Atomic force microscope, atomic force microscopy, and controlling method of an atomic force microscopy

An atomic force microscope includes a raster scan control mechanism configured to perform a raster scan between a cantilever having a probe at a free end and a sample relative to each other across an XY plane in a fluid, an interaction control mechanism configured to vibrate the cantilever and to control an interaction generated between the probe and the sample, and a sample information acquisition circuit configured to acquire sample information including inclination information of a sample surface with respect to the XY plane based on a control result of the interaction control mechanism. The interaction control mechanism is configured to control the interaction generated between the probe and the sample in accordance with inclination of the sample surface with respect to the XY plane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning probe microscope, particularly, an atomic force microscope used under an in-solution environment, an atomic force microscopy, and a controlling method of the atomic force microscopy.

2. Description of the Related Art

A scanning probe microscope (SPM) is a scanning microscope configured to obtain information on a sample surface while mechanically scanning a mechanical probe, and includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), a scanning magnetic force microscope (MFM), a scanning capacitance microscope (SCaM), a scanning near-field light microscope (SNOM), etc.

The scanning probe microscope performs a raster scan between the mechanical probe and the sample relative to each other in the X and Y directions to acquire desired surface information of the sample through the mechanical probe, so as to mapping-display the surface information on a display. In particular, the atomic force microscope uses a cantilever having a mechanical probe at its free end to generate a dynamic interaction between the mechanical probe and the sample, and acquires sample information based on the deformation of the cantilever caused by the dynamic interaction. For example, Japanese Patent No. 4083517 discloses one of such atomic force microscopes. Atomic force microscopes can be used also in various environments such as ultra-high vacuum and solutions as well as in the atmosphere, and are the most widely used devices.

BRIEF SUMMARY OF THE INVENTION

An atomic force microscope according to the present invention includes a raster scan control mechanism configured to perform a raster scan between a cantilever having a probe at a free end and a sample relative to each other across an XY plane in a fluid, an interaction control mechanism configured to vibrate the cantilever and to control an interaction generated between the probe and the sample, and a sample information acquisition circuit configured to acquire sample information including inclination information of a sample surface with respect to the XY plane based on a control result of the interaction control mechanism. The interaction control mechanism is configured to control the interaction generated between the probe and the sample in accordance with inclination of the sample surface with respect to the XY plane.

An atomic force microscopy according to the present invention includes: a sample table configured to place on a sample; a cantilever configured to relatively move on the sample table; and one or more circuits configured to: scan on an XY plane of the sample by vibrating the cantilever; detect an first interaction between the cantilever and the sample; calculate inclination on a surface of the sample based on the first interaction; and control the cantilever or the sample table based on the inclination.

A controlling method of an atomic force microscopy according to the present invention includes: scanning on an XY plane of a sample by vibrating a cantilever; detecting an first interaction between the cantilever and the sample; calculating inclination relative to the XY plane on a surface of the sample based on the first interaction; and controlling the cantilever or a sample table based on the inclination, the sample table is configured to place on the sample.

Advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

FIG. 1shows a configuration of an atomic force microscope according to the first embodiment.

As shown inFIG. 1, in the atomic force microscope of the present embodiment, a cantilever102having a probe101at the free end is arranged so as to directly face a sample104. The cantilever102is held on the substrate103. In the present embodiment, at least the sample104, the probe101, and the cantilever102are immersed in a fluid (not shown) such as a solution.

A vibration element106is provided on the substrate103. The vibration element106vibrates the cantilever102through the substrate103. The vibration element106is supplied with a vibration signal generated by the vibration signal generation circuit107through an inclination correction circuit111, which will be described later, and thereby vibrates the cantilever102in a predetermined vibration state, namely, with a predetermined amplitude, a predetermined frequency, and a predetermined phase. The frequency for vibrating the cantilever102is set near the primary resonance frequency of the cantilever102in the solution. The vibration element106is constituted from a piezoelectric body, for example.

An interaction detection sensor108configured to is disposed above the cantilever102. The interaction detection sensor108detects the vibration state of the cantilever102to output the vibration state as interaction information including information on the interaction between the probe101and the sample104. The interaction information output from the interaction detection sensor108is supplied to the Z control circuit110through the inclination correction circuit111, which will be described later.

The interaction information includes vibration amplitude information, vibration frequency information, or phase information of the cantilever102.

The sample104is held by the Z scanner112through a sample table (not shown).

The Z scanner112scans the sample104with respect to the cantilever102along a Z axis perpendicular to an XY plane. That is, the Z scanner112performs a scan between the cantilever102and the sample104relative to each other along the Z axis perpendicular to the XY plane.

The Z scanner112is mounted on the Y scanner113band the X scanner113a. Specifically, the X scanner113ais mounted on the Y scanner113b, and the Z scanner112is mounted on the X scanner113a.

The X scanner113ascans the sample104with respect to the cantilever102along an X axis. That is, the X scanner113aperforms a scan between the cantilever102and the sample104relative to each other along the X axis.

The Y scanner113bscans the sample104with respect to the cantilever102along a Y axis. That is, the Y scanner113bperforms a scan between the cantilever102and the sample104relative to each other along the Y axis.

