JPH0529243B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a scanning tunneling microscope that uses tunneling current to measure the unevenness of a sample surface. The present invention relates to a probe scanning mechanism for moving a probe for detecting in the X direction and the Y direction.

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

This scanning tunneling microscope uses tunneling current. A metal probe such as tungsten whose tip has been polished to a fineness of about 1 μm (micrometer) is brought close to the surface of a cleaned silicon crystal or other sample to about 1 nm, and a few millivolts to several volts are applied between the probe and the sample. When a bias voltage of 2 is applied, a tunnel current flows between the two.
This tunneling current largely depends on the distance between the probe and the sample surface, and changes exponentially with the distance. Therefore, if the probe position is controlled so that the tunneling current value is kept constant (approximately 10 ^-10 to ^{10 -7} amperes) while moving the probe along the sample surface, the control signal can be used to determine the change in height of the sample surface. Then, move the probe along the sample surface in the X direction and Y direction.
A three-dimensional image of the sample surface can be obtained by scanning two-dimensionally in the direction.

A scanning tunneling microscope based on this principle can detect irregularities on the sample surface in the vertical direction.
It can measure with extremely high accuracy of 0.01 nm and 0.2 to 0.3 nm in the horizontal direction. Moreover, the sample surface is not affected by the electron beam, unlike in ordinary electron microscopes.

Incidentally, in such a scanning tunneling microscope, it is necessary to move the probe extremely accurately in three directions, X, Y, and Z. Therefore, a piezoelectric element actuator is generally used for the movement. The piezoelectric actuator is
It is made up of several to dozens of piezoelectric ceramics stacked and connected in parallel, and deforms in proportion to the voltage applied from the outside. By using such a piezoelectric element, a voltage of several tens of μm can be achieved at a relatively low voltage of about 100 volts.
control becomes possible.

Conventionally, three piezoelectric elements in the X direction, Y direction, and Z direction are combined into a tripod shape, and a probe is attached to the tip of the tripod to control the position of the probe three-dimensionally.

(Problem to be solved by the invention) However, in such a combination of three piezoelectric elements, when one piezoelectric element is expanded or contracted, the other two piezoelectric elements are also deformed accordingly. . In other words, the three piezoelectric elements have their base ends fixed to the base and are connected to each other at their tips, so when the piezoelectric elements are expanded or contracted in the X direction, for example, as the tips of the piezoelectric elements move, the Y The tips of the piezoelectric elements in the direction and Z direction also move in the X direction. Therefore, the piezoelectric elements in the Y direction and the Z direction are curved in the X direction. As a result, the piezoelectric element in the X direction also curves. As a result, the probes attached to the tips of these piezoelectric elements change not only in the X direction but also in the Y and Z directions. Therefore, accurate position control of the probe becomes difficult.

Therefore, as shown in Fig. 5, six piezoelectric elements X ₁ to X ₆ in the X direction and six piezoelectric elements Y ₁ to Y ₆ in the Y direction are combined in a lattice shape, and a The probe is attached via the Z-direction piezoelectric element _Z0 , and the entire probe is connected to four Z-direction piezoelectric elements _Z1.
It is considered to be supported by ~Z ₄ .

According to such a mechanism, the probe can be moved independently in any of the X, Y, and Z directions, and its position can be easily controlled.

By the way, in a scanning tunneling microscope equipped with such a probe scanning mechanism using a piezoelectric element,
Its scanning area is limited. For this reason, for example, the steps themselves in a monoatomic layer can be observed, but the arrangement of the steps cannot be observed. On the other hand, in the field of crystallography,
It is believed that how the step structure of a monoatomic layer is arranged has a very important meaning.

For this reason, a scanning tunneling microscope is used together with a scanning electron microscope that has a wider scanning area, and after observing the step arrangement using the electron microscope, the step structure at the same position of the same sample can be observed using the tunneling microscope. It is becoming increasingly desirable to be able to observe things.

