WO2009064081A1 - Linear-focused beam ellipsometer - Google Patents

Linear-focused beam ellipsometer Download PDF

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Publication number
WO2009064081A1
WO2009064081A1 PCT/KR2008/006268 KR2008006268W WO2009064081A1 WO 2009064081 A1 WO2009064081 A1 WO 2009064081A1 KR 2008006268 W KR2008006268 W KR 2008006268W WO 2009064081 A1 WO2009064081 A1 WO 2009064081A1
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WO
WIPO (PCT)
Prior art keywords
light
focusing
specimen
ellipsometer
beam splitting
Prior art date
Application number
PCT/KR2008/006268
Other languages
French (fr)
Inventor
Yong Jai Cho
Won Chegal
Hyun Mo Cho
Original Assignee
Korea Research Institute Of Standards And Science
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Application filed by Korea Research Institute Of Standards And Science filed Critical Korea Research Institute Of Standards And Science
Publication of WO2009064081A1 publication Critical patent/WO2009064081A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
    • G01B11/0641—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of polarization
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/211—Ellipsometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/447—Polarisation spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/8422—Investigating thin films, e.g. matrix isolation method

Definitions

  • the present invention relates to an ellipsoraeter, and more particularly, to a linear focused-beam ellipsoraeter which linearly focuses a light on a specimen using a cylindrical optical system and then measures variation in polarization state of the reflected light.
  • a variety of methods is currently known as a principle of measuring optical properties of a material and a thickness of a thin film.
  • An ellipsometry has largely increased applications as its performance is much improved with development of a light source, a photodetector and a computer and processes using a thin film and a surface are increased.
  • the ellipsometry can be divided into a reflection type and a transmission type and the widely used is the reflection type ellipsometry which analyzes a polarization state of a light reflected from a surface of a specimen with an angle of incidence.
  • the specimen By measuring variation in the polarization state of the light reflected by the specimen, it may be used mainly to extract the optical properties of the specimen such as a refractive index or an extinction coefficient and may be used to extract properties such as interfacial state of the specimen as well.
  • measuring accuracy is excellent since it is possible to accurately control an angle of incidence as all light rays are irradiated onto the specimen with the same incidence angle, but it is difficult to reduce a size of a beam incident to the specimen to less than a mm since diffraction is increased when reducing the size of the incident beam using an iris.
  • a wafer particularly provided with a measuring region limited in an area of tens ⁇ m x tens ⁇ m is used to evaluate the variety of thin film manufacturing processes for the manufacture of semiconductor devices through the measurement.
  • a technology of focusing a parallel light incident in an inclined direction on the surface of a specimen using an optical system consisting of a lens or a reflective mirror is used.
  • a linear focused-beam ellipsometer of an aspect of the present invention includes a beam splitting part for splitting a light generated in a light source into a polarized light; a focusing part for focusing the light split by the beam splitting part onto a specimen; and a photodetection part for detecting the light passed through the focusing part and the beam splitting part after reflected from the specimen, wherein the focusing part linearly focuses the split light onto the specimen.
  • a linear focused-beam ellipsometer of another aspect of the present invention includes a polarization generation part for polarizing a light generated in a light source; a beam splitting part for splitting the light polarized by the polarization generation part; a focusing part for focusing the light split by the beam splitting part onto a specimen; a polarization detection part for detecting a specific polarization state from the light passed through the focusing part and the beam splitting part after reflected from the specimen; and a photodetection part for detecting the light passed through the polarization detection part, wherein the focusing part linearly focuses the split light onto the specimen.
  • the linear focused-beam ellipsometer may further includes an aperture plate for allowing some of the light split by the beam splitting part to pass therethrough, the aperture plate being placed between the beam splitting part and the focusing part.
  • the focusing part includes a cylindrical optical system for linearly focusing the light onto the specimen.
  • the cylindrical optical system includes at least one of a semi-cylindrical lens, a semi-cylindrical mirror and a curved mirror.
  • the beam splitting part consists of a polarizing beam splitter or a non-polarizing beam splitter
  • the linear focused-beam ellipsometer further comprised a linear polarizer between the beam splitting part and the focusing part in the case that the beam splitting part consists of the non-polarizing beam splitter.
  • the light source is a white light source or a monochromatic light source.
  • the linear focused-beam ellipsometer may further include a band-pass filter for allowing a specific range of wavelength of the light to pass therethrough.
  • the linear focused-beam ellipsometer further include, between the beam splitting part and the focusing part, a compensating part for changing a phase of the light according to the polarization state of the light split by the beam splitting part.
  • the photodetection part includes a two-dimensional imaging device consisting of a plurality of pixels.
  • Fig. 1 is a structural view illustrating a linear focused-beam ellipsometer according to a first embodiment of the present invention.
  • Fig. 2 is a structural view illustrating a linear focused-beam ellipsometer according to a second embodiment of the present invention.
  • Figs. 3 and 4 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical lens according to an embodiment of the present invention .
  • Figs. 5 and 6 are views illustrating a focusing part which linearly focuses a light onto a specimen using a curved mirror according to an embodiment of the present invention.
