JPH06259820A - Recording and reproducing device and method - Google Patents

Abstract

PURPOSE:To eliminate recording errors by detecting the contact state between a recording medium and the front end of a conductive probe from a change in the value of the capacity reactance of the piezoelectric unimorph structure or piezoelectric bimorph structure of a piezoelectric cantilever. CONSTITUTION:The value of the capacity reactance is changed from C1 to C2 by contacting of the front end of the conductive probe 110 with an insulating thin film 12. Consequently, the contact state of the insulating thin film 12 and the conductive probe 110 is detected by measuring the capacity reactance. The contact state of the insulating thin film 12 and the conductive probe 110 is, thereupon, controlled, by which the scanning with the conductive probe 110 is executed while the contact state of the front end of the insulating thin film 12 and the conductive probe 110 is maintained at all times. As a result, the recording errors and reproducing errors are eliminated even if there is mechanical relaxation between the members.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus and a recording / reproducing method, and more particularly to a recording / reproducing apparatus and a recording / reproducing method capable of performing recording and reproduction of high density and large capacity.

[0002]

2. Description of the Related Art Conventionally, US Patent US-P-434399.
As described in Japanese Patent No. 3, a scanning tunneling microscope (STM) capable of observing the surface of a conductive material with a resolution of nanometer or less has been developed, and the atomic arrangement on the surfaces of metals and semiconductors, the orientation of organic molecules, etc. Have been made on the atomic and molecular scale. Further, it has been proposed that a high density memory is realized by applying the principle of the scanning tunneling microscope to access a recording medium on an atomic and molecular scale to perform recording and reproduction (US Patent US-P). No. 4,575,822, US-P-501
5850, JP-A-63-161552,
JP-A-63-161553).

Meanwhile, an atomic force microscope (AFM) capable of observing the surface of an insulating material with the same resolution as that of a scanning tunnel microscope has been developed by developing the scanning tunnel microscope technique (US Pat. No. US-P- No. 4724318). In the atomic force microscope, the atomic force acting between the material surface and the probe is detected by detecting the displacement of the cantilever that supports the probe that is brought close to the surface of the object to be observed. As such a cantilever displacement detection method,
A method using a tunnel current, a method using a light wave interferometer, an optical lever method, a method of detecting a resonance frequency shift of a cantilever (European Patent Publication EP-A-290648), and the like have been proposed.

In addition, a device configuration in which a scanning tunneling microscope and an atomic force microscope are combined is applied to a high-density memory,
A recording / reproducing apparatus has also been proposed which controls the probe position during recording and reproducing by applying the principle of an atomic force microscope (Japanese Patent Laid-Open No. 1-245445).

[0005]

However, in the conventional recording / reproducing apparatus, the principle of the atomic force microscope is applied to control the probe position, and the tunnel current method or the light wave interferometer method is used as the cantilever displacement detection method. Since the optical lever method and the like are used, it is difficult to say that it is suitable for downsizing because the device configuration of the electric system, mechanical system, and optical system for displacement detection becomes large. This means that when considering multiple probes for speeding up recording / reproducing, the displacement detection system of each cantilever supporting each probe becomes large, and the size of the entire device is not practical. Means Also,
The resonance frequency shift detection method proposed as another cantilever displacement detection method is also an application of the optical lever method,
Since it is a cantilever with a crystal unit attached, the device configuration of the electrical system, mechanical system, and optical system for displacement detection is large as it is, and it is suitable for downsizing. There wasn't.

An object of the present invention is to provide a recording / reproducing apparatus and a recording / reproducing method which can reduce the size of the entire apparatus.

[0007]

In the recording / reproducing apparatus of the present invention, a recording state and a non-recording state can be distinguished by the presence or absence of a current flowing between a conductive probe and the tip of the probe. A recording medium, a pair of electrodes to which the probe is attached at one end so that the tip of the probe faces the recording medium, a piezoelectric body sandwiched by the pair of electrodes, and the pair of electrodes and the piezoelectric body. A piezoelectric cantilever including a piezoelectric unimorph structure having a support for supporting a body, a driving means for driving the piezoelectric cantilever so that the tip of the probe moves in a direction perpendicular to the surface of the recording medium, and the recording. Information recording voltage applying means for applying an information recording voltage between a medium and the tip of the probe, and information reproducing voltage for applying an information reproduction voltage between the recording medium and the tip of the probe. Applying means, A current detecting unit that detects a current flowing between the recording medium and the tip of the probe, and a capacitive reactance between the pair of electrodes is detected to detect a contact state between the recording medium and the tip of the probe. And a contact state control unit that controls the drive unit according to the contact state detected by the contact state detection unit.

Alternatively, a recording medium in which a recording state and a non-recording state can be distinguished by the presence or absence of a current flowing between the conductive probe and the tip of the probe, and the tip of the probe is the recording medium. Two or more pairs of electrodes each having the probe attached to one end so as to face the medium, a plurality of piezoelectric bodies sandwiched between the pair of electrodes, and two or more pairs of electrodes and the plurality of piezoelectric bodies. A piezoelectric cantilever provided with a piezoelectric bimorph structure having a support for supporting the piezoelectric cantilever, drive means for driving the piezoelectric cantilever so that the tip of the probe moves in a direction perpendicular to the surface of the recording medium, and the recording medium. Information recording voltage applying means for applying an information recording voltage between the tip of the probe and information reproducing voltage applying means for applying an information reproducing voltage between the recording medium and the tip of the probe. And before Current detecting means for detecting a current flowing between a recording medium and the tip of the probe, and a capacitive reactance between the pair of electrodes are respectively detected to determine a contact state between the recording medium and the tip of the probe. It includes contact state detecting means for detecting, and contact state controlling means for controlling the driving means according to the contact state detected by the contact state detecting means.