The X scanner113aand the Y scanner113bare controlled by an XY control circuit113c. Specifically, the X scanner113aand the Y scanner113bare respectively controlled by an X scanning signal and a Y scanning signal generated by the XY control circuit113c.

The X scanner113a, the Y scanner113b, and the XY control circuit113cconstitute a raster scan control mechanism113. The raster scan control mechanism113can perform a raster scan between the cantilever102and the sample104relative to each other across the XY plane.

Here, a raster scan will be described with reference toFIGS. 2 and 3.

FIG. 2shows the movement of the raster scan between the probe101provided on the cantilever102and the sample104relative to each other across the XY plane. This raster scan is generally used in atomic force microscopes, and a scanning line direction (a direction in which the scanning speed is high) of the raster scan is generally set in an X direction.

FIG. 3shows waveforms of the Y scanning signal and the X scanning signal for performing the raster scan shown inFIG. 2, and respective synchronization signals for the Y scanning signal and the X scanning signal. These synchronization signals are output from the XY control circuit113cand supplied to a sample information acquisition circuit114, which will be described later.

InFIG. 1again, the interaction reference information setting circuit109sets interaction reference information indicating the desired magnitude of the interaction between the probe101and the sample104. The set interaction reference information is supplied to the Z control circuit110through the inclination correction circuit111, which will be described later.

The Z scanner112is controlled by the Z control circuit110. Specifically, the Z control circuit110receives interaction information including information regarding the vibration state of the cantilever102, namely, the interaction between the probe101and the sample104, and interaction reference information indicating a desired magnitude of interaction between the probe101and the sample104to generate deviation information between the interaction information and the interaction reference information. The Z control circuit110generates a Z control signal for keeping a vibration state of the cantilever102, for example, the magnitude of the vibration amplitude, constant based on the deviation information, to cause the Z scanner112to expand and contract along the Z direction based on the Z control signal, so as to scan the sample104along the Z direction with respect to the cantilever102. That is, the relative distance along the Z direction between the cantilever102and the sample104is controlled by the Z control circuit110. The Z control signal generated by the Z control circuit110is also supplied to the sample information acquisition circuit114.

The vibration element106, the vibration signal generation circuit107, the interaction detection sensor108, the interaction reference information setting circuit109, the Z control circuit110, the inclination correction circuit111(described later), and the Z scanner112constitute an interaction control mechanism105. The interaction control mechanism105can vibrate the cantilever102and control the interaction generated between the probe101provided at the free end of the cantilever102and the sample104.

The sample information acquisition circuit114acquires sample information based on the Z control signal and synchronization signals for the raster scan output from the XY control circuit113c. This sample information includes inclination information of a sample surface104awith respect to the XY plane. This sample information is, for example, information reflecting the uneven shape of the sample surface104a.

The sample information acquired by the sample information acquisition circuit114is supplied to the sample information display115. The sample information display115displays the acquired sample information.

Further, the sample information acquisition circuit114extracts inclination information of the sample surface104awith respect to the XY plane from the acquired sample information by image processing such as filtering, and then supplies the inclination information to an inclination correction circuit111included in the interaction control mechanism105.

As described above, the atomic force microscope of the present embodiment used in the fluid such as a solution includes: the interaction control mechanism105, which is constituted by the vibration element106, the vibration signal generation circuit107, the interaction detection sensor108, the interaction reference information setting circuit109, the Z control circuit110, the inclination correction circuit111(described later), and the Z scanner112, configured to vibrate the cantilever102and to control the interaction generated between the probe101provided at the free end of the cantilever102and the sample104; the raster scan control mechanism113, which is constituted by the X scanner113a, the Y scanner113b, and the XY control circuit113c, configured to perform the raster scan between the cantilever102and the sample104relative to each other across the XY plane; the sample information acquisition circuit114configured to acquire the sample information including the inclination information of the sample surface with respect to the XY plane based on the Z control signal as the control result of the interaction control mechanism105; and the sample information display115configured to display the sample information.

The atomic force microscope of the present embodiment is characterized by the interaction control mechanism105. For this purpose, the interaction control mechanism105includes the inclination correction circuit111.

Before describing the inclination correction circuit111, the conventional problem will be described in detail with reference toFIGS. 4 to 10.

FIGS. 4 and 5show the relationship between the vibration state of the cantilever102, for example, the magnitude of the vibration amplitude, and the interaction between the probe101and the sample104.

FIG. 4shows a case where the probe101and the sample104are spaced, namely, where the interaction between the probe101and the sample104is zero. In this case, the magnitude of the vibration amplitude of the cantilever102is A0.

FIG. 5shows a case where the interaction between the probe101and the sample104is larger than zero. In this case, the magnitude of the vibration amplitude of the cantilever102is A′0.

The relationship between A0 and A′0 is A0>A′0. As the interaction between the probe101and the sample104increases, A′0 decreases.

FIGS. 6 and 7show a positional relationship between the cantilever102and a sample104whose surface partially is partially inclined with respect to the XY plane. Such sample104whose surface is partially inclined with respect to the XY plane is formed by a combination of a sample substrate131(not shown inFIG. 1) arranged parallel to the XY plane and a cell sample132cultured thereon as shown inFIG. 8, for example.

In the sample104whose surface is partially inclined with respect to the XY plane, the range from a point A to a point B located on the inclined portion is set as a range RX for the raster scan along the X axis. In other words, the range from the point A to the point B is set as a range for acquiring the sample information along the X axis. In addition, the edge of the inclined portion on the +X side along the X axis is set as a point C. Furthermore, in the sample104, assume that a sample surface104afrom the point C in the +X direction is generally parallel to the XY plane.

In this case, when the probe101is located at the point A of the sample104, the distance between the cantilever102and the sample surface104ais DH. When the probe101is located at the point B of the sample104, the distance between the cantilever102and the sample surface104ais DL. DH and DL have a relationship of DH>DL.

Incidentally, if the cantilever102is vibrated in the solution, an interaction in accordance with the viscosity of the solution acts between the cantilever102and the solution. The interaction between the cantilever102and the solution varies depending on the distance between the cantilever102and the sample surface104a.

Specifically, if the distance between the cantilever102and the sample surface104adecreases, the interaction acting between the cantilever102and the solution increases, so that the vibration state of the cantilever102changes; for example, the magnitude of the vibration amplitude decreases. On the contrary, if the distance between the cantilever102and the sample surface104aincreases, the interaction acting between the cantilever102and the solution decreases, so that the vibration state of the cantilever102changes; for example, the magnitude of the vibration amplitude increases.

Accordingly, at the point A of the sample104, the interaction acting between the cantilever102and the solution decreases, so that the magnitude of the vibration amplitude increases. At the point B of the sample104, the interaction acting between the cantilever102and the solution increases, so that the magnitude of the vibration amplitude decreases.

The interaction acting between the cantilever102and the solution varies depending on the area of the cantilever102in addition to the distance between the cantilever102and the sample surface104a. That is, the interaction between the cantilever102and the solution varies depending on the volume of the solution that exists between the cantilever102and the portion104bof the sample surface104athat faces the cantilever102. Therefore, the interaction between the cantilever102and the solution is obtained as an integral value of the interaction acting on each part of the cantilever102.

As described above, change in the vibration state of the cantilever102, for example, change in the change in the magnitude of the vibration amplitude, has two factors: the interaction between the probe101and the sample104and the interaction between the cantilever102and the solution. The interaction information includes not only information related to the interaction between the probe101and the sample104but also information related to the interaction between the cantilever102and the solution.

Specifically, the vibration state (interaction information), for example, a vibration amplitude, of the cantilever102when the probe101and the sample104are not in contact with each other is set to A0, and the desired vibration state (interaction reference information), for example, a vibration amplitude, of the cantilever102indicating the magnitude of the interaction between the probe101and the sample104is set to A1. In this case, the deviation information between the interaction information and the interaction reference information, namely, (A0−A1), indicates the interaction between the probe101and the sample104. In the atomic force microscopes, while this (A0−A1), namely, the interaction between the probe101and the sample104, is controlled to be constant, sample information is acquired.

However, the deviation information (A0−A1) includes not only information on the interaction between the probe101and the sample104but also information on the interaction between the cantilever102and the solution, which causes a problem that the interaction between the probe101and the sample104cannot be actually maintained constant.

FIG. 9is a bar graph showing the proportions of information DI1 on the interaction between the probe101and the sample104and information DI2 on the interaction between the cantilever102and the solution at the point A and the point B of the sample104, which are included in the deviation information (DI=A0−A1). InFIG. 9, white parts of bars represent the information DI1 on the interaction between the probe101and the sample104, and shaded parts of the bars represent the information DI2 on the interaction between the cantilever102and the solution.

At the point A, since the distance between the cantilever102and the sample surface104ais large, the proportion of the information DI2 on the interaction between the cantilever102and the solution is small. On the other hand, at the point B, since the distance between the cantilever102and the sample surface104ais small, the proportion of the information DI2 on the interaction between the cantilever102and the solution is large.

The atomic force microscope controls the magnitude of the signal of the deviation information (DI=A0−A1) to be constant. Accordingly, at the point A, the sample information is acquired with the interaction between the probe101and the sample104being large. On the other hand, at the point B, sample information is acquired with the interaction between the probe101and the sample104being small. This decreases the accuracy of acquiring the sample information.

Specifically, since the interaction between the probe101and the sample104is smaller at the point B than at the point A, the sample information at the point B displayed on the sample information display115is blurred (out of focus) compared with the sample information at the point A.

In order to solve the above problem, the atomic force microscope of the present embodiment includes the interaction control mechanism105. In other words, the interaction control mechanism105has a function to solve the above problem. Furthermore, the interaction control mechanism105includes the inclination correction circuit111, which solves the above problem.

The function of the interaction control mechanism105will be described below.

