JPH1038900A - Probe / sample approach mechanism of scanning probe microscope - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When a cantilever is hard, a small vibration and a large vibration are applied to the cantilever to enhance the responsiveness of the cantilever, and a high-speed automatic approach is safely performed by an approach operation between a probe and a sample. To provide a probe / sample approach mechanism for a scanning probe microscope. SOLUTION: The oscillator 55 is applied to a scanning probe microscope in which a probe 12 and a sample 16 are brought close to each other, and the fine property of the surface is measured by an interaction between the two, and a micro vibration is applied to the cantilever 11.
A signal generating mechanism 51, 52, 53, 54 that gives a large vibration to the cantilever using micro vibration, a pulse generating mechanism 42 that generates a pulse 76 based on a low frequency signal corresponding to the large vibration,
It comprises a motor driver 43 controlled by a pulse signal, and a Z stage 31 for bringing the probe and the sample closer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe / sample approaching mechanism of a scanning probe microscope, and more particularly to a probe / sample approaching mechanism which is operated by a stepping motor or the like controlled by a pulse signal. The present invention relates to a probe / sample approach mechanism of a scanning probe microscope capable of safely approaching at high speed.

[0002]

2. Description of the Related Art For example, when observing the surface of a sample with an atomic force microscope, a probe provided at the tip of a cantilever is brought close to a predetermined minute distance from the surface of the sample in a stage before the observation. is required. Therefore, the atomic force microscope has a probe / sample approach mechanism. In controlling the operation of the probe / sample approach mechanism, it is important to avoid damage to the probe and the sample due to collision of the probe with the sample. As an example of a conventional probe / sample approach mechanism having such a function, there is a technique disclosed in Japanese Patent Application Laid-Open No. 5-45111. This technical document discloses a probe automatic approach mechanism that automatically causes a probe (tip) to approach a sample in a scanning probe microscope without colliding with a sample. The probe automatic approach mechanism includes a fine movement mechanism for finely moving the probe, a coarse movement mechanism for moving the sample stage, and control means for controlling each operation of these fine movement mechanism and coarse movement mechanism. When the distance between the sample and the probe is detected and it is determined that the distance has reached a predetermined distance,
The operation of the coarse movement mechanism is stopped, and the fine movement mechanism is retracted in a direction in which the probe moves away from the sample. in this way,
The collision between the probe and the sample is avoided by stopping the coarse movement mechanism that causes a large motion and retracting the probe by the fine movement mechanism. When the fine movement mechanism performs the retreat operation, the feedback circuit used in the normal control is not used, and the responsiveness is improved.

[0003]

In the above-mentioned conventional apparatus,
The approach of the probe to the sample is suddenly stopped by combining the operation of the coarse movement mechanism and the operation of the fine movement mechanism to prevent contact between the probe and the sample. In such a configuration, the responsiveness is determined by the operating characteristics of the fine movement mechanism, and the frequency related to the responsiveness is generally several kHz. However, at present, the atomic force microscope is required to have a higher speed, and the responsiveness of the fine movement mechanism is an obstacle to the increase in the approach speed. This is not only an atomic force microscope,
This is a common problem for a scanning probe microscope having a similar configuration.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to enhance responsiveness and to safely achieve high-speed automatic approach in the approach operation between the probe and the sample. To provide a probe / sample approach mechanism of a scanning probe microscope in which, when hard (having a large spring constant), the cantilever generates microvibration and movement corresponding to large vibration, thereby increasing the response of the cantilever. It is in.

[0005]

A probe and sample approaching mechanism of a scanning probe microscope according to a first aspect of the present invention (corresponding to claim 1) has a probe at a leading end to achieve the above object. It has a cantilever with a needle, is applied to a scanning probe microscope that moves a probe and a sample close together and measures the fine property of the surface based on the interaction between the probe and the surface of the sample. Oscillating means (oscillator)
And a signal generating means (HPF, waveform shaper, up / down counter, etc.) for generating a low frequency signal using the micro vibration of the cantilever and applying a large vibration to the cantilever with the low frequency signal, and a large vibration of the cantilever. Pulse generating means (LPF, pulse generator, etc.) for extracting a low-frequency signal using the signal and generating a pulse signal based on the low-frequency signal
And an approach device (Z stage which is a coarse movement mechanism) configured to control the operation based on the pulse signal (a motor driver or the like) and to approach the probe and the sample. In such a configuration, when the approaching device is driven to approach the probe and the sample, a low-frequency signal is generated based on the fine vibration of the cantilever, and the pulse signal is generated using the low-frequency signal.

