JP3134456B2 - Probe manufacturing method and probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a probe and a probe manufactured thereby. This probe is useful as a probe for a transmission photon scanning microscope.

[0002]

2. Description of the Related Art In recent years, non-contact, non-destructive, high-resolution microscopes have become increasingly important in a wide range of fields such as biology and semiconductor device development. Conventionally used optical microscopes have excellent characteristics in terms of non-contact and non-destruction, but the range of use is limited due to the limitation of resolution due to the diffraction limit due to the principle of using an imaging optical system. Was.

[0003] The transmission type photon scanning tunneling microscope has been developed to solve these problems. A measuring method using a transmission photon scanning tunneling microscope will be described. First, illumination light is incident from the back surface of the sample so as to satisfy the condition of total reflection on the surface of the sample. The irradiation of the illumination light generates an electric field called an evanescent wave on the sample surface. The evanescent wave decays exponentially with the distance from the sample surface, and becomes 1 / e (e is the number of napier) at a height of about the wavelength. A high vertical resolution can be obtained by detecting this evanescent wave with a probe that scans the sample surface in a non-contact manner. Further, by providing an opening portion smaller than the wavelength of light in the probe and limiting the area in the surface where the evanescent wave is detected, a higher lateral resolution can be obtained as compared with a conventional optical microscope.

[0004] As described above, the evanescent wave decays exponentially with the distance from the sample surface. for that reason,
In order to obtain high resolution, a minute opening at the tip of the probe is not always necessary, and the tip of the probe may be merely sharpened. The resolution is determined by the signal S / N for the vertical resolution and the effective small aperture diameter for the horizontal resolution. Therefore, to obtain a high vertical resolution, it is necessary to increase the aperture diameter, and to obtain a high horizontal resolution, it is necessary to reduce the aperture diameter. There is a trade-off relationship between the vertical resolution and the horizontal resolution. It can be said that there is.

Since the required vertical and horizontal resolutions differ depending on the sample to be measured, it is necessary to change the sharp angle of the probe tip for each sample to be measured. Therefore, when manufacturing a probe, it is important how a probe having a desired sharp angle can be manufactured with high reproducibility. The probe is manufactured by using an optical fiber composed of a quartz core and a clad to which germanium oxide is added as a starting material, cutting this into an appropriate length, and sharpening the tip. Conventionally, as a method of sharpening, mechanical polishing (Chiang Shu-dong, Naoyuki Tomita, Ken-ichi Nakagawa, Gen-ichi Otsu “optical scanning tunneling microscope (Photon ST
M)-Analysis and Design-", IEICE Technical Report, IM-89-45, pp. 1-9, (1987)) and melt drawing (E.Betz
ing, M. Isaacson, A. Lewis “Collection mode near-fie
ld scanning opticalmicroscopy ”, Appl.Phys.Lett., 5
1, (25), pp. 2088-2090, (1987)).

[0006] However, these methods have problems in that the sharp angle of the probe does not become too sharp and that the processing accuracy and the like are high. In order to manufacture a probe for obtaining a high lateral resolution, it has been proposed to sharpen it by (chemical) etching using hydrofluoric acid as an etchant.

[0007]

However, the method of manufacturing a probe by etching using hydrofluoric acid has a problem that the reproducibility of the shape is poor, the range of the sharp angle .theta. There is a problem that the surface is not smooth. An object of the present invention is to solve these problems.

[0008]

In order to solve the above-mentioned problems, according to the present invention, an optical fiber consisting of a quartz core and a clad to which germanium oxide is added is mixed with a mixed etching solution comprising an aqueous solution of hydrofluoric acid and ammonium fluoride. In the method of manufacturing a probe obtained by etching and sharpening the tip of the optical fiber, germanium oxide is added to the quartz core in an amount of 20 mol% or more, and the mixed etching solution is mixed with water at a concentration of water. A mixture obtained by mixing a 50% by weight aqueous solution of hydrofluoric acid with an aqueous solution of ammonium fluoride having a concentration of 40% by weight. 1 hydrofluoric acid aqueous solution having a concentration of 50% by weight and a concentration of 40
The weight percent of the aqueous ammonium fluoride solution was 2 to 10.

Further, in the present invention, the mixing ratio of the water of the etching solution, the aqueous solution of hydrofluoric acid, and the aqueous solution of ammonium fluoride is adjusted so that the sharp angle of the tip of the optical fiber is 25 degrees or less. The amount of the hydrofluoric acid aqueous solution was set to 1, and the amount of the ammonium fluoride aqueous solution was set to 6 to 10.

