JP3044417B2 - Information processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information processing apparatus to which a technique such as a scanning tunnel microscope is applied.

[0002]

2. Description of the Related Art In recent years, the use of memory materials is at the core of the electronics industry such as computers and related equipment, video disks, digital audio disks, and the like, and the development of such materials has been extremely active. The performance required of such a memory material varies depending on the application, but it is essential that the response speed of recording and reproduction be high.

Conventionally, semiconductor memories and magnetic memories made of a magnetic material or a semiconductor have been mainly used. However, with the recent advancement of laser technology, low-cost optical memories using organic thin films such as organic dyes and photopolymers have been used. And high-density recording media have appeared.

On the other hand, recently, a scanning tunneling microscope (hereinafter referred to as STM) capable of directly observing the electronic structure of atoms on the surface of a conductor has been proposed.
Is abbreviated as [G. Binnig et. a
l. Phys. Rev .. Lett, 49, 57 (19
82)], it is possible to measure a real space image with a high resolution regardless of whether it is single crystal or amorphous, and has the advantage that damage due to current can be observed at low power without damaging the sample.
Furthermore, since it can operate in the air and can be used for various materials, a wide range of applications is expected.

[0005] This STM utilizes the fact that a tunnel current flows when a voltage is applied between a metal probe (probe electrode) and a conductive material to approach a distance of about 1 nm. This current is very sensitive because it responds exponentially to changes in distance between them. By scanning the probe so as to keep the tunnel current constant, it is possible to read various kinds of information on all electron clouds in the real space. At this time, the resolution in the in-plane direction is about 0.1 nm.

Therefore, if the principle of STM is applied, it is possible to perform high-density recording / reproducing on the order of atoms (sub-nanometer). For example, JP-A-61-
In the information processing apparatus disclosed in Japanese Patent No. 80536,
Atomic particles adsorbed on the medium surface are removed by an electron beam or the like, writing is performed, and this data is reproduced by STM. As disclosed in U.S. Pat. No. 4,575,822, charges are injected into a dielectric layer formed on the surface of a recording medium using a tunnel current flowing between the surface of the recording medium and a probe electrode. And record. Alternatively, a method has been proposed in which recording is performed by physical collapse of the medium surface using laser light, an electron beam, a particle beam, or the like. STM is used for recording / reproduction by using a material having a memory effect on the switching characteristics of voltage and current, for example, a thin layer of a conjugated π-electron organic compound or chalcogen compound as a recording layer.
[JP-A-63-16155].
No. 2, JP-A-63-161553]. According to this method, if the recording bit size is 10 nm,
A large capacity recording / reproduction of 10 ¹² bit / cm ² is possible. The control of the distance between the probe electrode and the recording medium in these information processing apparatuses is disclosed in Japanese Patent Application Laid-Open No. 2-5339.

[0007]

In the information processing apparatus, the probe electrode and the recording medium are brought close to each other until a current flows between them, and the probe electrode is moved in the plane of the recording medium while maintaining the current flowing state. The scanning is performed in the direction, and the distance is controlled in accordance with the increase and decrease of the current amount due to the unevenness of the surface of the recording medium and the change of the electronic state.

In the conventional invention, a circuit as shown in the block diagram of FIG. 4 is used to set the interval between the recording medium and the probe electrode, and extracts the low frequency component of the current signal and controls the information as inclination information of the recording medium. The distance between the electrode and the recording medium is controlled. In such a control, when recording and reproducing information by area scanning as shown in FIG. 5, since the signal of the entire scanning period is used as inclination information through a low-frequency pass filter, the X-axis scanning signal is recorded on FIG. The medium tilt information is as shown in FIG. As shown by the auxiliary line in the figure, near the scanning end point, the error from the actual substrate inclination becomes large (shaded portion), and the accuracy of the distance control between the probe recording media is deteriorated.

In addition, since low-frequency components of the recorded information affect the tilt information, consideration must be given to selecting an NRZ method or the like as a recording modulation method, which has narrowed the application of the apparatus.

That is, the object of the present invention is to
An object of the present invention is to provide an information processing apparatus capable of improving the accuracy in recording and reproducing information and the like and achieving simplification as an apparatus.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the structure of the present invention is to detect a signal via a probe.
Information that reproduces information on a recording medium using a very small current
In the processing apparatus, a probe relatively moves the medium surface.
The probe and the recording medium are synchronized so as to perform reciprocal scanning.
Means for moving and detection via the probe
Means for detecting current, and current detected during the scanning period.
Is the signal excluding at least the data near the scanning end of the stream signal?
A tilt signal of the recording medium in the scanning direction is detected.
Output means and the probe based on the tilt signal.
And a means for controlling the distance between the recording media .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following embodiment, a tunnel current signal used for tilt detection is used for each direction of scanning in the X direction, and a signal component having a relatively high frequency near a scanning end is removed, so that the entire scanning region is removed. The distance between the probe recording media can be controlled with high accuracy over a wide range.

