JPH06288759A - Scanning probe microscope - Google Patents

Abstract

PURPOSE:To precisely observe an irregular image even in the case when a sample surface has a large irregularity including a fine irregularity by adding one eliminating a high frequency component from detection output of a piezoelectric body displacement detection part to the other one eliminating a low frequency component of information of Z directional position control. CONSTITUTION:By scanning the surface of a sample on a sample table by a cantilever and so as to keep the distance between a probe on the head end of the cantilever and the surface of the sample constant in accordance with a Z directional displacement detection signal, Z directional position control of a piezoelectric body is carried out. Thereafter, one acquired by removing a high frequency component from a detection signal of a piezoelectric body displacement detection part 12 by an LPF 24 and the other acquired by removing a low frequency component of information on Z directional position control by an HPF 23 are added by an adder 22. By making a composed data of a Z displacement position added and acquired in this way as irregularity information of the sample surface, it is possible to acquire irregularity information in high precision and with high resolving power by way of reciprocally interpolating lowering of reliability of the low frequency component by a displacement characteristic of the piezoelectric body and badness of reliability of the high frequency component held by the displacement detection part 12.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a scanning probe microscope.

[0002]

2. Description of the Related Art A scanning probe microscope is for observing a fine surface shape of a sample. Conventionally, a scanning tunnel microscope (STM),
Atomic force microscope (AFM), magnetic force microscope (MFM) and the like are known.

The scanning tunneling microscope uses a conductive probe and supports the probe near a conductive sample which is a sample to be observed. Then, for example, the tip of the probe is brought close to the sample surface to about 1 nm, and a voltage is applied between the probe and the sample. Then, a tunnel current flows between the probe and the sample. This tunnel current changes depending on the distance between the probe and the sample, and its magnitude changes by about one digit for a distance change of 0.1 nm.

The probe is moved along the sample surface (for example, raster scanning). During this movement, the tunnel current value flowing between the probe and the sample becomes constant so that the probe and the sample are Piezoelectric body (fine movement position adjustment device) that adjusts the distance between
A control voltage is applied to maintain a constant distance between the probe and the sample.

That is, by utilizing the fact that the piezoelectric body expands and contracts in accordance with the applied voltage, the sample is held on the piezoelectric body so that the tunnel current value flowing between the probe and the sample becomes constant. A control voltage is applied to the piezoelectric body to control expansion and contraction, and the distance between the probe and the sample is adjusted. The scanning of the sample surface by the probe may be performed by moving the probe or by moving the sample.

As described above, as a result of controlling the piezoelectric body so that the distance between the probe and the sample is kept constant, the tip of the probe moves on a curved surface that reflects the surface shape of the sample. Therefore, the position of the probe tip on each scanning point can be calculated from the control voltage applied to the piezoelectric body, and based on the position data of the probe tip calculated from the control voltage applied to this piezoelectric body, By forming a three-dimensional image showing the surface shape of the sample, the surface shape of the sample can be observed.

Further, the atomic force microscope is an apparatus capable of observing the surface shape of an insulator in atomic order, and a probe for scanning the sample surface is supported by a flexible cantilever. Further, similarly to the above, the sample is held on the piezoelectric body so that the distance between the probe and the sample can be adjusted.

Then, in the atomic force microscope, when the probe is brought close to the sample surface, a van der Waals (Vander Waa) is generated between the atom at the tip of the probe and the atom on the sample surface.
ls) An attractive force due to the interaction is exerted, and when it is brought closer to the bond distance of atoms, the repulsive force due to the Pauli exclusion rule is utilized.

These attractive force and repulsive force (atomic force) are very small. However, since the probe is supported by a flexible cantilever, when the atom at the tip of the probe receives an interatomic force, the cantilever is displaced according to its size.
Then, when the probe is scanned along the sample surface, the distance between the probe and the sample changes corresponding to the unevenness of the sample surface, so the cantilever is displaced, and this cantilever detects the displacement amount. The fine movement position adjusting device constituted by the fine movement element such as the piezoelectric body is feedback-controlled to keep the displacement amount of the cantilever constant.

Therefore, since the voltage applied to the piezoelectric body at this time has a relationship depending on the surface shape of the sample being scanned by the probe, an uneven image of the sample surface can be obtained from this applied voltage information. .

Like the atomic force microscope, the magnetic force microscope scans the sample surface by scanning the sample surface while keeping the magnetic force acting between the probe and the magnetic particles of the sample constant. To obtain the uneven image of.

If the probe provided on the cantilever used in the atomic force microscope or the magnetic force microscope is made of a conductive material so that the tunnel current can be detected,
It can also be used as a scanning tunneling microscope. Also in the atomic force microscope and the magnetic force microscope, the scanning of the probe surface with respect to the sample may be either a method of moving the probe or a method of moving the sample.

By the way, a basic configuration example of such a scanning probe microscope is shown in a block diagram as shown in FIG. In the figure, 1 is a host computer, 2 is a microcomputer, 3 is an A / D converter, and 4 is a D / A converter for controlling the Z direction. Further, 5 is a D / A conversion unit for controlling the X direction, 6 is a D / A conversion unit for controlling the Y direction, 7 is a cantilever displacement detecting unit for detecting a cantilever Z displacement, 8 is a cantilever, and 8a is The probe 10, 10 is a sample, 11 is a sample stand, and 9 is a XYZ driving cylindrical piezoelectric body, which can be displaced in the XYZ axis directions by receiving the outputs of the D / A converters 4 to 6.

The sample table 11 is for mounting and holding the sample 10, and the sample table 11 is fixedly provided on the cylindrical piezoelectric body 9 constituting the moving stage.
The sample stage 11 and the cylindrical piezoelectric body 9 constitute a moving stage for the sample 10, and the position of the sample 10 on the sample stage 11 can be adjusted in the XYZ axis directions.

As shown in FIG. 8, the piezoelectric body 9 is a cylindrical piezoelectric body 9 formed of a cylindrical piezoelectric material, and an inner peripheral surface electrode 9a is formed on the entire inner peripheral surface thereof. On the outer peripheral surface of the die piezoelectric body 9, the outer peripheral electrode 9b is formed in each of the regions obtained by dividing the peripheral surface into four along the axial direction of the cylinder.

