JP2000067462A - Probe having minute opening and information processor with the probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a probe to enlarge its signal detective area without lowering the resolution by providing a quadrant pyramid or a structure similar to the quadrant pyramid where a needle of the probe consists of four planes or curved surfaces and providing plural minute openings on the tip part of the needle. SOLUTION: When a needle 402 is irradiated with a laser beam, an evanescent beam occurs in the vicinity of a minute opening part, a light absorbing rate becomes high in a recording dot part and the evanescent beam is weakened. When the needle 402 approaches a distance of nearly 100 nm extent or below of a recording medium 403, the evanescent beam becomes so as to be scattered by the recording medium 403 surface and the scattered beam is detected by a photodetector 409. A photoelectric current signal detected by the photodetector 409 is converted into a voltage signal by an I-V conversion circuit 410, a shift with respect to a recording dot line at the position of the probe is detected from a change in the signal detected by the photodetector 409 in a signal comparison part and the position of the probe is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe having a plurality of minute openings and an information processing apparatus having the probe, and more particularly to a probe having a plurality of minute openings capable of detecting a signal, and a scanning near-field. The present invention relates to a probe used for an information processing device or the like to which a microscope or a near-field tunneling microscope is applied.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter referred to as S) capable of observing the surface of a conductive material with a resolution of less than nanometers.
TM) (US Pat. No. 4,343,99).
No. 3), observations of the atomic arrangement of metal / semiconductor surfaces, orientation of organic molecules, etc. have been made on an atomic / molecular scale.
In addition, by developing STM technology, the surface of green materials, etc.
Atomic force microscope (hereinafter A)
FM) (US Patent No. 4,724,3).
No. 18). As a development of the STM, a scanning near-field light microscope (hereinafter abbreviated as SNOM) for examining the surface state of a sample using evanescent light that exudes from a minute opening at the tip of a sharp probe [Durig et al.
J. Appl. Phys. 59, 3318 (198
6)] has been developed. Further, light is incident from the back surface of the sample through a prism under the condition of total reflection, and evanescent light that seeps onto the sample surface is detected from the sample surface with an optical probe, and a photon ST, which is a kind of SNOM, that examines the sample surface.
M (hereinafter abbreviated as PSTM) [Reddick et al., Phys.
s. Rev .. B39,767 (1989)].

In the above-mentioned SNOM, various methods for manufacturing optical probes have been devised so far because the tip diameter of the optical probe determines the resolution. For example, in the PSTM, a fine opening is not provided at the tip of an optical probe, and the tip is sharpened by optimizing chemical etching conditions of an end face of an optical fiber used as an optical probe, thereby improving resolution. Also, in the early SNOMs, the intersection of the cleavage planes of the transparent crystal was coated with metal, and this was pressed against a hard surface to remove the metal at the intersections, exposing the intersections, thereby producing minute openings (European Patent No. 112402). issue). After that, a method of forming a minute opening by using a lithography technique is also used. Further, a method of fabricating an optical probe by integrally forming a minute aperture and an optical waveguide has been proposed (US Pat. No. 5,354,985).

A recording / reproducing apparatus for recording information in a local area by applying the principle of the SNOM or the PSTM has been proposed [US Pat. No. 4,684,206]. In addition, a probe having a small aperture of several tens of nanometers, which is obtained by processing the tip of an optical fiber, has
Example of recording and reproducing a recording mark of nm on a platinum / cobalt multilayer film [Appl. Phys. Lett, 62,
142 (1992)]. The above SNOM
Alternatively, in a recording / reproducing apparatus to which the PSTM is applied, the recorded information that can be detected by the probe depends on the shape of the minute aperture and the distance from the recording medium, and is not limited to the wavelength of light. Information can be played,
The recording density can be dramatically improved as compared with conventional optical recording.

