JPH0571923A - Ellipsometry method and thin film measuring device - Google Patents

Abstract

PURPOSE:To obtain a simple and easy polarization analyzing method and a simple and easy thin film measuring apparatus. CONSTITUTION:For instance, a sample 13 is illuminated by an elliptically polarized light via phase plates 4, 5, and a beam splitter 6 is arranged in the optical path of the reflected light from the sample 13. The intensity of the split light in at least three different polarization directions is detected by photoelectric detectors 9-12 via analyzers 7, 8. Accordingly, the refractive index and thickness of a sample thin film are detected. Moreover, the apparatus is also provided with a measuring system of a spectral reflectance method or a white light interference fringe method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ellipsometry method and a thin film measuring apparatus.

[0002]

2. Description of the Related Art Generally, as a polarization analysis method for an object, there is known one which detects a change in relative polarization state of light from the object with respect to a polarization state of irradiation light to the object. It is roughly divided into photometric methods.

This polarization analysis is used, for example, to measure the refractive index of the sample surface and, in the case of a thin film sample, to measure the film thickness. The extinction method is a method of obtaining an elliptic state by rotating the phase plate to make the elliptically polarized light into linearly polarized light and further rotating the analyzer to extinguish the light. The photometric method is a method of obtaining an elliptic state by rotating one of a polarizer, a compensator, and an analyzer to measure the amount of light at at least three angles.

The extinction method and photometric method have the following features.

The advantage of the extinction method is that it can accurately measure any polarization state, and the disadvantage is that it has many driving parts and therefore the measurement time is long and there is a problem in terms of durability. Can be mentioned.

Further, the advantages of the photometric method are that the measurement time is short, the configuration of the optical system is simple, and the disadvantages are that
High precision measurement is difficult over the entire polarization state, and
Since it has a driving part, it lacks stability.

By the way, in recent years, in the field of semiconductors, with the miniaturization of integrated circuits, insulating films and the like are becoming thinner.
Conventionally, a spectroscopic analysis type film thickness meter is mainly used to measure the film thickness in terms of ease of measurement and speed. However, for example, a SiO ₂ / Si sample with a thickness of 100 Å (SiO ₂ ) or less cannot be stably measured by a spectroscopic analysis film thickness meter, and the film thickness measured by an ellipsometer (polarization analysis film thickness meter) is not possible. Measurements are being taken. Particularly, in the field of semiconductors, the polarization analysis method, especially the above-described photometric method is advantageous because high-speed and highly accurate measurement is required.

FIG. 23 shows a conventional example of a rotary analyzer type, which is the most general type of photometric method. The light from the light source 1 is imaged by the condenser lens 2 so as to form a minimum spot on the sample 13.

After passing through the condenser lens 2, it passes through the polarizer 3 to become linearly polarized light 21 in the x direction as shown in FIG. further,
As shown in FIG. 3, the light passes through the λ / 2 plate 4 whose axis is set in the direction of advancing the phase in the θ _H direction, and the transmitted light becomes the linearly polarized light 22 having the azimuth angle θ _P as shown in FIG. Then set the direction for advancing the phase axis theta _C direction as shown in FIG. 4 lambda /
The elliptically polarized light 25 as shown in FIG. 4 is transmitted through the four plates 5. Here, the angles of θ _C and θ _H are set to angles at which changes in the polarization state of the sample 13 can be accurately measured. As shown in FIG. 5, it may be arranged so that it becomes substantially circularly polarized light after the sample is reflected.

For example, when the sample 13 is a Si substrate, θ _H =
It may be set to 50 ° (θ _P = 10 °) and θ _C = −1 °. The light emitted from the λ / 4 plate 5 at this time is

[0011]

[Outer 1] As

[0012]

[Outside 2] Then, the amplitude ratio (tan ψ ₀ ) and the phase difference (Δ ₀ ) in the x and y directions can be expressed as tan ψ ₀ = a _y0 / a _x0 Δ ₀ = φ _y0 −φ _x0 .

That is, the elliptically polarized light in FIG. 4 can be expressed as (ψ ₀ , Δ ₀ ).

Now, wavelength = 780 nm, θ _H = 50 °, θ _C
= -1 °, ψ ₀ = 87.82 °, Δ ₀ = 94.94.
°.

