JPH0940486A - Single crystal manufacturing method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To increase the diameter of a single crystal in a floating zone method, and to easily bond a raw material rod and a seed crystal. When manufacturing a single crystal by a floating zone method, after joining a raw material rod and a seed crystal, a shoulder portion having a larger diameter in the single crystal growth direction and a larger diameter than the seed crystal is formed. A cylindrical straight body portion is formed on this.
It should be noted that the oxygen concentration Co ₁ in the atmospheric gas from the joining to the shoulder formation, the oxygen concentration Co ₂ during the shoulder formation, and the oxygen concentration Co ₃ during the straight body formation are Co ₁ = Co ₃ and Co ₁ <Co ₂ ,
It is preferable to have a relationship of Co ₃ <Co ₂ . Also,
When manufacturing a single crystal as described above, the material rod and the seed crystal are formed by a material system in which the density of the liquid in the vicinity of the melting point is lower than the density of the solid, and the material rod and the seed crystal are mixed in the atmosphere gas at the time of bonding. The oxygen concentration is made lower than the oxygen concentration in the subsequent process.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a single crystal used for electronic materials and the like. Specifically, in the method for producing a single crystal to which the floating zone method is applied, a shoulder which is common in the Czochralski method, and a method for producing a single crystal capable of producing a large diameter single crystal and a raw material rod The present invention relates to a method for producing a single crystal in which the oxygen concentration at the time of joining a seed crystal and a seed crystal is lowered to facilitate the joining.

[0002]

2. Description of the Related Art Single crystal materials such as silicon, quartz, diamond and sapphire are widely used as electronic materials and other materials, and their manufacturing techniques are important in various industrial fields.

Examples of the method for producing a single crystal include a melt method, a solution method, a solid phase method, and a gas phase method. For example, a method for producing a single crystal to which the melt method is applied is mainly the Czochralski method ( Hereinafter, the Cz method will be referred to) and the floating zone method (hereinafter referred to as the Fz method) will be mentioned.

The Cz method is a method in which a seed crystal is brought into contact with the melt in the crucible and the single crystal is pulled while rotating both the seed crystal and the crucible for taking the seed crystal. The Cz method is used for producing a single crystal of a material intended for a congruent melting compound having the same composition when the melt and the single crystal are melted. In addition, the Cz method is easy to control the manufacturing apparatus and is capable of manufacturing a large-diameter single crystal, and thus has good mass productivity.

In the above Cz method, in order to prevent the inclusion of defects into the single crystal, a seed crystal is brought into contact with the melt, and then a portion called a necking portion having a relatively small diameter is manufactured. The diameter is gradually increased in the crystal growth direction to form a portion called a shoulder portion having a diameter larger than that of the seed crystal, and then a portion called a cylindrical straight body portion is formed. Manufacturing crystals.

However, since the crucible is used in the Cz method, it is necessary to consider the melting point of the crucible material, the melting point of the material, and the reactivity of both, and there is a drawback that usable materials are limited. In addition, since the Cz method is a unidirectional solidification method, a single crystal of a material of a congruent melting compound having the same composition when the melt and the crystal are melted as described above in a system in which composition deviation does not occur It is only applicable to the above, and this also limits the usable materials. Further, the above Cz method can be applied only to the production of a single crystal of a low vapor pressure material in order to avoid composition shift due to evaporation of the melt, and this also limits the usable materials.

On the other hand, in the above Fz method, the raw material rod is held vertically at both ends, and a part of it is heated and melted to form a molten zone, which is moved from one end side to the other end side to successively form a single crystal. Is the way to do it. The Fz method is mainly used for producing crystals of high melting point materials or decomposed and fused compounds.

Since the Fz method does not use a crucible,
Since there is no contamination by the crucible material and the heater material to be heated is not limited, it is possible to widen the temperature range in which growth is possible. Further, the Fz method is suitable for material exploration and the like because it is possible to manufacture single crystals from raw material rods, and also to manufacture single crystals from a small amount of raw material powder. Furthermore, in the above Fz method, not only the congruent melting compound but also a single crystal of a decomposition melting compound can be produced, and the usable material is relatively limited. Furthermore, since the manufacturing apparatus to which the above Fz method is applied is a closed apparatus system and the single crystal is manufactured in the closed system, the atmosphere can be easily controlled.

However, the Fz method has a disadvantage that it is difficult to manufacture a large-diameter single crystal and it is difficult to cope with an increase in size of the single crystal.

[0010]

The reason why it is difficult to produce a large single crystal by the Fz method as described above is as follows.

In the above Fz method, the melting zone is relatively moved within the raw material rod to sequentially form a single crystal. Therefore, the single crystal is crystallized by the amount fed from the raw material rod to grow the single crystal. . Therefore, in order to increase the diameter of the single crystal, a method of making the feed rate of the raw material rod relatively faster than the growth rate of the single crystal is used.

By the way, in the above Fz method, the melting zone is held by the balance between the surface tension and gravity of the melting zone itself, and it is difficult to hold the melting zone in a material system having a small surface tension and a high density. .

Therefore, when such a material system is used, if the diameter of the single crystal is increased by the method as described above, it is difficult to hold the melting zone and the melting zone sags. It is difficult to increase the diameter of a single crystal.

