JP3497359B2 - Probe control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an actuator that automatically controls the distance between two objects. For example, it can be obtained from the distance between a sample and a probe in a near field microscope, a scanning tunneling microscope or the like. The present invention relates to a probe control device that controls a distance between a sample and a probe of a device that outputs a generated signal.

[0002]

2. Description of the Related Art A scanning tunneling microscope (STM), an atomic force microscope (AFM), a near field microscope (photon tunneling microscope: PTM) is used as a microscope capable of observing the structure of an atomic level microscopic fine sample in a real space. Is well known. Especially in the last 10 years, STM,
The research and development of AFM has progressed, and the products have already been released. Along with this, the range of application is rapidly expanding to various fields. There are many competing technologies and principles for these microscopes. The probe control device for controlling the distance between the signal detection unit and the sample described in the present invention can be used in any microscope and is the most important technique. As the conventional technique, the STM which has been commercialized and is most advanced will be described, but the STM is not limited thereto.

The detection signal of the STM is a tunnel current. The probe of the STM is a probe, and a tunnel current starts to flow when the probe and the sample are brought close to each other by a distance of about 1 nm, but they are very sensitive to the distance between them and change exponentially. Conventionally, the generally used method of approaching a sample with a probe tip is to check the distance with a magnifying glass and the like, and manually turn the micrometer to bring it closer, and turn the micrometer with a DC motor. The second step is to bring them closer together, and the third step is to bring them closer together by the fine displacement means using a piezoelectric element. That is, the first stage is coarse movement, the second stage is fine movement, and the third stage is extremely fine movement.

Solid State Physics (Vol. 28 No. 3 19
93) "Trial Manufacture of Scanning Tunneling Microscope", Kyushu University Engineering Bulletin (Vol. 64, No. 5, October 1991), "Manufacturing of Scanning Tunneling Microscope", JP-A-3-12507, or Japanese Patent Laid-Open No. 63-204672 discloses a technique of bringing a probe and a sample close to each other up to a distance of about 1 nm.

[0005]

However, the probe fine movement part in the above-mentioned conventional STM device is manually and visually irrespective of the progress of the application of the electronic technology, and therefore, the probe fine movement part is provided between the probe and the sample. Skill is required to approach the distance of about 1 nm. Also, when changing the sample so that the signal detection state from the sample becomes good,
No consideration is given when moving the probe or sample by changing the position or angle. Currently, if necessary, a plurality of fine movement parts having different movement amounts, that is, a plurality of blocks composed of piezoelectric elements are prepared, and an observation range required at the time of measurement,
It has been necessary to perform a very troublesome adjustment such as replacing the block in the moving range with another one and then adjusting the interval between the probe and the sample again.

In particular, it has been difficult to perform an observation that requires a fine position adjustment in which the probe and the sample are once separated and then brought closer to each other. In addition, when the sample chamber to be observed is in a vacuum state, the only method is to replace the fine movement part of the probe after releasing the vacuum, and repeat this procedure when fine position adjustment is required. Therefore, it took a lot of time and effort.

The present invention has been made to solve the above-mentioned problems, and by operating the three expanding / contracting portions at the same time, the distance between the probe and the sample can be adjusted reliably in a short time. It is to provide a probe control device.

[0008]

In order to solve the above-mentioned problems, a first probe control apparatus of the present invention is a probe control apparatus used in a microscope , wherein a target distance between a probe tip and a sample surface is converted into an electric signal. Difference between the reference signal generator that outputs the converted reference signal, the reference signal that is output from the reference signal generator, and the comparison signal that is obtained by converting the actual distance between the probe tip and the sample surface into an electrical signal. A multi-stage actuator including a plurality of expansion / contraction units for moving the probe, and a signal generation unit that generates a drive signal for driving the expansion / contraction units based on the output of the calculation unit. Equipped, by the drive signal,
It is characterized in that the plurality of expansion / contraction units are individually driven until the probe tip reaches a target distance.

Therefore, when the tip of the probe mounted on the multistage actuator and the surface of the sample are brought close to each other, the plurality of expansion / contraction parts operate independently and simultaneously, so that a large amount of displacement can be obtained in a short time. . In particular, since the total amount of displacement can be obtained by the plurality of elastic portions, it is possible to reduce an error due to inertial force during braking, which is a problem when a large amount of displacement is obtained by one elastic portion. Further, it is possible to reduce the size because there is no need for the coarse movement mechanism section which brings the probe tip and the sample surface in advance close to the target distance. Furthermore, since it is automatically controlled, the space between the probe tip and the sample surface can be stably held. Moreover, since the target distance for bringing the tip of the probe and the sample surface closer is replaced with an electric signal, the target value can be easily changed.

In order to solve the above-mentioned problems, the second probe control device of the present invention is the same as the first probe control device,
The signal generation unit includes a D / A converter for each digit of the digital signal value output from the calculation unit, and
A drive signal is generated for each A / A converter, and the drive signal for each digit is selected and output according to the required movement amount of the plurality of expansion / contraction parts of the multistage actuator, and is controlled.

