JPH07260803A - Scanning probe microscope - Google Patents

Abstract

PURPOSE:To remove adverse effects of polluting materials and to prevent a specimen from being damaged by providing a device to heat a specimen locally so that the parts of a microscope are not affected by heat. CONSTITUTION:A cantilever 102 deflects slightly according to a force applied to a probe 101 from a specimen 112. A laser 103 irradiates the lever 102 with a laser beam. A laser beam reflected on the lever 102 is projected on a bisected sensor 105. When the lever 102 deflects, the laser beam projected on the sensor 105 also deflects, varying the outputs of two diodes on the sensor 105. A deflectometer 106 calculates the deflections of the lever 102 from the output variations, and sends the deflections to a CPU 107. An X-Y direction position control circuit 108 applies a voltage indicating a position in X (Y) direction to a specimen stage drive mechanism 110. A Z-direction position control circuit 109 applies a voltage indicating a position in Z direction to the mechanism 110. A high frequency heating power supply 114 generates high frequency voltage and feeds it to a high frequency heating coil 115, thereby generating high frequency.

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 two-dimensionally scanning a probe electrode relative to the sample. .

[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 with atomic-order resolution [G. Binnig et al., Phys. Rev. Lett, 49, 57, (19
82)] was developed, and it has become possible to observe real space at the atomic and molecular level.

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

Furthermore, an atomic force microscope (hereinafter referred to as AFM) based on a minute force acting between the tip of the probe (tip) and the sample has been developed, and it is possible to observe even a sample which is not conductive by atomic resolution. Became. In addition to this, a scanning probe microscope such as Photon STM (hereinafter SP
M) has been developed, and it has become possible to observe the surface shape and physical state on the atomic or molecular scale.

However, in SPM, there are cases where accurate information on the sample surface cannot be obtained due to the presence of adsorbed substances such as water and contaminants on the sample surface. For example, when the surface of a sample having water adsorbed on the sample surface is observed by using the STM, the distribution of the water has an influence, and a correct sample surface shape cannot be obtained. Also, when observing a similar sample using AFM, the tip end of the tip is pressed against the sample by the surface tension caused by the adsorbed water and the sample is destroyed, or the correct force acting between the tip end and the sample is detected. It may not be possible to obtain the correct image.

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

[0007]

In the above-mentioned conventional scanning probe microscope, there is a problem that a correct sample surface shape cannot be obtained due to the influence of adsorbed substances and contaminants on the sample surface.

In the case of heating the sample in order to prevent the adverse effects of the adsorbed substances and contaminants on the sample surface, there is a problem that the sample is unnecessarily destroyed or the parts of the SPM device are adversely affected. .

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and does not damage the sample and has little thermal influence on the components of the scanning probe microscope. An object of the present invention is to realize a scanning probe microscope capable of eliminating the adverse effects of contaminants in a state.

[0010]

The scanning probe microscope of the present invention is produced by a physical interaction between a probe electrode and a sample when the probe electrode is two-dimensionally scanned relative to the sample. A scanning probe microscope for observing the sample using a signal is characterized by having a heating means for locally heating the sample.

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

The portion heated by the heating means is
It may be the surface of the sample to be observed.

Further, the heated portion may be a contaminant on the surface of the sample to be observed.

Further, the heated portion may be an interface between the surface of the sample to be observed and contaminants on the surface.

In any of the above cases, the heating means may be a heating means which locally heats by generating heat in a part of the sample depending on the material.

The mechanism for heating the sample may be any of electron beam heating, infrared heating and high frequency heating.

Examples of the scanning probe microscope include a scanning tunneling microscope and an atomic force microscope.

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

[0019]

In the apparatus of the present invention, the heating mechanism does not heat the entire sample, but heats it locally. As a result, it is possible to prevent the sample and the microscope apparatus from being heated more than necessary.

As the local heating, there is a case where the observed area of the sample surface and its periphery are heated particularly. 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, an excessive temperature rise of the sample and the microscope apparatus can be prevented.

In some cases, the surface of the sample on the observation side 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 existing on the surface of the sample to be observed may be heated to remove the contaminants by evaporation.

