JP2005001933A - Metal fluoride body and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal fluoride body, by which the highly oriented metal fluoride body can be manufactured easily in a short period of time; and to provide the metal fluoride body manufactured using the method. <P>SOLUTION: In the method for manufacturing the metal fluoride body by growing a metal fluoride single crystal by a Czochralski method or a floating zone melting method, when the metal fluoride single crystal is grown, the method for manufacturing the metal fluoride body is characterized in that millimeter-wave heating is utilized in at least a part of heating means for melting the metal fluoride. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal fluoride object used in an optical device or the like that uses high-power laser light in the ultraviolet region, such as an excimer laser, and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, in accordance with demands for miniaturization and higher density of semiconductor elements, ultrafine densification of circuit patterns on wafers has progressed, and light in the vacuum ultraviolet region having a shorter wavelength is used as a light beam for optical lithography. In addition, synthetic quartz glass excellent in ultraviolet transmittance is applied.
However, as the wavelength of light used becomes shorter and the energy becomes higher, the quartz glass itself is more likely to be damaged, and the service life is becoming shorter. This is because various structural defects are generated in the glass due to damage caused by light rays, and transmission characteristics are deteriorated due to a new absorption band and a change in refractive index and homogeneity due to a local density change. At present, quartz glass can be used up to the 197 nm (ArF laser) region, but in the use of the next-generation 157 nm (F ₂ laser) region, the light transmission characteristics and laser resistance characteristics have reached the limits. As a specific optical material, a metal fluoride single crystal including calcium fluoride (CaF ₂ ) is used (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-119098
[Problems to be solved by the invention]
As described above, it becomes difficult to cope with quartz glass as the laser wavelength is shortened, and a metal fluoride single crystal such as CaF _{2 is} mainly used as an optical component material. These metal fluorides are manufactured using single crystal growth techniques such as the Czochralski (CZ) method and the floating zone melting (FZ) method, as with silicon semiconductors. When growing a single crystal by the Czochralski method, floating zone melting method, etc., in order to grow a homogeneous crystal, a sufficient stabilization time is required before crystallization is started, and the pulling or pulling speed is increased. For example, it is necessary to carry out very slowly at 1 mm / hour or less. That is, since a very long time and energy required for operating the apparatus are required to produce a good single crystal, there is a disadvantage that the cost increases. In addition, since the manufacturing time is long, there is a high possibility that contamination in which impurities enter the single crystal body is generated. In particular, in order to maintain a stable laser resistance, it is necessary to avoid mixing impurities as well as crystal orientation.
[0005]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a production method capable of easily producing a highly oriented metal fluoride object in a short time and a metal fluoride object obtained by the method.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for producing a metal fluoride object by growing a metal fluoride single crystal by the Czochralski method or the floating zone melting method. There is provided a method for producing a metal fluoride object characterized by using heating.
In the method of the present invention, the metal fluoride is CaF ₂ , LiF, AlF ₃ , BaF ₂ , MgF ₂ , SrF ₂ , HfF ₄ , LaF ₃ , PrF ₃ , ZrF ₄ , NdF ₃ , CeF ₃ , YbF ₃ , One or more selected from the group consisting of YF ₃ and SiOF are preferred.
In addition, the present invention provides a metal fluoride object manufactured by the method for manufacturing a metal fluoride object.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, when a metal fluoride single crystal is formed by the Czochralski method (hereinafter referred to as CZ method) or the floating zone melting method (hereinafter referred to as FZ method), at least one of heating means is used. By using millimeter wave heating for the part, a highly oriented metal fluoride object is easily produced in a short time.
In the present invention, “millimeter wave” is defined as an electromagnetic wave in a frequency band of 3 GHz to 300 GHz including a near millimeter wave in addition to a frequency band generally called a millimeter wave.
[0008]
In the present invention, when a metal fluoride object is produced by the CZ method, a high-purity metal fluoride powder is placed in a clean crucible such as a graphite crucible, heated to melt the powder, and the seed crystal is brought into contact with the melt. The single crystal pulling is started, and at the same time, the single crystal is irradiated with millimeter waves to perform heat treatment. Further, when a metal fluoride object is produced by the FZ method, the metal fluoride single crystal is grown, and at the same time, the single crystal is irradiated with millimeter waves to perform heat treatment.
[0009]
In the present invention, examples of the metal fluoride include metal fluorides having high transparency in the ultraviolet region, for example, fluorides of metal elements of Groups 1 to 4 of the periodic table, and in particular, CaF ₂ , LiF, AlF ₃ , BaF ₂ , _{MgF 2, SrF 2, HfF 4} , LaF 3, PrF 3, ZrF 4, NdF 3, CeF 3, YbF 3, YF 3, 1 or two or more selected from the group consisting of SiOF is preferred.
[0010]
In the method of the present invention, the millimeter wave heating device used for heating the metal fluoride single crystal is not particularly limited, and for example, a commercially available millimeter wave heating device can be used. As a preferable commercially available millimeter wave heating device, for example, a millimeter wave heating device FMW-10-28 manufactured by Fuji Denpa Kogyo Co., Ltd. may be mentioned.
[0011]
Millimeter-wave melting is self-heating and uniform heating compared to an external heating method using a normal heater, etc., and due to its unique reaction mechanism, single crystallization is possible in a very short time, and there is little contamination with impurities. . As a result, according to the present invention, a high-quality and inexpensive laser-resistant material can be easily produced in a short time.
