Scanning Probe Microscope

Abstract

When measuring a force curve, a control device (100) controls a deflection amount (D2) that is a pressing amount for the pressing of a cantilever (12) against a sample (S) to a deflection amount (D1) that is a target value (DT) on the basis of set values (DS1, DS2) for the pressing amount. When measuring the force curve, the control device (100) changes set value (DS1) to set value (DS2) on the basis of a deflection amount (D3) that is differential data indicating the difference between the deflection amount (D1) that was the target value (DT) and the deflection amount (D2) that was the actual pressing amount for force curve measurement performed in the past.

Description

[Technical field]

[0001] The present invention relates to a scanning probe microscope. [Background technology]

[0002] In a scanning probe microscope, a cantilever including a probe is placed facing a sample. In a scanning probe microscope, the sample is observed with the cantilever and the sample brought close to each other. One example of a conventional scanning probe microscope is one that allows the probe to be stably installed and maintained at a position on a force curve where the atomic force is weak (Patent Document 1). The force curve is data that indicates the relationship between the distance between the probe and the sample and the force acting between the cantilever and the sample (the amount of deflection of the cantilever).

[0003] In conventional scanning probe microscopes, it is possible to measure the force curve by pressing a cantilever against a sample and then moving the cantilever away from the sample. Once the force curve is measured, information about the sample, such as the elastic modulus of the sample, can be obtained based on the measured force curve.

[0004] In conventional scanning probe microscopes, when measuring a force curve, a target value for the amount by which the cantilever is pressed against the sample (the amount of deflection of the cantilever) is set as a set value controlled by the control device of the scanning probe microscope. In measuring a force curve in a scanning probe microscope, the amount by which the cantilever is pressed against the sample (hereinafter referred to as the pressing amount) is detected, and the control device moves the probe and the sample closer together until the detected value of the pressing amount reaches the set value, and once the detected value of the pressing amount reaches the set value, the control device moves the probe and the sample away from each other, thereby obtaining a force curve. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3883790 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional scanning probe microscopes, when a force curve is measured, the control device initiates an operation to move the probe away from the sample when the detected value of the pressing amount reaches a set value.

[0007] However, for example, in a situation where the speed at which the sample and the cantilever are brought closer together is faster than a reference speed, even if the control device executes control to start the operation of moving the probe and the sample away from each other when the detected value of the amount of pressure (amount of deflection of the cantilever) reaches a set value, a time lag will occur between the time when the detected value of the amount of pressure reaches the set value and the time when the operation of bringing the probe and the sample closer together actually stops.

[0008] If such a time lag in control occurs, there is a problem in that when a force curve is measured, a clear difference occurs between the target value of the pressing amount and the actual pressing amount.

[0009] This invention has been made to solve such problems, and its purpose is to reduce the difference between the target amount of pressure and the actual amount of pressure when pressing a cantilever against a sample when measuring a force curve. [Means for solving the problem]

[0010] A scanning probe microscope according to one aspect of the present invention includes a sample stage on which a sample is placed, a cantilever including a probe, and a control device. The cantilever is disposed facing the sample stage. When measuring a force curve, the control device controls the pressing amount when pressing the cantilever against the sample to a target value based on a set value of the pressing amount, and when measuring a force curve, changes the set value based on difference data indicating the difference between the target value and the actual pressing amount in a force curve measurement performed in the past. Effect of the Invention

[0011] When measuring a force curve, it is possible to reduce the difference between a target value for the amount of pressure applied when the cantilever is pressed against the sample and the actual amount of pressure applied. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing the main structure and control circuitry of a scanning probe microscope 1. FIG. [Diagram 2] 4A to 4C are diagrams showing the operating state of the scanning probe microscope 1 over time when a force curve is measured. [Diagram 3] FIG. 13 is a diagram showing an example of a force curve measurement. [Figure 4] FIG. 2 is a diagram showing an example of a force curve measurement, divided into an approach line A and a release line B. [Diagram 5] 13 is a diagram showing a method for adjusting a set value DS of the maximum amount of deflection D in the case where the maximum value of the amount of deflection D on the approach line A exceeds a target value DT. FIG. [Figure 6] 13 is a diagram showing a method for adjusting a set value DS of the maximum amount of deflection D when the maximum value of the amount of deflection D on the approach line A is short of a target value DT. FIG. [Figure 7] 13 is a flowchart of a setting value adjustment process when measuring a force curve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are given the same reference characters, and their descriptions will not be repeated in principle.

[0014] [Main structure and control circuit configuration of scanning probe microscope 1] Fig. 1 is a diagram showing the main structure and control circuitry of a scanning probe microscope 1. In Fig. 1, the main structure of the scanning probe microscope 1 is shown in a side view, and the control circuitry is shown in a block diagram.

[0015] In the following description, the contact surface of the scanning probe microscope 1 is defined as the XY plane, and the axis perpendicular to the XY plane is defined as the Z axis.

[0016] With reference to FIG. 1, a scanning probe microscope 1 comprises, as main components, a cantilever 12, a support device 13, a sample stage 14, a laser light source 15, a photodetector 16, a Z-direction actuator 141, an XY-direction actuator 142, and a control device 100.

[0017] A sample S is placed on the sample stage 14. A Z-direction actuator 141 that moves the sample stage 14 in the vertical direction (Z direction) is provided below the sample stage 14. An XY-direction actuator 142 that moves the sample stage 14 and the Z-direction actuator 141 in the X and Y directions is provided below the Z-direction actuator 141.

[0018] A position changing device is configured by the Z direction actuator 141 and the XY direction actuator 142. Both the Z direction actuator 141 and the XY direction actuator 142 have piezoelectric elements. The Z direction actuator 141 and the XY direction actuator 142 have their positions controlled in the Z direction and the XY direction by voltages applied to the piezoelectric elements that they each have.

