JP2000203994A - Fluorite single crystal, its heat treatment and production of fluorite single crystal raw material - Google Patents
Fluorite single crystal, its heat treatment and production of fluorite single crystal raw materialInfo
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- JP2000203994A JP2000203994A JP10349671A JP34967198A JP2000203994A JP 2000203994 A JP2000203994 A JP 2000203994A JP 10349671 A JP10349671 A JP 10349671A JP 34967198 A JP34967198 A JP 34967198A JP 2000203994 A JP2000203994 A JP 2000203994A
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- Prior art keywords
- single crystal
- fluorite
- temperature
- ingot
- fluorite single
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- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は蛍石単結晶、その熱
処理方法及び蛍石単結晶素材の製造方法に関し、特に真
空紫外光（例えば、ＫｒＦ、ＡｒＦエキシマレーザー、
Ｆ2レーザー、固体レーザー、Ｘｅ2ランプ光、Ｋｒ2ラ
ンプ光）を光源とした光リソグラフィー装置の光学系
（光学部材）に用いて好適な蛍石単結晶、その熱処理方
法及び光学部材作製用の蛍石単結晶素材の製造方法に関
するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorite single crystal, a method for heat-treating the same, and a method for producing a fluorite single crystal material, and more particularly to vacuum ultraviolet light (for example, KrF, ArF excimer laser,
Fluorite single crystal suitable for use in an optical system (optical member) of an optical lithography apparatus using an F 2 laser, a solid laser, a Xe 2 lamp light, and a Kr 2 lamp light as a light source, a heat treatment method thereof, and a method for producing the optical member. The present invention relates to a method for producing a fluorite single crystal material.
【０００２】[0002]
【従来の技術】近年において、VLSIはますます高集積
化、高機能化され、論理VLSIの分野ではチップ上により
大きなシステムが盛り込まれるシステムオンチップ化が
進行している。これに伴い、その基板となるシリコン等
のウェハ上において、微細加工化及び高集積化が要求さ
れている。そして、シリコン等のウェハ上に集積回路の
微細パターンを露光・転写する光リソグラフィーにおい
ては、光リソグラフィー装置と呼ばれる露光装置が使用
されている。2. Description of the Related Art In recent years, VLSIs are becoming more highly integrated and more sophisticated, and in the field of logic VLSIs, system-on-chip, in which a larger system is incorporated on a chip, is in progress. Along with this, fine processing and high integration are required on a wafer made of silicon or the like serving as the substrate. In photolithography for exposing and transferring a fine pattern of an integrated circuit onto a wafer such as silicon, an exposure apparatus called an optical lithography apparatus is used.
【０００３】VLSIの中でDRAMを例にあげると、近年256M
以上の容量が現実のものとなり、加工線幅が0.35μm 以
下と微細になっているため、光リソグラフィー技術のか
なめである光リソグラフィー装置の投影レンズには、高
い結像性能（解像度、焦点深度）が要求されている。解
像度と焦点深度は、露光に用いる光の波長とレンズのＮ
Ａ（開口数）によって決まる。[0003] In the VLSI, taking DRAM as an example, in recent years 256M
Since the above capacity has become a reality and the processing line width is as fine as 0.35 μm or less, the projection lens of optical lithography equipment, which is the key to optical lithography technology, has high imaging performance (resolution, depth of focus) Is required. Resolution and depth of focus depend on the wavelength of light used for exposure and the N of the lens.
A (numerical aperture).
【０００４】露光波長λが同一の場合には、細かいパタ
ーンほど回折光の角度が大きくなるので、レンズのＮＡ
が大きくなければ回折光を取り込めなくなる。また、露
光波長λが短いほど、同一パターンにおける回折光の角
度は小さくなるので、レンズのＮＡは小さくてよいこと
になる。解像度と焦点深度は、次式により表される。[0004] When the exposure wavelength λ is the same, the angle of the diffracted light increases as the pattern becomes finer.
If it is not large, the diffracted light cannot be taken. Further, as the exposure wavelength λ is shorter, the angle of the diffracted light in the same pattern is smaller, so that the NA of the lens can be smaller. The resolution and the depth of focus are expressed by the following equations.
【０００５】解像度＝ｋ1 ・λ／ＮＡ 焦点深度＝ｋ2 ・λ／（ＮＡ）2 （ここで、ｋ1 、ｋ2 は比例定数） 上式より、解像度を向上させるためには、レンズのＮＡ
を大きくする（レンズを大口径化する）か、或いは露光
波長λを短くすればよく、またλを短くする方が焦点深
度の点で有利であることが判る。Resolution = k 1 · λ / NA Depth of focus = k 2 · λ / (NA) 2 (where k 1 and k 2 are proportional constants) From the above equation, in order to improve the resolution, the NA of the lens must be increased.
It is only necessary to increase (increase the lens diameter) or shorten the exposure wavelength λ, and it is found that shortening λ is more advantageous in terms of the depth of focus.
【０００６】まず、光の短波長化について述べると、露
光波長λがしだいに短波長となり、ＫｒＦエキシマレー
ザー光（波長248nm ）を光源とするステッパーも市場に
登場するようになってきた。250 nm以下の短波長領域に
おいては、光リソグラフィー用として使える光学材料は
非常に少なく、蛍石単結晶及び石英ガラスの２種類の材
料が用いられている。First, regarding the shortening of light wavelength, the exposure wavelength λ gradually becomes shorter, and a stepper using a KrF excimer laser beam (wavelength: 248 nm) as a light source has come to the market. In the short wavelength region of 250 nm or less, very few optical materials can be used for photolithography, and two types of materials, fluorite single crystals and quartz glass, are used.
【０００７】次に、レンズの大口径化について述べる
と、単に大口径であればよいというものではなく、光透
過率、低歪み（低複屈折）等の光学特性に優れた石英ガ
ラスや蛍石単結晶が要求される。蛍石単結晶は、ブリッ
ジマン法（ストックバーガー法、ルツボ降下法）により
育成（結晶成長）されている。このブリッジマン法によ
る蛍石単結晶の育成方法については、結晶成長ハンドブ
ック（１９９５年９月１日初版１刷発行Ｐ５８３〜）の
中で、ブリッジマン・ストックバーガー法（Ｂ−Ｓ法）
として紹介されている。ここで開示されている内容の概
要を示す。[0007] Next, regarding the enlargement of the lens diameter, quartz glass or fluorite excellent in optical characteristics such as light transmittance and low distortion (low birefringence) is not limited to a large diameter. Single crystals are required. Fluorite single crystals are grown (crystal grown) by the Bridgman method (Stockberger method, crucible descent method). Regarding the method of growing a fluorite single crystal by the Bridgman method, see the Bridgman-Stockberger method (BS method) in the Crystal Growth Handbook (September 1, 1995, first edition, first printing, page 583-).
It has been introduced as. The outline of the contents disclosed here is shown.
【０００８】ブリッジマン・ストックバーガー法は、結
晶成長炉内に設定された温度勾配（蛍石原料の融点前後
の温度間の勾配）中において、蛍石原料を収納したルツ
ボを降下させることにより、ルツボ中の原料融液を結晶
化させる方法である。前記ハンドブックには、ルツボ、
ヒータ、断熱材、ベルジャ、排気機構、降下機構からな
る結晶成長炉の構造が示されており（Ｐ５８４，図5.4.
2）、また蛍石単結晶の成長は、ブリッジマン法だけで
なく、引き上げ法やゾーンメルト法によっても可能であ
ると記載されている。In the Bridgman-Stockberger method, a crucible containing a fluorite material is lowered in a temperature gradient set in a crystal growth furnace (a gradient between temperatures around the melting point of the fluorite material). This is a method of crystallizing a raw material melt in a crucible. The handbook includes crucibles,
The structure of a crystal growth furnace consisting of a heater, a heat insulating material, a bell jar, an exhaust mechanism, and a descent mechanism is shown (P584, FIG. 5.4.
2) In addition, it is described that the growth of the fluorite single crystal can be performed not only by the Bridgman method but also by the pulling method or the zone melt method.
【０００９】ここで、光学部材作製用素材である蛍石単
結晶を製造する従来方法（一例）を示す。先ず、以下に
示すように前記ブリッジマン法を用いて蛍石単結晶を育
成することにより、蛍石単結晶のインゴットを形成す
る。紫外域または真空紫外域において使用される蛍石単
結晶の場合、原料として天然の蛍石を使用することはな
く、化学合成により作製された高純度原料を使用するこ
とが一般的である。Here, a conventional method (one example) for producing a fluorite single crystal as a material for producing an optical member will be described. First, an ingot of a fluorite single crystal is formed by growing a fluorite single crystal using the Bridgman method as described below. In the case of a fluorite single crystal used in an ultraviolet region or a vacuum ultraviolet region, it is common to use a high-purity raw material produced by chemical synthesis without using natural fluorite as a raw material.
【００１０】原料は粉末のまま使用することが可能であ
るが、この場合、熔融したときの体積減少が激しいた
め、半熔融品やその粉砕品を用いるのが普通である。ま
ず、育成装置（結晶成長炉）の中に前記原料を充填（収
納）したルツボを置き、育成装置内を１０-3〜１０-4Ｐ
ａの真空雰囲気に保持する。次に、育成装置内の温度を
蛍石の融点以上まで上昇させてルツボ内の原料を熔融す
る。この際、育成装置内温度の時間的変動を抑えるため
に、定電力出力による温度制御または高精度なＰＩＤ温
度制御を行う。The raw material can be used as a powder, but in this case, a semi-molten product or a pulverized product thereof is usually used because the volume of the material when melted is drastically reduced. First, a crucible filled (stored) with the above-mentioned raw material is placed in a growing apparatus (crystal growth furnace), and the inside of the growing apparatus is 10 −3 to 10 −4 P
a is maintained in the vacuum atmosphere. Next, the temperature in the growing apparatus is raised to the melting point of the fluorite or higher, and the raw material in the crucible is melted. At this time, in order to suppress temporal fluctuation of the temperature inside the growing apparatus, temperature control by constant power output or PID temperature control with high accuracy is performed.
【００１１】結晶育成段階では、育成装置内に設定され
た温度勾配（蛍石原料の融点前後の温度帯の勾配）中に
おいて、0.1 〜５ｍｍ／ｈ程度の速度でルツボを引き下
げることにより、ルツボの下部から徐々に結晶化させ
る。融液最上部まで結晶化したところで結晶育成は終了
し、育成した結晶（インゴット）が割れないように、急
冷を避けて簡単な徐冷を行う。育成装置内の温度が室温
程度まで下がったところで、装置を大気開放してインゴ
ットを取り出す。In the crystal growing stage, the crucible is pulled down at a rate of about 0.1 to 5 mm / h in a temperature gradient set in the growing apparatus (gradient in a temperature zone around the melting point of the fluorite raw material). Crystallize gradually from the bottom. When the crystal is crystallized up to the uppermost part of the melt, the crystal growth is completed, and simple slow cooling is performed avoiding rapid cooling so that the grown crystal (ingot) is not broken. When the temperature in the growing device has dropped to about room temperature, the device is opened to the atmosphere and the ingot is taken out.
