JPH07198359A - Fine movement mechanism and scanning probe microscope - Google Patents

Abstract

PURPOSE:To provide an apparatus in which the coordinates of fine displacements in the X-axis direction, the Y-axis direction and the Z-axis direction can be specified with high accuracy regarding a fine movement mechanism which is provided with the detection system of the fine displacements. CONSTITUTION:A fine movement mechanism is composed of a flexible system which is provided with a fixed end fixed to, and installed at, an outer wall and with a free end which is moved fine by an external force and of three pairs of detection systems in which outer spherical mirrors 10x, 10y, 10z are installed at the free end, in which beams of focused light radiated from focused-beam light sources 11x, 11y, 11z fixed to an outer wall are reflected by the outer spherical mirrors 10x, 10y, 10z so as to be incident on two-split light-receiving face-type photodetectors 12x, 12y, 12z and which photoelectrically convert the beams of focused light so as to be output. An electromotive force which is detected in every region of two-split light-receiving faces is input to a differential amplifier, and its output is converted into a coordinate value. Thereby, fine movements in the X-axis direction, the Y-axis direction and the Z-axis direction can be detected with high sensitivity. When a probe or a sample stand is fixed to, and installed at, the fine movement mechanism, the mechanism can be utilized for a scanning probe microscope.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine movement mechanism equipped with a detection device for minute displacements and a scanning probe microscope using the same.

[0002]

2. Description of the Related Art A scanning tunneling microscope has been developed as a means for observing the surface of an object more finely. A tunnel microscope is a phenomenon in which electrons can come and go between two conductors when the two conductors are brought close to the atomic size (nm size) by focusing on the “bleeding out” of the electron's wave function in a solid. Are using. In the case of a clean metal surface, the tunnel current flowing between both conductors flows about 1 nA when approaching 1 nm, and the current value at which the distance between the conductors increases or decreases by 0.1 nm decreases by one digit. The scanning tunneling microscope scans the sample surface by maintaining the probe-sample distance so that the tunnel current value flowing between both conductors (between the metal probe and the sample to be measured) becomes constant. This is a mechanism for observing the surface roughness image of the sample.

Therefore, there is required a technique for controlling the movement of the probe while finely moving it with a precision of 0.1 nm. Since the development of the scanning tunneling microscope (STM), another surface roughness meter utilizing the quantum effect acting between the probe and the sample has been developed. Typical examples thereof are an atomic force microscope (AFM) and a magnetic force microscope (MFM).

The AFM utilizes an attractive force or a repulsive force based on a dispersion force acting between non-polar objects and is suitable for observing the surface of a non-conductive object. Further, the AFM is for observing magnetic domains and domain walls of a magnetic material sample and utilizes magnetic attractive force and repulsive force. Each of these quantum effect microscopes uses two
While scanning dimensionally, the surface roughness (or characteristic difference) of nm size is to be measured by the trajectory of the vertical movement of the probe, which is generically called a scanning probe microscope (SPM).

In the scanning probe microscope, a fine movement mechanism is used for accurately grasping the fine movement position of the probe and controlling the movement thereof. The fine movement mechanism normally has one end fixed to the fixed portion (outer wall) of the microscope, and the external force is applied directly to a flexible jig with the other end having a probe in a free state, so that the Z-axis direction (probe / X axis perpendicular to the Z axis
There are a type in which the probe is moved in the -Y plane direction, and a type in which a device that is slightly moved by the action of an external force is sandwiched between the outer walls. In any case, in order to grasp and control the movement of the probe, a drive system for operating the probe with an accuracy of 0.1 nm or less and a detection system for quantitatively detecting the movement are required. .

The minute driving system often controls the movement by utilizing the relationship between the piezoelectric strain of the piezoelectric ceramics element and the applied voltage. As the detection system, in the case of STM, a device that electrically amplifies the tunnel current value is used, but in AFM and MFM, the movement of the free end of the flexible jig that is bent by the quantum force acting on the probe is expanded. A capture device is used.

