JPH09218205A - Scanning type probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning type probe microscope capable of accurately measuring not only the surface unevenness of a sample but also impurities such as foreign matter present on the surface of the sample. SOLUTION: The signal obtained from the probe part 1 for an AFM (interatomic force microscope) is processed by an AFM measuring circuit 4a to be stored in a surface shape memory part 4b. An STM (scanning type tunnel microscope) probe driving circuit 4c moves a probe 2a for an STM up and down along the surface shape of a sample on the basis of stored data according to the command of an operational control part 4b and the signal showing a tunnel current obtained from the probe part 2 for the STM is processed by an STM measuring circuit 4d to be successively stored in an STM signal memory part 4e. The operational control part 4f reads the measured data related to the tunnel current of a predetermined region from the STM signal memory part 4e and it is judged that impurities such as foreign matter are present at the position on the sample corresponding to the part where the read measured data is shifted from a predetermined value.

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 for measuring the shape of a sample surface by scanning the sample surface with a probe.

[0002]

2. Description of the Related Art Generally, a scanning tunneling microscope (STM) and an atomic force microscope (AFM) are widely used to measure the shape of a sample surface at the atomic level.

In a scanning tunneling microscope, for example, as shown in FIG. 9, a predetermined voltage is applied between a sample 101 and a probe 102 arranged opposite thereto, and a tunnel current flowing between the two becomes constant. The probe 102 to the scanning circuit 10
4, servo circuit 106, and tunnel current amplifier circuit 10
The shape of the sample surface is displayed on the display 105 with atomic level resolution by driving the piezoelectric element 103 via 7 and detecting the vertical movement of the probe 102.

On the other hand, the atomic force microscope is shown in FIG.
3, the probe 112 held by the cantilever 110 is arranged so as to face the sample 111, and the computer 118, the minute modulation circuit 117, the piezoelectric element drive circuit 11 are arranged.
The piezoelectric element 113 is driven via 6 and the laser light source 11
4, the laser beam emitted from the cantilever 110 and reflected by the laser beam detecting element 115 is detected by the probe 112.
The vertical movement of the tip portion of the cantilever 110 is determined according to the interatomic force acting between the sample 111 and the sample 111, and the shape of the sample surface is observed at the atomic level resolution from the determined vertical movement.

[0005]

However, when the scanning tunneling microscope is used, not only the unevenness of the sample surface as shown in FIG. 11a but also the sample surface as shown in FIGS. 11b and 11c exist. Since the tunnel current also fluctuates with respect to impurities such as foreign substances, when the impurities such as foreign substances are present on the sample surface, the shape of the sample surface cannot be accurately measured, and the foreign substances and impurities cannot be distinguished.

On the other hand, when an atomic force microscope is used, FIG.
As shown in 2a, it reacts with the unevenness of the sample surface,
As shown in FIG. 12b, since it does not react with impurities such as foreign substances existing on the sample surface, impurities such as foreign substances existing on the sample surface cannot be measured.

Therefore, the present invention was devised in order to solve these problems, and it is a scanning probe capable of accurately measuring not only the unevenness of the sample surface but also impurities such as foreign substances existing on the sample surface. The purpose is to provide a microscope.

[0008]

The present invention has a probe for a scanning tunnel microscope and a probe for an atomic force microscope, and measures the sample surface shape by the scanning tunnel microscope and the atomic force microscope. A scanning probe microscope capable of comparing the measurement results of the sample surface shape by the scanning tunneling microscope and the atomic force microscope, and thereby the shape of the sample surface and impurities existing on the sample surface with atomic level resolution. It is characterized in that a calculation means for obtaining information is provided.

The calculation means compares the measurement results of the sample surface shape by the scanning tunneling microscope and the atomic force microscope for each predetermined area on the sample surface, and based on the comparison result, the predetermined area on the sample surface. It is characterized in that the presence or absence of impurities such as foreign matter existing in the is determined.

Further, the present invention has a scanning tunnel microscope probe and an atomic force microscope probe, and a scanning probe capable of measuring a sample surface shape by the scanning tunnel microscope and the atomic force microscope. A microscope, a surface shape storage means for storing information of the sample surface shape obtained by measurement of the sample surface shape by the atomic force microscope, and along the obtained sample surface shape based on the stored information Probe scanning means for scanning the probe for a scanning tunnel microscope, and a portion where a signal change occurs based on the signal obtained by the scanning, and impurities are detected on the sample surface corresponding to the changed portion. And a calculation unit that determines that there is an existing unit.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
A description will be given based on FIG.

