WO2008128378A1

WO2008128378A1 - Vertical pulling and zone melting method for producing monocrystalline silicon

Info

Publication number: WO2008128378A1
Application number: PCT/CN2007/001288
Authority: WO
Inventors: Haoping Shen; Yutian Wang; Xiang Li; Xingli Zan; Shuliang Gao; Yuanqing Hu; Weigang Liu; Ju'an Wang; Fulin Gao; Huanxin Zhang
Original assignee: Tianjin Huanou Semiconductor Material And Technology Co., Ltd.
Priority date: 2007-04-19
Filing date: 2007-04-19
Publication date: 2008-10-30

Abstract

A vertical pulling and zone melting method for producing mono-crystalline silicon is disclosed, which includes a vertical pulling process and a zone melting process successively. The vertical pulling process includes: feeding material to the silica crucible in a vertical pulling furnace before vacuum pumping and charging argon; heating to melt material and welding seed crystal by dropping the seed crystal after inducting the cooling water; pulling thin neck; making the shoulder larger; equi-dimensional growth; lowering the pulling speed and tailing; stopping heating and taking the crystal rod out of the furnace; shaping, scavenging and corroding the crystal rod. The zone melting process includes feeding the rod and seed crystal into zone melting furnace before vacuum pumping and charging gas; preheating the crystal rod ; welding it with seed crystal; pulling thin neck; making the shoulder larger and equi-dimensional growing; holding the crystal and clamper to clip the crystal; tailing; slowly cooling and shutting down the furnace. The method of the present invention for producing mono-crystalline silicon can overcome the defects of higher oxygen concentration due to vertical pulling process and difficulty in doping special solid elements in mono-crystalline silicon. It decreases the cost and period of producing mono-crystalline silicon by zone melting process, and also solves the problem of short of polycrystal material in producing mono-crystalline silicon by zone melting process.

Description

Straight-drawing zone melting method for producing silicon single crystals

The invention relates to a method for producing a silicon single crystal, in particular to a defect that overcomes the high oxygen content in the silicon single crystal produced by the Czochralski method, and overcomes the fact that the zone melting method cannot produce a silicon single that is miserable into a special solid element. Crystalline defects, and reduced production costs, increased production efficiency of the straight-pull zone melting method for producing silicon single crystals. Background technique

At present, almost all silicon single crystals are produced by the Czochralski method or the zone melting method. However, in the silicon single crystal produced by the Czochralski method, the oxygen content is as high as 10 ¹⁸ atm / cm ³ , and the resistivity thermal instability and reversibility caused by oxygen formation cause the Czochralski silicon single crystal in the power helmet The limitations and difficulties in the manufacturing process; while the silicon single crystal produced by the zone melting method can reduce the oxygen content, the silicon single crystal production cost is high, it is difficult to have a low resistivity ratio, the radiation resistance is poor, and it cannot be incorporated into other places. The special solid elements required, therefore, also limit the wide application of silicon single crystals in the field of production devices. In science and technology, silicon single crystals used in devices such as silicon physical detectors and radiation-resistant reinforcements are required to have a low oxygen content (l X l0 ¹⁶ atm / _C m ) thermal stability, while incorporating a special solid state. The silicon single crystal of the element, however, the silicon single crystal produced by the zone melting method cannot be doped with other impurities due to the process limitation, and is generally sent to the neutron reactor after drawing the intrinsic single crystal, and the heat (slow) neutron flow is radiated. The purpose of preparing the N-type silicon single crystal by the phosgene can be achieved. However, this method has a long production cycle and a low production cost, and only an N-type silicon single crystal can be prepared. Summary of the invention

The invention provides a solution to overcome the technical problems existing in the prior art, that is, to overcome the defects of high oxygen content in the silicon single crystal produced by the Czochralski method, and overcome the problem that the zone melting method cannot produce silicon single crystals which are plagued into special solid elements. Defects, and: a reduced production costs, increased production efficiency of the straight-pull zone melting method for producing silicon single crystals. '

The technical scheme adopted by the invention is: A straight pull zone 瑢 method for producing a silicon single crystal, which is completed by two processes of a straight pull process using a straight pull furnace and a zone melting process of a crucible zone furnace.

