JP2000214175A - Measuring method for scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide measurement in high reliability by confirming errors, evaluating reliability of the measured data, and removing errors for less measurement error when wide-area measurement or long-time measurement in narrow- area scanning is performed with a scanning probe microscope. SOLUTION: Related to a measuring method by a scanning probe microscope for measuring a region 41 on the surface of a sample, reciprocation (42) is allowed in X-axis direction along the sample surface while fed (43) in Y-axis direction to acquire a first measurement data for the region, then reciprocation (44) is allowed in the Y-axis direction along the sample surface while fed (45) in the X-axis direction to acquire a second measurement data of that region, and the fist measurement data is compared to the second one to evaluate the measurement data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method of a scanning probe microscope, and more particularly to a measuring method of a scanning probe microscope suitable for measuring a relatively wide area determined by, for example, millimeters by wide area scanning. About.

[0002]

2. Description of the Related Art Scanning probe microscopes generally have a measurement resolution on the order of atoms (nanometers (nm) or less) and are being applied to various fields including surface shape measurement. Depending on the physical quantity used for detection, scanning tunneling microscope (STM), atomic force microscope (AF)
M), magnetic force microscope (MFM), etc., and the range of application is expanding. In particular, an atomic force microscope is suitable for detecting irregularities on a sample surface with high resolution, and has been proven in the fields of semiconductors and disks. Hereinafter, an example of an atomic force microscope will be described.

FIG. 4 shows an example of a conventional atomic force microscope. A sample stage 101a is formed below a frame 101 serving as a support of the apparatus, a sample stage 100 is provided on the sample stage 101a, and a sample 102 to be measured is arranged on the sample stage 100. The sample 102 is stationary and its position does not change. A probe approach mechanism (coarse movement mechanism) 103 is fixed to the upper part of the frame 101,
An XYZ fine movement mechanism 104 is fixed below the probe approach mechanism 103. The probe approach mechanism is used to bring the probe closer to the sample at a predetermined distance before the start of measurement, but it is of course also used to increase the distance between the probe and the sample. is there. The XYZ fine movement mechanism 104 is a mechanism for performing a fine movement operation in each of three orthogonal X, Y, and Z axes. Here, the X axis and the Y axis are axes forming a horizontal plane in the figure, and the Z axis is an axis perpendicular to the horizontal plane.

A cantilever 1 is located above the sample 102.
05 is arranged, and the probe 106 provided at the tip thereof is
It faces the surface of the sample 102. When measuring the surface of the sample 102, the probe 106 is placed close to the sample 102 at a distance such that an atomic force is generated between the probe 106 and the sample. The base end of the cantilever 105 is fixed to the edge of the lower end of the XYZ fine movement mechanism 104. Cantilever 1
05 has a predetermined flexibility, and has a characteristic that it bends and deforms in response to a change in an atomic force caused by a change in the distance between the probe and the sample.

The configuration shown in the figure is a system in which the side of the cantilever 105 is moved. The probe approach mechanism 103
Is used to quickly bring the probe 106 closer to the sample 102 before measurement, and is used for a relatively large distance movement (coarse movement). XYZ fine movement mechanism 104
For this, a tripod-type fine movement mechanism or a tube-type fine movement mechanism constituted by using a piezoelectric element is used. The tripod-type fine movement mechanism is constituted by X, Y, and Z actuators for generating fine movements in X, Y, and Z directions. When a tripod type fine movement mechanism is used for the XYZ fine movement mechanism 104, when performing measurement, the cantilever 105 performs a scanning operation by the operation of the X actuator and the Y actuator included in the XYZ fine movement mechanism 104, and performs the scanning operation by the operation of the Z actuator. Sample 102 and probe 106
The distance between is adjusted.

A displacement detector 107 for detecting the displacement of the cantilever 105 with respect to the cantilever 105 is provided.
As the displacement detector 107, an optical lever type detection optical system or a detector utilizing an interference method is used. The optical lever detection optical system includes a light source that emits laser light and a photodetector that receives laser light. The laser light emitted from the light source is reflected by the reflection surface on the back of the cantilever and is incident on the photodetector. Since the incident position of the laser beam changes according to the amount of deflection deformation of the cantilever, a change in the distance between the probe and the sample can be detected.

In the above configuration, the probe approach mechanism 103
As a result, when the distance between the probe 106 and the sample 102 is reduced to about 1 nm, an atomic force acts between the two, and the cantilever 105 bends and deforms. The deflection angle is detected by the displacement detector 107. The detection signal output from the displacement detector 107 is input to the adder 108. The adder 108 compares the detection signal with the reference value Vref, and outputs a deviation signal Vd. This deviation signal Vd is
It is input to the control unit 109. The control unit 109 generally performs proportional-integral compensation (PI control), and the output signal (Vz) is given to the Z actuator of the XYZ fine movement mechanism 104 to change the distance between the probe 106 and the sample 102. . The distance between the probe 106 and the sample 102 is maintained at a fixed distance set in advance by the reference value Vref.

With the above configuration, the probe 106 and the sample 102
The control which keeps the distance of the constant is realized. XY scanning circuit 1
The output signal (Vx, Vy) of the XYZ fine movement mechanism 10
4 X and Y actuators. The probe 106 scans the surface of the sample 102 in the XY directions in a plane according to the scanning signals (Vx, Vy) output from the XY scanning circuit 110. During this plane scan, the probe 10
The distance between 6 and the sample 102 is kept constant.

Data Vz corresponding to the amount of movement of the Z actuator and data (Vx, Vy) relating to the output signal of the XY scanning circuit 110 are stored in a memory (not shown). The display device 1 performs necessary processing using these data.
11 is displayed. Thus, the surface shape of the sample 102 can be observed. Actually, in order to perform image display, pixel data that enables image display is created in an image memory corresponding to the screen of the display device, but an arithmetic processing unit and a display processing unit that perform the data creation process are not shown. Omitted. An atomic force microscope that performs a measurement operation based on the above principle has a resolution of the order of an atom, and can easily realize observation by switching the measurement field of view from several nm to several hundred μm.

[0010]

Conventionally, the above-mentioned atomic force microscope is characterized in that it functions normally as a microscope having a fine resolution. The measuring device was intended to be used for measuring the shape of pits and the like formed on the surface of the disk. Therefore, at the time of measurement, the probe 106 is moved using the XYZ fine movement mechanism. As long as such a configuration is adopted, the scanning distance can be extended only up to a distance of at most several hundred μm. However, on the other hand, there has also been a demand for measuring, for example, the undulation of the surface of a silicon wafer based on a wide area scan by expanding the measurement range. In general, there is also a high need to measure a wide range of surface shapes by wide-area scanning from the technical aspect, and if the measurement range can be expanded with an atomic force microscope, which is a fine structure measurement device, as a measurement device Will also increase the value of use.
Thus, as a device configuration for realizing the expansion of the scanning range, there is a configuration as disclosed in, for example, JP-A-6-307489. According to this configuration, a motor-driven XY stage is used for XY scanning, which is probe scanning of the sample surface. However, if a motor drive type is adopted,
In the conventional method, there is a problem that the reliability of the measurement result is reduced. That is, when measuring a wide area undulation on the surface of a silicon wafer as a measurement target, the measurement accuracy in the Z direction (a direction orthogonal to the sample surface) is required to be, for example, several nm. However, such measurement accuracy includes drift due to temperature change over time, XY stage guidance accuracy, flatness of a chuck for mounting a sample such as a silicon wafer, and wear of the tip of a probe. Is included as an error factor. In particular, drift due to a temporal temperature change is caused by an increase in the measurement range (for example, 20 mm ×
It takes time to measure from a rectangular range of 20 mm) (for example, 1
30 minutes to create the screen), during which time the heat generated by the motor for moving the XY stage causes a temperature change, causing the sample to bend, and using a measuring device different from the undulation of the silicon wafer to be measured. A swell based on the effect of the generated heat is generated, and the result is that the measurement is performed. As described above, data obtained by wide-area measurement based on the conventional wide-area measurement device includes a large error component. With an atomic force microscope having such a conventional configuration, it is extremely difficult to confirm the reliability of the results obtained by the measurement, and it has not been established as a practical device and cannot sufficiently meet demand. Did not.

