Scanning probe microscope and method for evaluating cantilever

Abstract

The scanning probe microscope includes: a cantilever provided with a probe; a sample table 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 relative to each other; a displacement measurement unit for measuring the displacement of the cantilever; a notification unit for notifying the user of prescribed information; and a control unit. The control unit finds a gradient value indicating a variation amount of a displacement amount indicating the displacement of the cantilever with respect to a movement amount caused by the drive unit during the occurrence of the displacement of the cantilever. The control unit notifies, by means of the notification unit, suggestion information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage in at least one of a case where the feature amount corresponding to the gradient value is greater than a first threshold value and a case where the feature amount is less than a second threshold value that is lower than the first threshold value.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a scanning probe microscope and a method for evaluating a cantilever for a scanning probe microscope. BACKGROUND

[0002] Japanese Patent Application Publication No. 2000-346782 (Patent Literature 1) discloses a method for observing a sample characteristic using a scanning probe microscope. In the scanning probe microscope, a displacement amount of a cantilever including a probe is measured while changing a distance between the probe and a sample by moving the sample, and a force curve indicating a relationship between a movement amount of the sample and the displacement amount of the cantilever is obtained.

[0003] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Publication No. 2000-346782 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION When the sample is further moved after the sample is brought into contact with the probe, the probe is pressed against the surface of the sample. In a case where the surface of the sample is sufficiently hard compared to the probe, the movement amount of the sample coincides with the displacement amount of the cantilever. On the other hand, in a case where the surface of the sample is softer compared to the probe, the surface of the sample is deformed due to the pressing of the probe, and thus the movement amount of the sample becomes different from the displacement amount of the cantilever. Therefore, the user can observe the relative hardness of the sample with respect to the cantilever from the force curve indicating the relationship between the movement amount of the sample and the displacement amount of the cantilever.

[0004] The information obtained from the force curve is the relative hardness of the sample with respect to the cantilever. Therefore, in a case where the cantilever is too hard or too soft with respect to the sample, the hardness of the sample cannot be correctly observed. Therefore, the user needs to select a cantilever having an appropriate hardness according to the sample. However, it is difficult for a user who lacks experience to determine whether the cantilever is appropriate for the sample to be measured, depending largely on the user's experience.

[0005] An object of the present disclosure is to make it easier to select an appropriate cantilever according to a sample.

[0006] MEANS FOR SOLVING THE PROBLEMS The scanning probe microscope of the present disclosure includes a cantilever having one end fixed and the other end provided with a probe, a sample stage for placing a sample, a driving section that changes the distance between the sample and the probe by relatively moving the sample stage and the cantilever, a displacement measuring section that measures the displacement of the cantilever, a notification section that notifies a user of prescribed information, and a control section. The control section calculates a gradient value that indicates the variation in the displacement amount indicating the displacement of the cantilever with respect to the movement amount caused by the driving section during the displacement of the cantilever. The control section notifies the notification section of suggestion information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage in at least one of a case where a characteristic value corresponding to the gradient value is greater than a first threshold value or a case where the characteristic value is less than a second threshold value lower than the first threshold value.

[0007] The cantilever evaluation method of the present disclosure is an evaluation method for a cantilever of a scanning probe microscope. The scanning probe microscope includes a cantilever having one end fixed and the other end provided with a probe, a sample stage for placing a sample, a driving section that changes the distance between the sample and the probe by relatively moving the sample stage and the cantilever, and a displacement measuring section that measures the displacement of the cantilever. The evaluation method includes a step of calculating a gradient value that indicates the variation in the displacement amount indicating the displacement of the cantilever with respect to the movement amount caused by the driving section during the displacement of the cantilever, and a step of notifying suggestion information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage in at least one of a case where a characteristic value corresponding to the gradient value is greater than a first threshold value or a case where the characteristic value is less than a second threshold value lower than the first threshold value.

[0008] Effects of the Invention According to the present disclosure, since the suggestion information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage is notified, the user can more easily select an appropriate cantilever corresponding to the sample based on the notification. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 FIG. 1 is a schematic configuration diagram of a scanning probe microscope.

[0010] Figure 2 FIG. 3 is a graph indicating the displacement of the cantilever.

[0011] Figure 3 FIG. 5 is a graph indicating an example of a force curve.

[0012] Figure 4 FIG. 7 is a flowchart indicating the processing performed by the computer relating to the first embodiment.

[0013] Figure 5 FIG. 9 is a flowchart indicating the processing performed by the computer relating to the second embodiment.​​​​​

[0014]

Figure 6

[0015]

Figure 7

[0016]

Figure 8

[0017] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or equivalent portions are designated by the same reference numerals, and description thereof will be omitted.

[0018] [First Embodiment] [Scanning Probe Microscope 1] Figure 1 is a schematic configuration diagram of a scanning probe microscope. The scanning probe microscope 1 includes a measurement device 10, a computer 20, a display 30, and an input device 40. The measurement device 10 is configured to be able to communicate with the computer 20 and transmit a measurement result to the computer 20. The computer 20 notifies a user of a calculation result obtained by processing the transmitted measurement result via the display 30. The computer 20 accepts input of a measurement condition or the like via the input device 40 and controls the entire measurement device 10 in accordance with the accepted measurement condition.