The recording layer used in the recording medium of the present invention may be any layer that has a memory effect on the current-voltage characteristics between the probe electrode and the recording medium. For example, in the case of recording by forming irregularities on the surface, HOPG (Highly-Or
Evented-Pyrolithic-Graphite
e) A cleavage substrate, a Si wafer, a metal thin film such as Au, Ag, Pt, Mo, or Cu grown by vacuum evaporation or epitaxial growth, or a glass metal such as Rh25Zr75 or Co35Tb65. In the case of recording based on the electronic state of the surface, a thin film layer of amorphous Si, a π-electron organic compound, a chalcogen compound, or the like can be given.

Hereinafter, the present invention will be described specifically with reference to Examples.

(Embodiment 1) FIG. 1 is a block diagram showing the configuration of an information processing apparatus according to the present invention. In the figure, 10
1 is a stage, 102 is a lower electrode layer, 103 is a recording layer,
104, a track groove formed on the surface of the recording medium;
Is a probe electrode, and 106 is a cylindrical PZT actuator for scanning the probe electrode 105 along a data string on a recording medium, and can move up to 2 μm in each of the X, Y, and Z directions.

The probe electrode 105 is connected to a current amplifier 107. The output of the current amplifier 107 is the comparator 1
08, a high-pass filter 110 and an error amplifier 112. The output of the error amplifier is a slope information arithmetic unit 11
1 is input. The output of the tilt information calculation device is input to the comparator 113 through the sample and hold circuit 109 and the ΔZ drive electrode of the cylindrical PZT and the attenuator VR2. The output of the high-pass filter is output from the comparator 113
Connected to the other input of Further, the output of the comparator 113 is input to the data demodulator of the data modem 114. The data modulation output of the data modulation / demodulation unit is connected to the pulse generator 115, combined with the DC bias voltage VB1, and connected to the recording medium electrode.

The distance between the probe electrode and the surface of the recording medium is controlled by converting the value obtained by converting the voltage of the tunnel current into an error amplifier 11.
2 to compare with the reference voltage VB2.
Calculates only the tilt information by 11 and calculates the cylindrical PZT as ΔZ
Drive. Actually, the tilt information line B in FIG. 2 is obtained from the data between the points a and b in FIG. 2 where the data near the scanning end of the detected current signal as shown in the line A in FIG. Then, a signal that increases or decreases according to the position, as indicated by the line B, is added to the control signal of the PZT in the Z direction at the time of scanning the next line.

With this control, the probe electrode performs a recording or reproducing operation while scanning so as to follow the inclination of the recording medium. This is repeated alternately. That is, a two-stage scan is repeated in which the inclination is detected in the first scan, and recording or reproduction is performed in the second scan while following the above. The inclination information calculation device performs A / D conversion of an input, calculates inclination information by a digital signal processor (DSP), and performs D / A conversion at the time of output.

Next, the operation during reproduction will be described. After the tunnel current detected by the probe electrode is amplified by the current amplifier 107, a high-frequency component, that is, a data information component is extracted by a high-pass filter, and the comparator 113 appropriately attenuates the data stream envelope signal. Is used as a slice level to obtain binarized data.

Next, the operation at the time of recording will be described. The write pulse is output from the pulse generator 115 in a state where the sample-hold control signal is held in synchronization with the data write clock, and the control signal in the Z direction passing through the sample-hold circuit 109 becomes a constant value only when the recording voltage is applied. Generate. Therefore, when the recording voltage is applied, the movement of the probe electrode in the Z direction stops. This sample and hold circuit is in a through state during reproduction.

At the time of recording / reproduction, the edge detection signal forcibly switches the up / down counter to the up-count operation. Further, after counting up by a certain count value, the count value is again switched to down count.

The tracking control unit 116 drives the cylindrical PZT actuator 106 via an up / down counter 117 and a D / A converter 118. The up input of the up / down counter 117 is connected to the AND output of the output of the edge detection comparator 108 and the track movement STATUS signal from the tracking control unit by ORing the output with the up control signal from the tracking control unit.