[0005]

However, the above SNO
As M or PSTM, a probe whose tip has a very small opening diameter of usually 100 nm or less is used. Therefore, in such an information recording / reproducing apparatus to which SNOM or PSTM is applied, reproduction is performed on a fine recording dot having a size of about several tens nm using a probe having a fine opening of about several tens nm. Therefore, there is a problem that the scanning direction of the probe drifts under the influence of external disturbance such as heat or vibration, easily deviates from the direction of the dot row, and the reproduction becomes unstable. On the other hand, if the minute aperture is enlarged, the range in which the probe can detect the signal from the recording dot is widened, but another problem occurs in that the resolution is reduced.

Accordingly, the present invention has been made to solve the above-mentioned problems, and to provide a probe having a small aperture capable of widening a signal detection area without lowering the resolution, and an information processing apparatus having the probe. The purpose is.

[0007]

In order to achieve the above object, the present invention is characterized in that a probe having a minute opening and an information processing apparatus having the probe are configured as follows. is there. That is, the probe having a small aperture according to the present invention has a structure in which the probe tip of the probe has a quadrangular pyramid or a quadrangular pyramid composed of four planes or side surfaces formed of curved surfaces, and has a plurality of tips at the tip of the probe. Characterized in that it has a minute opening. Further, in the probe having a minute opening according to the present invention, the minute opening has a size of 1
It is characterized in that it is not more than 00 nm. Further, in the probe having a small opening according to the present invention, when the plurality of small openings contact a probe tip of the probe with a flat plate arranged opposite to the probe, the plurality of small openings are simultaneously formed. It is characterized by contact with a flat plate. Further, in the probe having a minute opening according to the present invention, when the tip of the plurality of minute openings is brought close to a flat plate arranged to face the probe, the plurality of minute openings may When one of the minute openings comes into contact with the flat plate, the distance between the other minute opening and the flat plate is set to 100 nm or less. Further, in the probe having a minute opening according to the present invention, the plurality of minute openings are directed to a direction in which a direction connecting these minute openings coincides with a scanning direction or a direction perpendicular to the scanning direction. And Further, in the probe having a small aperture according to the present invention, the probe has an optically transparent structure, and a conductive coating on the surface of the structure, and the tip of the probe covered with the conductive coating. It is characterized by having a minute opening in the portion. In the probe having a minute aperture according to the present invention, the probe is arranged on a cantilever. Also,
The probe having a small aperture according to the present invention is a probe arranged opposite to a recording medium, scanned in proximity to the surface of the recording medium, and detects near-field light near the surface of the recording medium to record and reproduce information. A processing apparatus is characterized by having any one of the probes of the present invention described above.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, optical signals from different locations on the surface of a sample can be detected simultaneously by using the above-described configuration having a plurality of minute openings at the tip of the probe.
In addition, for signals from the same location on the sample surface, signals for different distances can be detected simultaneously,
It is possible to widen the signal detection area without lowering the resolution. Further, such a plurality of minute openings can be easily formed by using ordinary semiconductor manufacturing process technology. Further, in the present invention, even with such a plurality of small apertures, it is easy to detect an optical signal with high resolution. That is, the detected optical signal is the sum of the optical signals detected by the plurality of small apertures, but since each small aperture is small, the signal detected by each small aperture has a steep characteristic. For example, the size of each minute opening is 100 n
By setting m or less, it is possible to obtain a resolution of about 100 nm or less.

Further, in the present invention, when the probe is brought close to a sample on a flat plate arranged opposite to the probe, when one of the small openings comes into contact with the sample, the other small opening is simultaneously placed on the sample. By making contact or setting the distance between the other minute apertures and the sample to be 100 nm or less, it becomes possible for all the small apertures to detect evanescent light near the recording medium of about 100 nm or less. In these cases, when a plurality of micro-apertures are made to come into contact with the sample at the same time, when the probe passes through a point where any evanescent light is strong, the distance between the point and each micro-aperture is adjusted. It is possible to observe the superposition signal of the signal of the intensity, and further, it is easy to adopt a configuration in which light from a plurality of minute apertures is detected by the same light detection means. Can be used to obtain the sum of optical signals detected by a plurality of minute apertures. Further, when one micro opening is brought into contact with the sample, and the other micro opening detects the signal in a state where it is slightly separated from the sample surface by about 100 nm or less,
When the probe passes through a point where any evanescent light is strong, it is possible to observe a superposition signal of a strong signal from a small aperture in contact with the sample and a weak signal from a small aperture far from the sample. It becomes possible.