[0019] [Measurement Device 10] As shown in Figure 1 , the measurement device 10 includes a sample stage 112, a piezoelectric scanner 111, a cantilever 113, a displacement measurement section 120, a feedback signal generation section 131, and a scanning signal generation section 133.

[0020] The sample stage 112 has a sample S placed thereon. The sample stage 112 is moved in three-dimensional directions by the piezoelectric scanner 111. Hereinafter, a placement surface of the sample stage 112 on which the sample S is placed is set as an XY plane, and a direction perpendicular to the XY plane is set as a Z-axis direction.

[0021] The piezoelectric scanner 111 is an example of a drive unit that moves the sample stage 112 relative to the cantilever 113. The piezoelectric scanner 111 moves the sample stage 112 in three dimensions in the XYZ directions. The piezoelectric scanner 111 includes a Z scanner 111z that moves the sample stage 112 in the Z direction based on an instruction voltage value Vz, and an XY scanner 111xy that moves the sample stage 112 in the XY directions based on instruction voltage values Vx, Vy, respectively. In addition, the drive unit can be configured to move the cantilever 113, or both the sample stage 112 and the cantilever 113, as long as the sample stage 112 is moved relative to the cantilever 113.

[0022] The cantilever 113 is disposed opposite the sample stage 112. The cantilever 113 is formed in a leaf spring shape. One end of the cantilever 113 is a fixed end that is supported by a holder not shown. The other end of the cantilever 113 is a free end that is disposed opposite the sample S on the sample stage 112. The probe 114 is disposed on a surface of the free end of the cantilever 113 that is opposite the sample S.

[0023] The displacement measurement unit 120 measures the amount of deflection of the cantilever 113 as the displacement of the cantilever 113. The displacement measurement 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 is reflected. The photodetector 119 detects the reflected light from the cantilever 113. When the cantilever 113 is deflected and displaced, the position of the reflected light in the photodetector 119 changes. The displacement measurement unit 120 calculates the amount of displacement (deflection) of the cantilever 113 based on the position of the light received by the photodetector 119, and transmits the calculated amount of displacement to the feedback signal generation unit 131 and the computer 20. As a result, the computer 20 acquires the change in the amount of displacement over time.

[0024] The feedback signal generating section 131 calculates the command voltage value Vz in the Z-axis direction in accordance with an instruction from the computer 20, and outputs it to the Z scanner 111z. The feedback signal generating section 131 receives a start signal from the computer 20, calculates the command voltage value Vz to drive the Z scanner 111z so as to move the cantilever 113 away from the sample stage 112 after moving the sample stage 112 close to the cantilever 113, and outputs the command voltage value Vz to the Z scanner 111z. The feedback signal generating section 131 controls the Z-direction position of the sample stage 112 based on the deflection amount sent from the displacement measuring section 120 so as to make the force acting on the probe 114 from the sample S not exceed a preset set value. The feedback signal generating section 131 calculates the command voltage value Vz in the Z-axis direction based on the sent deflection amount having reached the preset set value, so as to switch the moving direction of the sample stage 112 from the direction close to the cantilever 113 to the direction away, and outputs the command voltage value Vz to the Z scanner 111z. The feedback signal generating section 131 sends the command voltage value Vz corresponding to the moving amount in the Z-axis direction of the Z scanner 111z to the computer 20. Thus, the computer 20 acquires the moving amount in the Z-axis direction of the sample stage 112 with time.

[0025] The scanning signal generating section 133 calculates the command voltage values Vx, Vy in the X-axis, Y-axis directions in accordance with an instruction from the computer 20 so as to relatively move the sample S in the X-Y plane with respect to the probe 114, and outputs them to the XY scanner 111xy.

[0026] [Computer 20] The computer 20 is provided with a processor 22, a memory 24, and an input / output I / F 26. The respective sections in the computer 20 are configured to be able to communicate with each other via a bus.

[0027] The processor 22 is typically a calculation processing section 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 out and executing a program stored in the memory 24. The program includes a program that causes the computer 20 to control the measurement apparatus 10, the display 30, and the input device 40 by being executed by the processor 22.

[0028] The memory 24 is realized by, for example, a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an HDD (Hard Disk Drive). The ROM stores a program executed by the processor 22. The RAM temporarily stores data used by the processor 22 during execution of the program, and functions as a temporary data memory used as a work area. The HDD is a nonvolatile storage device. In addition to or instead of the HDD, a semiconductor storage device such as a flash memory can be employed. In addition, the above-described program and / or data can be stored in a storage device external to the processor 22.

[0029] The input / output I / F 26 is an interface that exchanges various data between the processor 22 and external devices connected to the input / output I / F 26. The external devices include the display 30, the input device 40, and the measurement device 10. The display 30 is an example of a notification section that notifies a user of prescribed information, and displays, for example, an image for accepting an input from the input device 40, and a result of an operation of the processor 22. In addition, the notification section can be a speaker, a printer, or another device. The input device 40 is typically constituted by a touch panel, a keyboard, a mouse, or the like. The input device 40 accepts an input operation of the user to the processor 22.

[0030] The computer 20 creates a force curve that indicates a relationship between a position of the Z-axis direction of the sample stage 112 and the displacement amount of the cantilever 113, based on the displacement amount of the cantilever 113 transmitted from the displacement measurement section 120 and the command voltage value Vz transmitted from the feedback signal generation section 131. The computer 20 determines whether the rigidity of the cantilever 113 is suitable for the rigidity of the sample S placed on the sample stage 112, according to the created force curve, and displays the determination result on the display 30. In addition, hereinafter, the creation of the force curve will be referred to as "force curve measurement".

