阅读说明：本技术 扫描型探针显微镜和分析方法 (Scanning probe microscope and analysis method ) 是由 新井浩 平出雅人 于 2018-01-29 设计创作，主要内容包括：扫描型探针显微镜(1)具备控制部(15)。控制部(15)包括信号获取处理部(151)、图像获取处理部(152)、扫描条件变更处理部(154)、扫描处理部(155)以及噪声判定处理部(156)。在扫描型探针显微镜(1)中,在去除试样的表面图像中含有的噪声的情况下,扫描条件变更处理部(154)变更扫描条件。并且,信号获取处理部(151)获取来自检测部(12)的输出信号。图像获取处理部(152)基于该输出信号来获取试样(S)的表面图像。噪声判定处理部(156)基于通过扫描条件变更处理部(154)变更了扫描条件时的输出信号的变化或者试样(S)的表面图像的变化,来判定输出信号中是否含有噪声。因此,在输出信号中含有噪声的情况下,能够正确地判定该情况。(The scanning probe microscope (1) is provided with a control unit (15). The control unit (15) is provided with a signal acquisition processing unit (151), an image acquisition processing unit (152), a scan condition change processing unit (154), a scan processing unit (155), and a noise determination processing unit (156). In a scanning probe microscope (1), a scanning condition change processing unit (154) changes a scanning condition when noise contained in a surface image of a sample is removed. The signal acquisition processing unit (151) acquires an output signal from the detection unit (12). An image acquisition processing unit (152) acquires a surface image of the sample (S) on the basis of the output signal. A noise determination processing unit (156) determines whether or not noise is contained in the output signal on the basis of a change in the output signal or a change in the surface image of the sample (S) when the scanning conditions are changed by the scanning condition change processing unit (154). Therefore, when the output signal contains noise, the situation can be accurately determined.)

1. A scanning probe microscope, comprising:

a scanning processing unit that scans in a main scanning direction and a sub-scanning direction by relatively moving a cantilever along a surface of a sample;

an image acquisition processing unit that acquires a surface image of the sample based on an output signal corresponding to the amount of deflection of the cantilever during scanning;

a scanning condition change processing unit that changes a scanning condition including at least one of a scanning speed and a scanning range in the main scanning direction; and

and a noise determination processing unit that determines whether or not noise is contained in the output signal based on a change in the output signal or a change in a surface image of the sample when the scanning condition is changed by the scanning condition change processing unit.

2. The scanning probe microscope according to claim 1,

when the scanning speed is changed by the scanning condition change processing unit, the noise determination processing unit determines that the output signal contains noise if a periodic feature contained in the output signal or a periodic feature contained in a surface image of the sample changes.

3. The scanning probe microscope according to claim 1, wherein the noise determination processing unit determines that the output signal contains noise if a periodic feature included in the output signal or a periodic feature included in a surface image of the sample does not change when the scanning range is changed by the scanning condition change processing unit.

4. The scanning probe microscope according to claim 1,

the scanning probe microscope further includes a noise removal processing unit configured to remove noise from the acquired surface image of the sample when the noise determination processing unit determines that the output signal contains noise.

5. An analysis method using a scanning probe microscope that scans in a main scanning direction and a sub-scanning direction by relatively moving a cantilever along a surface of a sample, thereby acquiring a surface image of the sample based on an output signal corresponding to an amount of deflection of the cantilever during scanning, the analysis method characterized by comprising the steps of:

a scanning condition changing step of changing a scanning condition including at least one of a scanning speed and a scanning range in the main scanning direction; and

a noise determination step of determining whether or not noise is contained in the output signal based on a change in the output signal or a change in a surface image of the sample when the scanning condition is changed in the scanning condition changing step.

6. The analytical method of claim 5,

in the noise determination step, when the scanning speed is changed in the scanning condition changing step, it is determined that noise is contained in the output signal if a periodic feature contained in the output signal or a periodic feature contained in a surface image of the sample changes.