The free end displacement measuring method includes a tunnel detection method using an STM probe, a light wave interference method using multiple interference of light, and light reflection at the free end which is received at a remote position and photoelectrically converted. An optical lever method and a piezo method using a strain sensor have been proposed and partially put into practical use.

[0008]

Among the detection systems in the fine movement mechanism of the SPM described above, the piezo system in which the displacement detection sensor is directly installed in the flexible system is disclosed in, for example, Japanese Patent Publication No. 4-7250.
As described in No. 4, a piezoelectric thin film element is formed on the upper surface of the cantilever, and a phenomenon in which the current flowing through the element changes due to piezoelectric strain is amplified and detected. There is also an attempt to detect by photoelectrically converting and amplifying the amount of change in the amount of light passing through the thin film optical path attached to the lower surface of the cantilever due to the displacement of the cantilever.

However, in these methods, the resolution is 1n.
It is difficult to detect displacement below m. A method of attaching a high-precision displacement gauge such as a laser displacement gauge to a flexible jig can be considered to increase the resolution, but this is not realistic because it miniaturizes the flexible jig and significantly impairs the minute driving capability.

Of the SPM detection systems described above, the method that does not directly contact the flexible jig is highly practical. However, in the tunnel detection method in which the tunnel current probe is placed close to the back surface of the cantilever, the detection sensitivity is limited because the force is exerted on the lever through various molecules adsorbed on the lever surface, and its operation becomes unstable. There is a drawback. On the other hand, in light wave interferometry and optical lever method using light, the radiation pressure of light is very small (radiation pressure of light of 1 mW is 7 × 10 ^-12 N) and the force of the detection system exerted on the lever is actually Can be ignored.

However, since the detection system using light uses photoelectric conversion as a photodetector, if the change in light quantity is small, S
The / N ratio decreases and the movement of the flexible jig cannot be captured with sufficient accuracy. As a result, a burden is placed on the flexible jig. That is, a flexible jig having high followability with respect to the surface unevenness of the sample to be measured is required. For this reason, the sharpness of the tip shape of the probe, the material of the flexible support portion, the film thickness, and the mechanical strength become problems, and the processing accuracy and durability of the flexible jig often become difficult. Has been done.

As a method of detecting a one-dimensional minute displacement by forming a small and highly sensitive detection system using the optical lever method, a combination of a cylindrical reflecting mirror and a semiconductor optical center of gravity position detecting element (PSD) is used. Is disclosed (Kitashima et al .; Journal of Precision Engineering, PP131-133, November 1993). In this method, a focused beam light is made incident on the reflecting mirror from a certain direction of an XY plane perpendicular to the straight axis of the cylindrical reflecting mirror, the reflected light is received by a PSD, and photoelectric conversion is performed to measure the output. . When the reflecting mirror shifts at a right angle to the incident direction, the light reflection point shifts. Therefore, a shift magnified by the optical lever method occurs at the light receiving point on the PSD and is highly sensitively detected as the displacement of the optical center of gravity.

An object of the present invention is to provide a three-dimensional small high-sensitivity fine movement mechanism that can be used for SPM by utilizing the high-sensitivity position detecting method using the optical lever method.

Another object of the present invention is to provide an SPM incorporating the above-described fine movement mechanism with high detection sensitivity, and disclose a method for controlling the fine movement position thereof.

[0015]

According to the present invention, a flexible system having a fixed end fixed to the outer wall and a moving end finely moved by the action of an external force, and a flexible system fixed at a predetermined position outside the flexible system at a predetermined interval. Three pairs of focused beam light sources and two split light receiving surface type light receiving elements, and each focused beam light emitted from the focused beam light source which is fixed at a predetermined position of the moving end and is reflected to the two split light receiving surface type light receiving element. And three spherical or cylindrical mirrors each having a function of making incident light, and three displacements in the X-, Y-, and Z-axis directions associated with the fine movement of the moving end are provided for each of the two light-receiving surface type light receiving elements. Provided is a fine movement mechanism that detects a change in output difference in each light receiving surface area.

