JP2003528795A - In particular, a method and apparatus for growing a single crystal of CaF2 - Google Patents

Abstract

SUMMARY The invention relates to a method and apparatus for single crystal growth, especially for CaF ₂ . Within the framework of this method, a stack of crucibles (100, 101,..., 106,...) Containing the starting materials is translated through a melting chamber (C1) and an annealing chamber (C2) sequentially. And this translation is continuous, smooth and uninterrupted. Invention is most preferably CaF _2, monocrystalline fluoride, in particular providing the creation of optical fluoride single crystal and lambda <optical element blank for 248nmUV light lithography.

Description

Detailed Description of the Invention

[0001] Cross-reference TO RELATED APPLICATIONS This application was filed on March 24, 2000, the name as "particularly to a method and apparatus for the single crystal growth of CaF _2", Patrick Erb (Patrick Herve ) Claims the benefit of French patent application No. 03000777.

The invention relates to a method for the growth of single crystals and related equipment suitable for carrying out said method. The method and apparatus are particularly suitable for single crystal growth of calcium fluoride (CaF ₂ ).

To increase the integration level of electronic devices on a semiconductor wafer, a very short UV is used.
Ultra-high-performance optical systems are required because radiated light of wavelength (248 nm or less) is required to improve resolution.

In order to obtain such an optical system, quartz glass is used in the most popular technique to date. Another technology that is already under development is calcium fluoride (C
A single crystal of aF ₂ ) is used.

Such single crystals or single crystals of the same type (generally alkaline earth metal fluoride single crystals and even single crystals of silicon dioxide) are obtained by the so-called Stockbarger or Bridgman method. . In this method, single crystals are produced in a furnace in which a crucible containing the molten material is moved from top to bottom along the vertical axis, ie from a hot zone to a cold zone. The temperature in the hot zone is maintained above the melting point of the material (above 1525 ° C. for CaF ₂ ). The progress speed of the crucible is about 0.3 to 5 mm / hour.

As the crucible progresses from the hot zone to the cold zone, the material passes through a region with a large temperature gradient. When the material reaches a zone where the temperature is below the melting point of the material,
Crystallization occurs in the crucible. Since the crucible is moved downward, the stationary crystallization front moves from the bottom to the top inside the crucible inside the material.

The furnace is generally maintained under vacuum to prevent any oxidation of the materials and furnace components. The crucible is made of a material that resists chemical attack and is typically a graphite crucible.

[0008]   In practice, the method described above is mainly carried out in two variants.

According to a first variant, which is carried out batch by batch, a vertical furnace in which the stack of crucibles (each of the crucibles in the stack containing the material in question) later becomes the hot zone of the furnace Is loaded in the upper zone at low temperature. The furnace loaded in the upper zone is heated. In the first stage, the stack of crucibles is maintained in the upper or hot zone of the furnace at an elevated temperature, ie above the melting point of the material. In the second stage, the stack is lowered, below the temperature of the hot zone,
It is held in the lower zone or cold zone of the furnace, which is maintained below the melting point of the material.

The main drawbacks of this mode of operation are low productivity and mediocre yields. Productivity is the dead time before and after crystal growth (loading into the furnace, exhausting inside the furnace, heating the two zones of the furnace,
Limited by the dead time for cooling and unloading the two zones).
Yield is affected by the fact that each of the crucibles in the stack will not be exposed to the same thermal conditions over the entire work cycle of the stack. In particular, the crucible at the bottom of the stack contacts the cold zone sooner and stays in the cold zone longer. Moreover, it is difficult to control such discontinuous thermal conditions (hot zone / cold zone) within the same single furnace.

According to a second variant described in Russian Patent No. 2161891 filed Aug. 8, 1975, the aim is to carry out a continuous heat treatment. The crucible stack occupies the entire height of the vertical furnace with the two heat treatment chambers being stacked.
When the stack is moved in a translational motion from top to bottom, each of the crucibles in the stack sequentially passes through the upper chamber and then the lower chamber. At the bottom of the stack,
The vertical translation of the stack is stopped to remove each of the crucibles (ie, the crucibles that have successively passed through the two heat treatment chambers) (the crucible on top of the crucible removed at the bottom of the stack is Clamped between the jaws to support and stabilize). In this mode of operation, there is some discontinuity in the heat treatment, with deceleration and acceleration and rapid movement of the stack's motion, which in any case causes vibrations in the material being processed. this is,
Very detrimental to optimal growth of the desired single crystal.

