JPH0518708A - Probe scanning device - Google Patents

Abstract

PURPOSE:To compensate nonlinear displacement of an actuator which exists in a scanning type probe microscope latently and improve quantitative accuracy. CONSTITUTION:A conversion table which corresponds to an actuator and the scope of scanning of a probe scanning device is formed by scanning standard sample in advance in data translators 24, 27. An image buffer 22 stores sample data per scanning point which is obtained at scanning point when sample is scanned. The data translators 24, 27 convert each scanning point by the conversion table which is prepared in advance, and generate the data on the converted scanning point. An operational circuit 25 corrects sample data in accordance with the data on scanning point from the data translators 24, 27.

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 (SXM) such as a scanning tunneling microscope (STM), and more particularly to a probe scanning device used in such an SXM.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (STM)
Is being used as a microscope with atomic scale resolution. Further, an atomic force microscope (AFM), a magnetic force microscope (MFM), and the like are known as the same type of microscope having a resolution equivalent to or close to that of the STM. These microscopes are collectively referred to as a scanning probe microscope (SXM) and are being put to practical use.

The above-mentioned SXM has a built-in probe scanning device and applies a voltage between the conductive sample and a probe such as a probe or a cantilever to bring the distance between them to 1 nm or less so that the sample surface becomes uneven. The change in distance due to is detected by the tunnel current,
While performing feedback control so that the distance is constant by the Z-direction actuator, the actuator that drives the probe in the X, Y, and Z directions drives the probe in the X and Y directions in a range of several nanometers to several tens of μm by raster scan driving. The feedback control signal is synchronized with the XY scan to achieve three-dimensional imaging of the sample.

Such an SXM has a size of several nm to several tens of μm.
Although the scanning area extending over the range is measured with extremely high resolution, distortion due to the nonlinear displacement of the actuator exists in the measurement image depending on the scanning range. For this reason, the conventional probe scanning device has an RO for correcting the scanning range in advance.
It was equipped with M.

[0005]

Causes of actuator distortion include actuator hysteresis and creep non-linearity. Further, the non-linear displacement of the actuator varies depending on the scanning range, and there is a large difference between the individual actuators. Therefore, it is difficult to correct by a unique method.

The present invention has been made in view of the above points, and provides a probe scanning apparatus capable of correcting non-linear displacement of an actuator potentially existing in a scanning probe microscope to improve quantitative accuracy. The purpose is to provide.

[0007]

A probe scanning device according to the present invention is a probe scanning device for a scanning probe microscope, which scans a two-dimensional space and converts physical information of a sample surface into a three-dimensional image. , Scanning standard table creating means for creating a scanning standard table corresponding to the scanning means and the scanning range of the probe scanning device by scanning the standard sample in advance, and each scan obtained at the scanning point when scanning the sample The sample data for each point is moved so as to correspond to the scanning point corrected based on the scanning standard table created by the scanning standard table creating means.

Alternatively, the probe scanning device according to the present invention is
A probe scanning device for a scanning probe microscope, which scans a two-dimensional space to form a three-dimensional image of physical information on a sample surface, wherein a scanning means and a scanning range of the probe scanning device are prepared by previously scanning a standard sample. Scanning standard table creating means for creating a scanning standard table corresponding to, and at the time of scanning the sample, at the scanning point corrected based on the scanning standard table created by the scanning standard table creating means, And a calculation means for moving the probe by the scanning means.

[0009]

In the probe scanning apparatus of the present invention, the scanning standard table creating means creates the scanning standard table corresponding to the scanning means and the scanning range of the probe scanning apparatus by scanning the standard sample in advance. Then, based on this scanning standard table, the calculating means moves the sample data for each scanning point obtained at the scanning point when the sample is scanned. Alternatively, when the sample is scanned, the probe is moved by the scanning means to the scanning point corrected based on the scanning standard table.

[0010]

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

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention. In the scanning probe microscope (SXM) 10, the probe (probe) 11 faces the sample 12 and
The sample surface is moved by the movement of the sample table 14 which is scanned in the X and Y directions by the Y scan drive circuit 13. Probe 11
The displacement r of the sample 12 and the distance d of the sample 12 is detected by the displacement detector 15 engaged with the probe 11, and the detection output is sent to the servo circuit 17 which controls the Z driving body 16 so as to keep the distance d constant. Is entered.