7. The analytical method of claim 5,

in the noise determination step, when the scanning range is changed in the scanning condition changing step, if the periodic feature included in the output signal or the periodic feature included in the surface image of the sample does not change, it is determined that the output signal contains noise.

8. The analytical method of claim 5,

the analysis method further includes a noise removal step of removing noise from the acquired surface image of the specimen in a case where it is determined by the noise determination step that the output signal contains noise.

Technical Field

The present invention relates to a scanning probe microscope that scans a surface of a sample by relatively moving a cantilever along the surface of the sample, and an analysis method using the scanning probe microscope.

Background

Conventionally, a scanning probe microscope has been used as a device for inspecting a fine surface shape of a sample. In a scanning probe microscope, a probe is moved relative to the surface of a sample to scan the sample, and a change in a physical quantity (such as a tunnel current or an atomic force) acting between the probe and the sample surface is detected during the scanning. Then, the relative position of the probe is feedback-controlled so that the physical quantity is kept constant during scanning, whereby the surface shape of the sample can be measured based on the feedback quantity (see, for example, patent document 1 below).

In such a scanning probe microscope, the cantilever is a very small member having a length of about 100 to 500 μm and a width of about several tens μm, for example. In the scanning probe microscope, the cantilever is moved relative to the surface of the sample, and a minute surface image of the sample is acquired with high resolution.

Disclosure of Invention

Problems to be solved by the invention

In the conventional scanning probe microscope as described above, there is a problem that an image that does not actually exist may be included in the acquired image. Specifically, the scanning probe microscope acquires an image at high resolution, and is therefore susceptible to the influence of the surroundings (external noise) during observation. For example, when a floor vibration, an air flow due to air conditioning, power supply noise, or the like occurs when a sample is observed using a scanning probe microscope, an image that does not actually exist (an image due to noise) appears as a pattern in an acquired image. In this case, an image representing the actual sample surface and an image generated by noise are mixed in the image, and thus the user may not be able to observe the image accurately.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a scanning probe microscope and an analysis method capable of accurately determining noise contained in an output signal.

Means for solving the problems

(1) The scanning probe microscope according to the present invention includes a scanning processing unit, an image acquisition processing unit, a scanning condition change processing unit, and a noise determination processing unit. The scanning processing unit scans in a main scanning direction and a sub-scanning direction by relatively moving the cantilever along the surface of the sample. The image acquisition processing unit acquires a surface image of the sample based on an output signal corresponding to the amount of deflection of the cantilever during scanning. The scanning condition change processing unit changes a scanning condition including at least one of a scanning speed and a scanning range in the main scanning direction. The noise determination processing unit determines whether or not noise is contained in the output signal based on a change in the output signal or a change in the surface image of the sample when the scanning condition is changed by the scanning condition change processing unit.

When a sample is observed using a scanning probe microscope, if floor vibration, air flow due to air conditioning, power supply noise, or the like occurs, an image that does not actually exist appears as a pattern in an acquired image. This is because the output signal contains noise.

In the scanning probe microscope, when scanning is performed while changing the scanning conditions, a signal indicating the actual sample surface and a signal generated due to noise change in different patterns in the output signal. Similarly, in the surface image, an image representing the actual sample surface and an image generated by noise change in different patterns.

According to the configuration of the present invention described above, the noise determination processing unit determines whether or not noise is contained in the output signal based on the output signal corresponding to the amount of deflection of the cantilever when the scanning condition is changed or the change in the surface image acquired by the image acquisition processing unit.

Therefore, when the output signal contains noise, the situation can be accurately determined.

(2) Further, when the scanning speed is changed by the scanning condition change processing unit, the noise determination processing unit may determine that the output signal contains noise if a periodic feature included in the output signal or a periodic feature included in a surface image of the sample changes.

In the scanning probe microscope, when scanning is performed while changing the scanning speed, the output signal does not change the signal indicating the actual sample surface, but changes the signal (periodic characteristic) generated by noise. Similarly, in the surface image, an image (periodic feature) representing the actual sample surface does not change, but an image generated by noise changes.