The inner peripheral surface electrode 9a is a common electrode, and by applying a voltage between the common electrode 9a and the outer peripheral side electrode 9b, the cylindrical piezoelectric body 9 is deformed according to the applied voltage ( Distortion). The lower part of the cylindrical piezoelectric body 9 is fixed and held by a solid base. A sample base 11 is fixedly attached to the upper end of the cylindrical piezoelectric body 9.

Of the four electrodes 9a of the cylindrical piezoelectric body 9 constituting the moving stage portion, a pair of electrodes facing each other are paired to drive one set for the X direction and the other set for the Y direction. By applying a voltage, it can be deformed in the X and Y directions. Further, by applying the same voltage level to the four electrodes 9a at the same time, the electrodes can be deformed in the Z direction.

As described above, the movable stage using the piezoelectric body 9 formed by forming the piezoelectric body into a cylindrical shape has a control signal (Z
The sample stage 2 can be moved in the X-axis, Y-axis, and Z-axis directions according to the control signal S2, the X control signal S3, and the Y control signal S4). As a result, the sample 1 is scanned in the X-axis and Y-axis directions with respect to the probe 8a of the cantilever 8 and the position is controlled in the Z-axis direction.

The cantilever 8 has its base end side fixed to a fixed position. Then, the cantilever 9 is configured so that the displacement of the free end tip side in the Z-axis direction is detected by the displacement detection unit 7 for detecting the cantilever Z displacement.

The cantilever displacement detector 7 detects the displacement in the Z-axis direction and generates a Z displacement signal S1 which is an output corresponding to the detected amount.

The microcomputer 2 plays a central role in controlling the system, and in order to scan the sample table 11 in the XY direction when measuring the sample 10, a scanning drive signal for the XY scanning is generated during observation to generate the X direction. , And Y-direction D / A converters 5 and 6, and in order to control the sample stage 11 in the Z-axis direction (axial direction of the cylindrical piezoelectric body 9), the control amount thereof is calculated to perform Z control. It also has a function of supplying the data to the host computer 1 by converting the data corresponding to the Z-axis direction control amount into information of the unevenness data of the sample surface and providing it to the host computer 1.

D / A converters 5 and 6 for the X and Y directions
Is for generating an X control signal S3 and a Y control signal S4 by scanning command outputs D3 and D4 for the X direction and the Y direction from the microcomputer 2 and giving them to the piezoelectric body 9. The piezoelectric body 9 is the X control signal. According to S3 and Y control signal S4, X-axis direction,
The piezoelectric body 9 is configured to be displaced in the Y-axis direction, and the displacement of the piezoelectric body 9 causes the X-axis of the sample 10 with respect to the probe 8a.
The Y scanning can be performed.

The A / D conversion unit 3 is a device for receiving the Z displacement signal S1 from the cantilever displacement detection unit 7 and converting it into digital data D1. The microcomputer 2 receives the digital data D1 and Z In order to keep the displacement signal S1 at the reference value, it has a function of outputting the digital data D2 of the Z control signal S2 for expanding and contracting the cylindrical piezoelectric body 9 in the Z-axis direction, and also the Z control signal S2. The digital data D2 of No. 2 is transferred to the host computer 1 as the unevenness data D8 indicating the unevenness information of the sample surface. Further, the host computer 1 forms an image of the surface unevenness of the sample 10 based on the unevenness data D8 and the XY scanning command information, and outputs and displays it on an output device such as a display device or a printer.

In such a structure, when the sample 10 is set on the sample table 11 and started, the microcomputer 2 sends the X control signal S3 and the Y control signal S3 through the D / A converters 5 and 6 in a cylindrical shape. Output to the piezoelectric body 9 and the cylindrical piezoelectric body 9
The sample 10 is two-dimensionally scanned by displacing it in the Y direction. As a result, the probe 8a at the tip of the cantilever 8 is XY-scanned under the following Z-axis control so that the surface of the sample 10 is held at a predetermined distance.

That is, when the probe 8a is brought close to the surface of the sample 10 for scanning, the tip of the probe is attracted or repelled by the influence of the atomic force or the magnetic force according to the unevenness of the surface of the sample 10, and the cantilever 8 is displaced. To do.

The cantilever displacement detector 7 detects the displacement of the tip of the cantilever 8 in the Z-axis direction and outputs a Z displacement signal S1. The Z displacement signal S1 is input to the A / D conversion unit 3,
It is converted into digital data and input to the microcomputer 2. The microcomputer 2 obtains a Z-axis displacement amount that keeps the Z-displacement signal S1 at a reference value in accordance with the Z-displacement signal S1 and outputs it as a Z control signal S2.

In this way, the microcomputer 2 obtains the Z-axis displacement amount that keeps the Z-displacement signal S1 at the reference value in accordance with the Z-displacement signal S1 and outputs it as the Z control signal S2.
Therefore, the cylindrical piezoelectric body 9 is controlled to expand and contract in the Z-axis direction according to the distance of the probe 8a to the sample surface, and the distance between the sample 10 and the tip of the probe 8a is controlled.

Further, the microcomputer 2 transfers the data of the Z control signal S2 to the host computer 1 as uneven data, and also sends the positional information of XY scanning together to the host computer 1 as the positional data. The host computer 1 forms an image of the surface unevenness of the sample 1 based on these information and displays it.

The scanning probe microscope is basically like this, but the reproducibility of the image becomes a problem because the piezoelectric body 9 has nonlinearity in its Z-direction displacement. In order to improve such non-linearity, the proposed device has a configuration as shown in FIG.

That is, FIG. 9 shows a cylindrical piezoelectric body 9 provided with a piezoelectric body displacement detector 12 for detecting the amount of displacement of the piezoelectric body 9 in the Z direction. The signal S5 is A / D converted by the A / D converter 21 and given to the microcomputer 2. The microcomputer 2 sends the data of the Z control signal S2 to the host computer 1 for the unevenness data.
Instead of being transferred as data, the detection output S5 of the piezoelectric displacement detection unit 12 is A / D converted by the A / D conversion unit 21 and digital data D5 of S5 is transferred to the host computer 1 as uneven data. To do.