Further, in the above Fz method, it is general to grow a single crystal on a seed crystal, and the seed crystal and the raw material rod are joined together through a fusion zone, and the fusion zone is used as the first fusion zone. A single crystal is manufactured by the method as described above. At this time,
Since the seed crystal and the raw material rod are high melting point materials as described above, it is desirable to use, for example, an infrared lamp having a high output as the heating means.

However, as the infrared lamp, a halogen lamp having a low running cost is usually used, and in a halogen lamp having a large output, the filament of the lamp tends to be large. As a result, the melting zone formed by heating the condensing part becomes large. That is, there is a high possibility that the melted zone will sag, and it will be difficult to increase the diameter of the single crystal.

Therefore, in order to increase the diameter of the single crystal as described above, it is preferable to use a lamp having a small output as much as possible to enhance the light converging power. Joining via the fusion zone is difficult.

Therefore, the present invention has been proposed in view of the conventional circumstances, and facilitates the manufacturing method of a single crystal and the joining of a raw material rod and a seed crystal, which can increase the diameter of the single crystal in the Fz method. It is an object of the present invention to provide a method for producing a single crystal that

[0018]

Means for Solving the Problems As a result of intensive studies made by the present inventors in order to achieve the above-mentioned object, the Fz method and the Cz method have been carried out to prevent the inclusion of defects into a single crystal. If the diameter of the single crystal is increased, the diameter of the single crystal is increased because the diameter of the single body is formed on the shoulder that has a diameter larger than that of the seed crystal. I found it possible. When a single crystal is manufactured in this manner, a good quality single crystal that makes the most of the advantages of the Fz method is manufactured.

In general, the Cz method and TSSG (Top-S
In the single crystal growth of the melt-grown and solution-grown oxides in the seeded solution growth method, etc., the single crystal is melted (melted) and then the seed crystal is used to lower the temperature of the melt (solution). Are crystallized to grow a single crystal.

In recent years, in the field of melt growth as described above, for example, Shigeyuki Kimura pointed out that the physical properties of the melt have become important factors for controlling the growth of the single crystal in the growth of the single crystal by the melt growth. Has been done. (National Conference on Crystal Growth, Special Lecture, July 1992) That is, in crystal growth of a melt, lowering the viscosity and surface tension of the melt leads to uniform agitation of the melt, and the melt from a liquid is melted. It is desirable because it allows a substance to be uniformly supplied to a solid crystal.

[0021] For example, in a melt of an oxide, unlike a solid in which atoms are regularly arranged and bonded, the atom is considered to have a higher degree of freedom, but on the surface of the liquid, it is bridged with another atom via an oxygen atom ( Dangle bond) is formed, and it is considered that the bonding force of this cross-link is reflected in the surface tension. That is, the greater the force of cross-linking via oxygen atoms, the greater the surface tension.

Therefore, Kunihiko Oka and Toshimitsu Ito have grown copper oxide single crystals under a low oxygen partial pressure. Japan Society for Crystal Growth, v
ol. 21 (1994) No. As shown in No. 3 113, in an atmosphere with less oxygen and in a reducing atmosphere, the cross-linking by the oxygen atoms can be cut off, and the surface tension can be lowered. In other words, it can be said that the surface tension of the melt can be changed by changing the oxygen concentration in the atmosphere during crystal growth of the melt.

Therefore, as a result of intensive studies by the present inventors, even in the Fz method, the surface tension of the melting zone can be changed by changing the oxygen concentration in the atmosphere gas, and the oxygen concentration is increased. Therefore, it was found that if the surface tension of the melted zone is increased, sagging of the melted zone is less likely to occur, and thus the above-mentioned shoulder portion is easily formed.

In the Fz method, the amount of the melting zone is Cz.
It was also found that there is no inconvenience even if the stirring effect is weakened by increasing the surface tension because it is much smaller than the method.

Further, as a result of intensive studies, the present inventors have found that the oxygen concentration in the atmosphere gas, in other words, the oxygen partial pressure in the atmosphere gas, influences the melting points of the raw material rod and the seed crystal. That is, Clausius by thermodynamics of phase equilibrium
According to the us-Claperon equation, in a system in which a liquid phase and a solid phase coexist, if pressure is p, temperature is T, latent heat is L, liquid volume is V _L , and solid volume is V _S , these The relationship is expressed by the following formula 1.

Dp / dT = L / T / (V _L −V _S ) ... (Equation 1) Further, the following Equation 2 is derived from the above Equation 1.

[0027] dT = T / L · (V L -V S) · dp ··· ( Equation 2) Thus, to lower the oxygen partial pressure in the atmospheric gas, and dp <0, the volume volume of liquid is a solid If you are using larger material system than if the density of the liquid than solid in other words is small, i.e. is _{(V L -V S)> 0} , dT
It becomes <0, and it can be seen that the melting point is lowered in this material system when the oxygen partial pressure is lowered. Conversely, if the oxygen partial pressure is increased, the melting point will increase. In the case of water and ice, the opposite is true, but in many systems, the liquid has a lower density than the solid in the vicinity of the melting point, and the melting point decreases when the oxygen partial pressure in the atmosphere gas is lowered as described above.

