JP3270617B2 - Scanning probe microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope for recording information on a sample and reproducing the recorded information while scanning a probe electrode relative to the sample in two dimensions. .

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter, referred to as STM) capable of observing the surface of a substance at an atomic order of resolution [G. Binnig et al., Phys. Rev. Lett, 49, 57, (19)
82)] has been developed, and real-space observation at the atomic and molecular levels has become possible.

A scanning tunneling microscope scans while controlling the distance between a probe electrode and a conductive sample so as to keep the tunnel current constant, and uses a control signal at that time to obtain information on the electron cloud on the sample surface and the shape of the sample on the sub-nano. It can be observed on the order of meters. Applying the principle of STM,
Observation in the atomic order (sub-nanometer order) is possible.

Further, an atomic force microscope (hereinafter, referred to as AFM) based on a small force acting between a probe tip (tip) and a sample has been developed, so that non-conductive samples can be observed with atomic resolution. It became. In addition, scanning probe microscopes such as Photon STM (hereinafter referred to as SP
M) has been developed, and it has become possible to observe the surface shape and physical state on an atomic or molecular scale.

However, in the case of SPM, accurate information on the sample surface may not be obtained due to the presence of adsorbed substances such as water and contaminants on the sample surface. For example, when surface observation is performed using STM on a sample in which water is adsorbed on the sample surface, the distribution of the water affects the sample, and a correct sample surface shape cannot be obtained. In addition, when the same sample was observed using AFM, the tip of the tip was pressed against the sample by the surface tension caused by the adsorbed water, and the sample was destroyed. The correct image cannot be obtained without being obtained.

In order to avoid the above-mentioned problems, there is a method of heating the sample to remove adsorbed substances and contaminants on the surface of the sample. However, simply heating the sample may cause unnecessary destruction or the like of the sample. Alternatively, heat may diffuse from the sample and adversely affect components of the SPM device, for example, a piezo element for driving a probe.

[0007]

The above-described conventional scanning probe microscope has a problem that a correct sample surface shape cannot be obtained due to the influence of adsorbed substances and contaminants on the sample surface.

[0008] Heating a sample to prevent adverse effects due to adsorbed substances and contaminants on the surface of the sample has a problem that unnecessary destruction of the sample occurs and adversely affects parts of the SPM device. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and does not damage a sample and has little thermal influence on components of a scanning probe microscope. It is an object of the present invention to realize a scanning probe microscope that can eliminate the adverse effects of contaminants in a state.

[0010]

A scanning probe microscope according to the present invention provides a signal generated by a physical interaction between a probe and a sample when the probe is two-dimensionally scanned relative to the sample. In a scanning probe microscope for observing the sample by utilizing, heating means for heating a contaminant on the sample surface or an interface between the sample surface and the contaminant on the surface and removing the contaminant from the sample surface. It is characterized by having.

In this case, the portion heated by the heating means may be a region on the sample surface to be observed and a peripheral region thereof.

Further, the heating means may be heated by irradiating an electron beam.

The heating means may be heated by irradiating infrared rays.

Further, the heating means may heat by generating a high frequency.

Further, the heating may be performed in a dry gas.

The heating may be performed in an inert gas.

Further, the heating may be performed in a vacuum.

The sample may be placed in a dry gas, an inert gas, or a vacuum.

[0019]

As the local heating, there is a case where the observed region of the sample surface and its periphery are particularly heated. For example, when a beam-shaped heat source such as an electron beam is applied to the vicinity of the center of the observation area, the temperature of the sample and the microscope apparatus is prevented from being increased more than necessary.

In some cases, the observation side surface of the sample is particularly heated. For example, the case where light is irradiated from the observation surface side of the sample corresponds to this case.

In some cases, contaminants such as water and organic substances present on the surface of the sample to be observed are particularly heated to remove the contaminants by evaporation.

In addition, when the interface between the adsorbed substance and the contaminant (eg, water and organic substance) adhering to the surface to be subjected to SPM observation is particularly heated, the adsorbed substance and the contaminant are removed by peeling off from the sample. Is raised.

This makes it possible to clean and observe the observation surface of the sample without damaging the surface to be observed.

