JPH04556B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a sample position micro-movement mechanism used in precision measurement instruments such as electron microscopes and tunneling microscopes, and in particular, it relates to a sample position micro-movement mechanism using a piezoelectric element. This invention relates to a sample fine movement mechanism that controls the position.

(Prior technology) Scanning tunneling microscopes have recently been developed as microscopes with extremely high resolution on the order of nm (nanometers), and are used not only in the field of surface physics but also in a wide range of fields such as precision processing, superconductivity, medicine, and biology. It is attracting attention in various application fields.

This scanning tunneling microscope uses tunneling current to observe irregularities on the surface of a sample. A metal probe made of tungsten or other material whose tip has been polished to a fineness of about 1 μm (micrometer) is placed on the surface of a sample such as a cleaned silicon crystal.
When the probe is brought as close as 1 nm and a bias voltage of several millivolts to several volts is applied between the probe and the sample, a tunnel current flows between the probe and the sample. This tunneling current largely depends on the distance between the probe and the sample surface, and changes exponentially with the distance. Therefore, if the position of the probe is controlled so that the tunneling current value is kept constant while moving the probe along the sample surface, the height of the sample surface can be changed using the control signal. can be found. Then, by scanning the probe two-dimensionally along the sample surface in the X and Y directions,
A three-dimensional image of the sample surface can be obtained.

According to a scanning tunneling microscope based on this principle, irregularities on the sample surface can be detected in the vertical direction.
It can be measured non-destructively with extremely high accuracy of 0.01 nm and 0.2 to 0.3 nm in the horizontal direction.

By the way, when observing a sample using such a tunneling microscope, it is necessary to set the distance between the probe and the sample surface in advance to a size that allows a tunneling current to flow therebetween. Usually, the setting is performed by moving the sample stage on which the sample is placed. The sample stage is also moved when changing the observation position of the sample.

Conventionally, a mechanical mechanism such as a feed screw mechanism or a cross roller guide mechanism has been used as a mechanism for moving the sample stage in this manner.

(Problems to be Solved by the Invention) However, with such a mechanical sample moving mechanism, it is not possible to completely eliminate backlash, crosstalk, etc., and therefore precise position control is extremely difficult. Particularly in the case of the above-mentioned tunneling microscope, position control on the nanometer order is required, but such control is almost impossible with mechanical mechanisms.

To this end, in a scanning tunneling microscope, after a sample stage is moved by a mechanical sample moving mechanism, the probe is moved minutely by a probe scanning mechanism made of a piezoelectric element. However, since the expansion and contraction stroke of the piezoelectric element is extremely small, even in such a case, it is extremely difficult to set the sample within a range that can be positioned by the probe scanning mechanism. In addition, when the relative position between the probe and the sample is determined by the probe scanning mechanism, there is a problem that the scanning area is narrowed by the amount that the probe is moved. There is also.

It would be possible to use a piezoelectric element in the sample movement mechanism, but simply moving the sample stage using a piezoelectric element would not provide a sufficient stroke, so it is possible to use a piezoelectric element to move the sample stage. cannot be made to correspond to

The present invention has been made in view of these problems, and its purpose is to enable extremely precise position control of the sample stage and also to allow it to be moved with relatively large strokes. That's true.

(Means for solving the problem) In order to achieve this object, in the present invention, an upper clamp base and a lower clamp base to which piezoelectric elements are attached in the X direction and the Y direction are connected to When the piezoelectric elements are connected by an element and expanded in the X direction and the Y direction, the upper or lower clamp stand is fixed to the guide body. The X-direction and Y-direction piezoelectric elements each include a pair of piezoelectric elements that expand and contract in opposite directions.

In the first invention, the guide body is fixed to the base, and the upper and lower clamp stands are movable along the guide body, and the sample stand is provided on the upper clamp stand. .

Further, in the second invention, the lower clamp stand is fixed to the base, the guide body is movable, and the sample stand is provided on the guide body.

