JPH0454877A - Moving table and method of driving the same - Google Patents

Abstract

PURPOSE:To move parallel and turn a material by projecting two parallel cylindrical piezoelectric elements of the same shape on a base, with the mounts of the free ends thereof flush, and selecting a voltage applying electrode from the two piezoelectric elements. CONSTITUTION:A sample mount 9 is across the mounts of two piezoelectric elements 5 and 6 and the mounts and the sample mount 9 thereon can be moved horizontally in arbitrary two directions on one plane by moving the piezoelectric elements 5 and 6 in the same direction. That is, the piezoelectric elements 5 and 6 are moved in the directions of Y2 and X2 The sample mount 9 can be turned on one plane by moving the piezoelectric elements 5 and 6 in opposite directions of X1 and X2 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a moving table that requires minute horizontal movement, such as a stage for a microscope or the like.

(Prior art) STM (Scanning Tunneling)
Microscope (scanning tunneling microscope) brings a thin needle (probe) very close to the surface of an object and applies a voltage between the probe and the object. It also generates a tunnel effect phenomenon to flow a minute current, and uses this current to control the vertical movement of the probe to determine the irregularities on the surface of an object.

In other words, this STM is a high-resolution microscope based on a new principle that can distinguish each atom on the surface of a solid.
It is demonstrating its power in observing minute biological substances such as genes and proteins.

However, in conventional STM, the movable range of the probe is about 10 μm at most, and in order to cover the observation area on the sample beyond that range, other mechanisms that enable minute movements, such as There is a problem in that a so-called "shackle and repellent" mechanism made of a piezoelectric element is required.

FIG. 8 shows this conventional mechanism. In the figure, 23 and 24 are laminated piezoelectric elements for fixation, 25 are laminated piezoelectric elements for advancement, and these laminated piezoelectric elements 23
~25 is a piezoelectric element 23,24 in the groove 26 of the base 22.
are arranged in parallel, and the piezoelectric element 25 is arranged between them in a direction perpendicular to these piezoelectric elements 23 and 24 arranged in parallel. First, a voltage is applied to the piezoelectric element 23 for fixing, and it is stretched and held against the wall of the groove 26 to be stopped.
The piezoelectric element 24 is contracted without applying any voltage. Next, a voltage is applied to the advancing piezoelectric element 25 to extend it, and while the piezoelectric element 25 is in an extended state, a voltage is applied to the piezoelectric element 24 to extend it and stop it in a state where it is stretched against the wall of the groove 26. Then, the voltage application to the piezoelectric element 23 in the fixed state is removed, the piezoelectric element 23 is returned to its original length, and the restriction to the wall is released. Thereafter, the voltage application to the piezoelectric element 25 for advancement is removed and the piezoelectric element 23 is moved toward the piezoelectric element 24 side. By repeating the above operations, the piezoelectric element 25 advances toward the piezoelectric element 24 side.

However, since this mechanism is a combination of multiple piezoelectric elements with different movement directions, some of them exert adsorption force to the base and stick to it, so a function to separate them is required, which makes it difficult to manufacture. It becomes troublesome.

Therefore, the present applicant has already proposed a movement table for the minimum movement that is simple and has a simple driving method and eliminates the restriction on the movement distance of the observed sample (Japanese Patent Application No. 2-255
(See No. 4).

(Problems to be Solved by the Invention) However, the moving table already proposed by the present applicant is very superior because there is no restriction on the moving distance of the observed sample and it can be moved to a minimum. There is a problem in that the moving direction of the observed sample is limited to parallel movement, and rotational movement of the observed sample cannot be performed.

It is an object of the present invention to solve the above-mentioned drawbacks, and its objectives are: 1. To provide a moving table capable of not only parallel translation but also rotational movement of an object in a moving table which has no limit on the moving distance of an object placed on a stage and can be moved minutely, and a method for driving the same. There is a particular thing.

