surface of the sample with the XY fine movement mechanism to measure the sample. Attach the cantilever to the Z fine movement mechanism and attach the Z fine movement mechanism to
A drive unit that is coupled to the beak member via a flat elastic member
Material and pressure applied between the beak member and the driving member.
And an electric element .

The present invention is characterized in that, in the above structure, the auxiliary observation device is an optical microscope.

[0016]

[0017]

In the present invention, only the cantilever is attached Z
Since the fine movement mechanism can reduce the driving mass and the moment of inertia, the natural frequency is reduced, the characteristics of servo control in the Z-axis direction are improved, and the Z-axis servo speed is increased.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to FIGS. In this example, an atomic force microscope combined with an optical microscope will be described. FIG. 1 shows a basic configuration of the present invention, and FIG. 2 shows a partially enlarged specific configuration. In each drawing, substantially the same elements as those described with reference to FIG.

In FIG. 1, X is placed on the XY stage 26.
A Y fine movement mechanism 51 is provided. XY stage 26 and XY
The fine movement mechanism 51 is for placing a large sample, and the large measured sample 21 such as a silicon wafer is placed on the XY fine movement mechanism 51. The XY stage 26 includes an X-axis direction stage 26a and a Y-axis direction stage 26b, and is fixed to a table (not shown). On the upper side of the sample 21, a cantilever 13 having a probe 14 at its tip is arranged. A beak-shaped member 31 is attached to the fixed cantilever approach mechanism 24.
The Z-axis fine movement mechanism 52 is attached to the tip of the. The cantilever 13 has a Z fine movement mechanism 52 via a driving member 53.
Attached to. An optical microscope 25 is arranged above the sample 21, and the optical microscope 25 is fixed. The tip of the cantilever 13 and the probe 14 are included in the visual field of the optical microscope 25. Reference numeral 15 denotes a laser light source which is a part of the detection optical system. The detection optical system of the present embodiment is arranged in a direction orthogonal to the longitudinal direction of the cantilever 13. A photodetector (not shown) is arranged on the opposite side of the optical microscope 25.

As is apparent from FIG. 1, in this embodiment, X
A mechanism for performing fine movements in each of the axes, the Y-axis, and the Z-axis is separated into an XY fine movement mechanism 51 and a Z fine movement mechanism 52, and the Z fine movement mechanism 52 is provided at the tip of the beak member 31, and the XY fine movement mechanism 51 is provided, for example. It was configured to be provided on the side of the sample 21. Since the cantilever 13 having the probe 14 and the lightweight driving member 53 are attached to the Z fine movement mechanism 52, the mass (m) and the moment of inertia affecting the operation of the Z fine movement mechanism 52 are extremely small. It is possible to reduce the size, whereby the characteristics of servo control in the Z-axis direction can be improved and the response can be improved. Therefore, even in an atomic force microscope combined with the optical microscope 25 as an auxiliary observation device having a structure using the beak-shaped member 31, the measurement performance can be made extremely high.

A concrete example of the construction of the beak member and the Z fine movement mechanism will be described with reference to FIG. Reference numeral 31 denotes the block-shaped beak-shaped member, 53 denotes the drive member, the beak-shaped member 31 and the drive member 53 are joined together by a flat elastic member 54, and the beak-shaped member 31 and the drive member 53 are piezoelectric. The element 55 is interposed. The piezoelectric element 55 has a function as a Z-axis fine movement mechanism, and by applying a voltage to the piezoelectric element 55, the driving member 53 can be displaced in the Z-axis direction, and the probe can be finely moved in the Z-axis direction. You can The cantilever 1 attached to the drive member 53
FIG. 3 is an enlarged view of the portion of No. 3. The cantilever 13 is fixed to the drive member 53 via the holding portion 56. According to the above configuration, the driving mass and the moment of inertia can be made extremely small. The elastic member 54 is
A means for fine movement in the Z-axis direction, which has a role of guiding in the Z-axis direction, and can increase rigidity in the directions of the X-axis and the Y-axis, and further in the rotation direction, and perform higher-speed servo control. To enable. The size of the driving member 53 can be reduced as much as possible. In this case, even if the size of the drive member 53 is set to a size such that the cantilever 13 having the holding portion 56 can be easily attached to and detached from the drive member 53, the natural vibration of the entire mechanism including the Z fine movement mechanism. The number can easily be several KHz. Since the above structure has such characteristics, it actually has the same responsiveness as a conventional atomic force microscope having a structure that does not use a beak member.

Various other structures can be considered for the structure of the Z fine movement mechanism 52. Examples thereof are shown in FIGS. 4 and 5. The structure of FIG. 4 shows the structure described in FIG. 2 with the flat elastic member 54 removed. This can simplify the configuration and reduce the manufacturing cost. The structure shown in FIG. 5 shows an example in which a parallel leaf spring 57 is used as an elastic member. With this configuration, accurate movement in the Z-axis direction is possible, which can improve the measurement accuracy of the atomic force microscope.

In the above embodiment, the XY fine movement mechanism 51 is used.
Is not essential to be arranged on the side of the sample 21, and may be arranged between the beak-shaped member 31 and the cantilever approach mechanism 24. An example of the XY fine movement mechanism 51 is shown in FIG. In the XY fine movement mechanism 51, the fixing rigid bodies 51X, 5
The X fine movement mechanism is formed by 1X, the moving rigid body 51A, the parallel plate springs 61 to 64 connecting them, and the piezoelectric elements 65 and 65 interposed between the rigid bodies 51A and 51X, and voltage is applied to the piezoelectric elements 65 and 65. Is applied, the moving rigid body 51A
A displacement Ux in the X-axis direction occurs at. Similarly, the rigid bodies 51Y and 51Y, the rigid body 51A, the parallel leaf springs 71 to 74 connecting them and the piezoelectric elements 75 and 75 interposed between the rigid bodies 51A and 51Y form a Y fine movement mechanism. In this case, when a voltage is applied to the piezoelectric elements 75, 75, the rigid bodies 51Y, 51Y can be moved in the Y axis direction so that a displacement Uy is generated in the Y axis direction with the rigid body 51A as a reference.
The XY fine movement mechanism 51 can sufficiently cope with the scanning of a large sample such as a silicon wafer.

The structure according to this embodiment is not limited to the atomic force microscope for a large sample, but can be used as an optical microscope combined atomic force microscope for measuring a small sample. In this case, it can be sufficiently put to practical use even for a system in which the sample is scanned by the tube type XY fine movement mechanism.

FIG. 7 shows an example of the structure of a detection optical system comprising a laser light source 15 and a photodetector 17, (a) is a front view,
(B) is a side view. As is clear from the figure, the laser beam 1 is applied to a plane including the direction in which the cantilever 13 bends.
The detection optical system is arranged so that the optical paths of 6 are orthogonal to each other. This solves the problem of interference between the optical lever optical system and the optical microscope in the atomic force microscope combined with the optical microscope.

In the above embodiment, the atomic force microscope combined with the optical microscope as the auxiliary observation device has been described, but the present invention is not limited to this, and a scanning probe microscope equipped with other auxiliary observation devices can be used. It can be generally used.

[0027]

As is apparent from the above description, according to the present invention, the cantilever and the probe and the surface of the sample can be observed simultaneously in the scanning probe microscope by using an auxiliary observation device such as an optical microscope. Since the Z fine movement mechanism is provided at the tip of the beak-shaped member and the cantilever is attached to the Z fine movement mechanism, it is possible to reduce the mass or the like that affects the Z fine movement mechanism, and to control the Z-axis in the servo direction. It can improve the characteristics and exhibit high speed,
The measurement performance of the scanning probe microscope can be improved.

[Brief description of drawings]

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

FIG. 2 is a specific enlarged configuration diagram of a main part of FIG.

FIG. 3 is an enlarged side view of the cantilever portion shown in FIG.

FIG. 4 is a side view showing another embodiment of the beak member and the Z drive mechanism.

FIG. 5 is a side view showing another embodiment of the beak member and the Z drive mechanism.

FIG. 6 is an external perspective view showing a specific example of the XY stage.

FIG. 7 is a diagram showing an arrangement configuration example of a detection optical system.

FIG. 8 is a configuration diagram showing a basic configuration of a conventional atomic force microscope.

FIG. 9 is a configuration diagram showing another example of a conventional atomic force microscope.

FIG. 10 is a configuration diagram showing still another example of a conventional atomic force microscope.

11 is a diagram showing a state of a field of view of an optical microscope in the device shown in FIG.

FIG. 12 is a diagram for explaining a problem of the conventional example shown in FIG.

[Explanation of symbols]

13 cantilevers 14 probes 15 Laser light source 16 laser light 21 samples 24 Cantilever approach mechanism 25 Optical microscope 26 XY stage 31 Beak member 51 XY fine movement mechanism 52 Z fine movement mechanism 53 Drive member 54 Elastic member 55 Piezoelectric element

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-199904 (JP, A) JP-A-3-110403 (JP, A) JP-A-5-312563 (JP, A) JP-A-5- 340713 (JP, A) JP 5-113308 (JP, A) JP 5-126515 (JP, A) JP 5-209713 (JP, A) JP 7-181030 (JP, A) JP-A-8-122342 (JP, A) JP-A-8-35972 (JP, A) JP-A-8-68799 (JP, A) JP-A-8-226928 (JP, A) JP-A-7-198731 (JP, A) Actual Kaihei 5-55008 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00-21/24 JISST file (JOIS)

Claims (2)

(57) [Claims] 1. A cantilever provided with a probe facing a sample at its tip, an auxiliary observation device capable of observing the surface of the sample and the back surface of the cantilever, and the cantilever arranged in the field of view of the auxiliary observation device. A beak-shaped member
A displacement detection device for detecting the displacement of the cantilever, an XY fine movement mechanism and a Z fine movement mechanism for displacing the relative positions of the probe and the sample are provided, and based on a physical quantity acting between the probe and the sample. In a scanning probe microscope in which the amount of deflection of the cantilever is controlled by the Z fine movement mechanism, and the surface of the sample is scanned by the XY fine movement mechanism to measure the sample, the Z fine movement mechanism is provided at the tip of the beak member. attached to, when the cantilever Ru attached to said Z fine movement mechanism
In both cases, the Z fine movement mechanism has a flat plate shape on the beak member.
The driving member coupled via an elastic member and the beak
A piezoelectric element provided between the plate-shaped member and the driving member
Scanning probe microscope characterized in that Ranaru. 2. The scanning probe microscope according to claim 1, wherein the auxiliary observation device is an optical microscope.