According to the above configuration, the scanning condition change processing unit changes the scanning speed, and the noise determination processing determines whether or not the output signal contains noise.

Therefore, it is possible to accurately determine that the output signal contains noise by a simple control process.

(3) Further, when the scanning range is changed by the scanning condition change processing unit, the noise determination processing unit may determine that the output signal contains noise if there is no change in a periodic feature included in the output signal or a periodic feature included in a surface image of the sample.

In the scanning probe microscope, when scanning is performed while changing the scanning range, the output signal shows a change in the signal of the actual sample surface, and the signal (periodic characteristic) generated by noise does not change. Similarly, in the surface image, an image representing the actual sample surface changes, and an image (periodic feature) generated by noise does not change.

According to the above configuration, the scanning condition change processing unit changes the scanning range, and determines whether or not noise is included in the output signal by the noise determination processing.

Therefore, it is possible to accurately determine that the output signal contains noise by a simple control process.

(4) The scanning probe microscope may further include a noise removal processing unit. The noise removal processing unit removes noise from the acquired surface image of the sample when the noise determination processing unit determines that the output signal contains noise.

According to this structure, a surface image derived only from the surface shape of the sample can be acquired.

As a result, the sample can be accurately observed.

(5) The analysis method according to the present invention is an analysis method using a scanning probe microscope that scans a cantilever in a main scanning direction and a sub-scanning direction by relatively moving the cantilever along a surface of a sample, thereby acquiring an image of the surface of the sample based on an output signal corresponding to an amount of deflection of the cantilever during the scanning. The analysis method includes a scanning condition changing step and a noise determining step. In the scanning condition changing step, a scanning condition including at least one of a scanning speed and a scanning range in the main scanning direction is changed. In the noise determination step, it is determined whether or not noise is contained in the output signal based on a change in the output signal or a change in the surface image of the sample when the scanning condition is changed in the scanning condition changing step.

(6) In the noise determination step, when the scanning speed is changed in the scanning condition changing step, it may be determined that the output signal contains noise when a periodic feature included in the output signal or a periodic feature included in a surface image of the sample changes.

(7) In the noise determination step, when the scanning range is changed in the scanning condition changing step, if the periodic feature included in the output signal or the periodic feature included in the surface image of the sample does not change, it may be determined that the output signal includes noise.

(8) In addition, the analysis method may further include a noise removal step. In the noise removing step, when it is determined by the noise determining step that the output signal contains noise, the noise is removed from the acquired surface image of the sample.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, in the scanning probe microscope, the noise determination processing unit determines whether or not noise is contained in the output signal based on the output signal corresponding to the amount of deflection of the cantilever when the scanning condition is changed or the change in the surface image acquired by the image acquisition processing unit. Therefore, when the output signal contains noise, the situation can be accurately determined.

Drawings

Fig. 1 is a schematic diagram showing a configuration example of a scanning probe microscope according to a first embodiment of the present invention.

Fig. 2 is a block diagram showing an electrical configuration of the control unit and its peripheral components.

Fig. 3 is a flowchart illustrating an example of the control operation performed by the control unit.

Fig. 4A is a diagram showing an example of a surface image of a sample acquired by a scanning probe microscope, and shows the surface image before the noise removal processing is started.

Fig. 4B is a diagram showing an example of a surface image of a sample acquired by a scanning probe microscope, and shows the surface image with a scanning speed changed.

Fig. 4C is a diagram showing an example of a surface image of a sample acquired by the scanning probe microscope according to the second embodiment of the present invention, and shows the surface image with a changed scanning range.

Detailed Description

1. Integral structure of scanning probe microscope

Fig. 1 is a schematic diagram showing a configuration example of a scanning probe microscope 1 according to an embodiment of the present invention. The scanning probe microscope 1(SPM) includes, for example, a stage 2, a cantilever 3, a light irradiation unit 4, a beam splitter 5, a mirror 6, a light receiving unit 7, and the like, and the scanning probe microscope 1 is used to scan the surface of a sample S with the cantilever 3 to obtain an image of irregularities on the surface of the sample S.