In this apparatus, the structure of the sample scanning / detecting system including the piezoelectric body displacement detecting section 12 is schematically shown in FIG. 10, and the support column 13b is erected on the base 13a. The cantilever displacement detection part 7 is held on the upper portion of the support column 13b of the mold body 13. The cylindrical piezoelectric body 9 is erected on the base 13a of the mirror body 13 to fix the bottom portion.

A sample base 11 is fixed to the upper part of the cylindrical piezoelectric body 9, and a photodetector (light receiving element) 12a is positioned on the lower surface of the sample base 11 in the space inside the cylinder of the piezoelectric body 9.
Is provided. On the side of the base 13a, the laser diode 1 serving as a light source is arranged so as to face the inner space of the cylinder of the piezoelectric body 9.
2e is provided, and the collimator lens 12d and the condenser lens 1 are provided in the cylinder inner space of the piezoelectric body 9 near both ends thereof.
2b is provided.

When the piezoelectric body 9 is not deformed, the photodetector 12a and the laser diode 1 are
2e, the collimator lens 12d, and the condenser lens 12b are arranged with their optical axes aligned with the axis of the piezoelectric body 9.

As shown in FIG. 11, the photodetector 12a has a light receiving surface 101 in the center and has a circular shape. Then, the beam output from the laser diode 12e is collimated by the collimator lens 12d, then advances through the internal space of the cylinder of the piezoelectric body 9, is condensed by the condenser lens 12b, and forms a spot on the light receiving surface 101 of the photodetector 12a. .

When the piezoelectric body 9 has a standard length, FIG.
As shown in FIG. 11B, when the spot size is about two times larger than the diameter of the light receiving surface 101, the light is condensed on the light receiving surface 101 and the piezoelectric body 9 contracts in the Z direction, as shown in FIG. When the piezoelectric body 9 is focused on the light receiving surface 101 and extends in the Z direction with a spot size larger than that in the case of the length, FIG.
As shown in (c), by setting the position of the condenser lens 12b with respect to the photodetector 12a so that the light is condensed on the light receiving surface 101 with a spot size smaller than that of the standard length, the Z of the piezoelectric body 9 is reduced. The diameter of the focused spot 102 with respect to the light receiving surface 101 of the photodetector 12a increases or decreases depending on the expansion and contraction in the direction. Due to the change in the diameter of the focused spot 102,
This is a configuration in which the detection output corresponding to the expansion / contraction amount of the piezoelectric body 9 in the Z direction is obtained from the photodetector 12a by utilizing the change in the light amount of the light receiving surface 101.

According to the scanning probe microscope using the piezoelectric body displacement detecting section 12 having such a configuration, the sample 10 is scanned in the two-dimensional direction while moving in the Z direction, and the piezoelectric body 9 at this time in the Z direction. The amount of displacement is detected by the piezoelectric body displacement detector 12, and the detected Z displacement signal S5 is detected by the A / D converter 2
The data D5 obtained by A / D conversion in 1 can be used for image formation as unevenness information of the sample surface.

Therefore, in the case of this configuration, as long as the detection accuracy of the piezoelectric body displacement detection section 12 is ensured, it is possible to reproduce the uneven image in which the influence of the nonlinearity of the cylindrical piezoelectric body 9 is eliminated.

[0038]

In the conventional scanning probe microscope as shown in FIG. 7, the microcomputer 2 performs Z direction control (Z servo) calculation so as to keep the sample surface and the tip of the probe at a constant distance. , A Z control signal S2 is applied from the D / A converter (Z) 4 to the cylindrical piezoelectric body 9 to expand and contract the cylindrical piezoelectric body 9, and the sample 10 is scanned in the two-dimensional direction while moving in the Z direction. An image is formed using the Z control signal S2 (Z servo calculation value) at this time as the unevenness information of the sample surface.

Further, in the configuration of FIG. 9, in order to improve the nonlinearity of the displacement of the piezoelectric body 9 in the Z direction, the sample 10 is scanned in the two-dimensional direction while moving in the Z direction as in FIG. The displacement of the piezoelectric body 9 in the Z direction is detected by the piezoelectric body displacement detection unit 12, and the detected Z displacement signal S5 is A / D converted by the A / D conversion unit 21 to form an image as unevenness information of the sample surface. It is something that is done.

In any case, the scanning probe microscope is
Z the sample so that the sample surface and the tip of the probe are kept at a certain distance.
While controlling the direction, scanning is performed in a two-dimensional direction, and the information corresponding to the displacement amount of the piezoelectric body Z direction at this time is used as the unevenness information of the sample surface to form an image.

By the way, when the Z control signal S2 is generated so that the Z displacement signal S1 obtained from the cantilever displacement detection unit 7 becomes a constant value, and the Z direction displacement control of the piezoelectric body 9 is performed, the Z control signal S2 is generated. Level is affected by the characteristics of the piezoelectric body. That is, as the characteristic of the piezoelectric body, there is a hysteresis characteristic as shown in FIG. 12A in which the relationship with the displacement with respect to the applied voltage is present, and therefore the level of the Z control signal S2 is adapted to this hysteresis characteristic. Therefore, there is distortion along this hysteresis characteristic, and it does not accurately reflect the actual unevenness of the sample.

Due to the nature of the hysteresis characteristic, there is little effect on microscopic unevenness, which is a microscopic change, but it is directly affected by a macroscopic height change of the sample. Therefore, the resolution is good, but the overall accuracy becomes a problem.

On the other hand, in order to solve this problem, an apparatus provided with a Z displacement detecting means for detecting the Z displacement of the piezoelectric body is shown in FIG.
It is the structure of. However, since the Z displacement detection resolution is inferior to the piezoelectric applied voltage signal, only unevenness information with low resolution can be obtained.

That is, as described above, the piezoelectric body displacement detection section 12, which is the Z displacement detection means, is provided below the sample table above the cylindrical piezoelectric body by the optical system provided in the cylindrical space of the cylindrical piezoelectric body. The photodetector is configured to focus a light spot, and the Z-direction displacement amount of the cylindrical piezoelectric body is obtained in the form of a detection signal corresponding to the brightness per unit area.

