JPH06313847A - Cantilever type actuator, cantilever type probe, and scanning tunneling microscope and information processor using these actuator and probe - Google Patents

Abstract

PURPOSE:To provide a cantilever type actuator with a stable characteristic as well as with desirable controllability to obtain large displacement quantity so as to be used for a scanning tunneling microscope, an information processor or the like with this scanning tunneling microscope applied thereto. CONSTITUTION:In a cantilever type actuator, a cantilever 2 having a pair of coil like electrode layers 4, 6 at the upper and lower parts of an insulating layer 5 is formed on a base 1, and the electrode layers 4, 7 are electrically connected to each other through a through hole 6 to form one coil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever type actuator and a cantilever type probe used in a tunnel current detecting device, a scanning tunneling microscope, etc., and a scanning tunneling microscope using them and a scanning tunneling microscope. The present invention relates to an information processing apparatus that records, reproduces, erases, etc. information by a method.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter referred to as ST
(Abbreviated as M) was developed [G. Binning et
al. , Helvetica Physica Ac
Ta, 55, 726 (1982)], it has become possible to measure a real space image with extremely high resolution (nanometer or less) regardless of whether it is a single crystal or a non-crystal.

The STM is a conductive probe (probe).
A voltage is applied between the conductive material and the conductive material to bring them closer to a distance of about 1 nm, and a tunnel current flows during that time. This current is very sensitive to changes in the distance between the two and changes exponentially, so by observing the surface structure in real space with atomic resolution by scanning the probe so as to keep the tunnel current constant. You can

Although the analysis using this STM is limited to the conductive material, it has begun to be applied to the structural analysis of the insulating film thinly formed on the surface of the conductive material. Furthermore, the above-mentioned device,
Since the means uses a method of detecting a minute electric current, it has an advantage that it can be observed with low power without damaging the medium. Further, since it can be operated in the atmosphere, it is expected to have a wide range of applications of STM.

In particular, as proposed in Japanese Patent Laid-Open No. 63-161553, etc., the practical application as a high-density recording / reproducing apparatus is being actively promoted. In this, recording is performed by using a probe similar to the STM and changing the voltage applied between the probe and the recording medium.

Conventionally, as a method of forming a probe used in these recording / reproducing apparatuses, a semiconductor manufacturing process technology is used, and a processing technology for forming a fine structure on one substrate [K. E. Peterson, “Silicon
as a Mechanical Material
l ”, Proceedings of the IE
EE, 70 (5), 420-457 (1982)].
Was known. STM constructed by such a method
Is proposed in Japanese Patent Laid-Open No. 61-206148. This uses a single crystal silicon as a substrate, forms a parallel spring that can be finely moved in a direction parallel to the substrate surface (XY direction) by microfabrication, and further provides a cantilever (cantilever) part having a probe formed on its movable part. An electric field is applied between the cantilever portion and the bottom surface portion to displace in a direction (Z direction) perpendicular to the surface of the substrate by electrostatic force. In addition, a thin film having piezoelectricity is used for the cantilever portion,
It has also been proposed to apply a voltage with parallel plate electrodes and utilize the displacement due to the inverse piezoelectric effect.

[0007]

However, in the above-described conventional cantilever type actuator in which the bending displacement is generated by using the piezoelectric thin film, the piezoelectric thin film such as the zinc oxide film is displaced by the inverse piezoelectric effect. Therefore, it is necessary to control the piezoelectricity of the zinc oxide film.
Also, in order to obtain a highly accurate displacement, it is necessary to give the cantilever a certain degree of rigidity, but the amount of displacement of the cantilever and the rigidity are contradictory, and a large displacement is obtained in addition to a certain degree of rigidity. For this, a large voltage must be applied to the piezoelectric thin film. Furthermore, if the zinc oxide film is left in the atmosphere, the piezoelectricity is lowered due to the adsorption of water, and it becomes impossible to obtain a precise displacement.

Further, when a large number of actuators are integrated, the operating characteristics of each actuator may vary due to the above-described fluctuations in the characteristics of the piezoelectric thin film and defects during thin film formation.

Therefore, an object of the present invention is to provide a cantilever type actuator which can easily obtain a large displacement amount and has stable characteristics, and further an integrated cantilever type actuator in which the characteristics of each cantilever type actuator are uniform. To do.

Another object of the present invention is to provide a cantilever type probe using the above cantilever type actuator, and further, an S type excellent in reliability and stability using the cantilever type probe.
To provide a TM and an information processing device.