In the scanning probe microscope 1, a sample S is mounted on a stage 2. In the scanning probe microscope 1, one of the stage 2 and the cantilever 3 is displaced, whereby the cantilever 3 is relatively moved along the surface of the sample S.

The stage 2 is provided with, for example, a piezoelectric element (not shown) on an outer peripheral surface thereof. When the stage 2 is displaced (deformed), a voltage is applied to the piezoelectric element. Thereby, the stage 2 is appropriately deformed, and the position of the sample S on the stage 2 changes.

The cantilever 3 is provided at a position facing the sample S on the stage 2. The cantilever 3 is a very small elongated member having a length of, for example, about 150 μm and a width of about 30 to 40 μm, and is supported by the cantilever. A reflecting surface 31 is formed at the tip end of the free end side of the cantilever 3. A probe 32 is provided on the surface of the cantilever 3 opposite to the reflection surface 31. By moving the probe 32 along the surface of the sample S, an image of the unevenness of the surface of the sample S can be obtained.

The light irradiation unit 4 includes a laser light source such as a semiconductor laser.

The beam splitter 5 is disposed at a position where light from the light irradiation section 4 enters. Light from the light irradiation section 4 is incident on the cantilever 3 via the beam splitter 5.

Further, other optical members such as a collimator lens and a focusing lens (both not shown) may be provided in the optical path from the light irradiation section 4 to the cantilever 3. In this case, after the irradiation light from the light irradiation unit 4 is made parallel by the collimator lens, the parallel light can be condensed by the focusing lens and guided to the cantilever 3 side.

The collimator lens, the focusing lens, and the like described above constitute an optical system for guiding the irradiation light from the light irradiation section 4 to the cantilever 3 in addition to the beam splitter 5. The configuration of the optical system is not limited to this, and may be a configuration without at least one of the optical members described above.

The mirror 6 reflects the light reflected by the reflecting surface 31 of the cantilever 3 again to guide to the light receiving unit 7.

The light receiving unit 7 has a structure including a photodiode, such as a four-quadrant photodiode.

In the scanning probe microscope 1, when observing the sample S, the probe 32 of the cantilever 3 is moved relative to the surface of the sample S in a state where the sample S is placed on the stage 2, and thereby the sample S is scanned along the surface. During this scanning, physical quantities such as atomic force acting between the probe 32 of the cantilever 3 and the surface of the sample S change.

Further, the light irradiation unit 4 irradiates laser light. The light from the light irradiation section 4 passes through the beam splitter 5 toward the reflection surface 31 of the cantilever 3. The light (reflected light) reflected by the reflecting surface 31 of the cantilever 3 is reflected again by the mirror 6 and received by the light receiving unit 7.

Here, the reflecting surface 31 of the cantilever 3 is inclined at a predetermined inclination angle θ with respect to the direction orthogonal to the optical axis L of the irradiation light from the light irradiation section 4. Therefore, when the probe 32 of the cantilever 3 is moved along the irregularities on the surface of the sample S, the cantilever 3 is flexed, and the inclination angle θ of the reflecting surface 31 changes. At this time, the position of the light receiving unit 7 receiving the reflected light from the reflecting surface 31 changes. Therefore, the change in the physical quantity between the probe 32 acting on the cantilever 3 and the surface of the sample S during scanning can be detected based on the change in the light receiving position of the reflected light in the light receiving unit 7. Then, the relative position of the probe 32 of the cantilever 3 is feedback-controlled so that the physical quantity is kept constant, and the surface shape of the sample S is measured based on the feedback quantity (surface image acquisition).

When the sample S is observed using the scanning probe microscope 1 in this manner, there is a case where floor vibration, air flow due to air conditioning, or the like occurs, and the acquired signal contains noise. In order to discriminate and remove the noise, the scanning probe microscope 1 has the following configuration, and performs the following control operation.