In order to solve the above problem, the magnitudes of the components of the information DI1 on the interaction between the probe101and the sample104at the point A and the point B should be matched. Thereby, the sample information can be acquired with the interaction between the probe101and the sample104being constant at both of the point A and the point B. For this purpose, as shown inFIG. 10, the signal of the deviation information (DI=A0−A1) at the point B should be increased until the magnitude of the component of the information DI1 on the interaction between the probe101and the sample104at the point B matches the magnitude of the component of the information DI1 on the interaction between the probe101and the sample104at the point A. In other words, the interaction control mechanism105solves the above problem by increasing the signal of the deviation information (DI=A0−A1) at the point B.

That is, the interaction control mechanism105can control the interaction between the probe101and the sample104with high accuracy by changing the magnitude of the signal of the deviation information (A0−A1) in accordance with the inclination of the sample surface104awith respect to the XY plane, specifically, based on correction information for correcting the change in the influence of the interaction between the cantilever102and the solution due to the inclination of the sample surface104awith respect to the XY plane.

Here, the correction information includes inclination-related information related to the inclination of the sample surface104awith respect to the XY plane, and information for performing an adjustment of the inclination-related information. The inclination-related information is, for example, inclination correction information (described later) generated based on inclination information of the sample surface104awith respect to the XY plane. The information for performing the adjustment includes, for example, information for performing magnitude adjustment and offset addition. These will be described later.

Specifically, since the deviation information (A0−A1) is the deviation information between the interaction information (A0) and the interaction reference information (A1), in order to increase the signal of the deviation information (A0−A1), the signal of the interaction information (A0) should be increased, the signal of the interaction reference information (A1) should be decreased, or the signal of the interaction information (A0) should be increased and the signal of the interaction reference information (A1) should be decreased. Further, the vibration signal may be increased in order to increase the signal of the interaction information (A0). In order to decrease the signal of the deviation information (A0−A1), the signal of the interaction information (A0) should be decreased, the signal of the interaction reference information (A1) should be increased, or the signal of the interaction information (A0) should be decreased and the signal of the interaction reference information (A1) should be increased. Furthermore, the vibration signal may be decreased in order to decrease the signal of the interaction information (A0).

Therefore, the interaction control mechanism105can control the interaction between the probe101and the sample104with high accuracy by changing the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information, in accordance with the inclination of the sample surface104awith respect to the XY plane, specifically, based on the correction information for correcting the change in the influence of the interaction between the cantilever102and the solution due to the inclination of the sample surface104awith respect to the XY plane.

The interaction control mechanism105includes the inclination correction circuit111configured to change the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information, in order to control the interaction between the probe101and the sample104in accordance with the inclination of the sample surface104awith respect to the XY plane.

FIG. 11shows a configuration example of the inclination correction circuit111configured to change the magnitude of the signal of the interaction reference information. The inclination correction circuit111includes an inclination correction information generation circuit111bconfigured to generate inclination correction information based on the inclination information of the sample surface104awith respect to the XY plane output from the sample information acquisition circuit114, and an adjustment circuit111aconfigured to change the magnitude of the signal of the interaction reference information by operating the interaction reference information with the inclination correction information.

The inclination correction information generation circuit111bgenerates inclination correction information based on the inclination information of the sample surface104awith respect to the XY plane output from the sample information acquisition circuit114, and then supplies the inclination correction information to the adjustment circuit111a. This inclination correction information includes X inclination correction information related to the inclination of the sample surface104aalong the X axis and Y inclination correction information related to the inclination of the sample surface104aalong the Y axis. The X inclination correction information and the Y inclination correction information are supplied to the variable gain amplifier111dand the variable gain amplifier111eprovided in the adjustment circuit111a, respectively.

Here, the X inclination correction information and the Y inclination correction information will be described with reference toFIGS. 12-14.

FIG. 12shows a sample surface104ain an area for the raster scan, in other words, an area for acquiring the sample information. An arrow of the raster scan shown inFIG. 12represents the movement of the raster scan between the probe101provided on the cantilever102and the sample104relative to each other shown inFIG. 2. Although the raster scan by the raster scan control mechanism113is performed across the XY plane, since the probe101and the sample104are scanned relative to each other along the Z axis, the raster scan with respect to the sample104is performed across the sample surface104aas a result.

As shown inFIG. 13, the sample surface104ashown inFIG. 12has a plus-downward inclination of θX degrees with respect to the X axis and θY degrees with respect to the Y axis. Here, the plus-downward inclination means an inclination such that the Z value decreases as the X value increases and the Z value decreases as the Y value increases.

In this case, as shown inFIG. 14, the X inclination correction information is information indicating the movement in the XZ plane of the scanning line with respect to the sample surface104ashown inFIG. 12, which is synchronized with the X scanning signal (namely the X scan), and the Y inclination correction information is information indicating the movement in the YZ plane of the scanning line with respect to the sample surface104ashown inFIG. 12, which is synchronized with the Y scanning signal (namely the Y scan).

Referring again toFIG. 11, the X inclination correction information and the Y inclination correction information are respectively input to the variable gain amplifier111dand the variable gain amplifier111eincluded in the adjustment circuit111a, respectively, and the magnitudes of the signal of the X inclination correction information and the signal of the Y inclination correction information are adjusted in the variable gain amplifier111dand the variable gain amplifier111e.