[0019] Cantilever 12 is provided so as to be located above sample S placed on sample stage 14 during measurement of sample S. Cantilever 12 has probe 11 on the surface facing sample S at tip 121, which is one end side. Cantilever 12 has rear end 122, which is the other end side, fixed to support device 13 extending in the Z direction. When pressed against sample S, for example, cantilever 12 is flexible and can bend in the Z direction.

[0020] A laser light source 15 and a light receiver 16 are provided above the cantilever 12. When measuring a sample S, the laser light source 15 irradiates laser light LA ​​toward the back side of the tip 121 of the cantilever 12. The back side of the cantilever 12 is the surface opposite to the front side facing the sample S.

[0021] The photoreceiver 16 is a sensor that detects laser light. The photoreceiver 16 is provided at a position where it can receive the laser light LA ​​reflected by the back surface of the tip 121 of the cantilever 12. The photoreceiver 16 receives and detects the laser light LA ​​reflected by the back surface of the tip 121 of the cantilever 12.

[0022] As a device for changing the distance between the sample S and the tip 121 of the cantilever 12, in addition to the Z-direction actuator 141 that moves the sample stage 14 in the Z direction as shown by the solid line in Figure 1, a movable support device 13 that moves the cantilever 12 in the Z direction may also be used.

[0023] Such a movable support device 13 includes, inside the support device 13, a motor 19 as shown by the dashed line, a conversion mechanism that converts the rotational motion of a gear attached to the drive shaft of the motor 19 into linear motion in the Z direction, as in a rack-and-pinion mechanism, and a movable body provided on top of the conversion mechanism. The rear end 122 of the cantilever 12 is fixedly attached to the movable body. The cantilever 12 may be configured to move in the Z direction as the movable body moves in the Z direction.

[0024] As a device for changing the distance between the sample S and the tip 121 of the cantilever 12, only the Z-direction actuator 141 may be provided, only the movable support device 13 may be provided, or both of these two devices may be provided.

[0025] The control device 100 is realized by hardware such as a CPU (Central Processing Unit) and a memory, and software that performs the arithmetic processing described below.

[0026] The control device 100 controls the operation of each component constituting the scanning probe microscope 1. The control device 100 is configured according to a general-purpose computer architecture, as an example. Note that the control device 100 may be implemented in the scanning probe microscope 1 using dedicated hardware. The control device 100 includes a processor 101 and a memory 102. A display device 103 and an input device 104 are connected to the control device 100.

[0027] The control device 100 may be configured to include a display device 103 and an input device 104 in addition to the processor 101 and the memory 102 .

[0028] The processor 101 is typically a CPU (Central Processing Unit). P The processor 101 is an arithmetic processing unit such as a memory 102 (memory 102a), a microprocessing unit (MPU), or the like. The processor 101 reads out and executes programs stored in the memory 102, thereby implementing each of the processes of the control device 100, which will be described later. 1 In this example, a configuration in which there is a single processor is illustrated, but the control device 100 may have multiple processors.

[0029] The memory 102 is realized by a non-volatile memory such as a random access memory (RAM), a read only memory (ROM), and a flash memory. The memory 102 stores programs executed by the processor 101, data used by the processor 101, and the like. For example, the memory 102 stores various programs such as a program for executing the processes shown in FIG. 7.

[0030] In addition, memory 102 may be a CD-ROM (Compact Disc-Read Only Memory), a DVD-ROM (Digital Versatile Disk-Read Only Memory), a USB (Universal Serial Bus) memory, a memory card, a FD (Flexible Disk), a hard disk, an SSD (Solid State Drive), a magnetic tape, a cassette tape, an MO (Magnetic Optical Disc), an MD (Mini Disc), an IC (Integrated Circuit) card (excluding memory cards), an optical card, a mask ROM, or an EPROM, as long as it is capable of non-temporarily recording a program in a format readable by control device 100, which is a type of computer.

[0031] Display device 103 is configured with a liquid crystal display panel, etc. Display device 103 displays, for example, a setting screen for making various settings for performing measurement with scanning probe microscope 1, a screen showing the status during measurement with scanning probe microscope 1, and a screen showing the measurement results measured with scanning probe microscope 1.

[0032] The input device 104 is configured with a mouse, a keyboard, etc. The input device 104 is an input interface that receives information input via the input device 104. Note that the control device 100 may be equipped with a touch panel in which the display device 103 and the input device 104 are integrated.

[0033] The control device 100 sends a control signal to an optical system driving device (not shown). The optical system driving device drives the laser light source 15 and the photoreceiver 16 in response to the control signal. This executes light emission control and position control of the laser light source 15, and executes position control of the photoreceiver 16. The photoreceiver 16 outputs detection information of the laser light LA ​​to the control device 100.

[0034] The control device 100 sends a control signal to an actuator driving device (not shown), and the actuator driving device applies voltages to the piezoelectric elements of the Z-direction actuator 141 and the XY-direction actuator 142 in response to the control signal, thereby controlling the driving of the Z-direction actuator 141 and the XY-direction actuator 142. In this way, the control device 100 can execute control to change the relative positional relationship between the cantilever 12 and the sample S.

[0035] The control device 100 sends a control signal to an actuator driving device (not shown), and the actuator driving device drives the Z-direction actuator 141 and the XY-direction actuator 142 by applying voltages to the piezoelectric elements of the Z-direction actuator 141 and the XY-direction actuator 142 in accordance with the control signal.

[0036] Based on the detection information input from the photoreceiver 16, the control device 100 identifies the incident position of the laser light LA ​​detected by the photoreceiver 16, and based on that input position, calculates the Z-direction position of the tip 121 of the cantilever 12, i.e., the Z-direction deflection amount D of the cantilever 12.