Generally, the analog output of the servo circuit 17 (or the output of the image buffer 22 via the A / D converter 18 and the selection switching circuit 23) is synchronized with the XY scanning by the CRT1.
9 is displayed as a three-dimensional image.

In the present embodiment, the analog output of the servo circuit 17 is A / D converted by the A / D converter 18, and the digital signal thereof is output by the X counter 20 or the Y counter 21 which determines the scanning range. It is input to the controlled image buffer 22.

That is, the detection signal from the displacement detector 15 is the digital signal f (i, j) in the image buffer 22.
(However, j = 1, 2, 3, ..., J, i = 1, 2 ,.
In addition, I) is fetched for each scanning line in accordance with the output timing of the X counter 20 and treated as a bit string. For example, the signal f (100,4) indicates the digital amplitude value of the 100th scanning point on the 4th scanning line.

FIG. 2A shows grid points at the time of scanning by the SXM 10, which has J scanning lines and I scanning points for each scanning line. In the figure, the X counter 20
The output timing of the Y counter 21 is actually X,
This corresponds to the displacement in the Y direction. In the figure, X
It is considered that the direction has a length representing an I scan point, and the Y direction has a length representing a J scan line. FIG. 2B is a diagram showing the digital amplitude value f (i, j) of the j-th line of the three-dimensional image.

In FIG. 2A, the output timings of the X and Y counters 20 and 21 correspond to the displacements x and y in the X and Y directions, and x = m _x (i), y = It can be expressed by m _y (j). However, x = _mx (j) is the displacement amount of the actuator in the x direction up to the i-th scanning point, y = m
_y (j) is the displacement amount of the actuator in the y direction up to the j scan line. Therefore, the digital signal value f (i, j) at (i, j) is f (i, j) = f (m
can be represented by _{x (i), m y (} j)) = f (x, y). In these, x = m _x (i), y = m
_y (j) takes discrete values corresponding to i and j.

By the way, the displacement of the actuator is non-linear due to hysteresis, creep and other factors. 2C and 2D show an X counter 2 in each of the X and Y directions.
0, the output i of the Y counter 21, the actual X and j, Y direction displacement m _x (i), is a diagram showing the relationship m _y (j).
Here, m _x (i) is the displacement amount of the actuator corresponding to the output i of the X counter 20 in the X direction, and m _y (j) is Y
It is the displacement amount of the actuator corresponding to the output j of the Y counter 21 in the direction. Thus, the amount of displacement m _x in the X and Y directions
(I) and m _y (j) are not linear with respect to the outputs of the X and Y counters 20 and 21. Therefore, f (i, j) = f (m
_{x (i), m y (} j)) is not a signal value on a square lattice as shown in FIG. 2 (A), with the data on the lattice points of a lattice as shown in FIG. 3 (A) is there. Where i = 0,
1, ..., I, j = 0, 1, ..., J (integer), m
_{x (i), m y (} j) is a real number. That is, sample 12
An image that accurately represents the structure of the surface is f (x, y) = f
A _{(m x (i), m} y (j)), x-y at this time
The array of data in coordinates does not form a square grid.

However, the display on the CRT 19 is X, Y
The outputs i and j of the counters 20 and 21 are arranged on the square lattice points (x _c , y _c ) as shown in FIG. At this time, (x _c , y _c ) and (x, y) do not match, but here f (x, y) = f
(X _c , y _i ) (i = 0, 1, ..., I, j = 0, 1,
_{..., J, x c = l} x (i) = αi, y c = l y (j) =
The data strings are displayed as βj and ij values. Therefore, the scale of the image displayed on the CRT 19 in the X and Y directions does not match the scale of the actual image in the XY directions (that is, the displacement amount of the actuator). Figure 3 (A)
Since such data is displayed as shown in FIG. 3B, the displayed image is distorted. Further, at the same time as the distortion occurs, the scales in the X and Y directions do not match between the display image and the actual structure.

The image distortion due to the non-linearity of the displacement of the actuator and the calibration of the X and Y scales are performed using the selection switching circuit 23, the data translators 24 and 27, and the arithmetic circuit 25 in the following steps. It can be carried out.