The influence of the interaction between the cantilever102and the solution varies depending on the shape of the sample104other than the region where the sample information is acquired, the viscosity of the solution, the shape of the cantilever102, the length of the probe101, etc. The variable gain amplifier111dand the variable gain amplifier111eare provided for coping with this variation, and enable an operator to optimally adjust the magnitudes of the signal of the X inclination correction information and the signal of the Y inclination correction information while checking the sample information displayed on the sample information display115. The operation to optimally adjust may be automatically performed by an information recognition program such as AI (Artificial Intelligence) or deep learning based on the sample information acquired by the sample information acquisition circuit114.

In other words, the magnitudes of the signal of the X inclination correction information and the signal of the Y inclination correction information are adjusted based on information input to the inclination correction circuit111by an operator or an information recognition program.

Both the signal of the X inclination correction information and the signal of the Y inclination correction information having adjusted magnitudes are input to the addition circuit111c. The addition circuit111cadds the signal of the X inclination correction information and the signal of the Y inclination correction information having adjusted magnitudes to the signal of the interaction reference information. In this manner, the adjustment circuit111aadds the signal of the interaction reference information to the signal of the inclination correction information composed of the signal of the X inclination correction information and the signal of the Y inclination correction information having adjusted magnitudes, thereby changing the magnitude of the signal of the interaction reference information.

Specifically, the signal of the deviation information (A0−A1) needs to be larger on the lower side of the inclination than on the upper side of the inclination. For this purpose, the adjustment circuit111amakes the signal of the interaction reference information (A1) on the lower side of the inclination smaller than the signal of the interaction reference information (A1) on the upper side of the inclination. Since the magnitude of the signal of the inclination correction information is smaller on the lower side of the inclination than on the upper side of the inclination, the signal of the interaction reference information (A1) on the lower side of the inclination can be made smaller than the signal of the interaction reference information (A1) on the upper side of the inclination by adding the signal of the inclination correction information to the signal of the interaction reference information (A1).

The adjustment circuit111aprovided in the inclination correction circuit111shown inFIG. 11performs the addition operation using the addition circuit111cas an example in order to change the magnitude of the signal of the interaction reference information. The operation manner is not limited to the addition operation as long as the magnitude of the signal of the interaction reference information can be changed in accordance with the inclination of the sample surface104awith respect to the XY plane.

The inclination correction circuit111shown inFIG. 11is configured to change the magnitude of the signal of the interaction reference information as an example, but the configuration is not limited thereto. The inclination correction circuit111only needs to be configured to change the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information. Regarding the vibration signal, the signal of the interaction information, and the signal of the interaction reference information, a direction of change in the vibration signal and the signal of the interaction information is opposite to a direction of change in the signal of the interaction reference information.

FIG. 15shows a configuration example of the inclination correction circuit111configured to change the magnitude of the signal of the interaction information. The inclination correction circuit111shown inFIG. 15includes an adjustment circuit111fconfigured to change the magnitude of the signal of the interaction information by operating the interaction information with the inclination correction information. The adjustment circuit111fhas a configuration including a subtraction circuit111gin place of the addition circuit111c, in comparison with the adjustment circuit111ashown inFIG. 11. The subtraction circuit111gsubtracts the signal of the X inclination correction information and the signal of the Y inclination correction information having adjusted magnitudes from the signal of the interaction information. The adjustment circuit111fchanges the magnitude of the signal of the interaction information by such subtraction operation of the subtraction circuit111g.

Specifically, the signal of the deviation information (A0−A1) needs to be larger on the lower side of the inclination than on the upper side of the inclination. For this purpose, the adjustment circuit111fmakes the signal of the interaction information (A0) on the lower side of the inclination larger than the signal of the interaction information (A0) on the upper side of the inclination. Since the magnitude of the signal of the inclination correction information is smaller on the lower side of the inclination than on the upper side of the inclination, the signal of the interaction information (A0) on the lower side of the inclination can be made larger than the signal of the interaction information (A0) on the upper side of the inclination by subtracting the signal of the inclination correction information having an adjusted magnitude from the signal of the interaction information (A0). The adjustment circuit111fprovided in the inclination correction circuit111shown inFIG. 15performs the subtraction operation using the subtraction circuit111gas an example in order to change the magnitude of the signal of the interaction information. The operation manner is not limited to the subtraction operation as long as the magnitude of the signal of the interaction information can be changed in accordance with the inclination of the sample surface104awith respect to the XY plane.

FIG. 16shows a configuration example of the inclination correction circuit111configured to change the magnitude of the vibration signal. Since the vibration signal is an AC signal, changing the magnitude of the vibration signal means changing the magnitude of the amplitude of the vibration signal. The inclination correction circuit111shown inFIG. 16includes an adjustment circuit111aconfigured to change the magnitude of the vibration signal by operating the vibration signal with the inclination correction information. The adjustment circuit111hincludes a division circuit111i. First, the division circuit111inormalizes the signal of the X inclination correction information and the signal of the Y inclination correction information having adjusted magnitudes as shown inFIG. 17by processing such as offset addition. Next, the division circuit111idivides the vibration signal by the normalized signal of the X inclination correction information and the normalized signal of the Y inclination correction information. The adjustment circuit111hchanges the magnitude of the vibration signal by such operation of the division circuit111i.

