JPH08249732A - Probe control circuit for information processor - Google Patents

Abstract

PURPOSE: To provide a probe control circuit for information processor capable of correcting a displacement sensitive characteristic depending on a drive voltage value of an actuator performing position control of a probe and the stable position control and to provide a small-sized and precise multi-probe control circuit provided with plural probes. CONSTITUTION: In the probe control circuit for information processor detecting a signal generated from a physical phenomenon between the probe 2 and a medium opposite to it, and performing the position control of the probe by a position control signal based on the detected signal, the displacement sensitive characteristic depending on the drive voltage value of the actuator performing the position control of the probe 2 is corrected. Then, the circuit is provided with a control circuit 7 outputting a distance control signal so that a distance between the probe 2 and a specimen 1 becomes a fixed level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information processing device for writing or reading information by physical interaction between a probe and a recording medium, such as a recording / reproducing device, or an information processing device such as a scanning tunneling microscope (STM). Of the probe control circuit.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter abbreviated as STM) has been developed which can directly observe the electronic structure of surface atoms of a conductor [G. Binnig et al. Ph
ys. Rev. Lett, 49, 57 (1982)],
It has become possible to measure real space images with high resolution regardless of whether they are single crystals or amorphous. The STM utilizes the fact that a tunnel current flows when a voltage is applied between a metal probe (probe electrode) and a conductive substance to bring them closer to a distance of about 1 nm. This current is very sensitive to changes in the distance between the two. By scanning the probe so that the tunnel current is kept constant, it is possible to read various kinds of information regarding the whole electron cloud in the real space. At this time, the resolution in the in-plane direction is 0. It is about 1 nm. Therefore, if the principle of STM is applied, it is possible to sufficiently perform high-density recording / reproducing on the atomic order (sub-nanometer). For example, JP-A-61-1
In the recording / reproducing apparatus disclosed in Japanese Patent No. 80536, the atomic particles adsorbed on the surface of the medium are removed by an electron beam or the like to perform writing, and this data is reproduced by the STM. In addition, a method has been proposed in which recording / reproducing is performed by STM using a material having a memory effect on voltage / current switching characteristics as a recording layer, for example, a thin film layer of an n-electron organic compound or chalcogen compound. Kaisho 63
-161552, JP-A-63-161553]. According to this method, the recording bit size is 10n.
As m, a large capacity recording / reproducing of 10 ¹² bit / cm ² is possible. Furthermore, for the purpose of downsizing, a device has been proposed in which a plurality of probes are formed on a semiconductor substrate and a recording medium facing the probes is displaced to perform recording (JP-A-1-196).
751 publication). For example, by combining the multi-probe head in which 2500 probes are arranged in a matrix of 50 × 50 on a silicon chip of 1 cm ² square and the above-mentioned material having a memory effect, it is possible to obtain 4 probes per probe.
Recording / reproducing of digital data of 00 Mbit and total recording capacity 1 Tbit can be performed. At this time, a method of mounting this probe on a cantilever (cantilever beam) having a length of several 100 μm and driving it is considered. At this time, there is also proposed a storage device using an integrated probe head that controls the distance to the medium by driving the probe with an electrostatic force (Japanese Patent Laid-Open No. 62-281138).

[0003]

However, in order to actually perform information processing such as recording / reproducing by combining the probe and the medium facing the probe, there are the following problems. (1) It is necessary to accurately control the distance between the medium facing the probe during information processing such as recording and reproduction. When a cantilever driven by electrostatic force is used as an actuator for driving the probe, a linear relationship is not established between the applied voltage for driving and the generated electrostatic force. That is, the displacement sensitivity of the actuator changes with respect to the applied voltage. Normal ST
In M, in order to control the distance between the medium facing the probe, the detected tunnel current is Log-converted, and the difference between the Log-converted output and the set value is used as an error signal to perform actuator control by proportional-plus-integral control. If this is applied to a control target whose actuator displacement sensitivity is not constant, such as a cantilever driven by electrostatic force, the response of the servo becomes very bad due to the drive voltage, or conversely the loop gain becomes too high and oscillates. There was a problem that the stability deteriorated against disturbance. (2) When performing information processing using a multi-probe head composed of a plurality of probes, it is necessary to accurately control the distance between the medium facing each probe. When actually manufacturing a plurality of probes by fine processing such as an IC process, it is inevitable that the heating process varies. This process variation appears as height and warpage variation of each probe. In order to suppress this variation, it was necessary to control the distance of each probe independently. In this case, the control circuit that drives each probe generates a drive signal so as to follow the unevenness of the medium surface while correcting the warp variation of each probe. That is, the drive signal for driving each probe is a DC voltage for correcting the warp variation,
It becomes a superposition of the AC changes to follow the unevenness.
At this time, the DC voltage amount for correcting the warp variation is different for each probe. Therefore, if each probe is controlled by the same control parameter, an actuator having a large non-linear displacement characteristic, such as an electrostatic force-driven actuator, is used. There was a possibility that the response of the servo would be very poor each time, or conversely, the loop gain would be too high to cause oscillation, or the stability would be poor against external disturbances. For this purpose, for example, a control system for performing Z control between the probe and the medium may be provided outside the probe head by the number of probes. In this case, even if the multi-probe head can be made small, the control unit of the external structure becomes large by the number of the probes, and there is a problem in realizing a small-sized information processing device that makes the best use of the characteristics of STM.

