JPH0771912A - Fine adjustment, and scanning type probe microscope - Google Patents

Abstract

PURPOSE:To provide a fine adjustment capable of precisely grasping the moving coordinate of a device having a piezoelectric fine adjustment mechanism in a device finely moving in atomic scale. CONSTITUTION:One end surface vertical to a cylinder axis (Z-axis) of a piezoelectric ceramic 1 is fixed, an optical path device 2 for emitting three or more focused beams in total in parallel to the X and Y-axes of the cylinder is fixed to the other end surface, three or more light receivers 6a, 6b, 6c in total for receiving the focused beams emitted from the optical path device 2 are fixed close to the cylinder, and the change in the focused beam receiving position of the three or more light receivers is detected, thereby, the fine movement coordinate value by piezoelectric distortion is measured and recorded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a fine movement device for fine movement on an atomic scale and a scanning probe microscope fine.

[0002]

2. Description of the Related Art In recent years, a scanning probe microscope which is a probe type surface roughness meter utilizing the quantum effect has been noticed and developed as a suitable means for observing the state of a solid surface on an atomic scale. The scanning probe microscope includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), a magnetic force microscope (MFM), etc., depending on its operating principle. In both cases, the sharply pointed probe is brought very close to the sample surface, and at this time, the quantum effect that acts between them is used to keep the distance between them constant, and the movement of the probe that scans the sample is continuously captured. Thus, the uneven shape of the sample surface is measured on an atomic scale.

ST, which is a typical scanning probe microscope
M utilizes a phenomenon in which a tunnel current flows in the vicinity of about 1 nm when a voltage is applied between a metal probe such as an electrolytically polished tungsten wire and a conductive sample to bring them close to each other. Since the tunnel current value is sensitive to the distance between the two,
If the sample surface is two-dimensionally scanned while controlling the movement of the probe so that the current value becomes constant, a magnified image of the uneven shape of the sample surface can be obtained.

When detecting irregularities on an atomic scale, the distance required for scanning a sample ranges from several to several tens of μm. Therefore, a coarse position drive system and a fine position drive system are provided as scanning means.

The fine position drive system controls the movement of the probe on the order of nm, and uses X, which utilizes piezoelectric ceramics, etc.
A Y- and Z-axis orthogonal arm type or a cylindrical element is used. FIG. 5 shows a typical shape.

The tripod (tripod) type fine movement element 1 shown in FIG. 5A is a combination of three laminated piezoelectric elements 1a, 1b and 1c each having a length of several mm to several tens of mm. Each of the piezoelectric elements 1a, 1b, 1c is formed by stacking a plurality of individual elements including a piezoelectric portion and upper and lower electrodes provided on both sides of the piezoelectric portion. It has a function of expanding and contracting in the longitudinal direction when a voltage is applied between the electrodes. On the other hand, the tube type fine movement element 1 shown in FIG. 5 (B) has a diameter of several mm and a length of several mm.
The tens of millimeters hollow cylinder 1d is composed of piezoelectric ceramics, and is polarized so that the cylinder contracts when a voltage is applied between the inner and outer electrodes (hatched portions in the figure) 1e to 1g. The inner electrode 1h is common, the outer electrode 1g for the Z axis performs a simple contraction, but the electrodes 1e, 1f for the X axis and the Y axis are each divided into two, and voltages of opposite polarities. It has a function of causing a deflection of the cylinder by causing a displacement in a direction perpendicular to the Z axis.

As compared with the tripod type shown in FIG.
Since the tube type of (B) has excellent responsiveness and symmetry, it has been widely used recently, and the fine movement device of the present invention also uses this type of element.

In the tube type fine movement element, the upper end surface of the cylinder is fixed, and a predetermined voltage is applied between the electrodes to move the lower end surface of the cylinder which is a free surface. With a scanning probe microscope,
A probe is provided on this movement side to perform fine movement of the probe. Figure 5
In (B), for the sake of explanation of the principle, an example in which the x, y, and z electrodes are formed at different positions on the cylinder is shown. Recently, however, what is actually used is x, y, and z as shown in FIG. It is a three-electrode integrated type that integrates z electrodes. This type is X axis, Y
The electrodes on the circumference of the piezoelectric ceramic cylinder 1d are divided into four in order to be able to apply a voltage in the axial direction (only two electrodes 1i and 1j on the front side are disclosed in the figure, but the same applies to the back side). Two electrodes are provided), and when expanding and contracting in the Z-axis direction, all the outer peripheral upper electrodes 1i, 1j,
... and a voltage is applied to the inner peripheral electrode 1k.