Specifically, the signal of the deviation information (A0−A1) needs to be larger on the lower side of the inclination than on the upper side of the inclination. For this purpose, the adjustment circuit111hincreases the vibration signal in order to cause the signal of the interaction information (A0) on the lower side of the inclination to be larger than the signal of the interaction information (A0) on the upper side of the inclination. Since the magnitude of the normalized signal of the inclination correction information is smaller on the lower side of the inclination than on the upper side of the inclination, the vibration signal on the lower side of the inclination can be made larger than the vibration signal on the upper side of the inclination by dividing the vibration signal by the normalized signal of the inclination correction information.

The adjustment circuit111hprovided in the inclination correction circuit111shown inFIG. 16performs the division operation using a division circuit111ias an example in order to change the magnitude of the vibration signal, namely, the magnitude of the amplitude of the vibration signal. The operation manner is not limited to the division operation as long as the magnitude of the vibration signal can be changed accordance with the inclination of the sample surface104awith respect to the XY plane.

As described above, the atomic force microscope in accordance with the present embodiment includes the interaction control mechanism, so that the interaction generated between the probe and the sample can be controlled with good accuracy in accordance with the inclination of the sample surface with respect to the XY plane. Thereby, even if the sample surface is inclined with respect to the XY plane, highly accurate sample information can be acquired.

Furthermore, in the atomic force microscope of the present embodiment, since the interaction control mechanism105includes the inclination correction circuit111, the interaction between the probe and the sample can be accurately controlled by changing the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information based on the inclination information of the sample surface104awith respect to the XY plane output from the sample information acquisition circuit114. Thereby, even if the sample surface104ais inclined with respect to the XY plane, highly accurate sample information can be acquired.

Furthermore, in the present embodiment, a similar effect can be obtained even if the inclined portion of the sample surface104awith respect to the XY plane has a stepped shape (steps shape) as shown inFIG. 18. In this case, the X inclination correction information and the Y inclination correction information have a stepped shape (steps shape) similar to the stepped shape (steps shape) of the sample surface104a. If the step of the stepped shape (steps shape) of the sample surface104ais sufficiently small with respect to the length of the probe101, the X inclination correction information and the Y inclination correction information may be approximated as an inclined surface of the sample surface104awith respect to the XY plane.

Further, even if the inclined portion of the sample surface104awith respect to the XY plane is a curved surface, since a part of the curved surface can be locally approximated as an inclined surface, a similar effect can be obtained.

Second Embodiment

A second embodiment will be described below with reference toFIGS. 19 to 22.

FIG. 19shows a configuration of an atomic force microscope according to the second embodiment. The atomic force microscope of the present embodiment is different from the first embodiment in the interaction control mechanism. Specifically, the inclination correction circuit is different. InFIG. 19, members having the same reference numerals as those of the atomic force microscope shown inFIG. 1of the first embodiment are similar members, and detailed description thereof is omitted here. The following descriptions will be provided with an emphasis on the difference. Namely, the parts not described below are the same as those in the first embodiment.

As shown inFIG. 19, an interaction control mechanism120includes an inclination correction circuit121. The inclination correction circuit121receives an X scanning signal and a Y scanning signal generated by the XY control circuit113c, in place of the inclination information of the sample surface104awith respect to the XY plane output from the sample information acquisition circuit114.

That is, the interaction control mechanism105can control the interaction between the probe101and the sample104with high accuracy by changing the magnitude of the signal of the deviation information (A0−A1) in accordance with the inclination of the sample surface104awith respect to the XY plane, specifically, based on the correction information for correcting the change in the influence of the interaction between the cantilever102and the solution due to the inclination of the sample surface104awith respect to the XY plane.

Here, the correction information includes the X scanning signal, the Y scanning signal, and information for adjusting the X scanning signal and the Y scanning signal. Adjustments performed on the X scanning signal and the Y scanning signal include magnitude adjustment, offset addition, and signal inversion.

The interaction control mechanism105includes an inclination correction circuit121configured to change the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information, in order to control the interaction between the probe101and the sample104in accordance with the inclination of the sample surface104awith respect to the XY plane.

FIG. 20shows a configuration example of the inclination correction circuit121configured to change the magnitude of the signal of the interaction reference information. As shown inFIG. 20, the inclination correction circuit121includes an adjustment circuit121aconfigured to change the magnitude of the signal of the interaction reference information by operating the signal of the interaction reference information with an X scanning signal and a Y scanning signal.

The X scanning signal and the Y scanning signal are input to the variable gain amplifier121dand the variable gain amplifier121eprovided in the adjustment circuit121a, respectively. The variable gain amplifier121dand the variable gain amplifier121eare not only capable of adjusting the magnitudes of the X scanning signal and the Y scanning signal, but also capable of performing offset addition and signal inversion of the X scanning signal and the Y scanning signal.