According to a second aspect of the present invention (corresponding to claim 2), in the probe / sample approach mechanism of the scanning probe microscope according to the first aspect, the cantilever separates from the sample due to large vibration of the cantilever due to a low frequency signal. When the displacement is made as described above, the pulse generating means generates the above-described driving pulse.

According to a third aspect of the present invention (corresponding to claim 3), in the probe / sample approaching mechanism of the scanning probe microscope according to the first aspect, the approaching operation between the tip and the sample by the approaching device is performed. In the atmospheric environment, when the probe is pulled into the adsorption layer formed on the surface of the sample, the micro vibration of the cantilever stops, the large vibration stops, and the approach operation by the approach device stops. It is characterized by.

According to a fourth aspect of the present invention (corresponding to claim 4), in the probe / sample approach mechanism of the scanning probe microscope according to the first aspect, the unit movement amount (operation step) of approach by the approach mechanism is: Tip based on large vibration by signal generation means
It is characterized in that it is smaller than the unit change amount (operation step) of the inter-sample distance.

[0009] Based on the above configuration, the cantilever is finely vibrated with an amplitude of several nm to several hundred nm, and based on the waveform of the fine vibration, a large vibration having a frequency lower than the fine vibration and an amplitude of several µm. In such a state, the approach device, which is a coarse movement mechanism, is driven by a low frequency signal generated from a large vibration waveform of the cantilever. At this time, the output timing of the pulse signal for driving the approach device is generated from the waveform of the large vibration. Therefore, when the micro vibration of the cantilever stops, the large vibration generated by the micro vibration waveform also stops. Further, when the large vibration waveform stops, the drive signal of the approach device generated by the stop also stops, and the approach operation stops. In particular, when the cantilever approaches the vicinity of the sample and the probe is adsorbed on the adsorption layer on the sample surface, the micro-vibration stops. The operation stops.

The approach between the probe of the cantilever and the sample is given to the cantilever by applying a micro-vibration and a large vibration generated by the micro-vibration, and by operating the approach device with a pulse signal generated based on the large vibration. This is particularly suitable when the spring constant of the cantilever is large.

The output timing of the signal for driving the approach mechanism is preferably set when the probe is farthest from the sample surface due to large vibration. The operation step of the approaching device is set smaller than the operation step due to large vibration. Therefore, there is no fear that the probe is attracted to the sample surface due to the approach operation of the approach device. The case where the probe is attracted to the sample surface is limited to the case where the probe is approaching the sample due to large vibration. For this reason, there is no possibility that the probe is pressed against the sample surface with a large force by the operation of the approaching device and is broken.

[0012]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a typical embodiment of the present invention, which is a conventional contact (contact) mode equipped with a probe-sample approach mechanism according to the present invention, for example, of an atomic force microscope (AFM). 1 shows an embodiment. The AFM
Operates in contact mode when observing the sample surface.
In addition, it is assumed that the AFM is to be measured in an atmospheric environment. Therefore, before the start of the measurement, an adsorption layer is formed on the surface of the sample placed in the atmosphere. The adsorption layer is formed in a layered manner when water molecules in the atmosphere reach the surface of the sample, and is a layer of about several nanometers (nanometers). The probe / sample approach mechanism is a device for bringing the probe and the sample closer to a required distance at a stage before the measurement and observation of the sample surface in the air environment and in the contact mode by the AFM. The approach operation (coarse movement) is performed at a large moving distance. According to FIG.
The configuration and operation of the contact mode AFM including the probe / sample approach mechanism according to the present embodiment will be described.