Therefore, the expandable portion of the multistage actuator can be changed depending on the size of the difference between the target distance between the probe tip and the sample surface and the actual distance. In other words, when the difference is large, it is possible to bring them closer in a short time by moving the expansion / contraction part having a larger displacement amount. Further, the expandable portion having a large displacement amount has a portion that becomes a dead body and does not displace when the displacement amount is small. This problem is also solved by using a plurality of expansion / contraction parts, so that the expansion / contraction part having a displacement amount corresponding to the target distance is used.

In order to solve the above-mentioned problems, a third probe control device of the present invention includes, in the first or second probe control device, the multi-stage actuator which is coarse, in addition to the drive signal output from the signal generator. A coarse motion signal generator that outputs a plurality of coarse motion signals to be moved; and an adder that adds the coarse motion signal output from the coarse motion signal generator to the drive signal output from the signal generator. , Until the distance between the probe tip and the sample surface approaches a predetermined distance from the target distance, the multistage actuator is moved by the addition signal obtained by adding the coarse movement signal by the addition unit. Characterize. Therefore, by allowing the plurality of expansion / contraction parts of the multi-stage actuator to be largely deformed by the coarse movement operation, the probe tip and the sample surface can be brought close to the target value in a short time.

In order to solve the above problems, a fourth probe control device of the present invention is the probe control device according to any one of the first to third probe control devices, wherein the expandable portion of the multistage actuator is provided with a piezoelectric element. It is characterized by using an element.

Therefore, the expanding / contracting portion is small in size and can generate a large force by using a piezoelectric element which is displaced by an applied voltage, has a high responsiveness and a high displacement accuracy.
In addition, a lightweight, low-priced expansion / contraction part is possible.

In order to solve the above-mentioned problems, a fifth probe control apparatus of the present invention is the probe control apparatus according to any one of the first to fourth aspects, wherein a plurality of expansion / contraction parts of the multistage actuator are provided. The sample mounting portion on which the sample is mounted and the sample mounting portion surrounding the sample mounting portion are constituted by separate surrounding portions.

Therefore, the outer portion of the multistage actuator serves as a cover for the probe tip, and damage to the probe tip can be prevented.

In order to solve the above-mentioned problems, the sixth probe control apparatus of the present invention is the fifth probe control apparatus, wherein the space between the outer peripheral portion of the multistage actuator and the sample mounting portion is hermetically sealed. It is characterized by being capable of being vacuumed or filled with an inert gas. Therefore, accurate measurement is possible without being affected by environmental changes. The probe observes while moving a minute area of the sample,
Since the measurement is performed, it is possible to prevent a slight environmental change such as a change in the air flow from appearing as a drift.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a probe control apparatus of the present invention will be described in detail below with reference to the drawings. [Embodiment 1] FIG. 1 is a schematic configuration diagram according to Embodiment 1 of a probe control apparatus of the present invention. In FIG. 1, the reference signal generator 10 outputs a reference signal B obtained by converting the predetermined distance between the tip of the probe 26 and the surface of the sample 27 into an electric signal. The output reference signal a is the probe 2
6 shows a target distance between the tip of the probe No. 6 and the surface of the sample 27, and the tip of the probe 26 and the surface of the sample 27 are deformed by the deformation motion of the multistage actuator 20 composed of a plurality of elastic portions 23, 24, 25. The actual interval is compared with the comparison signal B obtained by detecting the distance detection means (not shown) provided in the multistage actuator in the arithmetic unit 11.

The signal generator 12 produces a control signal D for the multistage actuator 20 from the result signal C obtained by the arithmetic unit 11. At this time, the plurality of elastic portions 23, 2
In order to obtain signals suitable for 4 and 25, the first-stage driving unit 14, the second-stage driving unit 15, and the third-stage driving unit 16 convert the signals into driving signals E. The converted drive signal e is input to the respective expansion / contraction units 23, 24, 25, and it becomes possible to simultaneously move a plurality of expansion / contraction units.

Then, until the automatic control loop is entered, that is, the approach signal for notifying that the tip of the probe 26 has approached a predetermined distance to the target interval from the distance detecting means provided in the multi-stage actuator 20. The probe 26 and the sample 27 are brought close to each other until the specific signal of (2) is transmitted to the detection signal conversion unit 21. After that, by entering an automatic control loop, the distance between the tip of the probe 26 and the surface of the sample 27 is maintained at the target distance based on the reference signal a from the reference signal generator 10.

The approach signal is transferred to the detection signal converter 21.
Output as a detection signal to the A / D conversion unit 22,
The / D conversion unit 22 converts the digital comparison signal B that can be calculated by the calculation unit 11. As a result of comparing the reference signal (a) and the comparison signal (b), if there is no difference in the values and the result signal (c) becomes "0", the tip of the probe 26 and the sample 2
The distance from the surface of 7 is judged to have reached the target distance, and the operation of the plurality of stretchable portions 23, 24, 25 stops. That is,
The operation of the multistage actuator 20 stops.

