JPH01127902A - Minute position detecting device - Google Patents

Abstract

PURPOSE:To detect a minute position with high accuracy by providing piezoelectric element so that it abuts on a sample. CONSTITUTION:Piezoelectric elements 2 (2a, 2b) are placed so that they abut on a sample 4, and by detecting a voltage which is generated when the element 2 has been displaced by following up a movement of the sample 4, a displacement of a minute position is obtained. In such a way, when the sample 4 is brought to minute movement in the X and Y directions in a state that it has been set to a holder 3, a distortion is given to points Q, R of the elements 2a, 2b in accordance with its movement, and a voltage being proportional to this distortion can be read by voltmeters V1, V2. Accordingly, by converting this read voltage to a position of the sample 4 and monitoring it, a moving extent in the X and Y directions of the sample 4 is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a minute position detection device for detecting minute displacements of a sample in an analysis device such as an electron microscope.

[Conventional technology]

Generally, when the probe is brought close to the sample to a point where the atoms at the tip of the probe overlap with the electron cloud of the atoms of the sample, and in this state a voltage is applied between the probe and the sample, a current flows. This current is called tunnel current, and when the voltage is LmV, 1
It becomes about 10 nA. The magnitude of this tunnel current is
Since it changes depending on the distance between the sample and the probe, the distance between the sample and the probe can be measured with ultra-precision by measuring the magnitude of the tunnel current. Therefore, if the probe position is known, the surface shape of the sample can be determined.

Furthermore, if the probe position is controlled so that the tunneling current is constant, the surface shape of the sample can be similarly observed from the probe position locus.

In a scanning tunneling microscope (STM), which uses tunneling current to observe the surface shape of a sample, a probe made of W (tungsten) or the like is brought close to the sample in order to obtain an image of the irregularities from the sample, and the tunneling current is detected. There is a need. In this case, first, coarse movement brings the probe closer to the sample r4 to about 0.1 μm, and then fine movement brings the probe closer to the sample from 0.1 μm to about Inm, so control on the nanometer order is required.

FIG. 5 is a diagram showing a schematic configuration of a scanning tunneling microscope, in which 21 is a probe, 22 is a sample, 23 is a three-dimensional actuator, 24 is an XY scanning circuit, 25 is a servo circuit, and 26 is a tunneling current amplifier. , 27 is a battery, 28 is a memory, 29
indicates an MPU, and 30 indicates a display device.

In the fifth time, the three-dimensional actuator 23 is
Consists of Y-axis and Z-axis piezoelectric elements, MPL129,
Controlled through memory 28. In controlling the three-dimensional actuator 23, the probe 21 is moved and scanned in the X-axis and Y-axis directions by sweeping the voltages applied to the piezoelectric elements in the X-axis and Y-axis directions by the XY scanning circuit 24, and this scanning is performed. Servo circuit 2 so that the tunnel current remains constant while
5 to control the voltage to the Z-axis piezoelectric element.

Therefore, by reading this control voltage value into the MPU 29 and displaying it on the display device 30, the surface shape of the sample 22 can be observed.

As the three-dimensional actuator 23, a cantilever type actuator in which a piezoelectric element 31 is bonded to a tribot type is most commonly used, as shown in FIG. As shown in the figure, a piezoelectric element 31 is also used in which the X-axis and Y-axis are supported at both ends, and the Z-axis is supported at one end. With even higher rigidity,
As shown in FIG. 8, a piezoelectric element 31 having a cylindrical shape, four electrodes 32 attached to the front surface of the piezoelectric element 31, and a voltage applied between the piezoelectric element 31 and the back electrode is also used.

Further, in an electron microscope, particularly a transmission electron microscope, the sample moving distance is generally about 3 mm, and the movement accuracy becomes a bigger problem than the movement amount itself. conventionally,
It is common to attach a potentiometer or the like to a part of such a sample moving part and read out the amount of change in resistance.

[Problem that the invention seeks to solve]

However, when moving the sample in the scanning tunneling microscope mentioned above, fine movement can be detected accurately by moving the probe until the sample comes into contact without monitoring the tunneling current, but coarse movement cannot detect fine movement. , Accurate position detection is difficult, and when moving the probe close to the sample, trouble occurs in which the probe collides with the sample and breaks because the position of the probe cannot be accurately detected.

In addition, in transmission electron microscopes, a potentiometer is used in a part of the sample moving part, and because there is a distance between the sample and the detection part, the mechanical connection between them causes large play and backlash, which can be on the order of nanometers. There is a problem in that reading out the accuracy is actually impossible.

The present invention is intended to solve the above-mentioned problems, and aims to provide a micro-position detection device capable of detecting micro-positions with high precision in order to precisely control the movement of samples, probes, etc. in a microscope. That is.

[Means for solving problems]

To this end, the micro-position detection device of the present invention is a micro-position detection device for detecting micro-displacement of a sample in an analysis device such as an electron microscope, in which a piezoelectric element is arranged so as to be in contact with the sample to be detected, This method is characterized in that the voltage generated when the piezoelectric element is displaced as the sample moves is detected to determine the displacement of a minute position of the sample.