(Function) By configuring in this way, for example, the piezoelectric element of the upper clamp stand is extended and the clamp stand is fixed to the guide body, and the piezoelectric element of the lower clamp stand is contracted, and the upper clamp stand and the lower clamp stand are fixed. If the Z-direction piezoelectric element connecting the two is expanded or contracted, the relative position between the lower clamp base and the guide body changes. Then, in this state, fix the lower clamp base to the guide body, contract the piezoelectric element of the upper clamp base, and expand and contract the piezoelectric element in the Z direction, then the relative position of the upper clamp base and the guide body will change. changes.

Therefore, by repeating such an operation, in the case of the first aspect of the invention, the upper and lower clamp stands move along the guide body, and the sample stand provided on the upper clamp stand moves. moves. Further, in the case of the second invention, the guide body moves, and the sample stage provided on the guide body moves. The total amount of movement is determined by the length of the guide body. Therefore,
By making the guide body long, the movement stroke of the sample stage can be made sufficiently long. Furthermore, by controlling the voltage applied to the piezoelectric element in the Z direction, its position can be controlled extremely precisely.

And each pair of X on the upper and lower clamp base
If the voltage applied to the piezoelectric element in the direction or the piezoelectric element in the Y direction is different, the amount of expansion will be different. It is possible to make small movements in the direction.

(Example) Hereinafter, an example of the present invention will be described using the drawings.

In the figures, FIG. 1 shows an embodiment of the sample fine movement mechanism according to the present invention, and is a longitudinal sectional side view of a microscope equipped with the sample fine movement mechanism, and FIG. 2 is a perspective view of the movable part of the sample fine movement mechanism. It is a diagram.

As is clear from Fig. 1, a base 1 is provided in the sample chamber of the scanning electron microscope, which is moved by a feed screw mechanism or the like in the X direction parallel to the paper and the Y direction perpendicular to the paper. . A cylindrical guide body 2 is fixed on this base 1. This guide body 2 is fixed at any position within the X-Y plane by a piezoelectric clamping element 3 attached to a fixed part of the electron microscope.

A probe scanning mechanism 5 that can minutely move the probe 4 of the scanning tunneling microscope in the X direction, the Y direction, and the Z direction perpendicular thereto is attached to the upper surface of the guide body 2. The probe scanning mechanism 5 is composed of a plurality of piezoelectric elements that expand and contract in the X, Y, and Z directions, respectively.

The probe 4 of the tunneling microscope is positioned at its tip within a range where it can be irradiated with an electron beam 7 by the objective lens 6 of the electron microscope. Secondary electrons 8 emitted by the irradiation of the electron beam 7 are detected by a secondary electron detector 9 of the electron microscope.

The guide body 2 is used as a fixed part of the sample fine movement mechanism 11. A movable part of the sample fine movement mechanism 11 is provided inside the guide body 2. As is clear from FIGS. 1 and 2, the movable part has a disc-shaped upper clamp base 12 and a lower clamp base 13, and the upper clamp base 12 includes:
First piezoelectric elements X ₁ and X ₂ respectively protrude from both side surfaces in the X direction, and second piezoelectric elements Y ₁ and Y ₂ respectively protrude from both side surfaces in the Y direction. Therefore, the first piezoelectric elements X ₁ and X ₂ expand and contract in opposite directions on a straight line in the X direction, and the second piezoelectric elements Y ₁ and Y ₂ expand and contract in opposite directions on a straight line in the Y direction. It is considered a thing.

The lower clamp stand 13 also has a first piezoelectric element X ₁ ,
Third piezoelectric elements X ₃ , X ₄ similar to X ₂ and fourth piezoelectric elements Y ₃ , _{Y 4 similar} to the second piezoelectric elements Y 1 , Y ₂ are attached.