In the present invention, by utilizing such a characteristic due to a difference in arrangement of a plurality of small apertures, individual small openings can be detected when passing through a certain point where a steep optical characteristic changes. The signals from the individual minute apertures can be distinguished by the temporal spread of the optical signal or the slight difference in the detection time. In the present invention, the probe of the probe is formed of an optically transparent structure,
By applying a conductive coating on the surface of the structural portion, by having a configuration having a minute opening at the tip of the probe of the conductive coating,
At the same time as blocking the light with the conductive coating, it is possible to apply a voltage to the sample using the conductive coating. In the present invention, if the above-mentioned probe is constituted by a cantilever and a probe disposed on the cantilever, control similar to that of a normal scanning atomic force microscope is performed by utilizing the spring property of the cantilever. It is possible to make it. In the present invention, if such a probe having a plurality of small apertures is used in an information processing apparatus to which a scanning near-field optical microscope is applied,
Since a signal can be detected at a plurality of locations, it is possible to increase the area where a signal can be detected in one scan, as compared with a probe having one fine aperture, and the reliability of signal detection is improved. Moreover, the size of the openings is small, the signals detected by the respective openings can be separated at the time of signal detection, and an information processing device capable of reading information stably without lowering the resolution can be realized. .

[0011]

Embodiments of the present invention will be described below. Embodiment 1 FIG. 1 shows a probe according to Embodiment 1 of the present invention. FIG. 1 shows the shape of the probe section as viewed from directly above and from the side. The probe has an approximately pyramid shape with four sides surrounded by a curved surface. However, the four surfaces are slightly displaced without intersecting at one point, and have saddle-shaped tips. Further, the saddle-shaped tip portion forms a tip at two places.
A minute opening is formed at each of the distal ends.

The above probe was prepared as follows. First, as shown in FIG. 9A, an SiO ₂ mask excluding a rectangular portion of 3 μm square is used as a protective layer 902 on a Si substrate 901 having a plane orientation (100), and photolithography and a KOH solution are used. By performing crystal anisotropic etching, a pyramid-shaped groove is formed. Next, FIG.
As shown in FIG. 7, a pyramid-shaped groove is thermally oxidized to form a thermal oxide film 903 on the surface. As a result, the tip is sharpened so that one surface of the pyramid-shaped groove is convex inward. Next, as shown in FIG.
After forming a Pt film having a thickness of 0.1 μm by sputtering as a metal film to be No. 5, the probe tip coating portion and the electrode wiring are patterned. After that, a 1 μm-thick Si ₃ N ₄ film 904 is formed by low-pressure CVD, and then patterned into a predetermined shape to form a probe base. At this time, the shape of the probe base is arbitrary and may be a flat plate. Further, a plurality of probe portions may be formed at the probe base on the flat plate.

Further, as shown in FIG. 9D, a glass substrate is anodically bonded as a support 906 for supporting the probe. Next, the Si substrate 901 was removed with a KOH solution, and the thermal oxide film 903 was removed with a mixed aqueous solution of hydrofluoric acid and ammonium fluoride. As described above, a probe having a fine opening at the tip of the probe coated with Pt was formed. The prepared probe had a base length of about 3 μm, a height of about 4 μm, and a distance between two tips of about 0.1 μm. In the above-described sharpening process by thermal oxidation, the radius of curvature at the tip can be controlled by controlling the thermal oxidation time. As the thermal oxidation progresses and the radius of curvature is smaller, the area where the metal is not coated on the tip in the sputtering process becomes larger, and as a result, the fine opening becomes larger. The two tips can be formed stably and two small openings can be formed when the tip has a radius of curvature of about 10 to 30 nm, and the diameter of the small openings is about 20 to 50 nm at this time. . The thickness of the metal film is 100 nm, depending on the manufacturing method.
If it is smaller, it tends to be difficult to form a continuous film. Since this is not suitable for the probe of the present invention, the thickness of the metal film is preferably about 100 nm.