Therefore, the present invention solves the above problems and corrects a change in displacement sensitivity characteristic depending on a driving voltage value of an actuator for controlling the position of a probe, thereby enabling stable position control of a probe control circuit of an information processing apparatus. Another object of the present invention is to provide a small and highly accurate multi-probe control circuit including a plurality of such probes.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a probe control circuit for detecting a signal generated from a physical phenomenon between a probe and a medium facing the probe to perform information processing. The displacement sensitivity characteristic depending on the driving voltage value of the actuator for position control is corrected to enable stable position control of the probe.

That is, the present invention provides a probe control circuit of an information processing apparatus for detecting a signal generated from a physical phenomenon between a probe and a medium facing the probe and controlling the position of the probe by a position control signal based on the detection signal. , Having a control circuit that corrects the displacement sensitivity characteristic depending on the drive voltage value of the actuator that controls the position of the probe and outputs a distance control signal so that the distance between the probe and the sample becomes constant. It is a feature. In the present invention, the control circuit includes at least a signal detection circuit that detects a signal from the probe, a correction circuit that corrects the detection signal from the probe corresponding to the position control signal of the probe, and an output signal of the correction circuit. It can be configured by a probe position control signal generation circuit for controlling the position between the probe and the medium based on the above. In addition, the correction circuit,
Based on the output of the correction data memory that stores the correction data, the detection signal from the probe is corrected,
The correction data memory is configured to store the displacement sensitivity characteristic resulting from the nonlinearity of the actuator that controls the position of the probe as the correction data, and the correction data of the actuator that controls the position of the probe. The nonlinearity may be approximated to a polygonal line and stored in the correction data memory. Further, the present invention is an information processing device for detecting a signal generated from a physical phenomenon between a plurality of probes and a medium facing the probe through a signal detection circuit, and performing position control of the probe by a position control signal based on the detection signal. In the probe control circuit, the displacement sensitivity characteristic depending on the drive voltage value of the actuator for controlling the position of each probe is selected based on the output of the correction data memory by sequentially selecting one probe signal of a plurality of probes. The multi-probe control circuit is configured to have a control circuit that corrects the above and outputs a distance control signal so that the distance between each probe and the sample becomes constant. The control circuit of the multi-probe corresponds to at least a signal detection circuit that detects a signal from the probe, a selection circuit that sequentially selects one probe signal of a plurality of probes, a probe number and a probe position control signal. Of a probe position control signal that controls the position between the probe and the medium based on the output signal of the correction circuit, and a correction circuit that corrects the detection signal from the probe. It can be configured by a switching circuit that applies the output signal to the corresponding probe. The correction circuit has a configuration for correcting the detection signal from the probe based on the output of the correction data memory that stores the displacement sensitivity characteristic of the actuator, and the correction data is an actuator that controls the position of the probe. It is possible to adopt a configuration in which the displacement sensitivity characteristic of 1 is approximated to a broken line and stored in the correction data memory. Further, in the present invention, these control circuits can constitute a Z control circuit for controlling the distance between the probe and the sample facing each other, and the control circuit can control the probe and the sample according to the actuator drive signal amount. It may be configured to include a circuit that corrects the gain of the control loop that controls the distance therebetween.

[0007]

According to the present invention, the control circuit having the above configuration corrects the displacement sensitivity characteristic depending on the drive voltage value of the actuator for controlling the position of the probe, and stabilizes the position control for keeping the distance between the probe and the sample constant. In addition, the multi-probe head is configured by this, and a compact and highly accurate multi-probe is realized.