For this purpose, it is necessary to be able to accommodate the scanning tunneling microscope within the sample chamber of the scanning electron microscope. However, conventional scanning tunneling microscopes are intended to be used alone, and their probe scanning mechanisms have become extensive in order to minimize the effects of thermal factors such as vibrations and temperature changes. . Therefore, it was not possible to fit it into the sample chamber of the electron microscope.

Furthermore, in the mechanism shown in FIG. 5 mentioned above, many piezoelectric elements are arranged above the probe, so even if it is installed in the sample chamber of an electron microscope,
These piezoelectric elements become an obstacle, making it impossible to irradiate the sample surface at the tip of the probe with an electron beam and to detect secondary electrons emitted from the sample. In other words, it is not possible to observe a location observed using a scanning tunneling microscope using a scanning electron microscope.

The present invention was made in view of these problems, and its purpose is to enable images of the same sample at the same position to be easily obtained using both a scanning electron microscope and a scanning tunneling microscope. It is to do so.

Another object of the present invention is to obtain a probe scanning mechanism for a scanning tunneling microscope that is small and highly accurate.

(Means for solving the problem) In order to achieve this object, the present invention includes a first X-direction piezoelectric element that expands and contracts in the X direction and a first Y-direction piezoelectric element that expands and contracts in the Y direction. A movable block in the X direction is moved in the X direction by the piezoelectric element in the X direction, and a movable block in the Y direction is moved in the Y direction by the piezoelectric element in the Y direction, which are combined to form the four sides of a rectangle.
The X-Z direction movable block and the Y-Z direction movable block are supported via a first Z-direction piezoelectric element and a second Z-direction piezoelectric element that extend and contract in the Z direction, respectively. X
- A central block is connected to the Z-direction movable block and the Y-Z-direction movable block by a second Y-direction piezoelectric element and a second X-direction piezoelectric element, respectively;
It constitutes a probe scanning mechanism for a scanning tunneling microscope. The probe is attached to the central block via a control piezoelectric element that expands and contracts in the Z direction. And the first and second X
a direction piezoelectric element, first and second Y direction piezoelectric elements,
The first and second Z-direction piezoelectric elements are configured to expand and contract under the same conditions.

(Operation) By configuring in this way, the first and second
When the Z-direction piezoelectric element is expanded or contracted, the X-Z direction movable block and the Y-Z direction movable block simultaneously move in the Z direction, and the center block also moves in the Z direction, so the probe moves in the N direction. . Therefore,
The probe can be brought close to the sample surface until a predetermined tunneling current is generated.

In this state, if the first and second X-direction piezoelectric elements are expanded or contracted, the center block will simultaneously move in the X-direction by the same amount as the X-direction movable block and the X-Z direction movable block. Therefore, the probe is
move in the direction. At this time, no influence is exerted on the Y-direction piezoelectric element and the Z-direction piezoelectric element.

Furthermore, by expanding and contracting the first and second Y-direction piezoelectric elements, the probe similarly moves in the Y-direction.

In this way, the probe can be moved very precisely in the X, Y, and Z directions.

Therefore, if the probe is moved in the X and Y directions while the first and second Z-direction piezoelectric elements are fixed at a constant length, and the control piezoelectric element is controlled so that the tunnel current is constant, the The irregularities on the sample surface can be observed depending on the control voltage at the time.

By configuring the probe scanning mechanism using piezoelectric elements and blocks in this way, the entire structure can be made small enough to be housed in the sample chamber of a scanning electron microscope. . Moreover, since a sufficient space is formed above the probe, it becomes possible to observe the sample surface located at the tip of the probe using a scanning electron microscope.

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

In the drawings, FIG. 1 is a perspective view showing one embodiment of a probe scanning mechanism of a scanning tunneling microscope according to the present invention, and FIGS. 2 and 3 are a plan view and a longitudinal side view thereof, respectively.

As is clear from these figures, the base 2 of the probe scanning mechanism 1 has a rectangular shape. At its four corners, there are fixed blocks 3, 4,
5 and 6 are fixed. Between the fixed blocks 3 and 6 and between the fixed blocks 4 and 5 forming the sides in the X direction, X direction movable blocks 7 and 8 are respectively provided so as to be movable in the X direction. One movable block 7 has a pair of X-direction piezoelectric elements X ₁ and X ₂ that expand and contract in the X-direction.
It is connected to fixed blocks 3 and 6 at both ends, respectively. In addition, the other movable block 8 has a pair of X-direction piezoelectric elements X ₃ and X ₄ that expand and contract in the X-direction.
It is connected to fixed blocks 4 and 5 at both ends, respectively.

These piezoelectric elements X ₁ to _{X 4} are all the same and are adapted to be applied with voltages of the same magnitude. However, _adjacent piezoelectric element
, X ₂ , X ₃ and X ₄ are applied with voltages of opposite polarity. Therefore, when one piezoelectric element X ₁ and X ₃ is expanded, the other piezoelectric element X ₂
and X ₄ contract by the same amount. In this way, the movable blocks 7, 8 are moved by these piezoelectric elements _X1 to _X4 .
are simultaneously moved by the same amount in the X direction. That is, these piezoelectric elements X ₁ to _{X 4} constitute a first X-direction piezoelectric element that moves the X-direction movable blocks 7 and 8 in the X direction.

Between fixed blocks 3 and 4 and between fixed blocks 5 and 6, which form sides in the Y direction perpendicular to the X direction, Y direction movable blocks 9 and 10 are respectively provided movably in the Y direction. One movable block 9 is connected to fixed blocks 3 and 4 at both ends, respectively, by a pair of Y-direction piezoelectric elements Y ₁ and Y ₂ that extend and contract in the Y direction. In addition, the other movable block 10 has a similar Y
It is connected to fixed blocks 6 and 5 at both ends by directional piezoelectric elements Y ₃ and Y ₄ , respectively.

These piezoelectric elements Y ₁ to _{Y 4} are also all the same, and just by making the adjacent piezoelectric elements Y ₁ and Y ₂ and Y ₃ and Y ₄ have opposite polarities, the same voltage can be applied. It is becoming more and more popular. Therefore,
When one piezoelectric element Y ₁ and Y ₃ expands, the other piezoelectric element Y ₂ and Y ₄ contracts by the same amount. In this way, these piezoelectric elements _Y1 to _Y4 constitute a first Y-direction piezoelectric element that simultaneously moves the Y-direction movable blocks 9, 10 by the same amount in the Y direction.

The X-direction movable blocks 7 and 8 have
First Z-direction piezoelectric elements Z ₁ and Z ₂ that expand and contract in the Z direction perpendicular to both directions are respectively attached. Furthermore, the Y-direction movable blocks 9 and 10 are provided with second Z-direction piezoelectric elements Z ₃ , which also expand and contract in the Z-direction.
Z ₄ is attached to each. These piezoelectric elements Z ₁ to _{Z 4} are all the same, and the same voltage is applied to them. Therefore, these piezoelectric elements Z ₁ to _{Z 4} are made to expand and contract in the Z direction under the same conditions, that is, at the same time and by the same amount.

X-Z direction movable blocks 11 and 12 are attached to the ends of the first Z direction piezoelectric elements Z ₁ and Z ₂ , respectively. Moreover, the second Z-direction piezoelectric element Z ₃ ,
Y-Z direction movable blocks 13 and 14 are attached to the ends of _Z4 , respectively. Therefore,
These X-Z direction movable blocks 11, 12 and Y
-Z direction movable blocks 13 and 14 are respectively
It is supported by direction movable blocks 7, 8 and Y direction movable blocks 9, 10, and
Direction piezoelectric elements Z ₁ , Z ₂ and second Z direction piezoelectric element
It is designed to be moved in the Z direction under the same conditions by Z ₃ and Z ₄ .