【００１２】以上のようにして、蛍石単結晶のインゴッ
トを形成する。次に、サイズの小さい光学部品や均質性
の要求されない窓材などに用いられる蛍石単結晶の場合
には、インゴットを切断した後、丸めなどの工程を経て
最終製品まで加工される。これに対して、光リソグラフ
ィー装置の投影レンズなどに用いられ、高均質が要求さ
れる蛍石単結晶の場合には、インゴットのまま簡単な熱
処理が行われる。そして、目的の製品別に適当な大きさ
に切断加工された後、さらに熱処理が行われる。As described above, a fluorite single crystal ingot is formed. Next, in the case of a fluorite single crystal used for a small-sized optical component or a window material that does not require homogeneity, the ingot is cut, and then processed into a final product through a rounding process. On the other hand, in the case of a fluorite single crystal which is used for a projection lens of an optical lithography apparatus and requires high homogeneity, a simple heat treatment is performed in an ingot. Then, after being cut into an appropriate size for each target product, heat treatment is further performed.
【００１３】以上のようにして、目的の最終製品（光学
部材）に対応した蛍石単結晶素材（最終製品作製用の素
材）が製造される。しかしながら、前記従来法により蛍
石単結晶を製造しても光透過性に優れ、しかも複屈折の
小さな蛍石単結晶が得られなかった。そのため、従来法
で製造した蛍石単結晶は、真空紫外光（例えば、Ｋｒ
Ｆ、ＡｒＦエキシマレーザー、Ｆ2レーザー、固体レー
ザー、Ｘｅ2ランプ光、Ｋｒ2ランプ光）を光源とした光
リソグラフィー装置の光学系（光学部材）に使用できな
いという問題点があった。As described above, a fluorite single crystal material (material for producing a final product) corresponding to a desired final product (optical member) is manufactured. However, even if a fluorite single crystal was produced by the above-mentioned conventional method, a fluorite single crystal having excellent light transmittance and small birefringence could not be obtained. Therefore, the fluorite single crystal manufactured by the conventional method is vacuum ultraviolet light (for example, Kr
There is a problem that it cannot be used in an optical system (optical member) of an optical lithography apparatus using a light source of F, ArF excimer laser, F 2 laser, solid laser, Xe 2 lamp light, Kr 2 lamp light).
【００１４】本発明は、かかる問題点に鑑みてなされた
ものであり、真空紫外光（例えば、ＫｒＦ、ＡｒＦエキ
シマレーザー、Ｆ2レーザー、固体レーザー、Ｘｅ2ラン
プ光、Ｋｒ2ランプ光）を光源とした光リソグラフィー
装置の光学系（光学部材）に使用できる光学部材を作製
するための蛍石単結晶素材を製造する方法、その製造方
法にかかる熱処理方法、及び前記光学部材として使用で
きる蛍石単結晶を提供することを目的とする。The present invention has been made in view of the above problems, and uses a vacuum ultraviolet light (for example, KrF, ArF excimer laser, F 2 laser, solid-state laser, Xe 2 lamp light, Kr 2 lamp light) as a light source. For producing an optical member that can be used for an optical system (optical member) of a photolithography apparatus, a method for producing a fluorite single crystal material, a heat treatment method according to the production method, and a fluorite unit that can be used as the optical member It is intended to provide a crystal.
【００１５】[0015]
【課題を解決するための手段】そのため、本発明は第一
に「蛍石単結晶の構造支配温度帯を通過させて、それよ
りも高い第１温度まで蛍石単結晶を昇温させてから所定
時間保持した後に、前記第１温度から前記構造支配温度
帯よりも低い第２温度まで降温させることにより、蛍石
単結晶の熱処理を行う方法であって、前記第１温度から
前記第２温度まで降温させる際に、前記構造支配温度帯
における熱処理時間（滞留時間）を８００時間以下にす
ることを特徴とする蛍石単結晶の熱処理方法（請求項
１）」を提供する。For this purpose, the present invention firstly provides a method of "passing through a structure controlling temperature zone of a fluorite single crystal and raising the temperature of the fluorite single crystal to a first temperature higher than that. A method for performing a heat treatment of a fluorite single crystal by lowering the temperature from the first temperature to a second temperature lower than the structure governing temperature zone after holding for a predetermined time, wherein the first temperature is reduced to the second temperature. A fluorite single crystal heat treatment method (claim 1), wherein the heat treatment time (residence time) in the structure-dominated temperature zone is 800 hours or less when the temperature is lowered to the maximum.
【００１６】また、本発明は第二に「前記構造支配温度
帯の範囲が約６１０℃〜約１０１０℃であることを特徴
とする請求項１記載の熱処理方法（請求項２）」を提供
する。また、本発明は第三に「少なくとも、蛍石原料を
融解して形成した融液を固化させて蛍石単結晶を成長さ
せることにより、 蛍石単結晶のインゴットを作製する
工程と、前記インゴットから、或いは前記インゴットに
熱処理を施した後にそのインゴットから蛍石単結晶の成
形品を切り出す工程と、前記成形品を請求項１または２
記載の方法により熱処理する工程と、を備えた光学部材
作製用の蛍石単結晶素材の製造方法（請求項３）」を提
供する。Further, the present invention secondly provides "the heat treatment method according to claim 1 (claim 2), wherein the range of the structure dominant temperature zone is about 610 ° C to about 1010 ° C." . Further, the present invention is a third aspect of the present invention which comprises "at least, a step of producing a fluorite single crystal ingot by solidifying a melt formed by melting a fluorite raw material and growing a fluorite single crystal, Or a step of cutting out a fluorite single-crystal molded product from the ingot after heat-treating the ingot, or forming the molded product from the ingot.
A method for producing a fluorite single crystal material for producing an optical member, comprising: a step of performing a heat treatment by the method described above.
【００１７】また、本発明は第四に「少なくとも、蛍石
原料とスカベンジャーの混合物を加熱して脱酸素化反応
させた後に冷却することにより、或いは前記脱酸素化反
応と前記蛍石原料の融解及び冷却により、脱酸素化した
蛍石の焼結体または多結晶体である前処理品を得る工程
と、前記前処理品を融解して形成した融液を固化させて
蛍石単結晶を成長させることにより、蛍石単結晶のイン
ゴットを作製する工程と、前記インゴットから、或いは
前記インゴットに熱処理を施した後にそのインゴットか
ら蛍石単結晶の成形品を切り出す工程と、前記成形品を
請求項１または２記載の方法により熱処理する工程と、
を備えた光学部材作製用の蛍石単結晶素材の製造方法
（請求項４）」を提供する。[0017] The present invention also provides a fourth aspect of the present invention wherein "at least a mixture of a fluorite raw material and a scavenger is heated to cause a deoxygenation reaction and then cooled, or the deoxygenation reaction and the melting of the fluorite raw material are carried out. And a step of obtaining a pretreated product, which is a sintered or polycrystalline body of deoxidized fluorite by cooling, and solidifying a melt formed by melting the pretreated product to grow a fluorite single crystal Making a fluorite single crystal ingot, cutting the fluorite single crystal molded article from the ingot or after performing a heat treatment on the ingot, and claiming the molded article. A step of heat-treating according to the method of 1 or 2,
A method for producing a fluorite single crystal material for producing an optical member, comprising:
【００１８】また、本発明は第五に「少なくとも、蛍石
原料を融解して形成した融液を固化させて蛍石単結晶を
成長させることにより、蛍石単結晶のインゴットを作製
する工程と、前記インゴットから、或いは前記インゴッ
トに熱処理を施した後にそのインゴットから蛍石単結晶
の成形品及びテストピースを切り出す工程と、前記成形
品及びテストピースを請求項１または２記載の方法によ
り熱処理する工程と、を備えた光学部材作製用の蛍石単
結晶素材及びテストピースの製造方法（請求項５）」を
提供する。Further, the present invention is directed to a fifth aspect of the present invention which comprises at least a step of producing a fluorite single crystal ingot by solidifying a melt formed by melting a fluorite raw material and growing a fluorite single crystal. A step of cutting out a molded product and a test piece of a fluorite single crystal from the ingot or after performing a heat treatment on the ingot, and heat-treating the molded product and the test piece by the method according to claim 1 or 2. And a method for producing a fluorite single crystal material and a test piece for producing an optical member, the method comprising:
【００１９】また、本発明は第六に「少なくとも、蛍石
原料とスカベンジャーの混合物を加熱して脱酸素化反応
させた後に冷却することにより、或いは前記脱酸素化反
応と前記蛍石原料の融解及び冷却により脱酸素化した蛍
石の焼結体または多結晶体である前処理品を得る工程
と、前記前処理品を融解して形成した融液を固化させて
蛍石単結晶を成長させることにより、蛍石単結晶のイン
ゴットを作製する工程と、前記インゴットから、或いは
前記インゴットに熱処理を施した後にそのインゴットか
ら蛍石単結晶の成形品及びテストピースを切り出す工程
と、前記成形品及びテストピースを請求項１または２記
載の方法により熱処理する工程と、を備えた光学部材作
製用の蛍石単結晶素材及びテストピースの製造方法（請
求項６）」を提供する。Further, the present invention provides a sixth aspect of the present invention wherein "at least a mixture of a fluorite raw material and a scavenger is heated to cause a deoxygenation reaction and then cooled, or the deoxygenation reaction and the melting of the fluorite raw material are carried out. And obtaining a pretreated product which is a sintered or polycrystalline fluorite deoxygenated by cooling, and solidifying a melt formed by melting the pretreated product to grow a fluorite single crystal. Thereby, a step of producing an ingot of a fluorite single crystal, a step of cutting out a molded product and a test piece of the fluorite single crystal from the ingot or after performing a heat treatment on the ingot, and A method of manufacturing a fluorite single crystal material for producing an optical member and a test piece, comprising: a step of heat-treating the test piece by the method according to claim 1 or 2. .
【００２０】また、本発明は第七に「前記成形品及びテ
ストピースを同時に同条件で熱処理することを特徴とす
る請求項５または６記載の製造方法（請求項７）」を提
供する。また、本発明は第八に「前記光学部材が光リソ
グラフィー用の光学部材であることを特徴とする請求項
３〜７のいずれかに記載の製造方法（請求項８）」を提
供する。The present invention seventhly provides a "manufacturing method according to claim 5 or 6, wherein the molded article and the test piece are simultaneously heat-treated under the same conditions." Eighth, the present invention provides "the manufacturing method according to any one of claims 3 to 7, wherein the optical member is an optical member for photolithography (claim 8)."
【００２１】また、本発明は第九に「波長６３３ｎｍの
光に対する複屈折光路差が５ｎｍ／ｃｍ以下であり、波
長１９３ｎｍの真空紫外光に対する内部透過率が９９．
８％／ｃｍ以上である光リソグラフィー用の蛍石単結晶
が得られることを特徴とする請求項３〜８のいずれかに
記載の製造方法（請求項９）」を提供する。また、本発
明は第十に「波長６３３ｎｍの光に対する複屈折光路差
が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍの真空紫外
光に対する内部透過率が９９．８％／ｃｍ以上であり、
波長１５７ｎｍの真空紫外光に対する内部透過率が９
９．６％／ｃｍ以上である光リソグラフィー用の蛍石単
結晶が得られることを特徴とする請求項３〜８のいずれ
かに記載の製造方法（請求項10）」を提供する。The ninth aspect of the present invention is that a birefringent optical path difference with respect to light having a wavelength of 633 nm is 5 nm / cm or less, and an internal transmittance with respect to vacuum ultraviolet light having a wavelength of 193 nm is 99.
