JPH03287111A - Reflection type nearby visual field scanning microscope - Google Patents

Abstract

PURPOSE:To photodetect omnidirectionally reflected light in an equal direction and to improve measurement accuracy by arranging an optical lens which guides light to a photodetector nearby a body to be measured opposite and making a projection fiber penetrate its center. CONSTITUTION:The optical system 20 which forms an optical path from the light source 5 to the photodetector 10 consists of the projection fiber 22 which guides the light 21 from the light source 5 to the surface of the body 3 to be measured on a stage 2, a convex lens (optical lens) 24 which photodetects and guides reflected light 23, emitted by the light source 5 and reflected by the surface of the body 3 to be measured, to the photodetector 10, and a total reflecting mirror 25 and a condenser lens 26. Then the surface of the optical lens 24 which faces the body 3 to be measured closely is a continuous ring- shaped photodetection surface which surrounds the projection fiber 22. Consequently, the reflected light which is reflected by the surface 3 to be measured can be photodetected over the entire surface omnidirectionally and the measurement accuracy can be improved.

Description

[Detailed Description of the Invention] Industrial Field of Application] The present invention measures the surface shape of a workpiece with high resolution by scanning an aperture smaller than the wavelength of light from a light source in close proximity to the workpiece. This invention relates to a reflective optical close-field scanning microscope.

[Prior Art] Conventionally, this type of optical near-field scanning microscope (Near-F
ield Scanning 0ptLcat
Japanese Patent Laid-Open No. 121.310/1984 is known as a microscope (hereinafter referred to as N50M). Unlike general optical microscopes, this N50M can obtain high resolution F, equivalent to that of scanning electron microscopes (20 nm; approximately 200 to 300 nm in the case of optical microscopes), even in air or in solutions, and the optical It has excellent features such as the ability to obtain information on biological properties, and has great expectations, especially since it can be used to observe thin film samples and biological samples as they are. The basic principle of N50M is
1 The surface of the measured object is scanned with an aperture smaller than the wavelength of the visible light emitted from the light source to illuminate the measured object, and the surface shape, that is, the three-dimensional shape, is measured. It is called a close-field scanning microscope because it scans at a distance shorter than that (500 nm or less).

The aperture is usually obtained by forming the tip of the optical fiber into a conical shape and forming the apex to a diameter of 1 μm or less.

According to wave theory, the resolution of a normal optical microscope is λ
/2 (λ: wavelength), so the visible light range is limited to 200 nm to 300 nm. However,
” When light is guided through an extremely small aperture that is smaller than the wavelength, it cannot spread through free space like normal light, but it travels back and forth around the aperture and directs the radiant energy to the opposite side of the aperture. Can be moved to the side. This transferred light is called an evanescent wave, and by illuminating the measurement surface with it, high-resolution optical measurements are made possible.

Measurement methods using N50M include: 1) irradiating the adjacent group on the sample surface from the aperture and focusing the transmitted light with a microscope objective lens; 2) irradiating the light that has passed through the sample through the aperture of the nearby group There are three known methods: (2) a method of detecting light emitted from the aperture of a proximal group; Among these methods, the method for measuring the reflected light is the reflective type N5.
It is called 0M and has the characteristic of obtaining the highest resolution. Fig. 3 shows a conventional example of such a reflective type N50M (Japanese Patent Laid-Open No. 59-1-21-31-0). To briefly explain this, 1- is a base; 1 is not subjected to external vibration by a vibration isolator (not shown)! It is said to be of T4 construction. Reference numeral 2 denotes a stage disposed on the base 1''2, and this stage 2 is driven by an unillustrated drive device.
, Y, and directions, and the object to be measured 3 is installed on two sides. Reference numeral 4 denotes a column installed on the base 2, and 5 is a light source attached to the tip arm portion 4A of the column 4 via a vertical adjustment device W6.The light source 5 is composed of a semiconductor laser, etc. 3, and by moving the object to be measured 3 in the X and Y directions, the open lower relatively scans over the measurement surface. Reference numeral 8 denotes a sensor that detects the reflected light emitted from the light source 5 and reflected by the surface of the object to be measured 3 after passing through the open lower part. It is converted into an electrical signal.