FIG. 1 is an overall view of a scanning probe microscope according to the present invention, in which an AFM probe portion 1 comprising an AFM probe 1a and its holder 1b and an STM probe 2 are provided.
The STM probe part 2 consisting of a and its holder 2b is the sample 1
It is arranged in parallel to face 1a.

The sample 11a comprises a Z-axis fine movement mechanism 12, X, Y.
It is mounted on the sample holder 11 so that it can be finely moved in the XYZ axis directions by the fine movement mechanism 13, and the Z axis fine movement mechanism 12 and
The X, Y fine movement mechanism 13 includes a Z-axis driver 12a and X, Y,
The drive is controlled by the data processing control means 4 via the Y scan driver 13a. Further, the sample 11a is configured to be coarsely moved by the X, Y coarse movement stage 14 via the X, Y coarse movement driver 14a for positioning and the like.

The data processing control means 4 are respectively AFMs.
Alternatively, scanning control or the like for measuring the surface shape of the sample 11a by STM is performed by the AFM probe unit 1 and the STM probe unit 2.
On the other hand, the measurement result such as the measured surface shape of the sample 11a is displayed on the display unit 5.

FIG. 2 is a detailed block diagram of the data processing control means 4, in which the AFM measuring circuit 4a measures the signal obtained by the AFM scanning from the AFM probe portion 1 and the surface shape storage portion. 4b temporarily stores the measurement processing result in the AFM measurement circuit 4a as data indicating the surface shape.

The STM probe drive circuit 4c, based on the surface shape data stored in the surface shape storage unit 4b,
Alternatively, the vertical movement operation of the STM probe unit 2 is controlled based on an instruction from the arithmetic control unit 4f. STM measuring circuit 4d
Performs measurement processing of a signal related to the tunnel current obtained from the STM probe unit 2 by STM scanning, and the STM signal storage unit 4e temporarily stores the measurement result by the STM scanning.

The arithmetic control unit 4f includes an AFM measuring circuit 4a,
The operation control of the STM probe drive circuit 4c and the STM measurement circuit 4d is performed, and the surface shape of the sample 11a and impurities such as foreign substances present on the surface of the sample 11a are recognized from the measurement results obtained by the AFM and STM. It is displayed on the display unit 5.

Further, the arithmetic control unit 4f is provided with Z shown in FIG.
By driving the Z-axis fine movement mechanism 12 via the axis driver 12a, the AFM probe 1a, the STM probe 2a and the sample 1
The distance between 1a is adjusted to a distance capable of measuring the surface shape, and the X and Y fine movement mechanism 13 is driven via the X and Y scan driver 13a to finely move the sample 11a on the XY plane, for AFM. The scanning control of the probe 1a and the STM probe 2a on the surface of the sample 11a is performed.

Next, an operation example of the present invention will be described with reference to FIGS. 1 and 2 and a flow chart of FIG. 3 showing the operation of the data processing control means 4.

After the sample 11a is positioned with respect to the AFM probe 1a and the STM probe 2a so that the surface shape can be measured via the Z-axis driver 12a and the like, X and Y are transmitted via the XY scanning driver 13a. The fine movement mechanism 13 is scanned for AF
The signal obtained from the M probe portion 1 is processed by the AFM measuring circuit 4a to measure the surface shape of the sample 11a. And
The measured data is stored in the surface shape storage unit 4b one by one (S1).

Sample 1 to be measured by such AFM measurement
When the entire area of 1a is completed, the STM probe drive circuit 4c reads the surface shape data of the sample 11a by the AFM stored in the surface shape storage section 4b one by one according to the instruction of the arithmetic control section 4f, and reads the read surface shape. Based on the above data, the STM probe 2a is moved up and down along its surface shape. At the same time, the arithmetic control unit 4f appropriately sets the XY scanning driver 13a so that the STM probe 2a is positioned at a specific position on the sample 11a where the surface shape data read from the surface shape storage unit 4b is obtained. , X, Y fine movement mechanism 1
The sample 11a is moved through 3 (S2). Note that A
As described above, the FM probe 1a and the STM probe 2a are
Since the positions of the STM probe 2a with respect to the AFM probe 1a are arranged in parallel at a predetermined interval, the A
It becomes possible to position the STM probe 2a at a specific position on the sample 11a where the surface shape data was obtained by FM.

