JP3118106B2 - Probe scanning method and probe scanning device for scanning probe microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe scanning method and a probe scanning apparatus for a scanning probe microscope, and more particularly, to a probe scanning method using a single fine movement mechanism, regardless of whether the scanning range is wide or narrow. The present invention relates to a probe scanning method and a probe scanning device of a scanning probe microscope that enable measurement with the same high measurement resolution.

[0002]

2. Description of the Related Art A scanning probe microscope generally has a probe which is brought close to an area to be measured of a sample at a very small interval. It has a function of detecting a physical quantity acting between sample surfaces and measuring a fine uneven shape on the sample surface using the physical quantity. There are various types of scanning probe microscopes depending on the physical quantity to be used. For example, a scanning tunneling microscope (hereinafter referred to as STM) using a tunnel current and an atomic force microscope using an atomic force are typical devices. is there. Hereinafter, an STM will be described as an example for convenience of description.

A configuration of a main part of a conventional STM will be described with reference to FIG. 7, reference numeral 51 denotes a sample, and 52 denotes a sample 51.
And 53, a fine movement mechanism for attaching the probe 51. The fine movement mechanism 53 is an integrated three-dimensional fine movement mechanism, and includes three rod-shaped piezoelectric elements 5 arranged at right angles to each other.
4,55,56. The piezoelectric element 54 is an actuator for the X-axis direction, the piezoelectric element 55 is an actuator for the Y-axis direction, and the piezoelectric element 56 is an actuator for the Z-axis direction. The piezoelectric elements 54 and 55 have the function of scanning the probe 52 along the sample surface, and the piezoelectric element 56 has the function of adjusting the distance between the probe and the sample.

[0004] A bias voltage of several volts is applied between the probe 52 and the sample 51 by a power supply 57. When a bias voltage is applied between the probe and the sample and the probe 52 approaches the surface of the sample 51 at a distance of angstrom unit, a tunnel current I flows between the probe and the sample. This tunnel current I has an exponential relationship with the distance between the probe 52 and the sample 51. The tunnel current I is detected by a tunnel current detection / conversion circuit 58 and is converted into a voltage corresponding to the distance between the probe and the sample. The voltage corresponding to the distance is supplied to the Z-axis servo circuit 59. The Z-axis servo circuit 59 is a circuit for controlling the amount of expansion and contraction of the piezoelectric element 56 in order to maintain the distance between the probe and the sample at a predetermined constant distance. The Z-axis servo circuit 59 has a reference voltage corresponding to the certain distance inside, and detects a tunnel current.
The detection voltage supplied from the conversion circuit 58 is compared with a reference voltage, and the probe 52 is adjusted so that the detection voltage matches the reference voltage.
Is output as a drive signal for the piezoelectric element 56. This allows the probe
The distance between the samples is kept at a predetermined constant distance.

Reference numeral 60 denotes an XY scanning circuit, and reference numeral 61 denotes an XY scanning control unit. The XY scanning controller 61 generates and outputs digital signals for controlling the expansion and contraction of the piezoelectric elements 54 and 55 independently in the X-axis direction and the Y-axis direction. In the XY scanning circuit 60, the X-axis piezoelectric element 5
A set of an X-axis D / A converter 62X and an amplifier 63X and a set of a Y-axis D / A converter 62Y and an amplifier 63Y are provided for each of the Y-axis piezoelectric element 55 and the Y-axis piezoelectric element 55. Each A / D
The converters 62X and 62Y convert a digital control signal of a predetermined number of bits applied to the input side of the bus line into an analog signal, and the amplifiers 63X and 63Y amplify the analog signal to a drive signal level. XY scanning circuit 6
The circuits forming these sets of 0 convert each digital signal provided from the XY scan control unit 61 into an analog drive signal for operating the piezoelectric element, and the corresponding piezoelectric element 54,5.
5