[0031] [Force Curve] The force curve will be described in detail. Figure 2 is a graph that indicates a displacement condition of the cantilever. Figure 3 is a graph that indicates an example of the force curve. In Figure 2 , a displacement condition 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 is shown. Figure 3 The horizontal axis of indicates a position Z of the Z-axis direction of the sample stage 112. Since one end of the cantilever 113 on which the probe 114 is provided is a fixed end, the position Z corresponds to a distance in the vertical direction of the probe 114 and the sample S. In the horizontal axis of Figure 3 , the left direction of the paper is a direction in which the distance between the probe 114 and the sample S is shortened, and the right direction of the paper is a direction in which the distance between the probe 114 and the sample S is expanded. Figure 3The vertical axis represents the force F acting on the cantilever 113. The force F is obtained 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, a constant determined based on the cantilever 113. Furthermore, the sensitivity S is the sensitivity of the measuring device 10, a constant determined based on the measuring device 10. That is, the force F is equivalent to the displacement representing the displacement of the cantilever 113. Additionally, the vertical axis of the force curve can be any characteristic quantity representing the displacement of the cantilever 113, or it can be the displacement D[V] of the cantilever 113.

[0032] Figure 2 (1) to (4) and Figure 3 (1) to (4) correspond to the following. In (1) to (4), the sample S moves towards the probe 114 and comes into contact. In (4) to (6), the sample S moves away from the probe 114 and eventually leaves the probe 114. In (1), the probe 114 at the top of the cantilever 113 is completely separated from the sample S. Therefore, the cantilever 113 does not undergo displacement. In (2), the cantilever 113 is subjected to a small attractive force from the sample S and bends downward. This is called a jump in. In (3), the cantilever 113 is subjected to a repulsive force from the sample S and bends upward. In (4), the probe 114 is in closest contact with the sample S, and the repulsive force from the sample S is the greatest. In (5), the force on the cantilever 113 from the sample S changes from a repulsive force to an attractive force. In (6), there is an adsorption force between the cantilever 113 and the sample S, and the attraction force from the sample S is the greatest. After (6), the probe 114 immediately leaves the sample S and returns to the state in (1). This is called jump out.

[0033] Furthermore, the feedback signal generator 131 controls the Z-direction position of the sample stage 112 based on the displacement amount sent from the displacement measuring unit 120, so that the force on the probe 114 from the sample S does not exceed a preset value. Therefore, the maximum repulsive force on the cantilever 113 is designed to not exceed a preset value.

[0034] The force curve consists of the approach curve obtained when the sample S is approaching the probe 114, and the retreat curve obtained when the sample S is retreating away from the probe 114. For ease of explanation, the phenomenon during approach will be used as an example below.

[0035] When the sample S is further moved after the sample S is brought into contact with the probe 114, the probe 114 is pressed against the surface of the sample S. In a case where the surface of the sample S is sufficiently hard compared with the probe 114, the amount of movement of the sample S coincides with the amount of displacement of the cantilever 113. On the other hand, in a case where the surface of the sample S is softer compared with the probe 114, the surface of the sample S is deformed due to the pressing of the probe 114, and thus the amount of movement of the sample S becomes different from the amount of displacement of the cantilever 113. That is, the relative hardness of the sample S with respect to the hardness of the cantilever 113 can be observed from the slope al of the approach curve indicating the amount of displacement of the cantilever 113 with respect to the amount of movement of the sample S. In addition, the relative hardness of the sample S with respect to the hardness of the cantilever 113 can be observed from the slope a2 of the retreat curve.

[0036] The information obtained from the force curve is the relative hardness of the sample S with respect to the cantilever 113. For example, in a case where the cantilever 113 is too hard with respect to the sample S, the amount of displacement of the cantilever 113 becomes small regardless of the hardness of the sample S. In a case where the cantilever 113 is too soft with respect to the sample S, the sample S cannot be deformed by the probe 114, and thus the amount of movement of the sample S is equivalent to the amount of displacement of the cantilever 113 regardless of the hardness of the sample S. Therefore, in a case where the cantilever 113 is too hard or too soft with respect to the sample S, the hardness of the sample S is not sufficiently reflected in the amount of displacement of the cantilever 113, and thus the hardness of the sample S cannot be correctly observed. Therefore, the user needs to select the cantilever 113 having an appropriate hardness depending on the sample S. However, it is difficult for a user who lacks experience to determine whether the cantilever is appropriate for the sample to be measured.

[0037] The computer 20 is configured to notify the user of the advice information indicating the evaluation result of the cantilever 113 through the display 30 in order to assist the selection of the cantilever 113. The following describes the configuration.

[0038] [Process of the computer 20] Figure 4 is a flowchart indicating a process performed by the computer 20 related to the first embodiment. Figure 4 The processing steps illustrated (hereinafter, simply referred to as "S") are implemented by the processor 22 executing a program stored in the memory 24. In addition, the processing steps illustrated are implemented by the processor 22 executing a program stored in the memory 24. Figure 4 The processing illustrated is started, for example, when the user selects execution of a prescribed application in order to determine whether the cantilever 113 is appropriate.