11 cantilever, the tip of which is a probe 12
Is provided. The cantilever 11 is fixed to a holder above the frame 14 via the piezoelectric element 13 for vibration. An XYZ scanner 15 and a Z stage 31 are provided below the frame 14. The XYZ scanner 15 is provided on a Z stage 31, and the Z stage 31
4 is fixed to the lower part. A sample 16 is arranged on the upper surface of the XYZ scanner 15. The XYZ scanner 15 includes a fine movement drive unit (X-axis direction drive unit, Y-axis direction drive unit) including a piezoelectric element for generating minute displacement in each of three orthogonal axes (X-axis, Y-axis, Z-axis). Drive section, Z-axis direction drive section). Thus, the sample 16 can be moved by a small distance in an arbitrary direction. XYZ scanner 15
Functions as a fine movement mechanism for adjusting the distance between the probe and the sample during measurement / observation and for XY scanning movement. The Z stage 31 moves (coarsely moves) the XYZ scanner 15 and the sample 16 at a relatively large distance in the Z-axis direction, and performs the operation when the probe 12 and the sample 16 approach each other.
The Z stage 31 functions as a coarse movement mechanism for the approach operation. Z
The specific structure of the stage 31 includes, for example, a motor that operates with a pulse signal, such as a stepping motor, and the motor performs the above-described movement. Therefore,
A pulse signal S7 as a drive signal for operating the motor is input to the Z stage 31 from outside.

In the above configuration, when measuring the surface of the sample 16, the probe 12 approaches the sample 16 and its tip is substantially in contact with the measurement surface of the sample 16.
Oppose. The approach state between the probe 12 and the sample 16 is set by operating the Z stage 31 which is a coarse movement mechanism before the measurement in the normal contact mode is started.

In FIG. 1, the cantilever 11, the probe 1
2. The piezoelectric element 13 is somewhat exaggerated for convenience of explanation. The actual configuration will be described later with reference to FIG.

On the other hand, a laser light source 17 is disposed above the cantilever 11, and a laser beam 18 emitted from the laser light source 17 is applied to a reflection surface near the back end of the cantilever 11. The laser beam 18 reflected by the reflecting surface
Is incident on a light receiving surface of a position sensor (photodetector) 19.
The laser light source 17, the cantilever 11, and the position sensor 19 constitute an optical lever type displacement detector (detection optical system). The tip of the cantilever 11 is the probe 12 and the sample 1
When it is displaced in the Z-axis direction in FIG. 1 based on the interatomic force (physical action) generated between itself and the surface of the position sensor 6, the spot position of the reflected light is displaced within the light receiving surface of the position sensor 19. The position sensor 19 converts the displacement of the spot position of the reflected light into a change in the voltage value and outputs the change. Thus, a change in the Z-axis direction of the tip of the cantilever 11, that is, a change in the Z-axis direction of the probe 12 is extracted as a change in the output voltage of the position sensor 19.

Next, a control system (or a signal processing system) will be described. The voltage signal output from the position sensor 19 is supplied to one of the following two systems depending on the connection state of the changeover switch 33. The switching operation of the changeover switch 33 is performed automatically or manually.

The first system is a case where the changeover switch 33 is connected to the lower terminal 33a in FIG. 1, and comprises a signal amplifier 34 and a servo device 35. The first system is a control system related to the normal measurement of the surface of the sample 16. The voltage signal S0 output from the position sensor 19 at the time of measurement is a signal representing the position of the probe 12 in the Z-axis direction, that is, the amount of deflection of the cantilever 11, and the voltage signal is a signal amplifier 34 and a servo device 35. Via XY
The drive signal Vz for operating the Z-axis direction drive unit of the Z scanner 15 is converted and supplied to the XYZ scanner 15. The signal amplifier 34 amplifies the output signal of the position sensor 19 to a required level. The output signal of the signal amplifier 34 is input to the servo device 35. The servo device 35 converts an input signal into the drive signal Vz according to a servo control condition instructed via the bus 37 from the arithmetic processing device 36 including the arithmetic control unit 36a and the display unit 36b. The drive signal Vz causes the Z-axis drive unit in the XYZ scanner 15 to operate, the position of the sample 16 in the Z-axis direction is adjusted, and the distance between the probe 12 and the sample 16 becomes a predetermined distance (substantial contact state). And the uneven shape of the surface of the sample 16 is measured.

