JPH09304405A - Composite type probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable simultaneously measuring a plurality of physical properties, at completely the same position, in a minute range at an arbitrary position on a specimen, by detecting the change of deflection of a cantilever having a probe on the free end, and calculating the change amount of a force applied to the probe. SOLUTION: A specimen stand 6 is installed on the upper surface of a tube scanner 7 constituted of a cylindrical piezoelectric driving element. A cantilever 2 having a probe 21 on the free end is fixed to a post 13, and irradiated with a light from a light source 3. The light reflected by the back of the cantilever 2 is received by a quartered light receiving element 4. By detecting the center of gravity of a light spot received by the light receiving element 4, the displacement of the deflection of the cantilever 2 can be known. The displacement of the cantilever 2 changes in accordance with the force which the probe 21 receives from a specimen, so that the displacement can be made the force applied to the probe. A signal of the center of gravity of the light spot which is detected by the light receiving element 4 is subjected to A/D conversion 12 and inputted in the input detection part of a computer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring instrument capable of simultaneously measuring various physical properties in a minute range of a sample surface and a composite probe microscope for observing the state of the sample surface.

[0002]

2. Description of the Related Art Conventionally, there is an atomic force microscope for observing minute irregularities on a sample surface. This atomic force microscope is a technology that measures the shape of the sample surface by bringing a probe with a minute tip close to the sample and detecting the magnitude of the atomic force that acts between the probe and the sample. Is. The general structure of this atomic force microscope consists of a light source for fixing the probe to a cantilever, detecting the amount of bending of the cantilever, and a two-part photodetector for detecting the reflected light of the cantilever, The probe is equipped with an actuator that can scan the sample. And
Regarding the detection of the bending amount of the cantilever, the light emitted from the light source is applied to the cantilever, and the light is received by the two-divided photodetector. At this time, the deflection amount of the cantilever is detected by taking the difference between the current values from the respective photodetectors with respect to the light intensity applied to the respective light receiving surfaces of the photodetector.

Further, by using such an atomic force microscope, the torsion of the cantilever which occurs at the moment of scanning the sample is detected and detected by the same system as the atomic force microscope.
There is a friction force microscope that detects the frictional force in a minute area on the surface of a sample by the amount of twist. Also, an adsorption force microscope that detects the adhesive force of a microscopic area on the sample surface by capturing the change in the amount of bending of the cantilever obtained when the probe is brought close to the sample surface and when the probe is vertically separated, There is an elastic force microscope or the like that detects the elastic force of a microscopic region on the sample surface by also grasping the elastic force obtained when the probe is brought into contact with the sample as a change in the amount of bending of the cantilever.

These microscopes were only able to measure specific physical quantities. Therefore, in order to detect several types of physical quantities, the sample is transferred to a microscope (measuring device) for detecting the desired physical quantity, and the sample placement location is changed so that the probe is at the desired position on the sample. Was adjusted and measured.

[0005]

However, it has been extremely difficult to detect a physical quantity at the same point on the sample surface by various conventional microscopes using a minute probe. Since the measurement range of various microscopes using such a minute probe is the measurement of the physical quantity in the range of several nm,
It is very difficult to hold the probe at a predetermined position on the sample surface within such a range. Also, it is almost impossible to confirm with an optical microscope whether it has been placed in that position,
Even if other alternatives are used, a large investment is required in the equipment for that purpose.