[0039] In S101, the computer 20 sets the position (X, Y) of the sample stage 112 to an arbitrary position (Xa, Ya) set in advance.

[0040] In S102, the computer 20 instructs the scanning probe microscope 1 to move the position of the sample stage 112 to a set position.

[0041] In S103, the computer 20 executes a process for making a force curve. Specifically, the computer 20 sends a start signal of force curve measurement to the feedback signal generator 131. The feedback signal generator 131 receives the start signal, and after bringing the sample stage 112 close to the cantilever 113, controls the Z scanner 111z to switch the moving direction of the sample stage 112 from the direction of approaching the cantilever 113 to the direction of moving away, based on the deflection amount having reached a pre-set set value. The computer 20 acquires the moving amount of the sample stage 112 and the displacement amount of the cantilever 113 during driving of the Z scanner 111z. Thus, the computer 20 makes a force curve as illustrated. Figure 3

[0042] In S104, the computer 20 calculates a gradient value a from the made force curve. The gradient value a is a value indicating the variation amount of the displacement of the cantilever 113 with respect to the moving amount of the sample stage 112 caused by the Z scanner 111z during the displacement of the cantilever 113. In the first embodiment, the computer 20 calculates the gradient value a as the slope al of the approach curve. Referring to Figure 3 , the slope al of the approach curve is calculated according to Equation (1).

[0043] [Equation 1]

[0044] FM, Fml, Zm, and Zl in Equation (1) are the maximum repulsive force received by the cantilever 113, the attractive force received by the cantilever 113 at the jump-in, the position of the sample stage 112 in the Z-axis direction at the time when the cantilever 113 receives the maximum repulsive force, and the position of the sample stage 112 in the Z-axis direction at the time of the jump-in, respectively. As indicated in Equation (1), the slope al of the approach curve is calculated by dividing the moving amount in the Z-axis direction during the period from the jump-in to the time when the force received by the cantilever 113 becomes maximum by the variation amount of the force received by the cantilever 113.

[0045] Returning to Figure 4 In S111, the computer 20 determines whether the gradient value a is greater than a first threshold value Tl. The first threshold value Tl is a gradient value indicating that the sample S cannot be sufficiently deformed by the probe 114.

[0046] In a case where it is determined that the gradient value a is greater than the first threshold value Tl (YES in S111), in S112, the computer 20 notifies information recommending use of a harder cantilever through the display 30, and ends the process.

[0047] ​When the computer 20 determines that the gradient value a is equal to or lower than the first threshold value Tl (NO in Sll l), it determines whether the gradient value a is smaller than a second threshold value T2 in S113. The second threshold value T2 is a gradient value lower than the first threshold value Tl and indicates that the cantilever 113 is too hard and does not sufficiently displace with respect to the movement amount.

[0048] When the computer 20 determines that the gradient value a is smaller than the second threshold value T2 (YES in S113), it notifies, through the display 30, information recommending the use of a softer cantilever in S114, and ends the process.

[0049] When the computer 20 determines that the gradient value a is equal to or larger than the second threshold value T2 (NO in S113), it notifies, through the display 30, that the hardness of the cantilever 113 is appropriate in S115, and ends the process.

[0050] Further, the computer 20 can notify, through the display 30, information indicating that the rigidity of the cantilever 113 is inappropriate only when the gradient value a is larger than the first threshold value Tl. Further, it can notify, through the display 30, information indicating that the rigidity of the cantilever 113 is inappropriate only when the gradient value a is smaller than the second threshold value T2. Further, the information notified can be only information indicating that it is inappropriate.

[0051] Further, the gradient value a can be the slope a2 of the retraction curve as long as it is a value corresponding to the displacement amount of the cantilever 113 with respect to the movement amount of the sample stage 112 during the displacement of the cantilever 113. The slope a2 of the retraction curve is found with reference to Figure 3 to Formula (2).

[0052] [Formula 2]

[0053] Fm2 and Z2 in Formula (2) are the gravitational force received by the cantilever 113 at the time of jumping and the position of the Z axis of the sample stage 112 at the time of jumping, respectively. As shown in Formula (2), the slope a2 of the retraction curve is found by dividing the movement amount of the Z axis during the period from when the force received by the cantilever 113 becomes maximum to the time of jumping by the variation in the force received by the cantilever 113.

[0054] The gradient value a is simply a variation in the amount of displacement of the cantilever 113 with respect to the movement amount in the Z-axis direction during displacement of the cantilever 113. For example, the variation in the amount of displacement of the cantilever 113 can also be a variation in the amount of displacement of the cantilever 113. Further, the gradient value a can also be a slope of the approach curve in an arbitrary interval from when the cantilever 113 jumps in to when the force received by the cantilever 113 becomes maximum. Further, the gradient value a can also be a slope of the retreat curve in an arbitrary interval from when the force received by the cantilever 113 becomes maximum to when the cantilever 113 jumps out. In the case where the amount of displacement and the movement amount are not in a proportional relationship, the computer 20 can also calculate the gradient value by linear approximation.

[0055] Further, the first threshold value T1 and the second threshold value T2 can be simply set in advance, for example, by a vendor or the like that provides the scanning probe microscope 1 or the cantilever 113, and further, can be set in advance by a user of the scanning probe microscope 1.