[Structure of the invention]

(Means for Solving the Problems) A moving table of the present invention that achieves the above object is a moving table that moves an object on a stage, and is attached so that the stage is spanned over the free end side. cylindrical 2
Two piezoelectric elements are arranged so that the top surfaces of the stage are flush with each other with no voltage applied, and the other ends are fixed on the base. Electrode selection in which one electrode is formed on the entire circumferential surface, and the other electrode is divided into a plurality of parts in the circumferential direction on the opposing circumferential surface, and the electrodes to which voltage is applied to these two piezoelectric elements are selected respectively. It is characterized by the provision of means.

Further, in the movable table driving method of the present invention that achieves the above object, in the movable table configured as described above, the electrode selecting means selects an electrode to which a voltage is applied in each piezoelectric element according to the moving direction of the object. 2 by applying a voltage of a single cosine wave of one period to each selected electrode, or a voltage of an intermittent series of the single cosine wave.
The two piezoelectric elements are each deformed independently, and the object placed on the two stage is slid on the stage according to the direction of deformation of the two piezoelectric elements, and the object is placed on the stage. It is characterized by minute movement or minute rotation in any direction on the table.

(Function) According to the movable table of the present invention, two cylindrical piezoelectric elements of the same shape are juxtaposed and protruded on the base, and the workpieces are arranged flush with each other at their free ends. Furthermore, since the two cylindrical piezoelectric elements are configured to be deformable independently by a plurality of electrodes provided separately on the outer peripheral side, the electrode to which voltage is applied can be selected between the two piezoelectric elements. And if we apply a single waveform voltage to it,
Since the piezoelectric element is deformed in any direction by impact, the object on the stage slides and moves by a minute distance. By intermittently applying a large number of driving voltages, it is possible to eliminate restrictions on the moving distance of the sample, and by combining the sets of electrodes that apply driving voltages in the two piezoelectric elements,
It is also possible to rotate an object by deforming two piezoelectric elements in opposite directions.

(Example) Hereinafter, the present invention will be described in detail by way of an example with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of a sample moving table 1 of the present invention in an STM (scanning tunneling microscope), in which cylindrical piezoelectric elements 4.5.
6 is provided protrudingly. The piezoelectric element 4 is provided on the base 2 via the moving mechanism 3, and a mounting plate 1 is provided on the free end side of the piezoelectric element 4.
An arm 1 equipped with an STM probe 10 at the tip via 2
1 is installed. This moving mechanism 3 is capable of moving the piezoelectric element 4 in the axial direction, and has a function of roughly bringing the probe 10 close to the sample 8 to the order of μm, which is the driveable region of the piezoelectric element 4.

On the other hand, the two piezoelectric elements 5.6 have exactly the same shape, and a stage (not shown) is attached to the free end side so that the upper surfaces thereof are on the same plane when no voltage is applied. A sample stand 9 to which a sample 8 is fixed is placed on this stage so as to straddle both. 7 is an electrode provided on the outer peripheral surface of the piezoelectric element 4.5.6.

FIG. 2 shows the shape of this cylindrical piezoelectric element 4.5.6. An inner electrode 13 is formed on the entire inner circumferential surface of the cylindrical piezoelectric element 4, 5.degree. 6, and an outer electrode 7 is formed on the outer circumferential side surface thereof. In this embodiment, the external electrode 7 formed on the outer peripheral side surface is divided into four parts, and each of the four divided external electrodes 7 is connected to the power supply 1 via a switching circuit 18.
7 is connected. In addition, the power supply 17 and the switching circuit 1
8 is provided independently for each of the piezoelectric elements 4, 5, and 6.