That is, according to the present invention, a molten portion is formed at the tip of the raw material rod and / or the seed crystal in a predetermined atmosphere gas, the raw material rod and the seed crystal are joined to form a molten zone between them, By rotating the melting zone and relatively moving it in the raw material rod, the single crystal is sequentially formed into Fz.
When manufacturing a single crystal by the method, after joining the raw material rod and the seed crystal, the diameter of the shoulder is gradually increased in the single crystal growth direction to form a shoulder portion having a diameter larger than that of the seed crystal. It is characterized in that a body is formed.

At this time, the oxygen concentration in the atmosphere gas from the joining of the raw material rod and the seed crystal to the formation of the shoulder portion is Co _1, and the oxygen concentration in the atmosphere gas when the shoulder portion is formed is Co _2. When the oxygen concentration in the atmosphere gas at the time of forming the portion is Co ₃ , these are Co ₁ = Co ₃ , Co ₁ ≦ Co
₂ , it is preferable to have a relationship of Co ₃ ≦ Co ₂ , and by increasing the oxygen concentration at the time of forming the shoulder portion, sagging of the molten zone becomes difficult to occur, so that the shoulder portion is easily formed.

Further, the oxygen concentrations Co ₁ , C in the atmosphere gas
o ₂ and Co ₃ are 1 ≦ Co ₁ / Co ₂ ≦ 12.5, 1 ≦
It is preferable to have a relationship of Co ₃ / Co ₂ ≦ 12.5. If the oxygen concentration ratio as described above is less than 1, the effect of increasing the surface tension of the molten zone during shoulder formation is weak, and the oxygen concentration ratio as described above is greater than 12.5. Then, the melting point at the time of forming the shoulder portion becomes too high, which makes it difficult to manufacture a single crystal.

Further, according to the present invention, when a single crystal is produced by the Fz method as described above, the raw material rod and the seed crystal are formed by a material system in which the liquid density near the melting point is smaller than the solid density to obtain the raw material rod. It is characterized in that the oxygen concentration (oxygen partial pressure) in the atmosphere gas at the time of joining the seed crystals is made lower than the oxygen concentration (oxygen partial pressure) in the atmosphere gas in the subsequent step.

Furthermore, the present invention, as described above, uses Fz
When a single crystal is manufactured by the method, the raw material rod and the seed crystal are formed of a material system in which the density of the liquid near the melting point is smaller than the density of the solid, and the oxygen concentration in the atmosphere gas at the time of joining the raw material rod and the seed crystal. Is made lower than the oxygen concentration in the atmosphere gas in the post-process, and after joining the raw material rod and the seed crystal, the diameter is gradually increased in the single crystal growth direction to form a shoulder portion having a diameter larger than the seed crystal. Then, a cylindrical straight body portion may be formed subsequently.

In the method for producing a single crystal of the present invention, F
When a single crystal is manufactured by the z method, a shoulder having a diameter larger than that of the seed crystal is finally formed, and a straight body is formed on the shoulder, so that the diameter of the single crystal is increased. . And
When a single crystal is manufactured in this manner, a high quality single crystal that takes advantage of the Fz method can be manufactured.

Further, in the above manufacturing method, if the oxygen concentration in the atmosphere gas at the time of forming the shoulder portion is increased, the surface tension of the molten zone becomes high, the sag of the molten zone does not easily occur, and the shoulder portion is easily formed. It

Further, in the method for producing a single crystal of the present invention, when producing a single crystal by the Fz method, the raw material rod and the seed crystal are formed of a material system in which the density of the liquid near the melting point is smaller than the density of the solid, Since the oxygen concentration (oxygen partial pressure) in the atmospheric gas at the time of joining the raw material rod and the seed crystal is lower than the oxygen concentration (oxygen partial pressure) in the atmospheric gas in the subsequent process, the joining of the raw material rod and the seed crystal is performed. At that time, their melting points are lowered, and they are easily joined.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the present invention will be described below. First, a single crystal production apparatus used for producing a single crystal by the method for producing a single crystal of the present invention will be described.

As shown in FIG. 1, the above-mentioned single crystal manufacturing apparatus has a raw material rod 1a arranged in an infrared converging heating type growth furnace 2.
For example, in the portion where the seed crystal 1b is in contact, the infrared rays of the infrared lamps 3 and 4 arranged in the infrared focusing heating type growth furnace 2 are focused and irradiated to form the melting zone 1c, and the raw material rod 1a is predetermined. The melted zone 1c is moved by moving the raw material rod 1a and the seed crystal 1b by the upper shaft 5 which sends out downward in the drawing at a speed of 5 and the lower shaft 6 which pulls down the seed crystal 1b at a predetermined speed downward in the drawing. 1a is relatively moved upward in the figure, and the lower end of the melting zone 1c is sequentially made into a single crystal to continuously produce a single crystal. In the above single crystal production apparatus, a raw material rod may be used instead of the seed crystal 1b.

The infrared converging heating type growth furnace 2 has hollow portions 7a and 7b having a substantially elliptical cross section in which one end portion of an ellipse is cut out.
The furnace bodies 2a and 2b respectively having the
7b are opposed to each other. Then, in the infrared converging heating type growth furnace 2, a hollow portion 7 having a so-called bi-elliptical shape having a cross-section in which one of two ellipses' focal points are superposed is formed, and the center of the hollow portion 7 is formed. Is a bifocal, overlapping focus. At this time, the furnace body 2
Since the walls of the cavities 7a and 7b of a and 2b are reflection mirrors, the walls of the cavities 7 are bi-elliptical mirrors.