More specifically, the arithmetic processing unit 36 is constituted by a computer, and includes a CPU and a storage unit. The storage unit stores a program (measurement program) for controlling the operation of the AFM for measuring a desired portion of the sample surface, and measurement data, and from this measurement data, an image relating to the fine shape of the observation surface of the sample 16 is stored. A program (image creation program) for performing processing for creating image data to be displayed on the display unit 36b is stored. The servo device 35 controls the distance between the probe and the sample so that the distance between the probe and the sample is a predetermined distance.
A drive signal Vz of the Z-axis direction drive unit is given to the YZ scanner 15. With the servo device 35 performing the servo operation with respect to the operation in the Z-axis direction by the Z-axis direction drive unit of the XYZ scanner 15, the XYZ scanning circuit unit is used.
Operate the drive units in the X and Y axis directions of the scanner 15,
The probe 12 is caused to scan the XY plane of the sample 16. At this time, the coordinates of the measurement points on the XY plane and Vz (output voltage value of the servo device 35) at each measurement point are stored as measurement data in the storage unit of the arithmetic processing device 36. The measurement data stored in the storage unit is sequentially or collectively processed by the above-described image creation program, creates image data relating to the surface shape of the measurement location on the sample 16, and uses this image data to display the display unit 36b. Display the measurement image on the screen. Thus, the surface shape of the measurement location of the sample 16 is obtained.

In the normal measurement of the sample surface, as described above, in addition to the control in the Z-axis direction for adjusting the distance between the probe and the sample, a position for scanning the sample surface with the probe is used. Control is required. A drive signal for controlling the scanning position is provided to the XYZ scanner 15 as signals Vx and Vy from the XY scanning circuit section built in the arithmetic processing unit 36.

In the contact mode AFM, the cantilever 11 is in a non-vibrating state during the measurement operation, and the probe 12 and the sample 16 are kept substantially in contact. Also,
In the approaching operation, as described later, the cantilever 11 is moved.
Is vibrated by the piezoelectric element 13 and is in a state of micro-vibration. A function of high-speed automatic approach is realized using an AC signal obtained based on the state of micro-vibration. Micro vibration is generated in the cantilever 11 by the vibration action of the piezoelectric element 13,
At this time, the amplitude of the cantilever 11 is, for example, about several nm to several hundred nm between the peaks, and the amplitude is relatively small. Further, the spring constant of the cantilever 11 is large and its rigidity is relatively hard due to its manufacture, so that the amplitude becomes small. Since the approaching operation is performed using the AC signal obtained by the above-described micro-vibration state, a fail-safe function at the time of contact is also realized.

Next, a second system is a system when the changeover switch 33 is connected to the upper terminal 33b in FIG. 1, and is a control system related to a high-speed automatic approach mode. This second system is composed of two circuit routes provided in parallel circuits. In the second system,
One circuit route (lower part in FIG. 1) is composed of a low-pass filter (LPF) 41, a pulse generator 42, and a motor drive 43, and the other circuit route (upper part in FIG. 1) is a high-pass filter (HPF). 51 and waveform shaper 52
And an up / down counter 53 and a mixer 54. The low-frequency signal S5 is extracted from the detection signal S4 output from the terminal 33b by the LPF 41, and the pulse generator 42 generates a pulse signal S6 using the low-frequency signal S5. The motor driver 43 converts the pulse signal S6 into a driving signal (driving pulse signal) S7 and supplies the signal to the Z stage 31. The detection signal S4 is output by the HPF 51.
The waveform shaper 52 generates a rectangular wave signal S2 using the high frequency signal S1, and the up / down counter 53 generates a count signal S3 using the rectangular wave signal S2 as an input signal. Count signal S
3 generates a vibration signal having a relatively large amplitude. The count signal S3 is mixed with the oscillation signal output from the oscillator 55 by the mixer 54 to generate a drive signal S8 for driving the piezoelectric element 13 for causing the cantilever 11 to vibrate (fine vibration and large vibration). The waveform of the drive signal S8 is substantially the same as the signal S4 described above. The oscillator 55 is supplied with a periodic signal for generating an oscillation signal from the arithmetic processing unit 36.

Referring to FIG. 2, the structures of the cantilever 11 and the piezoelectric element 13 will be described in detail. In FIG. 2A, 6
Reference numeral 1 denotes a lower electrode, which is provided on the back surface of the cantilever 11. Reference numeral 62 denotes a ZnO thin film, for example, which is sandwiched between the lower electrode 61 and the upper electrode 63. Reference numeral 64 denotes a holder, which is a portion for fixing the cantilever 11 to the frame 14. 65
Are lands, which are connected to the upper electrode 63 and the lower electrode 61 by bonding wires 66. A signal line from the mixer 54 to the piezoelectric element 13 relating to the drive signal S8 shown in FIG. 1 is connected to a land 65. In this configuration, when a predetermined voltage is applied between the lower electrode 61 and the upper electrode 63, the ZnO thin film 62 contracts in the longitudinal direction of the cantilever 11, and as a result, as shown in FIG. 11 bends upward. When the application of the predetermined voltage is stopped, the bending displacement of the cantilever 11 disappears.