Further, the polarization characteristic of the sample 13 is (ψ, Δ)
In other words, the polarization characteristic (ψ ′, of the reflected light 26 (FIG. 5),
Delta ') _{is, tanψ' = tanψ 0 · tanψ} ~ 1.0 (ψ ~ 10
°, when Si substrate) Δ ′ = Δ ₀ + Δ to 270 ° (Δ = 170 °, when Si substrate), which is almost circularly polarized light.

Now, in FIGS. 23 and 7, if the transmission axis of the analyzer 66 is θ _A and the clockwise direction is positive with the y axis as the reference, the component of only the θ _A direction is transmitted through the analyzer 66 and the amount of light thereof is increased.

[0017]

[Outside 3] Is measured by the detector 67.

For example, θ _A = 0, 90, 45, -45 °
When the light quantity at that time is I ₀ , I ₉₀ , I ₄₅ , and I ₋₄₅ , it is expressed as in the following equation.

I ₀ = | vey | ² · | ay ₀ | ² · tan ² ψ · tan ² ψ ₀ (1) I ₉₀ = | vey | ² · | ay ₀ | ² (2) I ₄₅ = 1 / 2 | vey | ² · | ay ₀ | ² · [tan ² ψ · tan ² ψ ₀ + 1 + 2t an ψ · tan ψ ₀ · cos (Δ + Δ ₀ )] ... (3) I ₋₄₅ = 1/2 | vey | ² · | Ay ₀ | ² · [tan ² ψ · tan ² ψ ₀ + 1-2 −tan ψ · tan ψ ₀ · cos (Δ + Δ ₀ )] ... (4)

From (1), (2), (3) and (4), ψ,
As for Δ,

[0021]

[Outside 4]

Therefore, the analyzer 66 is set to 0 °, 90 °, 45
If the light amount at that time is measured by rotating it by ø, -45 °, then ψ ₀ , Δ ₀ are known, so from equations (5) and (6) ψ,
Δ, that is, the change in the polarization state of the sample can be obtained.

On the other hand, in the case of a sample having a thin film 72 on a substrate 71 as shown in FIG. 24, ψ and Δ are functions of the refractive index n and the film thickness D of the thin film 72. Therefore, if ψ and Δ are obtained, then n and D are obtained. As a method of obtaining n, D from ψ, Δ, there is a method of obtaining ψ, Δ curves for many n, D and then obtaining (n, D) closest to the measured value (ψ, Δ).

[0024]

However, the above-mentioned conventional example has the following first and second drawbacks. That is, the first drawback is that, for example, the analyzer needs to be rotated at the time of measurement, and the measurement time is long because of the mechanical drive section (it is faster than the extinction method, but it is faster than the spectroscopic film thickness meter). It is slower than that) and lacks stability due to the mechanical drive.

The second drawback is that the ellipsometry method has a small measuring range.

[0026]

In order to solve the above-mentioned first drawback, the present invention makes a light beam of a certain polarization state incident on a sample and detects a light beam from the sample in a plurality of polarization directions, or a plurality of light beams is detected. A polarization analysis method for injecting a light beam in a polarization state into a sample, detecting the light beam from the sample in a certain polarization direction, and analyzing the polarization characteristics of the sample, which is one of a polarizer, a phase plate, and an analyzer. One element is fixed in a plurality of optical paths so as to form a plurality of at least three different polarization states.

Further, according to the present invention, the optical path length information of a thin film is measured by a polarization analysis method in which a light beam having a certain polarization state is incident on a thin film sample to detect the polarization state of the light beam from the thin film in order to solve the second drawback. And a means for measuring optical path length information of the thin film by a spectral reflectance method or a white light interference method.

[0028]

In order to eliminate the above-mentioned first drawback, for example, as shown in the first embodiment, the sample is irradiated with elliptically polarized light through a polarizer and a phase plate without passing through a mechanical driving unit, and reflected light from the sample is reflected. Are individually detected via the analyzer in correspondence with at least three different polarization directions. The light detection is performed by at least three photodetectors simultaneously or sequentially by a single photodetector.

In order to solve the above-mentioned second drawback, a polarization analysis type optical path length measuring system and a spectral reflectance type or white light interference type optical path length measuring system are provided for the thin film.

[0030]

1 shows a first embodiment of the present invention. 1 is a light source such as a semiconductor laser or He-Ne laser, and 2
Is a lens for collecting the light of the light source, 3 is a polarizer, 4 is λ
/ 2 plate, 5 is a λ / 4 plate, and 6 is a beam splitter for splitting a light beam into two. Reference numerals 7 and 8 denote analyzers (polarizing prisms or polarizing beam splitters) for transmitting and reflecting the vibration components in two orthogonal directions on one side, and the analyzer 8 is rotationally displaced by 45 ° about the incident optical axis. It 9
˜12 is a photoelectric detector such as a photodiode, 13 is a sample, 14 is a luminous flux reflected by the beam splitter 6,
Reference numeral 5 is also a transmitted light flux.