The infrared converging heating type growth furnace 2 is provided with a quartz tube 8 extending vertically in the figure so as to penetrate the center thereof. Atmosphere gas inlet 9 and atmosphere gas exhaust port 10 are provided in the. In the quartz tube 8 filled with the atmospheric gas, the raw material rod 1a is held by the upper shaft 5 and the seed crystal 1b is held by the lower shaft 6, and these are placed at the center of the bi-elliptical cavity 7, that is, on the overlapping focus. Are arranged so that the contacting parts of are located.

Further, a drive device 11 is connected to the upper shaft 5 so that the raw material rod 1a can be fed downward in the drawing while rotating, and a drive device 12 is also connected to the lower shaft 6. The seed crystal 1b can be pulled down in the drawing while rotating.

An unillustrated hook of, for example, a platinum wire is provided at the tip of the upper shaft 5 to hold the raw material rod 1a, and the tip of the lower shaft 6 is centered by an alumina tube (not shown). Although the seed crystal 1b is fixed by this, the tip portion of the upper shaft 5 may have the same structure.

Then, a pair of infrared rays are positioned so as to be located at the other focal points of the cavity portions 7a, 7b of the furnace bodies 2a, 2b of the infrared converging heating type growth furnace 2, that is, at the focal points of the bi-elliptical cavity portions 7, respectively. Lamps 3 and 4 are arranged.

Therefore, the infrared rays emitted from the pair of infrared lamps 3 and 4 located at the focal point of the bi-elliptical hollow portion 7 are reflected by the bi-elliptical mirror on the wall surface of the hollow portion 7 and seeded with the raw material rod 1a. The light is always focused on the overlapping focal point of the cavity 7 that is in contact with the crystal 1b, and this portion is heated to form the melting zone 1c. In the above single crystal manufacturing apparatus, halogen lamps are used as the infrared lamps 3 and 4, but xenon lamps can also be used.

The infrared condensing heating type growth furnace 2 is
The furnace bodies 2a and 2b are moved in the left-right direction in the figure to enable opening and closing of the furnace as an opening / closing door, and the raw material rods can be attached / detached and single crystals can be taken out from the opening / closing portion.

In the above single crystal manufacturing apparatus, an observation window (not shown) is provided in the infrared converging heating type growth furnace 2 so that the inside of the infrared converging heating type growth furnace 2 can be observed. Lens 1 toward the observation window
A video camera 15 is provided via a filter 14.

Therefore, when a single crystal is manufactured by the above-described single crystal manufacturing apparatus according to the method for manufacturing a single crystal of the present invention, first, the raw material for the upper shaft 5 is placed in the quartz tube 8 filled with a predetermined atmosphere gas. While holding the rod, the lower shaft 6 holds the seed crystal.

Next, the raw material rod and the seed crystal held by the upper shaft 5 and the lower shaft 6 are rotated in the opposite direction, and, for example, a pair of infrared lamps 3, 3 are attached to the tip of the raw material rod held by the upper shaft 5. The infrared ray 4 is reflected by the bi-elliptical mirror of the cavity 7 and condensed and irradiated, and the above-mentioned tip is heated and melted to form a melt.

Then, the raw material rod held by the upper shaft 5 and the seed crystal held by the lower shaft 6 are joined together via the melt.

Next, a predetermined oxygen concentration C is placed in the quartz tube 8.
while filling the atmosphere gas of o ₁ with the above-mentioned melt as the first melting zone and rotating the raw material rod and the seed crystal joined by the upper shaft 5 and the lower shaft 6 in a reverse direction at a predetermined speed. The molten zone 1c is pulled down and moved downward in the figure to move the molten zone 1c to the raw material rod 1a on the upper shaft 5 side.
Of the melting zone 1c, the lower end of the melting zone 1c is sequentially made into a single crystal.

Then, the atmospheric gas in the quartz tube 8 is changed to an atmospheric gas having a predetermined oxygen concentration Co ₂ . At this time,
A relationship of Co ₁ ≦ Co ₂ is established between the oxygen concentrations Co ₁ and Co ₂ and preferably 1 ≦ Co ₁ / Co ₂ ≦ 12.5, and 1 ≦ Co ₁ / Co ₂ ≦ 7.5. Is more preferable.

When the oxygen concentration in the atmosphere gas is increased in this way, the surface tension of the melting zone 1c increases and the sag of the melting zone 1c hardly occurs. Therefore, the feed rate of the raw material rod is gradually increased and the crystal diameter is gradually increased. It is possible to make the diameter larger and the diameter gradually becomes larger in the single crystal growth direction, and finally it is possible to form a shoulder portion having a larger diameter than the seed crystal.

When the oxygen concentration in the atmosphere gas is increased as described above, the melting point is increased and the melting zone 1c may be solidified. Therefore, when increasing the oxygen concentration as described above, it is preferable to increase the outputs of the infrared lamps 3 and 4 to prevent the solidification of the melting zone.

