JP3181655B2 - Optical system and sample support in 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 which makes it possible to measure a change in film thickness due to, for example, an antibody and an antigen on an immune support by an ellipsometer, and more particularly to an optical system used in the ellipsometer. Further, the present invention relates to a sample support suitable for the optical system.

[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, which is a prior application, the complexity of the apparatus and the size of the optical system are increased. I will. As a result, the optical system used in the conventional automatic analyzer greatly hinders the automation of the analyzer.

According to the present invention, there is provided an ellipsometer provided with a small and simple optical system for measuring a change in film thickness caused by, for example, an antibody and an antigen on an immune support by an ellipsometer.
It is another object of the present invention to provide a sample support structure suitable for this optical system.

[0014]

In order to solve the above-mentioned problems, an optical system in a polarization analyzer of the present invention serves as a polarizer and an analyzer, and makes a first polarized light incident on a part of a sample.
And the p of the reflected light reflected by a part of the sample
It has a shape such that the phase difference between the polarized light and the s-polarized light is not changed, and the reflected light is incident on a portion different from a part of the sample, and the light reflected on the different portion is the first light.
A second optical element to be incident on the optical element, and an optical axis 1/2 provided on the optical axis connecting the sample and the second optical element and arranged at 45 ° with respect to the p direction or the s direction of polarized light. 4
It is characterized by having a λ plate and light detecting means for detecting light incident on the first optical element.

Further, in order to be suitable for this optical system, the sample support is divided into a region into which light from the first optical element is incident and a region into which light from the second optical element is incident. And a sample is formed.

[0016]

The optical element of the ellipsometer is constructed by providing one optical element with the functions of a polarizer and an analyzer, and a sample suitable for the optical system is formed.

[0017]

Embodiments of the present invention will be described below. Since the ellipsometer of the present invention is characterized by an optical system, the optical system will be described in detail.

The polarization analyzer of the present invention has an optical system as shown in FIG. This optical system includes a polarizing beam splitter 1 also serving as a polarizer and an analyzer, a 波長 wavelength plate 5, and a non-polarizing prism 7. Reference numeral 3 denotes a sample support (sample portion) suitable for the optical system, and the sample portion is movably supported on a stage (not shown).

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, and when light is polarized, the light source and the polarization beam splitter 1 are rotated. Is designed to rotate together. The 波長 wavelength plate 5 is fixed on the front surface of the non-polarizing prism 7 so that the azimuth angle is 45 ° with respect to the p or s direction.

FIG. 2 shows a configuration of the non-polarizing prism 7 and a light path in the non-polarizing prism 7. As shown in FIG. 2, the non-polarizing prism 7 has a shape such that light incident from point A is reflected four times in the prism. In this case, the p-polarized light incident from the point A is reflected on the reflection surface a to become s-polarized light, the polarization components are kept as they are on the next reflection surfaces b and c, and become p-polarized light on the next reflection surface d. From the point B. That is, the polarization state is p-s along the path of the reflecting surface abcd.
−sp. Similarly, the s-polarized light incident from point A is
In the path of the reflecting surface abcd, the path becomes spps in order, and the phase difference between the two is preserved. As described above, the non-polarizing prism 7 is configured to emit the light incident at the point A from the position B different from the point A without changing the polarization characteristics. Next, the entire light path of the optical system will be described.

The linearly polarized light that has passed through the polarizing beam splitter 1 is reflected by the sample unit 3 to become elliptically polarized light.
The light enters the four-wavelength plate 5. 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. 3 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. When the reflected light from the sample unit 3 is incident on the quarter-wave plate 5 at an angle of 45 ° (the angle formed by the main section of the quarter-wave plate and the vibration plane of the electric field vector), the polarization angle becomes as shown in FIG. As shown by φ, it becomes φ + π / 4. At this time, the phase changes to δ + π / 2. Next, the light passes through the non-polarizing prism 7 and again becomes 1 /
The light that has passed through the four-wavelength plate 5 becomes elliptically polarized light as shown in FIG. At this time, the polarization angle is φ + π / 2, and the phase changes to δ + π. When this elliptically polarized light is reflected again by the sample section 3, it is converted into linearly polarized light. At this time, the polarization angle changes to π / 2−φ, and the phase difference changes to π.