[0008]

Embodiments of the present invention will be described below. [Embodiment 1] FIG. 1 is a block diagram of an STM having a probe according to Embodiment 1 of the present invention. STM shown in this embodiment
Is to detect a tunnel current flowing when a bias voltage is applied between the observation sample and the probe facing the observation sample. Reference numeral 1 is an observation sample.
Are facing each other. The probe 2 is attached to a Z fine movement mechanism such as a laminated piezoelectric element (not shown). The probe 2 is a cantilever type actuator that can be driven in the Z direction by electrostatic force, and is displaced in the Z direction when a voltage is applied. Also, a sharp conductive Tip is attached to one end of the cantilever.
3 is formed, and the tunnel current flowing between the observation samples facing each other is detected. The configuration of the probe used at this time will be described. The probe 2 is an electrostatic force drive type cantilever. The cantilever type probe has an insulating layer 10 on a support 9.
It is made through. The probe 2 is the support 9
Also, by applying an actuator drive signal between the drive electrodes 11 configured on the probe 2 side, the actuator is displaced in the Z direction. When observing the surface, the Z fine movement mechanism is moved while the re-bias voltage is applied between the probe 2 and the sample 1 by the bias circuit 4, and the probe is brought close to the sample to the extent that the tunnel current flows so that the distance between them is constant. Control the probe 2 and apply the servo. In this state, the XY fine movement drive mechanism 6 is two-dimensionally scanned through the XY fine movement drive circuit 5 to observe the surface. At this time, a tunnel current (Jt) changed due to minute irregularities on the sample surface is detected. This is taken into the control circuit 7 and processed in synchronization with the XY scanning signal to obtain S
Obtain a TM image. The STM image is subjected to image processing such as two-dimensional FFT on the tunnel current image and the topo image (distance control signal image), and then the tunnel current image and the topo image are output to the display 8. Also, when changing the observation location, XY not shown
The sample is moved in the XY directions by the coarse movement mechanism, and the probe 2 is moved to a desired area for observation.

Next, the position control of the probe when observing the sample will be described. As described above, the control circuit applies servo so that the distance between the probe and the sample is constant during sample observation. The tunnel current Jt detected from the probe 2 in FIG. 1 is converted into a voltage by the current-voltage conversion circuit 12. The output (Vt) of the current-voltage conversion circuit 12 is input to the logarithmic conversion circuit 13, and the logarithmic conversion circuit output Log (V
t) enters the Z servo circuit 14. The Z servo circuit 14 corrects the difference in displacement sensitivity due to the nonlinearity of the actuator characteristics from the logarithmic circuit output Log (Vt) based on the output of the correction data memory 15 so that the distance between the probe and the sample becomes constant. The distance control signal 16 is output so that
After the distance output signal 16 is amplified by the amplifier 17, it is applied to the probe drive electrode for driving the probe in the Z direction and driven by electrostatic force, so that the distance between the probe and the sample is kept constant.

Next, the correction memory 1 which is a feature of the present invention
5 and the Z servo circuit 14 will be described with reference to FIG. In FIG. 2, the logarithmic conversion circuit 11 output Log (Vt)
Enters the Z servo circuit 14. When the current flowing between the probe and the medium is a tunnel current, the Log (Vt) output is proportional to the distance signal between the probe medium. The Z servo circuit 14 outputs a distance control signal 16 so as to keep this constant. First, the Log (Vt) output enters the subtractor 201, and subtracts it from the distance set value Z0 to generate an error signal (err). Then, the error signal err is output to the error signal correction circuit 20.
Enter 2. The error signal correction circuit 202 refers to the correction data memory 15, and the error signal err influenced by the actuator displacement sensitivity that changes depending on the driving voltage value.
Is converted into a correction error signal ERR that does not depend on the drive voltage. The contents of this correction memory will be described later. The correction error signal ERR enters the PI control circuit 203 and undergoes proportional-plus-integral control to become the distance control signal 16 (U). The PI control circuit 203 generates the following control signals for the input ERR. U = Kp.ERR + Ki.∫ERR ... (1) However, Kp. Ki is a control parameter. The distance control signal 16 is applied to the drive electrode 11 after being amplified by an amplifier (17 in FIG. 1). Further, the distance control signal 16 is corrected by the correction circuit 204 according to the value of the correction memory 15 to become a corrected distance control signal, which is output to the display 9 as a topo signal indicating the unevenness of the surface.

Further, the correction data memory will be described with reference to FIG. As described above, in this embodiment, the probe is Z
A cantilever type actuator that can be driven in the Z direction by electrostatic force was used as the actuator that drives in the direction. The Z displacement of the cantilever driven by electrostatic force is expressed by the following formula when the size of the cantilever is width W, length L, thickness t, and the gap g between the drive electrodes and the applied voltage V between the drive electrodes are given. . That is, the displacement amount (δ: gap change amount) of the probe tip in the Z direction is δ = 3/4 × ε / E × L ⁴ × V ² / t ³ / g ² (2) (FIG. 3 ( See A))). (However, E is Young's modulus.
(ε is the dielectric constant of vacuum, and when δ << g) In this embodiment, the cantilever has L = 200 μm, t = 1 μm, and g = 2 μm.
Composed of. Therefore, δ = 2.7 × 10 ⁻⁸ × V ² (m) (3) The displacement sensitivity at this time is dδ / dV = 5.4 × 10 ⁻⁸ × V (m / V): FIG. 3 (B) It is represented by (4). As is clear from this equation, this actuator displacement sensitivity changes greatly depending on the DC level of the applied voltage. Therefore, if it is attempted to control the actuator as it is, the re-servo performance is greatly affected by the change in displacement sensitivity. Therefore, in this embodiment, the applied voltage characteristic of the displacement sensitivity is approximated to a broken line with respect to the applied voltage as shown in FIG. In FIG. 3C, the displacement sensitivity characteristic shows that the applied voltage value is 0.
From Al (μm / V) at V, A2 (μm / V) → A3
(Μm / V) → A4 (μm / V), which is a polygonal line approximation that changes in four steps. Actually, when the drive voltage is applied from 0V to 5V according to the equation (4), the maximum displacement amount is 675n.
The displacement sensitivity is 0 to 270 nm / V.
Has changed. At this time, when the drive voltage value is 0 ≦ V <2, the displacement sensitivity is 54 nm / V → Al When the drive voltage value is 2 ≦ V <3, the displacement sensitivity is 135 nm / V → A2 When the drive voltage value is 3 ≦ V <4, the displacement is Sensitivity 189 nm / V → A3 When the drive voltage value is 4 ≦ V <5, displacement sensitivity is 243 nm / V → A4 and the displacement sensitivity is approximated by a broken line, and the displacement sensitivity of the actuator is constant with respect to the error signal at the input / output of the Z servo circuit. The input value of the Z servo signal: the error signal was corrected so that As a correction coefficient, 1 / Al for the drive voltage value,
A correction coefficient proportional to 1 / A2, 1 / A3, and 1 / A4 was set. Further, this correction coefficient is used as a memory 1 with a distance control signal corresponding to the drive voltage of the actuator as an address line.
Stored in 5. By controlling the actuator while referring to this memory, stable Z-servo control that compensates the nonlinearity of the actuator is realized regardless of the drive voltage level of the actuator, and a stable STM image is obtained.
In this embodiment, the displacement characteristic of the actuator is approximated by four broken lines to compensate the displacement sensitivity variation in four steps. However, if the memory capacity has a margin, it may be compensated more finely. Further, instead of correcting the detection signal from the probe as in this embodiment, the control parameters (Kp, Ki) of the Z servo circuit are set to the actuator D.
You may make it correct | amend with the drive voltage value of C.

[Embodiment 2] FIG. 4 is a block diagram of a recording / reproducing apparatus having a multi-probe according to a second embodiment of the present invention. The recording / reproducing apparatus according to the present embodiment includes a recording medium,
Information is exchanged using a plurality of probes that detect a tunnel current flowing when a bias voltage is applied between the probes facing each other. According to FIG.
The configuration of the recording / reproducing apparatus will be described. Reference numeral 402 is a recording medium.
Are facing each other. 16 for multi-probe head 401
A book probe 400 is formed. The multi-probe head 401 is attached to an XY actuator 403, which is a driving mechanism in the XY directions, and a structure 404. On the other hand, on the recording medium 402, a tracking pattern 405 (a concave groove or a pattern having a different surface electronic state) is engraved and placed on the base 406. Base 406
Is attached to the structure 404 via a Z actuator 407 that moves it in the vertical direction and in the α and β directions. The multi-probe head 401 is a Si multi-probe head in which 16 probes are arranged in a 4 × 4 matrix. Each probe is a torsion type actuator that drives a flat plate portion formed on both cantilever beams by electrostatic force by utilizing the torsional elasticity of both cantilever beams. Unlike the cantilever type of the first embodiment, this actuator can set the flexural elasticity of the lever and the torsional elasticity of the beam independently,
It is possible to design an actuator with flexibility in rigidity and resonance frequency. Further, when a voltage is applied between the drive electrodes 420, it is displaced in the Z direction. (Details of the torsion type actuator and a method of making the same will be described later.) A sharp conductive tip is formed at one end of the lever to detect a tunnel current between opposing recording media.

