JP3765036B2 - Optical evaluation method and apparatus for measurement sample - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for optically evaluating a measurement sample using surface plasmon resonance by a total reflection attenuation method.
[0002]
[Prior art]
Surface plasmon resonance (SPR) is an electron density wave localized on a metal surface. The dispersion relation of SPR is related between the wave number k and the frequency ω, and is closely related to the material surface shape and composition. Knowing this SPR dispersion relationship will deepen the understanding of the material surface.
[0003]
However, since matching with SPR cannot be achieved even if light is directly irradiated, measurement is generally performed by the total reflection attenuation method (ATR method) using a prism. In the conventional ATR method, the dispersion relation of SPR is evaluated by dependence on angle (wave number) or wavelength (frequency). The ATR method is applied to the measurement of the film thickness and dielectric constant of thin films, or the measurement of physical properties of biological materials such as proteins, and includes SPR sensors and SPR microscopes.
[0004]
For example, the following technical documents can be listed.
[0005]
As described above, the conventional ATR method is generally a method of obtaining a signal change of reflected light as an angle dependency of SPR by rotating a prism.
[0006]
As a sensor,
[1] Kawada et al., Measurement and Control Vol. 36, no. 4, pp. 275-281 (1997)
[2] Kurosawa et al. Phys. Rev. B Vol. 33, no. 2, pp. 789-798 (1986)
[3] Dai et al. , J .; J. et al. Appl. Phys. , Vol. 32, Part 2, no. 9A, pp. L1269-L1272 (1993)
[4] Liberdi et al. , Thin Solid Films 333, pp. 82-87 (1998)
[5] JP-A-6-102184 [6] JP-A-7-208937
[7] Hickel et al. , J .; Appl. Phys. Vol. 67, no. 8, pp. 3572-3575 (1990)
[8] Berger et al. Rev. Sci. Instrum. Vol. 65, no. 9, pp. 2829-2836 (1994)
There is.
[0007]
There is also a method for detecting wavelength dependence using a spectroscope without rotating the prism.
[0008]
For example,
[9] Saito et al. , J .; J. et al. Appl. Phys. Vol. 33, Part 1, no. 11, pp. 6218-6219 (1994)
The inventors of the present application aim to observe thin film growth processes in real time and to apply in-process control in thin film characteristic measurement. For this purpose, a measurement system without a drive unit such as a prism or a diffraction grating rotating mechanism of a spectroscope is required.
[0009]
There is no report on a method for detecting the SPR using the ATR method and measuring the angular distribution and the wavelength distribution at the same time without using the drive unit. The inventors of the present application have made a previous presentation aiming at the angle / wavelength distribution in the ATR method. However, these are obtained by synthesizing the respective data and imaged as a two-dimensional image (spectral ATR image), and are not measured simultaneously.
[0010]
[10] [Academic presentation: Applied physics-related joint lecture, 45th (1998. 3), 47th (2000.3)]
In contrast, the present invention describes a method for simultaneously measuring spectral ATR images (spectral ATR method).
[0011]
Hereinafter, the conventional ATR method will be described.
[0012]
FIG. 6 is a configuration diagram of a measurement sample setting unit (part 1) for illustrating an example of wavelength dependency of SPR.
[0013]
As shown in this figure, P-polarized light (white light) 4 is incident on a measurement sample 5 (Ag film) installed on the bottom surface of a 45 ° quartz prism 6. It is assumed that an insulator film 5A is formed on the surface of the Ag film 5. The incident angle α is the incident angle to the prism, the normal is 0, and the prism bottom side is +. In FIG. 6, the incident angle is 46.5 ° (α = + 1.5 °), and the film thickness d _Ag of the Ag film 5 is 50 nm. In the air / insulator / silver / prism, the refractive indexes of air, insulator, and quartz prism are n _a = 1, n _d = 1.46, and n _p = 1.46, respectively.
[0014]
The wavelength and reflectivity in that case are shown in FIG. In FIG. 7, the vertical axis represents reflectance (%), and the horizontal axis represents wavelength (nm).
[0015]
FIG. 8 is a configuration diagram of a measurement sample setting unit (part 2) for illustrating an example of the angle dependency of SPR.
[0016]
As shown in this figure, a He—Ne laser 9 (wavelength 633 nm) is incident on a measurement sample (Ag film 5 and insulator 5A) placed on the bottom surface of the prism 6 at an incident angle of 35 ° to 105 ° (α = −10 °). Incident at ~ 60 °. Others are the same as FIG.