Since the automatic control loop is used, even if an external trigger causes a change in the distance between the tip of the probe 26 and the surface of the sample 27, the result signal C fluctuates immediately. The expansion / contraction units 23, 24, 25 start moving, and the automatic control starts moving so that the result of the calculation unit 11 becomes "0" again. In the multi-stage actuator 20, a plurality of expansion / contraction parts 23, 24, 25 move at the same time, but each expansion / contraction part moves differently depending on the size or state of the distance between the tip of the probe 26 and the surface of the sample 27. Has been done. The multistage actuator 20 will be described in detail later, but the signal generation unit 12 determines how to operate the expansion / contraction units 23, 24, and 25 depending on the value of the result signal C. .

[Second Embodiment] A second embodiment of the signal generation unit according to the probe control apparatus of the present invention will be described with reference to FIG. In the first embodiment, the signal generator 12 generates the control signal D for the multistage actuator 20 from the result signal C, and the expansion / contraction unit 23,
A signal corresponding to each of 24 and 25 is input to each expansion / contraction unit, and a plurality of expansion / contraction units are simultaneously moved. As a method, a threshold value corresponding to the operation of each expansion / contraction unit is provided in the result signal C, and the expansion / contraction unit 23, 2 is selected depending on whether the result signal C is larger or smaller than the threshold value.
A signal suitable for each of 4 and 25 is generated. But,
This makes it very difficult to move a plurality of expansion / contraction parts at the same time due to the configuration.

Therefore, as another method, the signal generator 12
The internal structure of the above is shown in FIG. The signal generation unit 12 includes the calculation unit 1
A plurality of binary code conversion units corresponding to the number of digits of the result signal C output from 1 and a D / A converter are provided, and a method of generating a control signal D corresponding to the number of digits of each digit is used. The control signal D output from the signal generating unit 12 has a larger value as the digit becomes higher, and the expanding / contracting unit having a larger displacement can be moved. Therefore, the tip of the probe 26 and the sample 27 can be moved in a shorter time. You will be able to get closer to the surface of. When the value of the control signal D is small, that is, when the digit is lower, the expansion / contraction unit having a small displacement amount is used.

Further, by operating each expansion / contraction part for each digit, the movements of each expansion / contraction part are added, and the desired displacement amount can be obtained in a short time. Further, in the expansion / contraction part having a large displacement amount, which has been a defect in the related art, it is possible to solve a problem that cannot be dealt with due to the inertial force of the expansion / contraction part when the value of the control signal D becomes very small. The reference signal B and the comparison signal B are input by the ASCII code to the arithmetic unit 11 in FIG. The reference signal B of the second embodiment is “1.000”. The comparison signal b is assumed to be “0.877”. The digital value represented by the ASCII code is calculated and output by the calculation unit 11 as a reference signal B-comparison signal B = result signal C. Result signal C is ASCII code 2
As "00", "0.123" is obtained. This value is broken down into numbers for each digit, and each digit20 is used as the number of digits.
Sort by 1.

The result signal "0.123" is 1 from the bottom.
It is decomposed into three, that is, the third digit "3", the second lower digit "2", and the third lower digit "1". The first digit "3" is
As the signal No, the second digit “2” is converted to the signal C, and the third digit “1” is converted to the signal No. by the respective binary code conversion units 204, 203 and 202 to convert the ASCII code to the binary code. To be done.

The signal converted into a binary code,
C and NO are guided to the D / A converters 205, 206, 207. In the second embodiment, an 8-bit 1-quadrant D / A converter is used. Since the reference voltage 208 is set to 10V, its output voltage range is from 0V to 10V. Therefore, in order to make the range of voltage change that can respond to changes in both positive and negative directions, center 5V. It must be set to operate as a value. The control signal D is supplied to the first stage driving unit 14, the second stage driving unit 15 and the third stage driving unit 15 of FIG.
The data is output to the stage drive unit 16 to operate the expansion / contraction units 23, 24, 25.

Further, if necessary, the drive units 14 of the respective stages,
Before leading to 15, 16, D / A converters 205, 206,
It is also possible to amplify the output voltage of 207. In particular, as will be described later, the stretchable portions 23, 24, 2
When 5 is a piezoelectric element, amplification by a high voltage amplifier is necessary. It is desirable that the calculation unit 11 always output with the same number of digits in the format so as not to change depending on the value of the calculation result. Whether the calculation result is large or small, such as close to zero, by outputting the same number of digits with the same number of digits, it is possible to reliably lead to each expansion / contraction part.

[Third Embodiment] A third embodiment of the probe control apparatus of the present invention will be described. Coarse movement is performed until the probe control device enters an automatic control loop, that is, until the specific signal in the approach signal is transmitted to the detection signal conversion unit 21 from the distance detection means provided in the multistage actuator 20. It is necessary for the signal generator 13 to add the coarse movement signal H to the drive signals E of the expansion / contraction units 23, 24, 25 by using the adders 17, 18, 19. At this time, the signal from the coarse movement signal generator 13 is gradually changed, and addition is continued until the approach signal is output until the specific signal is detected. When the detection signal conversion unit 21 can confirm the specific signal in the approach signal, it outputs a stop signal RE to the coarse movement signal generation unit 13 to stop the output of the coarse movement signal H. By the above method, the multi-stage actuator 20 can be deformed by the coarse movement operation without automatic control, and the probe tip and the sample surface can reach the target distance in a short time.