2. Control part and electric structure of peripheral members thereof

Fig. 2 is a block diagram showing an electrical configuration of the control unit 15 and its peripheral components of the scanning probe microscope 1.

The scanning probe microscope 1 includes a display unit 11, a detection unit 12, an operation unit 13, a displacement unit 14, a control unit 15, and the like as electrical components.

The display unit 11 is constituted by, for example, a liquid crystal display or the like.

The detection section 12 detects the feedback amount of the relative position of the probe 32 of the cantilever 3, and outputs a signal based on the detection result. That is, the detection unit 12 outputs a signal (output signal) according to the amount of deflection of the cantilever 3.

The operation unit 13 is configured to include, for example, a keyboard and a mouse.

The displacement unit 14 is configured to displace the relative position of the cantilever 3 with respect to the sample S on the stage 2, and to scan in the main scanning direction and the sub-scanning direction. Specifically, the displacement unit 14 performs an operation of displacing the stage 2 with the position of the cantilever 3 fixed, or an operation of displacing the cantilever 3 with the position of the stage 2 fixed.

The control Unit 15 is configured to include a CPU (Central Processing Unit), for example. The display unit 11, the detection unit 12, the operation unit 13, the displacement unit 14, and the like are electrically connected to the control unit 15. The CPU executes the program to cause the control unit 15 to function as a signal acquisition processing unit 151, an image acquisition processing unit 152, a setting reception unit 153, a scan condition change processing unit 154, a scan processing unit 155, a noise determination processing unit 156, a correction information acquisition processing unit 157, a noise removal processing unit 158, and the like.

The signal acquisition processing section 151 acquires an output signal from the detection section 12.

The image acquisition processing unit 152 acquires a surface image of the sample S based on the output signal of the detection unit 12 acquired by the signal acquisition processing unit 151.

The setting accepting unit 153 accepts various settings based on the user's operation of the operation unit 13. Specifically, the setting receiving unit 153 receives a setting for noise removal.

The scanning condition change processing unit 154 changes the scanning conditions in the scanning probe microscope 1 based on the settings received by the setting receiving unit 153.

The scan processing unit 155 operates the displacement unit 14 based on the scan conditions changed by the scan condition change processing unit 154 to scan in the main scanning direction and the sub-scanning direction. The scan processing unit 155 operates the displacement unit 14 based on the output signal of the detection unit 12 acquired by the signal acquisition processing unit 151, and performs scanning in the main scanning direction and the sub-scanning direction (performs feedback control).

In response to the setting accepted by the setting acceptance unit 153, the noise determination processing unit 156 determines whether or not noise is contained in the output signal based on the image acquired by the image acquisition processing unit 152 or the output signal acquired by the signal acquisition processing unit 151.

The correction information acquisition processing section 157 acquires information (correction information) for removing noise based on the determination result of the noise determination processing section 156.

The noise removal processing unit 158 removes noise from the surface image of the sample S acquired by the image acquisition processing unit 152 based on the correction information acquired by the correction information acquisition processing unit 157.

3. Control operation of the control unit

Fig. 3 is a flowchart illustrating an example of the control operation performed by the control unit 15.

In the scanning probe microscope 1, when acquiring a surface image of the sample S, the detection unit 12 first detects a feedback amount of the relative position of the probe 32 of the cantilever 3. The signal acquisition processing unit 151 acquires an output signal from the detection unit 12. Further, the image acquisition processing unit 152 starts acquiring the surface image of the sample S based on the output signal acquired by the signal acquisition processing unit 151.

At this time, floor vibration, air flow due to air conditioning, and the like may occur, and noise may be included in the output signal from the detection unit 12. In this case, the surface image of the sample S acquired by the image acquisition processing unit 152 also contains noise.