In this case, the piezoelectric element 5.6 has the function of moving the sample stage 9 only within its plane, and the piezoelectric element 4 has the function of moving the sample 8 vertically and horizontally. Therefore, the inner surface electrodes 13 of the piezoelectric elements 5.6 are each connected to the ground side of its own power source 17. Furthermore, the inner surface electrode 13 of the piezoelectric element 4 is connected to its own power source,
The ground terminal of the power source is commonly connected to the ground terminal of the power source for the external electrode 7. As described above, in this embodiment, the external electrode 7 is divided into four parts facing each other, and by applying a voltage having the same absolute value and opposite polarity to each facing electrode, the piezoelectric elements 4, 5, 6 can be bent and deformed in the horizontal direction.

Here, it goes without saying that the same function can be achieved even if divided electrodes are arranged on the inner peripheral side surfaces of the piezoelectric elements 4, 5, 6 and continuous electrodes are formed on the entire opposing surface. Although the number of each divided electrode is four in the above embodiment, this number is not limited to four, nor is it limited to an even number. When the number of divided electrodes is an odd number, the same operation as described above can be achieved by appropriately selecting the voltage application method.

At the free end of the cylindrical piezoelectric element configured in this way,
A stage 14 as shown in FIG. 3 is attached, and a sample stage 9 is placed across the stage 14 as shown in FIG. 1 on top of this stage 14.

FIG. 4 shows the movement of the sample stage 9 when viewed from above when the two piezoelectric elements 5, 6 are bent with reference to the ends fixed to the base 2. As mentioned above, the sample stage 9 has two piezoelectric elements 5,
By bending the piezoelectric elements 5 and 6 in the same direction,
Therefore, the sample stage 9 thereon can be moved in any two horizontal directions on the plane. The two-dot chain line in FIG. 4(a) indicates the piezoelectric element 5.6, for example, Y in FIG.
Sample stage 9 in a state bent in two directions and in the X2 direction
The state of movement is shown. On the other hand, by bending the piezoelectric element 5 in the X+ force direction piezoelectric element 6 in FIG. 1 in directions opposite to the X2 direction, the sample stage 9 can be rotated on its plane. The two-dot chain line in FIG. 4(b) shows the state of movement of the sample stage 9 in a state in which the piezoelectric element 5.6 is bent in the opposite direction.

In STM, the probe 10 is driven in a direction perpendicular to the surface of the sample 8 fixed to the sample stage 9 placed on the stage 14. That is, in STM, as shown in FIG.
By applying a voltage to the inner surface electrode 13 of the piezoelectric element 4
is driven in the axial direction, a probe 10 whose tip is sharp to the atomic order approaches the sample 8 on the nanometer order, and a control voltage is applied to the piezoelectric element 4 by the tunnel current that flows when a potential difference is applied between the two. Then, the surface shape of the sample 8 is measured with a resolution on the order of nm. The drive mechanism and drive method for this probe IO are known techniques.

When performing measurements on the order of nanometers, instability phenomena and decreased accuracy due to differences in thermal expansion of various parts of the mechanism are major problems.
By using this, the negative effects of this part can be removed.

Next, a method of moving the sample stage 9 on the moving table shown in FIG. 1 will be explained. Generally, the deformable amount of the piezoelectric element 5.6 is at most 10 μm, but in the moving table shown in FIG. I can do it. In other words, the acceleration is such that the inertial force (the product of the acceleration and mass of the sample stage 9) at the beginning of movement that acts on the sample stage 9 on which the sample 8 is placed is greater than or equal to the frictional force between the sample stage 9 and the stage 14. By driving the sample stage 9 impulsively, relative sliding is caused between the sample stage 9 and the stage 14, and the sample stage 9 to which the sample 8 is fixed is moved on the stage 14.

FIG. 5 is a diagram showing the movement of the sample stage 9 for five piezoelectric elements. FIG. 5(a) shows the piezoelectric element 5 in its natural state with no voltage applied. It shows the state of the stage 14 and the sample stage 9.

When the piezoelectric element 5 is bent from this state to 2, the sample stage 9 on the stage 14 will slide while moving towards the stage 14.
It moves later in the direction of deflection. This state is shown in Figure 5 (
Shown in b). During the subsequent process in which the piezoelectric element 5 returns to its original state (FIG. 5(C)), the sample stage 9 slides on the stage 14, so after the piezoelectric element 5 stops moving, the As shown in FIG. 5(d), the sample stage 9 is stopped at a position shifted by a distance d from the stage 14.