Thus, the first and second piezoelectric elements X ₁ , X ₂ ;
When Y ₁ and Y ₂ are extended, they are crimped onto the inner surface of the guide body 2, and the upper clamp base 12 is fixed to the guide body 2, and the third and fourth piezoelectric elements X ₃ and
When X ₄ ; Y ₃ and Y ₄ are extended, the lower clamp base 13 is fixed to the guide body 2. Moreover, those piezoelectric elements X ₁ to X ₄ , Y ₁ to _{Y 4}
When contracted, each clamp stand 12, 13
can freely move up and down with respect to the guide body 2.

These piezoelectric elements X ₁ to X ₄ and Y ₁ to _{Y 4} have a third
The voltage is applied by a control device as shown in the figure. That is, a +V potential is applied to the + pole of one first piezoelectric element X ₁ via the switch S ₁ , and the other first piezoelectric element X ₂
A potential of -V is applied to the negative pole of the switch _S2 through the switch S2. Then, the - pole of one first piezoelectric element X ₁ and the + pole of the other first piezoelectric element X ₂
A fine vibration control potential ΔV _x is applied to the pole. The fine movement control potential ΔV _x can be varied within a certain range around 0.
In this way, one first piezoelectric element X ₁ has V−ΔV _x
A voltage of V+ΔV _x is applied to the other first piezoelectric element X ₂ .

second piezoelectric elements Y ₁ , Y ₂ , third piezoelectric elements X ₃ , X ₄ ,
The fourth piezoelectric elements Y ₃ and Y ₄ are also connected in the same way.
The third piezoelectric elements X ₃ and X ₄ are given the same fine movement control potential ΔV _x as the first piezoelectric elements X ₁ and X ₂ . Moreover, the second piezoelectric elements Y ₁ , Y ₂
The same fine movement control potential ΔV _y applied to the fourth piezoelectric elements Y ₃ and Y 4 is also applied to the fourth piezoelectric elements Y 3 and Y ₄ . Furthermore, the switches S ₁ and S ₂ of the second piezoelectric elements Y ₁ and Y ₂ are the switches of the first piezoelectric elements X ₁ and X _2.
The switches S _{3 and 3} of the third piezoelectric elements X ₃ and X ₄ are opened and closed by the same control signal as that for opening and closing S 1 and S ₂ .
The switches S _{3 and S 4 of S 4 and the fourth piezoelectric elements Y 3 and Y 4} are also
They are each opened and closed by the same control signal.

As shown in FIGS. 1 and 2, the upper clamp base 12 and the lower clamp base 13 are connected to each other by a fifth piezoelectric element _Z1 that expands and contracts in the Z direction. This fifth piezoelectric element Z ₁ has a voltage applied to the first and second piezoelectric elements X ₁ , X ₂ ; Y ₁ , Y ₂ or _the third _{and fourth piezoelectric elements X 3 ,} X ₄ ; A control voltage is applied from the control device at a predetermined timing with respect to the application timing.

A sample stand 14 on which a sample is placed is provided on the upper clamp stand 12.

Next, the sample fine movement mechanism 11 configured as described above will be explained.
The effect of this will be explained.

When observing a sample, the sample is placed on the sample stage 14 with the movable part of the sample fine movement mechanism 11 being lowered. First, switches S ₁ and S ₂ are opened, and switches S ₃ and S ₄ are closed. At this time, the fine movement control potentials ΔV _x and ΔV _y are both set to 0. Then, the first and second piezoelectric elements X ₁ , X ₂ ; Y ₁ , Y ₂ contract, and the third and fourth piezoelectric elements X ₃ , X ₄ ; Y ₃ , Y ₄ expand. As a result, the upper clamp stand 12 becomes free, and the lower clamp stand 13 is fixed to the guide body 2.

Therefore, a voltage is applied to the fifth piezoelectric element _Z1 . Then, the fifth piezoelectric element _Z1 expands, and the upper clamp table 12 rises.

