JP4080933B2 - Probe position correction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a probe position correction how to correct the probe position of the scanning probe microscope.
[0002]
[Prior art]
FIG. 9 is a schematic diagram of an atomic force microscope (AFM), which is one of conventional scanning probe microscopes (SPM), and cantilever 901, cantilever deflection detector 902, XYZ translator 903, sample 904, and sample stage 905. , A controller 906 and a computer 907.
[0003]
The AFM includes a cantilever scan system that scans a cantilever with an XYZ translator and a sample scan system that scans a sample. FIG. 9 shows a cantilever scanning method in which the XYZ translator 903 scans the cantilever 901.
[0004]
In the conventional AFM, the sharpened probe at the tip of the cantilever 901 attached to the lower end of the XYZ translator 903 is brought into contact with the sample 904 on the sample stage 905, and the sample is placed in the XY plane by the XYZ translator 903. To scan. At this time, the deflection of the cantilever is monitored by the deflection detector 902 and the controller 906 performs feedback control so that the deflection becomes constant, and the XYZ translator 903 adjusts the position of the cantilever 901 in the Z direction. By mapping the adjustment amount at each position on the sample surface on the screen by the computer 907, the fine structure of the sample surface can be observed.
[0005]
In the field of SPM, a fine movement mechanism is disclosed that scans a sample surface with high accuracy while positioning the detection probe and the sample surface with high accuracy (see, for example, Patent Document 1). Here, as shown in FIG. 10, the SPM uses a tube-type piezoelectric body 1006 with electrodes 1008 and 1007 formed on the inside and outside. FIG. 10A shows an XY scanning translator, and FIG. 10B shows a Z-direction position control translator. In FIG. 10A, the outer electrode 1007 is divided into four parts. When voltages having different signs are applied to the outer electrodes 1007 facing each other, the piezoelectric body 1006 is bent, thereby scanning in the XY plane. In FIG. 10B, the outer electrode 1007 covers the entire piezoelectric body 1006 like the inner electrode 1008. When a voltage is applied to the outer electrode 1007 and the inner electrode 1008, the piezoelectric body 1006 expands and contracts in the Z direction. This adjusts the distance between the cantilever and the sample.
[0006]
Actually, it is possible to realize all the functions of XYZ with the configuration shown in FIG. 10A, and even when the XY electrode and the Z electrode are separated, one tube type piezoelectric body is combined with XYZ. There are a type in which the electrode is formed, a piezoelectric body in which the XY electrode is formed, and a piezoelectric body in which the Z electrode is formed.
[0007]
[Patent Document 1]
JP-A-2-81487 (page 2-3, FIG. 1)
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention will be described with reference to FIGS. 11, 12 and 13 by taking a tube type piezoelectric body as an example.
[0009]
FIG. 11A is a schematic view of a tube-type Z translator, and FIG. 11B is a sectional view thereof. In FIG. 11, a cantilever 1101, an outer electrode 1102, an inner electrode 1103, and a tube type piezoelectric body 1104 are shown. The tube-type piezoelectric body 1104 is manufactured by cutting the center of a cylindrical piezoelectric body by machining. For this reason, the center position of the hole is shifted due to insufficient precision during machining, and the thickness of the piezoelectric body is biased as shown in FIG. As a result, the amount of expansion / contraction with respect to the voltage is different, so that the piezoelectric body 1104 does not expand / contract straight but curves as shown in FIG. FIG. 12 shows a case where there is a thickness deviation in the X direction. In FIG. 12, the outer electrode 1202, the inner electrode 1203, the piezoelectric body 1204, the position 1205 in the Z direction when no voltage is applied, the position 1207 in the X direction of the cantilever when no voltage is applied, and the cantilever when extended by applying a voltage A position 1206 in the Z direction and a position 1208 in the X direction of the cantilever when expanded by applying a voltage are shown.
[0010]
When driving the Z translator, a voltage is applied to the inner electrode 1203 and the outer electrode 1202, but the expansion amount is small because the electric field is strong on the thin side of the piezoelectric body, and the expansion amount is small on the thick side because the electric field is weak. . As a result, as shown in FIG. 12, as the cantilever 1201 is displaced by Δz in the Z direction, a displacement Δx in the X direction also occurs. When the ratio Δx / Δz between the displacement Δz in the Z direction and the displacement Δx in the X direction is large, an error is particularly large in the cross-sectional measurement of the sample.