[0017]
The angle and reflectance in that case are shown in FIG. 9, where the vertical axis represents the reflectance (%) and the horizontal axis represents the incident angle (degrees). In the measurement of SPR by the conventional ATR method, evaluation based on such angle dependency or wavelength dependency is general.
[0018]
[Problems to be solved by the invention]
As described above, the conventional ATR method has a problem that the amount of information to be obtained is small by only evaluating the angle dependency or the wavelength dependency of SPR. In addition, in-process measurement requires a measurement system without a mechanical drive.
[0019]
The present invention eliminates the above-described problems and simultaneously obtains information on both the angle dependency and wavelength dependency of SPR, thereby providing a highly reliable optical measurement method and apparatus for a measurement sample with a large amount of information. The purpose is to provide.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, the present invention
[1] In the optical evaluation method of the measurement sample by the total reflection attenuation method, white light is incident on the prism to which the sample is attached at a wide range of incident angles, and a spectral slit is arranged in parallel with the direction of angular spread. After passing through, a two-dimensional photo detector is arranged at the image position to obtain a two-dimensional image showing the angle dependence and wavelength dependence of surface plasmon resonance at the same time.
[0021]
[2] In a measurement sample optical evaluation apparatus, a white light source, a prism with a measurement sample attached to the bottom, a spectral slit arranged in parallel with the angle spread direction of the reflected light, a spectroscope, and an image position And a two-dimensional photodetector.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0023]
FIG. 1 is a configuration diagram of a main part of an optical evaluation apparatus for a measurement sample showing an embodiment of the present invention.
[0024]
As shown in this figure, incident white light 4 is incident on a prism 6 to which a measurement sample 5 is attached at a wide range of incident angles, and the reflected light 8 is arranged with a spectral slit 11 parallel to the angular spread direction. After passing through the spectroscope 20, a two-dimensional photodetector 31 such as a CCD camera is disposed at the image position. Thereby, it is possible to acquire a two-dimensional image that simultaneously shows the angle dependency and wavelength dependency of SPR.
[0025]
In that case, the white light 4 incident on the prism 6 has a rectangular shape of several hundred μm × several mm, and the optical system is arranged so as to be a minute spot of 1 × 1 mm or less on the surface of the measurement sample 5. . A spectroscopic slit 11 is arranged in the spectroscope 20 in parallel with the angular spread direction of the reflected light 8 emitted from the prism 6, and the light that has passed through the spectroscopic slit 11 passes through the spectroscope 20, and then a two-dimensional photodetector (CCD). The camera) 31 detects the output. Since the incident light 4 has an angular spread, the output light also has an angular spread, and its angular dependence can be measured. In addition, since the light source is white, wavelength dependency is output by passing through the spectroscope 20. These can be simultaneously measured by the two-dimensional photodetector 31.
[0026]
In addition, the prism 6 can use a triangular prism shape or a semicircular sphere. Further, a transparent substrate is attached to the bottom surface of the prism 6 and a film is formed on the opposite side of the transparent substrate from the prism 6. That is, the thin film growth process can be monitored by using the transparent substrate as a part of the vacuum vessel.
[0027]
Here, FIG. 2 (a) shows a spectral ATR image for the measured measurement sample Ag film, FIG. 2 (b) shows a spectral ATR image for the measurement sample Au film, and FIG. 2 (c) shows a measurement sample Cu. Fig. 3 (a) shows a spectral ATR image of a non-oxidized Ag film, and Fig. 3 (b) shows a spectral ATR image of a partially oxidized Ag film. The images are respectively formed with P-polarized light shown in the upper part. Since S-polarized light shown in the lower part shows no absorption, it can be confirmed that it is SPR.
(Experimental example)
Here, a W lamp was used as the white light source, and the polarizing plate was adjusted to P-polarized light. The prism is made of quartz and has a triangular prism shape. As a measurement sample, the Ag film, Au film, and Cu film in FIG. 2 are different depending on the type of metal. Further, in FIG. 3, when the Ag film was not oxidized and partially oxidized, a difference due to oxidation was observed. The slit was about 0.1 mm × 10 mm in the experiment. The spectroscope was manufactured by Spectrometer Co., Ltd., M10-TP, and spectroscopic analysis was performed with 150 reflective gratings / mm. The CCD camera has a ½ inch type and 380,000 pixels, and as the acquired data, the light-absorbed portion appears black. The incident angle α is 0 on the prism incident surface, and + on the prism bottom surface side.
