JP3625636B2 - Method for producing quartz glass crucible for pulling silicon single crystal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a silicon single crystal for pulling quartz Garasuru pot, more particularly, to a method of manufacturing a silicon single crystal pulling yield silicon single crystal for pulling quartz Garasurutsu board with improved.
[0002]
[Prior art]
A silicon single crystal used for a substrate of a semiconductor device is generally manufactured by the Czochralski method (CZ method). In this CZ method, a polycrystalline silicon raw material is loaded into a quartz glass crucible, and the loaded silicon raw material is used. The seed crystal heated and melted from the surroundings and suspended from above is brought into contact with the silicon melt and then pulled up.
[0003]
The quartz glass crucible used in the CZ method is required to have a high purity in the quartz glass crucible as the silicon single crystal is highly purified.
[0004]
The quartz glass crucible used in this CZ method is generally supplied into this mold while rotating a rotatable mold of quartz powder that has been crushed and purified, and the quartz powder is filled in a crucible around the mold by centrifugal force. At the same time, it is melted by an arc from the inside.
[0005]
However, the quartz glass crucible produced by this mold manufacturing method has a problem that many bubbles are contained in the quartz glass.
[0006]
On the other hand, when a single crystal is produced from polycrystalline silicon by the CZ method using such a quartz glass crucible containing bubbles, the crystallization becomes unstable due to the bubbles present in the quartz glass crucible and pulled up. In addition, dislocations were likely to occur in the silicon single crystal, causing a decrease in yield.
[0007]
The main reason is the mixing of spotted cristobalite into the melted silicon.
[0008]
That is, it is considered that the spotted cristobalite is formed in the quartz glass crucible by the following phenomenon.
[0009]
First, during the pulling of the silicon single crystal, the inner surface of the silicon crucible is eroded by the silicon melt, the bubbles are cleaved, and the inner surface of the crucible is roughened, and the fine protrusions generated by the roughening become the nucleus for crystallization of quartz glass. Spotted cristobalite is formed.
[0010]
Next, during the pulling of the single crystal, the precipitated impurities existing in the vicinity of the inner surface of the crucible promote the formation of cristobalite on the inner surface of the crucible to form the same spot-like cristobalite as described above.
[0011]
The cristobalite produced in this way has peeled from the crucible and mixed into the molten polycrystalline silicon, which has a problem of adversely affecting the growth of the pulled silicon single crystal.
[0012]
To solve this problem, the substrate of the silica was placed in a rotating mold for example, as described in JP fairness 4-22861, substantially bubble-free supply silica powder to the substrate inner surface There is a disclosure of a method for producing a quartz glass crucible in which a transparent quartz glass layer is formed into two layers.
[0013]
However, this method has a problem that the process is complicated and it is difficult to appropriately control the thickness of the bubble-free transparent quartz glass layer.
[0014]
In order to prevent impurities due to cristobalite from mixing into the molten silicon, a devitrification accelerator is attached to the inner surface of the quartz glass crucible, and the silica devitrified when the quartz glass crucible is heated to a high temperature. JP-A-9-110579 discloses a method for forming a layer and preventing crystalline silica particles from being mixed into molten silicon.
[0015]
However, since this method uses, for example, metal oxides or other oxides as devitrification accelerators, these oxides may melt into molten silicon, which may adversely affect single crystallization and silicon wafer characteristics, and may be reliable. There is also doubt about sex.
[0016]
Furthermore, in order to suppress the expansion of the bubbles in the quartz glass crucible and prevent the SiO ₂ debris from being mixed into the molten silicon due to the opening of the bubbles, the inner surface of the quartz glass crucible is heat-treated at a predetermined temperature for a long time. A method for producing a quartz glass crucible is disclosed in Japanese Patent Application Laid-Open No. 5-1224889. However, this method involves heating at a relatively high temperature for a long time, resulting in poor productivity and high production cost. There are problems.
[0017]
[Problems to be solved by the invention]
Therefore, there has been a demand for a method for producing a quartz glass crucible for pulling a silicon single crystal that has a high yield of pulling a silicon single crystal and is excellent in productivity.
