JP2007114520A - Optical components for ultraviolet light - Google Patents

Abstract

Property degradation is difficult to occur, and transmittance is not deteriorated by ultraviolet light.
A right crystal Z-cut optical rotation plate a and a left crystal Z-cut optical rotation plate b in which the aluminum concentration of the artificial crystal is less than 1 ppm, the transmittance of which does not easily deteriorate even when the ultraviolet ray is continuously irradiated, are used. In consideration of high-precision polishing and transmittance, each plate has a thickness of 1 mm or more and 5 mm or less, and has a function of a half-wave plate by creating a predetermined thickness difference between the two optical rotation plates. Produces optical components for ultraviolet light. As a result, the thickness tolerance of the quartz plate can be made about 10 times that of the conventional half-wave plate, and the wavelength dependency and incident angle dependency of the phase difference are greatly improved. Between the two optical rotation plates, there is an air layer, a nitrogen atmosphere or a vacuum. In addition, the two optical rotation plates may be directly joined without using an organic adhesive or the like.
[Selection] Figure 1

Description

  The present invention relates to an optical component for ultraviolet light used in optical equipment such as semiconductor manufacturing equipment, light source equipment, and exposure equipment.

  Conventionally, a half-wave plate for ultraviolet light is used in optical equipment such as a semiconductor manufacturing apparatus, a light source apparatus, and an exposure apparatus. This half-wave plate is made of a birefringent crystal plate such as quartz or fluoride.

  For example, as an example of a conventional ultraviolet light quartz half-wave plate, a quartz plate a made of Y-cut right quartz and a quartz plate b made of right quartz or a quartz plate made of left quartz As shown in FIG. 5, an optical axis a and an optical axis b are incident on a quartz half-wave plate for ultraviolet light in which the thickness difference between the crystal plate b made from a and the left crystal is 7.2 ± 0.2 μm. The optical axis a and the optical axis b are bonded so as to have an angle of 45 ° from the polarization direction of the light. Note that either the crystal plate a or the crystal plate b may be thicker.

  For example, when the phase difference design value of the half-wave plate for wavelength 193 nm ultraviolet light is 180 ° ± 5 °, the thickness difference between the two Y-cut quartz plates must be 7.2 ± 0.2 μm . Here, high-precision thickness polishing is performed in order to accurately control the thickness difference between the two quartz plates. When the quartz plate is polished with a thickness difference tolerance of ± 0.2 μm, the thickness of the quartz plate is preferably 1 mm or more in consideration of the polishing accuracy and the strength of the quartz plate.

  For example, the wavelength dependence of the phase difference of a half-wave plate for 193 nm ultraviolet light manufactured using quartz plates with a plate thickness of 1.0072 mm and 1 mm so that the phase difference is 180 ° at the design wavelength of 193 nm. As shown in FIG. 6, as can be seen from the characteristic graph of the phase difference on the vertical axis and the wavelength on the horizontal axis, the phase difference of the emitted light varies greatly with respect to the variation from the design wavelength of the incident light.

  FIG. 7 shows the incident angle dependence of the phase difference of the 193 nm ultraviolet light half-wave plate. As can be seen from the characteristic graph of the phase difference on the vertical axis and the incident angle on the horizontal axis, the level of the emitted light is shown. The phase difference varies greatly with respect to variations from normal incidence of incident light.

  In addition, there exist the patent document 1 and the patent document 2 which are published below as a prior art, and patent document 1 is related with the apparatus which generate | occur | produces predetermined light, controlling a polarization state with simple structure, and there are several polarization adjustment apparatuses. After aligning the polarization state of the plurality of light beams emitted from the optical fiber, the polarization direction conversion device converts all the light beams through the plurality of optical fibers into a plurality of linearly polarized light beams having the same polarization direction. Thus, the polarization direction of the linearly polarized light is set to a polarization direction in which the wavelength conversion is efficiently performed for the first-stage nonlinear optical crystal in the subsequent wavelength conversion device, and the plurality of linearly polarized light beams having the same polarization direction thus obtained are converted into wavelengths. A light source device and an exposure device that efficiently obtain light having a predetermined wavelength by performing wavelength conversion by being incident on a conversion device.