Further, even if the sample is moved to the predetermined position, it is technically difficult to minutely move the sample in an arbitrary direction, and it takes a very long time to position the sample.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a flexible cantilever, a probe having a minute tip diameter at the free end of the cantilever, and a cantilever are provided. A force detection unit that detects a change in the amount of bending of the beam, a first scanning drive member that is displaced at least in a direction parallel to the surface of the sample, and a second scanning drive that is displaced in a direction perpendicular to the surface of the sample. A member and a scanning drive member control means for controlling a second scanning drive member that brings the probe and the sample close to each other until the cantilever portion of the probe has a predetermined deflection amount, and then separates the probe and the sample; The information about the moving distance of the sample with respect to the direction in which the probe is present is obtained from the scanning drive member control means, and the information about the force acting on the probe is obtained from the force detecting means to move the sample in the direction in which the probe is present. Calculates the amount of change in force acting on the probe with respect to changes in distance And a display means for displaying the calculation result output from the calculation means as the physical property of the sample, thus performing the operation of bringing the probe and the sample close to or apart from each other. By calculating the amount of change in the force acting on the probe with respect to the change in the interval, the physical properties of the sample at that point can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to the embodiments of the present invention. By the way, FIG. 1 is a conceptual configuration diagram of a compound probe microscope according to an embodiment of the present invention. In this composite probe microscope, a sample stage 6 is provided on the upper surface of a tube scanner 7 composed of a cylindrical piezoelectric drive element. Also, pillar 1
The cantilever 2 is fixed to 3. A probe 21 is provided at the free end of the cantilever 2.

Above the cantilever 2, a light source 3 and a four-division light receiving element 4 are provided. These are fixed to the main body 1. The light from the light source 3 is applied to the cantilever 2. Then, the light emitted to the cantilever 2 is reflected by the back surface of the cantilever 2 and is received by the four-division light receiving element 4. By detecting the position of the center of gravity in the light spot received by the four-division light receiving element 4, the displacement of the bending amount of the cantilever 2 can be detected. This displacement of the cantilever 2 is caused by the probe 2 provided on the cantilever 2.
Since 1 is displaced according to the force received from the sample, the displacement amount of the cantilever 2 can be the force received by the probe 21. In addition, the signal relating to the position of the center of gravity of the light spot detected by the four-division light receiving element 4 is sent to the A / D conversion converter 12
Is input to the force detection unit in the computer 8 as a digital signal.

The tube scanner 7 has a plurality of divided electrodes attached to the surface of a cylinder. Further, electrodes are attached to the entire back surface of the cylinder. A desired voltage can be applied to the electrodes on each surface with respect to the electrodes provided on the back surface of these cylinders. The voltage applied to the tube scanner 7 is controlled by the tube scanner control unit in the computer 8.

By the way, the computer 8 is shown in FIG.
It has the following configuration. In this computer 8,
The scanner control unit 81 that controls the scanning drive of the tube scanner 7 and the A / that outputs the displacement amount of the cantilever 7
A force detection unit 82 that detects the force received by the probe from the digital signal from the D converter 12 and outputs information regarding the force received by the probe, and a position that is a signal regarding the position of the sample 5 that is output from the scanner control unit 81. The information about the moving distance of the sample is obtained from the control signal, and further the information about the force received by the probe output from the force detecting unit 82 is obtained, and the moving distance of the sample 5 with respect to the direction in which the probe is present or the opposite direction is obtained. A force curve creating unit 83 that creates a correlation with the force received by the probe, and a second differential processing unit 84 that performs second differential of the graph of the force curve obtained by the force curve creating unit 83 and a second differential processing. The storage unit 85 that stores the force curve obtained by the force curve creation unit in consideration of the information processed by the storage unit and various physical curves from the force curve stored in the storage unit. A calculation unit 86 for calculating the sex output,
It has an image means 87 for imaging the information obtained by the arithmetic unit.

The scanner controller 81 outputs a signal relating to the amount of movement of the sample 5 with respect to the probe 21 to the D / A converters 9, 10, 11. D / A converter 1
Reference numerals 0 and 11 perform D / A conversion on a signal related to the driving amount in the X and Y directions substantially parallel to the sample surface. Further, the D / A converter 9 outputs a signal regarding the drive amount of the sample 5 in the direction perpendicular to the sample surface. The scanner controller 81 controls the operation required to detect the amount of force received by the probe 21 with respect to the moving distance of the sample 5 in the direction perpendicular to the sample surface. In this scanner control unit 81, the probe 21 is driven in the direction in which the probe 21 exists until the probe 21 comes into contact with the sample 5 and the drive amount generated when the sample 5 moves and the change in the deflection amount of the cantilever 2 become the same. Control is performed, and when the force received by the probe 21 and the force generated by driving the tube scanner 7 become the same, drive control is performed in the opposite direction. In this way, the operation of the scanner for obtaining the force curve is controlled.