[0018]
The present invention has been made in consideration of the above-described circumstances, and provides a method for producing a quartz glass crucible for pulling a silicon single crystal with less generation of cristobalite during pulling of the single crystal and improving the yield of pulling the silicon single crystal. For the purpose.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present invention provides a crucible molding die in which a melting chamber having an oxygen concentration of 21% or less is filled with quartz powder in a crucible shape and can be decompressed. Hold the mold for a predetermined time while depressurizing, and then start arc discharge while depressurizing the crucible molding die and flow a predetermined amount of reducing gas into the melting chamber for a predetermined time immediately after the start of the arc discharge, and then crucible molding die The gist of the present invention is to produce a quartz glass crucible for pulling up a silicon single crystal, which is characterized by melting in a reducing atmosphere by stopping the decompression of this and further performing arc discharge for a predetermined time in the stopped state.
[0020]
According to the second aspect of the present invention, the crucible molding die is held for a predetermined time while reducing the pressure, and further, the arc discharge is started while reducing the pressure of the crucible forming die, and at the same time, 50 to 300 liters / minute of hydrogen is generated immediately after the start of the arc discharge. the flow in the melter 5-15 minutes, then stopped decompression of crucible mold, by performing a further predetermined time arc discharge in this stop state, to claim 1, characterized in that melt in a reducing atmosphere The gist of the present invention is a method for producing a quartz glass crucible for pulling a silicon single crystal as described.
[0021]
The invention of claim 3 of the present application is characterized by melting in a reducing atmosphere by stopping the inflow of hydrogen at the same time as the depressurization of the crucible molding die is stopped, and further performing arc discharge for a predetermined time in this state. The gist of the method is a method for producing a quartz glass crucible for pulling a silicon single crystal described in 2 .
[0022]
According to the invention of claim 4 of the present application, a quartz glass crucible is placed in a processing furnace with its bottom facing up, the inside and outside of the quartz glass crucible are kept airtight, and a predetermined amount of inert gas is allowed to flow inside the quartz glass crucible. Reduce the concentration to 1% or less, raise the temperature in the processing furnace to a predetermined temperature, replace the inert gas with the reducing gas while maintaining this temperature, and maintain it for a predetermined time. The gist of the present invention is a method for producing a silica glass crucible for pulling a silicon single crystal, in which an inert gas is introduced and the temperature in the furnace is lowered to room temperature, whereby heat treatment is performed in a reducing atmosphere.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a method for producing a quartz glass crucible according to the present invention will be described below with reference to the accompanying drawings.
[0024]
FIG. 1 shows a quartz glass crucible 1 produced by the method for producing a quartz glass crucible according to the present invention. A layer 3 within 1 mm from the inner surface 2 of the quartz glass crucible 1 is an oxygen-deficient defect layer having an oxygen-deficiency defect of 20 to 150 ppm. It is formed as.
[0025]
A manufacturing apparatus used to manufacture such a quartz glass crucible 1 will be described with reference to FIG.
[0026]
A melting chamber 5 having a floor of 3 × 3 m and a height of 5 m, for example, is formed in the building by a partition wall 4. The melting chamber 5 is provided with an inlet 6 and an outlet 7 for atmospheric gas. In the melting chamber 5, a crucible manufacturing apparatus 8 is installed, and the crucible manufacturing apparatus 8 has a crucible forming mold 10 mounted on a turntable 9.
[0027]
The crucible molding die 10 is formed of a gas permeable member, for example, carbon, a carbon die 12 filled with quartz powder 11 in a crucible shape, and a gas ventilation path 13 provided on the outer periphery of the carbon die 12. The holding jacket 14 is made of SUS and is water-cooled.
[0028]
Above the crucible mold 10, for example, an arc electrode 15 is provided as a heat source facing the quartz powder 11 filled in a crucible shape.
[0029]
The gas ventilation path 13 is connected to a gas introduction path 19 provided in the center of a rotating shaft 18 driven by a motor 17 through an opening 16 provided in a lower portion of the holding jacket 14. 19 is connected to the vacuum pump 20.
[0030]
The holding jacket 14 is provided with a cooling passage 21 for water cooling, and the cooling passage 21 is connected to a water passage 22 provided at the center of the rotating shaft 18.
[0031]
The manufacturing apparatus used in the method for manufacturing a silica glass crucible according to the present invention has the above-described structure. Next, a method for manufacturing a silica glass crucible according to the present invention will be described.
