JP3359181B2 - Scanning probe microscope and image measurement method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope which scans a probe by approaching the surface of the sample and measures the shape of the sample surface by using a physical quantity generated between the probe and the sample surface. The present invention relates to a method for measuring an image.

[0002]

2. Description of the Related Art A scanning tunneling microscope (STM) is one of surface microscopes having a spatial resolution of an atomic scale.
Alternatively, a scanning probe microscope such as a scanning atomic force microscope (AFM) has been put into practical use. This is an information processing apparatus that writes information in a local area because its probe can access a sample surface at an atomic level. And so on. Hereinafter, a scanning tunneling microscope (STM) will be described as an example of such a scanning probe microscope.
In STM, the axial direction (Z direction) of the probe and the sample surface (XY)
And the probe is fixed to a piezoelectric element displaced in the XYZ directions. The probe is made of a conductive material such as Pt-Ir or W. When a voltage is applied between the probe and the sample and the probe is brought close to the sample by about 1 [nm], the probe and the probe are connected. The tunnel current flowing between the samples is measured. At this time, the position (Z) of the probe is controlled so that the tunnel current becomes a preset constant value, and the unevenness at the position coordinates on the sample surface is obtained from the displacement amount. Then, the probe scans a predetermined area on the sample surface in the X and Y directions to obtain a shape image of the area. Measurement data is X,
It is determined by each of the Y and Z coordinates, and is displayed as a luminance modulation image or a color modulation image with respect to the Z coordinate. The fine shape on the sample surface can be analyzed from this image. The scanning of the probe at the time of the measurement will be described. The probe is sequentially moved to measurement points at preset intervals on the measurement sample surface (X, Y), and a physical quantity such as a predetermined tunnel current is measured at each measurement point. The probe is moved to the position (Z) where is measured, and the displacement is recorded. As shown in FIG. 1, the moving procedure in the XY plane first moves the probe at a predetermined interval in the X + direction, and measures the position (Z) of the probe at each position. When the recording of the predetermined number is completed, the probe returns on the same line in the X-direction. After moving in the Y direction at predetermined intervals, measurement in the X + direction is started again.

[0003]

However, in such a conventional device, the information (X,
Y, Z) are information obtained at the time of scanning in the X + direction.
Time and information in the movement of the probe in the-direction were not utilized. Further, in the position control in the Z-axis direction, after moving to the measurement position (X, Y), the probe is displaced in the Z direction to a position where a physical quantity such as a set tunnel current can be measured. Therefore, when the surface of the measurement sample has severe irregularities, the probe may come into contact with the sample and be damaged. In addition, a method has been proposed in which the unevenness of a scanning area is measured in advance, predicted data of a measurement target area is created based on the measured data, and used for scanning (Japanese Patent Laid-Open No. 6-50707). Even in this case, the safety of the probe and the sample when measuring the unevenness of the scanning area in advance and the speed of observing the measurement target area based on the expected data are still insufficient. Was.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide a scanning probe microscope capable of measuring an image at high speed and safely and an image measuring method using the same.

[0005]

According to the present invention, in order to achieve the above object, a probe is brought close to a sample surface and scanned, and the sample is made using a physical quantity generated between the probe and the sample surface. A scanning probe microscope for measuring the surface shape is used to record at least the forward and backward position information of the probe.
A measured value storage section to be recorded, and a data processing section for comparing information obtained by scanning the forward and backward passes of the same X-direction line in the surface direction of the probe with respect to the sample surface and correcting the difference.
, So that measurement can be performed faster and more safely than conventional measurement means. Further, the scanning probe microscope of the present invention calculates the predicted scanning data of the next forward probe in the X direction line based on the recording data of the measured value storage unit and the processing data of the data processing unit. , Can be configured to store this data,
Further, when the same scanning area as the already scanned area is scanned, if there is a difference between the recording data of the already scanned area and the measurement data by the current scanning, the difference is corrected. Can be configured. And
As a method of measuring the image of the scanning probe microscope, a calculation of matching the forward and backward information of scanning of the same X-direction line in the surface direction of the sample surface of the probe is calculated,
While performing the correction process based on the calculation, it is possible to configure so that the forward path and the return path are alternately measured by the 1X direction line in the Y direction in the plane direction of the sample surface of the probe.
Further, based on the information on the forward path and the return path, a scanning position of the next forward path of the probe is predicted, and the probe is moved to the predicted position and then measured, and the same scanning area as the already scanned area is measured. When scanning is performed, the probe is scanned in accordance with the measurement data of the scanning area, the difference between the recording data of the already scanned area and the measurement data of the current scan is measured, and the difference is corrected. It can also be configured.