FIG. 5 shows a light path from the light emitted from the light source to the polarizing beam splitter 1 and returning to the polarizing beam splitter 1 again through the sample unit 3 and the non-polarizing prism 7. This is easily shown. Light passing through the polarizing beam splitter 1 is applied to one side 3 of the sample section 3.
The light is reflected by a and enters the point A of the non-polarizing prism 7. A
The light incident at the point is repeatedly reflected four times in the prism as described above, is emitted from the point B, is reflected by the other side surface 3b of the sample unit 3, and is incident on the polarization beam splitter 1 again. The sample section 3 is arranged such that light from the polarizing beam splitter 1 side and light from the non-polarizing prism 7 side are incident on one side 3a and the other side 3b of the sample section 3, respectively. The one side surface 3a and the other side surface 3b are symmetric about the central axis M of the sample section 3. The output light from the polarization beam splitter 1 is detected by the photoelectric detector 10 or
Alternatively, a change in the amount of light can be visually observed.

As described above, the reflected light from the sample section 3
By making the light incident on the 波長 wavelength plate 5 at an angle of 45 °,
The extinction condition can be obtained in the polarization beam splitter 1. Here, the reflected light from the sample part 3 is incident on the quarter-wave plate 5 at an angle of 45 ° (the angle formed by the main section of the quarter-wave plate and the vibration plane of the electric field vector) so as to prevent the reflected light.
It is assumed that the wave plate 5 has been arranged. Then, FIG.
The changes in the polarization angles shown in FIGS.
(A) and (B). That is, the light that has passed through the quarter-wave plate 5 again has a polarization angle like K in FIG. 6B, and thus cannot be extinguished in the polarization beam splitter 1. Next, the structure of the immune support suitable for the above-described optical system and a method for measuring the same will be described.

A silicon oxide film having a film thickness of 1000 to 1900 angstroms (hereinafter referred to as A) is formed on a silicon single crystal (having 100 orientation planes).
Sample 3 was prepared by silane treatment and immobilization of the antibody by the method presented in No. 4. 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.

An immunoassay method using the above-described 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 unit 3 is positioned so that only the portions 25 and 26 of the sample unit are irradiated with the light from the polarizing beam splitter 1 and the light from the non-polarizing prism 7. That is. (E). The operation performed in (d) corresponds to zero adjustment. (F). Next, the position of the sample unit 3 is shifted so that only the portions 25 and 27 of the sample unit 3 are irradiated with the light from the polarizing beam splitter 1 and the light from the non-polarizing prism 7, and the output of the photoelectric detector 10 is changed. Read. 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. Each of the regions 32 to 36 is a site where the same antibody is immobilized and then sensitized with five kinds of control solutions having known and different antigen concentrations.

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.

[0031]

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 showing a detailed configuration of a non-polarizing prism in the optical system of FIG.

FIG. 3 is a diagram illustrating a relationship between a polarization angle and a phase difference of light reflected by a sample unit with respect to an electric field vector component in the optical system of FIG. 1;

FIG. 4 includes (A) and (B), and in the optical system of FIG. 1, the quarter-wave plate has an angle of 45 ° (a main cross section of the quarter-wave plate and a vibration plane of an electric field vector). (Angle), the polarization angle when the reflected light from the sample part is incident, and the polarization angle of the light that has passed through the non-polarizing prism and passed through the quarter-wave plate again.

FIG. 5 is a diagram schematically showing a light path in the optical system of FIG. 1;

FIGS. 6A and 6B respectively correspond to FIG. 4 and show an angle of 45 ° to a quarter-wave plate in the optical system of FIG. 1;
FIG. 9 is a diagram showing a state in which reflected light from a sample unit does not enter in °.

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, 5 ... 1/4 wavelength plate, 7 ... Non-polarization prism, 10 ... Photoelectric detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 G01B 11/00-11/30

Claims (2)

(57) [Claims] 1. A first optical element which also serves as a polarizer and an analyzer and in which linearly polarized light is incident on a part of a sample, and a phase difference between p-polarized light and s-polarized light of reflected light reflected on a part of the sample And a second shape in which the reflected light is incident on a portion different from a part of the sample, and the light reflected on the different portion is incident on the first optical element. A 1/4 λ plate provided on an optical axis connecting the sample and the second optical element and arranged at 45 ° to the p direction or the s direction of polarized light; An optical system in a polarization analyzer comprising: a light detection unit configured to detect light incident on an optical element. 2. The method according to claim 1, wherein the sample is divided into a region into which light from the first optical element is incident and a region into which light from the second optical element is incident. A sample support suitable for the optical system according to claim 1.