  • Figs. 7 and 8 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical mirror and a curved mirror according to an embodiment of the present invention.
  • Fig. 9 is a view illustrating a reflection path of a light on the specimen according to an embodiment of the present invention.
  • Fig. 10 is a view illustrating a two-dimensional image signal corresponding to intensity of a light measured by pixels of a photodetector according to an embodiment of the present invention.
  • Fig. 1 is a structural view illustrating a linear focused-beam ellipsometer according to a first embodiment of the present invention.
  • the linear focused-beam ellipsometer includes a light source part 10, a polarization generation part 20, a beam splitting part 3OA, an aperture plate 50, a focusing part 60, a polarization detection part 80, a photodetection part 90 and a central processing unit 100.
  • the polarization generation jppart 20 makes a parallel light emitted from the light source part 10 into a specific polarization state.
  • the beam splitting part 3OA splits some of the light passed through the polarization generation part
  • the split light passes through the focusing part 60 placed below the beam splitting part 3OA.
  • the focusing part 60 refracts the split light and linearly focuses the split light onto the specimen 70.
  • the light split by the beam splitting part 3OA may pass through the aperture plate 50 before passes through the focusing part 60.
  • the aperture plate 50 blocks the periphery of the light and allows the center of the light to arrive at the focusing part 60. Structures of the aperture plate 50 and the focusing part 60 will be described later.
  • the light reflected from the specimen 70 passes through the polarization detection part 80 for filtering a specific polarization state after passing through the focusing part 60 and the beam splitting part 3OA. After that, the light passed through the polarization detection part 80 is inputted into the photodetection part 90, and the photodetection part 90 measures the intensity of the inputted light.
  • the photodetection part 90 consists of pixel, and information obtained by the pixels is transferred to the central processing unit 100 and stored as a digital signal.
  • Fig. 2 is a structural view illustrating a linear focused-beam ellipsometer according to a second embodiment of the present invention.
  • the linear focused-beam ellipsometer includes a light source part 10, a beam splitting part 3OB, a focusing part 60, a photodetection part 90 and a central processing unit 100.
  • the light emitted from the light source part 10 is reflected with a linear polarization from or transmitted through the beam splitting part 3OB.
  • Some of the light split by the beam splitting part 3OB is linearly focused onto the specimen 70 through the focusing part 60.
  • the light reflected from the specimen 70 is inputted into the photodetection part 90, which detects a parallel light filtered as a specific polarization state while passing through the focusing part 60 and the beam splitting part 3OB with the pixels.
  • the central processing unit 100 corrects the intensity of the light detected by the photodetection part 90 and processes it. Comparing to the linear focused-beam ellipsometer of Fig. 1, the linear focused-beam ellipsometer of Fig.
  • the beam splitting part 3OB includes the functions of the polarization generation part 20 and the polarization detection part 80.
  • the central processing unit 100 (for example, a computer) analyzes the waveform of the voltage or current detected by the photodetection part 90, thereby extracting optical properties of the specimen 70, e.g. in the case of a thin film, thickness and optical constants of the thin film.
  • a compensating part 40 that changes the phase of the progressive wave according to the polarization state may be optionally further provided between the beam splitting part 3OB and the focusing part 60.
  • the aperture plate 50 for preventing the periphery of the light from arriving at the focusing part 60 may be further provided between the beam splitting part 3OB and the focusing part 60 or the compensating part 40 and the focusing part 60.
  • the compensating part 40 has a characteristic that when the linearly polarized light is vertically incident to the surface of the compensator 40, it has the value of phase difference between the light transmitted when the polarization direction is parallel to the light axis of the compensator 40 and the light transmitted when the polarization direction is vertical to the light axis of the compensator 40.
  • the linear focused-beam ellipsometer includes the compensator 40 and/or the aperture plate 50
  • the light split by the beam splitting part 3OB is inputted into the focusing part 60 after passing through the compensator 40 and/or the aperture plate 50, and the light reflected from the specimen 70 is transferred to the beam splitting part 3OB after passing through the aperture plate 50 and/or the compensator 40.
  • the beam splitting part 3OB may consist of a polarizing beam splitter.
  • a linear polarizer may be provided between the non-polarizing beam splitter and the compensating part 40.
  • the light source part 10 may include a white light source such as a tungsten-halogen lamp, a xenon discharge lamp and a monochromatic light source such as a laser which are generally used in the art.
  • a white light source such as a tungsten-halogen lamp, a xenon discharge lamp and a monochromatic light source such as a laser which are generally used in the art.
  • a band-pass filter for allowing a specific range of wavelength of the light emitted from the light source part 10 to pass therethrough has to be placed at the back of the light source part 10 or in front of the photodetector 90.
  • the light emitted from the light source part 10 is made into a parallel light using a reflection and refraction optical systems and some of the light is reflected by the beam splitting part 3OB, of which polarization direction is aligned in an X-axis direction, i.e. the direction parallel to the inclined reflection face within the beam splitting part 3OB.