[0056] For example, the first threshold value T1 and the second threshold value T2 are set based on a gradient value calculated from a force curve obtained by measuring a plurality of samples having different hardnesses, and a state of the surface of the sample after the force curve is obtained, and the like. As an example, the second threshold value T2 is set to a gradient value between a gradient value when damage is generated and a gradient value when damage is not generated, depending on whether or not damage is generated on the surface of the sample after the force curve is obtained.

[0057] Further, Figure 4 S104 and S111 to S115 can also be executed in a case where a force curve is created at at least one point on the surface of the sample. For example, the computer 20 can also execute S104 and S111 to S115 in a case where a force curve is created for the purpose of evaluating the mechanical characteristics of the sample S, rather than for the purpose of evaluating the cantilever. Figure 4 S104 and S111 to S115, and evaluate whether or not the cantilever 113 used is appropriate.

[0058] In the first embodiment, the computer 20 notifies, via the display 30, the suggestion information indicating that the hardness (stiffness) of the cantilever 113 is not appropriate, based on the gradient value a calculated from the force curve, in at least one of a case where the gradient value a is greater than the first threshold value T1 or a case where the gradient value a is less than the second threshold value T2. The user can more easily select an appropriate cantilever according to the sample S based on the information notified.

[0059] In the first embodiment, the computer 20 notifies, through the display 30, information recommending use of a cantilever harder (higher rigidity) than the cantilever 113 currently in use, in a case where the gradient value a is greater than the first threshold value Tl. The user can consider changing to a cantilever harder than the cantilever 113 currently in use, based on the notified information. Since the rigidity of the cantilever is defined by the spring constant, the user can consider changing to a cantilever having a greater spring constant than the cantilever 113 currently in use, based on the notified information.

[0060] In the first embodiment, the computer 20 notifies, through the display 30, information recommending use of a cantilever softer (lower rigidity) than the cantilever 113 currently in use, in a case where the gradient value a is less than the second threshold value T2. The user can consider changing to a cantilever softer than the cantilever 113 currently in use, based on the notified information. More specifically, the user can consider changing to a cantilever having a smaller spring constant than the cantilever 113 currently in use, based on the notified information.

[0061] In the first embodiment, the computer 20 uses the slope al of the approach curve as the gradient value a. The slope al of the approach curve is a value corresponding to the amount of change in the amount of displacement of the cantilever 113 with respect to the amount of movement in the Z-axis direction during the period when the sample S is approaching the probe 114 and the cantilever 113 is being displaced. Although the sample S deforms following the force applied to the sample S and the cantilever 113 is displaced, generally, the followability of the displacement of the cantilever 113 with respect to the force applied to the sample S is higher at the approach than at the retreat. Therefore, by using the slope al of the approach curve as the gradient value a, the computer 20 can more correctly evaluate the relative rigidity of the cantilever 113 with respect to the sample S.

[0062] [Second Embodiment] In the first embodiment, evaluation of whether the rigidity of the cantilever 113 is suitable for the structure of the sample S as the measurement target based on the force curve obtained by the computer 20 measuring one position on the surface of the sample S is described.

[0063] In the second embodiment, an example of evaluating the rigidity of the cantilever 113 based on a plurality of gradient values obtained by measuring a plurality of positions on the surface of the sample S is described. Specifically, the computer 20 scans the sample stage 112 in the XY direction of the sample S, performs force curve measurement at a plurality of positions on the XY plane, and calculates the gradient value at each position on the XY plane. The computer 20 calculates a feature quantity corresponding to the gradient value based on the distribution of the gradient value at each position, and evaluates the cantilever 113 based on the calculated feature quantity. Figure 5 is a flowchart showing the process performed by the computer relating to the second embodiment. In addition, the description of the process common to the process described in the first embodiment is omitted.

[0064] In the second embodiment, as an example, the scanning range of the sample S is set to X0< X < Xmax, Y0< Y < Ymax. Further, the distance between adjacent measurement points is set to a prescribed value b.

[0065] In S101a, the computer 20 sets the position (X, Y) of the sample stage 112 to the initial position (X0, Y0).

[0066] S102a to S104a are common to S102 to S104 relating to the first embodiment, and therefore the explanation of S102a to S104a is omitted. That is, in S102a to S104a, the computer 20 creates a force curve at the set position (X, Y), and calculates the gradient value a at the set position from the created force curve.

[0067] In S105a, the pixel value of the position of the distribution map corresponding to the set position is set to the gradient value a.

[0068] In S106a, the computer 20 determines whether X is Xmax or more. In the case where 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.

[0069] In the case where X is Xmax or more (YES in S106a), the computer 20 determines whether Y is Ymax or more in S108a. In the case where Y is less than Ymax (NO in S108a), the computer 20 sets X = X0, Y = Y + b in S109a, executes S102a to S105a, and enters S108a after repeating S102a to S107a until X reaches Xmax. The computer 20 repeats S102a to S109a until Y reaches Ymax. Thus, the gradient value at each position on the XY plane is calculated, and a distribution map is created.

[0070] In S10a, the computer 20 executes the cantilever evaluation process. With regard to the cantilever evaluation process, refer to Figure 6 which is described later.

[0071] In S120a, the computer 20 displays the distribution map created in S101a to S108a and the evaluation result obtained in S10a on the display 30, and ends the process.

[0072] Figure 6 is a flowchart showing the cantilever evaluation process executed by the computer.