[0011]

SUMMARY OF THE INVENTION The present invention, which has been made to achieve the above object, is, firstly, a cantilever type actuator displaceable by an external magnetic field, wherein the cantilever is a thin film insulator and a thin film electrode. It is configured by stacking
At least one upper and lower layers of the thin film insulator has a pair of thin film electrodes forming a coil in a flat plate shape, and the pair of thin film electrodes are connected to each other at the innermost portion of the flat plate coil. It is a cantilever type actuator characterized by forming two coils.

Secondly, there is provided an integrated cantilever type actuator characterized in that a plurality of the first cantilever type actuators are arranged on the same silicon single crystal substrate.

Thirdly, a conductive probe is provided at the free end of the cantilever of the first or second cantilever type actuator, and the probe has a pair of drawers wired around the periphery of the cantilever. An electrode is connected, and the pair of extraction electrodes are connected to each other on a substrate supporting the cantilever, which is a cantilever type probe.

Fourthly, there is provided a scanning tunneling microscope including the third cantilever type probe.

Fifth, in an information processing apparatus for recording / reproducing information on / from a recording medium using a tunnel current,
It is an information processing apparatus comprising the third cantilever type probe.

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

FIG. 1 is a configuration diagram of a cantilever type actuator that best represents the features of the present invention. FIG. 1A shows a lower layer thin film electrode pattern, and FIG. 1B shows an upper layer thin film electrode pattern. 1C is a cross-sectional view at the position of the broken line AA ′ in FIG.

In FIG. 1, 1 is a substrate, 2 is a cantilever portion, 3 is a lower insulating film, 4 is a lower layer electrode, 5 is an upper insulating film, 6 is a through hole, and 7 is an upper layer electrode.

In this embodiment, the lower electrode 4 is formed in a coil shape on the lower insulating film 3 of the cantilever portion 2 supported by the substrate 1 (see FIG. 1 (a)).

The upper insulating film 5 is formed on this structure, and the through hole 6 is formed in the upper insulating film 5 on the innermost part of the coil-shaped lower layer electrode 4. Also,
A coil-shaped upper layer electrode 7 is formed on the upper insulating film 5 in a pattern symmetrical to the pattern of the lower layer electrode 4 (see FIG. 1).
(See (b)).

Both the coil-shaped lower layer electrode 4 and the upper layer electrode 7 are electrically connected to each other through the through hole 6 at the innermost portion thereof (see FIG. 1 (c)).

With the above structure, a magnetic field is generated by applying a drive current to the lower electrode 4 and the upper electrode 7 from the outside. FIG. 2 schematically shows the state of the magnetic field generated by this drive current. In FIG. 2, reference numerals 21 and 22 indicate the directions of the drive current flowing in the thin film electrode.
Indicates the magnetic field formed by the drive current.
The strength and direction of this magnetic field 23 depend on the magnitude and direction of the drive current and can be adjusted.

In the cantilever type actuator of the present invention, when an external magnetic field is formed around the cantilever in the direction perpendicular to the cantilever surface, the cantilever portion is generated by the interaction with the magnetic field generated by the driving current as shown in FIG. 2 can be displaced upwards or downwards.
The displacement amount and displacement direction at that time can be controlled by the magnitude and direction of the drive current.

The material of the thin film electrode according to the present invention is, for example, A
Metals such as 1, Au, Pt, and Cr, and other conductive substances can be used, and are not particularly limited.

The material of the thin film insulator is not particularly limited, but a thermally and chemically stable material is preferable, for example, SiO ₂ , Si ₃ N ₄ , SiON, PSG, B.
PSG or the like can be used.

The cantilever type actuator of the present invention having the above-mentioned structure does not use a piezoelectric material such as zinc oxide, which is conventionally thermally and chemically unstable and whose orientation must be controlled. Therefore, an actuator with stable characteristics can be provided.
Since the thin film electrodes of more than one layer can be laminated in the same direction of the magnetic field generated by the drive current, a large displacement amount can be obtained with a smaller drive current.

Next, the cantilever type probe of the present invention will be described. 3A and 3B are configuration diagrams of a cantilever type probe of the present invention configured by using the cantilever type actuator of the present invention shown in FIG. 1. FIG. 3A is a plan view and FIG. 3B is FIG. It is sectional drawing in the position of the broken line AA 'in a).

In FIG. 3, components designated by the same reference numerals as those in FIG. 1 are the same members, and 31L and 31R are extraction electrodes and 3
Reference numeral 2 is a probe, and 33 is a signal extracting electrode.