  • the photodetection part 90 has a plurality of pixels and an example thereof includes a charge-coupled device
  • CCD Compact Disc
  • Figs. 1 and 2 Locations of the light source part 10 and the photodetection part 90 shown in Figs. 1 and 2 are only illustrative, a linear focused-beam ellipsometer having different locations of the light source part 10 and the photodetection part 90 will be laid within the scope of the present invention, provided that it performs the same function.
  • Figs. 3 and 4 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical lens according to an embodiment of the present invention.
  • Fig. 3 is a perspective view of the focusing part 60
  • Fig. 4 is a front view of the focusing part 60 when viewed in an X-axis. Referring to Figs. 3 and 4, the light split by the beam splitting part 3OA, 3OB passes through the aperture plate 51.
  • the aperture plate 51 has a rectangular shape formed with a rectangular hole at the center thereof, and some of the light split by the beam splitting part 3OA, 3OB is transferred to the focusing part 60 through the rectangular hole and the rest of the light is blocked by the aperture plate 51.
  • the aperture plate 51 is optional and the light split by the beam splitting part 3OA, 3OB may be directly transferred to the focusing part 60 without passing through the aperture plate 51.
  • the rectangular hole at the center of the aperture plate 51 is only illustrative, and the aperture plate 51 of the present invention may have a hole of various shapes .
  • the focusing part 60 may be made up of a semi- cylindrical lens 61, and the semi-cylindrical lens 61 has an aperture plate-side surface which is a curved surface having a semicircular cross-section and a specimen-side surface which is a rectangular plane. Therefore, the light transferred to the semi-cylindrical lens 61 is refracted while passing through the semi-cylindrical lens 61 and then linearly converged into the specimen 70. As shown in Fig. 4, the light passed through the semi-cylindrical lens 61 is reflected from the specimen 70 with the same angle ⁇ of reflection as the angle ⁇ of incidence, and then refracted while passing through the semi-cylindrical lens 61 and transferred to the aperture plate 51.
  • Figs. 5 and 6 are views illustrating a focusing part which linearly focuses a light onto a specimen using a curved mirror according to an embodiment of the present invention.
  • Fig. 5 is a perspective view of the focusing part 60
  • Fig. 6 is a front view of the focusing part 60 when viewed in an X-axis.
  • the light split by the beam splitting part 3OA, 3OB passes through the aperture plate 52.
  • the aperture plate 52 has structure and function same as or similar to the aperture plate 51 shown in Figs. 3 and 4.
  • the aperture plate 52 is optional and the light split by the beam splitting part 3OA, 3OB may be directly transferred to the focusing part 60 without passing through the aperture plate 52.
  • the focusing part 60 may be made up of a curved rectangular mirror 62, and the curved mirror 62 has an aperture plate- side surface which is a concaved surface and is inclinedly provided with respect to the specimen 70. Therefore, the light transferred to the curved mirror 62 is reflected from the curved mirror 62 and then linearly converged into the specimen 70. As shown in Fig. 6, the light reflected from the curved mirror 62 is reflected from reflected from the specimen 70 with the same angle ⁇ of reflection as the angle ⁇ of incidence, and then reflected again from the curved mirror 62 and transferred to the aperture plate 52.
  • Figs. 7 and 8 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical mirror and a curved mirror according to an embodiment of the present invention.
  • Fig. 7 is a perspective view of the focusing part 60
  • Fig. 8 is a front view of the focusing part 60 when viewed in an X-axis.
  • the light split by the beam splitting part 3OA, 3OB passes through the aperture plate 53.
  • the aperture plate 53 has structure and function same as or similar to the aperture plate 51, 52 shown in Figs. 3 and 4 and Figs. 5 and 6.
  • the aperture plate 53 is optional and the light split by the beam splitting part 3OA, 3OB may be directly transferred to the focusing part 60 without passing through the aperture plate 53.
  • the focusing part 60 may be made up of a semi- cylindrical mirror 64 and a rectangular curved mirror 63.
  • the curved mirror 63 has an aperture plate-side surface which is a convexed surface and is inclinedly provided with respect to the specimen 70
  • the semi -cylindrical mirror 64 has an aperture plate- side surface which is a convexed surface. Therefore, the light passed through the aperture plate 53 is reflected from the semi -cylindrical mirror 64 and then reflected again the curved mirror 63 to be linearly converged into the specimen 70. As shown in Fig.
  • the light reflected from the curved mirror 66 is reflected from the specimen 70 with the same angle ⁇ of reflection as the angle ⁇ of incidence and then reflected at the curved mirror 63 and the semi-cylindrical mirror 64 to be transferred to the aperture plate 53.
  • the structures of the focusing part 60 described above are illustrative, and any focusing part 60 can be employed provided that it linearly focuses the light onto the specimen 70 .
  • Fig. 9 is a view illustrating a reflection path of a light on the specimen according to an embodiment of the present invention
  • Fig. 10 is a view illustrating a two- dimensional image signal corresponding to intensity of a light measured by pixels of a photodetector according to an embodiment of the present invention.