Next, the force curve creating section 83 is supplied with a signal output from the scanner control section 81 regarding the moving distance of the sample and a signal output from the force detection section 82 regarding the force received by the probe 21. It Then, in the force curve creation unit 83, the probe 2 with respect to the moving distance of the sample 5 in the direction in which the probe 21 exists or in the opposite direction.
By taking the correlation of the force that 1 receives, the force curve as shown in FIG. 3 is created. By the way, the horizontal axis of FIG. 3 shows the moving distance of the probe 21 and the sample 5 in the direction perpendicular to the sample surface, and the vertical axis shows the force received by the probe 21. Further, on the vertical axis, when the force is 0, the minus side is the force (negative force) for pulling the probe 12 toward the sample 5, and the plus side is the force for bending the probe 12 (plus force). Then, on the horizontal axis, the probe 2 is on the left side.
1 is the direction in which the sample 5 approaches, and the right side is in the direction away from each other. The force curve will be described. When the tube scanner is driven to bring the sample 5 close to the probe 12, the force curve receives a negative force so that the probe 12 is suddenly drawn into the sample 5 at the point b. Then, when the force received by the probe 12 reaches the point c, it increases in the positive direction in proportion to the distance between the probe 12 and the sample 5. Finally, the force generated by the tube scanner 7 for driving and the force received by the probe 12 become the same (point d). Further, when the probe 12 is then separated from the sample 5, the force received by the probe 12 becomes proportional to the moving distance of the sample and becomes a negative force, and finally returns to the original force. . By the way, in the force curve shown in FIG. 3, the position where the force is 0 is exactly the position a.

Such a force curve contains information on the physical properties of the sample. Point e in FIG.
The difference between the distance and the point b is the film thickness of the adsorbed water adhering to the sample surface. Also, the difference between the force at point b and the force at point c is
The suction force on the sample surface, and the gradient of the force with respect to the moving distance of the sample on the straight line connecting the points c and d just indicates the elastic force of the sample. From the force curve obtained by testing the sample in this way, three physical quantities at the same point of the sample can be measured.

By the way, it is very difficult to accurately detect the position of the point b or the point c and the point e in the force curve obtained by the force curve creating section 83. Normally, the force curve obtained will not be as shown in Fig. 3. Therefore, the positions of the point b or the points c and e cannot be accurately detected. In view of this point, the compound probe microscope according to the embodiment of the present invention is provided with the second-order differentiation processing unit. The second-order differentiation processing unit can accurately calculate the moving distance of the sample at the points b, c, and e by performing the second-order differentiation with respect to the change in the force with respect to the distance. The second-order differential processing unit will be described using the point c as a model. In the second-order differentiation processing unit, the obtained force curve as shown in FIG. 4A is first differentiated. By doing so, a curve as shown in FIG. 4B can be obtained. Then, by further differentiating such a curve, a curve as shown in FIG. 4C is obtained. The 0 cross point of this curve is exactly the distance of the point c.

In this way, the substantial movement distance of the sample at the point c is calculated. Further, in the present invention, it is also used to calculate the substantial sample moving distance at the point e. And 2
The force curve obtained by the force curve creation unit 83 is corrected by using the values of the moving distances of the sample at the substantial points c and e obtained by the hierarchical differentiation processing unit 84 to obtain a normal force curve. The force curve is stored in the storage unit 85. Then, based on the force curve stored in the storage unit 85, the calculation unit 86 calculates various physical property values.

