JP2003095678A - Doped quartz glass crucible for producing silicon single crystal and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crucible having an inner layer and a bulk layer, the inner layer having a crystallization agent distributed therein and maintaining smoothness even when contacting with silicon melt, the crucible being excellent in dimensional stability and capable of pulling up good silicon single crystal, and to provide a method for manufacturing the same. SOLUTION: The quartz glass crucible for producing a silicon single crystal has a wall including a bottom and a side wall, an inner layer being formed in the inner portion thereof in which a crystallization agent is distributed comprising the elements selected from the group consisting of barium, aluminum, titanium, strontium and a mixture thereof. The method for manufacturing the quartz glass crucible for producing a silicon single crystal comprises introducing silica powders to the inner surface of a rotating crucible mold to form a bulk powder layer having a bottom and a side wall and defining an inner cavity, generating a high temperature atmosphere in the inner cavity, and then introducing inner portion powders and a crystallization agent into the high temperature atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of quartz glass crucibles and a method for producing the same, and more particularly to a quartz crucible having a multi-layer wall in which one or more wall layers are doped with a crystallization agent, and a method for producing the same. It is a thing.

[0002]

2. Description of the Related Art The Czochralski method (CZ method) is well known as a manufacturing technique of a single crystal silicon ingot for manufacturing a silicon wafer used in the semiconductor industry. C
In the Z method, polycrystalline silicon is loaded into a crucible housed in a susceptor, melted, and a silicon single crystal is pulled from the molten silicon.

In recent years, the semiconductor industry has tended to seek larger diameter wafers, for example 300 mm diameter wafers. In order to grow this large-diameter silicon ingot, it is necessary to increase the operating time of the CZ method to sometimes 100 hours or more. Besides, slowing down the crystal pulling speed,
It is necessary to extend the execution time of CZ and reduce the frequency of structural defects in the silicon crystal, but it is better to improve the useful life of the crucible.

[0004]

In the manufacture of silicon ingots, there is also a method of "pulling" a multi-layer silicon crystal in the CZ method. In such a use, the side wall of the crucible is alternately exposed to the melt and to the atmosphere due to the lowering of the melt level and then to the melt from the next melting of the silicon charge. In such usage, the inner surface of the crucible is strongly stressed for a long period of time, and therefore the integrity of the inner surface becomes more important.

At the operating temperature, the interior of a conventional quartz crucible reacts with the silicon melt. The inner surface of the crucible typically undergoes morphological changes, causing roughening during the CZ operation.
In addition, the high heat of the CZ method softens the crucible wall and causes structural deformation of the crucible. Crystal defects occur in the ingot pulled up due to the roughness of the inner surface of the crucible. When most of the inner surface of the crucible becomes rough, the crystal structure collapses at the crystal-melt interface and the pulling of the silicon single crystal must be stopped. Roughness therefore makes continuous use of the crucible unsuitable for the production of silicon ingots.

Devitrification, or crystallization, occurs in the innermost shallow layer of the crucible. The volume of the ordinary crucible quartz glass changes with the crystal, and stress is generated at the interface between the glass phase and the crystal phase. Although this stress is released by a small deformation of the crucible glass layer, the smoothness of the inner surface is deteriorated. Devitrification of the crucible typically occurs as a ring pattern (rosette) that develops inside the crucible. The rosette was found to be surrounded by cristobalite. The center of the rosette has a rough surface that is not covered with cristobalite or covered with a very thin cristobalite layer. During the CZ method, the rosette is formed on the inner surface of the crucible, and the central surface of the rosette becomes rough. The rosette grows and coalesces to enlarge the coarse area.

In addition to the above, the inner layer of the crucible is partially dissolved in the silicon melt during the CZ process. Silicon and oxygen,
These are the main components of the quartz crucible, but they are not harmful to the growing silicon ingot. However, impurities in the inner layer may migrate to the silicon melt during this process and mix into the silicon single crystal. As an attempt to control devitrification on the inner surface of the crucible, for example, US Pat. No. 5,976,247 discloses formation of a film containing a crystal promoter. In this example, a devitrification enhancing solution is applied to the surface of a commercial crucible. It is said that the inner surface is crystallized to some extent by heating at 600 ° C. or higher.
However, this surface coating technique has several drawbacks. That is, only crystallization of quartz is promoted. The coated crucible cannot prevent crystallization and protect the glass on the inner surface of the crucible. The coating technique also fails to control the depth and rate of crucible crystallization. Careless contact may remove the crystallization promoting coating from the inner surface and requires special handling.

[0008]

The crucible of the present invention is used for producing a silicon single crystal. The crucible has an inner layer formed inwardly of its wall. A crystallization agent containing an element selected from the group consisting of barium, aluminum, titanium and strontium is distributed in the inner layer. The inner layer of the disclosed crucible maintains the smooth inner surface of the crucible wall upon heating and enhances the structural rigidity of the wall so that crystallization may be accomplished by any of the three operating methods.

In the crucible of the present invention, a bulk powder layer is generally formed on the inner surface of a rotating crucible type, the interior cavity is made to have a high temperature atmosphere, and then the interior powder and the crystallization agent are introduced to form the interior powder. Is melted to form an inner layer of the dope.

[0010]

The structure of the crucible of the present invention will be described below.
Although the manufacturing method and the operating method are described in detail, the present invention is not limited thereto.