[0073] In S110a, computer 20 calculates the mode A of the gradient value a. Computer 20 calculates the gradient values ​​at various locations on the XY plane by executing S101a to S108a. Based on the multiple calculated gradient values ​​a, computer 20 calculates the mode A of the gradient value a.

[0074] In S111a, the computer 20 determines whether the value is greater than the first threshold T1. Furthermore, S111a and S113a are common to S111 and S113 of the first embodiment, except that the object compared with the first threshold T1 and the second threshold T2 is the mode A. Moreover, S112a, S114a, and S115a are common to S112, S114, and S115 of the first embodiment, except that they only determine the information to be notified. Therefore, the description of S111a to S115a is omitted. After executing S112a, S114a, or S115a, the computer 20 returns... Figure 5 The processing is performed, and S120a is executed.

[0075] Figure 7 This is a diagram illustrating an example of a screen displayed on a monitor. Screen 300 is displayed on monitor 30 by computer 20 executing S120. Screen 300 includes a distribution graph 310 of gradient value a, a histogram 320 of gradient value a, and suggestion information 330.

[0076] Recommendation information 330 is an evaluation result obtained in the cantilever evaluation process, indicating whether the cantilever's stiffness is appropriate.

[0077] In the second embodiment, the computer 20 calculates the feature quantity corresponding to the gradient value a based on the distribution of the gradient value a, and evaluates the cantilever 113 based on the calculated feature quantity. The hardness of the sample S at various locations on its surface has a distribution. Therefore, even if the hardness at a certain location on the surface of the sample S is suitable for the hardness of the cantilever 113, the hardness at other locations may not be suitable. In the second embodiment, by calculating the gradient values ​​at multiple different locations on the surface of the sample S and evaluating the cantilever 113 based on the distribution of multiple gradient values, it is easier to select a cantilever 113 suitable for the entire surface of the sample S.

[0078] in addition, Figure 6 The cantilever evaluation process shown can also be performed when force curves are generated at multiple locations on the sample surface to evaluate the mechanical properties of sample S. That is, it can also be performed when force curves are generated at multiple locations for the purpose of evaluating the mechanical properties of sample S, rather than for evaluating the cantilever. Figure 6The cantilever evaluation process shown is performed to evaluate whether the cantilever 113 used is appropriate. In this case, the computer 20 can also be configured to notify the recommendation information only in the case where it is judged that the cantilever 113 used is inappropriate.

[0079] [3rd Embodiment] In the 2nd embodiment, the structure in which the cantilever evaluation process is performed by the computer 20 after the force curve at each position on the XY plane is made is explained.

[0080] In the 3rd embodiment, the structure in which the cantilever evaluation process is performed every time a force curve is made is explained. In the 3rd embodiment, the computer 20 performs the cantilever evaluation process every time a force curve is made in the case where the force curve measurement is performed at a plurality of positions on the XY plane. Figure 8 is a flowchart showing the cantilever evaluation process performed by the computer relating to the 3rd embodiment. In addition, the explanation of the process common to the processes explained in the 1st embodiment and the 2nd embodiment is omitted.

[0081] The computer 20 performs the cantilever evaluation process shown at an arbitrary timing after one force curve is made. Figure 8

[0082] In Sllb, the computer 20 calculates the gradient value a. Sllb is common to S104 relating to the 1st embodiment, so the explanation of Sllb is omitted.

[0083] In S12b, the computer 20 determines whether the gradient value a is the 3rd threshold value T3 or more. The 3rd threshold value T3 is the gradient value in the case where the movement amount of the sample S and the variation amount of the displacement amount of the cantilever 113 coincide. For example, in the case where the ordinate axis of the force curve is the displacement amount of the cantilever 113, the 3rd threshold value T3 is 1.

[0084] In the case where it is judged that the gradient value a is the 3rd threshold value T3 or more (YES in S12b), the computer 20, in S13b, notifies the information recommending the use of a harder cantilever by the display 30, and ends the process.

[0085] In the case where it is judged that the gradient value a is less than the 3rd threshold value T3 (NO in S12b), the computer 20 makes the process proceed to S14b.

[0086] In S14b, the computer 20 determines whether the number of times of the force curve measurement (measurement number) is the predetermined prescribed number n (n≥2, n is an integer) or more. In the case where it is judged that the measurement number is less than the prescribed number n (NO in S14b), the computer 20 ends the process.

[0087] ​The computer 20, in a case where it is determined that the number of determinations is the prescribed number n or more (YES in S14b), causes the process to proceed to S110b.

[0088] In S110b, the computer 20 calculates the mode A of the gradient values a. The process after S110b is executed after a plurality of force curve determinations are performed and a plurality of gradient values a are obtained. The computer 20 calculates the mode A from the plurality of gradient values a obtained.

[0089] After that, the computer 20 executes S111b to S114b and ends the process. Note that S111b to S114b are common to S111a to S114a related to the second embodiment except that the notification information is constituted in S112b and S114b. Therefore, the explanation of S111b to S114b is omitted.

[0090] As described above, in the third embodiment, in a case where the computer 20 performs force curve determinations at a plurality of positions on the XY plane, in a case where the gradient value a at at least one position is the third threshold value T3 or more, the computer 20 notifies the information recommending the use of a harder cantilever. On the other hand, in a case where the gradient value a at each position is less than the third threshold value T3, the computer 20 notifies the information recommending the use of a harder cantilever when the mode A is greater than the first threshold value T1 and the information recommending the use of a softer cantilever when the mode A is less than the second threshold value T2. That is, in a case where the gradient value a at each position is less than the third threshold value T3, the computer 20 evaluates the cantilever 113 based on the distribution of the gradient values at each position.