[0011]
FIG. 13 is a schematic view of a cross section of a sample having a concavo-convex pattern, showing an actual pattern shape 1301 and a shape 1302 obtained from a measurement result by the tube-type piezoelectric body shown in FIGS. As shown in the figure, since the piezoelectric body expands and contracts in the Z direction while curving in the X direction, the cross-sectional shape cannot be measured accurately.
[0012]
The problem to be solved by the present invention has been described by taking the tube-type piezoelectric body as an example, but the same problem arises not only in the tube-type piezoelectric body but also in all scanners mounted on the scanning probe microscope. It is another object of the present invention to provide a probe position correction method for correcting an error caused by the movement of the probe in the XY plane that occurs when the probe moves in the Z direction and obtaining a highly accurate observation image. It is what.
[0013]
[Means for Solving the Problems]
The first aspect of the present invention that solves the above-described problems includes a first scanning axis that is substantially parallel to the sample surface and a second surface that is substantially parallel to the sample surface and perpendicular to the first scanning axis. A raster scan is performed with a fine probe in the plane consisting of the scan axis of the sample, and at the same time, the probe is moved in the direction of the third scan axis perpendicular to both the first scan axis and the second scan axis so as to follow the unevenness of the sample surface. a probe position correcting how to correct the probe position of the scanning probe microscope for observing a minute structure of the sample surface by relatively moving, in accordance with the movement of the probe to a third scan axis What is claimed is: 1. A probe position correcting method comprising: measuring a moving amount of a probe in a plane direction in a plane; and correcting a probe position based on the moving amount obtained in the moving amount measuring step. is there
[0014]
According to a second aspect of the present invention, there is provided the probe position correcting method according to the first aspect, wherein the movement amount is measured by a displacement measuring instrument.
[0015]
According to a third aspect of the present invention, in the first aspect, the step of measuring the amount of movement is obtained from the step of measuring a sample having a concavo-convex pattern with a known cross-sectional shape to obtain an observation image, and the observation image. The probe position correcting method includes a step of obtaining a cross-sectional image perpendicular to the plane and a step of comparing the cross-sectional image and the cross-sectional shape of the concavo-convex pattern.
[0016]
According to a fourth aspect of the present invention, in the third aspect, the step of comparing the cross-sectional image and the cross-sectional shape is a step of obtaining a function representing the cross-sectional shape from the cross-sectional image, and the cross-sectional shape of the function and the concavo-convex pattern is The probe position correcting method is characterized by comprising a step of comparing with a function to be expressed.
[0017]
According to a fifth aspect of the present invention, in the third aspect, the step of comparing the cross-sectional image with the cross-sectional shape is a step of obtaining the side wall angle from the cross-sectional image, and the side wall angle is compared with the side wall angle of the concavo-convex pattern. The probe position correction method is characterized by comprising steps.
[0018]
According to a sixth aspect of the present invention, in the third aspect, the step of comparing the cross-sectional image and the cross-sectional shape compares slopes at the same height of the cross-sectional image and the cross-sectional shape of the concavo-convex pattern. The probe position correction method is as follows.
[0019]
Further, according to a seventh aspect of the present invention, in the third aspect, the step of comparing the cross-sectional image and the cross-sectional shape is an arbitrary reference at the same height of the cross-sectional image and the cross-sectional shape of the concavo-convex pattern. The probe position correction method is characterized by comparing distances from points.
[0020]
According to an eighth aspect of the present invention, in the second aspect, the displacement measuring means is a displacement sensor using at least one of an optical change, an electrical change, a magnetic change, and a mechanical change. The probe position correction method is characterized by the following.
[0021]
According to a ninth aspect of the present invention, in the first aspect, in the step of correcting the probe position, the coordinates of the pixels constituting the observation image of the sample are corrected based on the movement amount. There is a position correction method.