In the present invention, the fine movement mechanism is used to fix a probe or a sample table at a part of the moving end, and the output difference in each light receiving surface area of the three divided light receiving surface type light receiving elements is three. There is provided a scanning probe microscope having a function of controlling the fine movement mechanism of the probe by feeding back the displacements of the moving end in the X, Y, and Z-axis directions detected as changes in the above, and controlling the external force.

The focused beam light is preferably laser light. Further, the flexible system may be composed of a hollow piezoelectric ceramic cylinder having electrically independent drive electrodes arranged on the inner circumference and the outer circumference.

The present invention relates to the detection of minute positions using the optical lever method. Three spherical or cylindrical mirrors for reflecting the focused beam light are fixedly provided at the moving end of the fine movement mechanism, and three light receiving elements for receiving the respective reflected beam lights at a distance L from the reflecting surface are provided. By using a two-divided light receiving surface type light receiving element, a small displacement in one axis direction is detected by a combination of a pair of focused beam light sources and light receiving elements.

That is, in order to detect displacement in the X-axis direction, a light-receiving element whose light-receiving surface is divided into two along the Z-axis and a focused beam light source are installed substantially in the Y-axis direction, and conversely for detecting displacement in the Y-axis direction. In this case, a light-receiving element whose light-receiving surface is divided into two along the Z-axis and a focused beam light source are installed substantially in the X-axis direction. Further, for Z-axis direction displacement detection, a light receiving element having a bisecting line in an XY plane perpendicular to the Z axis and a focused beam light source are provided in directions different from the biaxial direction, for example, in X and Y directions. Install in a direction inclined by 45 degrees from each axis.

When a cylindrical mirror is used, its major axis may be oriented in the Z-axis direction for X and Y movement, and may be oriented in the XY plane for Z axis movement. Installed at the moving end of the flexible system.

When the movable end of the flexible system is minutely moved in an arbitrary direction by the action of an external force, the movement is decomposed into the amount of movement in each axial direction by the X, Y and Z axial fine movement detecting systems. Be punished. No matter which direction the moving end is slightly moved, the curvature about the major axis of the spherical mirror or the cylindrical mirror for each axis is always constant (r ₀ ), so the displacement amplified by the optical lever method is divided into the two parts. It is electrically differentially amplified as the output difference on the light receiving surface, and can be accurately detected as the movement amount of each axis. In order to use the optical lever method more effectively, multiple reflections may be used by preparing a plurality of the spherical mirrors.

[0022]

EXAMPLES The present invention will be described in more detail based on the following examples. FIG. 1 is a perspective view showing the main components of the fine movement mechanism according to the embodiment. 1 is a cylindrical piezoelectric element, and 3
A flexible system of the fine movement mechanism is configured with the cylindrical mirrors 10x, 10y, 10z (all having a radius r ₀ ). The cylindrical piezoelectric element 1 is composed of a hollow ceramic cylinder and a plurality of electrodes electrically and independently arranged on the inner and outer peripheral surfaces thereof. Four of the electrodes are inner electrodes and are used as common electrodes (ground electrodes) when applying piezoelectric strain in each axial direction. In addition, 5x ₁ (not shown) and 5x ₂ are X-axis direction displacement electrodes arranged along the X axis of the hollow piezoelectric ceramic cylinder, and 5y ₁ and 5y ₂ are along the Y axis of the cylinder. It is the arranged electrode for Y-axis direction displacement. Further, 5z is a Z-axis displacing electrode which is arranged along the circumferential surface of the cylinder without interruption.

The upper end 2 of the hollow ceramic cylinder is fixed to an outer wall (not shown), while the lower end 3 is a free end (moving end). At the lower end portion 3, there are three cylindrical surface mirrors 10.
x, 10y and 10z are attached to the outer circumference thereof. Each of the outer spherical mirrors has a hemispherical structure in which the outer side of a sphere having a radius r ₀ is a light reflecting surface, and each of the X, Y, and Z coordinate axes with the center of the lower end portion 3 of the cylinder as the coordinate origin. It is fixed on the Y-axis (for detecting displacement in the X-axis), approximately on the X-axis (for detecting displacement in the Y-axis), and at a position inclined by 45 degrees from the X and Y axes (for detecting displacement in the Z-axis). .

