JPH04355232A - Probing unit and information recording and/or reproducing device using it - Google Patents

Abstract

PURPOSE:To make it difficult to be affected by external oscillation, to enable accurate displacement control of a probing electrode, to improve response speed and to increase a displacement amount. CONSTITUTION:The part of a piezo-electric bimorph panel 8d is supported by one side of the circumference of a cavity part 8c formed on a substrate 8b, the other end of the piezo-electric bimorph panel 8d is attached to the opposite side of the cavity part 8c via a pattern part 8e having smaller elastic modulus than that of the piezo-electric bimorph panel 8d, and the tip of the piezo-electric bimorph panel 8d is provided with a probing electrode 8a. The piezo-electric bimorph panel 8d is constructed in layers of piezo-electric elements and electrodes and capable of displacing the probing electrode 8a. By displacing the probing electrode 8a in the vertical direction to the face of the substrate 8b, the unit can be prevented from being affected by external oscillation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe unit for recording and reproducing high-density, large-capacity information, and an information recording and/or reproducing apparatus using the probe unit.

0002

BACKGROUND OF THE INVENTION In recent years, a scanning tunneling microscope (hereinafter referred to as STM) that can directly observe the electronic structure on and near the surface of a material has been developed [G. Binnig et al. ，
Helbetica Physica Acta, 55
, 726 (1982)], it has become possible to observe real space images with high resolution regardless of whether it is single crystal or amorphous, and this STM has the advantage of being able to perform measurements with low power while causing almost no damage to the sample material due to the current. Furthermore, it is expected to have a wide range of applications because it can operate not only in ultra-high vacuum but also in the atmosphere and in solutions, and can be applied to various materials.

[0003] In STM, a voltage is applied between a metal probe and a conductive sample, and when the probe is brought close to a distance of about 1 nm,
It takes advantage of the phenomenon of tunnel current. Recently, for example, Japanese Patent Application Laid-Open No. 161552/1983,
As disclosed in Publication No.-161553, this STM
Many proposals have been made to apply this principle to construct information processing devices mainly for ultra-high-density recording and playback. That is, S
A probe electrode corresponding to a TM tip physically deforms a recording medium corresponding to a sample or changes the electronic state of the medium surface to record information, and a tunnel current flowing between the two causes recording bits to be recorded. It is said that by using a method for reproducing information, it is possible to record and reproduce large-scale information at a high density on the order of molecules or atoms.

[0004] Among the above-mentioned recording methods, in order to cause physical deformation, in addition to pressing a sharp recording probe against the recording medium to form a dent, holes may be formed on a recording medium such as graphite by applying a pulse voltage. It has recently been reported that this can be done. That is, by bringing the probe electrode close to the surface of the recording medium and applying a voltage of 3 to 8 V between the two with a pulse width of 1 to 100 μs, a hole with a diameter of about 40 angstroms can be formed, and the recording bit It is fully usable as On the other hand, in order to perform recording by changing the electronic state, a method is known in which a voltage is applied between the recording medium, the base electrode, and the probe electrode to change the electrical resistance characteristics of the microscopic part. It is attracting attention because it is easy.

As the recording medium, a thin film layer of a material exhibiting memory-like switching characteristics in voltage-current characteristics, such as chalcogenides or π-electron based organic compounds, is used. For example, the Langmuir-Blodgett method (
A cumulative film of an appropriate organic substance prepared by the LB method (hereinafter referred to as the LB method) is used.

[0006] As a probe electrode, it is common to use a needle tip made of tungsten, Pt-Ir, Pt, etc., which has been mechanically polished and then electropolished, and which is attached to a piezoelectric element and whose displacement is controlled by an applied voltage. . As a method for manufacturing the flexible part that moves the probe electrode, for example, a processing technology that uses semiconductor process technology to create a fine structure on a single substrate (K. E. Peterson, "Silicon") is used.
as Mechanical Material”,
Proceedings of the IEEE, 7
0 vol. 420p, 1982). As a result, a cavity 1a is provided in the single crystal silicon substrate 1 that is movable in the XY axis directions shown in FIG. is also now possible.

This tongue-shaped portion 2 is composed of a layered piezoelectric element and an electrode, and by applying a voltage between the electrodes, the probe electrode 3 is moved in a direction perpendicular to the plane of the single crystal silicon substrate 1 (Z-axis direction). Changes to Of course, at this time, the tongue 2
It is also possible to realize a storage device including a transducer array in which a large number of transducers are arranged. In addition to the tongue-shaped portion 2 having a cantilever structure, a structure having a bridge-like double-end structure is also known.

[0008]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional examples, the cantilever structure is easily affected by external vibrations, and in order to perform precise displacement control with good reproducibility, a vibration isolation mechanism is required. has been done. Further, when the flexible portion itself undergoes sudden displacement, parasitic vibrations, ie, oscillations, are likely to occur, making it difficult to control the displacement at times, resulting in the possibility that the probe electrode 3 may come into contact with the recording medium and be damaged. If the high frequency characteristics of the control signal are cut off in order to suppress this parasitic vibration, control stability can be obtained, but the responsiveness of the displacement of the probe electrode will be sacrificed.

On the other hand, the double-supported beam structure has a problem in that the flexible range of the probe electrode is relatively small.

An object of the present invention is to solve the problems of the conventional example described above, and to provide a probe unit that is not easily affected by external vibrations, allows precise displacement control of the probe, has a fast response speed, and has a large displacement amount of the probe. and to provide an information recording and/or reproducing device using the same.

[0011]

[Means for Solving the Problems] To achieve the above-mentioned objects, the present invention provides a flexible portion of a double-supported beam structure connected by two or more structures having different elastic properties, and a This is a probe unit characterized by having an attached probe and a driving means for displacing the probe via the flexible portion.

[0012] The present invention related to the above-mentioned specific invention provides a flexible section having a double-supported beam structure connected by two or more structures having different elastic properties, a probe attached to the flexible section, and a probe attached to the flexible section. recording or reproducing information by bringing the probe close to the recording medium and changing or detecting a physical quantity on the surface of the recording medium; This is an information recording and/or reproducing device characterized by:

[0013]

[Operation] In the probe unit having the above-mentioned configuration and the information recording and/or reproducing device using the same, the probe is attached to the substrate in a double-supported beam structure and attached to one end of the movable part, so that the displacement of the probe Control can be performed reliably, the response speed is fast, and the amount of displacement is large.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the embodiments shown in FIGS. 1 to 4. FIG. 1 shows a configuration diagram of an embodiment of an information processing device, in which an XY direction drive mechanism 5 is mounted on an XY stage 4.
is mounted, and a recording medium 7 with a base electrode 6 attached is provided on the XY direction drive mechanism 5. A probe unit 8 is disposed so that a probe electrode 8a faces the recording medium 7. Unit 8 is Z direction coarse movement mechanism 9
is attached to. Probe electrode 8a, base electrode 6
A voltage application circuit 10 and a current detection circuit 11 are connected to the microcomputer 12 . Also, XY stage 4
The output of the XY stage drive circuit 13 is connected to
The output of the XY direction drive circuit 14 is connected to the direction drive mechanism 5, the output of the probe unit drive circuit 15 is connected to the probe unit 8, and the output of the Z direction coarse motion drive circuit 16 is connected to the Z direction coarse motion mechanism 9. The XY stage drive circuit 13 , the XY direction drive circuit 14 , the probe unit drive circuit 15 , and the Z direction coarse movement drive circuit 16 are connected to the microcomputer 12 .

FIG. 2 shows a perspective view of the probe unit 8, in which a piezoelectric bimorph plate 8d having a width of 50 μm and a length of 300 μm, for example, is supported in a cantilever on one side around a hole 8c formed in a substrate 8b. There is. The other end of the piezoelectric bimorph plate 8d that crosses the cavity 8c is connected to the cavity 8 via a pattern 8e having elastic properties different from those of the bimorph plate 8d.
The bimorph plate 8d is attached to the opposite side of c and has a double-supported beam structure. A probe electrode 8a is attached to the tip of the piezoelectric bimorph plate 8d.

The procedure for forming this probe unit 8 is shown in FIG.
It is shown in the figure below. First, in FIG. 3(a), an insulating film with a thickness of 500 mm is deposited on both sides of the silicon semiconductor substrate 8f.
After forming a silicon nitride film 8g with a thickness of 80 nm by high-frequency sputtering, as shown in FIG. 3(b), a concave portion of a pattern portion 8e on the front surface and an opening for a hole portion 8c on the back surface are formed on the silicon nitride film 8g by photolithography processing as shown in FIG. 3(b). . Thereafter, as shown in FIG. 3(c), a lower electrode 8h, a piezoelectric layer 8i, a middle electrode 8j, a piezoelectric layer 8i, and an upper electrode 8k are sequentially formed to produce a piezoelectric bimorph plate 8d. Here, the lower electrode 8h is made of Au with Cr undercoating, and the middle electrode 8h is made of Au with Cr subbing.
j, A1 is applied to the upper electrode 8k, and Zn with a thickness of 1.2 μm deposited by high frequency sputtering is applied to the piezoelectric layer 8i.
O film is used.

Furthermore, as shown in FIG. 3(d), a silicon nitride film is deposited on the entire surface of the piezoelectric bimorph plate 8d by sputtering to form a protective layer 8L, and then Au is deposited on the tip of the piezoelectric bimorph plate 8d. In this way, a conical protrusion-shaped probe electrode 8a is formed. Then, as shown in FIG. 3(e), anisotropic etching is performed from below using a KOH aqueous solution to form a hole 8c.

The piezoelectric bimorph plate 8d thus formed has a positive (negative) polarity between the upper electrode 8k and the middle electrode 8j.
By applying a bipolar voltage such as positive (negative) to the lower electrode 8h, the tip of the piezoelectric bimorph plate 8d, that is, the probe electrode 8a is displaced. Although not shown, the wiring from the probe electrode 8a and the piezoelectric bimorph plate 8d
A circuit for guiding the drive voltage can be formed on the silicon semiconductor substrate 8f, and is connected to a voltage application circuit 10, a current detection circuit 11, and a probe unit drive circuit 15. Although only one piezoelectric bimorph plate 8d is shown in FIGS. 2 and 3, it is also possible to install a plurality of piezoelectric bimorph plates, and the probe unit 8 is arranged such that the probe electrode 8a faces the recording medium 7. It is attached to the Z-direction coarse movement mechanism 9 with the probe electrode 8a facing downward.

During recording, signals from the microcomputer 12 drive the XY stage drive circuit 13, the XY direction drive circuit 14, the Z direction coarse movement drive circuit 16, and the Z direction coarse movement mechanism 9 to perform approximate positioning. After
When the probe electrode 8a is moved to a target position with respect to the recording medium 7 by the Y-direction drive circuit 14 and the XY-direction drive mechanism 5, and a pulse voltage is applied between the probe electrode 8a and the recording medium 7 by the voltage application circuit 10, the recording medium 7
changes its characteristics, creating a region with low electrical resistance, which allows recording to occur.

During reproduction, for example, two
While applying a DC voltage of 0.00 mV, the current detection circuit 11 detects the generated tunnel current, and the microcomputer 1 controls the voltage applied to the piezoelectric bimorph plate 8d so that the tunnel current becomes a constant value of, for example, 0.1 nA.
2. Controlled by the probe unit drive circuit 15, the probe electrode 8a is moved in a direction perpendicular to the recording medium 7. Since the feedback drive amount of the piezoelectric bimorph plate 8d at that time corresponds to the recorded information on the recording medium 7, the probe electrode 8a is moved within the horizontal plane by the XY direction drive mechanism 5 driven by the XY direction drive circuit 14. You can move around and play the information. Further, information can be erased by applying a triangular wave pulse voltage or the like. Note that if a plurality of probe electrodes 8a are present, the selection may be performed by the drive circuit 15 or the microcomputer 12.

In this example, a two-layer Langmuir-Prodgett film of polyimide was laminated on an Au electrode as the base electrode 6 and the recording medium 7, and first, a bias voltage of 0.1V was applied to a wave height of -6V and +1V. A voltage with a continuous pulse wave of .5 V superimposed was applied between the probe electrode 3 and the base electrode 6 to record and confirm the reading of the information.

Next, the scanning in the X and Y directions was stopped, and an experiment was conducted to examine the stability of position control of the probe electrode 8a. This is done by bringing the probe electrode 8a and the recording medium 7 close to each other so that a tunnel current of about 0.1 nA flows between them, and while performing servo control of the probe electrode 8a, the tunnel current target value is set to 0.1 nA. -1.2d (dB/oct) inserted in series in advance, changing periodically between and 1nA.
By changing the cutoff frequency of the low-pass filter, we measured the frequency at which the servo system becomes unstable, that is, the actual measured value of the tunnel current begins to cause damped oscillation or oscillation. As a result, it was confirmed that stable displacement control was possible even in the cutoff frequency range of 3 to 5 kHz. Note that this frequency is approximately 8 to 1
Since it is greatly influenced by the mechanical natural frequency of 0 kHz, the response frequency of the probe unit 8 alone is considered to be even higher.

On the other hand, a comparative experiment was conducted using the probe unit 8 having the conventional structure shown in FIG.
When the tunnel current target value was periodically changed between 0.1 and 1 nA, it was found that the cutoff frequency was required to be 10 to 30 Hz or less. Also, set the tunnel current target value to 0.
．． If it is limited to a range of 1 to 0.3 nA, the number of cutoff cycles can be increased, but only to about 100 Hz, and stable operation on the order of kHz as in this embodiment was not achieved. Note that the comparative experiment was conducted without adding any special vibration isolation mechanism as in the previous embodiment.

In the conventional cantilever structure, the reason why the tongue 2 is sensitive to vibrations is that the length of the tongue 2 in the longitudinal direction is several 1.
This is thought to be due to the minute size of about 0 to several 100 μm, and as a result, the Q value for vibration of the tongue 2 was extremely high at 10 to 100, making it easy for parasitic vibration to occur. . However, if pattern portions 8e with different elastic properties are provided in a part of the beam as in this embodiment, and the piezoelectric bimorph plate 8d is supported on both sides, the seismic properties can be improved without sacrificing the amount of displacement or sensitivity. , it is possible to realize a probe unit 8 with excellent operating characteristics such as controllability,
Since other earthquake-resistant structures can be omitted, the device can be simplified and downsized. Note that erasing was performed by superimposing a pulse voltage with a peak value of 3 V on the bias voltage, and reading of the information was also confirmed.

In this embodiment, the pattern portion 8e was created by controlling the shape of the silicon nitride film through a photolithography process, but by selecting the same material as the support of the piezoelectric bimorph plate 8d, the manufacturing process can be simplified. is extremely simple and there is almost no need to change the manufacturing process of the conventional probe unit 8, which is effective from the viewpoint of processing accuracy and manufacturing cost. The material and manufacturing method are not limited to those in this embodiment. For example, the pattern portion 8 is
It is also possible to improve etching resistance by doping impurities into the shape to be left as 8e, and then remove only the non-implanted region during the anisotropic etching process shown in FIG. 3(f) to form the pattern of pattern portion 8e. Alternatively, after forming a thin film having an arbitrary shape that connects the substrate 8b and the piezoelectric bimorph plate 8d, it is also possible to irradiate unnecessary areas with energy such as a laser beam or an electron beam and remove the thin film by heating.

The material for the pattern portion 8e must be elastically deformable, but since most materials generally exhibit elasticity, metals, insulators, inorganic materials, organic materials, etc. may be considered. However, it is limited by processing technology and aging.

FIG. 4 shows a perspective view of the probe unit 8 according to the second embodiment, in which the shape of the pattern portion 8e is different from that of the first embodiment, and the piezoelectric bimorph plate 8d is attached to the substrate 8 at three points.
b, and the other configurations are the same as in the first embodiment.

Similar to the first embodiment, this probe unit 8 was installed in a recording/reproducing apparatus and an experiment was conducted to examine the stability of displacement control. As a result, stable servo control was achieved in the frequency range of 1 to 5 kHz. Since it has been confirmed that this is possible, it can be used in actual recording and playback devices. The shape of the pattern portion 8e is not limited to the above embodiment, and there is no problem as long as it has a small elastic constant and does not hinder the displacement of the probe electrode 8a. In addition, this probe unit 8
is applicable to a scanning tunnel current detection device such as STM.

Although the above-described embodiment is a recording/reproducing device, it can also be applied to a device that only performs recording or reproducing.

[0030]

Effects of the Invention As explained above, the probe unit according to the present invention and the information recording and/or reproducing apparatus using the same are provided with a double-supported beam connected by two or more structures exhibiting different elastic properties with respect to the substrate. Since a probe is attached to a part of the flexible part of the structure and the probe is displaced in a direction perpendicular to the substrate surface, precise displacement control is possible without being easily affected by external vibrations, and the response speed is fast.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a perspective view of the probe unit.

FIG. 3 is an explanatory diagram of the manufacturing process of the probe unit.

FIG. 4 is a perspective view of a probe unit according to another embodiment.

FIG. 5 is a perspective view of a conventional probe unit.

[Explanation of symbols]

7 Recording medium 8 Probe unit 8a Probe electrode 8b Board 8c　Void part 8d Piezoelectric bimorph board 8e Pattern part 8f Silicon semiconductor substrate 8g Silicon nitride film 8h Lower electrode 8i piezoelectric layer 8j Middle electrode 8k upper electrode 10 Voltage application circuit 11 Current detection circuit 12 Microcomputer

Claims (2)

[Claims] Claims: 1. A flexible section having a double-supported beam structure connected by two or more structures having different elastic properties, a probe attached to the flexible section, and the probe being displaced via the flexible section. What is claimed is: 1. A probe unit characterized by having a driving means for driving the probe unit. 2. A flexible section having a double-supported beam structure connected by two or more structures having different elastic properties, a probe attached to the flexible section, and a probe that is displaced via the flexible section. Information recording is characterized in that information is recorded or reproduced by using a probe unit having a driving means to cause the probe to approach the recording medium and changing or detecting a physical quantity on the surface of the recording medium. as well as/
Or a playback device.