JPH0829148A - Near field microscope - Google Patents

Abstract

PURPOSE:To measure a minute shape of the surface of a material accurately by providing a piece of fiber which has a minute projection at the tip edge and emits light, and detects the reflected light from the surface irregularities, an electro-mechanical energy transducer, a vibration exciting member, an actuator and the like. CONSTITUTION:In fiber 6, a minute needle shape is formed, and a minute projection 7 at an acute angle is formed so that the tip agrees with the axial core of the fiber 6. As a mechanical to electric energy transducer, piezoelectric element 17 having the same shape and the same material at those of a piezoelectric element 16 is bonded and fixed with the GND face of an electromechanical energy transducer as the common electrode. The changing amount of vibration is outputted from an edge electrode. A taper shape 11 and the fiber 6, which are positioned at the approximately central part of a vibration exciting member 8, are finely vibrated in the axial direction of the fiber 6 in conformity with the vertical vibration of a thin elastic beam 9. The changing amount of the vibration is used as the distance information between the projection 7 and a material surface 15. The movement of an actuator 14, which brings the tip of the fiber 6 close to the material surface 15, is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical near field microscope for observing minute shapes on the surface of a substance.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for observing a minute shape of a material surface, an atomic force microscope which detects a tunnel current by a conductive tunnel tip and determines a bending amount of a cantilever by utilizing a fluctuation of the current is used. Is generally known. Also, as disclosed in Japanese Patent Laid-Open No. 63-309803, there is an atomic force microscope that does not utilize a cantilever or a tunnel current. As shown in FIG. 9, the device described in the publication is attached to one of the surfaces of a transmission body 33 having a pair of electrodes 32 on both sides of which a chip 31 can apply an electric potential. When the tip 31 is sufficiently far from the material surface during operation, the transmitter body 33 is excited at its resonant frequency. Then, when approaching the surface of the substance 34, the frequency of the transmission body 33 deviates from its original resonance frequency. The distance in the Z direction is controlled by this amount of deviation, and the contour image of each scan of the chip 31 is plotted.

[0003]

In the above-mentioned conventional example, a crystal oscillator is used as the transmission body 33, and the resonance of Y-cut crystal transmission is mentioned. When the deformation of the crystal oscillator 33 is schematically drawn, it is deformed as shown by the dotted line in FIG. 9.
As a result, the chip 3 provided on the surface of the transmitter main body 33
1 moves in the axial direction and also in the direction perpendicular to the axial direction, and moves in the direction of arrow A in FIG.
Therefore, vibration perpendicular to the sample surface 34 cannot be obtained (vibration does not occur in the axial direction of the chip 31).

Further, the tip has a small diameter with respect to the transmitter main body 33 and extends in one direction. Therefore, vibration that does not move in the axial direction (vibration in the direction of arrow A)
In this case, as shown in FIG. 10, bending vibration (dotted line B) is likely to occur in the tip extension portion 35, and the tip of the tip 31 is indicated by the arrow A.
There is a case where the vibration becomes a substantially elliptical vibration which is a combined vibration of the directional vibration and the bending vibration.

In such a case, the distance from the sample surface 34 is not accurately determined, and accurate distance information cannot be fed back to the Z direction distance, and the contour image of the scanning position of the chip 31 is different from the actual one. There is a problem of becoming.

Therefore, the present invention has been made in view of the above problems, and in order to accurately measure a minute shape of a material surface, a near-field microscope that surely vibrates an optical tip vertically to the material surface. For the purpose of providing.

[0007]

In order to achieve the above object, as a means according to claim 1, the present invention provides a near-field microscope for observing a minute shape of a material surface, which has a minute projection on a tip end surface, A fiber for irradiating the surface of the with light and detecting the reflected light from the surface irregularities, an electromechanical energy conversion element for vibrating the fiber in the axial direction by applying an alternating voltage, and the fiber and the electromechanical energy conversion element. A vibration excitation member supported by a thin elastic beam, a mechanical-electrical energy conversion element fixed to the electromechanical energy conversion element and detecting a change amount of axial vibration of the fiber and the vibration excitation member, and a change amount of the axial vibration. And an actuator that moves the fiber and the vibration excitation member toward the surface of the material. It is characterized in.