Corresponding to each of these cylindrical surfaces 10x, 10y, 10z, a pair of focused beam light sources 11x and 2 are provided.
Divided light receiving surface type light receiving elements 12x, 11y and 12y, 11z
And 12z are respectively fixed to the outer wall with a predetermined distance. The X-axis direction displacement detection system is arranged so that the focused beam light source 11x fixed along the Y axis and the emitted focused beam light is reflected by the cylindrical mirror 10x and is incident on the two-divided light receiving surface. And a two-divided light receiving surface type light receiving element 12x for detecting the X-axis direction displacement. Similarly, the Y-axis direction displacement detection system includes a focused beam light source 11y and a cylindrical surface mirror 10.
y and a two-divided light receiving surface type light receiving element 12y.
The Z-axis direction displacement detection system is composed of 11z, 10z and 12z. Of these, 12x and 12y have a light receiving surface divided into two by a groove along the Z axis, and 12z is X-.
In the Y plane, the light receiving surface is divided into two along a groove perpendicular to the 45 ° axis which is shifted by 45 ° from the X and Y axes.

Focused beam light sources 11x, 11y, 11z
Is an emitting end of an optical fiber that guides He-Ne laser light, for example. The emission direction of the laser light is 2 when the spot of the light reflected by the cylindrical mirrors 10x, 10y, 10z is 2.
The split light receiving surface type light receiving elements 12x, 12y, 12z are adjusted so as to enter both light receiving regions across the light receiving surface dividing grooves.

FIG. 2 is a diagram for explaining fine movement of the moving end of the piezoelectric element 1 shown in FIG. In the figure, a side view of the cylinder viewed from the XZ plane is shown. Figure 2 (A)
Shows the case where no voltage is applied between any electrodes of the cylinder. The cylinder is not deformed because no piezoelectric strain is induced. FIG. 2B shows a case where an electrode having a direction in which tensile strain acts on a cylinder is applied between the electrodes 4-5Z. It is shown that the piezoelectric element 1 extends in the Z-axis direction. Although not shown, if the polarity of the applied voltage is reversed, the piezoelectric element 1 contracts in the Z-axis direction.

On the other hand, FIG. 2C shows a state where the cylinder is bent in the X-axis direction. In this case, electrodes 4-5x
A voltage having a polarity such that a compressive strain is induced is applied between the _two electrodes, and a voltage having a polarity such that a tensile strain is induced is applied between the electrodes 4-5x ₁ . Although not shown, the Y-direction displacement can be similarly generated.

FIG. 3 shows the light receiving surface of the two-divided light receiving surface type light receiving element. In the figure, the case of 12x is shown as an example, but the same applies to other light receiving elements. The light-receiving surface is a two-divided region 12x _a having a uniform area and a uniform light-receiving sensitivity, 1
It consists of 2x _b . A region separation groove is formed between the light receiving regions along the X ₁ -X ₂ direction. The 12x isolation groove is cut along the Z axis as shown.

[0029] Before the piezoelectric ceramic cylindrical variant of FIG. 2 (A), the focused beam spot, as shown by the solid line in FIG. 3, in such a manner that the center of the spot 14a in the vicinity just separation grooves, i.e. 12x _a and 12x The position of the focused beam light source 11x is adjusted so that the difference between the photoelectric conversion outputs of _b is zero.
Then, as shown in FIG. 2 (C), the piezoelectric ceramic cylinder is
In the case of a slight movement in the axial direction, the focused beam light spot 14a reflected by the cylindrical surface mirror 10x and incident on the two-divided light receiving surface type light receiving element 12x is the dotted line spot position 1 in FIG.
4b causes a position shift (corresponding to Δx). Here, in addition to the displacement Δb in the X-axis direction, a displacement Δz in the Z-axis direction may be accompanied, but since 12X is a light receiving element for detecting displacement in the X-axis direction, the displacement of Δz is not detected. That is,
According to the detection method of the present invention, it is possible to detect only the target axial movement amount.