The influence of the interaction between the cantilever102and the solution varies depending on the shape of the sample104other than the region where the sample information is acquired, the viscosity of the solution, the shape of the cantilever102, the length of the probe101, etc. The variable gain amplifier121dand the variable gain amplifier121eare provided for coping with this variation, and enable an operator to optimally perform the magnitude adjustment, the offset addition, and the signal inversion of the X scanning signal and the Y scanning signal, while checking the sample information displayed on the sample information display115. The operation to optimally perform the magnitude adjustment, the offset addition, and the signal inversion may be automatically performed by an information recognition program such as AI (Artificial Intelligence) or deep learning based on the sample information acquired by the sample information acquisition circuit114.

In other words, the magnitude adjustment, the offset addition, and the signal inversion of the X scanning signal and the Y scanning signal are performed based on information input to the inclination correction circuit111by an operator or an information recognition program. Here, “the magnitude adjustment, the offset addition, and the signal inversion . . . are performed” means, of course, that those operations are performed as necessary, and includes cases where those operations, for example signal inversion, are not performed.

Both the X scanning signal and the Y scanning signal that have undergone the magnitude adjustment, the offset addition, and the signal inversion are input to the addition circuit121c. The addition circuit121cadds the X scanning signal and the Y scanning signal, which have undergone the magnitude adjustment, the offset addition, and the signal inversion, to the signal of the interaction reference information. In this way, the adjustment circuit121achanges the magnitude of the signal of the interaction reference information by adding the signal of the interaction reference information with the X scanning signal and the Y scanning signal, which have undergone the magnitude adjustment, the offset addition, and the signal inversion.

Specifically, the signal of the deviation information (A0−A1) needs to be larger on the lower side of the inclination than on the upper side of the inclination. For this purpose, the adjustment circuit121amakes the signal of the interaction reference information (A1) on the lower side of the inclination smaller than the signal of the interaction reference information (A1) on the upper side of the inclination.

For example, assume that the sample surface104ais inclined plus-downward with respect to the X axis and the Y axis as shown inFIGS. 12 and 13. In this case, in the first embodiment, the X inclination correction information and the Y inclination correction information are as shown inFIG. 14, but in the atomic force microscope of the present embodiment, the X scanning signal and the Y scanning signal are used in place of the X inclination correction information and the Y inclination correction information used in the first embodiment. This is because the X scanning signal and the Y scanning signal shown inFIG. 3respectively have similar waveforms to the X inclination correction information and the Y inclination correction information shown inFIG. 14, and the X scanning signal and the Y scanning signal can respectively replace the X inclination correction information and the Y inclination correction information used in the first embodiment if the magnitude adjustment, the offset addition, and the signal inversion are performed on the X scanning signal and the Y scanning signal shown inFIG. 3.

In other words, the X scanning signal and the Y scanning signal can be regarded as inclination-related information that is related to the inclination of the sample surface104awith respect to the XY plane.

In this manner, the adjustment circuit121aperforms the magnitude adjustment, the offset addition, and the signal inversion to the X scanning signal and the Y scanning signal shown inFIG. 3, so as to transform the X scanning signal and the Y scanning signal into the waveforms shown inFIG. 14. Then, the adjustment circuit121aadds the X scanning signal and the Y scanning signal, which have undergone the magnitude adjustment, the offset addition, and the signal inversion, to the signal of the interaction reference information (A1), thereby making the signal of the interaction reference information (A1) on the lower side of the inclination smaller than the signal of the interaction reference information (A1) on the upper side of the inclination.

The adjustment circuit121aprovided in the inclination correction circuit121shown inFIG. 20performs the addition operation using the addition circuit121cas an example in order to change the magnitude of the signal of the interaction reference information. The adjustment circuit121amay perform various operations, not limited to the addition operation, as long as the magnitude of the signal of the interaction reference information can be changed according with the inclination of the sample surface104awith respect to the XY plane. The adjustment circuit121acan perform the magnitude adjustment, the offset addition, and the signal inversion to the X scanning signal and the Y scanning signal shown inFIG. 3. Various operations, not limited to the addition operation, can be performed by combination with such signal processing.

The inclination correction circuit121shown inFIG. 20is configured to change the magnitude of the signal of the interaction reference information as an example, but the configuration is not limited thereto. The inclination correction circuit121only needs to be configured to change the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information. Regarding the vibration signal, the signal of the interaction information, and the signal of the interaction reference information, a direction of change in the vibration signal and the signal of the interaction information is opposite to a direction of change in the signal of the interaction reference information.

FIG. 21shows a configuration example of the inclination correction circuit121configured to change the magnitude of the signal of the interaction information. The inclination correction circuit121shown inFIG. 21includes an adjustment circuit121fconfigured to change the magnitude of the signal of the interaction information by operating the signal of the interaction information with the X scanning signal and the Y scanning signal. The adjustment circuit121fincludes an addition circuit121g. The addition circuit121gadds the signal of the interaction information to the X scanning signal and the Y scanning signal that have undergone the magnitude adjustment and the offset addition. The adjustment circuit121fchanges the magnitude of the signal of the interaction information by such an addition operation of the addition circuit121g.