[Fourth Embodiment] FIG. 3 shows the structure of a multistage actuator according to a fourth embodiment of the probe controller of the present invention. The multistage actuator includes a plurality of first to third stages of expansion / contraction parts, and each expansion / contraction part is composed of a piezoelectric element made of a piezoelectric material capable of reversibly converting electrical energy into mechanical energy. As the piezoelectric material, a necessary amount of transfer can be obtained by using any one of polycrystalline barium titanate having a perovskite crystal structure, lead titanate, and lead titanate dilyconate. Further, even if the piezoelectric element is small, a large amount of displacement can be secured, responsiveness is fast, displacement accuracy is high, and the weight and cost can be reduced.

In FIG. 3, the cylindrical first-stage telescopic portion 2
In the inside of 4, the second-stage expansion / contraction part 23 in the Z direction shown by the dotted line.
In order to deform the expandable part 23, a part of the expandable part 23 is provided with a fine movement part 30 made of a piezoelectric element that is displaced in the X direction, and both ends of the expandable part 23 are attached to the inner surface of the expandable part 24. Has been done. Further, the third-stage cylindrical expansion / contraction part 25 has a structure that can be inserted from below into the expansion / contraction part 24. The expansion / contraction part 24 is provided with fine movement parts 31 and 33 in the X direction (back side of the fine movement part 31), fine movement parts 34 and 32 in the Y direction (back side of the fine movement part 34), and a fine movement part 35 in the Z direction. There is. The expansion / contraction part 25 includes fine movement parts 41 and 43 in the X direction (back side of the fine movement 41), fine movement parts 44 and 42 in the Y direction (back side of the fine movement part 44), and a fine movement part 45 in the Z direction. .

In this embodiment, the side surfaces of the expandable portions 24 and 25 are each formed of one piezoelectric element. As will be described later, the electrodes for applying a voltage to the piezoelectric element are divided. By providing the fine moving parts 31, 32, 33, 34, 35, 41, 42, and
43, 44, and 45. Then, the expandable portion 25
The expansion / contraction part 24 is mounted on and integrated with the table 36 for fixing the. Further, the base 36 fixing the expansion / contraction part 25 is also made of a piezoelectric element, so that the height (Z direction) and angle of the base 36 are changed, and the insertion degree of the expansion / contraction part 24 placed on the base 36 is changed. Can be changed.

A top plate 28 is provided on the upper end of the cylindrical expansion / contraction part 25.
Is provided as a table on which the sample 27 is placed. A top plate 36 is also provided on the upper end of the cylindrical expansion / contraction part 24, and the expansion / contraction part 25 on which the sample 27 is placed is inserted into the expansion / contraction part 24.
The sample 27 is arranged to be close to the probe 26 attached to the expansion / contraction part 23. A distance detection signal is obtained by operating the respective expansion / contraction units after integrating the expansion / contraction unit 24 and the expansion / contraction unit 25.

In this way, the probe 26 is not exposed and the probe can be protected because the probe 26 and the sample 27 are stored inside the cylindrical expansion / contraction part 24 like an envelope. The sample 27 can also be protected from dust. There is little effect from changes in the external environment during measurement. In particular,
Since the measurement is performed in the minute scan range, the influence of the air flow can be prevented. It can block external light. It is possible to block external magnetism that may affect the measurement. For example, magnetic shield paper and permalloy are provided so as to surround the expandable portion 24 which is an envelope. It is possible to adjust the temperature of each expansion / contraction part by changing the internal temperature of the expansion / contraction part 24. It is possible to make the inside of the expansion / contraction part 24 in a vacuum state. Hysteresis can be suppressed to a minimum by properly using the plurality of fine movement parts constituting each expansion / contraction part, that is, the degree and direction of expansion / contraction of the piezoelectric element. If one piezoelectric element operates in the extending direction and the other piezoelectric element operates in the contracting direction with respect to a minute movement in the same direction, and a drive signal is generated so that the added displacement amount changes little by little, the piezoelectric element It is possible to reduce the hysteresis due to the difference in the amount of displacement between the time of stretching and the time of contracting.

Next, the piezoelectric elements forming the expansion / contraction part 24 and the expansion / contraction part 25 will be described. A piezoelectric element has a longitudinal effect when the direction of the electrode and the direction of stretching strain are the same (piezoelectric constant d
₃₃ ) and the case where the lateral effect electrode direction and the stretching strain direction are vertical (piezoelectric constant d ₃₁ ). The relationship between the applied voltage and the expansion / contraction direction depends on whether the vertical effect or the horizontal effect is used.

The actual expansion / contraction operation will be described in detail with reference to FIG. Piezoelectric elements 61 and 6 shown in FIG.
2 is a partially enlarged view of the piezoelectric elements used in the fine moving parts 31 to 35 and 41 to 45 of FIG. 3, and FIG.
Explanatory drawing when the lateral effect design of the piezoelectric element 62 of (A),
FIG. 5C is an explanatory diagram of a deformed state of the piezoelectric element shown in FIG. 5B. In the lateral effect design, the electrode direction and the expansion / contraction part displacement direction are perpendicular. Polarized electrode 1 of piezoelectric element 62
When a positive voltage 102 is applied to 00, the polarization electrode 100 tries to extend in the polarization direction due to the lateral effect, and as a result, the height shrinks in the direction of 105 (the direction in which the distance between the probe and the sample is narrowed), A rectangle 10 shown by a dotted line in FIG.
It becomes a shape like 3.