[0030] Each light-receiving regions 12x _a in FIG. 3, respectively E _xa photoelectric conversion output in 12x _b, and E _xb. The photoelectric conversion output of each light receiving region is proportional to the amount of received light for focused beam light having the same emission spectrum. That is,

[Equation 1] The photoelectric conversion output difference Δ corresponding to the difference between the left and right light amounts
By detecting E _X , the illustrated displacement in the X-axis direction can be detected. Here, the light receiving area 12x _a
The incremental spot area due to the shift amount Δx to the area becomes as shown by the diagonal line, and if the area is ΔS, EX _a is C ₁ Δ
Increase by S (however, C ₁ is a proportional constant). On the other hand, EX _b decreases by C ₁ ΔS. Therefore, Delta] E _X becomes 2C ₁ [Delta] S. That, Delta] E _X becomes proportional to the change in area [Delta] S. On the other hand, when the amount of change Δx is small, it may be considered that ΔS is almost proportional to ΔX, and C ₂ is a proportional constant.
It becomes C ₂ Δx (C ₂ is a proportional constant). Even if Δx is not very small, there is no proportional function, but ΔE _X and Δx have a certain relationship, and in any case, ΔX can be detected by measuring ΔE _X. The light intensity distribution of the beam spot in the radial direction is approximated to be uniform. Similarly, when the two-division light receiving surface type light receiving element 12y for detecting the Y-axis direction displacement is used,

[Equation 2] The photoelectric conversion output difference ΔE _Y represented by 1
In 2z,

[Equation 3] It is sufficient to detect the photoelectric conversion output difference ΔE _Z represented by

In order to increase the detection sensitivity, the Δ
The values E _X , ΔE _Y , and ΔE _Z are highly sensitively amplified through a differential amplifier (not shown). Therefore, it becomes possible to detect a fine movement of about submicron at the moving distance of the focused beam light spot on the light receiving surface.

A method of detecting the fine movement Δb in the X-axis direction using the flexible system and the detection system shown in FIGS. 1 and 3 will be described below.

FIG. 4 shows the cylindrical mirror 10x in FIG.
FIG. 3 is a top view of FIG. First, when no voltage is applied to each electrode in FIG. 1, the laser beam light is adjusted in position so as to be reflected at point 0 (vertex of the outer spherical mirror 10) in FIG. Next, the inner peripheral electrode 4 of FIG.
And outer electrodes 5x _1, 5x _2, 5y _1, predetermined polarity 5y _2, With a voltage of magnitude, distorted lower end surface 3 of the piezoelectric element 1, the vertex of the cylindrical surface mirror 10 of the laser beam It is assumed that the voltage is applied to point 0 _{1 in} FIG. 0 ₁ is from the X axis to Y
It is a position shifted in the axial direction by an angle α and by a distance Δr from the zero point. Since the laser beam light source 11 and the four-division light receiving surface type light receiving element 12 are fixed, the reflection point on the cylindrical mirror 10 remains at 0 point. A top view of the moved cylindrical mirror 10 is shown by a dotted line.

Further, in FIG. 4, the focused beam light enters the cylindrical surface mirror 10x from the focused beam light source 11x at an angle of θ.
The cylindrical piezoelectric element 1 is depicted as being reflected at an angle θ from the 0 point before being deformed and incident on a two-divided light receiving surface type light receiving element 12x separated by a distance L from the reflecting surface. The projection is shown on a plane that passes through the center of the cylindrical mirror 10x of the piezoelectric element 1 and is perpendicular to the Z axis. Therefore, the angle of incidence and reflection at the actual zero point is not θ.

Before the deformation of the cylindrical piezoelectric element 1, Y
The axis passes through point 0 in the figure (the vertex of the outer spherical mirror 10x at this time). The reflected beam from the 0 point is received by the light receiving element 12
So that the spot is at the center of x (see FIG. 3), that is,
The position of the focused beam light is adjusted so that ΔE _X = 0.

Now, it is assumed that the cylindrical piezoelectric element 1 is distorted and the moving end, and hence the cylindrical mirror 10x, is shifted by Δx in the X-axis direction. As shown by the dotted line in the figure, since the vertex 0 ₁ of the cylindrical mirror 10x shifts in the moving direction, the tangent plane at the 0 point (focusing beam entrance / reflection point) is inclined by Δψ.

As a result, the incident beam angle (θ + Δψ) and the reflection angle are also (θ + Δψ) with respect to the perpendicular line passing through the zero point standing on this tangential plane (a plane in contact with the spherical surface at the zero point).
That is, the reflected beam from the 0 point is inclined by (θ + 2Δψ) with respect to the Z axis due to the outer spherical mirror shift of Δx. Of course, the incident beam angle to the 0 point is invariable (θ) with respect to the Z axis.

This result shows that the two-divided light-receiving surface type light-receiving element 12
The light receiving beam spot on the light receiving surface of x (see FIG. 3) is deflected by Δb = 2Δφ · L in the direction opposite to the moving direction of the piezoelectric element 1 by the principle of light lever. In FIG. 4, the focused beam light source 11x and the light receiving element 12x are described by being projected on the paper surface. Therefore, the incident / reflection angle θ of the focused beam light with respect to the Z axis projected on the paper surface is also different from the actual incident / reflection angle shown in FIG. 1, but the magnitude of θ is the deviation Δb of the focused beam spot on the light receiving surface of the light receiver. Is not relevant, the conclusions obtained in FIG. 4 are unaffected. However, since Δx is a minute displacement, it means r ₀ >> Δx, that is, Δψ is minute.

Below, Δφ is obtained as a function of distance.
In FIG. 4, the semicircle coordinates indicating the position of the cylindrical surface mirror 10x shifted by the deformation of the cylindrical piezoelectric element 1 are represented by (x
This semi-circle, the equation for _a, and y _a)

[Equation 4] It is the upper half of the circle represented by. When y _a is obtained from this equation,

[Equation 5] When this equation is differentiated by x _a and the equation expressing the inclination of the point on the circumference is obtained,

[Equation 6] Since the slope of the point on the circumference when x _a = Δx (in equation 6) is Δψ

[Equation 7]

Here, considering Δx / r ₀ << 1

[Equation 8] Is obtained. Therefore, the deflection of the focused beam light spot on the light receiving surface of the light receiving element is

[Equation 9] Becomes This swing is shown in FIG. Electromotive force difference Delta] E _X corresponding to the difference between the left and right light amount as shown by the deflection of Δb in equation (1) is measured. Therefore, in advance

[Equation 10] By experimentally obtaining, it is possible to conversely find an arbitrary Δx generated when an external force acts from F ⁻¹ (ΔE _X ). For example, r ₀ = 1 mm, L = 50 mm, Δx
If it is = 1 nm, Δb = 100 nm is enlarged and observed on the light receiving surface of the light receiving element by the optical lever method. The fluctuation of the focused beam light spot is a value that can be detected by using a differential amplifier. FIG. 7 shows a characteristic example of the displacement Δb of the He—Ne laser beam spot on the light receiving surface of the two-divided light receiving surface type light receiving element 12x and the photoelectric conversion output of the light receiving element 12x via the differential amplifier (amplification factor 100 times). Indicated. It can be seen from FIG. 7 that an output of 21.5 mV can be obtained for a displacement of 1 μm. When measuring this output with a general-purpose 12-bit A / D converter (0-5V), the converter resolution is 1.22 mV / bit, so the measurable displacement is 1.22 (mV / bit) /21.5 (mV).
/Μm)=0.057 μm / bit. That is, as described above, displacement measurement can be performed with submicron resolution. The same conclusion can be obtained for fine movements in the Y-axis and Z-axis directions. From (Equation 9), since the deflection of the focused beam light spot on the light receiving element surface and the displacement in the X-axis direction due to the piezoelectric strain of the cylindrical piezoelectric element 1 are in a proportional relationship, the displacement at the moving end in the X-axis direction due to piezoelectric strain is Y. It is possible to detect only the translational motion component Δx (or Δy) without being affected by the rotation of the outer spherical mirror in the axial direction.

The input / output linearity of the light receiving element 12 is shown in FIG.
As shown in the example, since it can be kept up to 0.1% (10 ^-3 ) or less, the displacement detection accuracy by this method is also 0.1%.
Can be a digit of

By driving the fine movement mechanism of FIG.
FIG. 9 shows an example of measuring the relationship with the differential amplification output of the divided light receiving surface type light receiving element. In FIG. 9, the radius r _{0 of the} outer spherical mirror
Was 1 mm, and the mirror / light-receiving surface distance L was 50 mm. Further, although this data was measured with respect to the X-axis direction shift, almost the same linear relationship was obtained in the sub-micron region also in the other two axis directions. The horizontal axis of FIG. 9 shows the displacement of the moving end detected by a capacitance type displacement sensor (resolution: 0.01 μm or less).

By repeatedly using the optical lever method, it is possible to further increase the deflection of the focused beam spot on the light receiving surface of the light receiving element. For example. Figure 3
An example is shown in which a circular cylindrical surface mirror 10x (having a radius r ₀ ) is used. The position where the light receiving element 12x is arranged in FIG.
The second cylindrical surface mirror is arranged at a position (distance L from the outer spherical surface mirror 10x) to reflect the light, and further, the first cylindrical surface mirror 1
The third cylindrical mirror is arranged at the same position on the XY plane as 0x (the position separated from the second outer spherical mirror by the distance L), and is reflected once again. The light is made incident on the two-divided light-receiving surface of the light-receiving element 12x fixed at the same position on the XY plane as the cylindrical mirror (a position separated from the third cylindrical mirror by a distance L). As a result, the optical lever is used in three stages, and the deflection Δb of the focused beam light spot on the light receiving surface of the light receiving element is

[Equation 11] Therefore, the one-digit deviation can be enlarged as compared with the example of FIG. That is, the detection sensitivity can be increased accordingly.

According to the embodiments of FIGS. 1 and 5 described above, it is possible to accurately measure the displacement coordinates of the fine movement mechanism on the X, Y and Z axes.

In the above embodiment, a cylindrical mirror is used as a mirror for reflecting the focused beam light. However, the same effect can be obtained by using a concave mirror having a curvature r ₀ other than this. The cylindrical surface mirror may be an external cylindrical surface or a concave cylindrical surface type. A spherical mirror can be used instead of the cylindrical mirror.

In principle, it is possible to use an arbitrary curved mirror if the minute displacement coordinates of (x, y, z) and the curved surface curvature at each coordinate position are measured and stored in advance.

FIG. 6 is a block diagram of the control and measurement circuit of the flexible system and the detection system by the fine movement mechanism of the present invention described above.

The cylindrical piezoelectric element 1 is a piezoelectric element drive circuit 15
A piezoelectric strain is induced by applying a drive voltage from the electrodes to each electrode. The fine movement is caused by the He-Ne laser oscillation circuit 13
The laser light emitted from the focused beam light source 11 such as the exit end of the optical fiber through the light is reflected by the cylindrical mirror 10 and
The divided light receiving surface type light receiving element 12 receives and detects light in each area. The laser light spot received in each area is photoelectrically converted for each area, and the output is sent to the signal differential amplifier circuit 14 and amplified with high sensitivity. Elements 11, 12, and 14 are X,
Three Y and Z axes are provided for each of the three axes.

Since the differential output amplified with high sensitivity is proportional to the displacement of the cylindrical piezoelectric element 1 in each axial direction, the differential output voltage value detected by measuring the displacement / output characteristic in advance. Therefore, the displacement amount of each axis can be captured. By sending this signal to the controller 16, it becomes possible to calculate the deviation from the set value by the controller 16 and feed it back to the cylindrical piezoelectric element drive circuit 15 to accurately control the operation of the fine movement mechanism.

The fine movement mechanism of the present invention described above can be used as a fine movement device of a scanning probe microscope, particularly a scanning tunnel microscope (STM). A probe or a sample stage is fixedly mounted on the lower surface of the lower end portion 3 of the piezoelectric element 1, and the X, Y, and Z axis coordinate values detected as described above are fed back to the fine movement control section, and the deviation from the predetermined coordinate value is detected. Piezoelectric element 1 so that it becomes zero
The tremor value of can be controlled.

Although not described in the above embodiment, the piezoelectric element 1
Alternatively, if a cantilever with one end fixed is used as the flexible system and the cylindrical mirror is installed on the back side of the probe, the fine motion detection system of the present invention can be used as an atomic force microscope (AFM). Further, as the above-mentioned embodiment, the case of piezoelectric strain as the external force has been described, but it is obvious that the present invention also includes the case where other forces such as atomic force and magnetic force act on the flexible system. is there.

[0052]

As described above, according to the present invention, the fine movement mechanism of the scanning probe microscope (SPM) can be made compact and highly sensitive, and the fine movement in the X, Y, and Z axis directions can be performed with high accuracy. Coordinates can be measured and controlled. Therefore, it is considered that the present invention can contribute to improving the characteristics of the fine movement mechanism, particularly the fine movement device of the SPM.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main component of a fine movement mechanism according to an embodiment.

FIG. 2 is a diagram showing a fine movement operation of the cylindrical piezoelectric element of FIG.

3 is a diagram showing a light receiving region of the two-divided light receiving surface type light receiving element of FIG.

FIG. 4 is a diagram showing a fine movement position of a cylindrical surface mirror of FIG. 1 and light reflection / reflection.

FIG. 5 is a diagram for explaining fine movement of a cylindrical mirror and shift of a reflection angle according to another embodiment.

FIG. 6 is a block diagram of a fine movement mechanism drive circuit in FIG.

FIG. 7 is a diagram showing a characteristic example of differential amplified output corresponding to the displacement on the two-divided light receiving surface type light receiving element surface of the present invention.

FIG. 8 is a diagram showing input / output linearity of a photodiode which is a light receiving element.

9 is a diagram showing an example of measuring a minute displacement of a moving end by the fine movement mechanism of FIG.

[Explanation of symbols]

1 cylindrical piezoelectric element 2 upper part 3 lower part 4 inner circumference (ground) electrode 5x ₂ X-axis direction displacement electrode 5y _1, 5y ₂ Y-axis direction displacement electrode 5z Z axis direction displacement electrode 10x, 10y, 10z cylinder surface mirror 11,11x, 11y, 11z focused beam light source 12,12x, 12y, 12z 2-split light receiving surface light-receiving device 13 the He-Ne laser oscillator 12x _a, 12x _b, 2-divided light receiving regions 14 signal differential amplifier 15 Cylindrical piezoelectric element drive circuit 16 Controller

Claims (2)

[Claims] 1. A flexible system having a fixed end fixed to an outer wall and a moving end finely moved by the action of an external force, and three pairs fixed at a predetermined position outside the flexible system at a predetermined interval. Of the focused beam light source and the two-divided light receiving surface type light receiving element, and each of the focused beam light emitted from the focused beam light source that is fixed at a predetermined position of the moving end and is incident on the two divided light receiving surface type light receiving element. And three spherical or cylindrical mirrors having a function of causing X to accompany fine movement of the moving end,
A fine movement mechanism that detects each displacement in the Y- and Z-axis directions as a change in output difference in each light-receiving surface area of each of the two light-receiving surface-type light-receiving elements. 2. The probe according to claim 1, wherein a probe or a sample table is fixedly provided on a part of the moving end, and the change is detected as a change in output difference in each light receiving surface region of the three light receiving surface type light receiving elements. A scanning probe microscope having a function of controlling the fine movement mechanism of the probe by controlling the external force by returning the displacement of the moving end in the X-, Y-, and Z-axis directions.