JPH03246448A - Magnetic field sweep ellipsometer - Google Patents

Abstract

PURPOSE:To simulataneously measure Kerr ellipticity as well by including a magnetic field sweeping part which can sweep a magnetic field to a sample in a sample stage. CONSTITUTION:Light 62 emitted from an output system 10 transmits the sample 20 in the magnetic field sweeping part 52 and arrives at a photodetecting system 14. The measurement of not only the reflected light from the sample 20 but the transmitted light of the transparent sample 20 as well is, therefore, possible. The measurement of the reflected light of the light from an exit optical system 10 by admitting the light at various angles to the sample 20 is possible as well. On the other hand, the adequate photodetection of the reflected light from the sample 20 is not possible unless a photodetecting system 14 is not rotated by an angle 2theta when the stage 12 is rotated by an angle theta in the mode for measuring the reflected light of the sample 20. The transmitted light or reflected light of the sample 20 is measured in the state of applying the magnetic field to the sample 20 in such a manner. The simultaneous measurement of the Kerr ellipticity by a function to measure elliptically polarized light is also possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic field sweeping ellipsometer, and particularly to improvements in its magnetic field sweeping mechanism.

[Prior Art] Ellipsometers that measure the polarization state of light upon reflection are well known in order to measure physical properties such as the thickness or refractive index of thin films on various objects such as semiconductors.

When linearly polarized light is obliquely incident on the surface of a sample that has a thin film on its surface, the polarization state of the reflected light changes depending on the thickness and refractive index of the thin film on the sample surface, and is usually reflected as elliptically polarized light.

Therefore, by measuring the amount of polarization of this reflected light and performing analytical calculations, the thickness and refractive index of the thin film can be determined.

[Problems to be Solved by the Invention] In recent years, there has been an increasing demand for evaluation devices in fields where magneto-optic effects are applied, such as evaluation of recording films in magneto-optical recording and Faraday elements.

Conventionally, evaluation devices that measure the angle of optical rotation have been used as devices for measuring the Kerr effect, Faraday effect, etc., but recently there has been a strong demand for an evaluation device that can also measure the Kerr ellipticity at the same time.

That is, when linearly polarized light is incident, the light reflected from a normal metal surface is linearly polarized, but when a ferromagnetic material is placed in a magnetic field, a magnetic Kerr effect occurs and the light becomes elliptically polarized.

By measuring the Kerr ellipticity based on this magnetic Kerr effect, the physical property data to be evaluated can be expanded.

In particular, the ability to measure Kerr ellipticity is indispensable for physical property evaluation equipment used in the development and manufacture of magneto-optical recording films, optical isolators, etc., where not only Kerr rotation but also Kerr ellipticity determines device performance.

However, it has not been possible to obtain data based on such magnetic Kerr effects using conventional general evaluation devices.

The present invention has been made in view of the problems of the prior art, and its object is to provide an ellipsometer that can also measure Kerr ellipticity at the same time.

[Means for Solving the Problems] To achieve the above object, a magnetic field sweeping ellipsometer according to claim 1 of the present application is characterized in that the sample stage includes a magnetic field sweeping unit capable of sweeping a magnetic field to the sample. .

The ellipsometer according to a second aspect of the present invention is characterized in that the sample stage can take a polar car arrangement, a longitudinal car arrangement, or a faraday arrangement for the sample with respect to the magnetic field.

[Function] Since the ellipsometer according to the present invention includes the above-described means, it is possible to measure the polarization state while applying a magnetic field to the sample.

As a result, the ellipsometry function of the ellipsometer allows us to measure not only the angle of rotation due to the Kerr effect or Faraday effect, but also the Kerr ellipticity due to the magnetic Kerr effect, which was impossible to measure with conventional general evaluation equipment. It becomes possible to measure simultaneously.

Further, according to the ellipsometer according to the second aspect, since samples can be placed in various arrangements and data can be obtained for each arrangement, versatility can be greatly improved.

[Example] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a schematic configuration diagram of an ellipsometer according to an embodiment of the present invention.