[0022]
According to a tenth aspect of the present invention, in the first aspect, at the stage of correcting the probe position, the first scanning axis direction and the second scanning axis are set such that an observation image is obtained and the movement amount is corrected. A probe position correcting method is characterized in that the probe is moved in the direction.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. Here, the coordinate axes substantially parallel to the sample surface and perpendicular to each other are defined as the X axis and the Y axis, and the coordinate axes perpendicular to both are defined as the Z axis.
[0024]
FIG. 1 is a flowchart of a position correction method according to the present invention. First, when the probe moves relatively in the Z-axis direction, the amount of movement in the XY plane that occurs because the probe trajectory is not completely a straight line is measured. Next, the probe position is corrected based on the measured movement amount of the probe in the XY plane direction. As a result, it is possible to obtain a highly accurate observation image that eliminates the influence of the movement of the probe in the XY plane direction.
[0025]
Next, the step of measuring the movement amount will be described. First, in the stage of measuring the amount of movement in the XY plane, there are two types of measurement of the amount of movement: direct measurement by a displacement measuring instrument and indirect measurement in which the amount of movement is obtained by measuring a sample. In the direct measurement, the displacement measuring instrument can be used regardless of the method such as an optical interference method or a capacitance method.
[0026]
FIG. 2 is a flowchart of the indirect measurement method at the stage of measuring the amount of movement of the probe in the XY direction. First, an observation image of a sample having a pattern with a known cross-sectional shape is acquired by a scanning probe microscope.
[0027]
Next, a cross-sectional image is obtained from the observed image. FIG. 3 shows the cross-sectional shape of the observation image and the cross-sectional shape of the concavo-convex pattern. 301 is a cross-sectional shape of the concavo-convex pattern, and 302 is a cross-sectional shape obtained from an observation image of the concavo-convex pattern. Both have a cross-sectional shape in the X-axis direction. As shown in FIG. 3, the movement amount Δx can be obtained by comparing the cross-sectional shapes.
[0028]
Next, the step of comparing cross-sectional shapes will be described. FIG. 4 shows a cross section in the X direction. 401 is a cross-sectional shape of a concavo-convex pattern having a known cross-sectional shape, and 402 is a cross-sectional shape obtained from an observation image of the concavo-convex pattern. A function g (x) representing the cross-sectional shape 402 is obtained and compared with a function f (x) representing the cross-sectional shape 401. Thus, the movement amount Δx at an arbitrary height can be easily obtained.
[0029]
FIG. 5 shows a cross-section in the X direction of the concavo-convex pattern and its observation image, where 501 is the cross-sectional shape of the concavo-convex pattern, and 502 is the cross-sectional shape obtained from the observation image. The concavo-convex pattern has a known cross-sectional shape and the side wall angle is α. As described above, the movement amount Δx can be obtained by measuring the concave / convex pattern having a known side wall angle and comparing the side wall angle β obtained from the observed image with the side wall angle α of the concave / convex pattern. Here, as an example of a sample whose sidewall angle is known, there is a pattern having a sidewall angle of about 55 degrees formed by anisotropic etching of silicon.
[0030]
FIG. 6 shows a cross-section in the X direction of the concavo-convex pattern and its observation image, 601 is the cross-sectional shape of the concavo-convex pattern, and 602 is the cross-sectional shape obtained from the observation image. As shown in the drawing, in the cross-sectional shapes 601 and 602, the probe movement amount Δx can be obtained by comparing the slopes Δx1 / Δz and Δx2 / Δz at the same height z.
[0031]
FIG. 7 shows a cross section in the X direction of the concavo-convex pattern and its observation image, where 701 is the cross-sectional shape of the concavo-convex pattern and 702 is the cross-sectional shape obtained from the observation image. Reference numeral 703 denotes a point on the cross-sectional shape 701 having a height z, and reference numeral 704 denotes a pixel constituting an observation image. The pixel 704 corresponds to the point 703 on the cross-sectional shape 701, and its coordinates should be (x1, z). However, since the probe moves in the XY plane as the Z moves, the pixel 704 The coordinates are (x2, z). Here, if correction is performed based on the movement amount Δx obtained by the method described above, the correct coordinates of the pixel 704 can be obtained, and the position of the probe when the pixel 704 is sampled can be corrected. Here, one pixel has been described for the sake of explanation, but it goes without saying that correction is performed on all the pixels constituting the observation image.
