RU164856U1 - STANDARD OF PRECISION MOVEMENTS - Google Patents

Abstract

1. A standard of precision movements containing an element of a piezoelectric material with a reverse piezoelectric effect with electrodes deposited on its two opposite sides connected to a voltage source, characterized in that the standard is supplemented by a second element of a piezoelectric material with a reverse piezoelectric effect with electrodes deposited on its two opposite sides wherein, one of the electrodes of the second element is brought into contact with one of the electrodes of the first element, the external electrodes of the assembly obtained are grounded, elements of piezoelectric material are configured such that when the control voltage to the electrodes occurs simultaneously both deformation elements in one napravlenii.2. The standard according to claim 1, characterized in that the central electrode is connected to the voltage source through the complex resistance, and the external electrodes and the central electrode are connected to each other through the complex resistance parallel to the complex resistance of the elements of the piezoelectric material.

Description

The utility model relates to the field of precision instrumentation and can be used as a reference for determining the displacements and linear dimensions of objects in the nanometer range and for calibrating confocal microscopes and optical interferometers.

A device for precision movements is known, which allows for linear displacement in the nanometer range (US 4787148/1 /). The known device in essence is an improvement of the known micrometer equipped with a two-stage mechanical gearbox with an appropriate gear ratio.

A disadvantage of the known device is the relatively low accuracy of the specified bias and low reproducibility of the results, which is inherent in any mechanism that has moving parts and components.

A reference device is known which is used for testing profilometers and scanning probe microscopes. The device is a single-crystal plate in which stepped recesses with the same fixed height of each of the steps are made using the methods of microelectronic technologies (US 6028008121).

Linear size transmission using such a device can only be carried out when conducting multiple measurements in various areas of the surface and followed by mathematical processing of the measurement results.

This device has certain drawbacks. With it, you can measure linear displacements in only one direction - in depth. In addition, since the etching method is used for manufacturing, the accuracy of manufacturing the step height can be several atomic layers, and taking into account that the crystal lattice parameter for silicon is 5.43 A, the accuracy of the step height will differ by 5-7 nm from one another that for a number of applications is unacceptable.

Known photoelectric device for determining the displacement (GB 1063060/3 /) - The device contains a collimated light beam source, a photodetector and two diffraction gratings located between the source and the photodetector with different periods and fill factors.

When one lattice is shifted relative to another, periodic cross-section (or opening) of the cross section of the light beam occurs, which is detected by the photodetector.

A disadvantage of the known device is that the displacement of one object relative to another is measured and each of them must be equipped with a diffraction grating, the manufacture of which is always carried out with some error.

A device for precision measurement of distances is known, which includes two sectioned electrodes placed opposite each other with the possibility of moving in the direction of changing the area of their mutual overlap while maintaining a constant gap between the reciprocal surfaces of the sections of the said electrodes. The sections in the first and second sectioned electrodes are made of the same length, while the sections of the first of the electrodes are electrically connected to each other and connected to the first output of the alternating voltage generator. The second sectioned electrode is made with sections electrically isolated from one another, each of which is connected to the corresponding input of the system for determining the moment of difference in currents passing through zero in the circuits of two adjacent sections of this sectioned electrode. Another input of the said system is connected to the second output of the alternating voltage generator, and the length of any of the sections of the first sectioned electrode is different from the length of any of the sections of the second sectioned electrode by an amount equal to the specified resolution of the device. The technical result is an increase in the resolution of the device to the nanometer range with technologically permissible restrictions on the execution of the sections of the electrodes along the length (RU 2221217/4 /).

A disadvantage of the known device is the complexity of the design and manufacturing technology, because it requires high accuracy (up to one nanometer) of the manufacture of electrodes. In addition, due to the need to determine the moment when the difference between the currents passes through zero in the circuits of two adjacent sections of the sectioned electrode, the requirements for recording equipment increase, which will introduce unacceptable errors in the measurements.

Closest to the claimed is a device for precision displacements, which can be used as a reference for determining displacements and linear dimensions of objects in the nanometer range and includes a plate of piezoelectric material with electrodes deposited on its two opposite sides connected to a voltage source (RU 2284464 [ 5]). The device allows you to controllably move the reference surface with a spatial resolution of fractions of nanometers. However, at such magnitudes of displacements, the influence of external electromagnetic fields on the accuracy of displacements becomes significant.

The inventive device aims to increase the accuracy of calibration of modern, used in industry confocal microscopes and optical interferometers.

This result is achieved by the fact that the standard of precision movements contains an element of a piezoelectric material with a reverse piezoelectric effect with electrodes deposited on two opposite sides connected to a voltage source, and is supplemented by a second element of a piezoelectric material with a reverse piezoelectric effect with electrodes deposited on its two opposite sides moreover, in contact with one of the electrodes of the first element introduced one of the electrodes of the second element, the outer electrodes of the obtained Assembly ground, and the elements of the piezoelectric material are made so that when a control voltage is applied to the electrodes, both elements are simultaneously deformed in the same direction. This result is achieved by the fact that the central electrode is connected to the voltage source through the complex resistance, and the external electrodes and the central electrode are connected to each other through the complex resistance parallel to the complex resistance of the elements of the piezoelectric material.