Structure of Crucible Having Doped Layer One embodiment of a quartz glass crucible is shown in FIGS. Quartz glass crucible 1
Has a wall 2 defining an internal cavity 12. The wall 2 comprises a side wall 4 and a bottom 6. The side wall 4 of this embodiment comprises a bulk layer 14 of pure quartz and an inner layer 16 formed as an internal structure of the side wall 4 and the bottom 6. The bulk layer 14 is a transparent glass layer substantially made of quartz. The inner layer 16 is substantially composed of a fused-doped quartz glass layer and has a thickness of 0.2 mm.
~ 1.2 mm. The inner layer is preferably bubble-free. The bubbles trapped in the inner layer generate particles when the layer is crystallized. As the crucible expands, the particles separate or separate from the inner surface, erode the inner surface, and dissolve in the silicon melt. These particles cause defects in the single crystal structure of the silicon ingot. The crystallizing agent is distributed in the inner layer 16 and is selected from the group consisting of aluminum, barium, strontium, titanium and mixtures thereof. The crystallization agent may be an element (for example, Al), or an organic compound such as an oxide, a hydroxide, a peroxide, a carbonate, a silicate, an oxalate, a formate, an acetate, a propionate, a salicylate, a stearate, a tarrate, a fluorine, or a chlorine. It may be in various chemical forms such as an inorganic compound. By distributing the crystallization agent in the inner layer 16, crystallization of the inner layer 16 is promoted. The crystallization agent contained in the inner layer 16 is 5
It is 0 to 500 ppm, preferably 80 to 160 ppm, and more preferably 100 to 120 ppm. About 50p
Crucibles made with doping levels below pm do not undergo the desired partial silica crystallization in the inner layer 16 during a typical CZ process. On the contrary, the inner layer 16 has about 5
Doping with more than 00 ppm of aluminum provides only insignificant additional benefits.

In another aspect, the inner layer 16 is formed over the intermediate layer 18. The latter is made from synthetic quartz glass or pure quartz glass (Fig. 3). The side wall 4 of this embodiment includes a bulk layer 14, an intermediate layer 18 and an inner layer 16. As seen in the embodiments of FIGS. 1 and 2, the bulk layer 14 is typically translucent fused silica and the inner layer 16 is a doped fused silica layer. The intermediate layer 18 is preferably undoped quartz glass made of natural or synthetic quartz powder, but various materials may be incorporated into the intermediate layer 18 or may be a doped layer. The crystallizing agent present may be the same as or different from that used in the inner layer 16.

In another embodiment of the crucible shown in FIG. 4, an outer layer 19 is also formed on the outer side of the side wall 4 at the outer position.
In one aspect, the outer layer 19 is about 0.5-2.5 m thick.
At m, it can be doped with aluminum, barium, strontium, titanium or mixtures thereof. Similarly, mixtures of these reagents can be used effectively. The content of the crystallization agent in the outer layer is about 50 to 500 ppm.

In the crucible represented in FIG. 4, the sidewall 4 typically has a thickness of about 10.0 mm, the bulk layer 14 is 6.5-9.4 mm and the inner layer 16 is 0.2-1. .2
mm, and the outer layer 19 comprises the remaining 0.5-2.5 mm. The bottom 6 is made in a structure similar to the sidewall 4 of FIGS. 2-4, but is preferably formed without the outer layer 19. The bottom 6 typically has a thickness of about 10.0 mm, about 0.2 to 1.0 mm of which is the inner layer 16. The crucible of this embodiment has an inner layer 16, an intermediate layer 18, a bulk layer 14,
It is obvious that the structure has the outer layer 19 and the outer layer 19.

Manufacturing Method of Crucible Having Doped Layer A method for forming a doped inner layer suitable for devitrification during the CZ step will be described here. The method shown in FIGS. 5 and 6 produces the crucible of the embodiment shown in FIGS. A general method for manufacturing fused silica glass crucibles is described in US Pat. No. 5,174,80.
1 (Matsumura et al.). In that method, a crucible body made of quartz powder is prepared in a rotating mold (FIG. 5) (FIG. 5), and the crucible body is heated from its internal cavity until it is at least partially melted, thereby forming a crucible substrate.

A high temperature atmosphere is formed in the internal cavity of the crucible base, and the internal quartz powder is supplied into this high temperature atmosphere (FIG. 6). The internal quartz powder is at least partially melted and deposited on the inner wall surface of the crucible substrate to form a transparent synthetic quartz glass inner layer having a predetermined thickness.

A suitable method of making a crucible for use in forming a silicon single crystal is forming a crucible having an inner layer 16 doped with a crystallization agent. In order to produce the crucible shown in FIGS. 1 and 2, first, the bulk quartz powder 30 is introduced from the bulk quartz powder hopper 22a into the rotating mold 20 through the flow rate control valve 26a and the supply pipe 24 to obtain the bulk quartz powder. Form layer 36 (FIG. 5). The bulk quartz powder 30 is preferably pure quartz powder. The stirring blade 28a of the bulk quartz powder hopper is the bulk quartz powder 30 in the hopper 22a.
Is used to stir and improve its flow. The spatula 32 is shaped to smooth the inner surface of the mold and is used to shape the introduced bulk quartz powder. In this way, bulk powder layer 36 is formed to a selected thickness. In this method, the formed bulk powder layer 36 is melted (FIG. 6). An electrode assembly including a power supply 37 and electrodes 38a, 38b is partially disposed within the internal cavity of mold 20. An electric arc is supplied between the electrodes 38a and 38b by supplying a direct current of, for example, 250 to 350 V and about 1800 A. A high temperature atmosphere 42 is created inside the bulk powder layer 36. The bulk powder layer 36 formed in the mold is melted in the high temperature atmosphere 42.
The melting proceeds from the side closer to the electrodes 38a, 38b to the end. The melting mechanism for advancing to the quartz powder layer by this technique is known to those skilled in the art, and is disclosed, for example, in U.S. Pat. Nos. 4,935,046 and 4,956,208.

