JP4418898B2 - Preparation method of probe used for scanning probe excitation optical measurement - Google Patents

Description

The present invention, a scanning probe microscope or the like measuring equipment, such as in strain distribution measuring apparatus of the silicon substrate, to a method for manufacturing a probe for use in scanning probe excitation optical measurement.

  In recent years, research and development in the fields of nanostructures and nanodevices are rapidly progressing, and optical measurement techniques with high resolution are required in these fields for the purpose of characterizing various samples. For example, in a silicon device, since strain entering silicon has a great influence on device characteristics such as mobility, it is very important to know the spatial distribution of strain in a sample with high resolution. Conventionally, a method using Raman measurement is known as one means for measuring the distortion. The principle of this Raman measurement is that the peak position of the Raman signal shifts according to the distortion, so that if the mapping of the peak position of the Raman signal is taken, the distribution of the distortion can be known.

  Conventionally, one of the techniques proposed in the field of Raman spectroscopy is measurement using a metal AFM (Atomic Force Microscope) probe. According to this method, the local electric field at the tip of the metal probe enhances the Raman signal only at the vicinity of the tip of the probe, so that the spatial resolution is improved. In this method, a great enhancement effect can be obtained when two metals are brought close to each other with a very small gap and a sample to be measured is placed between them. Therefore, although some results have been obtained in the measurement of molecules and ultrafine particles, it cannot be applied to the measurement of opaque solids. In solids, it is impossible to place a sample to be measured between two metals as described above, and the far field signal excited at a position away from the metal probe has a strong and weak proximity. This is because the signal of the field is obscured.

  In order to solve such a problem, the applicant of the present invention first made a measurement with a far-field signal obscuring a near-field signal in a scanning probe excitation optical measurement using a metal probe. An application was made to solve the problem of reducing the spatial resolution (Japanese Patent Application No. 2003-313901). Excitation light is incident on the single crystal substrate sample in the polarization direction prohibited by the selection rule. Here, when a metal probe is placed on the irradiation part, the excitation light is scattered by the probe and the polarization is canceled, so the selection rule is relaxed and Raman scattering is activated, and the surface plasmon induced at the probe tip is further reduced. The strength is also increased by the electric field. That is, a Raman signal from only the probe tip proximity portion is detected, and high resolution is realized. However, when a probe made entirely of metal is used, the excitation light is scattered at portions other than the tip of the probe, and the selection rule is relaxed at portions other than the tip, thereby reducing the spatial resolution.

Therefore, it is necessary to produce a probe in which only the tip portion scatters excitation light. As the method, a method is used in which the raw material liquid is transported to the tip of the probe through the inside of a capillary-like quartz probe and reacted at the tip to precipitate silver. In this method, a special quartz probe having two capillaries must be used, and the reaction is difficult to control. In addition, there is known a method of removing unnecessary portions by FIB (focused ion beam device) after depositing metal on the entire surface of the probe (see Patent Document 1), but a special device called FIB must be used. There was a problem that the throughput was very low.
JP 2004-101425 A

  Therefore, the present invention aims to produce a probe with high throughput, in which only the tip portion scatters excitation light in order to detect a Raman signal only from the probe tip proximity portion and realize high resolution. Yes.

The method for producing a probe used for the scanning probe excitation optical measurement of the present invention is a substance having a refractive index different from that of a substrate that becomes insoluble in a developer when irradiated with actinic rays on the probe substrate tip made of a material transparent to excitation light. Alternatively, a substance on which a metal is deposited is coated, only the tip portion of the coated probe is irradiated with actinic rays, developed, and the substance or metal having a different refractive index is supported only on the tip portion.

In addition, a method for producing a probe used for scanning probe excitation optical measurement according to the present invention includes a probe base made of a material transparent to excitation light, dipped in a resin solution, pulled up, and dried at the tip formed after drying. After the metal is attached to the part not covered with the resin, the metal is supported on the tip part produced by removing the resin of the other part with a solvent.

  According to the present invention, it is possible to manufacture a probe that can detect a Raman signal only from a portion near the probe tip, realize high resolution, and scatter excitation light only at the tip portion, with ease and high throughput. Enable.

  In order to produce a probe (probe) in which only the tip part scatters the excitation light, the tip part is made of a material having a large scattering ability with respect to the excitation light, and the other part is a material having a low scattering ability. What is necessary is just to produce the probe comprised by these. Specifically, a structure in which a metal or a substance having a refractive index different from that of the probe base is supported on the tip of a probe made of a material transparent to excitation light such as quartz may be manufactured.

