JPH063595A - Transmissive photon scanning tunneling microscope - Google Patents

Abstract

(57) [Abstract] [Purpose] To simplify the inspection of samples using a transmission photon scanning microscope. [Structure] Light irradiation means (1) for simultaneously irradiating a plurality of minute inspection areas, a plurality of probes (3) for detecting an electric field generated in each of the areas, and a scanning means for simultaneously scanning a plurality of probes (3). (4), scanning means (4) control means (6), a plurality of detection means (5) for converting the electric field detected by the probe (3) into an electric signal, information from the detection means (5) and control means ( The sample is inspected with the transmission photon scanning microscope which is composed of the image display means (8) for synthesizing and displaying the image based on the position information from 6).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type photon scanning tunneling microscope.

[0002]

2. Description of the Related Art Recently, 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 had excellent characteristics in terms of non-contact and non-destructive, but due to the principle of using an imaging optical system, the range of use is limited due to the limited resolution due to the diffraction limit. It was

A transmission type photon scanning tunneling microscope was developed to solve these problems. An inspection method using a transmission photon scanning tunneling microscope will be described. First, illumination light is made incident from the back surface of the sample so that the total reflection condition is satisfied on the surface of the sample. An electric field called an evanescent wave is generated on the sample surface by the irradiation of this illumination light. The evanescent wave decays exponentially with the distance from the sample surface, and becomes 1 / e (e is the number of Napiers) at a height of about the wavelength. A high longitudinal resolution can be obtained by detecting this evanescent wave with a probe that scans the surface of the sample in a non-contact manner. Further, by providing the probe with an opening smaller than the wavelength of light and limiting the region within the surface for detecting the evanescent wave, a higher lateral resolution can be obtained as compared with the conventional optical microscope.

The evanescent wave decays exponentially with the distance from the sample surface as described above. for that reason,
In order to obtain a high lateral resolution, the minute opening at the tip of the probe is not always necessary, and a probe whose tip is only sharpened may be used. The resolution is determined by the S / N of the signal in terms of vertical resolution and the effective minute aperture diameter in terms of lateral resolution. Therefore, it is necessary to increase the aperture diameter in order to obtain high vertical resolution, and to reduce the aperture diameter in order to obtain high lateral resolution, and 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 resolution differs depending on the sample to be inspected, it is necessary to change the sharpness angle of the probe tip for each sample to be inspected. Therefore, when manufacturing a probe, the important point is how reproducible a probe having a desired sharp angle can be manufactured. The probe uses, as a starting material, an optical fiber composed of a quartz core doped with germanium oxide and a clad composed of only quartz. Conventionally, this optical fiber has been used in which one core is formed in the clad as shown in FIG. The core has a high refractive index by adding germanium oxide to quartz.

Conventionally, this optical fiber is cut into an appropriate length, and a mechanical polishing method (Jiangxiao Dong,
Naoyuki Tomita, Kenichi Nakagawa, Motoichi Otsu "Optical Scanning Tunneling Microscope (Photon STM) -Analysis and Design-", IEICE Technical Report, IM-89-45, pp. 1-9, (1987)) And melt drawing (E.Betzing, M.Isaacson, A.Lewis “Collection
mode near-field scanning opticalmicro-scopy ”, App
L. Phys. Lett., 51, (25), p.2088-2090, (1987)) and other methods have been tried.

However, these methods have problems in that the sharp angle of the probe does not become an acute angle and the processing accuracy is high. In order to manufacture a probe for obtaining a high lateral resolution, it has been proposed to sharpen by (chemical) etching using hydrofluoric acid as an etchant, and the present inventor has also changed the chemical composition ratio (chemical) etching. Has proposed a method of manufacturing a probe using the method (Japanese Patent Application No. 4-
39755).

As the probe scanning device, a scanning device used in a scanning tunneling microscope or an atomic force microscope can be used. The sample inspection method uses a sharpened one end of an optical fiber as a probe (even a minute aperture is possible), and it is installed on a scanning tunnel microscope etc. to irradiate light from the back side of the sample and detect the evanescent wave generated on the surface. To do. At this time, the probe is brought close to the sample and the region to be inspected is scanned to detect the evanescent wave.

[0009]

However, even in the transmission type photon scanning tunnel microscope, the scanning range is very small, about 40 μm or less, as in other scanning microscopes using a probe. Therefore, when inspecting a sample, for example, only a small portion of the sample (several mm or less) can be inspected, and when the inspection range is wide, it takes time to move the probe and perform the inspection. There is a problem in that the operability of the probe and the device such as the movement of the field of view to be inspected and the identification of the inspection object is difficult.

The object of the present invention is to solve these problems.