[0006]

According to the present invention, the scanning in the X + direction of the probe is performed by alternately using the scanning in the backward (X +) direction and the forward (X-) direction of the same X direction line for each line in the Y direction as described above. Is compared with the image obtained by scanning in the X-direction, and the correction is performed to eliminate the difference, and the measurement is performed.
High-speed measurement can be performed as compared with a conventional method in which scanning in the X-direction is not used for measuring information. In addition, the scan data in the X + direction of a certain line and the scan data in the X-direction after being moved by the set value in the Y direction are corrected.
The next scan data in the X + direction is predicted. In controlling the probe at each set measurement position, an image can be obtained safely by moving the probe to the predicted position and then performing fine correction in the Z direction. If measurement data of the same area exists, the data is scanned as expected data, and the image is corrected by measuring the deviation from the set value of the measured physical quantity, thereby making the measurement much faster than the conventional measurement method. In addition, an image can be obtained safely by preventing collision between the probe and the sample.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] In this embodiment, a scanning tunneling microscope (STM) will be described as an example of a scanning probe microscope. FIG. 2 shows the configuration of the probe and scanning mechanism of the STM and the data processor. Reference numeral 1 denotes a probe, the tip of which is sharpened and faces the sample 2. The probe 1 is fixed to a probe driving piezoelectric element 3, and the piezoelectric element 3 is
It is composed of actuators used for movement in the direction, Z direction, and scanning. A power supply 4 is connected between the probe 1 and the sample 2, and a set voltage is applied. Probe 1 in this state
Is brought closer to the sample 2, a tunnel current starts to flow, and the detected tunnel current is converted into a voltage by the current-voltage converter 10. This voltage value is input to the feedback circuit 9, and a voltage is applied from the feedback circuit 9 to the Z-direction control actuator of the piezoelectric element 3 so that the voltage becomes equal to the set value, and the height of the probe 1 changes. In normal shape measurement, the probe 1 is scanned in the X and Y directions while controlling the height of the probe 1 as described above. X
The scanning in the Y direction is performed by driving the actuator for controlling the X direction and the actuator for controlling the Y direction of the piezoelectric element 3 by applying a voltage from the XY scanning control unit 5. X at this time
The displacement in the YZ directions is recorded in the measured value storage unit 6, subjected to data processing, and displayed on the display device 11.

In an actual measurement, first, an actuator for controlling in the Y direction is used.
Fixed voltage applied to eta, line scanning only in X direction
I do. X on the same line as the measurement data a in the X + direction scan
The measurement data b of the − direction scan is sent to the data processing unit 7.
You. In the data processing unit 7, the measurement data a and b are obtained for each measurement point.
Fx such that the data of a and b match
Is estimated. The calculation fx is the sum of the errors at the measurement points a and b.
Set to the minimum. At this time, the tip of the probe is sharp
In addition, the better the symmetry, the smaller the error. Next, in the XY plane
Is performed on the movement path shown in FIG. As an example
200 A method for obtaining measurement data of × 200 points will be described.
The scanning of the first line in the Y direction measures 200 points in the X + direction.
Z is measured at a fixed point and recorded in the measured value storage unit 6.
Next, it moves one step in the Y direction,
Scanning measures Z at 200 points in the X-direction.
Set. The measurement data in the X-direction is stored in the data processing unit 7.
And processed by the calculation fx, and recorded in the measured value storage unit 6.
You. The probe 1 moves one step in the Y direction and performs the above operation.
Repeat 100 times. This allows scanning in the X + direction and the X- direction.
The scan is measured alternately for a total of 200 lines. Conventional method
In this case, the scanning in the X-direction was wasted time.
Scans in the X + and X- directions are used for each line.
By using it, high-speed measurement can be performed.