[0091] The third threshold value T3 is a gradient value in a case where the movement amount of the sample S coincides with the variation amount of the displacement amount of the cantilever 113. The movement amount of the sample S coinciding with the variation amount of the displacement amount of the cantilever 113 means that the surface of the sample S is hard enough compared to the probe 114, and even if the probe 114 is pressed against the sample S, the sample S does not deform but the cantilever 113 is displaced in conjunction with the movement of the sample S. That is, the movement amount of the sample S coinciding with the displacement amount of the cantilever 113 means that the hardness of the sample S is hardly reflected in the displacement amount of the cantilever 113.

[0092] In the third embodiment, the computer 20, in a case where it can be determined that the hardness of the sample S is not significantly reflected in the displacement amount of the cantilever 113, notifies the evaluation result of the cantilever 113 based on the result of the force curve determination at one position on the surface of the sample S. On the other hand, in a case where the hardness of the sample S is reflected in the displacement amount of the cantilever 113, the computer 20 determines whether the degree of reflection is sufficient based on the determination result of each position of the sample surface. Therefore, the user can consider the change of the cantilever 113 without performing determinations beyond the necessary number of times, and thus the time required for the selection of the cantilever 113 can be shortened.

[0093] [Mode] The person skilled in the art will understand that the above-described embodiments are specific examples of the following modes.

[0094] (1) A scanning probe microscope of a mode including: a cantilever having one end fixed and the other end provided with a probe; a sample stage for placing a sample; a drive section that changes the distance between the sample and the probe by relatively moving the sample stage and the cantilever; a displacement measuring section for measuring the displacement of the cantilever; a notification section for notifying a user of prescribed information; and a control section. In this case, the control section calculates a gradient value that indicates the variation in the amount indicating the displacement of the cantilever with respect to the amount of movement caused by the drive section during the displacement of the cantilever, and the control section can 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 through the notification section in at least one of the cases where a characteristic value corresponding to the gradient value is greater than a first threshold value or the characteristic value is less than a second threshold value that is lower than the first threshold value.

[0095] The scanning probe microscope according to the first aspect can allow the user to more easily select an appropriate cantilever for the sample based on the notification of the advice information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage.

[0096] In addition, the "characteristic value corresponding to the gradient value" can be the "gradient value" itself as long as it corresponds to the gradient value.

[0097] (2) In the scanning probe microscope according to the first aspect, the control section can notify the user of information recommending that the cantilever be changed to a cantilever having a rigidity higher than that of the cantilever as the advice information in the case where the characteristic value is greater than the first threshold value.

[0098] The scanning probe microscope according to the second aspect can allow the user to consider changing the cantilever to a cantilever harder than the currently used cantilever based on the notified information.

[0099] (3) In the scanning probe microscope according to the first or second aspect, the control section can notify the user of information recommending that the cantilever be changed to a cantilever having a rigidity lower than that of the cantilever as the advice information in the case where the characteristic value is less than the second threshold value.

[0100] The scanning probe microscope according to the third aspect can allow the user to consider changing the cantilever to a cantilever softer than the currently used cantilever based on the notified information.

[0101] (4) In the scanning probe microscope according to any one of (1) to (3), the gradient value can also indicate a variation in the amount of displacement of the cantilever with respect to the amount of movement caused by the driving section during a period in which the sample is being brought closer to the probe by the driving section and during a period in which the cantilever is displaced.

[0102] According to the scanning probe microscope of (4), since information during a period in which the sample is being brought closer to the probe with high followability of displacement of the cantilever with respect to a force applied to the sample is used, the relative stiffness of the cantilever 113 with respect to the sample can be evaluated more correctly.

[0103] (5) In the scanning probe microscope according to any one of (1) to (4), the driving section relatively scans the cantilever with respect to a sample stage in a direction along a placement surface of the sample stage on which a sample is placed, the displacement measuring section measures displacement of the cantilever at a plurality of positions in a scanning direction of the cantilever, the control section calculates a gradient value at each position in the scanning direction, and the control section can calculate the characteristic quantity based on a distribution of the gradient value at each position in the scanning direction.

[0104] According to the scanning probe microscope of (5), a user can easily select a cantilever suitable for a surface of a sample in which the hardness has a distribution at each position on the surface.

[0105] (6) In the scanning probe microscope according to (5), the control section, in a case where the gradient value at any one of the plurality of positions is equal to or greater than a first threshold value and equal to or greater than a third threshold value, notifies, as the recommendation information, information recommending that the cantilever be changed to a cantilever having higher rigidity than the cantilever through the notification section, and the control section can also, in a case where the gradient value at each position in the scanning direction is less than the third threshold value and the characteristic quantity is less than a second threshold value, notify, as the recommendation information, information recommending that the cantilever be changed to a cantilever having lower rigidity than the cantilever through the notification section.

[0106] According to the scanning probe microscope of (6), since the recommendation information is notified in a case where the gradient value at one position is equal to or greater than the third threshold value, a user can consider a change in the cantilever without performing calculation of the gradient value beyond a necessary number of times, and thus the time required for selection of the cantilever can be shortened.