In addition, when the interface between the adsorbed substance and the contaminants (for example, water and organic substances) attached to the surface to be observed by the SPM is particularly heated to remove the adsorbed substance and the contaminants from the sample, etc. Can be given.

As a result, it becomes possible to clean and observe the observation surface without giving a large damage to the surface of the sample to be observed.

As described above, since heat is generated in a part of the sample depending on the material for heating the part of the sample,
You may use the heating means which heats locally. This is, for example, a method in which radiation having a wavelength that is easily absorbed by a specific substance is used as a heat source. For example, it is possible to generate heat with a specific substance by adjusting the frequency using high frequency heating. Similar effects can be expected by heating with infrared rays.

Water is often used as the pollutant on the surface of the sample. In this case, the effect is further enhanced by placing the sample in a dry gas. Heating in a gas with a low water content promotes desorption of water from the sample and reduces reattachment of water.

Further, since the heat is easily diffused from the sample surface by placing it in a gas, it is possible to suppress the heat diffusion to other parts of the sample and the constituent parts of the microscope apparatus.

Although the sample may react with the atmospheric gas by arranging the sample in the inert gas, this phenomenon can be prevented by arranging the sample in the inert gas. Further, since the heat is easily diffused from the surface of the sample when placed in the gas, it is possible to suppress the heat diffusion to other parts of the sample and the components of the microscope apparatus.

By disposing the sample in a vacuum, the detachment of the adsorbed substance due to heating is promoted and the reattachment of the adsorbed substance is prevented. At the same time, there is an effect that reaction between the sample and the atmospheric gas due to heating is prevented.

[0030]

Embodiments of the present invention will now 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 as a local heating device to an AFM.

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

The tip of the probe 101 moves while contacting the sample 112. The cantilever 102 has a weak cantilever structure, and the probe 101 is arranged at the tip thereof. The cantilever 102 flexes slightly according to the force that the probe 101 receives from the sample 112.

The laser 103 irradiates the cantilever 102 with laser light, and the laser light reflected by the cantilever 102 enters the two-divided sensor 105. Two-division sensor 10
Reference numeral 5 is composed of two photodiodes arranged close to each other, and the laser light is incident on the boundary so that the outputs of the two photodiodes become substantially equal. When the cantilever 102 bends, the laser light incident on the two-divided sensor 105 shifts, and the outputs of the two diodes of the two-divided sensor 105 change. This change is detected by the deflection amount detector 10
6 detects the deflection amount of the cantilever 102, and sends the result to the microcomputer 107.

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

The microcomputer 107 sends a control signal indicating a position in the X and Y directions in the figure to the XY direction position control circuit 108, and a position in the Z direction in the figure to the Z direction position control circuit 109. Is transmitted. The X-Y direction position control circuit 108 applies a drive voltage indicating the position in the X direction and the Y direction to the sample stage drive mechanism 110, and the 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 drive mechanism 110 moves the sample stage 111 in the XY and Z directions based on the drive voltage. The sample 112 fixed to the sample stage 111 moves along with the operation of the sample stage 111, whereby the positions of the probe 101 and the sample 112 are defined. When observing the surface of the sample 112, the microcomputer 107 brings the probe 101 into contact 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, and the probe is moved in the XY directions. 101 is scanned, the surface shape is imaged by the Z direction control signal and the XY direction control signal, and the image is output to the display 113.

In this case, the microcomputer 107 may bring the probe 101 and the sample 112 into contact with each other and scan them in the XY directions, and directly image the output of the deflection amount detecting device accompanying the scanning.

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

The high-frequency heating power source 114 appropriately generates a high frequency in accordance with 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 device, the frequency of the high frequency generated is adjusted to be almost equal to the frequency of water molecules. Therefore, the high frequency is mainly absorbed by the water adsorbed on the sample surface, and heat is generated there. This allows samples and ST
It is possible to remove the adsorbed water without seriously damaging the M device. Further, the apparatus of this embodiment has an advantage that water adsorbed on the probe 101 can be removed together.