Next, switches S ₁ and S ₂ are closed, and switches S ₃ and
Open _S4 . Then, the first and second piezoelectric elements X ₁ ,
X ₂ ; Y ₁ , Y ₂ expand, and the upper clamp base 12 is fixed to the guide body 2 at that position, and the third and fourth piezoelectric elements X ₃ , X ₄ ; Y ₃ , Y ₄ contract. As a result, the lower clamp table 12 becomes free. Therefore, the voltage applied to the fifth piezoelectric element _Z1 is removed. Thereby, the fifth piezoelectric element Z ₁ contracts,
The lower clamp stand 13 rises.

In this state, the lower clamp base 13 is fixed to the guide body 2 again, and the upper clamp base 12 is set free. Then, the fifth piezoelectric element _Z1 is expanded. Then, the upper clamp stand 12 further rises.

By repeating such operations, the sample stage 14 rises and the sample approaches the probe 4. At this time, the voltage applied to the fifth piezoelectric element Z ₁ is made smaller so that the amount of expansion and contraction of the piezoelectric element Z ₁ becomes smaller, so that fine adjustment is performed.

In this way, when a tunneling current begins to flow between the probe 4 and the sample, the first to fourth piezoelectric elements X ₁ to X ₄ and Y ₁ to Y ₄ are all extended in this state, and the upper clamping table 12 and The lower clamp stand 13 is both fixed to the guide body 2.

Then, in this state, the sample is observed using a scanning electron microscope. When changing the observation position of the sample, the base 1 of the electron microscope is moved within the X-Y plane, thereby moving the sample stage 14 within the X-Y plane.

When it is necessary to further magnify the sample for observation, the sample stage 14 is positioned so that the observation area is approximately located at the tip of the probe 4. Then, the guide body 2 is fixed at that position by the clamping piezoelectric element 3. Next, the first and third piezoelectric elements
The fine movement control potential ΔV _x given to X ₁ to _{X 4} and the second
and the fine movement control potential ΔV _y given to the fourth piezoelectric elements Y ₁ to _{Y 4} are changed as appropriate. Then, the amount of expansion of the first and third piezoelectric elements X ₁ and X ₃ on the one hand and the first and third piezoelectric elements X ₂ and X ₄ on the other hand, and the amount of extension of the second and fourth piezoelectric elements Y ₁ and Y ₃ on the other hand. and the other second and fourth piezoelectric elements Y ₂ and Y ₄ have different extension amounts. As a result, the upper and lower clamping bases 12,
The sample stage 14 is minutely moved within the XY plane while the sample stage 13 remains fixed to the guide body 2.

In this way, the magnified observation area of the sample is
can be accurately positioned at the tip of the

Next, the probe scanning mechanism 5 is activated to finely adjust the position of the probe 4 in the Z direction so that the tunnel current flowing between the probe 4 and the sample becomes a predetermined value. Then, while scanning the probe 4 in the X-Y plane, the position of the probe 4 in the Z direction is controlled so that the tunnel current is maintained at a constant value. By image processing the control signal, it is possible to obtain an enlarged image of the same part of the sample observed with an electron microscope.

In this way, according to this sample fine movement mechanism 11,
The sample stage 14 can be moved in the Z direction by a distance corresponding to the length of the guide body 2, and the sample can be moved to the extent that a tunnel current flows between the probe 4 and the sample, that is, on the nanometer order. Z
The position of the direction can be controlled. Furthermore, the position of the sample in the X direction and Y direction can also be finely adjusted on the order of nanometers.

Since the guide body 2 is cylindrical and the upper and lower clamp tables 12 and 13 are disk-shaped, they can be processed with high precision. Therefore, highly accurate position control is possible. Moreover, the cylindrical guide body 2
Since the movable parts are housed inside the
The movable part can be made smaller.

FIG. 4 is a perspective view showing an embodiment of the sample fine movement mechanism according to the second aspect of the present invention.