[0037] In addition, when a movable support device 13 that moves the cantilever 12 in the Z direction is used as a device for changing the distance between the sample S and the tip 121 of the cantilever 12, the control device 100 drives and controls a motor 19 as shown by the dashed line.

[0038] [Method of measuring force curve] Next, a method for measuring a force curve using the scanning probe microscope 1 will be described.

[0039] Fig. 2 is a diagram showing the operation state of the scanning probe microscope 1 over time when a force curve is measured, and Fig. 3 is a diagram showing an example of a force curve measurement.

[0040] 2(a) to 2(e), when measuring a force curve, the sample stage 14 is moved in the Z direction by the Z direction actuator 141. This changes the position of the rear end 122 in the Z direction with respect to the surface of the sample S.

[0041] The control device 100 determines the Z-direction position Z of the rear end portion 122 based on the voltage value applied to the piezoelectric element of the Z-direction actuator 141. 2 The position where the laser beam LA is incident on the light receiver 16 differs depending on the position of the tip 121 of the cantilever 12 in the Z direction. Thus, the control device 100 can obtain the Z-direction position Z 1 In this way, the control device 100 determines the Z-direction position Z1 of the tip end 121 and the Z-direction position Z2 of the rear end 122 of the cantilever 12, and determines the amount of deflection D of the cantilever 12 based on the difference between them (Z1-Z2).

[0042] The amount of deflection D of the cantilever 12 is also data that can specify the amount of pressure applied when the cantilever 12 is pressed against the sample S.

[0043] 3, when measuring a force curve, the control device 100 moves the sample stage 14 so that the probe 11 approaches the surface of the sample S until the position of the rear end 122 of the cantilever 12 in the Z direction reaches the maximum position Zf of the deflection amount D, which is the set value DS of the maximum value of the deflection amount D of the cantilever 12. Thereafter, the control device 100 moves the sample stage 14 so that the position of the rear end 122 of the cantilever 12 in the Z direction returns to the initial position Zi.

[0044] Thus, the movement range of the sample stage 14 in the Z direction is conditioned to be between the initial position Zi and the maximum position Zf described above. In addition to this condition of the movement range, in order to prevent the sample stage 14 from moving due to an erroneous operation and the probe 11 from colliding with the sample stage 14 when the sample S is not placed on the sample stage 14, a limit position that is the movement limit of the sample stage 14 is set in the Z direction. That is, when the deflection amount D of the cantilever 12 does not reach the maximum deflection amount setting value DS even when the position of the sample stage 14 in the Z direction reaches the limit position, the control device 100 moves the sample stage 14 so that the sample stage 14 returns to the initial position Zi without reaching the maximum position Zf.

[0045] In the following description, the deflection amount D is defined as follows, assuming that the Z-direction position of the tip 121 when the cantilever 12 is not deflected is the initial position Z1i, and the actual position of the tip 121 when the force curve is measured is Z1. For example, assuming that the direction from the cantilever 12 toward the sample stage 14 is the positive direction of the Z-direction coordinate, and assuming that Z0 is Z1i-Z2, which is the difference in the positive Z-direction position between the initial Z-direction position Z1i of the tip 121 and the Z-direction position Z2 of the rear end 122, the position of which is fixed, in the Z-direction coordinate, the deflection amount D is defined as D=(Z0-(Z1-Z2)). As a result, when the cantilever 12 is deflected so that the tip 121 rises when viewed from the side, the actual position Z1 of the tip 121 moves in the negative direction from the initial position Z1i in the Z-direction coordinate, and therefore Z0>(Z1-Z2), and the deflection amount D becomes a positive value. On the other hand, when the cantilever 12 is bent so that the tip 121 is lowered when viewed from the side, the actual position Z1 of the tip 121 moves in the positive direction from the initial position Z1i in the Z-direction coordinate, so that Z0<(Z1-Z2), and the amount of deflection D becomes a negative value.

[0046] In Fig. 3, the vertical axis of the force curve indicates the amount of deflection D of cantilever 12 or the force F acting on cantilever 12. In Fig. 3, the horizontal axis of the force curve indicates the position Z in the Z direction of rear end 122 of cantilever 12. As shown on the vertical axis of Fig. 3, the amount of deflection D of cantilever 12 is a positive value when a repulsive force acts, and is a negative value when an attractive force acts.

[0047] When measuring a force curve, first, as shown in Fig. 2(a), the sample stage 14 is moved upward from the initial position to bring the tip of the probe 11 closer to the surface of the sample S. As long as the distance between the tip of the probe 11 and the surface of the sample S is to a certain extent, the atomic force between the tip of the probe 11 and the surface of the sample S is negligibly small, so the amount of deflection D continues to be 0 from the initial position Zi, as shown in section (a) of Fig. 3.

[0048] As shown in FIG. 2(b), when the tip of the probe 11 and the surface of the sample S come even closer, the van der Waals force, which is the atomic force between the tip of the probe 11 and the surface of the sample S, becomes large enough that it cannot be ignored. As a result, as shown in FIG. 2(b), the cantilever 12 is bent in a direction in which the tip 121 is lowered due to the action of an attractive force. In this case, the amount of bending of the cantilever 12 becomes a negative value as shown in section (b) of FIG.

[0049] As shown in FIG. 2(c), when the sample stage 14 moves further upward, the rear end 122 of the cantilever 12 approaches the surface of the sample S with the tip of the probe 11 in contact with the surface of the sample S. As a result, as shown in FIG. 2(c), the cantilever 12 bends in a direction in which the tip 121 rises, opposite to the state shown in FIG. 2(b). In this case, the amount of bending D of the cantilever 12 becomes a positive value as shown in section (c) of FIG. 3, and as the tip of the probe 11 is pressed against the surface of the sample S, the cantilever 12 bends so that the absolute value of the amount of bending D increases. Then, as the tip of the probe 11 is pressed against the surface of the sample S, the tip of the probe 11 receives a reaction force from the surface of the sample S, i.e., a repulsive force.