[0107] (7) An evaluation method of a cantilever, which is an evaluation method of a cantilever of a scanning probe microscope including the cantilever, a sample stage on which a sample is placed, a driving section, and a displacement measuring section, wherein one end of the cantilever is fixed, and the other end is provided with a probe, the driving section changes the distance between the sample and the probe by relatively moving the sample stage with respect to the cantilever, and the displacement measuring section measures the displacement of the cantilever, and the evaluation method can include: a step of calculating a gradient value indicating the variation in the amount indicating the displacement of the cantilever with respect to the amount of movement caused by the driving section during the displacement of the cantilever; and a step of notifying, in at least one of a case where a characteristic value corresponding to the gradient value is greater than a first threshold value or a case where the characteristic value is smaller than a second threshold value lower than the first threshold value, suggestion information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage.

[0108] The evaluation method of the cantilever according to (7) can allow a user to more easily select an appropriate cantilever according to a sample based on the notification of the suggestion information indicating that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage.

[0109] (8) A recording medium of a type that can be a computer-readable recording medium in which a program causing a computer to execute the evaluation method of the cantilever according to (7) is recorded.

[0110] (9) A program of a type that can be a program causing a computer to execute the evaluation method of the cantilever according to (7).

[0111] The embodiments disclosed herein are intended to be within the scope of the technical idea and can be appropriately combined within a range in which the technical idea does not contradict. It should be considered that the embodiments disclosed herein are illustrative and not restrictive in all points. The scope of the present application is not represented by the above-described embodiments but by the claims, and it is intended to include all modifications within the meaning and range equivalent to the claims.

[0112] Explanation of Reference Signs 1 scanning probe microscope, 10 measuring device, 20 computer, 22 processor, 24 memory, 26 input / output I / F, 30 display, 40 input device, 111 piezoelectric scanner, 111xy XY scanner, 111z Z scanner, 112 sample stage, 113 cantilever, 114 probe, 115 laser diode, 119 photodetector, 120 displacement measuring section, 131 feedback signal generating section, 133 scanning signal generating section, 300 screen, 310 distribution chart, 320 histogram, 330 suggestion information, S sample.

Claims

1. A scanning probe microscope, characterized in that, have: A cantilever, with one end fixed and the other end equipped with a probe; Sample stage, used to place samples; The drive unit changes the distance between the sample and the probe by moving the sample stage relative to the cantilever. A displacement measuring unit is used to measure the displacement of the cantilever. The notification department is used to notify users of specified information. as well as Control Department The control unit calculates a gradient value, which represents the change in the amount of displacement of the cantilever relative to the amount of movement caused by the drive unit during the displacement of the cantilever. In at least one of the following cases, where the feature value corresponding to the gradient value is greater than a first threshold or the feature value is less than a second threshold lower than the first threshold, the notification unit notifies the user of a suggestion that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage.

2. The scanning probe microscope according to claim 1, characterized in that, When the feature quantity is greater than the first threshold, the control unit notifies the notification unit of information recommending that the cantilever be changed to a cantilever with higher rigidity than the cantilever, as the suggestion information.

3. The scanning probe microscope according to claim 1 or 2, characterized in that, When the characteristic quantity is less than the second threshold, the control unit notifies the notification unit of information recommending that the cantilever be changed to a cantilever with lower stiffness as the suggestion information.

4. The scanning probe microscope according to claim 1 or 2, characterized in that, The gradient value represents the amount of change relative to the amount of movement caused by the drive unit during the period when the sample is brought closer to the probe by the drive unit and during the period when the cantilever is displaced.

5. The scanning probe microscope according to claim 1 or 2, characterized in that, The drive unit performs a relative scan of 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 measuring unit measures the displacement of the cantilever at multiple positions along the scanning direction of the cantilever. The control unit calculates the gradient value at each position along the scanning direction. The feature quantity is then calculated based on the distribution of the gradient values ​​at each position along the scanning direction.

6. The scanning probe microscope according to claim 5, characterized in that, If the gradient value at any of the plurality of positions is a third threshold or higher than the first threshold, the control unit notifies the notification unit of information recommending that the cantilever be changed to a cantilever with higher stiffness than the current cantilever as the suggestion information. If the gradient value at each position in the scanning direction is less than the third threshold and the feature quantity is less than the second threshold, the notification unit will notify the user of information recommending that the cantilever be changed to a cantilever with lower rigidity than the cantilever, as the recommendation information.

7. A method for evaluating cantilever arms, specifically for evaluating cantilever arms of scanning probe microscopes, characterized in that... The scanning probe microscope has the following features: A cantilever, with one end fixed and the other end equipped with a probe; Sample stage, used to place samples; The drive unit changes the distance between the sample and the probe by moving the sample stage relative to the cantilever. as well as The displacement measuring unit is used to measure the displacement of the cantilever. The evaluation methods include: The step of determining the gradient value, which represents the change in the amount of displacement of the cantilever relative to the amount of movement caused by the drive unit during the displacement of the cantilever; and The step of notifying the user of a suggestion that the rigidity of the cantilever is not suitable for the rigidity of the sample placed on the sample stage is initiated when the feature quantity corresponding to the gradient value is greater than a first threshold or when the feature quantity is less than a second threshold lower than the first threshold.

Images