  • the light in a specific polarization state passed through the focusing part 60 is reflected from the specimen 70 with the same angle ⁇ of reflection as the angle ⁇ of incidence and then transferred again to the focusing part 60.
  • the light incident to 7OA is reflected at the position 72C of the specimen 70 to 7OB
  • the light incident to 7OB is reflected at the position 72C of the specimen 70 to 7OA
  • the light incident to 7OC is reflected at the position 72C of the specimen 70 to 7OC, i.e. the same path.
  • the light incident to 71A is reflected at the position 73C of the specimen 70 to 71B
  • the light incident to 71B is reflected at the position 73C of the specimen 70 to 71A
  • the light incident to 71C is reflected at the position 72C of the specimen 70 to 71C, i.e. the same path.
  • the light reflected from the specimen 70 is transferred to the photodetection part 90 through the focusing part 60 and the beam splitting part 3OA, 3OB.
  • Figs. 9 and 10 it can be seen distribution of light intensity measured by the pixels of the photodetection part 90. While the light in a specific polarization state incident to 7OA is transmitted through the beam splitting part 3OA, 3OB after reflected from the specimen 70 to the 7OB, a polarization component parallel to a Y-axis direction alone is filtered. After that, the polarization component parallel to a Y-axis is arrived at a position 9OB of the two-dimensional signal obtained by the photodetection part 90 and is detected as an electric signal such as voltage and current corresponding to the light intensity by the pixel of the photodetection part 90.
  • the polarization component parallel to the Y-axis direction alone is filtered.
  • the polarization components are arrived at positions 9OA, 91B and 91A of the two- dimensional signal obtained by the photodetection part 90 and are detected as electric signals such as voltage and current corresponding to the light intensity by the pixel of the photodetection part 90. As shown in Fig.
  • the two-dimensional image signal measured by the photodetection part 90 is represented in a shape parallel to the X-axis direction. Therefore, it is possible to measure a plurality of specimens at the same time when the plurality of specimens is placed along the X-axis direction.
  • the light split by the beam splitting part is linearly focused onto a plurality of specimens using the focusing part consisting of a cylindrical optical system and then variation in polarization state of the reflected light is measured with respect to multiple angles of incidence. Therefore, it is possible to obtain information for optical properties of the specimen, i.e., in the case of a thin film, thickness and refractive index of the thin film at the same time with respect to a plurality of the specimens. Consequently, it is possible to reduce the time and efforts for measuring the optical properties of the plurality of the specimens.

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Abstract

The present invention relates to The present invention relates to an ellipsometer, and more particularly, to a linear focused-beam ellipsometer which linearly focuses a light on a specimen using a cylindrical optical system and then measures variation in polarization state of the reflected light. A light split by the beam splitting part is linearly focused onto a plurality of specimens and variation in polarization state of the reflected light is measured with respect to multiple angles of incidence. Therefore, it is possible to measure a plurality of specimens at the same time.

Description

[DESCRIPTION] [invention Title]
LINEAR-FOCUSED BEAM ELLIPSOMETER
[Technical Field]
The present invention relates to an ellipsoraeter, and more particularly, to a linear focused-beam ellipsoraeter which linearly focuses a light on a specimen using a cylindrical optical system and then measures variation in polarization state of the reflected light.
[Background Art]
In general, in studies in the fields of physics, chemistry and material, it is very important to measure optical properties of a material and measure a thickness of a thin film. Particularly, a variety of nano-thin film manufacturing processes is used in semiconductor industries, and an ellipsometer which is non-destructive and contactless real-time measuring equipment is widely used as a measuring equipment to evaluate physical properties of the manufactured thin films.
A variety of methods is currently known as a principle of measuring optical properties of a material and a thickness of a thin film. An ellipsometry has largely increased applications as its performance is much improved with development of a light source, a photodetector and a computer and processes using a thin film and a surface are increased. The ellipsometry can be divided into a reflection type and a transmission type and the widely used is the reflection type ellipsometry which analyzes a polarization state of a light reflected from a surface of a specimen with an angle of incidence. By measuring variation in the polarization state of the light reflected by the specimen, it may be used mainly to extract the optical properties of the specimen such as a refractive index or an extinction coefficient and may be used to extract properties such as interfacial state of the specimen as well. In the case that a parallel light is incident in an inclined direction, measuring accuracy is excellent since it is possible to accurately control an angle of incidence as all light rays are irradiated onto the specimen with the same incidence angle, but it is difficult to reduce a size of a beam incident to the specimen to less than a mm since diffraction is increased when reducing the size of the incident beam using an iris.
In semiconductor industries, a wafer particularly provided with a measuring region limited in an area of tens μm x tens μm is used to evaluate the variety of thin film manufacturing processes for the manufacture of semiconductor devices through the measurement. In order to measure the thickness of the thin film within the measuring region limited in the micrometer level using an ellipsometer, a technology of focusing a parallel light incident in an inclined direction on the surface of a specimen using an optical system consisting of a lens or a reflective mirror is used. However, in this case, it is difficult to ensure and maintain the measuring accuracy compared to using the parallel in an inclined direction since light rays having a plurality of incidence angles are incident to the specimen at the same time.
