JPH0518707A - Minute displacement element and its manufacture and information processing device and tunnel current detection device using the same - Google Patents

Abstract

PURPOSE:To enable to maintain accuracy which does not rely on the thickness of a substrate and increase machining accuracy by providing an electrode which displaces thin film of piezoelectric body, providing a probe for inputting and outputting information at a free end on the top face of a minute displacement element, and constituting the substrate by a monocrystal crystal substrate whose main face is a vertical face for Z-axis. CONSTITUTION:Si3N4 films 2, 3 of about 200mm are formed on both faces of a crystal substrate 1 whose main face is a vertical face in the vertical direction of a probe 15. Next, patterning of square markers is done at two places of the film 3 at the rear face of the substrate 1. Then, anisotropic etching of the substrate 1 is done by using HF solution from the rear face of the substrate 1 to form a marker hole 8. ZnO is used for thin films 9, 10 of piezoelectric body, and Au is used for electrodes 11, 12, 15. Crystal membrane of the substrate 1 and Si3N4 films are etched by reactionary ionetching by use of CF4, O2 plasma to form a through hole 6 and a cantilever 7 which drives piezoelectric body. Thus, it is possible to decrease the number of processes and obtain minute displacement element which has high dimensional accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a minute displacement element used in a tunnel current detecting device, a scanning tunnel microscope and the like, a manufacturing method thereof, a large capacity and high density information processing device and a tunnel current detecting device to which the minute displacement element is applied. It is a thing.

[0002]

2. Description of the Related Art Currently, a scanning tunneling microscope (hereinafter referred to as ST
(Hereinafter referred to as “M”), atomic order or molecular order observation and evaluation of semiconductors or polymer materials, and microfabrication (EE Ehrichs, 4th Internet).
Ional Conference on Scann
ing Tunneling Microscopy /
Application of the recording / reproducing apparatus to various fields has been studied.

In particular, there is an increasing demand for a recording device having a large capacity for computer calculation information and the like, and due to the progress of semiconductor process technology, the microprocessor has become smaller and the computing power has been improved. The miniaturization of is desired. In order to meet these requirements, by changing the work function of the surface of the recording medium by applying a voltage from a converter consisting of a tunnel current generating probe that is present on a driving means that can be finely adjusted with respect to the recording medium. A recording / reproducing apparatus has been proposed in which recording / writing is performed and information is read out by detecting a change in tunnel current due to a change in work function, and a minimum recording area is 10 nm square.

In such a recording / reproducing apparatus, a tunnel current detecting probe is arranged on a free end portion of an upper surface of a cantilever (cantilever) in which a piezoelectric thin film is laminated in a bimorph structure on a semiconductor substrate by using a semiconductor process technology. However, there has been proposed a drive means for finely adjusting the distance to the recording medium by displacing the cantilever.

A plurality of such minute displacement elements can be manufactured on a substrate. Also, this small displacement element is
There are many advantages such as the miniaturization of TM, the speeding up of probe scanning, the ease of multi-processing, and the integral formation of an electric circuit system for driving the cantilever on a semiconductor chip.

Regarding a method of manufacturing a cantilever on a semiconductor substrate, the processing accuracy is high, and a method of manufacturing a cantilever utilizing anisotropic etching of silicon that can easily obtain a three-dimensional structure, and a micromachine using semiconductor processing technology. Technology (KE Peterson, “Sili
con as a Mechanical Material
al ”, Proceedings of the IE
EE, vol. 70p420, 1982) and S
Method for forming cantilever type STM probe composed of piezoelectric bimorph on i substrate (TR Albrec
htetal. , "Microfabrication
of Integrated Scanning Tu
nnelling Microscope ”, Proce
edings of 4th International
al Conference on STM / STS
S10-2 July 9-14, 1989) and the like are famous.

For example, (CF Quate et al., "Mic
rofabricated ofIntegrated
  Scanning Tunneling Micro
Scope "STM'89 Fourth Inter
national Conference S10-2
Jul. 9-14, 1989), as shown in FIG.
Anisotropic etching from the back surface of the Si (100) substrate 22
To produce a 50 μm thick Si membrane,
Make a cantilever on the membrane and finally dry it.
Etching the remaining Si substrate from the backside
It is something. Where 3 is Si₃N_FourMembrane, 9, 10 Is pressure
Electric thin film, 11, 12, 13 are electrodes, 15 is tunnel electric
It is a probe for detecting the flow. This method is
Can withstand materials that are not resistant to anisotropic anisotropic etchants
It is an excellent method when used as a constituent material of lever
It

However, in the above-mentioned conventional micro displacement element,
There are various problems as described below.

(1) As a method of anisotropically etching a Si substrate from the back surface to manufacture a minute displacement element, it is necessary to perform lithography using both surfaces of the substrate. For this reason, it is important to align the back and front masks. Therefore, a method that is often taken is to form a through hole from the back surface and use this as a marker for the back surface and the front surface. This is the Si (100) substrate 2 as shown in FIG.
On both sides of the 2 to an Si ₃ N ₄ film 2, the back surface the Si ₃ N ₄
The film 3 is patterned by lithography and dry etching to have a desired shape to be a marker hole. Next, anisotropic etching with a KOH aqueous solution is performed. At this time, the etching rates of Si are (110) and (111)
Since it is significantly different from the surface, the holes are formed in a pyramid shape as shown in FIG.

The through hole is used as an index for aligning the back surface and the front surface. Since the through hole is formed by anisotropic etching, the size of the through hole formed on the substrate surface depends on the thickness of the Si substrate. It has the drawback of changing. This is because the angle formed by the Si (100) plane and the Si (111) equivalent plane is 54.7 °. Therefore, for example, the thickness accuracy of the Si substrate is ± 10 μm.
At this time, if anisotropic etching is performed, the length accuracy of one side of the opening formed on the surface becomes ± 14 μm. For this reason, there is a problem that the processing accuracy of the alignment on both sides is reduced.

(2) Conventionally, in the micro displacement element, ZnO, which can be easily formed by the sputtering method or the vacuum evaporation method, is used as the piezoelectric thin film, and Al is used as the electrode, as shown in FIG. In general, when Al is used as an electrode, it is known that ZnO on Al has a poor orientation and diffuses. To improve orientation and insulation, SiO is formed between Al and ZnO as shown in FIG. _Two films are provided. However, in this process, since four SiO ₂ layers are required, the number of process steps is large.
There is a drawback that the effective voltage to ZnO is reduced and the displacement amount is reduced with respect to the applied voltage.

(3) As mentioned above, ZnO is often used as the piezoelectric thin film in the small displacement element.

Since such a minute displacement element requires a process such as anisotropic etching of Si, NaOH, K
Although harsh etching conditions of a strong alkaline solution such as OH are required, ZnO cannot withstand the harsh etching solution, so a protective layer is provided to protect the ZnO film from the etching solution, or the ZnO film is directly etched. The back surface of the Si substrate had to be etched so as not to be exposed to the liquid.

Further, the etching process of the ZnO film and the etching process of the protective layer have been performed many times. Therefore, the manufacturing process itself becomes complicated, the number of steps is increased, and the cost is increased. Also, in terms of electrical characteristics (piezoelectric characteristics), since ZnO has a low breakdown voltage, the displacement voltage cannot be increased.

[0015]

In view of the problems of the conventional example as described above, the first object of the present invention is to maintain the accuracy independent of the thickness of the substrate. Increase processing accuracy.

It is an object of the present invention to provide a minute displacement element that can satisfy both the above and the above.

Next, a second object of the present invention is to use ZnO as a bimorph electrode material using ZnO as a piezoelectric material.
The orientation of O is good. The effective voltage to ZnO is large.
The manufacturing process is simple.

It is another object of the present invention to provide a ZnO bimorph-driven micro-displacement element using an electrode material which can satisfy all of the above requirements.

A third object of the present invention is to improve electric characteristics. Simplify process steps.

The above is to provide a stable small displacement element and a method for manufacturing the same.

Another object of the present invention is to provide an information processing device and a tunnel current detecting device using the above minute displacement element.

[0022]

That is, according to the present invention, which has been accomplished to achieve the first object, firstly, at least a piezoelectric thin film and the piezoelectric thin film are displaced on a substrate by a piezoelectric inverse effect. A micro-displacement element having an electrode for use in the micro-displacement element, in which a probe for information input / output is provided at a free end portion of an upper surface of the micro-displacement element, a surface of the substrate perpendicular to the Z axis (direction perpendicular to the probe). A micro-displacement element characterized by being a single crystal quartz substrate whose main surface is.

The present invention, which has been made to achieve the second object, secondly provides a cantilever (cantilever) having at least two layers of piezoelectric thin films and electrodes for displacing the piezoelectric thin films by an inverse piezoelectric effect. In a micro displacement element in which a probe for information input / output is provided at the free end of the upper surface of a (burr) -shaped displacement element, the piezoelectric thin film is made of ZnO, and the entire bonding surface between the electrode and the piezoelectric thin film is made of Au or Au alloy. The micro-displacement element is characterized in that

In the micro-displacement element, the Au or Au alloy thin film used for the electrodes is oriented in the (111) plane,
The dispersion angle of the X-ray rocking curve showing the orientation is 5 °
It is preferably within the range.

The present invention made to achieve the third object, thirdly, has at least a piezoelectric thin film on an Si substrate and an electrode for displacing the piezoelectric thin film by an inverse piezoelectric effect, and A micro-displacement element whose electrodes are produced by anisotropic etching of Si is characterized in that the piezoelectric thin film is tantalum oxide.

Fourthly, in anisotropic etching,
Utilizing the difference in etching rate between tantalum oxide and Si,
At the same time, it is a method of manufacturing a micro displacement element, which is characterized by etching tantalum oxide and Si.

Further, as an information processing device and a tunnel current detecting device using the minute displacement element having the above-mentioned first to third configurations, fifthly, the minute displacement element is arranged so as to face the recording medium, and the minute displacement is performed. The element is provided with a driving means for driving the minute displacement element and a control means for controlling the driving means, and further comprises an information processing bias voltage applying circuit which can be applied between the recording medium and the probe. Information processing device.

Sixth, a plurality of minute displacement elements are arranged so as to face the recording medium, and each of the minute displacement elements is provided with driving means for driving the minute displacement element and control means for controlling the driving means. In addition, the information processing apparatus includes an information processing bias voltage applying circuit that can be applied between the recording medium and the probe.

The control means in the information processing apparatus of the present invention changes the bias voltage for displacing the minute displacement element based on the detection result of the tunnel current flowing between the recording medium and the probe, and minutely changes the signal thereof. It is preferable that the means is a means for applying the electrodes to the displacement element.

The recording medium in the information processing apparatus of the present invention preferably has an electric memory effect or has a non-conductive surface.

Seventh, the minute displacement element is arranged so as to face the electric conductor, and the minute displacement element is provided with driving means for driving the minute displacement element and control means for controlling the driving means, and the electric conductor and the probe. There is a tunnel current detecting device that outputs a data on the surface of the electric conductor on the basis of the detection result of the tunnel current by applying a voltage between and.

The above is the basic configuration of the present invention, and the details and operation thereof will be described in the following embodiments.

[0033]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 This example shows a micro-displacement element having the first structure.

FIG. 1 shows a perspective view of a portion of the micro displacement element of the present invention. Further, FIG. 2 is a sectional view taken along the line AA of the schematic process. First, the Si ₃ N ₄ films 2 and 3 are formed to a thickness of about 200 nm by LPCVD on both surfaces of a quartz substrate (Z-cut) 1 (thickness 500 μm) whose both surfaces are perpendicular to the Z axis. Next, square markers are patterned at two places on the Si ₃ N ₄ film 3 on the back surface of the quartz substrate 1. For patterning, a positive resist AZ1370 (made by Hoechst) is used, and CF _{4 is formed by} a reactive ion etching method (RIE method).
The Si ₃ N ₄ film 3 was etched with gas. Then Figure 2
As shown in (a), the marker substrate 8 was formed by anisotropically etching the quartz substrate 1 from the back surface of the quartz substrate 1 at room temperature with an HF aqueous solution (10 mol / l). In anisotropic etching of the quartz substrate 1, the etching rates are greatly different between the Z-axis surface and the X- and Y-axis surfaces. Therefore, since the angle formed by the Z axis and the X and Y axes is 90 °, the accuracy is not deteriorated even if the thickness of the crystal substrate 1 changes.

Thereafter, as shown in FIG. 2B, the Si ₃ N ₄ film 2 on the surface of the quartz substrate 1 was patterned so that the cantilever 7 would be formed in the future by using the marker hole 8 as a marker. Then, the quartz substrate 1 was anisotropically etched again with an HF aqueous solution to leave a thickness of 20 μm to the surface.

Next, as shown in FIG. 2C, two layers of piezoelectric thin films 9, 10 and three layers of electrodes 11, 1 which are driving parts of the piezoelectric body.
2 and 13 are formed. ZnO is used for the piezoelectric thin films 9 and 10.
Was used. Au was used for the electrodes 11, 12, and 13. The piezoelectric thin films 9 and 10 are formed by a sputtering method and wet-etched with an acetic acid aqueous solution to form a pattern. Au is vapor-deposited by a resistance heating method and wet-etched with an aqueous solution of iodine and potassium iodide to form a pattern. Further, the insulator layer 14, the information processing probe 15 (hereinafter referred to as a probe) and the extraction electrode 16 thereof are formed. As the insulator layer 14, an amorphous Si ₃ N ₄ film having a thickness of about 200 nm formed by a CVD method and patterned by dry etching using an RIE apparatus is used. The extraction electrode 16 is formed by forming a pattern of Au and using it. Probe 15
Is formed by isotropic etching using an aqueous solution of iodine and potassium iodide while forming a film of W by a sputtering method and leaving the photoresist of the probe portion in a circular shape.

Finally, as shown in FIG. 2 (d), by the reactive ion etching (RIE method) using CF ₄ and O ₂ plasma, the quartz membrane remaining 20 μm from the back surface of the quartz substrate 1 and the remaining Si ₃ N _{4 were used.} Etching the film, through hole 6
(The surface of the through hole is the X-axis equivalent surface 4 and the Y-axis equivalent surface 5 of quartz.) And the piezoelectric body-driven cantilever 7 was formed.

An HF aqueous solution is typically used as an etching solution for the quartz substrate 1, but an aqueous solution having an etching rate greatly different depending on the crystal orientation of the quartz substrate 1 (for example, NH ₄ F, NH ₄ NH ₂ etc.). ), The same applies.

Further, in this embodiment, Si ₃ N ₄ was used as the material of the front surface layer and the back surface layer of the quartz substrate 1, but other materials may be used as long as they can be selectively etched with quartz.

Embodiment 2 In this embodiment, another mode of the minute displacement element having the first structure is shown.

FIG. 3 is a sectional view of a schematic process of the micro displacement element of this embodiment. The process is the same as that of the first embodiment, but there are two differences in the present embodiment: there is no step of forming the marker hole and that the anisotropic etching step is performed last.

First, as shown in FIG. 3A, directly patterned marker 17 is formed on the back surface layer 3. Since the quartz substrate 1 is transparent, the image seen through the marker 17 on the back surface can be used as a marker on the front surface and can be used as an index for aligning the back surface and the front surface. However, at the point of alignment, the thickness distance between the mask and the quartz substrate 1 is out of focus, so there is a problem of the depth of focus of the aligner used. However, the deeper the depth of focus, the more accurate alignment can be performed. . By this alignment, Fig. 3 (b)
As described above, the surface layer 2 was patterned so that a cantilever was formed in the future as in Example 1. Next, a cantilever and a probe were formed in the same process as in Example 1. Finally, anisotropic etching of the crystal was performed from the back surface to form a through hole.

By the above method, the number of steps can be greatly reduced, and the minute displacement element having high dimensional accuracy can be obtained.

Embodiment 3 In this embodiment, an information processing apparatus for recording and reproducing information using the minute displacement element having the first structure will be described. FIG. 4 shows an example of a schematic diagram in recording and reproducing information of the information processing apparatus of the present invention. In FIG. 4A, after forming a conductor thin film 19 made of a conductive organic material on a substrate 20, a recording layer 18 made of an organic material is laminated to form a recording medium. In the present invention, as shown in FIG. 4B, the surface shape of the recording medium is changed by bringing the recording medium into contact with the probe 15 attached to the minute displacement element of the present invention to form the recording bit 21. Is recording.
By scanning the surface of the recording medium with the probe 15, the tunnel current is utilized to change the surface shape, that is, the recording bit 21 is read out to reproduce the information. As the material of the recording layer 18 used in the present invention,
Any organic compound may be used. Further, as the film forming method, a vapor deposition method, a sputtering method, a plasma polymerization method, an electrolytic polymerization method, or the like can be used.

Further, as the material of the recording layer 18, an organic material capable of forming a monomolecular film or a monomolecular cumulative film by the LB method is also suitable.

According to this LB method, a monomolecular film of an organic compound having a hydrophobic site and a hydrophilic site in one molecule or a cumulative film thereof can be easily formed on the substrate 20, and the monomolecular film can be formed in a molecular order. Has thickness and is uniform over a large area,
Since it is possible to stably supply a homogeneous organic ultra-thin film,
In order to perform high-density information processing as in the present invention, it is necessary to reduce defects in the recording layer 18 and irregularities on the surface of the recording layer 18. From this point, the LB method is very suitable for forming the recording layer 18. ing.

In the LB method, in a molecule having a structure having a hydrophilic site and a hydrophobic site in the molecule, when the balance between them (the amphipathic balance) is appropriately maintained, the molecule is hydrophilic on the water surface. This is a method for producing a monomolecular film or a cumulative film thereof by utilizing the fact that the base is turned downward to form a monomolecular layer.

Examples of the group constituting the hydrophobic moiety include various well-known saturated and unsaturated hydrocarbon groups, condensed polycyclic aromatic groups, and various hydrophobic groups such as chain polycyclic phenyl groups. Each of these may be used alone or in combination to form a hydrophobic site. On the other hand, the most representative components of the hydrophilic moiety are, for example, a carboxyl group, an ester group, an acid amide group, an imide group, a hydroxyl group, and further an amino group (1, 2, 3 and 4). And hydrophilic groups thereof. Each of these alone or in combination of a plurality thereof constitutes a hydrophilic part of the molecule.

Organic molecules having these hydrophobic groups and hydrophilic groups in a well-balanced manner can form a monomolecular film on the surface of water, and are extremely suitable materials for the present invention. become.

The material of the conductor thin film 19 may be any material having high conductivity, such as Au, Pt, Ag,
There are many materials such as metals such as Pd, Al, In, Sn, Pb, and W, alloys thereof, and conductive oxides such as graphite, silicide, and ITO.
Application of these to the present invention is conceivable. As a thin film forming method using such a material, a conventionally known thin film technique is sufficient. However, since the conductor thin film 19 also functions as a part of the recording medium, a material and a thin film forming method that can form a thin film with few defects and good surface smoothness are selected. The film thickness of the conductor thin film 19 depends on the material and film thickness of the recording layer 18, but is preferably about 10 to 50 nm for stable information processing.

Next, the information processing apparatus of the present invention will be described with reference to the block diagram of FIG. In FIG. 5, reference numeral 15 is a probe for contacting a recording medium to perform recording, or detecting a tunnel current to read out a recording bit, and 23 is a schematic view of the minute displacement element used in the first embodiment. . In this minute displacement element, 25 is a Z-direction fine movement control mechanism that can be driven by a piezoelectric effect, and 24 is a Y-direction fine movement control mechanism that can be driven by an electrostatic actuator. Information processing is performed by accessing the recording medium from the probe 15 by driving the minute displacement element 23. The target recording medium is installed on the XY stage 30.
28 is a bias voltage source and a probe current amplifier.
Reference numeral 7 denotes a reproducing servo circuit that reads the probe current and controls the voltage applied to the piezoelectric body so that the height of the probe 15 becomes constant. Reference numeral 29 is a recording voltage source and a servo circuit. The recording voltage from 29 is the Z direction fine movement control mechanism 25.
The probe 15 is moved up and down to contact the recording medium to perform recording. However, at this time, the probe current is monitored to detect a sudden current increase, that is, the contact between the probe 15 and the conductor thin film layer 19, and the servo circuit is controlled so as to control the contact amount between the recording layer 18 and the probe 15 thereafter. It is provided so that the applied voltage for recording can be adjusted. The contact amount (Z-direction indentation amount) at the time of recording information depends on the film thickness of the recording layer 18 and the conductor thin film layer 19 and the desired recording bit size, but is several nm to 500 nm.
About nm is preferable.

When recording information, the probe 15 and the conductor thin film layer 19 come into contact with each other and the probe current sharply increases, so that the reproducing servo circuit 27 turns on the HOLD circuit so that the output voltage becomes constant during that time. Control. Two
6 uses the Y-direction fine movement control mechanism 24 to move the probe 15 to the Y direction.
It is an XY scanning drive circuit for controlling movement in directions. Three
1 and 32 are used in advance to make a large relative displacement in the Y direction between the probe 15 and the substrate 20 (outside the range of the fine movement control mechanism) so that a probe current of about 10 ⁻⁹ A can be obtained. Each of these devices is a microcomputer 3
Centrally controlled by 3. Reference numeral 34 represents a display device.

The mechanical performance in movement control using the minute displacement element described in the first embodiment of the present invention is shown below.

Z direction fine movement control range: 0.1 nm to 5 μm Y direction fine movement control range: 1 nm to 20 μm X direction fine movement control range: 1 nm to 100 μm XY direction coarse movement control range: 10 nm to 10 mm Z direction coarse movement control range: 10 nm -10 mm Hereinafter, a recording / reproducing experiment using the information processing apparatus described above will be described.

As the recording layer 18, a polyimide LB film having four layers (about 1.5 nm) was used. This was set in the information processing device. Next, a bias voltage of 1.5 V is applied between the probe 15 and the recording medium, and the probe 1
The distance (Z) between 5 and the conductor thin film 19 was adjusted. At this time, the probe current Ip for controlling the distance Z is set to 10 ^−8.
It was set so that A ≧ Ip ≧ 10 ⁻¹⁰ A.

Next, by applying a recording voltage to the piezoelectric body of the fine displacement element of the Z direction fine movement control mechanism 25 of the probe 15 while fixing the position in the XY direction, the probe 1
Recording was carried out by changing the surface shape of the recording medium by moving 5 up and down and bringing the probe 15 into contact with the recording medium. However, at this time, the contact amount between the probe 15 and the recording medium is set to 1
It was adjusted to 5 nm. Further, the reproducing servo circuit 27 controls to turn on the HOLD circuit so that the output voltage becomes constant during that time.

Next, the tunnel current is observed while applying a voltage between the probe 15 and the recording medium, and the probe 15 is applied to the recording position X while keeping the distance Z constant.
When scanning was performed in the Y direction, a change in the surface shape of the recording medium was confirmed, and the recording bit 21 could be reproduced.

Fourth Embodiment In this embodiment, the STM is used by using the information processing apparatus described above.
The result of the experiment will be described.

An STM image is obtained by scanning the recording medium described in Example 3 as an object to be observed, applying a voltage between the probe 15 and the object to be observed, and outputting the result of the tunnel current value. In this embodiment, a Si substrate (100) is used as the object to be observed.
When an STM image was obtained using, the image could be observed over a wide area of the Si substrate in atomic order, and a more stable image was obtained.

Example 5 In the method of manufacturing a micro-displacement element according to the second structure of the present invention, first, an insulating layer is formed on both surfaces of a semiconductor substrate, and a crystal of the substrate is formed from an etching hole formed in the insulating film on the back surface of the substrate. The substrate is etched by an azimuth-dependent etching method to form a membrane. Next, a bimorph constituent element is formed on the surface of the substrate in the order of lower electrode / lower ZnO / middle electrode / upper ZnO / upper electrode and patterned. Here, in order to increase the crystal orientation of ZnO, increase the effective voltage to ZnO, and simplify the process, Au or Au alloy, preferably Au or Au alloy oriented in the (111) plane is used as an electrode. After further patterning two layers of ZnO into a cantilever shape, an extraction electrode and a probe are formed on the bimorph, and finally the silicon membrane is removed to form a minute displacement element.

FIGS. 10 and 11 show ZnO on the Au electrode.
3 is a graph relating to the orientation and piezoelectricity of the. Figure 10
It is an experimental value showing the relationship between the standard deviation of the X-ray rocking curve of the Au (111) plane and the standard deviation of the X-ray rocking curve of the ZnO (002) plane. From this figure, Au (11
1) It can be seen that when the plane orientation is improved, the ZnO (002) plane orientation (C-axis orientation) is also improved. FIG. 11 shows A
Standard deviation of X-ray rocking curve of u (111) plane and Z
It is an experimental value showing the relationship of the electromechanical coupling constant of nO. Z
Since the electromechanical coupling constant of nO and the piezoelectricity are proportional to each other, it can be seen from this figure that the piezoelectricity of ZnO sharply decreases when the standard deviation of the X-ray rocking curve of the (111) plane of Au is 5 ° or more. I understand. From these two figures, ZnO
It is necessary to improve the orientation of the Au electrode (111) surface in order to improve the piezoelectricity of X.
The dispersion angle of the line rocking curve is within 5 °, preferably within 3 °. Similar results were obtained with respect to the orientation and piezoelectricity of ZnO on the Au alloy electrode. Au
In the case of an alloy electrode, it is necessary to have a face-centered cubic structure at room temperature because its crystal plane is oriented in the (111) plane, and such an Au alloy is, for example, A containing Ag, Cu, Pd.
u or 17% or less Cd, 15% or less Zn, 5
% Au or the like containing Fe or less. Since the Au alloy thin films having these compositions are oriented in the crystal plane (111) plane,
By improving the orientation, ZnO has the same effect as the Au electrode.

The case where an Au electrode is used will be described below as a specific example. 6 is a vertical sectional view thereof, and FIG. 7 is a horizontal sectional view thereof. The size of the cantilever is 500 μm in the vertical direction,
The width is 150 μm.

The manufacturing process is shown below. First, 2000 Å of Si ₃ N ₄ films 2 and 3 were formed by LPCVD on both surfaces of an n-type silicon substrate 22 (thickness: 525 μm) whose both surfaces were crystallographically oriented (100) planes. Next, the Si ₃ N ₄ film 4 on the back surface of the Si substrate 22 was patterned, and a 20 μm Si membrane was formed by Si crystal anisotropic etching with a KOH aqueous solution. Further, a bimorph structure as shown in FIG. 8 was formed on the surface of the Si substrate 22. The bimorph structure was formed by patterning Cr as a lower electrode 30 Å and Au as a 1000 Å vacuum evaporation method as a lower electrode 11 on the Si ₃ N ₄ film 3. The lower piezoelectric thin film 9 made of ZnO is formed by magnetron sputtering to 3
A film was formed at 000Å. Zn is used as a target and Ar.O
_The film was formed in ₂ atmospheres. Au as the middle electrode 12 is 20
00Å A film was formed by a vacuum evaporation method and patterned.
An upper piezoelectric thin film 10 made of ZnO was formed into a film of 3000 Å by magnetron sputtering. Au was formed into a film as the upper electrode 13 and the take-out electrode 16 by a 1000 Å vacuum deposition method, and patterned.

X showing the orientation of the upper electrode 13 and the middle electrode 12
The dispersion angles of the line rocking curves were all 3 °.
Each of the lower electrode 11, the middle electrode 12, and the upper electrode 13 has a lead-out portion connected to a driving amplifier circuit. Lower electrode 1
Each of the upper electrode 13 and the upper electrode 13 is divided into two, and is a cantilever having five electrodes in total and capable of being driven in three axial directions.

Next, piezoelectric thin films 9 and 10 made of ZnO.
Was patterned into a cantilever shape, and then W (tungsten) was deposited by a vacuum deposition method to form the probe 15.

Finally, the Si membrane was removed by reactive ion etching using CF ₄ and O ₂ gas to form a cantilever.

Embodiment 6 This embodiment shows another micro displacement element according to the second constitution of the present invention. In this embodiment, as shown in FIG. 9, Au90% Zn1 is used for the middle electrode 12 and the upper electrode 13 of the bimorph.
By using a 0% alloy, the adhesion between the middle electrode 12 and the lower piezoelectric thin film 9 made of ZnO, and the upper electrode 13 and Zn
The adhesion with the upper piezoelectric thin film 10 made of O was improved as compared with the fifth embodiment. The configuration other than the electrode configuration is the same as that of the fifth embodiment, and the vertical sectional view of FIG. 6 and the horizontal sectional view of FIG. 7 are applied as they are.

The bimorph structure is formed on the Si ₃ N ₄ film 2 by
As the lower electrode 11, 30 Å of Cr and 1000 Å of Au were formed into a film by a vacuum evaporation method and patterned. The lower piezoelectric thin film 9 made of ZnO is formed by magnetron sputtering to 30
00Å A film was formed. Au 90% Zn1 as the middle electrode 12
A 0% alloy was formed into a film by a 2000Å vacuum deposition method and patterned. An upper piezoelectric thin film 10 made of ZnO was formed into a film of 3000 Å by magnetron sputtering. Au9 as the upper electrode 13 and the tunnel current extraction electrode 16
A 0% Zn10% alloy was formed into a film by the 1000Å vacuum deposition method and patterned.

X showing the orientation of the upper electrode 13 and the middle electrode 12
The dispersion angles of the line rocking curves were all 5 °.

Embodiment 7 In this embodiment, an information processing apparatus using a plurality of minute displacement elements having the second structure of the present invention will be described.

FIG. 12 shows the configuration and block diagram of the main part of the present invention. Explaining with reference to this figure, a plurality of minute displacement elements 41 according to the present invention are arranged on the recording / reproducing head 40. The plurality of minute displacement elements 41 are arranged so as to uniformly face the recording medium. 42 is a recording medium for recording information, 43 is a base electrode for applying a voltage between the recording medium 42 and the probe 15, and 44 is a recording medium holder. The recording medium 42 has a metal, a semiconductor, an oxide, an organic thin film capable of deforming the shape of the surface of the recording medium into a convex shape or a concave shape by a tunnel current generated from the probe 15, or an electric property thereof is changed by a tunnel current. It is composed of an organic thin film having an electric memory effect. The electric memory effect exceeds the threshold value that allows the organic thin film to transit to a state in which two or more different electric conductivities (ON state, OFF state) in FIG. Reversible low resistance state (ON state) and high resistance state (O
It is possible to make a transition (switching) to the FF state). Further, each state can be retained (memory) without applying a voltage. The organic thin film whose electric characteristics change is preferably Langmuir
It is a blow jet film (see Japanese Patent Laid-Open No. 63-161552). For example, a base electrode 43 on a quartz glass substrate
As 50 Å of Cr deposited by vacuum evaporation method and further 300 Å of Au deposited thereon by using the same method, on which four layers of SOAZ (squarylium-bis-6-octylazulene) are laminated by LB method, etc. To use.

Reference numeral 46 is a data modulation circuit for modulating the data to be recorded into a signal suitable for recording, and 47 is a recording medium by applying a voltage between the recording medium 42 and the probe 41 to the signal modulated by the data modulation circuit. 42 is a recording voltage applying device for recording on. When the probe 41 is brought close to the recording medium 42 by a predetermined distance and a rectangular pulse voltage having, for example, a 3-volt width of 50 ns is applied by the recording voltage applying device 47, the recording medium 42 undergoes a characteristic change and a portion having a low electric resistance is generated. Information is recorded by performing this operation while scanning the surface of the recording medium 42 with the probe 41 using the XY stage 48. Although not shown in the figure,
As a scanning mechanism by the XY stage 48, a control mechanism such as a cylindrical piezo actuator, a parallel spring, a differential micrometer, a voice coil, and an inch worm is used.

Reference numeral 49 is a recording signal detection circuit for applying a voltage between the probe 41 and the recording medium 42 to detect a tunnel current flowing between them, and 50 is for demodulating the tunnel current signal detected by the recording signal detection circuit 49. This is a data demodulation circuit. During reproduction, the probe 41 and the recording medium 42 are arranged at a predetermined interval, and a DC voltage lower than the recording voltage, for example, 200 mV is applied between the probe 41 and the recording medium 42. In this state, the tunnel current signal detected by the recording signal detection circuit 49 during scanning with the probe 41 along the recording data string on the recording medium 42 corresponds to the recording data signal. Therefore,
A reproduced data signal can be obtained by current-voltage converting the detected tunnel current signal, outputting the tunnel current signal, and demodulating by the data demodulation circuit 50.

Reference numeral 51 is a probe height detection circuit. The probe height detection circuit 51 receives the detection signal of the recording signal detection circuit 49, cuts off the high frequency vibration component due to the presence or absence of an information bit, processes the remaining signal, and makes the remaining signal value constant. A command signal is transmitted to the x-axis and z-axis drive control circuit 52 in order to control the vertical movement of the probe 41. This keeps the distance between the probe 41 and the medium 42 substantially constant.

Reference numeral 53 is a track detection circuit. When the probe 41 scans the recording medium 42, the track detection circuit 53 deviates from a path along which the data of the probe 41 should be recorded, or a deviation from a recorded data string (hereinafter, these are referred to as tracks). This is the detection circuit.

The above data modulating circuit 46, recording voltage applying device 47, recording signal detecting circuit 49, data demodulating circuit 5
0, the probe height detection circuit 51, the x, z axis drive control circuit 52, and the track detection circuit 53 form a recording / reproducing circuit 54. In the recording / reproducing head 40 shown in FIG. 12 as an example, one recording / reproducing circuit 54 is provided for each of the plurality of probes facing the recording medium and its driving mechanism. Elements such as displacement control (tracking, interval adjustment, etc.) are performed independently. The material of the recording medium and the tracking method of the minute displacement element do not limit the present invention.

Although all of the above-mentioned information processing devices are recording / reproducing devices, it goes without saying that the present invention can be applied to recording / reproducing only devices or scanning tunnel current detecting devices.

Comparative Example In the minute displacement elements of Examples 5 and 6, C of ZnO was used.
The dispersion angle of the X-ray rocking curve showing the axial orientation is 3 to 5 °.
Since it is small and the C-axis orientation is high, the piezoelectricity of ZnO is improved and the displacement amount can be increased. Z between electrodes
Since there is no layer other than nO, the effective voltage to ZnO is large, and the amount of displacement with respect to the applied voltage can be increased. Since there is no interlayer film between the electrode and the ZnO piezoelectric body,
The electrode formation process is easy. There are the above effects.

As a comparative example of the cantilever type probes according to Examples 5 and 6, a bimorph structure as shown in FIG. 18, that is, a micro displacement element composed of three layers of Al electrodes and two layers of ZnO piezoelectric thin film (Comparative Example 1), and A displacement amount was compared by selecting a micro-displacement element (comparative example 2) having a bimorph structure as shown in FIG. 19, ie, three layers of Al electrodes, two layers of ZnO piezoelectric thin film and four layers of SiO ₂ intermediate insulating layer. . The results are shown below.

[0081]

[Table 1] From the above results, the displacement amount of Example 5 was 100 of Comparative Example 1.
The amount of displacement was 10 times that of Comparative Example 2. Further, the displacement amount of Example 6 is slightly smaller because the dispersion angle of the X-ray rocking curve showing the orientation of the electrode is larger than that of Example 5, but the upper electrode 13 is Au 90% Zn 10%.
By using the alloy, the adhesiveness between the lower piezoelectric thin film 9 made of ZnO and the middle electrode 12 and the adhesiveness between the upper piezoelectric thin film 10 made of ZnO and the upper electrode 13 were further improved.

Example 8 Tantalum oxide is known to be chemically stable. Further, regarding piezoelectricity, both piezoelectric constant and electromechanical coupling constant exhibit good characteristics. It is known that the insulating property is high in both resistivity and breakdown voltage.

Generally, a sputtering method is usually used for forming the piezoelectric thin film. For example, in order to obtain a good piezoelectricity in a ZnO thin film, it is formed at a substrate temperature of about 200 ° C., but tantalum oxide has a drawback that it needs to be formed at a high temperature of about 500 ° C. Also, from the viewpoint of effect, tantalum oxide is good.

In the anisotropic etching of Si, a KOH aqueous solution (20 to 30 wt.
%) Is used. For example, KOH aqueous solution (28 wt
%) Si is 4 μm / m when etched at 110 ° C.
etched in. On the other hand, ZnO is 5 μm /
min, tantalum oxide is 0.05 μm / min.
That is, tantalum oxide has a speed difference of 1:80 compared to Si. When an Au mask is used for etching on tantalum oxide, the undercut of tantalum oxide is very small, and etching with a high aspect ratio can be performed.

The minute displacement element having the third structure of the present invention will be described in detail with reference to FIG. First, in FIG. 14A, a Si ₃ N ₄ film 3 was formed on the back surface of the Si (100) substrate 22 having a thickness of 0.15 mm by the CVD method to a thickness of about 1500 Å. The gas used was SiH ₂ Cl ₂ : NH ₃ = 1: 9, and the film formation temperature was 800 ° C. Next, the Si ₃ N ₄ film 3 is formed by photolithography and CF ₄ dry etching.
Was patterned into a desired shape. After this, Au
Was deposited to form a lower electrode 11, and patterning was performed by photolithography and wet etching. Then, a lower piezoelectric thin film 9 made of tantalum oxide was formed to a thickness of 1 μm by the sputtering method. Ta was used as a target, and sputtering was performed in an O ₂ atmosphere at a substrate temperature of 500 ° C. Then, the middle electrode 12 made of Au
Was formed by patterning by photolithography and wet etching, and similarly, the upper piezoelectric thin film 10 made of tantalum oxide was formed, and further the upper electrode 13 was formed. Next, a tungsten film was formed as the probe 15, and the probe 15 was manufactured by photolithography and lift-off. After that, KOH (28wt%) 11
Anisotropic etching was performed at 0 ° C. to remove desired Si and the tantalum oxide thin film at the same time, as shown in FIG. 14B, to fabricate a minute displacement element.

In this way, the number of steps of the manufactured micro-displacement element could be significantly reduced as compared with the manufacture of the conventional micro-displacement element using, for example, ZnO as the piezoelectric thin film.

When the minute displacement element manufactured by the above method was operated, the displacement amount was 50% or more larger than that of the minute displacement element manufactured by the piezoelectric thin film made of ZnO at the same voltage, and the breakdown voltage was 2 It was more than twice as high, and eventually three times or more displacement was obtained.

In this embodiment, the cantilever-shaped micro displacement element using the piezoelectric thin film made of tantalum oxide is shown. However, the present invention can be applied to other micro displacement elements such as a doubly supported beam shape. In the process of simultaneously etching the Si substrate and the piezoelectric thin film by anisotropic etching, the film thickness of the piezoelectric thin film made of tantalum oxide and Si
By designing the thickness of the portion of the substrate to be removed, it can be applied to various cases.

Embodiment 9 This embodiment shows another method for manufacturing a micro displacement element having the third structure of the present invention. FIG. 15 is a process step diagram thereof.

In FIG. 15A, first, Si (10
0) Si ₃ N ₄ film 2 on both sides of substrate 22 by the CVD method,
3 is deposited to 2000 Å, the Si ₃ N ₄ film 2 on the back surface is patterned into a desired shape by photolithography and dry etching, and then KOH is applied from the back surface of the Si substrate 22.
The Si substrate 22 was etched with a 30 wt% aqueous solution at 110 ° C. to form a 20 μm Si membrane.

Next, in FIG. 15B, the Au lower electrode 11 is formed and patterned by photolithography and wet etching, and thereafter, the lower piezoelectric thin film 9 made of tantalum oxide is formed as in the eighth embodiment. Formation,
After that, the lower piezoelectric thin film 9 made of tantalum oxide was patterned by photolithography and wet etching. This process is repeated, and FIG.
The configuration as shown in (b) was performed. Next, the probe 15 was formed in the same manner as in Example 8.

Next, the remaining Si membrane was etched again with a KOH 30 wt% aqueous solution at 110 ° C. In this embodiment, since tantalum oxide is used as the piezoelectric thin film, tantalum oxide is less damaged even in severe etching with a 30 wt% KOH aqueous solution, and Si can be etched without a protective layer. Next, by dry etching, the remaining Si ₃ N ₄ film 3
Then, the micro displacement element shown in FIG. 15C was manufactured.

The micro-displacement element thus manufactured can be manufactured without providing a protective layer on the piezoelectric thin film because the tantalum oxide film is less damaged even when immersed in a Si etching solution, and there is little wraparound. The number of steps can be reduced.

[0094]

As described above, first of all, a micro-displacement element using a single crystal quartz substrate having a plane perpendicular to the Z-axis as a main surface, an information processing apparatus using the same, and a tunnel current detection apparatus. According to the method, the accuracy is maintained regardless of the thickness of the substrate. Improves processing dimensional accuracy. There is such an effect.

Secondly, an information input / output probe is provided at the free end of the upper surface of a cantilever-shaped displacement element having two layers of ZnO piezoelectric thin films and electrodes for displacing the piezoelectric thin films by the inverse piezoelectric effect. In the small displacement element,
By using Au or Au alloy, preferably Au or Au alloy oriented in the (111) plane for the bonding surface between the electrode and ZnO, the orientation of ZnO is improved and the displacement amount can be increased. The amount of displacement can be increased by increasing the effective voltage applied to ZnO. The electrode formation process is easy. There are the above effects.

Further, in the information processing device and the tunnel current detecting device using such a minute displacement element, since the length of the cantilever type probe with respect to the displacement amount can be shortened, the density of a plurality of probes can be increased,
It can be miniaturized. Since the length of the cantilever type probe for the amount of displacement can be shortened,
The resonance frequency can be increased, and the response speed of the probe is improved. Since it is possible to reduce the drive voltage with respect to the displacement amount of the cantilever probe, it is possible to reduce noise to the tunnel current due to the drive voltage. There are the above effects.

Thirdly, a piezoelectric thin film made of tantalum oxide and an electrode for displacing the piezoelectric thin film by an inverse piezoelectric effect are provided on a Si substrate, and the electrode is formed by anisotropic etching of Si. By using the micro-displacement element and its manufacturing method, it becomes possible to manufacture a micro-displacement element having excellent electrical characteristics as compared with the conventional micro-displacement element using, for example, a ZnO film. Furthermore, in the anisotropic etching process, S
Since i and the tantalum oxide film can be removed at the same time, the number of process steps can be significantly reduced. This allows
It has become possible to provide a more inexpensive micro displacement element.

[Brief description of drawings]

FIG. 1 is a perspective view of a part of a minute displacement element having a first structure according to the present invention.

FIG. 2 is a schematic process sectional view of the minute displacement element having the first structure of the present invention.

FIG. 3 is a schematic process cross-sectional view of a minute displacement element according to another embodiment of the first configuration of the present invention.

FIG. 4 is a schematic diagram showing the principle of recording / reproduction of the present invention.

FIG. 5 is a block diagram of a recording / reproducing apparatus of the present invention.

FIG. 6 is a vertical cross-sectional view of a minute displacement element having a second structure according to the present invention.

FIG. 7 is a transverse cross-sectional view of a minute displacement element having a second structure according to the present invention.

FIG. 8 is a configuration diagram of a bimorph of Au and ZnO.

FIG. 9 is a bimorph block diagram of AuZn, ZnO.

FIG. 10 is a graph showing the relationship between the standard deviation of the X-ray rocking curve of the Au (111) plane and the standard deviation of the X-ray rocking curve of the ZnO (002) plane.

FIG. 11 is a graph showing the relationship between the standard deviation of the X-ray rocking curve on the Au (111) plane and the electromechanical coupling constant of ZnO bimorph.

FIG. 12 is a structural conceptual diagram of an information processing apparatus of the present invention.

FIG. 13 is a graph showing an electric memory effect of an organic thin film.

FIG. 14 is a sectional view of a minute displacement element having a third structure of the present invention.

FIG. 15 is a cross-sectional view of another example of the minute displacement element having the third structure of the present invention.

FIG. 16 is a cross-sectional view of a conventional small displacement element.

FIG. 17 is a cross-sectional view of a conventional micro displacement element.

FIG. 18 is a configuration diagram of a bimorph of Al and ZnO.

FIG. 19 is a bimorph block diagram of Al, SiO ₂ , ZnO.

[Explanation of symbols]

1 Crystal substrate 2, 3 Si ₃ N ₄ film 4 X-axis equivalent surface 5 Y-axis equivalent surface 6 Substrate through hole 7 Cantilever 8 Marker hole 9 Lower piezoelectric thin film 10 Upper piezoelectric thin film 11 Lower electrode 12 Middle electrode 13 Upper electrode 14 Insulator layer 15 Information input / output probe 16 Extraction electrode 17 Marker 18 Recording layer 19 Conductive thin film 20 Substrate 21 Recording bit 22 Si substrate 40 Recording / reproducing head 41 Small displacement element 42 Recording medium 43 Base electrode 44 Recording medium holder 46 Data modulation Circuit 47 Recording voltage applying device 48 XY stage 49 Recording signal detection circuit 50 Data demodulation circuit 51 Probe height detection circuit 52 x, z axis drive control circuit 53 Track detection circuit 54 Recording / reproducing circuit

Continued front page    (72) Inventor Takayuki Yagi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Yu Nakayama             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Yasuhiro Shimada             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Osamu Takamatsu             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Yutaka Hirai             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation

Claims (11)

[Claims] 1. A micro-displacement element having at least a piezoelectric thin film and an electrode for displacing the piezoelectric thin film by a piezoelectric inverse effect on a substrate, and information input / output at a free end portion of an upper surface of the micro-displacement element. Displacement element provided with a probe for use, wherein the substrate is a single crystal quartz substrate having a plane perpendicular to the Z-axis (perpendicular to the probe) as a main surface. 2. An information input / output is provided at an upper surface free end portion of a cantilever displacement element having at least two layers of piezoelectric thin films and electrodes for displacing the piezoelectric thin films by an inverse piezoelectric effect. A microdisplacement element having a probe for use, wherein the piezoelectric thin film is made of ZnO, and all the bonding surfaces between the electrodes and the piezoelectric thin film are made of Au or an Au alloy. 3. The Au or Au alloy thin film surface used for the electrode is oriented in the (111) plane, and the dispersion angle of the X-ray rocking curve showing the orientation is within 5 °. The minute displacement element described. 4. A micro-displacement element having at least a piezoelectric thin film and an electrode for displacing the piezoelectric thin film by an inverse piezoelectric effect on a Si substrate, and the electrode being manufactured by anisotropic etching of Si. 2. A micro displacement element, wherein the piezoelectric thin film is tantalum oxide. 5. The method of manufacturing a micro displacement element according to claim 4, wherein in the anisotropic etching, the tantalum oxide and Si are simultaneously etched by utilizing the difference in etching rate between tantalum oxide and Si. 6. The minute displacement element according to claim 1 is arranged to face a recording medium, and the minute displacement element controls a driving means for driving the minute displacement element and the driving means. An information processing apparatus comprising a control means and an information processing bias voltage applying circuit which can be applied between a recording medium and a probe. 7. A plurality of the minute displacement elements according to claim 1 are arranged so as to face a recording medium, and each of the minute displacement elements has a driving means for driving the minute displacement element. An information processing apparatus comprising: a control unit that controls the driving unit; and an information processing bias voltage applying circuit that can be applied between a recording medium and a probe. 8. The control means changes a bias voltage for displacing the micro displacement element based on a detection result of a tunnel current flowing between the recording medium and the probe, and outputs the signal to an electrode constituting the micro displacement element. The information processing apparatus according to claim 6 or 7, wherein the information processing apparatus is provided to the user. 9. The information processing apparatus according to claim 6, wherein the recording medium has an electric memory effect. 10. The information processing apparatus according to claim 6, wherein the surface of the recording medium is non-conductive. 11. A micro-displacement element according to any one of claims 1 to 4 is arranged so as to face an electric conductor, and the micro-displacement element controls a driving means for driving the micro-displacement element and the driving means. A tunnel current detecting device, characterized in that a control means is provided, a voltage is applied between the electric conductor and the probe, and information on the surface of the electric conductor is output based on the detection result of the tunnel current.