JP3117304B2 - Apparatus and method for separating and measuring surface information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface information separating apparatus for synthesizing individual information obtained by separating a plurality of pieces of surface information of the same sample to form surface information.

[0002]

2. Description of the Related Art In general, there is a scanning probe microscope which forms an image from surface information obtained by scanning the surface of a sample with a cantilever which vibrates on the surface of the sample by a predetermined natural vibration.

For example, the atomic force microscope proposed in Japanese Patent Application Laid-Open No. 63-309802 discloses a scanning method in which a cantilever having a sharp tip is brought close to a sample surface to a distance at which an atomic force can be generated. Then, a shift is detected from the natural frequency of the frequency of the cantilever needle generated by being affected by the atomic force. Here, the detected frequency shift is used as information indicating the distance between the tip of the cantilever needle and the sample surface, and an image of the sample surface is formed.

Further, by attaching magnetic powder to the tip of the cantilever needle, a scanning magnetic microscope (MFM) capable of obtaining magnetic force information of the sample is obtained.

A method for detecting the shift of the natural frequency of the cantilever needle will be described with reference to the vibration characteristics of the cantilever shown in FIG.

FIG. 7A shows a vibration characteristic of a cantilever in a state where the cantilever needle is not affected by an external force.
Is the natural frequency. FIG. 7B shows a state in which the cantilever needle is affected by a weak attractive force, and the natural frequency is f.
Go down to 2.

Further, when the cantilever needle is affected by a strong attractive force, the vibration characteristics of the cantilever are as shown in FIG. 7C, and the natural frequency drops to f3.

At this time, the cantilever is vibrated at the frequency f4, and the amplitude of the tip of the cantilever at that time is detected. With this amplitude, the change of f1, f2, f3 is V
1, V2, and V3.

FIG. 8 shows and explains the configuration of a conventional scanning magnetic force microscope.

In this scanning magnetic force microscope, an XYZ driving piezoelectric element on which a sample 5 is placed is mounted by a Z control unit 2, an X control unit 3, and a Y control unit 4 controlled by a microcomputer (hereinafter, referred to as a microcomputer) 1. The body 6 is expanded and contracted, and the sample 5 is moved in any X, Y, and Z directions.

A cantilever 7 provided so as to bring a sharp tip to the surface of the sample is attached to a probe displacement detecting unit 9 via a vibrating piezoelectric body 8. The cantilever 7 is vibrated by the vibrating piezoelectric body 8, and the displacement of the cantilever 7 caused by scanning on the sample surface is as follows.
The signal is detected by the probe displacement detector 9 and output to the amplitude detector 10 as a displacement signal S1.

The amplitude detecting section 10 includes the vibrating piezoelectric body 8
Sinusoidal signal S3 for exciting the cantilever 7
And a signal having the same frequency as that of the sine wave is detected by the lock-in amplifier and output to the A / D converter 11 as an amplitude signal S2.

The microcomputer 1 controls the X control unit 3 and the Y control unit 4 to perform measurement while scanning the sample 5 on the XYZ drive piezoelectric body 6 two-dimensionally, and to measure the displacement of the cantilever 7 by measurement data. To the host computer 12. The host computer 12 includes the microcomputer 1
It stores the measurement data transferred from, and forms an image to display and output.

Such conventional measuring methods using a scanning magnetic force microscope include a constant magnetic force gradient measurement and a constant height measurement. In the case of the constant magnetic gradient measurement, the XYZ piezoelectric body 6 is expanded and contracted in the Z direction via the Z control unit 2 based on information read from the A / D conversion unit 11. That is, the Z control unit 2 is controlled so as to keep the amplitude signal S2 at a constant value, and the Z control data is used as measurement data.

On the other hand, in the case of the constant height measurement, the signal read from the A / D converter 11 is fixed with the distance from the surface of the sample 5 to the center of vibration of the tip of the vibrating cantilever 7 fixed. That is, the amplitude signal S2 is used as measurement data.

[0016]

However, when the magnetic force information on the sample surface is measured by the above-mentioned conventional scanning magnetic microscope, the surface state of the sample affects the measured data value (image).

That is, in the case of a magnetic sample having no irregularities on the surface of the sample as shown in FIG. 9A, the measurement image as shown in FIG. 9B reflects the magnetic force information on the sample surface purely. A magnetic force image (MFM image) is obtained.

However, there are few samples with completely flat surfaces.
Actually, the sample surface has irregularities as shown in FIG. 10A, and as shown in FIG. 10B, the measurement image becomes an image in which the irregularity information and the magnetic force information are mixed on the sample surface. There is a problem that pure magnetic force information cannot be obtained. Similarly,
In the measurement as shown in FIG. 11A, a mixed image shown in FIG. 11B may be obtained.