[0032]
FIG. 8 shows a scanner combining an XY scanning tube actuator and a Z driving tube actuator. 801 is an XY scanning tube actuator, 802 is a Z driving tube actuator, 803 is an X scanning electrode, 804 is a Y scanning electrode, 805 is a tube-type piezoelectric body, 806 is a common electrode, 807 is a Z driving electrode, 808 Is a cantilever, and 809 is a probe. As the Z drive tube actuator 802 is extended, a probe displacement Δx is generated. Δx is obtained by the method described above, and the XY scanning tube actuator is controlled to move the probe by Δx in the opposite direction. Thereby, the position of the probe can be corrected. Here, a tube type actuator has been described as an example. However, the actuator is not limited to this, and the same effect can be obtained for all actuators having XYZ and three axes.
[0033]
Further, by using the same actuator as the actuator 801 as the Z drive actuator, the displacement Δx can be corrected by controlling the voltage applied to the electrodes 803 and 804. Here, the electrode of the actuator 801 is divided into four, but if there are two or more electrodes, the displacement Δx can be corrected.
[0034]
As described above, in the present embodiment, for the purpose of explanation, the probe position correction has been described mainly with respect to the X-axis direction, but the same applies to the Y-axis direction. In addition, not only the moving amount but also the moving direction can be obtained.
[0035]
Further, it is desirable that the concave / convex pattern has a side wall angle smaller than the angle formed by the side wall of the probe and the sample surface, and the tip of the probe is not in contact with the sample surface.
[0036]
【The invention's effect】
As described above, according to the present invention, it is possible to correct the positional deviation of the probe due to the movement of the probe in the XY plane caused by the movement of the probe in the Z-axis direction.
[0037]
Further, according to the present invention, the position of the probe can be corrected with high accuracy by measuring the amount of movement of the probe by the displacement measuring instrument.
[0038]
Further, according to the present invention, a cross-sectional image perpendicular to the sample plane is generated from an observation image obtained by measuring a sample having a concavo-convex pattern with a known cross-sectional shape, and the cross-sectional shape of the concavo-convex pattern is compared. Thus, the amount of movement of the probe can be obtained, and in this way, the amount of movement of the probe can be easily measured without using an external device such as a displacement sensor.
[0039]
Further, according to the present invention, in the step of comparing the cross-sectional image and the cross-sectional shape, the step of obtaining the function representing the cross-sectional shape from the cross-sectional image, and the function and the function representing the cross-sectional shape of the concavo-convex pattern are compared. A detailed change in the amount of movement of the probe in the XY plane with respect to the amount of movement of the probe in the Z direction can be obtained.
[0040]
Further, according to the present invention, the amount of movement of the probe in the XY plane can be easily obtained by measuring the side wall angle in the cross-sectional image obtained from the observation image and comparing the side wall angle with the concave-convex pattern. .
[0041]
Further, according to the present invention, by comparing the cross-sectional image obtained from the observed image and the inclination of the cross-sectional shape of the concavo-convex pattern at the same height, even if the concavo-convex pattern having a non-planar side wall is used, The amount of movement in the XY plane can be obtained.
[0042]
Further, according to the present invention, the coordinates of the pixels constituting the observation image are corrected based on the movement amount of the probe in the XY plane obtained by the method as described above. By doing so, the position of the probe can be easily corrected, and an accurate observation image can be obtained for the sample.
[0043]
Further, according to the present invention, the position of the probe can be corrected in real time by moving the probe so as to correct the movement of the probe in the XY plane at the same time as obtaining an observation image.
[Brief description of the drawings]
FIG. 1 is a flowchart of a probe position correcting method according to the present invention.
FIG. 2 is a flowchart for measuring the amount of movement of the probe in the XY plane according to the present invention.
FIG. 3 is an explanatory diagram related to measurement of the amount of movement in the XY plane of a probe according to the present invention.
FIG. 4 is an explanatory diagram relating to measurement of the amount of movement of the probe according to the present invention in the XY plane.
FIG. 5 is an explanatory diagram related to measurement of the amount of movement of the probe according to the present invention in the XY plane.