Also, the Patent Document 2, machining error is reduced, in order to create a wavelength dependence small ultraviolet region wavelength plate, small Mg or Be added lithium fluoride calcium aluminum birefringence 10- ³ (hydrofluoric This is a technique for producing a wave plate using a chemical material.
JP 2001-85307 A JP, 2004-53631, A In addition to the prior art document specified by the above-mentioned prior art document information, the applicant has not found prior art documents related to the present invention by the time of filing of the present application. .

  As described in the background art, the conventional half-wave plate needs to be polished with high accuracy, and there is a problem that it is difficult to manufacture. In addition, the wavelength difference and the incident angle dependency of the phase difference are large. Therefore, the characteristic deterioration is likely to occur after the half-wave plate is incorporated in the optical device. There is also a problem that the transmittance is deteriorated by continuously irradiating the half-wave plate with ultraviolet light.

  The present invention uses a right quartz Z-cut optical rotator and an artificial quartz quartz with an aluminum concentration of 1 ppm or less, and a left quartz Z-cut optical rotator. By making the thickness 1 mm or more and 5 mm or less and creating a predetermined thickness difference between the two optical rotation plates, an optical component for ultraviolet light having the function of a half-wave plate can be obtained.

The present invention is an optical component for ultraviolet light in which the thickness tolerance of a quartz plate can be made about 10 times that of a conventional half-wave plate and the wavelength dependency and incident angle dependency of phase difference are greatly improved. .
In order to suppress absorption of ultraviolet light by oxygen, a nitrogen atmosphere or a vacuum is desirable between the two optical rotatory plates used in the optical component for ultraviolet light. In addition, the two optical rotation plates may be directly joined without using an organic adhesive or the like. In direct bonding, the optical rotatory plate is subjected to plasma treatment, etc., the pollutants of the optical rotatory plate are removed cleanly, van der Waals force works by applying stress by overlaying optical rotatory plates with improved hydrophilicity, and This can be done by annealing. In addition, by producing an optical rotatory plate from an artificial quartz crystal having an aluminum concentration of 1 ppm or less, an optical component for ultraviolet light was obtained in which the transmittance is not easily deteriorated even if ultraviolet light is continuously irradiated.

  The present invention converts the 90 ° vibration direction from the vibration surface of incident light by making linearly polarized light incident on an optical component for ultraviolet light using a right crystal Z-cut optical rotator and a left crystal Z-cut optical rotator. Linearly polarized light with a vibrating surface can be extracted.

As described above, by using the present invention, the thickness tolerance can be made larger than that of the conventional half-wave plate for ultraviolet light, and the thickness tolerance can be made about 10 times wider than the conventional one. Therefore, polishing processing can be performed more easily than before. In addition, the influence of the wavelength difference and the incident angle dependency of the phase difference is reduced, and deterioration of characteristics after the ultraviolet light optical component is incorporated into the optical device can be suppressed.
In addition, even if it irradiates with ultraviolet light by manufacturing an optical rotation plate from the artificial quartz whose aluminum concentration is 1 ppm or less, the deterioration of the transmittance can be suppressed.

Embodiments of the present invention will be described below with reference to the drawings.
The optical component for ultraviolet light can be used as a half-wave plate for ultraviolet light in optical equipment such as a semiconductor manufacturing apparatus.
As an embodiment of the present invention, an optical component for ultraviolet light having a thickness difference of 276.5 ± 2.0 μm between the right quartz Z-cut optical rotator and the left quartz Z-cut optical rotator is shown in FIG. In this way, the right crystal Z-cut optical rotation plate a and the left crystal Z-cut optical rotation plate b are bonded so that the optical axes thereof are parallel to each other. In addition, the optical component for ultraviolet light manufactured from the right crystal Z-cut optical rotator and the left crystal Z-cut optical rotator has a thickness of 1 mm to 5 mm, respectively. And the left crystal Z-cut optical rotator are combined, and the plate thickness difference is 276.5 ± 2.0μm when both the right crystal side and the left crystal side are thick. If it exists, the optical component for ultraviolet light which has a function of a 1/2 wavelength plate is realizable.

  The design wavelength of the optical component for ultraviolet light shown in FIG. 1 is 193 nm. At this design wavelength, the thickness of the right quartz Z-cut optical rotator is 1.2765 mm, and the thickness of the left quartz Z-cut optical rotator is 1 mm. At this time, the tolerance of the thickness difference between the optical rotation plates may be about 2 μm.

  FIG. 2 shows the wavelength dependence of the phase difference of the optical component for ultraviolet light according to the present invention. As can be seen from the characteristic graph of the phase difference on the vertical axis and the wavelength on the horizontal axis, the phase difference of the outgoing light is the design of the incident light. There is almost no change with respect to variation from wavelength.

  Further, FIG. 3 shows the dependency of the phase difference of the optical component for ultraviolet light on the incident angle. As can be seen from the characteristic diagram of the phase difference on the vertical axis and the incident angle on the horizontal axis, the phase difference of the emitted light is the incident light. The change is very small with respect to the variation from the normal incidence.

  Further, as shown in FIGS. 2 and 3, the optical component for ultraviolet light according to the present invention has better characteristics than the wavelength and incident angle dependency of the phase difference of the conventional ultraviolet light quartz half-wave plate. I understand that.

  Here, the relationship of the transmittance | permeability of wavelength 193nm with respect to the aluminum concentration in artificial quartz is shown in FIG. FIG. 4 shows that the transmittance tends to be higher as the aluminum concentration is lower. Therefore, the deterioration of the transmittance due to the continuous irradiation with ultraviolet rays can be suppressed by using an artificial quartz that has low absorption, that is, low aluminum concentration. When the theoretical calculation of the transmittance is performed on the assumption that there is no absorption based on the measured refractive index of the artificial quartz, the transmittance at the wavelength of 193 nm is 88.2%, and the transmittance at the wavelength of 193 nm in FIG. From the comparison of the concentration, when the aluminum concentration is 1 ppm or less, it approaches the theoretical transmittance.

  Therefore, by combining the right crystal Z-cut optical rotator and the left crystal Z-cut optical rotator described above, and making each plate thickness 1 mm or more and 5 mm or less, the wavelength difference and the incident angle dependency of the phase difference are good. In addition, an ultraviolet optical component having the function of a half-wave plate with good transmittance could be realized. Furthermore, by setting the aluminum concentration contained in the right quartz Z-cut optical rotator and the left quartz Z-cut optical rotator to 1 ppm or less, it is possible to suppress the deterioration of the transmittance due to continuous irradiation with ultraviolet rays.

  In addition, the two optical rotation plates may be directly joined without using an organic adhesive or the like. In direct bonding, the optical rotatory plate is subjected to plasma treatment, etc., the pollutants of the optical rotatory plate are removed cleanly, van der Waals force works by applying stress by overlaying optical rotatory plates with improved hydrophilicity, and This can be done by annealing.

It is a schematic diagram of the optical component for ultraviolet light of this invention. It is a characteristic view of the simulation which shows the wavelength dependence of the phase difference of the optical component for ultraviolet light of this invention. (Value by the rotation analyzer method) It is a characteristic view of the simulation which shows the incident angle dependence of the phase difference of the optical component for ultraviolet light of this invention. (Value by the rotation analyzer method) It is a characteristic view which shows the relationship between the aluminum concentration of artificial quartz and the transmittance | permeability of wavelength 193nm. It is a schematic diagram of a conventional half-wave plate. It is a characteristic view of the simulation which shows the wavelength dependence of the phase difference of the conventional 1/2 wavelength plate. (Value by the rotation analyzer method) It is a characteristic view of the simulation which shows the incident angle dependence of the phase difference of the conventional 1/2 wavelength plate. (Value by the rotation analyzer method)

Claims (5)

In optical components for ultraviolet light that change the polarization angle of incident light,
An optical component for ultraviolet light comprising a combination of a right crystal Z-cut optical rotator and a left crystal Z-cut optical rotator. In the optical component for ultraviolet light that changes the polarization angle of incident light according to claim 1,
An optical component for ultraviolet light, wherein the thickness of each of the optical rotation plates is 1 mm or more and 5 mm or less. In the optical component for ultraviolet light that changes the polarization angle of incident light according to claim 1,
An optical component for ultraviolet light, wherein when the wavelength of incident light is 193 nm, the thickness difference of the optical rotation plate is 0.2765 ± 0.002 mm. In the optical component for ultraviolet light that changes the polarization angle of incident light according to claim 1,
An optical component for ultraviolet light, wherein an aluminum concentration contained in a quartz rotatory plate is 1 ppm or less. In the optical component for ultraviolet light that changes the polarization angle of incident light according to claim 1,
The optical rotatory plates of the right quartz Z-cut plate and the left quartz Z-cut rotatory plate are cleanly removed, and the optical rotators with improved hydrophilicity are directly joined together by van der Waals force. An optical component for ultraviolet light.

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