As a critical dimension patterned in a wafer is expected to be continuously reduced with recent continuous development in a semiconductor device manufacturing technology, the area of the limited measuring region have to be correspondingly reduced. However, in the case of the inclined directional focused-beam ellipsometer, it is actually difficult to reduce the size any more due to barrier such as aberration and structural limitation of the focused-beam optical system despite to many studies and efforts for reducing the area of the light beam irradiated onto the specimen as small as possible. Also, in the case of focusing on the surface of the specimen in a dot shape using an optical system, a plurality of the specimens cannot be measured at the same time and thus it takes much time since the thickness or properties of the specimen has to be measured one after another.
[Disclosure] [Technical Problem]
It is an object of the present invention to provide a linear focused-beam ellipsometer which makes a parallel light to be incident in the direction vertical to a surface of a specimen, focuses the light on a straight line on the surface of the specimen using a cylindrical optical system and then measures variation in polarization state of the reflected light with respect to multiple angles.
[Technical Solution]
A linear focused-beam ellipsometer of an aspect of the present invention includes a beam splitting part for splitting a light generated in a light source into a polarized light; a focusing part for focusing the light split by the beam splitting part onto a specimen; and a photodetection part for detecting the light passed through the focusing part and the beam splitting part after reflected from the specimen, wherein the focusing part linearly focuses the split light onto the specimen.
A linear focused-beam ellipsometer of another aspect of the present invention includes a polarization generation part for polarizing a light generated in a light source; a beam splitting part for splitting the light polarized by the polarization generation part; a focusing part for focusing the light split by the beam splitting part onto a specimen; a polarization detection part for detecting a specific polarization state from the light passed through the focusing part and the beam splitting part after reflected from the specimen; and a photodetection part for detecting the light passed through the polarization detection part, wherein the focusing part linearly focuses the split light onto the specimen.
The linear focused-beam ellipsometer may further includes an aperture plate for allowing some of the light split by the beam splitting part to pass therethrough, the aperture plate being placed between the beam splitting part and the focusing part.
The focusing part includes a cylindrical optical system for linearly focusing the light onto the specimen.
The cylindrical optical system includes at least one of a semi-cylindrical lens, a semi-cylindrical mirror and a curved mirror.
The beam splitting part consists of a polarizing beam splitter or a non-polarizing beam splitter, and the linear focused-beam ellipsometer further comprised a linear polarizer between the beam splitting part and the focusing part in the case that the beam splitting part consists of the non-polarizing beam splitter.
The light source is a white light source or a monochromatic light source. The linear focused-beam ellipsometer may further include a band-pass filter for allowing a specific range of wavelength of the light to pass therethrough. The linear focused-beam ellipsometer further include, between the beam splitting part and the focusing part, a compensating part for changing a phase of the light according to the polarization state of the light split by the beam splitting part.
The photodetection part includes a two-dimensional imaging device consisting of a plurality of pixels.
[Description of Drawings]
Fig. 1 is a structural view illustrating a linear focused-beam ellipsometer according to a first embodiment of the present invention. Fig. 2 is a structural view illustrating a linear focused-beam ellipsometer according to a second embodiment of the present invention.
Figs. 3 and 4 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical lens according to an embodiment of the present invention .
Figs. 5 and 6 are views illustrating a focusing part which linearly focuses a light onto a specimen using a curved mirror according to an embodiment of the present invention.
Figs. 7 and 8 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical mirror and a curved mirror according to an embodiment of the present invention.
Fig. 9 is a view illustrating a reflection path of a light on the specimen according to an embodiment of the present invention.
Fig. 10 is a view illustrating a two-dimensional image signal corresponding to intensity of a light measured by pixels of a photodetector according to an embodiment of the present invention.
[Detailed Description of Main Elements]
10: light source part 20: polarization generation part 3OA, 3OB: beam splitting part 40: compensating part 50: aperture plate 60: focusing part 70: specimen
80: polarization detection part 90: photodetection part 100: central processing unit
[Best Mode]
All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, However, several of the terms may not be generally understood, and general definitions of these terms are provided herein. While it is not intended that the present invention be restricted by shortcomings in these definitions, it is believed helpful to provide these definitions as guidance to those unfamiliar with the terms .
Herein after, preferred embodiments of the present invention will be described in detail with reference to accompanying drawings . Fig. 1 is a structural view illustrating a linear focused-beam ellipsometer according to a first embodiment of the present invention. Referring to Fig. 1, the linear focused-beam ellipsometer includes a light source part 10, a polarization generation part 20, a beam splitting part 3OA, an aperture plate 50, a focusing part 60, a polarization detection part 80, a photodetection part 90 and a central processing unit 100.
The polarization generation jppart 20 makes a parallel light emitted from the light source part 10 into a specific polarization state. The beam splitting part 3OA splits some of the light passed through the polarization generation part
20. The split light passes through the focusing part 60 placed below the beam splitting part 3OA. The focusing part 60 refracts the split light and linearly focuses the split light onto the specimen 70.
Optionally, the light split by the beam splitting part 3OA may pass through the aperture plate 50 before passes through the focusing part 60. The aperture plate 50 blocks the periphery of the light and allows the center of the light to arrive at the focusing part 60. Structures of the aperture plate 50 and the focusing part 60 will be described later.
The light reflected from the specimen 70 passes through the polarization detection part 80 for filtering a specific polarization state after passing through the focusing part 60 and the beam splitting part 3OA. After that, the light passed through the polarization detection part 80 is inputted into the photodetection part 90, and the photodetection part 90 measures the intensity of the inputted light. The photodetection part 90 consists of pixel, and information obtained by the pixels is transferred to the central processing unit 100 and stored as a digital signal.
Fig. 2 is a structural view illustrating a linear focused-beam ellipsometer according to a second embodiment of the present invention. Referring to Fig. 2, the linear focused-beam ellipsometer includes a light source part 10, a beam splitting part 3OB, a focusing part 60, a photodetection part 90 and a central processing unit 100.
As described above, the light emitted from the light source part 10 is reflected with a linear polarization from or transmitted through the beam splitting part 3OB. Some of the light split by the beam splitting part 3OB is linearly focused onto the specimen 70 through the focusing part 60. After that, the light reflected from the specimen 70 is inputted into the photodetection part 90, which detects a parallel light filtered as a specific polarization state while passing through the focusing part 60 and the beam splitting part 3OB with the pixels. The central processing unit 100 corrects the intensity of the light detected by the photodetection part 90 and processes it. Comparing to the linear focused-beam ellipsometer of Fig. 1, the linear focused-beam ellipsometer of Fig. 2 is distinguished from that the beam splitting part 3OB includes the functions of the polarization generation part 20 and the polarization detection part 80. The central processing unit 100 (for example, a computer) analyzes the waveform of the voltage or current detected by the photodetection part 90, thereby extracting optical properties of the specimen 70, e.g. in the case of a thin film, thickness and optical constants of the thin film. In order to arbitrarily control the polarization state of the light incident to the specimen 70, a compensating part 40 that changes the phase of the progressive wave according to the polarization state may be optionally further provided between the beam splitting part 3OB and the focusing part 60. Also, the aperture plate 50 for preventing the periphery of the light from arriving at the focusing part 60 may be further provided between the beam splitting part 3OB and the focusing part 60 or the compensating part 40 and the focusing part 60. The compensating part 40 has a characteristic that when the linearly polarized light is vertically incident to the surface of the compensator 40, it has the value of phase difference between the light transmitted when the polarization direction is parallel to the light axis of the compensator 40 and the light transmitted when the polarization direction is vertical to the light axis of the compensator 40.
In the case that the linear focused-beam ellipsometer includes the compensator 40 and/or the aperture plate 50, the light split by the beam splitting part 3OB is inputted into the focusing part 60 after passing through the compensator 40 and/or the aperture plate 50, and the light reflected from the specimen 70 is transferred to the beam splitting part 3OB after passing through the aperture plate 50 and/or the compensator 40.
Also, in Fig. 2, the beam splitting part 3OB may consist of a polarizing beam splitter. In the case that the beam splitting part 3OB consists of a non-polarizing beam splitter instead of the polarizing beam splitter, a linear polarizer may be provided between the non-polarizing beam splitter and the compensating part 40.
The light source part 10 may include a white light source such as a tungsten-halogen lamp, a xenon discharge lamp and a monochromatic light source such as a laser which are generally used in the art. When the white light source is used, a band-pass filter for allowing a specific range of wavelength of the light emitted from the light source part 10 to pass therethrough has to be placed at the back of the light source part 10 or in front of the photodetector 90.
The light emitted from the light source part 10 is made into a parallel light using a reflection and refraction optical systems and some of the light is reflected by the beam splitting part 3OB, of which polarization direction is aligned in an X-axis direction, i.e. the direction parallel to the inclined reflection face within the beam splitting part 3OB.
The photodetection part 90 has a plurality of pixels and an example thereof includes a charge-coupled device
(CCD) . Information obtained from the respective pixels of the photodetection part 90 is transferred to the central processing unit 100 and stored as a digital signal.
Locations of the light source part 10 and the photodetection part 90 shown in Figs. 1 and 2 are only illustrative, a linear focused-beam ellipsometer having different locations of the light source part 10 and the photodetection part 90 will be laid within the scope of the present invention, provided that it performs the same function.
Hereinafter, the focusing part 60 of the linear focused-beam ellipsometer will be described in detail. Figs. 3 and 4 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical lens according to an embodiment of the present invention. Fig. 3 is a perspective view of the focusing part 60 and Fig. 4 is a front view of the focusing part 60 when viewed in an X-axis. Referring to Figs. 3 and 4, the light split by the beam splitting part 3OA, 3OB passes through the aperture plate 51. The aperture plate 51 has a rectangular shape formed with a rectangular hole at the center thereof, and some of the light split by the beam splitting part 3OA, 3OB is transferred to the focusing part 60 through the rectangular hole and the rest of the light is blocked by the aperture plate 51. As aforementioned, the aperture plate 51 is optional and the light split by the beam splitting part 3OA, 3OB may be directly transferred to the focusing part 60 without passing through the aperture plate 51. The rectangular hole at the center of the aperture plate 51 is only illustrative, and the aperture plate 51 of the present invention may have a hole of various shapes . The focusing part 60 may be made up of a semi- cylindrical lens 61, and the semi-cylindrical lens 61 has an aperture plate-side surface which is a curved surface having a semicircular cross-section and a specimen-side surface which is a rectangular plane. Therefore, the light transferred to the semi-cylindrical lens 61 is refracted while passing through the semi-cylindrical lens 61 and then linearly converged into the specimen 70. As shown in Fig. 4, the light passed through the semi-cylindrical lens 61 is reflected from the specimen 70 with the same angle Φ of reflection as the angle Φ of incidence, and then refracted while passing through the semi-cylindrical lens 61 and transferred to the aperture plate 51.
Figs. 5 and 6 are views illustrating a focusing part which linearly focuses a light onto a specimen using a curved mirror according to an embodiment of the present invention. Fig. 5 is a perspective view of the focusing part 60 and Fig. 6 is a front view of the focusing part 60 when viewed in an X-axis. Referring to Figs. 5 and 6, the light split by the beam splitting part 3OA, 3OB passes through the aperture plate 52. The aperture plate 52 has structure and function same as or similar to the aperture plate 51 shown in Figs. 3 and 4. As aforementioned, the aperture plate 52 is optional and the light split by the beam splitting part 3OA, 3OB may be directly transferred to the focusing part 60 without passing through the aperture plate 52.
The focusing part 60 may be made up of a curved rectangular mirror 62, and the curved mirror 62 has an aperture plate- side surface which is a concaved surface and is inclinedly provided with respect to the specimen 70. Therefore, the light transferred to the curved mirror 62 is reflected from the curved mirror 62 and then linearly converged into the specimen 70. As shown in Fig. 6, the light reflected from the curved mirror 62 is reflected from reflected from the specimen 70 with the same angle Φ of reflection as the angle Φ of incidence, and then reflected again from the curved mirror 62 and transferred to the aperture plate 52.
Figs. 7 and 8 are views illustrating a focusing part which linearly focuses a light onto a specimen using a semi- cylindrical mirror and a curved mirror according to an embodiment of the present invention. Fig. 7 is a perspective view of the focusing part 60 and Fig. 8 is a front view of the focusing part 60 when viewed in an X-axis. Referring to Figs. 7 and 8, the light split by the beam splitting part 3OA, 3OB passes through the aperture plate 53. The aperture plate 53 has structure and function same as or similar to the aperture plate 51, 52 shown in Figs. 3 and 4 and Figs. 5 and 6. As aforementioned, the aperture plate 53 is optional and the light split by the beam splitting part 3OA, 3OB may be directly transferred to the focusing part 60 without passing through the aperture plate 53.
The focusing part 60 may be made up of a semi- cylindrical mirror 64 and a rectangular curved mirror 63. The curved mirror 63 has an aperture plate-side surface which is a convexed surface and is inclinedly provided with respect to the specimen 70, and the semi -cylindrical mirror 64 has an aperture plate- side surface which is a convexed surface. Therefore, the light passed through the aperture plate 53 is reflected from the semi -cylindrical mirror 64 and then reflected again the curved mirror 63 to be linearly converged into the specimen 70. As shown in Fig. 8, the light reflected from the curved mirror 66 is reflected from the specimen 70 with the same angle Φ of reflection as the angle Φ of incidence and then reflected at the curved mirror 63 and the semi-cylindrical mirror 64 to be transferred to the aperture plate 53.
The structures of the focusing part 60 described above are illustrative, and any focusing part 60 can be employed provided that it linearly focuses the light onto the specimen 70 .
Fig. 9 is a view illustrating a reflection path of a light on the specimen according to an embodiment of the present invention and Fig. 10 is a view illustrating a two- dimensional image signal corresponding to intensity of a light measured by pixels of a photodetector according to an embodiment of the present invention.
As described above, the light in a specific polarization state passed through the focusing part 60 is reflected from the specimen 70 with the same angle Φ of reflection as the angle Φ of incidence and then transferred again to the focusing part 60. Referring to Fig. 9, the light incident to 7OA is reflected at the position 72C of the specimen 70 to 7OB, the light incident to 7OB is reflected at the position 72C of the specimen 70 to 7OA, and the light incident to 7OC is reflected at the position 72C of the specimen 70 to 7OC, i.e. the same path. Likewise, the light incident to 71A is reflected at the position 73C of the specimen 70 to 71B, the light incident to 71B is reflected at the position 73C of the specimen 70 to 71A, and the light incident to 71C is reflected at the position 72C of the specimen 70 to 71C, i.e. the same path. The light reflected from the specimen 70 is transferred to the photodetection part 90 through the focusing part 60 and the beam splitting part 3OA, 3OB.