The method according to any one of claims 3 to 8, wherein a fluorite single crystal for photolithography having a density of 8% / cm or more is obtained. In addition, the present invention tenthly states that “the birefringence optical path difference with respect to light with a wavelength of 633 nm is 5 nm / cm or less, and the internal transmittance with respect to vacuum ultraviolet light with a wavelength of 193 nm is 99.8% / cm or more,
Internal transmittance of 9 for vacuum ultraviolet light having a wavelength of 157 nm is 9
The method according to any one of claims 3 to 8, wherein a fluorite single crystal for photolithography having a density of 9.6% / cm or more is obtained.
【００２２】また、本発明は第十一に「波長６３３ｎｍ
の光に対する複屈折光路差が５ｎｍ／ｃｍ以下であり、
波長１９３ｎｍの真空紫外光に対する内部透過率が９
９．８％／ｃｍ以上であることを特徴とする光リソグラ
フィー用の蛍石単結晶（請求項11）」を提供する。ま
た、本発明は第十二に「波長６３３ｎｍの光に対する複
屈折光路差が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍ
の真空紫外光に対する内部透過率が９９．８％／ｃｍ以
上であり、波長１５７ｎｍの真空紫外光に対する内部透
過率が９９．６％／ｃｍ以上であることを特徴とする光
リソグラフィー用の蛍石単結晶（請求項12）」を提供す
る。The present invention is an eleventh embodiment of the present invention.
Has a birefringence optical path difference of 5 nm / cm or less,
The internal transmittance for vacuum ultraviolet light having a wavelength of 193 nm is 9
Fluorite single crystal for photolithography, characterized in that the single crystal is at least 9.8% / cm (claim 11). In addition, the present invention twelfthly states that "the birefringent optical path difference with respect to light having a wavelength of 633 nm is 5 nm / cm or less, and
Wherein the internal transmittance for vacuum ultraviolet light is 99.8% / cm or more, and the internal transmittance for vacuum ultraviolet light having a wavelength of 157 nm is 99.6% / cm or more. Single crystal (Claim 12) is provided.
【００２３】[0023]
【発明の実施の形態】本発明者らは、単結晶蛍石（蛍石
単結晶）を熱処理する際に、構造支配温度帯を通過させ
るとともに、降温側の滞留時間を８００時間以下に制御
することにより、透過率に優れ、複屈折の小さな蛍石単
結晶が得られることを見いだした。そこで、蛍石単結晶
の構造支配温度帯を通過させて、それよりも高い第１温
度まで蛍石単結晶を昇温させてから所定時間保持した後
に、前記第１温度から前記構造支配温度帯よりも低い第
２温度まで降温させることにより、蛍石単結晶の熱処理
を行う本発明（請求項１，２）にかかる熱処理方法にお
いては、前記第１温度から前記第２温度まで降温させる
際に、前記構造支配温度帯における熱処理時間（滞留時
間）を８００時間以下にすることとした。BEST MODE FOR CARRYING OUT THE INVENTION The present inventors, when heat-treating single-crystal fluorite (fluorite single crystal), pass the structure-controlling temperature zone and control the residence time on the cooling side to 800 hours or less. As a result, it has been found that a fluorite single crystal having excellent transmittance and small birefringence can be obtained. Then, after passing through the structure controlling temperature zone of the fluorite single crystal and raising the temperature of the fluorite single crystal to a first temperature higher than the first temperature, and holding the fluorite single crystal for a predetermined time, the first temperature and the structure controlling temperature zone In the heat treatment method according to the present invention in which the fluorite single crystal is heat-treated by lowering the temperature to a lower second temperature, the temperature may be reduced from the first temperature to the second temperature. The heat treatment time (residence time) in the structure-dominated temperature zone was set to 800 hours or less.
【００２４】ここで、本発明にかかる構造支配温度帯と
は、熱処理対象物における複屈折（歪み）の低減、屈折
率の均質化等の光学特性向上に対して影響度が特に大き
い熱処理の温度域を示し、蛍石単結晶にかかる構造支配
温度帯の範囲は、例えば約６１０℃〜約１０１０℃であ
る（請求項２）。本発明（請求項１、２）にかかる熱処
理方法によれば、透過率に優れ、複屈折の小さな蛍石単
結晶が得られる。Here, the structure-dominated temperature zone according to the present invention refers to the temperature of the heat treatment which has a particularly large influence on the improvement of the optical properties such as the reduction of birefringence (strain) and the homogenization of the refractive index in the heat treatment object. The range of the structure-dominated temperature zone for the fluorite single crystal is, for example, about 610 ° C. to about 1010 ° C. (Claim 2). According to the heat treatment method of the present invention (claims 1 and 2), a fluorite single crystal having excellent transmittance and small birefringence can be obtained.
【００２５】また、少なくとも、蛍石原料を融解して形
成した融液を固化させて蛍石単結晶を成長させることに
より、蛍石単結晶のインゴットを作製する工程と、前記
インゴットから、或いは前記インゴットに熱処理を施し
た後にそのインゴットから蛍石単結晶の成形品を切り出
す工程と、前記成形品を請求項１，２にかかる方法によ
り熱処理する工程と、により本発明（請求項３）にかか
る光学部材作製用の蛍石単結晶素材の製造方法を構成す
ることとした。Further, at least a step of producing a fluorite single crystal ingot by solidifying a melt formed by melting a fluorite raw material and growing a fluorite single crystal, According to the present invention (claim 3), a step of cutting out a molded article of fluorite single crystal from the ingot after subjecting the ingot to heat treatment, and a step of heat-treating the molded article by the method according to claims 1 and 2 are provided. A method for producing a fluorite single crystal material for producing an optical member is to be constituted.
【００２６】本発明（請求項３）にかかる製造方法によ
れば、透過率に優れ、複屈折の小さな光学部材作製用の
蛍石単結晶素材が得られる。また、少なくとも、蛍石原
料とスカベンジャーの混合物を加熱して脱酸素化反応さ
せた後に冷却することにより、或いは前記脱酸素化反応
と前記蛍石原料の融解及び冷却により、脱酸素化した蛍
石の焼結体または多結晶体である前処理品を得る工程
と、前記前処理品を融解して形成した融液を固化させて
蛍石単結晶を成長させることにより、蛍石単結晶のイン
ゴットを作製する工程と、前記インゴットから、或いは
前記インゴットに熱処理を施した後にそのインゴットか
ら蛍石単結晶の成形品を切り出す工程と、前記成形品を
請求項１または２記載の方法により熱処理する工程と、
により本発明（請求項４）にかかる光学部材作製用の蛍
石単結晶素材の製造方法を構成することとした。According to the production method of the present invention (claim 3), a fluorite single crystal material for producing an optical member having excellent transmittance and small birefringence can be obtained. Further, at least, a mixture of the fluorite raw material and the scavenger is heated and subjected to a deoxygenation reaction and then cooled, or the deoxygenated fluorite is melted and cooled by the deoxygenation reaction and the melting and cooling of the fluorite raw material. Obtaining a pretreated product which is a sintered body or a polycrystalline body, and solidifying a melt formed by melting the pretreated product to grow a fluorite single crystal, whereby an ingot of fluorite single crystal is obtained. A step of preparing a fluorite single crystal molded article from the ingot or after performing a heat treatment on the ingot, and a step of heat-treating the molded article by the method according to claim 1 or 2. When,
Accordingly, a method for producing a fluorite single crystal material for producing an optical member according to the present invention (claim 4) is constituted.
【００２７】本発明（請求項４）にかかる製造方法によ
れば、透過率が特に優れ、複屈折がさらに小さな光学部
材作製用の蛍石単結晶素材が得られる。本発明において
は、蛍石単結晶素材と併せてその光学特性を評価するた
めのテストピースを製造することが好ましい（請求項
５，６）。また、本発明にかかる光学特性評価用のテス
トピースは、蛍石単結晶素材（成形品）の正確な特性評
価ができるように、成形品と同時に同条件で熱処理する
ことが好ましい（請求項７）。According to the manufacturing method of the present invention (claim 4), it is possible to obtain a fluorite single crystal material for producing an optical member having particularly excellent transmittance and further lowering birefringence. In the present invention, it is preferable to manufacture a test piece for evaluating the optical characteristics of the fluorite single crystal material in combination with the fluorite single crystal material. In addition, the test piece for evaluating optical properties according to the present invention is preferably heat-treated at the same time as the molded article under the same conditions so that accurate property evaluation of the fluorite single crystal material (molded article) can be performed. ).
【００２８】本発明にかかる製造方法は、特に優れた光
学特性が要求される光リソグラフィー用光学部材に使用
できる蛍石単結晶素材の製造に好適である（請求項
８）。例えば、本発明にかかる製造方法によれば、波長
６３３ｎｍの光に対する複屈折光路差が５ｎｍ／ｃｍ以
下であり、波長１９３ｎｍの真空紫外光に対する内部透
過率が９９．８％／ｃｍ以上である光リソグラフィー用
の蛍石単結晶（素材）が得られる（請求項９）。The production method according to the present invention is suitable for producing a fluorite single crystal material that can be used for an optical member for photolithography that requires particularly excellent optical characteristics (claim 8). For example, according to the manufacturing method of the present invention, light having a birefringence optical path difference of 5 nm / cm or less for light having a wavelength of 633 nm and an internal transmittance of 99.8% / cm or more for vacuum ultraviolet light having a wavelength of 193 nm. A fluorite single crystal (raw material) for lithography is obtained (claim 9).
【００２９】或いは、本発明にかかる製造方法によれ
ば、波長６３３ｎｍの光に対する複屈折光路差が５ｎｍ
／ｃｍ以下であり、波長１９３ｎｍの真空紫外光に対す
る内部透過率が９９．８％／ｃｍ以上であり、波長１５
７ｎｍの真空紫外光に対する内部透過率が９９．６％／
ｃｍ以上である光リソグラフィー用の蛍石単結晶（素
材）が得られる（請求項10）。Alternatively, according to the manufacturing method of the present invention, the birefringent optical path difference with respect to light having a wavelength of 633 nm is 5 nm.
/ Cm or less, the internal transmittance to vacuum ultraviolet light having a wavelength of 193 nm is 99.8% / cm or more, and the wavelength 15
The internal transmittance for 9 nm vacuum ultraviolet light is 99.6% /
A fluorite single crystal (raw material) for photolithography having a diameter of at least 10 cm is obtained (claim 10).
【００３０】また、例えば本発明にかかる製造方法によ
り得られた蛍石単結晶を製品形状に加工すれば、光リソ
グラフィー用の光学部材が得られる。この光リソグラフ
ィー用の光学部材は、波長６３３ｎｍの光に対する複屈
折光路差が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍの
真空紫外光に対する内部透過率が９９．８％／ｃｍ以上
である蛍石単結晶により構成される（請求項11）。Further, for example, if the fluorite single crystal obtained by the manufacturing method according to the present invention is processed into a product shape, an optical member for photolithography can be obtained. This optical member for photolithography has a fluorite single crystal having a birefringence optical path difference of 5 nm / cm or less for light having a wavelength of 633 nm and an internal transmittance of 99.8% / cm or more for vacuum ultraviolet light having a wavelength of 193 nm. (Claim 11).
【００３１】或いは、光リソグラフィー用の光学部材
は、波長６３３ｎｍの光に対する複屈折光路差が５ｎｍ
／ｃｍ以下であり、波長１９３ｎｍの真空紫外光に対す
る内部透過率が９９．８％／ｃｍ以上であり、波長１５
７ｎｍの真空紫外光に対する内部透過率が９９．６％／
ｃｍ以上である蛍石単結晶により構成される（請求項1
2）。Alternatively, the optical member for photolithography has a birefringence optical path difference of 5 nm for light having a wavelength of 633 nm.
