JPH10267943A - Scanning type probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately correct a distortion of a scale of a scanning tunnel microscope(STM) image, etc., caused by a temperature change, etc., by a method wherein a plurality of probes are provided and a correcting probe out of the proves is made follow a specific position of a sample. SOLUTION: A scanning probe 4 scans a sample W surface in a two-dimensional direction to obtain data of the probe W surface. In the meantime, image correcting probes 5 to 7 are move-controlled so as to follow a specific position of a sample W, and the move amount is set as data which corrects the sample W image by the scanning probe 4. Namely, they are moved temporally in x, y directions and in a z direction only by an amount corresponding to fluctuations of a relative position relationship of the sample W and the respective correcting probes 5 to 7. Accordingly, the move amount of the correcting probes 5 to 7 indicates a temporal fluctuation amount in x, y, z directions in which the respective correcting probes 5 to 7 are relative to each specific position of the sample W initially opposing thereto. Therefore, based on each move amount of the respective correcting probes 5 to 7, it is possible to correct a relative position fluctuation of the scanning probe 4 and a scanning region of the sample W, namely a distortion of an image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scanning probe microscope such as an STM (scanning tunnel microscope) and an AFM (atomic force microscope).

[0002]

2. Description of the Related Art In a scanning probe microscope, generally, the interaction between a probe and a sample surface, for example, a tunnel current and an atomic force become constant while scanning the probe in the xy directions along the sample surface. The distance z of the probe from the sample surface is changed as described above, and information such as unevenness on the sample surface is obtained from the amount of change of the z.

[0003] In such a scanning probe microscope, there is known a scanning probe microscope in which a plurality of probes and respective driving mechanisms are provided, and each part of a large sample surface is simultaneously scanned to perform surface analysis.

As a method of accurately knowing the scanning position of a scanning probe with respect to a sample in an xy direction in a scanning probe microscope, a method of mounting a sample and moving the sample table in the xy direction on each of a front side and a back side is described. In addition, a probe having a function of moving in the z direction is provided, a sample is placed on the front side of the sample table, a crystal serving as a scale reference is mounted on the back side, and the probe on the front side is a normal probe. While used as a scanning probe,
A technique is known in which an image of a crystal lattice is observed with a probe on the back side, and instantaneous positional information between the scanning probe on the front side and the sample is obtained using the image of the crystal lattice structure as a scale. (Kawakatsu et al., Production Studies 43, 11, pp585
-590).

[0005]

By the way, when observing a sample with a scanning probe microscope, as the size of the analysis room or the analysis sample increases, the sample or sample stage and the scanning drive unit of the probe may be changed due to a temperature change or the like. May change over time, and the scale of the STM image or AMF image may be distorted. In particular, this is a problem when scanning a large area over time, or when repeatedly scanning the same area to obtain a moving image.

As one measure for solving such a problem, a method of constructing an image while sequentially grasping the positional relationship between the scanning probe and the sample table or the sample using the above-mentioned crystal lattice as a scale. Can be considered.

However, according to such a method, it is necessary not only to prepare a crystal having a known lattice pitch in advance in order to provide the scale, but also to use a probe for scanning a sample and a crystal lattice for scanning. It is difficult to thermally couple both tips because they need to be placed on both sides of the sample table, or if the sample and the crystal are placed on the same plane. However, there is a limit to the proximity of the two probes due to the area of the sample, etc., and eventually, the temporal change in the positional relationship between the sample scanning probe and the crystal lattice scanning probe due to temperature change, etc. The accompanying error cannot be eliminated.

The present invention has been made in view of such circumstances, and it is possible to accurately correct a scale distortion such as an STM image due to a temperature change or the like without preparing a crystal or the like to be used as a scale. The purpose is to provide a scanning probe microscope.

[0009]

In order to achieve the above object, a scanning probe microscope of the present invention comprises a probe and a probe.
A plurality of driving means for driving in the dimensional direction are provided,
At least one of them is configured to scan the sample surface in a two-dimensional direction as a scanning probe to obtain information on the sample surface, while at least one of the other probes is an image correction probe. The movement control is performed by the tracking control means so as to follow a specific position of the sample or the sample table on which the sample is mounted, and the moving amount of the correction probe is used to correct the sample image by the scanning probe. It is characterized by being configured to be supplied as data to the image correction means.

According to the present invention, information on the relative positional relationship between a sample or a sample table and a drive unit of a scanning probe is obtained by following a specific position of the sample or the sample table using a probe different from the scanning probe. It is what we are trying to get.