The light from the light source 1 is imaged by the condenser lens 2 so as to form a minimum spot on the sample 13.

The light from the light source 1 passes through the condenser lens 2,
The light is transmitted through the polarizer 3 and becomes linearly polarized light in the direction shown in FIG. Further, as shown in FIG. 3, λ with the fast axis set in the θ _H direction
After passing through the / 2 plate 4, the transmitted light becomes linearly polarized light 22 having an azimuth angle θ _P as shown in FIG. Next, as shown in FIG. 4, the light passes through the λ / 4 plate 5 having the fast axis set in the θ _C direction, and becomes elliptically polarized light 25 as shown in FIG. 4, for example. Here, the angles θ _C and θ _H are set so that the change in the polarization state of the sample 13 can be accurately measured, that is, a large amount of reflected light can be obtained. It may be circularly polarized after the sample is reflected.

For example, when the sample 13 is a Si substrate, θ _H =
It may be set to 50 ° (θ _P = 10 °) and θ _C = −1 °.

The light emitted from the λ / 4 plate 5 at this time is

[0035]

[Outside 5] As

[0036]

[Outside 6] Then, the amplitude ratio (tan ψ ₀ ) in the x and y directions, the phase difference (Δ ₀ ), tan ψ ₀ = a _y0 / a _x0 , and Δ ₀ = a _y0 −a _x0 can be expressed.

That is, the elliptically polarized light in FIG. 4 can be expressed as (ψ ₀ , Δ ₀ ).

When θ _H = 50 ° and θ _C = -1 °, ψ ₀ = 8
7.82 ° and Δ ₀ = 94.94 °.

Further, the polarization characteristic of the sample 13 is (ψ, Δ)
If you put the polarization characteristics of the reflected light 26 as shown in FIG. 5 (ψ ', Δ') _{is, tanψ '= tanψ 0 · tanψ} ~ 1.0 (ψ ~ 10
°, when Si substrate) Δ ′ = Δ ₀ + Δ to 270 ° (Δ = 170 °, when Si substrate), which is almost circularly polarized light.

Next, the circularly polarized light 26 is divided into a reflected light beam 14 and a transmitted light beam 15 by the beam splitter 6, and only the components 29 and 30 in the directions shown in FIG. Then, the analyzer 8 can obtain only the components in the directions 32 and 33 as shown in FIG. 7 from the reflected light flux 14. Here, the reflected light beam 14 and the transmitted light beam 15 are generally elliptically polarized light due to the influence of the amplitude and phase characteristics of the beam splitter. 6, the angle as positive a clockwise y axis reference in FIG. 7, if _{θ A, θ A = 0 °} ( reference numeral 29) 90 ° (reference numeral 30) 45 ° (reference numeral 32) -45 ° (code 33), and sensor 12, sensor 11, sensor 10, sensor 9 in that order.
Detected by. The outputs I ₀ , I ₉₀ , I ₄₅ , and I ₋₄₅ will be described below.

Here, the characteristics of the beam splitter 6 are

[0042]

[Outside 7] Toki, further

[0043]

[Outside 8] If we say Δ _BR = φ _RP −φ _RS , the output of each sensor 9-12 is

[0044]

[Outside 9] (Here, K ² _{A1 to} K ² _A4 are sensors 12, 11, 10,
9 gain sensitivity × transmittance of each analyzer, V _ey represents the amplitude reflectance of the sample 13 in the S direction. )

From (A), (B), (C), and (D), ψ,
As for Δ,

[0046]

[Outside 10]

Therefore, in the equations (E) and (F), the characteristics <ψ ₀ , Δ ₀ > before the incidence of the sample, the beam splitter characteristics <ψ _BT , ψ _BR , Δ _BR , | T _S |, | _RS |>, Sensitivity of each sensor × analyzer transmittance <K ² _{A1 to} K ² _A4 >, the outputs I ₀ , I ₉₀ , I of the sensors 12, 11, ₁₀ , ₉ are input.
By measuring ₄₅ and I ₋₄₅ , the characteristics of sample 13 <ψ,
Δ> can be measured.