First, the straight pull process is performed, including the following steps:

(1) The corrosion-cleaned bulk silicon raw material is placed in a quartz crucible in a straight pull furnace, and then vacuumed and filled with argon gas;

(2) Passing the cooling water before heating, starting the rotating mechanism, starting the heating button, melting all the bulk silicon raw materials, starting the seed crystal rotating mechanism, and lowering the seed crystal welding seed crystal;

(3) Adjust the twinning stroke to zero position, rotate the crystal lift potentiometer, and pull the neck;

(4) Decrease the seed crystal speed, open the crystal lift switch button, expand the crystal pulling diameter, and use the diameter controller to control the pulling speed to carry the shoulder;

(5) Adjusting the diameter sensor to control the pulling speed to perform equal-diameter pulling;

(6) Lower the crystal pulling speed to finish the tail; (7) Increase the crystal to leave the liquid surface, stop heating, turn the 埚 turn, crystal lift, crystal turn potentiometer all to zero, cut off the power supply, stop argon gas after half an hour, stop the water after four hours, close the line valve switch, stop The main vacuum pump is evacuated and the ingot is released;

(8) performing ingot processing, cleaning and etching on one of the discharged polycrystalline silicon rods and single crystal silicon rods to prepare single crystal growth on the zone melting furnace;

Then, performing the zone melting process, including the following steps:

(1) cleaning the furnace, installing the furnace, adjusting the furnace device, installing one of the polycrystalline silicon rod and the single crystal silicon rod to the end of the upper shaft of the furnace, aligning the crystal material, and mounting the seed crystal to the lower shaft Top, close each door;

(2) vacuuming and inflating the furnace chamber, and preheating one of the polysilicon bar and the single crystal silicon bar;

(3) smelting and seeding the seed crystal and the molten silicon;

(4) growing a thin neck;

(5) Carrying out the shoulder extension;

(6) turning the shoulder, keeping the single crystal and the holder released to clamp the single crystal;

(7) Finishing, slowly cooling the crystal, and stopping the furnace.

The vacuum pumping and argon charging of the straight pull furnace is performed by charging argon gas to a vacuum pressure of 20 Torr after evacuating to a pressure of 100 mTorr to start heating.

The diameter of the neck of one of the polycrystalline silicon rod and the single crystal silicon rod pulled out by the straight pull furnace is 3 to 10 mm, the length is 10 to 200 mm, and the diameter after the shoulder is 50 to 300 mm.

The sinter gas is pressurized to a pressure of less than 0. 5mbr when the pressure is less than 0. 5mbr, argon gas, pressure to 1. Preheat at 2-6 bar, preheating set point 25~40%, preheating time is 10~20 minutes.

The material in the zone furnace is welded, the seed crystal and the molten silicon are welded and seeded, and is transferred to the voltage file during the chemical conversion, the generator set point is 40 to 60%, and, in the seed crystal and the molten silicon After the welding, the melting zone is shaped.

The thin neck is grown in the zone furnace, and after the end of the seeding, the neck is grown. The diameter of the drawn single crystal of the silicon single crystal is 2 to 6 emp., and the length is about 30 to 60 mm.

Said shoulder comprises expansion, the speed is slowly reduced to 3 ± 2mm / mi _n, while expanding gradually reduced with the increase of the diameter of the shoulder go 8 ± 6rpm, while also slowly reduced on Go 1 ± 0 . 8rpm.

The rotating shoulder, the holding single crystal and the holder release the single crystal, and the shoulder is rotated when the diameter of the shoulder is different from the single crystal holding diameter by 3 to 20, until the set diameter is maintained, the single crystal is maintained, etc. Keep the diameter at 50im! ~ 220ran, single crystal growth rate lmm / min ~ 5mm / min, in the process of expanding the shoulder, when the distance of the pin of the single crystal shoulder single crystal holder is less than 2mm, the holder is released, the single crystal is clamped .