Now, if we apply a displacement X of a single cosine wave expressed by FIG. 6 and equation (1) to the stage 14, the conditions for relative slippage between the sample stage 9 and the stage 14 are expressed by the equation ( 2) and
It was analytically found that the relative displacement d caused by and - times of impact is maximum when expressed by equation (3), and the amount of movement is expressed by equation (4), and this was also confirmed experimentally.

x=-acos(ωt)+a=(1)μgγ=3.76... (3)
d/2 a=0. 625 - (4) where a is the half amplitude of the waveform, ω is the angular frequency, μ is the friction coefficient, and g
is the gravitational acceleration. As an example that satisfies formula (3),
When a=1 μm and μ=0.15, the frequency is 3747. In the case of a cylindrical piezoelectric element with a height of 40 m and a diameter of 10 square meters, the resonance frequency of the bending motion is about 10 KHz, and it is easy to drive a single wave of the above frequency and amplitude.

Furthermore, if the waveform shown in Fig. 6 is repeatedly driven in isolation,
The sample 8 can be moved without distance limitations.

The moving table of the present invention is capable of moving the sample stage 9 without any distance restriction using the impact drive method described above, and since it is placed on a piezoelectric element, the sample stage 9 can be moved easily. Movement on the order of angstroms is also possible without causing the table 14 to slide. The two methods of moving the sample stage 9 are shown in FIGS. 4(a) and 4(b).
) is possible, and a high-performance moving table can be realized.

FIG. 7 shows a cylindrical piezoelectric element 5 constructed as shown in FIG.
6 shows a cross-section of the main part of a movable table that has an additional configuration for fixing the sample stage 9 placed on the stage 14 attached to the free end side of the stage 6. be.

The stage 14 is an electromagnet and includes a yoke 19 made of a material with high residual magnetization, and a coil 20 wound around the yoke 19. Further, the sample stage 9, on which the sample 8 placed on the stage 14 is fixed, is made of a magnetic material.

In the movable table having the function of fixing the sample stage 9 on the stage 14 as described above, in the present invention, the coil 20 of the stage 14 is momentarily energized, and then the current is turned off to zero. As mentioned above, the yoke 19 of the stage 14 is made of a material with a large residual magnetization, so even if the current is reduced to 0 after the coil 13 is energized, the stage 14, which is an electromagnet, will remain attached to the sample stage due to the residual magnetic force. 9 is suctioned, and the sample stage 9 is fixed on the yoke 19. In this way, since the coil 20 is energized instantaneously, almost no heat is generated in the coil 20.

In addition, in order to remove the suction force of the sample stage 9 of this stage 14,
An alternating magnetic field whose amplitude decreases over time may be applied to the coil 20, and the residual magnetic force of the yoke 19 disappears by this alternating magnetic field.

Therefore, if the method of the present invention is applied to the movable table having the configuration shown in FIG. 7, the sample 8 can be fixed on the stage 14 with good reliability.

〔Effect of the invention〕

As explained above, according to the present invention, there is no limit to the movement distance of an object placed on the stage, and the object can be moved not only in parallel but also rotationally on a moving table that can be moved minutely. I can do it. As a result, the method for fixing a sample on a moving table of the present invention is most suitable for fixing a sample such as STM after minute movement.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the overall configuration of a moving table to which the present invention is applied, FIG. 2 is a perspective view of the cylindrical piezoelectric element shown in FIG. 1, and FIG. 3 is a perspective view of the cylindrical piezoelectric element shown in FIG. 2. Fig. 4 is a plan view of the sample stand showing the movement of the sample stand, Fig. 5 is an explanatory view showing the movement of the piezoelectric element of the present invention, and Fig. 6 is a perspective view of the sample stand attached to the free end. A diagram showing an example of a driving waveform of a piezoelectric element, FIG. 7 is a cross-sectional view of a main part showing the structure of a stage, and FIG. 8 is a perspective view showing the configuration of a conventional moving table using three laminated piezoelectric elements. It is a diagram. DESCRIPTION OF SYMBOLS 1... Moving table, 2... Base, 3... Moving mechanism, 4.5.6... Cylindrical piezoelectric element, 7... External electrode, 8... Sample, 9... Sample stage, 10... Probe, 13... Inner surface electrode, 14... Stage, 19... Yoke, 20... Coil,