  For this purpose, the probe is coated with a substance having a different refractive index or a metal depositing substance that becomes insoluble in the developer when irradiated with an electron beam or light (hereinafter abbreviated as actinic light), and only the tip is irradiated with actinic light. Then, if necessary, development is performed, and the probe or the reaction product can be supported on the tip portion to produce a probe. For example, a probe in which silver is supported only on the tip portion can be produced by coating the tip portion of the probe with silver halide or silver oxide and irradiating with an electron beam or light.

  Evanescent light can be used as one method of irradiating only the tip with light. As shown in FIG. 1, when light is incident on a transparent substrate such as quartz, if it is incident so as to be totally reflected inside the substrate, the light is reflected on the nanometer order from the inside of the substrate to the outside in the totally reflected portion. Therefore, if a probe base is applied to the exuded light, only a very narrow region can be irradiated with light. This method has an advantage that a large number of probes can be irradiated with light at one time because it is not necessary to squeeze light individually. In addition, it is possible to accurately irradiate the portion of the probe tip that contacts the sample surface. This point is extremely useful when the produced probe is used as an AFM probe.

  In addition, in order to support metals and substances with different refractive indexes on the tip of the probe, a positive resist is coated on the probe base, actinic rays are irradiated and developed only on the tip, and a window is opened at the tip. Metal fine particles can be attached to the portion. That is, as shown in FIG. 2, only the probe tip coated with a positive resist is irradiated with light or an electron beam (EB) (1), and the resist only on the probe tip is removed by development (2). A probe carrying the metal fine particles at the tip is prepared by dipping in a solution containing the metal fine particles and attaching the metal fine particles to the tip.

  In addition, before the metal fine particles are carried on the tip, a substance that easily adsorbs the metal fine particles is attached only to the tip portion from which the resist has been removed after development (3) (4). The material of the probe base is, for example, quartz, and a gold colloid solution can be used as a solution containing metal fine particles, and aminosilane can be used as a substance that easily attaches metal fine particles. In this case, the gold colloid is supported on the probe tip via aminosilane (6) by being immersed in the gold colloid solution (5). When PMMA is removed, gold particles are supported on the tip (7).

  Further, as shown in FIG. 3, when the probe base is immersed in a resin solution such as PMMA (polymethyl methacrylate) and slowly pulled up, the sharply sharpened tip portion has poor wettability. Not coated. Therefore, metal can be attached only to this portion. Immerse the probe base in the resin solution (A), pull it up (B), attach a metal to the portion of the tip that is formed after drying that is not covered with resin (C), and then use the solvent for the other portion of the resin. A metal is carried on the tip part produced by removing (D). Vacuum deposition can be used as a method for attaching the metal, and the metal fine particles can be supported on the tip after attaching a substance that is easily adsorbed by the metal fine particles. PMMA can be used as the resin, aminosilane can be used as the substance that can easily adsorb the metal fine particles, and gold colloid can be used as the metal fine particles.

  FIG. 4 is a diagram for explaining another method for supporting a metal on the tip of the probe. As shown in the figure, when a resist is applied to the tip of a quartz fiber probe and light is incident on the fiber, the refractive index of the resist is generally larger than that of quartz. Leaks from the inside of the fiber to the outside (A). Therefore, light does not reach the tip part having a diameter shorter than the wavelength of light. Therefore, if a positive resist is applied, the resist remains only at the tip after development. If a negative resist is applied, a window opens at the tip after development (B). By depositing metal by vapor deposition or the like (C), the metal can be attached only to the probe tip. Yes (D). FIG. 4 shows an example in which a negative resist is applied.

  AgCl is deposited as a photosensitive material to a thickness of 100 nm on a quartz fiber AFM probe (probe) substrate. Next, the probe base is mounted on an AFM (atomic force microscope), the AFM is operated, and the probe base is brought into contact with a quartz plate (transparent substrate). Next, as shown in FIG. 1, using a quartz right angle prism, ultraviolet light emitted from an argon laser and having an output of 10 mW and a wavelength of 364 nm is incident on the quartz plate. The tip of the probe is brought into contact with the substrate surface where the ultraviolet light is totally reflected, and the substrate is exposed for 30 minutes with evanescent light that oozes out on the quartz plate surface. Then, immerse in photographic developer (for example, Fuji Film: Super Fujidol L, reducing agent) and fixer (Fuji Film: Super Fujix, the main component is sodium thiosulfate) for 10 minutes each and then rinse with pure water To do. When the tip portion was observed with an electron microscope, it was observed that silver particles of about 50 nm were supported on the tip.