Accordingly, the present invention provides a surface information separation / measurement apparatus which separates a plurality of pieces of surface information of the same sample and forms an image of the combined surface information in which information is individually detected and which is not affected by the surface condition. Aim.

[0020]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a cantilever having a sharp tip and a test piece.
Material and the cantilever along the surface of the sample
A sample moving means for moving the cantilever,
A vibrating body that vibrates at the frequency and stops the vibration
Displacement of the tip caused during scanning of the cantilever
A displacement detecting means for detecting the amplitude of the cantilever;
Output from the amplitude detecting means and the displacement detecting means.
To keep the vibration-free displacement signal of the cantilever constant
Surface information obtained from a control signal that controls
And the vibrating sent out from the amplitude detecting means
Control to keep the cantilever amplitude signal constant
From the second surface information obtained from the control signal, the same measurement point
The difference between the second surface information and the first surface information at
Surface information separation measurement comprising:
Provide a setting device. Also, cantilever with a sharp tip
A lever, and the sample and the cantilever are placed on the surface of the sample.
Sample moving means for relatively moving along the
Vibrates the bar at a predetermined frequency and stops the vibration
The tip generated when scanning the vibrator and the cantilever
Displacement detecting means for detecting displacement of the portion, and the cantilever
Amplitude detecting means for detecting the amplitude of
From the vibration-free displacement signal of the cantilever
The first obtained from the control signal for controlling to keep constant
Surface information and the amplitude transmitted from the amplitude detection means.
So that the amplitude signal of the moving cantilever is kept constant
From the second surface information obtained from the control signal to be controlled,
The second surface information and the first surface information at the same measurement point
Surface information separation image forming method that forms an image from the difference
provide.

[0021]

The surface information separation / measurement device having the above configuration is
The unevenness measurement (AFM measurement) and the magnetic force information measurement (MFM measurement) are separately and continuously performed on the sample surface, and the sample surface unevenness information and the magnetic force information are obtained separately. Is subtracted from each other to obtain an MFM image, and the MFM is measured while scanning the cantilever along the unevenness image obtained by the unevenness measurement.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a surface information separation / measurement apparatus according to the present invention. In the surface information separation / measurement apparatus, an XYZ on which a sample 25 is placed is placed by a Z control unit 22, an X control unit 23, and a Y control unit 24 controlled by a microcomputer (hereinafter referred to as a microcomputer) 21.
The driving piezoelectric body 26 is extended and contracted, and the sample 25 is moved in any X, Y, and Z directions.

A cantilever 27 provided so as to bring a sharp tip to the surface of the sample 25 is attached to a probe displacement detector 29 via a vibrating piezoelectric body 28. The cantilever 27 is vibrated by the vibrating piezoelectric body 28, and the tip displacement of the cantilever 27, which is determined by scanning on the surface of the sample or does not vibrate or not, is detected by the probe displacement detector 29, and a displacement signal S1 is generated. Is output to the amplitude detector 30 and the A / D converter 31.

The amplitude detecting section 30 is provided with the vibrating piezoelectric body 2
A sine wave signal S3 for vibrating the cantilever 27 is output to 8, a signal having the same frequency as the sine wave is detected by a lock-in amplifier, and output to the A / D converter 31 as an amplitude signal S2. The amplitude detector 30 can output or stop the amplitude signal S2 under the control of the microcomputer 21.

The A / D converter 31 includes the microcomputer 2
By the control of 1, any one of the displacement signal S1 and the amplitude signal S2 can be selected and output.

The microcomputer 21 is provided with the X control unit 2.
3. The Y control unit 24 is controlled to measure the XYZ drive piezoelectric body 26 while scanning the cantilever 27 two-dimensionally, and the displacement of the cantilever 27 is transferred to the host computer 32 as measurement data. The host computer 32 stores the measurement data transferred from the microcomputer 21, forms an image, and displays and outputs the image.

Further, a storage unit 33 for storing the unevenness information obtained by the AFM measurement is provided.

Next, with reference to the flow chart of FIG. 2, the constant magnetic gradient M
The measurement in the FM measurement mode will be described.

First, without vibrating the cantilever 27,
The XYZ drive piezoelectric body 26 is expanded and contracted so that the scanning start position on the sample surface is located below the tip of the cantilever.
Is moved (step S1).

Then, one line is scanned in the X direction while controlling the Z control unit 22 so as to keep the displacement signal S1 constant without vibrating the cantilever 27, and the AFM is performed.
Measure (Step S2). The unevenness data for one line by the AFM measurement is stored in the storage unit 33 (step S3).

Then, it is determined whether the AFM measurement for one line has been completed (step S4).
O), the process returns to step S2, and if it has been completed (YE)
S), the XYZ drive piezoelectric body 26 is expanded and contracted to return the tip end of the cantilever 27 to the scanning start position of the scan line in the X direction (step S5).