[0050] As shown in section (c) of Fig. 3, when the deflection amount D of the cantilever 12 reaches a preset maximum set value DS, the movement direction of the sample stage 14 is switched from upward to downward as shown in Figs. 2(c) and (d). This causes the deflection amount D to start decreasing as shown in Fig. 3. As shown in Fig. 3, when the deflection amount D of the cantilever 12 reaches the preset maximum set value DS, the rear end 122 of the cantilever 12 reaches the maximum position Zf.

[0051] When the sample stage 14 moves downward, initially, the tip of the probe 11 is in contact with the surface of the sample S, while the rear end 122 of the cantilever 12 moves away from the surface of the sample S. In the cantilever 12, the tip of the probe 11 is attached to the surface of the sample S due to the adhesiveness of the surface of the sample S.

[0052] Due to such adhesion of the surface of the sample S, even when the tip of the probe 11 no longer receives the repulsive force from the surface of the sample S while the sample stage 14 is moving downward, the tip of the probe 11 does not immediately leave the surface of the sample S, and for a while, the cantilever 12 bends in the direction in which the tip 121 descends, as shown in Fig. 2(d). In this case, the amount of bending D of the cantilever 12 becomes a negative value as shown in section (d) of Fig. 3, and as the tip of the probe 11 is pressed against the surface of the sample S, the cantilever 12 bends so that the absolute value of the amount of bending D increases. Then, as the rear end 122 of the cantilever 12 moves away from the surface of the sample S, the tip of the probe 11 receives an attractive force from the surface of the sample S.

[0053] Thereafter, as the amount of bending of tip 121 of cantilever 12 in the downward direction increases, an upward force acts on the tip of probe 11 based on the elastic force caused by the bending, causing the tip of probe 11 to move away from the surface of sample S, as shown in Fig. 2(e). When the tip of probe 11 moves away from the surface of sample S, the bending of cantilever 12 suddenly decreases, and the amount of bending D becomes 0, as shown in section (e) of Fig. 3.

[0054] 2(a) to 2(e), a force curve as shown in FIG. 3 is acquired at one point on the surface of the sample S. Such force curve measurement is performed in the same manner at multiple points on the surface of the sample S. In this way, force curves are measured continuously at multiple points for one sample S.

[0055] The force curve measured in this manner contains, for example, the following information about the surface of the sample S. The force curve obtained in section (c) of FIG. 3 represents the flexibility of the surface of the sample S. The smaller the amount of deflection D that changes as the rear end 122 of the probe 11 of the cantilever 12 approaches the surface of the sample S, the greater the flexibility of the sample S. In other words, the smaller the slope of the force curve in section (c) of FIG. 3, the greater the flexibility of the sample S. The closer the position where the amount of deflection D suddenly decreases in section (d) of FIG. 3 is to the right of the horizontal axis of the force curve, the greater the adhesive force of the sample S to the probe 11.

[0056] [Adjusting the maximum value of the deflection D when measuring the force curve] Next, a method for adjusting the set value DS of the maximum value of the amount of deflection D when measuring a force curve with the scanning probe microscope 1 will be described.

[0057] The adjustment of the set value DS described below is effective when measuring the force curve multiple times for one sample, when measuring the force curve multiple times for multiple samples of the same type, and when measuring the force curve for one sample or multiple samples with similar flexibility, such as samples of different types but with similar flexibility.

[0058] In the following description, the maximum setting value D of the deflection amount D is set using an example of a force curve in the case where no attractive force acts on the cantilever 12, such as in the section (b) of FIG. SA method of adjustment will be described below. For ease of explanation, an example of a force curve in the case where no attractive force acts on the cantilever 12, such as section (b) in FIG.

[0059] <Approach and release lines in the force curve> FIG. 4 is a diagram showing an example of a force curve measurement, divided into an approach line A and a release line B.

[0060] The force curve in Figure 4 differs from that in Figure 3 in the following way: The force curve in Figure 4 is a force curve in the case where no attractive force acts on the cantilever 12, as in section (b) in Figure 3. In the force curve in Figure 4, the position of the origin (D=0) of the vertical axis is intentionally made different in order to make it easier to distinguish between the approach line A and the release line B on the drawing.

[0061] The reason why the approach line A and the release line B are shown in FIG. 4 is because a method of adjusting the set value DS of the maximum amount of flexure D using the approach line A will be described below.

[0062] The force curve can be shown divided into an approach line A and a release line B. The approach line A is data of the force curve that indicates the line in the approach process where the distance between the cantilever 12 and the sample stage 14 is decreased. The release line B is data of the force curve that indicates the line in the release process where the distance between the cantilever 12 and the sample stage 14 is increased. In the following, a method of adjusting the setting value DS of the maximum setting value of the deflection amount D will be explained using the approach line A.

[0063] <When the maximum deflection amount D exceeds the target value DT> FIG. 5 is a diagram showing a method for adjusting the set value DS of the maximum amount of deflection D in the case where the maximum value of the actual amount of deflection D on the approach line A exceeds the target value DT.

[0064] Fig. 5(A) shows an example of an approach line A in an excess state where the maximum value of the actual deflection amount D exceeds the target value DT. Fig. 5(B) shows an example of adjustment of the set value DS of the maximum value of the deflection amount D for the excess state as shown in Fig. 5(A), and an example of the approach line A after the adjustment.

[0065] 5(A), in the control device 100, a target value DT of the maximum value of the deflection amount D is set as a set value DS1. The target value DT is the deflection amount D1. In the control device 100, data of the target value DT (= the deflection amount D1) input from the input device 104 is set as the set value DS1 of the maximum value of the deflection amount D. Then, when measuring the force curve, the control device 100 performs control to switch the moving direction of the sample stage 14 from upward to downward as shown in FIG. 2(c) when the deflection amount D detected as described above increases as shown by the approach line A and reaches the set value DS1.