The closing and stopping of the furnace is when the single crystal is pulled to the tail and begins to finish. The diameter of the single crystal is Φ 10~80 round, and the melting zone is pulled apart, so that the lower shaft continues to move downward, and the upper shaft is changed. Move up, while maintaining the power at 50% 20%, slowly cooling the crystal.

It is also possible to incorporate a desired solid element while charging a raw material of the silicon polycrystal and the silicon single crystal into a straight pull furnace. The Czochralski melting method for producing a silicon single crystal of the present invention has the following characteristics:

1. The defect of high oxygen content in the production of silicon single crystal by the straight pull method. The oxygen atoms in the Czochralski silicon are produced by the high temperature reaction of the molten silicon with the quartz crucible (Si+SiO 2 = 2 SiO) into the silicon crystal during the growth of the single crystal. In general, the oxygen content is as high as 10 ^t8 atm / cm ³ , and the thermal instability and reversibility caused by the oxygen donor formed by the high content of the Czochralski silicon cause the limitation of the Czochralski silicon single crystal in the manufacturing process of the power device. And difficult. In the process of growing single crystals, the oxygen atoms entering the melt are supplied by two parts, namely oxygen atoms in the raw silicon polycrystalline rod and trace oxygen molecules in the inert gas at high temperature (800 ° C - 1350 ° C). The SiO film (2Si+0 ₂ = 2SiO) formed by the reaction with the raw material silicon polycrystalline rod, the high temperature silicon melt will almost completely deplete the SiO entering the silicon. Only a small part of the oxygen atoms finally enter the zone melting crystal. From the results of a large number of experiments, although the oxygen content in the raw silicon rods differs by nearly three orders of magnitude (from 10 ¹⁶ _a tm / _C m ^{3 to} 10 ¹⁸ atm / c _m ³ ), the zone melting after zone melting once crystallized The oxygen content of the single crystal tends to be the same as the number of 10 ¹⁶ atm / cm ³ . Therefore, the high oxygen content (10 ^l8 atm / _C m ³ ) introduced during the Czochralski process has been reduced to 10 ¹⁶ atm / _C ra ³ by zone melting and has reached the standard.

2. Overcome the defect that the zone melting method cannot produce silicon single crystals doped with special solid elements. When the single crystal silicon is produced by the straight-pull zone melting method, the characteristics of easy-doping by the straight-drawing device can be utilized, and the impurities which are required to be intruded are mixed in the process of drawing the straight-drawing polycrystalline bar material, and then drawn by the zone melting furnace. A silicon single crystal doped with an N-type or P-type impurity or other special-desired impurity and having a low oxygen content is obtained, thereby achieving the purpose of doping.

3. Greatly improved the production capacity of the zone furnace and reduced the production cycle and production cost of the zoned silicon single crystal. The furnace of the same diameter is more than eight times more expensive than the straight pull furnace. Due to the shortage of raw materials, the zone furnace purifies the silicon polycrystalline rod, and then uses the zone furnace to make a silicon single crystal, and then neutron irradiation. The straight-pull zone melting method first uses a straight pull furnace to form a silicon polycrystalline rod, and then uses a zone melting furnace to form a silicon single crystal, and saves the time and cost of neutron irradiation, thereby reducing the production cost and improving the production cost. The production utilization rate of the zone furnace shortens the production cycle.

4. Developed the source of polycrystalline materials, avoiding the limitation that the zone melting method can only use advanced bar stocks. The straight-pull zone melting method can remove the impurities such as scraps, blocks and the like by straight-drawing method, and shape the bar used for the zone melting method.

5. The straight-drawing zone melting method can make up for the shortcomings of high-strength zone melting single crystal in high-bar production. It can make the diameter of multi-(mono)crystalline bar to 300mm, which solves the production of large-diameter polycrystalline in polycrystalline production plant. Difficult question. detailed description

The straight-drawing zone melting method for producing a silicon single crystal of the present invention will be described in detail below with reference to specific embodiments as follows:

The CZ process for producing a silicon single crystal according to the present invention is carried out by two processes of a straight pull process using a straight pull furnace and a zone process using a zone furnace. The first is to use a Czochralski casting method (single crystal or polycrystalline ingot), and then the crystal or polycrystalline ingot cast by the straight drawing process is shaped and processed into an ingot which meets the requirements of the molten silicon single crystal in the drawn region, and finally The single crystal is formed by zone melting. ·

(a) First, the straight pull process is carried out, including the following steps:

(1) The corrosion-cleaned bulk silicon raw material (polycrystalline silicon and single crystal silicon or polycrystalline silicon or single crystal silicon) is placed in a quartz crucible in a straight crucible, and then evacuated and filled with argon gas;

(2) Pass the cooling water before heating, start the 坩埚 rotation mechanism, start the heating button, and put all the bulk silicon raw materials After melting, the seed crystal rotating mechanism is activated to lower the seed crystal to weld the seed crystal;

(3) Adjust the seed crystal stroke to zero position, rotate the crystal lift potentiometer, and pull the neck;

(5) adjusting the diameter sensor, controlling the pulling speed to perform equal-diameter pulling;

(6) Lower the crystal pulling speed to finish the tail;

(7) Lifting the crystal away from the liquid surface, stopping the heating, turning the twisting, crystal rising, and crystal turning potentiometers to zero, cutting off the power supply, stopping the argon gas after half an hour, stopping the water after four hours, and closing the line valve switch. Stop the main vacuum pump to evacuate and release the multi (single) crystal rod;

(8) of the latter into the single crystal silicon rod and the polycrystalline silicon rods baked in an ingot drawing processing fi ^1, washed etching to prepare single crystal grown on the region of the furnace;.

(b) Then, the zone melting process is carried out, including the following steps:

(1) cleaning the furnace, loading the furnace, adjusting the furnace device, installing one of the polycrystalline silicon rod and the single crystal silicon rod to the end of the upper shaft of the furnace, performing the centering of the crystal material, and mounting the seed crystal to the top end of the lower shaft. Close each furnace door;

(3) smelting and seeding the seed crystal and the molten silicon;

(4) growing a thin neck;

(5) Carrying out the shoulder extension;

(7) Finishing, slowly cooling the crystal, and stopping the furnace.

The diameter of the thin neck of one of the polycrystalline silicon rod and the single crystal silicon rod pulled out by the straight pull furnace is 3 to 10 ram, the length is 1Q to 200, and the diameter after the shoulder is 50 to 300 legs.

The sinter gas is pressurized to a pressure of less than 0. 5mbr when the pressure is less than 0. 5mbr, argon gas, pressure to 1. Preheat at 2-6 bar, 'Preheating set point 25~40%, preheating time is 10~20 minutes.

The thin neck is grown in the zone furnace, and the neck is grown after the seeding is finished. The diameter of the drawn silicon single crystal neck is 2 to 6 legs and the length is about 30 to 60 mm.

The extension of the shoulder includes: slowly reducing the down speed to 3 ± 2 mm / _m in, while gradually decreasing to 8 ± 6 rpm as the diameter of the shoulder increases, while slowly reducing the up to 1 ± 0. 8rpm.

The rotating shoulder, the holding single crystal and the holder release the single crystal, and the shoulder is rotated when the diameter of the shoulder is different from the single crystal holding diameter by 3 to 20, until the set diameter is maintained, the single crystal is maintained, etc. Diameter diameter is 50mm~220mm, single The crystal growth rate is 1 mm/min to 5 mm/min. In the process of expanding the shoulder, when the distance of the pin of the single crystal shoulder single crystal holder is less than 2 mm, the holder is released to sandwich the single crystal.

The closing and stopping of the furnace is when the single crystal is pulled to the tail, and the finishing is finished. The diameter of the single crystal is Φ 10~80, and the melting zone is pulled apart, so that the lower shaft continues to move downward, and the upper shaft is changed. Move upwards while maintaining a power of 50 ± 20%, slowly cooling the crystal.

When it is desired to intrude into a special solid element in a silicon single crystal, it is also possible to incorporate a desired solid element while charging the silicon polycrystalline raw material into a straight pull furnace. The purpose of doping is achieved.