Each of the piezoelectric elements 54 to 5 of the fine movement mechanism 53
6 and the configuration of the Z-axis servo circuit 59 for controlling the expansion and contraction operation of each of the piezoelectric elements 54 to 56 and the configuration of the XY scanning controller 61, the probe 52 scans the measurement surface of the sample 51 and its height. The position is adjusted. The probe 5 via the piezoelectric element 56
The control amount of the Z-axis servo circuit 59 for adjusting the height of 2 is taken into the measurement data storage unit 64 as height information of the sample surface. The amplifiers 63X and 63 of the XY scanning circuit 60
The signal amount output from Y is taken into the measurement data storage unit 64 as scanning position information of the probe 52. The data processing unit 65 obtains surface unevenness information at each position on the scan surface of the sample 51 based on the spatial coordinate data of X, Y, and Z relating to the movement of the probe 52 obtained in this manner. Such surface unevenness information is displayed as an image on the screen of the display device 66, and is subsequently used for surface analysis.

In the above configuration, for example, the XY scanning control section 61, the measurement data storage section 64, the data processing section 65
Is a calculation / control unit 67 including a computer.
It is realized as software as a functional means.

[0008]

The conventional STM described above.
Based on the circuit configuration of the XY scanning circuit 60 in ST,
Regarding the measurement resolution of M, the following problems are raised.
Here, the measurement resolution of the STM refers to the fineness of a scale for drawing an image when displaying an uneven image of the measurement surface on the screen of the display device 66, in other words, the number of samplings of the measurement data. Since the measurement resolution is determined by the unit of change of the stroke of the scanning piezoelectric element, that is, the scanning pitch, it can also be called the scanning accuracy.

The scanning piezoelectric element 5 in the fine movement mechanism 53
In 4,55, the number of stages that can change the stroke to the maximum is determined based on the number of bits of the digital signal that can be handled by the D / A converters 62X and 62Y. For example, when the number of bits is 16 bits, the state can be continuously changed in 2 ¹⁶ ways, so that the number of stages is 2 ¹⁶ = 65536. Also, the piezoelectric elements 54 and 5
In the case of changing the stroke of No. 5, the scanning pitch for changing the stroke is obtained by dividing the maximum stroke (full stroke) by the number of steps (2 ¹⁶ = 65536). This scanning pitch is hereinafter referred to as “minimum scanning pitch”. The minimum scanning pitch is the D / A converter 62
In the configuration of the conventional scanning circuit corresponding to 1 digit of X and 62Y, the minimum scanning pitch is always kept at a constant value. On the other hand, when considering the applied voltage at the piezoelectric elements 54 and 55, that is, the output voltages of the amplifiers 63X and 63Y, for example, when the range of the applied voltage is 0 to 100 volts, the applied voltage is changed to change the stroke of the piezoelectric element. The unit voltage is also fixedly determined by dividing 100 volts by the number of steps.

Therefore, when scanning and measuring the surface of the sample 51 based on the expansion and contraction operation of the piezoelectric elements 54 and 55, the size of the stroke set for the expansion and contraction operation of each of the piezoelectric elements 54 and 55 (hereinafter referred to as the scanning width) ), The scanning accuracy in the X-axis direction and the Y-axis direction, in other words, the measurement resolution is determined. For example, it is assumed that the scanning range on the sample surface is a scanning range determined by the maximum stroke with each scanning width of the piezoelectric elements 54 and 55 being the maximum stroke. When an uneven image of the scanning surface is displayed on the screen of the display device 66 using the measurement data obtained by this scanning, an image can be created with the measurement data of the sampling number determined by the minimum scanning pitch. Therefore, the number of measurement data is maximized, and the measurement has the highest resolution. Further, it is assumed that the scanning range on the sample surface is a scanning range determined by this stroke, with each scanning width of the piezoelectric elements 54 and 55 being a stroke smaller than the maximum stroke. In this case, since the scanning pitch is the same minimum scanning pitch as described above, the number of measurement data obtained by scanning decreases, and the measurement resolution decreases. As described above, the smaller the scanning width of the piezoelectric elements 54 and 55, the lower the accuracy of the image displayed on the display screen.