Next, the operation and control procedure of the control system related to the high-speed automatic approach mode will be described with reference to FIG. 1 and FIGS.

When the probe 12 and the sample 16 are brought closer to each other, the changeover switch 33 is connected to the upper terminal 33b. Now, it is assumed that the sample 16 is mounted on the XYZ scanner 15. At this time, the sample 16 and the cantilever 11 are apart from each other by several mm (mm). In this state, an oscillation signal (oscillation voltage) output from the oscillator 55 is transmitted to the piezoelectric element 13 provided on the back of the cantilever 11.
Is applied between the upper electrode 63 and the lower electrode 61 included in
The cantilever 11 is vibrated. The oscillation voltage of the oscillator 55 is supplied to the piezoelectric element 1 as a drive signal S8 via the mixer 54.
At this stage, it is assumed that the count signal S3 from the up / down counter 53 is 0. When an oscillation voltage is applied to the ZnO thin film 62 of the piezoelectric element 13, the cantilever 11 has its resonance frequency (f ₀ ).
Vibrates slightly. The minute vibration of the cantilever 11 is detected by an optical lever type displacement detector (detection optical system), and a signal S representing the minute vibration of the cantilever 11 is output from the position sensor 19.
4 is output. The signal S4 is shown in FIG. In the waveform of FIG. 4A, a high-frequency fine waveform (caused by an oscillation signal from the oscillator 55) representing a minute vibration and a low-frequency waveform (a count signal from the up / down counter 53) representing a large vibration are shown. S3) is shown in a superimposed and superimposed state, but only microvibration exists at the initial stage as described above.

From the signal S 4 detected by the position sensor 19, the cantilever 11 is filtered by the high-pass filter 51.
(Frequency f ₀ : shown as (a) in FIG. 3 as a signal S1). Next, the signal S1 is converted by the waveform shaper 52 into a rectangular wave (signal S2: shown in FIG. 3B). This square wave signal S2
Is input to the up / down counter 53 and is converted into a count signal S3 having a staircase waveform (shown in FIG. 3C). The up / down counter 53 includes an arithmetic control unit 36
Between the upper limit value and the lower limit value set by a, the up-count operation and the down-count operation are repeated to generate the count signal S3. FIG. 3D shows the overall waveform shape of the count signal S3 when the time axis is reduced and several periods are drawn. The waveform shown in FIG. 3C is an enlarged view of a part 71 of the waveform shown in FIG. The count signal S3 is used as a drive signal for causing the cantilever 11 to generate a large vibration with a relatively large amplitude and a low frequency. The count signal S3 is added to the oscillation signal from the oscillator 55 by the mixer 54, and supplied to the piezoelectric element 13 as a drive signal S8 (similar to the signal S4 in FIG. 4A).

As described above, the drive signal S8 output from the mixer 54 includes the oscillation signal for micro vibration and the count signal S3 for low frequency large vibration. When such a drive signal S8 is applied to the piezoelectric element 13, the piezoelectric element 13 causes the cantilever 11 to combine a micro vibration and a large vibration at a low frequency.
As is clear from the detection signal S4 in FIG. 4A, a small waveform portion corresponds to the fine vibration, and a large waveform (as an envelope) generated as a whole corresponds to the large vibration. The frequency of the micro-vibration is, for example, 20 KHz and the amplitude is preferably several tens to several hundreds of nm, and the frequency of the large vibration is, for example, 1 KHz.
And the amplitude is preferably several μm.

Also, as is apparent from the correspondence between the signal S4 and the cantilever 11 (indicated by arrows 72, 73 and 74) shown in FIG. Cantilever 1 that performs vibration 75
In 1, the bending action of the piezoelectric element 13 based on the low frequency signal S3 causes the cantilever 11 to vibrate greatly. When the voltage value of the signal S3 becomes equal to or more than a predetermined value and the ZnO thin film 62 contracts, the cantilever 11 causes upward bending displacement. The upward bending displacement occurs periodically, and generates large vertical vibrations as a whole.

