WO2025032942A1 - Scanning probe microscope and cantilever evaluation method - Google Patents

Abstract

This scanning probe microscope comprises: a cantilever provided with a probe; a sample stage on which a sample is placed; a drive unit for changing the distance between the sample and the probe by moving the sample stage and the cantilever relative to each other; a displacement measurement unit for measuring displacement of the cantilever; a notification unit for notifying a user of predetermined information; and a control unit. The control unit determines a gradient value indicating the amount of variation in the amount of displacement representing the displacement of the cantilever with respect to the amount of movement by the drive unit during the displacement of the cantilever. The control unit causes the notification unit to notify the user of advice information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage when a feature quantity corresponding to the gradient value is larger than a first threshold value and/or when the feature quantity is smaller than a second threshold value smaller than the first threshold value.

Description

Scanning probe microscope and cantilever evaluation method

This disclosure relates to a scanning probe microscope and a method for evaluating a cantilever used in a scanning probe microscope.

　Japanese Patent Laid-Open Publication No. 2000-346782 (Patent Document 1) discloses a method for observing the characteristics of a sample using a scanning probe microscope. In a scanning probe microscope, the sample is moved to change the distance between the probe and the sample while measuring the amount of displacement of the cantilever including the probe, thereby obtaining a force curve that shows the relationship between the amount of movement of the sample and the amount of displacement of the cantilever.

JP 2000-346782 A

If the sample is moved further after the probe comes into contact with the sample, the probe will be pressed against the sample's surface. If the sample surface is sufficiently hard compared to the probe, the amount of sample movement and the amount of cantilever displacement will match. On the other hand, if the sample surface is softer than the probe, the sample surface will deform when the probe is pressed in, and the amount of sample movement and the amount of cantilever displacement will no longer match. Therefore, the user can observe the relative hardness of the sample to the hardness of the cantilever from the force curve, which shows the relationship between the amount of sample movement and the amount of cantilever displacement.

The information obtained from the force curve is the relative hardness of the sample with respect to the cantilever. Therefore, if the cantilever is too hard or too soft for the sample, the hardness of the sample cannot be observed accurately. Therefore, the user must select a cantilever with an appropriate hardness depending on the sample. However, determining whether a cantilever is suitable for the sample to be measured relies heavily on the user's experience, making it difficult for inexperienced users.

One objective of this disclosure is to make it easier to select an appropriate cantilever for a given sample.

The scanning probe microscope disclosed herein includes a cantilever having one end fixed and a probe at the other end, a sample stage on which a sample is placed, a drive unit that changes the distance between the sample and the probe by moving the sample stage and the cantilever relatively, a displacement measurement unit that measures the displacement of the cantilever, a notification unit that notifies a user of predetermined information, and a control unit. The control unit finds a gradient value that indicates the amount of variation in the amount of displacement that represents the displacement of the cantilever relative to the amount of movement by the drive unit while the cantilever is displaced. The control unit notifies, via the notification unit, advisory information indicating that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage when at least one of the following cases is true: a feature value corresponding to the gradient value is greater than a first threshold value, or the feature value is smaller than a second threshold value that is less than the first threshold value.

The cantilever evaluation method disclosed herein is a method for evaluating a cantilever used in a scanning probe microscope. The scanning probe microscope includes a cantilever having one end fixed and a probe attached to the other end, a sample stage on which a sample is placed, a drive unit that changes the distance between the sample and the probe by moving the sample stage and the cantilever relatively, and a displacement measurement unit that measures the displacement of the cantilever. The evaluation method includes a step of determining a gradient value that indicates the amount of variation in the amount of displacement that represents the displacement of the cantilever relative to the amount of movement by the drive unit while the cantilever is displaced, and a step of notifying advisory information that indicates that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage when at least one of the following cases is true: a feature value corresponding to the gradient value is greater than a first threshold value, or the feature value is smaller than a second threshold value that is less than the first threshold value.

According to the present disclosure, advisory information is provided to indicate that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage, allowing the user to more easily select an appropriate cantilever for the sample based on the notification.

FIG. 1 is a schematic diagram of a scanning probe microscope. FIG. 13 is a diagram showing the state of displacement of a cantilever. FIG. 13 is a diagram showing an example of a force curve. 4 is a flowchart showing a process according to the first embodiment executed by a computer. 10 is a flowchart showing a process according to a second embodiment executed by a computer. 13 is a flowchart showing a cantilever evaluation process executed by a computer. 13 is an example of a screen displayed on a display. 13 is a flowchart showing a cantilever evaluation process according to a third embodiment executed by a computer.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings will be given the same reference numerals and their description will not be repeated.

[First embodiment]
[Scanning Probe Microscope 1]
1 is a schematic diagram of a scanning probe microscope. The scanning probe microscope 1 includes a measuring device 10, a computer 20, a display 30, and an input device 40. The measuring device 10 is configured to be able to communicate with the computer 20, and sends measurement results to the computer 20. The computer 20 processes the sent measurement results and notifies the user of the calculation results obtained via the display 30. The computer 20 accepts inputs such as measurement conditions via the input device 40, and controls the entire measuring device 10 in accordance with the accepted measurement conditions.