From another viewpoint, considering the above-mentioned problem of drift due to temporal temperature change, this problem occurs not only in wide-area scanning but also in narrow-area scanning. In other words, if the measurement is performed with a sufficient measurement time when performing narrow-area scanning with an atomic force microscope, the temperature due to the heat from the heat source (motor, etc.) of the measuring device affects the sample, and as a result, Thus, the above-mentioned problem of the undulation of the sample is brought up. Such a problem is also a problem that must be solved from the viewpoint of realizing a highly practical microstructure measuring device.

An object of the present invention is to solve the above-mentioned problems. In a scanning probe microscope such as an atomic force microscope, when the scanning range is expanded to a wide range of, for example, a millimeter unit, or When measuring over time in a narrow area scan, it is possible to confirm the measurement error that may occur, evaluate the reliability of the obtained measurement data, remove the measurement error and reduce the measurement error Another object of the present invention is to provide a scanning probe microscope measuring method capable of performing highly reliable measurement.

[0013]

The measuring method of the scanning probe microscope according to the present invention is constituted as follows to achieve the above object. In the measurement method according to the present invention, in a measurement target area defined on a surface of a sample, a probe arranged opposite to the sample is moved in a first direction and a second direction intersecting the first direction.
While moving in the direction, the conditions related to the probe are controlled so that the physical quantity generated between the sample and the probe is maintained in the initial setting state, and measurement data about the measurement target area is obtained from the electric quantity required for this control. It is performed by a scanning probe microscope configured as described above. The sample is usually like a silicon wafer having a microstructure to be measured on the surface, and the measurement target region is a portion set in advance as an observation target. When wide-area scanning is assumed, the measurement target area is an area having a relatively large area. The probe is usually a needle-like portion formed at the tip of a cantilever in an atomic force microscope, for example. At the stage of starting the measurement, the probe is arranged at a distance such that a physical quantity such as an atomic force is generated between the probe and the sample in a part of the measurement target area on the surface of the sample. This distance is a very fine distance corresponding to the size of an atom. While the measurement is taking place,
The state set at the start of measurement is maintained. In the measurement,
The probe is moved along the sample surface and moves within the measurement target area. At this time, the probe is moved in the first direction by the fine movement mechanism, and is moved in the second direction intersecting the first direction, for example, in an orthogonal relationship, whereby the entire area of the measurement target area is measured. become. More specifically, measurement points (sampling points) at which measurement data are acquired at predetermined intervals are defined, and measurement data regarding a plurality of measurement points is acquired. In the case of an atomic force microscope,
The displacement in the height direction of the probe becomes measurement data. In the above scanning probe microscope, the measuring method according to the present invention,
A first reciprocating operation is performed in the first direction along the surface of the sample and a feeding operation is performed in the second direction to obtain first measurement data of the measurement target area, and then a second measurement is performed along the surface of the sample. The second measurement data of the measurement target area is obtained by performing the reciprocating operation in the direction and the feeding operation in the first direction, and comparing the first and second measurement data. When performing measurement with a scanning probe microscope on a measurement target area, it is necessary to perform a feed operation while reciprocating the probe. However, the measurement is performed twice by exchanging the first direction and the second direction. ing. By obtaining two measurement data and comparing these measurement data, it is possible to evaluate whether or not the sample is undulating with respect to the portion of the measurement target area. In other words, when measuring the same portion twice, for example, it takes time to move the probe in the feed direction. In this case, if there is undulation in the feed direction, it should occur remarkably. Therefore, it is possible to accurately evaluate the state of undulation by comparing measurement data obtained by two measurements at the same location. In addition, it is most preferable that the crossing relationship between the first direction and the second direction is orthogonal from the viewpoint of the conventional general measurement method. However, in principle, if the reciprocating direction and the feeding direction are determined, It is not always necessary that the first direction and the second direction are orthogonal to each other.