Next, the low-pass filter 41 calculates the frequency f from the signal S4 detected by the position sensor 19.
A signal component (signal S5: shown in FIG. 4B) having a lower frequency than the ₀ fundamental wave (signal S1) is extracted.
The signal S5 is input to the pulse generator 42. The pulse generator 42 generates a pulse 76 when a value that reaches a threshold value set by the arithmetic control unit 36a of the arithmetic processing unit 36 is input for the signal S5. The signal composed of the pulse 76 is referred to as the pulse signal S6. This state is
This is shown in FIGS. 4B and 4C. When the signal S5 reaches the maximum value (t1), the pulse signal S
A pulse 76 as 6 is output. The pulse signal S6 is supplied to the motor driver 43. Motor driver 43
As is apparent from the change in the driving signal S7 (FIG. 4D) output from the motor driver 43, when the pulse 76 rises with the pulse signal S6, the driving signal S7 corresponding to the pulse 76 is generated from the motor driver 43. You. The driving signal S7 is given to the Z stage 31, whereby the internal stepping motor operates to move the Z stage 31 upward, and the sample 16 approaches the probe 12 by a predetermined distance.

Based on this control, the cantilever 11
Is bent upward, and after the probe 12 is separated from the sample 16, when the probe 12 is displaced so as to approach the sample 16,
The sample 16 is displaced upward and approaches the probe 12.

Next, referring to FIG. 5, the sample 16 and the probe 1
The state in which 2 comes close and the state in which they come into contact will be described. FIG. 5A shows a state in which the cantilever 11 is slightly vibrating near the surface of the sample 16 and further bends up and down to perform large vibration due to displacement. The fine vibration and the large vibration of the cantilever 11 are generated by the piezoelectric element 13 operated by the drive signal S8 supplied from the mixer 54. The sample 16 is Z with respect to the cantilever 11.
It approaches by the operation of the stage 31. The motor built in the Z stage 31 performs an approach operation in response to the pulse 76, and a predetermined distance (for example, 0.5 μm) for each pulse
approach. As is clear from the relationship between the waveforms in FIG. 4, at time t1, the amplitude of the low-frequency signal S5 becomes maximum, and as a result,
The cantilever 11 bends most, and the distance of the probe 12 to the sample 16 increases. At that time, a pulse 76 is generated, and the approach operation of the Z stage 31 is started. Therefore, when the cantilever 11 approaches the sample 16 due to large vibration, the cantilever 1
Move to approach 1. Since the sample 16 exists in the atmosphere on the surface of the sample 16, an adsorption layer 81 is formed. In the state of FIG. 5B, the cantilever 11
It moves downward by the large vibration of
The probe 12 has just approached the sample 16 and is about to touch the adsorption layer 81 on the sample surface. In FIG. 5C,
The state where the probe 12 is drawn into the adsorption layer 81 due to the surface tension of the adsorption layer 81 is shown. At this time, the cantilever 11
Micro vibration stops. As a result, since the high-frequency signal S1 disappears, the output of the up / down counter 53 disappears, and the bending displacement of the cantilever 11 stops. At the same time, the low frequency signal S5 is not generated, so that the Z stage 3
1 does not perform the approach operation, and the approach operation of the sample 16 to the probe 12 is completely stopped.

According to the probe / sample approach mechanism of the above embodiment, the cantilever 11, that is, the probe, is moved to a distance operable as an AFM by using an approach device (Z stage 31) including a pulse drive type motor such as a stepping motor. A system capable of automatically bringing the sample 12 and the sample 16 into close proximity can be realized, and the system can be configured very simply. Further, the operation of the present probe / sample approach mechanism has a fail-safe function by itself. For example, even when the movement of the cantilever 11 cannot be monitored due to a defect in the laser light source, the high-frequency signal S1 disappears.
The approaching operation of 6 stops. In addition, since the probe 12 normally stops oscillating in a state of trying to escape from the adsorption layer 81, there is a low possibility that the probe 12 is damaged by a large repulsive force.

In the probe / sample approach mechanism having the above structure, the approach operation of the Z stage 31 is controlled by adjusting the oscillation frequency of the oscillator 55 or adjusting the count operation of the up / down counter 53. The generation cycle of the pulse 76 can be appropriately changed. Thus, at high speed, when a contact state occurs between the probe and the sample, the vibration disappears, and an automatic approach that can automatically stop is performed.