In this case, the detection characteristic of the photodetector is low in its ability to detect a minute Z displacement because it detects the amount of light. Therefore, although the resolution is low, on the other hand, as shown in FIG. 12B, the detection characteristic of the photodetector shows a saturation characteristic with respect to the Z displacement amount of the cylindrical piezoelectric body, but the linear range is wide. . This means that the degree of macroscopic change of the sample can be accurately detected.

Therefore, in the case where the surface of the sample has large unevenness as a whole and includes fine unevenness, the uneven image of the sample cannot be accurately observed by any of the above methods.

Therefore, the object of the present invention is to
An object of the present invention is to provide a scanning probe microscope capable of accurately observing an uneven image even when the surface of the sample has large unevenness as a whole and further includes fine unevenness.

[0048]

In order to achieve the above object, the present invention has the following constitution. That is, according to the present invention, the sample stage is controlled by the displacement control of the piezoelectric body in the XYZ directions.
Scanning and Z position control are performed, the surface of the sample on the sample table is scanned by the cantilever, the Z direction displacement of the cantilever is detected at that time, and the probe at the tip of the cantilever and the sample surface are detected based on this detection signal. In the scanning probe microscope, the piezoelectric body is controlled in the Z direction so as to keep a constant distance, and an uneven image on the surface of the sample is reproduced based on the information on the Z direction. The piezoelectric body Z-direction displacement detection means for optically detecting the Z-direction displacement, the first means for removing high-frequency components from the detection output of the piezoelectric body Z-direction displacement detection means, and the Z-direction position control information. A second means for removing the low frequency component of this information and an adding means for adding the outputs obtained through the first and second means to obtain the Z-direction position information are configured. did.

[0049]

In such a configuration, the one obtained by removing the high frequency component from the detection output of the piezoelectric body Z direction displacement detecting means and the one obtained by removing the low frequency component of the Z direction position control information are added. By using the synthetic data of the Z displacement position obtained by this addition as the unevenness information of the sample surface, the reliability of the low frequency component due to the displacement characteristics of the piezoelectric body is lowered (the accuracy for the microscopic change of the sample surface is good. However, the precision with respect to macroscopic changes) and the reliability of the high frequency component of the piezoelectric body Z-direction displacement detection means (the precision with respect to macroscopic changes on the sample surface is good, but the precision with respect to microscopic changes is poor). Is mutually interpolated so that highly accurate and high resolution unevenness information can be obtained.

In the present invention, the Z direction displacement detecting means for optically detecting the Z displacement of the piezoelectric body, which is the sample fine movement scanning mechanism, is provided, and the Z control (so as to keep the sample surface and the tip of the cantilever probe at a constant distance). (Z servo) system, the piezoelectric body is expanded and contracted and displaced, and when the sample is scanned in the two-dimensional direction while moving in the Z direction, the low frequency component of the Z displacement signal and the high frequency component of the Z control signal detected by the Z displacement detection means. Of the combined signal
This is used for image formation as unevenness information of the sample surface.

This makes it possible to obtain highly accurate and high-resolution ruggedness information. Therefore, according to the present invention, even when the surface of the sample has large ruggedness as a whole, and includes fine ruggedness, It is possible to provide a scanning probe microscope capable of accurately observing the unevenness image.

[0052]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows the arrangement of a scanning probe microscope according to the first embodiment of the present invention. In the figure,
Reference numeral 1 is a host computer, 2 is a microcomputer (microcomputer), 3 is an A / D converter, and 4 is a D / A converter for controlling the Z direction. Further, 5 is a D / A converter for controlling the X direction, and 6 is a D / A converter for controlling the Y direction.
A conversion unit, 7 is a cantilever displacement detection unit that detects the displacement of the cantilever Z, 8 is a cantilever, and 8a is a probe.

Reference numeral 12 is a piezoelectric displacement detection unit, and 21 is A.
A / D converter, 22 is an adder, 23 is a high-pass filter (HPF), and 24 is a low-pass filter (LPF).

Further, 10 is a sample, 11 is a sample stand, and 9 is X.
A cylindrical piezoelectric body for YZ drive, comprising the D / A converter 4
It is possible to displace in the XYZ axis directions by receiving the outputs of ~ 6.

The sample table 11 is for mounting and holding the sample 10, and the sample table 11 is fixedly provided on the cylindrical piezoelectric body 9 constituting the moving stage.
The sample stage 11 and the cylindrical piezoelectric body 9 constitute a moving stage for the sample 10, and the position of the sample 10 on the sample stage 11 can be adjusted in the XYZ axis directions.

As described with reference to FIG. 8, the piezoelectric body 9 is a cylindrical piezoelectric body 9 formed by forming a piezoelectric material into a cylindrical shape, and an inner peripheral surface electrode 9a is formed on the entire inner peripheral surface thereof. On the outer peripheral surface of the cylindrical piezoelectric body 9, the outer peripheral side electrode 9b is formed in each of the regions obtained by dividing the peripheral surface into four along the axial direction of the cylinder.

The inner peripheral surface electrode 9a is a common electrode, and by applying a voltage between the common electrode 9a and the outer peripheral side electrode 9b, the cylindrical piezoelectric body 9 is deformed according to the applied voltage ( Distortion). The lower part of the cylindrical piezoelectric body 9 is fixed and held by a solid base. A sample base 11 is fixedly attached to the upper end of the cylindrical piezoelectric body 9.

Of the four electrodes 9a of the cylindrical piezoelectric body 9 constituting the moving stage portion, a pair of electrodes facing each other are paired to drive one set for the X direction and the other set for the Y direction. By applying a voltage, it can be deformed in the X and Y directions. Further, by applying the same voltage level to the four electrodes 9a at the same time, the electrodes can be deformed in the Z direction.

The moving stage using such a cylindrical piezoelectric body 9 has control signals (Z control signal S3, X control signal S).
4, the Y-control signal S5),
It can move in the Z-axis direction. As a result, the sample 1 is scanned in the X-axis and Y-axis directions with respect to the probe 8a of the cantilever 8.
Further, the position is controlled in the Z-axis direction.

The cantilever 8 has its base end side fixed to a fixed position. Then, the cantilever 9 is configured so that the displacement of the free end tip side in the Z-axis direction is detected by the displacement detection unit 7 for detecting the cantilever Z displacement.

The cantilever displacement detector 7 detects the displacement in the Z-axis direction and generates the Z displacement signal S1 which is an output corresponding to the detected amount.