FIG. 6 is an explanatory diagram relating to measurement of the amount of movement of the probe according to the present invention in the XY plane.
FIG. 7 is an explanatory diagram relating to a probe position correcting method according to the present invention.
FIG. 8 is an explanatory diagram relating to a probe position correcting method according to the present invention.
FIG. 9 is a schematic view of an atomic force microscope which is one of conventional scanning probe microscopes.
FIG. 10 is a schematic diagram showing a tube-type XYZ translator.
FIG. 11 is a schematic diagram showing a tube-type Z translator.
FIG. 12 is a schematic diagram showing a tube-type Z translator having a thickness deviation in the X direction.
FIG. 13 is a schematic view showing a cross section of a sample having a concavo-convex pattern.
[Explanation of symbols]
301 Cross-sectional shape of uneven pattern 302 Cross-sectional shape obtained from observation image 401 Cross-sectional shape of uneven pattern 402 Cross-sectional shape obtained from observation image 501 Cross-sectional shape of uneven pattern 502 Cross-sectional shape obtained from observation image 601 Cross-sectional shape of uneven pattern 602 Observation Cross-sectional shape 701 obtained from the image Cross-sectional shape 702 of the concavo-convex pattern Cross-sectional shape 703 obtained from the observation image Point 704 having a height z on the concavo-convex pattern Pixel 801 constituting the observation image XY scanning tube actuator 802 Z drive tube type Actuator 803 X scanning electrode 804 Y scanning electrode 805 Tube type piezoelectric body 806 Common electrode 807 Z driving electrode 808 Cantilever 809 Probe 901 Cantilever 902 Deflection detector 903 XYZ translator 904 Sample 905 Sample cost 906 Controller 907 Computer 1006 Tube-type piezoelectric body 1007 Electrode 1008 Electrode 1101 Cantilever 1102 Outer electrode 1103 Inner electrode 1104 Tube-type piezoelectric body 1201 Cantilever 1202 Outer electrode 1203 Inner electrode 1204 Tube-type piezoelectric body 1205 Position of the cantilever in the Z direction when no voltage is applied 1206 Cantilever Z-direction position 1207 when expanded by applying voltage 1208 Cantilever position in X-direction when not applying voltage 1208 Cantilever position in X-direction when expanded by applying voltage 1301 Convex pattern cross-sectional shape 1302 From measurement results Obtained cross-sectional shape

Claims (18)

Raster scanning is performed with a probe in a plane consisting of a first scanning axis substantially parallel to the sample surface and a second scanning axis substantially parallel to the sample surface and perpendicular to the first scanning axis. Scan for observing a minute structure on the sample surface by moving the probe relatively in the direction of the third scan axis perpendicular to both the first scan axis and the second scan axis so as to follow the unevenness. Is a probe position correction method for correcting the probe position of a scanning probe microscope,
The scanning probe microscope is
A cylindrical first electrode arranged along the third scanning axis direction, a cylindrical second electrode arranged outside the first electrode, and the first electrode and the second electrode A third axis driving unit comprising a piezoelectric body that is sandwiched and moves the probe in the third scanning axis direction by applying a voltage to the first electrode and the second electrode; In the third shaft drive unit, each of the distance between the first electrode and the second electrode has a different size,
An other-axis drive unit that moves the probe in the first scanning axis direction and the second scanning axis direction,
Measuring the amount of movement of the probe in the plane that occurs as the probe moves in the third scanning axis direction;
Correcting the probe position based on the amount of movement,
The step of measuring the amount of movement includes a step of measuring a sample having a concavo-convex pattern with a known cross-sectional shape to obtain an observation image, a step of obtaining a cross-sectional image perpendicular to the plane obtained from the observation image, A probe position correcting method comprising: comparing a cross-sectional image with a cross-sectional shape of the concavo-convex pattern.   The probe position correcting method according to claim 1, wherein in the step of measuring the movement amount, the movement amount is measured by a displacement measuring instrument.   The step of comparing the cross-sectional image and the cross-sectional shape includes a step of obtaining a function representing the cross-sectional shape from the cross-sectional image, and a step of comparing the function and a function representing the cross-sectional shape of the concavo-convex pattern. The probe position correcting method according to claim 1.   2. The step of comparing the cross-sectional image and the cross-sectional shape includes a step of obtaining a side wall angle from the cross-sectional image and a step of comparing the side wall angle and a side wall angle of the concavo-convex pattern. Probe position correction method.   