[0014] The method for measuring a scanning probe microscope according to the present invention, more preferably, in the above-mentioned method, relates to a comparison between the first and second measurement data. Is a method of calculating the difference between the two. There are various ways of performing the comparison process (difference, least mean square, etc.), but as a configuration of a control system for controlling the measurement method, a method of calculating the difference and evaluating the content of the error component is simple in configuration. , Effective evaluation can be performed. Further, the measurement method according to the present invention is a method in which the measurement target region is a square having a distance of 1 mm or more in each of the first direction and the second direction, and more preferably a square having a side of 20 mm. is there. The measuring method of this scanning probe microscope is to evaluate an error component included in measurement data due to a drift due to a temporal temperature change, and the drift due to such a temperature change is,
This occurs in the case of measurement by a wide area scan that requires a long time for measurement. Therefore, it has been clarified that the measurement target area to which the measurement method according to the present invention is applied is a wide area of 1 mm or more. More preferably, the difference between the first and second measurement data is that the observation of the measurement target area by the scanning probe microscope is a measurement at each of a plurality of set measurement points. The method is characterized by the differences for each of the points, and therefore, when the maximum of these differences exceeds the target accuracy, the measurement is taken again. More preferably, the measurement may be performed again when the average value of the differences regarding the plurality of measurement points exceeds the target accuracy.
The measuring method of the scanning probe microscope according to the present invention may be configured such that, in the above method, the measurement is repeated until the value obtained by the measurement becomes lower than the target accuracy.
As described above, when a difference is calculated as a comparison between the first measurement data and the second measurement data, by setting a target accuracy serving as a reference for evaluating the difference in advance,
Perform measurement again to obtain more effective measurement data,
Further, it is possible to realize a configuration of automation of measurement so that the measurement operation can be repeated until valid measurement data is obtained. Further, the measuring method of the scanning probe microscope according to the present invention includes the steps of:
It is also possible to finally create the most reliable observation image from which the error component has been removed by comparing and judging the observation images based on the measurement data, and to visualize this observation image on the screen of the display device It is.

[0015]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

A typical embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram schematically showing a configuration of a scanning probe microscope for carrying out a measuring method according to the present invention, FIG. 2 is a diagram conceptually showing a measuring method,
FIG. 3 shows a diagram for explaining how to calculate the difference data.

The configuration of the scanning probe microscope will be described with reference to FIG. In the present embodiment, the scanning probe microscope is an atomic force microscope as an example. Frame 11
A sample stage 11a is formed below the sample stage 11 and an XY scanning mechanism 12 is provided on the sample stage 11a. Further, a sample stage 13 is fixed on the XY scanning mechanism 12, and a sample 14 to be measured is mounted on the sample stage 13. The XY scanning mechanism 12 is a mechanism for moving the sample 14 in the X-axis direction and the Y-axis direction. Here, the X-axis direction and the Y-axis direction are orthogonal two-axis directions included in a horizontal plane in FIG. The sample 14 is stopped on the sample stage 13,
The XY scanning mechanism 12 performs the scanning operation in the X-axis direction and Y-direction.
Moved in the axial direction. A probe approach mechanism (coarse movement mechanism) 15 is fixed to the tip of the upper portion 11b of the frame 11,
A Z fine movement mechanism 16 is fixed below the probe approach mechanism 15. The probe approach mechanism 15 is for initially bringing a probe located at a position distant from the surface of the sample 14 close to the surface of the sample at the start of measurement. Also used when moving away from. In this embodiment, the atomic force microscope is configured as a microscope that can perform wide-area measurement on the surface of the sample 14, and therefore, the XY scanning mechanism 12 enables wide-area scanning, and a motor-driven scanning mechanism is usually used. ing. In practice, XY
The scanning mechanism 12 is not limited to a motor-driven mechanism,
Of course, any of a variety of mechanisms can be used.

In the atomic force microscope, the scanning operation is
This is an operation in which a later-described probe arranged so as to face the sample surface moves as if tracing the sample surface. Since the displacement is a relative displacement between the probe and the sample in the XY axis directions, either the probe or the sample may be moved. In this embodiment, the motor-driven XY is moved to the sample 14 side. By providing the scanning mechanism 12, the sample side is moved to perform scanning movement. When performing a wide area scan using a motor-driven XY scanning mechanism, it is usually preferable to move the sample side because the XY scanning mechanism is relatively heavy.

The cantilever 17 is located above the sample 14.
Is arranged. Tip 1 at the tip of cantilever 17
8 is formed, and the probe 18 faces the surface of the sample 14 so as to be able to observe the surface of the sample. Sample 14
When the surface of the sample 14 is measured, the probe 18 is moved downward by the above-described probe approach mechanism 15 and brought close to the sample 14 at a distance such that an atomic force is generated between the probe 18 and the surface of the sample 14. Placed. The cantilever 17 has a base end
The Z fine movement mechanism 16 is fixed to an edge at the lower end. The cantilever 17 has a predetermined flexibility, and has a characteristic that it bends and deforms in response to a change in an atomic force caused by a change in the distance between the probe and the sample. The Z fine movement mechanism 16 is a mechanism for moving the cantilever 17 a minute distance in the Z direction perpendicular to the horizontal plane, and is usually configured using a piezoelectric element.