[0012]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited only to description of a following example.
[0013]
(Example 1)
Result of heating 800 g of commercially available high-purity calcium fluoride powder (Stella Chemifa Co., Grade-1) with a millimeter wave heating device (FMW-10-28, Fuji Radio Industry Co., Ltd.) at the same time as the CZ method. A transparent calcium fluoride single crystal was obtained.
The time required for the CZ method and the millimeter wave heating at this time was 1 hour in total. When the obtained transparent single crystal was cut into a desired size and the surface was optically polished and examined with a spectrophotometer, laser light with an energy density of 50 to 500 mJ / cm ² and 50 to 500 Hz was emitted from 10 ⁴ to 10. The internal transmittance when irradiated with ⁷ shots was 90.0% or more per 10 mm thickness, and a value comparable to that produced only by the ordinary CZ method or FZ method was obtained. For birefringence measurement, a birefringence measuring apparatus EXICOR manufactured by Tokyo Instruments was used. A multipoint measurement of 1000 points was performed for each heat-treated product, and all the birefringence optical path differences with respect to light having a wavelength of 633 nm were all 5 nm / cm or less, and there was no variation in numerical values. From these results, it was confirmed that the calcium fluoride transparent material produced by millimeter-wave melting has excellent homogeneity and has laser resistance comparable to that of a normal production method.
[0014]
(Comparative example)
A single crystal of transparent calcium fluoride was prepared by a conventional method using high-purity calcium fluoride powder equivalent to Example 1 (Grade-1 manufactured by Stella Chemifa). First, the melt formed by melting calcium fluoride powder is solidified to grow a fluorite single crystal, thereby producing an ingot of the fluorite single crystal, and the fluorite from the ingot subjected to further heat treatment A single crystal molded product and a test piece were cut out, and the molded product and the test piece were heat treated. First, the powder was filled in a clean container such as a graphite container, and placed in a predetermined position of a vertical Bridgman apparatus (crystal growth furnace) that can be evacuated. Under sufficient exhaust, the fluorite raw material was heated and melted by energization heating of the heater. Immediately after reaching the melting point, crystallization by pulling was not started, but crystallization was started after 6 hours. Pulling down was performed at a rate of 1 mm per hour, and when all of the melt was crystallized, it was gradually cooled to room temperature and taken out as an ingot. Heat treatment (annealing) was performed with the ingot. Incidentally, the total time required for this step was 1100 hours (about 1.5 months). After the obtained ingot was cut and polished, laser resistance and birefringence measurement were evaluated. The evaluation of laser resistance was carried out in the same manner as in Example 1, and the internal transmittance when 10 ⁴ to 10 ⁷ shots of laser light having an energy density of 50 to 500 mJ / cm ² and 50 to 500 Hz were irradiated was 90 per 10 mm thickness. 0.0% or more. For the birefringence measurement, a birefringence measuring apparatus EXICOR manufactured by Tokyo Instruments was used. Multipoint measurement of 1000 points was performed for each heat-treated product, and it was confirmed that all the birefringence optical path differences with respect to light having a wavelength of 633 nm were 5 nm / cm or less.
[0015]
(Example 2)
As in Example 1, 500 g of commercially available barium fluoride powder (manufactured by Stella Chemifa) was pulled up by the FZ method and simultaneously heat treated with a millimeter-wave melting apparatus (FMW-10-28, manufactured by Fuji Denpa Kogyo Co., Ltd.). A transparent barium fluoride single crystal was obtained. The time required for the FZ method and millimeter wave melting at this time was 1 hour in total. When the obtained transparent single crystal was cut into a desired size and the surface was optically polished and examined with a spectrophotometer, laser light with an energy density of 50 to 500 mJ / cm ² and 50 to 500 Hz was emitted from 10 ⁴ to 10 ^7. The internal transmittance upon shot irradiation was 90.0% or more per 10 mm thickness, and a value comparable to that produced by only the ordinary CZ method or FZ method was obtained. For birefringence measurement, a birefringence measuring apparatus EXICOR manufactured by Tokyo Instruments was used. A multipoint measurement of 1000 points was performed for each heat-treated product, and all the birefringence optical path differences with respect to light having a wavelength of 633 nm were all 5 nm / cm or less, and there was no variation in numerical values. From these results, it was confirmed that the calcium fluoride transparent material produced by millimeter wave melting was excellent in homogeneity and had laser resistance comparable to that of a normal production method.
[0016]
【The invention's effect】
According to the present invention, a high-quality and inexpensive laser-resistant material can be easily produced in a short time.

Claims (3)

In the method for producing a metal fluoride object by growing a metal fluoride single crystal by the Czochralski method or the floating zone melting method, the metal fluoride object is characterized by using millimeter wave heating as at least a part of the heating means. Manufacturing method. Wherein the metal fluoride is _comprised of _{CaF 2, LiF, AlF 3,} BaF 2, MgF 2, SrF 2, HfF 4, LaF 3, PrF 3, ZrF 4, NdF 3, CeF 3, YbF 3, YF 3, SiOF It is 1 type, or 2 or more types selected from the group, The manufacturing method of the metal fluoride body of Claim 1 characterized by the above-mentioned. A metal fluoride object produced by the method for producing a metal fluoride object according to claim 1 or 2.