[Problems to be Solved by the Invention] However, in the conventional reflective N50M described above, although a plurality of sensors 8 are arranged around the open lower part in order to increase the intensity of the received light, There is an anisotropy in the reception of light, and there is a problem that the measurement accuracy cannot be improved due to the influence of shadows caused by the slope. Therefore, increasing the number of sensors 8 may be considered as a method of solving this problem, but doing so would not only increase the number of parts but also make mounting and adjusting the sensors cumbersome.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to have a large light-receiving area with a minimum number of parts, and to receive reflected light equidirectionally from all around the aperture. The object of the present invention is to provide a reflection type optical near-field scanning microscope that can improve measurement accuracy and enable visual observation.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a light source, a light source having a diameter smaller than the wavelength of the light emitted from the light source, and a light source that is close to the surface of the object to be inspected. a light emitting fiber that guides the light from the light source to the aperture; a photodetector that receives the light from the light source that passes through the aperture and is reflected by the object to be measured, and converts it into an electrical signal; , an optical lens that condenses the light reflected by the object to be measured and guides it to the photodetector, the optical lens being disposed close to and facing the object to be measured, and passing through the light projection fiber 22 in the center. This is what I did.

[Function] In the present invention, the surface of the optical lens that closely faces the object to be measured forms a continuous ring-shaped light-receiving surface surrounding the light emitting fiber, and the surface of the optical lens that closely faces the object to be measured forms a continuous ring-shaped light-receiving surface that surrounds the light emitting fiber, so that the reflected light reflected from the surface of the object to be measured is completely absorbed. The light is received in the same direction.

[Example] Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a reflective optical near-field scanning microscope according to the present invention. Components in the figure that are the same as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In the figure, the present embodiment includes a light emitting fiber 22 that guides light 21 from the light source 5 to the surface of the object to be measured 3 on the stage 2, as an optical system 20 forming an optical path from the light source 5 to the photodetector 10. , receives the reflected light 23 emitted from the light source 5 and reflected on the surface of the object to be measured 3, and transmits the light to the photodetector (
a convex lens (optical lens) 24 that guides the light to zero, a total reflection mirror 25, a condensing lens 26, and a condensing lens 27 that condenses the light 21 emitted from the light source 5 and makes it enter the light incident surface of the light projection fiber 22. and an open lower portion provided on the light emitting surface of the light emitting fiber 22 that closely faces the object to be measured 3.

As the light source 5, for example, an Ar laser with a wavelength of 488 nm is used.

The light emitting fiber 22 is made of quartz or the like, and has a diameter of 200 /
It has a diameter of about 1 m. The end of the light emitting fiber 22 on the side of the object to be measured 3 is inserted and fixed into an insertion hole 28 formed through the center of the convex lens 24 . The light emitting fiber 22 and the convex lens 24 are attached to the arm portion 4A of the support column 4 via a vertical adjustment device 6 so as to be movable and adjustable in the vertical direction.

The vertical adjustment device 6 generally includes a coarse adjustment device such as a micrometer, and a fine adjustment device such as a laminated piezo element that expands and contracts in response to an applied voltage.
As a result, the open lower part is set at a distance shorter than the wavelength of the light from the light source 5 from the measurement surface of the object 3 to be measured.

Note that a piezo element is also used for a drive device (not shown) that moves the stage 3 in the X and Y directions to scan the measurement surface with the open lower part. In that case, four stacked piezo elements may be arranged in a cross shape, and the stage 2 may be placed at the center thereof.

As shown in FIG. 2, the open lower lower part is formed by processing the end of the light emitting fiber 22 on the side of the object 3 into a conical shape, and the pointed tip thereof has a diameter smaller than the wavelength of the light emitted from the light source 5. , for example, by making it less than ■μm. On the conical portion provided at the end of the light emitting fiber 22, except for the open lower portion, two metal light-shielding films (thickness approximately 200 μm) made of aluminum or the like are formed by means of sputtering or the like. When forming the open lower part, the light shielding film 29 is formed on the entire conical part in advance, and then the tip of the conical part and the light shielding film are removed by ion cutting.