Further, according to the present invention, an optical fiber comprising a quartz core and a clad doped with germanium oxide is provided.
In the method of manufacturing a probe, in which the tip of the optical fiber is sharpened by etching with a mixed etchant comprising an aqueous solution of hydrofluoric acid and ammonium fluoride, the tip ratio of the desired probe is changed by changing the component ratio of the mixed etchant. A corner was formed.

Further, the present invention provides a probe whose tip is sharpened by using the above-mentioned method.

[0012]

The optical fiber used as the starting material has a core whose refractive index is slightly increased by adding germanium oxide to quartz (1).
And a cladding (2) covering the periphery of the core. The diameter of the core (1) is generally between 6 and 10 μm. The cladding (2) must have a lower refractive index than the core, and quartz or a material obtained by adding fluoride glass, phosphate glass, borate glass to quartz, or the like is used. Cladding (2)
Is typically 125 μm. Generally, the amount of germanium oxide added to the core is suitably about 3 to 30 mol%, but if the sharp angle θ is desired to be an acute angle of 100 degrees or less, about 20 to 30 mol% is appropriate.

The present invention is characterized in that a "mixed etching solution comprising hydrofluoric acid, water and ammonium fluoride" is used as an etching solution. By changing the component ratio of this mixed etching solution, the sharp angle θ of the probe can be set to 1
It can be changed freely within a range of less than 80 degrees. In particular, the mixing ratio of the mixed etching solution is set to 1 for the amount of water.
The amount of the hydrofluoric acid aqueous solution having a concentration of 50% by weight is 1, and the amount Y of the aqueous solution of ammonium fluoride having a concentration of 40% by weight is Y (Y = 2 to 10).
Can be changed freely within a range of less than 180 degrees. When the tip of an optical fiber composed of a quartz core and a quartz clad to which germanium oxide is added in an amount of 20 mol% or more is sharpened, the amount of the ammonium fluoride aqueous solution is set to Y (Y = 6 to 1).
An etching solution mixed at a ratio of 0) is used. The tip portion of an optical fiber having a quartz core to which germanium oxide is added in an amount of 20 mol% or more with such a mixed etching solution,
The sharp angle can be formed to 25 degrees or less. In addition, according to the present invention, by changing the component ratio of the mixed etching solution, one kind of optical fiber can be used, and the sharp angle θ can be freely changed over a wide range.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0015]

Embodiment 1 A quartz core having a diameter of 3 μm and a thickness of 125 μm
An optical fiber made of quartz clad is prepared. 23 mol% of germanium oxide is added to the core. One end of the fiber is cut perpendicular to the optical axis by cleavage. On the other hand, an aqueous solution of hydrofluoric acid having a concentration of 50% by weight, water, and an aqueous solution of ammonium fluoride having a concentration of 40% by weight were prepared, and 1 part by volume of the aqueous solution of hydrofluoric acid, 1 part by volume of water,
Ammonium fluoride aqueous solution in Y volume part (Y = 2-10)
The mixture was weighed and mixed with a Teflon beaker (5) to prepare various mixed etching solutions.

As shown in FIG. 2, the tip of the optical fiber (3) is brought into contact with the liquid surface of the mixed etching solution (end surface cut perpendicular to the optical axis), and is left. When left for 90 to 180 minutes, the etching proceeds as shown in FIGS. 1A to 1D, and the tip naturally sharpens to form a probe. At this time, the etching solution does not need to be particularly agitated, and was left still here.

As a result, a probe having a sharp angle θ of 20 to 120 degrees was manufactured. The etched surfaces are all smooth and the radius of curvature of the probe tip is 10 nm.
Before and after. At this time, the relationship between the concentration of the aqueous ammonium fluoride solution (Y capacity part) and the sharpness angle θ was as shown by the graph A (open circle) in FIG. Therefore, it can be seen that a probe having a Y of 6 to 10 should be used to produce a probe having a θ of 25 or less.

Even if a number of probes are manufactured using the same etching solution, the variation of the sharp angle θ is 0.5
Degrees.