Distinctive features of the proposed device are:

- supplementing the device with a second element of piezoelectric material with electrodes deposited on its two opposite sides connected to a voltage source;

- the elements are connected to form a common electrode for both elements;

- the external electrodes of the resulting assembly are grounded;

- the elements are made so that when the control voltage is applied, their deformation vectors are directed in one direction;

- the central electrode is connected to the voltage source through the complex resistance, and the external electrodes and the central electrode are interconnected via the complex resistance parallel to the complex resistance of the elements of the piezoelectric material.

If we use two elements of piezoelectric material mounted on top of one another with the formation of a common electrode for both elements and with grounding of the external electrodes of the resulting assembly, then on the one hand the effect of external electromagnetic fields on the magnitude and accuracy of movements is reduced, and on the other hand, for To obtain the required displacement, it is necessary to apply half the voltage as compared with the prototype, which also affects the accuracy.

The elements are designed so that when a control voltage is applied, their deformation vectors are directed to one side

Depending on the desired direction of movement, the plate is made with the orientation of the crystallographic axes (in the case of using single-crystal material) or the polarization vector (in the case of using polarized piezoceramics) providing, when voltage is applied to the electrodes, the plate is resized in a direction parallel to the plane of the electrodes, or the plate is oriented crystallographic axes, which, when voltage is applied to the electrodes, provides a change in the size of the plate in the direction are perpendicular plane electrodes.

The most optimal is to connect the elements to a voltage source so that the central electrode is connected to the voltage source through the complex resistance, and the external electrodes and the central electrode are connected to each other through the complex resistance parallel to the complex resistance of the elements of the piezoelectric material. Since the voltage source is located outside the calibrating installation, when the signal is transmitted from the voltage source to the elements of the piezoelectric material, the waveform is distorted. To reduce distortion, a correction chain is used, consisting of series and parallel connected complex resistances, which corrects temporary distortions during transmission of control voltage. The value of the series-connected complex resistance connecting the central electrode and the voltage source is selected directly proportional to the value of the complex resistance consisting of elements connected in parallel from a piezoelectric material and a second complex resistance connected in parallel with them. As a result of this ratio, the distortion of the shape of the electrical signals supplied from the voltage source is minimal compared to the shape of the electrical signal on the elements of the piezoelectric material.

In addition, in particular cases of implementation, the electrodes are made porous to reduce mechanical stresses due to differences in temperature expansion coefficients of the electrodes and the piezoelectric material of the elements. Thus, the stiffness of the electrode structure decreases in the horizontal direction, which increases the magnitude and accuracy of the movement of the standard.

The essence of the proposed device is illustrated by examples of implementation and drawings. In FIG. Figure 1 shows schematically an embodiment of a device providing displacement in a direction perpendicular to the plane of the electrodes (arrows indicate the direction of deformation when voltage is applied). In FIG. 2 is a schematic diagram of an embodiment of the device providing bias in a direction parallel to the plane of the electrodes. In FIG. Figures 3 and 4 show schematically preferred embodiments of the device with optimal circuits for connecting to a voltage source.

The device comprises an assembly installed on the base 1, consisting of two identical elements 2 and 3 of a piezoelectric material with a reverse piezoelectric effect with electrodes 4 deposited on two opposite sides thereof connected to a voltage source 5. The external electrodes of the resulting assembly are grounded.

In preferred embodiments of the device with optimal circuits for connecting to a voltage source, the central electrode of the assembly is connected to voltage source 5 through a complex resistance 6. Piezoelectric elements 2 and 3, which are components of the electrical circuit for connecting them to a voltage source, are represented by a complex resistance 7, in parallel with which a complex resistance 8, connecting the central electrode of the assembly and one of the external electrodes.

The device is used as follows.

First, the dependence of the total size change of the piezoelectric elements 2 and 3 on the voltage applied to the electrodes 4 is measured, i.e. build a calibration schedule. The calibration graph is constructed by applying a fixed voltage to the electrodes of the device and measuring the corresponding displacement of the upper surface.

The measurement of displacement is carried out by known methods using a reference 3D laser interferometric system for measuring nanoscale displacements (based on an atomic force microscope and 3 laser interferometers).

To measure the displacement perpendicular to the surface of the electrodes, a device is placed that provides displacement in the direction perpendicular to the plane of the electrodes in the nanoscale measuring system, a microscope probe is brought to the surface of the device at a distance at which the gap stabilization system operates, voltage is applied to the device, and the distance that the surface has moved is measured devices when voltage is applied. Next, change the magnitude of the applied voltage and again measure the magnitude of the displacement of the surface of the device.

