JPH11271333A - Scanner system of scanning type probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanner system in a simple configuration for acquiring measurement data even for the measurement of a small region while being related to accurate XY positions. SOLUTION: A sample 3 is retained on a tube scanner 1 that can be displaced in X, Y, and Z directions. The tube scanner 1 is scanned in X, Y, and Z directions by an XY scanning control part 2 while being subjected to feedback control in the Z direction by a Z drive part 6 so that the output of a probe displacement detection means 5 becomes constant. Mirrors 7 and 8 are mounted to the tube scanner 1, and the movement is monitored by laser length measurement equipment 9 and 10. The output pulses of the laser length measurement equipment 9 and 10 are inputted to UP/DOWN counters 101 and 102, are divided by n using 1/n circuits 103 and 104, and are supplied to a frame memory 107 as an address. Also, simultaneously with the generation of the address, a Z drive signal is stored in the frame memory 107 as measurement data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a scanner system used for a scanning probe microscope for observing a minute area.

[0002]

2. Description of the Related Art A scanning probe microscope is a device capable of observing a fine shape of a sample surface at an atomic level, and includes a scanning tunnel microscope (STM) and an atomic force microscope (AFM). I have.

As described in Japanese Patent Application Laid-Open No. Sho 62-130302, AFM utilizes the interatomic force acting between the atom at the tip of the probe and the atom at the surface of the sample to form the surface of the sample. Is a device for measuring When the probe is brought close to the surface of the sample, a small force called interatomic force (repulsive force, Van der Waalska, covalent force, etc.) represented by the Lennard-Jones potential with an attractive region and a repulsive region is generated. AF
In M, the tip is supported by the free end of a flexible cantilever,
The atomic force acting between the probe and the sample is detected as the amount of deflection of the cantilever (lever), and the positional relationship between the probe and the sample is controlled so that the amount of deflection, that is, the force, is constant. By measuring the control voltage when the probe is scanned, the distribution image of the surface shape and interaction (such as interatomic force, contact force, and magnetic force) of the sample is measured with atomic-level resolution. Thus, unlike STM, AFM can be measured independently of the conductivity of the sample.

[0004] In the industrial market, a measuring device is always required to have a high resolution in a minute area. For this reason, in the scanning probe microscope, a piezoelectric scanner, particularly a piezoelectric tube scanner, which can control the position with high resolution, is often used as the scanning mechanism.

In a scanning probe microscope, for example, a probe or a sample is moved in a Z direction while a probe or a sample is moved using a piezoelectric scanner to perform XY scanning. Control to keep the cantilever displacement constant.

In an early scanning probe microscope, a timing at which an XY drive signal supplied to a piezoelectric scanner for performing XY scanning changes by a fixed amount is used as a sampling pulse, and a piezoelectric body is used for controlling the cantilever displacement to be constant. The Z drive signal supplied to the scanner was used as height information of the sample surface.

However, since the piezoelectric scanner has a hysteresis in its displacement characteristics and exhibits a creep phenomenon, even if it is intended to scan the piezoelectric scanner linearly in one direction (for example, the X direction), it is actually distorted. Scanning. Therefore, an image in which the drive signal of the piezoelectric scanner is formed as image data includes distortion due to hysteresis and creep.

For this reason, recent scanning probe microscopes are usually provided with a displacement sensor for detecting the displacement of the piezoelectric scanner in the X and Y directions.
The servo is applied to the piezoelectric scanner in accordance with the displacement information, and then sampling is performed at XY drive signal intervals.

[0009]

This method has a problem of 10-1.
It is effective for a relatively large area of about 00 μm, but for a small area of about 10 to 100 nm, the influence of the coarseness of the resolution of the displacement sensor and the hunting by the servo is great, and the constant XY drive signal Since the position corresponding to the measurement data sampled at intervals is not always at a constant distance interval, it is difficult to obtain a high-resolution image.

Japanese Patent Application Laid-Open No. Hei 8-248041 proposes a method of measuring the displacement of a piezoelectric scanner in the X and Y directions using a laser length measuring device having a wide dynamic range, and directly generating a sampling pulse from the length measuring pulse. According to this, X
During scanning in the direction, sampling is performed at exactly constant distance intervals. However, since the sample must not move in the Y direction during one line of X scanning, measures such as applying a servo in the Y direction are required.