When a negative voltage 102 is applied to the polarized electrode 100 of the piezoelectric element 62, the polarized electrode 1 is caused by the lateral effect.
00 tries to contract in the polarization direction, and as a result, extends in the height direction (direction in which the distance between the probe and the sample is widened), and extends like a rectangle 104 shown by a dotted line in FIG. By performing this operation with the first piezoelectric element 61 and the second piezoelectric element 62 as described above, the position of the probe 26 attached to the expandable portion 24 can be freely changed. Further, the position of the sample 27 can be changed by operating the expandable portion 25.

[0038] In FIG. 3, X ₁ electrode on the outside of the fine portion 31, Y ₁ electrode is provided on the outer side of the fine portion 32, further, on the outside of the fine positioning unit 33 located on the back side of the fine movement unit 31 X
_The Y ₂ electrode is provided outside the fine moving unit 34, which is located on the back side of the fine moving unit 32.

FIG. 9B shows the cylindrical expansion / contraction portion 24 cut open and shown in a plane. Telescopic part 2 cut open
In 4 ', the electrode 31' is the X ₁ electrode, the electrode 32 'is the Y ₁ electrode,
Electrode 33 'is X ₂ electrode, electrode 34' is Y ₂ electrode, electrode 3
5'corresponds to the Z electrode, and five electrodes are provided.

The expandable / contractible part 24 'constructed as described above is expanded / compressed by a slight deformation of a plurality of fine moving parts formed in a portion sandwiched by the above-mentioned electrodes and the common electrode provided inside the expandable part 24. The telescopic portion 23 mounted on the telescopic portion 24 can be finely moved in a two-dimensional manner, and the position of the probe 26 attached to the telescopic portion 23 is changed. In addition, as another embodiment,
The Z electrode may be eliminated as shown in FIG. As described above, the expandable part is composed of a plurality of fine movement parts, and the probe 26 can be moved by applying a voltage to each electrode and the common electrode. The applied voltage is applied to the Y electrode 90 and the common electrode 91 according to the circuit diagram shown in FIG. 10, for example.

The operation of the minute movement described above will be described in detail with reference to FIG. As a principle, FIG. 9 (B)
'"+Voltage" in, X ₂ electrode 33' X ₁ electrode 31 of the - the application of a "voltage", X ₁ electrode 31 by a lateral effect 'fine motion portion 31 which is provided contracts, X ₂ electrode 33' is Since the provided fine movement part 33 extends, the cylindrical shape of the expansion / contraction part 24 inclines,
It will swing in the X-axis direction. Similarly, the Y ₁ electrode 32 '
When a "+ voltage" is applied to the Y ₂ electrode 34 'and a "-voltage" is applied to the Y ₂ electrode 34', it is swung in the Y-axis direction, and X ₁ electrode 31 ', X ₂ electrode 33', Y
₁ electrodes 32 ', Y ₂ electrode 34' in, it is possible to fine deformed by applying a voltage, such as a ramp waveform. Also in the Z-axis direction, by applying a "± voltage" to the Z electrode 35 ', expansion and contraction in the Z-axis direction can be obtained by the lateral effect, and by combining all five electrodes, as shown in FIG. Three
Dimensional microscopic deformation is possible.

FIG. 7 is a vertical sectional view showing X electrodes 31 ', 3
3'and Z electrode 35 'are shown, but the Y electrode is also X
The same operation as the electrode is performed. In FIG. 7, the expandable / contractible part 23 having the probe 26 mounted therein is inside the expandable / contractible part 24 having a cylindrical shape. The principle of movement of the probe 26 will be described. 'The application of a "+ voltage" to, X ₁ electrode 31 by a lateral effect (FIG. 5B)' X ₁ electrode 31 as a piezoelectric element is provided moiety will Nobiyo to the polarization direction, the result Z The axial direction (parallel to the axis of the cylinder) shrinks as shown by the arrow. Further, X ₂ electrode 33 'to - the application of a "voltage", X ₂ electrode 33' as a piezoelectric element portion is provided will Chijimimo in the polarization direction, resulting in the Z-axis direction, as indicated by the arrow ' It will grow.

Therefore, the expanding / contracting portion 24 is tilted, and the movement of the tip end thereof is swung in the X-axis direction as indicated by the arrow ". The upper part of the expanding / contracting portion 24 is not swung in the X-axis direction as indicated by the arrow". , the tip of the probe 26 will move in the direction opposite to the arrow "Similarly, X ₁ electrode 31. 'in - the application of a" voltage ", X ₁ electrode 31' piezoelectric element portion is provided To shrink, the Z-axis direction extends as shown by the arrow. 'The application of a "+ voltage" in, X ₂ electrode 33' X ₂ electrode 33 Z-axis direction will Nobiyo the piezoelectric element portion provided would shrink as arrow '. Therefore, the expansion / contraction part 24 is inclined in the opposite direction, and the movement of the tip end swings in the X-axis direction as indicated by the arrow ".