In the above situation, the inventors have designed and developed a method optimized for single crystal growth. This method is also based on the so-called Stockburger or Bridgman method described above. The method ensures that each of the crucibles in the stack that moves in translational motion through the furnace has the same history (excellently, especially with respect to thermal conditions) without abrupt movements and vibrations. It is optimized in that it is a true continuous heat treatment method.

The above-mentioned prior art and the invention described below are explained only with regard to the mechanical aspects of the process (and associated apparatus); the chemical aspects, and in particular the useful presence of fluorinating agents, are generally described in the literature. , And will not be described again here.

The method and apparatus of the present invention is referred to herein as a method and apparatus for growing a single crystal. This phrase is not meant to be limiting. Because the method and apparatus of the present invention it is clear to be suitable for the creation of multi-crystal, the present method and apparatus more generally may be expressed as crystalline (polycrystalline and single crystal) growth method and apparatus it can. The use of the method and apparatus solely for the production of such polycrystals is excluded from the framework of the present invention (although it does not seem practical because polycrystals can be obtained very easily). It will not be done. The method and apparatus of the present invention can be more precisely described as a method and apparatus for growing a crystal optimized to provide a beneficial single crystal yield.

Therefore, the method of the present invention has two stacked heat treatment chambers, namely, a first chamber or a melting chamber and a second chamber or an annealing chamber. (CaF ₂ , in a vacuum and / or in a controlled atmosphere) in a vertical furnace in which a considerable temperature gradient is created between the chambers of the (CaF ₂ , This is a method of growing a single crystal (of BaF ₂ , magnesium fluoride, and a fluoride optical crystal).

The above method of the invention comprises: a stack of crucibles containing starting materials (the starting materials within each crucible are generally introduced in the form of powder or previously melt formed discs), A translational movement in the furnace while supporting it along a vertical axis; and-upstream of the first chamber, with a new crucible at one end of the stack, and of the crucible passing through the first and second chambers in sequence. The stack is removed at the other end; the height of the stack of crucibles is greater than the sum of the heights of the stacked first and second chambers during operation, each stack being Under the action of a means arranged in a third or transfer chamber located below the pair of first and second chambers, which acts on at least one crucible at the bottom of the Each of the crucibles that make up the tack are sequentially supported and translated in a direction such that they pass through the first chamber and then the second chamber; loading and unloading operations are performed during operation of the stack. It is carried out at the same frequency so that the height remains substantially constant.

Therefore, the method of the present invention is of the same type as the method described in the above-mentioned Russian inventor's specification. However, in the method of the present invention it can be straightforwardly shown that the stack of crucibles can be moved upwards or downwards, depending on the arrangement of the stacking melting chambers and annealing chambers.

In a first variant, the crucible stack is moved in translation from top to bottom, in which case the first (melting) chamber rests on top of the second (annealing) chamber and the second The chamber itself sits above the transfer chamber.

In a second variant, the crucible stack is moved in translation from bottom to top, where the first (melting) chamber rests on top of the transfer chamber and the second (annealing) chamber It is placed under.

[0020]   The first variant is a priori preferred.

The thermal conditions ensured and the resulting temperature gradients in each of the two melting and annealing chambers depend on the thermal conditions necessary to obtain the expected effect, ie the formation and growth of single crystals inside the crucible. And temperature gradient.

Characteristically, within the framework of the method of the invention as specified above, after the loading operation (of the crucible filled with the starting material) and the sequential passage through the two stacked heat treatment chambers The removal operation of the filled crucible is carried out without stopping the translational movement of the stack of crucibles in the furnace. This translational movement is carried out in a completely continuous manner. According to the invention, the stack is driven continuously and smoothly. The heat treatment applied in this way is completely continuous, perfectly equivalent for all crucibles and free of any unevenness.

The method of the present invention as described above generally begins with a first stack of crucibles, referred to as the lead stack. This stack can be a stack of empty crucibles or, directly, a stack of crucibles, in which case the contents of the crucible in the lead stack will be discarded.

Within the framework of the implementation of the method of the invention, the stack of filled crucibles can be moved through the melting chamber and then through the annealing chamber with only a continuous translational movement carrying each crucible one after the other. It is preferable to move each of the crucibles in combination with the continuous translational motion and the rotational motion around itself. This optimizes the uniformity of the heat treatment in the material bulk inside each crucible in the stack.