PZT or the like is used for the piezoelectric ceramics, which is the material of the cylinder 1d, and it has a predetermined displacement with respect to the applied voltage.

[0010]

In the above-mentioned conventional piezoelectric fine movement element, it is known that the displacement amount with respect to the drive voltage has a non-linearity when operating at a large amplitude. Also,
It has been reported that a hysteresis phenomenon occurs between the applied voltage and the amount of strain, and a relaxation phenomenon called creep after applying a large voltage. Further, in the case of the tube type fine movement element shown in FIGS. 5 and 6, since one end face (upper end face) perpendicular to the cylindrical Z axis is fixed, movement of the lower end face in the X and Y axis directions is performed in each axis. Accompanied by rotation (distortion) around.

Therefore, in the scanning probe microscope in which the probe is fixed to the free end surface (lower end surface) of the tube type fine movement element, the applied voltage to each related electrode is proportionally changed to move the sample surface in the X and Y directions. When observing the uneven shape by scanning,
There is a problem that the image is distorted without correction.

In order to address this, conventionally, a XY pattern is obtained by using a test pattern whose accurate length and angle are known in advance.
The plane was scanned and the correction coefficient of the displacement amount with respect to the applied voltage was obtained. However, it is difficult to accurately calibrate the coordinate position because the nonlinearity and the hysteresis phenomenon change depending on the voltage value at the start of driving and the maximum applied voltage, and there is creeping.

An object of the present invention is to provide a fine movement device capable of accurately grasping movement coordinates.

Another object of the present invention is to provide a scanning probe microscope capable of obtaining a distortion-free observation image by performing coordinate calibration while scanning the sample surface with a probe.

[0015]

The present invention has a hollow cylindrical shape, and one end surface perpendicular to the cylindrical axis (Z axis) is fixed,
In a fine movement device in which the other end surface perpendicular to the Z-axis performs a slight movement of translation and / or rotation by an external force acting on the cylinder, a total fixed in parallel to the X-axis or Y-axis direction of the cylinder fixed to the other end surface. An optical path device for emitting three or more focused beam lights, and a total of three or more light receivers provided independently near the optical path device for respectively receiving the focused beam lights emitted from the optical path device, There is provided a fine movement device comprising means for detecting changes in the focused beam light receiving positions of three or more light receivers and calculating coordinate values due to the fine movement.

Further, according to the present invention, the hollow cylinder is formed of a piezoelectric material, and one end surface perpendicular to the cylinder axis (Z axis) is fixed,
Electrodes are provided on the circumferential surface of the cylinder, and by applying a voltage between these electrodes, the end of the other cylinder perpendicular to the Z-axis performs a fine movement of translation and / or rotation, An optical path device fixed to the optical path device for emitting a total of three or more focused beam lights in parallel to the X-axis or Y-axis direction of the cylinder, and an optical path device independently provided near the optical path device and emitted from the optical path device. A total of three or more light receivers for respectively receiving the focused beam lights, and means for detecting a change in the focused beam light receiving positions of the three or more light receivers to calculate coordinate values due to the minute movement. And a fine movement device.

Further, according to the present invention, in the above-mentioned light receiver, the light receiving surface is divided into at least four, and the change in the light receiving position can be detected by the magnitude of the photoelectromotive force on the divided light receiving surface.

Further, the present invention is characterized in that, in the scanning probe microscope using the fine movement device, the voltage applied between the electrodes is controlled by feeding back the measured change of the focused beam light receiving position. A scanning probe microscope is provided.

[0019]

When a voltage is applied between the piezoelectric ceramic cylindrical electrodes having the above construction, the optical path device fixed to the lower end surface of the cylinder also moves in the same manner as the lower end surface. As a result, the position and direction of the focused beam light emitted from the optical path device changes, and the light receiving portions on the light receiving surfaces of the light receivers provided close to each other move. This change in the light receiving portion includes information about translation and / or rotation of the lower end surface of the cylinder, and thus the probe. It can also be applied to the fine movement side due to external force other than piezoelectric.

Therefore, by detecting the light receiving position change on the light receiving surface of each of the light receivers and performing the calculation in consideration of the geometrical relative positional relationship, it is possible to obtain the corrected accurate moving coordinate of the fine motion device probe. it can. If an observation image of the scanning probe microscope is output based on this moving coordinate, distortion-free data can be obtained.

[0021]

EXAMPLES The present invention will be described in detail below based on examples. FIG. 1 is a perspective view of a main part of a fine movement device according to an embodiment of the present invention. In the figure, 1 is a tube-type piezoelectric element, 2
Is a beam path device fixedly attached to the lower end side thereof, 3a and 3b are beam splitters provided in the light path device 2, 4 is a laser light source, 5 is one end fixedly connected to the laser emission hole of the laser light source 4, and the other end is Optical fibers 6a to 6c fixedly connected to the entrance hole of the optical path device 2 are light receiving elements provided near the optical path device 2 for receiving the laser light from the beam splitters 3a and 3b. The light-receiving elements 6a to 6c are installed independently of the piezoelectric element 1 and the optical path device 2, and do not move even if the piezoelectric element 1 and the optical path device 2 integrally move.

The upper end surface of the tube-type piezoelectric element 1 perpendicular to the Z axis is fixed to a holder (not shown). The optical path device 2 has a hollow cylindrical shape, and as shown in the drawing, two beam splitters 3a in which the laser light incident from the laser light source 4 through the optical fiber 5 passes through the inside (for example, the center) thereof and is parallel to the X axis. 3b are provided along the X-axis direction and perform beam splitting of the incident laser light. The beam splitters 3a and 3b are illustrated as right-angled prisms for the sake of simplicity, but they are usually in the shape of a cube in which the slopes of isosceles right-angled prisms are combined. A thin air layer of about λ / 3 is interposed on the slope, or a semi-permeable film is coated on the slope of one prism and an antireflection film is coated on the slope of the other prism. The laser light incident on the beam splitters 3a and 3b is reflected light and transmitted light on the slope. In this configuration, one laser light is divided into three, so that 3a is divided into 1: 2 and 3b is divided into 1: 1. It

The optical path device 2 is provided with appropriate holes 2a, 2b, 2c through which the transmitted light of the beam splitter 3b and the reflected light of 3a, 3b can be emitted as shown in the figure. The laser light reflected in the Y-axis direction by the beam splitter 3a is on the light-receiving surface of the light receiver 6b, and the laser light reflected in the Y-axis direction by 3b is on the light-receiving surface of the light receiver 6a. The laser light in the X-axis direction that has passed through is incident on the light receiving surface of the light receiver 6c and converted into a voltage.

The light receiving surfaces of the light receivers 6a to 6c are divided into, for example, four parts as shown in FIG. 2 in order to clearly capture the change in the light receiving position, and the electromotive force value is measured separately for each area. It

As shown in FIG. 2, when no voltage is applied to the piezoelectric ceramics of the fine movement device, the laser beam spot 9a is evenly received by each of the regions 8a to 8d of the photodetector. It is set to come to the center of.
Each photovoltaic V _a ~V _d in each area 8a~8d
Will be represented by.

When a voltage is applied between the piezoelectric ceramic electrodes of the fine movement device, the lower end surface of the tube-shaped piezoelectric element shown in FIG. 1 moves in a predetermined direction according to the selected electrode and the magnitude of the applied voltage. The emission direction and position of each laser beam change accordingly. This appears as a displacement of the laser light spot on the light receiving surface of the light receiver, for example, as indicated by 9b shown by the dotted line in FIG. In this case, when the coordinates of the light receiving surface of the light receiver are represented by (h, v) as shown in the figure, the laser light spots are 9a to 9a.
changes arising out of the move to b is horizontally by the photodetector _{(V c + V d) -} (V a + V b) as a change in, also in the vertical direction _{(V a + V c) -} (V b + V d) Will appear as a change.

Therefore, if the displacement of the laser beam spot is measured in advance for each of the light receiving elements 6a to 6c and the relationship of the above-mentioned change in photovoltaic power is measured, each light receiving element corresponds to the amount of displacement of the tube type piezoelectric element. coordinate values (h, v), i.e. _{(h a, v a),} (h b, v b), it is possible to determine the (h _c, v _c).

Next, using these (h, v) coordinate values, the displacement amount of the tube-type piezoelectric element, that is, the coordinate value (x,
A method for automatically obtaining y, z, θ _x , θ _y , θ _z ) by a microcomputer (not shown) will be described.

FIG. 3 is an X-Y plan view showing the relative position between the optical components shown in the perspective view of FIG. The origin of the coordinates is set in the center of the piezoelectric ceramic cylinder and on the plane where the three laser beams are present. θ _x is a minute rotation angle around the x axis, θ _y is a minute rotation angle around the y axis, and the distances l _{1 to} l ₅ are defined as follows. l ₁ ... distance from the origin of the beam splitter 3b in the x-axis direction, l ₂ ... distance from the origin of the beam splitter 3a in the x-axis direction, l ₃ ... distance from the origin of the beam splitters 3a, 3b in the y-axis direction, l ₄ ... Distance of the light receiving elements 6a and 6b from the origin in the y-axis direction, l ₅ ... Distance of the light receiving element 6c from the origin in the x-axis direction. In addition, for the sake of simplicity, the minute rotation angle θ _z about the Z axis is ignored at first.

The coordinates (h, v) in each of the light receivers 6a to 6c are expressed by the following equations from the geometrical relation.

[Equation 1]

[Equation 2]

[Equation 3]

As a result, each displacement amount of the lower end surface of the tube-type piezoelectric element 1 is

[Equation 4]

[Equation 5]

[Equation 6]

[Equation 7]

[Equation 8]

Next, when the minute rotation angle θ _z about the Z axis is a size that cannot be ignored, h _a to h _c in the above (Equation 1) to (Equation 3) are the following (Equation 9) to It becomes like (Equation 11). However, v _a, v _b, for v _c are as (number 1) through (3).

[0033]

[Equation 9]

[Equation 10]

[Equation 11] From (Equation 9) and (Equation 10), θ _z can be obtained from the following equation.

[Equation 12]

The plus / minus sign of θ _z is selected by substituting (Equation 12) into (Equation 9) and (Equation 10) to obtain x from the respective equations, and the voltage applied to the tube-type piezoelectric element 1 or the like. In consideration of the above, decide the one that does not cause contradiction. By substituting this θ _z into (Equation 11), y can be obtained.

FIG. 4 is an XY plan view showing the arrangement of optical components in another embodiment of the present invention. In the case of this embodiment,
A beam splitter that radiates transmitted light in the X-axis direction and two reflected lights in opposite directions along the Y-axis at the central portion of the optical path device 2 fixed to the lower end surface of the piezoelectric ceramic cylinder. (Not shown) is installed. That is, the laser light emitted from the laser light source 4 is divided into three directions at the coordinate origin via the optical fiber 5, is emitted from the hole (not shown) of the optical path device 2, and is respectively received by the light receivers 6a to 6c. The light is received and converted into photovoltaic power.

When the tube type piezoelectric element 1 is slightly displaced by (x, y, z, θ _x , θ _y , θ _z ) by applying a voltage to each electrode, a laser beam spot on the light receiving surface of the light receiving elements 6a to 6c. The position change coordinate (h, v) of is expressed by the following formula. However, as the light receiving elements 6a to 6c, those shown in FIG. 2 are used as they are.

[Equation 13]

[Equation 14]

[Equation 15]

From (Equation 13) to (Equation 15), the following equation is established.