Then, the STM measuring circuit 4d processes the signal indicating the tunnel current obtained by scanning from the STM probe section 2 one by one, and the measured data is stored in the STM signal storage section 4e one by one (S3).

Sample 1 to be measured by such STM measurement
When all the areas of 1a are completed, the arithmetic control unit 4f
The measurement data regarding the tunnel current obtained in the predetermined region of the sample 11a is read from the STM signal storage unit 4e, and it is determined whether or not there is a portion where the read measurement data deviates from the predetermined value (S4).

If there is no portion that deviates from the predetermined value, it is determined that there is no foreign matter or impurities, and the AFM measurement data of the predetermined area of the sample 11a is stored in the surface shape storage section 4b.
The surface shape of the predetermined area is displayed on the display unit 5 (S5).

Here, FIG. 4 shows an example in which irregularities are present on the surface of the sample but no foreign matter is present. In this case, in the above-described AFM measurement, measurement data corresponding to the convex portion can be obtained. In the STM measurement described above, the STM probe 2
Since a is scanned according to the surface shape obtained by the AFM measurement, the STM probe 2a and the sample 1a are always kept at a constant distance, the tunnel current flowing between them is constant, and the obtained measurement data is the sample surface. It has a constant value regardless of the upper convex portion. Therefore, when the measured data obtained by the STM described above has a constant value, it is determined that no foreign matter or impurities are present on the sample surface.

In step S4, if there is a portion where the measured data deviates from the predetermined value, it is judged that a foreign substance exists on the sample corresponding to that portion, and the sample obtained based on the AFM measured data of the predetermined area. The surface shape is displayed on the display unit 5, and the foreign matter is also displayed on the display unit 5 based on the STM measurement data regarding the tunnel current (S
6).

Here, FIGS. 5 and 6 show an example of the case where foreign matter is present on the sample surface. In the above-mentioned AFM measurement, measurement data corresponding to only the sample surface shape including the foreign matter is obtained, In the STM measurement described above, the STM probe 2a
Since the tunnel current flowing between the foreign matter and the foreign matter changes, a signal corresponding to the foreign matter can be obtained and the presence of the foreign matter can be recognized. Also,
By associating the signal strength with the type of foreign matter,
It is possible to infer the type of recognized foreign matter.

Then, a series of these operations (S4 to S
After performing 6) for all the regions on the sample 11a, the measurement operation is ended (S7).

By the above operation, it becomes possible to measure the surface shape of the sample 11a and impurities such as foreign substances existing on the surface.

Next, another embodiment of the present invention for measuring the surface shape of the sample 11a and impurities such as foreign substances existing on the surface will be described with reference to the flowchart of FIG. 7 showing the operation of the data processing control means 4. .

First, the AFM probe 1a and the STM probe 2
After positioning the sample 11a with respect to a so that the surface shape can be measured via the Z-axis driver 12a or the like, the X, Y fine movement mechanism 13 is scanned via the XY scanning driver 13a, and the AFM probe unit 1 The signal obtained from the above is processed by the AFM measurement circuit 4a to measure the surface shape of the sample 11a.
Then, the measured data is stored in the surface shape storage unit 4b one by one (S10). When the AFM measurement is completed for the entire area of the sample 11a to be measured, the XY scan drivers 13a, X, Y are instructed according to the instruction from the arithmetic control unit 4f.
Through the fine movement mechanism 13, the STM probe 2a scans the same region as the sample 11a that is the measurement target in the AFM measurement, and the STM probe unit 2 outputs each one S one by one.
Upward and downward motion control of the STM probe unit 2 is performed via the STM probe drive circuit 4c so that the data regarding the tunnel current obtained via the TM measurement circuit 4d becomes a constant value.
Further, the arithmetic control unit 4f measures the surface shape of the sample 1a from its vertical movement (S11). When the STM measurement is completed for all areas of the sample 11a to be measured, the obtained AFM measurement data and STM measurement data are compared for a predetermined area on the sample 11a to be measured (S).
12).

Here, as shown in FIG. 8A, the AFM measurement data and the STM measurement data coincide with each other as information indicating the surface shape in a region where a foreign substance does not exist on the sample surface. The surface shape of the sample can be obtained by using the STM measurement data as it is. On the other hand, as shown in FIG. 8B, in the region where the foreign matter exists on the sample surface, the measurement data obtained by the AFM measurement faithfully reproduces the sample surface shape including the foreign matter, and the STM
In the measurement, the measurement data including the sample surface shape including the foreign matter and the information regarding the foreign matter will be obtained.