In the reflective type N50M having such a configuration, when measuring the surface shape of the object to be measured 3, the light emitted from the light source 5 is focused by the condensing lens 27, and the light is transmitted from the light incident surface of the light projection fiber 22 to the fiber. The measurement surface of the object to be measured 3 is irradiated with the light (extinguishing light) that passes through the open lower part. Further, in this state, the surface of the object to be measured 3 is scanned by the open lower.

The irradiation light that passes through the open lower door and irradiates the measurement surface of the object to be measured 3 hits the measurement surface and is reflected, and the reflected light 23 is received by the 20,000 lens 2.1 and becomes parallel light rays, resulting in total internal reflection. The light is guided to the photodetector 1-0 via the mirror 25 and the condensing lens 26, where it is converted into an electrical signal. Although the reflected light that hits the measurement surface is reflected in all directions, the amount of reflected light in each reflection direction changes depending on the surface shape, so the output signal of each light receiving element of the photodetector 10 also changes. Therefore, by detecting the reflected light 23, the three-dimensional shape of the measurement surface of the object to be measured 3 can be measured with a high resolution equal to or less than the wavelength of the light from the light source 5 (approximately 20 nm).

In this case, the convex lens 24 is a continuous annular light-receiving surface 24 that closely faces the measurement surface and surrounds the light-emitting fiber 22.
a, there is no anisotropy in the reception of the reflected light 23, and the reflected light reflected in all directions can be received in the same direction. Therefore, the amount of received light, in other words, the intensity of light, increases, and the influence of light shadows due to surface irregularities is reduced, making it possible to improve measurement accuracy.

Note that the thickness of the light-shielding film 29 near the opening lower part is thin, and there is a possibility that light leaking from this part may enter the convex lens 24, so it is desirable to provide the convex lens 24 a little apart from the opening lower part.

Further, although the total reflection mirror 25 is used in the two-legged embodiment, it is not necessary if the photodetector 10 is placed above the convex lens 24. Further, if a half mirror is used instead of the total reflection mirror 25, detection by the photodetector 10 and surface observation with the naked eye can be performed simultaneously.

[Effects of the Invention] As explained above, the reflection type optical near-field scanning microscope according to the present invention is configured to receive the light from the light source reflected on the surface of the object to be measured by the optical lens and guide it to the photodetector. Therefore, there is no anisotropy in light reception, and reflected light that is reflected in all directions around the irradiation point can be received in the same direction with one lens. Therefore, compared to the case where multiple sensors are placed around the aperture, the structure is not only simpler and cheaper, but also increases the intensity of the received light, reduces the influence of shadows, and further improves measurement accuracy. be able to. Additionally, since it uses an optical lens, it can also be used for observation with the naked eye.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a reflective optical near-field scanning microscope according to the present invention, FIG. 2 is an enlarged sectional view of the aperture, and FIG. 3 is a conventional example of a reflective optical near-field scanning microscope. FIG. 1... Base, 2... Stage, 3... Measured object,
5... Light source, 6... Vertical adjustment device, 7... Aperture,
DESCRIPTION OF SYMBOLS 10... Photodetector, 22...-Light projection fiber, 24-- Convex lens, 24a
...-Light receiving surface, 25... Total reflection mirror, 26.27-...
Condenser lens, 28... insertion hole, 29... light shielding film.

Claims (1)

[Claims] a light source; an aperture having a diameter smaller than the wavelength of the light emitted from the light source and located close to the surface of the object to be inspected; a light projecting fiber that guides the light from the light source to the aperture; a photodetector that receives the light from the light source that passes through the aperture and is reflected by the object to be measured and converts it into an electrical signal; and a photodetector that collects the light that is reflected by the object to be measured and guides it to the photodetector. 1. A reflection type optical close-field scanning microscope, comprising: an optical lens, the optical lens being disposed close to and facing the object to be measured, and having the projection fiber 21 penetrated through the center thereof.