[Measuring device 10]
As shown in FIG. 1, the measurement apparatus 10 includes a sample stage 112 , a piezoelectric scanner 111 , a cantilever 113 , a displacement measuring unit 120 , a feedback signal generating unit 131 , and a scanning signal generating unit 133 .

The sample S is placed on the sample stage 112. The sample stage 112 is moved in three dimensions by the piezoelectric scanner 111. In the following, the surface of the sample stage 112 on which the sample S is placed is defined as the XY plane, and the direction perpendicular to the XY plane is defined as the Z-axis direction.

The piezoelectric scanner 111 is an example of a drive unit that moves the sample stage 112 and the cantilever 113 relatively. The piezoelectric scanner 111 moves the sample stage 112 in three dimensions, the X, Y, and Z directions. The piezoelectric scanner 111 includes a Z scanner 111z that moves the sample stage 112 in the Z direction based on a command voltage value Vz, and an XY scanner 111xy that moves the sample stage 112 in the X and Y directions based on command voltage values Vx and Vy. Note that the drive unit only needs to move the sample stage 112 and the cantilever 113 relatively, and may move the cantilever 113, or may move both the sample stage 112 and the cantilever 113.

The cantilever 113 is disposed opposite the sample stage 112. The cantilever 113 is formed in the shape of a leaf spring. One end of the cantilever 113 is a fixed end supported by a holder (not shown). The other end of the cantilever 113 is a free end, and is disposed opposite the sample S on the sample stage 112. A probe 114 is provided on the surface of the free end of the cantilever 113 that faces the sample S.

The displacement measuring unit 120 measures the amount of deflection of the cantilever 113 as the displacement of the cantilever 113. The displacement measuring unit 120 includes a laser diode 115 and a photodetector 119. Laser light emitted from the laser diode 115 is incident on the cantilever 113 and reflected. The photodetector 119 detects the reflected light from the cantilever 113. When the cantilever 113 is deflected and displaced, the position at which the photodetector 119 receives the reflected light changes. The displacement measuring unit 120 calculates the amount of displacement (amount of deflection) of the cantilever 113 based on the light receiving position of the photodetector 119, and sends the calculated amount of displacement to the feedback signal generating unit 131 and the computer 20. In this way, the computer 20 obtains the change in the amount of displacement over time.

The feedback signal generating unit 131 calculates a command voltage value Vz in the Z-axis direction in accordance with instructions from the computer 20 and outputs it to the Z scanner 111z. The feedback signal generating unit 131 receives a start signal from the computer 20, calculates a command voltage value Vz so that the Z scanner 111z moves so as to move the sample stage 112 closer to the cantilever 113 and then moves the cantilever 113 away from the sample stage 112, and outputs it to the Z scanner 111z. The feedback signal generating unit 131 controls the Z direction position of the sample stage 112 based on the amount of deflection sent from the displacement measuring unit 120 so that the force acting on the probe 114 from the sample S does not exceed a predetermined set value. When the amount of deflection sent reaches a predetermined set value, the feedback signal generating unit 131 calculates a command voltage value Vz in the Z-axis direction to switch the direction of movement of the sample stage 112 from a direction approaching the cantilever 113 to a direction away from it, and outputs the command voltage value Vz to the Z scanner 111z. The feedback signal generating unit 131 sends the command voltage value Vz corresponding to the amount of movement of the Z scanner 111z in the Z-axis direction to the computer 20. In this way, the computer 20 acquires the change over time in the amount of movement of the sample stage 112 in the Z-axis direction.

The scanning signal generating unit 133 calculates command voltage values Vx, Vy in the X-axis and Y-axis directions so that the sample S moves relative to the probe 114 in the XY plane according to instructions from the computer 20, and outputs them to the XY scanner 111xy.

[Computer 20]
The computer 20 includes a processor 22, a memory 24, and an input/output I/F 26. The components within the computer 20 are configured to be able to communicate with each other via a bus.

The processor 22 is typically an arithmetic processing unit such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor 22 controls the operation of the computer 20 by reading and executing programs stored in the memory 24. The programs include programs that, when executed by the processor 22, cause the computer 20 to control the measuring device 10, the display 30, and the input device 40.

The memory 24 is realized by a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a HDD (Hard Disk Drive). The ROM stores the programs executed by the processor 22. The RAM temporarily stores data used by the processor 22 while the programs are being executed, and functions as a temporary data memory used as a working area. The HDD is a non-volatile storage device. In addition to or instead of the HDD, a semiconductor storage device such as a flash memory may be adopted. The above programs and/or data may be stored in an external storage device accessible by the processor 22.

The input/output I/F 26 is an interface for exchanging various types of data between the processor 22 and external devices connected to the input/output I/F 26. The external devices include a display 30, an input device 40, and the measurement device 10. The display 30 is an example of a notification unit that notifies the user of specific information, and displays, for example, an image for accepting input from the input device 40 and the results of calculations by the processor 22. The notification unit may be other devices such as a speaker or a printer. The input device 40 is typically composed of a touch panel, a keyboard, a mouse, etc. The input device 40 accepts input operations by the user to the processor 22.