[0032]
First, the motor 17 is energized to rotate the crucible molding die 10 via the rotating shaft 18 to rotate the carbon mold 12 and the holding jacket 14 constituting the crucible molding mold 10. 11 is filled in a crucible shape.
[0033]
Next, the crucible molding die 10 filled with quartz is transferred to the melting chamber 5. Then, an inert gas, such as nitrogen, is flowed from the inlet 6 into the melting chamber 5 for replacement, and the atmosphere in the melting chamber 5 is set to an oxygen concentration of 21% or less, for example, 1% or less.
[0034]
The inert gas includes nitrogen, and may be argon, helium, or a mixed gas of nitrogen and nitrogen in addition to nitrogen.
[0035]
Thereafter, the arc electrode 15 is energized, and the quartz powder 11 filled in a crucible shape is sequentially melted from the inside by heating by arc discharge. Immediately after the start of the arc, the vacuum pump 20 is operated and held in a reduced pressure state for a predetermined time, for example, 10 minutes.
[0036]
Immediately before the start of the arc discharge, a reducing gas such as hydrogen is allowed to flow into the melting chamber at 50 to 300 liters / minute, for example 150 liters / minute, and this state is continued for 5 to 15 minutes, for example, 10 minutes to reduce the melting chamber 3. Keep atmosphere, ie hydrogen atmosphere.
[0037]
After elapse of a predetermined time, for example, after 10 minutes, the decompression was stopped and the pressure was returned to the atmospheric pressure, and the inflow of hydrogen was stopped. In this state, arc discharge was maintained for a predetermined time, for example, 30 minutes, thereby producing a quartz glass crucible 1.
[0038]
In this manufacturing process, since layers other than the layer 3 of the crucible 1 are melted, it is not always necessary to send hydrogen to the melting chamber 5 to maintain a complete reducing atmosphere, but the supply of hydrogen may be stopped. , Hydrogen may be continuously supplied.
[0039]
The reducing gas may be carbon monoxide or a hydrocarbon gas such as methane.
[0040]
The crucible 1 manufactured by melting in a reducing atmosphere as described above has a thickness of 12 to 20 mm, and has a transparent layer portion of 3 to 7 mm on the inner side. When measured by a meter, strong absorption was observed at 245 nm, and the oxygen deficiency defect was about 120 ppm.
[0041]
Next, another embodiment of the method for producing a quartz glass crucible according to the present invention will be described.
[0042]
FIG. 3 is a schematic view showing an atmospheric treatment furnace used in another embodiment of the method for producing a quartz glass crucible according to the present invention. The treatment furnace 31 is provided with a main body 32 and a bottom portion of the main body 32 provided in the main body 32. A gas flow in a quartz tube crucible 38 and a gas supply tube 37 provided with a gate 34 fixed to 33, a gate valve 35, 36 for supplying inert gas, for example, nitrogen, and a reducing gas, for example, hydrogen, to the gas furnace 34. An exhaust pipe 39 for discharging is provided.
[0043]
A quartz ring 41 is provided at the outer periphery of the upper end portion 40 of the quartz glass crucible 38 placed on the furnace table 34 with the bottom face up, and an airtight space is provided between the quartz ring 41 and the upper end portion 40. A powder seal 42 is laid down.
[0044]
A through hole 43 provided in the bottom 33 and the furnace table 34 through which the air supply pipe 37 and the exhaust pipe 39 penetrate is sealed with a seal member 44 made of powder seal and quartz wool.
[0045]
Since the atmosphere treatment furnace used in another embodiment of the method for producing a silica glass crucible according to the present invention has the above-described structure, the above method for producing a silica glass crucible is used to produce the silica glass crucible. The same manufacturing process as that described above is performed.
[0046]
That is, for example, a 28-inch crucible molding die is filled with quartz powder in a crucible shape, and this crucible molding die is rotated and melted by arc discharge to produce a quartz glass crucible having an outer diameter of 28 inches.
[0047]
The upper end portion of the quartz glass crucible thus manufactured is cut out by a certain width, for example, 100 mm, and the parallelism of the upper end portion is made uniform.
[0048]
Thereafter, as shown in FIG. 3, the quartz glass crucible 38 is placed on the furnace table 34 with the bottom surface of the quartz glass crucible 38 facing up so that the air supply pipe 37 and the exhaust pipe 39 are located inside the quartz glass crucible 38. Then, a powder seal 42 is laid between the outside of the upper end portion 40 and the quartz ring 41 to keep the inside and outside of the quartz glass crucible 38 airtight.
[0049]
Thereafter, the temperature in the processing furnace 31 is set to 800 to 1200 ° C. while flowing a predetermined amount, for example, 0.5 m ³ / hour of an inert gas, for example, nitrogen into the quartz glass crucible 38 through the gate valve 35 and the air supply pipe 37. For example, the temperature is raised to 1100 ° C., the gate valve 35 is closed, and the gate valve 36 is opened, and a reducing gas instead of nitrogen, for example, hydrogen, is supplied through the air pipe 37 to a predetermined amount, for example, 0.5 cubic rice / hour. Hydrogen, which is a reducing gas, is continuously supplied for 0.5 to 10 hours, for example, 3 hours, and this state is maintained.
[0050]
Thereafter, the gate valve 36 is closed, the gate valve 35 is opened, the hydrogen is switched to nitrogen, and the temperature is lowered to room temperature while flowing nitrogen.
[0051]
The quartz glass crucible 1 manufactured by heat treatment in a reducing atmosphere as described above has a wall thickness of 12 to 20 mm, and has a transparent layer portion of 3 to 7 mm on the inner side. The transparent layer portion is visible. When measured with an ultraviolet spectrophotometer, strong absorption was observed at 245 nm, and it had a 100 ppm oxygen deficiency defect.
[0052]
The absorption wavelength of 245 nm indicates an oxygen deficiency defect in which O is removed from Si—O—Si, and this concentration is based on the Lamber-Beer law.
[Expression 1]
A = log I0 / I = kcd
The value of c (absorbing component concentration) can be calculated by the following equation.
[0053]
In the above formula, A is the absorbance, I0 is the intensity of the incident light, I is the intensity of the transmitted light, k is the extinction coefficient, and d is the thickness of the sample.
[0054]
【Example】
(1) Example 1 Using a quartz glass crucible having an outer diameter of 28 inches and an oxygen-deficient defect of 120 ppm, a silicon single crystal having a diameter of 300 mm, for example, was pulled using a cusp type MCZ single crystal pulling apparatus. . Even when the raw material polysilicon was used for about 100 hours with a 200 kg charge, no dislocation was observed, and a complete silicon single crystal was obtained.
[0055]
The inner surface of the quartz glass crucible after being used for pulling a single crystal maintained a glossy state as a whole, and the area where cristobalite was observed was about 20%.
[0056]
(2) Example 2 Using a quartz glass crucible manufactured according to another embodiment of the method for manufacturing a silica glass crucible according to the present invention, using a cusp type MCZ single crystal pulling apparatus, for example, a silicon single crystal having a diameter of 300 mm Was raised. Even when used for about 100 hours with a 200 kg polysilicon charge, no dislocations were observed, and a complete silicon single crystal was obtained.
[0057]
The inner surface of the quartz glass crucible after being used for pulling the single crystal maintained a glossy state as a whole, and the area where cristobalite was observed was 20%.
[0058]
(3) Comparative Example 1 Quartz powder is filled into a depressurizable rotary mold consisting of a carbon mold and a SUS water-cooled jacket, moved to a melting chamber in an atmospheric atmosphere, and melting is started by arc discharge. Hydrogen was introduced at 150 liters / minute.
[0059]
After 10 minutes, the decompression and hydrogen inflow were stopped, and the arc was maintained for 20 minutes to melt, producing a quartz crucible with an outer diameter of 28 inches.
[0060]
This crucible had a wall thickness of 12 to 20 mm and had a transparent layer of 3 to 7 mm on the inner surface side. When the transparent layer portion was measured with a visible / ultraviolet spectrophotometer, weak absorption was observed at 245 nm and it had a 20 ppm oxygen deficiency defect.
[0061]
Using this crucible, single crystal pulling was performed by a cusp type MCZ pulling apparatus.
[0062]
Using a polysilicon 200 kg charge for about 100 hours, a single crystal having a diameter of 300 mm was pulled up. Dislocation occurred in the pulled tail portion, and the single crystallization rate was 80%. The inner surface of the quartz glass crucible after use for pulling was conspicuous on the entire surface, and the area where cristobalite was observed was about 70%.
[0063]
(4) Comparative Example 2 Quartz powder is filled into a depressurizable rotary mold composed of a carbon mold and a SUS water-cooled jacket, and the mold is moved to a melting chamber substituted with an oxygen concentration of 1% or less by nitrogen flow, while depressurizing. Hold for 10 minutes. After that, melting was started by arc discharge, and when hydrogen was flowed in at 300 liters / min immediately after the start of the arc, SiO ₂ vapor was vigorously generated, and the arc was frequently interrupted due to adhesion to the electrodes. After 10 minutes, the decompression and hydrogen inflow were stopped, and the arc was maintained for 20 minutes to melt, producing a quartz crucible with an outer diameter of 28 inches.
[0064]
On the inner surface of this crucible, many defects due to the fall of the paper from the electrodes were observed. Moreover, the transparent layer part had a 200 ppm oxygen deficiency defect.
[0065]
【The invention's effect】
Is According to the method for manufacturing a silica glass crucible according to the present invention as described above, generates less cristobalite in the single crystal pulling, thus improving the yield of silicon single crystal without generating dislocations of the single crystal the possible quartz Garasuru pot can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a quartz glass crucible manufactured by a method for manufacturing a silica glass crucible according to the present invention.
FIG. 2 is a conceptual diagram of a production apparatus used in a method for producing a quartz glass crucible according to the present invention.
FIG. 3 is a conceptual diagram of a manufacturing apparatus used in another embodiment of a method for manufacturing a quartz glass crucible according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Quartz glass crucible 2 Inner surface 3 Layer 4 Partition 5 Melting chamber 6 Inlet 7 Outlet 8 Crucible manufacturing apparatus 9 Turntable 10 Crucible molding die 11 Quartz powder 12 Carbon die 13 Air passage 14 Holding jacket 15 Arc electrode 16 Opening 17 Motor 18 Rotating shaft 19 Gas introduction path 20 Vacuum pump 21 Cooling path 22 Water path 31 Processing furnace 32 Main body 33 Bottom 34 Furnace 35 Gate valve 36 Gate valve 37 Air supply pipe 38 Quartz glass crucible 39 Exhaust pipe 40 Upper end 41 Quartz ring 42 Powder Seal 43 Through hole 44 Seal member

Claims (4)

Prepare a crucible molding die that can be decompressed by filling the melting chamber with an oxygen concentration of 21% or less in a crucible shape, hold the crucible molding die for a predetermined time while reducing the pressure, and further reduce the pressure of the crucible molding die. While starting the arc discharge, a predetermined amount of reducing gas is allowed to flow into the melting chamber for a predetermined time immediately after the start of the arc discharge, and then the pressure reduction of the crucible molding die is stopped, and arc discharge is further performed for a predetermined time in this stopped state. it allows the method for manufacturing a silicon single crystal for pulling up the quartz glass crucible, wherein soluble Torusu Rukoto in a reducing atmosphere. Holding the crucible molding die for a predetermined time while reducing the pressure, starting arc discharge while reducing the pressure of the crucible molding die, and adding 50 to 300 liters / minute of hydrogen to the melting chamber for 5 to 15 minutes immediately after the start of the arc discharge. flow, then the pressure reduction of the crucible mold was stopped, by performing a further predetermined time arc discharge in this stop state, a silicon single crystal for pulling quartz according to claim 1, characterized in that melt in a reducing atmosphere A method for producing a glass crucible. 3. The silicon single crystal pulling according to claim 2 , wherein the melting of the crucible molding die is stopped while the inflow of hydrogen is stopped and arc discharge is further performed in this state for a predetermined time to melt in a reducing atmosphere. Of manufacturing quartz glass crucibles for use. Place the quartz glass crucible in the processing furnace with its bottom facing up, keep the inside and outside of the quartz glass crucible airtight, flow a predetermined amount of inert gas inside the quartz glass crucible to reduce the oxygen concentration to 1% or less, and process The temperature inside the furnace is raised to a predetermined temperature, and while maintaining this temperature, the inert gas is replaced with a reducing gas and maintained for a predetermined time, and after this time has passed, the inert gas is again flowed into the processing furnace. A method for producing a quartz glass crucible for pulling a silicon single crystal, which is heat- treated in a reducing atmosphere by lowering the temperature to room temperature.

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