As described above, when a part of the sample is heated, heat is generated in the part of the sample depending on the material,
Heating means for locally heating may be used. This is, for example, a method in which radiation having a wavelength easily absorbed by a specific substance is used as a heat source. For example, heat can be generated by a specific substance by adjusting the frequency using high-frequency heating. Similar effects can be expected by heating with infrared light.

The contaminant on the surface of the sample is often water, but in this case, placing the sample in a dry gas produces a further effect. Heating in a gas with low moisture promotes desorption of water from the sample and reduces reattachment of water.

Further, since heat is easily diffused from the sample surface by being placed in a gas, heat diffusion to other portions of the sample and components of the microscope apparatus can be suppressed.

In some cases, placing the sample in an inert gas causes the sample to react with the atmospheric gas. By placing the sample in the inert gas, this phenomenon is prevented. In addition, since heat is easily diffused from the sample surface by being placed in a gas, heat diffusion to other parts of the sample and components of the microscope apparatus can be suppressed.

Further, by disposing the sample in a vacuum, desorption of the adsorbed substance by heating is promoted and re-adhesion of the adsorbed substance is prevented. At the same time, there is an effect that the reaction between the sample and the atmosphere gas due to heating is also prevented.

[0030]

Next, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention in which a high-frequency heating device is added to an AFM as a local heating device.

The apparatus according to the present embodiment includes a probe 101
, A cantilever 102, a laser 103, a laser power supply 104, a two-part sensor 105, a deflection detector 106, a microcomputer 107, an XY position control circuit 108, and a Z direction position control circuit 109. When,
Sample stage drive mechanism 110 and sample stage 111
, A sample 112, a display 113, a high-frequency heating power supply 114, and a high-frequency heating coil 115.

The probe 101 moves while its tip contacts the sample 112. The cantilever 102 has a weak cantilever structure, and the probe 101 is disposed at the tip thereof. The cantilever 102 bends slightly according to the force received by the probe 101 from the sample 112.

The laser 103 irradiates the cantilever 102 with a laser beam, and the laser beam reflected by the cantilever 102 enters the two-way sensor 105. 2-split sensor 10
Numeral 5 is composed of two photodiodes arranged close to each other, and the laser beam is incident on the boundary so that the outputs of the two photodiodes are substantially equal. When the cantilever 102 bends, the laser light incident on the two-piece sensor 105 shifts, and the outputs of the two diodes of the two-piece sensor 105 change. This change is detected by the deflection amount detector 10.
6 detects and calculates the amount of deflection of the cantilever 102 and sends the result to the microcomputer 107.

Of the above components, the probe 101
, A cantilever 102, a laser 103, a two-piece sensor 105, a sample stage driving mechanism 110, a sample stage 111, a sample 112, and a high-frequency heating coil
115 are enclosed in an electromagnetic shield 116.

The microcomputer 107 sends a control signal indicating the position in the X direction and the Y direction in the figure to the XY direction position control circuit 108, and the position in the Z direction in the figure is sent to the Z direction position control circuit 109. Is transmitted. An XY direction position control circuit 108 applies a drive voltage indicating a position in the X direction and the Y direction to the sample stage driving mechanism 110, and a Z direction position control circuit 109.
Applies a drive voltage indicating a position in the Z direction to the sample stage drive mechanism 110.

The sample stage driving mechanism 110 moves the sample stage 111 in the XY direction and the Z direction based on the driving voltage. The sample 112 fixed to the sample stage 111 moves with the operation of the sample stage 111, and thereby the positions of the probe 101 and the sample 112 are defined. When observing the surface of the sample 112, the microcomputer 107 contacts the probe 101 with the sample 112, and controls the position in the Z direction so that the force received by the probe 101 from the surface of the sample 112 is constant. 101 is scanned, the surface shape is imaged by the Z-direction control signal and the XY-direction control signal, and output to the display 113.

In this case, the microcomputer 107 may make the probe 101 and the sample 112 come into contact with each other and scan them in the X and Y directions, and directly output the output of the bending amount detecting device.

The operation and operation described so far are generally performed by the AFM.
Is the same as the method performed in The AFM according to the present invention further includes a high-frequency heating power supply 114 and a high-frequency heating coil 1.
15 are provided.