X-Z direction movable blocks 11 facing each other,
A central block 15 is provided at the center of the movable blocks 13 and 14 in the Y-Z directions.
This central block 15 has a second block extending and contracting in the X direction.
It is connected to the Y-Z direction movable blocks 13 and 14 by the X direction piezoelectric elements _X5 and _X6 , and
It is connected to the X-Z direction movable blocks 11, 12 by second Y-direction piezoelectric elements _Y5 , _Y6 which expand and contract in the X-Z direction. This second X-direction piezoelectric element X ₅ , X ₆
are constructed similarly to the first X-direction piezoelectric elements X ₁ , X ₂ and X ₃ , X ₄ . i.e. piezoelectric element x ₅
and X ₆ are the same as piezoelectric elements X ₁ to X ₄ ,
The same voltage as the piezoelectric elements X ₁ and X ₃ is applied to the piezoelectric element X ₅ , and a voltage of the same magnitude and opposite polarity is applied to the piezoelectric element X ₆ . In addition, second Y-direction piezoelectric elements Y ₅ , Y ₆
They are also configured similarly to the first Y-direction piezoelectric elements Y ₁ , Y ₂ and Y ₃ , Y ₄ .

In this way, the central block 15 is moved in the X direction under the same conditions as the X-direction movable blocks 7 and 8, and in the Y direction under the same conditions as the Y-direction movable blocks 9 and 10.

A control piezoelectric element _Z0 that expands and contracts in the Z direction is attached to the central block 15. Then, in the holder 16 provided at the end of the piezoelectric element _Z0 ,
A probe 17 can be attached.

The base 2 is provided with an opening 18 through which a sample stage on which a sample is placed is inserted.

In the probe scanning mechanism 1 configured in this way, when a constant voltage is applied to the first and second Z-direction piezoelectric elements _Z1 to _Z4 , these piezoelectric elements _Z1 to _Z4 expand and contract by a constant amount. The X-Z direction movable block 11,1
2 and the Y-Z direction movable blocks 13, 14 move by the same amount in the Z direction. At this time, the X direction and Y direction
The direction is not affected in any way. Therefore, the second X-direction piezoelectric elements X ₅ , X ₆ and the second Y
The direction piezoelectric elements _Y5 , _Y6 are the first X direction piezoelectric elements _X1 to _X4 and the first Y direction piezoelectric elements Y1 _{to Y6} , respectively.
kept parallel to Y ₄ . As a result, the central block 15 moves between the X-Z direction movable blocks 11, 12 and the Y
-Z direction It moves in the Z direction together with the movable blocks 13 and 14, and the position of the probe 17 in the Z direction,
In other words, the height changes.

With the probe 17 maintained at a predetermined height in this manner, the first and second X-direction piezoelectric elements X ₁ to _{X 6}
Apply a constant voltage to Then, one piezoelectric element,
For example, X ₁ , X ₃ , and X ₅ expand by a certain amount, and the other piezoelectric elements X ₂ , X ₄ , and X ₆ contract by the same amount. As a result, the X-direction movable blocks 7, 8 and the central block 15 move by the same amount in the X-direction. At this time, X
-Z direction movable blocks 11 and 12 also move together with X direction movable blocks 7 and 8. Therefore,
The Y and Z directions are unaffected.
In this way, the probe 17 is moved by a predetermined amount in the X direction.

Moreover, the first and second Y-direction piezoelectric elements Y ₁ to _{Y 6}
Similarly, when a constant voltage is applied to Y, the probe 17
direction by a predetermined amount.

Therefore, by appropriately changing the voltages applied to the X-direction piezoelectric elements _X1 to _X6 and the Y-direction piezoelectric elements _Y1 to _Y6 , the probe 17 can be caused to scan the XY plane.

The probe scanning mechanism 1 with such a configuration has a width of 2.5 cm on one side if the scanning range is approximately 1 μm x 1 μm.
It can be about the following. Therefore, as shown in FIG. 4, it can be installed within the sample chamber of a scanning electron microscope. Also,
By forming each of the blocks 3 to 15 from a light alloy such as aluminum, the whole becomes lightweight and its natural frequency can be increased to about 20 KHz. If the natural frequency of the probe scanning mechanism 1 is so high, the influence of external vibrations can be suppressed only by the vibration isolation mechanism of the scanning electron microscope. Furthermore, since the sample chamber of the scanning electron microscope is kept in a vacuum, by installing the probe scanning mechanism 1 within the sample chamber, thermal effects on the probe 17 can be eliminated.