In this case, the user checks the surface image of the sample S displayed on the display unit 11 to determine whether or not noise may be included. When it is determined that there is a possibility that noise is contained in the surface image of the sample S, the user operates the operation unit 13 to input a start of the noise removal process (step S101: "yes"). Note that the noise removal processing may be automatically started without depending on an input operation (setting operation) by the user. For example, the noise removal process may be automatically started in accordance with the presence of a periodic feature in the surface image of the sample S.

Fig. 4A is a diagram showing an example of a surface image of the sample S acquired by the scanning probe microscope 1, and shows the surface image before the noise removal processing is started. In fig. 4A, an image (feature) expressed as a surface image of the sample S is represented by a, and an image (feature) expressed as noise is represented by B.

The X-axis direction in fig. 4A is the main scanning direction, and the Y-axis direction is the sub-scanning direction. In the scanning probe microscope 1, an operation of linearly (linearly) moving the surface of the sample S and the cantilever 3 relative to each other in the main scanning direction and an operation of shifting the relative position of the surface of the sample S and the cantilever 3 in the sub-scanning direction by one line are alternately performed. That is, the moving direction when the relative position of the sample S and the cantilever 3 is linearly changed (along a line) is the main scanning direction, and the direction orthogonal to the main scanning direction is the sub-scanning direction.

As shown in fig. 4A, image a is an aperiodic image (characteristic), whereas image B appears as an image (characteristic) with periodic periods. The image B is represented as a periodic characteristic because floor vibration, which becomes a cause of noise, a flow of air caused by air conditioning, or the like is periodically generated.

In the scanning probe microscope 1, when the acquisition of the surface image of the sample S is started and the image shown in fig. 4A is displayed on the display unit 11 as a result, the user determines whether or not the image A, B may contain noise. For example, when a periodic image (periodic feature) such as B is included in the surface image, it can be determined that the image is highly likely to be noise. In this case, the user performs an input operation (setting operation) for starting the noise removal process in step S101.

In this manner, the setting receiving unit 153 receives a setting performed by the user. Then, the scanning condition change processing unit 154 changes the scanning conditions in the scanning probe microscope 1 in accordance with the settings received by the setting receiving unit 153 (step S102: scanning condition changing step). After the setting accepting unit 153 accepts the setting of noise removal, the noise determination processing unit 156 determines whether or not noise is generated based on the surface image of the sample S acquired by the image acquisition processing unit 152 (step S103: noise determination step).

Specifically, the scanning condition change processing unit 154 changes the speed of displacement of the relative position of the cantilever 3 with respect to the sample S (scanning speed in the scanning probe microscope 1). Then, under the changed conditions, the signal acquisition processing unit 151 acquires the output signal from the detection unit 12 again, and the image acquisition processing unit 152 acquires the surface image of the sample S again based on the output signal.

Fig. 4B is a diagram showing an example of the surface image of the sample S acquired by the scanning probe microscope 1, and shows the surface image after the scanning speed is changed.

As shown in fig. 4B, in the surface image of the sample S acquired after the scanning speed was changed, the image a did not change, and the image B changed. In this example, the scanning condition change processing unit 154 changes the scanning conditions so that the speed of displacement of the relative position of the cantilever 3 with respect to the sample S becomes faster (so that the scanning speed becomes higher). Then, a surface image of the sample S is acquired based on the condition. Comparing fig. 4A with fig. 4B, the interval of the image B shown periodically in fig. 4B becomes large. This is because: as a result of the speeding up of the scanning speed, intervals at which noise appears in the signal acquired by the signal acquisition processing section 151 become large. On the other hand, since the image a is derived from the surface shape of the sample S, the image a does not change even if the scanning speed is changed.

The scanning condition change processing unit 154 may change the scanning conditions so that the scanning speed becomes low. In this case, the intervals of the images of the noise appearing in the surface image become small.

Then, when the scanning speed is changed by the scanning condition change processing unit 154 based on a comparison between fig. 4A and 4B, the noise determination processing unit 156 determines that the output signal from the detection unit 12 contains noise based on a change in the image B, which is a periodic feature contained in the surface image. At this time, the noise determination processing unit 156 determines that the image B included in the surface image is an image representing noise.