As is clear from this figure, in this embodiment, the guide body 2 has a cylindrical shape, and a ring-shaped upper clamp table 12 and a lower clamp table 13 are provided on the outer circumferential side of the guide body 2. A pair of first piezoelectric elements X ₁ and X ₂ are attached to the upper clamp base 12, which protrude from the inner circumferential surface on a straight line in the X direction, and also protrude from the inner circumferential surface on a straight line in the Y direction. A pair of second piezoelectric elements Y ₁ and Y ₂ are attached. These piezoelectric elements X ₁ , X ₂ and Y ₁ , Y ₂
simultaneously expands and contracts toward the guide body 2 on the center side, is fixed to the guide body 2 when expanded, and becomes free when contracted.

The lower clamp stand 13 also has a first piezoelectric element X ₁ ,
Third piezoelectric elements X ₃ , X ₄ similar to X ₂ and fourth piezoelectric elements Y ₃ , _{Y 4 similar} to the second piezoelectric elements Y 1 , Y ₂ are attached.

The upper clamp table 12 and the lower clamp table 13 are connected by a plurality of fifth piezoelectric elements _Z1 that extend and contract in the Z direction.

The lower clamp stand 13 is fixed to the base 1. Further, the guide body 2 is movable, and its upper surface forms a sample stage 14.

The rest of the structure is almost the same as the embodiment shown in FIGS. 1-3. However, in this case, the probe scanning mechanism 5 is supported on the base 1 by a support stand separate from the guide body 2.

In the sample fine movement mechanism 11 configured in this way, _the first and second piezoelectric elements X ₁ , X _{2 ;} , when the third and fourth piezoelectric elements X ₃ , X ₄ ; Y ₃ , Y ₄ of the lower clamp base 13 are extended, the lower clamp base 13 is fixed to the guide body 2, and the fifth piezoelectric element Z ₁ is contracted. , the upper clamp table 12 is lowered while the guide body 2 remains in that position. Therefore, when the upper clamp base 12 is fixed to the guide body 2 and the lower clamp base 13 is separated from the guide body 2 to extend the fifth piezoelectric element _Z1 , the upper clamp base 12 is pushed up and the guide body 2 is raised.

By repeating these actions, the first
Similar to the embodiment shown in Figures 1 to 3, the sample stage 14 rises significantly. Further, by controlling the voltage applied to the fifth piezoelectric element _Z1 , the position of the sample stage 14 in the Z direction can be finely adjusted. Furthermore, by varying the voltages applied to the piezoelectric elements X ₁ , X ₃ and X ₂ , X ₄ in the X direction, and the piezoelectric elements Y ₁ , Y ₂ and Y ₂ , Y ₄ in the Y direction, The position in the X direction and Y direction can be finely adjusted.

According to such a sample fine movement mechanism 11, there is no need to fix the long guide body 2 on the base 1, so that the height above the base 1 can be reduced. Therefore, the space within the sample chamber of the scanning electron microscope can be used effectively. Furthermore, since the clamp stands 12, 13 and the piezoelectric elements _X1 to _X4 , _Y1 to _Y4 , and _Z1 are supported by the base 1, the degree of freedom in designing these weights is increased. By forming the guide body 2 from a light alloy such as aluminum and making it lightweight, its movement can be performed smoothly and the accuracy of position control can be further improved.

In the above embodiment, the sample fine movement mechanism 11 is used in a scanning tunneling microscope built into the sample chamber of a scanning electron microscope. It is also extremely useful for use in microscopes or tunneling microscopes. Moreover, it can be used not only for microscopes but also for other precision measuring instruments. In such a case, the Z direction may be the horizontal direction. Therefore, the terms "upper clamp stand" and "lower clamp stand" are used merely to differentiate, and do not necessarily refer to their positional relationship.