By heating the sample 112 as described above and then observing the sample surface by AFM, 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 drive mechanism 110, a sample stage 111, a sample 112, a high frequency heating power source 114,
The high frequency heating coil 115 and the high frequency heating coil 115 are enclosed in the chamber 201, and the electromagnetic shield 116 is the chamber 2
It is arranged so as to cover 01.

The chamber 201 has a dry air cylinder 20.
2 are connected by a pipe via a valve 203, and are configured to introduce dry air. Further, the exhaust can be performed through the valve 204.
Adjust the valves 203 and 204 to adjust 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. The configuration other than these is the same as that of the first embodiment shown in FIG.

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

In the apparatus according to the present embodiment, the sample surface can be observed in a state in which re-adhesion of adsorbed water is small by exposing the sample surface to dry air even during observation by AFM.

[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 similar to that of the second embodiment shown in FIG. 2. According to the apparatus of this embodiment, the argon gas is supplied to the chamber 201.
By filling the inside of the sample 112, the sample 112 is placed in an argon atmosphere which is an inert gas, and its surface is exposed to the argon atmosphere.

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

[Fourth Embodiment] 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 source 403, a microcomputer 404, a current amplifier 405, and a servo circuit 406.
And 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 compares the current set value sent from 4 and the current detected by the current amplifier 405, sends a control signal to the Z direction position control circuit 407 so that the two become equal, and
The generated control signal is sent to the microcomputer 404. The Z direction position control circuit 407 is the servo circuit 40.
Z of the sample stage drive mechanism 409 according to the signal from
Generate drive signals for directions.

The XY direction position control circuit 408 also generates a signal for driving the sample stage drive mechanism 409 in the XY direction in response 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 position between the probe 401 and the sample 402.

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

When the sample 402 is to be observed, the microcomputer 404 sends information regarding the position in the XY direction in the drawing to be observed to the XY direction position control circuit 408, and the XY direction position control circuit 408 outputs the information. A control signal is sent to the sample stage drive mechanism 409 based on the information, and the sample stage drive mechanism 409 responds to the sample 4
10 in the XY direction, and the probe 401 moves the sample 40
Adjust so that it is the position you want to observe.

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 signals 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 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 source 413 are provided.

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

In this embodiment, the microcomputer 404 controls the infrared lamp power source 4 before observing the sample 402.
13 to turn on the infrared lamp 412. The infrared lamp 412 is arranged so as to emit infrared rays from the observation surface side of the sample 402 as described above.
This is a mechanism for heating only the observation surface side of No. 02. Normally, the wavelength of the infrared lamp 412 is widened so that the surface of the sample 402 can be heated even if the material of the sample 402 is changed.

It is also 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 rays that are 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 infrared rays 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. It can be removed efficiently.

[Fifth Embodiment] 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 to a vacuum by the vacuum exhaust device 502.

By heating the surface of the sample 402 with infrared rays in the same manner as in the fourth embodiment shown in FIG. 4 with the surface of the sample 402 in a vacuum as described above, the adsorbed substances can be more effectively removed. Can be removed. Particularly in the case of a sample that easily reacts with the atmospheric gas by heating, the reaction between the sample and the atmospheric gas can be prevented by placing the sample in vacuum.

[Sixth Embodiment] 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 (4) is electron beam heating. In this embodiment, the infrared lamp 412 and the infrared lamp power source 413 in the fifth embodiment are removed, and instead, an electron gun 601, an electron gun power source 602,
Is provided.

The electron gun 601 irradiates the surface of the sample 402 with an electron beam, and the electron gun power source 602 is a microcomputer 40.
Power is supplied to the electron gun 601 based on the control signal from the No. 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 device shown in this embodiment, the electron gun 6
01 irradiates the surface of the sample 402, and the center position of the electron beam irradiation 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 observed region of the surface of the sample 402 is mainly heated and the adsorbed substance in this region is removed. In this way, the electron beam is heated by the electron beam centering on the region of the sample 402 to be observed, the temperature rise in the region other than the region to be observed is suppressed, and unnecessary sample destruction and S
The PM device can be prevented from being destroyed. When observing the sample 402, the influence is removed by the temperature rise when observing after the electron beam irradiation is stopped.