Next, the probe was incorporated into an information recording / reproducing apparatus, and a reproducing operation was performed on a row of recording dots arranged in a line. FIG. 4 shows the configuration of the information processing apparatus. The probe base 401 and the probe 402 constituting the probe are
04. The support 404 was fixed to the main body such that the probe 402 was opposed to the recording medium 403. At this time, they were arranged so that the direction connecting the two openings was parallel to the scanning direction. Substrate 40 on which recording medium 403 is loaded
Reference numeral 5 denotes a conductive electrode for applying a voltage to the recording medium 403. The substrate 405 is a conductive sample pedestal 40.
6 is installed. The sample pedestal 406 is fixed to the XY actuator 407. A voltage application circuit 412 is formed from a Pt thin film coating the probe 402 via a wiring.
It is connected to the. Also, the substrate 405 is mounted on the sample base 406.
Is connected to the voltage application circuit 412 through the, so that a voltage can be applied to the recording medium 403. The laser light emitting element 408 is disposed on the rear surface of the probe and close to the probe, and emits laser light to the probe base 40.
1 and is designed to irradiate the probe 402 portion from the back. Light scattered in the vicinity of the probe of near-field light seeping out from the minute opening at the tip of the probe is received by the photodiode 409.

Recording dots reproduced using the probe of the present invention were formed as follows. As a recording medium,
As an example of a recording medium in which the optical characteristics are changed by applying a voltage, as described in JP-A-4-90152, when a voltage is applied, a structural change is caused in a diacetylene derivative polymer by Joule heat caused by a locally flowing current. Occurs, and the peak wavelength of the light absorption band shifts.
12-pentacosadioic acid. Further, as an example of a recording medium whose optical characteristics are changed by application of a voltage under light irradiation, a cis- → trans-type photoisomer reaction only when irradiated with light as described in JP-A-2-98849. To form a redox pair, and an azo compound having a quinone group and a hydroquinone group that causes proton transfer between the redox pair when an electric field is applied. In the recording device, the recording data is binarized and converted into a data string associated with a recording point specified by coordinates on a recording medium. Here, the recording points are set in a grid pattern with a fixed interval. At this time, the interval between the recording points in the recording point row direction was set to 50 nm in order to secure a sufficient separation between the recording dots. At the recording point, a voltage was applied to the recording medium by using a recording probe to cause a current to flow through the recording medium to locally change the optical characteristics of the recording medium.

Next, the operation at the time of reproducing recorded dots will be described. When the probe 402 is irradiated with laser light, evanescent light is generated near the minute opening. The wavelength of the laser light is adjusted to the absorption peak of the recording dot on the recording medium. Therefore, in the recording dot portion, the light absorption rate is high, and the evanescent light is weak. Although not shown, the coarse movement mechanism is driven to move the probe closer to the surface of the recording medium. When the probe 402 approaches a distance of about 100 nm or less of the recording medium 403, the evanescent light is scattered on the surface of the recording medium surface 403, and the scattered light is detected by the light receiving element (photodiode) 409. . The photocurrent signal detected by the light receiving element 409 is converted into a voltage signal by the IV conversion circuit 410. In this embodiment, the probe is brought into contact with the recording medium. Next, the XY actuator 407 is driven to cause the probe to scan over the recording medium. At this time, the scanning direction was made to coincide with the direction connecting the two minute openings. In the signal comparing section, the light receiving element 40
The shift of the position of the probe with respect to the recording dot row is detected from the change in the signal detected by No. 9, and information for correcting the position of the probe is obtained. When the minute aperture of the probe approaches the recording dot, it is observed that the evanescent light is most modulated in the recording dot portion. Actually, since the tip of the probe usually has a radius of curvature of about several tens of nm, the current distribution on the time axis becomes a distribution curve reflecting the diameter of the minute aperture, and the minute aperture is closest to the recording dot. It has a peak at time t.