Next, the computing unit 86 detects the difference in the force received by the probe 21 at the points b and c from the normal force curve as shown in FIG. Just from this difference, the adsorption force on the sample surface can be shown. In addition, the calculation unit 86
From this, the slope of the force curve between points c and d is calculated. The rate of change of the force received by the probe with respect to the moving distance of the sample between the points c and d can be indicated as the elastic force of the sample. Then, the difference between the value of the moving distance of the sample at the point b or the point c and the value of the moving distance of the probe at the point e is calculated. This difference can be shown as the film thickness of the adsorbed water on the sample surface.

As described above, the computing unit 86 can calculate the adsorption force of the sample, the elastic force, and the film thickness of the adsorbed water at the measurement position from the Fores curve stored in the storage unit 86.
By the way, the difference in force between the points b and c is equivalent to a physical property value generally called viscosity. Further, by slightly moving the sample vertically to the beam direction of the cantilever and detecting the amount of twist of the beam at that time, the frictional force at the measurement position of the sample can be obtained. In the composite probe microscope according to the embodiment of the present invention, the four-division light receiving element 4 is used. Therefore, for example, when the four-division light receiving element 4 is modeled in FIG. 5, when detecting the bending amount of the cantilever 2, the sum of the signals from the light receiving surfaces A and B and the signals from the light receiving surfaces C and D are detected. When the difference is obtained from the sum of ((A + B)-(C + D)) and detected, the friction force is detected, the sum of the signals from the light receiving surface A and the light receiving surface C and the light receiving surface B are detected. By obtaining the difference from the sum of the signals from the light receiving surface D, the amount of twist of the cantilever 2 can be obtained.

In this manner, the sample 5 is moved toward or away from the probe 12, the adsorption force, the elastic force, and the film thickness of the adsorbed water are detected, and then the sample 5 is finely divided. The frictional force can also be detected by moving in the direction perpendicular to the direction in which the frictional force approaches. Then, in the calculation unit 86, the calculation unit 86
The image means 87 outputs the information about the adsorption force, the elastic force, the film thickness of the adsorbed water, and the frictional force, which are obtained in (1).

Then, the image means displays these pieces of information. In this composite probe microscope, this procedure was performed according to the flowchart shown in FIG. First, when the measurement is started, the sample 5 is moved by the tube scanner 7 to a desired position for measurement. Next, a signal for making the sample 5 approach from the tube scanner controller 81 is set to D /
The sample 5 is supplied to the A converter 9, and the tube scanner 9 is driven to bring the sample 5 close to the probe 21. Then, when the proximity is completed, the tube scanner control unit 81 moves the probe 2
A signal for moving the sample 5 away from 1 is output to the D / A converter 9. At this time, the force detection unit 82 detects the signal output from the A / D converter 12,
Outputs the signal detected in step 3 to the force curve creation part 83,
The force curve creating unit 83 simultaneously monitors changes in force with respect to the moving distance of the sample. Then, the force curve creation unit 83 creates a force curve. Then, the force curve created by the force curve creating unit 83 is set to 2
It is output to the differential processor 84. The second-order differentiation processing unit 84 performs second-order differentiation on the change in force with respect to the moving distance, and the point b,
The normal moving distance between the points c and e is obtained by the second-order differentiation processing unit 84, and the force curve created by the force curve creating unit is corrected to obtain a normal force curve. The force curve corrected by the second-order differentiation processing unit 84 is stored in the storage unit 85. Based on the stored force curve, the calculation unit 86 calculates the adsorption force, the elastic force, and the film thickness of the adsorbed water.

In addition, when frictional force is also detected, the scanner control unit 81 outputs to the D / A converters 10 and 11 a signal for scanning minutely in the direction parallel to the sample surface and perpendicular to the direction of the cantilever beam. Then, the amount of torsion of the cantilever at that time is detected by the force detection unit 82 by the signal output from the A / D converter 12, and the calculation unit 86 calculates the friction force. At the same time, the physical property values calculated by the calculation unit 86 are output to the image means 87 and displayed.