[0011]

DISCLOSURE OF THE INVENTION As a result of earnest research, the inventor of the present invention has found that one probe having a plurality of sharpened cores simplifies scanning of a sample.
Therefore, the present invention is, firstly, "a light irradiation unit that irradiates a plurality of minute inspection regions at the same time, a plurality of probes that detect electric fields generated in each of the regions, and a scanning unit that simultaneously scans the plurality of probes. A position control means of the scanning means, a plurality of detection means for converting an electric field detected by the probe into an electric signal, and an image for combining and displaying images based on the information from the detection means and the position information from the position control means And a transmission photon scanning tunneling microscope (claim 1) comprising display means.

Secondly, according to the present invention, "In the transmission photon scanning tunneling microscope according to claim 1, a structure in which the plurality of probes bundle a plurality of optical fiber cores and coat them in a common clad. The microscope according to claim 1, wherein the plurality of probes are optical fibers, and the cores of the optical fibers are spread on a cut surface cut perpendicular to the optical axis of each optical fiber. Further, there is provided a transmission type photon scanning tunneling microscope (claim 2) characterized in that a plurality of two-dimensionally configured in the clad.

A third aspect of the present invention is that "a plurality of detecting means are two-dimensional detecting means for detecting electric field signals from the plurality of cores for each core. A microscope (claim 3) ".

[0014]

The starting optical fiber has a single or multiple cores in the cladding. It consists of a core (13) whose refractive index is slightly increased by adding germanium oxide to quartz, and a clad (14) which covers the core. Core (1
The diameter of 3) is generally 3 to 10 μm. Clad (14)
Must have a lower refractive index than the core, and quartz, or quartz with fluorinated glass, phosphate glass, or borate glass added, is used. The diameter of the clad (14) is generally 100 to 250 μm. The appropriate amount of germanium oxide added to the core is generally about 0.3 to 23 mol%, but when the sharpness angle θ is desired to be 25 ° or less,
About 20 to 23 mol% is suitable.

The present invention uses "a mixed etching solution composed of ammonium fluoride, hydrofluoric acid and water" as the etching solution. By changing the component ratio of this mixed etching solution, the sharpness angle θ of the probe can be freely changed within the range of less than 180 degrees. In particular, using an optical fiber consisting of a quartz core and a quartz clad to which germanium oxide is added in an amount of 20 mol% or more, "ammonium fluoride aqueous solution with a concentration of 40% by weight: Y capacity 1 (Y = 6 to 10), concentration of 50% by weight By using a mixed etching solution composed of an aqueous solution of hydrofluoric acid: 1 part by volume and water: 1 part by volume, a probe having a sharpness angle θ of 25 degrees or less can be manufactured. By changing the composition ratio of the mixed etching solution, it is possible to freely change the sharpness angle θ in a wide range with one type of optical fiber.

In the case of inspecting a sample using the probe formed in this way, when the back side of the sample is irradiated with light by the light irradiation means, an evanescent wave is emitted from the surface of the sample. The change in the intensity of the evanescent wave is detected by the probe and detected by the detecting means. By scanning the probe relative to the sample in this manner, a signal corresponding to the intensity of the evanescent wave in each part of the sample is obtained from the detection means, and operates as a microscope.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0018]

Example 1 As shown in FIG. 4 (a), a silica clad having a diameter of 100 μm and 20 mol% with respect to quartz were contained in the clad.
49 μm diameter core with the addition of germanium oxide
A book and an optical fiber two-dimensionally formed so as to have a spread on a cut surface cut perpendicular to the optical axis of the optical fiber are prepared.

One end of this fiber is cut by cleavage to be perpendicular to the optical axis. On the other hand, ammonium fluoride aqueous solution with a concentration of 40% by weight, hydrofluoric acid aqueous solution with a concentration of 50% by weight,
Prepare water and add ammonium fluoride aqueous solution to Y capacity part (Y
= 2 to 10), 1 part by volume of hydrofluoric acid aqueous solution and 1 part by volume of water were weighed, and the mixed etching solution (11) was prepared by mixing the three with a Teflon beaker (12).

As shown in FIG. 2, mixed etching solution (11)
The tip of the optical fiber (10) having a plurality of cores in the clad (the end surface cut perpendicular to the optical axis) is brought into contact with the liquid surface of (1) and left to stand. When left for 15 to 120 minutes, etching progresses as shown in FIGS. 3 (a) to 3 (d), and the tips of the cores are naturally sharpened, and a plurality of sharpened tips having uniform heights are formed. A probe having a portion is formed.

As a result, the sharp angles of the plurality of tips are 20 to 12
A 0 degree probe is manufactured. All the etched surfaces were smooth, and the radius of curvature of the tip of the probe was about 5 nm. As shown in Japanese Patent Application No. 4-39755, the relationship between the angle of the sharpness of the tip of the probe (θ) and the volume of the ammonium fluoride aqueous solution in the mixed etching solution (11) is as follows: To manufacture
What has Y of 6 to 10 may be used.

The distance between cores was 10 μm.