[0028]
FIG. 4 is a diagram showing the measurement results and calculation results of the Ag film, and it can be seen that the measurement results shown in FIG. 4A match the calculation results shown in FIG.
[0029]
FIG. 5 is an overall configuration diagram of an optical evaluation apparatus for a measurement sample according to another embodiment of the present invention.
[0030]
In this figure, 101 is a white light source, 102 is a polarizing plate, 103 is a first lens, 104 is white light, 105 is a measurement sample, 106 is a prism, 107 is a second lens, 108 is reflected light, and 110 is optical. System, 111 is a slit (lateral slit), 112 is a third lens, 113 is an image rotation optical element, 114 is a fourth lens, 115 is a spectral slit (longitudinal slit), 120 is a spectroscope (imaging type polychromator) ), 121 is a first mirror, 122 is a first concave mirror, 123 is a reflective grating (100 lines / mm), 124 is a second concave mirror, 125 is a second mirror, and 131 is a two-dimensional light detector. The device (CCD camera) 132 is a computer or monitor device for processing data from the two-dimensional photodetector.
[0031]
Although the image rotation optical element 113 is originally unnecessary, it is used to rotate the slit image of the reflected light by 90 ° when it is difficult to use the spectroscope 120 in a large position.
[0032]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0033]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0034]
(A) White light is incident on a prism to which a sample is attached at a wide range of incident angles, and a spectral slit is disposed in parallel with the direction of angular spread, thereby passing through a spectroscope to show angular dependence and wavelength dependence. An image (spectral ATR image) can be obtained.
[0035]
(B) Real-time information can be obtained by arranging a two-dimensional photodetector such as a CCD at the image position.
[0036]
(C) In addition to academic contributions such as elucidation of thin film growth processes and surface phenomena as measurement samples, industrial application to monitoring and control of film formation processes can be expected.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a main part of an optical evaluation apparatus for a measurement sample according to an embodiment of the present invention.
FIG. 2 is a diagram (part 1) illustrating image examples for various measurement samples;
FIG. 3 is a diagram (part 2) illustrating examples of images of various measurement samples;
FIG. 4 is a diagram showing calculation results and measurement results of a sample according to the present invention.
FIG. 5 is an overall configuration diagram of an optical evaluation apparatus for a measurement sample according to another embodiment of the present invention.
FIG. 6 is a configuration diagram of a measurement sample setting unit (part 1) for illustrating an example of wavelength dependency of SPR;
7 is a diagram showing the reflectance with respect to the wavelength of the measurement sample shown in FIG. 6. FIG.
FIG. 8 is a configuration diagram of a measurement sample setting unit (part 2) for illustrating an example of the SPR angle dependency;
FIG. 9 is a diagram showing the reflectance with respect to the incident angle of the measurement sample shown in FIG.
[Explanation of symbols]
4,104 Incident light (white light)
5 Sample (metal film)
5A Sample (insulator film)
6,106 Prism 8 Reflected light 9 Incident light (laser)
11 Spectral slit 20, 120 Spectroscope (imaging type polychromator)
31, 131 Two-dimensional photodetector (CCD camera)
101 White light source 102 Polarizing plate 103 First lens 105 Measurement sample 107 Second lens 108 Reflected light 110 Optical system 111 Slit (lateral slit)
112 Third lens 113 Image rotation optical element 114 Fourth lens 115 Spectral slit (vertical slit)
121 First mirror 122 First concave mirror 123 Reflective grating (100 / mm)
124 Second concave mirror 125 Second mirror 132 Computer or monitor device

Claims (2)

In the total reflection attenuation method, white light is incident on a prism to which a sample is attached at a wide range of incident angles, a spectral slit is arranged parallel to the direction of angular spread, and the two-dimensional light is projected to the image position. An optical evaluation method for a measurement sample, characterized in that a two-dimensional image showing the angle dependence and wavelength dependence of surface plasmon resonance is simultaneously obtained by arranging a detector. (A) a white light source;
(B) a prism with a measurement sample attached to the bottom surface;
(C) a spectral slit disposed in parallel with the angular spread direction of the reflected light;
(D) a spectrometer;
(E) A measurement sample optical evaluation apparatus comprising a two-dimensional photodetector arranged at an image position.

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