The microcomputer 2 plays a central role in controlling the present system, and in order to perform XY scanning of the sample table 11 when observing the sample 10, generates a scanning drive signal for XY scanning to generate X.
To the D / A converters 5 and 6 for the direction and the Y direction, and
In order to control the sample table 11 in the Z-axis direction (axial direction of the cylindrical piezoelectric body 9), the control amount is calculated and the D / A for Z control is used.
It has a function of supplying the data to the conversion unit 4 or converting data corresponding to the Z-axis direction control amount into information of unevenness data of the sample surface and supplying the information to the host computer 1.

D / A converters 5 and 6 for the X and Y directions
Is for generating an X control signal S3 and a Y control signal S4 by scanning command outputs D3 and D4 for the X direction and the Y direction from the microcomputer 2 and giving them to the piezoelectric body 9. The piezoelectric body 9 is the X control signal. According to S3 and Y control signal S4, X-axis direction,
The piezoelectric body 9 is configured to be displaced in the Y-axis direction, and the displacement of the piezoelectric body 9 causes the X-axis of the sample 10 with respect to the probe 8a.
The Y scanning can be performed.

The A / D converter 3 is a device for receiving the Z displacement signal S1 from the cantilever displacement detector 7 and converting it into digital data D1. The microcomputer 2 receives the digital data D1 and outputs the Z signal. In order to keep the displacement signal S1 at the reference value, it has a function of outputting the digital data D2 of the Z control signal S2 for expanding and contracting the cylindrical piezoelectric body 9 in the Z-axis direction.

The piezoelectric body displacement detector 12 detects the displacement amount of the cylindrical piezoelectric body 9 in the Z direction and outputs a signal corresponding to the displacement amount as an analog signal. I am using one. Low pass filter 2
Reference numeral 4 is a filter that passes the low frequency component of the detection output S5 of the piezoelectric body displacement detection unit 12.

The high pass filter 23 receives the signal S2 for Z displacement control output from the D / A converter 4,
The adder 22 is a filter that passes the high frequency component, and the adder 22 adds the signals that have passed through the filters 23 and 24. The A / D converter 21 is for A / D converting and outputting the output S8 of the adder 22, and the data A / D converted by the A / D converter 21 is given to the microcomputer 2. It is as a configuration.

In the microcomputer 2, instead of transferring the data of the Z control signal S2 to the host computer 1 as uneven data, the digital data from the A / D converter 21 is transferred to the host computer 1 as uneven data. The configuration is

Further, the host computer 1 forms an image of the surface unevenness of the sample 10 based on the unevenness data and the XY scanning command information, and outputs and displays it on an output device such as a display device or a printer.

Next, the operation of the apparatus having the above configuration will be described.

In the above structure, the sample 10 is placed on the sample table 1
Set it on 1 and start it.
The X control signal S3 and the Y control signal S are transmitted through the A conversion units 5 and 6.
3 is output to the cylindrical piezoelectric body 9, the cylindrical piezoelectric body 9 is displaced in the XY directions, and the sample 10 is two-dimensionally scanned. As a result, the cantilever 8 probe 8a is XY-scanned under the following Z-axis control so that the surface of the sample 10 is held at a predetermined distance.

That is, when the probe 8a is brought close to the surface of the sample 10 for scanning, the tip of the probe is attracted or repelled by the influence of the atomic force or the magnetic force according to the unevenness of the surface of the sample 10, and the cantilever 8 is displaced. To do.

The cantilever displacement detector 7 detects the displacement of the tip of the cantilever 8 in the Z-axis direction and outputs a Z displacement signal S1. The Z displacement signal S1 is input to the A / D conversion unit 3,
It is converted into digital data and input to the microcomputer 2. The microcomputer 2 obtains a Z-axis displacement amount that keeps the Z-displacement signal S1 at a reference value in accordance with the Z-displacement signal S1 and outputs it as a Z control signal S2.

In this way, the microcomputer 2 obtains a Z-axis displacement amount that keeps the Z-displacement signal S1 at a reference value in accordance with the Z-displacement signal S1 and outputs it as a Z control signal S2.
Therefore, the cylindrical piezoelectric body 9 is controlled to expand and contract in the Z-axis direction according to the distance of the probe 8a to the sample surface, and the distance between the sample 10 and the tip of the probe 8a is controlled.

The displacement of the cylindrical piezoelectric body 9 in the Z direction is detected by the piezoelectric body displacement detector 12. Then, the signal S6 obtained by removing the low frequency component of the Z control signal S2 by the high pass filter 23 and the signal S7 obtained by removing the high frequency component of the Z displacement signal S5 by the low pass filter 24 are added by the adder 22,
The added signal is input to the A / D converter 21 as a Z composite signal S8 and converted into digital data. This A /
The Z displacement combined data from the D conversion unit 21 is input to the microcomputer 2, and the microcomputer 2 transfers this Z displacement combined data to the computer 1 as unevenness information of the sample surface.
Also, the position information of the XY scanning is combined and sent as position data to the host computer 1. The host computer 1 forms an image of the surface irregularities of the sample 10 based on these information and displays it.

Here, the Z control signal S2 from the D / A converter 4 has good resolution but poor accuracy. Therefore, by removing the low-frequency component of the Z control signal S2 with the high-pass filter 23, only the information on the fine unevenness is extracted, and the signal S6 of that information is obtained.

Further, the Z direction displacement amount detection signal S5 of the piezoelectric body 9 from the piezoelectric body displacement detection section 12 is the overall accuracy, that is,
Although it deals with macro displacement, it does not deal with small changes and has poor resolution. Therefore, the high-frequency component of the Z displacement signal S5 from the piezoelectric body displacement detection unit 12 is removed by the low-pass filter 24 to remove the information of the fine unevenness component, and the highly accurate overall change signal S7 is extracted. To get

Then, the signal S6 and the signal S7 are combined by the adder 22 to obtain the Z displacement combined signal S8, and this Z displacement combined signal S8 reflects the unevenness information of the actual surface of the scanned sample 10. Become a signal. Therefore, if the Z displacement composite signal S8 is converted into digital data by the A / D converter 21, and this data is given to the host computer 1 to form an image of the surface unevenness of the sample 10, the state of the scanning surface of the sample will be obtained. An image that accurately captures is obtained.

