CN114616361B - Method for producing silicon single crystal - Google Patents
Method for producing silicon single crystal Download PDFInfo
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- CN114616361B CN114616361B CN202080078286.9A CN202080078286A CN114616361B CN 114616361 B CN114616361 B CN 114616361B CN 202080078286 A CN202080078286 A CN 202080078286A CN 114616361 B CN114616361 B CN 114616361B
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- single crystal
- crucible
- oxygen concentration
- quartz glass
- glass crucible
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- 239000013078 crystal Substances 0.000 title claims abstract description 158
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 106
- 239000010703 silicon Substances 0.000 title claims abstract description 106
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 104
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 91
- 239000001301 oxygen Substances 0.000 claims abstract description 91
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 91
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 79
- 238000000034 method Methods 0.000 claims abstract description 27
- 238000009826 distribution Methods 0.000 abstract description 17
- 239000000155 melt Substances 0.000 description 23
- 239000011261 inert gas Substances 0.000 description 15
- 238000002474 experimental method Methods 0.000 description 14
- 239000010453 quartz Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 239000002994 raw material Substances 0.000 description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 230000007423 decrease Effects 0.000 description 7
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 230000005855 radiation Effects 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- -1 silicon alkoxide Chemical class 0.000 description 2
- 201000006935 Becker muscular dystrophy Diseases 0.000 description 1
- 208000037663 Best vitelliform macular dystrophy Diseases 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000005247 gettering Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 229920005591 polysilicon Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 208000020938 vitelliform macular dystrophy 2 Diseases 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/10—Crucibles or containers for supporting the melt
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Abstract
The present invention provides a method for producing a silicon single crystal, which can produce a silicon single crystal having a more uniform oxygen concentration distribution in the longitudinal direction of the silicon crystal. A method for producing a silicon single crystal by pulling up a silicon single crystal from a silicon melt contained in a quartz glass crucible (3) by the Czochralski method, wherein the quartz glass crucible is adjusted from the upper portion to the lower portion of the side wall of the quartz glass crucible by using the ratio (T/T) of the thickness (T) of the transparent inner layer to the side wall thickness (T) of the quartz glass crucible, and the difference in oxygen concentration in the crystal growth axis direction of the pulled up silicon single crystal is 20% or less.
Description
Technical Field
The present invention relates to a method for producing a silicon single crystal by the Czochralski method (CZ method), and to a method for producing a silicon single crystal which can produce a silicon single crystal having a more uniform oxygen concentration in the crystal length direction.
Background
Growth (growth) of a silicon single crystal by the CZ method is performed as follows: a quartz glass crucible 51 provided in a chamber (chamber) 50 shown in fig. 8 is filled with polycrystalline silicon as a raw material, the polycrystalline silicon is heated by a heater 52 provided around the quartz glass crucible 51 to be melted to prepare a silicon melt M, and then a seed (seed) P mounted on a seed chuck is immersed in the silicon melt M, and the seed chuck and the quartz glass crucible 51 are pulled up while rotating in the same direction or in opposite directions, whereby a silicon single crystal is grown.
In general, when the temperature of the silicon melt M stabilizes before the pulling-up starts, the seed crystal P is brought into contact with the silicon melt M to melt the tip portion of the seed crystal P, and then the neck is performed. The neck is an indispensable step for removing dislocations generated in the silicon single crystal due to thermal shock (thermal shock) generated by contact of the seed crystal P with the silicon melt M.
The neck portion P1 is formed by the neck portion. In the case of a crystal having a diameter of 300mm, for example, the neck portion P1 needs to have a diameter of about 5mm and a length of 30 to 40mm or more.
In addition, as a step after the start of pulling, the following steps are performed after the completion of necking: a step of forming a shoulder C1, in which the crystal is expanded to the diameter of a straight tube portion (straight body portion); a step of forming a straight tube portion C2 to grow a single crystal as a product; and a step of forming a tail portion (not shown), wherein the diameter of the single crystal after the straight tube portion forming step is gradually reduced.
However, since the inner surface of the silica glass crucible 51 is melted by contact with the silicon melt M, oxygen contained in the silica glass crucible 51 dissolves out in the silicon melt M and reacts with the silicon melt M to form SiOx. Most of the SiOx evaporates from the free surface of the melt and is discharged together with an inert gas (Ar or the like) introduced into the single crystal pulling apparatus.
Here, a part of SiOx is taken into the growing single crystal, and oxygen taken into the silicon single crystal brings about an effect of suppressing gettering or slip dislocation of heavy metals due to oxygen precipitates in the semiconductor device manufacturing process.
However, in the semiconductor device manufacturing process, if the oxygen precipitates are present in the active layer, there is a concern that the electric characteristics may be adversely affected. Therefore, it is required to manufacture wafers having an appropriate oxygen concentration according to the type of semiconductor device.
Further, since the amount of silicon melt in the quartz glass crucible is large and the contact area between the inner wall surface of the crucible and the silicon melt is large, the upper part of the straight tube portion grown in the initial stage of pulling is pulled in a state where the amount of oxygen released from the quartz glass crucible is large. As the pulling of the single crystal progresses, the amount of silicon melt in the crucible decreases, and therefore the contact area between the inner wall surface of the crucible and the silicon melt becomes smaller, and the amount of oxygen eluted from the quartz glass crucible into the silicon melt decreases.
Therefore, the oxygen concentration in the silicon melt is unstable, and the oxygen concentration distribution in the growth direction of the single crystal tends to become uneven (for example, the higher the oxygen concentration is, the lower the oxygen concentration is, etc.). In the step of growing the single crystal, it is desirable to control the oxygen concentration in the crystal growth axis direction so as to be uniform in order to increase the yield.
To solve the above problem, patent document 1 (japanese patent laid-open No. 6-56571) discloses the following method: an inverted truncated cone or cylindrical heat insulating jig is arranged above the silicon melt, and the gap between the silicon melt surface and the lower end of the heat insulating jig is adjusted to control the oxygen concentration of the single crystal.
According to the method disclosed in patent document 1, the cooling of the melt surface by the inert gas supplied to the melt surface from above the heat insulating jig and the degree of shielding of heat emitted from the crucible to the melt surface can be accurately controlled, and as a result, the diffusion and evaporation of oxygen in the melt can be controlled, and the oxygen supply amount to the single crystal can be controlled.
In addition, patent document 2 (japanese re-public table WO 2001/061027) discloses that: the oxygen concentration is controlled by changing the flow rate and pressure of the inert gas flowing into the furnace according to the pulling amount.
According to the method disclosed in patent document 2, by changing the flow rate or pressure of the inert gas in the furnace, the amount of oxygen evaporated as an oxide from the melt surface in the vicinity of the crystal growth interface can be easily adjusted, and the amount of oxygen contained in the silicon melt can be easily controlled.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 6-56571;
patent document 2: japanese re-public Table WO 2001/061027.
Disclosure of Invention
Problems to be solved by the invention
However, in the methods disclosed in patent documents 1 and 2, although the crystal oxygen concentration in the crystal growth axis direction can be made uniform, the following problems are involved.
Specifically, in the method disclosed in patent document 1, the temperature of the silicon melt surface changes due to the gap between the silicon melt surface and the heat insulating jig, and the temperature distribution in the height direction of the crystal changes, which affects the formation of crystal defects such as void defects (COPs) and oxygen precipitates (BMDs), and there is a problem that the distribution of crystal defects is not uniform.
In the method disclosed in patent document 2, the amount of evaporation of SiO gas from the melt is adjusted by the flow rate and pressure of the inert gas, and when the flow rate of the inert gas is large, the exhaust pump needs a vacuum pump with high exhaust performance, which results in a problem of high cost. On the other hand, when the flow rate of the inert gas is small, the scale in the furnace is not discharged, and there is a problem that the single crystallization rate is lowered.
The present inventors have studied a new method without using a heat insulating jig as in the method disclosed in patent document 1 or adjusting the amount of SiO gas evaporated from the melt by the flow rate and pressure of the inert gas as in the method disclosed in patent document 2.
The result shows that: the present invention has been accomplished by adjusting the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the quartz glass crucible in the height direction of the quartz glass crucible to control the oxygen concentration in the crystal growth axis direction of the pulled silicon single crystal.
The present invention has been completed under the circumstances as described above, and an object thereof is to: a method for producing a silicon single crystal is provided, which can produce a silicon single crystal having a more uniform oxygen concentration distribution in the longitudinal direction of the silicon crystal by adjusting the ratio T/T of the thickness T of the transparent inner layer to the wall thickness T of the quartz glass crucible.
Means for solving the problems
The method for producing a silicon single crystal according to the present invention, which has been completed to solve the above-described problems, has the following features: a method for producing a silicon single crystal by pulling up a silicon single crystal from a silicon melt contained in a quartz glass crucible by the Czochralski method using a quartz glass crucible having an opaque outer layer and a transparent inner layer, wherein the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the side wall of the quartz glass crucible is adjusted from the upper portion to the lower portion of the side wall of the quartz glass crucible, and the variation in oxygen concentration in the crystal growth axis direction of the pulled up silicon single crystal is 20% or less.
Here, the quartz glass crucible is divided into a plurality of regions from the upper portion to the lower portion of the side wall of the quartz glass crucible, and it is desirable to adjust the ratio T/T of the thickness T of the transparent inner layer to the side wall thickness T of the quartz glass crucible for each of the plurality of regions.
Further, it is preferable that the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the side wall of the quartz glass crucible is in a range of more than 0.05 and less than 0.8.
In this way, according to the method for producing a silicon single crystal of the present invention, the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the quartz glass crucible is adjusted in the height direction of the quartz glass crucible, and the oxygen concentration in the crystal growth axis direction of the pulled silicon single crystal is controlled, whereby the variation in the oxygen concentration in the crystal growth axis direction of the pulled silicon single crystal can be controlled, and the oxygen concentration can be made more uniform.
Effects of the invention
According to the present invention, a method for producing a silicon single crystal having a more uniform oxygen concentration distribution in the longitudinal direction of the silicon crystal can be obtained by adjusting the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the wall of the quartz glass crucible.
Drawings
FIG. 1A is a sectional view of a single crystal pulling apparatus for carrying out the method for producing a silicon single crystal according to the present invention.
FIG. 2 is a sectional view of a quartz glass crucible provided in the single crystal pulling apparatus of FIG. 1.
FIG. 3A sectional view of a part of the quartz glass crucible of FIG. 2 enlarged.
FIG. 4 is a flowchart showing a flow of a method for producing a silicon single crystal according to the present invention.
FIG. 5A, B and C are sectional views showing the relationship between the amount of silicon melt and the crucible as the crystal is pulled up.
Fig. 6 is a graph showing the result of example (experiment 1).
Fig. 7 is a graph showing the results of example (experiment 2).
FIG. 8 is a sectional view for explaining a process of pulling a silicon single crystal by the Czochralski method.
Detailed Description
The method for producing a silicon single crystal according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a single crystal pulling apparatus for carrying out the method for producing a silicon single crystal according to the present invention. FIG. 2 is a sectional view of a quartz glass crucible provided in the single crystal pulling apparatus of FIG. 1.
The single crystal pulling apparatus 1 includes a furnace body 10 formed by stacking a pulling chamber (pull chamber) 10b on a cylindrical main chamber 10a, and the furnace body 10 includes: a carbon susceptor (or graphite susceptor) 2 rotatably and liftably provided around a vertical axis; and a quartz glass crucible 3 (hereinafter, simply referred to as crucible 3) held by the carbon susceptor 2. The crucible 3 is rotatable about a vertical axis while the carbon susceptor 2 is rotated.
Here, the structure of the crucible 3 will be described in detail with reference to fig. 2 and 3.
The crucible 3, for example, has an aperture of 800mm, and comprises: a bottom 31 having a predetermined curvature; corner portions 32 formed around the bottom 31 and having a predetermined curvature; and a straight tube portion 33 extending upward from the corner portion 32. A crucible opening (upper end opening) is formed at the upper end of the straight tube portion 33.
As shown in fig. 2, the crucible 3 has a double-layer structure of an opaque outer layer 3A (opaque layer) and a transparent inner layer 3B (transparent layer).
The opaque outer layer 3A is made of a natural quartz glass, and the transparent inner layer 3B is made of a synthetic quartz glass having a high purity, for example.
The opaque state refers to a state in which many bubbles (pores) are inherent in the quartz glass and the appearance is cloudy. The natural raw material silica glass is silica glass produced by melting a natural raw material such as crystal, and the synthetic raw material silica glass is silica glass produced by melting a synthetic raw material synthesized by hydrolysis of a silicon alkoxide (silicon alkoxide), for example.
In this manufacturing method, a quartz glass crucible is used in which the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the quartz glass crucible is adjusted (set) in the crucible height direction.
As described above, in the process of pulling up the single crystal, the oxygen concentration in the silicon melt is unstable, and the oxygen concentration distribution in the growth direction of the single crystal tends to be uneven. How the oxygen concentration in the melt changes is determined by the influence of parameters such as the magnetic field strength, the magnetic field center position, the flow rate of the inert gas, the furnace internal pressure, the rotation of the quartz glass crucible 3, and the rotation of the single crystal.
Therefore, in the present invention, in a single crystal pulling apparatus, the tendency of the non-uniform oxygen concentration distribution of the pulled single crystal (for example, the distribution of the oxygen concentration in the upper part of the crystal is higher than that in the lower part) is grasped in advance, and the ratio T/T is adjusted accordingly.
In this embodiment, a case where the oxygen concentration in the upper part of the crystal is higher than the distribution in the lower part will be described as an example, and the tendency of the oxygen concentration distribution will be described.
As shown in fig. 3 by enlargement, along the height direction of the straight tube portion 33 of the crucible 3, for example, in the crucible upper portion 33A, the crucible middle portion 33B, and the crucible lower portion 33C, the ratio T/T of the thickness T of the transparent inner layer 3B to the thickness T of the crucible wall (the total thickness of the opaque outer layer 3A and the opaque inner layer 3B) is set to be greater than 0.05 and less than 0.8.
For example, the ratio T/T is set from a small value to a large value from the upper portion 33A to the lower portion 33C. Specifically, for example, the ratio T/T of the thickness T of the transparent inner layer 3B to the crucible wall thickness T in the upper portion 33A is set to 0.10, the ratio T/T in the intermediate portion 33B is set to 0.3, and the ratio T/T in the lower portion 33C is set to 0.6.
When the ratio T/T is 0.05 or less (when the thickness of the transparent inner layer 3B is too small), the transparent inner layer 3B is completely melted during crystal growth, and the opaque outer layer 3A containing bubbles is exposed to the silicon melt M side, and there is a concern that fine quartz particles are peeled off. In this case, the following problems may occur: the particles reach the surface of the melt, and the dislocation rate increases, or bubbles are taken into the crystal to form a gas pocket.
On the other hand, when the ratio T/T is 0.8 or more (when the thickness of the transparent inner layer 3B is too thick), uniform heat diffusion by the opaque outer layer 3A is insufficient, and there are disadvantages such as difficulty in temperature control and an increase in product price.
The reason why the ratio T/T is specified above is that the heat transfer coefficients of the opaque outer layer 3A and the transparent inner layer 3B are different. The opaque outer layer 3A contains a large number of bubbles, and therefore uniformly diffuses heat to have a uniform temperature distribution. On the other hand, the transparent inner layer 3B has high thermal conductivity, and it is difficult to control the temperature.
Therefore, when the ratio T/T of the thickness T of the transparent inner layer 3B to the thickness T of the crucible 3 is small, the opaque outer layer 3A which uniformly diffuses heat becomes thick, and the crucible 3 does not need to be heated to a desired temperature or more, so that the temperature of the inner surface of the crucible can be reduced, and the amount of quartz melted in the silicon melt M can be reduced.
On the other hand, when the ratio T/T of the wall thickness T of the transparent inner layer 3B to the crucible 3 is large, the heat conduction is large, and therefore the temperature of the inner surface of the crucible is high, and the amount of quartz melted increases, so that the amount of quartz melted in the silicon melt M increases.
Since the amount of the silicon melt decreases as the crystal growth progresses, the effect of the oxygen concentration on the grown single crystal is to shift from the upper portion 33A to the intermediate portion 33B and the lower portion 33C of the crucible where the silicon melt level M1 is located.
In addition, as described above, the larger the amount of silicon melt in the quartz glass crucible, the larger the amount of oxygen in the silicon melt at the initial stage of pulling, and therefore the higher the oxygen concentration tends to be toward the upper portion of the single crystal.
Accordingly, in the embodiment according to the present invention, the following configuration is formed: the ratio T/T of the upper, middle and lower crucible portions 33A, 33B, 33C, respectively, which sequentially move the silicon melt level M1 most influencing the crystal oxygen concentration, is set to be larger from the upper portion to the lower portion of the quartz glass crucible, for example, so that the oxygen concentration in the crystal growth axis direction is controlled to be more uniform.
Next, returning to the description of fig. 1, below the carbon base 2, there is provided: a rotation driving unit 14 such as a rotation motor for rotating the carbon susceptor 2 about a vertical axis; and a lift driving unit 15 for moving the carbon susceptor 2 up and down.
The rotation driving unit 14 is connected to a rotation driving control unit 14a, and the elevation driving unit 15 is connected to an elevation driving control unit 15a.
The single crystal pulling apparatus 1 further includes: a side heater 4 for melting a semiconductor raw material (raw material polycrystalline silicon) charged in the crucible 3 to produce a silicon melt M (hereinafter, simply referred to as a melt M); and a pulling mechanism 9 for pulling up the grown single crystal C by winding up the wire rod 6. A seed crystal P is attached to the tip of the wire rod 6 provided in the pulling mechanism 9.
The heater driving control unit 4a for controlling the amount of power supplied is connected to the intermediate heater 4, and the rotation driving control unit 9a for controlling the rotation driving of the pulling mechanism 9 is connected thereto.
In the single crystal pulling apparatus 1, for example, a magnetic field applying electromagnetic coil 8 is provided outside the furnace body 2. When a predetermined current is applied to the magnetic field application electromagnetic coil 8, a horizontal magnetic field having a predetermined intensity is applied to the silicon melt M in the crucible 3. A solenoid control unit 8a for controlling the operation of the magnetic field application solenoid 8 is connected to the magnetic field application solenoid 8.
That is, in the present embodiment, the MCZ method (Magnetic field applied CZ method) is performed in which a magnetic field is applied to the melt M to grow single crystals, thereby controlling convection of the silicon melt M and stabilizing single crystallization.
Further, a radiation shield 7 surrounding the periphery of the single crystal C is provided above the melt M formed in the crucible 3. The radiation shield 7 is opened at upper and lower portions to shield excessive radiant heat from the intermediate heater 4 or the melt M or the like for the growing single crystal C while rectifying the gas flow in the furnace.
The gap between the lower end of the radiation shield 7 and the melt surface is controlled so as to be constantly maintained at a predetermined distance according to the desired characteristics of the single crystal to be grown.
The single crystal pulling apparatus 1 includes a computer 11, and the computer 11 includes a storage device (storage means) 11a and a calculation control device 11b, and the rotation drive control unit 14a, the elevation drive control unit 15a, the electromagnetic coil control unit 8a, and the rotation drive control unit 9a are connected to the calculation control device 11b, respectively.
In the single crystal pulling apparatus 1 thus configured, for example, when a single crystal C having a diameter of 300mm is grown, pulling is performed as follows. That is, the crucible 3 is initially charged with raw material polysilicon (for example, 350 kg), and the crystal growth process is started according to a program stored in the memory device 11a of the computer 11.
First, a predetermined environment (mainly, inert gas such as argon) is formed in the furnace body 10, and the raw material polycrystalline silicon charged in the crucible 3 is melted by heating by the intermediate heater 4 in a state where the crucible 3 is rotated at a predetermined rotation speed (rpm) to prepare a melt M (step S1 in fig. 4).
Then, a predetermined current is applied to the magnetic field application solenoid 8, and the horizontal magnetic field starts to be applied at a magnetic flux density (for example, 2500 Gauss) set in the range of 1000 to 4000Gauss in the melt M (step S2 in fig. 4).
The wire rod 6 is lowered to bring the seed crystal P into contact with the silicon melt M, the tip portion of the seed crystal P is melted, and then the neck portion P1 is formed (step S3 in fig. 4).
When the neck portion P1 is formed, the pulling condition is adjusted by using the power supplied to the intermediate heater 4, the pulling speed, the magnetic field application strength, and the like as parameters, and the seed crystal P is rotated at a predetermined rotation speed in a direction opposite to the rotation direction of the crucible 3.
Then, the crystal diameter is gradually increased to form the shoulder portion C1 (step S4 in fig. 4), and the process proceeds to a step of forming the straight tube portion C2 which becomes the product portion (step S5 in fig. 4).
Here, the oxygen concentration in the single crystal grown from the silicon melt M into which the oxygen eluted from the crucible 3 is introduced is affected by parameters such as the magnetic field strength, the magnetic field center position, the flow rate of inert gas or the furnace internal pressure, the rotation of the quartz glass crucible 3, and the rotation of the single crystal.
Although the oxygen concentration distribution in the crystal growth axis direction is affected by the above-described parameters, it has been difficult to make the oxygen concentration in the crystal growth axis direction uniform by controlling only the above-described parameters.