Next, FIGS. 8 to 13 show a second embodiment.
In the first embodiment, the polarization components in four directions are detected as shown in FIGS. 6 and 7, but in the present embodiment, Δ and ψ are obtained by detection in only three directions as shown in FIG. Also in Example 1,
Even if detection in four directions is not performed, Δ and ψ can be obtained by polarizing the calculation formula in only three directions.

Next, FIGS. 10 to 11 show a third embodiment. This embodiment is a modification of the first embodiment and detects polarization components in four directions, but the beam splitter 41,
After splitting the optical path twice with the two 42, the analyzers 43, 44,
The photodetectors 46 to 49 detect the light in four directions through the three photosensors 45.

Here, the analyzers 44 and 45 are rotated around the incident optical axis by 45 ° in the clockwise and counterclockwise directions, respectively. Next, FIGS. 12 to 13 show a fourth embodiment. The transmitted light flux of the beam splitter 51 is changed to the beam splitter 5
2, the light beam reflected by the beam splitter 51 is split into two optical paths by the beam splitter 53, and the rays split into a total of four optical paths are analyzed by the analyzers 54 to 57.
As shown in FIG. 3, a total of eight polarization components different from each other are formed, and photometry is performed by the detectors 58 to 65. Here the analyzers 56, 57, 5
8 are each rotated by 45 ° about the incident optical axis. In this embodiment, it is possible to improve accuracy by detecting multi-components. Although the formulas for calculating Δ and ψ are different in the second, third, and fourth embodiments, they can be obtained by the same procedure as that shown in the first embodiment.

In the above embodiment, the analyzer is rotationally displaced and fixed in the optical path. However, even if the polarizer is rotationally displaced and fixed in the optical path as shown in FIGS. well,
The phase plate may be rotationally displaced and fixed in the optical path as shown in FIGS. That is, in FIG. 14, among the polarizers P ₁ and P ₂ , the polarizer P ₁ is rotationally displaced by 45 ° around the incident optical axis, and the light sources LD ₁ and LD ₂ such as a semiconductor laser transmit the polarizer P ₁ respectively. , And the polarization component of FIG. 15 is maintained. The light sources LD ₃ and LD ₄ respectively reflect and transmit the polarizer P ₂ to maintain the polarization component of FIG.

Light sources LD _{1 to} L which are sequentially blinked in time series
Light from D ₄ is beam splitter BS, λ / 4 plate C
Incident on the sample at four elliptically polarized light through the substantially is received simultaneously by a single photodetector via an analyzer A which is fixed in any direction, the output of the sequentially obtained photodetectors I ₀ , I ₉₀ ,
It is detected as I ₄₅ and I ₋₄₅ .

Next, in the embodiment shown in FIG. 17, the polarizers P ₁ ,
Both P ₂ are not rotationally displaced around the incident optical axis, but instead, the axes of the directions in which the λ / 4 plates C ₁ and C ₂ advance the phase are θ ₁ and θ ₂ (θ ₁ respectively) around the incident optical axis. And θ ₂ are different angles).

Then, similarly to the embodiment of FIG. 14, the light source LD ₁
Light from LD ₄ has a polarization component shown in FIG.
The four types of elliptically polarized light are incident on the sample through the four plates C ₁ and C ₂ and the beam splitter BS, and are received substantially simultaneously by a single photodetector through an analyzer A fixed in an arbitrary direction. , The outputs of the photodetectors obtained in sequence are detected as I ₀ , I ₉₀ , I ₄₅ , and I ₋₄₅ .

Next, in addition to the polarization analysis method, Japanese Patent Laid-Open No. 63-4
4106, Japanese Patent Laid-Open No. 62-201304, and the like, or the spectral reflectance method, or Japanese Laid-Open Patent Publication No. 59-1055.
An embodiment having a film thickness measuring system of a white light interference method known from Japanese Patent Laid-Open No. 08 etc. will be described with reference to FIGS.
In this case, the polarization analysis method may be the conventional rotary type as shown in FIG. 23 or the fixed type as shown in FIGS. 1, 14, and 17. In addition to the polarization analysis method, according to the embodiment having a spectral reflectance method or a white light interference method film thickness measurement system, the measurement range is expanded as compared with a single device of the polarization analysis method. That is, the optical path length that cannot be measured by the polarization analysis method can be measured by the spectral reflectance method or the white light interference method. or,
When measuring the same test portion, it is possible to switch between the polarization analysis method with a larger measurement spot and the spectral reflectance method with a smaller measurement spot, or the white light interference method.