Specifically, the signal of the deviation information (A0−A1) needs to be larger on the lower side of the inclination than on the upper side of the inclination. For this purpose, the adjustment circuit121fmakes the signal of the interaction information (A0) on the lower side of the inclination larger than the signal of the interaction information (A0) on the upper side of the inclination.

The adjustment circuit121fperforms the magnitude adjustment and the offset addition to the X scanning signal and the Y scanning signal shown inFIG. 3, but does not perform signal inversion. Then, the adjustment circuit121fadds the X scanning signal and the Y scanning signal that have undergone the magnitude adjustment and the offset addition to the signal of the interaction information (A0), thereby making the signal of the interaction reference information (A1) on the lower side of the inclination larger than the signal of the interaction reference information (A1) on the upper side of the inclination.

The adjustment circuit121fprovided in the inclination correction circuit121shown inFIG. 21performs the addition operation using the addition circuit121gas an example in order to change the magnitude of the signal of the interaction information. The adjustment circuit121fmay perform various operations, not limited to the addition operation, as long as the magnitude of the signal of the interaction information can be changed according with the inclination of the sample surface104awith respect to the XY plane. The adjustment circuit121fis capable of performing the magnitude adjustment, the offset addition, and the signal inversion to the X scanning signal and the Y scanning signal shown inFIG. 3. Various operations, not limited to the addition operation, can be performed by a combination with the signal processing.

FIG. 22shows a configuration example of the inclination correction circuit121configured to change the magnitude of the vibration signal. Since the vibration signal is an AC signal, changing the magnitude of the vibration signal means changing the magnitude of the amplitude of the vibration signal. The inclination correction circuit121shown inFIG. 22includes an adjustment circuit121hconfigured to change the magnitude of the vibration signal by operating the vibration signal with the X scanning signal and the Y scanning signal. The adjustment circuit121hincludes a multiplication circuit121i. First, the multiplication circuit121inormalizes the X scanning signal and the Y scanning signal that have adjusted magnitudes as shown inFIG. 23by processing such as offset addition. Next, the multiplication circuit121imultiplies the vibration signal by the normalized X scanning signal and the Y scanning signal. The adjustment circuit121hchanges the magnitude of the vibration signal by such operation of the multiplication circuit121i.

Specifically, the signal of the deviation information (A0−A1) needs to be larger on the lower side of the inclination than on the upper side of the inclination. For this purpose, the adjustment circuit121hincreases the vibration signal by multiplying the vibration signal by the X scanning signal and the Y scanning signal that have undergone the magnitude adjustment and the offset addition, so as to make the signal of the interaction information (A0) on the lower side of the inclination larger than the signal of the interaction information (A0) on the upper side of the inclination.

The adjustment circuit121hprovided in the inclination correction circuit121shown inFIG. 22performs the multiplication operation using a multiplication circuit121ias an example in order to change the magnitude of the vibration signal, namely, the magnitude of the amplitude of the vibration signal. Various operations, not limited to the multiplication operation, may be performed as long as the magnitude of the vibration signal can be changed. The adjustment circuit121his capable of performing the magnitude adjustment, the offset addition, and the signal inversion to the X scanning signal and the Y scanning signal shown inFIG. 3. Various operations, not limited to the multiplication operation, can be performed by a combination with such signal processing.

As described above, the atomic force microscope of the present embodiment includes the interaction control mechanism similarly to the first embodiment, so that the interaction generated between the probe and the sample can be controlled with good accuracy in accordance with the inclination of the sample surface104awith respect to the XY plane. Thereby, even if the sample surface is inclined with respect to the XY plane, highly accurate sample information can be acquired.

Further, in the atomic force microscope of the present embodiment, the interaction control mechanism comprises the inclination correction circuit. This enables the atomic force microscope to control the interaction between the probe and the sample with good accuracy by changing the magnitude of at least one of the vibration signal, the signal of the interaction information, and the signal of the interaction reference information, in accordance with the inclination of the sample surface104awith respect to the XY plane, specifically, based on correction information for correcting the change in the influence of the interaction between the cantilever102and the solution caused by the inclination of the sample surface104awith respect to the XY plane, which is input to the inclination correction circuit111. Thereby, even if the sample surface is inclined with respect to the XY plane, highly accurate sample information can be acquired.

Furthermore, the atomic force microscope of the present embodiment has a simpler configuration than that of the first embodiment, but can obtain effects similar to those of the first embodiment.

Furthermore, in the present embodiment, if the step of the stepped shape (steps shape) of the sample surface104ais sufficiently small with respect to the length of the probe101, since the inclination-related information, namely, the X scanning signal and the Y scanning signal, can be approximated as an inclined surface of the sample surface104awith respect to the XY plane, a similar effect can be obtained even if the inclined portion of the sample surface104awith respect to the XY plane has a stepped shape (steps shape) as shown inFIG. 18.

Further, even if the inclined portion of the sample surface104awith respect to the XY plane is a curved surface, since a part of the curved surface can be locally approximated as an inclined surface, a similar effect can be obtained.

In the above embodiments, the fluid is described as a solution. However, the atomic force microscope according to each embodiment may be applied to sample observation in any fluid that interacts with the probe, such as a liquid or gas.