Alternatively, a recording medium in which a recording state and a non-recording state can be distinguished by the presence or absence of a current flowing between a conductive probe and the tip of the probe, and the tip of the probe is the recording medium. Piezoelectric unimorph structure having a pair of electrodes with the probe attached to one end so as to face the medium, a piezoelectric body sandwiched by the pair of electrodes, and a support for supporting the pair of electrodes and the piezoelectric body A piezoelectric cantilever having a body, an information recording voltage applying unit for applying an information recording voltage between the recording medium and the tip of the probe, and information between the recording medium and the tip of the probe. Information reproducing voltage applying means for applying a reproducing voltage, current detecting means for detecting a current flowing between the recording medium and the tip of the probe, and capacitive reactance between the pair of electrodes for detecting Recording medium and the above Contact state detecting means for detecting a contact state with the tip of the needle, and the tip of the probe moves in a direction perpendicular to the surface of the recording medium in accordance with the contact state detected by the contact state detecting means. Contact state control means for driving and controlling the piezoelectric cantilever.

Alternatively, a recording medium in which a recording state and a non-recording state can be distinguished by the presence or absence of a current flowing between the conductive probe and the tip of the probe, and the tip of the probe is the recording medium. Two or more pairs of electrodes each having the probe attached to one end so as to face the medium, a plurality of piezoelectric bodies sandwiched between the pair of electrodes, and two or more pairs of electrodes and the plurality of piezoelectric bodies. A piezoelectric cantilever provided with a piezoelectric bimorph structure having a support for supporting an information recording voltage applying means for applying an information recording voltage between the recording medium and the tip of the probe; Information reproducing voltage applying means for applying an information reproducing voltage to the tip of the probe, current detecting means for detecting a current flowing between the recording medium and the tip of the probe, and each of the pair of Capacitive reactance between electrodes Contact state detecting means for detecting the contact state between the recording medium and the tip of the probe, and the tip of the probe is the recording medium according to the contact state detected by the contact state detecting means. Contact state control means for driving and controlling the piezoelectric cantilever so as to move in a direction perpendicular to the surface of the.

The recording / reproducing method of the present invention is a piezoelectric cantilever including a piezoelectric unimorph structure having a pair of electrodes, a piezoelectric body sandwiched by the pair of electrodes, and a support body for supporting the pair of electrodes and the piezoelectric body. A conductive probe attached to one end of the recording medium is brought into contact with the surface of a recording medium in which a recording state and a non-recording state can be distinguished by the presence or absence of an electric current flowing between the probe and the tip of the probe, The capacitive reactance between the electrodes is detected to detect the contact state between the recording medium and the tip of the probe, and the probe is adjusted to adjust the contact state based on the detection result of the contact state. While moving in the direction perpendicular to the surface of the recording medium, at the time of recording, an information recording voltage is applied between the recording medium and the probe to record information on the recording medium, and at the time of reproduction, With the recording medium The information recording voltage is applied between the probe and the probe, and is recorded on the recording medium based on the result of detecting the current flowing between the recording medium and the probe. Play the information.

Here, the adjustment of the contact state and the movement of the probe in the direction perpendicular to the surface of the recording medium, in the non-contact state, move the probe toward the surface of the recording medium to a predetermined value. In the weak contact state below the threshold value, the movement of the probe is stopped, and in the strong contact state above the predetermined threshold value, the probe is moved in a direction away from the surface of the recording medium. It may be.

Alternatively, a piezoelectric bimorph structure having two or more pairs of electrodes, a plurality of piezoelectric bodies sandwiched between the pair of electrodes, and a support for supporting the two or more pairs of electrodes and the plurality of piezoelectric bodies. A conductive cantilever attached to one end of a piezoelectric cantilever having a contact with a surface of a recording medium in which a recording state and a non-recording state can be distinguished by the presence or absence of a current flowing between the tip of the piezoelectric cantilever. , Detecting the contact state between the recording medium and the tip of the probe by respectively detecting the capacitive reactance between each pair of electrodes, and adjusting the contact state based on the detection result of the contact state. While moving the probe in a direction perpendicular to the surface of the recording medium, at the time of recording, an information recording voltage is applied between the recording medium and the probe to record information on the recording medium. Then play The information reproducing voltage is applied between the recording medium and the probe and the probe, and based on the result of detecting the current flowing between the recording medium and the probe, The information recorded on the recording medium is reproduced.

Here, in the non-contact state, the adjustment of the contact state and the movement of the probe in the direction perpendicular to the surface of the recording medium move in a direction to bring the probe closer to the surface of the recording medium, and a predetermined value is obtained. In the weak contact state below the threshold value, the movement of the probe is stopped, and in the strong contact state above the predetermined threshold value, the probe is moved in a direction away from the surface of the recording medium. It may be.

[0015]

According to the recording / reproducing apparatus of the present invention, the contact state detecting means for detecting the contact state between the recording medium and the tip of the probe, and the contact controlling the driving means according to the contact state detected by the contact state detecting means. By including the state control means, the contact state between the recording medium and the tip of the probe can always be maintained even if there are large irregularities on the surface of the recording medium.

In particular, a piezoelectric cantilever having a probe attached to one end so that the tip of the probe faces the recording medium is provided with a pair of electrodes, a piezoelectric body sandwiched between the pair of electrodes, the pair of electrodes, and the pair of electrodes. When a piezoelectric unimorph structure having a support for supporting the piezoelectric body is provided, when the tip of the probe comes into contact with the surface of the recording medium, the free end of the piezoelectric cantilever (that is, the side where the probe is attached) One end of) becomes a fixed end by contact. As a result, the piezoelectric cantilever changes from a cantilever structure to a cantilever structure,
The mechanical resonance frequency of the piezoelectric cantilever shifts to the high frequency side. Moreover, the shift amount of the mechanical resonance frequency changes in proportion to the degree of contact between the recording medium and the tip of the probe (that is, the magnitude of the force acting between the recording medium and the tip of the probe). . Therefore, by detecting the shift amount of the mechanical resonance frequency of the piezoelectric cantilever, the degree of contact between the recording medium and the tip of the probe can be detected. In other words, by utilizing the fact that the mechanical properties and the electrical properties of the piezoelectric cantilevers are closely related to each other, the mechanical properties of the piezoelectric cantilevers can be known by measuring the electrical properties of the piezoelectric cantilevers. From this, the contact state between the recording medium and the tip of the probe is detected by detecting the capacitive reactance between the pair of electrodes forming the piezoelectric cantilever, and based on this detection result, the tip of the recording medium and the tip of the probe are detected. By controlling the contact state with, even if there are large irregularities on the surface of the recording medium,
The contact state between the recording medium and the tip of the probe can always be maintained.

