JP3290684B2 - Ellipsometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ellipsometer for measuring a change in film thickness due to, for example, an antibody and an antigen on an immune support by ellipsometry.

[0002]

2. Description of the Related Art In the ellipsometry, the change in the state of polarization when light is reflected on the surface of an object is observed to determine the optical constant of the object itself, or the thickness and optical constant of a thin film attached to the surface. Is the way. Recently, this ellipsometry has been applied to the biophysics field, and has also been applied to the measurement of the thickness of proteins used for antigen-antibody reactions, the measurement of protein adsorption membranes, and the study of plasma coagulation. It has become so.

[0003] Techniques for measuring the thickness of a protein used in the antigen-antibody reaction include, for example, A. Rothen and C. Mat.
hot.Helvetica Chimica Aacta, Vol.54 (1971) Immunological Reactios Carried out at a Liquid-Sol
The technology disclosed in id Interface is known.
Techniques related to the measurement of the protein adsorption film include:
ULF JOENSSON, M.MALMQVIST, INGER ROENNBERG. Journal
of Colloid and Interface Science.Vol.103, No.2,198
5 Adsorption of Immunoglobulin G, ProteinA, and Fibr
onectin in the Submonolayer Region Evaluated by a
Combined Study of Ellipsometry and Radiotracer Tec
hniqs and A.Rothen, C.Mathot.Surface Chemistr
y of BiologicalSystems.1970 IMMUNOLOGICAL REACTIO
NS CARRIED OUT AT A LIQUID-SOLID INTERFACE WITH TH
The technology disclosed in E HELP OF A WEAK ELECTRIC CURRENT is known. In addition, technologies relating to plasma coagulation include L. VROMAN AND ALADAMS. SURFACE SCIENCE
16 (1969) FINDINGS WITH THE RECORDING ELLIPSOMETER
SUGGESTING RAPIDEXCHANGE OF SPECIFIC PLASMA PROTEI
The technology disclosed in NS AT LIQUID / SOLID INTERFACES is known. In ellipsometry, the refractive index

[0004]

(Equation 1) Thickness d, refractive index on the substrate surface with

[0005]

(Equation 2) (See FIG. 9), when linearly polarized light is incident on the thin film at an incident angle φ, P and S
The amplitude reflectance of the polarization component is

[0006]

(Equation 3)

[0007] Where r _1P , r _2P , r _1s ,
r _2S is P, S in vacuum-film and film-substrate, respectively.
In the amplitude reflectance of the component, δ is a phase difference generated in the film.
This δ is

[0008]

(Equation 4) Given by Here, φ _f is the refraction angle in the film,

[0009]

(Equation 5) Holds. At this time,

[0010]

(Equation 6) And tanφ (amplitude reflectance ratio) and iΔ (phase difference) are measured by ellipsometry.

There are various methods for performing ellipsometry in the past, but for example, an ellipsometer shown in FIG. 10 is used. This device uses Ki using Faraday cell.
ng of the photoelectric polarization analyzer, showing the arrangement of the measurement method with the fixed incident angle. This device allows the polarizer and analyzer to be rotated with a precision equivalent to ± 0.002 ° by a stepping motor or the like, and furthermore, modulates the polarization state by the Faraday effect and makes it easy to find the extinction position. ing. As described above, by obtaining the extinction condition using the ellipsometer shown in FIG. 10, it is possible to know the thickness and the optical constant of the thin film attached to the sample surface.

[0012]

However, in the conventional apparatus, as shown in FIG. 10, a Faraday cell must be provided, or a mechanism for rotating both the polarizer and the analyzer with high accuracy must be provided. The disadvantage is that it is inferior in convenience, for example. When an optical system provided in a conventional apparatus is to be used for an immunoassay apparatus described in Japanese Patent Application No. 3-080124 (Japanese Patent Application Laid-Open No. Hei 4-305051), the complexity of the apparatus and This leads to an increase in the size of the optical system. As a result, the optical system used in the conventional automatic analyzer greatly hinders the automation of the analyzer.

An object of the present invention is to provide a compact and simple ellipsometer for measuring a change in film thickness due to, for example, an antibody and an antigen on an immune support by ellipsometry.

[0014]

In order to solve the above-mentioned problems, an ellipsometer according to the present invention comprises: an optical element which also serves as a polarizer and an analyzer for causing polarized light to enter a part of a sample section; The phase difference before and after each of the p-polarized light and the s-polarized light of the reflected light reflected by a part of the sample is set to π, and the reflected light is made incident on the other part different from the part of the sample part. The sample includes an optical system including a １ ／ λ prism that causes light reflected by the other part to enter the optical element, and a light detection unit that detects light incident on the optical element. parts are Ri Majiwa at 45 ° to the optical axis plane of the optical system, having an axis positioned to divide them between the portion and the other portion, movable along this axis It is characterized by having.

[0015]

An optical element is provided with the functions of a polarizer and an analyzer to constitute an optical system of a polarization analyzer, and a sample support suitable for the optical system is provided.

[0016]

Embodiments of the present invention will be described below. Since the ellipsometer of the present invention is characterized by the arrangement of the optical system and the sample support, these parts will be described in detail.

The polarization analyzer of the present invention is configured as shown in FIG. Reference numeral 1 in this figure polarizer, a polarizing beam splitter which also serves as an analyzer, numeral 3 sample holder suitable for this optical system (sample portion), reference numeral 7 denotes a lambda / 2 prisms. The sample section 3 is movable on a stage (not shown) so that the axis of the sample is 4 with respect to the optical axis plane .
It is tilted and supported by 5 ° (see FIG. 6). A sample whose actual film thickness is to be measured is formed on the sample support.

When light emitted from a light source (not shown) and incident on the polarization beam splitter 1 is unpolarized, the light source is fixed and only the polarization beam splitter 1 rotates. Is designed to rotate together.

FIG. 2 shows the configuration of the λ / 2 prism 7 and the path of light in the λ / 2 prism 7. The λ / 2 prism 7 has such a polarization characteristic that the light incident from the point A is reflected four times in the prism, the phase is advanced by π, and the light is emitted from the point B. Hereinafter, the refractive index of the λ / 2 prism 7 will be described with reference to FIG. 3 and the following equation.

[0020]

(Equation 7) Therefore,

[0021]

(Equation 8) In this case, since the λ / 2 prism reflects four times and the phase advances by π, the phase change is π / 4 by one refraction.
Therefore, from (δ _p −δ _s ) = π / 4

[0022]

(Equation 9) Becomes Since φ = π / 4, n12 that satisfies the above equation
Is calculated, the refractive index of the λ / 2 prism 7 can be calculated. Here, the λ / 2 prism is an optical element that advances the phase of incident light by π by four reflections.

Next, the entire light path of the optical system will be described. The linearly polarized light that has passed through the polarization beam splitter 1 is reflected by the sample unit 3 to become elliptically polarized light,
/ 2 prism 7. In this case, the polarization angle of the linearly polarized light passing through the polarization beam splitter 1 is φ, and the light reflected by the sample unit 3 is elliptically polarized light having a phase difference δ. FIG. 4 shows the relationship between the polarization angle and the phase difference at this time for the electric field vector component.

Here, the change of the polarization angle at each point is illustrated. Since the λ / 2 prism 7 is arranged at an angle of 45 ° with respect to the optical axis of the light reflected by the sample unit 3, the polarized light incident on the λ / 2 prism 7 as shown in FIG. FIG.
As shown in (B), the electric field vector changes from K to K1 and is emitted. At this time, the polarization angle is φ + π / 4, and the phase is δ + π, which is linearly polarized light. When this linearly polarized light is reflected again by the sample section 3, the polarization angle changes to elliptically polarized light having a phase angle of π / 4-φ and a phase difference of π. This elliptically polarized light enters the polarization beam splitter 1.

