JP2789244B2 - Method of forming microprobe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a scanning tunneling microscope (hereinafter abbreviated as STM).
And high-density recording / reproducing devices. The present invention relates to a method for forming a probe having a very small radius of curvature at the tip.

[Prior art] Conventional general STM detects a tunnel current flowing between the conductive sample surface and the tip of the conductive detection probe, and adjusts the distance between the sample surface and the detection probe so that the tunnel current becomes constant. Is controlled by electrical feedback to display the structure of atoms and molecules as an image. The resolution of such an STM is determined by the radius of curvature of the probe tip. In order to increase the resolution, it is necessary to make the tip of the probe sharper.

Conventional methods for producing a probe include a method in which the tip of a platinum or tungsten rod is sharpened conically by mechanical polishing, or a method in which the tip is sharpened by electrolytic polishing (Japanese Patent Laid-Open No. 61-32326, Is generally used. The tip radius of curvature obtained from these is at most 0.1 micron meter. In addition, there is a method of performing electrolytic evaporation in an ultra-high vacuum chamber in order to further sharpen the tip of the probe formed by using mechanical polishing or electrolytic polishing.

[Problems to be Solved by the Invention] However, a probe manufactured using a conventional mechanical polishing or electrolytic polishing method requires a tip curvature when observing atoms and molecules and when observing the bonding state of atoms or molecules. Since the radius was too large, about 0.1 micron meters, high-precision observation was not possible. In addition, in the method of sharpening the probe tip using the electrolytic evaporation method, it is necessary to perform heating and a high electric field in an ultra-high vacuum chamber.
In order to prevent the sample from being damaged, it is necessary to take measures to prevent the sample from being damaged, resulting in a problem that the apparatus becomes large.

The present invention has been made in view of the above-described drawbacks of the related art, and has as its object to provide a method for forming a microprobe having a simple configuration and a sharpened tip compared to the related art.

[Means and Actions for Solving the Problems] According to the present invention, a voltage is applied between the conductive probe and the conductive member while the tip of the conductive probe is brought close to the conductive member to a very small distance. Then, in the method for forming a microprobe, in which the tip of the conductive probe is melted to form a microprotrusion, a protrusion is provided at a position of the conductive member closer to the conductive probe, and a voltage is applied between the protrusion and the conductive probe. Then, by forming a micro probe, it is intended to obtain a high resolution by improving the radius of curvature of the tip.

Reference Examples and Examples Hereinafter, reference examples and examples of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of a configuration and an electric block of a reference example according to the present invention. Reference numeral 1 denotes a conductive probe in which a conductive material such as tungsten, platinum, platinum rhodium, and platinum iridium is sharpened at its tip by electrolytic polishing or mechanical polishing. Reference numeral 2 denotes a conductive material and a conductive probe coating material prepared by a sputtering method, a plating method, or the like. 3 is a conductive sample. Reference numeral 4 denotes a minute projection formed at the tip of the conductive probe 1 covered with the conductive probe coating material 2. 5 is a substrate for fixing the conductive sample 3, 6 is a vertical position control means for controlling the distance between the conductive probe 1 and the conductive sample 3, and 7 is the conductive probe 1.
A bias power supply for sweeping and applying a bias voltage between the conductive probe and the conductive probe coating material 2, a pulse power supply 8 for varying the bias voltage, and 9 detecting a tunnel current flowing between the conductive probe 1 and the conductive sample 3. The tunnel current detection circuit 10 is a probe vertical position control circuit for controlling the vertical position control means 6. In this reference example, a tunneling current was used as a detecting means for controlling the distance between the probe and the sample, but the present invention is not limited to this.For example, a detecting means such as an atomic force, a magnetic force, and an electrostatic force is used. You may. The method for forming the minute projections with the configuration as described above will be further described in detail with reference to FIGS.