Next, an outline of recording / reproducing will be described. When recording / reproducing, each probe 4 of the multi-probe head 401
00 is close to the recording medium 402 facing it to the extent that a tunnel current flows. At this time, the tunnel current signal from each probe is transmitted to Z through the probe head control circuit 411.
Entering the servo circuit 408, the Z servo circuit 408 outputs a distance control signal 409 for keeping the distance between the recording medium facing each probe constant. The distance control signal 409 for independently driving each probe in the Z direction is applied to the electrode of each actuator via the actuator drive circuit 410. Further, based on this distance control signal 409, the tilt correction circuit 412 causes the multi-probe head 401 and the recording medium 40
Correct the inclination between the two. Further, at the time of recording / reproducing, the scanning circuit 4
15 is a reprobe head 401 according to an XY scanning signal 416.
Is scanned in the XY directions with respect to the recording medium 402. At this time, the tracking control circuit 417 detects the edge position of the tracking pattern 405 from the change in the tunnel current of each probe 400, and detects the positional deviation between the tracking pattern 405 and the multi-probe head 401 from the XY actuator 40.
Correct with 3. In this state, the voltage application circuit 414 modulates the tunnel current between each probe and the recording medium to form a recording bit on the recording medium. FIG. 5 is a perspective view illustrating the structure of the torsion actuator used in this example. Substrate 5 with fixed electrode 503 formed on insulating layer 502
A movable machine part is formed with a void 504 in 01.
The mechanically movable portion is composed of a beam 509 having both ends and a probe 508 for supporting the rotation, and is supported by a supporting portion 510.
An upper electrode 507 for driving, an information input / output tip 512, and an information input / output wiring 513 are formed on the lever 508. The method of driving the probe according to this embodiment is as follows. By applying a voltage to the fixed electrode 503, the rear end of the lever is pulled to the fixed electrode 503 and the beam 509 is twisted, so that the entire probe 508 is supported by the beam 509.
The tip 512 provided at the tip of the probe 508 approaches the facing recording medium side.

The manufacturing process of the electrostatic actuator according to this embodiment will be described with reference to the manufacturing process chart of FIG. First, Si
Pressure CVD of a silicon nitride film on a substrate 501 made of
An insulating layer 502 was formed by forming a film of 3000 angstrom by (LPCVD). Next, after applying and patterning a resist, Ti of 50 angstrom and Pt of 2000 angstrom were deposited by a sputtering method, and the fixed electrode 503 was formed by removing the resist. Next, zinc oxide is sputtered to 200
After depositing 00 angstrom, a photoresist was applied and patterned, and zinc oxide was etched by a mixed aqueous solution of hydrogen peroxide and ammonia to form a sacrificial layer 505 (FIG. 6A). Next, silicon oxide was deposited to a thickness of 10000 angstrom by the sputtering method. Next, after applying and patterning a resist, Ti is sputtered by 50 angstrom and Au by sputtering.
Is deposited to 2000 angstrom and the resist is removed to form the upper electrode 507 and the tunnel current wiring 513.
Was formed (FIG. 6B). Next, after patterning silicon oxide using a resist, etching was performed using CF4 gas by a reactive ion etching method to obtain a probe 508 having a mechanically movable portion shape (FIG. 6C).

Information input / output tips 5 which are carried out in parallel
The manufacturing process of 12 will be described. First, a Si second substrate 601 having an azimuth plane (100) is prepared. Next, the second substrate 601
A silicon nitride film 602 is formed on the surface by low pressure CVD (LPCV
D) deposits 1000 angstroms (FIG. 6).
(D)). Next, the silicon nitride film is removed by photoetching in the pattern shape shown in FIG. 6 to expose the surface of the second substrate. Next, the second substrate 601 is processed by crystal anisotropic etching using an aqueous solution of potassium hydroxide heated to 100 ° C. to form an inverted pyramid-shaped concave portion 603 which serves as a mold for the probe portion (FIG. 6E). ). Next, the remaining silicon nitride is removed by the reactive ion etching method. Next, the resist was patterned, Au was formed into a film having a thickness of 10000 angstrom by a vacuum evaporation method, and then the resist was dissolved in acetone to form a pattern of Au serving as the probe 512 (FIG. 6E). In the next step, the probe 512 was pressed on the substrate 501 and peeled off from the interface of the second substrate 601, thereby producing the information input / output tip 512. (FIG. 6 (g)) As a method of etching the second substrate 601, not only crystal anisotropic etching of single crystal silicon, GaAs semiconductor, etc., but also isotropic etching if it can be etched into a transferable shape. Can also be used. Further, since the protective layer 602 is a protective film when the second substrate 601 is etched, any material that can withstand the etching liquid at this time may be used. In addition, the tip 512 and the second substrate 601
In order to reduce the adhesion of the interface with the second substrate 601,
You may form a peeling layer on it. Further, the method of joining the probe 508 formed on the first substrate 501 and the tip 512 formed on the second substrate 601 is metal-metal joining,
Anodic bonding or the like can be used. Finally, the zinc oxide sacrificial layer 505 was removed by etching with an acetic acid aqueous solution to form a gap 504 between the probe 508 and the fixed electrode 503. The torsion lever type probe shown in FIG. 5 was able to be obtained by the above manufacturing process (FIG. 6 (h)). A total of 16 4 × 4 pieces of this torsion type probe were formed in a matrix shape, and a tunnel current detection anzo was formed by using an IC process in the vicinity of each torsion type probe on the Si wafer to obtain a multi-probe head 401.

Next, the structure of the recording medium 402 facing the multi-probe head 401 will be described. Recording medium 4
02, a strip-shaped tracking pattern is engraved by fine processing such as a semiconductor process. On the substrate electrode of the recording medium 402, concave grooves having a width of 200 nm and a depth of 30 nm are engraved in the X direction with a pitch of 2 μm and a length of 50 μm in the Y direction. As the recording medium 402, a material having a memory effect with respect to voltage-current switching characteristics was used. A gold epitaxial growth surface on a flat substrate such as glass or mica was used as a substrate electrode. A tracking groove is formed on this, and a squalium-
Bis-6-octylazulene (hereinafter abbreviated as SOAZ) was used to form a cumulative film of two monomolecular films on this substrate electrode by the Langmuir-Projet method to form a recording medium 402.
And Reference numerals 413 and 408 are a correction data memory and a Z servo circuit, which are features of the present invention.

From the block diagram of the control block shown in FIG.
The details of probe control will be described. The sequence of the entire probe control system is controlled by the timing from the probe head control circuit 411. The control circuit shown in this embodiment relates to a distance control circuit between a plurality of probes for detecting a tunnel current and a medium facing each other. In this embodiment, the tunnel current signal from each probe is converted into a digital signal, and the probe head control circuit 41 is converted from this signal.
A digital servo system for generating a control signal for sequentially performing Z control on each probe at the timing of 1 was constructed. Details of Z control of the multi-probe will be described with reference to FIG. 7. Multi-probe 70 indicated by probe numbers 1 to n
The tunnel current signal from 1 is connected to the selection circuit 702. The selection circuit 702 selects one, for example, the nth probe from the multi-probes 701 according to the control timing. (In the figure: ln) After the tunnel current signal detected from the selected n-th probe is voltage converted,
A / D conversion is performed by the A / D converter 703. (Ln
(T, t are certain sampling times) Further, the digitized tunnel current signal is linearized by the logarithmic conversion circuit 704 with respect to the distance between the probe and the medium.
(In the figure: Log1n (t)) and the logarithmic conversion circuit 704.
Of the servo circuit is compared with the set value Z0 of the servo circuit 70
5, the error signal (: en (t)) is obtained. This time,
The control circuit 411 sets the number of the selected probe to low.
Address, drive voltage amount U currently driving probe n
The correction data memory 413 is addressed using n as a column address. The memory 413 outputs a correction coefficient 711 (for example, 1 / Aln) according to the probe number and the drive voltage to the error signal correction circuit 706. Therefore, the correction circuit 7
06 multiplies the subtractor 705 output en (t) by the correction coefficient from the memory 413 to obtain a correction error signal (: En (t)). The PI control circuit 707 generates the distance control signal Un (t) so as to make the correction error signal zero. At this time P
The I control circuit 707 stores the distance control signal and the correction error signal data at the sampling time (t−1) stored in the memories 712 and 713, and the sampling time (t).
A new distance control signal 714Un (t) at time (t) is generated from the correction error signal En (t) at. At the same time, the values in the memories 712 and 713 are updated. The distance control signal Un (t) is converted into an analog signal again by the D / A converter 708 and then applied to the drive electrode 710 that drives the number n probe in the Z direction by the switching circuit 709. The control circuit 411 sequentially switches the probes to be selected and Z-controls all the probes. The actuator is in a floating state until a signal is applied to the actuator once and then a signal is applied to the same actuator again. During this time, the control voltage is held by the capacitance between the electrodes of the actuator, and the displacement of the actuator is maintained.

Next, the contents of the data correction memory 413 will be described. As described above, in the data memory 413,
The correction coefficient 711 is output to the error signal correction circuit 706 according to the probe number being accessed and the drive voltage. Similar to the first embodiment, the data memory 413 absorbs the displacement sensitivity change of the actuator depending on the drive voltage value. The size of the probe actually manufactured is L = 100 μm, W in FIG.
= 100 μm, t = 1 μm, a = 10 μm, b = 50 μm
It was m. At this time, the parameters of the torsion type lever were estimated as follows. The characteristics of the twisted portion of both dovetail beams are rotational elastic constants K = 2 · G · t ³ · a · m / b (N · m) (5) where G is Young's modulus and m is a constant tip determined by a and t. The Z-direction elastic constant of the lever in the part is k = K / L ² (N / m) (6) When calculated according to the equation (6), k = 0.87 (N / m)
Becomes On the other hand, the electrostatic force generated by applying a voltage between the fixed electrode 503 and the upper electrode 507 has a small amount of twist and a small amount of displacement in the Z direction at the tip of the tip is F = ε0 · W · L · V ² / (2 · d ² ) (N) ... (7) Therefore, in FIG. 5, the gap d is 10 μm and the applied voltage is 50 μm.
When V is set, the displacement amount (δ: gap change amount) of the probe tip in the Z direction is δ = 1.3 μm from δ = F / k.
The displacement sensitivity at this time is dδ / dV = av · (m / V) as in the first embodiment, where a is a constant ... (8), and the displacement sensitivity greatly changes depending on the DC level of the applied voltage. Re-servo performance is greatly affected by. Therefore, the applied voltage characteristic of the displacement sensitivity is shown in FIG.
As shown in (C), a polygonal line approximation was applied to the applied voltage.
That is, when the driving voltage is applied from 0 V to 50 V, the maximum displacement is 1.3 μm, and the displacement sensitivity at this time is 0 to 52 n.
It changed to m / V. Therefore, the displacement sensitivity when the drive voltage value 0 ≦ V <10 is 5 nm / V → Anl The displacement sensitivity when the drive voltage value 10 ≦ V <20 is 15 nm / V → The displacement when the An2 drive voltage value 20 ≦ V <30 Sensitivity 25 nm / V → An3 Displacement sensitivity when driving voltage value 30 ≦ V <40 35 nm / V → An4 Displacement sensitivity when driving voltage value 40 ≦ V <50 45 nm / V → An5 To absorb the change in sensitivity,
A value proportional to the reciprocal value of each displacement sensitivity was stored in the memory. (For example, 1 / Anl, 1 / An2, 1 / An3,
1 / An4, 1 / An5. n means a compensation amount for the n-th probe. ) In this embodiment, a plurality of probes are driven. When producing a plurality of probes by fine processing such as IC process, it is unavoidable that the variations in the processing process.
This process variation results in, for example, variation in the thickness of the probe and the gap, resulting in variation in displacement sensitivity characteristics of the re-actuator according to the above equation. In the second embodiment, the correction data memory 413 is used so as to absorb the displacement characteristic variation for each probe. For example, if the probe number is n, the drive signal amount for this probe number is 25
Suppose it was V. At this time, for the correction data memory, row address = probe number n, column address =
The address corresponding to the drive signal amount 25V is accessed, and the correction data memory 413 outputs 1 / An3 as the correction coefficient 711. The error signal is corrected according to this correction coefficient to generate a new distance control signal. For the measurement of the correction coefficient, the displacement characteristic of each probe is measured in advance by an optical method. Or, the probe head control circuit 4 can detect the tunnel current from all the probes.
Reference numeral 11 generates a Z modulation signal having a frequency equal to or lower than the response frequency of the torsion lever, and modulates all the probes in the Z direction (Δ
Un). At this time, the output of the logarithmic conversion circuit from each probe (△
Vn) is monitored and PI control output U for each probe
Transfer characteristic from n to logarithmic conversion circuit output Gmulti = ΔVn / Δ
Measure Un. The coefficient of the correction memory is determined so that this is constant for all probes. By performing this measurement while moving the probe head little by little in the Z direction, the drive signal dependence of the correction coefficient was measured.

Recording and reproduction were performed as follows. Between the probes 400 and the recording medium 402, a bias voltage of 0. LV was applied, and the voltage was brought close to the extent that a constant tunnel current (lnA) flowed. Z for each probe
Independently driven in the Z direction by the servo circuit 408, ln
Feedback control was performed so that the current A could flow.
Further, based on the distance control signal 409 of each probe, the tilt correction circuit 412 generates an α rotation signal and a β rotation signal for correcting the tilt between the multi-probe head 401 and the recording medium, and applied this to the Z actuator 407. . In this state, the probe is moved to a desired position on the recording medium 402, the bias voltage is modulated, and a pulse voltage of 6 V is applied between the probe 400 and the recording medium 402. A bit having a size of 10 nmφ in which a current of 1 μA flows was formed (recorded), and when scanning was performed after applying a pulse voltage, the state was maintained. (Reproduction) Therefore, the bit in the low resistance state is associated with "1" to distinguish it from "0" in the high resistance state. An encoder 418 is added to the recorded data.
Then, the binary data of "0" and "1" was coded, and the decoder 419 reproduced the information of the binary data to perform the binary recording / reproduction. In the present embodiment, the displacement characteristics of each probe were approximated to a broken line for control. For this reason, even if the number of probes increased, it was possible to control without using a huge memory and without variation of any probe. Even if the number of probes increases, the control system does not become large,
A compact recording / reproducing device has been realized. In this example, the displacement characteristic of the probe was proportional to the square of the applied voltage, and this was approximated by a broken line. However, the displacement characteristic of the probe of this embodiment may deviate from the square characteristic when the applied voltage increases. At this time as well, the characteristics could be approximated by the polygonal line approximation, and the control could be successfully performed.