Even when the clamp tables 12 and 13 are provided inside the guide body 2 as in the embodiment shown in FIGS. 1 and 2, the guide body 2 is made movable as in the embodiment shown in FIG. 13 may be fixed to the base 1 and the guide body 2 may be provided with the sample stage 14. In addition, as in the embodiment shown in FIG.
Even when the guide body 2 is provided inside the clamp bases 12 and 13, the guide body 2 is fixed to the base 1 as in the embodiment shown in FIGS. It can also be configured to move along.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, a piezoelectric element is used as a drive mechanism for moving the sample stage, so precise position control is possible and remote control is possible. Therefore, all controls such as the amount of movement and the direction of movement can be easily performed.

In addition, since the sample stage is moved in the Z direction by repeatedly expanding and contracting the piezoelectric element that expands and contracts in the Z direction, it is possible to make the amount of movement sufficiently large, and it is possible to It can be made to correspond to the sample, and it is also possible to easily set the sample on the sample stage.

Further, the upper and lower clamp stands are fixed to the guide body by a pair of piezoelectric elements that expand and contract in opposite directions on a straight line in the X direction and a pair of piezoelectric elements that expand and contract in opposite directions on a straight line in the Y direction. Therefore, by varying the amount of extension, the sample stage can also be moved in the X direction and the Y direction.

[Brief explanation of drawings]

FIG. 1 is a vertical side view showing an embodiment of a microscope equipped with a sample fine movement mechanism according to the present invention, and FIG.
FIG. 3 is a perspective view showing a movable part of the sample fine movement mechanism, FIG. 3 is a circuit diagram of a control device for a piezoelectric element in the sample fine movement mechanism, and FIG. 4 is a perspective view showing another embodiment of the sample fine movement mechanism according to the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1... Base, 2... Guide body, 11... Sample fine movement mechanism, 12... Upper clamp stand, 13... Lower clamp stand, 14... Sample stand, _X1 , _X2 ... First piezoelectric element, Y ₁ , Y ₂ ... second piezoelectric element, X ₃ , X ₄
...Third piezoelectric element, Y ₃ , Y ₄ ... Fourth piezoelectric element,
Z ₁ ...Fifth piezoelectric element.

Claims (1)

[Claims] 1. A pair of first piezoelectric elements that expand and contract in mutually opposite directions on a straight line in the X direction, and a Y that is orthogonal thereto.
an upper clamp base to which a pair of second piezoelectric elements that expand and contract in opposite directions on a straight line are respectively attached; and third and fourth piezoelectric elements similar to the first and second piezoelectric elements, respectively, are attached to the upper clamp base; and a lower clamp base connected to the upper clamp base by a fifth piezoelectric element that expands and contracts in the Z direction perpendicular to the X and Y directions, and the first to fourth piezoelectric elements contract. When the first and second piezoelectric elements are extended, the upper clamp base is fixed by crimping them. , a guide body to which the lower clamp stand is fixed by crimping the third and fourth piezoelectric elements when they are extended; and controlling voltages applied to each of the first to fifth piezoelectric elements. A sample fine movement mechanism, comprising: a control device; and the guide body is fixed to a base, and a sample table is provided on the upper clamp table. 2 A pair of first piezoelectric elements that expand and contract in mutually opposite directions on a straight line in the X direction, and a Y that is orthogonal thereto.
an upper clamp base to which a pair of second piezoelectric elements that expand and contract in opposite directions on a straight line are respectively attached; and third and fourth piezoelectric elements similar to the first and second piezoelectric elements, respectively, are attached to the upper clamp base; and a lower clamp base connected to the upper clamp base by a fifth piezoelectric element that expands and contracts in the Z direction perpendicular to the X and Y directions, and the first to fourth piezoelectric elements contract. When the first and second piezoelectric elements are extended, the upper clamp base is fixed by crimping them. , a guide body to which the lower clamp stand is fixed by crimping the third and fourth piezoelectric elements when they are extended; and controlling voltages applied to each of the first to fifth piezoelectric elements. A sample fine movement mechanism, comprising: a control device; the lower clamp table is fixed to a base; the guide body is movable; and a sample table is provided on the guide body.