The high-frequency heating power supply 114 generates an appropriate high frequency according to a command from the microcomputer 107 and supplies it to the high-frequency heating coil 115, whereby the high-frequency heating coil 115 generates a high frequency. In this apparatus, the frequency of the generated high frequency is adjusted to be approximately equal to the frequency of water molecules. Therefore, the high frequency is mainly absorbed by the water adsorbed on the sample surface, where heat is generated. This allows the sample and ST
The adsorbed water can be removed without causing significant damage to the M device. Further, the apparatus according to the present embodiment also has an advantage that water adsorbed on the probe 101 can be removed together.

By heating the sample 112 as described above and then performing AFM observation on the sample surface, a clean surface can be observed.

[Embodiment 2] Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is shown in FIG.
The probe 101, the cantilever 102, the laser 103, and the two-divided sensor 1 of the first embodiment shown in FIG.
05, a sample stage driving mechanism 110, a sample stage 111, a sample 112, a high-frequency heating power supply 114,
A high-frequency heating coil 115 is enclosed in a chamber 201, and an electromagnetic shield 116 is
01 is arranged.

The chamber 201 has a dry air cylinder 20.
2 are connected by piping via a valve 203, and are configured to introduce dry air. Exhaust can also be performed via the valve 204.
By adjusting the valves 203 and 204, the chamber 20
By filling the inside of the sample 1 with dry air, the surface of the sample 112 can be made a dry atmosphere. Other configurations are the same as those of the first embodiment shown in FIG.

As described above, while the surface of the sample 112 is exposed to a dry atmosphere, by applying the same high frequency as in the first embodiment shown in FIG. 1, the adsorbed water on the surface of the sample 112 can be removed. it can. In the case of this embodiment, since the sample 112 is placed in a closed space surrounded by the chamber 201, the effect of removing the adsorbed water is greater than in the first embodiment, and the reattachment of the adsorbed water is also reduced. Few.

In the apparatus according to the present embodiment, by exposing the sample surface to dry air even during the observation by the AFM, the sample surface can be observed in a state in which the adsorbed water does not re-attach.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, the dry air cylinder 202 in the second embodiment shown in FIG. 2 is replaced with an argon gas cylinder 301. The other structure is the same as that of the second embodiment shown in FIG.
The sample 112 is placed in an argon atmosphere, which is an inert gas, by charging the inside, and the surface thereof is exposed to the argon atmosphere.

As described above, by applying the high frequency as shown in Embodiment 1 while the surface of the sample 112 is exposed to the argon atmosphere, the water adsorbed on the surface of the sample 112 can be removed. In particular, in the case of a sample which easily reacts with the atmosphere gas by heating, the reaction between the sample 112 and the atmosphere gas can be suppressed by setting the atmosphere in the chamber 201 to an inert gas as shown in this embodiment.

Embodiment 4 Next, a fourth embodiment of the present invention using an infrared heating device will be described with reference to FIG.

FIG. 4 is a schematic block diagram showing a fourth embodiment of the present invention. In this embodiment, STM is used as SPM.

The microscope shown in this embodiment has a probe 401
, A sample 402, a power supply 403, a microcomputer 404, a current amplifier 405, and a servo circuit 406.
, A Z-direction position control circuit 407, an XY direction position control circuit 408, a sample stage drive mechanism 409, a sample stage 410, a display 411, an infrared lamp 412, and an infrared lamp power supply 413. ing.

The probe 401 detects a tunnel current flowing through the sample 402. The power supply 403 applies a bias voltage to the sample 402. Current amplifier 405
Is for amplifying the current detected by the probe 401. The servo circuit 406 is the microcomputer 40
4 is compared with the current detected by the current amplifier 405, and a control signal is output to the Z-direction position control circuit 407 so that the two become equal.
The generated control signal is sent to the microcomputer 404. The Z direction position control circuit 407 is a servo circuit 40
6 according to the signal from the sample stage driving mechanism 409
Generate a drive signal in the direction.

The XY direction position control circuit 408 generates a signal for driving the sample stage driving mechanism 409 in the X and Y directions according to a signal from the microcomputer 404. The sample stage drive mechanism 409 moves the sample 402 based on the drive signal, and moves the relative positions of the probe 401 and the sample 402.