Further, since the refractive index of the sample can be actually measured as described above by performing the polarization analysis method, the spectral reflectance method or the white interference with respect to the sample can be compared with the conventional example in which the refractive index is predicted in advance. It is also possible to obtain the film thickness accurately by dividing the optical path length data by the method by the refractive index obtained by the polarization explanation method.

Further, compared with the case where separate devices are provided, the installation area can be reduced and the transport system can be shared. 20 and 22 show the main parts of FIGS. 19 and 21, respectively.

In FIG. 19, 101 is an illumination unit used for the spectral reflectance method, 102 is an objective lens used for observation of the spectral reflectance method and polarization analysis method, 103 is a spectroscope used for the spectral reflectance method, 104 is a microscope lens barrel, 105,
Reference numeral 106 is a TV camera and TV monitor used for observing the measurement position of the spectral reflectance method and polarization analysis method, 107 is a light emission section of the polarization analysis method, 108 is also a light reception section 107,
The light emitting portion and the light receiving portion of 108 are integrally connected to the microscope barrel. Reference numeral 109 is a controller for driving a device of the spectral reflectance system and ellipsometry system, 110 is a computer unit for calculating the film thickness from the measured values and controlling the entire system, 11
1 is a transfer unit for automatically transferring a sample, for example, a silicon wafer,
112 is a sample. When performing the measurement, first, the transport unit 1
When the sample 112 is conveyed to the measurement position by 11 and the control value of the film thickness on the sample is several Å to several 100 Å,
According to an instruction from the computer 110, the measurement is performed by the polarization analysis method, and in the case of 100Å to 30 μm, the measurement is performed by the spectral reflectance method. When measuring with the spectral reflectance method, if the film thickness to be measured is a film thickness capable of measuring the refractive index (for example, about 500 Å or more for the SiO film on the Si substrate), the polarization analysis method is used in advance to improve the measurement reliability. Then, the refractive index is measured by using the spectral reflectance method. When the thickness is several thousand Å, the measured film thickness value D ₁ is obtained from the spectral reflectance method, and further, the measured film thickness value D ′ _n (n = 1, 2, ...
D ′ _i close to D ₁ can be determined until n−1, n) are obtained.

FIG. 21 shows another embodiment, 106 and 10.
Reference numerals 7, 108, 110, and 112 represent the TV monitor, the light emitting unit, the light receiving unit, the computer, and the sample described above.
Reference numeral 109 'is a controller for driving a white interference type and polarization analysis type device, and 113 is a white interference type optical unit. A TV camera for observation is included in the optical section, and it is also used for polarization analysis observation.

FIG. 22 shows a polarization analysis type measurement system.
Reference numeral 13 is a light source, 114 is a polarizer and a phase plate, 115 is an analyzer, and 116 is a photodetector. In the present embodiment, the sample transfer section is excluded, but a system with a transfer section is also possible.

In the measurement, the sample is first placed at the measurement position, and the control value of the film thickness on the sample is from several Å to several 1
In the case of 00Å, the measurement is performed by the polarization analysis method according to the instruction from the computer 110, and in the case of 2 μm to 30 μm, the measurement is performed by the white interference method. When performing measurement by the white light interference method, when the film thickness to be measured is a film thickness capable of measuring the refractive index (for example, about 500 Å or more for the SiO film on the Si substrate), the polarization analysis method is used in advance in order to improve the measurement reliability. Then, the refractive index is measured by using the white interference method.

[0062]

As described above, according to the present invention, simple ellipsometry,
Accurate film thickness measurement is possible.

[Brief description of drawings]

FIG. 1 is a diagram of a first embodiment of the present invention using a plurality of analyzers.

FIG. 2 is a diagram showing linearly polarized light passing through a polarizer.

FIG. 3 is a diagram showing linearly polarized light through a λ / 2 plate.

FIG. 4 is a diagram showing elliptically polarized light through a λ / 4 plate.

FIG. 5 is a diagram showing circularly polarized light reflected from a sample.

FIG. 6 is a diagram showing a polarization component via one analyzer.

FIG. 7 is a diagram showing a polarization component via the other analyzer.

FIG. 8 is a diagram showing a modification of the embodiment of FIG.

9 is a diagram showing polarization components of the modified example of FIG.

FIG. 10 is a diagram showing a modification of the embodiment of FIG.

FIG. 11 is a diagram showing polarization components of the modified example of FIG.

FIG. 12 is a diagram showing a modification of the embodiment of FIG.