[Embodiment 2] Embodiment 2 of the present invention will be described below.
4 will be described. 200 as an example × 200point
The method for obtaining the measurement data of FIG. The scanning in the XY plane is shown in FIG.
Is performed on the movement route shown in FIG. 200 lines in the Y direction
To measure the data, scan 200 lines in the X + direction and X-
Scanning 199 lines in the direction are performed alternately. First X +
Z measurement is performed at 200 points per line
It is recorded in the measured value storage unit 6 in FIG. 4 (data A). next
After moving one step in the Y direction, scanning in the X-direction is performed, and measurement is performed.
The constant value is recorded in the measured value storage 6 (data B). Day
Data B is processed by the calculation fx used in the first embodiment and
B ′. Next, the next X + direction from data A and data B '
Direction data is predicted and input to the reference value storage 8.
You. After moving one step in the Y direction, scanning in the X + direction is performed.
You. Point1 measurement as a method of moving the probe at the time of measurement
Is completed, the data of point2 in the reference value storage unit 8 is used.
The probe 1 moves to the expected Z value, and then moves in the X direction.
The tunnel current set at the end.
Then, fine adjustment in the Z direction is performed. 20 obtained in this way
0 point data is used again as data A.
Is displayed on the display device.

A method of predicting the next scan data in the X + direction from data A and data B 'will be described with reference to FIG. X
An arbitrary position of the measurement value data A of the + direction scanning is set to point 1 and
The positions of the measurement value data B 'in the 2,3,4,5 and X-direction scans are point 6,7,8,9,10, and the expected positions in the X + direction are point11,12,13,14,15. In order to predict point13, point1 and 7,3
, 8, 5 and 9 are calculated by linear approximation. However, for the first two points and the last two points of the line, calculation is performed using only existing measurement data. By making use of the scanning in the X-direction, which has been moved uselessly in the conventional method, it is possible to minimize the contact between the probe 1 and the sample 2 and measure safely.

Third Embodiment A third embodiment of the present invention will be described below. The present embodiment is a measuring method for re-scanning the same area as the once measured area, which will be described below with reference to FIG. First, data (A) for one image is recorded in the reference value storage unit 8. A voltage is applied to the X, Y, and Z direction control piezoelectric elements so that the probe 1 moves in exactly the same manner as the recording of the data (A). The scanning method in the XY plane may be the same as the conventional method (FIG. 1). When the data (A) is exactly the same as the measurement sample (FIG. 8), the tunnel current does not deviate from the set value. Further, the probe 1 cannot come into contact with the sample 2 and can measure safely and at high speed. When there is a difference between the data (A ′) and the measurement sample (FIG. 9),
At that position, a difference occurs between the tunnel current value and the set value. In this case, the difference between the tunnel current value and the set value due to the above method is measured at the time of scanning in the X + direction, and a correction value of the Z value is calculated from the difference at the time of scanning in the X− direction to correct the data (A ′). indicate.