As a result of multiple measurements of displacements performed at different voltage values, a table of experimental measurements is compiled, based on which a calibration graph is plotted against the magnitude of the displacement of the surface of the device in the direction perpendicular to the plane of the electrodes on the magnitude of the applied voltage.

The amount of displacement in the horizontal plane can be determined by binding to any defect on the surface that undergoes displacement when voltage is applied to the electrodes, since any surface has defects whose size can range from one atom to several hundred nanometers. For ease of use, a contrasting, easily detectable mark can be placed on a movable surface. For example, it can be an atom of a substance other than the substance of the electrode and the substance of the crystal, or a group of atoms, planted using a probe microscope. A mark can be sprayed through a mask or a line of marks can be applied that are located at equal or different distances from each other (for example, a linear or logarithmic scale) and their size can reach several hundred nanometers.

When measuring movement parallel to the plane of the electrodes, measurements are made by placing a standard that provides movement in a direction parallel to the plane of the electrodes, bringing the microscope probe to the distance at which the gap stabilization system works, to the mark surface, scanning the surface in the mark location area, applying voltage to the device, re-scanning the surface in the same mode and measuring the distance that the mark moved when voltage was applied. Next, change the magnitude of the applied voltage and again measure the magnitude of the movement of the mark on the surface of the device. As a result of multiple measurements of displacements performed at different voltage values, a table of experimental measurements is compiled, based on which a calibration graph is constructed of the magnitude of the movement of the mark on the surface of the device in a direction parallel to the plane of the electrodes on the value of the applied voltage.

Using the proposed device used as a reference, it is possible to graduate various measuring equipment, which should provide measurements in two mutually perpendicular directions.

To calibrate a device (for example, a probe microscope) along the normal or horizontal to the surface under study, the proposed device (providing movement along the normal or horizontal to the plane of the electrodes, respectively) is placed in it. For example, if you need to calibrate a scanning probe microscope, the device is placed on the stage of a scanning probe microscope and brought to the surface of the device with the probe mark at a distance of the gap (of the order of 0.5 nm) between the tip of the probe and the surface of the device at which the stabilization system operates. The stabilization of the gap can be achieved by stabilizing the tunneling current (when operating in tunnel microscopy mode) or by stabilizing the magnitude of the force acting on the probe (when operating in atomic force microscopy mode). The gap is stabilized by an electronic control system that compares signals from measuring devices with specified values and generates control signals to actuators.

When calibrating the tested measuring device vertically, a fixed voltage is applied to the electrodes to the device for precision movements, providing vertical movement, to the electrodes. In this case, the surface of the device moves a distance, the value of which is determined by the calibration table. The gap stabilization system ensures that the probe moves appropriately at the same distance that the sample surface moves. The amount of probe movement is measured by the measuring devices of the probe microscope. In this way, the magnitude of the readings known from the calibration curve by which the surface of the device is associated with the value of the readings of the measuring instruments of the probe microscope, measuring the distance over which the probe moves. Further, the voltage supplied to the device changes and the measurement process is repeated. As a result of a series of measurements at various voltage values, a table is compiled of the correspondence of the displacement of the device and the readings of the probe microscope devices that measure the displacement of the probe.

When calibrating the measured device horizontally in a plane parallel to the plane of the electrodes, the microscope probe is brought to the mark, the surface is scanned in the area of the mark and the device for precision movements, which provides horizontal movement to the plane of the electrodes, is supplied with a fixed voltage. In this case, the surface of the device moves a distance, the value of which is determined by the calibration table.

Repeated scanning by a probe of a microscope over the surface of the device with a mark and comparing the results of repeated scanning with the previous ones makes it possible to measure its displacement with measuring instruments of a probe microscope.

In this way, the magnitude of the readings of the measuring instruments of the probe microscope, measuring the distance by which the mark has moved, is associated with the magnitude of the movement of the mark, known from the calibration curve. Further, the voltage supplied to the device changes and the measurement process is repeated. As a result of a series of measurements at various voltage values, a table is compiled of the correspondence between the magnitude of the displacement of the mark and the readings of the probe microscope instruments measuring its displacement.

Claims (2)

1. A standard of precision movements containing an element of a piezoelectric material with a reverse piezoelectric effect with electrodes deposited on its two opposite sides connected to a voltage source, characterized in that the standard is supplemented by a second element of a piezoelectric material with a reverse piezoelectric effect with electrodes deposited on its two opposite sides wherein, one of the electrodes of the second element is brought into contact with one of the electrodes of the first element, the external electrodes of the assembly obtained are grounded, elements of piezoelectric material are configured such that when the control voltage to the electrodes occurs simultaneous deformation of both elements in the same direction. 2. The standard according to claim 1, characterized in that the central electrode is connected to the voltage source through the complex resistance, and the external electrodes and the central electrode are connected to each other through the complex resistance parallel to the complex resistance of the elements of the piezoelectric material.

Images