JP2934057B2 - Probe unit and information recording and / or reproducing apparatus using the same - Google Patents

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 / reproducing high-density, large-capacity information and an information recording / reproducing apparatus using the same.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter, referred to as STM) capable of directly observing an electronic structure on and near a material surface has been developed [G. Binnig et al., Helbetica Physica.
Acta, 55, 726 (1982)], real-space images can be observed at high resolution regardless of whether they are single crystals or non-crystals.
TM also has the advantage of being able to measure at low power with little damage to the sample material due to electric current, and because it operates not only in ultra-high vacuum but also in air and solutions, it can be applied to various materials. Extensive applications are expected.

In STM, when a voltage is applied between a metal probe and a conductive sample to approach a distance of about 1 nm,
The phenomenon that a tunnel current occurs is used. Recently, for example, Japanese Patent Application Laid-Open Nos. 63-161552 and
As disclosed in JP-A-3-161553, this ST
Many proposals have been made to apply an M principle to configure an information processing apparatus mainly for ultra-high density recording / reproduction. That is,
The probe electrode corresponding to the STM probe gives physical deformation on the recording medium corresponding to the sample, or changes the electronic state of the medium surface to record information. It is said that by using a method for reproducing information, large-scale information can be recorded and reproduced at a high density of the order of molecules and atoms.

Among the above recording methods, in order to impart physical deformation, a sharp recording probe is pressed against a recording medium to be depressed, and a hole is formed by applying a pulse voltage on a recording medium such as graphite. What can be done recently has been reported. That is, by bringing the probe electrode close to the surface of the recording medium and applying a voltage between the two with a pulse width of 3 to 8 V and 1 to 100 μs, a hole having a diameter of about 40 Å can be formed. Can be used as well. On the other hand, in order to perform recording by changing the electronic state, there is known a method in which a voltage is applied between a recording medium, a base electrode, and a probe electrode to change the electrical resistance characteristics of a minute portion. Attention has been paid to its ease.

[0005] As the recording medium, a material exhibiting a memory switching characteristic in voltage-current characteristics, for example, a thin film layer of chalcogenides or a π-electron organic compound is used. For example, a Langmuir-Blodgett method ( A film obtained by forming an appropriate organic substance accumulation film by the LB method is used.

As a probe electrode, for example, one in which a tip of a needle such as tungsten, Pt-Ir, Pt or the like is mechanically polished and then electropolished is attached to a piezoelectric element, and displacement is controlled by an applied voltage. . As a method of manufacturing a flexible portion for moving a probe electrode, for example, a processing technology for forming a fine structure on one substrate using a semiconductor process technology (KEPeterson, "Silicon as Mechanical Materia
l ", Proceedings of the IEEE, 70 vol. 420p, 1982). Thus, a hole 1a is provided in the single-crystal silicon substrate 1 movable in the X and Y directions shown in FIG. The processing of attaching the probe electrode 3 to the tip of the part 2 provided with cantilever support is also enabled.

The tongue-shaped portion 2 is composed of a layered piezoelectric element and electrodes. By applying a voltage between the electrodes, the probe electrode 3 is perpendicular to the plane of the single-crystal silicon substrate 1 (Z-axis direction). Changes to Of course, at this time, it is also possible to realize a storage device provided with a converter array in which a plurality of tongue-shaped portions 2 are arranged. In addition to the cantilever portion 2 having such a cantilever structure, a bridge-like double-supported beam structure is known.

[0008]

However, in the conventional example described above, the cantilever structure is easily affected by external vibrations and the like, and in order to perform precise displacement control with good reproducibility, a vibration isolation mechanism is required. Have been. In addition, when the flexible portion itself undergoes a sudden displacement, parasitic vibration, that is, oscillation easily occurs,
At times, displacement control becomes difficult, and there is a possibility that the probe electrode 3 may be damaged by contact with the recording medium. When the high frequency characteristics of the control signal are cut off to suppress this parasitic oscillation,
Although control stability is obtained, the response of displacement of the probe electrode is sacrificed.

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

An object of the present invention is to provide a probe unit which solves the above-mentioned problems of the prior art, is less susceptible to external vibrations, enables precise displacement control of the probe, has a high response speed, and has a large probe displacement. And an information recording and / or reproducing apparatus using the same.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a flexible portion having a double-supported beam structure connected by two or more structures having different elastic characteristics, A probe unit comprising: a mounted probe; and a driving unit for displacing the probe via the flexible portion.

The present invention, which is related to the above specific invention, comprises a flexible portion having a double-supported beam structure connected by two or more structures having different elastic characteristics, a probe attached to the flexible portion, Using a probe unit having driving means for displacing the probe through the unit, recording or reproducing information by bringing the probe close to the recording medium and changing or detecting a physical quantity on the recording medium surface. An information recording and / or reproducing apparatus characterized in that the information recording and / or reproducing apparatus is performed.