[0066] However, due to factors such as the relatively high moving speed of the sample stage 14, the sample stage 14 is difficult to stop at the time of executing the control to switch the moving direction of the sample stage 14, and the maximum actual deflection amount D2 may exceed the target value DT, i.e., the set value DS1, as shown in Fig. 5(A). Fig. 5(A) shows a state in which the maximum actual deflection amount D2 exceeds the deflection amount D1, which is the target value DT set as the set value DS1, by a deflection amount D3.

[0067] As shown in Figure 5(A), when the maximum actual deflection amount D2 exceeds the target value DT, which is the deflection amount D1 set as the setting value DS1 of the maximum deflection amount, by the deflection amount D3, the control device 100 adjusts the setting value when measuring the force curve next time, as shown in Figure 5(B), by changing the setting value DS of the maximum deflection amount to the setting value DS2 to which data of the deflection amount D4, which is a value smaller than the target value DT, which is the deflection amount D1 by the deflection amount D3, is set.

[0068] 5B, when the set value DS is adjusted, the control device 100 executes the control of switching the moving direction of the sample stage 14 when the detected deflection amount D becomes the set value DS2 set with the data of the deflection amount D4 smaller than the deflection amount D1, which is the target value DT, by the deflection amount D3. In that case, when the deflection amount D at the time of measuring the force curve exceeds the deflection amount D4 at the time of controlling the switching of the moving direction of the sample stage 14 by the deflection amount D3 predicted to be exceeded at the time of measuring the previous force curve, it can become the deflection amount D1, which is the target value DT.

[0069] In this way, when measuring a force curve, as shown in Fig. 5(A), the maximum deflection amount setting value DS is changed based on the deflection amount D3, which is the difference data indicating the difference between the deflection amount D1 of the target value DT and the maximum actual deflection amount D2, as shown in Fig. 5(B). Specifically, when the detected deflection amount D becomes the maximum setting value DS, the control device 100 controls to switch the moving direction of the sample stage 14, and then changes the maximum deflection amount setting value DS in anticipation of the actual deflection amount D exceeding the deflection amount D3, which is the difference data. Specifically, when the deflection amount exceeds the setting value DS2 by the deflection amount D3, which is the difference data, the control device 100 of the maximum deflection amount sets the data of the deflection amount D4, which is the target value DT, i.e., "DT-D3=DS2", as the adjusted setting value DS2.

[0070] When measuring a force curve, the control device 100 changes the set value DS1 to the set value DS2 based on the deflection amount D3, which is differential data indicating the difference between the deflection amount D1, which is the target value DT in a previously performed force curve measurement, and the actual deflection amount D2, thereby reducing the difference between the deflection amount D1, which is the target value DT when pressing the cantilever 12 against the sample S, and the actual deflection amount D2.

[0071] When the maximum actual deflection amount D2 is greater than the deflection amount D1, which is the target value DT, the control device 100 reduces the set value DS1 to the set value DS2, so that the set value DS1 can be changed to the set value DS2 so that the actual deflection amount D2 becomes the deflection amount D1, which is the target value DT.

[0072] <When the maximum deflection amount D is less than the target value DT> FIG. 6 is a diagram showing a method for adjusting the set value DS of the maximum amount of deflection D when the maximum value of the actual amount of deflection D on the approach line A falls short of the target value DT.

[0073] Fig. 6(A) shows an example of an approach line A in a shortage state where the maximum value of the actual deflection amount D is short of the target value DT. Fig. 6(B) shows an example of adjustment of the set value DS of the maximum value of the deflection amount D for the shortage state as shown in Fig. 6(A), and an example of the approach line A after the adjustment.

[0074] 6(A), in the control device 100, a target value DT of the maximum value of the deflection amount D is set as a set value DS1. The target value DT is the deflection amount D5. In the control device 100, data of the target value DT (= the deflection amount D5) input from the input device 104 is set as the set value DS1 of the maximum value of the deflection amount D. Then, when measuring the force curve, the control device 100 performs control to switch the moving direction of the sample stage 14 from upward to downward as shown in FIG. 2(c) when the deflection amount D detected as described above increases as shown by the approach line A and reaches the set value DS1.

[0075] However, as described above, when the deflection amount D of the cantilever 12 does not reach the set value DS1 of the maximum deflection amount D even when the position of the sample stage 14 in the Z direction reaches the limit position, the control device 100 controls the sample stage 14 to move so that the sample stage 14 returns to the initial position Zi. When such control is performed, the maximum value D6 of the actual deflection amount D falls short of the deflection amount D5 which is the target value DT, i.e., the set value DS1, as shown in Fig. 6(A). Fig. 6(A) shows a state in which the maximum value D6 of the actual deflection amount falls short of the deflection amount D5 which is the target value DT set as the set value DS1 by a deflection amount D7.

[0076] As shown in Figure 6(A), if the maximum value D6 of the actual deflection amount D falls short of the target value DT, that is, deflection amount D5, set as the set value DS1, by a deflection amount D7 due to reasons such as insufficient driving force in the Z direction by the Z direction actuator 141, the control device 100 adjusts the set value DS of the maximum value of the deflection amount D to a set value DS2, as shown in Figure 6(B), in which data for a deflection amount D8, which is a value larger than the target value DT, that is, deflection amount D5, by the deflection amount D7, is set, when measuring the force curve next time.

[0077] 6B, when the set value DS is adjusted, the control device 100 executes the switching control of the moving direction of the sample stage 14 when the detected deflection amount D becomes the set value DS2 set with the data of the deflection amount D8 which is larger than the deflection amount D5 which is the target value DT by the deflection amount D7. In that case, when the deflection amount D at the time of measuring the force curve falls short of the deflection amount D8 at which the switching control of the moving direction of the sample stage 14 is executed by the deflection amount D7 which was predicted to be insufficient at the time of measuring the previous force curve, it may become the deflection amount D5 which is the target value DT.