Further, the oxygen concentration in the atmosphere gas Co ₁ , C
If the ratio of O ₂ is Co ₁ / Co ₂ is less than 1, the effect of increasing the surface tension of the molten zone at the time of shoulder formation is weak, and the above oxygen concentration ratio is larger than 12.5. Then, the melting point at the time of forming the shoulder portion becomes too high, which makes it difficult to manufacture a single crystal.

Further, in the step before forming the shoulder portion as described above, the feeding speed of the raw material rod 1a is decreased,
It is preferable to manufacture a single crystal having a small diameter to form a so-called necking portion, and the necking portion as described above facilitates formation of the shoulder portion.

Along with this, as the raw material rods 1a which are successively single-crystallized, a small-diameter raw material rod and a large-diameter raw material rod are gradually increased in diameter through a connecting portion made of a raw material rod constituent material. It is preferable to use a raw material rod to be connected, and if the necking portion is formed by a raw material rod having a small diameter and the shoulder portion is formed by the connecting portion, it is easy to form the necking portion and the shoulder portion as described above. Becomes

Next, the oxygen concentration in the atmosphere gas in the quartz tube 8 is gradually lowered to a predetermined oxygen concentration Co ₂ and the outputs of the infrared lamps 3 and 4 are gradually lowered so that the oxygen concentration in the atmosphere gas in the quartz tube 8 is lowered. A straight body part having the same diameter as the uppermost part of the shoulder part is formed. At this time, C is between the oxygen concentrations Co ₂ and Co _3.
The relationship of o ₃ ≦ Co ₂ holds, and 1 ≦ Co ₃ / Co ₂ ≦
12.5 is preferable and 1 ≦ Co ₃ / Co ₂ ≦
It is more preferably 7.5.

Further, the oxygen concentration Co ₂ and C in the atmosphere gas
When the ratio of o ₃ is Co ₃ / Co ₂ is less than 1, the effect of increasing the surface tension of the molten zone at the time of shoulder formation is weak, and the above oxygen concentration ratio is larger than 12.5. Then, the melting point at the time of forming the shoulder portion becomes too high, which makes it difficult to manufacture a single crystal.

Then, if a single crystal is continuously manufactured, and finally the material rod on the upper shaft 5 side is almost entirely made into a single crystal, the same is formed on the shoulder portion having a diameter larger than that of the seed crystal. Since the straight body portion having the diameter is formed, a large single crystal is manufactured, and the single crystal is enlarged. In addition, when a single crystal is manufactured in this manner, a high quality single crystal that makes the most of the advantages of the Fz method can be manufactured.

Further, when a single crystal is produced according to the method for producing a single crystal of the present invention as described above, the raw material rod and the seed crystal are formed by a material system in which the liquid density near the melting point is smaller than the solid density. However, if the oxygen concentration (oxygen partial pressure) in the atmosphere gas when joining the raw material rod and the seed crystal is made lower than the oxygen concentration (oxygen partial pressure) in the atmosphere gas in the subsequent process, the joining of the raw material rod and the seed crystal is performed. At that time, their melting points are lowered, and they are easily joined. Further, if the melting point at the time of bonding is lowered as described above, an infrared lamp that is a heating means does not need to have a very high output and a highly focused light can be used. Is also preferable.

When the oxygen concentration is lowered when joining the raw material rod and the seed crystal in this way, and the oxygen concentration is increased in the subsequent step, the melting point becomes higher when the oxygen concentration is raised, so the oxygen concentration is raised. Immediately after that, it is preferable that the starting rod and the seed crystal rotate in the same direction until the melting zone becomes stable.

[0061]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results. An example of producing a YVO ₄ single crystal will be described here.

Preparation of Raw Material Rod First, a raw material rod was manufactured. First, the ignition loss of yttrium oxide reagent (Y ₂ O ₃ ) having a purity of 4N was set to 1 in air.
Obtained by heating at 000 ° C. for 10 hours, and determine the ignition loss of vanadium oxide reagent (V ₂ O ₅ ) having a purity of 4N by 5 in air.
It was obtained by heat treatment at 00 ° C. for 10 hours. Then, the above Y ₂ O ₃ and V ₂ O ₅ were weighed so that the molar ratio was 1: 1.

Next, these were wet mixed using ethanol as a dispersion medium and dried to prepare a raw material powder. Then, the raw material powder was filled in a bag-shaped raw rubber (rubber tube) having a diameter of about 5 to 8 mm, and a hydrostatic pressure of 3 kg /
A material rod was formed by applying a pressure of cm ² . Next, this raw material rod was fired in air at 1300 ° C. for about 6 to 10 hours to obtain raw material rod sample 1. The obtained raw material rod sample 1 had a diameter of about 5 mm and a length of about 50 to 100 mm.

In addition, the above raw material powder has a small diameter portion having a diameter of about 5 to 8 mm and a large diameter portion having a diameter of about 10 mm having a length of 5 to 10 mm.
It is filled in a bag-shaped raw rubber (rubber tube) connected via a conical connection part of mm, and a hydrostatic pressure of 3 kg /
A material rod was formed by applying a pressure of cm ² . Next, this raw material rod was fired in air at 1300 ° C. for about 6 to 10 hours to obtain a raw material rod sample 2. In the obtained raw material rod sample 2, the diameter of the small diameter portion is about 5 mm and the diameter of the large diameter portion is 8 mm.
The length was about 9 mm and the length was about 100 mm.