That is, the scanning probe microscope scans the sample in the two-dimensional direction while controlling the sample in the Z direction so that the sample surface and the tip of the probe are kept at a constant distance. An image is formed by using the corresponding information as the unevenness information of the sample surface.

Then, when the Z control signal S2 is generated so that the Z displacement signal S1 obtained from the cantilever displacement detection unit 7 becomes a constant value and the Z direction displacement control of the piezoelectric body 9 is performed, the Z control signal S2 is generated. Level is affected by the characteristics of the piezoelectric body. That is, as the characteristic of the piezoelectric body, there is a hysteresis characteristic as shown in FIG. 12A in which the relationship with the displacement with respect to the applied voltage is present, and therefore the level of the Z control signal S2 is adapted to this hysteresis characteristic. Therefore, there is distortion along this hysteresis characteristic, and it does not accurately reflect the actual unevenness of the sample.

Due to the nature of the hysteresis characteristics, there is little effect on microscopic unevenness, which is a microscopic change, but it is directly affected by a macroscopic height change of the sample. Therefore, originally, for a sample having irregularities as shown in FIG. 2A, the signal becomes as shown in FIG. 2B and the resolution is good, but the overall accuracy becomes a problem.

On the other hand, as described above, the piezoelectric body displacement detection unit 12 for detecting the Z displacement of the piezoelectric body is provided below the sample table above the cylindrical piezoelectric body by the optical system provided in the cylindrical space of the cylindrical piezoelectric body. The configuration is such that a light spot is focused on the provided photodetector, and the displacement amount of the cylindrical piezoelectric body in the Z direction is obtained in the form of a detection signal corresponding to the brightness per unit area.

In this case, since the detection characteristic of the photodetector is the detection of the amount of light, the noise component becomes the main component for a minute Z displacement, and the detection capability is low.
Therefore, although the resolution is low, on the other hand, as shown in FIG. 12B, the detection characteristic of the photodetector shows a saturation characteristic with respect to the Z displacement amount of the cylindrical piezoelectric body, but the linear range is wide. . This means that the degree of macroscopic change of the sample can be accurately detected. Therefore, for a sample having irregularities as shown in FIG.
And the resolution is low.

Therefore, when the surface of the sample has large unevenness as a whole as shown in FIG. 2 (a) and includes fine unevenness, the piezoelectric body displacement detection unit 12 also receives the Z control signal S2. Also in the output S5 of 1., the signal does not accurately reflect the condition of the surface of the sample.

Therefore, in this embodiment, although the resolution is good, the low-precision Z control signal S2 having a low precision is removed by the high-pass filter 23 to obtain a signal S6 as shown in FIG. 2D. This signal S6 is obtained by extracting only the information on the fine unevenness for which the accuracy is guaranteed and removing the component for which the accuracy is not guaranteed.

The accuracy of the degree of macroscopic change of the sample is guaranteed, but the Z displacement signal S with low resolution is obtained.
5 is removed by the low-pass filter 24, the information of the fine unevenness component is removed as shown in FIG. 2 (e), and the signal S7 in which a highly accurate overall variation is extracted is obtained. .

Then, the signal S6 and the signal S7 are combined by the adder 22, and the Z displacement combined signal S as shown in FIG.
By being obtained as 8, the Z displacement combined signal S8 becomes a signal reflecting the unevenness information of the actual surface of the scanned sample 10. Therefore, if the Z displacement composite signal S8 is converted into digital data by the A / D converter 21, and this data is given to the host computer 1 to form an image of the surface unevenness of the sample 10, the state of the scanning surface of the sample will be obtained. It is possible to obtain an image that accurately captures.

As described above, in the case of the first embodiment, the displacement of the cantilever 8 is detected by the cantilever displacement detection unit 7, the Z displacement signal S1 is obtained, and the Z displacement signal S1 is kept at a constant value by the microcomputer 2. Generate a Z control signal such as
The XYZ driving cylindrical piezoelectric body 9 is displaced by Z, and
A Y control signal is given to perform two-dimensional scanning.
2, the signal S6 obtained by removing the low frequency component of the Z control signal S2 by the high pass filter 23 and the signal S7 obtained by removing the high frequency component of the Z displacement signal S5 by the low pass filter 24 are added by the adder 22. The obtained signal is obtained as a Z displacement combined signal S8, which is transferred as the unevenness information of the sample surface from the microcomputer 2 to the computer 1 to form an image.

Therefore, as is clear from FIG. 2, the Z-displacement composite signal S8 is a signal that accurately reflects the condition of the sample surface, and by utilizing this as unevenness information for image formation, the conventional drawbacks are eliminated. The device can obtain highly accurate and high resolution unevenness information.

In this embodiment, the high pass filter 23 and the low pass filter 24 can be replaced with filters such as band pass filters having different pass frequency bands. Therefore, an embodiment in this case will be described next as a second embodiment.

(Second Embodiment) FIG. 3 shows the configuration. In the case of this embodiment, the high-pass filter 23 in the first embodiment is replaced with a band-pass filter 25, and the low-pass filter 24 is replaced with a band-pass filter 26.

The second embodiment is the same as the first embodiment in that the Z displacement control, the XY scanning control, and the composite signal S8 are obtained and used for image formation in the host computer 1. The difference from the first embodiment is that the amount of expansion and contraction of the cylindrical piezoelectric body 9 in the Z direction is detected by the piezoelectric body displacement detection unit 12, and at this time, the Z displacement signal S5 from the piezoelectric body displacement detection unit 12 is passed through the low pass filter 24. While the signal S7 from which the high frequency component has been removed is obtained, the bandpass filter 2
In the first embodiment, the Z control signal S2 is obtained as the signal S6 from which the low frequency component is removed through the high pass filter 23, whereas the band pass filter 25 is obtained. The signal S10 is taken out via the adder 22 and the signals S10 and S9 are added by the adder 22 to obtain the Z displacement combined signal S8.