At the same time as the surface of the formed bulk powder layer 36 is melted, the internal quartz powder 44 is fed into the internal quartz powder hopper 2.
2b through the supply pipe 40 into the high temperature atmosphere 42. The internal powder flow rate control valve 26b is used to control the flow rate of the internal quartz powder 44. The hopper stirring blade 28b is used as described above. The internal quartz powder 44 may be essentially pure quartz powder such as natural quartz powder which has been cleaned of contaminants and doped with a crystallization agent. Also, synthetic quartz powder doped with a crystallization agent can be used.

The high temperature atmosphere 42 created by the electrode arc creates a very strong plasma field that at least partially melts the internal quartz powder 44. The at least partially melted internal quartz powder 44 is extruded to the outside and the inner layer 16 is formed on the side wall and the bottom of the formed bulk powder layer 36 / molten bulk layer 14.
Are fused together to form.

In FIG. 6, the bulk layer is 3 for convenience.
Represented by the number 6. At this stage, of course, the layer is a combination of unmelted bulk powder layer 36 and molten bulk layer. The internal quartz powder 44 continuously flows into the high temperature atmosphere 42 and forms the inner layer 16 while being deposited on the bulk layer 14. The inner layer thus formed is essentially transparent and free of bubbles. The thickness of the inner layer 16 is controlled by the introduction speed of the internal quartz powder and the flowing time of the internal powder during melting.

A method of manufacturing a crucible having an inner layer 16 and an intermediate layer 18 is shown in FIGS. After formation of the bulk powder layer 36 (FIG. 5), the electrode assembly is placed within the inner cavity of the crucible. The intermediate layer quartz powder 48 is supplied from the intermediate layer powder hopper 22c through the flow rate control valve 26c. The stirring blade 28c of the hopper is the stirring blade 28a,
Used the same as 28b. The intermediate layer quartz powder 48 is at least partially melted in the high temperature atmosphere 42, and is fused on the formed bulk powder layer / molten bulk layer to form the intermediate layer 18. The thickness of the intermediate layer 18 can be controlled by regulating the flow rate and time of the intermediate layer quartz powder 48.

After the intermediate layer 18 is formed, the internal quartz powder 44 is introduced into the high temperature atmosphere 42 (FIG. 8). Quartz powder for internal use 4
4 is at least partially melted and deposited on the intermediate layer 18 to form the inner layer 16.

A crystallizing agent-doped inner layer is formed on the various transparent intermediate layers. For example, the intermediate layer 18 may be a pure quartz layer or a doped layer. The crystallizing agent-doped inner layer is formed by depositing on a transparent layer made of synthetic quartz powder or pure quartz powder (ie, purified natural quartz).

A similar method is used to construct a crucible having an outer layer 19 (FIG. 4). An outer powder layer 49 is first formed in the rotary mold (Fig. 9). External powder hopper 22d
Communicates with the inside of the mold 20 via a supply pipe 24. A valve 26d is used in the supply pipe 24 to regulate the flow rate of the external quartz powder 46 sent from the hopper 22d to the inside of the mold. The thickness of the outer powder layer 49 can be controlled by using a spatula 47. Thus, the production of the crucible proceeds. The outer layer 19 may also be doped with a crystallization agent. The doped outer layer 19 is configured to crystallize easily, affecting the silicon melt and improving the dimensional stability of the crucible at high temperatures without contamination. The outer layer 19 is about 100-5
It may be doped with 00 ppm, preferably 120-500 ppm of crystallization agent. Doping below 100 ppm does not show uniform crystallization, and doping levels above 500 ppm do not provide the crucible of the invention with further advantages.

Aluminum is more cost effective than other compounds
Cheap and unfused aluminum-doped external quartz powder treatment
Is also environmentally convenient. Therefore, other dopants or
Quartz powder and aluminum-doped quartz powder that are purer than compound powder 46
The use of a mixture with is preferred. The aluminum compound
As for aluminum nitrate (Al (NO₃)₃・ 9H
₂ O), aluminum hydroxide (Al (OH)₃, Al chloride
Minium (AlCl₃), Aluminum hydrogen carbonate (Al
(HCO₂)₃And so on.

Crystallizing Agent Introducing Method In this embodiment of the method, the internal quartz powder 44 is doped with a crystallizing agent. As mentioned above, the crystallizing agent contains aluminum, barium, strontium, titanium or mixtures thereof in elemental form or as compounds. Of the compound forms, two are preferred, oxides and nitrides. Mixtures of doped and undoped quartz powders can also be used as long as the final agent content selected is obtained. When synthetic quartz powder is used as the undoped quartz powder of the mixture, the crystallization promoting power of the crystallization agent is increased. Glass made of synthetic quartz is softer than natural quartz glass (ie fused quartz glass). The soft substrate of synthetic quartz glass is most convenient for crystallization. Stiffness (that is, reduced structural resistance) due to volume change during layer conversion from amorphous quartz glass to crystallized quartz glass such as cristobalite
Will increase. As a result, when synthetic quartz powder is incorporated into the molten inner layer 16 or outer layer 19, the same level of deformation is obtained even at low doping levels.

By preparing a quartz sol containing a crystallization agent, uniformly doped silica gel can be obtained. This gel is also another example of dope powder. The gel is preferably calcined to convert it to pure dioxide.

Further, for doping the quartz powder, it is possible to coat the quartz powder with a crystallization agent or form silica gel containing the agent to support the silica powder. The coated quartz powder may be pure quartz powder coated with an organic material such as alcoholate. As another introduction method that can be selected, there is also an example in which a crystallization agent is mixed with undoped quartz powder such as natural or synthetic quartz powder and introduced at the same time. For example, barium carbonate (BaC
O ₃ ) and aluminum nitrate are added to the internal quartz powder 44 in the hopper 22b. The mixing blade 28 uniformly mixes barium carbonate or aluminum nitrate with the internal quartz powder. The mixture of internal quartz powder and barium carbonate or aluminum nitrate is then introduced into the high temperature atmosphere 42 as described above.

During the melting of the internal quartz powder 44, the crystallization agent is an inorganic powder such as oxide (BaO), (Al ₂ O ₃ ), hydroxide (Al (OH) ₃ and hydrogen carbonate (Al (HCO)). ₂ )
₃ , complex oxide (TiBaO ₃ ), nitride (BaN)
₂ ), chloride (BaCl ₃ ), (AlCl ₃ ), or a mixture of a plurality of the above compounds is supplied into the high temperature atmosphere 42. Organic compounds which can be converted to any of the above compounds at the elevated temperature of melting the crucible can likewise be used.

In another embodiment of the method, the crystallization agent can be separately introduced into the high temperature atmosphere 42 simultaneously with the internal quartz powder 44 from a predetermined hopper. The valve for controlling the flow rate of the contents discharged from the internal powder hopper and the agent hopper is opened so that both of them can flow at the same time as the above-mentioned valve.

In yet another example, the crystallizing agent may be a liquid such as barium hydroxide (Ba (OH) ₂ ) or barium chloride (BaCl ₂ ). The liquid solution is introduced into the internal quartz powder 44 before or simultaneously with the introduction of the internal quartz powder 44 into the high temperature atmosphere 24.

The liquid solution is a quartz powder for internal use 4 in a high temperature atmosphere.
4 can be directly introduced at the same time. For example, it can be introduced from an injector arranged near the end of the flow pipe 40 adjacent to the high temperature atmosphere 42. The liquid solution may be an aqueous solution or an organic solution as long as the selected solvent does not represent a potential source of ingot contamination. The crystallizing agent in the liquid solution can also be fed to the powder layer formed before melting. The organic compound, organic solution or aqueous solution of the crystallization agent can be sprayed onto the powder layer 49 formed. The application advantage of this agent is that the crystallization agent can be placed in specific areas of the layer. For example, the crystallization agent may be applied only to the inside of the side wall 4 or the bottom 6, to the entire inner surface (side and bottom) of the side wall 4 or the bottom 6, or to the inside of the side wall 4 below the expected melt line (the melt line is It is a line that comes into contact with the inner wall of the crucible after meltdown).

In the above method in which the crystallization agent is introduced simultaneously with the internal quartz powder, but separately, the intermediate layer quartz powder 48 can also be used as the internal quartz powder 44. For example, the intermediate layer quartz powder 48 is introduced into the high temperature atmosphere 42 to form the intermediate layer 18 as described above. The inner layer 16 can be formed by stopping the flow of the intermediate layer powder hopper and simultaneously introducing the intermediate layer quartz powder 48 and the barium compound or aluminum compound into the high temperature atmosphere 42.

In a similar manner, pure internal quartz powder 44 is introduced as first described, and then barium carbonate or aluminum nitrate is introduced at the same time as the internal quartz powder 44 being introduced, and barium carbonate or aluminum nitrate is introduced. An inner layer 16 having is formed. The flow rate of barium carbonate or aluminum nitrate can be varied so that there is a gradient in the amount of barium carbonate or aluminum nitrate from the inner surface to the bulk layer 14. The crucible of this mode includes the bulk layer 14 and the intermediate layer 18.
And a crucible having the inner layer 16. The inner layer 16 can contain barium carbonate or aluminum nitrate with a gradient such that the content of the agent is low near the bulk layer and is high near the inner cavity 12 of the crucible.

Method of Operating Crucible Having Doped Layer The choice of doping element used in the inner layer 16 depends on the desired method of operation. Each crystallization agent has a unique crystallization promoting power, and the crystallization rate and degree of quartz in the inner layer 16 can be controlled according to the doping level of the agent. The explanation of the operating method and the usage of various agents therefor begin by investigating the rosette phenomenon observed on the inner surface of the crucible used in the CZ method. When using a crucible to form a silicon ingot, it is desirable to first smooth the surface of the inner layer that comes into contact with the melt. Therefore, in the following description, it should be noted that the "inner layer" and "inner surface" of the crucible are the most important parts of the inner layer in the present operation.

More specifically, the rosette phenomenon is shown in FIGS.
Observed on the inner surface of a prior art crucible shown at 14. FIG. 10 shows an inner surface 50 of the crucible which is in contact with the silicon melt and has a large number of rosettes formed on the inner surface. Rosettes generally have a ring 52, and the ring and the area within the ring are cristobalite 56.

During the CZ process, the rosette increases its area and spreads over the inner surface 50 as seen in FIG. 11 increasing its proportion. Rough surface texture 5 as rosettes increase
4 appears in the center. A rough surface texture area 54 within the rosette boundaries extends to the inner surface of the crucible. FIG. 12 shows a conventional C
The inner surface of the typical crucible by Z method is shown. The rosettes fuse and increase the rough surface texture area 54. As described above, the rough inner surface has a strong influence on the crystal structure of the growing silicon ingot.

An enlarged top and cross-sectional view of a prior art rosette is shown in FIGS. The center of the rosette has a rough surface texture 54 surrounded by cristobalite (crystalline silica) 56 and appears to extend from the inner surface 50 to the crucible wall. The cristobalite ring 52 is decorated with a brown substance and is usually observed as a brown ring on the inner surface of the crucible used. In some prior art rosettes, a small smooth surface boundary 55 exists between the rough region 54 and the inner edge of the ring 52.

With respect to the rosettes and associated surface roughness, the present invention is described below in order to provide a crucible inner layer suitable for operation by the following three crystallization methods: complete method, corona method and smoothing method. Adopt a combination of each element. In both of these methods, the crucible is suitable for use in the extended CZ method, and the inner surface is neither rough nor significantly melted.

"Complete" method: In this method, the inner surface of the crucible is heated and crystallized before it contacts the silicon melt. In this way, rosette generation is suppressed and the rosette is not observed during or after the CZ step. Therefore, the inner surface of the full process crucible is coated with β-cristobalite after heating and before the silicon melts down. As a result, the rosette is not formed by the reaction of the silicon melt with the crystallized silica. The inner surface of the crucible remains smooth because there is no formation of rosettes that roughen the inner surface.

"Corona" method: The second method of keeping the inner surface of the crucible smooth is to suppress the expansion of the rosette (FIGS. 15 and 16). The rosette ring 52 is cristobalite and acts as a nucleation site for growing the crystalline silica 56 in the quartz glass of the inner layer 16. However, there is a difference in the rate at which the phase transition expands between the central region of the rosette and the corona around the ring 52. The cristobalite corona or halo grows faster than the cristobalite ring 52 and the ring 52 is surrounded by the crystalline silica 56. The ring 52 is constrained by the crystalline silica 56 so that the growth rate of the rosette is at least 50.
%Decrease. Taking advantage of this imbalance in crystallization rate, the ring is surrounded by a corona-shaped crystal layer “corona” to stop the growth of the ring. As a result, the phase transition of the inner layer 16 from quartz glass to β-cristobalite proceeds slowly (ie,
Most of the original glass can be retained for long periods of time, as rapid crystallization does not occur as in the full process).

The "corona" crucible has a large smooth surface and a slowly growing smooth cristobalite surface 56.
Because of this, the vitreous inner layer can be maintained for a longer period than a normal crucible and does not deteriorate rapidly as in the prior art.

"Smooth" Method: A third way of maintaining the usefulness of the crucible is to prevent the formation of rough surface texture areas 54. A "smooth" crucible (Fig. 17) similar to a rosette formed on the wall of a prior art crucible (compare Fig. 10).
Rosettes are also formed on the inner surface of the. The "smooth" crucible rosette grows and continues to coalesce as it does on the inner surface 50 of prior art crucibles (FIGS. 18, 19). Nevertheless, the crystallization of the quartz glass in the inner layer 16 proceeds more slowly than either the "perfect" or "corona" crucibles. Because the inner layer 16 does not undergo a rapid phase transition, the vitreous quartz layer does not suffer from the conventional undesired devitrification (ie roughness and potential degradation). The inner surface 60 of the “smooth” crucible remains a smooth surface texture 62. 20 and 21 are a plan view and an enlarged sectional view of a rosette that grows on the inner surface of the crucible of the "smooth" method. The rosette consists of a ring 52 at the outer interface of the rosette, in which cristobalite 56 can be seen. Cristoba light 5
6 also extends to the inner layer 16. In contrast to prior art inner crucible surface 50 (FIGS. 13 and 14), the "smooth" method crucible retains a smooth surface in the ring 52 and rosette.
Even if the crucible surface of the “smooth” method is covered with a united ring, the roughness can be prevented as compared with the conventional crucible.

Selection and Control of Operating Method The present invention selects a desired method from the above three methods. The crucible is constructed by operating in one of the above three operating methods based on a number of factors including the crystallizing agent itself and its level, the method of introducing the agent into a high temperature atmosphere, and the handling of the crucible after melting. To be done.

Control of Crystallizing Agent and Cristobalite Formation The above method is selected with the growth rate of cristobalite as a first measure. Crystallization is "perfect" and fastest, followed by the "corona" method and finally the "smooth" method. Regarding the strength of crystallization promotion of quartz glass, the elements of the 2A group of the periodic table are the strongest, followed by the elements of the 3B group,
It is an element of the A4 group. However, regarding the strength of the crystallization agent at the same doping level, the strongest is strontium (3B group), then barium (2A group), aluminum (3B group), titanium 4A.
Group). Mixtures of two or more of these elements or combinations of multilayer crucibles are also used. Alkaline element (ie 1A group such as Li, Na, K)
Can be used, but is not preferred because it is easily diffused and is not limited to the doped layer. In the smoothing method, the crystallizing agent is preferably titanium or aluminum. The titanium distributed in the inner layer is 50
~ 130 ppm range, preferably 70-130 ppm
The range is good. Also, aluminum is 50 to 150 pp
The range of m is preferably 75 to 150 ppm. Crystallization of quartz is also affected by the level of crystallization agent. Higher doping levels generally result in faster cristobalite growth rates. Using aluminum as an example, cristobalite formation proceeds much faster in the 250 ppm doped layer than in the 25 ppm doped layer. The growth rate of cristobalite is increased by using thinner layers. The crucible having the inner layer 16 having a thickness of 0.2 mm has a faster phase transition than the crucible having a layer having a thickness of 1.2 mm. Fast cristobalite growth is generally due to non-uniform doping. It is especially noticeable in heterogeneous doping using a mixture containing synthetic quartz powder (Amorphophus) rather than crystalline quartz powder (quartz).

As mentioned above, the above factors are the "perfect" method,
Limited in the production of crucibles by either the "corona" method or the "smooth" method. For simplicity, the inner layer 16 is shown in the following example, but the same principle can be applied to the outer layer 19.

[0047]

Examples Example 1: Crucible of "perfect" process In a typical crucible operating in the "complete" process, a relatively strong crystallization agent or a relatively high doping level is used, eg natural internal quartz powder 44. Was doped with barium and introduced to form an inner layer 16 with a crystallization agent level of about 70 ppm. Conversely, barium-doped natural internal quartz powder and pure synthetic quartz powder were mixed to give about 20 ppm of barium distributed. The inner layer 16 of the "perfect" method crucible has a typical thickness of 0.2-1.2 mm.
The exact thickness of the inner layer 16 must be determined in relation to the quartz powder, the particular crystallization agent and its method of introduction. Instead of doping the crystallizing agent in a "perfect" process crucible, the coated internal quartz powder 44 can be produced by melting. By using the quartz powder 44 for the inside of the coating, the crystallization agent is unevenly distributed in the inner layer 16. Similarly, when the internal quartz powder 44 and the crystallization agent were made to flow substantially simultaneously, the crystallization agent was distributed inhomogeneously in the molten layer 16.

Example 2: "Corona" Crucible An exemplary crucible operating in the "Corona" method has an inner layer of crystallization agent that has a moderate level of moderate crystallization promoting power to moderate doping levels. Contained in. For example, the inner layer 16 is formed of natural quartz powder 44 doped with aluminum. The preferable aluminum content in the inner layer 16 is 50 to 150 ppm. The thickness of the doped layer is about 0.2
~ 1.2 mm. In this method, it is not preferable to use an agent having a strong crystallization promoting ability such as barium or strontium so as not to give a rapid crystallization ability to the entire inner layer. Similarly, as the inner layer quartz powder 44, natural quartz powder is preferable as compared with synthetic quartz powder. However, adding the synthetic quartz powder to the dope inner layer powder 44 (or use of the doped synthetic quartz powder) enables the use of a weaker crystallization agent.

Similarly, doped quartz powder is preferred over coated quartz powder or co-introduced because the crystallization promoter is evenly distributed in the inner layer 16. This advantage is also good when the crystallization agent is distributed in the inner layer 16 with a gradient as described above.

Example 3: Crucible of "smooth" method: In the crucible operated by this method, the crystallization of the quartz glass inside the side wall 4 and the bottom 6 proceeds slowly, and a smooth surface remains. The inner layer 16 of the crucible of the "smooth" method should preferably use a weak crystallization agent having a moderate crystallization accelerating power. As the crystallization agent, for example, titanium is used in the dope layer obtained by using fused natural internal quartz powder. A distribution of 100 ppm is preferable.A thin inner layer that can be effectively operated can be formed by using a specific crystallizing agent selected and synthetic internal quartz powder 44. The crucible design is based on the conditions of the intended CZ method, especially the process. It should be combined with the heating plan.

Example 4: Aluminum-doped crucible Four crucibles A, B, C and D of the present invention were manufactured to have the same size. Crucible P was manufactured by the prior art. The size of each crucible is 22 inches. The inner layer 16 of crucible A was made of a mixture with aluminum-doped internal quartz powder. An internal quartz powder doped to a level of 105 ppm and a pure internal quartz powder with a natural aluminum content of about 8 ppm were mixed. The mixed internal quartz powder 44 is 5
Mixing ratio of 4:46 and contained 60 ppm average aluminum.

Crucible B is a similarly doped inner layer 16
Was created to have. The mixture used to make the inner layer 16 of the crucible consisted of 105 ppm aluminum-doped internal quartz powder and pure synthetic quartz powder, the latter having an aluminum content of 0.5 ppm or less. Doped and pure internal quartz powder were mixed in a ratio of 1: 2. As a result, the average aluminum content of this mixture was 35 ppm.

The aluminum-doped inner layer 16 of the crucible C was produced using coarse natural quartz powder coated with aluminum. The average aluminum content of this internal powder is 85
In ppm, 42% of the powder was larger than 200 μm in size.

Crucibles A to C having the inner layer 16 doped with aluminum, which adopts the above-mentioned perfect method, corona method and smoothing method.
It was created. The three crucibles were taken out and cooled in the mold for 5 minutes before the final step.

The prior art crucible P is 22 inches in diameter. In the manufacturing method, pure natural quartz powder was used instead of the aluminum-doped internal quartz powder. This natural quartz powder contains approximately 8 ppm of aluminum.

Crucibles A to P were used in the CZ method for 120 hours. That is, the silicon substrate was used at the selected temperature after melting for 120 hours. The results are shown in Table 1.

[0057]

[Table 1]

Rosettes 52 were found on the inner surface 50 and inner layer 16 of crucible A. These rosettes were not high enough to cover the inner surface of crucible A. Therefore, in the crucible of this example, the smoothness of the inner surface is maintained by preventing the silica crystals from spreading.

The rosettes found on the inner surface 50 of the crucibles A and C are located on both sides and in the middle of the rosette ring (FIG. 20, FIG.
21) was surrounded by cristobalite. The inner surface 50 in the rosette remained smooth.

Crucible B was similarly used in the 120 hour CZ process. Rosettes were formed in the inner layer 16 and spread and fused to cover most of the inner surface 50. The inner surface in the rosette had a smooth surface, although very little of the initial surface remained. During the CZ method, the pulled silicon crystal ingot was not damaged by the rosette formed in the inner layer 16 of this embodiment and its spread.

The crucible of D was prepared by the complete method of the present invention.
Crucible D was prepared in the same manner as crucible C except that it was held at 1400 to 1600 ° C. for 1 minute and then cooled in the same manner as described above, that is, about 5 minutes.

After the crucible D was applied to the CZ method for 120 hours, the inner layer 16 was examined. The inner surface 50 consisted essentially of crystalline silica and no rosette pattern was clearly visible.

A prior art crucible P was also used in the CZ method for 120 hours. However, at about 80 hours, powder boundary defects that destroy the crystal structure occurred in the initial silicon ingot. Due to this defect, the CZ method was forcibly stopped and a silicon crystal suitable for the intended use could not be obtained.

When the inner surface of the crucible P was examined, it was found that almost the entire surface was covered with the rosette, and the initial vitreous surface was not left. During the rosette ring, the surface has a rough texture and silicon crystal interference (interferen).
ce).

The above method distributes the crystallization agent in the inner layer of the crucible rather than coating the inner surface of the crucible with the devitrification accelerator, and the doping layer has several advantages as compared with the usual coating method.

In the present invention, the crystallization agent level of the inner layer 16 or the outer layer 19 can be controlled in detail. In the above aspect,
The internal quartz powder 44 is doped with barium or aluminum before its introduction and melting. The amount of crystallization agent contained in the dope powder is accurately determined by the analysis done previously. The content of the crystallization agent in the inner layer 16 is accurately controlled by, for example, mixing doped quartz powder and pure quartz powder in the hopper.

The thickness of the inner layer 16 can also be manipulated by changing the introduction rate and time of the internal quartz powder. There is no loss of crystallization promoter during manufacture, eg due to sublimation. Substantially all of the introduced agent is fixed within the inner layer 16. Moreover,
The doping of the three-dimensional layer also requires less crystallization agent compared to the prior art. The amount of crystallization agent introduced into the high temperature atmosphere or the inner surface area of the crucible can be calculated. It has been shown in the data that crucibles constructed by the method of the present invention operate effectively with about one tenth of the "devitrification promoter" used in prior art surface coated crucibles.

Since the crystallizing agent is distributed and melted in the quartz glass, the crucible is also dimensionally stable and can be treated like a normal pure quartz crucible for cleaning and etching. No additional manufacturing methods or specific handling of crucibles are required. For example, unmelted powder remaining on the outside of a normal crucible can be removed cleanly by a sand blast method and washed with water. After cutting the crucible to a specific size, it is cleaned by etching with dilute hydrofluoric acid and washing with pure water. The crucible is then dried in a clean air bath, packaged and boxed for shipping.

The crucible constructed by the method of the present invention has an inner layer 1
6 or the crystallization agent does not move from the outer layer 19 and is easy to handle.

Those skilled in the art will be able to implement the present invention by the description of this document. Much has been given to understand the invention. As another example, well-known features have not been described in detail so as not to unnecessarily obscure the present invention.

While the invention has been disclosed in preferred form, and particular embodiments have been disclosed and described, they should not be construed in a limiting sense. Indeed, it will be apparent to those skilled in the art from the present description that the invention can be modified in many ways. The inventor regards the subject matter of the invention to include all combinations and subcombinations of the various elements, features, functions and / or properties.

[0072]

The crucible of the present invention has an inner layer and a bulk layer, and the crystallization agent is distributed and crystallized in the inner layer to maintain the smoothness of the inner surface of the crucible even when the inner layer comes into contact with the silicon melt. In addition, the crystallization can increase the dimensional stability of the crucible and can pull the silicon single crystal for a long time. The crucible is
It can be manufactured by a method of forming an inner layer doped with a crystallization agent on the inner surface of the bulk layer using a conventionally known manufacturing method, and has high industrial value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a quartz glass crucible of the present invention.

FIG. 2 is an enlarged partial sectional view of a wall portion of the quartz glass crucible of FIG.

FIG. 3 is an enlarged partial sectional view of a wall portion of the first mode of the quartz glass crucible of the present invention.

FIG. 4 is an enlarged partial sectional view of a wall portion of a second embodiment of the quartz glass crucible of the present invention.

FIG. 5 is an explanatory view of a method for manufacturing a quartz glass crucible according to the present invention.

FIG. 6 is an explanatory view of a method for manufacturing a quartz glass crucible according to the present invention.

FIG. 7 is an explanatory view of a method for manufacturing a silica glass crucible according to the present invention.

FIG. 8 is an explanatory view of a method for manufacturing a quartz glass crucible according to the present invention.

FIG. 9 is an explanatory diagram of a method for manufacturing a silica glass crucible according to the present invention.

FIG. 10 is a partial plan view of the inner surface of a conventional quartz glass crucible showing the generation of rosettes during the CZ method.

FIG. 11 is a partial plan view of the inner surface of a conventional silica glass crucible showing the generation of rosettes during the CZ method.

FIG. 12 is a partial plan view of the inner surface of a conventional silica glass crucible showing the generation of rosettes during the CZ method.

13 is an enlarged partial top view and cross-sectional view of the conventional crucible wall shown in FIG.

14 is an enlarged partial top view and cross-sectional view of the conventional crucible wall shown in FIG.

FIG. 15 is an enlarged top view and a cross-sectional view of an inner surface of a quartz glass crucible according to the corona method of the present invention.

16A and 16B are an enlarged partial top view and a cross-sectional view of an inner surface of a quartz glass crucible according to the corona method of the present invention.

FIG. 17 is an enlarged top view and a cross-sectional view of an inner surface of a quartz glass crucible according to the smoothing method of the present invention.

FIG. 18 is an enlarged partial top view and a cross-sectional view of the inner surface of a quartz glass crucible according to the smoothing method of the present invention.

FIG. 19 is an enlarged top view and a cross-sectional view of an inner surface of a quartz glass crucible according to the smoothing method of the present invention.

FIG. 20 is an enlarged top view and a cross-sectional view of FIG. 17, illustrating the generation of rosettes.

FIG. 21 is an enlarged top view and a cross-sectional view of FIG. 17, illustrating the generation of rosettes.

[Explanation of symbols]

1 Quartz glass crucible 2 crucible wall 4 side walls 6 bottom 14 Bulk layer 16 inner layer 18 Transition layer 19 Outer layer 20 crucible type 22a-d hopper 26a-d control valve 28a-d stirrer 32, 47 spatula 37 electrode assembly 42 high temperature atmosphere 50 Crucible inner surface 52 Rosette Ring 54 Surface texture 56 Cristobalite 62 smooth surface texture

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Robert Moshe             Washington, United States 98684             Vancouver nines circle             15903 N (72) Inventor Paul Spencer             Washington, United States 98684             Stephenson Vista Drive 250               NA F-term (reference) 4G014 AH02 AH08                 4G062 AA01 AA15 BB02 CC01 DA08                       DB02 DC01 DD01 DE01 DF01                       EA01 EA10 EB01 EC01 ED01                       EE01 EF01 EG01 FA01 FB02                       FC01 FD01 FE01 FF01 FG01                       FH01 FJ01 FK01 FL01 GA01                       GA10 GB01 GC01 GD01 GE01                       HH01 HH03 HH05 HH07 HH09                       HH11 HH13 HH15 HH17 HH20                       JJ01 JJ03 JJ05 JJ07 JJ10                       KK01 KK03 KK05 KK07 KK10                       MM01 NN40 PP01 PP03 PP04                       PP11                 4G077 AA02 BA04 CF10 EG02 PD01                       PD05

Claims (29)

[Claims] 1. A quartz glass crucible for producing a silicon single crystal, wherein the crucible has a wall including a bottom portion and a side wall, and the inner portion thereof is selected from the group consisting of barium, aluminum, titanium, strontium and a mixture thereof. A quartz glass crucible having an inner layer in which a crystallization agent containing the above-mentioned element is distributed. 2. The quartz glass crucible according to claim 1, wherein the crucible wall further has an intermediate layer between the bulk layer and the inner layer. 3. The quartz glass crucible according to claim 1, further comprising an outer layer on the outer side of the bulk layer. 4. The quartz glass crucible according to any one of claims 1 to 3, wherein the crystallization agent is distributed in the inner layer in the range of 50 to 200 ppm. 5. The quartz glass crucible according to claim 4, wherein the crystallizing agent is distributed in the range of 80 to 160 ppm. 6. The quartz glass crucible according to claim 5, wherein the crystallizing agent is distributed in the range of 100 to 120 ppm. 7. A quartz glass crucible according to claim 3, wherein a crystallizing agent containing an element selected from the group consisting of barium, aluminum, titanium, strontium and mixtures thereof is distributed in the outer layer. 8. The quartz glass crucible according to claim 7, wherein the crystallizing agent is distributed in the range of 100 to 500 ppm. 9. The quartz glass crucible according to claim 8, wherein the crystallizing agent is distributed in the range of 120 to 500 ppm. 10. The quartz glass crucible according to claim 1, wherein the crystallizing agent is an agent containing an aluminum element. 11. The quartz glass crucible according to claim 1, wherein the inner layer has a thickness of 0.2 to 1.2 mm. 12. The quartz glass crucible according to claim 1, wherein the inner layer crystallizes when heated. 13. A quartz glass crucible according to claim 12, wherein the inner layer crystallizes upon heating before contacting with the silicon charge. 14. A crucible has a wall including a bottom and a side wall, and a vitreous inner layer in which a crystallizing agent is distributed is formed in an inner portion of the crucible. A quartz glass crucible characterized by being delayed. 15. The quartz glass crucible according to claim 14, wherein the crystallizing agent is aluminum or titanium. 16. The quartz glass crucible according to claim 15, wherein titanium is distributed in the inner layer in the range of 50 to 130 ppm. 17. The quartz glass crucible according to claim 16, wherein titanium is distributed in the inner layer in the range of 70 to 130 ppm. 18. Aluminum of 50 to 150 pp in the inner layer
The silica glass crucible according to claim 15, wherein the silica glass crucible is distributed in the range of m. 19. The inner layer contains aluminum of 75 to 150 pp.
The quartz glass crucible according to claim 18, which is distributed in the range of m. 20. A silica powder is introduced into an inner surface of a rotating crucible to form a bulk powder layer having a bottom and side walls and defining an inner cavity, and a high temperature atmosphere is generated in the inner cavity. Then, a method for producing a quartz glass crucible for producing a silicon single crystal, which comprises introducing an internal powder and a crystallization agent into the high temperature atmosphere. 21. The production of a silica glass crucible for producing a silicon single crystal according to claim 20, wherein the crystallizing agent contains an element selected from the group consisting of barium, aluminum, titanium, strontium and mixtures thereof. Method. 22. The method for producing a quartz glass crucible for producing a silicon single crystal according to claim 21, wherein the crystallization agent is a compound which is converted into an oxide, a nitride or a halide in a high temperature atmosphere. 23. The method for producing a quartz glass crucible for producing a silicon single crystal according to claim 20, wherein the internal powder is natural or synthetic quartz. 24. The method for producing a silica glass crucible for producing a silicon single crystal according to claim 20, wherein the internal powder is a powder doped with a crystallization agent. 25. The method for producing a quartz glass crucible for producing a silicon single crystal according to claim 20, wherein the pure internal powder and the dope internal powder are simultaneously introduced into a high temperature atmosphere. 26. The method for producing a quartz glass crucible for producing a silicon single crystal according to claim 20, wherein the internal powder is a powder coated with a crystallization agent. 27. The internal powder is a mixture of a pure internal powder and a dope internal powder.
0. A method for producing a quartz glass crucible for producing a silicon single crystal according to 0. 28. The method for producing a quartz glass crucible for producing a silicon single crystal according to claim 20, wherein the crystallizing agent is introduced by spraying a liquid crystallizing agent. 29. A silica powder is introduced into an inner surface of a rotating crucible to form a bulk powder layer having a bottom, a side wall and defining an internal cavity, and then crystallized into the formed internal powder layer. A method for producing a quartz glass crucible for producing a silicon single crystal, which comprises applying a chemical agent, making the inside of the internal crucible cavity a high temperature atmosphere, and melting the internal powder layer together with the distributed crystallizing agent.