That is, the correction probe is controlled so as to follow a specific position of the sample, for example, a specific peak position of irregularities on the atomic scale of the sample surface. Therefore, the amount of movement of the correction probe in the x, y, and z directions indicates the relative change in the x, y, and z directions between the drive unit of the correction probe and the sample. become.

The scanning probe and the correction probe both face the surface of a sample (or a sample stage in some cases), and the specific position to be followed by the correction probe is particularly The present invention is not limited to this, and it can be set at any peak position of the unevenness. Therefore, these two probes can be brought very close to each other, and thermal coupling of these two probes becomes easy. Therefore, it is possible to accurately know the change in the relative positional relationship between the scanning probe drive unit and the sample or the sample stage from the amount of movement of the correction probe, and by using the amount of movement, Over time displacement between the probe drive unit for use and the sample or the sample stage can be accurately corrected.

Here, in the present invention, the number of correction probes is arbitrary, and when the scanning area of the sample by the scanning probe is relatively narrow, the temporal displacement within the area can be ignored. In this case, the number of correction probes can be set to one, and in this case, the positional deviation of the scanning region on the entire surface of the sample can be corrected. If the scanning area is relatively large and distortion is expected to occur in the area, the number of correction probes is set to, for example, three, so that in addition to the above-described correction, the number of correction probes in the x and y directions is increased. The magnification can be corrected.

Further, in the present invention, z of the correction probe
The temporal displacement of the probe drive unit and the sample or the sample stage in the z direction can be corrected from the amount of movement in the direction. In the present invention, the number of scanning probes is not limited to one, but may be arbitrary. Further, the correction probe of the present invention does not necessarily need to be limited to correction, and the control of the driving means is the following control as described above,
If it is possible to select any one of the scanning controls equivalent to the scanning probe, it can be selectively used for both the correction probe and the scanning probe, which is preferable.

[0015]

FIG. 1 is a schematic perspective view showing a mechanical structure of an embodiment when the present invention is applied to an STM, and FIG. 2 is a block diagram showing an electrical configuration thereof. .

A sample table 2 for mounting a sample W on the table 1 is provided. Above the sample table 2, the table 1
The probe drive system support base 3 supported by the column portion 1a is provided.

In this example, one scanning probe 4, three correction probes 5, 6, 7, and driving portions 4a, 5a, 6a of these probes are provided on the probe drive system support base 3 in this example. And 7
a is supported. Drive units 4a to 7a of the probes 4 to 7
Are piezoelectric elements 4 that expand and contract in the x, y, and z directions, respectively.
It has a known mechanism constituted by x, 4y, 4z to 7x, 7y, 7z. The probes 4 to 7 and the respective driving units 4a to 7a are housed in a common temperature control chamber 8 having a heating or cooling function controlled by a temperature control circuit (not shown). Can be thermally coupled to each other.

The positional relationship between the correction probes 5 to 7 is such that the correction probe 6 and the correction probe 5 are located at positions shifted from the correction probe 5 by a predetermined amount in the x direction. The correction probe 7 is arranged at a position shifted by a predetermined amount in the y direction.

A predetermined potential difference is applied to each of the probes 4 to 7 with respect to the sample W, and a tunnel current flowing between each of the probes 4 to 7 and the sample W is caused by the potential difference. 7b, and the detection result is taken into z-direction control circuits 41z to 71z for controlling the piezoelectric elements 4z to 7z in the z-direction of the driving units 4a to 7a. The z-direction control circuits 41z to 71z control the piezoelectric elements 4z to 7z in each z-direction so that the detection result of the tunnel current is always constant.

In each of the probes, the x-direction piezoelectric element 4x and the y-direction piezoelectric element 4y of the scanning probe 4 move along the surface of the sample W along with the control signal supplied from the xy scanning control circuit 41s. , Y.

On the other hand, the x-direction piezoelectric elements 5x to 7x and the y-direction piezoelectric elements 5y to 7y of the three correction probes 5 to 7 are:
The follow-up control circuits 51f to 71f control to follow the peak position of specific irregularities on the surface of the sample W. In this control, it is preferable to apply a small vibration (dither) to each of the probes 5 to 7 in the x and y directions in order to determine the direction of the displacement of the probe with respect to the corresponding peak position.

The amount of movement of the scanning probe 4 in the z direction, that is, z
The control signal supplied from the direction control circuit 41z to the z-direction piezoelectric element 4z is taken into the image memory 9 in synchronization with the scanning signal of the probe 4 in the x and y directions. The contents of the image memory 9 are corrected by the image correction circuit 10 and then imaged by the CRT 11.

The image correction circuit 9 comprises three correction probes 5
7, the amounts of movement in the x, y, and z directions, that is, follow-up control circuits 51f to 71f and z-direction control circuits 51z to 51f.
Using the control signal supplied from 1z to the corresponding piezoelectric element, the contents of the image memory 9 are corrected by the following method.