The probe position correcting method according to claim 1, wherein the step of comparing the cross-sectional image and the cross-sectional shape compares inclinations of the cross-sectional image and the cross-sectional shape of the concavo-convex pattern at the same height.   2. The step of comparing the cross-sectional image and the cross-sectional shape compares a distance from an arbitrary reference point at the same height of the cross-sectional image and the cross-sectional shape of the concavo-convex pattern. Probe position correction method.   3. The probe position correcting method according to claim 2, wherein the displacement measuring means is a displacement sensor using at least one of an optical change, an electrical change, a magnetic change, and a mechanical change.   2. The probe position correcting method according to claim 1, wherein, in the step of correcting the probe position, the coordinates of the pixels constituting the observation image of the sample are corrected based on the movement amount.   The probe is moved in the first scanning axis direction and the second scanning axis direction so as to obtain an observation image and correct the movement amount in the step of correcting the probe position. 2. The probe position correcting method according to 1. Raster scanning is performed with a probe in a plane consisting of a first scanning axis substantially parallel to the sample surface and a second scanning axis substantially parallel to the sample surface and perpendicular to the first scanning axis. Scan for observing a minute structure on the sample surface by moving the probe relatively in the direction of the third scan axis perpendicular to both the first scan axis and the second scan axis so as to follow the unevenness. Is a probe position correction device for correcting the probe position of a scanning probe microscope,
The scanning probe microscope is
A cylindrical first electrode arranged along the third scanning axis direction, a cylindrical second electrode arranged outside the first electrode, and the first electrode and the second electrode A third axis driving unit comprising a piezoelectric body that is sandwiched and moves the probe in the third scanning axis direction by applying a voltage to the first electrode and the second electrode; In the third shaft drive unit, the distance between the first electrode and the second electrode in each having a different size,
An other-axis drive unit that moves the probe in the first scanning axis direction and the second scanning axis direction,
The scanning probe microscope measures the amount of movement of the probe in the plane caused by the movement of the probe in the third scanning axis direction, corrects the probe position based on the amount of movement,
The scanning probe microscope measures a sample having a concavo-convex pattern with a known cross-sectional shape to obtain an observation image, obtains a cross-sectional image perpendicular to the plane obtained from the observation image, and obtains the cross-sectional image and the cross-sectional image The probe position correcting apparatus characterized in that the amount of movement is measured by comparing the cross-sectional shape of the concavo-convex pattern.   The probe position correcting apparatus according to claim 10, wherein the scanning probe microscope measures the movement amount using a displacement measuring instrument. The scanning probe microscope, said calculating a function representing the cross-sectional shape from a cross-sectional image, the function and the and comparing the function representing the cross sectional shape of the concavo-convex pattern according to claim 1 0 probe position correction according apparatus. The scanning probe microscope calculates the sidewall angle from the cross-sectional image, the side wall angle and the uneven pattern probe position correcting device according to claim 1 0, wherein the comparing the angle of the sidewall.   The probe position correcting apparatus according to claim 10, wherein the scanning probe microscope compares the cross-sectional image and the inclination of the cross-sectional shape of the concavo-convex pattern at the same height.   The probe position correcting apparatus according to claim 10, wherein the scanning probe microscope compares a distance from an arbitrary reference point at the same height of the cross-sectional shape of the cross-sectional image and the concavo-convex pattern.   The probe according to claim 11, wherein the displacement measuring means is a displacement sensor using at least one of an optical change, an electrical change, a magnetic change, and a mechanical change. Position correction device.   11. The probe position correcting apparatus according to claim 10, wherein the scanning probe microscope corrects the coordinates of pixels constituting the observation image of the sample based on the movement amount in the step of correcting the probe position. .   In the step of correcting the probe position, the scanning probe microscope moves the probe in the first scanning axis direction and the second scanning axis direction so as to obtain an observation image and correct the movement amount. The probe position correction apparatus according to claim 10.

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