The computer 20 creates a force curve that indicates the relationship between the position of the sample stage 112 in the Z-axis direction and the displacement of the cantilever 113, based on the displacement of the cantilever 113 sent from the displacement measurement unit 120 and the command voltage value Vz sent from the feedback signal generation unit 131. From the created force curve, the computer 20 determines whether the stiffness of the cantilever 113 is suitable for the stiffness of the sample S placed on the sample stage 112, and displays the result of the determination on the display 30. Note that below, creating a force curve may be referred to as "force curve measurement."

[Force Curve]
The force curve will be described in detail. FIG. 2 is a diagram showing the state of displacement of the cantilever. FIG. 3 is a diagram showing an example of a force curve. FIG. 2 shows the state of displacement of the cantilever 113 when the sample S approaches the probe 114 in the Z-axis direction and when the sample S moves away from the probe 114 in the Z-axis direction. The horizontal axis of FIG. 3 represents the position Z of the sample stage 112 in the Z-axis direction. Since one end of the cantilever 113 on which the probe 114 is provided is a fixed end, the position Z corresponds to the vertical distance between the probe 114 and the sample S. In the horizontal axis of FIG. 3, the left direction of the paper surface is the direction in which the distance between the probe 114 and the sample S decreases, and the right direction of the paper surface is the direction in which the distance between the probe 114 and the sample S increases. The vertical axis of FIG. 3 is the force F that the cantilever 113 receives. The force F is calculated by multiplying the displacement D [V] of the cantilever 113 by the spring constant K [N/m] and the sensitivity S [m/V]. The spring constant K is a physical property value of the cantilever 113 and is a constant determined by the cantilever 113. Moreover, the sensitivity S is the sensitivity of the measurement device 10 and is a constant determined by the measurement device 10. In other words, the force F corresponds to a displacement amount representing the displacement of the cantilever 113. Note that the vertical axis of the force curve may be any characteristic amount representing the displacement of the cantilever 113, and may be the displacement D [V] of the cantilever 113.

(1) to (4) in Figure 2 correspond to (1) to (4) in Figure 3. In (1) to (4), the sample S moves toward the probe 114 and makes contact, and in (4) to (6), the sample S moves away from the probe 114 and finally separates from the probe 114. In (1), the probe 114 at the tip of the cantilever 113 and the sample S are completely separated. Therefore, the cantilever 113 does not displace. In (2), the cantilever 113 receives a slight attractive force from the sample S and bends downward. This is called jumping in. In (3), the cantilever 113 receives a repulsive force from the sample S and bends upward. In (4), the probe 114 and the sample S come closest to each other and the repulsive force received from the sample S is the greatest. At (5), the force that the cantilever 113 receives from the sample S changes from a repulsive force to an attractive force. At (6), an adhesive force acts between the cantilever 113 and the sample S, and the attractive force from the sample S becomes maximum. Immediately after (6), the probe 114 separates from the sample S, returning to the state of (1). This is called a jump-out.

The feedback signal generating unit 131 controls the Z-direction position of the sample stage 112 based on the amount of displacement sent from the displacement measuring unit 120 so that the force that the probe 114 receives from the sample S does not exceed a predetermined set value. Therefore, the maximum repulsive force that the cantilever 113 receives is designed not to exceed a predetermined set value.

The force curve is composed of an approach curve obtained during approach when the sample S approaches the probe 114, and a release curve obtained during release when the sample S moves away from the probe 114. For ease of explanation, the events occurring during approach will be used as an example below.

After the sample S and the probe 114 come into contact, if the sample S is further moved, the probe 114 is pressed against the surface of the sample S. If the surface of the sample S is sufficiently hard compared to the probe 114, the amount of movement of the sample S and the amount of displacement of the cantilever 113 will match. On the other hand, if the surface of the sample S is softer than the probe 114, the surface of the sample S will be deformed by the pressure of the probe 114, and the amount of movement of the sample S and the amount of displacement of the cantilever 113 will no longer match. In other words, the relative hardness of the sample S to the hardness of the cantilever 113 can be observed from the slope a1 of the approach curve, which indicates the amount of displacement of the cantilever 113 relative to the amount of movement of the sample S. The relative hardness of the sample S to the hardness of the cantilever 113 can also be observed from the slope a2 of the release curve.

The information obtained from the force curve is the relative hardness of the sample S with respect to the cantilever 113. For example, if the cantilever 113 is too hard for the sample S, the amount of displacement of the cantilever 113 will be small regardless of the hardness of the sample S. If the cantilever 113 is too soft for the sample S, the probe 114 cannot deform the sample S, so the amount of movement of the sample S and the amount of displacement of the cantilever 113 will be approximately the same regardless of the hardness of the sample S. Therefore, if the cantilever 113 is too hard or too soft for the sample S, the hardness of the sample S is not fully reflected in the amount of displacement of the cantilever 113, so the hardness of the sample S cannot be accurately observed. Therefore, the user needs to select a cantilever 113 with an appropriate hardness depending on the sample S. However, the judgment of whether the cantilever is suitable for the sample to be measured relies heavily on the user's experience, and is difficult for inexperienced users to make.

The computer 20 is configured to notify, via the display 30, advice information showing the evaluation results of the cantilever 113 in order to aid in the selection of the cantilever 113. This configuration will be described below.