Next, the arrangement state of the sample section 3 and the position of light incident on the sample section 3 will be described in detail again with reference to FIG. The sample section 3 receives light from the polarizing beam splitter 1 side and light from the λ / 2 prism 7 side.
Are arranged to be incident on one side surface 3a and the other side surface 3b, respectively. Further, the one side surface 3a and the other side surface 3b are symmetric about the central axis M of the sample section 3.
As described above, the center axis M is 45 ° with respect to the optical axis plane .
The sample unit 3 is supported by a stage (not shown) movably along the central axis M.

The light that has passed through the polarizing beam splitter 1 is reflected by one side surface (a part) 3 a of the sample section 3 and enters the point A of the λ / 2 prism 7. The light incident from the point A is repeatedly reflected four times in the prism as described above, is emitted from the point B, is reflected on the other side surface (other part) 3b of the sample unit 3, and is incident on the polarization beam splitter 1. Then, the output light from the polarizing beam splitter 1 is detected by the photoelectric detector 10 or a change in the amount of light can be visually observed.

The structure of the immunological support suitable for the above-mentioned constitution,
And a measuring method thereof will be described. A silicon oxide film having a thickness of 1000 to 1900 angstroms was formed on a silicon single crystal (100 planes in the orientation plane).
Sample portion 3 was prepared by silane treatment and immobilization of the antibody by the method disclosed in No. 0124. FIG. 7 shows the structure of the sample section 3. 7, reference numeral 20 denotes a Si single crystal substrate, reference numeral 21 denotes an SiO ₂ film, reference numeral 22 denotes a silane coupling agent, and reference numeral 23 denotes an antibody.

FIG. 8A is a plan view of the sample section 3. The sample section 3 is arranged as shown in FIG. One side surface 3a of the sample portion is a surface 25 on which only the antibody is immobilized as a reference, and the other side surface 3b is divided into three regions 26 to 28. Reference numeral 26 indicates a portion where the same concentration of the antigen is reacted with the same antibody as the surface 25, and reference numerals 27 and 28 indicate portions where the actual sample was sensitized.

The method of immunoassay using the above-mentioned sample section is described below. (A). The sample section 3 shown in FIG. 8A is arranged as shown in FIG. (B). To the portions indicated by reference numerals 26, 27, and 28 in the sample section 3, the required amounts of the control solution and the specimen having the lowest concentration are respectively dropped. The reaction time is set to the optimal time depending on the measurement item. (C). After the completion of the reaction, the portions indicated by reference numerals 26, 27 and 28 are washed with distilled water, and the surface moisture is blown off with N ₂ gas or the like. (D). When the light source to be used is non-polarized light, the polarization beam splitter 1 is rotated, and the polarization angle of extinction is obtained by the photoelectric detector 10. At this time, it should be noted that the sample section 3 is positioned so that only the sections 25 and 26 of the sample section are irradiated with the light from the polarizing beam splitter 1 and the light from the λ / 2 prism 7. It is to be. (E). The operation performed in (d) corresponds to zero adjustment. (F). Next, the position of the sample unit 3 is shifted so that the light from the polarization beam splitter 1 and the light from the λ / 2 prism 7 are irradiated only to the portions 25 and 27 of the sample unit 3. Read the output. The same operation is performed on the portions 25 and 28 of the sample section 3. (G). From the calibration curve prepared in advance, the concentration of the sample dropped on 27 and 28 of the sample section 3 can be detected.