Tungsten was used as the material of the conductive probe 1,
The radius of curvature of the tip of a tungsten probe manufactured by electrolytic polishing using a general electrolytic polishing method to sharpen the tungsten probe was about 0.1 μm. Probe 1 made by electrolytic polishing
On the surface, use an ion beam sputtering device to deposit 10 gold
It was coated on the order of nanometers. Materials for the conductive sample 3 include:
A platinum deposited film was used. As the vertical position control means 6, a commercially available PZT element (displacement: 1 μm / 1000 V) was used. The tunnel current detection circuit 9 was used so that the distance between the coating material 2 of the probe 1 and the sample 3 was several nanometers with the above-mentioned material and element configuration. The probe vertical position control circuit 10 and the vertical position control means 6 control the distance between the probe 1 and the sample 3 by applying electrical feedback so that the distance does not change due to disturbances such as temperature drift and external vibration. Environmental conditions are in the atmosphere. In this state, the condition values of pulse width 4 μs, pulse height, and 4 V are swept from the pulse power supply 8 to the variable bias power supply 7 in which the probe is set to the plus side, and FIG. 1 or FIG. ) Was formed. The size of the formed microprojections was about 10 nanometers in height and about 15 square nanometers in bottom area.

The probe material, the probe coating material, and the sample material are not limited to these, and can be appropriately selected. However, the sample needs to have a higher melting point than the probe coating material.

Also, the pulse condition value can be appropriately selected depending on the size of the microprojections to be formed, but it is necessary not to damage both the sample and the probe coating material.

By forming the fine projections 4 as described above, it is possible to provide a high-resolution microprobe capable of decomposing a molecular bonding state regardless of whether it is in a vacuum or in the air. In addition, if an appropriate material is selected so as not to damage the sample by applying a pulse voltage, even if the probe comes into contact with the sample during STM operation and the resolution of atoms and molecules cannot be obtained, It is possible to easily reproduce the minute projections having the resolution with the STM configuration.

Next, an embodiment of the present invention will be described with reference to FIG. This embodiment is similar to the sample 3 in the configuration described in the reference example.
Only exchanged. The sample 3 has a mountain-shaped projection 31 with a sharp tip formed in advance. This projection 31
Is prepared by a known appropriate method. The method of forming the minute projections 4 is the same as that of the reference example. However, since the mountain-shaped projections 31 are provided on the sample 3, when the pulse voltage is swept, the concentration of the electric field increases as compared with the plane. Therefore, it is possible to form the minute projections 4 having a smaller tip radius of curvature than the minute projections 4 of the reference example (FIGS. 1 and 2).

[Effects of the Invention] As described above, a microprojection having a smaller tip radius of curvature is easily formed on the tip of a probe having a tip radius of curvature of 0.1 micron meter using an STM configuration device regardless of whether it is in a vacuum or in the atmosphere. It is possible to form a high-resolution microprobe that is capable of sufficiently resolving atoms and molecules by a simple method.
Significant effects can be obtained in terms of improvement in performance, downsizing of the manufacturing apparatus, and simplification of the manufacturing method.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a surface detecting means using a microprobe according to a reference example. FIGS. 2 (a) and (b) are explanatory diagrams of microprotrusion portions formed at the tip of the microprobe of the reference example. FIGS. 7A and 7B are explanatory views of another method for forming a micro projection formed on the tip of a micro probe according to the present invention. 1: Conductive probe, 2: Conductive coating material, 3: Conductive sample, 4: Microprojection, 5: Substrate, 6: Vertical position control means, 7: Variable bias power supply, 8: Pulse power supply, 9: Tunnel Current detection circuit, 10: Probe vertical position control circuit.

Continued on the front page (72) Inventor Miya ▲ saki ▼ Toshihiko 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Takahiro Oguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-1-149355 (JP, A) JP-A-63-265101 (JP, A) JP-A-63-265102 (JP, A) (58) Fields investigated (Int. Cl. ^6, DB name) G01B 7/34 G01B 21/30 G01N 37/00

Claims (2)

(57) [Claims] A voltage is applied between the conductive probe and the conductive member while the tip of the conductive probe is brought close to the conductive member to a very small distance to melt the conductive probe tip. A method for forming a microprobe that forms a microprotrusion, comprising: providing a protrusion at a position of the conductive member closer to the conductive probe, and applying a voltage between the protrusion and the conductive probe. 2. The method according to claim 1, wherein said conductive member has a higher melting point than said conductive probe.
The method for forming a microprobe described in the above item.