[0078] In this way, when measuring a force curve, the maximum deflection amount in the past force curve measurement as shown in Fig. 6(A) is changed based on the deflection amount D7, which is the difference data indicating the difference between the deflection amount D5, which is the target value DT, and the maximum actual deflection amount D6, as shown in Fig. 6(B). Specifically, the control device 100 predicts that the deflection amount D at the time of measuring the force curve is less than the deflection amount D8 at which the movement direction of the sample stage 14 is switched by the deflection amount D7, which is the difference data, and sets the data of the deflection amount D8, which is the difference data, as the adjusted set value DS2, so that the data of the deflection amount D8 becomes the target value DT of the maximum deflection amount when it is less than the set value DS2 by the deflection amount D7, i.e., "DT+D7=DS2".

[0079] When measuring a force curve, the control device 100 changes the set value DS1 to the set value DS2 based on the deflection amount D7, which is differential data indicating the difference between the deflection amount D5, which is the target value DT in a previously performed force curve measurement, and the maximum value D6 of the actual deflection amount D, thereby reducing the difference between the deflection amount D5, which is the target value DT when pressing the cantilever 12 against the sample S, and the maximum value D6 of the actual deflection amount D.

[0080] When the maximum value D6 of the actual deflection amount is smaller than the deflection amount D5 which is the target value DT, the control device 100 sets the set value DS1 to the set value DS2. increase Therefore, the set value DS1 can be changed to the set value DS2 so that the maximum value D6 of the actual amount of deflection becomes the amount of deflection D5 which is the target value DT.

[0081] [Adjustment of maximum deflection D during force curve measurement] The process of adjusting the maximum setting value of the amount of deflection D when measuring a force curve will be described with reference to FIG.

[0082] 7 is a flowchart of the process of adjusting the set values ​​when measuring a force curve. A program for executing the process of adjusting the set values ​​when measuring a force curve is stored in the memory 102 of the control device 100 and is executed by the processor 101.

[0083] The processor 101 executes the following process in the process of adjusting the setting values ​​during force curve measurement.

[0084] In step S1, it is determined whether there is stored data from the previous force curve measurement. The previous means one time before. The stored data from the previous force curve measurement includes data of the target value of the maximum deflection amount D at the previous force curve measurement, data of the actual detected value of the deflection amount D, and the set value DS of the maximum deflection amount D, which are stored in memory 102 in step S9 described later.

[0085] If it is determined in step S1 that there is no stored data from the previous force curve measurement, the process proceeds to step S8, which will be described later. On the other hand, if it is determined in step S1 that there is stored data from the previous force curve measurement, the process proceeds to step S2.

[0086] In step S2, the stored data from the previous force curve measurement is read, and based on the read stored data, a deflection difference is calculated, which is the difference data between the target value DT of the maximum deflection amount D from the previous force curve measurement and the detected value of the actual deflection amount D. The deflection difference calculated in step S2 is, for example, a deflection amount D such as the deflection amount D3 in FIG. 5 or the deflection amount D7 in FIG. 6.

[0087] In step S3, it is determined based on the stored data read out in step S2 whether or not the actual detected value of the amount of deflection D was greater than the target value DT of the maximum value of the amount of deflection D when the force curve was measured last time.

[0088] If it is determined in step S3 that the detected value of the actual deflection amount D is larger, for example, as in the case shown in Fig. 5(A), in step S4, a calculation is performed to subtract the calculated value of the deflection amount difference as the difference data obtained as the calculation result in step S2 from the set value DS1 of the maximum deflection amount from the previous time that is scheduled to be set when measuring the current force curve, and the set value DS2 to be corrected and set as shown in Fig. 5(B) is obtained as the calculation result. In step S4, for example, a calculation is performed to subtract the deflection amount D3 from the deflection amount D1, which is the set value DS1 in Fig. 5, to obtain the deflection amount D4 as the set value DS2. After step S4, the process proceeds to step S7.

[0089] On the other hand, if it is determined in step S3 that the detected value of the actual deflection amount D is not larger, then in step S5, it is determined based on the stored data read out in step S2 whether or not the detected value of the actual deflection amount D was smaller than the target value DT of the maximum value of the deflection amount D at the time of the previous force curve measurement.

[0090] If it is determined in step S5 that the actual amount of deflection D is not smaller, that is, the maximum setting value DS1 of the amount of deflection is the same as the actual amount of deflection D, the process proceeds to step S8. On the other hand, if it is determined in step S5 that the actual amount of deflection D is smaller, for example, as in the case shown in FIG. 6A, in step S6, the calculation result value of the amount of deflection difference as the difference data obtained in the calculation in step S2 is added to the maximum setting value DS1 of the previous amount of deflection that is scheduled to be set when measuring the current force curve. Add The calculation is performed as shown in Fig. 6 The set value DS2 to be corrected and set is obtained as shown in (B). In step S6, for example, a calculation is performed to add the amount of deflection D7 to the amount of deflection D5, which is the set value DS1 in Fig. 6, to obtain the amount of deflection D8 as the set value DS2. After step S6, the process proceeds to step S7.

[0091] In step S7, the setting value of the maximum amount of deflection during the current force curve measurement is changed from the previous setting value DS1 to the setting value DS2 obtained in step S4 or step S6. Next, in step S8, if the process proceeds from step S1 to step S8, the maximum setting value DS1 is used to measure the force curve, and if the process proceeds from either step S4 or S6 to step S8, the changed maximum setting value DS2 is used to measure the force curve, and measurement data of the force curve is obtained.