Due to the support and movement of the stack-simply a translational movement or a combination of translational and rotational movements, in each case completely continuous, a suitable arrangement provided in the transfer chamber, as indicated above. Means act on the at least one crucible at the bottom of the stack. In order for this stack to be stable and to be perfectly driven, it is obviously preferable that said means act on at least two crucibles (2, 3 or even 4 crucibles) at the bottom of the stack.

In the framework of a preferred variant of implementation of the method according to the invention, said means act on the side wall of at least one crucible at the bottom of the stack, preferably at least two crucibles (2,3) at the bottom of the stack. Or it acts on the side walls of four crucibles. A horizontal action of this kind is particularly suitable for ensuring continuous driving of the stack without interruption.

Since the crucible is generally cylindrical (and therefore has only one side wall), the side wall of the crucible is designated by the singular. This singular representation has no limiting meaning at all. If a parallelepiped-shaped crucible-intuitively unlikely-is used,
The means for supporting and moving the stack is obviously at least two sidewalls of at least one crucible at least at the bottom of the stack (opposing sidewalls are preferred)
It is preferable to act on.

There are various ways in which a new crucible can be loaded and a crucible that has been sequentially passed through two stacked heat treatment chambers can be unloaded. In particular, these operations can be based on the techniques described in the Russian inventor's specification cited above. Within the framework of the implementation of the method according to the invention, the loading and / or unloading operations are preferably carried out along the axis of the stack of crucibles (both the loading and unloading operations are carried out. Is preferred). The axis of the crucible stack preferably corresponds to the furnace axis inside the furnace in which the stack is carried.

As already indicated, the method of the invention as described in general terms above
Perfectly suited for F ₂ (single) crystal growth.

Preferred variants of the implementation of the above method will be explained later, without any limiting meaning, with reference to the accompanying drawings.

According to a second subject of the invention, the invention relates to a device suitable for carrying out the method described above, ie for continuous growth of single crystals, which device is arranged in an envelope with a vertical axis. Placed under three stacked chambers: a first heat treatment chamber or melting chamber, a second heat treatment chamber or annealing chamber, and a pair of first and second chambers. A third chamber or transfer chamber; suitable for the interior of each of the two heat treatment chambers, with a substantial temperature gradient between the two chambers associated with each of the above two heat treatment chambers. Heating means for maintaining the heat treatment temperature; means for ensuring support and translational movement along the vertical axis of the stack of crucibles through the three stacked chambers. And being translated into a third chamber, acting on at least one crucible at the bottom of the stack, each crucible of the stack passing sequentially through the first chamber and then the second chamber. Means for ensuring movement; -when the stack of crucibles is being moved in translation from top to bottom, the first chamber is connected to the crucible loading zone at the top of the stack and the third chamber is connected to the stack. The crucible unloading zone at the bottom of the stack; or the third chamber at the bottom of the stack and the crucible loading zone at the bottom of the stack when the stack of crucibles is being moved in translation from bottom to top. Means for connecting the chamber of the chamber with the crucible unloading zone at the top of the stack; means for ensuring the loading and unloading operation; A chamber and means for maintaining the loading and unloading zone free of impurities; means for ensuring support and translational movement of the stack, coupling means and means for ensuring loading and unloading operations Coordinate so that the loading and unloading operations are ensured without stopping the translational movement of the stack.

[0032]   The means cooperate to ensure continuous translation of the stack.

The envelope (crystallization furnace) thus comprises from top to bottom: -in a first variant: + loading zone; + melting chamber; + annealing chamber; + transfer chamber; + ejection zone; , In a first variant the means for ensuring the support and translation of the stack of crucibles ensure a translation from top to bottom; in a second variant: + withdrawal zone; + annealing chamber; + Melting chamber; + transfer chamber; + loading zone; in a second variant, the means for ensuring support and translation of the stack of crucibles ensure translation from bottom to top.

The device of the invention is preferably arranged according to the first variant described above.

In one or the other framework of the above variants, three stacked, melting, annealing and transfer chambers have the same axis, preferably coincident with the axis of the crucible stack, The zones and / or the unloading zones are preferably arranged along this same axis (preferably both the loading zone and the unloading zone are along the same axis).