When this probe scanning mechanism 1 is installed in a sample chamber of a scanning electron microscope, a coarse sample movement mechanism 21 is attached on a sample moving stage 20 of the electron microscope, as shown in FIG. The sample moving stage 20 is
- It is movable within the Y plane. The sample coarse movement mechanism 21 has a cylindrical guide 22 with a
It has two upper and lower discs 24, 25 connected by a piezoelectric element 23, and the discs 24, 2
5 is adapted to be locked to or released from the guide 22 by piezoelectric elements 26 and 27, respectively. A sample stand 28 is provided on the upper disk 24, and a sample 2 is placed on the upper surface of the sample stand 28.
9 is now placed.

Therefore, the lower disk 2 of the sample coarse movement mechanism 21
5 to the guide 22 and move the upper disc 24 away from the guide 22 to expand and contract the piezoelectric element 23. Next, move the lower disc 25 away from the guide 22 and move the upper disc 24 to the guide 22. By repeating the operation of locking and expanding and contracting the piezoelectric element 23, the sample 29 is moved up and down, that is, in the Z direction.

The base 2 of the probe scanning mechanism 1 is a sample coarse movement mechanism 2.
It is attached to the upper end surface of the guide 22 of No. 1. At this time, an electron beam 31 emitted from the objective lens 30 of the electron microscope is transmitted from above any one of the fixed blocks 3 to 6 of the probe scanning mechanism 1 to the second X-direction piezoelectric elements X ₅ , X ₆ and the second The surface of the sample 29 near the tip of the end needle 17 is irradiated through the space between the two Y-direction piezoelectric elements Y ₅ and Y ₆ , and the secondary electrons 32 emitted from the sample 29 are transmitted to the opposite side. X-direction piezoelectric element X ₆ ,
The secondary electron detector 33 is made to be reached through the space between X ₅ and the Y-direction piezoelectric elements Y ₆ and Y ₅ . X
Direction piezoelectric elements X ₅ , X ₆ and Y direction piezoelectric elements Y ₅ , Y ₆
are just combined into a cross, so
Such a space can be sufficiently secured.

The cylindrical guide 22 of the sample coarse movement mechanism 21 is fixed at an arbitrary position by a piezoelectric clamping element 34 attached to a fixed part of the electron microscope.

When observing the sample 29 using such a microscope, first, the sample coarse movement mechanism 21 moves the sample 29 in the Z direction to position it within a range that can be observed using the electron microscope. Next, by moving the sample moving stage 20, the sample 29 is
The probe 17 is moved within a plane so that the place to be observed is located at the tip of the probe 17. In this state, the guide 22 of the sample coarse movement mechanism 21 is fixed by the clamping piezoelectric element 34, and the sample 29 is
- Position within the Y plane.

Next, the sample coarse movement mechanism 21 is activated, and the probe 17
The sample 29 is brought close to the probe 17 until a tunnel current is generated between the probe 17 and the sample 29. Further, a voltage is applied to the Z-direction piezoelectric elements Z ₁ to _{Z 4} of the probe scanning mechanism 1, and the position of the probe 17 in the Z-direction is finely adjusted so that the tunnel current becomes a predetermined value.

In this state, the electron beam 31 is scanned and the surface of the sample 29 is observed using a scanning electron microscope.
Then, the probe 17 is positioned at a location to be further enlarged and observed. For this purpose, appropriate voltages may be applied to the X-direction piezoelectric elements X ₁ to X ₆ and the Y-direction piezoelectric elements Y ₁ to _{Y 6} of the probe scanning mechanism 1.