In the above-described embodiment, the Z stage 31, which is a coarse movement mechanism, is provided on the sample side. However, it is needless to say that the Z stage 31 can be provided on the cantilever side.

In the above embodiment, the cantilever 1
1 is caused by the bending displacement by the piezoelectric element 13, but the bending vibration is not caused by the bending displacement but by the cantilever 1.
It is also possible to use a displacement generating device for displacing 1 in parallel.

In the above embodiment, the AFM has been described. However, the probe / sample approaching device according to the present invention can be applied to a scanning probe microscope having a similar configuration and operation.

Further, in the above-described embodiment, the operation at the time of measurement is set to the contact mode. However, the operation is not necessarily limited to this.
Even in the case of FM, the probe / sample approach mechanism according to the present invention can be applied to set the desired distance between the probe and the sample at the stage before starting the measurement / observation. is there.

[0039]

As is apparent from the above description, according to the present invention, when approaching between the probe and the sample with the scanning probe microscope, micro-vibration is given to the cantilever, and this micro-vibration is used. The generated large vibration is given to the cantilever, and the approaching device is driven by the pulse signal generated based on the large vibration to perform the approach between the probe and the sample.By appropriately generating the pulse signal, The responsiveness is improved, and the approach operation can be performed at a high speed, and when the vibration operation of the cantilever stops, the pulse disappears, so that the operation can be stopped automatically, and the high-speed automatic approach can be performed.

In particular, when the measurement is performed in an atmospheric environment,
Since an adsorption layer is formed on the surface of the sample, when the probe and the sample approach each other at a sufficient distance, the probe is caught by the adsorption layer on the surface of the sample, and the micro vibration of the cantilever stops automatically. Therefore, the approach operation between the probe and the sample automatically stops.

Further, according to the structure of the present invention, in particular, an AFM using a hard cantilever having a relatively large spring constant.
, Safe high-speed approach can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a typical embodiment of the present invention.

FIG. 2 is a diagram showing a detailed structure of a cantilever.

FIG. 3 is a waveform diagram showing signals S1 to S3 of various parts of a circuit of a signal processing system.

FIG. 4 is a timing chart showing signals S4 to S7 of each section of the circuit of the signal processing system.

FIG. 5 is a diagram for explaining stop of vibration of a cantilever.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Cantilever 12 Probe 13 Piezoelectric element 14 Frame 15 XYZ scanner 16 Sample 17 Laser light source 19 Position sensor 31 Z stage 33 Changeover switch 36 Arithmetic processing unit 55 Mixer

Claims (4)

[Claims] 1. A scan for providing a cantilever having a probe at a tip thereof, approaching the probe and a sample, and measuring fine properties of the surface based on an interaction between the probe and the surface of the sample. In the scanning probe microscope, a low-frequency signal is generated by using an oscillating unit that applies a minute vibration to the cantilever and the minute vibration of the cantilever,
Signal generating means for giving a large vibration to the cantilever with the low frequency signal, and a pulse generating means for extracting the low frequency signal using the large vibration of the cantilever and generating a pulse signal based on the low frequency signal, An operation device is configured to be controlled based on the pulse signal, comprising an approach device for approaching the probe and the sample, when the approach device is driven to approach the probe and the sample, The probe / sample approaching mechanism of a scanning probe microscope, wherein the low frequency signal is generated based on the fine vibration of the cantilever, and the pulse signal is generated using the low frequency signal. 2. The scanning according to claim 1, wherein said pulse generating means generates said pulse when said cantilever is displaced away from said sample by a large vibration of said cantilever due to said low frequency signal. Probe / sample approach mechanism of a scanning probe microscope. 3. An approach operation between the probe and the sample by the approach device is performed in an atmospheric environment, and when the probe is drawn into an adsorption layer formed on a surface of the sample, the cantilever is moved. 2. The probe / sample approach mechanism for a scanning probe microscope according to claim 1, wherein the micro-vibration stops, and the large vibration stops, and the approach operation by the approach device stops. 4. The probe according to claim 1, wherein the unit movement amount of the approach by the approach mechanism is based on the probe based on the large vibration by the signal generating means.
2. The probe / sample approaching mechanism of a scanning probe microscope according to claim 1, wherein the distance between the samples is smaller than a unit change amount.