Further, the correction information acquisition processing unit 157 acquires correction information for removing noise based on the noise determination processing unit 156 determining that noise is generated (step S104). Specifically, the correction information acquisition processing unit 157 creates a frequency filter for removing the image B determined as noise by the noise determination processing unit 156. The scan processing unit 155 completes the scanning operation (step S105).

Then, the noise removal processing unit 158 removes the image B as noise from the surface image using the correction information (frequency filter) acquired by the correction information acquisition processing unit 157 (step S106: noise removal step).

Then, when the next sample S is present (step S107: NO), the sample S is scanned, and then the scanning is completed. The signal acquisition processing unit 151 acquires an output signal from the detection unit 12. The image acquisition processing unit 152 acquires a surface image of the sample S based on the output signal. Further, the noise removal processing portion 158 removes noise from the surface image acquired by the image acquisition processing portion 152 using the correction information (frequency filter) acquired by the correction information acquisition processing portion 157 in step 104.

When the measurement of all the samples S is completed (yes in step S107), the control operation of the control unit 15 is completed.

In step S103, the noise determination processing unit 156 may determine whether or not noise is contained in the output signal from the detection unit 12 based on a change in the output signal acquired by the signal acquisition processing unit 151. Specifically, the noise determination processing unit 156 may determine whether or not noise is contained in the output signal based on data indicating the intensity distribution of the output signal acquired by the signal acquisition processing unit 151. In this case, the signal indicating the actual sample surface and the signal generated by the noise change in different patterns in the output signal, and therefore the noise determination processing section 156 determines whether or not the output signal contains the noise.

In this case, in step S104, the correction information acquisition processing unit 157 creates a frequency filter for removing the signal determined as noise by the noise determination processing unit 156. In step S105, the noise removal processing unit 158 removes a signal as noise from the output signal using the correction information (frequency filter) acquired by the correction information acquisition processing unit 157.

4. Effect of action

(1) According to the present embodiment, the scanning probe microscope 1 includes the control unit 15. The control unit 15 includes a signal acquisition processing unit 151, an image acquisition processing unit 152, a scan condition change processing unit 154, a scan processing unit 155, and a noise determination processing unit 156. In the scanning probe microscope 1, when removing noise included in the surface image of the sample S, the scanning condition change processing unit 154 changes the scanning conditions (step S102 in fig. 2: scanning condition changing step). The noise determination processing unit 156 determines whether or not noise is contained in the output signal based on the change in the output signal or the change in the surface image of the sample S when the scanning conditions are changed by the scanning condition change processing unit 154 (step S103: noise determination step).

Therefore, when the output signal contains noise, the situation can be accurately determined.

(2) Further, according to the present embodiment, when the scanning speed is changed by the scanning condition change processing unit 154, the noise determination processing unit 156 determines that the output signal contains noise when the periodic feature contained in the output signal or the periodic feature contained in the surface image of the sample S (image B in fig. 4B) changes.

That is, when the scanning speed is changed, the noise determination processing unit 156 focuses on a change in the feature (periodic feature) indicating the actual sample surface and caused by noise in the output signal, or focuses on a change in the image (periodic feature) indicating the actual sample surface and caused by noise in the surface image of the sample S, and determines whether or not the output signal contains noise.

Therefore, it is possible to accurately determine that the output signal contains noise by a simple control process.

(3) In addition, according to the present embodiment, in the scanning probe microscope 1, the control unit 15 includes the noise removal processing unit 158. When the noise determination processing unit 156 determines that the output signal contains noise, the noise removal processing unit 158 removes the noise from the acquired surface image of the sample S.

Therefore, a surface image derived only from the surface shape of the sample S can be acquired.

As a result, the sample can be accurately observed.

5. Second embodiment

Another embodiment of the present invention will be described below with reference to fig. 4C. Note that the same reference numerals as those used above are used for the same structure as that of the first embodiment, and the description thereof is omitted.