Experimental Example 1 In this experimental example, the relationship between the oxygen concentration in the atmospheric gas and the melting points of the raw material rod and the seed crystal was investigated. That is, in this experimental example, the oxygen concentration in the atmosphere gas was changed, and the raw material rod was heated by an infrared lamp under each condition,
The output of the infrared lamp when the raw material rod melted was investigated, and the relationship between the oxygen concentration in the atmospheric gas and the output of the infrared lamp was investigated.

A 100 V-1.5 kW lamp is used as the infrared lamp of the single crystal manufacturing apparatus having the above-mentioned structure, and the YVO ₄ single crystal of <001> orientation is 3 to 4 mm square and has a length of 20 to 20 mm. A material rod of 30 mm is used, and the length of the raw material rod sample 1 is 50 mm.
Something was used.

Infrared lamps of 1.5 kW and 3.5 kW were prepared, and these 15 V to 20 V
When the light-collecting area at the time of output corresponding to the voltage of V was printed on the paper and confirmed, the light of 1.5 kW was collected in the area of 5 mm in diameter and the one of 3.5 kW was collected in the area of 10 mm in diameter. Was done. When the condensing area is 10 mm, it is highly possible that melt dripping occurs.
It was decided to use the one of 5 kW.

First, the above raw material rod was held on the upper shaft of the single crystal manufacturing apparatus by a hook, and the seed crystal was centered and held on the lower shaft by a tube made of alumina. Next, a predetermined atmosphere gas was filled in the quartz tube of the single crystal manufacturing apparatus having the above-described structure.

In the single crystal manufacturing apparatus having the above-mentioned structure,
Since no exhaust device is provided, it is impossible to completely exhaust the air in the quartz tube and replace it with a predetermined atmospheric gas. Therefore, a predetermined atmosphere gas is allowed to flow overnight through the atmosphere gas inlet and the atmosphere gas outlet to perform replacement and filling.

As the atmosphere gas, a gas having an oxygen concentration of 0 to 20% was used, in which nitrogen gas was changed to 2.5 liters per minute and oxygen gas was changed to 0 to 0.6 liters per minute. At this time, since the inside of the quartz tube is sufficiently replaced with the atmospheric gas, the oxygen concentration is represented by the flow rate as described above.

Subsequently, the raw material rod was rotated at a rotation speed of 6.5 rpm, the seed crystal was rotated in the opposite direction at a rotation speed of 6 rpm, and the tip of the raw material rod was irradiated with light from the infrared lamp.

The output control of the infrared lamp is performed by voltage control, and the output control of the two infrared lamps is performed by one program meter. Then, the output of the infrared lamp is automatically increased by using a program up to the voltage near the point where the raw material rod starts to melt, and then it is manually increased until the raw material rod begins to melt. The output was also investigated and the output of the infrared lamp when the width of the solid-liquid interface of the melting zone was 4 mm was also investigated. The relationship between the oxygen concentration and the output of the infrared lamp is shown in Table 1. The output of the infrared lamp when the raw material bar starts to melt (melting point) is Pw ₁ , and the output of the infrared lamp when the solid-liquid interface width is 4 mm. Is shown as Pw ₂ . The relationship between the oxygen concentration and the output Pw ₂ of the infrared lamp is also shown in FIG.

[0073]

[Table 1]

From the results of Table 1 and FIG. 2, the lower the oxygen concentration in the atmospheric gas, the smaller the output of the infrared lamp when the raw material rod is melted and the width of the solid-liquid interface in the melting zone is 4 mm. I understand.

FIG. 3 shows the relationship between the output of the infrared lamp and the temperature at the condensing part. It can be seen from FIG. 3 that the higher the output of the infrared lamp, the higher the temperature of the condensing part.

Therefore, from these facts, it was confirmed that when the oxygen concentration in the atmosphere gas is lowered, the melting point of the raw material rod is lowered, and when the oxygen concentration in the atmosphere gas at the time of joining the raw material rod and the seed crystal is lowered. , It was also found that these can be easily joined. Furthermore, by lowering the oxygen concentration in the atmosphere gas at the time of bonding, the output of the infrared lamp at this time can be suppressed to a small value, so there is no need for an infrared lamp with a large output, and a single crystal It was found that it is also preferable from the viewpoint of increasing the diameter.

Experimental Example 2 In this Experimental Example, an example of producing a YVO ₄ single crystal is shown.
First, a raw material rod sample in which the length of the small diameter portion having a diameter of about 5 mm is about 5 to 10 mm and the length of the large diameter portion having a diameter of about 8 to 9 mm is about 50 mm in the quartz tube of the single crystal manufacturing apparatus having the above-described configuration. 2 is held by a platinum wire hook on the upper shaft, and a seed crystal of YVO ₄ single crystal of <100> orientation with a 3 to 4 mm square and a length of 20 to 30 mm is centered and held on the alumina tube of the lower shaft. did.

Then, nitrogen gas is fed into the quartz tube at a rate of 2.5 per minute.
It was circulated overnight in the vicinity of liter, and the inside of the quartz tube was replaced with nitrogen gas and filled.