Claims (4)

[Claims] 1. This is a moving table for moving an object on the stage, and the two cylindrical piezoelectric elements, which are attached to the free end so that the stage is spanned, are moved on the stage when no voltage is applied. The two piezoelectric elements are arranged so that their top surfaces are flush with each other, and the other end is fixed on a base, and one electrode is formed on either the inner or outer circumferential surface of the two piezoelectric elements, and the opposing circumferential surface is The moving table is characterized in that the other electrode is formed by dividing into a plurality of parts in the circumferential direction, and is provided with electrode selection means for selecting each electrode to which a voltage is applied in these two piezoelectric elements. 2. 2. The moving table according to claim 1, wherein the object table is composed of an electromagnet consisting of a yoke and a coil. 3. Two cylindrical piezoelectric elements are attached to the free end so that the workpiece is spanned across the workpiece, and when no voltage is applied, the two cylindrical piezoelectric elements are lined up so that the top surface of the workpiece is flush with the other end. one electrode is formed on the entire circumferential surface of either the inner or outer circumferential surface of the two piezoelectric elements, and the other electrode is formed on the opposing circumferential surface by dividing it into a plurality of electrodes in the circumferential direction. and an electrode selection means for selecting each electrode to which a voltage is applied in these two piezoelectric elements, and a method for driving a moving table for moving an object placed on the two mounting stages, comprising: The electrodes to which voltage is applied in each piezoelectric element are selected by the electrode selection means according to the moving direction of the object, and a single cosine wave voltage of one period is applied to each selected electrode, or a voltage of the single cosine wave is applied to each selected electrode. Applying an intermittent series of voltages to impact and independently deform the two piezoelectric elements,
An object placed on one stage is slid on the stage with an impact according to the deformation direction of the two piezoelectric elements, and the object is moved or rotated minutely in any direction on the stage. A method for driving a moving table characterized by: 4. A stage consisting of an electromagnet with a yoke made of a material with large residual magnetization and a coil on the free end side is attached so as to span two cylindrical piezoelectric elements, with no voltage applied. The top surfaces of the mounting tables are arranged so that they are flush with each other, and the other ends are fixed on a base, and one electrode is formed on the entire circumferential surface of either the inner or outer circumference of the two piezoelectric elements, The other electrode is formed by dividing it into a plurality of parts in the circumferential direction on the opposing circumferential surface, and an electrode selection means is provided for selecting the electrode to which a voltage is applied in each of these two piezoelectric elements, and A method for driving a moving table for moving an object placed on a table, the method comprising applying an alternating current whose amplitude decreases over time to the coil to eliminate the residual magnetic force, and moving the object on the table. After enabling movement, the electrode selection means selects an electrode to which a voltage is applied in each piezoelectric element according to the direction of movement of the object, and applies a voltage of a single cosine wave of one period to each selected electrode, Alternatively, by applying an intermittent series of voltages of the single cosine wave to impact and independently deform the two piezoelectric elements, the object placed on the two mounting stages can be transformed into two piezoelectric elements. According to the deformation direction of the yoke, the yoke is caused to slide on the stage with an impact, and is caused to move or rotate slightly in any direction on the stage, and then instantaneously energizes the coil. A method for driving a moving table, characterized in that the object is fixed on the document table by a residual magnetic force.