JPH0631737B2 - Specimen fixing method for moving table - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a method for fixing a sample on a moving table, and in particular, it requires a small horizontal movement like a stage for a microscope or the like. The present invention relates to a method of fixing a sample on a moving table.

(Prior Art) In STM (Scanning Tunneling Microscope), a thin needle (probe) is brought very close to the surface of an object, and a voltage is applied between the probe and the object to form a needle tip. Even if there is a gap between the object surfaces, a tunnel effect phenomenon is generated to allow a minute electric current to flow, and the vertical movement of the probe is controlled using this electric current to determine the unevenness of the object surface. That is, this STM is a high-resolution microscope based on a new principle that can identify atoms on a solid surface one by one. In recent years, surface observation of ultrafine-machined semiconductor devices and optical disks, and minute biological materials such as genes and proteins It is very useful for observing.

However, in the conventional STM, the movable range of the probe is about 10 μm at the maximum, and if it is attempted to cover the observation area on the sample beyond this range, another mechanism that enables minute movement, for example, There is a problem in that a so-called "scraping" mechanism or the like composed of a piezoelectric element is required.

FIG. 6 shows this conventional mechanism. In the drawing, reference numerals 23 and 24 denote fixed laminated piezoelectric elements, and 25 denotes a traveling laminated piezoelectric element.
3 to 25 are piezoelectric elements 22, 2 in the groove 26 of the substrate 22.
3 are arranged in parallel, and the piezoelectric element 24 is arranged between them in a direction orthogonal to the piezoelectric elements 22 and 23 arranged in parallel. First, a voltage is applied to the fixing piezoelectric element 23, and the piezoelectric element 23 is expanded and stretched and stopped on the wall of the groove 26. The piezoelectric element 24 is contracted without applying a voltage. Next, a voltage is applied to the advancing piezoelectric element 25 to extend it, and when the piezoelectric element 25 is extended, a voltage is applied to the piezoelectric element 24 and it is stopped while being stretched on the extended wall 26. Then, the piezoelectric element 23 in the fixed state is returned to the original length except for applying the voltage, or further contracted to release the constraint on the wall 26. After that, the piezoelectric element 25 is contracted except for the voltage application to the piezoelectric element 25 for movement, and the piezoelectric element 23 is moved to the piezoelectric element 24 side. By repeating the above operation, 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 require the function of exerting adsorption force to the substrate to fix it and release it, which is troublesome to manufacture. Is.

Therefore, the present applicant has already proposed a movement table for minimum movement in which the movement method of the sample to be observed is eliminated while the driving method is simple and simple (Japanese Patent Application No. 2-255).
(See No. 4).

In this proposal, when the sample table of the moving table is fixed on the table by the applicant, the sample table is made of an electromagnet, the sample table is made of a magnetic material, and the sample is obtained by energizing the electromagnet. The table was fixed on the table.

(Problems to be solved by the invention) However, in the moving table already proposed by the present applicant, since the electromagnet is energized in order to fix the sample stage on the stage, heat is generated in the coil during energization. Then there is the problem that it is not very appropriate.

An object of the present invention is to solve the above-mentioned drawbacks, and an object of the present invention is to provide a moving table for minute movement, which can eliminate the limitation of the moving distance of a sample table on which a sample is placed. Another object of the present invention is to provide a method capable of reliably fixing a sample stage on a stage without generating heat.

[Structure of Invention]

(Means for Solving the Problems) A method for fixing a sample of a moving table according to the present invention that achieves the above-mentioned object includes at least one piezoelectric element having one end fixed, and a stage mounted at the other end of the piezoelectric element. Consists of
By applying a voltage of a single cosine wave of one cycle or an intermittent continuous voltage of the single cosine wave to the piezoelectric element, the piezoelectric element is flexibly deformed, and the platform is shockedly driven. A method of fixing the sample on a moving table for sliding a sample on the table in the deformation direction of the piezoelectric element to make a minute movement, wherein the table is composed of a yoke and a coil made of a material having a large residual magnetization. It consists of an electromagnet,
The sample is placed on the sample table fixed to a sample table made of a magnetic material, and the coil is instantaneously energized to cause the residual magnetic force generated in the yoke to move the sample table to the sample table. It is characterized in that the residual magnetic force is extinguished by fixing it on the coil and applying an alternating current whose amplitude decreases with time to the coil.