Step 1 The data string f (i, j) in the image buffer 22 is input to the data translator 24 via the selection switching circuit 23. The data translator 24 has a displacement amount conversion table calculated from a calibration curve (x = m _x (i)) of the displacement amount of the actuator corresponding to the output value i of the X counter 20. In synchronization with the timing, the conversion of i → x = m _x (i) is executed in real time, and f (x, j) is output to the arithmetic circuit 25. That is, the data array f (i, j) sent from the image buffer 22 is f (x, j) = f
It is rewritten as ( _mx (i), j) and output to the arithmetic circuit 25.

Step 2 In the arithmetic circuit 25, f (x, j) = f (m
f from the value of _x (i), j) (i = 0, 1, 2, ..., I)
(X _c , j) = f (l _x (i), j) is calculated. That is, f on the grid point (x _c ) in the x direction of the display
Since the value corresponding to (x _c , j) does not exist as measurement data, it is calculated by the following method.

As shown in FIG. 4, f (x _c , j) = (1 / ΔX) {Δx _{i + 1} × f (m _x (i + 1), j) + Δx _i × f (m _x (i), j)} to calculate f (x _c , j). However, ΔX corresponds to the distance (displacement) between the data, and ΔX × I corresponds to the amount of displacement in the x direction in the image.

Further, Δx _{i + 1} = | m _x (i + 1) -l _x (i + 1) | Δx _i = | m _x (i) -l _x (i) | Now, here, f (x _c , j) = f (l
The values of _x (i), j) are converted into f (m _x (i), j) and f (m
_Although linear interpolation is performed using the signal value of the measurement data of _x (i + 1), j, spline interpolation or the like may be performed.

That is, in the arithmetic circuit 25, at the timing of the Y counter 21, from the data array f (x, j) sent from the data translator 24 to the X counter 20.
Interpolation is performed at the timing i, and f (x _c , j) is output to the image buffer 26.

Step 3 The data string f (x _c , j) in the image buffer 26 is transferred to the data translator 27 at the timing j of the y counter 21.
Entered in. The data translator 27 has a displacement amount conversion table calculated from a calibration curve (y = m _y (j)) of the displacement amount of the actuator corresponding to the output value j of the Y counter 21, and In sync with the timing,

The conversion j → y = m _y (j) is executed in real time, and f (x _c , y) is output to the arithmetic circuit 25. Similar to step 1 above, the data array f (x _c , j) sent from the image buffer 26 is
_{f (x c, y) =} f is rewritten to _{(x c, m y (j} )), it is outputted again to the arithmetic circuit 25.

Step 4 In the arithmetic circuit 25, f (x _c , y) = f (x _c ,
f from the value of m _y (j)) (j = 0, 1, ..., J)
(X _c, y _c) obtaining in _{= f (x c, l y} (j)) the same as in step 2 of the method. y-direction of the grid points (y _c) on the f (x _c, y _c) the value corresponding to the absence as measurement data, calculated in the same operation as in step 2.

In [0028] _{f (x c, y c)} = (1 / ΔY) {Δy i + 1 × f (x c, m y (j + 1)} + Δy i × f (x c, m y (j))} , F (x _c , y _c ) where ΔY corresponds to the distance between the data and ΔY × J corresponds to the amount of displacement in the y direction in the image.

[0029] In _{addition, Δy i + 1 = | m} y (j + 1) -l y (j + 1) | Δy i = | m y (j) -l j (j) |

In step 4, the arithmetic circuit 25
Is Y from the data array f (x _c , j) sent from the data translator 27 at the timing i of the X counter 20.
Interpolation is performed at the timing j of the counter 21, and f (x _c ,
y _c ) is output to the image buffer 26. The f (x _c , y _c ) thus obtained is output from the image buffer 21 to the CRT 19 after the distortion in each of the X and Y directions is removed. The output data array f (x _c , y _c ) can be expressed as follows by the processing of steps 1 to 4 described above.