Specific embodiment:

First, carry out the straight pull process -

(1) 75 kg of corroded and cleaned bulk silicon polycrystalline material is placed in a quartz crucible in a straight pull furnace, and evacuated to a pressure of 100 mTorr for 30 to 60 minutes to a vacuum pressure of about 16 Torr. .

(2) Before the heating, the cooling water is turned on, the rotating mechanism is activated, and the heating button is activated. It takes about 2.5 hours to heat to 1500 ° C to 160 (TC causes the bulk polycrystalline material to be completely melted into a molten state and then starts the seed crystal rotating mechanism. , drop the seed crystal, weld the seed crystal.

(3) Adjust the seed crystal stroke to zero position, rotate the crystal lift potentiometer, and use a seed crystal to pull a thin neck with a diameter of about 8 mm and a length of about 30 mm from the molten polycrystalline material for 30 minutes.

(4) Decrease the seed crystal speed, turn on the crystal growth button, and use the diameter controller to control the pulling speed. The diameter of the crystal pulling is expanded from about 8mm to 150mm in about 30 minutes.

(5) Adjust the diameter sensor to control the crystal pulling speed after 36 hours of equal diameter growth.

(6) Reduce the pulling speed and close the tail after about 3. 5 hours.

(7) Increase the crystal leaving the liquid surface, stop heating, rotate the 埚, crystal, and crystal potentiometers to zero position, cut off the power supply, stop the ammonia gas after half an hour, stop the water after four hours, close the line valve switch, Stop the main vacuum pump to evacuate and release the polycrystalline bar.

(8) The baked polycrystalline rod is subjected to ingot processing, and is cleaned and etched to prepare single crystal growth on the zone melting furnace. Then, carry out the zone melting process:

(1) Cleaning furnace, loading furnace: cleaning the inner wall of the furnace and the heating coil, reflector, crystal holder, upper shaft and lower shaft, adjusting the level of the heating coil and the reflector and the alignment with the upper and lower shafts Fixing the polycrystalline fixture to the groove at the end of the polycrystalline material, then mounting it to the end of the upper shaft for centering the polycrystalline material; loading the seed into the seed chuck and then mounting it to the seed holder Lower shaft top; close each furnace door and tighten the fastening bolts;

■ (2) Pumping out, inflating, preheating the polycrystalline material: Open the vacuum pump and the suction pipe valve, vacuum the furnace chamber. When the pressure reaches 0. 05 mbar, close the suction pipe valve and the vacuum pump, and quickly fill the furnace. Argon gas; when the inflation pressure reaches 3 bar relative pressure, stop rapid inflation, use slow inflation, open the exhaust valve for argon flow; preheat the polysilicon bar, preheat the graphite preheat ring, use current file , preheating set point 30%, preheating time is 15 minutes;

(3) Chemical material, seeding: After the preheating is finished, the chemical material is transferred, and the material is transferred to the voltage file, and the generator is set. The point is at 50%; after the polycrystalline material is melted, the seed crystal is fused with the molten silicon, and after the fusion, the molten region is shaped and seeded; (4) Growing the neck: after the end of the seeding, the growth of the neck is fine. The diameter of the neck is 3mm and the length is 40瞧. (5) Expanded shoulder: After the neck is finished, the shoulder is extended, the speed is slowly reduced to 3mm/min, and the diameter is continuously reduced as the diameter of the shoulder increases. 5rpm;

(6) Rotating shoulder, holding and gripper release: When the shoulder diameter is different from the single crystal holding diameter by 5mm, the shoulder is turned until the desired diameter is reached, the single crystal is kept, and the equal diameter is maintained at 130mm, the growth rate of the single crystal 2mm / min, in the process of expanding the shoulder, when the distance of the pin of the single crystal shoulder single crystal holder is less than 2mm, the holder is released, and the single crystal is clamped;

(7) Closing and stopping the furnace: When the single crystal is pulled to the tail, the finishing is started. The diameter of the single crystal is Φ 80ΜΙ, and the melting zone is pulled open. At this time, the lower shaft continues to move downward, and the upper shaft is changed upward. Movement, while maintaining power at 50%, slowly cools the crystal.

Claims

A straight-drawing zone melting method for producing a silicon single crystal, which is characterized in that it is completed by two processes of a straight pull process using a straight pull furnace and a zone process of a zone furnace.

First, the straight pull process is performed, including the following steps:

(1) ^ Corrosion cleaned bulk silicon raw material is placed in a quartz crucible in a straight pull furnace, and then vacuumed and filled with argon gas;

(4) Decreasing the seed crystal speed, opening the crystal lift switch button, expanding the crystal pulling diameter, and using the diameter controller to control the pulling speed to carry the shoulder;

(6) Lower the crystal pulling speed to finish the tail;

(7) Increase the crystal leaving the liquid surface, stop heating, turn the twisting, crystal rising, and crystal turning potentiometers to zero, cut off the power supply, stop the argon gas after half an hour, stop the water after four hours, close the line valve switch, stop The main vacuum pump is evacuated and the ingot is released;

Then, performing the zone melting process, including the following steps:

(3) smelting and seeding the seed crystal and the silicon;

(4) growing a thin neck;

(5) Carrying out the shoulder extension;

(7) Finishing, slowly cooling the crystal, and stopping the furnace.

2. The Czochralski casting method for producing a silicon single crystal according to claim 1, wherein the vacuum furnace is filled with argon gas and is charged at a pressure of 100 mTorr. Argon gas was brought to a vacuum pressure of 20 Torr to start heating.

3. The Czochralski casting method for producing a silicon single crystal according to claim 1, wherein a diameter of one of the polycrystalline silicon rod and the single crystal silicon rod pulled out by the straight pull furnace is 3 to 10 Painting, length 10~200mm, put the diameter of the shoulder after 50隠~300 earned.

4. The Czochralski casting method for producing a silicon single crystal according to claim 1, wherein said opposite zone is melted The argon gas is filled with a pressure of 1. 2 6 bar. The pressure is increased to 1. 2 6 bar. Preheating, preheating set point 25~40%, preheating time is 10~20 minutes.

The straight-drawing zone melting method for producing a silicon single crystal according to claim 1, wherein the material in the furnace is welded, the seed crystal is melted and melted, and the crystal is formed. Turning into the voltage range, the generator set point is 40~60%, and the melting zone is shaped after the seed crystal and the molten silicon are welded.

6. The Czochralski casting method for producing a silicon single crystal according to claim 1, wherein the thin neck is grown in the furnace in the zone, and after the end of the seeding, the neck is grown and pulled out. The silicon single crystal has a neck diameter of 2 to 6 mm and a length of about 30 to 60.

7. The Czochralski casting method for producing a silicon single crystal according to claim 1, wherein the expansion of the inner portion of the furnace includes: slowly reducing the lower speed to 3 ± 2 mm/min, and simultaneously expanding the shoulder The increase in diameter is gradually reduced to 8 ± 6rpra, and the vertical rotation is slowly reduced to l ± 0. 8rpra.

8. The Czochralski casting method for producing a silicon single crystal according to claim 1, wherein the hole in the furnace is rotated, the single crystal is held, and the holder releases the single crystal, and the shoulder is expanded. When the diameter is different from the single crystal holding diameter by 3~20ram, the shoulder is turned until the set diameter is reached, and the single crystal is kept, and the diameter is kept at 50mn! ~ 220ram, single crystal growth rate lmm / min ~ 5mm / min, in the process of expanding the shoulder, when the distance of the pin of the single crystal shoulder single crystal holder is less than 2mm, the holder is released, the single crystal is clamped .

9. The Czochralski method for producing a silicon single crystal according to claim 1, wherein the furnace is closed and stopped in the furnace, and when the single crystal is pulled to the tail, the finishing is started, and the finishing is completed. The diameter of the crystal reaches Φ 10~80ΙΜ, the melting zone is pulled apart, the lower shaft continues to move downward, the upper shaft changes upward, and the power is kept at 50±20%, and the crystal is slowly cooled.

10. The Czochralski melting method for producing a silicon single crystal according to claim 1, wherein a material of the silicon polycrystal and the silicon single crystal is incorporated into the straight pull furnace while being incorporated Solid elements are required.