Next, the raw material rod was rotated at a rotation speed of 6.5 rpm and the seed crystal was rotated in the opposite direction at a rotation speed of 6 rpm, and the light from the infrared lamp was focused and irradiated onto the tip of the raw material rod. The infrared lamp is 100 V-
It was decided to use an infrared lamp of 1.5 kW, and to control the output of the lamp by voltage, and to control two infrared lamps with one program meter.

Then, the program meter automatically raises the voltage of the infrared lamp to 60 V (1.3 kW), which is close to the voltage corresponding to the output at which the raw material bar starts to melt, for about 2 hours to automatically collect the light. The temperature was raised, and then the voltage was increased by manual operation to melt the tip of the raw material rod to form a melt, and the raw material rod and the seed crystal were joined via this as a melting zone. The voltage at this time is 64V (1.4k
W) was around.

When joining the raw material rod and the seed crystal as described above, as described in Japanese Patent Application No. 6-16853, the portion where the raw material rod and the seed crystal contact each other contains oxygen and vanadium. If the composition ratio of yttrium and yttrium is V / Y, the above V / Y has a composition of 0.8 ≦ V / Y ≦ 1.25 and absorbs light in the wavelength band of 0.4 μm or more and 1.3 μm or less. The black substance may be included.

Next, the raw material rod and the seed crystal were rotated in the same direction at a rotation speed of 6 rpm to adjust the oxygen concentration Co ₁ in the atmospheric gas to 0.8%. If the oxygen concentration is increased in this way, the melting point of the melting zone rises and some of it may solidify, making the melting zone unstable.Therefore, rotate the raw material rod and the seed crystal in the same direction as described above. And Subsequently, the voltage of the infrared lamp was increased until the width of the solid-liquid interface of the melting zone became about 4 mm. The voltage at this time is 68 to 70 V (1.5 to 1.
It was about 7 kW).

Next, the raw material rod is rotated at a rotation speed of 6.5 rpm, the seed crystal is fed to the lower shaft side while rotating the seed crystal in the opposite direction at a rotation speed of 6 rpm, and the melting zone is relatively moved in the raw material rod. And the lower end of the melting zone was sequentially made into a single crystal to produce a single crystal. However, at this time, the growth rate of the single crystal was set to 5.0 mm / hour, and the feed rate of the raw material rod was gradually decreased from 3.9 mm / hour to 3.4 mm / hour to reduce the diameter of the single crystal. The necking portion was formed to have a length of about 5 to 10 mm.

Next, while increasing the oxygen concentration in the atmosphere gas in the quartz tube, the output of the infrared lamp was also increased to increase the feed rate of the raw material rod to gradually increase the crystal diameter and gradually increase the diameter in the single crystal growth direction. And finally formed a shoulder having a diameter larger than that of the seed crystal. If the oxygen concentration in the atmosphere gas is simply increased, the melting point of the melting zone rises and some of it may solidify, making the melting zone unstable, so keep the width of the solid-liquid interface in the melting zone constant. The voltage of the infrared lamp was also raised. The oxygen concentration was gradually increased up to about 80% of the shoulder forming step, and the final oxygen concentration Co ₂ was 10%. That is, Co ₁ ≦ Co ₂ , and Co
₁ / Co ₂ = 12.5. Further, the feed rate of the raw material rod was increased to 7.5 mm / hour.

Next, in the remaining 20% of the shoulder forming process,
The oxygen concentration was gradually lowered while lowering the voltage of the lamp so that the width of the solid-liquid interface of the melting zone was constant, and the oxygen concentration Co ₃ was lowered to 0.8%. Then, the feed rate of the raw material rod was set to 7.5 mm / hour, and a straight body portion having the same diameter as the uppermost portion of the shoulder portion was formed on the shoulder portion. At this time, the relationship of Co ₃ ≦ Co ₂ is established between the oxygen concentrations Co ₂ and Co ₃ , and Co ₃ / Co ₂ = 12.5. The obtained straight body part had a diameter of about 9 mm and a length of about 30 to 50 mm.

In this experimental example, the oxygen concentrations Co ₁ , C
Although o ₃ is 0.8%, this is because the oxygen concentration is relatively low to lower the melting point, and because the vapor pressure of vanadium is high, its evaporation is suppressed.

In the single crystal thus obtained, since the straight body is finally formed on the shoulder portion having a larger diameter than that of the seed crystal, it is possible to increase the diameter of the single crystal. In addition, it was confirmed that it has good quality characteristics that make use of the advantages of the Fz method.

Experimental Example 3 In addition, the inventors of the present invention used the raw material rod sample 1 as a raw material rod to manufacture a single crystal while keeping the oxygen concentration constant at 0.8%. It was confirmed that the feed rate of the raw material bar that does not exist was about 4 mm / hour, and that it was difficult to form the shoulder portion. Also, the diameter of the obtained single crystal is 4
It was about 6 mm, and it was also confirmed that it was difficult to cope with an increase in the size of a single crystal.

Furthermore, since the diameter of the raw material rod is large, the irradiation density of the infrared lamp on the raw material rod is low, and it is difficult to form a melt. Even if the voltage of the infrared lamp reaches about 80V, no melt is formed and 84V is used. Then, a problem such as sudden melt formation under high voltage and dripping occurred.

From the above, it was confirmed that it is difficult to form the shoulder portion or to join the raw material rod and the seed crystal without changing the oxygen concentration.

Experimental Example 4 The present inventors also investigated the range of oxygen concentration for preventing the molten zone from sagging when forming the shoulder. As a result, 3
It was found that the content is not less than% and not more than 12%, preferably not more than 6%. That is, the oxygen concentration Co ₁ in the atmosphere gas,
Co ₂ and Co ₃ are 1 ≦ Co ₁ / Co ₂ ≦ 12.5, 1
≦ Co ₃ / Co ₂ ≦ 12.5, preferably 1 ≦ Co ₁ /
If _{Co 2 ≦ 7.5,1 ≦ Co 3 /} Co 2 ≦ 7.5, it was confirmed that the dripping of the molten zone does not occur.

[0092]

As is apparent from the above description, in the method for producing a single crystal according to the present invention, when the single crystal is produced by the Fz method, the diameter of the shoulder finally becomes larger than that of the seed crystal. Since the straight body portion is formed on the portion as it is, the diameter of the single crystal is increased. When a single crystal is manufactured in this manner, a good quality single crystal that makes the most of the advantages of the Fz method is manufactured.

Further, in the above manufacturing method, if the oxygen concentration in the atmosphere gas at the time of forming the shoulder portion is increased, the surface tension of the molten zone becomes high, the sagging of the molten zone does not easily occur, and the shoulder portion is easily formed. It

Further, in the method for producing a single crystal of the present invention, when producing a single crystal by the Fz method, the raw material rod and the seed crystal are formed of a material system in which the density of the liquid near the melting point is smaller than the density of the solid, Since the oxygen concentration in the atmosphere gas at the time of joining the raw material rod and the seed crystal is made lower than the oxygen concentration in the atmosphere gas in the subsequent step, the melting point of these at the time of joining the raw material rod and the seed crystal becomes low, Will be easy to join. Further, if the melting point at the time of joining is lowered as described above, even when an infrared lamp or the like is used as the heating means, a high output is not required, and it is preferable from the viewpoint of increasing the crystal diameter.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration example of a single crystal manufacturing apparatus.

FIG. 2 is a characteristic diagram showing the relationship between oxygen concentration and infrared lamp output Pw ₂ .

FIG. 3 is a characteristic diagram showing the relationship between the output of the infrared lamp and the temperature at the condensing part.

[Explanation of symbols]

 1a Raw material rod 1b Seed crystal 1c Melting zone 2 Infrared focusing heating type growth furnace 3,4 Infrared lamp 5 Upper shaft 6 Lower shaft 7 Cavity

Claims (5)

[Claims] 1. A molten zone is formed at a tip of a raw material rod and / or a seed crystal in a predetermined atmosphere gas, a raw material rod and a seed crystal are joined to form a molten zone between them, and the molten zone is formed. In the method for producing a single crystal in which a single crystal is produced by sequentially moving the raw material rod into a single crystal while rotating the raw material rod, a large diameter gradually increases in the single crystal growth direction after joining the raw material rod and the seed crystal. And forming a shoulder portion having a diameter larger than that of the seed crystal, and then forming a cylindrical straight body portion. 2. The straight body portion is formed by setting the oxygen concentration in the atmosphere gas from the joining of the raw material rod and the seed crystal to the shoulder formation to Co ₁ and the oxygen concentration in the atmosphere gas when forming the shoulder portion to Co _2. When the oxygen concentration in the atmosphere gas at this time is Co ₃ , these are Co ₁ = Co ₃ , Co ₁ ≤Co ₂ , Co ₃ ≤Co ₂
The method for producing a single crystal according to claim 1, having the following relationship. 3. Oxygen concentration Co ₁ , Co in the atmosphere gas
₂ , Co ₃ is 1 ≦ Co ₁ / Co ₂ ≦ 12.5, 1 ≦ C
The method for producing a single crystal according to claim 2, having a relationship of o ₃ / Co ₂ ≦ 12.5. 4. A molten zone is formed at the tip of a raw material rod and / or a seed crystal in a predetermined atmosphere gas, a raw material rod and a seed crystal are joined to form a molten zone between them, and this molten zone is formed. In the method for producing a single crystal in which a single crystal is sequentially produced by sequentially moving the raw material rod while rotating the raw material rod, the density of the liquid near the melting point of the raw material rod and the seed crystal is higher than that of the solid. And the oxygen concentration in the atmosphere gas at the time of joining the raw material rod and the seed crystal are made lower than the oxygen concentration in the atmosphere gas in the subsequent step. 5. A melting zone is formed at the tip of a raw material rod and / or a seed crystal in a predetermined atmosphere gas, a raw material rod and a seed crystal are joined to form a melting zone between them, and the melting zone is formed. In the method for producing a single crystal in which a single crystal is sequentially produced by sequentially moving the raw material rod while rotating the raw material rod, the density of the liquid near the melting point of the raw material rod and the seed crystal is higher than that of the solid. Is formed from a small material system, the oxygen concentration in the atmosphere gas at the time of joining the raw material rod and the seed crystal is made lower than the oxygen concentration in the atmosphere gas in the subsequent process, and after joining the raw material rod and the seed crystal, a single crystal is formed. A method for producing a single crystal, which comprises forming a shoulder portion having a diameter gradually increasing in a growing direction and having a diameter larger than that of a seed crystal, and then forming a cylindrical straight body portion.