[0031] _{f (x c, y c)} = (1 / ΔY) {Δy j + 1 × R (Δy j + 1) × f (x c, m y (j + 1) + Δy j × R (Δy j) × f (x _c , m _y (j))} = (1 / ΔX) (1 / ΔY) [Δy _{j + 1} × R (Δy _{j + 1} ) × {Δx _{i + 1} × R (Δx _{i + 1} ) _{× f (m x (i +} 1), m y (j + 1) + Δx i × R (Δx i) × f (m x (i), m y (j + 1))} + Δy j × R (Δy j) × {Δx i _{+1 × R (Δx i + 1} ) × f (m x (i + 1), m y (j)) + Δx i × R (Δx i) × f (m x (i), m y (j))}]

Now, in the arithmetic circuit 25, when performing linear interpolation, when performing R (k) = 1 spline interpolation,

[0033]

[Equation 1] Can be expressed as

The calibration table of the actuator included in the data translators 24 and 27 is generated as follows. The displacement amount of the actuator can be measured using a measuring instrument such as an electric micro or a fiber sensor in a region of several μm or more. However, a standard sample having a clear structure (the size of the structure in the xy direction is accurately determined) is used to accurately determine the displacement amount calibration curve or to determine the calibration curve in a narrow region of 1 μm or less.
That is, a standard sample is measured, and a calibration curve is calculated from the measurement result.

For example, a calibration curve is obtained by using a grating having a pitch of 3600 as a standard sample. FIG. 5A shows a cross section in a direction perpendicular to the grating of 3600 gratings. An ideal tunnel current trace of this structure, that is, a trace when the actuator is linearly displaced is as shown in FIG. 5B (specifically, in the x direction of the measurement image). The cross-sectional shape).

However, in the actual measurement, the trace as shown in FIG. 5C is obtained due to the non-linear displacement of the actuator. The calibration curve of the actuator is calculated based on the trace as shown in the figure. The calculation method is as follows.

FIG. 6 is a trace of the tunnel current obtained by scanning in the direction perpendicular to the grating of the grating. In this trace, the peak position of the structure is obtained and set as x ₀ , x ₁ , ..., X _n , respectively. In the actual grating structure, the intervals between the gratings are equal. That is, d = x _{n + 1} −x _n should be constant. Using this condition, the least squares method is performed to calculate the calibration curve of the m-th order actuator. Usually 3rd-
The measurement results can be calibrated well with a quartic curve. For calibration in a small scanning range of about several nm, a crystal surface of graphite or Si is used as a standard sample.

Next, a second embodiment of the present invention will be described. In the first embodiment, the data f (i, j) fetched by the A / D converter 18 at the timings of the outputs i, j of the X, Y counters 20,21 are temporarily stored in the image buffer 2.
After the data is stored in 2 (or after being directly displayed on the CRT 19), the circuit for calibrating the displacement amount in the x and y directions performs the calibration in the x and y directions.

In the second embodiment, the captured line data f (i, j) is synchronized with the timing of the output j of the Y counter 21 without storing the data in the image buffer.
(J is constant) is directly sent to the data translator 24,
The calibration in the x direction can be performed simultaneously with the measurement. The calibration can be performed in steps as described below. Further, FIG. 7 shows a conceptual diagram thereof.

Step 1 The data A / D converted in synchronization with the timing i of the X counter 20 is sent to the data translator 24 in synchronization with the timing j of the Y counter 21. The data translator 24 outputs x corresponding to the output i of the X counter 20.
It has a conversion table for calibrating the displacement amount of the actuator in the direction, in synchronization with the timing of the X counter 20,

The conversion i → x = m _x (i) is executed in real time and f (x, j) is output to the arithmetic circuit 25. That is, the A / D-converted x-scan data string f (i, j) is f (x, j) = f (m _x
It is rewritten as (i), j) and output to the arithmetic circuit 25.

Step 2 In the arithmetic circuit 25, the same arithmetic processing as in the first embodiment described above is performed, and the data array f sent from the data translator 24 at the timing j of the Y counter 21.
The interpolation data f (x _c , j) is output from (x, j) to the selection switching circuit 23 in synchronization with the timing i of the X counter 20. In the selection switching circuit 23, the output data f (x _c ,
j) is sent to the CRT 19 for display or to the image buffer 26.

Step 3 The data string f (x _c , j) in the image buffer 26 is input to the data translator 27 at the timing of the X counter 20, and in synchronization with the output value j of the Y counter 21,

The conversion j → y = m _y (j) is executed in real time. As a result, data sequence f (x _c, j) is _{f (x c, y) =} F (x c, m y
It is rewritten as (j)) and output again to the arithmetic circuit 25. Step 4

In the arithmetic circuit 25, the same arithmetic processing as in the first embodiment described above is performed, and the data array f (x _c , y) sent from the data translator 27 at the timing i of the X counter 20 is used. , And outputs the interpolation data f (x _c , y _c ) to the selection switching circuit 23 in synchronization with the timing j of the Y counter 21. From the selection switching circuit 23, CR
It is sent to T19 and displayed as calibrated data.

Next, a third embodiment of the present invention will be described.
In the first and second embodiments, the digital signal train f obtained at the timings of the X and Y counters 20 and 21.
For (i, j), the x and y coordinates of the data were calibrated based on the data conversion table obtained from the calibration curve of the actuator to remove the image distortion. In the third embodiment, the xy scanning signal is converted from the conversion table of the xy scanning signal obtained from the calibration curve of the actuator to calibrate the xy scale and remove the image distortion. . That is, the xy scale of the digital signal sequence f (i, j) stored in the image buffer 22 is calibrated, and the data displayed on the CRT 19 is not distorted.

Such a method has a data translator 28 having a calibration table of xy scanning signals for calibrating the non-linearity of the displacement of the actuator as shown in FIG.
Can be carried out by inserting after the xy scan drive circuit 13.

In the above first and second embodiments,
In synchronization with the timings i and j of the X and Y counters 20 and 21, the xy drive circuit 13 outputs xy as shown in FIG.
The scanning signals V _x (i) and V _y (j) were output. Here, V _x (i) and V _y (j) are proportional to the timings of i and j as shown in FIG. That is, the scanning signal is a triangular wave. The scanning range at this time is V _x
It is determined by the amplitudes of (i) and V _y (j).

[0049] In the third embodiment, the output V _x in the xy scan drive circuit 13 (i), after the V _y (j), containing the data translator _{28, V x (i),} V y (J)
Is converted as shown in FIG. 9A, and scanning in the xy directions is performed. The data translator 28 corrects the non-linear displacement of the actuator and outputs V _x (i), V of the xy drive circuit 13 so that the displacement in the xy direction becomes linear.
_It has a conversion table for calibrating _y (j).
Therefore, although the xy drive voltage from the xy scan drive circuit 13 becomes non-linear as shown in FIG. 9 (B), the x, y counters 20 and 21 outputs i, j respectively in x, y directions. The displacement of is linear. That is, an image without distortion is displayed on the CRT 19 as data and stored in the image buffer 22.

FIG. 10 is a diagram showing the configuration of the fourth embodiment of the present invention which further has a temperature compensation function. In the SXM 10 of the fourth embodiment, the probe 11 is scanned in the X and Y directions by the XY scanning drive circuit 13 so as to face the sample 12, and the sample surface is moved by this scanning. Probe 11
The displacement r of the sample 12 and the distance d of the sample 12 is detected by the displacement detector 15 engaged with the probe 11, and the detection output is a servo circuit 17 for controlling the Z driving body 29 so as to keep the distance d constant. Entered in. Generally, the analog output of the servo circuit 17 or the digital output of the image buffer 22 is
It is displayed as a three-dimensional image on the CRT 19 in synchronization with the X and Y scans.

In the fourth embodiment, the servo circuit 1
The analog output 7 is A / D converted by the A / D converter 18, and the digital signal is input to the image buffer 22 controlled by the X counter 20 or the Y counter 21 which determines the scanning range.

The detection signal from the displacement detector 15 is a digital signal f (i, j) (where i =
1, 2, 3, ..., I, j = 1, 2, 3, ..., J) are fetched for each scanning line at the output timing of the X counter 20 and treated as a bit string. For example, f (100,5) is 100 at the 5th scan line.
The digital amplitude value of the th scanning point is shown.

The displacement of the actuator 30 in the X and Y directions is performed by the XY drive circuit 13. The actuator 30 is displaced by applying a voltage to the electrodes in each of the X and Y directions. This applied voltage V _X (i), V
_Y (j) is the X, Y counter 20, 2 from the arithmetic circuit 31.
A control signal at the reference temperature T _b output in synchronization with the counter outputs i and j of 1.

[0054]

[Equation 2] Is output from the XY drive circuit 13.

11A and 11B show the voltage outputs V _X (i) and V _Y (j) of the XY drive circuit 13 synchronized with the counter outputs of the X and Y counters 20 and 21, respectively. Since V _X (i) and V _Y (j) at this time are output so that the nonlinear displacement of the actuator 30 is corrected, they are not linearly displaced with respect to i and j. But,
Displacement amounts m _X (i) and m _Y of the actuator 30 when V _X (i) and V _Y (j) are applied to the actuator 30.
(J) is as shown in (C) and (D) of FIG.
It is linearly displaced with respect to i and j. The setting of the applied voltage so as to correct the non-linear displacement of the actuator can be performed as in the third embodiment described above.

The XY drive circuit 13 is composed of a D / A converter and an amplifier for amplifying the D / A converted output. What determines the D / A conversion output and the amplification factor is the control signal shown in the above equation 2 transmitted from the arithmetic circuit 31.

The D / A converter and the amplifier constituting the XY drive circuit 13 operate as follows. Now, it is assumed that a 14-bit D / A converter with ± 10 V _PP output is used. At this time, the resolution of the output voltage of the D / A converter is 1.2 mV, and if the actuator 30 having the piezoelectric constant of 10 nm / V is used, the resolution of the XY displacement is 0.12 angstrom. Assuming that the actuator 30 is displaced in the X direction in steps of 0.5 nm to 100 nm, m _x (1) = 0.5, m _x (2) =
1.0, ..., M _X (200) = 100 nm, and the output voltage corresponding to each displacement is output from the XY drive circuit 13 as V _X (1), V _X (2), ..., V _X (200). Has been done.

By the way, in the SXM, the scanning range is as wide as several nm to several tens of μm. Even if the D / A converter and the actuator as described above are used, only a scanning range of 200 nm at the maximum can be obtained, so that it is necessary to amplify the output of the D / A converter. That is, the gain is set to 10 according to the scanning area.
The output amplitude is increased to 10 times and 100 times by switching to 100 times and 100 times.

As described above, the output voltage V _X of the D / A converter
The magnifications of (i), V _Y (j) and the amplifier vary depending on the scanning range, which is controlled by the arithmetic circuit 31. That is, the arithmetic circuit 31 synchronizes with the output timings i and j of the X and Y counters 20 and 21 to the XY drive circuit 12 so as to obtain the set scanning range. Send amplification factor.

The control signal as shown in the above equation 2 is a digital signal train which is determined so that the voltage is output from the D / A converter according to the scanning range at the reference temperature T _b. .

The arithmetic circuit 31 outputs a ROM in which a plurality of digital signal sequences as shown in Formula 2 are prepared and stored according to the scanning range, which table is output, and how the amplification factor is set. It has a selection circuit and the like for determining whether or not and outputting to the XY drive circuit 13.

Taking the actuator described above as an example, the scanning range is 20 nm, 200 nm, 2 μm, 20 μ.
In order to output the voltage for scanning m to the XY drive circuit 13, the arithmetic circuit 31 transmits the content as shown in the following Expression 3 to the XY drive circuit 13 as a digital signal.

[0063]

[Equation 3]

That is, before scanning, a rate is sent in the case of an amplifier, and then a digital signal sequence as shown in the above equation 2 is used as a scanning signal, and the counter output i of the X, Y counters 20 and 21
It is transmitted in synchronization with j. Control signal sequence that can be stored in ROM

[0065]

[Equation 4] The number of tables is the size of the table and the ROM
Depending on the storage capacity of, for example, ROM is 64K bytes,
Control signal table

[0066]

[Equation 5]

If the size of 512 bytes is 128
Each table can be stored. To increase the number of tables to be stored, the ROM memory may be expanded. With the method described above, the actuator 30 can be displaced according to the designated scanning range.

By the way, as a feature of SXM, in the atmosphere,
There is a point that the measurement environment does not matter, such as in vacuum or in liquid, and measurement is performed in various environments. One of them is to measure at low temperature by using liquid helium (lq helium) or liquid nitrogen to lower the temperature. The measurement at such a low temperature is actively carried out for superconducting substances and the like.

For low temperature measurements, the temperature of the cryogen (ie,
In addition to 4.2 K for lqHe and 77 K for lqN ₂ , it is required to carry out the measurement by changing the temperature in the range from the temperature of the cryogen to room temperature or high temperature.