That is, since each of the correction probes 5 to 7 is controlled so as to follow a specific position of the sample W, the sample W and each of the correction probes 5 to 7 (each of the drive units 5a to 5a) are controlled.
X, x, by an amount corresponding to the change in the relative positional relationship in 7a).
It moves in the y and z directions over time. Therefore, the amount of movement of each of the correction probes 5 to 7 is equal to the amount of each of the correction probes 5 to 7.
7 represents the amount of change in the relative position in the x, y, and z directions over time with respect to each of the specific positions of the sample W that initially faced the sample W. As described above, each of the correction probes 5 to 7 is thermally coupled to the scanning probe 4, and accordingly, the amount of movement of each of the correction probes 5 to 7 in the x, y, and z directions. From the positional relationship between the scanning probe 4 and each of the correction probes 5 to 7, it is possible to know the relative positional change of the scanning probe 4 and its driving unit 4a with the scanning region of the sample W over time, If the image in the image memory 9 is corrected according to the result and displayed on the CRT 11,
Image distortion due to a temperature change or the like can be corrected.
Specifically, for example, the amount of change in the relative position between the scanning probe 4 and the sample W is determined from the amount of movement of the correction probe 5 in the x and y directions. 6 are displaced in the x direction, the difference in the amount of movement in the x direction
The amount of expansion / contraction in the direction is determined, and similarly, the amount of expansion / contraction in the y direction of the sample W is determined from the difference in the amount of movement between the correction probes 5 and 7 in the y direction. Furthermore, each correction probe 5-7
From the movement amount in the z direction, the approach / separation amount of the sample W from the probe drive system support base 3 at the corresponding position can be known.

Such correction is performed when the scanning time by the scanning probe 4 is relatively long, or by sequentially changing the scanning region by the scanning probe 4 and connecting the images corresponding to the individual scanning regions. This is effective in obtaining an image of a large area of the sample W by scanning, or when trying to obtain a moving image of the same area by repeatedly scanning the same area with the scanning probe 4. It is possible to accurately correct image distortion caused by a temporal displacement between the driving unit 4a and the sample W.

In the above embodiment, three correction probes are used. However, one correction probe may be used. In this case, only the temporal movement of the scanning probe 4 and the sample W as a whole will be known, but this is effective when the scanning area is narrow and expansion / contraction data in the area is unnecessary. .

The above description is based on a scanning tunneling microscope (ST).
Although the example in which the present invention is applied to M) has been described, it goes without saying that the present invention is equally applicable to an atomic force microscope (AFM).

[0028]

As described above, according to the present invention, in addition to the scanning probe, the correction probe controlled to follow a specific position of the sample is provided, and the amount of movement of the correction probe is provided. , The amount of movement of the scanning probe and the sample over time is known, and the results are used to correct the image by the scanning probe. In addition, even if the position of the driving unit is shifted with time, an accurate sample image can be obtained without being affected by the positional deviation.
In addition, such correction is performed by using a crystal lattice image obtained by scanning a crystal provided on the back surface side of the sample table with a probe as a scale, as compared with a conventional method in which a crystal lattice image is obtained. Since the correction is performed using the movement amount of the probe that follows the peak position in the unevenness, the correction probe and the scanning probe can be arranged close to each other, and these can be easily thermally coupled, and the correction is performed. There is an advantage that it becomes more accurate and there is no need to prepare a reference crystal.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a mechanical configuration according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mount 1a Column part 2 Sample stand 3 Probe drive system support stand 4 Scanning probe 4a Driving unit 5, 6, 7 Correction probe 5a, 6a, 7a Driving unit 41s Scanning control circuit 51f, 61f, 71f Tracking control circuit 8 Temperature control room 9 Image memory 10 Image correction circuit 111 CRT

Claims (1)

[Claims] 1. A probe provided with independent driving means in three-dimensional directions so that the interaction between the probe and the sample surface becomes constant while scanning the sample surface in two-dimensional directions. In a microscope in which the distance of the probe from the sample surface is changed and information on the sample surface is obtained from the amount of change, at least one of the probe and its driving means is provided, at least one of which is a scanning probe as a scanning probe. Is scanned in two-dimensional directions to obtain information on the surface of the sample, while at least one of the other probes is used as an image correction probe by mounting the sample or the sample by the tracking control means. The movement of the correction probe is controlled so as to follow a specific position of the sample table to be placed, and the amount of movement of the correction probe is supplied to image correction means as data for correcting the sample image by the scanning probe. Features that Scanning probe microscope.