/ Cm or less, the internal transmittance to vacuum ultraviolet light having a wavelength of 193 nm is 99.8% / cm or more, and the wavelength 15
The internal transmittance for 9 nm vacuum ultraviolet light is 99.6% /
cm or more.
2).
【００３２】ここで、光リソグラフィー用光学部材の作
製に用いられる蛍石単結晶素材の本発明にかかる製造方
法（一例、図１参照）を示す。この製造方法は、少なく
とも、粉末原料を前処理により脱酸素化してから結晶成
長させる過程と、結晶成長により得られたかたまり（イ
ンゴット）を、或いはさらに熱処理を施したインゴット
を切断及び成形して成形品を得る工程と、この成形品に
熱処理を施すことにより複屈折を低減した蛍石単結晶素
材を得る工程と、により構成される。なお、この蛍石単
結晶素材を加工することにより光リソグラフィー用光学
部材が得られる。Here, a method for manufacturing a fluorite single crystal material used for manufacturing an optical member for photolithography according to the present invention (one example, see FIG. 1) will be described. This production method comprises, at least, a process of deoxidizing a powder raw material by pretreatment and then growing a crystal, and cutting and shaping a lump (ingot) obtained by the crystal growth or an ingot further subjected to a heat treatment. And a step of obtaining a fluorite single crystal material having reduced birefringence by subjecting the molded article to a heat treatment. By processing this fluorite single crystal material, an optical member for photolithography can be obtained.
【００３３】まず、粉末原料を脱酸素化反応させる前処
理について述べる。紫外域または真空紫外域で使用され
る蛍石単結晶をブリッジマン法により育成する場合に
は、前述したように原料に天然の蛍石を使用することは
なく、人工合成の高純度原料を使用することが一般的で
ある。さらに、原料のみを融解して結晶化すると白濁し
て失透する傾向を示すため、スカベンジャーを添加して
加熱することにより、白濁を防止する処置を施してい
る。蛍石単結晶の前処理や育成において使用される代表
的なスカベンジャーとしては、フッ化鉛（ＰｂＦ2）が
挙げられる。First, a pretreatment for causing a deoxygenation reaction of the powder raw material will be described. When fluorite single crystals used in the ultraviolet or vacuum ultraviolet region are grown by the Bridgman method, natural fluorite is not used as a raw material as described above, and high-purity raw materials of artificial synthesis are used. It is common to do. Further, when only the raw material is melted and crystallized, it tends to be clouded and devitrified. Therefore, a treatment for preventing clouding is performed by adding a scavenger and heating. A typical scavenger used in pretreatment and growth of fluorite single crystal is lead fluoride (PbF 2 ).
【００３４】なお、原料中に含有される不純物と化学反
応し、これを取り除く作用をする添加物質のことを一般
にスカベンジャーという。蛍石原料にスカベンジャーと
してフッ化鉛を添加することにより、白濁による失透を
防止する機構は以下のとおりである。フッ化鉛は、蛍石
原料中に含有される不純物の酸素と反応して酸化鉛（Ｐ
ｂＯ）となり、この反応式を以下に示す。An additive substance which chemically reacts with impurities contained in the raw material and acts to remove the impurities is generally called a scavenger. The mechanism of preventing devitrification due to cloudiness by adding lead fluoride as a scavenger to the fluorite raw material is as follows. Lead fluoride reacts with oxygen, an impurity contained in the fluorite raw material, to lead oxide (P
bO), and this reaction formula is shown below.
【００３５】ＣａＯ＋ＰｂＦ2→ＣａＦ2＋ＰｂＯ この反応の結果、生成した酸化鉛は高温で揮発するた
め、蛍石から酸素を取り除くことができる。白濁による
失透は、蛍石に含まれる酸素によるため、この酸素を除
去することにより、蛍石単結晶の失透を防止することが
できる。本発明にかかる前処理（一例）においては先
ず、高純度な粉末原料に粉末状のフッ化鉛を１ｍｏｌ％
程度添加して良く混合させてから、これを黒鉛製容器な
どの清浄な容器に充填（収納）する。CaO + PbF 2 → CaF 2 + PbO As a result of this reaction, the lead oxide generated is volatilized at a high temperature, so that oxygen can be removed from the fluorite. Since the devitrification due to cloudiness is due to oxygen contained in fluorite, by removing this oxygen, devitrification of the fluorite single crystal can be prevented. In the pretreatment (one example) according to the present invention, first, 1 mol% of powdery lead fluoride is added to a high-purity powder material.
After adding and mixing well, the mixture is filled (stored) in a clean container such as a graphite container.
【００３６】次に、この容器を真空排気が可能で、通電
加熱ヒーターなどの加熱手段を備えた真空加熱装置の所
定位置に設置する。充分な排気下において、スカベンジ
ャーであるフッ化鉛の融点以上で、蛍石の融点未満の温
度まで加熱昇温させることにより脱酸素化反応を進め
る。ここで便宜上、この脱酸素化反応が進行する温度を
脱酸素化反応温度とよび、温度の下限値と上限値の温度
範囲を脱酸素化反応温度帯とよぶこととする。本発明に
かかる脱酸素化反応温度帯（一例）は８５０℃〜１３５
０℃である。Next, this container is placed at a predetermined position of a vacuum heating device which can be evacuated and provided with heating means such as an electric heater. Under sufficient evacuation, the deoxygenation reaction proceeds by heating to a temperature above the melting point of lead fluoride as a scavenger and below the melting point of fluorite. Here, for convenience, the temperature at which the deoxygenation reaction proceeds is called a deoxygenation reaction temperature, and the temperature range between the lower limit and the upper limit of the temperature is called a deoxygenation reaction temperature zone. The deoxygenation reaction temperature zone (one example) according to the present invention is 850 ° C to 135 ° C.
0 ° C.
【００３７】脱酸素化反応温度帯を通過させた後は、そ
のまま室温まで降温して焼結体としても良いし、或いは
脱酸素化反応温度帯を通過させてから更に温度を上昇さ
せて一旦原料を融解させた後、室温まで降温して多結晶
体としても良い。以上のようにして脱酸素化がなされた
焼結体や多結晶体を前処理品という。次に、この前処理
品を用いてさらに結晶成長させることによりインゴット
を得る過程（一例）について以下に示す。After passing through the deoxygenation reaction temperature zone, the temperature may be lowered to room temperature as it is to obtain a sintered body, or the temperature may be further raised after passing through the deoxygenation reaction temperature zone to further increase the temperature of the raw material. After melting, the temperature may be lowered to room temperature to form a polycrystal. The sintered body or polycrystalline body deoxygenated as described above is referred to as a pre-treated product. Next, a process (an example) of obtaining an ingot by further growing a crystal using this pretreated product will be described below.
【００３８】結晶成長の方法には、融液の固化、溶液か
らの析出、気体からの析出、固体粒子の成長に大別でき
ることが広く知られているが、本例においては垂直ブリ
ッジマン法により結晶成長させる（前処理品をいったん
融解し、融液から固化させる）。まず、前処理品を黒鉛
製容器などの清浄な容器に充填（収納）し、真空排気が
可能な垂直ブリッジマン装置（結晶成長炉）の所定位置
に設置する。It is widely known that crystal growth methods can be roughly classified into solidification of a melt, precipitation from a solution, deposition from a gas, and growth of solid particles. In this example, the vertical Bridgman method is used. The crystal is grown (the pretreated product is once melted and solidified from the melt). First, the pre-processed product is filled (stored) in a clean container such as a graphite container, and installed at a predetermined position of a vertical Bridgman apparatus (crystal growth furnace) capable of evacuating.
【００３９】充分な排気下において、通電加熱ヒーター
などの加熱手段により容器内に充填された前処理品を加
熱して融解させる。前処理品の融点に到達した後は、す
ぐに引下げによる結晶化を開始するよりも、１〜１０時
間程度以上を経過させた後に結晶化を開始する。引下げ
は１時間あたり０．２ｍｍから２ｍｍ程度の速度で行
い、また１時間あたり０．１回転から１００回転程度の
割合でルツボを回転させることも可能である。融液のす
べてが結晶化したら、室温まで徐冷してインゴットとし
て取り出す。Under sufficient exhaust, the pretreatment product filled in the container is heated and melted by a heating means such as an electric heating heater. After reaching the melting point of the pre-treated product, crystallization is started after a lapse of about 1 to 10 hours or more, rather than immediately starting crystallization by pulling down. The lowering is performed at a speed of about 0.2 mm to 2 mm per hour, and the crucible can be rotated at a rate of about 0.1 to 100 rotations per hour. When all of the melt crystallizes, it is gradually cooled to room temperature and taken out as an ingot.
【００４０】そして、インゴットを切断し、さらにまる
め加工などの成形加工を行って成形品とする。 光リソ
グラフィー用の光学部材に使用する蛍石は単結晶である
ことが不可欠である。これは、多結晶（単結晶の集合
体）では、単結晶どうしの界面に歪が残留して大きな複
屈折を示すからである。従って、光リソグラフィー用の
光学部材に使用する蛍石は成形品の段階でも単結晶であ
る必要がある。以下に、この単結晶成型品を熱処理して
除歪する熱処理過程（一例）について述べる。Then, the ingot is cut, and a molding process such as rounding is performed to obtain a molded product. It is essential that fluorite used for an optical member for photolithography is a single crystal. This is because, in a polycrystal (a single crystal aggregate), strain remains at the interface between the single crystals and shows large birefringence. Therefore, the fluorite used for the optical member for photolithography needs to be a single crystal even at the stage of a molded product. Hereinafter, a heat treatment process (an example) of heat-treating the single crystal molded product to remove strain will be described.
【００４１】熱処理する際の単結晶成形品は、目的とす
る製品（光学部材）より大きければ、熱処理後の加工に
より光学部材が作製可能であるが、形状と大きさ共に目
的とする光学部材と同程度が望ましい。例えば、光学レ
ンズが目的製品の場合には薄い円柱状形状であり、その
口径と厚さは光学レンズに合わせて決めることが望まし
い。If the single crystal molded product at the time of heat treatment is larger than the target product (optical member), the optical member can be produced by processing after the heat treatment. The same degree is desirable. For example, when the optical lens is a target product, it has a thin cylindrical shape, and its diameter and thickness are preferably determined according to the optical lens.
【００４２】この単結晶成形品と同じインゴットから
は、単結晶成形品とは別に小型の成形品（透過率測定
用）を製作し、この小型成形品を単結晶成形品と同時に
同条件で熱処理することが望ましい。小型成形品は、熱
処理が完了したら向かい合う２面を研磨して、透過率測
定用サンプル（テストピース）とする。熱処理する際に
は、単結晶成形品及び小型成形品を構造支配温度帯を通
過させるとともに、その降温側滞留時間が８００時間以
下となるように制御する。構造支配温度帯は蛍石におい
ては、約６１０℃〜約１０１０℃の範囲である。From the same ingot as this single-crystal molded product, a small-sized molded product (for measuring transmittance) is manufactured separately from the single-crystal molded product, and this small-sized molded product is heat-treated simultaneously with the single-crystal molded product under the same conditions. It is desirable to do. After the heat treatment is completed, the small molded product is polished on two opposing surfaces to obtain a transmittance measurement sample (test piece). During the heat treatment, the single-crystal molded product and the small-sized molded product are passed through the structure-controlling temperature zone, and the residence time on the cooling side is controlled to be 800 hours or less. The structure dominant temperature range is about 610 ° C to about 1010 ° C for fluorite.
【００４３】即ち、まず単結晶成形品及び小型成形品の
温度を室温から徐々に上昇させ、構造支配温度帯を通過
させて１０１０℃以上にする。その後、徐々に温度を降
下させ、構造支配温度帯を通過させて６１０℃以下とす
る。降温時に、構造支配温度帯に滞留している時間を８
００時間以下にすることにより、透過率の良好な蛍石単
結晶が得られる。That is, first, the temperature of the single crystal molded article and the small molded article is gradually raised from room temperature, and is passed through the structure governing temperature zone to 1010 ° C. or more. After that, the temperature is gradually lowered, and the temperature is lowered to 610 ° C. or lower by passing through the structure governing temperature zone. When the temperature drops, the time spent in the structurally
By setting the time to 00 hours or less, a fluorite single crystal having good transmittance can be obtained.
【００４４】ここで、構造支配温度帯を通過させる際に
は、単結晶成型品及び小型成形品に温度むらがないこと
が望ましい。そこで、単結晶成形品及び小型成形品を熱
伝導性の良好な黒鉛製などの容器に収容し、この容器の
周囲に加熱手段を設けると良い。この後、室温まで徐冷
して、熱処理を施した単結晶成型品及び小型成形品を取
り出す。この熱処理を施した単結晶成型品及び小型成形
品をそれぞれ熱処理品、小型熱処理品と呼ぶこととす
る。Here, when passing through the structure governing temperature zone, it is desirable that the single crystal molded product and the small molded product have no temperature unevenness. Therefore, it is preferable that the single crystal molded product and the small molded product are accommodated in a container made of graphite or the like having good thermal conductivity, and heating means is provided around the container. Thereafter, the product is gradually cooled to room temperature, and the heat-treated single crystal molded product and the small molded product are taken out. The single crystal molded product and the small molded product subjected to this heat treatment are referred to as a heat treated product and a small heat treated product, respectively.
【００４５】ところで、透過率の良好な蛍石単結晶を得
るために、熱処理の雰囲気は酸素や水分を避けることが
望ましい。また、蛍石単結晶と高温でむやみに反応しな
い雰囲気が望ましい。そこで、真空雰囲気、不活性ガス
雰囲気、またはフッ素系ガス雰囲気が望ましい。真空雰
囲気であれば、充分な排気により真空度を０．００１気
圧以下にすると良い。また、不活性ガスとしては、ドラ
イ窒素、ドライアルゴン、ドライネオンが望ましく、フ
ッ素系ガスとしては酸性フッ化アンモニウムやフッ素ガ
スが良い。By the way, in order to obtain a fluorite single crystal having good transmittance, it is desirable that the atmosphere of the heat treatment avoid oxygen and moisture. Also, an atmosphere that does not unnecessarily react with the fluorite single crystal at a high temperature is desirable. Therefore, a vacuum atmosphere, an inert gas atmosphere, or a fluorine-based gas atmosphere is desirable. In a vacuum atmosphere, the degree of vacuum may be reduced to 0.001 atm or less by sufficient exhaust. Further, as the inert gas, dry nitrogen, dry argon, or dry neon is desirable, and as the fluorine-based gas, ammonium acid fluoride or fluorine gas is preferable.
【００４６】以上のようにして、光リソグラフィー用光
学部材の作製に用いられる蛍石単結晶素材である、熱処
理を施した単結晶成形品（熱処理品）が熱処理を施した
小型成形品（小型熱処理品）とともに得られる。この熱
処理を施した単結晶成形品を更に加工することにより、
目的の製品（光リソグラフィー用光学部材）が得られ
る。As described above, a heat-treated single-crystal molded product (heat-treated product), which is a fluorite single-crystal material used for manufacturing an optical member for optical lithography, is subjected to a heat treatment to a small molded product (small heat-treated product). Product). By further processing this heat-treated single crystal molded product,
The desired product (optical member for photolithography) is obtained.
【００４７】なお、熱処理品を用いて複屈折を測定し、
６３３ｎｍ複屈折光路差を検査する。また、小型熱処理
品はテストピースに加工して透過率を検査する。このよ
うにして得られた熱処理品は光透過性に優れ、複屈折が
小さいという光リソグラフィーに好適な光学特性を有し
ているので、ＡｒＦレーザ光（１９３ｎｍ）、Ｘｅ2ラ
ンプ光（１７２ｎｍ）、Ｆ2レーザ光（１５７ｎｍ）、
Ｋｒ2ランプ光（１４６ｎｍ）または固体レーザ光など
の真空紫外光を光源とした光リソグラフィー用の光学部
材に使用することができる。The birefringence was measured using the heat-treated product,
Inspect the 633 nm birefringence optical path difference. The small heat-treated product is processed into a test piece and the transmittance is inspected. The heat-treated product thus obtained has excellent optical transparency and low birefringence, which is an optical characteristic suitable for photolithography. Therefore, ArF laser light (193 nm), Xe 2 lamp light (172 nm), F 2 laser light (157 nm),
It can be used for an optical member for photolithography using vacuum ultraviolet light such as Kr 2 lamp light (146 nm) or solid laser light as a light source.
【００４８】以下、本発明を実施例により具体的に説明
するが、本発明はこれらの例に限定されるものではな
い。Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.
【００４９】[0049]
【実施例】＜実施例１＞本実施例にかかる製造方法は、
蛍石原料を融解して形成した融液を固化させて蛍石単結
晶を成長させることにより、蛍石単結晶のインゴットを
作製する工程と、さらに熱処理を施した前記インゴット
から蛍石単結晶の成形品及びテストピースを切り出す工
程と、前記成形品及びテストピースを下記の方法により
熱処理する工程と、を備えており、この製造方法により
本実施例にかかる光学部材作製用の蛍石単結晶素材及び
テストピースを製造した。<Embodiment 1> The manufacturing method according to this embodiment is as follows.
A step of producing a fluorite single crystal ingot by solidifying a melt formed by melting a fluorite raw material and growing a fluorite single crystal, and further converting a fluorite single crystal from the ingot that has been subjected to a heat treatment. A step of cutting out a molded article and a test piece, and a step of heat-treating the molded article and the test piece by the following method. The fluorite single crystal material for producing an optical member according to the present embodiment is provided by this manufacturing method. And test pieces were manufactured.
【００５０】ここで、蛍石単結晶である成形品及びテス
トピースの前記熱処理は、蛍石単結晶の構造支配温度帯
（約６１０℃〜約１０１０℃）を通過させて、それより
も高い第１温度まで蛍石単結晶を昇温させてから所定時
間保持した後に、前記第１温度から前記構造支配温度帯
よりも低い第２温度まで降温させることにより行い、前
記第１温度から前記第２温度まで降温させる際に、前記
構造支配温度帯における熱処理時間（滞留時間）を８０
０時間以下にした。Here, the heat treatment of the molded article and the test piece, which is a fluorite single crystal, passes through the structure controlling temperature zone (about 610 ° C. to about 1010 ° C.) of the fluorite single crystal, and the heat treatment is carried out. After increasing the temperature of the fluorite single crystal to one temperature and holding it for a predetermined time, the temperature is lowered from the first temperature to a second temperature lower than the structure governing temperature zone, and the second temperature is reduced from the first temperature to the second temperature. When the temperature is lowered to the temperature, the heat treatment time (residence time) in the structure-dominated temperature zone is set to 80.
0 hours or less.
【００５１】本実施例においては、蛍石単結晶素材と併
せてその光学特性を評価するためのテストピースを製造
し、かつテストピースを蛍石単結晶素材（成形品）の正
確な特性評価ができるように、成形品と同時に同条件で
熱処理した。以下に、製造工程を具体的に示す。先ず、
蛍石原料を黒鉛製容器などの清浄な容器に充填し、真空
排気が可能な垂直ブリッジマン装置（結晶成長炉）の所
定位置に設置した。充分な排気下において、ヒーターの
通電加熱により蛍石原料を昇温させて融解させた。In this embodiment, a test piece for evaluating the optical properties of the fluorite single crystal material is manufactured together with the fluorite single crystal material, and the test piece is used for accurate property evaluation of the fluorite single crystal material (molded article). As much as possible, it was heat-treated under the same conditions as the molded article. Hereinafter, the manufacturing process will be specifically described. First,
The fluorite raw material was filled in a clean container such as a graphite container, and placed at a predetermined position of a vertical Bridgman apparatus (crystal growth furnace) capable of evacuating. Under sufficient exhaust, the fluorite raw material was heated and melted by energizing the heater.
【００５２】融点に到達した後は、すぐに引下げによる
結晶化を開始させず、６時間経過させた後に結晶化を開
始した。引下げは１時間あたり１ｍｍの速度で行い、融
液のすべてが結晶化したら、室温まで徐冷してインゴッ
トとして取り出した。インゴットのまま熱処理を行った
後にインゴットを切断し、さらにまるめ加工などの成形
加工を行って、口径２９０ｍｍ、厚さ６０ｍｍの円柱状
の単結晶成形品とした。After reaching the melting point, crystallization was not immediately started by pulling down, but was started after 6 hours. The lowering was performed at a rate of 1 mm per hour. When all of the melt crystallized, the melt was gradually cooled to room temperature and taken out as an ingot. After the heat treatment was performed on the ingot as it was, the ingot was cut, and further formed by rounding or the like to obtain a cylindrical single crystal molded product having a diameter of 290 mm and a thickness of 60 mm.
【００５３】この単結晶成形品と同じインゴットから
は、単結晶成形品とは別に口径４０ｍｍ、厚さ１５ｍｍ
の円柱状の小型成形品を製作した。次に、単結晶成形品
と小型成形品を黒鉛製容器に収容し、酸性フッ化アンモ
ニウム１３０ｇも黒鉛製容器に収容した。そして、黒鉛
製容器をさらにステンレス製の容器に収容した。From the same ingot as this single crystal molded product, a diameter of 40 mm, a thickness of 15 mm
Was manufactured. Next, the single crystal molded product and the small molded product were accommodated in a graphite container, and 130 g of ammonium acid fluoride was also accommodated in the graphite container. Then, the graphite container was further housed in a stainless steel container.
【００５４】このステンレス製容器は密閉可能であり、
排気設備を接続することにより真空排気も可能である。
また、ガス配管設備を設けることにより、不活性ガスな
どの気体の導入も可能である。このステンレス製容器の
周囲には通電加熱が可能なヒーターを配置してある。ス
テンレス容器内部を充分に排気した後に密閉して、徐々
に昇温した。温度条件は、構造支配温度帯を通過させる
とともに、その降温側滞留時間を８００時間以下にする
ことが重要である。構造支配温度帯は蛍石においては、
６１０℃〜１０１０℃の範囲である。 従って、まず単
結晶成形品及び小型成形品の温度を室温から徐々に上昇
させ、構造支配温度帯を通過させて１０２０℃にした。
その後、徐々に温度を降下させ、構造支配温度帯を通過
させて６００℃とした。構造支配温度帯を７８０時間で
通過させることにより降温側滞留時間を８００時間以内
とした。This stainless steel container can be sealed,
Evacuation is also possible by connecting exhaust equipment.