In this embodiment, a pair of extraction electrodes 31L and 31R are formed on the outermost peripheral portion of the cantilever portion 2, and the extraction electrodes 31L and 31R are electrically connected to the free end portion of the cantilever on the substrate 1. To form a closed circuit. Further, a conductive probe 32 electrically connected to the extraction electrodes 31L and 31R is formed at the free end of the cantilever.

The cantilever type probe of the present invention having such a structure can be used as a probe of a scanning tunneling microscope. That is, the cantilever portion 2 is displaced by applying a drive current to the thin film electrodes 4 and 7 in the presence of an external magnetic field, and the probe 32 is moved to a conductive medium to be observed up to a distance where a tunnel current flows between them. Bring them closer. This tunnel current is guided to the outside through the extraction electrode, amplified, fed back to the drive current, and the change thereof is monitored, so that it is possible to observe an extremely fine uneven shape on the medium surface.

At this time, an induced current may be generated in the extraction electrode due to the change in the magnetic field due to the drive current, and may be mixed in the tunnel current as noise.

Therefore, in the present invention, as shown in FIG. 3 (b), the extraction electrode is divided and is wired on the outermost side of the cantilever portion 2, and the extraction electrodes 31L and 31 are also divided.
R is connected on the substrate 1 to form a closed circuit, and a signal extraction electrode 33 is provided on a part of the closed circuit electrode to guide a tunnel current to the outside. With such a configuration, the induced current induced by the change in the magnetic field generated by the drive current flows only in the closed circuit including the extraction electrodes 31L and 31R, and is not mixed in the signal extraction electrode 33. . Therefore, the cantilever probe of the present invention can obtain a tunnel current image with a high S / N ratio.

In the present invention, as the method of forming the probe, metal pieces such as Pt, Rh, and W are adhered, or the semiconductor manufacturing process technique is used to apply the oblique deposition and the lift-off method. It is not particularly limited.

[0034]

EXAMPLES Examples of the present invention will be described below.

Example 1 In this example, a cantilever type probe of the present invention as shown in FIG. 3 was produced. Hereinafter, a method for manufacturing the cantilever type probe of this embodiment will be described with reference to FIG. First, 1500 Å of Si ₃ N ₄ film was formed on the single crystal silicon substrate 1 having the plane orientation (100) by the low pressure CVD method to form the lower insulating film 3 (see FIG. 4A).

Next, in order to secure adhesion, Cr was vacuum-deposited in a volume of 5Å and Au was vapor-deposited in a volume of 1000Å to form a metal thin film. Then, a photosensitive resist was applied and unnecessary portions of Au / Cr were removed by etching by general photolithography to form a coil-shaped lower layer electrode 4 (see FIG. 4B).

Further, a Si ₃ N ₄ film was formed thereon with a thickness of 3000 Å to form an upper insulating film 5. After that, the upper insulating film 5 on the innermost portion of the coil-shaped lower layer electrode 4 was removed by photolithography to form a through hole 6 to expose the innermost portion of the lower layer electrode 4 (FIG. 4C). reference).

Next, Cr is vacuum-deposited again to a thickness of 5Å, Au is deposited thereon to a thickness of 1000Å, and a metal thin film is formed. Then, photolithography is performed to remove unnecessary portions to remove the upper layer electrode 7 and the extraction electrode 31L. , 31R was formed.
At this time, the upper layer electrode 7 and the lower layer electrode 4 are connected at the position of the through hole 6 previously formed in the upper insulating film 5 (FIG. 4).
(See (d)).

Further, a thick photoresist was applied, and only the resist at the position where the probe 32 was formed was removed. After that, while rotating the substrate 1 in the in-plane direction, the metal material is vacuum-deposited in an oblique direction, and then the metal film deposited on the resist is removed together with the resist to remove the resist first. The probe 32 was formed on the open portion (see FIG. 4E).

Next, after covering the entire surface with a protective resist, anisotropic etching is performed from the back surface of the silicon single crystal substrate 1 to remove silicon up to the position of the lower insulating film 3, and then photolithography is performed. The unnecessary portion of the Si ₃ N ₄ film was removed to form the cantilever portion 2 (see FIG. 4 (f)).

In the above manufacturing process, the etching solution used for photolithography is KI: I for Au.
₂ aqueous solution, (NH ₄ ) ₂ Ce (NO ₃ ) ₆ for Cr;
HClO ₄ aqueous solution, K for anisotropic etching of silicon
An aqueous OH solution was used, and CF ₄ gas was used to remove Si ₃ N ₄ .

The cantilever manufactured in this example has a width of 10
The spring constant is 0.1 μm and the length is 350 μm.
N / m.

Next, as a result of conducting a drive experiment of the cantilever type probe of this embodiment, a tip displacement of 0.5 μm could be obtained with a current of 1 μA.

As a result of the above, the cantilever type probe of the present embodiment was able to obtain a relatively large displacement with a small driving current, and furthermore, the displacement amount and the displacement direction could be controlled with good controllability.

Example 2 In this example, a plurality of cantilever type probes of the present invention as shown in FIG. 3 were prepared on the same silicon substrate,
It is an integrated probe.

FIG. 5 shows a schematic plan view of the integrated probe of this embodiment.

In FIG. 5, 1 is a silicon substrate, 2 is a cantilever portion, 51 is an etching groove, and 52 is a semiconductor integrated circuit such as an amplifier and a shift register. Also,
Reference numeral 53 is an internal wiring, and 54 is an external extraction electrode.
The integrated probe 55 of the present embodiment can be manufactured by expanding the pattern of the photomask during photolithography in the manufacturing process shown in the first embodiment.

Even when a large number of cantilevers are integrated in this manner, a large number of minute structures are collectively formed on the same substrate by using a photolithography, so that the dimensional accuracy is extremely high and The variation in the characteristics of the cantilever can be suppressed to be extremely small.

FIG. 6 uses the integrated probe of this embodiment,
6 is a partial cross-sectional view showing a schematic configuration of a multi-head type STM device capable of simultaneously observing a plurality of ranges on the surface of an observation medium 61. FIG. In the figure, reference numerals 62 and 63 denote movable stages having fine and coarse movement mechanisms in the X, Y, and Z directions. An observation medium 61 is fixed to the movable stage 62, and the movable stage 63 is an integrated device manufactured in this embodiment. The probe 55 is fixed. Further, as a means for generating an external magnetic field, a permanent magnet 64,
65 are arranged. This may be an electromagnet or the like.

With such a structure, a predetermined drive current can be applied to each cantilever and the cantilevers can be individually displaced in the direction perpendicular to the substrate surface (Z direction). Further, the displacement in the direction parallel to the substrate surface (XY direction) is performed by minutely displacing the movable stages 62 and 63, and all the cantilevers can be collectively moved. Thereby, a plurality of observation regions can be simultaneously scanned by the probe provided on each cantilever, and STM images can be simultaneously obtained from the plurality of regions.

In the integrated probe of this embodiment, since the fluctuations in the operating characteristics of the actuator due to the fluctuations in the characteristics of the thin film insulating material forming the cantilever are small, the fluctuations in the characteristics of the actuators are small, and the extraction electrode is small. Since it is a closed circuit, the mixing of noise can be prevented, and the scanning tunneling microscope of the present embodiment constructed by using this can obtain a stable STM image with higher resolution.

Example 3 In this example, an information processing apparatus was manufactured using the integrated probe of the present invention as shown in FIG.

FIG. 7 shows a block diagram of the information processing apparatus of this embodiment.

In the figure, 101 is a substrate of a recording medium,
102 is a metal thin film electrode layer, and 103 is a recording layer. 20
1 is an XY stage, 202 is the integrated probe of the present invention,
Reference numeral 203 is a support for the integrated probe 202, 204 is a linear actuator for coarsely moving the integrated probe 202 in the Z-axis direction, 205 and 206 are linear actuators for driving the XY stage 201 in the X- and Y-axis directions, respectively, and 207. Is a bias circuit for recording and reproducing. 301
Is a recording / reproducing tunnel current detector for detecting a current flowing from the probe to the electrode layer 102 via the recording layer 103. 302 is a servo circuit for moving the cantilever in the Z-axis direction, and 303 is the linear actuator 2
This is a servo circuit for driving 04. 304 is a drive circuit for moving a plurality of cantilevers in the Z-axis direction, and 305 is a drive circuit for performing position control of the integrated probe 202, the support 203, and the linear actuator 204 as a whole in the Z-axis direction. A computer 306 controls these operations.

In this embodiment, a glass substrate is used as the substrate 101 of the recording medium, and Cr is used as the electrode layer 102 on the glass substrate.
/ Au was vapor-deposited, and four layers (about 15 Å) of a polyimide LB film were formed on the recording layer 103 as the recording layer 103.
The recording medium is characterized in that the resistivity changes by about two digits when a pulse voltage is applied. A voltage of 1 V is applied to the electrode 102 of the recording medium and the probe 202, and a current is caused to flow through the drive electrodes constituting each cantilever so that a tunnel current of about 1 nA is obtained. A magnetic field was formed in the axial direction and the position of the probe was moved in the Z-axis direction.