On the other hand, it is known that the displacement amount of the actuator 30 decreases as the temperature decreases. For example, at the liquid helium temperature (4.2 K), the displacement amount is 1/1
It will be 0-1 / 20. Therefore, even if the same outputs V _X (i) and V _Y (j) of the D / A converter are applied to the actuator 30, if the temperature is different, the displacement amount of the actuator, that is, the scanning range is different. Therefore, in order to obtain the same scanning range at different temperatures, it is necessary to change the control signal sent to the XY drive circuit depending on the temperature as shown in equation 4 according to the displacement of the actuator 30 at that temperature.

For example, liquid helium temperature (4.2K)
So, the displacement of the actuator 30 is 1/1
If it becomes 0, in order to scan at 200 nm at low temperature, the voltage applied to the actuator when scanning at 2 μm at room temperature (1 for scanning at 200 nm at room temperature)
It is necessary to apply a voltage of 0 times), and therefore the arithmetic circuit 31 selects and transmits a control signal.

The temperature T near the measurement point is detected by the detector 32 and sent to the arithmetic circuit 31. The arithmetic circuit 31 outputs a control signal as shown in Formula 2 based on the sent displacement curve of the actuator 30 at the measured temperature T in the following procedure.

FIG. 12 shows the displacement curve of the actuator 30 at each temperature. The temperature is t = t ₀ ,
It becomes high in order of t ₁ , t ₂ , ..., T _n . In the figure,
When the actuator 30 is displaced by l ₀ , the applied voltage to the actuator 30 is V ₀ , V depending on the temperature.
₁ , ...

[0074] In the figure, the reference temperature is indicated by curve for t = t _4, the actuator 30 in other words t = t ₄
The control signal table corresponding to the displacement curve of
No. 1 ROM. At this time, l at t = t _0
In order to displace the actuator 30 by ₀ , V ₀
Only the voltage needs to be applied to the actuator 30.
The control signal for outputting the voltage of V ₀ is for displacing the actuator 30 of l ₀ 'at the reference temperature, and this correspondence is as shown in FIG. 13, and is stored in the selection circuit. .

Further, although FIG. 12 is drawn continuously,
In the table of the displacement curve for each temperature, the temperature, the amount of displacement, and the voltage value are discrete. Therefore, the selection circuit performs a process of interpolating each parameter by using two pieces of data whose values are close to each other among the values stored in the selection circuit. The control signal finally output selects and outputs the closest one.

By doing so, the probe scanning device for continuously measuring while changing the temperature in the same scanning range, and the change in the displacement amount of the actuator due to the temperature are corrected and the temperature is changed. It is possible to provide a probe scanning device that scans the probe in a constant scanning range.

The control signal table stored in the ROM of the arithmetic circuit 31 can be created by measuring the standard sample as described in the above-mentioned another embodiment. Further, when creating a table of a wide area of 1 μm or more, it is possible to check by adjusting the displacement amount of the actuator. Since the SXM has a wide scan range, it is necessary to prepare some standard samples.

The displacement curve of the actuator to be stored in the selection circuit in the arithmetic circuit 31 is generated by performing the measurement in the following procedure. (1) Keep the temperature constant and measure a standard sample. (2) The applied voltage is changed and the scanning range is calculated. Since the amount of displacement of the actuator greatly differs depending on the temperature, the step of applied voltage is changed for each temperature. (Also,
The amount of displacement also differs depending on the type of actuator, so consider that point as well. ) The above method is repeated to create a table of displacement curves as shown in FIG.

The temperature interval for examining the displacement curve depends on the accuracy when changing the temperature of the SXM measurement, but is approximately the same as the step of temperature change during the SXM measurement, or doubles when the accuracy does not matter. Greater intervals are acceptable. A temperature displacement curve for which a displacement curve has not been examined does not pose a problem because the displacement curve before and after the measured temperature is interpolated and output when the control signal is output.

[0080]

According to the present invention, it is possible to provide a probe scanning device capable of correcting non-linear displacement of an actuator potentially existing in a scanning probe microscope and improving quantitative accuracy. That is, since the correction is performed for each individual actuator incorporated in the arithmetic circuit of the scanning device and for each scanning range, accurate sample information can be provided.

Further, according to the present invention, the probe scanning device for continuously measuring while changing the temperature in the same scanning range, and the change in the displacement amount of the actuator due to the temperature are corrected to change the temperature. It is also possible to provide a probe scanning device which scans the probe in a constant scanning range.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a first embodiment of the present invention.

FIG. 2A is a diagram showing grid points during SXM scanning;
(B) is the digital amplitude value f of the j-th line of the three-dimensional image
(I, j) is a diagram, (C) is a diagram showing a relationship between an output i of the X counter in the X direction and an actual displacement amount m _x (i) in the X direction, and (D) is a Y counter in the Y direction. is a diagram showing the relationship between the output j and the actual Y-direction displacement amount m _y (j).

FIG. 3A is a diagram showing a positional relationship of actual scanning points,
(B) is a diagram showing a positional relationship of scanning points to be displayed on the CRT.

FIG. 4 is a diagram for explaining parameters used for arithmetic processing in the arithmetic circuit in FIG.

5A is a diagram showing a cross section in a direction perpendicular to a grating of a grating, FIG. 5B is a diagram showing an ideal tunnel current trace of the structure shown in FIG. 5A, and FIG. It is a figure which shows the trace obtained by the actual measurement of the structure shown in FIG.

FIG. 6 is a diagram showing a trace of a tunnel current obtained by scanning in a direction perpendicular to a grating of a grating.

FIG. 7 is a block configuration diagram of a second embodiment of the present invention.

FIG. 8 is a block configuration diagram of a third embodiment of the present invention.

FIG. 9A is an output V of the data translator.
FIG. 3B is a diagram showing _x (i) and V _y (j), and FIG. 3B is a diagram showing voltages for driving xy from the xy scanning drive circuit.

FIG. 10 is a block diagram of a fourth embodiment of the present invention.

11A and 11B are voltage outputs V _X of an XY drive circuit synchronized with counter outputs of X and Y counters, respectively.
It is a figure which shows (i), _VY (j), (C) and (D).
FIG. 4 is a diagram showing displacement amounts m _X (i) and m _Y (j) of the actuator when V _X (i) and V _Y (j) are applied, respectively.

FIG. 12 is a diagram showing a displacement curve of an actuator at each temperature.

FIG. 13 is a diagram showing a table showing values of control signals according to temperature and displacement amount.

[Explanation of symbols]

10 ... Scanning probe microscope, 18 ... A / D converter, 2
0 ... X counter, 21 ... Y counter, 22, 26 ... Image buffer, 23 ... Selection switching circuit, 24, 27, 28 ... Data translator, 25 ... Operation circuit, 30 ... Actuator, 31 ... Operation circuit, 32 ... Temperature detection vessel.

Claims (4)

[Claims] 1. A probe scanning device for a scanning probe microscope, which scans a two-dimensional space to form a three-dimensional image of physical information on the surface of a sample. The scanning standard table creating means for creating a scanning standard table corresponding to the scanning means and the scanning range, and the scanning standard table creating means for the sample data for each scanning point obtained at the scanning point when the sample is scanned And a calculation unit that moves the scanning point corresponding to the calibrated scanning point table based on the scanning standard table created by. 2. A buffer for storing sample data for each scanning point obtained at the scanning point when the sample is scanned, wherein the computing means creates each scanning point by the scanning standard table creating means. Calibrated with the above scanning standard table,
It has a 1st calculating part which produces | generates the corrected scanning point data, and a 2nd calculating part which moves the said sample data according to the said scanning point data calculated by the said 1st calculating part, It is characterized by the above-mentioned. The probe scanning device according to claim 1. 3. A probe scanning device for a scanning probe microscope which scans a two-dimensional space to form a three-dimensional image of physical information on the surface of the sample. A scanning standard table creating means for creating a scanning standard table corresponding to the scanning means and the scanning range, and when the sample is scanned, it is calibrated based on the scanning standard table created by the scanning standard table creating means. A probe scanning apparatus comprising: a computing unit that moves the probe to the scanning point by the scanning unit. 4. A temperature detecting means for detecting the temperature of the scanning means, and a temperature conversion table storage means for storing a temperature conversion table indicating the temperature dependence of the scanning standard table created by the scanning standard table creating means. In addition to the correction of the scanning point based on the scanning standard table, the arithmetic means is detected by the temperature detecting means with reference to the temperature conversion table stored in the temperature conversion table storage means. 4. The probe scanning device according to claim 3, wherein temperature compensation is performed according to the temperature of the scanning means.