JPH10231194A - Apparatus and method for heat-treatment of fluorite single crystal - Google Patents
Apparatus and method for heat-treatment of fluorite single crystalInfo
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- JPH10231194A JPH10231194A JP9034708A JP3470897A JPH10231194A JP H10231194 A JPH10231194 A JP H10231194A JP 9034708 A JP9034708 A JP 9034708A JP 3470897 A JP3470897 A JP 3470897A JP H10231194 A JPH10231194 A JP H10231194A
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- Prior art keywords
- single crystal
- temperature
- fluorite single
- heat treatment
- fluorite
- Prior art date
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- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- 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、蛍石単結晶の熱処
理装置および熱処理方法に関するものである。本発明の
熱処理方法により処理された蛍石単結晶は、エキシマレ
ーザーステッパーの光学系を構成する、高精度な結像性
能が必要なレンズやプリズム等に有用である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorite single crystal heat treatment apparatus and a heat treatment method. The fluorite single crystal treated by the heat treatment method of the present invention is useful for a lens, a prism, and the like that require high-precision imaging performance and constitute an optical system of an excimer laser stepper.
【０００２】[0002]
【従来の技術】本発明は、エキシマレーザーステッパー
の光学系として使用可能な、蛍石単結晶の熱処理に関す
るものである。近年、ウエハ上に集積回路パターンを描
画するリソグラフィー技術が急速に発展している。集積
回路の高集積化の要求は高まるばかりであり、その実現
のためにはステッパー投影レンズの解像力を上げてやる
必要がある。投影レンズの解像力は、使用する光の波長
と、投影レンズのＮＡ（開口数）とに支配され、解像力
を上げるためには、使用する光の波長をより短くし、投
影レンズのＮＡをより大きく（大口径化）してやれば良
い。BACKGROUND OF THE INVENTION The present invention relates to a heat treatment of a fluorite single crystal which can be used as an optical system of an excimer laser stepper. In recent years, lithography technology for drawing an integrated circuit pattern on a wafer has been rapidly developing. The demand for higher integration of integrated circuits is only increasing, and to achieve this, it is necessary to increase the resolution of the stepper projection lens. The resolution of the projection lens is governed by the wavelength of the light used and the NA (numerical aperture) of the projection lens. To increase the resolution, the wavelength of the light used is made shorter and the NA of the projection lens is made larger. (Increase the diameter).
【０００３】まず、光の短波長化について述べる。ステ
ッパーに使用する波長は、すでにｇ線（波長４３６n
m）、ｉ線（波長３６５nm）と進んできており、今後さ
らに波長の短いＫｒＦエキシマレーザー光（波長２４８
nm）、ＡｒＦエキシマレーザー光（波長１９３nm）等に
なると、光学系に光学ガラスを使用することは、透過率
から考慮すると、もはや不可能である。このため、エキ
シマレーザーステッパーの光学系には、石英ガラスまた
は蛍石を使用するのが一般的となっている。[0003] First, the shortening of light wavelength will be described. The wavelength used for the stepper is already g-line (wavelength 436n
m), i-line (wavelength 365 nm), and a shorter wavelength KrF excimer laser light (wavelength 248)
nm), ArF excimer laser light (wavelength 193 nm) and the like, it is no longer possible to use optical glass for the optical system in view of transmittance. For this reason, it is common to use quartz glass or fluorite for the optical system of the excimer laser stepper.
【０００４】次に、大口径化について述べる。これは単
に大口径であれば良いというだけでなく、エキシマレー
ザーステッパーの光学系に用いる光学材料としては、蛍
石においては単結晶であることが必要である。ステッパ
ーの高性能化にともない、最近になって口径φ150 mm〜
φ250 mm程度の大口径の蛍石単結晶が要求されるように
なってきた。Next, the enlargement of the diameter will be described. This is not limited to a large diameter, and the optical material used in the optical system of the excimer laser stepper needs to be a single crystal in fluorite. With the higher performance of steppers, recently the diameter of φ150 mm ~
Fluorite single crystals having a large diameter of about 250 mm have been required.
【０００５】以下に従来の蛍石単結晶の製造方法を述べ
る。蛍石単結晶はブリッジマン法（ストックバーガー
法、ルツボ降下法とも呼ばれる）で製造されてきた。紫
外ないし真空紫外域で使用される蛍石単結晶の場合、原
料に天然の蛍石を使用することはなく、化学合成で作ら
れた高純度原料を使用することが一般的である。原料は
粉末のまま使用することも可能であるが、この場合、熔
融したときの体積の減少が激しいため、半熔融品やその
粉砕品を用いるのが普通である。育成装置の中に上記原
料を充填したルツボを置き、育成装置内を10-3〜10-4Pa
の真空雰囲気に保つ。次に育成装置温度を蛍石の融点以
上（1370℃〜1450℃）まで上げ、原料を熔融する。育成
装置温度の時間的変動を抑えるため、定電力出力による
制御または高精度なＰＩＤ制御を行う。結晶育成段階で
は、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、急冷を避け簡単
な徐冷を行う。育成装置温度が室温程度まで下がったと
ころで、インゴットを取り出す。Hereinafter, a conventional method for producing a fluorite single crystal will be described. Fluorite single crystals have been produced by the Bridgman method (also called the Stockberger method or the crucible descent method). In the case of a fluorite single crystal used in the ultraviolet or 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. 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. A crucible filled with the above-mentioned raw materials is placed in the growing apparatus, and the inside of the growing apparatus is 10 −3 to 10 −4 Pa
Keep in a vacuum atmosphere. Next, the temperature of the growing apparatus is raised to the melting point of fluorite or higher (1370 ° C. to 1450 ° C.), and the raw materials are melted. In order to suppress temporal fluctuations in the temperature of the growing apparatus, control using a constant power output or highly accurate PID control is performed. In the crystal growth stage, the crucible is pulled down at a speed of about 0.1 to 5 mm / H, whereby the crystal is gradually crystallized from the lower part of the crucible. When the crystal is crystallized to the uppermost part of the melt, the crystal growth is completed, and simple slow cooling is performed while avoiding rapid cooling so that the grown crystal (ingot) does not break. When the temperature of the growing apparatus has dropped to about room temperature, the ingot is taken out.
【０００６】このままでは残留応力と歪が非常に大きい
ため、インゴットのままで簡単な熱処理を行う。こうし
て得られた蛍石単結晶は、目的の製品別に適当な大きさ
に切断加工される。切断された蛍石単結晶は、アニール
装置内で簡単な熱処理を行う。Since the residual stress and strain are very large in this state, a simple heat treatment is performed in the ingot. The fluorite single crystal thus obtained is cut into an appropriate size for each target product. The cut fluorite single crystal is subjected to a simple heat treatment in an annealing apparatus.
【０００７】[0007]
【発明が解決しようとする課題】従来の技術における、
インゴットのままで簡単に行う熱処理は、結晶育成の段
階で生じた強力な歪を、切断が可能な程度にまでしか低
減できなかった。したがって、光学系を構成できる程度
まで良好な歪は得られなかった。また、適当な大きさに
切断した蛍石単結晶に実施する熱処理においても、エキ
シマレーザーステッパーのように高精度な光学系に使用
可能な歪の良好な蛍石単結晶は得られなかった。特に蛍
石単結晶が大口径化し、体積が増大すると、歪の除去は
さらに困難となっていた。SUMMARY OF THE INVENTION In the prior art,
The heat treatment simply performed with the ingot could reduce the strong strain generated at the stage of growing the crystal to such an extent that cutting was possible. Therefore, satisfactory distortion could not be obtained to the extent that an optical system could be configured. Further, even in a heat treatment performed on a fluorite single crystal cut to an appropriate size, a fluorite single crystal with a good strain that can be used for a high-precision optical system like an excimer laser stepper could not be obtained. In particular, when the fluorite single crystal has a large diameter and an increased volume, it has been more difficult to remove the strain.
【０００８】本発明は上記の点に鑑みてなされたもので
ある。高精度な光学系に使用できる蛍石単結晶を得るた
めの、熱処理装置および熱処理方法を提供することを目
的とする。[0008] The present invention has been made in view of the above points. An object of the present invention is to provide a heat treatment apparatus and a heat treatment method for obtaining a fluorite single crystal that can be used for a highly accurate optical system.
【０００９】[0009]
【課題を解決するための手段】上記問題点を解決するた
めに、本発明者らは、次の手段をとった。まず、第一の
手段として、蛍石単結晶を収納するための気密容器を有
し、この気密容器の外部側方に、独立に温度制御が可能
な２回路以上のヒーターを装備した蛍石単結晶の熱処理
装置を設け、その装置内の上部および（または）下部に
複数枚からなる反射板を設置した。In order to solve the above problems, the present inventors have taken the following measures. First, as a first means, an airtight container for storing a fluorite single crystal is provided, and a fluorite single crystal equipped with two or more circuits capable of independently controlling the temperature is provided outside the airtight container. A crystal heat treatment apparatus was provided, and a plurality of reflectors were installed on the upper and / or lower part of the apparatus.
【００１０】また、第二の手段として、上記装置を用い
て気密容器内の温度分布を平坦化しつつ、非酸素雰囲気
中で、蛍石単結晶を800 ℃から1300℃程度に維持し、そ
の後徐々に温度を室温まで降温することとした。As a second means, the fluorite single crystal is maintained at about 800 ° C. to 1300 ° C. in a non-oxygen atmosphere while flattening the temperature distribution in the airtight container by using the above-mentioned apparatus, and thereafter gradually. Then, the temperature was lowered to room temperature.
【００１１】[0011]
【発明の実施の形態】蛍石単結晶製造後に観察される歪
は、結晶育成過程で生じる。大きな温度勾配を有する育
成装置内の温度分布が原因で歪を引き起こす。一般に、
融液を結晶化させる単結晶の育成方法においては、育成
装置内に温度勾配を有することが本質的に必要である。
したがって、融液を結晶化させる単結晶の育成方法を実
施することにより育成された蛍石単結晶には、必然的に
歪は発生することになる。BEST MODE FOR CARRYING OUT THE INVENTION Strain observed after production of a fluorite single crystal occurs during the crystal growth process. Strain is caused by the temperature distribution in the growing device with a large temperature gradient. In general,
In a method of growing a single crystal for crystallizing a melt, it is essentially necessary to have a temperature gradient in a growing apparatus.
Therefore, strain is inevitably generated in the fluorite single crystal grown by implementing the single crystal growing method for crystallizing the melt.
【００１２】そこで、本発明における熱処理が必要とな
る。本発明における熱処理を行うことにより、育成時に
生じた蛍石単結晶の歪を消滅させることができる。本発
明の熱処理においては、蛍石の融点以下のできるだけ高
温で蛍石単結晶を維持した。この高温の過程で原子の再
配列を実施し、歪を消滅させるのである。さらに、熱処
理装置内部の温度を位置によらず等しくすること、すな
わち温度分布の平坦化も、高温維持時および降温時で歪
の除去のため重要である。この目的のため、本発明にお
ける熱処理においては、２回路以上の独立したヒーター
を用いた熱処理装置内に、上部および（または）下部に
複数枚の反射板を設置し、温度分布を平坦化する。Therefore, the heat treatment in the present invention is required. By performing the heat treatment in the present invention, the strain of the fluorite single crystal generated during the growth can be eliminated. In the heat treatment of the present invention, the fluorite single crystal was maintained at a temperature as high as possible below the melting point of fluorite. The rearrangement of atoms is performed in the process of this high temperature to eliminate the strain. Furthermore, it is important to equalize the temperature inside the heat treatment apparatus irrespective of the position, that is, to flatten the temperature distribution in order to remove the distortion when the high temperature is maintained and when the temperature is decreased. For this purpose, in the heat treatment according to the present invention, a plurality of reflectors are provided at an upper part and / or a lower part in a heat treatment apparatus using two or more independent heaters to flatten the temperature distribution.
【００１３】[0013]
【実施例】図１は本発明による装置の断面図である。熱
処理時には、気密容器１により、熱処理装置内部の雰囲
気を大気と遮断する。気密容器内にはさらにカーボン容
器２が置かれている。熱処理される蛍石単結晶８は、こ
のカーボン容器内に置かれる。カーボン容器内にはフッ
素化剤７としてテフロンおよび酸性フッ化アンモニウム
も収納する。熱処理装置の上部及び下部からの放熱によ
る温度分布のむらを防止するため、下部に５枚、上部に
１０枚のカーボン製の反射板９、１０を一定の間隔で設
置する。この後、真空に排気し、10-1Pa程度以下になる
ことを確認したら、真空排気を終了する。FIG. 1 is a sectional view of an apparatus according to the present invention. At the time of heat treatment, the atmosphere inside the heat treatment apparatus is shut off from the atmosphere by the airtight container 1. A carbon container 2 is further placed in the airtight container. The fluorite single crystal 8 to be heat-treated is placed in this carbon container. Teflon and ammonium acid fluoride are also stored as the fluorinating agent 7 in the carbon container. In order to prevent uneven temperature distribution due to heat radiation from the upper and lower parts of the heat treatment apparatus, five carbon reflectors 9 and 10 are provided at regular intervals at the lower part and at regular intervals. Thereafter, the chamber is evacuated to a vacuum, and when it is confirmed that the pressure becomes about 10 -1 Pa or less, the evacuation is terminated.
【００１４】通常の熱処理装置では、上部に取り出し口
を有する構造をとることが多い。その場合、熱処理装置
上部は熱の逃げが大きく、温度は相対的に低くなる。そ
こで、２回路のヒーターを独立に制御することにより、
熱処理装置内に良好な温度分布が得られる。熱処理装置
下部に設置面を有する構造の場合も、やはり熱処理装置
下部の温度も低くなる傾向がある。断熱材の増強により
下部の温度低下はある程度防止することができるが、よ
り良好な温度分布の形成には、３回路のヒーターをそれ
ぞれ独立に制御することが効果的である。具体的には上
ヒーター３、中ヒーター４および下ヒーター５を装備す
ることになる。An ordinary heat treatment apparatus often has a structure having an outlet at the top. In that case, heat escapes largely in the upper part of the heat treatment apparatus, and the temperature becomes relatively low. Therefore, by independently controlling the heaters of the two circuits,
Good temperature distribution is obtained in the heat treatment apparatus. In the case of a structure having an installation surface below the heat treatment apparatus, the temperature of the lower part of the heat treatment apparatus also tends to be low. Although the lowering of the temperature in the lower part can be prevented to some extent by strengthening the heat insulating material, it is effective to independently control the heaters of the three circuits to form a better temperature distribution. Specifically, an upper heater 3, a middle heater 4, and a lower heater 5 are provided.
【００１５】昇温の過程についても、３回路ヒーターの
温度を各々独立に制御する。この過程でフッ素化剤が気
化し、育成装置内はフッ素雰囲気となる。育成装置の全
体が1200℃の定常状態に達したら、24時間維持する。こ
の高温維持時の温度は、蛍石の融点に近い高温である13
00℃程度が望ましいのであるが、本熱処理装置の耐久性
を考慮すると、高温維持時の温度は1200℃程度以下に抑
えておいた方が良い。この気密容器内に熱電対を挿入し
温度分布を測定したところ、上下に反射板を入れなかっ
た場合と比較して、上下の均熱長は約２倍、図中のＡ点
とＢ点との温度差は１２℃から２℃に改善された。In the process of increasing the temperature, the temperatures of the three-circuit heaters are controlled independently. In this process, the fluorinating agent is vaporized, and the inside of the growing apparatus becomes a fluorine atmosphere. When the entire growing apparatus reaches a steady state of 1200 ° C., it is maintained for 24 hours. The temperature at which this high temperature is maintained is a high temperature close to the melting point of fluorite13
Although about 00 ° C. is desirable, considering the durability of the present heat treatment apparatus, it is better to keep the temperature at the time of maintaining the high temperature at about 1200 ° C. or less. The temperature distribution was measured by inserting a thermocouple into this hermetic container. Was improved from 12 ° C. to 2 ° C.
【００１６】この後は徐々に室温まで温度を降温し、大
気圧開放して蛍石単結晶を取り出す。Thereafter, the temperature is gradually lowered to room temperature, and the pressure is released to the atmospheric pressure to take out the fluorite single crystal.
【００１７】[0017]
【発明の効果】本発明による装置を用いた熱処理を実施
することにより、歪の良好な蛍石単結晶を製造すること
ができた。By performing the heat treatment using the apparatus according to the present invention, it was possible to produce a fluorite single crystal having a good strain.
【図１】 本発明の熱処理装置の、実施例における断面
図である。FIG. 1 is a cross-sectional view of a heat treatment apparatus according to an embodiment of the present invention.
１・・・気密容器 ２・・・カーボン容器 ３・・・上ヒーター ４・・・中ヒーター ５・・・下ヒーター ６・・・熱電対 ７・・・フッ素化剤 ８・・・蛍石単結晶 ９・・・上部反射板 １０・・下部反射板 Ａ、Ｂ・・・温度測定点 DESCRIPTION OF SYMBOLS 1 ... Airtight container 2 ... Carbon container 3 ... Upper heater 4 ... Middle heater 5 ... Lower heater 6 ... Thermocouple 7 ... Fluorinating agent 8 ... Single fluorite Crystal 9: Upper reflector 10: Lower reflector A, B: Temperature measurement point
───────────────────────────────────────────────────── フロントページの続き (72)発明者 塩澤 正樹 東京都千代田区丸の内３丁目２番３号 株 式会社ニコン内 (72)発明者 高野 修一 東京都福生市大字熊川1642番地26 応用光 研工業株式会社内 (72)発明者 西川 秀美 東京都福生市大字熊川1642番地26 応用光 研工業株式会社内 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Shiozawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation (72) Inventor Shuichi Takano 1642-26 Kumakawa, Fussa-shi, Tokyo 26 Applied Optical Laboratory Co., Ltd. (72) Inventor Hidemi Nishikawa 1642 Kumakawa, Fussa-shi, Tokyo 26-applied light laboratory
Claims (7)
し、該気密容器の外部側方に、独立に温度制御が可能な
２回路以上のヒーターを配置した熱処理装置において、
気密容器内の上部および／または下部に複数枚の反射板
を配置した蛍石単結晶の熱処理装置。1. A heat treatment apparatus having an airtight container for storing a fluorite single crystal, and having two or more heaters capable of independently controlling the temperature disposed outside the airtight container,
A fluorite single crystal heat treatment apparatus in which a plurality of reflectors are arranged at an upper part and / or a lower part in an airtight container.
またはステンレスからなることを特徴とする蛍石単結晶
の熱処理装置。2. A heat treatment apparatus for a fluorite single crystal, wherein the reflection plate is made of carbon, molybdenum or stainless steel.
ターを配置した熱処理装置内の気密容器に蛍石単結晶を
収納し、前記気密容器内の上部および／または下部の複
数枚の反射板により蛍石単結晶に生じる温度分布を平坦
化しつつ、非酸素雰囲気中で、蛍石単結晶を800 ℃以上
1300℃以下の一定温度に維持し、その後徐々に降温する
ことを特徴とする蛍石単結晶の熱処理方法。3. A fluorite single crystal is housed in an airtight container in a heat treatment apparatus having two or more heaters capable of independently controlling the temperature, and a plurality of upper and / or lower reflectors in the airtight container are provided. While flattening the temperature distribution generated in the fluorite single crystal by the plate, the fluorite single crystal is heated to 800 ° C or more in a non-oxygen atmosphere.
A heat treatment method for a fluorite single crystal, characterized in that the temperature is maintained at a constant temperature of 1300 ° C. or lower and then the temperature is gradually lowered.
において、前記気密容器内を１０ー1Ｐａ程度以下の真空
に排気した後昇温し、蛍石単結晶を800 ℃以上1300℃以
下の一定温度に維持し、その後徐々に降温することを特
徴とする蛍石単結晶の熱処理方法。4. A method for heat treating a fluorite single crystal according to claim 3, wherein the airtight container KoNoboru heated which is evacuated to a vacuum of about 10 @ 1 Pa, a fluorite single crystal 800 ° C. to 1,300 A heat treatment method for a fluorite single crystal, characterized in that the temperature is maintained at a constant temperature of not more than ℃ and then the temperature is gradually lowered.
において、前記蛍石単結晶を室温まで降温した後、真空
を開放することを特徴とする蛍石単結晶の熱処理方法。5. The method for heat treating a fluorite single crystal according to claim 4, wherein the vacuum is released after the temperature of the fluorite single crystal is lowered to room temperature.
晶の熱処理方法において、前記蛍石単結晶がブリッジマ
ン法により製造された蛍石単結晶インゴットを所望の大
きさに切断したものであることを特徴とする蛍石単結晶
の熱処理方法。6. The fluorite single crystal heat treatment method according to claim 3, wherein the fluorite single crystal is cut into a desired size from a fluorite single crystal ingot manufactured by the Bridgman method. A method for heat treating a fluorite single crystal, characterized in that:
晶の熱処理方法において、前記蛍石単結晶に生じる温度
分布が５℃以下であることを特徴とする蛍石単結晶の熱
処理方法。7. The fluorite single crystal according to claim 3, wherein the fluorite single crystal has a temperature distribution of 5 ° C. or less. Heat treatment method.
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| JP03470897A JP3698848B2 (en) | 1997-02-19 | 1997-02-19 | Heat treatment apparatus and heat treatment method for fluorite single crystal |
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| JP03470897A JP3698848B2 (en) | 1997-02-19 | 1997-02-19 | Heat treatment apparatus and heat treatment method for fluorite single crystal |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000075405A1 (en) * | 1999-06-07 | 2000-12-14 | Corning Incorporated | Crystal growth and annealing method and apparatus |
| US6350310B1 (en) | 1999-06-07 | 2002-02-26 | Sandia Corporation | Crystal growth and annealing for minimized residual stress |
-
1997
- 1997-02-19 JP JP03470897A patent/JP3698848B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000075405A1 (en) * | 1999-06-07 | 2000-12-14 | Corning Incorporated | Crystal growth and annealing method and apparatus |
| US6309461B1 (en) | 1999-06-07 | 2001-10-30 | Sandia Corporation | Crystal growth and annealing method and apparatus |
| US6350310B1 (en) | 1999-06-07 | 2002-02-26 | Sandia Corporation | Crystal growth and annealing for minimized residual stress |
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