Fig. 4C is a diagram showing an example of the surface image of the sample S acquired by the scanning probe microscope 1, and shows the surface image with the scanning range changed. The region C in fig. 4A corresponds to the surface image (whole image) of fig. 4C.

In the second embodiment, in step S102 of fig. 3 described above, the scanning condition change processing unit 154 changes the displacement region (scanning range of the scanning probe microscope 1) of the relative position of the cantilever 3 with respect to the sample S. Then, under the changed conditions, the signal acquisition processing unit 151 acquires the output signal from the detection unit 12 again, and the image acquisition processing unit 152 acquires the surface image of the sample S again based on the output signal.

When fig. 4A is compared with fig. 4C, in fig. 4C, which is the surface image of the sample S acquired after the scanning range is changed, the image B does not change, and the image a changes. In this example, the scanning condition change processing unit 154 changes the scanning conditions so that the displacement region of the relative position of the cantilever 3 with respect to the sample S becomes small (so that the scanning range becomes small). Then, a surface image of the sample S is acquired based on the condition.

Comparing fig. 4A with fig. 4C, in fig. 4C, the image a appears in an enlarged state. On the other hand, in fig. 4C, the image B does not change. This is because: even if the scanning range is reduced, the interval (number of times) at which noise appears does not change in the signal acquired by the signal acquisition processing section 151 as long as the scanning speed is fixed. The scanning condition change processing unit 154 may change the scanning conditions so that the scanning range is increased. In this case, the image of the noise shown in the surface image does not change.

Further, the noise determination processing unit 156 determines that the output signal from the detection unit 12 contains noise based on the fact that the image B, which is a periodic feature contained in the surface image, does not change when the scanning speed is changed by the scanning condition change processing unit 154, based on a comparison between fig. 4A and 4C. At this time, the noise determination processing unit 156 determines that the image B included in the surface image is an image representing noise.

Thereafter, as in the case of the first embodiment described above, the correction information is acquired by the correction information acquisition processing unit 157, and the noise is removed from the surface image by the noise removal processing unit 158.

As described above, according to the second embodiment, when the scanning range is changed by the scanning condition change processing unit 154, the noise determination processing unit 156 determines that the output signal contains noise if the periodic feature contained in the output signal or the periodic feature contained in the surface image of the sample S (image B in fig. 4C) does not change.

That is, when scanning is performed after the scanning range is changed, the noise determination processing unit 156 focuses on a change in a signal indicating an actual sample surface and no change in a signal (periodic feature) generated by noise in the output signal, or focuses on a change in an image indicating an actual sample surface and no change in an image (periodic feature) generated by noise in the surface image, and determines whether or not noise is contained in the output signal.

Therefore, it is possible to accurately determine that the output signal contains noise by a simple control process.

6. Modification example

In the above embodiment, it has been described that the scanning condition changing section 154 changes one of the scanning speed and the scanning range when the noise removal processing is to be performed (in step S102 in fig. 3). However, the scanning condition change processing unit 154 may change both the scanning speed and the scanning range. Further, the surface image may be acquired in a state where the scanning condition change processing unit 154 changes one of the scanning speed and the scanning range, and then the surface image may be acquired in a state where the scanning condition change processing unit 154 changes the other of the scanning speed and the scanning range.

In the above embodiment, the structure in which the sample S and the cantilever 3 are relatively moved on the horizontal plane has been described. However, the scanning probe microscope 1 may be configured to move the sample S and the cantilever 3 relative to each other in a vertical plane (a configuration in which scanning measurement is performed in the height direction). In this case, the height direction (Z-axis direction) may be the main scanning direction, and the above-described X-axis direction may be the sub-scanning direction.

Description of the reference numerals

1: a scanning probe microscope; 3: a cantilever; 15: a control unit; 32: a probe; 151: a signal acquisition processing unit; 152: an image acquisition processing unit; 154: a scanning condition change processing unit; 155: a scanning processing unit; 156: a noise determination processing unit; 158: and a noise removal processing unit.