Therefore, first, it is determined whether or not the two measurement data match (S13). If they match, it is determined that no impurities are present in that portion, and the sample surface shape is determined based on the AFM measurement data. Is displayed on the display unit 5 (S14). In such a case, it goes without saying that the sample surface shape may be obtained based on the STM measurement data instead of the AFM measurement data and displayed on the display unit 5.

If the two measurement data do not match, it is determined that a foreign substance is present on the sample surface, and the AFM measurement data and S
The foreign substance information existing on the sample surface is extracted based on the TM measurement data (S15).

That is, in the above-mentioned AFM measurement, the measurement data corresponding to the sample surface shape including the foreign matter is obtained, and in the above-mentioned STM measurement, the measurement data including the sample surface shape including the foreign matter and the information on the foreign matter is obtained. ST
By subtracting the sample surface shape data obtained based on the AFM measurement data from the sample surface shape data obtained based on the M measurement data, only the foreign substance information can be extracted.

When the foreign matter information is extracted, the foreign matter existing on the sample surface based on the extracted foreign matter information is displayed on the display unit 5 together with the sample surface shape obtained based on the AFM measurement data (S16).

Then, the series of operations described above (S12-S
16) is repeated until the comparison is completed for all areas on the sample 11a (S17).

By the above operation, it becomes possible to measure the surface shape of the sample 11a and impurities such as foreign substances existing on the surface.

In the above-mentioned embodiment, the presence of impurities such as foreign matter is confirmed and displayed, but the measured value obtained for the above-mentioned foreign matter information indicates the value peculiar to the elements constituting the foreign matter. Therefore, it is also possible to perform element identification of impurities such as foreign matter by measuring and holding a unique value as foreign matter information for known elements in advance.

[0040]

According to the present invention, a probe for a scanning tunnel microscope and a probe for an atomic force microscope are provided together, and the surface shape of the sample is measured by the scanning tunnel microscope and the atomic force microscope. Since it is configured to compare the measurement results of the surface shape, it is possible to obtain the shape of the sample surface and the impurity information such as foreign matter on the sample surface with atomic level resolution.

[Brief description of drawings]

FIG. 1 is an overall view showing an embodiment of the present invention.

FIG. 2 is a detailed block diagram of data processing control means according to the present invention.

FIG. 3 is a flowchart showing an operation of the data processing control means according to the present invention.

FIG. 4 is a diagram showing an example of an AFM signal and an STM signal obtained according to the state of the sample surface.

FIG. 5 is a diagram showing an example of an AFM signal and an STM signal obtained according to the state of the sample surface.

FIG. 6 is a diagram showing an example of an AFM signal and an STM signal obtained according to the state of the sample surface.

FIG. 7 is a flowchart showing the operation of the data processing control means according to the present invention.

FIG. 8 is a diagram showing an example of an AFM signal and an STM signal obtained according to the state of the sample surface.

FIG. 9 is a schematic view showing a conventional scanning tunneling microscope.

FIG. 10 is a schematic view showing a conventional atomic force microscope.

FIG. 11 is a diagram showing an example of an AFM signal and an STM signal obtained according to the state of the sample surface.

FIG. 12 is a diagram showing an example of an AFM signal and an STM signal obtained according to the state of the sample surface.

[Explanation of symbols]

 1 ... AFM probe 1a ... AFM probe 2 ... STM probe 2a ... STM probe 4 ... Data processing means

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01J 37/28 H01J 37/28 Z

Claims (2)

[Claims] 1. A scanning probe microscope having a scanning tunneling microscope probe and an atomic force microscope probe, which is capable of measuring a sample surface shape by the scanning tunneling microscope and the atomic force microscope. Comparing the measurement results of the sample surface shape with the scanning tunneling microscope and the atomic force microscope, it is equipped with a calculating means for obtaining the shape of the sample surface and the impurity information existing on the sample surface with atomic level resolution. Scanning probe microscope. 2. A scanning probe microscope having a scanning tunneling microscope probe and an atomic force microscope probe, which is capable of measuring a sample surface shape by the scanning tunneling microscope and the atomic force microscope. Surface shape storage means for storing information on the sample surface shape obtained by measuring the surface shape of the sample by an atomic force microscope, and a scanning tunneling microscope probe along the sample surface shape obtained based on the stored information. A probe scanning unit that scans the needle, and a computing unit that detects a portion where a signal change occurs based on the signal obtained by the scanning and determines that impurities exist on the sample surface corresponding to the changed portion. And a scanning probe microscope.