[0023]

Example 2 The probe manufactured in Example 1 is installed in a scanning device so that the sharpened tip and the sample (9) face each other. FIG. 1 shows a schematic configuration of a transmission scanning microscope according to an embodiment of the present invention. For convenience of explanation, all elements are drawn regardless of their actual proportions. Further, the structure of the probe (3) is also simplified for convenience of explanation.

In the microscope shown in the figure, the sample stage (2) on which the sample is placed is made of glass having a triangular shape, a hemispherical shape, a semicylindrical shape, or the like. The light irradiating means (1) is, for example, a semiconductor laser, and the light irradiating means is attached to a rotatable indicator member (not shown) in order to adjust the incident angle to the sample. Is configured so that the angle with respect to the sample table (2) can be adjusted.

When the sample stage (2) is irradiated with the laser light from the light irradiating means (1), the light from the light irradiating means (1) is totally reflected by the surface corresponding to the sample surface of the sample table (2). Then, the light is emitted through the emitting end surface of the sample table (2). An evanescent wave is generated on the surface (front surface) of the sample (9) irradiated with laser light from the back surface, and this is detected by the optical fiber probe (3). As shown in FIG. 1, a two-dimensional detection means (5) is installed in each of the plurality of cores at the other end of the probe which is not etched. As the detection means (5), for example, CCD, two-dimensional photodiode, multi-channel plate is used. The two-dimensional detection means (5) is connected to the signal processing means (7) and converts the electric field obtained from each of the plurality of cores into an electric signal for processing.

A scanning means (4) for moving the optical fiber probe (3) is installed. The scanning means is connected to the control means (6) for controlling the movement of the probe, which controls the movement of the probe (3) with respect to the sample. The control means (4) is also connected to the signal processing means (7) and is used in conjunction with each other. The probe (3) of the present invention has a plurality of cores (13) formed in a clad (14) as shown in FIG. Each core (13)
The signal obtained by (1) and converted into an electric signal by the signal processing means (7) is sent to the image display means (8). In the image display means (8), an image is synthesized and displayed based on the signal obtained from each core (13) of the probe (3) and the position information from the control means. A signal processing means may be installed in the image display device.

As for the scanning method of the probe (3), since the core (13) has a diameter of 10 μm and the interval between the cores is 10 μm, the probe (3) is scanned only by the interval of 10 μm. Then, the evanescent wave from each core (13) is detected.
If the probe (3) of this embodiment is used, the evanescent wave of the range (10 μm × 10 μm) in which the core (13) is scanned × the number of cores (49) is detected, photoelectrically converted, and converted into a scanning signal. The data is recorded in the image memory in synchronization. A composite image of the sample inspected by the display means (8) can be obtained by combining these.

As shown in FIG. 4, the plurality of cores (13) can be formed in the clad (14) so as to substantially fill the diameter of the clad (14), so that the diameter of the probe (3) (100 to 250).
It is possible to obtain a scan image in a wide range according to μm).

[0029]

According to the present invention, it is possible to inspect only a minute area (corresponding to one pixel) by using one probe in the conventional inspection. With such a device, a plurality of inspection areas (corresponding to a plurality of pixels) can be inspected by one inspection, the inspectable range can be widened, and the same area as the conventional area can be inspected in a short time. it can.

Therefore, the condition of the surface of the sample to be inspected, the range of use such as the inspection range is expanded, and the sample inspection becomes easy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a transmission photon scanning tunneling microscope according to an embodiment of the present invention.

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

FIG. 3 is a vertical cross-sectional view of the tip of an optical fiber, showing how it is sharpened by etching.

FIG. 4 is a vertical sectional view and a vertical sectional view of an optical fiber (a) and a conventional optical fiber (b) used in an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light irradiation means 2 ... Sample stand 3 ... Optical fiber probe 4 ... Scanning means 5 ... Detection means 6 ... Control means 7 ... Signal processing means 8 ... Image display Means 9 ・ ・ ・ Sample 10 ・ ・ Optical fiber 11 ・ ・ Mixed etching solution 12 ・ ・ Teflon beaker 13 ・ ・ Core 14 ・ ・ Clad (a) ・ ・ ・ Optical fiber used for probe of one embodiment of the present invention (b) ・..Optical fibers used for conventional probes

Claims (3)

[Claims] 1. A light irradiation means for irradiating a plurality of minute inspection areas at the same time, a plurality of probes for respectively detecting electric fields generated in the respective areas, a scanning means for simultaneously scanning the plurality of probes, and a scanning means. Transmission including a position control means, a plurality of detection means for converting an electric field detected by the probe into an electric signal, and an image display means for synthesizing and displaying an image based on the information from the detection means and the position information from the position control means Photon scanning tunneling microscope. 2. The transmission type photon scanning tunneling microscope according to claim 1, wherein the plurality of probes have a structure in which a plurality of cores made of optical fibers are bundled and covered in a common clad. microscope. 3. A transmission type photon scanning tunneling microscope, wherein the plurality of detecting means are two-dimensional detecting means for detecting electric field signals from the plurality of cores for each core.