According to the recording / reproducing method of the present invention, the contact state between the recording medium and the tip of the probe is detected, and the probe is moved in the direction perpendicular to the surface of the recording medium based on the detection result of the contact state. By performing the recording and the reproducing of the above, it is possible to perform the recording and the reproducing while always maintaining the contact state between the recording medium and the tip of the probe.

Further, in the recording / reproducing apparatus and the recording / reproducing method of the present invention, the piezoelectric cantilever is miniaturized and integrated by the micromachine technology, and the contact state detecting means is miniaturized by the microelectronic technology such as photolithography and Si process. And, by integrating, the size of the entire device becomes smaller, and in particular, when the number of probes is increased to speed up recording / reproducing, the size of the entire device becomes practical.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a first embodiment of a recording / reproducing apparatus of the present invention.

The recording / reproducing apparatus 100 includes a recording medium 10, a conductive probe 110, a piezoelectric cantilever 120, a Z-direction driving element 130, an XY-direction driving element 140, a recording pulse voltage applying circuit 150, and a reproducing device. Bias voltage application circuit 160
A current-voltage conversion circuit 170 and a contact state detection circuit 180
And a contact state control circuit 190. Recording / reproducing device 100
Each of the components will be described in detail below.

(1) Recording Medium 10 The recording medium 10 is formed on the conductive substrate 11 and a conductive substrate 11 made of a metal such as Au, Pt, or Cu or a semiconductor such as n ⁺ -Si, Ge, or GaAs. Was done,
For example, it is composed of an oxide film, a nitride film, an organic material such as polyimide, polymethylmethacrylate, arachidic acid, etc. of the metal or the semiconductor, and an insulating thin film 12 made of a biopolymer material. A recorded state and a non-recorded state can be distinguished by the presence or absence of a current flowing between the tip of the probe 110 and the tip. The insulating thin film 1
Examples of the manufacturing method of 2 include oxidation treatment of the substrate surface, vapor deposition of the above-mentioned insulating thin film material on the substrate surface, sputtering or spin coating, adsorption by the Langmuir-Blodgett method, and the like.

(2) Conductive probe 110, piezoelectric cantilever
120, Z-direction driving element 130 and XY-direction driving element 140 The conductive probe 110 is attached to one end of the piezoelectric cantilever 120. The piezoelectric cantilever 120 is made of, for example, Au or P, which are sequentially laminated by vapor deposition or sputtering.
a first electrode 121 made of t or the like, such as ZnO or PZ
A piezoelectric body 122 made of T, a second electrode 123 made of Au or Pt, an insulating support 124 made of SiO ₂ or Si ₃ N ₄ , and Au or P, for example.
It is composed of a third electrode 125 made of t or the like and is miniaturized and integrated by the micromachine technology. That is, the piezoelectric cantilever 120 includes a pair of electrodes (first electrode
121 and the second electrode 123), a piezoelectric unimorph structure including a piezoelectric body (piezoelectric body 122) sandwiched between a pair of electrodes, and a support body supporting the pair of electrodes and the piezoelectric body. The conductive probe 110 is electrically connected to the third electrode 125 of the piezoelectric cantilever 120. The Z-direction driving element 130 is for driving the piezoelectric cantilever 120 in the Z-axis direction in the drawing, and the XY-direction driving element 140 is also included.
Is for driving the piezoelectric cantilever 120 in the X-axis direction and the Y-axis direction in the figure.

(3) Recording pulse voltage application circuit 150, reproduction pulse voltage application circuit 160 and current-voltage conversion circuit 17
The recording pulse voltage application circuit 150 generates the recording pulse voltage V _R according to the recording information signal S _R input from the outside during recording.
By generating _P and supplying the generated recording pulse voltage V _P to the third electrode 125 of the piezoelectric cantilever 120,
The recording pulse voltage V _P is applied between the recording medium 10 and the tip of the conductive probe 110. Reproducing bias voltage application circuit 160, by supplying generated reproduction bias voltage V _B at the time of reproduction, the reproduction bias voltage V _B generated in the third electrode 125 of the piezoelectric cantilever 120, the recording medium 10 and the conductive This is for applying a reproducing bias voltage V _B between the tip of the sex probe 110. The current-voltage conversion circuit 170 detects the current flowing between the recording medium 10 and the tip of the conductive probe 110 during reproduction, and
The detected current is converted into a voltage and then binarized to create a reproduction information signal S _P.

(4) Contact state detection circuit 180 and contact state control circuit 190 The contact state detection circuit 180 includes the recording medium 10 and the conductive probe 11.
It is for detecting the contact state with the tip of 0, and as described later, the capacitive reactance between the first electrode 121 and the second electrode 123 of the piezoelectric cantilever 120 is detected, and Corresponding contact state detection signal S _C
To occur. The contact state control circuit 190 is for adjusting the contact state between the recording medium 10 and the tip of the conductive probe 110 according to the contact state detected by the contact state detection circuit 180. The Z-direction drive element control signal C _Z is generated in response to the contact state detection signal S _C sent from the Z-direction drive element 130, and the generated Z-direction drive element control signal C _Z is output to the Z-direction drive element 130. These contact state detection circuits 18
0 and the contact state control circuit 190 are provided in the vicinity of the piezoelectric cantilever 120 by being miniaturized and integrated by a microelectronic technique such as photolithography and Si process using a Si substrate.

Next, the recording and reproducing operations of the recording / reproducing apparatus 100 will be described in detail.

During recording, the piezoelectric cantilever 120 is driven in the X-axis direction and the Y-axis direction in the figure by the XY direction drive element 140 so that the tip of the conductive probe 110 is located at the recording position of the recording medium 10. , Conductive probe 110
The Z-direction driving element drive 130 drives in the Z-axis direction in FIG. Then, a recording voltage pulse V _P having a peak value exceeding the withstand voltage of the insulating thin film 12 is applied by the recording pulse voltage applying circuit 150 between the insulating thin film 12 and the tip of the conductive probe 110. . As a result, a local dielectric breakdown occurs in the insulating thin film 12. In the portion where the dielectric breakdown of the insulating thin film 12 occurs, the conductivity of the insulating thin film 12 in the film thickness direction changes from "0" to a finite value r. As a result, the recording bit 15 is formed on the insulating thin film 12.

During reproduction, a reproduction bias voltage V _B that does not exceed the withstand voltage of the insulating thin film 12 is applied between the insulating thin film 12 and the tip of the conductive probe 110.
Applied by 160. At this time, the current flowing between the insulating thin film 12 and the tip of the conductive probe 110 is detected by the current-voltage conversion circuit 170. In the portion where the recording of the insulating thin film 12 is performed (that is, the portion where the recording bit 15 is formed), the conductivity in the film thickness direction of the insulating thin film 12 has a finite value r, and therefore the insulating property is high. An electric current flows between the thin film 12 and the tip of the conductive probe 110. On the other hand, in the portion of the insulating thin film 12 where recording is not performed (that is, the portion where the recording bit 15 is not formed), the electrical conductivity in the film thickness direction of the insulating thin film 12 is “0”, so No current flows between the thin film 12 and the tip of the conductive probe 110. Therefore, the reproduction information signal S _P can be created by converting the current detected by the current-voltage conversion circuit 170 into a voltage and then binarizing the converted voltage. That is, the value of the reproduction information signal S _P of the part where the recording of the insulating thin film 12 is performed is “1”, and the value of the reproduction information signal S _P of the part where the recording of the insulating thin film 12 is performed is “ It becomes 0 ". FIG. 2A shows a current-voltage conversion circuit 170.
FIG. 2B is a graph showing an example of the waveform of the voltage converted in FIG. 2, and FIG. 2B is a graph showing the reproduction information signal S _P at this time. The current-voltage conversion circuit 170 has a minimum detectable current level, and when a current below the minimum detectable current level is input, the current-voltage conversion circuit 17
The value of the reproduction information signal S _P created at 0 is “0”.
That is, the shaded area in FIG. 2A is the dead zone.

The recording operation and the reproducing operation described above were performed without operating the contact state detection circuit 180 and the contact state control circuit 190 of the recording / reproducing apparatus 100. In this case, however, the following problems occur. Occurs.

The surface of the insulating thin film 12 is not always flat, and as shown in FIG. 3, the surface of the insulating thin film 12 has irregularities. If the size of the unevenness is small to some extent, the piezoelectric cantilever 120, which is an elastic body, flexes following the unevenness. As a result, the tip of the conductive probe 110 follows the surface of the insulating thin film 12 as indicated by the broken line arrow, so that no recording error or reproduction error occurs during recording or reproduction. However, FIG. 4 (A)
As shown in FIG.
When present on the surface of the
Since the piezoelectric cantilever 120 cannot fully follow in the recess sandwiched by the step 21 and the step 21, the tip of the conductive probe 110 separates from the surface of the insulating thin film 12 as shown by the arrow of the broken line in the figure. As a result, the recording bit 15 cannot be formed in this recess, and a recording error and a reproduction error occur. A waveform diagram of the reproduction information signal S _P at this time is shown in FIG. In this case, the recording bit that should be present in the concave portion of the insulating thin film 12 is, due to the above reason,
Since it is not formed during recording or cannot be reproduced even if formed, the reproduction information signal S _P is lost. Note that when the surface of the insulating thin film 12 is inclined, or when there is mechanical relaxation between a member (not shown) that supports the piezoelectric cantilever 120 and a member (not shown) that supports the recording medium 10. , A similar problem arises.

The operations of the contact state detection circuit 180 and the contact state control circuit 190 of the recording / reproducing apparatus 100 will be described below.

As described above, the piezoelectric cantilever 120 shown in FIG. 1 includes the piezoelectric body 122, the first electrode 121 and the second electrode 123 sandwiching the piezoelectric body 122, the piezoelectric body 122, and the first electrode 121. 121 and an insulating support 124 that supports the second electrode 123, and has a piezoelectric unimorph structure as a whole. When the tip of the conductive probe 110 contacts the surface of the insulating thin film 12, the free end of the piezoelectric cantilever 120 (that is, one end on the side where the conductive probe 110 is attached) becomes a fixed end by contact. As a result, the piezoelectric cantilever
Since 120 changes from a cantilever structure to a double-support structure, the mechanical resonance frequency of the piezoelectric cantilever 120 shifts to the high frequency side. Moreover, the shift amount of this mechanical resonance frequency is
It changes in proportion to the degree of contact between the insulating thin film 12 and the tip of the conductive probe 110 (that is, the magnitude of the force acting between the insulating thin film 12 and the tip of the conductive probe 110). Therefore, by detecting the shift amount of the mechanical resonance frequency of the piezoelectric cantilever 120, the insulating thin film 12 and the conductive probe can be detected.
The degree of contact with the tip of 110 can be detected. In other words, by utilizing the fact that the mechanical properties and the electrical properties of the piezoelectric cantilever 120 are closely related to each other, it is possible to know the mechanical properties of the piezoelectric cantilever 120 by measuring the electrical properties of the piezoelectric cantilever 120. .