The microcomputer 404 has a power supply 40
3. The XY direction position control circuit 408 is controlled. Also,
The current value to be set is sent to the servo circuit 406. The microcomputer 404 images the surface of the sample 402 from the obtained information and displays the image on the display 411.

When the sample 402 is to be observed, the microcomputer 404 sends information on the position in the XY direction to be observed to the XY direction position control circuit 408, and the XY direction position control circuit 408 A control signal is sent to the sample stage drive mechanism 409 based on the information, and the sample stage drive mechanism 409 responds accordingly to the sample 4.
10 in the X-Y direction, and the probe 401
Adjust so that it is the position you want to observe in 2.

The position of the probe 401 and the sample 402 in the Z direction can be defined by the magnitude of the tunnel current flowing between the probe 401 and the sample 402. The microcomputer 404 commands the magnitude of this current to the servo circuit 406, and the servo circuit 406 compares this command value with the output of the current amplifier 405 and outputs a signal to the Z-direction position control circuit 407.

The microcomputer 404 outputs an output signal to the XY direction position control circuit 408 and the servo circuit 4
The shape of the surface of the sample 402 is calculated based on the output of the reference numeral 06 and output to the display 411.

The configuration and operation up to this point are the same as those of the conventional STM.
Is similar to

The microscope apparatus shown in this embodiment further includes:
An infrared lamp 412 and an infrared lamp power supply 413 are provided.

The infrared lamp 412 irradiates the sample 402 with infrared light from the observation surface side of the sample 402. The infrared lamp power supply 413 is connected to the infrared lamp 41.
2 power supply.

In this embodiment, the microcomputer 404 operates the infrared lamp power supply 4 before observing the sample 402.
13 to turn on the infrared lamp 412. The infrared lamp 412 is disposed so as to emit infrared light from the observation surface side of the sample 402 as described above.
02 is a mechanism for heating only the observation surface side. Normally, the wavelength of the infrared lamp 412 is widened so that the surface of the sample 402 can be heated even when the material of the sample 402 is changed.

Further, it is possible to heat a specific material on the surface of the sample 402 by narrowing the wavelength range of the infrared lamp 412. For example, by using infrared light that is well absorbed by the adsorbate, the adsorbate adsorbed on the surface of the sample 402 can be heated, and damage to the sample 402 can be further reduced. Also,
By using an infrared ray corresponding to the adsorption energy at the interface between the surface adsorbate and the surface of the sample 402 to be observed, the adsorbate can be mainly desorbed. In this case, the adsorbate is removed. It can be efficiently removed.

Embodiment 5 Next, a fifth embodiment of the present invention will be described with reference to FIG. This embodiment is shown in FIG.
The probe 401, the sample 402, the sample stage driving mechanism 409, the sample stage 410, and the infrared lamp 412 in the fourth embodiment shown in FIG. The vacuum chamber 501 is evacuated by a vacuum exhaust device 502 to a vacuum.

While the surface of the sample 402 is in a vacuum state as described above, the surface of the sample 402 is heated with infrared rays similarly to the fourth embodiment shown in FIG. Can be removed. In particular, in the case of a sample which easily reacts with the atmosphere gas by heating, the reaction between the sample and the atmosphere gas can be prevented by setting the sample in a vacuum.

Embodiment 6 Next, a sixth embodiment of the present invention will be described with reference to FIG. This embodiment is shown in FIG.
The heating mechanism in the STM of the fifth embodiment shown in FIG. In this embodiment, the infrared lamp 412 and the infrared lamp power supply 413 in the fifth embodiment are removed, and instead, an electron gun 601, an electron gun power supply 602,
Is provided.

The electron gun 601 irradiates the surface of the sample 402 with an electron beam.
The power is supplied to the electron gun 601 based on the control signal from the control unit 4. Other configurations and operations are the same as those of the fourth and fifth embodiments shown in FIGS. 4 and 5, respectively.

In the STM apparatus shown in this embodiment, the electron gun 6
01 irradiates the surface of the sample 402, and the center position where the electron beam is irradiated is the position observed by the probe 401. That is, the electron beam mainly irradiates the observed region of the sample 402, and therefore, the observation region of the surface of the sample 402 is mainly heated, and the adsorbed material in this region is removed. As described above, the sample 402 is heated by the electron beam around the region to be observed of the sample 402 by the electron beam heating, so that the temperature rise in the region other than the region to be observed is suppressed, and unnecessary sample destruction and S
Destruction of the PM device can be prevented. When observing the sample 402 after stopping the irradiation of the electron beam, the influence is removed by increasing the temperature.