When observing the sample 29 with a scanning tunneling microscope, the probe 17 is centered at the current position along the surface of the sample 29, that is, X-
The probe 17 is scanned within the Y plane. And probe 1
A control voltage is applied to the control piezoelectric element Z ₀ so that the tunnel current generated between the sample 7 and the sample 29 is kept constant, and the control voltage is subjected to image processing.

In this way, the same sample 29 is placed at the same position.
Observations can now be made using a scanning electron microscope and a scanning tunneling microscope.

In the above embodiment, the base 2 is assumed to be rectangular, but the base 2 may have any shape such as a circle.

(Effects of the Invention) As is clear from the above description, according to the present invention, a movable block in the X direction is moved in the X direction by a piezoelectric element in the X direction, and a movable block in the Y direction is moved in the The Y-direction movable block is moved in the X-Z direction via the Z-direction piezoelectric element.
A direction movable block and a Y-Z direction movable block are supported by a Y-direction piezoelectric element connected to the X-Z direction movable block and an X-direction piezoelectric element connected to the Y-Z direction movable block. , the central block to which the probe is attached is supported, so the probe can be moved in the X direction, Y direction,
It becomes possible to independently move them in the and Z directions, and the position can be controlled accurately and easily.

Furthermore, since the probe scanning mechanism is constructed of only the fixed block, movable block, and piezoelectric element, the entire structure can be made lighter and smaller. Therefore, it becomes possible to install it inside the sample chamber of a scanning electron microscope. Furthermore, since a sufficient space is formed above the probe, the tip of the probe can be observed using an electron microscope. By doing so, the same position of the same sample can be easily observed using both a scanning electron microscope and a scanning tunneling microscope, dramatically increasing the usefulness of the tunneling microscope. be enhanced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the probe scanning mechanism of a scanning tunneling microscope according to the present invention, FIG. 2 is a plan view of the probe scanning mechanism, and FIG.
Figure 4 is a vertical cross-sectional side view of the probe scanning mechanism taken along the - line in the figure, Figure 4 is a vertical front view showing the sample chamber of the scanning electron microscope in which the probe scanning mechanism is installed, and Figure 5 is , is a perspective view showing an example of a conventional probe scanning mechanism. 1... Probe scanning mechanism, 2... Base, 3, 4, 5,
6... Fixed block, 7, 8... X direction movable block, 9, 10... Y direction movable block, 11, 12
...X-Z direction movable block, 13, 14...Y-Z
Directional movable block, 15...Central block, 17...
Probe, 28...Sample stand, 29...Sample, _X1 to _X4 ...First X-direction piezoelectric element, _X5 , _X6 ...Second X-direction piezoelectric element, _Y1 to _Y4 ...First Y Directional piezoelectric element, Y ₅ ,
_Y6 ...Second Y-direction piezoelectric element, _Z0 ...Control piezoelectric element, _Z1 , _Z2 ...First Z-direction piezoelectric element, _Z3 , _Z4 ...Second Z-direction piezoelectric element.

[Claims]

1. When a magnetic disk is rotated at a predetermined number of rotations and a magnetic head running at a small gap from the disk surface comes into contact with a protrusion present on the disk surface, the magnetic head attached to the slider arm of the magnetic head Peak voltage Vp of the output signal voltage generated by the acoustic emission sensor
The product Vp・R of the distance R from the disk rotation center of the protrusion that generated the peak voltage is calculated, and the Vp・R value obtained when the magnetic disk is rotated at the specified rotation speed and A method for measuring the height of a protrusion on a magnetic disk surface, characterized in that the height of the protrusion that provides the calculated Vp/R value is determined from a relationship diagram with the protrusion height.

Claims (1)

a central block connected to the X-Z direction movable block by a second Y-direction piezoelectric element; The probe is attached to the central block via a piezoelectric element, and the probe is connected to each of the X-direction piezoelectric elements or the Y-direction piezoelectric element.
By applying a scanning voltage to the directional piezoelectric element
- A scanning tunnel that is scanned in the Y plane and whose distance to the sample surface is adjusted by applying a control voltage to the Z-direction piezoelectric element or the control piezoelectric element. Microscope probe scanning mechanism.