The upper part of the expansion / contraction part 24 is X-shaped as indicated by the arrow ".
Swinging in the axial direction causes the tip of the probe 26 to move in the direction opposite to the arrow ".
By repeatedly applying the voltage, the tip of the expansion / contraction part 24 can be freely moved in the X-axis direction by "← →" as shown by the arrow. The probe 26 moves in the opposite direction to the movement of the tip of the expandable portion 24. Although the Y electrode is not shown in FIG. 7, by applying “± voltage”, the same lateral effect as that of the X electrode is performed, and the Y electrode can be freely moved in the Y axis direction just like the X axis operation. Become. These X
The expansion / contraction portion 24 is tilted in the X or Y axis direction by the operation of the Y electrode, so that two-dimensional microscopic deformation can be performed. The deformation range can be adjusted by the applied voltage value.

Further, in order to perform the three-dimensional microscopic deformation of the expandable portion 24, it is necessary to operate the Z electrode 35 '.
Since the Z electrode 35 'is provided on the entire circumference of the lower part of the expansion / contraction part 24, the cylindrical shape itself expands / contracts by ± voltage application. The Z electrode 35 'operates by the same lateral effect as the X electrode. When a "-voltage" is applied, the piezoelectric element in the portion provided with the Z electrode 35 'tries to contract in the polarization direction and Z
The axis extends in the direction of the arrow, and when a "+ voltage" is applied, it tends to extend in the polarization direction, and the Z-axis contracts in the direction of the arrow. Therefore, the cylindrical shape itself expands and contracts as indicated by the arrow or.

By combining the above X, Y and Z electrodes,
Applying a voltage enables three-dimensional microscopic deformation. Therefore, the probe 26 attached to the expansion / contraction part 23 can cope with changes such as approaching the sample 27. FIG. 7 explains the movement of the expansion / contraction part 24 on which the probe 26 on the envelope side is mounted, but the expansion / contraction part 25 on which the sample 27 is mounted has the same cylindrical shape, and the principle is Is the same. However, sample 27
Since it is mounted on the cylindrical upper part, the moving direction is the same as the cylindrical upper part.

Next, an example of a method of designing the fine moving part will be shown. First, an assumed value is determined by estimating the total length L of the cylindrical piezoelectric element, the length l _x of the XY electrode scanning portion, and the electrode width t in the polarization direction from the displacement amount which is the amount of fine movement. After that, each value is narrowed down by calculation.

At this time, if the electrode width t in the polarization direction is increased, the durability is improved, but the voltage value is increased.
This should be taken into consideration when deciding the hypothetical value such as the piezoelectric material ceramics being easily cracked when the thickness is made thin, but the advantage that the voltage value becomes low.
Such problems are determined by examining the purpose of use and selecting the best condition at the design stage. For example, the calculation formula of the present design example of the Z electrode is shown. Δz = (d ₃₁ LV) / t L: Length, V: Applied voltage, t: Width, d ₃₁ : Piezoelectric strain constant However, the formula for determining the displacement amount is the type of effect, material, electrode configuration, fine movement It is not limited to the above formula because it changes depending on the size of the part and the like.

As described above, the position of the probe 26 can be finely moved and controlled so that the detection signal with the sample 27 is in the best state by utilizing the inverse piezoelectric effect of the piezoelectric element of the expansion / contraction part 24.

[Embodiment 5] An expandable portion of a multistage actuator according to Embodiment 5 of the probe controller of the present invention will be described. FIG. 4 is an enlarged view of the expansion / contraction part 23 shown in FIG. In addition to the expanding / contracting part 24, the expanding / contracting part 23 that allows the probe to be slightly moved will be described with reference to FIG. The fine moving parts 30, 30 made of a piezoelectric element expand and contract in the X direction. One end of each of the two fine moving parts 30 and 30 is attached so as to be sandwiched from both sides of a thin flexible metal plate 53. Further, a member 54 having an arc-shaped end attachable to the circular inner wall of the expansion / contraction part 24 is attached to the other ends of the fine moving parts 30, 30. Therefore, when the fine moving parts 30 and 30 extend, the metal plate 53 bends and extends in the Z direction. That is, the probe 26 attached to the metal plate 53 descends in the Z direction.

The operating principle will be described in detail with reference to FIG. The fine movement parts 30 and 30 try to extend in the X direction, but the outer ends are attached to the inside of the elastic part 24 and the outward movement is restricted. 53 bends and descends in the Z direction, that is, in the direction of arrow c.
At this time, the length in the Z direction is 56, and the standard length is 55.
It will be longer. Further, when the fine moving parts 30, 30 contract in the direction of arrow b, the deflection of the metal plate 53 decreases, and the fine plate moves up in the direction of arrow d. The length 57 at this time is shorter than the standard length 56. Thus, the probe 26 attached to the metal plate 53 moves up and down in the Z direction.
This embodiment is characterized in that the flexure of the metal plate 53 is changed by expanding and contracting the fine moving parts 30, 30 at both ends to change the tip position of the probe 26 mounted on the metal plate 53.