Therefore, in the recording / reproducing apparatus 100, the capacitive reactance between the first electrode 121 and the second electrode 123 of the piezoelectric cantilever 120 is measured by the contact state detection circuit 180 to measure the insulating thin film 12 and the conductive probe. The contact state with the tip of the needle 110 is detected, and the Z-direction drive element control signal D generated by the contact state control circuit 190 based on the detection result.
_{In Z} , for example, a Z-direction driving element 130 including a piezo element
By controlling the insulating thin film 12 and the conductive probe 11
Controls the state of contact with the tip of 0.

Regarding the control of the contact state described above, FIG.
It will be described in detail below with reference to FIGS.

As shown in FIG. 5, the contact state detection circuit 180 includes a differential amplifier 181 having a positive side input terminal connected to the first electrode 121 of the piezoelectric cantilever 120, and a first electrode 121 of the piezoelectric cantilever 120. And a resistor 182 having a resistance value R provided between the negative input terminal of the differential amplifier 181 and
The second electrode 123 of the piezoelectric cantilever 120 and the differential amplifier 18
Oscillator provided between the negative input terminal of 1 and 183
And the output voltage V _SIG of the differential amplifier 181 and the oscillator 183
Lock-in amplifier 184 to which the reference voltage V _REF output from each is input.

In the contact state detection circuit 180, the sine wave voltage V
(ω) is applied from the oscillator 183 between the first electrode 121 and the second electrode 123 of the piezoelectric cantilever 120 via the resistor 182, and the potential difference across the resistor 182 at this time is applied to the differential amplifier 181. Detected by. The voltage component of the output voltage V _SIG of the differential amplifier 181 that reflects the capacitive reactance between the first electrode 121 and the second electrode 123 is the sine wave voltage V _SIG.
The phase is 90 ° behind that of (ω). Therefore, in the lock-in amplifier 183, the output voltage V _SIG of the differential amplifier 181 is phase-detected by the reference voltage V _REF output from the oscillator 183, so that the first electrode 121 and the second electrode 123 are separated. A contact state detection signal S _C indicating the magnitude of the capacitive reactance of can be created.

When the insulating thin film 12 and the tip of the conductive probe 110 are not in contact with each other, the frequency characteristic of the capacitive reactance between the first electrode 121 and the second electrode 123 is, for example, as shown in FIG. Piezoelectric cantilever 12
The mechanical resonance frequency of 0 When f _r, capacitive reactance also takes a minimum value at a frequency f _r. On the other hand, the conductive probe 110
When the tip of the electrode contacts the insulating thin film 12, the frequency characteristic of the capacitive reactance between the first electrode 121 and the second electrode 123 becomes the characteristic shown by the broken line in FIG. 6, for example. In this case, the mechanical resonance frequency of the piezoelectric cantilever 120 to shift to a larger f _r 'than f _r from f _r,
Frequency capacitive reactance becomes minimum value is also shifted to the higher frequency f _r 'than the frequency f _r from the frequency f _r.

Therefore, the sinusoidal voltage W (ω) having a frequency f _o slightly smaller than the frequency f _r is output from the oscillator 182 to cause the capacitive reactance between the first electrode 121 and the second electrode 123. When detected, the tip of the conductive probe 110 comes into contact with the insulating thin film 12, and the value of the capacitive reactance changes from C ₁ to C ₂ . In addition, the conductive probe 11
When the force acting between the tip of 0 and the insulating thin film 12 increases, the value of the capacitive reactance becomes larger than C ₂ in proportion to the magnitude of this force. As a result, the contact state between the insulating thin film 12 and the tip of the conductive probe 110 can be detected by measuring the capacitive reactance.

FIG. 7 shows a first electrode 121 and a second electrode 123.
An example of the result of measurement of the relationship between the capacitive reactance between and and the drive amount of the piezoelectric cantilever 120 by the Z-direction drive element 130 in the Z-axis direction in FIG.

When the piezoelectric cantilever 120 is driven in the Z-axis direction shown in FIG. 1 by the Z-direction driving element 130, the driving amount Z
_{At O} , the capacitive reactance between the first electrode 121 and the second electrode 123 changes from C ₁ to C ₂ . From this, it can be seen that the tip of the conductive probe 110 has come into contact with the insulating thin film 12. After that, as the piezoelectric cantilever 120 is further driven in the Z-axis direction in FIG. 1, the value of the capacitive reactance also increases. Therefore, the insulating thin film 12 and the tip of the conductive probe 110 are connected to each other from the increased amount of the capacitive reactance. The degree of contact (that is, the magnitude of the force acting between the insulating thin film 12 and the tip of the conductive probe 110) can be detected.

Specific examples of the control of the contact state between the insulating thin film 12 and the tip of the conductive probe 110 will be described below with reference to FIGS. 8A to 8D, respectively.

As shown in FIG. 8A, the conductive probe 110
When the tip of the conductive probe 110 is scanned up to the step 20 while the tip of the conductive tip 110 is being scanned in the right direction in the figure while being in contact with the insulating thin film 12, the insulating thin film 12 is formed before and after the step 20.
Since the contact state and the tip of the conductive probe 110 change from the contact state to the non-contact state, between the first electrode 121 and the second electrode 123 detected by the contact state detection circuit 180 (see FIG. 1). The capacitive reactance changes from C ₂ to C as shown in FIG.
Change to ₁ . In the contact state control circuit 190 (see FIG. 1), the amplitude of the Z-direction drive element control signal S _Z is the contact state detection signal S _C sent from the contact state detection circuit 180, as shown in FIG. Z is increased according to the change of
It is output to the direction driving element 130. As a result, the conductive probe
The tip of 110, as shown by the dashed arrow in FIG.
It is driven to the side of the insulating thin film 12 by the Z-direction driving element 130.

After that, when the tip of the conductive probe 110 is driven until it comes into contact with the insulating thin film 12, the capacitive reactance returns from C ₁ to C ₂ as shown in FIG. In the contact state control circuit 190, when the contact state detection signal S _C indicating that the capacitive reactance is C ₂ is sent, as shown in FIG. 7C, the Z direction drive element control signal S _Z The amplitude is held and output to the Z-direction drive element 130. As a result, the driving of the tip of the conductive probe 110 toward the insulating thin film 12 side by the Z-direction driving element 130 is stopped. In this state, the conductive probe 110 is scanned rightward in the figure with its tip in contact with the insulating thin film 12, as indicated by the dashed arrow in FIG.

Then, the tip of the conductive probe 110 is stepped 21.
When it is scanned up to, the insulating thin film 12 and the conductive probe 11
Since the degree of contact with the tip of 0 is strong (that is, the force acting between the insulating thin film 12 and the tip of the conductive probe 110 is large), the first state detected by the contact state detection circuit 180 is detected. The capacitive reactance between the electrode 121 and the second electrode 123 changes from C ₂ to C _{3 as shown} in FIG. In the contact state control circuit 190, the amplitude of the Z-direction drive element control signal S _Z changes according to the change of the contact state detection signal S _C sent from the contact state detection circuit 180, as shown in FIG. It is reduced in size and output to the Z-direction drive element 130. As a result, the tip of the conductive probe 110 has the Z-direction drive element 130 as shown by the broken arrow in FIG.
Is driven to the side opposite to the insulating thin film 12.

After that, the conductive probe 110 is separated from its tip.
It is driven until the degree of contact with the limbic thin film 12 returns to the original level.
And the capacitive reactance is as shown in FIG.
To C ₃ To C₂ Return to. In the contact state control circuit 190,
The capacitive reactance is C₂ Contact state indicating that
Detection signal S_C Is sent, as shown in FIG.
To the Z direction drive element control signal S_Z Holds the amplitude of
It is output to the Z-direction drive element 130. As a result, Z direction driving
Insulating thin film 1 on the tip of conductive probe 110 by moving element 130
The drive to the side opposite to 2 is stopped. In this state, conductive
As shown by the broken line arrow in FIG.
In the right direction in the figure with the tip of the
To be scanned.

By controlling the contact state between the insulating thin film 12 and the tip of the conductive probe 110 as described above,
Since the conductive probe 110 can be scanned while always maintaining the contact state between the insulating thin film 12 and the tip of the conductive probe 110, there are steps or holes on the surface of the insulating thin film 12. However, even if the surface of the insulating thin film 12 is inclined or there is mechanical relaxation between the member supporting the piezoelectric cantilever 120 and the member supporting the insulating thin film 12, the recording error and the reproduction error can be eliminated. it can. Figure 8 (D)
An example of the reproduction information signal S _P at this time is shown in FIG. From this figure, it is understood that the recording bit 15 can be surely formed in the concave portion sandwiched by the step 20 and the step 21, and the recording bit 15 formed in the concave portion can be surely reproduced. . Further, by driving the Z-direction drive element 130 only in the non-contact state and in the state where the Z-direction drive element is excessively contacted, and stopping the drive in the just-contact state, the drive control of the Z-direction drive element 130 is simplified. Therefore, the time required for control can be shortened.
This contributes to high-speed recording / reproduction, and further simplifies control of a plurality of drive elements when the probe is multi-plied.

FIG. 9 is a schematic block diagram showing a second embodiment of the recording / reproducing apparatus of the present invention.

In the recording / reproducing apparatus 100 shown in FIG. 1, the tip of the conductive probe 110 is driven in the Z-axis direction in the figure by using the Z-direction drive element 130 composed of, for example, a piezo element. On the other hand, in the recording / reproducing apparatus 200 of this embodiment, the tip of the conductive probe 210 is driven in the Z-axis direction in the figure by unimorph-driving the piezoelectric cantilever 220, and in the following points, It is different from the recording / reproducing apparatus 100 shown in FIG. (1) The contact state control circuit 290 outputs a piezoelectric cantilever drive voltage V _D (DC voltage) corresponding to the contact state detection signal S _C. (2) It includes an adder circuit 300 for adding the sine wave voltage V (ω) output from the contact state detection circuit 280 and the piezoelectric cantilever drive voltage V _D output from the contact state control circuit 290. (3) The output voltage of the adding circuit 300 is applied to the first electrode 221 of the piezoelectric cantilever 220. (4) Does not include means corresponding to the Z-direction drive element 130 shown in FIG.

The operation of the recording / reproducing apparatus 200 of this embodiment is the same as the operation of the recording / reproducing apparatus 100 shown in FIG.

Next, another embodiment of the recording / reproducing apparatus of the present invention will be described.

The recording / reproducing apparatus 100 shown in FIG. 1 and FIG.
Although the recording / reproducing apparatus 200 shown in FIG. 2 includes a unimorph piezoelectric cantilever (piezoelectric cantilever 120 and piezoelectric cantilever 220), a piezoelectric bimorph piezoelectric cantilever may be used instead of the piezoelectric unimorph piezoelectric cantilever. Alternatively, a plurality of piezoelectric cantilevers having a piezoelectric unimorph structure provided in parallel may be used. Particularly in the latter case, the time required for the recording operation and the reproducing operation can be shortened by performing the recording operation and the reproducing operation in parallel for each piezoelectric cantilever. However, in this case, it is important to miniaturize and integrate the mechanical drive mechanism and the electric control circuit for one piezoelectric cantilever. From this point as well, the piezoelectric cantilever itself as shown in FIG.
It is desirable to use it as a direction driving element.