At least one crucible at the bottom of the stack in order to achieve the expected result-the loading and unloading of the crucible, which does not stop the continuous translation of the stack of crucibles-by coordination between the appropriate means indicated above. Of the stack, preferably at least at the bottom of the stack, to the sides of the two crucibles, there are preferred means for ensuring the support and translation of the stack.

The above-mentioned means of ensuring stack support and continuous translational movement form a key part of the device of the invention. The above means may exist in various forms. In particular, the above means may be suitable for ensuring only a simple translational movement of the stack; the above means may also be suitable for ensuring both a translational movement of the stack and a rotational movement around the stack itself.

For purposes of explanation, three types of such means are detailed below. The first two types are suitable for simple translational movements, and the third type is suitable for translational movements combined with rotational movements.

The above-mentioned means for ensuring the support and the continuous translational movement of the crucible inside the envelope (vertical furnace) with a vertical axis are in particular: -a horizontal axis acting on the side wall of the crucible at the bottom of the stack. At least one roller set consisting of at least two rollers with; and, preferably, in addition to one roller set, acts on another at least one crucible at the bottom of the stack (at the bottom of the stack directly above said crucible). It is preferable to act on the crucible),
Another at least one roller set of the same type. Such a roller set preferably consists of four rollers spaced 90 ° apart. Therefore, use of two stacked roller sets, one acting on the crucible at the bottom of the stack and the other acting on the crucible directly above it, each consisting of four rollers made of a suitable material Is recommended (first type);-at least two jaw sets, each consisting of at least two jaws; each of the jaw sets being suitable for securing support of the stack by clamping the crucible at the bottom of the stack, In order to ensure a continuous translational movement of the stack, it can be pulled back from the stack alternately with another jaw set and the stack can be moved in translational movement along the vertical axis (second type).

Support and continuous translation of stack of crucibles inside enclosure (vertical furnace) with vertical axis
The above-mentioned means for ensuring rotational movement are in particular: at least one roller set consisting of at least two rollers, acting on the side wall of the crucible at the bottom of the stack, the axis of which is slightly tilted with respect to the vertical axis; And, preferably in addition to said one roller set, acting on at least one further crucible at the bottom of the stack (preferably on the crucible directly above said crucible at the bottom of the stack) of at least the same type One different roller set. Such roller sets are made of a suitable material, 3 at 120 ° intervals.
Preferably, it comprises three rollers (third type); To drive the stack of crucibles in translational motion by rotary motion, each roller of such a roller set is offset by an angle α with respect to the stack. Thus, each roller actually rotates about an axis which is not parallel to the vertical axis of the device and which does not intersect said axis.

Preferred variants of the device according to the invention are explained in more detail below with reference to the accompanying drawings.

Indeed, a description of the present invention with respect to methods and apparatus will now be presented with reference to the accompanying drawings.

The method and apparatus of the present invention is described below with reference to FIG. FIG. 1 shows the furnace of the present invention.

The outer structure of the furnace is defined by a water-cooled outer jacket 8 that isolates the atmosphere of the furnace from the surrounding atmosphere. The outer structure also comprises a heat shield 7 made of carbon fiber, which is arranged "a certain distance" away from the electric heating elements 2 and 4. Heat shield 7
Protects the outer jacket 8 from heat radiation.

[0045]   Inside the furnace, the following three stacked chambers:             Melting chamber C1;             Annealing chamber C2;             Transfer chamber C3; And in line with these three chambers: Above: loading zone B; Below: Extraction zone D; There is.

In practice, more precisely, zone A is the loading zone, zone B is the conditioning zone,
Zone E can be referred to as the unload zone and zone D as the reconditioning zone (see method description below).

Stack 1 of crucibles (100, 101, ..., 106, ...) is zone C = C1 +
Heat treated at C2. As shown in FIG. 1, the stack 1 is continuously moved in translational motion from top to bottom. The stack 1 actually consists of horizontal rollers 5 2
It is supported by a translation mechanism that includes two roller sets and is moved in translational motion.

The powdered material inside the crucible is melted in the upper melting zone C 1 which is heated by the graphite electric heating element 2. The molten material is then transferred from the melting zone C1 to an annealing zone C2, which is itself heated by another heating element 4 of the same type, and is slightly cooled. The temperature gradient in the furnace between zones C1 and C2 is provided by a diaphragm 3 which in part isolates the "hot" zone C1 from the "cold" zone C2. To obtain a greater gradient, cold water can be prepared for circulation inside the diaphragm 3. The temperature transition inside the material in each crucible as it passes through this zone creates a steady crystallization front.