[Processing of Computer 20]
Fig. 4 is a flowchart showing the process according to the first embodiment executed by a computer. The process steps (hereinafter abbreviated as "S") shown in Fig. 4 are realized by the processor 22 executing a program stored in the memory 24. The process shown in Fig. 4 is started, for example, when the user selects to execute a predetermined application to determine whether the cantilever 113 is suitable.

In S101, the computer 20 sets the position (X, Y) of the sample stage 112 to a predetermined arbitrary position (Xa, Ya).

In S102, the computer 20 instructs the scanning probe microscope 1 to move the position of the sample stage 112 to the set position.

In S103, the computer 20 executes a process for creating a force curve. Specifically, the computer 20 sends a force curve measurement start signal to the feedback signal generating unit 131. Upon receiving the start signal, the feedback signal generating unit 131 brings the sample stage 112 closer to the cantilever 113, and then controls the Z scanner 111z to switch the movement direction of the sample stage 112 from a direction approaching the cantilever 113 to a direction away from the cantilever 113 based on the amount of deflection reaching a predetermined set value. The computer 20 acquires the amount of movement of the sample stage 112 and the amount of displacement of the cantilever 113 while the Z scanner 111z is driving. As a result, the computer 20 creates a force curve as shown in FIG. 3.

In S104, the computer 20 determines a gradient value a from the created force curve. The gradient value a is a value indicating the amount of variation in the amount representing the displacement of the cantilever 113 relative to the amount of movement of the sample stage 112 by the Z scanner 111z while the cantilever 113 is displaced. In the first embodiment, the computer 20 determines the gradient value a as the gradient value a, which is the gradient a1 of the approach curve. The gradient a1 of the approach curve is determined according to formula (1) with reference to FIG. 3.

In equation (1), FM, Fm1, Zm, and Z1 respectively represent the maximum repulsive force received by the cantilever 113, the attractive force received by the cantilever 113 during jump-in, the position of the sample stage 112 in the Z-axis direction when the cantilever 113 receives the maximum repulsive force, and the position of the sample stage 112 in the Z-axis direction during jump-in. As shown in equation (1), the slope a1 of the approach curve can be calculated by dividing the amount of movement in the Z-axis direction from the time of jump-in until the force received by the cantilever 113 reaches its maximum by the amount of change in the force received by the cantilever 113.

Returning to FIG. 4, in S111, the computer 20 determines whether the gradient value a is greater than a first threshold value T1. The first threshold value T1 is a gradient value that indicates that the probe 114 cannot sufficiently deform the sample S.

If the computer 20 determines that the gradient value a is greater than the first threshold value T1 (YES in S111), in S112, it notifies the display 30 with information recommending the use of a stiff cantilever, and ends the process.

If the computer 20 determines that the gradient value a is equal to or less than the first threshold value T1 (NO in S111), it determines in S113 whether the gradient value a is smaller than the second threshold value T2. The second threshold value T2 is a gradient value that is less than the first threshold value T1 and indicates that the cantilever 113 is too stiff and has not been displaced sufficiently relative to the amount of movement.

If the computer 20 determines that the gradient value a is smaller than the second threshold value T2 (YES in S113), in S114, it notifies the display 30 with information recommending the use of a soft cantilever, and ends the process.

If the computer 20 determines that the gradient value a is equal to or greater than the second threshold value T2 (NO in S113), in S115 it notifies the display 30 that the hardness of the cantilever 113 is appropriate, and ends the process.

The computer 20 may notify, via the display 30, information indicating that the stiffness of the cantilever 113 is not suitable only when the gradient value a is greater than the first threshold value T1. Also, the computer 20 may notify, via the display 30, information indicating that the stiffness of the cantilever 113 is not suitable only when the gradient value a is less than the second threshold value T2. Also, the notified information may only be information indicating that it is not suitable.

Note that the gradient value a may be any value that corresponds to the amount of displacement of the cantilever 113 relative to the amount of movement of the sample stage 112 while the cantilever 113 is displaced, and may be the gradient a2 of the release curve. The gradient a2 of the release curve is calculated according to formula (2) with reference to FIG. 3.

In equation (2), Fm2 and Z2 are the gravitational force that the cantilever 113 receives at the time of jumping out, and the position of the sample stage 112 in the Z-axis direction at the time of jumping out, respectively. As shown in equation (2), the slope a2 of the release curve can be calculated by dividing the amount of movement in the Z-axis direction from when the force that the cantilever 113 receives reaches its maximum until the time of jumping out by the amount of change in the force that the cantilever 113 receives.

The gradient value a may be any value that represents the amount of variation in the amount of displacement of the cantilever 113 relative to the amount of movement in the Z-axis direction while the cantilever 113 is displaced. For example, the amount of variation in the amount of displacement of the cantilever 113 may be the amount of variation in the amount of displacement of the cantilever 113. The gradient value a may also be the slope of an approach curve in any section from the time of jump-in until the force received by the cantilever 113 becomes maximum. The gradient value a may also be the slope of a release curve in any section from the time of jump-in until the force received by the cantilever 113 becomes maximum until the time of jump-out. If the amount of displacement and the amount of movement are not proportional, the computer 20 may determine the gradient value by linear approximation.

The first threshold T1 and the second threshold T2 may be set in advance, for example, by a business that provides the scanning probe microscope 1 or the cantilever 113, or may be set in advance by a user of the scanning probe microscope 1.

For example, the first threshold T1 and the second threshold T2 are set based on the gradient value obtained from the force curve obtained by measuring multiple types of samples with different hardness, and the state of the sample surface after the force curve is obtained. As an example, the second threshold T2 is set to a gradient value between the gradient value when a scratch is formed and the gradient value when no scratch is formed, depending on whether or not a scratch is formed on the sample surface after the force curve is obtained.

Note that steps S104 and S111 to S115 in FIG. 4 may be executed when a force curve is created at at least one point on the sample surface. For example, even when creating a force curve for the purpose of evaluating the mechanical properties of the sample S, rather than evaluating the cantilever, the computer 20 may execute steps S104 and S111 to S115 in FIG. 4 to evaluate whether the cantilever 113 used is appropriate.

In the first embodiment, the computer 20 notifies the display 30 with advisory information indicating that the hardness (rigidity) of the cantilever 113 is not suitable when the gradient value a obtained from the force curve is greater than the first threshold value T1 or smaller than the second threshold value T2. The user can more easily select an appropriate cantilever for the sample S based on the notified information.

In the first embodiment, when the gradient value a is greater than the first threshold value T1, the computer 20 notifies the user on the display 30 of information recommending the use of a cantilever that is harder (higher rigidity) than the currently used cantilever 113. Based on the notified information, the user can consider changing to a cantilever that is harder than the currently used cantilever 113. Because the rigidity (rigidity) of a cantilever is defined by the spring constant, the user can consider changing to a cantilever with a larger spring constant than the currently used cantilever 113 based on the notified information.

In the first embodiment, when the gradient value a is smaller than the second threshold value T2, the computer 20 notifies the user on the display 30 of information recommending the use of a cantilever that is softer (lower rigidity) than the currently used cantilever 113. Based on the notified information, the user can consider changing to a cantilever that is softer than the currently used cantilever 113. More specifically, based on the notified information, the user can consider changing to a cantilever that has a smaller spring constant than the currently used cantilever 113.

In the first embodiment, the computer 20 uses the slope a1 of the approach curve as the gradient value a. The slope a1 of the approach curve is a value corresponding to the amount of variation in the amount representing the displacement of the cantilever 113 relative to the amount of movement in the Z-axis direction while the sample S is approaching the probe 114 and while the cantilever 113 is displaced. Although the sample S deforms and the cantilever 113 displaces in response to the force applied to the sample S, the displacement of the cantilever 113 generally has a higher ability to follow the force applied to the sample S during approach than during release. Therefore, by using the slope a1 of the approach curve as the gradient value a, the computer 20 can more accurately evaluate the relative hardness of the cantilever 113 with respect to the sample S.

[Second embodiment]
In the first embodiment, a configuration was described in which the computer 20 evaluates whether the hardness of the cantilever 113 is suitable for the sample S to be measured based on a force curve obtained by measuring a certain position on the surface of the sample S.

In the second embodiment, an example will be described in which the hardness of the cantilever 113 is evaluated based on multiple gradient values obtained by measuring multiple positions on the surface of the sample S. Specifically, the computer 20 scans the sample stage 112 in the XY direction of the sample S, performs force curve measurements at multiple positions on the XY plane, and obtains the gradient value at each position on the XY plane. The computer 20 obtains a feature value corresponding to the gradient value based on the distribution of the gradient values at each position, and evaluates the cantilever 113 based on the obtained feature value. Figure 5 is a flowchart showing the processing according to the second embodiment executed by the computer. Note that the description of the processing common to the processing described in the first embodiment will not be repeated.

In the second embodiment, the scanning range of the sample S is set to, for example, X0<X<Xmax, Y0<Y<Ymax. Also, the distance between adjacent measurement points is set to a predetermined value b.

In S101a, the computer 20 sets the position (X, Y) of the sample stage 112 to the initial position (X0, Y0).

Because S102a to S104a are the same as S102 to S104 in the first embodiment, the description of S102a to S104a will not be repeated. That is, in S102a to S104a, the computer 20 creates a force curve at the set position (X, Y) and obtains the gradient value a at the set position from the created force curve.

In S105a, the pixel value at the position on the distribution map that corresponds to the set position is set as the gradient value a.

In S106a, the computer 20 determines whether X is equal to or greater than Xmax. If X is less than Xmax (NO in S106a), the computer 20 sets X=X+b in S107a and executes S102a to S105a. The computer 20 repeats S102a to S107a until X reaches Xmax.

If X is equal to or greater than Xmax (YES in S106a), the computer 20 determines in S108a whether Y is equal to or greater than Ymax. If Y is less than Ymax (NO in S108a), the computer 20 sets X=X0 and Y=Y+b in S109a, executes S102a to S105a, and repeats S102a to S107a until X reaches Xmax, and then proceeds to S108a. The computer 20 repeats S102a to S109a until Y reaches Ymax. In this way, the gradient value at each position on the XY plane is determined, and a distribution diagram is created.

In S10a, the computer 20 executes a cantilever evaluation process. The cantilever evaluation process will be described later with reference to FIG. 6.

In S120a, the computer 20 displays on the display 30 the distribution diagram created in S101a to S108a and the evaluation results obtained in S10a, and then ends the process.

FIG. 6 is a flowchart showing the cantilever evaluation process executed by a computer.
In S110a, the computer 20 obtains the most frequent value A of the gradient value a. The computer 20 obtains the gradient value at each position on the XY plane by executing S101a to S108a. The computer 20 obtains the most frequent value A of the gradient value a from the obtained multiple gradient values a.

In S111a, the computer 20 determines whether the first threshold T1 is greater than the first threshold T1. S111a and S113a are the same as S111 and S113 in the first embodiment, except that the most frequent value A is compared with the first threshold T1 and the second threshold T2. S112a, S114a, and S115a are the same as S112, S114, and S115 in the first embodiment, except that they only determine the information to be notified. Therefore, the description of S111a to S115a will not be repeated. After executing S112a, S114a, or S115a, the computer 20 returns to the process of FIG. 5 and executes S120a.

FIG. 7 is an example of a screen displayed on the display. Screen 300 is displayed on display 30 by computer 20 executing S120. Screen 300 includes a distribution diagram 310 of gradient values a, a histogram 320 of gradient values a, and advice information 330.

The advice information 330 is the evaluation result obtained in the cantilever evaluation process, and is information indicating whether the hardness of the cantilever is appropriate or not.

In the second embodiment, the computer 20 determines a feature value corresponding to the gradient value a based on the distribution of the gradient value a, and evaluates the cantilever 113 based on the determined feature value. The sample S has a distribution of hardness at each position on its surface. Therefore, even if the hardness of the cantilever 113 is suitable for the hardness at a certain position on the surface of the sample S, it may not be suitable for the hardness at other positions. In the second embodiment, the gradient values at multiple different positions on the surface of the sample S are determined, and the cantilever 113 is evaluated based on the distribution of the multiple gradient values, making it easy to select a cantilever 113 suitable for the entire surface of the sample S.

The cantilever evaluation process shown in FIG. 6 may be executed when creating force curves at multiple positions on the sample surface to evaluate the mechanical characteristics of the sample S. In other words, even when creating force curves at multiple positions for the purpose of evaluating the mechanical characteristics of the sample S, rather than evaluating the cantilever, the cantilever evaluation process shown in FIG. 6 may be executed to evaluate whether the cantilever 113 used is appropriate. In this case, the computer 20 may notify advisory information only when it is determined that the cantilever 113 used is not appropriate.

[Third embodiment]
In the second embodiment, a configuration has been described in which the computer 20 creates a force curve at each position on the XY plane and then executes the cantilever evaluation process.

In the third embodiment, a configuration is described in which a cantilever evaluation process is executed each time a force curve is created. In the third embodiment, when force curve measurements are performed at multiple positions on the XY plane, the computer 20 executes a cantilever evaluation process each time a force curve is created. FIG. 8 is a flowchart showing the cantilever evaluation process according to the third embodiment executed by the computer. Note that the description of the processes common to the processes described in the first and second embodiments will not be repeated.

The computer 20 executes the cantilever evaluation process shown in FIG. 8 at any time after creating one force curve.

In S11b, the computer 20 calculates the gradient value a. Since S11b is the same as S104 in the first embodiment, the description of S11b will not be repeated.

In S12b, the computer 20 determines whether the gradient value a is equal to or greater than a third threshold value T3. The third threshold value T3 is equal to or greater than the first threshold value T1, and is the gradient value when the amount of movement of the sample S and the amount of fluctuation in the amount of displacement of the cantilever 113 match. For example, when the vertical axis of the force curve is the amount of displacement of the cantilever 113, the third threshold value T3 is 1.

If the computer 20 determines that the gradient value a is equal to or greater than the third threshold value T3 (YES in S12b), in S13b it notifies the user on the display 30 of information recommending the use of a stiff cantilever, and ends the process.

If the computer 20 determines that the gradient value a is less than the third threshold value T3 (NO in S12b), the process proceeds to S14b.

In S14b, the computer 20 determines whether the number of force curve measurements (measurements) is equal to or greater than a predetermined number n (n ≥ 2, n is an integer). If the computer 20 determines that the measurements are less than the predetermined number n (NO in S14b), it ends the process.

If the computer 20 determines that the number of measurements is equal to or greater than the predetermined number n (YES in S14b), the process proceeds to S110b.

In S110b, the computer 20 determines the most frequent value A of the gradient values a. The processes from S110b onwards are executed after the force curve measurement is performed multiple times and multiple gradient values a are obtained. The computer 20 determines the most frequent value A from the multiple gradient values a obtained.

Then, the computer 20 executes S111b to S114b and ends the process. Note that S111b to S114b are the same as S111a to S114a in the second embodiment, except that information is notified in S112b and S114b. Therefore, the description of S111b to S114b will not be repeated.

As described above, in the third embodiment, when performing force curve measurements at multiple positions on the XY plane, the computer 20 notifies information recommending the use of a hard cantilever if the gradient value a at at least one position is equal to or greater than the third threshold value T3. On the other hand, when the gradient value a at each position is less than the third threshold value T3, the computer 20 notifies information recommending the use of a hard cantilever when the mode A is greater than the first threshold value T1, and notifies information recommending the use of a soft cantilever when the mode A is less than the second threshold value T2. In other words, when the gradient value a at each position is all less than the third threshold value T3, the computer 20 evaluates the cantilever 113 based on the distribution of gradient values at each position.

The third threshold T3 is the gradient value when the amount of movement of the sample S and the amount of change in the displacement of the cantilever 113 match. The amount of movement of the sample S and the amount of change in the displacement of the cantilever 113 match means that the surface of the sample S is sufficiently hard compared to the probe 114, so that the sample S does not deform even when the probe 114 is pressed against the sample S, and the cantilever 113 is displaced in accordance with the movement of the sample S. In other words, the amount of movement of the sample S and the amount of displacement of the cantilever 113 match means that the hardness of the sample S is hardly reflected in the amount of displacement of the cantilever 113.

In the third embodiment, if the computer 20 determines that the hardness of the sample S is not clearly reflected in the amount of displacement of the cantilever 113, it notifies the evaluation result of the cantilever 113 based on the result of the force curve measurement at one position on the surface of the sample S. On the other hand, if the hardness of the sample S is reflected in the amount of displacement of the cantilever 113, the computer 20 determines whether the degree of reflection is sufficient based on the measurement results at each position on the sample surface. Therefore, the user can consider changing the cantilever 113 without repeating measurements more than necessary, thereby shortening the time required to select the cantilever 113.

[Aspects]
It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

　(1) A scanning probe microscope according to one embodiment includes a cantilever having one end fixed and a probe at the other end, a sample stage on which a sample is placed, a drive unit that changes the distance between the sample and the probe by moving the sample stage and the cantilever relatively, a displacement measurement unit that measures the displacement of the cantilever, a notification unit that notifies a user of predetermined information, and a control unit. The control unit determines a gradient value that indicates the amount of variation in an amount that represents the displacement of the cantilever relative to the amount of movement by the drive unit while the cantilever is displaced. The control unit may notify, via the notification unit, advisory information indicating that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage when at least one of the following cases is true: a feature value corresponding to the gradient value is greater than a first threshold value, or the feature value is less than a second threshold value that is less than the first threshold value.

The scanning probe microscope described in paragraph 1 provides advisory information indicating that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage, allowing the user to more easily select an appropriate cantilever for the sample based on the notification.

Note that the "feature corresponding to the gradient value" may be anything that corresponds to the gradient value, and may even be the "gradient value" itself.

(2) In the scanning probe microscope described in 1, when the feature amount is greater than a first threshold, the control unit may notify, via the notification unit, advice information recommending changing the cantilever to one having higher rigidity than the cantilever in question.

　With the scanning probe microscope described in paragraph 2, the user can consider changing to a cantilever that is harder than the one currently being used, based on the notified information.

(3) In the scanning probe microscope described in 1 or 2, when the feature amount is smaller than the second threshold, the control unit may notify, via the notification unit, advice information recommending changing the cantilever to one with lower rigidity than the cantilever in question.

　With the scanning probe microscope described in paragraph 3, the user can consider changing to a cantilever that is softer than the one currently being used, based on the notified information.

(4) In the scanning probe microscope described in any one of paragraphs 1 to 3, the gradient value may indicate the amount of variation relative to the amount of movement by the driving unit while the driving unit is moving the sample closer to the probe and while the cantilever is being displaced.

The scanning probe microscope described in paragraph 4 utilizes information from the time when the sample, which has high response of the cantilever's displacement to the force applied to the sample, is approaching the probe, making it possible to more accurately evaluate the relative hardness of the cantilever 113 with respect to the sample.

(5) In the scanning probe microscope described in any one of 1 to 4, the drive unit scans the cantilever relative to the sample stage in a direction along the mounting surface of the sample stage on which the sample is placed. The displacement measurement unit measures the displacement of the cantilever at multiple positions in the scanning direction of the cantilever. The control unit determines the gradient value at each position in the scanning direction. The control unit may determine the feature amount based on the distribution of the gradient values at each position in the scanning direction.

The scanning probe microscope described in paragraph 5 allows the user to easily select a cantilever that is suitable for the entire surface of a sample that has a distribution of hardness at each position on the surface.

(Section 6) In the scanning probe microscope described in Section 5, when the gradient value at any one of the multiple positions is equal to or greater than a third threshold value that is equal to or greater than the first threshold value, the control unit notifies, via the notification unit, information recommending changing the cantilever to one with higher rigidity than the cantilever in question as advice information. When the gradient value at each position in the scanning direction is smaller than the third threshold value and the feature value is smaller than the second threshold value, the control unit may notify, via the notification unit, information recommending changing the cantilever to one with lower rigidity than the cantilever in question as advice information.

　According to the scanning probe microscope described in paragraph 6, when the gradient value at a certain position is equal to or greater than the third threshold value, advisory information is notified, so that the user can consider changing the cantilever without repeatedly calculating the gradient value more than necessary, thereby reducing the time required to select a cantilever.

　(7) A cantilever evaluation method according to one embodiment is a method for evaluating a cantilever used in a scanning probe microscope including a cantilever, a sample stage on which a sample is placed, a drive unit, and a displacement measurement unit. The cantilever is fixed at one end and has a probe at the other end. The drive unit moves the sample stage and the cantilever relatively to change the distance between the sample and the probe. The displacement measurement unit measures the displacement of the cantilever. The evaluation method may include a step of determining a gradient value indicating the amount of variation in an amount representing the displacement of the cantilever relative to the amount of movement by the drive unit while the cantilever is displaced, and a step of notifying advisory information indicating that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage when at least one of the following cases is true: a feature value corresponding to the gradient value is greater than a first threshold value, or the feature value is less than a second threshold value that is less than the first threshold value.

　According to the cantilever evaluation method described in paragraph 7, advisory information is provided to indicate that the stiffness of the cantilever is not suitable for the stiffness of the sample placed on the sample stage, allowing the user to more easily select an appropriate cantilever for the sample based on the notification.

(Clause 8) The recording medium according to one embodiment may be a computer-readable recording medium having recorded thereon a program for causing a computer to execute the cantilever evaluation method described in Clause 7.

(Clause 9) The program according to one embodiment may be a program that causes a computer to execute the cantilever evaluation method described in Clause 7.

It is anticipated that the embodiments disclosed herein may be combined as appropriate to the extent that no technical contradiction occurs. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and is intended to include all modifications within the meaning and scope of the claims.

1 scanning probe microscope, 10 measuring device, 20 computer, 22 processor, 24 memory, 26 input/output I/F, 30 display, 40 input device, 111 piezo scanner, 111xy XY scanner, 111z Z scanner, 112 sample stage, 113 cantilever, 114 probe, 115 laser diode, 119 photodetector, 120 displacement measurement unit, 131 feedback signal generation unit, 133 scanning signal generation unit, 300 screen, 310 distribution diagram, 320 histogram, 330 advisory information, S sample.

Claims (7)

A cantilever having one end fixed and a probe at the other end;
A sample stage on which a sample is placed;
a drive unit that changes the distance between the sample and the probe by moving the sample stage and the cantilever relatively;
A displacement measuring unit that measures the displacement of the cantilever;
A notification unit that notifies a user of predetermined information;
A control unit.
The control unit is
A gradient value indicating a variation in an amount representing the displacement of the cantilever relative to an amount of movement by the driving unit while the cantilever is displaced is obtained;
a scanning probe microscope, wherein when a feature value corresponding to the gradient value is greater than a first threshold value or when the feature value is smaller than a second threshold value that is less than the first threshold value, the notification unit notifies advisory information indicating that the rigidity of the cantilever is not suitable for the rigidity of a sample placed on the sample stage. The scanning probe microscope of claim 1, wherein, when the feature amount is greater than the first threshold value, the control unit notifies, via the notification unit, the advice information recommending changing the cantilever to a cantilever having higher rigidity than the cantilever in question. The scanning probe microscope according to claim 1 or 2, wherein, when the characteristic amount is smaller than the second threshold value, the control unit notifies, via the notification unit, the advice information recommending changing the cantilever to a cantilever having a lower rigidity than the cantilever in question. The scanning probe microscope according to claim 1 or 2, wherein the gradient value indicates the amount of variation relative to the amount of movement caused by the driving unit while the driving unit is moving the sample closer to the probe and while the cantilever is being displaced. the driving unit scans the cantilever relatively to the sample stage in a direction along a mounting surface of the sample stage on which a sample is placed;
the displacement measuring unit measures the displacement of the cantilever at a plurality of positions in a scanning direction of the cantilever;
The control unit is
determining the gradient value at each position in the scanning direction;
3. The scanning probe microscope according to claim 1, wherein the characteristic amount is determined based on a distribution of the gradient values at each position in the scanning direction. The control unit is
when the gradient value at any one of the plurality of positions is equal to or greater than a third threshold that is equal to or greater than the first threshold, notifying, by the notification unit, as the advice information, information recommending that the cantilever be changed to a cantilever having higher rigidity than the cantilever;
6. The scanning probe microscope according to claim 5, wherein, when the gradient value at each position in the scanning direction is smaller than the third threshold value and the feature amount is smaller than the second threshold value, the notification unit notifies, as the advice information, information recommending changing the cantilever to a cantilever having lower rigidity than the cantilever in question. A method for evaluating a cantilever used in a scanning probe microscope, comprising the steps of:
The scanning probe microscope comprises:
A cantilever having one end fixed and a probe at the other end;
A sample stage on which a sample is placed;
a drive unit that changes the distance between the sample and the probe by moving the sample stage and the cantilever relatively;
a displacement measuring unit that measures the displacement of the cantilever,
The evaluation method includes:
determining a gradient value indicating a variation in an amount representing the displacement of the cantilever relative to an amount of movement by the driving unit while the cantilever is displaced;
A method for evaluating a cantilever, comprising a step of notifying advisory information indicating that the stiffness of the cantilever is not suitable for the stiffness of a sample placed on the sample stage when at least one of a feature corresponding to the gradient value is greater than a first threshold value or a feature corresponding to the gradient value is smaller than a second threshold value that is less than the first threshold value.

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