The structure of the atomic force microscope shown in FIG.
The operation of the scanning movement in the Y direction is performed by the XY scanning mechanism 12, and the distance between the probe and the sample, that is, the adjustment of the height position of the probe 18 with respect to the surface of the sample 14 (movement in the Z direction) is performed by the Z fine movement mechanism 16. In this configuration, the cantilever 17 is moved. The probe approaching mechanism 15 is used when the probe 18 is quickly approached to the sample 14 before starting the measurement, and is used for a relatively large distance movement (coarse movement).

A displacement detector 19 for detecting the displacement of the cantilever 17 with respect to the cantilever 17 is provided. As the displacement detector 19, for example, a detector utilizing an optical lever detection optical system or an interference method is used. The optical lever detection optical system includes a light source that emits laser light and a photodetector that receives laser light. The laser light emitted from the light source is reflected by the reflection surface on the back of the cantilever and is incident on the photodetector. Since the incident position of the laser beam changes in accordance with the amount of bending deformation of the cantilever, a change in the distance between the probe and the sample can be detected.

In the above configuration, when the distance between the probe 18 and the sample 13 is reduced to about 1 nm by the probe approach mechanism 15, an interatomic force acts between the two, and the cantilever 17 bends. . The deflection angle is detected by the displacement detector 19. The detection signal output from the displacement detector 19 is input to the adder 20. In the adder 20,
By adding the minus (-) detection signal and the plus (+) reference value Vref, a deviation signal Vd is output, and the subtraction is substantially performed. This deviation signal Vd is
It is input to the control unit 21. The controller 21 generally performs proportional-integral compensation (PI control), and outputs an output signal (V
z) is given to the Z fine movement mechanism 16 to operate the Z fine movement mechanism 16 to change the distance between the probe 18 and the sample 14 so as to keep the distance between the probe 18 and the sample 14 at a constant distance set at the start of measurement. The distance between the probe 18 and the sample 14 is kept at a constant distance set in advance by the reference value Vref.
Based on the configuration of the control system that forms the servo loop described above, control for maintaining the distance between the probe 18 and the sample 14 at a constant distance determined by the reference value is realized.

On the other hand, the operation of the XY scanning mechanism 12 is controlled by a signal output from the XY scanning control unit 22. The XY scanning control unit 22 controls the operation of the XY scanning mechanism 12 and
Since the operation of the scanning mechanism 12 determines the scanning area on the surface of the sample, the XY scan control unit 22 determines the measurement target area on the surface of the sample 14. The XY scanning control unit 22 itself is a control unit that controls the operation of the XY scanning mechanism 12. The measurement execution control unit 31 of the higher-level control unit that performs overall control of the measurement method transmits data and measurement execution instructions related to the measurement target area. In response, the control operation is performed. The scanning signal (Vx, Vy) output from the XY scanning control unit 22 is X
It is given to each motor in the X-axis direction and the Y-axis direction of the Y scanning mechanism 12. By moving the sample 13 in the XY directions based on the scanning signals (Vx, Vy) output from the XY scanning control unit 22, the probe 18 moves the surface of the sample 14 in the XY direction as a relative positional relationship. Scan. During this plane scan, the distance between the probe 18 and the surface of the sample 14 is kept constant as described above. In the above-described scanning movement operation, the measurement target area is usually set in advance on the sample surface. The measurement target region is preferably a region having a rectangular shape including a side in the X-axis direction and a side in the Y-axis direction. Since the scanning of the sample surface by the probe 18 with respect to the measurement target area moves so as to measure the entire measurement target area, the scanning movement usually includes, for example, a reciprocating operation in the X-axis direction and a feeding operation in the Y-axis direction. Is scanned based on the combination of. Regarding the scanning signal Vx for controlling the operation of the motor in the X-axis direction and the scanning signal Vy for controlling the operation of the motor in the Y-axis direction, which of the signals for the reciprocating operation and the signal for the feeding operation will be described later. It is determined according to the measurement method.