Next, while the cantilever 27 is vibrated and the Z control unit 22 is controlled so as to keep the amplitude signal S2 constant, the XYZ drive piezoelectric body 26 is expanded and contracted, and the sample 25 is expanded.
Are scanned in the X direction on the same scanning line (step S
6).

The Z control value of each measurement point on this scan line,
The difference between the previously measured concavo-convex data at the same measurement point at the time of AFM measurement is used as MFM data,
Transfer to Then, the MF is executed by the host computer 32.
An M image is formed and displayed (step S7).

It is determined whether the MFM measurement for one line has been completed (step S8).
If the measurement has not been completed (NO), the process proceeds to step S5, and if the measurement for one line has been completed (YES), it is determined whether the measurement of all lines has been completed (step S9).

If the determination has been completed for all lines (YES), the MFM measurement ends. However, if the measurement of all the lines is not completed (NO), the XYZ driving piezoelectric body 26 is expanded and contracted so that the scanning start position of the next scanning line in the X direction to be measured is located below the tip of the cantilever 27. Next, the sample 25 is scanned and moved in the Y direction (step S10). The same measurement is repeated for the second and subsequent lines to measure all the lines.

By the above-described measurement, the sample surface is scanned by AFM measurement as shown in FIG.
After obtaining the unevenness data as shown in FIG. 10, the same X scan line is scanned as shown in FIG. Then, the MFM data shown in FIG. 4 is obtained by subtracting the unevenness data at each measurement point from the obtained mixed data as shown in FIG. 10B.

Next, referring to the flowchart shown in FIG.
The measurement in the constant height MFM measurement mode by the surface information separation measurement device of the present invention will be described.

First, without vibrating the cantilever 27,
The XYZ drive piezoelectric body 26 is expanded and contracted so that the scanning start position on the sample surface is located below the tip of the cantilever.
Is moved (step S11).

Then, while controlling the Z control unit 22 so as to keep the displacement signal S1 constant without vibrating the cantilever 27, scanning for one line in the X direction is performed, and the AFM is performed.
Measure (Step S12). The unevenness data for one line by the AFM measurement is stored in the storage unit 33 (step S13).

Then, it is determined whether or not the AFM measurement for one line has been completed (step S14). If it has not been completed (NO), the process returns to step S2. If it has been completed (YES), the cantilever has been completed. The XYZ driving piezoelectric body 26 is moved until the leading end of the XYZ
Is expanded and contracted, and scanning is performed in the X direction and the process returns (Step S1
5).

Next, the unevenness data is read from the storage unit 33. Then, the trajectory (trajectory of the center of amplitude) of the tip of the cantilever 27 is kept at a fixed distance (height) from the sample surface, that is, at a position away from the sample surface by a fixed distance, the tip of the cantilever 27 is While the Z control unit 22 is controlled so as to trace irregularities on the surface of the sample, the cantilever 27 is vibrated to perform X scanning on the same scanning line (step S16). In the second scan, the probe
Vibrates, but the center of the vibration amplitude is obtained in the first scan
The height of the probe is controlled based on the irregularity information. Doing this
Can maintain a constant height from the sample surface
I have to.

At each measurement point on the scanning line,
The amplitude signal S2 at that time is A / D converted by the A / D converter 31 and sent to the microcomputer 21 as MFM data. The microcomputer 21 transfers the MFM data to the host computer 32. In the host computer 32, an MFM image is formed and displayed (step S17).

It is determined whether or not the above-described MFM measurement for one line has been completed (step S18).
If the M measurement has not been completed (NO), the process proceeds to step S5, and if the measurement for one line has been completed (YES), it is determined whether the measurement of all lines has been completed (step S1).
9).

If the determination has been completed for all the lines (YES), the MFM measurement ends. However, if the measurement of all the lines is not completed (NO), the XYZ driving piezoelectric body 26 is expanded and contracted so that the scanning start position of the next scanning line in the X direction to be measured is located below the tip of the cantilever 27. Then, the sample 25 is scanned and moved in the Y direction (step S20). The same measurement is repeated for the second and subsequent lines to measure all the lines.

According to the measurement in the constant height MFM measurement mode, the sample surface is first scanned by the AFM measurement as shown in FIG. 3A to obtain unevenness data as shown in FIG. 3B. By scanning the same X scan line so as to form a trajectory of the center of amplitude separated from the sample surface by a certain distance as shown in FIG. 6A, constant height MFM data shown in FIG. 6B is obtained.

In this embodiment, A is set for each line.
Although the measurement was performed while repeating the FM measurement / MFM measurement, it is also possible to repeat the AFM measurement / MFM measurement for every line.