In the above description, the method of applying the voltage pulse to cause the dielectric breakdown of the insulating thin film is taken as an example of the method of forming the recording bit, but the method is not limited to this method. Any method may be used as long as the conductivity of the recording medium itself changes between "0" and a finite value by applying a voltage pulse. For example, instead of an insulating thin film,
As the polydiacetylene conversion by the electric field polymerization of diacetylene, a material in which the monomer molecule is polymerized to generate conductivity may be used.

[0053]

Since the present invention is configured as described above, it has the following effects.

The conductive probe is supported by a piezoelectric cantilever,
The contact state between the recording medium and the tip of the conductive probe is detected from the change in the value of the capacitive reactance of the piezoelectric unimorph structure or the piezoelectric bimorph structure of the piezoelectric cantilever, and the contact state is optimized based on this detection result. By configuring the piezoelectric cantilevers as described above, individual elements such as a plurality of conductive probes, a plurality of piezoelectric cantilevers, and an electric control circuit can be formed by using a lithography technique such as a micromachine or microelectronics.
For example, it can be integrally formed on a Si substrate or the like. Therefore, it is possible to downsize the entire device,
Moreover, since individual elements are integrally formed, variations in characteristics among a plurality of elements are reduced and reliability is also improved.

Further, even if there are large irregularities on the surface of the recording medium, the contact state between the recording medium and the tip of the probe can always be maintained, so that mechanical vibration of the entire apparatus, surface shape of the recording medium, and Due to contamination between the recording medium and the probe or the influence of foreign matter, the distance between the recording medium and the probe fluctuates, which causes the recording medium and the tip of the probe to be in a non-contact state. It is possible to prevent a recording error and a reproduction error, and improve reliability, stability and SN ratio.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a recording / reproducing apparatus of the present invention.

2A and 2B are views for explaining an operation at the time of reproduction of the recording / reproducing apparatus shown in FIG. 1, FIG. 2A is a graph showing an example of a waveform of a voltage converted by a current-voltage conversion circuit, and FIG. Is a graph showing the reproduction information signal at this time.

FIG. 3 is a diagram for explaining the movement of the tip of the conductive probe when small irregularities are present on the surface of the insulating thin film.

FIG. 4 is a diagram for explaining a problem that occurs when the contact state detection circuit and the contact state control circuit are not operated, FIG. 4A is a diagram for explaining movement of the tip of the conductive probe, and FIG. ) Is a graph showing a reproduction information signal.

5 is a block diagram showing a contact state detection circuit shown in FIG. 1. FIG.

6 is a graph showing an example of frequency characteristics of capacitive reactance between the first electrode and the second electrode of the piezoelectric cantilever shown in FIG.

7 is a graph showing the relationship between the capacitive reactance between the first electrode and the second electrode of the piezoelectric cantilever shown in FIG. 1 and the driving amount of the piezoelectric cantilever by the Z-direction driving element in the Z-axis direction shown in FIG. It is a graph which shows an example of the measured result.

8A and 8B are views for explaining a specific example of the control of the contact state between the tip of the conductive probe and the insulating thin film in the recording / reproducing apparatus shown in FIG. 1, and FIG. FIG. 6B is a graph showing a scanning state of the tip, FIG. 6B is a graph showing a change in capacitive reactance, FIG. 6C is a graph showing a change in amplitude of a Z-direction drive element control signal, and FIG. .

FIG. 9 is a schematic configuration diagram showing a second embodiment of the recording / reproducing apparatus of the present invention.

[Explanation of symbols]

10,50 Recording medium 11,51 Conductive substrate 12,52 Insulating thin film 15,55 Recording bit 20,21 Step 100,200 Recording / reproducing device 110,210 Conductive probe 120,220 Piezoelectric cantilever 121,221 First Electrodes 122, 222 Piezoelectric materials 123, 223 Second electrodes 124, 224 Supports 125, 225 Third electrodes 130 Z-direction driving element 140, 240 XY-direction driving element 150, 250 Recording pulse voltage application circuit 160, 260 Playback Bias voltage application circuit 170,270 Current-voltage conversion circuit 180,280 Contact state detection circuit 181 Differential amplifier 182 Resistance 183 Oscillator 184 Lock-in amplifier 190,290 Contact state control circuit V _P Recording pulse voltage V _B Bias voltage for reproduction V _D Piezoelectric cantilever drive voltage S _R Recording information signal S _P Reproduction information signal S _C Contact state detection signal S _Z Z direction drive element control signal X, Y, Z axes C _{1 to} C ₃ Capacitive reactance value

Front page continued (72) Inventor Yoji Yano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kunihiro Sakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (8)

[Claims] 1. A conductive probe, a recording medium capable of distinguishing a recorded state and a non-recorded state by the presence or absence of a current flowing between the tip of the probe, and the tip of the probe is the recording medium. Piezoelectric unimorph structure having a pair of electrodes with the probe attached to one end so as to face the medium, a piezoelectric body sandwiched by the pair of electrodes, and a support for supporting the pair of electrodes and the piezoelectric body A piezoelectric cantilever including a body, driving means for driving the piezoelectric cantilever so that the tip of the probe moves in a direction perpendicular to the surface of the recording medium, and information between the recording medium and the tip of the probe. Information recording voltage applying means for applying a recording voltage, information reproducing voltage applying means for applying an information reproducing voltage between the recording medium and the tip of the probe, and the recording medium and the probe Between the tip And a contact state detecting unit for detecting the contact state between the recording medium and the tip of the probe by detecting the capacitive reactance between the pair of electrodes, and the contact state detecting unit. A recording / reproducing apparatus comprising: a contact state control unit that controls the driving unit according to the detected contact state. 2. A probe having conductivity, a recording medium capable of distinguishing a recording state from a non-recording state depending on the presence or absence of a current flowing between the tip of the probe, and the tip of the probe is the recording medium. Two or more pairs of electrodes each having the probe attached to one end so as to face the medium, a plurality of piezoelectric bodies sandwiched between the pair of electrodes, and two or more pairs of electrodes and the plurality of piezoelectric bodies. A piezoelectric cantilever provided with a piezoelectric bimorph structure having a support for supporting; a drive means for driving the piezoelectric cantilever so that the tip of the probe moves in a direction perpendicular to the surface of the recording medium; and the recording medium. Information recording voltage applying means for applying an information recording voltage between the tip of the probe and information reproducing voltage applying means for applying an information reproducing voltage between the recording medium and the tip of the probe. And the above Current detecting means for detecting a current flowing between a medium and the tip of the probe, and capacitive contact reactance between each of the pair of electrodes to detect a contact state between the recording medium and the tip of the probe. A recording / reproducing apparatus comprising: a contact state detecting means for controlling the contact state detecting means; and a contact state controlling means for controlling the driving means according to the contact state detected by the contact state detecting means. 3. A probe having conductivity, a recording medium capable of distinguishing a recording state and a non-recording state depending on the presence or absence of a current flowing between the tip of the probe, and the tip of the probe is the recording medium. Piezoelectric unimorph structure having a pair of electrodes with the probe attached to one end so as to face the medium, a piezoelectric body sandwiched by the pair of electrodes, and a support for supporting the pair of electrodes and the piezoelectric body A piezoelectric cantilever including a body, an information recording voltage applying unit that applies an information recording voltage between the recording medium and the tip of the probe, and information reproduction between the recording medium and the tip of the probe. Information reproducing voltage applying means for applying a recording voltage, current detecting means for detecting a current flowing between the recording medium and the tip of the probe, and the recording by detecting a capacitive reactance between the pair of electrodes. Of the medium and the probe Contact state detecting means for detecting a contact state with the tip, and the piezoelectric element for moving the tip of the probe in a direction perpendicular to the surface of the recording medium according to the contact state detected by the contact state detecting means. A recording / reproducing apparatus comprising: a contact state control unit that drives and controls a cantilever. 4. A conductive probe, a recording medium capable of distinguishing a recording state and a non-recording state by the presence or absence of a current flowing between the tip of the probe, and the tip of the probe is the recording medium. Two or more pairs of electrodes each having the probe attached to one end so as to face the medium, a plurality of piezoelectric bodies sandwiched between the pair of electrodes, and two or more pairs of electrodes and the plurality of piezoelectric bodies. A piezoelectric cantilever provided with a piezoelectric bimorph structure having a support for supporting the information recording voltage applying means for applying an information recording voltage between the recording medium and the tip of the probe, the recording medium and the Information reproducing voltage applying means for applying an information reproducing voltage to the tip of the probe, current detecting means for detecting a current flowing between the recording medium and the tip of the probe, and each of the pair of The capacitive reactance between the electrodes Contact state detecting means for respectively detecting and detecting the contact state between the recording medium and the tip of the probe, and the tip of the probe corresponds to the recording medium according to the contact state detected by the contact state detecting means. A recording / reproducing apparatus comprising: contact state control means for driving and controlling the piezoelectric cantilever so as to move in a direction perpendicular to the surface. 5. A piezoelectric cantilever provided with a piezoelectric unimorph structure having a pair of electrodes, a piezoelectric body sandwiched between the pair of electrodes, and a support body supporting the pair of electrodes and the piezoelectric body. A conductive probe is brought into contact with the surface of a recording medium that can be distinguished from a recorded state and a non-recorded state depending on the presence or absence of a current flowing between the probe and the tip of the probe, and the capacitive reactance between the pair of electrodes is The contact state between the recording medium and the tip of the probe is detected, and the probe is perpendicular to the surface of the recording medium so as to adjust the contact state based on the detection result of the contact state. While moving in the direction, during recording, an information recording voltage is applied between the recording medium and the probe to record information on the recording medium, and during reproduction, the recording medium and the probe are recorded. Needle with the probe The information recorded on the recording medium is reproduced based on the result of detecting the current flowing between the recording medium and the probe by applying an information reproducing voltage to the information recording medium. Recording and playback method. 6. In the non-contact state, the adjustment of the contact state and the movement of the probe in the direction perpendicular to the surface of the recording medium move in a direction of bringing the probe closer to the surface of the recording medium, In a weak contact state below a threshold value, the movement of the probe is stopped, and in a strong contact state above the predetermined threshold value, the probe is moved in a direction away from the surface of the recording medium. The recording / reproducing method according to claim 5, wherein 7. A piezoelectric bimorph structure having two or more pairs of electrodes, a plurality of piezoelectric bodies respectively sandwiched by the pair of electrodes, and a support for supporting the two or more pairs of electrodes and the plurality of piezoelectric bodies. A conductive cantilever attached to one end of a piezoelectric cantilever having a contact with a surface of a recording medium in which a recording state and a non-recording state can be distinguished by the presence or absence of a current flowing between the tip of the piezoelectric cantilever. The contact state between the recording medium and the tip of the probe is detected by detecting the capacitive reactance between each pair of electrodes, and the contact state is adjusted based on the detection result of the contact state. While moving the probe in a direction perpendicular to the surface of the recording medium, at the time of recording, an information recording voltage is applied between the recording medium and the probe to record information on the recording medium. And during playback The recording medium based on the result of applying an information reproducing voltage between the recording medium and the probe and detecting a current flowing between the recording medium and the probe. A recording / reproducing method characterized by reproducing the information recorded on the recording medium. 8. The adjustment of the contact state and the movement of the probe in the direction perpendicular to the surface of the recording medium are such that, in the non-contact state, the probe moves in a direction of approaching the surface of the recording medium, In a weak contact state below a threshold value, the movement of the probe is stopped, and in a strong contact state above the predetermined threshold value, the probe is moved in a direction away from the surface of the recording medium. 8. The recording / reproducing method according to claim 7, wherein.