Referring to Figs. 9 and 10, it can be seen distribution of light intensity measured by the pixels of the photodetection part 90. While the light in a specific polarization state incident to 7OA is transmitted through the beam splitting part 3OA, 3OB after reflected from the specimen 70 to the 7OB, a polarization component parallel to a Y-axis direction alone is filtered. After that, the polarization component parallel to a Y-axis is arrived at a position 9OB of the two-dimensional signal obtained by the photodetection part 90 and is detected as an electric signal such as voltage and current corresponding to the light intensity by the pixel of the photodetection part 90.
Likewise, while the light in a specific polarization state incident to 7OB, 71A, and 71B is transmitted through the beam splitting part 3OA, 3OB after reflected from the specimen 70 to the 7OA, 71B, and 71A respectively, the polarization component parallel to the Y-axis direction alone is filtered. After that, the polarization components are arrived at positions 9OA, 91B and 91A of the two- dimensional signal obtained by the photodetection part 90 and are detected as electric signals such as voltage and current corresponding to the light intensity by the pixel of the photodetection part 90. As shown in Fig. 10, it can be seen that the two-dimensional image signal measured by the photodetection part 90 is represented in a shape parallel to the X-axis direction. Therefore, it is possible to measure a plurality of specimens at the same time when the plurality of specimens is placed along the X-axis direction.
Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims .
[industrial Applicability]
According to the linear focused-beam ellipsometer of the present invention, the light split by the beam splitting part is linearly focused onto a plurality of specimens using the focusing part consisting of a cylindrical optical system and then variation in polarization state of the reflected light is measured with respect to multiple angles of incidence. Therefore, it is possible to obtain information for optical properties of the specimen, i.e., in the case of a thin film, thickness and refractive index of the thin film at the same time with respect to a plurality of the specimens. Consequently, it is possible to reduce the time and efforts for measuring the optical properties of the plurality of the specimens.

Claims

[CLAIMS] [Claim l]
A linear focused-beam ellipsoraeter, comprising: a beam splitting part for splitting a light generated in a light source into a polarized light; a focusing part for focusing the light split by the beam splitting part onto a specimen; and a photodetection part for detecting the light passed through the focusing part and the beam splitting part after reflected from the specimen, wherein the focusing part linearly focuses the split light onto the specimen.
[Claim 2] A linear focused-beam ellipsometer, comprising: a polarization generation part for polarizing a light generated in a light source ; a beam splitting part for splitting the light polarized by the polarization generation part; a focusing part for focusing the light split by the beam splitting part onto a specimen; a polarization detection part for detecting a specific polarization state from the light passed through the focusing part and the beam splitting part after reflected from the specimen; and a photodetection part for detecting the light passed through the polarization detection part, wherein the focusing part linearly focuses the split light onto the specimen.
[Claim 3]
The linear focused-beam ellipsometer as set forth in claim 1 or claim 2, wherein the linear focused-beam ellipsometer further comprises an aperture plate for allowing some of the light split by the beam splitting part to pass therethrough, the aperture plate being placed between the beam splitting part and the focusing part.
[Claim 4] The linear focused-beam ellipsometer as set forth in claim 1 or claim 2, wherein the focusing part includes a cylindrical optical system for linearly focusing the light onto the specimen.
[Claim 5]
The linear focused-beam ellipsometer as set forth in claim 4, wherein the cylindrical optical system includes at least one of a semi-cylindrical lens, a semi-cylindrical mirror and a curved mirror.
[Claim 6]
The linear focused-beara ellipsometer as set forth in claim 1, wherein the beam splitting part consists of a polarizing beam splitter or a non-polarizing beam splitter, and the linear focused-beam ellipsometer further comprised a linear polarizer between the beam splitting part and the focusing part in the case that the beam splitting part consists of the non-polarizing beam splitter.
[Claim 7j
The linear focused-beam ellipsometer as set forth in claim 1 or claim 2, wherein the light source is a white light source or a monochromatic light source.
[Claim 8]
The linear focused-beam ellipsometer as set forth in claim 7, wherein the linear focused-beam ellipsometer further comprises a band-pass filter for allowing a specific range of wavelength of the light to pass therethrough.
[claim 9]
The linear focused-beam ellipsometer as set forth in claim 1 or claim 2, wherein the linear focused-beam ellipsometer further comprises, between the beam splitting part and the focusing part, a compensating part for changing a phase of the light according to the polarization state of the light split by the beam splitting part.
[Claim lθ]
The linear focused-beam ellipsometer as set forth in claim 1 or claim 2, wherein the photodetection part includes a two-dimensional imaging device consisting of a plurality of pixels.
PCT/KR2008/006268 2007-11-14 2008-10-23 Linear-focused beam ellipsometer WO2009064081A1 (en)

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CN112147789B (en) * 2020-08-18 2022-05-10 深圳大学 OAM demultiplexing device and method based on coordinate transformation

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KR100742982B1 (en) * 2006-06-22 2007-07-26 케이맥(주) Focused-beam ellipsometer

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