[Sixth Embodiment] FIG. 11 is a horizontal cross-sectional view when the expandable portion 25 is inserted into the expandable portion 24. The movement directions can be subdivided by inserting the plurality of fine movement portions of the two expandable portions so that the fine movement directions do not match. As shown in FIG. 11, the outer stretchable portion 24 has an arrow 1
The direction of the arrow 4 from the direction of, and the elastic portion 25 on the inner side can be slightly deformed from the direction of the arrow to the direction of the arrow. In this way, by shifting the direction of the fine movement part constituted by the electrodes of each expansion-contraction part by 45 °, the movement can be decomposed in eight directions and a double deformation direction can be obtained. In the present embodiment, the fine movement part 30,
By mounting the displacement direction of 30 in a direction that does not coincide with the above eight directions, the displacement direction can be further decomposed.

[Seventh Embodiment] A multistage actuator according to a seventh embodiment of the probe controller of the present invention will be described with reference to the drawings. The narrower the distance between the probe and the sample, the smaller the environmental change during measurement, and the greater the influence on the result. Therefore, the multistage actuator 20
The expansion / contraction part 24 serving as an envelope is fixed on the base 38 of the expansion / contraction part 25 on which the sample is mounted.

FIG. 12 is an external perspective view of the multi-stage actuator.
1 is placed, and holes for inserting the fixing screws 132 of the fixing jig are formed in the vicinity of both ends of the horizontal rail.
Then, the fixing screw 132 is screwed into a screw hole 133 provided in the base 38 of the expansion / contraction part 25, and the expansion / contraction part 24 and the expansion / contraction part 25 are fixed.

FIG. 13 is an external perspective view of the expansion / contraction unit 25 and its base 36. The base 38 is provided with an O-ring 130 corresponding to the cross-sectional shape of the expansion / contraction unit 24 so as to be compatible with a vacuum state. Place the expansion / contraction part 24 on 130,
A cylindrical closed container is formed.

Therefore, the inside of the expansion / contraction portion 24 has a structure in which a vacuum or an inert gas can be enclosed. Probe 2
6, the probe signal line 38 and the elastic part signal line 39 necessary for the expansion / contraction part and the like are arranged in the hermetic port 1 as shown in FIG.
Connect via 40.

Although the respective embodiments have been described above, the expansion / contraction part including the first to third stages of the multi-stage actuator should be selected in accordance with the type of probe, the state of the sample surface, the change of the measurement environment and the like. , According to the required amount of movement of the expandable part,
The user can change each elastic part. When not used for measurement, the stretchable portion 24 or the stretchable portion 2
Even when the deterioration of the piezoelectric element of No. 5 is confirmed, the user can change it. In particular, for the cylindrical expansion / contraction part, prepare objects with various displacement amounts, and use the expansion / contraction part corresponding to the envelope and the expansion / contraction part that enters inside to use the total displacement amount. Wide specifications are possible.

[0058]

According to the present invention, it is possible to provide a probe control device capable of easily controlling the distance between the probe and the sample in a short time. Further, by making the expandable portion of the surrounding portion cylindrical, the probe and the sample can be protected. Further, since the fine movement part is composed of a piezoelectric element made of a piezoelectric material, it can be easily moved minutely by a voltage, and the moving direction can be freely selected by the user. Furthermore, the expandable part can be easily replaced according to the measurement situation.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a probe control device of the present invention.

FIG. 2 is a diagram showing a signal generation unit of the probe control device of the present invention.

FIG. 3 is a diagram showing an embodiment of a multistage actuator according to the present invention.

FIG. 4 is a diagram showing an embodiment of a probe expanding / contracting portion of a multistage actuator according to the present invention.

FIG. 5 is an operation explanatory view of the fine movement part of the multistage actuator according to the present invention.

FIG. 6 is an operation explanatory view of the probe expansion / contraction unit of the multistage actuator according to the present invention.

FIG. 7 is an operation explanatory view of the fine movement part of the multistage actuator according to the present invention.

FIG. 8 is an operation explanatory view of the expandable portion of the multi-stage actuator according to the present invention.

FIG. 9 is a development view of a telescopic portion of the multistage actuator according to the present invention.

FIG. 10 is an applied signal generation circuit diagram according to the probe control apparatus of the present invention.

FIG. 11 is a horizontal cross-sectional view of the expandable portion of the multi-stage actuator according to the present invention.

FIG. 12 is an external perspective view of a multistage actuator according to the present invention.

FIG. 13 is an external perspective view of a telescopic portion of the multistage actuator according to the present invention.

FIG. 14 is a partially cutaway external perspective view of a multistage actuator according to the present invention.