[0092] In step S9, data including the target value DT of the maximum amount of deflection in the current force curve measurement, the detected value of the actual amount of deflection D, and the set value DS of the maximum amount of deflection are stored in memory 102, and the process ends. The data thus written in step S9 will be determined in step S1 at the time of the next force curve measurement as the stored data from the previous force curve measurement.

[0093] By executing the above-described process, when measuring a force curve, the set value of the maximum amount of deflection can be changed based on the difference data indicating the difference between the target value of the maximum amount of deflection in a previously performed force curve measurement and the actual amount of deflection. More specifically, the set value of the maximum amount of deflection can be changed based on the difference data indicating the difference between the target value of the maximum amount of deflection in a previously performed force curve measurement and the actual amount of deflection so that the difference is eliminated.

[0094] [Modification of the embodiment] (1) In the above-described embodiment, when a force curve is measured, the setting value of the maximum amount of deflection is changed based on the difference data indicating the difference between the target value of the maximum amount of deflection and the actual amount of deflection in a force curve measurement performed in the past. In this case, the past means one time ago as described above, but it may include both one time ago and several times ago as follows. For example, when force curves are measured sequentially at multiple points on the same sample, the difference data indicating the difference between the target value of the maximum amount of deflection and the actual amount of deflection in the force curve measurement at the time of the first focus curve measurement may be stored in the memory 102 as reference data for the force curve measurement performed in the past, and the reference data may be stored as data at the time of the force curve measurement performed in the past. In the force curve measurement performed thereafter, the setting value of the maximum amount of deflection may be changed in the subsequent multiple force curve measurements based on the stored data of the reference data.

[0095] In this way, the setting value of the maximum amount of deflection when measuring a force curve may be changed in subsequent measurements of the force curve based on the data from the first measurement of the force curve. Also, as in the above-described embodiment, the setting value of the maximum amount of deflection when measuring a force curve may be changed each time a force curve is measured based on the data from the previous measurement of the force curve.

[0096] (2) The force curve is made up of data showing the relationship between the distance between the sample S and the tip 121 of the cantilever 12 and the force acting between the sample S and the cantilever 12. In the above-described embodiment, when the force curve is measured, the amount of deflection D of the cantilever 12 is detected as data specifying the force acting between the sample S and the cantilever 12. However, this is not limited to this, and the force acting on the sample stage 14 or the force acting on the cantilever 12 may be detected as data specifying the force acting between the sample S and the cantilever 12. In this way, the data showing the relationship between the force acting between the sample S and the cantilever 12 when measuring the force curve may be data that can specify the amount of pressing when the cantilever 12 is pressed against the sample S.

[0097] (3) The method of measuring a force curve when the maximum value of the deflection amount D shown in Figures 5 and 7 exceeds the target value DT can also be applied to a state in which an attractive force acts on the cantilever 12 as shown in section (b) of Figure 3. Moreover, the method of measuring a force curve when the maximum value of the deflection amount D shown in Figures 6 and 7 is short of the target value DT can also be applied to a state in which an attractive force acts on the cantilever 12 as shown in section (b) of Figure 3.

[0098] (4) As a device for changing the distance between the sample S and the tip 121 of the cantilever 12, it is possible to use only a Z-direction actuator 141 that moves the sample stage 14 in the Z direction as shown by the solid line in FIG. 1, or to use only a movable support device 13 that moves the cantilever 12 in the Z direction as shown by the dashed line in FIG. 1, or to use both of these devices.

[0099] (5) The control for changing the set value of the maximum amount of deflection when measuring a force curve may be performed on the condition that the difference data indicating the difference between the target value of the maximum amount of deflection and the actual amount of deflection in a previously performed force curve measurement, which is greater than "0", becomes greater than a set threshold value. For example, if such difference data is a small value that does not adversely affect the accuracy of the force curve measurement, the control for changing the set value of the maximum amount of deflection may not be performed. In addition, such a threshold value may be different depending on the type of sample to be measured.

[0100] (6) The control for changing the setting value of the maximum amount of deflection when measuring a force curve may be performed only in one of the cases where the maximum value of the deflection amount D shown in Figures 5 and 7 exceeds the target value DT, and where the maximum value of the deflection amount D shown in Figures 6 and 7 is short of the target value DT, for example, only when the maximum value of the deflection amount D exceeds the target value DT.

[0101] (7) In the example described above, when measuring a force curve, data including the target value of the maximum amount of deflection when measuring the current force curve, the detected value of the actual amount of deflection, and the set value of the maximum amount of deflection are stored in the memory 102. However, the present invention is not limited to this. Instead of or in addition to the target value of the maximum amount of deflection when measuring the current force curve and the detected value of the actual amount of deflection, differential data indicating the difference between the target value of the maximum amount of deflection when measuring the force curve and the actual amount of deflection may be stored in the memory 102. In this way, when measuring a force curve, any data may be stored as the data when measuring the current force curve, as long as it is data that can identify the differential data indicating the difference between the target value of the maximum amount of deflection when measuring the force curve and the actual amount of deflection.

[0102] [Note] The scanning probe microscope of the present disclosure (scanning probe microscope 1) has the following features.

[0103] (1) A device includes a sample stage (sample stage 14) on which a sample (sample S) is placed, a cantilever (cantilever 12) including a probe (probe 11), and a control device (control device 100). The cantilever (cantilever 12) is disposed opposite the sample stage (sample stage 14). The control device (control device 100) determines the setting value (setting values ​​DS1, DS2) of the pressing amount when the cantilever (cantilever 12) is pressed against the sample (sample S) when measuring a force curve. 2), the pressing amount (deflection amounts D2, D6) is controlled to a target value (target value DT, deflection amounts D1, D5) (step S7), and when measuring a force curve, the setting value (setting value DS1) is changed (setting value DS2) based on difference data (deflection amounts D3, D7) indicating the difference between the target value (target value DT, deflection amounts D1, D5) in a previously performed force curve measurement and the actual pressing amount (deflection amounts D2, D6) (step S7).