On the other hand, the down input of the up / down counter 117 is connected to the down control signal of the tracking control unit. The count output of the up / down counter is converted into an analog voltage by the D / A converter 118, and drives the cylindrical PZT by ΔX so that reciprocating motion is performed. Furthermore, D
The output of the / A converter 118 is combined with the wobbling signal from the tracking control unit via the variable resistor VR1 and the resistor R1 controlled by the scanning azimuth control signal, and drives the cylindrical PZT by ΔY so that the reciprocating motion is performed. . Thereby, for example, the scanning as shown in FIG. 5 is performed. The first tilt detection scan and the second follow-up scan are performed using the Δ
Scanning is performed in the same direction during X reciprocation. In this case, the inclination may be detected in the forward movement of the reciprocating movement, and the following and the recording or reproduction may be performed in the backward movement. In this case, the signal added to the control signal is reversed left and right with respect to the B line.

The tunnel voltage signal is compared with the threshold voltage VB3 by the edge detecting comparator 108. When the tunnel voltage signal falls below VB3 , the probe electrode approaches the concave edge of the track groove, and the probe electrode approaches the edge. To detect.

The scanning azimuth of the probe electrode is performed by changing the variable resistor VR1 according to the scanning azimuth control signal and changing the drive ratio of ΔX / ΔY of the cylindrical PZT actuator 106. The detection of the proper scanning direction is performed by driving the wobbling voltage by ΔY and monitoring the envelope signal of the tunnel voltage at this time.

By detecting the tilt during scanning for recording and reproduction as in this embodiment, there is an effect that it is possible to sufficiently cope with a partial tilt in the scanning area.

(Embodiment 2) The structure is the same as that of Embodiment 1, and when the distance between the probe electrode and the surface of the recording medium is controlled, A in FIG.
The slope information diagram is obtained from the data between the points a and b and the points c and d in FIG. 3 in which the data near the scanning end of the detected current signal as shown by the line and the reproduced signal in the signal recording / reproducing area are cut off. 3 line B is obtained and output when the next line is scanned.

When the tilt correction method of this embodiment is used, a recording layer that does not change its surface shape during a recording operation, such as a π-electron organic compound or a chalcogen compound that has a memory effect on the switching characteristics of voltage and current. When a thin film layer is used, it is possible to eliminate an error in a tilt correction amount due to a recording signal on a medium. Also, since the degree of freedom in selecting the DC component of the reproduction signal is increased, the recording information modulation method is NR.
Since the present invention is not limited to the Z method or the like, it has become possible to expand the application range of the apparatus.

In this embodiment, a follow-up scan based on the tilt information obtained by the previous scan is performed between b and c, and tilt information detection for the next scan is performed between a, b, c, and d. For example, the tilt detection scanning and the following scanning can be performed during the same scanning.

[0030]

As described above, according to the information processing apparatus of the present invention, the distance between the probe recording media can be controlled with high accuracy over the entire recording / reproducing area, so that errors in recording are small and the S / N is good. An information processing device with a high scanning speed was realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an information processing apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a tilt correction method of the information processing apparatus according to the first embodiment.

FIG. 3 is an explanatory diagram of a tilt correction method of an information processing apparatus according to a second embodiment.

FIG. 4 is a block diagram of a circuit system used for conventional distance control between a probe electrode and a recording medium.

FIG. 5 is an explanatory diagram of area scanning in a conventional example.

FIG. 6 is an X-axis scanning signal waveform in a conventional example.

FIG. 7 shows recording medium tilt information during scanning in a conventional example.

[Explanation of symbols]

 Reference Signs List 101 Stage 102 Lower electrode of recording medium 103 Recording layer 104 Track groove 105 Probe electrode 106 Cylindrical piezo actuator 107 Current amplifier 108 Comparator 109 Sample hold circuit 110 High-pass filter 111 Inclination information operation device 112 Error amplifier 113 Data detection comparator 114 Data modulation / demodulation unit 115 Data writing pulse generator 116 Tracking control unit 117 Up / down counter 118 D / A converter 119 Stage control unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shunichi Shido 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsunori Hatana 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon JP-A-4-186111 (JP, A) JP-A-4-359105 (JP, A) JP-A-4-212001 (JP, A) JP-A-2-147803 (JP, A A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 9/14 G01N 13/10

Claims (1)

(57) [Claims] 1. A method for detecting a minute current detected via a probe.
Information processing device that reproduces information on a recording medium using
So that the probe relatively reciprocally scans the medium surface.
Means for relatively moving the probe and the recording medium
, Means for detecting the current detected through the probe
And scanning at least the current signal detected during the scanning period.
From the signal excluding the data near the edge,
Means for detecting a tilt signal of the recording medium, and the probe and the recording medium based on the tilt signal.
Means for controlling a distance between the information processing apparatuses.