[Explanation of symbols]

10 Reference signal generator 11 Operation part 12 Signal generator 13 Coarse motion signal generator 20 Multi-stage actuator 23, 24, 25 telescopic part 21 Detection signal converter 26 probes 27 samples 31, 32, 33, 34, 35 Fine movement part 36 units 38 probe signal line 39 Elastic section signal line 140 hermetic port

Continuation of front page (56) Reference JP-A-6-119665 (JP, A) JP-A-2-262001 (JP, A) JP-A-9-89550 (JP, A) JP-A-5-190933 (JP , A) JP 5-56667 (JP, A) JP 7-83651 (JP, A) JP 4-348204 (JP, A) JP 4-248378 (JP, A) JP 7-159150 (JP, A) JP-A-11-112047 (JP, A) JP-A-6-265341 (JP, A) JP-A-3-209105 (JP, A) JP-B 7-62603 (JP, A) B2) Japanese Patent Publication 3-79677 (JP, B2) Japanese Patent Publication 7-24951 (JP, Y2) Patent 3180024 (JP, B2) Hiroshi Kawami, Seiji Inoue, Masamitsu Yoshimura, Takafumi Yao, "Scanning Tunnel" Microscope (STM) Prototype "Solid State Physics, Japan, Agne Technology Center Co., Ltd., March 15, 1993, Volume 28, No. 3, p. 37-42 Taki Shoji, Okabe Hirotaka, Matsushige Kazumi, "Production of Scanning Tunneling Microscope (STM)", Kyushu University Engineering Bulletin, Japan, Kyushu University Faculty of Engineering, October 30, 1991, Volume 64, Volume 5. Issue, p. 399-406 (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00-21/24 H01L 41/00-41/26 H02N 2/00-2 / 18 G01B 9/00-9/10 G05D 3/00-3/20 JISST file (JOIS)

Claims (9)

(57) [Claims] 1. A probe control device for use in a microscope , comprising: a reference signal generator for outputting a reference signal obtained by converting a target distance between a probe tip and a sample surface into an electric signal; and an output from the reference signal generator. A calculation unit for calculating a difference between a reference signal, a comparison signal obtained by converting the actual distance between the probe tip and the sample surface into an electric signal, and a multi-stage actuator having a plurality of expansion / contraction units for moving the probe. A signal generation unit that generates a drive signal that drives the plurality of expandable units based on the output of the arithmetic unit, the plurality of the plurality of units until the probe tip reaches the target distance by the drive signal. Of the expansion / contraction part of the probe controller , which is different from the drive signal output from the signal generation part.
In addition, a plurality of coarse
The coarse motion signal generator that outputs a motion signal and the coarse motion signal that is output from the coarse motion signal generator are
An adder for adding to the drive signal output from the signal generator,
With a distance between the probe tip and the sample surface, the target
From the distance until approaching a predetermined distance,
With the addition signal obtained by adding the coarse movement signal,
Plow characterized by moving multi-stage actuator
Control device . 2. The probe control device according to claim 1, wherein the signal generation unit includes a D / A converter for each digit of the digital signal value output from the calculation unit, and the D / A converter is provided. A probe control device characterized in that a drive signal is generated for each converter, and the drive signal for each digit is selected and output according to the required movement amount of a plurality of expansion / contraction parts of the multi-stage actuator and controlled. . 3. The probe control device according to claim 1 or 2.
In this case, a piezoelectric element is used for the expansion / contraction part of the multistage actuator.
Probe controller, characterized in that. 4. The professional according to any one of claims 1 to 3.
In the probe control device, the multiple expansion / contraction parts of the multi-stage actuator carry the sample.
Surround the sample mounting part and the sample mounting part
It is composed of a sample mounting part and a separate surrounding part.
A probe control device characterized in that 5. A probe control device used in a microscope.
There are, the target distance between the probe tip and the sample surface, varying the electrical signal
A reference signal generator for outputting a reference signal conversion, a reference signal outputted from the reference signal generator, the flop
The actual distance between the tip of the lobe and the surface of the sample above is calculated as an electrical signal.
A multi-stage array equipped with a computing unit for computing the difference from the comparison signal converted to the above and a plurality of telescopic units for moving the probe.
Based on the output of the actuator and the computing unit, drive the above-mentioned multiple expansion / contraction units.
And a signal generator that generates a drive signal for moving the probe tip, and the probe tip causes the target distance to be increased by the drive signal.
Drive each of the above expansion units individually until
In the moving probe control device, the plurality of expansion / contraction parts of the multi-stage actuator include a sample mounting portion for mounting a sample, and an outer peripheral portion surrounding the sample mounting portion and separated from the sample mounting portion. A probe control device characterized by being provided. 6. The probe control device according to claim 5,
Then, the signal generator is configured to output the digital signal output from the calculator.
A D / A converter is provided for each digit of the signal value, and
A drive signal is generated for each D / A converter, and the multi-stage actuator is
Depending on the required amount of movement of the multiple expansion and contraction parts of the data, each of the above digits
The feature is that the drive signal for each is selected, output, and controlled.
Probe control device . 7. The probe control device according to claim 5 or 6.
In this case, a piezoelectric element is used for the expansion / contraction part of the multistage actuator.
A probe control device characterized by the above. 8. A professional according to claim 4 or 7.
In the probe controller, the surrounding portion of the multistage actuator and the sample
The space between the mounting part and the
Probe control characterized by encapsulation of active gas
Equipment . 9. A scanning tunneling microscope, an atomic force microscope,
Specially used for any of the near field microscopes
The probe according to any one of claims 1 to 8, which is a characteristic of the probe.
Control device.