[0012]

As described above, according to the present invention, X +
Since the scanning is performed by alternately performing the directional scanning and the X-direction scanning and performing the correction processing, the measurement can be performed at a high speed.
A configuration is adopted in which the next scan data in the X + direction is predicted from the corrected scan data in the X-direction after being moved by the set value in the Y direction, and the probe is moved to the predicted position before measurement. Thereby, it is possible to form an image safely. In addition, it scans the measured data of the same area as expected data, measures the deviation from the set value of the measured physical quantity, and corrects the difference. Can be formed. Therefore, a large area is scanned at high speed by a method of alternately performing the rightward scan and the leftward scan for each line, and the measurement area is squeezed, and the observation target area is safely measured by the method of predicting the scan data described above. Finally, it is possible to properly use the above-described method of measuring the same area to perform fine correction of data quickly and safely.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional XY scanning method of a scanning probe microscope.

FIG. 2 is a first embodiment of a scanning probe microscope according to the present invention.
FIG. 3 is a configuration diagram illustrating a main configuration of the first embodiment.

FIG. 3 is a first embodiment of a scanning probe microscope according to the present invention.
FIG. 5 is a diagram showing an XY scanning method of FIG.

FIG. 4 is a second embodiment of the scanning probe microscope according to the present invention.
FIG. 3 is a configuration diagram illustrating a main configuration of the first embodiment.

FIG. 5 is a second embodiment of the scanning probe microscope according to the present invention.
FIG. 5 is a diagram showing an XY scanning method of FIG.

FIG. 6 is a conceptual diagram for explaining a scan data prediction method according to a second embodiment.

FIG. 7 is a scanning probe microscope according to a third embodiment of the present invention;
FIG. 3 is a configuration diagram illustrating a main configuration of the first embodiment.

FIG. 8 is a conceptual diagram illustrating a measurement method according to a third embodiment.

FIG. 9 is a conceptual diagram illustrating a measurement method according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Probe 2 ... Sample 3 ... Probe driving piezoelectric element 4 ... Power supply 5 ... XY scanning control unit 6 ... Measured value storage unit 7 ... Data processing unit 8 ... Reference value storage unit 9 ... Feedback circuit 10 ... Current-voltage conversion circuit 11 ... Display device

Continuation of the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00-21/24 G01B 21/30 H01J 37/28 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A scanning probe microscope for scanning a probe close to a sample surface and measuring a shape of the sample surface by using a physical quantity generated between the probe and the sample surface . Record the position information of the outbound and return trips respectively
And a data processing unit for comparing information obtained by scanning the forward and backward paths of the same X-direction line in the surface direction of the sample surface of the probe and correcting the difference.
A scanning probe microscope, comprising: 2. A means for calculating predicted scanning data of a probe in the next forward direction in the X direction line based on the recording data of the measured value storage section and the data of the data processing section, and storing the data. 2. The method according to claim 1, wherein
2. A scanning probe microscope according to claim 1. 3. A method according to claim 1, wherein when a scan area identical to the already scanned area is scanned, there is a difference between print data of the already scanned area and measurement data obtained by a current scan.
2. The scanning probe microscope according to claim 1, further comprising means for correcting the difference. 4. A scanning probe microscope which scans a probe by approaching the surface of the sample and using a physical quantity generated between the probe and the surface of the sample at a plurality of measurement points to measure the shape of the surface of the sample. In the image measurement method, a calculation is performed on the forward and backward scans of the same X-direction line in the plane direction of the sample surface of the probe so as to match them , based on the calculation.
A scanning probe microscope for alternately measuring the forward path and the return path by 1X lines in the Y direction in the plane direction of the sample surface of the probe while performing correction processing . 5. The scanning device according to claim 4, wherein a scanning position of the next forward path of the probe is predicted based on the information on the forward path and the return path, and the probe is moved to the predicted position and then measured. Image measurement method using a scanning probe microscope. 6. When scanning the same scanning area as the already scanned area, the probe is scanned according to the measurement data of the scanning area, and the recorded data of the already scanned area and the measurement data of the current scanning are scanned. 5. The method for measuring an image of a scanning probe microscope according to claim 4, wherein a difference between the measured values is measured and the difference is corrected.