The control signal Vz supplied from the control circuit 21 to the Z fine movement mechanism 16, that is, data (Vz) corresponding to the operation amount of the Z fine movement mechanism 16, and the XY scanning control section 22
The data (Vx, Vy) related to the scanning signal given to the XY scanning mechanism 12 from is used to create and display an image relating to the measurement target area.

With respect to the mechanical configuration and the configuration of the control system in the above-mentioned atomic force microscope, control signals and scanning signals obtained from the control system, that is, the data (Vz, V
(x, Vy), and a signal processing device 32 for processing data, and a measurement execution control unit 31 for controlling the entire measurement and executing the measurement. Signal processing device 32
Includes a memory 33 for storing data, an arithmetic processing unit 34 that performs an operation to be described later and issues an instruction regarding measurement to the measurement execution control unit 31, and a display control processing unit 36 that controls display on the display device 35. , An image memory 37 for storing image data displayed on the screen of the display device 35. Data Vz obtained from the control unit 21 and data Vx and Vy obtained from the XY scanning control unit 22 are stored in the memory 33 of the signal processing device 32. The arithmetic processing unit 34 performs necessary processing as described later using these data, and displays an image relating to the unevenness of the measurement target area measured on the screen of the display device 35 via the image memory 37. Thus, the surface shape of the sample 14 can be observed with the image displayed on the screen of the display device 35.

The scanning signals Vx and Vy output from the XY scanning control section 22 are given to the XY scanning mechanism 12,
Is moved two-dimensionally in the XY directions. Based on the planar movement of the sample 14, the probe 18 performs a planar scan on the surface of the sample 14 in a relative positional relationship. The planar movement of the sample 14 is performed based on a combination of the operation in the X-axis direction and the operation in the Y-axis direction. At this time, a reciprocating reciprocating operation is performed in one direction, and a feeding operation is performed at an arbitrary step in the other direction. Thus, for example, the entire area of the measurement target area set as a rectangular plane can be plane-scanned by the probe 18. The output scanning signals Vx and Vy determine which of the X-axis direction and the Y-axis direction is the reciprocating operation repeatedly and the other is the feeding operation.
Is determined based on

In the measuring method according to the present embodiment, a rectangular measurement target area such as a square or a rectangle is set in advance on the surface of the sample 14, and this measurement target area is, for example, a wide area whose one side is determined by a dimension of 1 mm or more. In the case of a measurement region, the measurement target region is measured by performing two-dimensional scanning on the measurement target region, and two measurement data are obtained for the same measurement target region.

In the first measurement, the scanning signal Vx is created as a signal for the reciprocating operation, and the scanning signal Vy is created as a signal for the feeding operation. Therefore, FIG.
As shown in (A), the probe 18 has a rectangular measurement target area 41.
The reciprocating operation 42 is repeated in the X-axis direction in the measurement of
While performing the feed operation 43 in the axial direction, the Z-direction data Vz of the probe is acquired at each of the set measurement points. Vz obtained in the first measurement and position data regarding each measurement point, that is, scan data Vx and Vy, are stored in the memory 33 in association with each other as first measurement data. In the second measurement, after the end of the first measurement, the roles and contents of the scanning signals Vx and Vy are exchanged, and the scanning signal Vx and Vy are switched.
y is generated as a signal for the reciprocating operation, and the scanning signal Vx is generated as a signal for the feed operation. Therefore, as shown in FIG. 2B, the probe 18 is
While repeating the reciprocating operation 44 in the Y-axis direction and performing the feeding operation 45 in the X-axis direction in the measurement 1, the Z-direction data Vz of the probe is acquired at each of the plurality of set measurement points. Vz obtained in the second measurement and position data regarding each measurement point, that is, scan data Vx and Vy are obtained by the second measurement.
As the measurement data of the memory 33
Is stored. According to the first measurement data and the second measurement data stored in the memory 33, the first measurement and the second measurement are performed for each of the plurality of measurement points in the wide measurement target area.
Measurement data (Vz) corresponding to each of the measurements is obtained.