According to a second aspect of the present invention, in a near-field microscope for observing a minute shape on the surface of a substance, a fine projection is provided on the tip end face to irradiate the surface of the substance with light and to reflect light reflected from the surface irregularities. Fiber to detect,
An electromechanical energy conversion element that vibrates the fiber in the axial direction by applying an alternating voltage, a vibration excitation member that supports the fiber and the electromechanical energy conversion element by a thin elastic beam, and is fixed to the thin elastic beam, the fiber A mechanical-electrical energy conversion element that detects the amount of change in axial vibration that is the distance information between the minute protrusions on the tip end face and the material surface, and the amount of movement changes based on the amount of change in axial vibration, and the fiber and vibration excitation An actuator for moving the member in the direction of the material surface.

According to a third aspect of the present invention, the alternating voltage applied to the electromechanical energy conversion element has a frequency at which a mode other than the axial vibration mode of the fiber is not excited.

[0010]

The action according to claims 1 and 2 is to irradiate the material surface with light sent through a fiber having minute projections on the tip end face, and to change the reflected light that is reflected by the unevenness of the material surface. The irregularities (fine shapes) on the surface of the substance are detected and measured by taking them into a fiber and comparing the irradiation light with the reflected light.

At this time, by keeping the distance between the minute projections on the end face of the fiber and the material surface constant, a certain correlation can be provided between the magnitude of the reflected light and the material surface irregularities. Here, as a mechanism for maintaining a constant distance, the fiber is supported by a vibration excitation member having a thin elastic beam, by applying an alternating voltage of the resonance frequency in the axial direction of the thin elastic beam, the electromechanical energy exchange element vibrates, Vibrates the fiber only in the axial direction.

As the minute protrusions on the end face of the fiber approach the surface of the substance, the influence of the interatomic force becomes stronger, and the vibration characteristics (resonance frequency, impedance, voltage-current phase difference,
A change appears in the capacitance). Based on this vibration change amount, the distance information between the minute protrusions on the fiber tip end surface and the substance surface is obtained, and the movement amount of the actuator that moves the fiber and the vibration excitation member in the substance surface direction is controlled, and the minute protrusions and the substance surface are Make sure that the distance is constant. As a result, reflected light corresponding to the amount of unevenness of the material surface is obtained on the fiber, and the contour of the surface can be accurately measured.

Here, the electromechanical energy conversion element for detecting the vibration change amount is fixed to the electromechanical energy conversion element as the vibration source or is fixed to a thin elastic beam having a large vibration displacement amount to grasp the vibration change amount. It is placed in a position that facilitates

According to a third aspect of the present invention, an alternating voltage having a resonance frequency for vibrating the thin elastic beam only in the axial direction is applied to the electromechanical energy conversion element so that the bending vibration mode or the like is not excited in the fiber. . This allows
Since the fiber is supported by a thin elastic beam,
It is possible to vibrate the fiber in the non-resonant state only in the axial direction. Therefore, the minute protrusions on the tip end face of the fiber vibrate perpendicularly to the material surface, and the amount of vibration change is accurately detected from the mechanical-electrical energy conversion element in response to the irregularities on the material surface.

[0015]

Embodiment 1 FIGS. 1 to 3 show Embodiment 1 of the present invention,
1 is a simplified perspective view around the fiber vibration excitation member, FIG.
1 is a sectional view of FIG. 1, and FIG. 3 is an enlarged perspective view of a fiber tip portion.

The fiber 6 for transmitting light has SiO ₂ as a main component and forms an extremely fine needle shape, and has SiO ₂ GeO as a main component at its tip as shown in FIG. A microprojection (chip) 7 having a tip of 2 μm and having a sharp edge with the axial center of the fiber 6 is formed.

The fiber 6 is passed through a hole at the center (center of gravity) of the vibration excitation member 8 and is fixed by bonding, with the length of the fiber 6 extended by several millimeters. The vibration exciting member 8 is made of a material such as stainless steel, aluminum alloy, duralumin, titanium alloy, phosphor bronze, brass, ceramic, etc., which has high vibration transmission efficiency.

Further, the vibration excitation member 8 has a fiber 6
A thin elastic beam 9 is formed in a direction orthogonal to the axial direction of. The thin elastic beam 9 is sufficiently thin with respect to the thickness 10 of the through hole of the fiber 6, and has a tapered shape 11 from the through hole of the fiber 6 to the thin elastic beam 9. The base portion of the taper shape 11 in this embodiment has a quadrangular shape.

The vibration excitation member 8 has a quadrangular shape when viewed from the axial direction, and a rectangular parallelepiped fixing portion 13 for fixing the vibration excitation member 8 to the external drive member 12 is formed on two opposing sides. The external drive member 12 is the laminated piezoelectric actuator 1
4, etc., components such as the fiber 6 and the vibration excitation member 8 are made to approach the substance surface (sample surface) 15 from the vertical direction, and are moved in parallel to the substance surface 15 to scan the substance surface 15. Let

The thin elastic beam 9 described above is formed in two places between the fixed portion 13 and the quadrangular pyramid shaped portion 11, and the two places are symmetrical with respect to the fiber 6. A plate-shaped piezoelectric element 16 as an electromechanical energy conversion element is bonded and fixed to the opposite side of the quadrangular pyramid-shaped portion 11 with the thin elastic beam 9 interposed therebetween.

The piezoelectric element 16 is made of lead zirconate titanate and has a quadrangular shape having the same shape as the base of the quadrangular pyramid portion 11, and a through hole for the fiber 6 is formed at the center (center of gravity). The piezoelectric element 16 is polarized in the thickness direction, silver vapor deposition electrodes are formed on both end faces, and one end face is grounded.
And is configured to apply an alternating voltage to the other end face.

Further, as a mechanical-electrical energy conversion element, a piezoelectric element 17 having the same shape and material as the piezoelectric element 16 described above.
Is bonded and fixed using the GND surface of the electromechanical energy conversion element as a common electrode, and the other end surface electrode outputs a vibration change amount.

The operation of the near-field microscope having this structure is that the electromechanical energy conversion element (piezoelectric element) 16
On the other hand, the thin elastic beam 9 applies an alternating voltage having a resonance frequency at which the thin elastic beam 9 vibrates as shown by the dotted line and the two-dot chain line in FIG. The quadrangular pyramid-shaped portion 11 and the fiber 6 located substantially in the center of the vibration excitation member 8 slightly vibrate in the axial direction of the fiber 6 in accordance with the vertical vibration of the thin elastic beam 9. In the present embodiment, the minute protrusions 7 on the tip end surface of the fiber 6 are provided in an axial direction of 10 to 100n.
Excitation with a vibration amplitude of m.

The fixed portion 13 of the vibration exciting member 8 is fixed to an external drive mechanism such as a laminated piezoelectric actuator 14 or the like,
The minute projections 7 on the tip end surface of the fiber 6 are brought close to the material surface 15 of the sample. When the minute projections 7 come close to the range affected by the atomic force on the material surface 15, the fiber 6
Of the axial vibration (Fig. 8), the impedance at the resonance point 18 (Fig. 8), the phase difference between the voltage waveform generated by the piezoelectric element 17 and the current waveform consumed by the piezoelectric element 17, the capacitance, etc. The amount of change is output as a vibration change amount from the piezoelectric element 17 as a mechanical-electrical energy conversion element.

This amount of vibration change is due to the minute projections 7 and the material surface 1.
It is used as distance information with respect to 5, and controls the movement amount of the actuator 14 (approaching laminated piezoelectric actuator) of the external drive mechanism that brings the tip of the fiber 6 closer to the material surface 15. By this control, the minute projections 7 and the material surface 15
The distance between and can be kept constant.

In accordance with the large swell of the material surface 15,
While maintaining a certain distance, the minute protrusions 7 move substantially parallel to the material surface 15 by the actuator 14 (scanning laminated piezoelectric actuator) of the external drive mechanism. The relationship between the irradiation light that is emitted from the fiber 6 perpendicularly to the material surface 15 and the reflected light that changes due to the unevenness of the material surface 15 becomes constant, and by comparing the irradiation light and the reflected light, the material surface 15 It is possible to measure minute shapes.

Since the thin elastic beam 9 is arranged perpendicular to the fiber 6, the resonance phenomenon of the vibration in the axial direction is
Excitation is stronger than the resonance phenomenon of other vibration modes (flexural vibration). Further, an alternating voltage having a frequency such that the thin elastic beam 9 resonates is applied to the electromechanical energy conversion element 16, but the fiber 6 vibrates in the axial direction in a non-resonant state, and bending vibration occurs in the fiber 6. It's getting harder.

According to the present embodiment, the fiber is vibrated in the axial direction, the amount of vibration change due to the approach to the material surface 15 is detected, and the movement amount of the actuator of the external drive mechanism is controlled as distance information to control the tip of the fiber. The minute protrusions 7 on the end face are always maintained at a constant distance from the material surface 15.

By doing so, the irradiation light from the fiber 6 and the reflected light that changes depending on the unevenness of the material surface 15 are compared, and the unevenness of the material surface 15 is measured. That is,
The fiber 6 can always detect a change in light at a constant distance, and it is possible to measure the unevenness of the material surface 15 with extremely high accuracy.

Further, since no mode other than the axial vibration mode such as bending vibration is generated in the fiber 6, the influence of the atomic force of the minute protrusions 7 can be accurately captured as the vibration change amount. Then, the variation of the distance from the surface of the substance 15 which causes the change of the light amount of the fiber 6 is eliminated, which promotes accurate measurement.

[0031]

Second Embodiment FIGS. 4 and 5 show a second embodiment of the present invention,
4 is a perspective view showing the configuration around the fiber and the vibration excitation member, and FIG. 5 is a sectional view of FIG. The present embodiment is different in that the vibration exciting member of the first embodiment is formed in a circular shape, and other configurations are similar to those of the first embodiment, and therefore the description thereof will be omitted.

The fiber 6 is passed through a hole at the center (center of gravity) of the vibration excitation member 19 in a state where the fiber 6 is extended by about 10 mm, and is fixed by adhesion. The vibration excitation member 19 includes
Materials such as stainless steel, aluminum alloy, duralumin, titanium alloy, phosphor bronze, brass and ceramics, which have high vibration transmission efficiency, are used.

Further, a thin elastic beam 20 is formed on the vibration excitation member 19 in a direction orthogonal to the axial direction of the fiber 6, and the thin elastic beam 20 is formed with respect to the thickness 21 of the through hole of the fiber 6. Is sufficiently thin, and has a tapered shape 22 from the through hole of the fiber 6 to the thin elastic beam 20. In this embodiment, it has a substantially conical shape.

The vibration exciting member 19 has a circular shape when viewed from the axial direction, and an annular fixing portion 23 for fixing the vibration exciting member 19 to an external drive mechanism (not shown) is formed on the outer circumference. The external drive mechanism uses a laminated piezoelectric actuator or the like (not shown) to bring the components such as the fiber 6 and the vibration excitation member 19 vertically close to the material surface, and to make the material surface scan parallel to the material surface. To move.

The thin elastic beam 20 described above is formed in an annular shape between the fixed portion 23 and the conical portion 22, and has an axially symmetric shape about the fiber 6. Thin elastic beam 2
A disk-shaped piezoelectric element 24 is bonded as an electromechanical energy conversion element to the opposite side of the conical portion 22 with 0 interposed therebetween. The piezoelectric element 24 has the same shape as the base of the conical portion 22, and has a hole (a center of gravity) that penetrates the fiber 6 at the center.

The voltage element 24 is lead zirconate titanate,
Polarized in the thickness direction, silver vapor deposition electrodes are formed on both end faces. Then, one end face is set to GND, and an alternating voltage is applied to the other end face. Further, as a mechanical-electrical energy conversion element, a piezoelectric element 25 having the same shape and the same material as the piezoelectric element 24 described above is bonded and fixed by using the GND of the piezoelectric element 24 as a common electrode, and the polarization directions are opposed to each other. Then, the vibration change amount is output from the other end surface electrode.

In this structure, when the thin elastic beam 20 is applied to the mechanical-electrical energy conversion element (piezoelectric element) 24 by an alternating voltage having a resonance frequency at which the thin elastic beam 20 vibrates as shown by a dotted line and a chain double-dashed line in FIG. The cone-shaped portion 22 and the fiber 6 located at the center of the fiber vibrate slightly in the axial direction according to the vertical vibration of the thin elastic beam 20. In this case, the thin elastic beam 20 resonates, but the fiber 6 vibrates in a non-resonant state.

The vibration excitation member 19 is formed axially symmetrical about the fiber 6, and the thin elastic beam 20 can also have uniform elasticity in the radial direction about the fiber 6, and the bending existing in the fiber 6 It becomes possible to completely eliminate modes other than the axial vibration mode such as vibration. Further, by adjusting the thickness T and the length L of the thin elastic beam 20, the fiber 6 can be vibrated in the axial direction at an arbitrary frequency.

As described above, even if the vibration exciting member 19 has a substantially disc shape, the fiber 6 can be vibrated in the axial direction as in the first embodiment, and the distance between the minute projections 7 and the material surface can be increased. Can be kept constant. The other operations are similar to those of the first embodiment, and thus the description thereof is omitted.

According to the present embodiment, the vibration excitation member 19 is circular, the thin elastic beam 20 is arranged so as to surround the fiber 6 as the center, and has uniform elasticity in the radial direction. Can be vibrated in the axial direction. Therefore, the bending vibration does not occur in the fiber 6 due to the change in the shape and size of the thin elastic beam 20,
The frequency can be set arbitrarily, and the degree of freedom in design can be improved. Further, since stable axial vibration can be obtained, it becomes possible to control the distance between the minute projections 7 and the material surface more accurately, and highly accurate measurement can be performed.

[0041]

Third Embodiment FIGS. 6 and 7 show a third embodiment of the present invention,
6 is a perspective view showing the configuration around the fiber and the vibration excitation member, and FIG. 7 is a sectional view of FIG. The present embodiment is different in that the shape and arrangement of the mechanical-electrical energy conversion element for detecting the vibration change amount of the second embodiment are changed, and other configurations are similar to those of the first embodiment. , The description is omitted.

On the surface of the annular thin elastic beam 27 connected to the vibration exciting member 26, the piezoelectric element 28 as an annular mechanical-electrical energy conversion element having substantially the same shape as the thin elastic beam 27 is adhered and fixed. Has been done. The piezoelectric element 28 is polarized in the thickness direction, silver vapor deposition electrodes are formed on both end surfaces, the electrode on the thin elastic beam 27 side is GND, and the vibration variation amount is output from the other electrode. The material of the voltage element 28 is a soft piezoelectric element having a large voltage constant.

Further, the piezoelectric element 24, which is an electromechanical energy conversion element serving as a vibration source for vibrating the fiber 6 in the axial direction, has an electrode on the thin elastic beam 27 side as GND, and the thin elastic beam 27 is implemented on the other electrode. In order to vibrate like Example 2, it is configured to apply an alternating voltage of the resonance frequency.

In this structure, the thin elastic beam 27 vibrates in a resonance state, so that the amount of vibration deformation is larger than that of the other structural members. Therefore, by installing the mechanical-electrical energy conversion element 28 in this portion, it is possible to easily detect a weak vibration change amount.

Moreover, by using a soft piezoelectric element having a large piezoelectric constant as the piezoelectric element 28, it becomes easy to take out the vibration change amount as a voltage change, and it is possible to output various characteristic values of the vibration change amount with large values. Becomes The other actions are similar to those of the second embodiment, and thus the description thereof is omitted.

According to this embodiment, the mechanical-electrical energy conversion element 28 for detecting the amount of vibration change is installed at the position of the thin elastic beam 27 vibrating in resonance.
A minute amount of vibration change can also be detected with high accuracy, and the distance between the minute protrusion 7 and the substance surface can be maintained more constant. Other examples of such a mechanical-electrical energy conversion element include a strain gauge and a polymer piezoelectric film (PVD).
F) and the like, but in any case, the same effect can be obtained.

Although the thin elastic beams in Examples 1 to 3 are arranged in the direction orthogonal to the axial direction of the fiber, this is because bending vibration is hardly excited in the fiber and the axial direction of the fiber is reduced. By generating the vibration only in the direction, it is possible to accurately detect the vibration change amount.

In the first to third embodiments, a piezoelectric is used as an electromechanical energy conversion element that excites vibration of minute displacement by applying an alternating voltage or a mechanical-electric energy conversion element that detects vibration of minute displacement as voltage. A device is used, which enables highly accurate and highly responsive control and highly sensitive measurement.

In the first to third embodiments, based on the distance information from the mechanical-electrical energy conversion element, the microtips are provided on the tip end surface of the fiber so as to maintain a constant distance from the material surface. Maintains a constant distance between the minute protrusions on the fiber tip and the material surface, enabling highly accurate measurement of minute shapes on the material surface by comparing irradiation light and reflected light with high accuracy. To do.

[0050]

As the effects of the first and second aspects, the fiber can be vibrated only in the axial direction, and the distance between the fine protrusions of the fiber and the substance surface can be maintained constant. Therefore, it is possible to accurately compare the irradiation light from the fiber and the reflection light due to the unevenness from the material surface, and it is possible to measure the minute shape of the material surface with high accuracy.

As an effect according to claim 3, by applying an alternating voltage of a frequency at which vibration is generated only in the axial direction to the electromechanical energy conversion element, the fiber is vibrated perpendicularly to the material surface, It is possible to accurately detect the vibration change amount.

[Brief description of drawings]

FIG. 1 is a simplified perspective view around a fiber vibration excitation member showing a first embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

FIG. 3 is an enlarged perspective view of a fiber tip portion.

FIG. 4 is a perspective view showing a configuration around a fiber and a vibration exciting member according to a second embodiment of the present invention.

5 is a sectional view of FIG.

FIG. 6 is a perspective view showing a configuration around a fiber and a vibration exciting member according to a third embodiment of the present invention.

7 is a sectional view of FIG.

FIG. 8 is a diagram showing impedance with respect to vibration frequency.

FIG. 9 is an explanatory diagram of a conventional atomic force microscope.

FIG. 10 is an explanatory diagram of a conventional atomic force microscope.

[Explanation of symbols]

1 chip 2 electrode 3 transmitter body 4 sample surface 5 chip extension part 6 fiber 7 small protrusion 8,26 vibration excitation member 9,19,27 thin elastic beam 10 fiber through hole thickness 11 taper shape (quadrangular pyramid shape part) 12 External Drive Mechanism 13,23 Fixed Part 14 Laminated Piezoelectric Actuator 15 Material Top (Sample Surface) 16,24 Piezoelectric Element (Electromechanical Energy Conversion Element) 17,25,28 Piezoelectric Element (Mechanical Electric Energy Conversion Element) 18 Resonance Point 19 Vibration Excitation Member 21 Through Hole Thickness 22 Tapered Shape (Cone Shaped Part)

Claims (3)

[Claims] 1. A near-field microscope for observing a minute shape of a material surface, which has a minute projection on a tip end face, irradiates the surface of the material with light, and detects light reflected from the surface irregularity, and an alternating voltage. An electromechanical energy conversion element that vibrates the fiber in the axial direction by the application of, a vibration excitation member that supports the fiber and the electromechanical energy conversion element by a thin elastic beam, fixed to the electromechanical energy conversion element, the fiber And a mechanical-electrical energy conversion element that detects the amount of change in the axial vibration of the vibration excitation member, and the actuator that changes the amount of movement based on the amount of change in the axial vibration to move the fiber and the vibration excitation member in the material surface direction. And a near-field microscope. 2. A near-field microscope for observing a minute shape of a material surface, which has a minute projection on the tip end face, irradiates the surface of the material with light, and detects reflected light from the surface unevenness, and an alternating voltage. An electromechanical energy conversion element for vibrating the fiber in the axial direction by the application of a vibration excitation member for supporting the fiber and the electromechanical energy conversion element by a thin elastic beam, and a fiber tip end surface fixed to the thin elastic beam. The mechanical-electrical energy conversion element that detects the amount of change in axial vibration, which is the distance information between the minute protrusions and the material surface, and the amount of movement changes based on the amount of change in axial vibration. A near-field microscope, comprising: an actuator that moves in the direction of the material surface. 3. The near field microscope according to claim 1, wherein the alternating voltage applied to the electromechanical energy conversion element has a frequency at which a mode other than an axial vibration mode of the fiber is not excited.