[Equation 16] Therefore,

[Equation 17]

The displacement coordinates of the fine movement device obtained as described above are applied to a scanning probe microscope when a probe is fixed along the Z axis at the center of the lower surface of the optical path device 2 of the present fine movement device. Gives an accurate value without distortion. Therefore, if the two-dimensional information obtained by scanning the sample surface with the probe is stored as it is and output to the display, an observation image of the surface without distortion can be obtained.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, in the above-described embodiment, the laser light for displacement measurement is introduced into the optical path device by the optical fiber and is divided into each direction by the beam splitter. However, three laser diodes each emitting a beam in each of the three directions are previously provided in the optical path device. It can also be prepared together with the fine movement device. Further, the focused beam is not limited to the laser beam, and spontaneous emission light focused by a lens can be used. Further, it will be apparent from the above description that the number of focused beams in the optical path device may be any number as long as it is three or more.

The external force acting on the cylindrical fine movement device is piezoelectric strain in the above-mentioned embodiment, but it is not limited to this. For example, it may be magnetostriction or mechanical vibration.
When driving the microscope, there are a probe driving example and a sample driving example, but the fine movement apparatus of this embodiment may be used for either.

[0041]

As described above, according to the present invention, it is possible to accurately grasp the displacement coordinate of the free end surface caused by the external force acting on the cylindrical fine movement device having one end fixed. In particular, in the case of a tube type piezoelectric element in which the cylinder of the fine movement device is composed of piezoelectric ceramics and translates and rotates due to piezoelectric strain generated by an applied voltage, a scanning probe microscope is provided by fixing a probe on its free end surface. The sample surface can be observed without distortion because it can be used in the micro-moving device.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a tube-type piezoelectric element according to an embodiment of the present invention.

FIG. 2 is a diagram showing the light receiving surface of the light receiver shown in FIG. 1 and the positions of laser light spots.

FIG. 3 is an explanatory diagram of a displacement detection method for the element shown in FIG.

FIG. 4 is an XY plan view showing an optical component configuration of a tube-type piezoelectric element according to another embodiment of the present invention.

FIG. 5 is a diagram showing a typical shape of a fine movement element for STM.

FIG. 6 is a diagram showing a conventional tube-type piezoelectric element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube type piezoelectric element 2 Optical path device 3a, 3b Beam splitter 4 Laser light source 5 Optical fiber 6a, 6b, 6c Light receiving element

Claims (4)

[Claims] 1. A hollow cylindrical shape having a cylindrical axis (Z axis).
In the fine movement device, one end surface of which is perpendicular to the cylinder is fixed, and the other end surface of which is perpendicular to the Z-axis performs a slight movement of translation and / or rotation by an external force acting on the cylinder. And an optical path device for emitting a total of three or more focused beam lights parallel to the axis or the Y-axis direction, and a total for independently receiving the focused beam lights emitted from the optical path device provided independently in the vicinity of the optical path device. 3 or more receivers,
A fine movement device comprising: a means for detecting a change in the receiving position of the focused beam light of the light receiving device of the above number or more to calculate a coordinate value by the fine movement. 2. A hollow cylinder is formed of a piezoelectric material, one end surface perpendicular to the cylinder axis (Z axis) is fixed, electrodes are provided on the circumferential surface of the cylinder, and a voltage is applied between these electrodes. In the fine movement device in which the end of the other cylinder perpendicular to the Z-axis makes a slight movement of translation and / or rotation, a total of three parallel to the X-axis or the Y-axis direction of the cylinder fixed to the end of the other cylinder. An optical path device for emitting the above focused beam light, a total of three or more light receivers provided independently in the vicinity of the optical path device for respectively receiving the focused beam light emitted from the optical path device, and the three optical receivers. A fine movement device comprising the above-mentioned means for detecting a change in the receiving position of the focused beam light of the light receiver and calculating a coordinate value by the fine movement. 3. The light receiving surface of the light receiver is divided into at least four, and a change in the light receiving position can be detected by the magnitude of the photoelectromotive force on the divided light receiving surface. Fine movement device. 4. A scanning probe microscope using the fine movement device according to claim 2, wherein the voltage applied between the electrodes is controlled by feeding back the measured change in the focused beam light receiving position. A scanning probe microscope characterized by the above.