The execution of the first measurement and the execution of the second measurement for the same measurement target area are performed by the measurement execution control unit 31.
It is performed based on the instruction from. The XY scan control unit 22 scans the scan signal V according to an instruction from the measurement execution control unit 31.
Only the scanning operation for performing two measurements is performed by exchanging the roles of x and Vy.

The above 2 for the same measurement target area 41
When the measurement is completed, the arithmetic processing unit 34 performs a process of comparing the first measurement data with the second measurement data. The comparison process in the present embodiment is, for example, a calculation process for obtaining a difference. FIG. 3 schematically shows the state of the arithmetic processing for obtaining the difference. In FIG. 3, (A) shows an arrangement state of measurement data obtained by the first measurement (reciprocating operation is performed in the X-axis direction), and (B) is a second measurement (reciprocating operation is performed in the Y-axis direction). ) Shows the arrangement state of the measured data, and (C) shows the first state.
2 shows an arrangement state of difference data obtained by calculating a difference between the measurement data of the second measurement data and the second measurement data. In FIG. 3, black circles indicate the positions of a plurality of measurement points in the measurement target area 41, and the positions are represented by (i, j). Each data of the first measurement is represented by Dx (i, j), and each data of the second measurement is represented by Dy (j, i). As shown in FIG. 3C, difference data Def (i, j) of each measurement point
Def (i, j) = Dx (i, j) -Dy by matching the measurement points of the first measurement data and the second measurement data.
It is calculated as (j, i). Thus, the difference between the first measurement data and the second measurement data is obtained, and
To memorize again.

Next, upon obtaining the difference data as shown in FIG. 3C, the arithmetic processing unit 34 evaluates the measurement result based on the difference data. Originally, the measurement was performed by scanning the same measurement target area on the surface of the sample 14 in a plane, so that the first measurement data in FIG.
The second measurement data in (B) should be the same for each measurement point. Therefore, in this case, the difference data should be 0. However, in actuality, as described above, it includes a temperature error over time, and further includes a measurement error such as a guide error of the XY moving mechanism 12 using a motor or a mechanical guide mechanism, and a worn probe. Is common, the difference data does not become zero. On the contrary, the reliability of the measurement can be evaluated and confirmed by the size of the difference data. For example, since the difference data is obtained for a plurality of measurement points in the measurement target area, by knowing the distribution state of the magnitude of the difference, it is possible to know in which direction the undulation is occurring. Also, for example, 1
When it is desired to measure the undulation of the surface of a silicon wafer with an accuracy of 0 nm or less, the obtained difference data is 10 nm.
Above, it can be determined that the measurement data is unreliable.

In the above configuration, the memory 33 stores the first
Since the measurement data, the second measurement data, and the difference data are stored in the storage device, the display control processing unit 36 and the image creation and display function of the image memory 37 allow the display device 35 An image using each data can be displayed on the screen.

For example, an image based on the first measurement data and an image based on the second measurement data are displayed on the screen of the display device 35.
When displayed in a flat display or 3D display, it is also possible to visually compare the two images and identify the difference.
In this state, if there is a clear difference between the two images at the same location, it can be determined that the reliability of the data is low, and for example, re-measurement is performed.

According to the difference data, as described above,
Since the occurrence state of the undulation of the sample or the like can be evaluated, the function of the arithmetic processing unit 34 uses the above-described first measurement data or second measurement data to correct the difference data so that the difference data becomes zero. Accordingly, it is possible to display an image from which the measurement error has been removed.

The arithmetic processing unit 34 is configured to instruct the measurement execution control unit 31 to perform another measurement when the obtained measurement data does not satisfy the required accuracy due to undulation or the like. Can also. According to this, automation of the re-measurement operation can be easily realized. By automatically performing the repeated measurement, it is possible to easily obtain measurement data of the accuracy finally required. In this case, the arithmetic processing unit 34 is provided with a comparison unit that sets a target accuracy and determines whether the accuracy of the data obtained by the measurement satisfies the target accuracy condition.

In the above-described embodiment, the measurement target area 41 is a rectangular area. However, the measurement target area 41 is not necessarily required to be rectangular. When performing two measurement operations, the direction in which the reciprocating operation is performed and the direction in which the feeding operation is performed are a combination of orthogonal X-axis and Y-axis directions, but the intersection angle of the two directions is limited to orthogonal. Not done. Further, the above-described measurement method can be generally applied to other scanning probe microscopes other than the atomic force microscope. In the above-described embodiment, the description has been given on the premise of wide-area measurement by wide-area scanning.However, when time is taken for measurement even in narrow-area measurement by narrow-area scanning, the measurement error of the temperature drift described above becomes a problem. Similarly, it goes without saying that the above-described measurement method can be applied.