Further, the applicant of the present invention discloses Japanese Patent Application Laid-Open No. 8-20140.
In No.3, X with coarse resolution which is usually used
Based on the output of the Y displacement sensor, a drive signal table for driving the piezoelectric scanner linearly in one direction (for example, the X direction) is created in advance, and the drive signal is equal to the table when actually forming an image. A method has been proposed in which sampling is performed every time, that is, each time the piezoelectric scanner moves a certain distance. This method does not require servo control in both the X and Y directions, and is very effective because an image without distortion can be obtained.

However, since sampling is performed based on a table created in advance, taking into account that the piezoelectric scanner exhibits a creep phenomenon, especially in the measurement of a very small area, the measured data is accurately spaced at a constant distance. It cannot be said that it has been sampled.

The present invention has been made in view of such circumstances, and has as its object to associate measurement data with accurate XY positions even for a measurement in a small area with a simple configuration. An object of the present invention is to provide a scanning probe microscope scanner system that can be acquired.

[0014]

SUMMARY OF THE INVENTION The present invention is a scanner system used in a scanning probe microscope. The scanner system is capable of moving a sample or a probe in XY directions, and detects a displacement of the scanner in X and Y directions. 1st and 2nd
A length measuring device, an address generation unit that generates an address composed of a digital value obtained by reducing the displacement of the scanner in the X and Y directions obtained by the first and second length measurement devices by 1 / n, and an address generation unit. A storage element for storing image data at the generated address.

The scanner system of the scanning probe microscope has, for example, a configuration in which the known data is stored in advance before the measurement, and another known data is stored in the address generated by the address generation unit. A determination storage element used for determining the presence or absence of image data at an address, and an address where image data is not stored in the image data storage element is obtained based on data stored in the determination storage element. And an interpolation data generation unit that obtains interpolation data from image data stored at addresses around the image data and stores the interpolation data at an address where image data is not stored in the image data storage element.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described with reference to FIG. FIG. 1 shows a scanning probe microscope provided with a scanner system according to the present embodiment.

As shown in FIG. 1, sample 3 has X
It is held on a tube scanner 1 that can be displaced in the YZ directions. The tube scanner 1 is feedback-controlled in the Z direction via the Z drive unit 6 so that the output of the probe displacement detecting means 5 becomes constant. With this control, the distance between the probe provided at the free end of the cantilever 4 and the sample 3 is always kept constant. The tube scanner 1 is X
Scanning is performed in the X and Y directions in accordance with the XY driving signal output from the Y scanning control unit 2. For example, after scanning one line in the X direction and sampling data of a required number of points, the line is moved by one line in the Y direction, and one line is similarly scanned in the X direction. This operation is performed for the entire area designated as the sample scanning range.

A mirror 7 oriented in the X direction and a mirror 8 oriented in the Y direction are attached to the tube scanner 1. The movement of the mirror 7 is measured by a laser length measuring device 9, and the movement of the mirror 8 is measured by the laser measuring device. It is monitored by the device 10.
The laser length measuring devices 9 and 10 output an UP pulse and a DOWN pulse that follow the movement of the mirrors 7 and 8, respectively. The image data generation unit 100 stores the image data in the memory using this signal.

The X-UP pulse and the X-DOWN pulse output from the laser length measuring device 9 correspond to the UP / DOWN counter 1
01, and the CPU 11
From the set number n. Similarly, the Y-UP pulse output from the laser length measuring device 10 and the Y-DO
The WN pulse is input to the UP / DOWN counter 102, and is further divided by a number n set by the CPU 11 in the 1 / n circuit 104.

For example, one pulse of the laser length measuring devices 9 and 10 is 0.1 nm and a region of 250 nm in the XY directions is 100 nm.
When imaging with 0 pixels × 1000 lines, the CPU uses n
= 2.5 is set. Therefore, 1 / n circuit 103 and 1 / n
The output of the n-circuit 104 means one pixel.

The outputs of the 1 / n circuit 103 and the 1 / n circuit 104 are supplied to the frame memory 107 via the buffer 105 and become the address of the frame memory 107, which always corresponds to the exact XY position of the tube scanner 1. . Simultaneously with the address generation, the Z drive signal is transmitted as measurement data to the frame memory 10
7 is stored. In this way, the measured data is converted to an accurate X
The image data of the sample 3 can be obtained in association with the Y position.

The CPU 11 operates in the frame memory 1 described above.
Regardless of the writing operation to 07, image data is read from the frame memory 107 via the buffers 109 and 110 and displayed on a monitor (not shown).

At the time of reading, the CPU 11
9 and a buffer 110, and the permission signal is also input to the AND circuit 106, and the frame memory 107
Write operation is prohibited.