Next, the above contents will be described quantitatively. For example, a set scan width in the X-axis direction (hereinafter referred to as X
Axis scan width) is the maximum stroke in the X-axis direction (hereinafter X
In the case of 1/10 of the maximum shaft stroke),
Regarding the scanning of the X-axis scanning width, the X-axis D / A converter 62
This means that only 1/10 of the highest measurement resolution determined by the characteristic of X is used. That is, the smaller the scanning width of the X-axis maximum stroke, the lower the resolution. Assuming that the highest measurement resolution provided by X-axis D / A converter 62X is X1, X
The measurement resolution Xa is given by the following equation according to the axial scanning width.

Xa = X1 × (X-axis scanning width) / (maximum stroke of X-axis) This holds true in the setting of the scanning width in the Y-axis direction. That is, the following expression holds for the highest measurement resolution Y1 and the maximum measurement resolution Ya in the Y-axis direction.

## EQU2 ## Ya = Y1.times. (Y-axis scanning width) / (Maximum stroke of Y-axis)

As described above, in the conventional STM, the measurement resolution is defined by the characteristics of the D / A converters 62X and 62Y, and a high measurement resolution can be maintained while the scanning width of the scanning piezoelectric element is used at the maximum stroke. Although there is no problem, when the scanning width is smaller than the maximum stroke, there is a problem that the measuring resolution is reduced as the scanning width becomes smaller.

In general, in the fine movement mechanism, the size of the measurement target area is determined according to the size of the stroke of the scanning piezoelectric element. For example, a piezoelectric element having a maximum stroke of several μm can measure at a high resolution, but cannot measure a wide area. Conversely, a piezoelectric element having a maximum stroke of several tens of μm can measure a wide area, but cannot expect a high resolution at the atomic level. Therefore, the conventional S
In TM, a plurality of types of fine movement mechanisms were prepared to enable measurement in various ranges, and these were selected and used as needed. Therefore, there is a problem that the structure becomes complicated, the number of parts increases, and the cost increases.

An object of the present invention is to provide a scanning device capable of always performing measurement with the same high measurement resolution from a scanning range having a scanning width of an atomic level to a scanning range having a relatively wide scanning width of several tens of μm using a single fine movement mechanism. An object of the present invention is to provide a probe scanning method and a probe scanning device for a probe microscope.

[0015]

A probe scanning method and a probe scanning apparatus for a scanning probe microscope according to the present invention are configured as follows. A scanning circuit including a D / A converter and an amplifier is provided in connection with a piezoelectric element for causing the probe to scan on the surface of the sample, and a digital signal for scanning control given from the scanning control unit is analogized by the D / A converter. This is a method of scanning the probe by converting the analog signal into a drive signal by amplifying the analog signal with an amplifier, and applying the drive signal to the piezoelectric element to move the probe. In this method, A variable gain amplifier for amplifying the output signal is added to the output side of the D / A converter, so that when the scanning range is arbitrarily set in the maximum scanning range determined by the maximum stroke of the piezoelectric element, Based on the ratio between the corresponding scan width of the piezoelectric element and its maximum stroke, the highest measurement resolution determined by the characteristics of the D / A converter is always maintained. By adjusting by changing the gain of the gain amplifier, and to perform probe scanning. In this probe scanning method, it is also possible to include a shift signal corresponding to the offset in the output signal of the variable gain amplifier in consideration of the fact that an offset exists in an arbitrary set scanning range. Similarly, as the probe scanning device, a scanning circuit including a D / A converter is provided in relation to the probe scanning piezoelectric element, and a scanning control digital signal given from the scanning control unit is provided by the scanning circuit. The variable gain amplifier amplifies the output signal of the D / A converter, and the piezoelectric element is set when an arbitrary scanning range is set, on the premise that the piezoelectric element is configured to generate a driving analog signal based on the following. Based on the ratio of the scan width to its maximum stroke, D
Control means for changing and adjusting the gain of the variable gain amplifier so as to always maintain the highest measurement resolution determined by the characteristics of the / A converter. Further, in the above configuration, it is possible to further comprise an offset setting device for outputting a shift signal added to the output signal of the variable gain amplifier, and a control means for giving a command for setting the required offset amount to the offset setting device. It is. Furthermore, it is preferable to add an amplifier that amplifies a signal obtained by adding a shift signal to the output signal of the variable gain amplifier to generate a drive signal. Of course, the variable gain amplifier itself can be configured to set a required gain level to generate a drive signal. As another modification example of the amplifier, an amplifier that inputs the output signal of the variable gain amplifier to one input terminal and inputs the shift signal to the other input terminal may be provided. Furthermore, a variable gain amplifier and an amplifier may be provided for each piezoelectric element of the two axes defining the plane of the scanning range, and the offset setting device may be formed as a single unit common to the two axes. it can.

