JPH04219386A - Apparatus for production of silicon single crystal - Google Patents

Abstract

PURPOSE:To provide the subject apparatus for production of a silicon single crystal. CONSTITUTION:An apparatus for production of a silicon single crystal 5 by Czochralski method, equipped with a fusion crucible 1 divided into a unit (C) for fusing a row material and a unit (D) for growth of the single crystal by a partition member 8 and with a heat-insulating cover 10 made of a metal plate and a thermoshielding member 12 made of a metal plate respectively covering the above-mentioned partition member 8. Both the heat-insulating cover and the thermoshielding member constitute a gas-circulating opening 21 for circulating an ambient gas and located at a position higher than an electrical resistance heater 3. There is no danger of generation of a coagulation at the partition member and SiO particles generated in an oven can be reduced. Thus the silicon single crystal can be stably produced over a long period.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing large diameter silicon single crystals using the Czochralski method.

0002

BACKGROUND OF THE INVENTION The diameter required for silicon single crystals tends to increase year by year. Today, cutting-edge devices use silicon single crystals that are 6 inches in diameter. It is said that silicon single crystals with a diameter of 10 inches or more will be needed in the future.

Silicon single crystals used in the LSI field are usually manufactured using the Czochralski method (Czochralski method), in which a seed crystal is soaked in a silicon melt in a rotating quartz crucible and then gradually pulled up while rotating. In this CZ method, the silicon melt in the crucible decreases as the silicon single crystal grows. Therefore, as the silicon single crystal grows, the dopant concentration in the silicon single crystal increases and the oxygen concentration decreases. That is, the properties of the silicon single crystal vary in the direction of its growth. This problem must be solved because the quality required of silicon single crystals is becoming stricter year by year as the density of LSIs increases.

As a means to solve this problem, the inside of the quartz crucible for the CZ method is partitioned with a cylindrical quartz partition member having small holes for the silicon melt, and the raw material silicon is placed outside of this partition member (raw material melting part). A method of growing a cylindrical silicon single crystal inside a partition member (single crystal growth section) while supplying the silicon has been known for a long time (for example,
- Publication No. 10184, Detailed Description of the Invention, lines 13 to 28). The problem with this method is that
As pointed out in Publication No. 1889 (page 2, problems to be solved by the invention, lines 12 to 16),
The silicon melt tends to solidify inside the partition member starting from the partition member. That is, solidification occurs from the surface of the silicon melt in the crystal growth section and the portion that is in contact with the partition member. This solidification grows toward the center of the crucible where the temperature is lower and inhibits the growth of silicon single crystals. The reason for this is that the transparent quartz glass normally used as a partition member is easily penetrated by hot rays, and in normal cases, the part exposed above the silicon melt surface at the top of the partition member is exposed to the water-cooled furnace wall. Since the heat radiation is large, the heat in the silicon melt is transmitted upward through the partition member and is radiated from the portion of the partition member exposed above the silicon melt surface. Therefore, the temperature of the molten liquid is greatly reduced near the partition member. Furthermore, due to strong stirring of the melt, the surface temperature of the melt is uniform and just above the solidification temperature. In this way, the surface of the molten liquid in contact with the partition member is in a state where solidification is very likely to occur. In order to solve this problem, the above-mentioned Japanese Patent Laid-Open No. 62-241889 proposes a method that does not use a partition member. However, this method has a narrow raw material melting zone, so it is especially difficult to manufacture silicon crystals with a large diameter.
It is difficult to melt enough raw material silicon to pull the silicon single crystal.

Recently, it has become possible to produce high-quality granular silicon, and it is considered relatively easy to continuously supply this granular silicon as raw material silicon into a silicon melt. However, if sufficient melting heat is not applied to the granular silicon when the granular silicon is supplied to the surface of the silicon melt, there is a possibility that the granular silicon remains undissolved. It is not rare for the undissolved particulate silicon to solidify and expand. This is due to the difference in specific gravity between the melt and the granular silicon.
This is because the solid granular silicon floats on the surface of the molten liquid, and because the solid has a higher emissivity than the silicon molten liquid, heat is easily removed. In particular, when granular silicon adheres to and aggregates on the partition member at the surface of the silicon melt in the raw material melting zone, heat is rapidly removed through the partition member, as in the case of solidification in the crystal growth zone, resulting in solidification. The occurrence and spread of this disease is likely to occur. This problem does not essentially change even if the raw material silicon to be supplied is in a form other than granular. Regarding this problem, Japanese Patent Application Laid-Open No. 61-36197
In the method disclosed in the publication, a "thermal insulation cover" (Claim 6) is disposed over the raw material melting section to promote rapid melting of the granular silicon.

[0006] Japanese Patent Application Laid-Open No. 1999-1992 proposes a method of using a partition member and preventing the occurrence of coagulation therefrom.
There is a publication No.-153589. This invention proposes to completely cover the partition member with a heat retaining cover. By this method, dissipation of heat from the partition member can be prevented, and therefore the occurrence of coagulation can be prevented. Furthermore, it has sufficient ability to dissolve the supplied raw material silicon. However, it has been found that this invention is insufficient for stable growth of silicon single crystals.

[0007] After various studies, the inventors found that
The reason why silicon single crystals cannot be stably grown using the method disclosed in Publication No. 1-153589 is that the atmospheric gas in the furnace (
It turned out that this was due to an inappropriate flow of argon gas. This will be explained in detail using FIG. 11. Unexamined Patent Publication 1-15
In the method shown in No. 3589, since the heat insulating cover 10 is installed, the flow of atmospheric gas becomes as shown in B in FIG. That is, most of the atmospheric gas introduced into the furnace in the pulling chamber 15 is distributed between the lower end of the heat insulating cover 10 and the liquid surface 18 of the silicon melt 7, and between the heat insulating cover 10 and the partition member 8.
The gap, then the gap formed at the upper end of the quartz crucible 1 and the graphite crucible 2, and then the electric resistance heating element 3.
and the graphite crucible 2, or between the electric resistance heating element 3 and the heat insulating material 6, and is discharged from the bottom of the furnace. Since the atmospheric gas is at approximately room temperature, when passing near the silicon melt surface, it mixes with SiO vapor evaporated from the silicon melt surface and cools it. As a result, SiO fine particles are generated near the surface of the silicon melt. These fine particles aggregate and fall onto the surface of the silicon melt, and adhere to the solidification interface of the silicon single crystal 5. This causes dislocations and collapses the silicon single crystal. When the pressure inside the furnace is atmospheric pressure (1 atm), even if some SiO fine particles are generated, there is little possibility that they will fall. This is because the SiO fine particles are discharged along with the strong flow of atmospheric gas. However, in a furnace such as the present invention, which is designed to grow large-diameter silicon single crystals over a long period of time, in order to reduce the adhesion of SiO fine particles to the inner wall of the furnace, it is necessary to In order to prevent the generated carbon from being mixed into the silicon single crystal, the pressure inside the furnace is reduced to 0.01 to 0.1 atm. Therefore, the generated SiO fine particles are very likely to fall.

On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. 61-36197, a "thermal insulation cover" is provided to cover the raw material melting section, but this prevents solidification from occurring from inside the partition member. No countermeasures have been taken to prevent this, and it is difficult to put it into practical use.

The present invention has been made in view of the above circumstances, and it is possible to prevent the occurrence of solidification from the partition member, and to reduce the fall of SiO particles in the atmosphere onto the surface of the silicon melt. An object of the present invention is to provide a silicon single crystal manufacturing device that can stably grow silicon single crystals over a long period of time.

0010

[Means for Solving the Problems] In order to achieve the above object, the silicon single crystal production apparatus of the present invention includes a quartz crucible containing a silicon melt, and an electric resistance heating element that heats the quartz crucible from the side. a quartz partition member that divides the silicon melt into a single crystal growth section and a raw material melting section in the quartz crucible and has a small hole through which the silicon melt can flow; Silicon single crystal manufacturing comprising: a heat insulating cover having an opening at the top; a raw material supply device that continuously supplies raw silicon to the raw material melting section; and a pressure reducing device that reduces the pressure in the furnace to 0.1 atmosphere or less. In the apparatus, a heat shielding member made of an opening of the heat insulating cover and a metal plate is provided at a position higher than the upper end of the heating body, and a cross-sectional area of a gas flow opening formed by the heat shielding member and the heat insulating cover is The heat shielding member is provided above or below the opening so as to be larger than the gap formed between the lower end of the heat insulating cover and the surface of the silicon melt.

The heat shielding member is provided above or below the opening of the heat insulating cover, and the opening formed by the heat shielding member and the heat insulating cover opens toward the center of the furnace. As a result, most of the gas flow within the furnace is discharged from the bottom of the furnace without passing near the liquid level. Furthermore, in order to further suppress disturbances in the gas flow within the furnace, it is preferable that the heat shielding member is composed of a plurality of metal plates that are parallel to each other at the opening.

[0012] The gas flow ports are provided in a circular arc shape opening toward the center of the furnace, the number of which corresponds to the openings of the heat insulating cover. The width of the gas flow port is preferably 2 to 8 cm, taking into consideration the internal configuration of the furnace and practicality.

[0013]

[Operation] Most of the atmospheric gas flows from the upper part of the furnace through the opening, passes between the silicon crucible and the furnace wall (19), flows toward the bottom of the furnace, and is discharged outside the furnace. Neighborhood flow is almost non-existent with the method of the invention. In order to achieve this flow, it is desirable that the height of the opening of the heat insulating material be as high as possible, at least above the upper end of the electrical resistance heating element. Further, from the viewpoint of gas flow, the larger the opening, the better. However, the presence of a large opening is not desirable for the original purpose of the heat retaining cover 10. In other words, there is a risk that the purpose of the heat insulating cover to prevent solidification from the partition member will be lost, and in particular, if the opening is located above the raw material melting section, the supplied raw material silicon will not be able to melt quickly. , there is a possibility that it will eventually accumulate on the outside of the partition member while remaining in a solid state. If there is an opening, the silicon melt surface will face the water-cooled furnace wall 19 above the furnace, and this phenomenon is extremely likely to occur. In particular, if the silicon single crystal to be grown becomes larger in diameter or the pulling speed of the silicon single crystal increases, the amount of silicon single crystal pulled increases, and it becomes necessary to supply a commensurate amount of raw silicon. , this issue becomes extremely important.

Therefore, in the present invention, a heat shielding member is provided above or below the opening 11. This heat shielding member is shaped so as not to obstruct the flow of atmospheric gas. thus,
By ensuring the size of the opening necessary for gas flow and further adding a heat shielding member to cover the opening, the original purpose of the heat insulating cover can be satisfied.

[0015] The present invention is characterized in that the heat shielding member is made of a metal plate. The reason for this is as follows. Graphite, which is commonly used as a material for the internal components of silicon single-crystal furnaces, has a high emissivity, so it has a small heat shielding effect, and in some cases, it may actually promote heat dissipation from the surface of the silicon melt. There is a possibility that it will go away. Since the metal plate has a low emissivity, it has a large heat shielding effect and is well suited for the purpose of use as a heat shield member.

Furthermore, the present invention is characterized in that the heat insulating cover is made of a metal plate. The reason for this is that although various materials such as graphite and ceramics can be considered for the heat insulating cover, metal has a greater heat insulating effect. Even if the heat shielding member is provided, it is impossible to avoid a decrease in the heat retaining effect of the heat retaining cover due to the provision of the opening. By constructing the heat retaining cover from metal, this decrease in the heat retaining effect can be minimized as much as possible. As a result, even when pulling a large-diameter silicon single crystal at high speed, stable pulling operation is possible without solidification from the partition member or undissolved raw material remaining in the raw material melting section.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a vertical cross-sectional view schematically showing the silicon single crystal manufacturing apparatus of this example. In the figure, 1
is a quartz crucible (20 inches in diameter) supported by a graphite crucible 2, which is supported on a pedestal 4 by a rotatable mechanism. 7 is a silicon melt placed in the crucible 1, from which a silicon single crystal 5 grown in a cylindrical shape is pulled. In this example,
The diameter of the silicon single crystal is 6 inches, and the average pulling speed is 1.6 mm per minute. 3 is an electric resistance heating element surrounding the graphite crucible 2; 6 is a heat insulating material surrounding the electric resistance heating element 3; all of these are housed in a chamber surrounded by a furnace wall 13. Atmospheric gas (argon gas) is introduced into the furnace from a gas inlet (not shown) provided above the pulling chamber 15, and is introduced into the furnace through an exhaust port 1 located at the bottom of the furnace.
4 is discharged by a pressure reducing device 20. The pressure inside the furnace is 0
．． The pressure is 0.03 atm.

8 is made of high-purity quartz glass, and crucible 1
It is a partition member provided concentrically with the crucible 1 inside. A small hole 9 is bored in this partition member 8, and the silicon melt in the raw material melting section C (outside the partition member 8) passes through the small hole 9 into the single crystal growth section D (inside the partition member 8). flows into. The upper edge of this partition member 8 is exposed above the liquid level of the silicon melt 7, and the lower edge is either fused to the quartz crucible 1 in advance or made by melting the raw material silicon in the initial stage. They are fused together by the heat generated when the melt 7 is created. Particulate silicon is continuously supplied to the raw material melting section C from a raw material supply chamber 16 via a cutting device (not shown) and guided to a raw material supply pipe 17 . The supply amount is constant at approximately 70 g per minute, which is equal to the amount of silicon single crystal pulled from the single crystal growth section D.

[0019] 10 is a heat insulating cover, and the plate thickness is 0.2 mm.
It is made of tantalum plate. 11 is the thermal cover 10
As shown in FIG. 4, there are four openings in the upper part of the heat retaining cover, and approximately 80% of the entire circumference of the heat retaining cover corresponds to the openings 11. As shown in FIG. 5, above these openings 11, except for the introduction position of the raw material supply pipe 17, a heat shielding member 12 made of a tantalum plate is placed, and a heat insulation cover 10 is placed on the outer peripheral side. The space between the heat shielding member 12 and the heat shielding member 12 is almost closed, but there is a width of 5 cm in the height direction on the inner circumferential side. The area of the passage port 21 for the furnace atmosphere gas thus formed is sufficiently larger than the area of the entire circumference of the gap 18 between the lower end of the heat insulating cover 10 and the surface of the silicon melt in the single crystal growth section D.
Most of the atmospheric gas follows the flow path A shown in FIG. FIG. 8 is a partial diagram of the silicon single crystal production apparatus shown in FIG. 1 divided by a center line, and shows the flow of atmospheric gas.

Note that FIG. 9 corresponds to FIGS. 2 and 3, which will be described later.
, FIG. 10 also shows a partial view separated by the center line.

As schematically shown in FIG. 8, the atmospheric gas flows downward from the pulling chamber 15 located at the center and upper part of the furnace, and spreads toward the periphery in the space above the furnace to maintain heat. Since the gas is sucked from the opening 11 of the cover 10 toward the bottom of the furnace, in order not to disturb this gas flow, the distance between the heat insulating cover 10 and the heat shielding member 12 is set at least 2 cm or more and 8 cm or less on the inner peripheral side of the furnace of the heat insulating cover 10. Separate them to ensure a gas flow path. From the viewpoint of ensuring a gas flow path, the wider the distance between the heat retaining cover 10 and the heat shielding member 12, the better. However, it is not practically preferable to make the width significantly wider than the width of the opening 11.

If the heat shielding member 12 is not used, granular silicon remains undissolved or solidified in the raw material melting section C during silicon single crystal pulling, and granular silicon often cannot be supplied and the silicon single crystal is Although this was a major impediment to growth, by using the heat shielding member 12, this phenomenon no longer occurs.

Although there are four openings in this embodiment, there is no particular restriction on the number of openings. However, in order to stabilize the growth of silicon single crystals, it is desirable to improve the symmetry of the thermal environment within the furnace, and from this point of view, it is more desirable to have two or more locations than one location.

FIG. 2 is a vertical cross-sectional view of a silicon single crystal manufacturing apparatus schematically showing another embodiment. The explanation of the drawings is the same as that of FIG. 1 above. However, the differences from Figure 1 are as follows.
The rest is the same as in FIG. 1 except that the heat shielding member 12 is installed below the opening 11 of the heat insulating cover 12 and is suspended from the opening 11. Thermal cover 1 in this case
0 is as shown in FIG. 4, and a perspective view of the heat shielding member 12 is as shown in FIG. The flow path of the atmospheric gas follows the flow path A as shown in FIG.

FIG. 3 is a longitudinal sectional view of a silicon single crystal manufacturing apparatus schematically showing another embodiment of the present invention. The explanation of the drawings is the same as in the case of FIG. 1 above. However, the difference from FIG. 1 is that the heat shielding member 12 is composed of metal plates parallel to each other, and the other points are the same as FIG. 1. The heat retaining cover 10 in this case is as shown in FIG. 4, and a perspective view of the heat shielding member 12 is as shown in FIG. The flow path of the atmospheric gas follows the flow path A as shown in FIG. In this case, the gas flow path is divided into a plurality of flow paths at the gas flow port 21, and turbulence in the gas flow is reduced. Although FIG. 7 of this embodiment shows a case where the heat shielding member 12 is placed on the heat retaining cover 10, it is also possible to provide the heat shielding member 12 under the heat retaining cover.

Next, the reason why the width of the opening formed by the heat insulating cover 10 and the heat shielding member 12 is specified to be 2 cm or more and 8 cm or less will be described below.

It is assumed that only a small amount of atmospheric gas passes through the gap (flow path B) formed between the lower end of the heat-insulating cover 10 and the surface of the silicon melt, and most of the atmospheric gas is as shown in FIGS.
Or in order to pass through the flow path A shown in FIG.
The area of the gap through which the gas passes in the flow path A must be larger than the area of the gap through which the gas passes through the flow path B. Since the lower end of the heat insulating cover 10 is normally located 1.5 to 2 cm above the silicon melt level, even if the opening 11 is formed around the entire circumference of the heat insulating cover 10, this can be used as a flow path for atmospheric gas. A gap of at least 2 cm must be secured. Upper limit 8cm
This was done with practicality in mind.

With the silicon single crystal production apparatus of this embodiment as described above, the flow of low-temperature gas directly above the silicon melt surface is almost eliminated, and the generation of SiO fine particles and the flow to the silicon melt surface in the single crystal growth area are prevented. The falling of SiO fine particles was suppressed, and the collapse of the silicon single crystal was significantly reduced. Furthermore, due to the improved heat shielding effect, solidification from the partition member on the surface of the silicon melt does not occur, and the raw material silicon to be supplied can now be stably melted. As a result, silicon single crystals with a large diameter of 5 inches or more can be pulled at a speed of approximately 1.6 m/min while supplying raw silicon in an amount commensurate with the amount of silicon single crystal pulled.
Stable production is now possible with high-speed pulling of m.

[0029]

Effects of the Invention According to the silicon single crystal manufacturing apparatus of the present invention, the communication port through which atmospheric gas flows is constituted by a heat insulating cover made of a metal plate and a heat shielding member, and the cross-sectional area of the communication port is ,
Since the cross-sectional area is larger than the cross-sectional area of the flow path passing above the surface of the silicon melt, it is possible to stably grow a silicon single crystal over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a silicon single crystal manufacturing apparatus of this embodiment.

FIG. 2 is a longitudinal sectional view showing a silicon single crystal manufacturing apparatus of a different embodiment.

FIG. 3 is a longitudinal sectional view showing a silicon single crystal manufacturing apparatus according to yet another embodiment.

FIG. 4 is a perspective view of the heat retaining cover of this embodiment.

5 is a perspective view of the heat insulation cover opening and the heat shielding member shown in FIG. 1. FIG.

6 is a perspective view of the heat insulation cover opening and the heat shielding member shown in FIG. 2. FIG.

7 is a perspective view of the heat insulation cover opening and the heat shielding member shown in FIG. 3. FIG.

FIG. 8 is a schematic diagram of gas flow in the embodiment of FIG. 1;

FIG. 9 is a schematic diagram of gas flow in the embodiment of FIG. 2;

FIG. 10 is a schematic diagram of gas flow in the embodiment of FIG. 3;

FIG. 11 is a schematic diagram of gas flow in the prior art.

[Explanation of symbols]

1 Quartz crucible 2 Graphite crucible 3 Electric resistance heating element 4 Pedestal 5 Silicon single crystal 6 Heat insulating material 7 Silicon melt 8 Partition member 9 Small hole 10 Heat insulation cover 11 Heat insulation cover opening 12 Heat shielding member 13 Furnace wall 14 Atmospheric gas outlet 15 Pulling chamber 16 Raw material supply chamber 17 Raw material supply pipe 18 Gap between the lower end of the insulation cover and the surface of the silicon melt 20 Pressure reducing device 21 Flow port A Gas flow of atmospheric gas through the opening of the insulation cover B Lower end of the insulation cover Gas flow of atmospheric gas C through the gap between silicon melt surface and raw material melting section D Single crystal growth section

Claims (5)

[Claims] 1. A quartz crucible (1) containing a silicon melt (7), an electric resistance heating element (3) for heating the quartz crucible from the side, and a device for growing a single crystal of the silicon melt in the quartz crucible. A partition member (8) made of quartz that is divided into a part (D) and a raw material melting part (C) and has a small hole (9) through which the silicon melt can flow; A heat insulating cover (10) having an opening (11) at the top, a raw material supply device that continuously supplies raw silicon to the raw material melting section, and a pressure reducing device (20) that reduces the pressure in the furnace to 0.1 atmosphere or less. In the silicon single crystal manufacturing apparatus, a heat shielding member (12) consisting of an opening of the heat insulating cover and a metal plate is provided at a position higher than the upper end of the heating body, and the heat shielding member and the heat insulating cover are formed. The heat shielding member is placed above the opening so that the area of the gas flow opening (21) is larger than the gap (18) formed between the lower end of the heat insulating cover and the surface of the silicon melt. Or a silicon single crystal manufacturing device characterized by being provided below. 2. The silicon single crystal manufacturing apparatus according to claim 1, wherein the heat shielding member is installed above an opening of the heat insulating cover and placed on the heat insulating cover. 3. The silicon single crystal manufacturing apparatus according to claim 1, wherein the heat shielding member is installed below an opening of the heat insulating cover so as to be suspended from the opening. . 4. An opening formed by the heat shielding member and the heat retaining cover is provided in an arc shape opening toward the center of the furnace, and the width of the opening is 2 to 8 cm. The silicon single crystal manufacturing apparatus according to any one of claims 1, 2, and 3. 5. The silicon single crystal manufacturing apparatus according to claim 4, wherein the heat shielding member is composed of a plurality of metal plates parallel to each other at the opening.