In addition, by providing gas piping equipment, it is possible to introduce a gas such as an inert gas. Around the stainless steel container, a heater that can be electrically heated is arranged. After the inside of the stainless steel container was sufficiently evacuated, it was sealed and gradually heated. It is important that the temperature conditions be such that the structure-passing temperature zone is passed and that the residence time on the cooling side is 800 hours or less. The structure-dominated temperature zone is
It is in the range of 610 ° C to 1010 ° C. Therefore, first, the temperature of the single crystal molded article and the small molded article was gradually raised from room temperature, and was passed to the structure governing temperature zone to reach 1020 ° C.
Thereafter, the temperature was gradually lowered, and the temperature was lowered to 600 ° C. by passing through the temperature zone for controlling the structure. By passing through the structure dominant temperature zone in 780 hours, the residence time on the cooling side was set to within 800 hours.
【００５５】この後、室温まで徐冷して、熱処理品（光
学部材作製用の素材）と小型熱処理品（テストピース
用）を取り出した。熱処理品の複屈折は以下のように測
定した。複屈折測定には、オーク製作所製の複屈折自動
測定装置（ＡＤＲシリーズ）を用いた。熱処理品一つに
つき、１０００ポイントの多点測定を行い、波長６３３
ｎｍの光に対する複屈折光路差がすべて５ｎｍ／ｃｍ以
下であることを確認した。Thereafter, the product was gradually cooled to room temperature, and a heat-treated product (material for producing an optical member) and a small heat-treated product (for a test piece) were taken out. The birefringence of the heat-treated product was measured as follows. For the birefringence measurement, an automatic birefringence measuring device (ADR series) manufactured by Oak Manufacturing Co., Ltd. was used. For each heat-treated product, multi-point measurement at 1000 points was performed and the wavelength was 633.
It was confirmed that the birefringence optical path difference for light of nm was 5 nm / cm or less.
【００５６】小型熱処理品はテストピースに加工して透
過率を測定し、波長１９３ｎｍの光に対する内部透過率
が９９．８％／ｃｍ以上であることを確認した。なお、
分光光度計にはＶａｒｉａｎ社製のCary５を使用した。
また、テストピースは平行２面間の距離（厚さ）が１０
ｍｍ、平行度が３０秒以下、表面粗さＲＭＳが５Å以下
となるように鏡面研磨した。The small heat-treated product was processed into a test piece, and the transmittance was measured. It was confirmed that the internal transmittance for light having a wavelength of 193 nm was 99.8% / cm or more. In addition,
Cary5 manufactured by Varian was used for the spectrophotometer.
The test piece has a distance (thickness) of 10 between the two parallel surfaces.
mm, the mirror surface was polished so that the parallelism was 30 seconds or less and the surface roughness RMS was 5 ° or less.
【００５７】こうして得られた熱処理品は光透過性に優
れ、複屈折が小さいという光リソグラフィーに好適な光
学特性を有しているため、ＡｒＦレーザ光（１９３ｎ
ｍ）を光源とした光リソグラフィー装置の光学部材に使
用可能であった。 ＜比較例１＞実施例１と同様にして本比較例の熱処理品
及び小型熱処理品を作製したが、実施例１との比較実験
のため、本比較例においては、単結晶成形品及び小型成
形品の温度を室温から徐々に上昇させたが、構造支配温
度帯を通過させずに９２０℃までとし、その後徐々に温
度を降下させて６００℃とした。さらに室温まで徐冷し
て、熱処理品と小型熱処理品を取り出した。Since the heat-treated product thus obtained has excellent light transmittance and small birefringence and suitable optical characteristics for photolithography, the ArF laser beam (193n) is used.
m) could be used as an optical member of an optical lithography apparatus using a light source. <Comparative Example 1> A heat-treated product and a small heat-treated product of this comparative example were produced in the same manner as in Example 1. However, for comparison with Example 1, in this comparative example, a single-crystal molded product and a small-sized molded product were produced. Although the temperature of the product was gradually raised from room temperature, the temperature was raised to 920 ° C. without passing through the temperature zone for controlling the structure, and then the temperature was gradually lowered to 600 ° C. Furthermore, it was gradually cooled to room temperature, and the heat-treated product and the small heat-treated product were taken out.
【００５８】熱処理品の複屈折は以下のように測定し
た。複屈折測定には、オーク製作所製の複屈折自動測定
装置（ＡＤＲシリーズ）を用いた。熱処理品一つにつ
き、１０００ポイントの多点測定を行った。、波長６３
３ｎｍの光に対する複屈折光路差は、すべてが５ｎｍ／
ｃｍ以下であることはなく、１０００ポイントのうち１
４８ポイントが５〜１５ｎｍ／cmの範囲であった。この
ように、本比較例により製造した熱処理品は、明らかに
複屈折が劣っていた。The birefringence of the heat-treated product was measured as follows. For the birefringence measurement, an automatic birefringence measuring device (ADR series) manufactured by Oak Manufacturing Co., Ltd. was used. For each heat-treated product, a multipoint measurement of 1000 points was performed. , Wavelength 63
The birefringent optical path difference for 3 nm light is 5 nm /
cm or less, 1 out of 1000 points
Forty-eight points ranged from 5 to 15 nm / cm. Thus, the heat-treated product manufactured according to this comparative example was clearly inferior in birefringence.
【００５９】小型熱処理品は、テストピースに加工して
透過率を測定し、波長１９３ｎｍの光に対する内部透過
率が９９．８％／ｃｍ以上であることを確認した。つま
り光透過性には優れていた。なお、分光光度計にはＶａ
ｒｉａｎ社製のCary５を使用した。また、テストピース
は平行２面間の距離（厚さ）が１０ｍｍ、平行度が３０
秒以下、表面粗さＲＭＳが５Å以下となるように鏡面研
磨した。The small heat-treated product was processed into a test piece, and the transmittance was measured. It was confirmed that the internal transmittance for light having a wavelength of 193 nm was 99.8% / cm or more. That is, the light transmittance was excellent. The spectrophotometer has Va
Cary5 manufactured by Rian was used. The test piece had a distance (thickness) between two parallel surfaces of 10 mm and a parallelism of 30.
Mirror polishing was performed so that the surface roughness RMS was 5 ° or less for seconds or less.
【００６０】こうして得られた熱処理品は光透過性には
優れているが、複屈折が大きいため光リソグラフィー装
置の光学部材には使用できなかった。 ＜比較例２＞実施例１と同様にして本比較例の熱処理品
及び小型熱処理品を作製した。本比較例においては、実
施例１と同様に単結晶成形品及び小型成形品の温度を室
温から徐々に上昇させ、構造支配温度帯を通過させてか
ら１０２０℃まで昇温させた。 その後、徐々に温度を
降下させることにより、構造支配温度帯を通過させて６
００℃としたが、実施例１との比較実験のため、降温時
において構造支配温度帯を９００時間で通過させた。The heat-treated product thus obtained was excellent in light transmittance, but could not be used as an optical member of a photolithography apparatus because of its large birefringence. Comparative Example 2 A heat-treated product of this comparative example and a small heat-treated product were produced in the same manner as in Example 1. In this comparative example, the temperature of the single crystal molded article and the small molded article were gradually increased from room temperature, and passed through the structure governing temperature zone, and then increased to 1020 ° C. as in Example 1. Then, by gradually lowering the temperature, it is passed through the structure-dominated temperature zone to
Although the temperature was set to 00 ° C., for the purpose of a comparative experiment with Example 1, the sample was allowed to pass through the structurally controlled temperature zone in 900 hours at the time of cooling.
【００６１】即ち、本比較例では、「降温側滞留時間を
８００時間以内にする」という条件を意図的に満たさな
いようにした。その後、室温まで徐冷して、熱処理品と
小型熱処理品を取り出した。熱処理品の複屈折は以下の
ように測定した。複屈折測定には、オーク製作所製の複
屈折自動測定装置（ＡＤＲシリーズ）を用いた。熱処理
品一つにつき、１０００ポイントの多点測定を行い、波
長６３３ｎｍの光に対する複屈折光路差がすべて５ｎｍ
／ｃｍ以下であることを確認した。That is, in the present comparative example, the condition that the “residence time on the cooling side should be within 800 hours” was not intentionally satisfied. Thereafter, the mixture was gradually cooled to room temperature, and the heat-treated product and the small heat-treated product were taken out. The birefringence of the heat-treated product was measured as follows. For the birefringence measurement, an automatic birefringence measuring device (ADR series) manufactured by Oak Manufacturing Co., Ltd. was used. For each heat-treated product, multi-point measurement at 1000 points is performed, and the birefringence optical path difference for light with a wavelength of 633 nm is all 5 nm.
/ Cm or less.
【００６２】小型熱処理品は、テストピースに加工して
透過率を測定したところ、波長１９３ｎｍの光に対する
内部透過率が９９．１％／ｃｍと良くないことが判明し
た。なお、分光光度計にはＶａｒｉａｎ社製のCary５を
使用した。また、テストピースは平行２面間の距離（厚
さ）が１０ｍｍ、平行度が３０秒以下、表面粗さＲＭＳ
が５Å以下となるように鏡面研磨した。When the small heat-treated product was processed into a test piece and measured for transmittance, it was found that the internal transmittance for light having a wavelength of 193 nm was 99.1% / cm, which was not good. In addition, Cary5 manufactured by Varian was used for the spectrophotometer. The test piece has a distance (thickness) between two parallel surfaces of 10 mm, a parallelism of 30 seconds or less, and a surface roughness RMS.
Was mirror-polished so as to be 5 ° or less.
【００６３】このようにして得られた熱処理品は、複屈
折は小さいものの、光透過性に劣っているため、光リソ
グラフィー装置の光学部材には使用できなかった。 ＜実施例２＞本実施例にかかる製造方法は、蛍石原料と
スカベンジャーの混合物を加熱して脱酸素化反応させた
後に冷却することにより、或いは前記脱酸素化反応と前
記蛍石原料の融解及び冷却により脱酸素化した蛍石の多
結晶体である前処理品を得る工程と、前記前処理品を融
解して形成した融液を固化させて蛍石単結晶を成長させ
ることにより、蛍石単結晶のインゴットを作製する工程
と、さらに熱処理を施した前記インゴットから蛍石単結
晶の成形品及びテストピースを切り出す工程と、前記成
形品及びテストピースを下記の方法により熱処理する工
程と、を備えており、この製造方法により本実施例にか
かる光学部材作製用の蛍石単結晶素材及びテストピース
を製造した。The heat-treated product thus obtained had a small birefringence, but was inferior in light transmittance, so that it could not be used as an optical member of a photolithography apparatus. <Embodiment 2> The production method according to the present embodiment is characterized in that a mixture of a fluorite raw material and a scavenger is heated to cause a deoxygenation reaction and then cooled, or the deoxygenation reaction and the melting of the fluorite raw material are performed. And a step of obtaining a pretreated product, which is a polycrystal of fluorite deoxygenated by cooling, and solidifying a melt formed by melting the pretreated product to grow a fluorite single crystal. A step of producing a stone single crystal ingot, and a step of cutting out a fluorite single crystal molded article and a test piece from the ingot that has been further heat-treated, and a step of heat-treating the molded article and the test piece by the following method, According to this manufacturing method, a fluorite single crystal material and a test piece for manufacturing an optical member according to the present example were manufactured.
【００６４】ここで、蛍石単結晶である成形品及びテス
トピースの前記熱処理は、蛍石単結晶の構造支配温度帯
（約６１０℃〜約１０１０℃）を通過させて、それより
も高い第１温度まで蛍石単結晶を昇温させてから所定時
間保持した後に、前記第１温度から前記構造支配温度帯
よりも低い第２温度まで降温させることにより行い、前
記第１温度から前記第２温度まで降温させる際に、前記
構造支配温度帯における熱処理時間（滞留時間）を８０
０時間以下にした。Here, the heat treatment of the molded article and the test piece, which is a fluorite single crystal, passes through the structure controlling temperature zone (about 610 ° C. to about 1010 ° C.) of the fluorite single crystal, and the heat treatment is performed at a higher temperature. After increasing the temperature of the fluorite single crystal to one temperature and holding it for a predetermined time, the temperature is lowered from the first temperature to a second temperature lower than the structure governing temperature zone, and the second temperature is reduced from the first temperature to the second temperature. When the temperature is lowered to the temperature, the heat treatment time (residence time) in the structure-dominated temperature zone is set to 80.
0 hours or less.
【００６５】本実施例においては、蛍石単結晶素材と併
せてその光学特性を評価するためのテストピースを製造
し、かつテストピースを蛍石単結晶素材（成形品）の正
確な特性評価ができるように、成形品と同時に同条件で
熱処理した。以下に、製造工程を具体的に示す。先ず、
蛍石の粉末原料に粉末状のフッ化鉛１ｍｏｌ％を添加し
て良く混合させ、これを黒鉛製の清浄な容器に充填し
た。そして、この容器を真空排気が可能であり、通電加
熱ヒーターを有する真空加熱装置の所定位置に設置し
た。充分な排気下において、脱酸素化反応温度帯を通過
させた後、さらに温度を上昇させて一旦原料を融解させ
た後、室温まで降温して多結晶体とした。以上のよう
に、注意深く脱酸素化処理を行うことにより前処理品
（蛍石の多結晶体）を作製した。In this embodiment, a test piece for evaluating the optical characteristics of the fluorite single crystal material is manufactured together with the fluorite single crystal material, and the test piece is used for accurate property evaluation of the fluorite single crystal material (molded product). As much as possible, it was heat-treated under the same conditions as the molded article. Hereinafter, the manufacturing process will be specifically described. First,
1 mol% of powdery lead fluoride was added to the fluorite powder raw material, mixed well, and filled in a clean graphite container. The container was evacuated and set at a predetermined position of a vacuum heating device having an electric heater. After passing through a deoxygenation reaction temperature zone under sufficient exhaust, the temperature was further raised to once melt the raw material, and then lowered to room temperature to obtain a polycrystal. As described above, a pre-treated product (fluorite polycrystal) was prepared by carefully performing deoxygenation treatment.
【００６６】前処理品を黒鉛製容器などの清浄な容器に
充填し、真空排気が可能な垂直ブリッジマン装置（結晶
成長炉）の所定位置に設置した。充分な排気下におい
て、ヒーターの通電加熱により前処理品を昇温させて融
解させた。融点に到達した後は、すぐに引下げによる結
晶化を開始させず、６時間経過させた後に結晶化を開始
した。引下げは１時間あたり１ｍｍの速度で行い、融液
のすべてが結晶化したら、室温まで徐冷してインゴット
として取り出した。The pretreated product was filled in a clean container such as a graphite container, and set at a predetermined position in a vertical Bridgman apparatus (crystal growth furnace) capable of evacuating. Under sufficient evacuation, the pre-processed product was heated and melted by energizing the heater. After reaching the melting point, crystallization by pulling was not immediately started, but crystallization was started after elapse of 6 hours. The lowering was performed at a rate of 1 mm per hour. When all of the melt crystallized, the melt was gradually cooled to room temperature and taken out as an ingot.
【００６７】インゴットのまま熱処理を行った後にイン
ゴットを切断し、さらにまるめ加工などの成型加工を行
って、口径２９０ｍｍ、厚さ６０ｍｍの円柱状の単結晶
成形品とした。この単結晶成形品と同じインゴットから
は、単結晶成形品とは別に口径４０ｍｍ、厚さ１５ｍｍ
の円柱状の小型成形品を製作した。After the heat treatment was performed on the ingot as it was, the ingot was cut, and further subjected to molding such as rounding to obtain a cylindrical single crystal molded product having a diameter of 290 mm and a thickness of 60 mm. From the same ingot as this single crystal molded product, a diameter of 40 mm and a thickness of 15 mm separately from the single crystal molded product
Was manufactured.
【００６８】次に、単結晶成形品と小型成形品を黒鉛製
容器に収容し、酸性フッ化アンモニウム１３０ｇも黒鉛
製容器に収容した。そして、黒鉛製容器をさらにステン
レス製の容器に収容した。このステンレス製容器は密閉
可能であり、排気設備を接続することにより真空排気も
可能である。また、ガス配管設備を設けることにより、
不活性ガスなどの気体の導入も可能である。このステン
レス製容器の周囲には通電加熱が可能なヒーターを配置
してある。Next, the single crystal molded article and the small molded article were accommodated in a graphite container, and 130 g of ammonium acid fluoride was also accommodated in the graphite container. Then, the graphite container was further housed in a stainless steel container. This stainless steel container can be hermetically sealed, and can be evacuated by connecting exhaust equipment. In addition, by providing gas piping equipment,
It is also possible to introduce a gas such as an inert gas. Around the stainless steel container, a heater that can be electrically heated is arranged.
【００６９】ステンレス容器内部を充分に排気した後に
密閉して、徐々に昇温した。温度条件は、構造支配温度
帯を通過させるとともに、その降温側滞留時間を８００
時間以下にすることが重要である。構造支配温度帯は蛍
石においては、６１０℃〜１０１０℃の範囲である。
従って、まず単結晶成形品及び小型成形品の温度を室温
から徐々に上昇させ、構造支配温度帯を通過させて１０
２０℃にした。その後、徐々に温度を降下させ、構造支
配温度帯を通過させて６００℃とした。構造支配温度帯
を７８０時間で通過させることにより降温側滞留時間を
８００時間以内とした。After the interior of the stainless steel container was sufficiently evacuated, it was sealed and gradually heated. The temperature condition is to pass through the structure-dominant temperature zone and to set the cooling-side residence time to 800
It is important to keep it below time. The structure dominant temperature range is 610 ° C to 1010 ° C for fluorite.
Therefore, first, the temperature of the single crystal molded article and the small molded article is gradually raised from room temperature, and the temperature is passed through the temperature zone for controlling the structure to 10 ° C.
20 ° C. Thereafter, the temperature was gradually lowered, and the temperature was lowered to 600 ° C. by passing through the temperature zone for controlling the structure. By passing through the structure dominant temperature zone in 780 hours, the residence time on the cooling side was set to within 800 hours.
【００７０】この後、室温まで徐冷して、熱処理品（光
学部材作製用の素材）と小型熱処理品（テストピース
用）を取り出した。熱処理品の複屈折は以下のように測
定した。複屈折測定には、オーク製作所製の複屈折自動
測定装置（ＡＤＲシリーズ）を用いた。熱処理品一つに
つき、１０００ポイントの多点測定を行い、波長６３３
ｎｍの光に対する複屈折光路差がすべて５ｎｍ／ｃｍ以
下であることを確認した。Thereafter, the product was gradually cooled to room temperature, and a heat-treated product (material for producing an optical member) and a small heat-treated product (for a test piece) were taken out. The birefringence of the heat-treated product was measured as follows. For the birefringence measurement, an automatic birefringence measuring device (ADR series) manufactured by Oak Manufacturing Co., Ltd. was used. For each heat-treated product, multi-point measurement at 1000 points was performed and the wavelength was 633.
It was confirmed that the birefringence optical path difference for light of nm was 5 nm / cm or less.
【００７１】小型熱処理品はテストピースに加工して透
過率を測定し、波長１９３ｎｍの光に対する内部透過率
が９９．８％／ｃｍ以上、波長１５７ｎｍの光に対する
内部透過率が９９．６％／ｃｍ以上であることを確認し
た。なお、分光光度計にはＶａｒｉａｎ社製のCary５
（１９３ｎｍ内部透過率の測定）と日本分光社製のＶＵ
Ｖ２００（１５７ｎｍ内部透過率の測定）をそれぞれ使
用した。The small heat-treated product was processed into a test piece and measured for transmittance. The internal transmittance for light having a wavelength of 193 nm was 99.8% / cm or more, and the internal transmittance for light having a wavelength of 157 nm was 99.6% / cm. cm or more. The spectrophotometer has a Cary5 manufactured by Varian.
(Measurement of 193 nm internal transmittance) and VU manufactured by JASCO Corporation
V200 (measurement of 157 nm internal transmittance) was used.
【００７２】なお、テストピースは平行２面間の距離
（厚さ）が１０ｍｍ、平行度が３０秒以下、表面粗さＲ
ＭＳが５Å以下となるように鏡面研磨した。こうして得
られた熱処理品は光透過性に優れ、複屈折が小さいとい
う光リソグラフィーに好適な光学特性を有しているた
め、ＡｒＦレーザ光（１９３ｎｍ）を光源とした光リソ
グラフィー装置の光学部材だけでなく、Ｆ2レーザ光
（１５７ｎｍ）用の光学部材にも使用できた。The test piece had a distance (thickness) between two parallel surfaces of 10 mm, a parallelism of 30 seconds or less, and a surface roughness R.
Mirror polishing was performed so that MS was 5 ° or less. The heat-treated product thus obtained has excellent optical transparency and low birefringence, and has optical characteristics suitable for photolithography. Therefore, only the optical members of a photolithography apparatus using an ArF laser beam (193 nm) as a light source are used. And could be used as an optical member for F 2 laser light (157 nm).
【００７３】[0073]
【発明の効果】以上説明したように、本発明（請求項
１、２）にかかる熱処理方法によれば、透過率に優れ、
複屈折の小さな蛍石単結晶が得られる。また、本発明
（請求項３〜10）にかかる製造方法によれば、透過率に
優れ、複屈折の小さな光学部材作製用の蛍石単結晶素材
が得られる。As described above, according to the heat treatment method of the present invention (claims 1 and 2), the transmittance is excellent,
A fluorite single crystal with small birefringence is obtained. Further, according to the manufacturing method of the present invention (claims 3 to 10), a fluorite single crystal material for producing an optical member having excellent transmittance and small birefringence can be obtained.
【００７４】また、本発明（請求項11、12）にかかる蛍
石単結晶は、優れた光学特性（透過率、複屈折）が要求
される光リソグラフィー用の光学部材に使用できる。Further, the fluorite single crystal according to the present invention (claims 11 and 12) can be used for an optical member for photolithography requiring excellent optical characteristics (transmittance and birefringence).
【図１】は、本発明にかかる光学部材作製用の蛍石単結
晶素材とその評価用テストピースを製造する方法（一
例）を示す工程図である。 以上FIG. 1 is a process chart showing a method (one example) for producing a fluorite single crystal material for producing an optical member and a test piece for evaluating the same according to the present invention. that's all
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 4G077 AA02 AB04 BE02 CD02 EC05 FE12 FE13 5F046 BA03 CA04 CA08 CB12 CB25 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G077 AA02 AB04 BE02 CD02 EC05 FE12 FE13 5F046 BA03 CA04 CA08 CB12 CB25
Claims (12)
て、それよりも高い第１温度まで蛍石単結晶を昇温させ
てから所定時間保持した後に、前記第１温度から前記構
造支配温度帯よりも低い第２温度まで降温させることに
より、蛍石単結晶の熱処理を行う方法であって、 前記第１温度から前記第２温度まで降温させる際に、前
記構造支配温度帯における熱処理時間（滞留時間）を８
００時間以下にすることを特徴とする蛍石単結晶の熱処
理方法。1. After passing through a structure dominating temperature zone of a fluorite single crystal, raising the temperature of the fluorite single crystal to a first temperature higher than the first temperature, and holding the fluorite single crystal for a predetermined time, the structure is changed from the first temperature to the structure. A method for performing a heat treatment of a fluorite single crystal by lowering the temperature to a second temperature lower than the governing temperature zone, wherein the heat treatment in the structure governing temperature zone is performed when the temperature is decreased from the first temperature to the second temperature. Time (residence time) 8
A heat treatment method for a fluorite single crystal, wherein the heat treatment is performed for not more than 00 hours.