[0016]

According to the present invention, a D / A in a scanning circuit provided in association with a piezoelectric element involved in scanning in the probe fine movement mechanism is provided.
By using a configuration in which a variable gain amplifier is attached to the output side of the converter, the gain of the variable gain amplifier can be adjusted appropriately when the scanning range set on the sample surface is scanned by the probe of the scanning probe microscope. Adjust to D / A
The highest measurement resolution determined by the characteristics of the converter is always exerted. Therefore, when each of a plurality of scanning ranges having different widths is measured, measurement can be performed using a single scanning piezoelectric element unit while always maintaining high measurement resolution. Further, even if an offset exists for an arbitrarily set scanning range, a shift signal for performing the movement related to the offset is provided by a configuration configured to perform the movement related to the scanning only on the probe side. Since the configuration is such that an offset setting device to be generated is provided, this can be dealt with.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The feature of the present invention resides in an XY scanning circuit 60 that supplies a driving signal to each of the piezoelectric elements 54 and 55 in the X-axis direction and the Y-axis direction related to the scanning of the probe 52 and a configuration related thereto. 1 shows only the embodiment of the XY scanning circuit 60 and the parts related thereto, and the illustration of the entire configuration of the scanning probe microscope is omitted. 1 and 2 are diagrams for explaining a scanning range and a scanning width.
6 to 6 are diagrams each showing an embodiment of the XY scanning circuit 60. 3 to 6, elements substantially the same as the elements described in FIG. 7 are denoted by the same reference numerals. In this embodiment, when changing the positional relationship between the sample and the probe,
An example in which the position is changed only on the probe side will be described.

In FIG. 1, Lx0 indicates the maximum stroke of the X-axis piezoelectric element 54, and Ly0 indicates the maximum stroke of the Y-axis piezoelectric element 55. Therefore, the range R1 determined by Lx0 and Ly0
Is the scanning range of the maximum area. The range R2 is a partial area of the scanning range R1, and is a scanning range determined by the strokes Lx1 and Ly1. Since the scanning range R2 includes the origin O, there is no offset, and it is not necessary to consider this. Comparing the scanning ranges R1 and R2, when the minimum scanning pitch is constant, measuring the scanning range R1 having a large number of samplings of the measurement data has a higher measurement resolution than measuring the scanning range R2 having a small number of samplings. . In this embodiment, the minimum scanning pitch is determined by the width of the scanning range, that is, the size of each stroke of the piezoelectric elements 54 and 55 (scanning width).
XY in the measurement of various scanning ranges.
The maximum measurement resolution determined by the characteristics of the D / A converter used in the scanning circuit is always maintained.

A first method for always performing measurement with the same high measurement resolution for an arbitrary scanning range partially included in the maximum scanning range R1 determined by the maximum stroke of the XY scanning piezoelectric elements 54 and 55. A configuration example will be described with reference to FIG. 1 and FIG. FIG. 3 shows an arithmetic / control section 67, an XY scanning control section 61 therein, an XY scanning circuit 60, a fine movement mechanism 53, and an X-axis piezoelectric element 54 and a Y-axis piezoelectric element 55 therein. In this embodiment, the XY scanning circuit 6
0 and the configuration related to control from the XY scanning control unit 61.

The gist of the present invention is that, when the scanning range is arbitrarily set in the maximum scanning range R1, the D / A converters 62X and 62Y correspond to the width of the scanning range.
The idea is to change the minimum scanning pitch originally determined by. First, this concept will be described. The scanning range R2 shown in FIG. 1 is an example in which it is not necessary to consider the offset. X-axis and Y-axis piezoelectric elements 54, 5
The maximum stroke of No. 5 is Lx0, Ly0 as described above, and the strokes of the piezoelectric elements 54, 55 corresponding to the scanning range R2 are Lx1, Ly1.

In the following, for convenience of explanation, the X-axis piezoelectric element 54 will be described as an example. The minimum scanning pitch is determined based on the maximum stroke Lx1 of the piezoelectric element 54 and the measurement resolution inherently provided by the X-axis A / D converter 62X (shown in FIG. 3) in the XY scanning circuit 60. Piezoelectric element 54
Is the maximum stroke, and when measuring the maximum scanning range R1, the gain set in the variable gain amplifier 2 (shown in FIG. 3) for amplifying the signal output from the D / A converter 62X. (Ax) is the maximum gain Ax0 for achieving the maximum stroke in the piezoelectric element 54.
It is necessary to be. At this time, the probe is the piezoelectric element 5
4 moves at the minimum scanning pitch in the X-axis direction and samples measurement data at each measurement point determined by the minimum scanning pitch. Next, the scanning width of the piezoelectric element 54 is set to Lx1,
Assume that the scanning range R2 is measured. In this case, when the gain of the variable gain amplifier 2 is maintained at the maximum gain Ax0, the scanning pitch is maintained at the aforementioned minimum scanning pitch. As a result, when the probe is scanned in the X-axis direction with respect to the scanning width Lx1 by changing the stroke of the piezoelectric element 54 in such a state, the measurement data is sampled at the minimum scanning pitch. As compared with the case of (1), the value decreases according to the ratio of Lx1 / Lx0.
Therefore, as the number of obtained measurement data decreases, the measurement resolution decreases. In other words, in a state where the gain of the variable gain amplifier 2 is held at the maximum gain Ax0, the scanning pitch is held at the minimum scanning pitch. Therefore, as the scanning width of the piezoelectric element 54, that is, the stroke range becomes smaller, the measurement resolution becomes smaller. Becomes smaller. Therefore, the piezoelectric element 5
When the scan width of 4 is set small, it can be seen that the measurement resolution can be kept constant by further reducing the minimum scan pitch so that the number of data samplings is kept the same as in the case of the maximum stroke. Therefore, it is necessary to reduce the gain Ax of the variable gain amplifier 2 in accordance with the decrease in the scanning width of the piezoelectric element 54. Specifically, when the scanning width of the piezoelectric element 54 becomes smaller than the maximum stroke by, for example, the ratio of Lx1 / Lx0, the gain of the variable gain amplifier 2 is simultaneously reduced with respect to the maximum gain Ax0 by Lx1 / Lx0. , The number of data samplings in the X-axis direction can always be held at the maximum constant value, so that the measurement resolution can be held at the highest state (measurement resolution determined by the characteristics of the D / A converter 62X). .

The configuration shown in FIG. 3 is employed based on the above concept. On the input side of the X-axis D / A converter 62X, data for determining the amount of expansion and contraction of the X-axis piezoelectric element 54 is transmitted from the XY scanning control unit 61 of the calculation / control unit 67 to the bus 1.
Is provided in digital form via The D / A converter 62X performs D / A conversion on the input data. D /
The analog signal output from the A converter 62X is amplified to a required level by the variable gain amplifier 2 at the next stage.
The gain Ax of the variable gain amplifier 2 can be changed, and a gain command is received from the XY scanning control unit 61 via the bus 1 and adjusted to a required gain. Adjustment of the gain Ax of the variable gain amplifier 2 based on the gain command is performed as follows. In the scanning range arbitrarily set for the measurement, the scanning width by the X-axis piezoelectric element 54 is the maximum stroke L
When set to x0, the gain of the variable gain amplifier 2 is set to be the maximum gain Ax0. Therefore, a gain command for setting the maximum gain is provided from the XY scanning control unit 61 to the variable gain amplifier 2 via the bus 1. The scanning width by the piezoelectric element 54 is the stroke L
When set to x1, the gain of the variable gain amplifier 2 is set to (Lx1 / Lx0) .Ax0. Again, in this case,
Similarly, the gain command for setting the gain is X
Provided to the variable gain amplifier 2 from the Y scan control unit 61. As described above, based on the variable gain amplifier 2 provided on the output side of the D / A converter 62X, the gain is adjusted to an appropriate value according to the scanning width of the piezoelectric element 54 determined according to the scanning range. As a result, it is possible to always maintain the highest constant resolution in the measurement resolution in the X-axis direction. The signal output from the variable gain amplifier 2 has its power increased to a required level by the amplifier 3 and is supplied to the piezoelectric element 54 as a drive signal.

A similar configuration is provided for the piezoelectric element 55 in the Y-axis direction. That is, the Y-axis converter 62Y
A variable gain amplifier 4 having a variable gain Ay is provided on the output side. The gain of the variable gain amplifier 4 is adjusted to an appropriate gain according to the scanning width of the Y-axis piezoelectric element 55 determined according to the scanning range, based on a gain command given from the XY scanning controller 61 via the bus 1. Is done. The manner of adjustment is the same as in the case of the X-axis piezoelectric element 54 described above. The signal output from the variable gain amplifier 4 is amplified to a required level by the amplifier 5 and supplied as a drive signal to the Y-axis piezoelectric element 55 for scanning in the Y-axis direction.

In the above description, the command for adjusting the respective gains of the variable gain amplifiers 2 and 4 is given from the XY scanning control unit 61.
7, a control unit for executing the function may be provided as a gain adjustment unit of the variable gain amplifier.

As shown in FIG. 3, an X-axis offset setting device 6 is provided in parallel with the variable gain amplifier 2. X
The axis offset setting device 6 sends the bus 1 from the XY scanning control 61.
, And outputs a shift signal corresponding to the set offset amount. This shift signal is added to the output signal of the variable gain amplifier 2. The X-axis offset setting device 6 is a means for shifting the position of the origin in accordance with the scanning range when an arbitrary scanning range to be measured is offset. Similarly, a Y-axis offset setting device 7 is also provided for the variable gain amplifier 4.

Next, an example in the case of an arbitrarily set scanning range R3 will be described with reference to FIG. Scan range R3
Is an example where the offset must be considered. In the scanning range R3, the scanning width in each axis direction is the same as that in the scanning range R2, and the X-axis direction is Lx1 and the Y-axis direction is Ly1.
Compared to the scanning range R2, the origin is O in the scanning range R3.
Need to be considered as having shifted from to O1. Therefore, as is apparent from FIG. 2, the offset amount x in the X-axis direction
2. Let y2 be the offset amount in the Y-axis direction.

In the case where the scanning range R3 is scanned as a measurement area, in the XY scanning circuit 60 shown in FIG. 3, the setting of each gain of the variable gain amplifiers 2 and 4 has the same scanning width. Same as in the example. Next, in the scanning range R3, the scanning of the probe must be started by shifting by the offset amounts x2 and y2.
Therefore, the X-axis offset setting device 6 has an offset amount x2
Is set, and a shift signal corresponding to x2 is output.
It is added to the output signal of the variable gain amplifier 2. An offset amount y2 is set in the Y-axis offset setting device 7,
A shift signal corresponding to y2 is output and added to the output signal of variable gain amplifier 4. With the above configuration,
The drive signals supplied to the piezoelectric elements 54 and 55 include a shift signal corresponding to the offset amount to cope with the offset and achieve a scanning pitch that maintains a required resolution based on the gain set by the variable gain amplifiers 2 and 4. It becomes a signal, and the scanning range R3 can be measured with a high measurement resolution.

In the above description, the commands for setting the offset amounts of the X-axis and Y-axis offset setting units 6 and 7 are given from the XY scanning control unit 61. Control means for executing the function may be provided as an offset amount setting command means inside the 67.

With the above arrangement, a variable gain amplifier is provided so that the measurement resolution is always maintained at the highest measurement resolution determined by the characteristics of the D / A converter for the scanning range arbitrarily set within the scanning range R1 of the maximum area. The X-axis offset setting unit 6 adjusts the variable gains 2 and 4 and, when an offset exists, copes with the offset.
And the set amount of the Y-axis offset setting device 7 is determined. Thus, the measurement can be performed in an arbitrary scanning range while always maintaining the highest measurement resolution determined by each of the D / A converters 62X and 62Y.

In the circuit configuration shown in FIG. 3, a signal enters the inverting input terminal (-) on the input side of the amplifiers 3 and 5, and the non-inverting input terminal (+) is grounded. Therefore, this circuit configuration is a circuit suitable for shifting only in one direction on the plus side when performing a shift related to the offset of the scanning range.

FIG. 4 shows a variable gain amplifier 2 as an example.
2 shows a specific circuit of the X-axis offset setting device 6. The variable gain amplifier 2 and the X-axis offset setting device 6 are basically formed of amplifiers having the same circuit configuration, and their variable resistors 2a, 6
By changing the resistance value of “a” based on the command value sent by the bus 1, an appropriate gain or offset amount is set. A power supply 8 for supplying an input voltage is connected to the input side of the X-axis offset setting device 6.

In the above-described embodiment, the configuration in which the probe is moved not on the sample side but on the probe side to change the relative positional relationship between the two, and the probe scans the scanning range of the sample has been described. However, for a movement related to a shift to cope with an offset, for example, the movement may be performed on the sample stage. In such a configuration, it is not necessary to provide the X-axis offset setting device 6 and the Y-axis offset setting device 7 in the XY scanning circuit 60.

Next, referring to FIG. 5, an XY scanning circuit 60
Another embodiment will be described. In this embodiment, an amplifier 1 is used instead of the amplifiers 3 and 5 described in the above embodiment.
1, 12 are provided. In the amplifier 11, the output signal of the variable gain amplifier 2 is input to its inverting input terminal, and the output signal of the X-axis offset setting device 6 is input to its non-inverting input terminal. Similarly, in the amplifier 12, the output signal of the variable gain amplifier 4 is input to its inverting input terminal, and the output signal of the Y-axis offset setting device 7 is input to its non-inverting input terminal. The other configuration is substantially the same as the configuration shown in FIG.

According to the above configuration, when shifting is performed in accordance with the offset in the X-axis direction and the Y-axis direction, it is possible to shift to the plus side or the minus side with respect to the origin.

Referring to FIG. 6, another embodiment of the XY scanning circuit 60 will be described. In this embodiment, the X-axis offset setting device 6 and the Y-axis offset setting device 7 are not provided. Instead, an X- and Y-axis offset control unit 21 is provided, and amplifiers 22 and 23 are connected. Amplifier 2
2, the output signal of the variable gain amplifier 2 is input to the non-inverting input terminal, and the output signal of the variable gain amplifier 4 is input to the non-inverting input terminal of the amplifier 23. Also amplifier 2
Output signals of the X, Y offset control unit 21 are input to the inverting input terminals 2 and 23, respectively. Other configurations are the same as those of the other embodiments.

According to the above configuration, it is not necessary to provide a shift amount for the offset on each of the X-axis and the Y-axis, and a single control unit can deal with the offset of each axis. The configuration can be simplified. Further, according to the configuration of the amplifiers 22 and 23, the shift can be made to either the plus side or the minus side about the origin.

In this embodiment, the STM has been described as an example of the scanning probe microscope. However, the probe is provided, and the relative positional relationship between the sample and the probe is changed by using the scanning piezoelectric element. The configuration of the present invention can be applied to other scanning probe microscopes in which a probe scans a scanning range on a sample surface. Although another amplifier as a power amplifier for generating a drive signal is provided for the variable gain amplifier, the variable gain amplifier itself may have a function as a power amplifier.

[0038]

As is apparent from the above description, according to the present invention, the D / A converter included in the scanning circuit of the scanning piezoelectric element is provided with a variable gain amplifier so as to correspond to the scanning width of the piezoelectric element. Since the gain of the variable gain amplifier is configured to be changed under predetermined conditions, in each of a plurality of scanning ranges having different widths, the highest measurement resolution determined by the characteristics of the D / A converter is always maintained. A measurement can be made. Using a single fine movement mechanism, a scanning range from an atomic level scanning width to a relatively wide scanning width of several tens of μm, that is, a plurality of scanning ranges having different widths can be measured with high measurement resolution. . In addition, since the offset setting device is provided, even if there is an offset in the setting of the scanning range, the scanning width of each piezoelectric element is set corresponding to the scanning range, and the scanning is performed with high measurement resolution. It can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a scanning range in which an offset is not considered.

FIG. 2 is a diagram for explaining a scanning range in consideration of an offset.

FIG. 3 is a circuit diagram showing an embodiment of an XY scanning circuit.

FIG. 4 is a circuit diagram showing a specific circuit of a variable gain amplifier and an offset setting device.

FIG. 5 is a circuit diagram showing another embodiment of the XY scanning circuit.

FIG. 6 is a circuit diagram showing another embodiment of the XY scanning circuit.

FIG. 7 is a configuration diagram showing a general configuration of a conventional scanning probe microscope.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bus 2,4 ... Variable gain amplifier 3,5 ... Amplifier 6 ... X-axis offset setting device 7 ... Y-axis offset setting device 11,12 ... Amplifier 21 ... X, Y-axis offset control unit 22,23 ... Amplifier 53 ... Fine movement mechanism 54 X-axis piezoelectric element 55 Y-axis piezoelectric element 60 XY scanning circuit 61 XY scanning control unit 62X X-axis D / A converter 62Y Y-axis D / A converter 67 arithmetic / control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B ^7/ 00-7/34 102 G01B 21/00-21/32 G01N 37/00 H01J 37/28

Claims (7)

(57) [Claims] 1. D / A related to a piezoelectric element for scanning a probe
A scanning circuit including a converter and an amplifier is provided, and a digital signal for scanning control provided from a scanning control unit is supplied to the D / A
The analog signal is converted into an analog signal by a converter, the analog signal is amplified by the amplifier and converted into a drive signal, and the drive signal is applied to the piezoelectric element to move the probe for scanning. In the probe scanning method, when a variable gain amplifier for amplifying an output signal of the D / A converter is added and a scanning range is arbitrarily set within a maximum scanning range determined by a maximum stroke of the piezoelectric element,
The variable gain amplifier is controlled to maintain a measurement resolution determined by characteristics of the D / A converter based on a ratio between a scanning width of the piezoelectric element and a maximum stroke of the piezoelectric element determined according to the scanning range. A probe scanning method for a scanning probe microscope, comprising: adjusting a gain. 2. The probe scanning method for a scanning probe microscope according to claim 1, wherein when an offset exists in the set arbitrary scanning range, an output signal of the variable gain amplifier corresponds to the offset. A probe scanning method for a scanning probe microscope, comprising: 3. A D / A related to a piezoelectric element for scanning a probe.
A scanning circuit including a converter is provided. In the scanning circuit of the scanning probe microscope configured to generate a driving analog signal based on the scanning control digital signal given from the scanning control unit, the scanning circuit includes: A variable gain amplifier for amplifying an output signal of the D / A converter, and a measurement resolution determined by characteristics of the D / A converter based on a ratio between a scanning width set for the piezoelectric element and a maximum stroke thereof. And a control means for adjusting the gain of the variable gain amplifier. 4. The probe scanning device for a scanning probe microscope according to claim 3, wherein an offset setting device that outputs a shift signal added to an output signal of the variable gain amplifier;
Control means for giving a command for setting a required offset amount to the offset setting device. A probe scanning device for a scanning probe microscope, comprising: 5. The probe scanning device for a scanning probe microscope according to claim 4, wherein an amplifier for generating a drive signal by amplifying a signal obtained by adding the shift signal to an output signal of the variable gain amplifier is provided. A probe scanning device for a scanning probe microscope, comprising: 6. A probe scanning device for a scanning probe microscope according to claim 3, wherein an offset setting device for outputting a shift signal corresponding to the offset, and a command for setting an offset amount necessary for the offset setting device. And a control means for inputting the output signal of the variable gain amplifier to one input terminal and an amplifier for inputting the shift signal to the other input terminal. . 7. A probe scanning apparatus for a scanning probe microscope according to claim 6, wherein said variable gain amplifier and said amplifier correspond to respective piezoelectric elements on two axes defining a plane of a scanning range. Provided, the offset setting device,
A probe scanning device for a scanning probe microscope, wherein the probe scanning device is formed as a single unit common to the two axes.