The AND circuit 106 outputs a permission signal to the buffer 105 and the buffer 108 at the timing of the clock signal CLK during the scanning based on the scanning signal of the XY scanning controller 2 during the scanning.

Data is written in the tube scanner 1
The operation is performed at the timing of the high-speed clock signal CLK which is completely unrelated to the operation of FIG. That is, more data is sampled in the X direction than the number of pixels, and scanning is performed in the Y direction with more lines than the required number of lines.

As a result, the measurement data can be acquired in association with the correct XY position, and thus an accurate image without distortion can be obtained. Next, a scanner system according to a second embodiment will be described with reference to FIG. FIG. 2 shows another image data generation unit which replaces the image data generation unit 100 of FIG.

As shown in FIG. 2, the image data generating section 200 according to the present embodiment includes a first image data storing section 200 for storing image data.
In addition to the frame memory 107, the first frame memory 1
A second frame memory 201 for determining the presence / absence of image data 07 is provided. Second frame memory 201
Is equivalent to the first frame memory 107.

Known data is written in the second frame memory 201 via the buffer 203 before scanning, and during scanning, another known data is stored in the first frame memory 107 at an address corresponding to the written address of the data. Data is written.

For example, prior to scanning, "0" is written to all memory cells of the second frame memory 201,
"1" at the same timing as the first frame memory 107
Is written. As a result, after the end of scanning, the memory cell in which the image data is stored, that is, the pixel becomes “1”,
The memory cell in which the image data is not stored, that is, the pixel becomes “0”.

The CPU 11 reads out the data of the second frame memory 201 via the buffer 202, and reads out the data of the memory cell, that is, the pixel of the first frame memory 107 corresponding to the memory cell whose data is "0" in the second frame memory 201. The first frame memory 10 corresponding to the memory cell whose data is "1" in the second frame memory 201
7, interpolation data is generated based on the image data of the memory cell, that is, the pixel, and the interpolation data is written.

That is, based on the data stored in the second frame memory 201, the pixels for which the writing of the image data has not been performed are identified, and the pixels for which the writing of the image data has not been performed are assigned to the neighboring pixels. The interpolation data generated based on the image data of the written pixel is written.

Thus, for example, even if scanning is performed with a smaller number of lines than the number of pixels in the Y direction, an image of a necessary area can be obtained. Scanning with a small number of lines in the Y direction in this way reduces the measurement time.

As can be seen from the above description of the two embodiments, the measurement data is stored at the address of the frame memory corresponding to the XY position on the sample from which the measurement data has been sampled. That is, the scanner system of the present invention
Even with a simple configuration in which servo is not applied to the tube scanner, measurement data can be acquired in association with accurate XY positions. Therefore, a scanning probe microscope using this can obtain a high-resolution image with little distortion.
The present invention is not limited to the above-described embodiment at all, and includes all implementations without departing from the gist of the invention.

[0034]

According to the present invention, there is provided a scanner system having a simple configuration capable of acquiring measurement data in association with an accurate XY position even for measurement of a minute area. Accordingly, there is provided a scanning probe microscope capable of acquiring a high-resolution image with a small distortion with a simple configuration.

[Brief description of the drawings]

FIG. 1 shows a scanning probe microscope provided with a scanner system according to a first embodiment of the present invention.

FIG. 2 illustrates another image data generation unit that replaces the image data generation unit of FIG. 1 in the scanner system according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube scanner 2 XY scanning control part 5 Probe displacement detector 6 Z control part 7, 8 mirror 9, 10 Laser length measuring device 11 CPU 101, 102 UP / DOWN counter 103, 104 1 / n circuit 107 Frame memory

Claims (2)

[Claims] 1. A scanner system used for a scanning probe microscope, comprising: a scanner capable of moving a sample or a probe in XY directions; and first and second length measuring devices for detecting displacements of the scanner in X and Y directions. An address generator for generating an address composed of a digital value obtained by reducing the displacement of the scanner in the X and Y directions obtained by the first and second length measuring devices to 1 / n, and an address generated by the address generator A scanner system for a scanning probe microscope having an image data storage element for storing image data. 2. The image data of each address in the image data storage element according to claim 1, wherein known data is stored in advance before measurement, and another known data is stored in an address generated by the address generation unit. Based on the data stored in the determination storage element and the data stored in the determination storage element, an address where no image data is stored in the image data storage element is determined, and an address around the address is determined. Further comprising: an interpolation data generation unit that obtains interpolation data from the image data stored in the image data and stores the interpolation data at an address where the image data in the image data storage element is not stored.
Scanning probe microscope scanner system.