In the above embodiment, the structure in which the electron beam is irradiated from the side of the sample 402 to be observed has been described, but the structure in which the electron beam is irradiated from the side opposite to the side of the sample 402 to be observed as shown in FIG. . FIG. 7 shows an example of the microscope apparatus shown in FIG.
Sample stage 701 in which the shape of the portion for holding 2 has been changed
It is what it was. In FIG. 7, a sample 402 is mounted on a sample stage 701 having a hole. An electron gun 601 is arranged so that the sample is irradiated with an electron beam through the opening. The electron beam is irradiated on the back side of the sample 402, and the electron beam is irradiated on the back side of the region observed at that time. Since the region heated by the electron beam is small, large heat is not transmitted to the sample stage 701.

In each of the embodiments described above, the heating of the sample is described as being applied mainly to the observation area. However, the heating may be applied to places other than the observation area of the sample. In any case, the configuration of the present invention in which heat is locally applied makes it possible to heat the sample without affecting components constituting the microscope apparatus. The sample may be observed after heating or while heating.

[0069]

Since the present invention is configured as described above, it has the following effects.

An image can be obtained without affecting the components constituting the microscope apparatus and the place other than the observation area of the sample, without removing the adsorbed substances and contaminants on the sample surface, and accurate observation can be performed. There are effects that can be performed.

Another effect of the present invention is that the sample can be heated without affecting the place other than the observation region of the sample and the components constituting the microscope apparatus. In this case, observation may be performed after heating, or observation may be performed while heating.

Further, there is an effect that adsorbed substances and contaminants on the sample surface can be efficiently removed.

[0073]

[0074]

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a fifth example of the present invention.

FIG. 6 is a diagram showing a configuration of a sixth example of the present invention.

FIG. 7 is a diagram showing a main configuration of a modification of the sixth embodiment of the present invention.

[Explanation of symbols]

 101, 401 Probe 102 Cantilever 103 Laser 104 Laser power supply 105 Two-part sensor 106 Deflection detector 107, 404 Microcomputer 108, 408 XY direction position control circuit 109, 407 Z direction position control circuit 110, 409 Sample stage drive Mechanism 111, 410, 701 Sample stage 112, 402 Sample 113, 411 Display 114 High-frequency heating power supply 115 High-frequency heating coil 116 Electromagnetic shield 201 Chamber 202 Dry air cylinder 203, 204 Valve 301 Argon gas cylinder 403 Power supply 405 Current amplifier 406 Servo circuit 412 Infrared lamp 413 Infrared lamp power supply 501 Vacuum chamber 502 Vacuum exhaust device 601 Electron gun 602 Electron gun power supply

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-287246 (JP, A) JP-A-3-98244 (JP, A) JP-A-4-326007 (JP, A) JP-A-4- 361110 (JP, A) JP-A-5-79833 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00-21/24 G01B 21/30 H01J 37/20 H01J 37/28 G01B 7/34 G01B 11/30 JICST file (JOIS)

Claims (8)

(57) [Claims] 1. A scanning probe microscope for observing a sample using a signal generated by a physical interaction between the probe and the sample when the probe is two-dimensionally scanned relative to the sample. A scanning probe microscope comprising heating means for heating a contaminant on a sample surface or an interface between the sample surface and the contaminant on the surface and removing the contaminant from the sample surface. 2. A part heated by the heating means,
The scanning probe microscope according to claim 1, wherein the scanning probe microscope is a region where the sample surface is observed and a peripheral region thereof. 3. The scanning probe microscope according to claim 1, wherein said heating means heats by irradiating an electron beam. 4. The scanning probe microscope according to claim 1, wherein said heating means heats by irradiating infrared rays. 5. The scanning probe microscope according to claim 1, wherein said heating means heats by generating a high frequency. 6. The scanning probe microscope according to claim 1, wherein the heating is performed in a dry gas. 7. The scanning probe microscope according to claim 1, wherein the heating is performed in an inert gas. 8. The scanning probe microscope according to claim 1, wherein the heating is performed in a vacuum.