[0037]

As is apparent from the above description, according to the present invention, the reciprocating operation and the feeding operation during scanning can be performed even if the scanning area is enlarged and the wide area is measured by the measuring method of the scanning probe microscope. Since the measurement is performed twice by exchanging the measurement data, the measurement data can be evaluated by comparing the obtained two measurement data, the measurement error can be reduced, and the reliability of the measurement can be confirmed. As a result, the reliability of the measurement data can be improved, and wide area measurement by wide area scanning can be performed. For wide-area measurement, a motor or the like that enables wide-area scanning is used as an XY scanning mechanism. In this case, the problem of temperature drift due to heat generated by a heat source included in the XY scanning mechanism can be solved, and highly accurate measurement can be performed. Data can be obtained. In addition, by setting a target accuracy and providing a comparison means for comparing the target accuracy with the accuracy of the measurement data, it is possible to obtain high-precision measurement data even in wide-area measurement, and until measurement data satisfying the target accuracy is obtained. Automatic measurement that repeats measurement can be easily realized.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a typical configuration of a scanning probe microscope for performing a measuring method according to the present invention.

FIG. 2 is a diagram conceptually showing a measuring method according to the present invention.

FIG. 3 is a diagram for explaining how to calculate difference data based on two measurement data.

FIG. 4 is a configuration diagram showing an example of a conventional scanning probe microscope.

[Explanation of symbols]

 Reference Signs List 11 frame 12 XY scanning mechanism 13 sample stage 14 sample 15 probe approach mechanism 16 Z fine movement mechanism 17 cantilever 18 probe 19 displacement detector 41 measurement target area 42 reciprocating operation 43 feed operation

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA43 BD11 CA09 CA10 DA01 DB05 DC08 DD02 EA16 EC00 FA07 GA57 JA04 LA13 LA23 LA29 MA05 2F069 AA60 EE02 EE09 GG01 GG04 GG39 GG62 GG72 HH05 JJ06 JJ14 JJ26 LL03

Claims (7)

[Claims] 1. A probe arranged in a measurement target area defined on a surface of a sample and opposed to the sample in a first direction and a second direction intersecting the first direction relative to the sample. While controlling, the conditions related to the probe are controlled so that a physical quantity generated between the sample and the probe is maintained in an initial setting state, and measurement data related to the measurement target area is obtained from the amount of electricity required for this control. A scanning probe microscope configured to obtain a first measurement data of the measurement target area by performing a reciprocating operation in a first direction and a feeding operation in a second direction along the surface of the sample. Acquiring, and then performing a reciprocating operation in a second direction along a surface of the sample and performing a feeding operation in a first direction to acquire second measurement data of the measurement target area, And the second measurement data Measuring method of a scanning probe microscope, wherein a. 2. The method according to claim 1, wherein the processing of comparing the first and second measurement data is an arithmetic processing for calculating a difference between the first and second measurement data. Measurement method of scanning probe microscope. 3. The measuring method for a scanning probe microscope according to claim 1, wherein the distance of each of the measurement target region in the first direction and the second direction is 1 mm or more. 4. The difference between the first and second measurement data is a difference with respect to each of a plurality of measurement points in the measurement target area, and the measurement is performed when a maximum value among these differences exceeds a target accuracy. 4. The method according to claim 1, wherein
The measurement method of a scanning probe microscope according to any one of the above. 5. The difference between the first and second measurement data is a difference regarding each of a plurality of measurement points in the measurement target area, and when the average value of these differences exceeds a target accuracy, the measurement is performed again. The method for measuring a scanning probe microscope according to claim 1, wherein the measurement is performed. 6. The method according to claim 4, wherein the measurement is repeated until a value obtained by the measurement falls below the target accuracy.
Or the measuring method of the scanning probe microscope of 5. 7. The scanning type apparatus according to claim 1, wherein an observation image is created and visualized by comparing and judging an observation image based on the first measurement data and an observation image based on the second measurement data. Probe microscope measurement method.