[Effect]

In the minute position detection device of the present invention, the piezoelectric element is arranged so as to be in contact with the sample to be detected, so even if the sample moves minutely, the piezoelectric element will be distorted and the size corresponding to the distortion will be generated. Voltage is generated. Therefore, by reading this voltage, minute displacement of the sample can be detected and the position can be determined.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the micro-position detection device according to the present invention. FIG. 2 shows another embodiment of the micro-position detection device applied to a probe scanner of a scanning tunnel microscope.

In the figure, 1 is the main body, 2a, 2b and 6 are piezoelectric detectors,
3 is a holder, 4 and 7 are samples, 5 is a fixed end, 8 is a probe,
9 is a probe scanner, and V, , V2 are voltmeters.

First, an example of a minute position detection device applied to a sample moving unit of an electron microscope or the like will be described.

In FIG. 1, it is assumed that a sample 4 is set in a holder 3 of an electron microscope or the like, and is moved in the ±X and ±Y directions. It is also assumed that the piezoelectric detectors 2a and 2b are fixed to the main body 1, and are subjected to distortion at point Q and point R as the sample moves. At this time, the piezoelectric detectors 2a and 2b
Since a voltage proportional to this strain is generated, the voltage is measured by a voltmeter V, ,V.A typical piezoelectric detector is 45 mm long x 13 mm wide x 5 mm thick Q. In a case of about 0.5 mm, the output voltage is about 60 V for a displacement of about 0.5 mm.

Therefore, when the sample 4 is set in the holder 3 and is slightly moved in the x and y force directions shown in the figure, distortion is applied to the Q and R points of the piezoelectric detectors 2a and 2b in response to the movement. Proportional voltages can be read by voltmeters V, , Vt.

Therefore, by converting this read voltage into the position of the sample and monitoring it, it is possible to measure the amount of movement of the sample in the X and Y directions.

Next, a case will be described in which minute displacements are detected using a scanning tunneling microscope. In a scanning tunneling microscope, as shown in FIG. 2, a probe 8 is brought close to the sample 7 by a probe scanner 9 using a piezoelectric element, etc. At this time, the probe 8 approaches the sample 7 in order to obtain a tunneling current. It is necessary to get closer to dozens to hundreds of people. However, the Z-axis piezoelectric element of the probe scanner 9 has a diameter of several μm at most.
Small ones can only move within a range of about 1 μm.

Therefore, it is brought closer by mechanical driving, but in this case there is a problem of backrunch, and it is necessary to monitor this order. Therefore, as shown in FIG. 2, a bimorph type piezo element 6 is attached to the fixed end 5, and the position is monitored by reading the voltage generated in the piezo element 6 as in the case of FIG. 1 while bringing the probe scanner 9 closer. Then, the position of the probe scanner 9 can be precisely measured, and the position can be automatically corrected, and by adding a safety circuit, it is possible to safely bring the sampling needle close to the sample without destroying it. Become.

Figure 3 fal, (bl is a diagram showing another example of the detection method in minute position detection, Figure 4 is a diagram for explaining the relationship between typical voltage and displacement amount of a bimorph piezoelectric element.Bimorph The typical relationship between voltage and displacement of a piezoelectric element is t2, as shown in Figure 4. Here, d3+ is the piezoelectric constant of the piezoelectric element, and in devices that detect minute displacements, l is Since it cannot be made very large, it is about 0.1 to 0°4 μm with an applied voltage of 50 V. However, when used in a small position detection device such as an electron microscope, a displacement of about 3 mm is required as l. , as shown in FIG. 3 fa+, the bimorph piezoelectric element 11
A method may be adopted in which a buff-like temporary 12 is added to the tip. According to this method, even if the amount of displacement of the spring plate 12 is large up to point P, the amount of displacement of the bimorph piezoelectric element 11 can be kept small (suppressed), and the amount of detected displacement can be increased.

Furthermore, by installing bimorph piezoelectric elements 3a and 13b on both sides of the sample 4, which is a displaced object, as shown in FIG. 3 (bl), the same effect can be obtained with half the amount of displacement.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a piezoelectric element is used as a displacement detection device to apply a strain corresponding to the displacement of a moving object, and the distortion is generated in proportion to the displacement of the moving object.
Since voltage is detected, minute position changes can be detected and detection accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the micro-position detection device according to the present invention, FIG. 2 is a diagram showing another embodiment of the micro-position detection device applied to a probe scanner of a scanning tunneling microscope, and FIG.
Figure (81, (bl is a diagram showing another example of the detection method in minute position detection, Figure 4 is a diagram for explaining the relationship between typical voltage and displacement of a bimorph piezoelectric element, Figure 5
The figure shows the schematic configuration of a scanning type I/N microscope.
8 to 8 are diagrams showing examples of various shapes of the three-dimensional actuator. 1...Main body, 2a, 2b and 6...Piezo piezoelectric detector, 3...Holder, 4 and 7...Sample, 5...Fixed end, 8...Tip, 9...・Probe scanner, V, ,
V, ... voltmeter. Applicant: JEOL Co., Ltd. Agent: Patent attorney Ryukichi Abe (3 others) Figure 1

Claims (1)

[Claims] (1) A micro-position detection device for detecting minute displacements of a sample in an analytical device such as an electron microscope, in which a piezoelectric element is placed in contact with the sample to be detected, and as the sample moves, the piezoelectric A micro-position detection device characterized by detecting the voltage generated when an element is displaced to determine the displacement of a micro-position of a sample.