〜約１０１０℃であることを特徴とする請求項１記載の
熱処理方法。2. The structure controlling temperature range is about 610 ° C.
The method of claim 1 wherein the temperature is from about 10 ° C to about 1010 ° C.
晶を成長させることにより、 蛍石単結晶のインゴット
を作製する工程と、 前記インゴットから、或いは前記インゴットに熱処理を
施した後にそのインゴットから蛍石単結晶の成形品を切
り出す工程と、 前記成形品を請求項１または２記載の方法により熱処理
する工程と、を備えた光学部材作製用の蛍石単結晶素材
の製造方法。At least a step of producing a fluorite single crystal ingot by solidifying a melt formed by melting a fluorite raw material to grow a fluorite single crystal; and A fluorite for producing an optical member, comprising: a step of cutting out a molded article of a fluorite single crystal from an ingot after heat-treating the ingot; and a step of heat-treating the molded article by the method according to claim 1 or 2. Manufacturing method of single crystal material.
反応させた後に冷却することにより、或いは前記脱酸素
化反応と前記蛍石原料の融解及び冷却により、脱酸素化
した蛍石の焼結体または多結晶体である前処理品を得る
工程と、 前記前処理品を融解して形成した融液を固化させて蛍石
単結晶を成長させることにより、蛍石単結晶のインゴッ
トを作製する工程と、 前記インゴットから、或いは前記インゴットに熱処理を
施した後にそのインゴットから蛍石単結晶の成形品を切
り出す工程と、 前記成形品を請求項１または２記載の方法により熱処理
する工程と、を備えた光学部材作製用の蛍石単結晶素材
の製造方法。4. Deoxygenation at least by heating a mixture of a fluorite raw material and a scavenger to cause a deoxygenation reaction, followed by cooling, or by the deoxygenation reaction and melting and cooling of the fluorite raw material. Obtaining a pretreated product that is a sintered or polycrystalline body of the obtained fluorite, and solidifying a melt formed by melting the pretreated product to grow a fluorite single crystal, thereby obtaining a fluorite single crystal. A step of producing a crystal ingot, a step of cutting out a molded product of a fluorite single crystal from the ingot or after performing a heat treatment on the ingot, and cutting the molded product by the method according to claim 1 or 2. A method of producing a fluorite single crystal material for producing an optical member, comprising: a heat treatment step.
晶を成長させることにより、蛍石単結晶のインゴットを
作製する工程と、 前記インゴットから、或いは前記インゴットに熱処理を
施した後にそのインゴットから蛍石単結晶の成形品及び
テストピースを切り出す工程と、 前記成形品及びテストピースを請求項１または２記載の
方法により熱処理する工程と、 を備えた光学部材作製用の蛍石単結晶素材及びテストピ
ースの製造方法。5. A process for producing an ingot of a fluorite single crystal by solidifying a melt formed by melting a fluorite raw material and growing a fluorite single crystal, at least from the ingot or from the ingot. An optical system comprising: a step of subjecting an ingot to heat treatment and then cutting out a fluorite single crystal molded article and a test piece from the ingot; and a step of heat treating the molded article and the test piece by the method according to claim 1 or 2. A method for producing a fluorite single crystal material for producing members and a test piece.
反応させた後に冷却することにより、或いは前記脱酸素
化反応と前記蛍石原料の融解及び冷却により脱酸素化し
た蛍石の焼結体または多結晶体である前処理品を得る工
程と、 前記前処理品を融解して形成した融液を固化させて蛍石
単結晶を成長させることにより、蛍石単結晶のインゴッ
トを作製する工程と、 前記インゴットから、或いは前記インゴットに熱処理を
施した後にそのインゴットから蛍石単結晶の成形品及び
テストピースを切り出す工程と、 前記成形品及びテストピースを請求項１または２記載の
方法により熱処理する工程と、を備えた光学部材作製用
の蛍石単結晶素材及びテストピースの製造方法。6. At least a mixture of a fluorite raw material and a scavenger is deoxygenated by heating and causing a deoxygenation reaction followed by cooling, or by the deoxygenation reaction and melting and cooling of the fluorite raw material. A step of obtaining a pretreated product which is a sintered or polycrystalline fluorite; and solidifying a melt formed by melting the pretreated product to grow a fluorite single crystal. Producing an ingot, and cutting out a molded product and a test piece of a fluorite single crystal from the ingot or after performing a heat treatment on the ingot, and cutting the molded product and the test piece from the ingot. 3. A method for producing a fluorite single crystal material and a test piece for producing an optical member, comprising a step of performing heat treatment by the method according to 2.
条件で熱処理することを特徴とする請求項５または６記
載の製造方法。7. The method according to claim 5, wherein the molded article and the test piece are heat-treated simultaneously under the same conditions.
学部材であることを特徴とする請求項３〜７のいずれか
に記載の製造方法。8. The method according to claim 3, wherein the optical member is an optical member for photolithography.
差が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍの真空紫
外光に対する内部透過率が９９．８％／ｃｍ以上である
光リソグラフィー用の蛍石単結晶が得られることを特徴
とする請求項３〜８のいずれかに記載の製造方法。9. A fluorite single crystal for photolithography having a birefringence optical path difference with respect to light having a wavelength of 633 nm of 5 nm / cm or less and an internal transmittance of 99.8% / cm or more with respect to vacuum ultraviolet light having a wavelength of 193 nm. The method according to any one of claims 3 to 8, wherein is obtained.
差が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍの真空紫
外光に対する内部透過率が９９．８％／ｃｍ以上であ
り、波長１５７ｎｍの真空紫外光に対する内部透過率が
９９．６％／ｃｍ以上である光リソグラフィー用の蛍石
単結晶が得られることを特徴とする請求項３〜８のいず
れかに記載の製造方法。10. A birefringent optical path difference with respect to light with a wavelength of 633 nm is 5 nm / cm or less, an internal transmittance with respect to vacuum ultraviolet light with a wavelength of 193 nm is 99.8% / cm or more, and a light transmittance with respect to vacuum ultraviolet light with a wavelength of 157 nm is used. The method according to any one of claims 3 to 8, wherein a fluorite single crystal for photolithography having an internal transmittance of 99.6% / cm or more is obtained.
差が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍの真空紫
外光に対する内部透過率が９９．８％／ｃｍ以上である
ことを特徴とする光リソグラフィー用の蛍石単結晶。11. An optical lithography method, wherein a birefringence optical path difference with respect to light having a wavelength of 633 nm is 5 nm / cm or less, and an internal transmittance with respect to vacuum ultraviolet light having a wavelength of 193 nm is 99.8% / cm or more. Fluorite single crystal.
差が５ｎｍ／ｃｍ以下であり、波長１９３ｎｍの真空紫
外光に対する内部透過率が９９．８％／ｃｍ以上であ
り、波長１５７ｎｍの真空紫外光に対する内部透過率が
９９．６％／ｃｍ以上であることを特徴とする光リソグ
ラフィー用の蛍石単結晶。12. A birefringent optical path difference with respect to light having a wavelength of 633 nm is 5 nm / cm or less, an internal transmittance with respect to vacuum ultraviolet light having a wavelength of 193 nm is 99.8% / cm or more, and a light transmittance with respect to vacuum ultraviolet light having a wavelength of 157 nm is obtained. A fluorite single crystal for photolithography, having an internal transmittance of 99.6% / cm or more.
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|---|---|---|---|
| JP34967198A JP4158252B2 (en) | 1998-11-09 | 1998-12-09 | Fluorite single crystal, heat treatment method thereof, and method for producing fluorite single crystal material |
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|---|---|---|---|
| JP31731398 | 1998-11-09 | ||
| JP10-317313 | 1998-11-09 | ||
| JP34967198A JP4158252B2 (en) | 1998-11-09 | 1998-12-09 | Fluorite single crystal, heat treatment method thereof, and method for producing fluorite single crystal material |
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| JP2000203994A true JP2000203994A (en) | 2000-07-25 |
| JP4158252B2 JP4158252B2 (en) | 2008-10-01 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002193697A (en) * | 2000-12-27 | 2002-07-10 | Nikon Corp | Method for producing fluoride crystal and fluoride crystal produced thereby |
| WO2003009017A1 (en) * | 2001-07-17 | 2003-01-30 | Nikon Corporation | Method for producing optical member |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012165334A1 (en) | 2011-05-27 | 2012-12-06 | 株式会社ニコン | CaF2 POLYCRYSTALLINE BODY, FOCUS RING, PLASMA TREATMENT APPARATUS, AND METHOD FOR PRODUCING CaF2 POLYCRYSTALLINE BODY |
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|---|---|---|---|---|
| JPH04158909A (en) * | 1990-10-23 | 1992-06-02 | Hitachi Metals Ltd | Roll for hot rolling nonferrous metal and its manufacture |
| JPH07289566A (en) * | 1994-04-27 | 1995-11-07 | Kawasaki Steel Corp | Orthodontic parts made of titanium |
| JPH10260349A (en) * | 1997-03-18 | 1998-09-29 | Nikon Corp | Image formation optical system for ultraviolet-ray laser |
| JPH10265300A (en) * | 1997-03-25 | 1998-10-06 | Nikon Corp | Heat treating device for fluorite single crystal and heat treatment therefor |
| JPH10270352A (en) * | 1997-03-25 | 1998-10-09 | Shinetsu Quartz Prod Co Ltd | Aligner for manufacturing integrated circuit |
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|---|---|---|---|---|
| JPH04158909A (en) * | 1990-10-23 | 1992-06-02 | Hitachi Metals Ltd | Roll for hot rolling nonferrous metal and its manufacture |
| JPH07289566A (en) * | 1994-04-27 | 1995-11-07 | Kawasaki Steel Corp | Orthodontic parts made of titanium |
| JPH10260349A (en) * | 1997-03-18 | 1998-09-29 | Nikon Corp | Image formation optical system for ultraviolet-ray laser |
| JPH10265300A (en) * | 1997-03-25 | 1998-10-06 | Nikon Corp | Heat treating device for fluorite single crystal and heat treatment therefor |
| JPH10270352A (en) * | 1997-03-25 | 1998-10-09 | Shinetsu Quartz Prod Co Ltd | Aligner for manufacturing integrated circuit |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002193697A (en) * | 2000-12-27 | 2002-07-10 | Nikon Corp | Method for producing fluoride crystal and fluoride crystal produced thereby |
| JP4569001B2 (en) * | 2000-12-27 | 2010-10-27 | 株式会社ニコン | Method for producing fluoride crystals |
| WO2003009017A1 (en) * | 2001-07-17 | 2003-01-30 | Nikon Corporation | Method for producing optical member |
| US6994747B2 (en) | 2001-07-17 | 2006-02-07 | Nikon Corporation | Method for producing optical member |
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| Publication number | Publication date |
|---|---|
| JP4158252B2 (en) | 2008-10-01 |
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