After that, a pulse voltage (5
V, 1 μsec) was added and information was recorded at the desired position.

Next, a voltage of 1 V was applied between the probe 202 and the electrode layer 102 of the recording medium, and the change in tunnel current was observed. As a result, the portion where the resistance value changed in the previously recorded area was detected. As described above, in this example, it was confirmed that the recording information could be written and read.

Further, in the integrated probe according to the present invention used in the above information processing apparatus, the fluctuation of the operating characteristics of each actuator due to the fluctuation of the characteristics of the thin film insulating material forming the cantilever is small, and further, the tunnel current is increased. Since it was possible to prevent the noise from being mixed in, it was possible to further reduce the error occurrence rate during reading and writing.

[0059]

As described above, the present invention has the following effects.

(1) In the cantilever actuator of the present invention, a coil-shaped thin film electrode having two or more layers is laminated in the same direction of the magnetic field generated when a driving current is passed, so that a smaller driving current is obtained. It is possible to obtain a large amount of displacement. In addition, because it does not use a piezoelectric material that is thermally and chemically unstable and whose orientation must be controlled, it has little effect on material physical properties, is highly durable, and has stable characteristics. The resulting product has the same characteristics of each actuator.

(2) In the cantilever type probe of the present invention, the extraction electrode from the probe is divided, and the electrodes are wired around the cantilever and connected on the substrate, so that the induced current generated by the electromagnetic induction is the tunnel current. Can be prevented from being mixed in as noise, and a high S / N ratio can be obtained.

(3) With the scanning tunneling microscope constructed using the cantilever type probe of the present invention, a stable STM image with higher resolution can be obtained.

(4) In the information processing apparatus constructed by using the cantilever type probe of the present invention, the error occurrence rate at the time of recording / reproducing is reduced and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a cantilever type actuator of the present invention.

FIG. 2 is a diagram for explaining a driving principle of the cantilever type actuator of the present invention.

FIG. 3 is a configuration diagram showing an example of a cantilever probe of the present invention.

FIG. 4 is a manufacturing process diagram of the cantilever probe of the present invention shown in Example 1.

5 is a schematic configuration diagram of an integrated cantilever type probe of the present invention shown in Example 2. FIG.

FIG. 6 is a partial cross-sectional view of a scanning tunneling microscope using the integrated probe of the present invention shown in Example 2.

FIG. 7 is a block configuration diagram of an information processing device using the integrated probe of the present invention shown in a third embodiment.

[Explanation of symbols]

 1 substrate 2 cantilever portion 3 lower insulating film 4 lower layer electrode 5 upper insulating film 6 through hole 7 upper layer electrodes 21, 22 current direction 23 magnetic field direction 31L, 31R extraction electrode 32 probe 33 signal extraction electrode 51 etching groove 52 semiconductor integrated Circuit 53 Internal wiring 54 External extraction electrode 55 Integrated actuator 61 Observation medium 62,63 Movable stage 64,65 Permanent magnet 101 Recording medium substrate 102 Metal electrode layer 103 Recording layer 201 XY stage 202 Integrated probe 203 Support 204 Z direction linear Actuator 205 X-direction linear actuator 206 Y-direction linear actuator 207 Recording / reproducing bias circuit 301 Tunnel current detector 302 Servo circuit 303 Servo circuit 304 Cantilever drive circuit 305 Drive circuit 306 Computer

Front page continuation (72) Inventor Haruki Kawata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A cantilever actuator that can be displaced by an external magnetic field, wherein the cantilever is formed by laminating a thin film insulator and a thin film electrode, and at least one layer above and below the thin film insulator has a flat coil shape. A cantilever type actuator having a pair of thin film electrodes forming a coil, the pair of thin film electrodes being connected to each other at an innermost portion of the flat coil to form one coil. 2. An integrated cantilever actuator, wherein a plurality of the cantilever actuators according to claim 1 are arranged on the same silicon single crystal substrate. 3. The cantilever actuator according to claim 1 or 2, wherein the cantilever has a conductive probe at a free end thereof, and the probe has a pair of extraction electrodes wired around the periphery of the cantilever. Is connected, and the pair of extraction electrodes are connected to each other on the substrate supporting the cantilever. 4. A scanning tunneling microscope comprising the cantilever type probe according to claim 3. 5. An information processing apparatus for recording / reproducing information to / from a recording medium using a tunnel current, comprising the cantilever type probe according to claim 3.