In this embodiment, the microcomputer 21 stores the AFM data in the storage unit 33 and performs the arithmetic processing. However, the host computer 1 stores the AFM measurement data in the storage unit of the host computer and performs the arithmetic processing. It is possible to

[0049]

As described above, the surface information separation / measurement apparatus according to the present embodiment continuously performs the unevenness measurement (AFM measurement) and the magnetic force information measurement (MFM measurement), and separates the unevenness information and the magnetic force information on the sample surface. By obtaining the MFM image by subtracting the concavo-convex image from the mixed image, or by scanning the cantilever along the concavo-convex image obtained by the concavo-convex measurement, the MFM measurement is performed to obtain an accurate MFM image. be able to.

The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications and applications can be made without departing from the spirit of the invention.

[0052]

As described above in detail, according to the present invention, a plurality of pieces of surface information of the same sample are separated, the information is individually detected to form combined surface information, and the surface information is not affected by the surface state. An apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a surface information separation and measurement device according to the present invention.

FIG. 2 is a flowchart for explaining measurement in a constant magnetic force gradient MFM measurement mode by the surface information separation measurement device shown in FIG. 1;

FIG. 3 (a) shows an uneven trajectory in which the tip of a cantilever scans a sample having unevenness on the sample surface.
(B) is a diagram showing an uneven image of the sample surface.

FIG. 4 is a view showing a constant magnetic force gradient MFM image obtained by the surface information separation and measurement device shown in FIG. 1;

FIG. 5 is a flowchart for explaining measurement in a constant height MFM measurement mode by the surface information separation and measurement device shown in FIG. 1;

FIG. 6 (a) shows an amplitude center trajectory scanned by a tip of a cantilever at a certain distance from a sample surface having irregularities, and FIG. 6 (b) shows a constant height MFM image of the sample surface. FIG.

FIG. 7A is a diagram showing the vibration characteristics of a cantilever in a state where the cantilever needle is not affected by an external force,
FIG. 7B is a diagram showing the vibration characteristics of the cantilever in a state where the cantilever needle is affected by a weak attractive force.
(C) is a diagram showing the vibration characteristics of the cantilever in a state where the cantilever needle is affected by a strong attractive force.

FIG. 8 is a diagram showing a configuration of a conventional scanning magnetic microscope.

FIG. 9A shows a state in which the tip of a cantilever scans over a magnetic material sample having a flat sample surface.
(B) is a diagram showing magnetic force information (MFM image) on the sample surface.

10A shows a state in which the tip of a cantilever scans a magnetic material sample having irregularities on the surface of the sample, and FIG. 10B shows magnetic force information (MFM image) of the sample surface. FIG.

11A shows a state in which the tip of a cantilever scans a magnetic material sample having irregularities on the surface of the sample, and FIG. 11B shows a mixed image of the sample surface.

[Explanation of symbols]

1,21 ... microcomputer, 2,2
2 ... Z control unit, 3,23 ... X control unit, 4,24 ... Y control unit, 5,25 ... sample, 6,26 ... XYZ drive piezoelectric body,
7, 27: cantilever, 8, 28: vibrating piezoelectric body, 9,
29: probe displacement detecting section, 10, 30: amplitude detecting section, 1
1, 31: A / D conversion unit, 12, 32: host computer, 33: storage unit.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 21/00-21/32 G01N 27/87 G01N 37/00

Claims (2)

(57) [Claims] A cantilever having a sharp tip; a sample moving means for relatively moving a sample and the cantilever along the surface of the sample; and vibrating the cantilever at a predetermined frequency. A vibrating body that stops, a displacement detection unit that detects displacement of the tip that occurs when the cantilever scans, an amplitude detection unit that detects the amplitude of the cantilever, and a vibrationless sent from the displacement detection unit. The first surface information obtained from a control signal for controlling the displacement signal of the cantilever to be kept constant, and the amplitude signal of the vibrating cantilever sent from the amplitude detecting means is kept constant. Image formation based on a difference between the second surface information and the first surface information at the same measurement point from second surface information obtained from a control signal to be controlled Surface information separating measuring apparatus characterized by comprising an image forming unit that. 2. A cantilever having a sharp tip, sample moving means for relatively moving a sample and the cantilever along the surface of the sample, and vibrating the cantilever at a predetermined frequency. Displacement detecting means for detecting the displacement of the vibrating body to be stopped and the tip portion generated at the time of scanning of the cantilever, amplitude detecting means for detecting the amplitude of the cantilever, and vibration-free transmitted from the displacement detecting means. First surface information obtained from a control signal for controlling the displacement signal of the cantilever to be kept constant, and control for keeping the amplitude signal of the vibrating cantilever sent from the amplitude detecting means constant. Forming an image from the difference between the second surface information and the first surface information at the same measurement point from the second surface information obtained from the control signal A method for forming a surface information separation image, comprising: