JP2000266666A - Ellipsometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an accurate measurement realizable without changing the incidence angle on a sample by using a semiconductor laser where a plurality of laser chips for emitting a different wavelength is packaged in a piece for a light source. SOLUTION: The main ray of three beams emitted from a semiconductor laser 15 enter a collimator lens 17 in parallel with one another, are emitted from the collimator lens 17, and then enter a wavelength dispersion prism 18 while being converged. Three beams 2 emitted from the wavelength dispersion prism 18 become circular polarization beams 4 by a 1/4-wavelength plate 3. In beams through the 1/4-wavelength plate 3, beams 6 of linear polarization constituent are taken out by a polarizer 5, and then elliptic polarization beams 8 are formed by a compensator 7. The beams 8 enter a substrate 11 that is placed on a placement stand 9 at a center with a specific incidence angle. Since the beams with the three wavelengths are set to completely the same light path, the three beams all enter the substrate 11 at the same incidence angle, thus suppressing a measurement error due to the wavelength change of a light source by temperature change or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to analyzing the polarization state of light incident on a substrate having a single-layer or multiple-layer thin film formed on its surface, and the polarization state of light reflected from the thin film and the substrate. By the optical constant of the thin film, the thickness, and related to an ellipsometer that measures the optical constant of the substrate,
In particular, it relates to an ellipsometer.

[0002]

2. Description of the Related Art FIG.
Shown in

In the ellipsometer shown in FIG. 2, a light source 1 splits light emitted from a He—Ne laser having a wavelength of λ0, or a halogen lamp or a xenon lamp into a light having a wavelength of λ0.
A lamp unit that selectively emits light is used, and light 2 emitted from a light source 1 is converted into circularly polarized light 4 by a quarter-wave plate 3. The light transmitted through the quarter-wave plate 3 is extracted as a linearly polarized light component 6 by a polarizer 5, and an elliptically polarized light 8 is formed by a compensator (quarter-wave plate) 7 disposed thereafter. Is done. The elliptically polarized light 8 is disposed on a center stage 9 and has a single-layer or multiple-layer thin film on the surface.
Irradiation is performed at an incident angle Θ0 on the substrate 11 on which the substrate 10 is formed.

An analyzer 13 and a photodetector 14 are placed on the optical path of the reflected light 12 from the thin film 10 and the substrate 11.

In the ellipsometer having such a configuration, after the azimuth of the compensator (1/4 wavelength plate) 7 is fixed, the polarizer 5 is rotated (azimuth angle α0) and the compensator (1/4 wavelength plate) is rotated. ) 7
A position where the elliptically polarized light emitted from the thin film 10 and the substrate 11 is completely canceled out by reflection by the thin film 10 and a linearly polarized reflected light is obtained, and then the direction of the linearly polarized light is rotated (the azimuth angle β0 ) To obtain from the extinction position of the light emitted from the analyzer 13.

Here, if the optical constant of the substrate 11 is assumed to be the refractive index n
0, absorption coefficient k0, thin film 10 has refractive index n1, absorption coefficient k
1. Consider a case of a single-layer film having a thickness T1.

[0007] Since the measurement factors of this system are only two azimuth angles α0 and β0 of the polarizer 7 and the analyzer 13, n is one measurement.
It is impossible to determine the five values 0, k0, n1, k1, and T1. Therefore, in the conventional ellipsometer, the wavelength λ0 or the incident angle Θ0 of the light source is variously changed, and the azimuth angle of the polarizer 7 and the analyzer 13 must be checked each time to calculate the values of the five unknowns. Did not.

[0008]

However, the conventional ellipsometer cannot change the wavelength because a single wavelength He-Ne laser is used as a light source. Further, even if the light source is a spectroscope type light source, the selected wavelength depends on the mechanical accuracy of the measuring device, so that the wavelength error cannot be completely eliminated and high-precision measurement cannot be performed. On the other hand, when the incident angle Θ0 is changed, there is a problem in that the set position is inevitably fluctuated due to a physical arrangement error and a change in the environmental temperature, which lowers the measurement accuracy.

Further, the incident angle Θ0 is changed with high accuracy,
Further, there is a disadvantage that the apparatus itself becomes very expensive if the mechanical accuracy of the apparatus is to be satisfied for setting.

An object of the present invention has been made in consideration of the above-mentioned problems, and enables high-precision measurement to be realized without changing an incident angle on a sample in an ellipsometer, and to prevent temperature change and the like. It is an object of the present invention to provide an ellipsometer capable of minimizing a decrease in measurement accuracy due to a change in wavelength of a light source due to a change in an external environment.

[0011]

In order to solve the above-mentioned problems, a semiconductor laser in which a plurality of laser chips emitting different wavelengths are packaged as one light source is used as a light source to select the wavelength of light incident on a sample. I do. In addition, a collimator lens is provided to convert the light emitted from the semiconductor laser light source into parallel light, and a plurality of lights having different wavelengths transmitted through the collimator lens travel on the same optical path, after the collimator lens. A wavelength dispersion prism is provided. At least one of the plurality of laser chips used for the light source uses a GaN blue semiconductor laser chip. Further, as another means, a plurality of He-Ne lasers emitting different wavelengths are used as light sources to select the wavelength of light incident on the sample.

[0012]

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
This is an embodiment of the present invention.

In the ellipsometer shown in FIG. 1, a semiconductor laser 15 emitting a different wavelength is used as a light source. The inside of the semiconductor laser 15 has the structure shown in FIG. 3, and a plurality of laser chips having different oscillation wavelengths (in FIG. 3,
15-1 to 15-3) are packaged together in a semiconductor laser.

Each of a plurality of lights 16 (three beams in FIG. 1 having wavelengths of λ1, λ2, and λ3) emitted from the semiconductor laser 15 is then collimated by a collimator lens 17. And enters the wavelength dispersion prism 18. On the other hand, the principal rays of the three beams emitted from the semiconductor laser 15 enter the collimator lens 17 in parallel to each other, and after exiting the collimator lens 17, enter the wavelength dispersion prism 18 while converging.

At this time, as shown in the enlarged view of FIG. 4, the semiconductor laser 15 is disposed so that the light beams of three wavelengths λ1, λ2, and λ3 emitted from the wavelength dispersing prism 18 have completely the same optical path. The arrangement interval of the plurality of laser chips, the focal length of the collimator lens 17, and the shape and arrangement position of the wavelength dispersion prism 18 are designed.

After that, the light emitted from the wavelength dispersing prism 18
The light 2 is converted into circularly polarized light 4 by a quarter-wave plate 3. 1
The light 6 transmitted through the quarter-wave plate 3 is extracted as a linearly polarized light component 6 by the polarizer 5, and the elliptically polarized light 8 is formed by the compensator (quarter-wave plate) 7 disposed thereafter. You.
The elliptically polarized light 8 is placed on the center stage 9,
Substrate 11 having a single-layer or multiple-layer thin film 10 formed on its surface
At an incident angle Θ1. Since the three wavelengths of light are completely on the same optical path, all of the three lights enter the substrate 11 at the same incident angle Θ1.

An analyzer 13 and a photodetector 14 are placed on the optical path of the reflected light 12 from the thin film 10 and the substrate 11.

In the ellipsometer having such a configuration, after the azimuth of the compensator (1/4 wavelength plate) 7 is fixed,
Rotate the polarizer 5 (azimuth α1) and compensator (1/4 wavelength plate)
A position where the elliptically polarized light emitted from the light 7 is completely canceled out by the reflection by the thin film 10 and the substrate 11 to obtain a linearly polarized reflected light is searched, and then the azimuth of the linearly polarized light is rotated. β1) is obtained from the extinction position of the light emitted from the analyzer 13.

Here, if the optical constant of the substrate 11 is assumed to be the refractive index n
0, absorption coefficient k0, thin film 10 has refractive index n1, absorption coefficient k
1. Consider a case of a single-layer film having a thickness T1.

The two measurement factors of this system are the azimuthal angles α1 and β1 of the polarizer 7 and the analyzer 13, which are the wavelengths λ1,
This value is for the incident angle Θ1. By switching between the wavelengths λ2 and λ3 of the light source, the corresponding azimuthal angles (α2, β2) and (α3, β3) of the polarizer 7 and the analyzer 13 can be obtained. Therefore, only by switching the light source without physically changing the configuration of the apparatus and without changing the angle of incidence ６, (α1, β1), (α2, β2), (α3, β3)
N0, k0, n1, k1, T
It becomes possible to calculate five values of 1.

If, for example, the optical constants n0 and k0 of the substrate are known among the five unknowns, the measurement accuracy of n1, k1, and T1 is determined by performing the above-described multi-wavelength measurement. Can be increased for the case of (Embodiment 2) The second embodiment of the present invention relates to the ellipsometer described in Embodiment 1, wherein one of a plurality of laser chips having different oscillation wavelengths used for a light source is provided as a GaN blue semiconductor laser chip. Is used. GaN-based semiconductor lasers generally have a smaller dependence on wavelength change with respect to temperature change than GaAs-based semiconductor lasers, which can reduce the measurement error of the ellipsometer with respect to the wavelength change of the light source.
Measurement accuracy can be improved. (Embodiment 3) FIG. 5 shows a third embodiment of the present invention.

In the ellipsometer shown in FIG. 5, a plurality of He-Ne lasers 19 emitting different wavelengths are used as light sources (in FIG. 5, a He-Ne laser 19-1 and a He-Ne laser 19 are used).
−2, the wavelengths of these lights are λ1 and λ2).
As this type of light source, for example, red He-N having a wavelength of 632.8 nm
There is an e-laser, a green He-Ne laser with a wavelength of 543.5 nm.

A plurality of lights 20-emitted from the He-Ne laser 19
Each of 1, 20-2 is then synthesized by the half mirror 21, so that light of two wavelengths λ1 and λ2 travels completely on the same optical path.

Thereafter, the three lights 2 emitted from the half mirror 21 are converted into circularly polarized lights 4 by the quarter-wave plate 3. The light transmitted through the quarter-wave plate 3 is extracted as a linearly polarized light component 6 by the polarizer 5, and the compensator (1/4
The elliptically polarized light 8 is formed by the wavelength plate 7. The elliptically polarized light 8 is irradiated at an incident angle Θ1 on a substrate 11 disposed on a central stage 9 and having a surface on which a single layer or a plurality of thin films 10 are formed. Since the three wavelengths of light are completely on the same optical path, all of the two lights enter the substrate 11 at the same incident angle Θ1.

An analyzer 13 and a photodetector 14 are placed on the optical path of the reflected light 12 from the thin film 10 and the substrate 11.

In the ellipsometer having such a configuration, after fixing the azimuth of the compensator (1/4 wavelength plate) 7,
Rotate the polarizer 5 (azimuth α1) and compensator (1/4 wavelength plate)
A position where the elliptically polarized light emitted from the light 7 is completely canceled out by the reflection by the thin film 10 and the substrate 11 to obtain a linearly polarized reflected light is searched, and then the azimuth of the linearly polarized light is rotated. β1) is obtained from the extinction position of the light emitted from the analyzer 13.

Here, suppose that the optical constant of the substrate 11 is the refractive index n
0, absorption coefficient k0, thin film 10 has refractive index n1, absorption coefficient k
1. Consider a case of a single-layer film having a thickness T1.

There are only two measurement factors in this system, the azimuths α1 and β1 of the polarizer 7 and the analyzer 13, which are the wavelengths λ1,
And it is a value for the incident angle Θ1. Light source wavelengths λ1, λ
By switching to 2, the azimuthal angle (α2, β2) between the polarizer 7 and the analyzer 13 corresponding to the wavelength λ2 is obtained. Therefore, only by switching the light source without physically changing the configuration of the device and changing the incident angle （(α
Since four data of (1, β1) and (α2, β2) can be obtained, if one of the five values of n0, k0, n1, k1, and T1 is known, the remaining four values are calculated. It becomes possible to do.

If, for example, the optical constants n0 and k0 of the substrate are known among the five unknowns, the measurement accuracy of n1, k1, and T1 is determined by performing the multi-wavelength measurement described above. Can be increased for the case of

[0030]

As described above, according to the present invention, the wavelength of light incident on a sample is selected by using a semiconductor laser in which a plurality of laser chips emitting different wavelengths are packaged as a single light source. . In addition, a collimator lens is provided to convert the light emitted from the semiconductor laser light source into parallel light, and a plurality of lights having different wavelengths transmitted through the collimator lens travel on the same optical path, after the collimator lens. A wavelength dispersion prism is provided. At least one of the plurality of laser chips used for the light source uses a GaN blue semiconductor laser chip.

As another means, a plurality of He-Ne lasers emitting different wavelengths are used as light sources to select the wavelength of light incident on the sample.

By doing so, highly accurate measurement can be realized without changing the angle of incidence on the sample in the ellipsometer, and the change in the wavelength of the light source due to a change in the external environment such as a temperature change. Since a decrease in the measurement error can be kept small, an ellipsometer with high measurement accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of an ellipsometer of the present invention.

FIG. 2 is an overall configuration diagram showing an example of a conventional ellipsometer.

3 is an internal structural diagram of the semiconductor laser for ellipsometer shown in FIG.

FIG. 4 is an explanatory diagram for explaining a light source portion of the ellipsometer shown in FIG. 1 in detail.

FIG. 5 is an overall configuration diagram showing another embodiment of the ellipsometer of the present invention.

[Explanation of symbols]

1: He-Ne laser light source, 2: Light emitted from He-Ne laser light source, 3: 1/4 wavelength plate, 4: 1/4 wavelength plate transmitted light, 5: Polarizer, 6: After passing through polarizer Linearly polarized light, 7: 1/4 wavelength plate, 8: Elliptically polarized light after passing through 1/4 wavelength plate, 9: stage, 10: thin film, 11: substrate, 12: reflection from thin film and substrate Light, 13 ... analyzer, 14 ... photodetector, 15 ... semiconductor laser,
15-1… Laser chip, 15-2… Laser chip, 15-3…
Laser chip, 16: semiconductor laser emission light, 17: collimator lens, 18: wavelength dispersion prism, 19: He-Ne laser,
20-1 ... He-Ne laser emission light, 20-2 ... He-Ne laser emission light, 21 ... Half mirror.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA00 AA30 BB01 BB17 CC31 DD11 FF50 GG05 GG06 GG13 GG23 HH09 HH10 HH12 JJ01 JJ08 JJ15 LL04 LL33 LL34 LL36 LL47 2G059 AA02 BB10 EJ10 GG11 JJ10 GG11 KK01 MM04 NN02 NN05 5F072 AA01 JJ20 KK15 KK30 RR03 YY11 5F073 CA02 EA07 EA29 FA11 HA02 HA10

Claims (4)

[Claims] 1. Light emitted from a light source is formed into linearly polarized light or elliptically polarized light through an optical element such as a wave plate or a polarizer, and the linearly polarized light or elliptically polarized light is used as incident light. An irradiation is performed at an angle on a substrate having a single layer or a plurality of layers of thin films formed on the surface, and a polarization state of the reflected light is checked on an optical path of the reflected light from the thin film and the substrate. In a polarization analyzer that provides a photon and a photodetector, and measures the optical constant of the thin film, the film thickness, and the optical constant of the substrate by analyzing the polarization state of the incident reflected light, the light source has different wavelengths. An ellipsometer characterized by using a semiconductor laser in which a plurality of laser chips emitting light are packaged in one. 2. An ellipsometer according to claim 1, wherein:
A collimator lens is provided to convert light emitted from a semiconductor laser light source packaged into one into a plurality of laser chips emitting different wavelengths, and a plurality of lights having different wavelengths transmitted through the collimator lens are the same. An ellipsometer characterized in that a wavelength dispersion prism is provided after the collimator lens in order to advance on the optical path. 3. An ellipsometer according to claim 1, wherein:
An ellipsometer characterized in that at least one of a plurality of laser chips used for a light source uses a GaN-based blue semiconductor laser chip. 4. Light emitted from a light source is converted into linearly polarized light or elliptically polarized light through an optical element such as a wave plate or a polarizer, and the linearly polarized light or elliptically polarized light is used as incident light. An irradiation is performed at an angle on a substrate having a single layer or a plurality of layers of thin films formed on the surface, and a polarization state of the reflected light is checked on an optical path of the reflected light from the thin film and the substrate. In a polarization analyzer that provides a photon and a photodetector, and measures the optical constant of the thin film, the film thickness, and the optical constant of the substrate by analyzing the polarization state of the incident reflected light, the light source has different wavelengths. He that emits
-An ellipsometer characterized by using a Ne laser.