FIG. 8B shows the structure of the immune support.
It is also possible to configure as shown in FIG. Reference numeral 40 denotes a portion for sensitizing the specimen, and reference numeral 31 denotes a surface on which only the antibody is immobilized. One side 3a of the sample portion is divided into five regions 32 to 36 except for the surface 31 on which only the antibody is immobilized. The number of divided regions is arbitrary, and is five in this embodiment. Further, in the drawing, each region is divided into squares for easy understanding, but in actuality, each region is divided into an optimal state according to the position where light enters and the amount of movement of the sample unit 3. . After immobilizing the same antibody, these regions 32 to 36 have known and different antigen concentrations.
This is the site where the seed control solution is sensitized.

The measurement of the antigen concentration in the portion 40 where the sample has been sensitized is performed by the following procedure. First, zero adjustment is performed using the surface 31 on which only the antibody on one side 3a of the sample section 3 is immobilized and the surface 31 on which only the antibody on the other side 3b is immobilized. Next, while shifting the sample portion 3 in the M-axis direction, the region 32 and the portion 40 where the sample was sensitized,
, And the portion 40 where the sample was sensitized, and subsequently the region 34 and the portion 40 where the sample was sensitized.

Since the antigen concentration of each of the regions 32 to 36 is known, the regions 32 to 36 serve as a calibration curve. For example, if the output becomes zero when photometry is performed using the region 34, the antigen concentration in the portion 40 where the sample is sensitized is equal to the antigen concentration in the region 34. The use of such an immune support structure eliminates the need for a calibration curve. Of course, one side 3a of the sample part
Is further divided into a larger number of regions, it is possible to detect a more accurate density.

[0033]

As described in the foregoing, the polarization analyzer of the present invention uses an optical system having a polarization beam splitter which also serves as a polarizer and an analyzer, this result, simple and compact ellipsometer Can be realized.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an optical system in an ellipsometer of the present invention.

FIG. 2 is a diagram illustrating a detailed configuration of a λ / 2 prism in the optical system of FIG. 1;

FIG. 3 is an explanatory diagram for calculating a refractive index of a λ / 2 prism.

FIG. 4 illustrates a relationship between a polarization angle and a phase difference of light reflected by a sample unit in the optical system of FIG. 1 with respect to an electric field vector component.

5 includes (A) and (B), in the optical system of FIG. 1, respectively, the polarization angle when the reflected light from the sample part enters, and the polarization angle of the light passing through the λ / 2 prism. It is shown.

FIG. 6 is a diagram schematically showing a light path in the optical system of FIG. 1;

FIG. 7 is a sectional view of a sample support used in the optical system of FIG. 1;

8A and 8B are plan views showing a configuration of a sample support suitable for the optical system of FIG. 1, wherein FIG. 8A is a diagram showing a first embodiment, and FIG. 8B is a diagram showing a second embodiment.

FIG. 9: When there is an isotropic homogeneous thin film on a substrate,
It is a figure which shows the path | route of the light when linearly polarized light enters this.

FIG. 10 is a diagram showing a configuration of a conventional polarization analyzer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polarization beam splitter, 3 ... Sample part, 7 ... λ / 2 prism, 10 ... Photoelectric detector.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-151717 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21 / 17-21/61 G01J 4/00-4/04 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (2)

(57) [Claims] An optical element which also serves as a polarizer and an analyzer for causing polarized light to be incident on a part of a sample part; and p-polarized light and s of reflected light reflected on a part of the sample part.
The phase difference between before and after each polarized light is set to π, and the reflected light is made incident on another part different from the part of the sample part, and the light reflected on this other part is made incident on the optical element. A 1 / 2λ prism, a light detection unit that detects light incident on the optical element,
Has an optical system having a, the sample portion, said Ri exchange <br/> I at 45 ° to the optical axis plane of the optical system, so as to divide them between the portion and the other portion having an axis which is located in, ellipsometer, characterized in that is movable along this axis. 2. The same or different samples are formed on the sample stage in a region where light from the optical element is incident and in a region where light from the 1 / 2λ prism is incident. 2. The method according to claim 1, wherein
Ellipsometer described in 1.