[0020]

According to the present invention, with the above-mentioned simple circuit configuration, the displacement sensitivity characteristic depending on the driving voltage value of the actuator for controlling the position of the probe is corrected, and the information for stable position control of the probe is obtained. A control circuit for the probe in the processing device can be realized. Further, according to the present invention, even when a multi-probe head including a plurality of probes having a non-linear displacement sensitivity is configured, stable control without variations among the probes is possible, and an information processing device that can be easily miniaturized. It is possible to realize a multi-probe control circuit in.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a scanning tunneling microscope according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a Z control circuit used in FIG.

FIG. 3 is a graph showing displacement characteristics of the actuator used in FIG.

FIG. 4 is a configuration diagram of a recording / reproducing apparatus using a multi-probe head according to a second embodiment of the present invention.

FIG. 5 is a perspective view of one probe used in FIG.

FIG. 6 is a process drawing of the probe used in FIG.

7 is a configuration diagram of a Z control system used in FIG.

[Explanation of symbols]

 1 Observation Sample 2 Probe 3 Conductive Tip 4 Bias Circuit 7 Control Circuit 11 Drive Electrode 14 Z Servo Circuit 15 Correction Data Memory 401 Multi-Probe Head 402 Recording Medium 408 Z Servo Circuit 408 Display 411 Probe Head Control Circuit 413 Correction Data Memory 414 Voltage application circuit 415 Scanning circuit 418 Encoder 419 Decoder 702 Selection circuit 705 Subtractor 706 Error signal correction circuit 707 PI control circuit 709 Switching circuit

Claims (11)

[Claims] 1. A probe control circuit of an information processing apparatus for detecting a signal generated from a physical phenomenon between a probe and a medium facing the probe, and controlling the position of the probe by a position control signal based on the detection signal. A probe having a control circuit that corrects displacement sensitivity characteristics depending on the drive voltage value of an actuator that performs position control and outputs a position control signal so that the distance between the probe and the sample becomes constant. Control circuit. 2. The control circuit includes a signal detection circuit that detects a signal from the probe, and a correction circuit that corrects the detection signal from the probe in response to the position control signal of the probe.
The probe control circuit according to claim 1, further comprising a probe position control signal generation circuit that controls the position between the probe and the medium based on the output signal of the correction circuit. 3. The correction circuit according to claim 2, wherein the correction circuit has a configuration for correcting the detection signal from the probe based on the output of the correction data memory storing the correction data. Probe control circuit. 4. The probe according to claim 3, wherein the correction data memory stores displacement sensitivity characteristics resulting from non-linearity of an actuator that controls the position of the probe as the correction data. Control circuit. 5. The probe control circuit according to claim 4, wherein the correction data is stored in the correction data memory by performing a polygonal line approximation on the nonlinearity of an actuator that controls the position of the probe. 6. An information processing apparatus for detecting a signal generated from a physical phenomenon between a plurality of probes and a medium facing the probe through a signal detection circuit, and controlling the position of the probe by a position control signal based on the detection signal. In the probe control circuit, the displacement sensitivity characteristic depending on the drive voltage value of the actuator that controls the position of each probe is selected based on the output of the correction data memory by sequentially selecting one probe signal of the plurality of probes. And a control circuit for outputting a position control signal so that the distance between each probe and the sample becomes constant. 7. The probe control circuit corresponds to a signal detection circuit that detects a signal from a probe, a selection circuit that sequentially selects one probe signal from a plurality of probes, and a probe number and a probe position control signal. And a correction circuit for correcting the detection signal from the probe, a probe position control signal generation circuit for controlling the position between the probe and the medium based on the output signal of the correction circuit, and a probe position control signal generation circuit 7. A switching circuit for applying the output signal of the above to the corresponding probe.
The probe control circuit according to. 8. The correction circuit has a configuration for correcting a detection signal from a probe based on an output of a correction data memory storing displacement sensitivity characteristics of an actuator. The probe control circuit according to. 9. The probe control circuit according to claim 8, wherein the correction data is stored in a correction data memory by performing a polygonal line approximation of a displacement sensitivity characteristic of an actuator that controls the position of the probe. 10. The probe control circuit according to claim 1, wherein the control circuit is a Z control circuit that controls a distance between the sample facing the probe and the sample. . 11. The control circuit has a circuit for correcting the gain of a control loop for controlling the distance between the probe and the sample according to the actuator drive signal amount. 10. The control circuit for the probe according to any one of 10.