(Operation) According to the method for fixing a sample of a moving table of the present invention, the stage at the free end of the piezoelectric element is composed of a yoke made of a material having a large residual magnetization and an electromagnet made of a coil, and the sample is made of a magnetic material. Since it was placed on the sample stand described above while being fixed to the sample table, a residual magnetic force is generated in the yoke due to the instantaneous energization of the coil, and the residual magnet force fixes the sample table on the sample table. . The residual magnetic force can be extinguished by applying an alternating current whose amplitude decreases temporally to the coil built in the stage.

(Example) Hereinafter, the method of the present invention will be described in detail with reference to the drawings.

FIG. 1 illustrates a schematic configuration of an STM (scanning tunneling microscope) equipped with a moving table to which the method of the present invention is applied. In the figure, 2 is a stage for mounting the sample 6 on the moving table 1, 3 is a piezoelectric element for driving the stage 2.
Reference numeral 4 is an STM probe, 5 is a piezoelectric element that drives the STM probe 4, 7 is a moving mechanism for the piezoelectric element 5, and 8 is a base.
The piezoelectric elements 3 and 5 have a cylindrical shape. In this embodiment, the lower end of the piezoelectric element 3 is fixed to the base 8, and the lower end of the piezoelectric element 5 is fixed to the base 8 via the moving mechanism 7. The moving mechanism 7 is capable of moving the piezoelectric element 5 in the axial direction, and has a function of roughly moving the probe 4 to the sample 6 up to the order of μm which is the drivable area of the piezoelectric element 5.

FIG. 2 shows a single shape of the cylindrical piezoelectric elements 3 and 5. An electrode 10 is formed on the entire inner peripheral surface of the cylindrical piezoelectric elements 3 and 5, and an electrode 9 is formed on the outer peripheral side surface portion thereof. In this embodiment, the electrodes 9 formed on the outer peripheral side surface are divided into four parts. By applying a voltage to the two electrodes 9 facing each other in opposite phases, the piezoelectric element is fixed with the fixed end to the base 8 as a reference. Each of 3 and 5 can be flexibly deformed. Therefore, the piezoelectric element 3 can be driven in two horizontal directions on the surface of the stage 2.

In the STM, the probe 4 is driven in the direction perpendicular to the surface of the sample 6 fixed to the sample table 12 mounted on the table 2. That is, in the STM, the piezoelectric element 5 is driven in the axial direction by applying a voltage to the electrode 10 in FIG. 2, and the probe 4 whose tip is sharply formed to the atomic order approaches the sample 6 in the nm order. A control voltage is applied to the piezoelectric element 5 by a tunnel current flowing when a potential difference is applied to both, and the surface shape of the sample 6 is measured with a resolution of nm order.

In the case of performing measurement on the order of nm, an unstable phenomenon due to a difference in thermal expansion of each part of the mechanism and a decrease in accuracy and accuracy are serious problems, but as shown in FIG.
By using 5, the adverse effect of this portion can be eliminated.

Next, a method of moving the sample 6 on the moving table of FIG. 1 will be described. Generally, the deformable amount of the piezoelectric elements 3 and 5 is at most 10 μm. However, in the moving table of FIG. 1, by moving the stage 2 on which the sample 6 is placed by the deformation of the piezoelectric element 3, The sample 6 placed on the stage 2 is moved in the moving direction of the stage 2. That is, the inertial force acting on the sample 6 (the product of the acceleration of the stage 2 and the mass of the sample 2) is
By impulsively driving the stage 2 with an acceleration that is equal to or greater than the frictional force between them, relative sliding is caused between the sample 6 and the stage 2, and the sample 6 is moved on the stage 2. -ing

Now, assuming that the displacement x of a single cosine wave represented by FIG. 3 and the following equation (1) is given to the stage 2, the condition for causing relative slip between the sample 6 and the stage 2 is the formula ( It is 2), and the relative displacement d that occurs in one impact becomes the maximum in the case of the formula (3), and it is analytically understood that the movement amount is the formula (4). Was given.

Here, a is one-sided amplitude of the waveform, ω is an angular frequency, μ is a friction coefficient, and g is gravitational acceleration. As an example of satisfying the expression (3), when a = 1 μm and μ = 0.15, the frequency is 37
It is 4 Hz. In the case of a cylindrical piezoelectric element having a height of 40 mm and a diameter of 10 mm, the resonance frequency of the bending motion is ten and several KHz, and it is easy to drive a single wave having the above frequency and amplitude.

Furthermore, if the waveform of FIG. 3 is repeatedly driven independently,
The sample 6 can be moved without limitation of the distance.

FIG. 4 shows a cylindrical piezoelectric element 3 constructed as shown in FIG.
5 shows a moving table to which the stage 15 and the sample table 12 are attached on the free end side of 5, and shows the structure of the moving table to which the sample fixing method of the present invention is applied. In this configuration, the sample 6 is fixed on the sample table 12.

FIG. 5 shows a cross section of the main part of FIG. 4, and shows the structure of the stage 15. The stage 15 is an electromagnet, and explains the fixing function of the stage 12 which the stage 15 has. The stage 15 includes a yoke 11 made of a material having a large residual magnetization, and a coil 13 wound around the yoke 11.
It consists of and. The sample table 12 to which the use 6 mounted on the table 15 is fixed is made of a magnetic material. The movement of the sample table 12 with respect to the stage 15 is
As described with reference to FIGS. 1 to 3, this is an impact due to expansion of the piezoelectric element 3 due to the application of voltage to the piezoelectric element 3, and the impact drive causes the sample stage 12 to slide on the stage 15. It is like this.

In the moving table configured as described above, in the present invention, the coil 13 of the stage 15 is instantaneously energized, and then the current is set to zero. As described above, the yoke 1 of the stage 15
Since 1 is made of a material having a large residual magnetization, even if the current is set to 0 after the coil 13 is energized, the stage 15 which is an electromagnet attracts the sample stage 12 by the residual magnetic force,
The sample table 12 is fixed on the yoke 11. As described above, since the power supply to the coil 13 is instantaneous, the coil 1
Almost no heat is generated in 3.

To remove the attraction force of the sample table 12 of the table 15, it is sufficient to apply an alternating magnetic field whose amplitude decreases temporally to the coil 13, and the residual magnetic force of the yoke 11 disappears due to this alternating magnetic field.

Therefore, by applying the method of the present invention to the moving table having the configuration shown in FIGS. 4 and 5, the sample 6 can be fixed on the stage 15 with high reliability.

〔The invention's effect〕

As described above, according to the present invention, it is possible to eliminate the limitation of the moving distance of the sample to be observed on the sample stage on which the sample is placed, in the moving table for minute movement, without generating heat, and There is an effect that the sample table can be fixed on the table with high reliability. As a result, the sample fixing method of the moving table according to the present invention is most suitable for fixing a sample such as STM after minute movement.

[Brief description of drawings]

FIG. 1 is a perspective view showing the entire configuration of a moving table to which the present invention is applied, FIG. 2 is a perspective view of the cylindrical piezoelectric element alone of FIG. 1, and FIG. 3 is a diagram showing an example of a drive waveform of the piezoelectric element. 4, FIG. 4 is a perspective view showing the structure of a suitable moving table for explaining the method of the present invention, FIG. 5 is a sectional view of the main part of the moving table of FIG. 4, and FIG. It is a perspective view which shows the structure of the conventional moving table used individually. 1 ... moving table, 2,15 ... mounting table, 3,5 ... cylindrical piezoelectric element, 4 ... probe, 6 ... sample, 7 ... moving mechanism, 8 ... base, 9,10 ...... Electrode, 12 …… Sample stand, 13 …… Coil, 23,24,25 …… Multilayer piezoelectric element. 26 ... Groove.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G05D 3/00 G 9179-3H H01J 37/20 A

Claims (1)

[Claims] 1. A piezoelectric element having at least one end fixed thereto and a stage mounted at the other end of the piezoelectric element, wherein the piezoelectric element has a voltage of a single cosine wave for one cycle or the single cosine wave. By applying an intermittent continuous voltage of a cosine wave, this is flexibly deformed, and the above-described table is driven impulsively and the sample on the above-mentioned table is slid in the deformation direction of the piezoelectric element. A method of fixing the sample on a moving table for minute movement, wherein the table is composed of an electromagnet consisting of a yoke and a coil made of a material having a large residual magnetization, and the sample is fixed to a sample table made of a magnetic material. In the state described above, the sample table is fixed on the above-described object table by the residual magnetic force generated in the yoke by instantaneously energizing the coil, and the coil is temporally applied. Intersection with decreasing amplitude A method for fixing a sample on a moving table, characterized in that the residual magnetic force is extinguished by applying a flowing current.