Next, the detection signal will be described with reference to FIG. In the figure, the signal detected by the minute aperture is expressed such that the part that is most modulated has an upwardly convex peak. Note that the actual signal on the recording dot depends on the optical properties of the recording dot whether the detection light is larger or smaller than the light detected in the surrounding area. Since the two small openings of the probe are arranged before and after with respect to the scanning direction, when the probe passes over the recording dot, the one of the two small openings that precedes the scanning direction in the scanning direction has a signal first. And the other detects the signal with a delay with respect to it. Therefore, the detection signal waveform, which is the superposition of these signals, has two peaks as shown in FIG. However, since the detected signal has a spread centered on the peak according to the distribution curve, when the two signals overlap, a peak appears at a position slightly shifted from the original peak position. As described above, two peaks were observed before and after in time for one recording dot, and each signal could be clearly distinguished.
Further, even if one detection system is used for two small apertures, signals detected by the respective small apertures can be identified on the time axis.

[Embodiment 2] The probe according to Embodiment 2 of the present invention has two micro openings at the tip. When the probe approaches the sample, when one of the micro openings contacts the sample, The other minute opening is configured not to contact the sample. However, it is not always necessary that the minute openings do not touch. 5 and 6 show the probe of this embodiment. This is a shape when the probe is viewed from directly above and from the side. The probe has an approximately pyramid shape surrounded by four faces. However, the four surfaces are slightly displaced without intersecting at one point, and have saddle-shaped tips. Further, the saddle-shaped tip portion forms a tip at two locations, and a minute opening is formed at each of the two locations. The height from the bottom surface of the probe to the minute opening is different for each minute opening. As shown in FIG. 6, a probe 601 is arranged at the tip of the cantilever 603.

FIG. 7 is a side view of the probe.
A probe composed of a probe 701 and a cantilever 702 is fixed to a probe base 703. Probe 70
When the probe is set so that the bottom surface of 1 is horizontal to the sample surface which is a flat plate, the probe 701 is brought close to the sample 704,
When one of the small openings A contacts the sample, the other small opening B does not contact the sample 704. However, sample 70
The distance from 4 to the opening A is about 100 nm or less. The probe was produced by using the same process as the method for producing the probe in Example 1. However, in Example 1, a Si substrate having a crystal orientation plane of (100) was used, but here, a silicon substrate having a crystal orientation plane having an offset angle from (100) was used. When the substrate is subjected to anisotropic etching, a concave portion having two local depressions surrounded by the (111) plane is formed. Each depression is
The depth from the Si substrate surface is different. In addition, the shape of the bottom surface of the pyramid-shaped depression is trapezoidal.

In the step of FIG. 9C, the probe base was patterned so as to have a long shape in the uniaxial direction, and the probe base was given a spring property to form a cantilever.

The probe was prepared such that the line connecting the two minute openings was perpendicular to the scanning direction, and the line connecting the long axis direction of the cantilever and the two minute openings was parallel. . The scanning direction was perpendicular to the direction connecting the two minute openings. In the near-field optical microscope, the resolution depends on the distance between the probe and the sample, and the resolution decreases as the distance increases. This is because as the distance from the sample increases, the contribution from a place other than immediately below the probe relatively increases. FIG. 8 shows a signal detected when a certain recording dot is passed. Small aperture B far from sample surface
However, the small aperture B that is in contact with the sample detects the light component from a wide area of the sample surface, while detecting the combined signal of the light component from the small area of the sample surface immediately below the small aperture. Become. The signal from the small aperture at a distance from the sample is
Since a signal from a relatively large area is detected, it is effective, for example, at the beginning of recording dots. On the other hand, since the actual detection of the recording signal is performed using the signal from the minute aperture closer to the sample, the signal can be reproduced with good S / N.