That is, in order to keep the Z displacement detection signal S1 at a constant value, the XYZ driving cylindrical piezoelectric body 9 is expanded and contracted in the Z direction via the D / A conversion section (Z) 4. The displacement of the piezoelectric body 9 in the Z direction is detected by the piezoelectric body displacement detection unit 12, and at this time, a frequency component effective as the unevenness signal of the Z control signal S2 (a high frequency noise component unsuitable as the unevenness signal or the piezoelectric body) is detected. Only the signal S8 extracted by the band pass filter 25 and the frequency component effective as the uneven signal of the Z displacement signal S5 (a high-frequency noise component unsuitable as the uneven signal or Only the band (excluding the low frequency component affected by thermal drift) is added by the adder 22 to the signal S9 extracted by the bandpass filter 26, and this added signal is referred to as the Z displacement combined signal S8. .

As a result, high frequency noise components unsuitable for the concavo-convex signal and low frequency components affected by the hysteresis of the piezoelectric body are removed, and high frequency noise components unsuitable for the concavo-convex signal and low influences such as thermal drift. Both signals S2, S5 of only effective frequency components excluding frequency components
It is possible to reproduce as a synthetic signal that accurately reflects the sample surface condition due to the component whose accuracy is guaranteed.

The Z displacement composite signal S8 reproduced in this way is output to the A / D conversion unit 21, and the A / D conversion unit 21 is output.
The Z displacement combined data read from the device is transferred from the microcomputer 2 to the computer 1 as image information on the sample surface to form an image.

By using the Z displacement combined signal S8 as the unevenness information of the sample surface, an image having the unevenness information with high accuracy and high resolution can be obtained.

(Third Embodiment) FIG. 4 shows a scanning probe microscope according to a third embodiment of the present invention. In the third embodiment, the bandpass filter 25 in the second embodiment is replaced with a series circuit of a highpass filter 27 and a lowpass filter 28,
Further, the bandpass filter 26 is replaced by a highpass filter 29.
And the low pass filter 30 is replaced with a series circuit.

The third embodiment is the same as the first embodiment in that the Z displacement control, the XY scanning control, and the composite signal S8 are obtained and used for image formation in the host computer 1. The difference from the second embodiment is that the amount of expansion and contraction of the cylindrical piezoelectric body 9 in the Z direction is detected by the piezoelectric body displacement detection unit 12, and at this time, the Z displacement signal S5 from the piezoelectric body displacement detection unit 12 is sent to the bandpass filter 26. What has been taken out via the high pass filter 27 and the low pass filter 30 is taken out as a signal S11, and the Z control signal S2 is taken out via the band pass filter 25 in the second embodiment. The points are obtained as a signal S12 through the high-pass filter 29 and the low-pass filter 30, and the points where these signals S11 and S12 are added by an adder 22 to obtain a Z displacement combined signal S8.

That is, the cylindrical piezoelectric body 9 for XYZ driving is expanded and contracted in the Z direction via the D / A converter (Z) 4 so as to keep the Z displacement detection signal S1 at a constant value. The displacement of the piezoelectric body 9 in the Z direction is detected by the piezoelectric body displacement detection unit 12, and at this time, a frequency component effective as the unevenness signal of the Z control signal S2 (a high frequency noise component unsuitable as the unevenness signal or the piezoelectric body) is detected. Only the band excluding the low frequency component affected by the hysteresis) is extracted by passing through the high pass filter 27 and the low pass filter 28 (signal S11),
These are added by the adder 22, and the added signal is set as the Z displacement combined signal S8.

The high-pass filter 29 and the low-pass filter of only the frequency component effective as the uneven signal of the Z displacement signal S5 (the band excluding the high-frequency noise component unsuitable as the uneven signal and the low-frequency component that is affected by thermal drift etc.) The signal S9 is extracted by passing through 30 (signal S12), and the signal S9 extracted by the bandpass filter 26 is added by the adder 22, and the added signal is taken as the Z displacement combined signal S8.

As a result, high frequency noise components unsuitable for the concavo-convex signal and low frequency components affected by the hysteresis of the piezoelectric body are removed, and high frequency noise components unsuitable for the concavo-convex signal, thermal drift, etc. are low. Both signals S2, S5 of only effective frequency components excluding frequency components
It is possible to reproduce as a synthetic signal that accurately reflects the sample surface condition due to the component whose accuracy is guaranteed.

The Z displacement composite signal S8 reproduced in this way is output to the A / D conversion unit 21.
The Z displacement combined data read from the device is transferred from the microcomputer 2 to the computer 1 as image information on the sample surface to form an image.

By using the Z displacement combined signal S8 as the unevenness information of the sample surface, an image having the unevenness information with high accuracy and high resolution can be obtained.

In this embodiment, the high-pass filter 27 removes high-frequency noise components that are inappropriate as the unevenness signal of the Z control signal S2, and the low-pass filter 28 removes low-frequency components affected by the hysteresis of the piezoelectric material. As a result, the signal S11 is obtained, and the high-frequency noise component unsuitable as the unevenness signal of the Z displacement signal S5 has a high pass filter 2
9 and the low-frequency component affected by the thermal drift is removed by the low-pass filter 30.
To get

Passing the series circuit of the high-pass filter 27 and the low-pass filter 28 and the series circuit of the high-pass filter 29 and the low-pass filter 30 is the same as passing the band-pass filter.
9. The cutoff frequencies of the low-pass filters 28 and 30 can be changed independently, so that finer component extraction can be performed than the method of the second embodiment in which the effective component is extracted only by the bandpass filter. As a result, it becomes possible to reproduce more accurate unevenness information.

(Fourth Embodiment) In the structure of the third embodiment shown in FIG. 4, if there is no influence of thermal drift or the like, as shown in the block diagram of FIG.
The high-pass filter 29 may be removed from the above configuration.

(Fifth Embodiment) In the configurations of the scanning probe microscopes shown in the first to fourth embodiments, the Z displacement combined signal S8 is obtained by the analog circuit in all of them, but in the fifth embodiment. The Z displacement synthetic data D8 is obtained by signal processing by software in the microcomputer 2.

An example will be described in the case of being applied to the first embodiment. FIG. 6 is a flowchart showing a case where the generation system of the Z signal combined signal S8 shown in the first embodiment is applied to the software in the microcomputer 2 by signal processing. In this case, the high-pass filter 23, the low-pass filter 24, and the adder 22 are unnecessary, and the output S5 of the piezoelectric body displacement detection unit 12 is given to the microcomputer 2 via the A / D conversion unit 21. Therefore, the A / D converter 21 is not for digitizing the Z signal composite signal S8, but exclusively for digitizing the output S5 of the piezoelectric body displacement detector 12.