[0104] According to this configuration, when measuring a force curve, the control device (control device 100) changes (set value DS2) the set value (set value DS1) based on difference data (deflection amounts D3, D7) indicating the difference between the target value (target value DT, deflection amounts D1, D5) in a previously performed force curve measurement and the actual pressing amount (deflection amounts D2, D6) (step S7), thereby reducing the difference between the target value (target value DT, deflection amounts D1, D5) of the pressing amount when pressing the cantilever (cantilever 12) against the sample (sample S) and the actual pressing amount (deflection amounts D2, D6).

[0105] (2) The control device (control device 100) changes (set value DS2) the set value (set value DS1) to a value (set value DS2) that makes the actual pressing amount (deflection amounts D2, D6) the target value (target value DT, deflection amounts D1, D5) based on the difference data (deflection amounts D3, D7) (step S7).

[0106] According to this configuration, the control device (control device 100) changes (set value DS2) the set value (set value DS1) to a value (set value DS2) at which the actual pressing amount (deflection amount D2, D6) becomes the target value (target value DT, deflection amount D1, D5) based on the difference data (deflection amount D3, D7) (step S7), so that the actual pressing amount (deflection amount D2, D6) can become the target value (target value DT, deflection amount D1, D5).

[0107] (3) When the actual pressing amount (deflection amount D2) is greater than the target value (target value DT, deflection amount D1), the control device (control device 100) decreases (set value DS2) the set value (set value DS1) (steps S4, S7).

[0108] According to this configuration, when the actual amount of pressure (deflection amount D2) is greater than the target value (target value DT, deflection amount D1), the control device (control device 100) reduces (set value DS2) the set value (set value DS1) (steps S4, S7), so that the set value (set value DS1) can be changed so that the actual amount of pressure (deflection amount D2, D6) becomes the target value (target value DT, deflection amount D1, D5).

[0109] (4) When the actual pressing amount (deflection amount D6) is less than the target value (target value DT, deflection amount D5), the control device (control device 100) increases the set value (set value DS1) (set value DS2) (steps S6, S7).

[0110] According to this configuration, when the actual pressing amount (deflection amount D6) is less than the target value (target value DT, deflection amount D5), the control device (control device 100) increases (set value DS2) the set value (set value DS1) (steps S6, S7), so that the set value (set value DS1) can be changed so that the actual pressing amount (deflection amount D2, D6) becomes the target value (target value DT, deflection amount D1, D5).

[0111] (5) The control device (control device 100) stores data that can identify differential data (deflection amounts D3, D7) when a force curve is measured (step S9), and changes (setting value DS1) the setting value for subsequent force curve measurements (setting value DS2) based on the differential data (deflection amounts D3, D7) identified by the stored data (step S7).

[0112] According to this configuration, the control device (control device 100) stores data that can identify differential data (deflection amounts D3, D7) when a force curve is measured (step S9), and changes (setting value DS1) the setting value for subsequent force curve measurements (setting value DS2) based on the differential data (deflection amounts D3, D7) identified by the stored data (step S7).Therefore, the setting value (setting value DS1) can be changed (setting value DS2) based on the differential data (deflection amounts D3, D7) identified by the stored data when a force curve is measured.

[0113] (6) The control device (control device 100) stores data that can identify differential data (deflection amounts D3, D7) each time a force curve is measured (step S9), and changes (setting value DS2) the setting value (setting value DS1) based on the differential data (deflection amounts D3, D7) identified by the data stored in the previous force curve measurement each time a force curve is measured (step S7).

[0114] According to this configuration, the control device (control device 100) stores data that can identify differential data (deflection amounts D3, D7) when a force curve is measured (step S9), and each time a force curve is measured, the setting value (setting value DS1) for the subsequent force curve measurement is changed (setting value DS2) based on the differential data (deflection amounts D3, D7) identified by the data stored in the previous force curve measurement (step S7). Therefore, each time a force curve is measured, the difference between the target value of the pressure amount (target value DT, deflection amounts D1, D5) and the actual pressure amount (deflection amounts D2, D6) can be reduced.

[0115] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0116] S sample, 11 probe, 14 sample stage, 12 cantilever, 100 control device, 1 scanning probe microscope.

Claims

1. A sample stage on which a sample is placed; a cantilever including a probe; a control device; The cantilever is disposed opposite the sample stage, The control device includes: When measuring a force curve, the cantilever is pressed against the sample by moving the sample stage, and then the amount of pressing is controlled to a target value based on a set value of the amount of pressing when controlling the cantilever to be separated from the sample by switching the moving direction of the sample stage; A scanning probe microscope that, when measuring a force curve, changes the setting value based on difference data that indicates the difference between the target value and the actual pressing amount in a force curve measurement performed previously on a sample of the same type as the sample for which the force curve is to be measured.

2. 2. The scanning probe microscope according to claim 1, wherein the control device changes the set value to a value that makes the actual pressing amount the target value based on the difference data.

3. 3. The scanning probe microscope according to claim 1, wherein the control device reduces the set value when the actual pressing amount is greater than the target value.

4. 2. The scanning probe microscope according to claim 1, wherein the control device increases the set value when the actual pressing amount is smaller than the target value.

5. 2. The scanning probe microscope according to claim 1, wherein the control device stores data capable of identifying the difference data when a force curve is measured, and changes the setting values ​​in subsequent force curve measurements based on the difference data identified by the stored data.

6. 6. The scanning probe microscope according to claim 5, wherein the control device stores data capable of identifying the difference data each time a force curve is measured, and changes the setting value each time a force curve is measured based on the difference data identified by the data stored in a previous force curve measurement.

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