In the above embodiment, the electron beam is irradiated from the side of the sample 402 to be observed, but as shown in FIG. 7, the electron beam may be irradiated from the side opposite to the side of the sample 402 to be observed. . FIG. 7 shows a sample 40 of the microscope apparatus shown in FIG. 6 in which the arrangement of the electron gun 601 is changed.
Sample stage 701 in which the shape of the portion holding 2 is changed
It is what In FIG. 7, the sample 402 is mounted on the sample stage 701 having holes. An electron gun 601 is arranged so that the sample is irradiated with the electron beam through this opening. The back side of the sample 402 is irradiated with the electron beam, and the back side of the region observed at that time is irradiated with the electron beam. Since the area heated by the electron beam is narrow, a large amount of heat is not transferred 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 region, but the heating may be applied to a place other than the observation region of the sample. In any case, the configuration of locally applying heat according to the present invention makes it possible to heat the sample without affecting the components constituting the microscope apparatus. The sample may be observed after heating or while heating.

[0069]

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

According to the first aspect of the present invention, the image is obtained in a state where the influence of the adsorbed substances or contaminants on the sample surface is removed without affecting the parts other than the observation area of the sample and the components constituting the microscope apparatus. Therefore, there is an effect that accurate observation can be performed.

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

According to the second to ninth aspects, there is an effect that the adsorbed substances and contaminants on the sample surface can be efficiently removed.

According to the tenth and the first aspects, there is an effect that a scanning tunnel microscope and an atomic force microscope which have the above respective effects can be realized.

In the twelfth to fourteenth aspects, there is an effect that each of the above effects can be further improved.

[Brief description of 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 exemplary embodiment of the present invention.

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

FIG. 6 is a diagram showing a configuration of a sixth exemplary embodiment 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 reference numerals] 101,401 probe 102 cantilever 103 laser 104 laser power source 105 two-divided sensor 106 deflection amount 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 Power supply for high frequency heating 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

Claims (14)

[Claims] 1. The probe electrode is relatively disposed with respect to the sample.
In a scanning probe microscope, which observes the sample by using a signal generated by a physical interaction between the probe electrode and the sample during a two-dimensional scan, a heating means for locally heating the sample is provided. Characteristic scanning probe microscope. 2. The scanning probe microscope according to claim 1, wherein the portion locally heated by the heating means is an observed region of the sample surface and a peripheral region thereof. The scanning probe microscope shown in. 3. The scanning probe microscope according to claim 1 or 2, wherein the portion heated by the heating means is a surface of the sample to be observed. 4. The scanning probe microscope according to claim 1 or 2, wherein the heated portion is a contaminant on the surface of the sample to be observed. 5. The scanning probe microscope according to claim 1 or 2, wherein the heated portion is an interface between a surface of the sample to be observed and a contaminant on the surface. Scanning probe microscope. 6. The scanning probe microscope according to any one of claims 1 to 5, wherein the heating means locally heats by generating heat in a part of the sample depending on the material. A scanning probe microscope characterized in that 7. The scanning probe microscope according to claim 1, wherein the mechanism for heating the sample is electron beam heating. 8. A scanning probe microscope according to claim 1, wherein the mechanism for heating the sample is infrared heating. 9. The scanning probe microscope according to any one of claims 1 to 6, wherein the mechanism for heating the sample is high-frequency heating. 10. The scanning probe microscope according to any one of claims 1 to 9, wherein the scanning probe microscope is a scanning tunneling microscope. Type probe microscope. 11. The scanning probe microscope according to any one of claims 1 to 9, wherein the scanning probe microscope is an atomic force microscope. 12. The scanning probe microscope according to any one of claims 1 to 6 or claim 8 to 11, wherein the sample is placed in a dry gas. Type probe microscope. 13. The scanning probe microscope according to any one of claims 1 to 6 or claim 8 to 11, wherein the sample is placed in an inert gas. Scanning probe microscope. 14. The scanning probe microscope according to claim 1, wherein the sample is placed in a vacuum.