[0013]

In the probe unit having the above-described structure and the information recording and / or reproducing apparatus using the same, the probe is mounted on the substrate in a double-supported beam structure, and is attached to one end of the movable part. The control can be performed reliably, the response speed is high, and the displacement is large.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a configuration diagram of an embodiment of an information processing apparatus, and an XY direction driving mechanism 5 is provided on an XY stage 4.
And a recording medium 7 having a base electrode 6 attached thereto is provided on the XY-direction drive mechanism 5, and a probe unit 8 is disposed so that the probe electrode 8a faces the recording medium 7. Unit 8 is a Z-direction coarse movement mechanism 9
Attached to. Probe electrode 8a, base electrode 6
Is connected to a voltage application circuit 10 and a current detection circuit 11, and the voltage application circuit 10 and the current detection circuit 11 are connected to a microcomputer 12. The output of the XY stage drive circuit 13 is connected to the XY stage 4,
The output of the XY direction drive circuit 14 is connected to the Y direction drive mechanism 5, the output of the probe unit drive circuit 15 is connected to the probe unit 8, and the Z direction coarse movement drive circuit 16 is connected to the Z direction coarse movement mechanism 9. The outputs are connected, and the XY stage drive circuit 13, the XY direction drive circuit 14, the probe unit drive circuit 15, and the Z direction coarse drive circuit 16 are connected to the microcomputer 12.

FIG. 2 is a perspective view of the probe unit 8. A piezoelectric bimorph plate 8d having a width of, for example, 50 μm and a length of 300 μm is cantilevered on one side around a hole 8c formed in the substrate 8b. I have. The other end of the piezoelectric bimorph plate 8d traversing the hole 8c is attached to the opposite side of the hole 8c via a pattern portion 8e having elasticity different from that of the bimorph plate 8d, and the bimorph plate 8d has a doubly supported structure. It has become. Then, the piezoelectric bimorph plate 8d
The probe electrode 8a is attached to the tip of the.

The procedure for forming the probe unit 8 is shown in FIG.
It is shown as follows. First, in FIG. 3A, a 500 nm-thick insulating film is formed on both surfaces of the silicon semiconductor substrate 8f.
After the silicon nitride film 8g is formed by high frequency sputtering, a concave portion of the pattern portion 8e on the front surface and an opening of the hole portion 8c on the rear surface are formed on the silicon nitride film 8g by photolithography in FIG. 3B. Then,
As shown in FIG. 3C, 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 form a piezoelectric bimorph plate 8d. Here, the lower electrode 8h
Au with Cr as the lower electrode, the middle electrode 8j and the upper electrode 8
A1 is used for k, and a 1.2 μm thick ZnO film deposited by high frequency sputtering is used for the piezoelectric layer 8i.

Further, in FIG. 3D, the piezoelectric bimorph plate 8d
A silicon nitride film is deposited on the entire surface by sputtering to form a protective layer 8L, and then Au is deposited on the tip of the piezoelectric bimorph plate 8d to form a conical protruding probe electrode 8a. Then, as shown in FIG. 3 (e), anisotropic etching is performed with KOH aqueous solution from below to form a hole 8
Form c.

The thus formed piezoelectric bimorph plate 8d applies a bipolar voltage such as positive (negative) to the upper electrode 8k and positive (negative) to the lower electrode 8h with respect to the middle electrode 8j. As a result, the tip of the piezoelectric bimorph plate 8d, that is, the probe electrode 8a is displaced. Although illustration is omitted, the wiring from the probe electrode 8a and the circuit for guiding the driving voltage of the piezoelectric bimorph plate 8d can be formed on the silicon semiconductor substrate 8f.
0, current detection circuit 11, probe unit drive circuit 15
It is connected to the. 2 and 3, only one piezoelectric bimorph plate 8d is shown, but a plurality of piezoelectric bimorph plates can be provided in parallel.
The probe electrode 8a is attached to the Z-direction coarse movement mechanism 9 with the probe electrode 8a facing downward so that the recording medium 7 faces the recording medium 7.

At the time of recording, the 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 alignment. After the X
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
Causes a change in the characteristics, resulting in a portion having a low electric resistance, and recording can be performed.

At the time of reproduction, for example, 2
A current detecting circuit 11 detects a generated tunnel current while applying a DC voltage of 00 mV, and applies a voltage applied to the piezoelectric bimorph plate 8d to the microcomputer 1 so that the tunnel current becomes a constant value of, for example, 0.1 nA.
2. The probe electrode 8a is moved in a direction perpendicular to the recording medium 7 under the control of the probe unit drive circuit 15. 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 XY direction drive mechanism 5 driven by the XY direction drive circuit 14 moves the probe electrode 8a within the horizontal plane. To reproduce the information. Further, information can be erased by applying a triangular pulse voltage or the like. If there are a plurality of probe electrodes 8a, the selection may be made by the drive circuit 15 or the microcomputer 12.

In this embodiment, as the base electrode 6 and the recording medium 7, a two-layer Langmuir-Projet film made of polyimide is laminated on an Au electrode. A voltage on which a continuous pulse wave of 0.5 V was superimposed was applied between the probe electrode 3 and the base electrode 6, and recording was performed to confirm reading of information.

Next, the scanning in the XY directions was stopped, and an experiment on the stability of the position control of the probe electrode 8a was performed. This is because the target of the tunnel current is set to 0.1 nA while performing servo control of the probe electrode 8 a in a state where both are brought close to each other so that a tunnel current of about 0.1 nA flows between the probe electrode 8 a and the recording medium 7. The servo system becomes unstable by changing the cutoff frequency of the low-pass filter of -1.2 dB (dB / oct) inserted in series in advance, ie, the tunnel current is measured. A measurement was made of the frequency at which the value began to cause damped oscillation or oscillation. as a result,
It was confirmed that stable displacement control was possible even in a cutoff frequency range of 3 to 5 kHz. Since this frequency is greatly affected by the mechanical natural frequency of about 8 to 10 kHz of the entire recording / reproducing apparatus including the sample support, the response frequency of the probe unit 8 alone is considered to be higher. Can be

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

In the conventional cantilever structure, the reason that the tongue 2 is sensitive to vibration or the like is that the tongue 2 has a length of 1 in the longitudinal direction.
This is considered to be caused by a minute size of about 0 to several hundreds μm. As a result, the Q value with respect to the vibration of the tongue-shaped portion 2 became an extremely high value of 10 to 100, and parasitic vibration was easily generated. . However, if a pattern portion 8e having a different elastic property is provided in a part of the beam as in this embodiment and the piezoelectric bimorph plate 8d has a dual-support structure, the seismic resistance can be reduced without sacrificing the displacement and sensitivity. And a probe unit 8 having excellent operating characteristics such as controllability and the like.
Since other seismic structures can be omitted, the device can be simplified and downsized. The erasing was performed by superimposing a pulse voltage having a peak value of 3 V on the bias voltage, and reading of information was confirmed.

In this embodiment, the pattern portion 8e is formed by controlling the shape of the silicon nitride film by a photolithography process. In this manner, by selecting the same material as the support of the piezoelectric bimorph plate 8d, the manufacturing process is performed. 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 the method of formation are not limited to those of the present embodiment.
The impurity may be doped into the shape left as e to improve the etching resistance, and at the time of the anisotropic etching step of FIG. 3 (f), only the non-implanted region may be removed to form the pattern of the pattern portion 8e. Alternatively, after forming a thin film of an arbitrary shape connecting the substrate 8b and the piezoelectric bimorph plate 8d, it is possible to irradiate unnecessary regions with energy such as a laser beam or an electron beam and to remove them by heating.

The material of the pattern portion 8e is required to be elastically deformable. However, generally, most materials show an elastic after-effect. Therefore, application of metals, insulators, inorganic materials, organic materials and the like is considered. However, it is limited by processing technology and aging.

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

An experiment was conducted to examine the stability of the displacement control by installing the probe unit 8 in the recording / reproducing apparatus in the same manner as in the first embodiment. As a result, stable servo control was performed in the frequency range of 1 to 5 kHz. Since it has been confirmed that it is possible, it can be used in an actual recording / reproducing apparatus.
The shape of the pattern portion 8e is not limited to the above-described embodiment, and there is no problem as long as the elastic constant is small and the displacement of the probe electrode 8a is not prevented. In addition, this probe unit 8
Is applicable to a scanning type tunnel current detecting device such as an STM.

Although the above-described embodiment is a recording / reproducing apparatus, it can be applied to a recording / reproducing only apparatus.

[0030]

As described above, the probe unit according to the present invention and the information recording and / or reproducing apparatus using the same have a doubly supported beam connected to a substrate by two or more structures having different elastic characteristics. Since a probe is attached to a part of the flexible portion of the structure and the probe is displaced in the direction perpendicular to the substrate surface, precise displacement control is possible without being affected by external vibration, and the response speed is high.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment.

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

FIG. 3 is an explanatory diagram of a 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]

 Reference Signs List 7 recording medium 8 probe unit 8a probe electrode 8b substrate 8c hole 8d piezoelectric bimorph plate 8e pattern portion 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

Continued on the front page (72) Inventor Miya ▲ saki ▼ Toshihiko 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Osamu Takamatsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-4-143943 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 9/00 G01N 37/00 G01B 7/34

Claims (2)

(57) [Claims] 1. A flexible portion having a doubly supported structure connected by two or more structures having different elastic characteristics, a probe attached to the flexible portion, and displacing the probe via the flexible portion. A driving unit for driving the probe unit. 2. A flexible portion having a double-supported beam structure connected by two or more structures having different elastic characteristics, a probe attached to the flexible portion, and displacing the probe via the flexible portion. Recording or reproducing information by using a probe unit having a driving unit for causing the probe to approach the recording medium and changing or detecting a physical quantity on the recording medium surface. as well as/
Or a playback device.