The ellipsometer according to this embodiment includes a light output system 10, a sample stage 12, and a light reception system 14.

The light output system 10 includes a monochromator 16 and a polarizer 18, and the light adjusted to a constant wavelength by the monochromator 16 is converted into linearly polarized light with a predetermined polarization direction by the polarizer 18, and the sample stage 12 It is emitted towards.

The sample stage 12 holds a sample 20 , and linearly polarized light is reflected on the surface of the sample 20 and is incident on the light receiving system 14 .

Here, a predetermined magnetic field is applied to the sample 20 on the sample stage 12, and the elliptically polarized light due to the magnetic Kerr effect is incident on the photoelastic modulator (PEM) 22 of the light receiving system 14, and left at a predetermined modulation angular velocity ω. It changes alternately into circularly polarized light and clockwise elliptically polarized light. The light polarization-modulated by the PEM 22 is incident on the analyzer 24, and then
The light emitted from the sensor 4 is incident on a photodetector (PM) 26 such as a photomultiplier, and is converted into an electrical signal.

The ellipsometer according to this embodiment is controlled by a personal computer 28, which controls the stage controller 32 via the I10 port 3o. Then, the stage controller 32
is the sample stage 12 according to various measurement modes.
The angle with respect to the incident light and the position of the light receiving system 14 are controlled to a position where it can appropriately receive the reflected light from the sample stage 12.

Further, the computer 28 adjusts the magnetic force of the magnet provided on the sample stage 12 via the D/A converter 34, and also gives commands to the PEM controller 36 to
Modulation amplitude δ of EM22. Adjust. The modulation phase information from the PEM controller 36 is sent as reference information to the amplifier unit 38, and the modulation frequency (ω/2π) component and second harmonic (2ω/2π) component are lock-in detected from the detection information of the PM 26. The signal is input to the computer 28 via the A/D converter 40.

Furthermore, these two signal components are divided by the effective DC component due to the function of a feedback loop that keeps the DC (direct current) component constant.

Note that the processing data of the computer 28 is output to a CRT 42 and a printer 44.

On the other hand, the monochrome controller 46 supplies lighting power to the light source 48, controls the monochromator 16, and adjusts the wavelength of the emitted light, etc. Further, the monochrome controller 46 controls the raw data 50 and performs desired rotation control of the polarizer 18 and analyzer 24.

FIG. 2 shows the main parts of the ellipsometer according to the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

As is clear from the figure, the sample stage 12 is provided with a magnetic field sweeping section 52. Then, the sample 20 is placed within the magnetic field sweeping section 52, and the magnetic field by the magnetic field sweeping section 52 can be applied to the sample 54.

The magnetic field sweeping section 52 includes a mouth-shaped yoke 54, and the yoke 5
4 has coils 56a, 56b, and 56c.

56d is wound. Therefore, by conducting current through the coil 56, the yoke 54 is excited. On the other hand, pole pieces 58a and 58b are provided on both sides of the yoke 54.
are installed, and the sample 20 can be placed in a magnetic field via the pole pieces 58a, 58b.

In the illustrated example, the magnetic field sweeping section 52 includes a pole piece! Light conducting holes 60a and 60b passing through 58a and 58b are provided.

As a result, the light 62 emitted from the light emitting system 10 passes through the sample 20 in the magnetic field sweeper 52 and reaches the light receiving system 14 . Therefore, the ellipsometer according to this embodiment can measure not only the light reflected from the sample 20 but also the light transmitted through the transparent sample 20.

Further, in this embodiment, the sample stage 12 is formed to be rotatable with respect to the base 64, and is interlocked with a worm wheel 68 that meshes with the worm 66. Therefore, by rotating the worm 66, the sample stage 12 can be rotated via the worm wheel 68.

It is also possible to make the light from the light output system 10 enter the sample 20 at various angles and measure the reflected light.

On the other hand, in the reflected light measurement mode of the sample 20, the light receiving system 1
4 must also be rotated appropriately as the sample stage 12 rotates. That is, when the sample stage 12 is rotated by an angle θ, the light receiving system 14 cannot properly receive the reflected light from the sample 20 unless the sample stage 12 is rotated by an angle of 26 degrees.

For this reason, the light receiving system 14 is formed to be rotatable coaxially with the sample stage 12. That is, the light receiving system 14 is supported by the support member 70. And the support member 7
0 is interlocked with a worm wheel 72, and the rotation of the worm 74 allows the light receiving system 14 to rotate coaxially with the sample stage 12. Therefore, if the worm 74 is rotated at twice the speed of the worm 66, the light receiving system 14 will be rotated at a rotation angle of 2 with respect to the rotation angle θ of the sample stage 12.
It can be rotated by θ.

As described above, according to the ellipsometer according to this embodiment, when a magnetic field is applied to the sample 20, the sample 20
The transmitted light or reflected light can be measured.

In addition to the conventional measurement of the angle of optical rotation, the Kerr ellipticity can also be measured at the same time using the ellipsometry function of the ellipsometer.

FIG. 3 shows a state in which the ellipsometer according to this embodiment is set to the transmitted light measurement mode and the Faraday effect is measured from the transmitted light of the sample 2o.

As is clear from the figure, the pole piece 58a.

58b is formed into a substantially rectangular shape, and the light 62 is placed in the center of the rectangular shape.
Light conducting holes 60a and 60b are provided to allow the light to pass through. Moreover, notch grooves 76a, 76b, 78a, and 78b are provided at both sides of the center of each pole piece 58a, 58b.

In the state shown in the figure, the light that has passed through the light guide hole 60a of the pole piece 58a is transmitted through the transparent sample 20, and further passes through the light guide hole 60b of the pole piece 58b to reach the light receiving system.

Here, since a magnetic field is applied to the sample 20 by the pole pieces 58a and 58b, the influence of the Faraday effect on the sample can be measured.

On the other hand, FIG. 4 shows a state in which the ellipsometer according to this embodiment is set to the first reflected light measurement mode and the influence of the polar Kerr effect is measured.

As is clear from the figure, the arrangement of the sample 20 is the same as that in FIG. 3, but the light emitting system 10 and the light receiving system 14 are arranged at symmetrical positions with the pole piece 58a in between. Therefore, the light is not incident through the light guide hole 60 but through the notch groove 76a, and the light reflected by the sample 20 is transmitted through the notch groove 76b to the light receiving system 14.
leading to.

As described above, in this embodiment, since the notch grooves 76a and 76b are provided in the pole piece 58a, it is possible to measure the influence of the polar Kerr effect on the sample 20 at a wide angle of incidence of light.

Further, FIG. 5 shows a state in which the ellipsometer according to this embodiment is set to the second reflected light measurement mode and the influence of the Longitudinal Kerr effect is measured.

As is clear from the figure, the arrangement of the sample 20 is in a direction perpendicular to the state shown in FIGS. 3 and 4, but
The light emitting system 10 and the light receiving system 14 are arranged on one side of the pole piece 58. The incident direction of the light is the same as that shown in FIG. 4, and the reflected light is emitted through the notch 78a of the pole piece 58b.

As described above, in this embodiment, the pole piece 58a,
Since the grooves 76 and 78 are provided in each of the grooves 58b, it is possible to measure the influence of the longitudinal directional Narker effect on the sample 20 at a wide angle of incidence.

Next, the calculation operation of the ellipsometer according to this embodiment will be explained with reference to the optical characteristic diagram shown in FIG.

In a state without magnetic field sweeping, each optical characteristic is shown as follows.

First, the Stokes vector of incident natural light is expressed by the following equation (2).

Also, The Mueller matrix of the polarizer 18 is expressed by the following equation (2).

Further, the Mueller matrix of reflection in sample 20 is expressed by the following equation (2).

Also, The Mueller matrix of PEM22 is expressed by the following formula (■).

However, δ is the angular frequency (angular velocity) of modulation of PEM22 as ω
, the amplitude is δ. It is defined as δ=δo−8inωt.

Further, the Mueller matrix of the analyzer 24 is expressed by the following equation (2).

Therefore, the output I from the PM 26 is given by the first component multiplied by the above formulas (1) to (2), and is expressed by the following formula.

I = (1-cosδ・C082ψ −5inδ・sin2ψ・sinΔ)・1/4 And if the output from PM26 is separated into DC component, ω component, and 2ω component, I (DC) = (1-JO( δo) −cos2ψ)
-1741 (ω) = (2J1 (δ.)・5in2ψ
・sinΔ)−174I(2ω)=(2J2 (δo)
-cos2ψ)-174 Here, the modulation amplitude of the PEM 22 is set to J, (δ0) = 0 (δo = 2.405 rad).

And the signal divided by I (DC) is a (ω)
=-sin2ψ・SinΔa (2ω) =-cos
2ψ.

On the other hand, when a magnetic field is applied, the polarizer 1 with the transmission axis direction φ
The Mueller matrix of 8 is expressed by the following formula (■).

Further, the Mueller matrix of reflection in sample 20 is expressed by the following equation (2).

Further, the Mueller matrix (■) of the PEM22 is expressed by the following formula.

Further, the Mueller matrix (■) of the analyzer 24 is expressed by the following formula.

Therefore, the detection output I from the PM 26 is expressed by the following equation using the same calculation as described above.

I=[1+cosδ−(sin2φ”cosΔ・cos
2φ+5in2ψ・sinΔ・5in2φ) 10 sin
δ・cos2ψko・1/4 Here, as is clear from Fig. 6, since 2ψ=2ε+90'', the normalized signal is a (ω) = cos2ψ= −5in2 ea (
2ω) = sin2ψ・cos(2φ−Δ)= cos
2ε·cos(2φ−Δ).

From the above results, the ellipticity angle ε, the azimuth angle φ, and the optical angle are expressed by the following equations.

ε = 1/2-sin-” (-a(ω)) = 45≦
ε≦45 (deg) rotation φ°miφ−Δ/2 = 1/2・cos−” (a(2ω)/cos2 ε
) θ = -Δ/2 = 172-coS-' (a(2ω)/cos2ε)
-φ Thus, according to the ellipsometer according to this embodiment, it is possible to simultaneously measure not only the angle of optical rotation but also the Kerr ellipticity.

Moreover, depending on the sample and measurement purpose, the computer
8, set each mode of transmitted light measurement mode, first reflected light measurement mode, and second reflected light measurement mode, and obtain various data from samples of polar car arrangement, longy tudynar car arrangement, and Faraday arrangement. be able to.

[Effects of the Invention] As explained above, according to the magnetic field sweep ellipsometer according to claim 1 of the present application, by measuring the polarization state with a magnetic field applied to the sample, it is possible to eliminate the influence of the Kerr effect or Faraday effect. It becomes possible to measure not only the angle of optical rotation but also the Kerr ellipticity at the same time.

Further, according to the ellipsometer according to the second aspect, since samples can be placed in various arrangements and data can be obtained for each arrangement, versatility can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a magnetic field sweep ellipsometer according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a sample stage of the ellipsometer shown in FIG. 1, and FIGS. FIG. 6 is an explanatory diagram of the relationship between the sample and the magnetic field sweeping section using the ellipsometer shown in the figure, and FIG. 6 is an explanatory diagram showing the polarization state using the ellipsometer shown in FIG. 0 2 4 2 Light output system sample stage Light reception system Magnetic field sweep section

Claims (2)

[Claims] (1) A light output system capable of emitting linearly polarized light in a specific direction; a sample stage on which a sample is placed; and a sample stage that transmits or reflects incident light from the light output system to the sample; 1. A magnetic field sweeping ellipsometer, comprising: a light receiving system capable of obtaining data on elliptically polarized light; and the sample stage is equipped with a magnetic field sweeping unit capable of sweeping a magnetic field across the sample. (2) The magnetic field sweeping ellipsometer according to claim 1, wherein the sample stage allows the sample to take a polar Kerr configuration, a longitudinal Kerr configuration, or a Faraday configuration with respect to the magnetic field.