FIG. 13 is a diagram showing polarization components of the modified example of FIG.

FIG. 14 is a diagram of a second embodiment of the present invention using a plurality of polarizers.

FIG. 15 is a diagram showing a polarization component via one of the polarizers.

FIG. 16 is a diagram showing a polarization component via the other polarizer.

FIG. 17 is a diagram of a third embodiment of the present invention using a plurality of phase plates.

FIG. 18 is a diagram showing polarization components incident on a phase plate.

FIG. 19 is a diagram of an embodiment having both a polarization analysis type optical path length measurement system and a spectral reflectance type optical path length measurement system.

20 is a schematic view of a main part of FIG.

FIG. 21 is a diagram of an embodiment having both a polarization analysis type optical path length measurement system and a white light interference type optical path length measurement system.

22 is a schematic diagram of a main part of the ellipsometry measurement system in FIG. 21. FIG.

FIG. 23 is a diagram of a conventional example.

FIG. 24 is a diagram showing a sample having a thin film on a substrate.

[Explanation of symbols]

 1 Light Source 3 Polarizer 4 λ / 2 Plate 5 λ / 4 Plate 6 Beam Splitter 7, 8 Analyzer 9, 10, 11, 12 Photoelectric Detector 101 Illuminator Used for Spectral Reflectance Method 103 Spectroscope 105 TV Camera 106 TV monitor 107 Polarization analysis light emitting unit 108 Polarization analysis light receiving unit 109, 109 ′ Controller 111 Transport unit 112 Sample 113 White interference type optical unit

Claims (9)

[Claims] 1. A light beam having a certain polarization state is made incident on a sample, and light beams from the sample are detected in a plurality of polarization directions, or light beams having a plurality of polarization states are made incident on the sample and the light beam from the sample is made into a certain polarization. A polarization analysis method for detecting light in a specific direction and analyzing the polarization characteristics of the sample, wherein a plurality of elements of one of a polarizer, a phase plate, and an analyzer are formed to form at least three different polarization states. An ellipsometry method characterized by being fixed in a plurality of optical paths. 2. A plurality of analyzers are fixed in a plurality of optical paths so as to form at least three different linearly polarized lights, and light detection is simultaneously performed corresponding to at least three different polarization directions. Polarization analysis method. 3. A plurality of polarization or phase plates, fixed in a plurality of optical paths so as to form at least three different elliptically polarized lights, sequentially turn on the corresponding light sources, and a polarization direction via an analyzer. The polarization analysis method according to claim 1, wherein the light detection is sequentially performed by. 4. A means for measuring optical path length information of a thin film by a polarization analysis method in which a light beam having a certain polarization state is made incident on a thin film sample and the polarization state of the light beam from the thin film is detected; and a spectral reflectance method or a white light interference method. A thin film measuring apparatus having means for measuring optical path length information of the thin film. 5. A means for calculating the thickness of the thin film based on the refractive index of the thin film detected by the polarization analysis method and the optical path length of the thin film detected by the spectral reflectance method or the white light interference method. Item 4. The thin film measurement apparatus according to item 4. 6. The means for measuring the optical path length information of the thin film by the polarization analysis method is one of a polarizer, a phase plate and an analyzer.
The thin film measuring apparatus according to claim 4, wherein a plurality of elements are fixed in the plurality of optical paths so as to form at least three different polarization states. 7. A single light source and a polarizer are provided in the incident light path to the thin film, a light splitting means is provided in the reflection light path from the thin film, and a plurality of analyzers are fixed in each light path split by the light splitting means. 7. The thin film measuring apparatus according to claim 6, wherein the thin film measuring apparatus is provided with at least three photodetectors through the analyzer, and the at least three photodetectors simultaneously detect corresponding polarization directions. 8. A light splitting means is provided in an optical path incident on the thin film,
A plurality of light sources, a plurality of polarizers or a phase plate are fixedly provided in each light path on the light source side divided by the light splitting means to form at least three different elliptically polarized lights, and a single light path in a reflection light path from the thin film is formed. 7. The thin film measuring apparatus according to claim 6, wherein each light source is sequentially turned on corresponding to different elliptically polarized lights through an analyzer and a photodetector, and the single photodetector sequentially detects. 9. The method for measuring optical path length information of a thin film by the polarization analysis method, wherein the optical path length information of the thin film is measured by inputting characteristics of the light beam splitting means or the photodetector. 8. The thin film measuring device according to 8.