The fifth embodiment will be described with reference to FIG. 6. S1 output from the cantilever displacement detector 7
Is digitally converted by the A / D conversion unit 3 to obtain cantilever displacement data D1 (ST1). Based on this, the microcomputer 2
Then, the Z control data D2, which is the digital data of S2 given to the Z D / A converter 4, is obtained (ST2).

On the other hand, the Z control data D2 is high-pass filtered by software processing in the microcomputer 2 to obtain data D6 (ST3), and the Z displacement signal S5 is A / D converted by the A / D converter 21. Z converted and input
The displacement data D5 is acquired (ST4), and the acquired Z displacement data D5 is low-pass filtered to obtain data D7 (ST5).

The data D6 thus obtained and the data D7 are added together to calculate the Z displacement combined data D8 (ST6). Then, the calculated Z displacement combined data D8 is transferred from the microcomputer 2 to the computer 1 as the unevenness information of the sample surface (ST7).

Next, it is checked whether or not the measurement is completed (ST
8) If not, create X scan data D3 and Y scan data D4 to specify the next scan position,
The XY control signals S3 and S4 are generated by giving the corresponding D / A converters 5 and D / A converters 6, respectively, and the operation returns to ST1 to repeat the above operation (ST9). If the measurement is completed in the check of ST8, the above process is ended.

In the present embodiment, the signal processing by software in the microcomputer 2 is not limited to the high pass filter and the low pass filter, but may be a filter such as a band pass filter having a different pass frequency band in the second embodiment, or the third embodiment. The cutoff frequency in the example can be replaced with a filter in which a high-pass filter, a low-pass filter, and the like, which can be changed and set independently, are combined.

Further, the signal processing by the soft filter is not limited to the microcomputer 2, but the host computer 1 may be used, or the microcomputer 2 may be replaced with a DSP or the like to perform more complicated filter processing.

Although various embodiments have been described above,
The present invention performs XY scanning and position control in the Z direction by controlling the displacement of the piezoelectric body in the XYZ directions, scans the surface of the sample on the sample stage with a cantilever, and detects the Z direction displacement of the cantilever at that time. Based on this detection signal, the Z-direction position of the piezoelectric body is controlled so that the distance between the probe at the tip of the cantilever and the surface of the sample is kept constant.
In a scanning probe microscope that reproduces an uneven image of the surface of a sample based on information on the directional position, piezoelectric body Z-direction displacement detection means for optically detecting Z-direction displacement of the piezoelectric body, and this piezoelectric body. A first means for removing a high frequency component from the detection output of the Z direction displacement detecting means, a second means for removing a low frequency component of this information using the information of the Z direction position control, and the first and the second means. 2 is added to the output obtained via the means to obtain information on the position in the Z direction, and the combined data of the Z displacement position obtained by the addition is used as the unevenness of the sample surface. By using the information, the reliability of the low frequency component due to the displacement characteristic of the piezoelectric body is lowered (the accuracy is good for microscopic changes on the sample surface, but the accuracy is poor for macroscopic changes), and the displacement detection of the piezoelectric body in the Z direction is performed. High frequency of means Reliability of poor component (accuracy good for macroscopic change of the sample surface, poor accuracy for microscopic changes) so the by mutual interpolation high accuracy and high resolution unevenness information obtained.

[0116]

As described above in detail, according to the present invention, a scanning probe capable of performing highly accurate and high-resolution sample surface shape measurement without being affected by the displacement voltage hysteresis characteristic of the piezoelectric body. A microscope can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining how the Z displacement combined signal is generated based on the processing according to the present invention.

FIG. 3 is a block diagram showing the overall configuration of a second embodiment of the present invention.

FIG. 4 is a block diagram showing the overall configuration of a third embodiment of the present invention.

FIG. 5 is a block diagram showing the overall configuration of a fourth embodiment of the present invention.

FIG. 6 is a flowchart illustrating a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional example.

FIG. 8 is a perspective view showing the configuration of a cylindrical piezoelectric body.

FIG. 9 is a block diagram showing a configuration of a conventional example.

FIG. 10 is a cross-sectional view showing a configuration example of the piezoelectric body displacement detection unit 12 and its vicinity.

FIG. 11 is a diagram for explaining how the piezoelectric body displacement detection unit 12 detects.

FIG. 12 is a piezoelectric displacement characteristic and a piezoelectric displacement detection unit 12
The figure which shows the relationship between the output signal detected by and the displacement of a piezoelectric material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Host computer 2 ... Microcomputer 3 ... A / D converter 4 ... D / A converter for Z direction control 5 ... D / A converter for X direction control 6 ... D / A converter for Y direction control 7 ... Cantilever displacement detector 8 ... Cantilever 8a ... Probe 9 ... XYZ driving cylindrical piezoelectric body 10 ... Sample 11 ... Sample stand 12 ... Piezoelectric displacement detector 21 ... A / D converter 22 ... Adder 23 ... High-pass filter (HPF) 24, 28, 30 ... Low-pass filter (LPF) 25, 26 ... Band-pass filter (HPF)

Claims (1)

[Claims] 1. A XY scanning and a Z-direction position control are performed on a sample stage by displacement control of a piezoelectric body in the XYZ directions, and a surface of a sample on the sample stage is scanned by a cantilever.
The Z-direction displacement of the cantilever is detected, and based on this detection signal, the Z-direction position of the piezoelectric body is controlled so that the distance between the probe at the tip of the cantilever and the sample surface is kept constant.
In a scanning probe microscope adapted to reproduce an uneven image of the surface of a sample based on the information on the Z-direction position, piezoelectric body Z-direction displacement detection means for optically detecting the Z-direction displacement of the piezoelectric body, First means for removing a high-frequency component from the detection output of the piezoelectric body Z-direction displacement detection means, second means for removing a low-frequency component of this information by using the information of the Z-direction position control, and these first means And a means for adding the outputs obtained through the second means to obtain information on the position in the Z direction, and a scanning probe microscope.