Then, the scanner controller 81 determines whether or not the entire measurement area of the sample has been measured. If the measurement is not completed, a signal is sent from the scanner controller 81 to the D / A converters 10 and 11. This output is performed, the tube scanner 7 is driven, and this series of operations is performed until the measurement area of the sample is measured. At this time, similarly to the conventional atomic force microscope, the unevenness of the sample surface at each measurement position is detected by the force detection unit 82, which is output to the calculation unit 86 and output to the image means 87. The height of the unevenness may be displayed in the same manner as each physical property value of.

Then, in the image means 87, the measurement position on the sample is represented by X and Y coordinates, and the adsorption force, the elastic force, the film thickness of the adsorbed water, the friction force, and the unevenness information are digitized and displayed. Alternatively, one of these physical property values may be displayed on the Z axis using X, Y, and Z coordinates. At this time, other physical property values may be displayed using a plurality of types of colors or numerical values may be displayed.

As described above, in the composite probe microscope of the present invention, in the measurement region of the sample, it becomes possible to measure the physical properties in a minute region on the sample surface and simultaneously measure a plurality of types. In the composite probe microscope according to the embodiment of the present invention, the adsorption force, the elastic force, the film thickness of the adsorbed water, the frictional force, and the unevenness information are simultaneously measured. It is also possible to simultaneously measure any one physical property and the other physical property among the film thicknesses of.

[0025]

According to the present invention, it is possible to measure a plurality of physical properties in a minute range at an arbitrary position on a sample at exactly the same position. Furthermore, since multiple physical properties can be measured simultaneously in this way, the alignment required for measuring other physical properties as before is no longer necessary, and measurement speed can be increased. It became so.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a composite probe microscope according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a computer 8 of the composite probe microscope according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a force curve that is an example of measurement results obtained with the composite probe microscope according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining second-order differentiation processing performed by a second-order differentiation processing unit 84 of the computer 8 of the composite probe microscope according to the embodiment of the present invention.

FIG. 5 is a model diagram of a four-division light receiving element 4.

FIG. 6 is a flowchart regarding processing performed by the compound probe microscope according to the embodiment of the present invention.

[Explanation of symbols]

1 main body 2 cantilever 3 light source 4 4-split light receiving element 5 sample 6 sample stage 7 tube scanner 8 computer 9 D / A converter for vertical control with respect to sample surface 10 and 11 D for horizontal control with respect to sample surface / A converter 12 A / regarding the signal obtained from the 4-split light receiving element
D converter

Claims (5)

[Claims] 1. A flexible cantilever, a probe having a minute tip diameter at a free end of the cantilever, and force detection means for detecting a change in the bending amount of the cantilever. First displacing at least in a direction parallel to the surface of the sample
Scanning drive member, a second scanning drive member that is displaced in a direction perpendicular to the surface of the sample, and the probe and the sample until the cantilever portion of the probe has a predetermined deflection amount. Scanning drive member control means for controlling the second scanning drive member for bringing the probe and the sample apart from each other, and a movement distance of the sample from the scanning drive member control means in the direction in which the probe exists. Information about the force acting on the probe from the force detection means, and a change amount of the force acting on the probe with respect to a change in the moving distance of the sample in the direction in which the probe exists. And a display unit for displaying the calculation result output from the calculation unit as the physical property of the sample. 2. The calculation means is a second differential calculation means for performing a second differential calculation from the amount of change in the force acting on the probe with respect to the change in the moving distance of the sample with respect to the direction in which the probe is present. The composite probe microscope according to claim 1, further comprising: 3. The calculation means stores a change amount of a force acting on the probe with respect to a change in a distance between the probe and the sample, which is obtained when the probe and the sample are brought close to or apart from each other. Storage means, and second-order differential operation means for performing second-order differential operation from the amount of change in the force acting on the probe with respect to the change in the distance between the probe and the sample obtained from the storage means. The composite probe microscope according to claim 2, wherein 4. The force detecting means is a light source that irradiates the back surface of the cantilever with light, and a four-division photo detector that receives the light reflected from the cantilever. 1 or 3 composite probe microscope 5. The first scan drive member control means for driving the first scan drive member in a direction perpendicular to the projecting direction of the cantilever, according to claim 4. Combined probe microscope