AgCl is deposited to 100 nm on a quartz fiber AFM probe substrate. Next, 1 C / cm ^{2 was} irradiated to the region of the probe tip 50 nm with an electron beam. After that, the film is immersed in a photographic developer (Fuji Film: Super Fuji Doll L) and a fixer (Fuji Film: Super Fujix) for 10 minutes, respectively, and washed with pure water. When the tip portion was observed with an electron microscope, it was observed that silver particles of about 50 nm were supported on the tip.

PMMA is applied to a quartz fiber AFM probe substrate to a thickness of 100 nm and dried. Next, an electron beam was irradiated to the area of the probe tip 50 nm at 0.01 C / cm ² . After development with methyl isobutyl ketone, it is immersed in an aminosilane aqueous solution for 5 minutes, and then immersed in a solution in which a colloidal 50 nm diameter gold colloid is dispersed in citric acid for 1 hour. As shown in FIG. 2, the colloidal gold is supported on the probe tip via aminosilane. After removing PMMA with acetone, the tip portion was observed with an electron microscope, and it was observed that 50 nm gold particles were supported on the tip.

  As shown in FIG. 3, the quartz fiber AFM probe substrate is immersed in an MCA (1-acetoxy-2-methoxyethane) solution of PMMA (A) and slowly pulled up and dried (B). Next, after washing and drying with isopropyl alcohol for 1 minute, platinum is deposited to 50 nm by electron beam heating vacuum deposition (C). After lift-off using acetone (D), the tip portion was observed with an electron microscope, and it was observed that platinum was deposited only on the tip portion.

  The quartz fiber AFM probe substrate is immersed in an MCA solution of PMMA and slowly pulled up and dried. Next, it is washed with isopropyl alcohol for 1 minute, immersed in an aminosilane aqueous solution for 5 minutes, and then immersed in a solution of 50 nm diameter gold colloid dispersed in citric acid for 1 hour. After removing PMMA with acetone, the tip portion was observed with an electron microscope, and it was observed that 50 nm gold particles were supported on the tip.

  As shown in Fig. 4, a negative resist SAL600 (Shipley) was applied to a quartz fiber probe, pre-baked at 100 ° C for 1 minute, and an argon laser beam with a power of 1 mW and a wavelength of 364 nm was incident on the fiber for 30 minutes. Exposed. After post-baking at 115 ° C. for 1 minute, after developing for 10 minutes with a developer (TMAH, tetramethylammonium hydroxide aqueous solution 2.38%), silver was deposited to 50 nm by vacuum evaporation. Observation with an electron microscope after lift-off with acetone confirmed that silver had adhered to a region having a probe tip diameter of about 50 nm.

It is a figure which illustrates the method of irradiating only a probe front-end | tip part with a light ray. It is a figure which shows the probe preparation example (1). It is a figure which shows the probe preparation example (2). It is a figure which shows the probe preparation example (3).

Claims (8)

In a method for producing a probe used for scanning probe excitation optical measurement,
The tip of the probe base made of a material that is transparent to the excitation light is coated with a substance that has a refractive index that is insoluble in the developer when irradiated with actinic light, or a substance that deposits a metal.
Irradiate only the tip of the coated probe with actinic rays,
A method for producing a probe, which is developed and loaded with a substance or metal having a refractive index different from that of the probe substrate only at the tip portion. The coating substances on the probe base tip, a silver halide, and a metal wherein supported only on the probe tip portion The method for manufacturing a probe according to claim 1 is silver. Irradiation of the active rays, the light incident to the total reflection at the transparent substrate in, by approaching the probe tip portion to the transparent substrate surface, according to claim 1 for irradiating light only to the probe distal end portion Probe fabrication method. In a method for producing a probe used for scanning probe excitation optical measurement,
A probe base made of a material transparent to excitation light is immersed in a resin solution, pulled up,
A method for producing a probe in which a metal is supported on a tip portion produced by attaching a metal to a portion of the tip portion formed after drying that is not covered with a resin and then removing the resin in other portions with a solvent. The method for producing a probe according to claim 4 , wherein the metal is attached by vacuum deposition. 5. The method for producing a probe according to claim 4 , wherein the metal is attached by attaching a substance that can easily adsorb metal fine particles, and then supporting the metal fine particles on the tip portion. The method for producing a probe according to claim 4 , wherein PMMA is used as the resin. The method for producing a probe according to claim 6 , wherein aminosilane is used as the substance that the metal fine particles are likely to adsorb, and gold colloid is used as the metal fine particles.

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