[0019]

Example 2 Etching was performed in exactly the same manner as in Example 1 except that the amount of germanium oxide added was not 23 mol% but an optical fiber of 3.6 mol% was used, and various probes were manufactured. The sharp angle θ of the manufactured probe was 100 degrees or more, and the concentration of the ammonium fluoride aqueous solution (Y capacity part) and the sharp angle θ were in a relationship shown by a graph A (open circle) in FIG. The etched surfaces were all smooth, and the radius of curvature at the tip of the probe was around 10 nm. No matter how many probes were manufactured using the same etching solution, the variation of the sharp angle θ was 0.5 degrees or less.

[0020]

Example 3 The mixed etching solution of Example 1 was prepared by adding a 50% by weight aqueous solution of hydrofluoric acid to a mixed solution consisting of 1 part by volume of water and 1 part by volume of an aqueous solution of ammonium fluoride having a concentration of 40% by weight. It can be expressed as a mixed etching solution obtained by addition. At this time, the ratio of the hydrofluoric acid aqueous solution having a concentration of 50% by weight occupied therein was defined as X% by weight, and the relationship between X% by weight and the sharp angle θ of the tip of the optical fiber after etching was examined. (In FIG. 4,
The vertical axis is sin (θ / 2).

Equation 1: It was found that sin (θ / 2) = 17.8 (X / 100) ² −3.0 (X / 100) +0.30 was satisfied. Therefore, in order to manufacture a probe having a desired θ, X is obtained by solving Equation 1, and the mixed etching solution is prepared according to the X and used. When X is less than 8, a probe with θ = 20 degrees is manufactured.

According to the etching method of the present invention, the tip angle of the probe can be made 180 ° or more, that is, the probe tip can be processed into a concave shape by further increasing the concentration of hydrofluoric acid. It is.

[0023]

According to the present invention, the reproducibility of the shape of the tip portion (sharpened portion) of the probe is improved, and even if only one kind of optical fiber is used, the composition ratio of the etching solution can be changed. The sharpness angle θ can be freely changed over a wide range, and the effect of smoothing the etched surface is brought about.

Further, according to the formula 1, when a probe having a desired θ is manufactured, a necessary etching solution is immediately determined.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a tip of an optical fiber, showing a state where the tip is sharpened by etching.

FIG. 2 is a schematic view of an etching apparatus.

FIG. 3 is a graph showing a relationship between a sharp angle θ of a probe manufactured in Examples 1 and 2 of the present invention and a ratio of an aqueous solution of ammonium fluoride as an etching solution (Y capacity part).

FIG. 4 is a graph showing the sharpness angle θ and the ratio of the hydrofluoric acid aqueous solution of the etching solution (X wt%) when using an optical fiber in which germanium oxide was added to the core at 23 mol% among the probes manufactured in Example 1 of the present invention. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Core 2 ... Clad 3 ... Optical fiber 4 ... Mixed etching liquid 5 ... Teflon beaker

Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/06 H01J 37/28 G01B 11/30 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. An optical fiber comprising a quartz core and a clad to which germanium oxide has been added is etched with a mixed etching solution comprising an aqueous solution of hydrofluoric acid and ammonium fluoride to sharpen the tip of the optical fiber. In the method of manufacturing a probe, the germanium oxide is 20 mol% in the quartz core.
The mixed etching solution is obtained by mixing water, a hydrofluoric acid aqueous solution having a concentration of 50% by weight and an aqueous solution of ammonium fluoride having a concentration of 40% by weight, and the water and the hydrofluoric acid are mixed. A probe, wherein the mixing ratio of the aqueous solution and the ammonium fluoride aqueous solution is such that the amount of the water is 1, the amount of the hydrofluoric acid aqueous solution is 1, and the amount of the ammonium fluoride aqueous solution is 2 to 10. Manufacturing method. 2. The mixing ratio of the water, the aqueous solution of hydrofluoric acid and the aqueous solution of ammonium fluoride in the mixed etching solution is such that the amount of the aqueous solution is 1, the amount of the aqueous solution of hydrofluoric acid is 1, and the amount of the aqueous solution of hydrofluoric acid is 1, The amount of the aqueous ammonium solution is 6 to 10
2. The method of manufacturing a probe according to claim 1, wherein the probe has a pointed angle of 25 degrees or less at the tip of the optical fiber. 3. An optical fiber comprising a quartz core and a clad to which germanium oxide has been added is etched with a mixed etching solution composed of an aqueous solution of hydrofluoric acid and ammonium fluoride to sharpen the tip of the optical fiber. A method of manufacturing a probe, comprising: forming a desired sharp angle at the tip of the probe by changing a component ratio of the mixed etching solution. 4. A probe manufactured by the method for manufacturing a probe according to claim 1. Description: