JPH10251097A - Apparatus for production of fluorite single crystal and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for producing a fluorite single crystal capable of producing the fluorite single crystal having a large diameter and high quality usable as an optical material for a stepper at a good yield and a process for producing the same. SOLUTION: This apparatus for producing the fluorite single crystal has a crucible 25 which houses fluorite raw materials, a mechanism 24 which perpendicularly lowers this crucible 25 in a crystal growth furnace K, heating mechanisms 21, 21' which heat up the inside of this crystal growth furnace K and a heat shielding plate (partition section) for forming a temp. gradient (temp. inclination) around the m.p. of the fluorite raw materials in the crystal growth furnace K. The apparatus described above is provided with the heat radiating mechanism or cooling mechanism for the heat shielding plate (partition section).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for producing a fluorite single crystal suitable for use in general optical instruments and optical systems for photolithography.

[0002]

2. Description of the Related Art In recent years, high integration of LSIs has been progressing, and a light source used in an exposure apparatus (stepper) in fine processing by optical lithography has been shortened in wavelength. Short wavelength K
For a light source such as rF or ArF, quartz glass or fluorite is suitable as an optical material. Conventional applications of fluorite are lenses for microscopes, cameras, and TV cameras, and most of them are 200 mm or less in diameter.
As a fluorite for a stepper, a large-diameter (250 mm or more in diameter) and high-quality fluorite single crystal is required.

FIG. 2 (schematic diagram) shows an example of a crystal growth furnace (fluorite single crystal manufacturing apparatus) by the vertical Bridgman method which is a method for manufacturing such a fluorite single crystal. When producing a fluorite single crystal using a crystal growth furnace as shown in FIG.
Utilizing a temperature gradient from the melting temperature range to the solidifying temperature range (around the melting point of the fluorite raw material), the crystal is grown while the crucible is lowered.

FIG. 3 shows a temperature gradient in a crystal growth furnace which is considered to be ideal when performing crystallization. Generally, in order to increase the temperature gradient near the solid-liquid interface, a heat shut-off plate that partitions the crystal growth furnace is provided. When growing a large crystal, the temperature gradient changes when a crucible having a large heat capacity passes near the heat shield plate, but the temperature gradient depending on the heat shield plate cannot be changed.

[0005] Therefore, when a complete crystal is to be obtained using a conventional crystal growth furnace as shown in FIG. 2, the output of the heater is changed or the growth rate is changed so that the temperature gradient is not changed as much as possible. A method of reducing the speed as much as possible is adopted.

[0006]

However, when producing a large-diameter fluorite single crystal, a crucible having a large heat capacity moves in the crystal growth furnace, and a solid-liquid interface is formed in the process of lowering the crucible. Is changed, the temperature distribution inside the melt and the solidified crystal changes, and as a result, there is a problem that a heterogeneous crystal is formed.

Furthermore, the temperature gradient in the crystal growth furnace also changes, resulting in a problem that the crystal becomes polycrystalline and impurities cannot be removed. The present invention has been made in view of the above problems, and is intended to produce a fluorite single crystal capable of producing a large-diameter and high-quality fluorite single crystal that can be used as an optical material for a stepper with high yield. An object is to provide an apparatus and a manufacturing method.

[0008]

Therefore, the present invention firstly provides a "crucible for storing at least a fluorite raw material, a mechanism for vertically lowering the crucible in a crystal growth furnace, A fluorite unit comprising: a heating mechanism for raising the temperature of the inside; and a heat blocking plate (partition portion) for forming a temperature gradient (temperature gradient) extending around the melting point of the fluorite raw material in the crystal growth furnace. In a crystal manufacturing apparatus, there is provided a fluorite single crystal manufacturing apparatus (claim 1), wherein a heat radiating mechanism or a cooling mechanism for the heat shielding plate (partition portion) is provided.

[0009] The present invention also provides a second aspect of the invention wherein the heat radiating mechanism is
2. The heat sink or the opening provided in the heat insulation plate (partition), and the cooling mechanism is a refrigerant circulation pipe provided adjacent to or close to the heat insulation plate (partition). Manufacturing apparatus (claim 2). " The third aspect of the present invention is "a manufacturing apparatus according to claim 1 or 2, wherein a mechanism for controlling a heat release amount by the heat release mechanism or a cooling amount by the cooling mechanism is further provided." I will provide a.

[0010] The present invention is a fourth aspect of the present invention wherein the mechanism for controlling the amount of heat release includes a heat insulation member for suppressing or preventing heat release from the heat insulation plate (partition portion), and the heat insulation plate of the heat insulation member. A mechanism for controlling the presence or absence of contact with the (partition part), the area of the contact, or the distance, to provide a manufacturing apparatus according to claim 3 (claim 4). Fifth, the present invention provides a method in which a crucible containing a fluorite raw material is vertically lowered in a crystal growth furnace having a temperature gradient (temperature gradient) around the melting point of the fluorite raw material, whereby the fluorite raw material is reduced. The fluorite single crystal according to the vertical Bridgman method performed by using the manufacturing apparatus according to claim 1, wherein the melt is formed by melting, and the melt is sequentially solidified from one end to grow a fluorite single crystal. The manufacturing method of the above, using the heat dissipation mechanism, the cooling mechanism, the mechanism for controlling the heat dissipation amount, or the mechanism for controlling the cooling amount, the fluctuation of the temperature gradient and / or the solid-liquid interface during the descent of the crucible A method for producing a fluorite single crystal, characterized in that the position variation of the single crystal is suppressed or the position of the temperature gradient and / or the solid-liquid interface during the lowering of the crucible is adjusted. .

The sixth aspect of the present invention is characterized in that the above-mentioned adjustment is performed such that the temperature gradient and / or the position of the solid-liquid interface during the crystal growth of the fluorite single crystal is optimal or in the optimal range. A manufacturing method according to claim 5 (claim 6) "is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The apparatus for producing a fluorite single crystal according to the vertical Bridgman method of the present invention (claim 1) provides a temperature gradient (temperature gradient) around the melting point of a fluorite raw material in a crystal growth furnace. Since a heat-dissipating mechanism or a cooling mechanism is provided in the heat-shielding plate (partition portion) to be formed, fluctuations in the temperature gradient and / or fluctuations in the position of the solid-liquid interface during the lowering of the crucible can be suppressed.

Therefore, according to the manufacturing apparatus of the present invention (claim 1), a large-diameter and high-quality fluorite single crystal usable as an optical material for a stepper can be manufactured with a high yield. As the heat radiation mechanism according to the present invention, for example, a heat sink or an opening provided on a heat shielding plate (partition) is provided, and as the cooling mechanism, for example, a heat shielding plate (partition) is provided adjacent to or close to the heat shielding plate (partition). Refrigerant circulation pipes can be used respectively (claim 2).

It is preferable that the manufacturing apparatus of the present invention further includes a mechanism for controlling the amount of heat radiation by the heat radiation mechanism or the amount of cooling by the cooling mechanism. With this configuration, it is possible not only to suppress the fluctuation of the temperature gradient and / or the position of the solid-liquid interface during the lowering of the crucible, but also to adjust the temperature gradient and / or the position of the solid-liquid interface during the lowering of the crucible. Can be.

Therefore, the manufacturing apparatus according to the present invention (claim 3) can adjust the temperature gradient and / or the position of the solid-liquid interface during the crystal growth of the fluorite single crystal so as to be an optimum or an optimum range. it can. Therefore, the present invention (claim 3)
According to the manufacturing apparatus of (1), a higher-quality, larger-diameter fluorite single crystal usable as an optical material for a stepper can be manufactured with higher yield.

The mechanism for controlling the amount of heat radiation according to the present invention includes, for example, a heat insulating member for suppressing or preventing heat release from the heat insulating plate (partition), and a heat insulating member for the heat insulating plate (partition). A mechanism having a mechanism for controlling the presence / absence of contact and the area or distance of contact can be used (claim 4). The method for producing a fluorite single crystal by the vertical Bridgman method performed by using the production apparatus according to claims 1 to 4 of the present invention (claim 5) includes a method of changing a temperature gradient during a descent of a crucible and / or a solid-liquid process. Not only can the fluctuation of the interface position be suppressed, but also the temperature gradient and / or the position of the solid-liquid interface during the descent of the crucible can be adjusted.

Therefore, according to the manufacturing method of the present invention (claim 5), the temperature gradient and / or the position of the solid-liquid interface during the crystal growth of the fluorite single crystal can be adjusted to be more optimal. it can. Therefore, it is preferable that the above adjustment is performed so that the temperature gradient and / or the position of the solid-liquid interface during the crystal growth of the fluorite single crystal is optimal or in the optimal range (claim 6).

Therefore, according to the manufacturing method of the present invention (claims 5 and 6), a higher quality (or extremely high quality) large-diameter fluorite single crystal usable as an optical material for a stepper can be collected. It can be manufactured efficiently (or in extremely good yield). Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors fabricated a crystal growth furnace having a crucible inner diameter of 300 mm and measured the temperature distribution inside the growth furnace. As shown in FIG.
showed that. Such a temperature gradient (gradient) is formed, for example, by suppressing heat flow in two temperature ranges, an upper heating temperature range by the upper heater 21 and a lower heating temperature range by the lower heater 21 ′. This is made possible by providing the plate 23.

However, by providing the heat blocking plate 23 in this manner, even if a temperature gradient (gradient) near ideal is formed, if fluorite is actually manufactured using the crystal growth furnace having the crucible inner diameter of 300 mm, Even when the crucible was pulled down at a very low speed of 0.5 mm / H, it became polycrystalline fluorite. Then, when the temperature of the crucible was measured, it was significantly different from the temperature distribution 41 in the furnace as shown by the temperature curves 42 and 43 in FIG.

Therefore, in the present embodiment, the partition having the heat shield plate has a heat radiation effect (heat radiation mechanism) in order to increase the temperature gradient and release the heat of solidification to the outer periphery.
Further, in this embodiment, for example, in order to control the heat radiation effect during the crystal growth, a heat retaining member (carbon felt) is provided outside the heat shielding plate (carbon plate) 11 having the heat radiation effect, and the heat retaining member is provided. Movable parts (rotary shaft 13, drive unit 14, conductive member 1) that can be opened and closed from outside the furnace
5) is provided as a mechanism for controlling the presence / absence of contact of the heat retaining member 12 with the heat shield plate 11 and the area or distance of the contact.

FIG. 1 shows an apparatus (schematic configuration) for producing a fluorite single crystal according to the present embodiment. The heat retaining member 12 is divided and fixed to each of the rotating shafts 13, a conductive member 15 for rotating the rotating shaft 13 is provided, and the heat retaining member 12 can be opened and closed by rotating the conductive member 15 from outside the furnace. . The driving unit 14 for rotating the rotating shaft 13 was installed outside the vacuum furnace. In addition, a transmission member such as a chain is provided to simultaneously rotate the remaining divided rotation shafts.

Further, the drive unit was automatically controlled under conditions previously determined by experiments so that the temperature gradient in the crystal growth furnace did not change significantly after the lowering of the crucible 25 was started. In order to provide a heat-dissipating effect to a partition having a heat-shielding plate, for example, a heat-sink or an opening may be provided in the heat-shielding plate (or the partition). It is sufficient to provide a pipe.

Since the fluorite single crystal manufacturing apparatus of this embodiment employs the above-described configuration, not only can the temperature gradient (gradient) during crystal growth be controlled by controlling the heat radiation effect,
It has also become possible to reduce the required power in the melting process that does not require a temperature gradient. That is, in the melting process where the temperature gradient is unnecessary, the holding member is closed with respect to the heat shielding plate (or the partition), and the heat shielding plate (or the partition) is closed.
The feature is that during the crystal growth, the solidification heat is released (dissipated) from the heat blocking plate (or partition) that has a heat radiation effect by opening the heat retaining member during crystal growth by opening the heat retaining member. There is.

The present invention is characterized in that the heat insulating material is moved. In this embodiment, a rotating mechanism is used as an example.
A linear motion mechanism may be used for opening and closing the heat insulating material. Fluorite was crystal-grown using the fluorite single crystal manufacturing apparatus (crucible inner diameter φ300 mm) of the present example. During the melting, the heat retaining member was arranged near a heat shielding plate (or a partition) having a heat radiation effect to prevent heat radiation. Then, as the lowering is started and the heat retaining member is opened in conjunction with the lowering as the straight body portion approaches the heat shielding plate (or the partition portion), the heat radiation effect is increased.

Further, the movement of the heat retaining member was stopped while the straight body portion passed beside the heat shield plate (or the partition portion). By doing so, the temperature gradient could be kept constant during the lowering, and the position of the solid-liquid interface (with respect to the crystal growth furnace) could be kept constant. The grown fluorite ingot was a single crystal throughout, and a φ270 mm lens material could be collected.

By growing the fluorite crystal using the fluorite single crystal manufacturing apparatus (crucible inner diameter φ300 mm) of the present embodiment, the large-diameter fluorite, which has often been polycrystalline in the past, is very stable. It became a single crystal.

[0028]

As described above, according to the present invention,
A large-diameter and high-quality fluorite single crystal that can be used as an optical material for a stepper can be produced with high yield. That is, according to the present invention, a large-diameter fluorite single crystal having a diameter exceeding 250 mm can be stably obtained, and can be provided as an optical material of a stepper for a short wavelength light source.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an apparatus for manufacturing a fluorite single crystal according to an embodiment.

FIG. 2 is a schematic configuration diagram showing a conventional crystal growth furnace.

FIG. 3 is a temperature distribution diagram showing a temperature gradient in a crystal growth furnace which is considered to be ideal when performing crystallization.

FIG. 4 is a temperature distribution diagram showing a furnace temperature gradient and a crucible temperature curve in a conventional crystal growth furnace.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 heat shield plate having heat dissipation effect 12 heat retaining member 13 rotating shaft 14 drive unit 15 conductive member 21 upper heater 21 ′ lower heater 22 heat insulating material 23 heat shield plate 24 pulldown rod 25 crucible 26 liquid phase 27 solid phase 31 ideal Temperature gradient 41 Furnace temperature distribution curve 42 Temperature curve below crucible 43 Temperature curve above crucible K Crystal growth furnace

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shuichi Takano 1642-26 Kumagawa, Oaza, Fussa-shi, Tokyo Inside (72) Inventor Hidemi Nishikawa 1642-26 Kumakawa, Oaza, Fussa-shi, Tokyo Inside the corporation

Claims (6)

[Claims] 1. A crucible containing at least a fluorite raw material, a mechanism for vertically lowering the crucible in a crystal growth furnace, a heating mechanism for raising the temperature in the crystal growth furnace, and a fluorite raw material A heat blocking plate (partition portion) for forming a temperature gradient (temperature gradient) in the crystal growth furnace around the melting point of the fluorite single crystal, wherein the heat blocking plate (partition portion) ) A fluorite single crystal manufacturing apparatus characterized by comprising a heat dissipation mechanism or a cooling mechanism. 2. The heat radiating mechanism is a heat sink or an opening provided on the heat shielding plate (partition), and the cooling mechanism is a refrigerant circulation pipe provided adjacent to or close to the heat shielding plate (partition). The manufacturing apparatus according to claim 1, wherein 3. The manufacturing apparatus according to claim 1, further comprising a mechanism for controlling a heat radiation amount by the heat radiation mechanism or a cooling amount by the cooling mechanism. 4. A mechanism for controlling the amount of heat radiation, comprising: a heat insulating member for suppressing or preventing heat release from the heat insulating plate (partition); and a contact member for contacting the heat insulating member with the heat insulating plate (partition). The manufacturing apparatus according to claim 3, further comprising a mechanism for controlling presence / absence, a contact area, or a distance. 5. The fluorite raw material is melted by vertically lowering a crucible containing a fluorite raw material in a crystal growth furnace having a temperature gradient (temperature gradient) around the melting point of the fluorite raw material. A liquid is formed, and the melt is sequentially solidified from one end to grow a fluorite single crystal.
5. A method for producing a fluorite single crystal by the vertical Bridgman method performed by using the production apparatus according to 4, wherein the heat dissipation mechanism, the cooling mechanism, the mechanism for controlling the heat dissipation amount, or the mechanism for controlling the cooling amount are used. Suppressing the fluctuation of the temperature gradient and / or the position fluctuation of the solid-liquid interface during the lowering of the crucible, or adjusting the position of the temperature gradient and / or the position of the solid-liquid interface during the lowering of the crucible. For producing a fluorite single crystal. 6. The adjustment is performed so that the temperature gradient and / or the position of the solid-liquid interface during the crystal growth of the fluorite single crystal is optimal or optimal.
The manufacturing method as described.