The transfer chamber C3 has a lower temperature than the annealing chamber C2. A second diaphragm 6, which can also be cooled by water circulation, is inserted in order to isolate chamber 3 from chamber 2 to some extent. That is, the diaphragm 6 protects the roller 5 from excessive heat. The roller 5 is covered with silicone and the crucible (100
, 101, ..., 106, ...) is preferred. Two roller sets consisting of four rollers 5 are used in the variant shown, i.e. the first roller set acts on the crucible 100 at the bottom of the stack and the second roller set acts on the crucible 101. . This gives the stack 1 of the crucible sufficient stability in all directions so that the stack is driven perfectly in translation from top to bottom.

One of the four horizontal roller set is shown fully in FIG. Each roller 5 penetrates the outer jacket 8 of the furnace and has a heat shield 7
Driven by a shaft 19, which also penetrates. The penetration of the jacket 8 is made completely airtight and the furnace is generally operated under vacuum. The bearings and mechanical drives are all located outside the furnace. The two shaft sets of four shafts 19 are linked by a gear train and are rotated by a single motor (not shown) in order to ensure a simple and reliable synchronization of the rotation of the rollers 5.

[0051]   The device of the invention as shown in FIGS. 1 and 2 functions in the following manner.

New crucibles 9 are regularly loaded inside. The loading zone B (airlock chamber) is at ambient temperature and atmospheric pressure and preferably the two symmetrical doors 12 open and the support 10 moves to the gripping position for gripping a new crucible 9. The support 10 descends into the zone B together with the crucible 9. The two doors 12 are closed. The inside of zone B is evacuated by a pump (not shown) and the temperature is raised by an electric heating element 11, similar to the electric heating elements 2 and 4 located inside the furnace. When the pressure and temperature conditions inside the zone B become the same as those of the melting chamber C1, the door 13
Automatically opens and a new crucible 9 is loaded on top of the stack 1. The support 10 is then pulled back inside zone B and the door 13 is closed again. Zone B returns to ambient temperature and atmospheric pressure.

A similar but inverted procedure is used for removal at the bottom of stack 1.
The door 14 opens automatically when the crucible 100 attempts to leave the roller 5 at the bottom of the stack 1. The support 16 is then raised to receive the crucible 100.
The support 16 descends with the crucible and enters the unloading zone D (airlock chamber under the same pressure and temperature conditions as the transfer chamber C3). Electric heating element 17
Raises the temperature. Door 14 is then closed and zone D can return to ambient temperature and atmospheric pressure. In this way, the crucible separated from stack 1
Reference numeral 100 'is provided in FIG. When the zone D reaches ambient temperature and atmospheric pressure, the two doors 18 open and the support 16 descends, allowing the crucible 100 'to be regained. The support 16 then rises into zone D and the crucible 1
Standing position for 00. The two doors 18 close again and zone D is placed under the same temperature and pressure conditions as transfer chamber C3.

The device according to FIGS. 3 and 5 functions by similar, but different, means for ensuring the support and continuous translational movement of the stack 1 of crucibles.

Just like the means shown in FIGS. 1 and 2, the device shown in FIGS. 3 and 4 ensures a simple translational movement of the stack 1 of crucibles. The means according to FIGS. 3 and 4 are more complex than the means according to FIGS. 1 and 2, but have the advantage of acting on the crucible without any rotational or frictional effect. The means according to FIGS. 3 and 4 are suitable for holding and moving downwards the stack of crucibles with four jaws 20, 23, 24 and 25.
Equipped with. The movement of these jaws 20, 23, 24 and 25 is not a rotational movement, but a mechanically synchronized, continuous vertical and radial translational movement.

The diametrically opposed jaws 20 and 23 alternately function with the diametrically opposed jaws 24 and 25. FIG. 4 clearly shows the jaws 20 and 23 driving the stack 1 downward, while the jaws 24 and 25 are no longer in contact with the stack 1 and are moving upwards. Jaws 24 and 25 clamp stack 1 before jaws 20 and 23 reach bottom dead center,
It continues to ensure that the stack 1 is supported and carried downwards. Joe 20
And 23 are then pulled back radially and moved upwards.

Each jaw has two types of movement (horizontal and vertical movements)
Operated independently by the shaft and cam. That is, the cam 21 participates in the vertical translational motion of the jaw 20, and the cam 22 participates in the radial translational motion. That is, the use of such a cam is preferred because the drive movement is entirely rotational. There is no practical airtightness problem due to the penetration of the heat shield 7 and the outer jacket 8 related to the shaft.

Synchronization of all jaw movements can be accomplished mechanically with a single motor and suitable gearing, or with a brushless motor with precise control feedback.

In the device according to FIGS. 5, 6 and 7, suitable means for ensuring a continuous translational movement of the stack 1 of crucibles with support and rotation are incorporated in the transfer chamber C3.

The above means consists of three rollers 30, 30 ′ and 30 ″.
, 30 'and 30''are slightly tilted with respect to the vertical axis. The tilt angle is referred to as α in Fig. 7 and extends to the plane (YOZ). The tilt angle is generally about 1 °.
One of the rollers--the roller 30--is rotated by a motor 31 via a belt or chain type transmission means 32. The other two rollers 30 'and 30 "are free moving.

The invention can be explained exactly by the following data, purely by way of explanation.

A furnace of the type shown schematically in the accompanying drawings is used for CaF ₂ single crystal growth.

The size of the entire furnace is about 2 to 3 m, and the diameter is about 1 m. A graphite crucible is used. The crucible has a diameter of 300 to 400 mm and a height of about 100 mm.
Is. Furnace throughput is approximately one crucible per day, or one crucible every other day.

The temperature in each chamber of the furnace is:> 1525 ° C. in the melting chamber (upper chamber); <1525 ° C. in the annealing chamber (1200-1500 ° C. top and 200-300 ° C. bottom chamber). And in the transfer chamber (lower chamber), 200 ° C. or lower;

[Brief description of drawings]

1 is a longitudinal sectional view of an apparatus of the present invention (single crystal growth furnace) equipped with a first type of means for ensuring support and continuous (simple) translation of a crucible stack.

[Fig. 2]   Sectional view along II-II in FIG. 1, showing in detail the first type of means

FIG. 3 is a partial longitudinal sectional view of the device of the present invention with means of the second type for ensuring support and continuous (simple) translation of the crucible stack.

[Figure 4]   Sectional view along IV-IV in FIG. 3, showing in detail the second type of means

FIG. 5 is a partial cross-sectional view of a device of the invention with means for supporting a stack of crucibles and means of a third type for ensuring translational movement (with rotational movement).

[Figure 6]   Sectional view along line VI-VI of FIG. 5, showing in detail the third type of means

[Figure 7]   Sectional view taken along line VII-VII of FIG.

[Explanation of symbols]

      1 stack       2, 4, 11, 17 Electric heating element       3,6 diaphragm       5,30,30 ', 30 "roller       7 heat shield       8 exterior jacket       9,100,100 ', 101,106 crucible       10, 16 support       12, 13, 14, 18 doors       20,23,24,25 Joe       B mounting zone       C1 melting chamber       C2 annealing chamber       C3 transfer chamber       D take-out zone

Claims (18)

[Claims] 1. Inside, two stacked heat treatment chambers (C1 and C2),
That is, the first chamber (C1) or melting chamber, and the second chamber (
C2), that is, the annealing chamber is arranged, and the first and second chambers (
In a method for growing a single crystal carried out in the absence of impurities in a vertical furnace in which a considerable temperature gradient is created between C1 and C2), the method comprises: -a crucible containing starting material (100) , 101, ..., 106, ...) stack (
Translating 1) in the furnace while supporting it along a vertical axis; and-loading a new crucible at one end of the stack (1) upstream of the first chamber (C1), An operation of taking out the crucible that has sequentially passed through the first and second chambers (C1 and C2) at the other end of the stack (1); and the crucible (100, 101, ..., 106, ...) the height of the stack (1) is greater than the sum of the heights of the stacked first and second chambers (C1 and C2) during operation; Is at least at the bottom of the stack (1) disposed in a third chamber (C3) or transfer chamber located below the pair of first and second chambers (C1 and C2). Means acting on one said crucible (100) (5; 20 and 23, 24 and 5; 30, 30 ', under the action of 30 "),
Each of the crucibles (100, 101, ..., 106, ...) constituting the stack sequentially passes through the first chamber (C1) and then the second chamber (C2). Supported in different directions and moved in translation; the loading and unloading operations are carried out at the same frequency so that during operation the height of the stack (1) remains substantially constant; Method, characterized in that the translational movement of the stack (1) is continuous and the loading and unloading operations are carried out without stopping the translational movement. 2. In addition to the translational movement, the crucible (100, 101, ...,
Method according to claim 1, characterized in that it also comprises the step of rotating said stack (1) of (106, ...) About itself. 3. The stack (1) of the crucibles (100, 101, ..., 106, ...) At least one sidewall of the crucible (100) at the bottom of the stack (1), preferably Is at least two of the crucibles (10) at the bottom of the stack (1).
0 and 101) acting on the side walls (5; 20 and 23, 24 and 25; 3)
Method according to claim 1 or 2, characterized in that it is supported and moved in simple translational or translational and rotational movements under the action of 0, 30 ', 30 "). 4. The loading operation and / or the unloading operation are performed along the axis of the stack (1), preferably along the common axis of the stack (1) and the furnace. Method according to any one of claims 1 to 3, characterized. 5. The method according to claim 1, wherein the method is carried out to grow a CaF ₂ crystal. 6. A device suitable for continuous growth of single crystals, arranged in an envelope with a vertical axis: -3 stacked chambers (C1, C2 and C3), ie a first A heat treatment chamber (C1) or melting chamber, a second heat treatment chamber (C2) or annealing chamber, and a pair (C1) of the first and second chambers (C1 and C2).
A third chamber (C3) or transfer chamber located below + C2);-between the two chambers (C1 and C2) incidental to each of the two heat treatment chambers (C1 and C2) A heating means (2, 4) for maintaining a suitable heat treatment temperature inside the chamber with a considerable temperature gradient in the chamber; a stack of crucibles (100, 101, ..., 106, ...). (1) Support and
Means (5; 20 and 23, 24 and 25; 30, for ensuring translational movement along the vertical axis through the three stacked chambers (C1, C2 and C3).
30 ′, 30 ″), arranged in the third chamber (C3) and acting on at least one of the crucibles (100) at the bottom of the stack (1),
Each of the crucibles (100, 101, ..., 106, ...) in (1) passes through the first chamber (C1) and then the second chamber (C2) sequentially. Said means for ensuring said translational movement in a direction (5; 20 and 23, 24 and 25;
30, 30 ', 30 ");-when the stack (1) of the crucibles (100, 101, ..., 106, ...) is translated in translation from top to bottom, One chamber (C1) is connected to the crucible loading zone (B) at the top of the stack (1) and the third chamber (C1)
C3) at the bottom of the stack (1) for connection with the crucible removal zone (D); or when the stack of crucibles is being translated in translation from bottom to top,
Connecting the third chamber at the bottom of the stack with a crucible loading zone,
Means (13,14) for connecting the second chamber to the crucible unloading zone at the top of the stack; Means (10,16) for ensuring the loading and unloading operations; and Means for keeping the three stacked chambers (C1, C2 and C3) and the loading and unloading zones (B and D) free of impurities; The means for ensuring the translational movement (5
20 and 23, 24 and 25; 30, 30 ′, 30 ″), the connecting means (13,
14) and the means (10, 16) for ensuring the loading and unloading operations are coordinated such that the loading and unloading operations are ensured without stopping the translational movement of the stack (1). A device characterized by: 7. The stack (1) is provided with the means (5; 20 and 23, 24 and 25; 30, 30 ', 30 ") for ensuring the support and translational movement of the stack (1). At least one side wall of the crucible (100) at the bottom of the stack, preferably at least two crucibles (100 and 101) at the bottom of the stack (1)
7. A device according to claim 6, characterized in that it acts on the side wall of the. 8. The three chambers (C1, C2 and C3) are connected to the crucible (
100, 101, ..., 106, ...) preferably having the same axis, said loading zone (B) or / and said unloading zone having the same axis.
8. Device according to claim 6 or 7, characterized in that (D) is arranged along said axis. 9. The means for ensuring the support and the translational movement of the stack (1) has a horizontal axis acting on the side wall of the crucible (100) at the bottom of the stack (1). At least one roller set consisting of at least two rollers (5), preferably at least one acting on at least one further crucible (101) at the bottom of said stack (1) in addition to said roller set
9. Another set of rollers of the same type is provided.
The apparatus according to claim 1. 10. The means for ensuring said support and said translational movement of said stack (1) are respectively provided with at least two jaws (20,23; 24,2).
5) comprising at least two jaw sets (20 and 23; 24 and 25), each of said jaw sets (20 and 23; 24 and 25) being said crucible (100) at the bottom of said stack (1). Stack by clamping the stack (1)
In order to secure the support of the stack (1) and to secure the translational movement of the stack (1),
Alternating with the other jaw set, it can be pulled back from the stack (1) to move the stack (1) in a translational motion along a vertical axis. Equipment. 11. The means (5; 20 and 23; 24 and 25; 30, 30 ', 30 ") for ensuring the support and the continuous translational movement of the stack (1) is the stack (1) itself. 9. Device according to any one of claims 6 to 8, characterized in that it also ensures rotation around the. 12. The means comprises the crucible (10) at the bottom of the stack (1).
0) acting on said side wall, comprising at least one roller set consisting of at least two rollers (30, 30 ′, 30 ″), the axis of which is slightly (α) inclined with respect to the vertical axis, preferably In addition to the roller set, the stack (1)
Device according to claim 11, characterized in that it comprises at least one further roller set of the same type, which acts on at least one further crucible at the bottom of the. 13. A method of making a fluoride crystal optical element blank for λ <248 nm UV light, wherein the making comprises two stacked heat treatment chambers, namely a first chamber and a second chamber. Performed without impurities in a vertical furnace, arranged and having a substantial temperature gradient between the first chamber and the second chamber, said preparation: Performing a translational movement of the stack of crucibles inside the furnace while supporting it along a vertical axis; loading a new crucible at one end of the stack, upstream of the first chamber, Unloading the crucible that has passed through the first and second chambers at the end sequentially; and the translational motion of the stack is continuous, and the loading and unloading are continuous. A step of growing the fluoride crystal blank such that a manipulating operation is carried out without stopping the translational movement, the height of the stack of crucibles being Is greater than the sum of the heights of the first and second chambers, the stack is configured such that each of the crucibles that make up the stack is disposed below a pair of the first and second chambers. By means of means arranged in three chambers for acting on at least one of the crucibles at the bottom of the stack, in such a direction as to pass sequentially through the first chamber and then the second chamber. Wherein the steps of loading and unloading are performed at the same frequency so that the height of the stack remains substantially constant during operation. Method. 14. The method of claim 13 wherein the method includes, in addition to the translational movement, rotation of the crucible about itself in the stack. 15. The stack of crucibles comprises at least one sidewall of the crucible at the bottom of the stack, preferably at least two at the bottom of the stack.
14. Method according to claim 13, characterized in that it is supported and moved in simple translational or translational and rotational movements under the action of the means acting on the side walls of one of the crucibles. 16. The method of claim 13, wherein the loading and / or unloading operations are performed along an axis of the stack, preferably along a common axis of the stack and the furnace. Method. 17. The method of claim 13, wherein the method is performed to grow a CaF ₂ crystal. 18. A vertical furnace for continuous growth of a fluoride crystal optical element blank for λ <248 nm UV light, arranged in an envelope with a vertical axis: -3 stacked chambers, A first heat treatment melting chamber, a second heat treatment chamber, and a third heat treatment chamber disposed below the pair of first and second chambers.
A plurality of heaters attached to the two heat treatment chambers for maintaining a proper heat treatment temperature in the two heat treatment chambers with a considerable temperature gradient between the two heat treatment chambers; A translational support for providing translational movement along the vertical axis of the stack of crucibles through the three stacked chambers, the translational support being disposed in the third chamber and having at least one at the bottom of the stack. Said translational support acting on said crucible and ensuring said translational movement in a direction such that each of said crucibles of said stack successively passes through said first chamber and then said second chamber; A furnace member: a crucible mounting the first chamber at the top of the stack when the tack of the crucible is moved in translation from top to bottom. At the bottom of the stack when connected to a filling zone and at the bottom of the stack to connect the third chamber to a crucible removal zone; or when the stack of crucibles is translated from bottom to top. A member for connecting the third chamber with a crucible loading zone and, at the top of the stack, for connecting the second chamber with a crucible unloading zone; -a loading member for ensuring the loading and unloading operation; And-impurity suppressing means for keeping the three stacked chambers and the loading and unloading zones free of impurities, wherein the furnace comprises the support and translational movement of the stack and the loading. And a unloading operation, wherein the loading and unloading operations are ensured without stopping the translational movement of the stack. .