[0022]

As described above, according to the present invention,
With the configuration having a plurality of minute openings at the tip of the probe described above, a signal can be detected at a plurality of places, so that the area in which a signal can be detected in one scan is widened as compared with a probe having one minute opening. And the reliability of signal detection is improved. Moreover, it is possible to realize a probe with excellent resolution that can separate the signals detected by the respective apertures at the time of signal detection by the small aperture. Further, in the present invention, the probe of the probe is formed of an optically transparent structure, a conductive coating is applied to the surface of the structure, and the probe has a fine opening at the tip of the probe. With this structure, it is possible to shield the light with the conductive coating and to apply a voltage to the sample using the conductive coating. Further, in the present invention, if the above-mentioned probe is constituted by a cantilever and a probe arranged on the cantilever, the same control as that of a normal scanning atomic force microscope is performed by utilizing the spring property of the cantilever. Can be performed. In the present invention, by configuring an information processing apparatus to which a scanning near-field optical microscope is applied by using the above-described probe, an information processing apparatus capable of performing stable reading can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a shape of a probe according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a probe according to the first embodiment of the present invention.

FIG. 3A shows a signal waveform according to the first embodiment of the present invention,
FIG. 4B is a diagram showing the relationship between the arrangement of the minute openings and the recording dot passing position.

FIG. 4 is a diagram illustrating an information processing apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a shape of a probe according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of a probe according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a contact state between a probe and a sample surface according to a second embodiment of the present invention.

FIG. 8A shows a signal waveform according to the second embodiment of the present invention,
FIG. 4B is a diagram showing the relationship between the arrangement of the minute openings and the recording dot passing position.

FIG. 9 is a diagram showing a probe forming process.

[Explanation of symbols]

401: probe base 402: probe 403: recording medium 404: support 405: substrate 406: sample pedestal (holder) 407: XY actuator 408: light emitting element 409: light receiving element (photodiode) 410: IV conversion circuit 411 : Signal detection circuit 412: Voltage application circuit 413: Actuator drive circuit 601: Probe 602: Opening 603: Cantilever 701: Probe 702: Cantilever 703: Probe base 704: Sample 901: Si substrate 902: Protective layer 903: Thermal oxidation Film 904: Si ₃ N ₄ layer 905: Conductive coating layer 906: Probe base

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G11B 11/00 G11B 11/00 F term (reference) 2F063 AA43 DB01 DB05 EA16 EB15 EB23 JA04 2F069 AA60 BB40 GG04 GG07 GG52 GG62 HH02 HH30 JJ07 5D119 AA11 AA22 BA01 CA20 EB02 EB13 JA06 JA64 KA07 MA05

Claims (8)

[Claims] 1. A probe having a structure similar to a quadrangular pyramid or a quadrangular pyramid having four flat surfaces or curved side surfaces, and having a plurality of minute openings at the tip of the probe. Probe to be characterized. 2. The probe according to claim 1, wherein the small aperture has a size of 100 nm or less. 3. A method according to claim 1, wherein the plurality of minute openings contact the flat plate at the same time when the probe tip of the probe is brought into contact with a flat plate arranged to face the probe. The probe according to claim 1 or 2, wherein 4. A method according to claim 1, wherein when the probe tip of the probe is brought close to a flat plate arranged opposite to the probe, one of the plurality of fine openings is formed on the flat plate. The probe according to claim 1 or 2, wherein a distance between the other minute opening and the flat plate is set to 100 nm or less upon contact. 5. A method according to claim 1, wherein said plurality of minute openings have a direction connecting said minute openings in a direction coinciding with a scanning direction or a direction perpendicular to the scanning direction. Item 5. The probe according to any one of items 4 to 6. 6. The probe has an optically transparent structure, a conductive coating on the surface of the structure, and a fine opening at the tip of the probe covered with the conductive coating. The probe according to any one of claims 1 to 5, characterized in that: 7. The probe according to claim 1, wherein the probe is arranged on a cantilever. 8. An information processing apparatus for scanning a probe arranged in opposition to a recording medium in proximity to the surface of the recording medium, detecting near-field light near the surface of the recording medium, and performing recording and reproduction. An information processing apparatus comprising the probe according to any one of claims 1 to 7.