Therefore, in the embodiment of the present invention, in addition to the above-described parameter conditions, the crystal oxygen concentration in the crystal growth axis direction is controlled by adjusting the ratio T/T of the thickness T of the transparent inner layer 3B in the height direction of the crucible 3 to the thickness T of the crucible wall.
Specifically, a tendency of oxygen concentration in the growth axis direction of the single crystal C pulled up based on the above parameters such as the magnetic field intensity, the magnetic field center position, the flow rate of inert gas, the furnace internal pressure, the rotation of the quartz glass crucible 3 serving as a base, the rotation of the single crystal, and the like is recorded as data in the storage device 11a, and the ratio T/T in the quartz glass crucible 3 is determined in accordance with the tendency, whereby the crucible is manufactured and used.
In the initial stage of the growth of the straight tube portion C2, as shown in FIG. 5 (a), the silicon melt level M1 is located at the crucible upper portion 33A. The amount of oxygen taken into the single crystal C has the greatest influence on the oxygen concentration in the melt M in the vicinity of the silicon melt level M1.
In the initial stage of the growth of the straight tube portion C2, the amount of the silicon melt is large and the contact area with the inner surface of the crucible is large, so that the concentration of oxygen in the melt is high as a whole, and the ratio T/T of the thickness T of the transparent inner layer 3B to the thickness T of the crucible wall in the crucible upper portion 33A is set to be as small as 0.08, for example. That is, the thickness of the transparent inner layer 3B is made thin, so that the opaque outer layer 3A is thick, and heat is diffused and homogenized. Thereby, the temperature of the inner surface of the crucible is lowered, and the amount of quartz melted from the crucible 3 into the silicon melt M is suppressed.
As the growth of the straight tube portion proceeds, as shown in fig. 5 (B), when the silicon melt level M1 decreases to reach the position of the crucible middle portion 33B, the ratio T/T of the thickness T of the transparent inner layer 3B to the crucible wall thickness T is set to, for example, 0.3 in the crucible middle portion 33B.
Here, the oxygen concentration in the silicon melt tends to decrease because the amount of silicon melt in the crucible decreases, but the amount of quartz melted from the crucible 3 into the silicon melt M increases because the thickness of the transparent inner layer 3B in the crucible middle portion 33B where the silicon melt level M1 is located is thicker than that in the crucible upper portion 33A.
As the growth of the straight tube portion proceeds further, as shown in fig. 5 (C), when the silicon melt level M1 reaches the position of the crucible lower portion 33C, the ratio T/T of the thickness T of the transparent inner layer 3B to the crucible wall thickness T is set to, for example, up to 0.6 in the crucible lower portion 33C.
Here, the amount of the silicon melt in the crucible is further reduced to be small, so that the oxygen concentration in the silicon melt is low, but the thermal conductivity is improved because the transparent inner layer 3B is formed thick in the crucible lower portion 33C. Thereby, the temperature of the inner surface of the crucible increases, and the amount of quartz melted from the crucible 3 into the silicon melt increases.
By thus growing the straight tube portion C2, the oxygen concentration is corrected to be uniform in the growth axis direction of the straight tube portion C2.
Then, when the straight tube portion C2 is formed to a predetermined length, the process proceeds to a final tail process (step S6 in fig. 2). In this tail step, the contact area between the lower end of the crystal and the melt M gradually decreases, and the single crystal C and the melt M are separated, thereby producing a silicon single crystal.
As described above, according to the present embodiment, the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the wall of the silica glass crucible is adjusted in the height direction of the silica glass crucible, so that the oxygen concentration in the crystal growth axis direction of the pulled silicon single crystal can be controlled to be close to a desired value and uniform.
In addition, with the conventional single crystal pulling apparatus, the thickness T of the transparent inner layer 3B is only required to be adjusted with respect to the wall thickness T of the crucible 3, so that the related cost can be suppressed.
In addition, since the temperature of the silicon melt surface can be controlled to be constant, the distribution of crystal defects can be prevented from becoming uneven.
In the above embodiment, the case where the ratio T/T of the thickness T of the transparent inner layer 3B to the crucible wall thickness T is set to 0.08, 0.3, 0.6 was described, but the ratio T/T may be appropriately changed by changing parameters such as the magnetic field strength, the magnetic field center position, the flow rate of the inert gas or the furnace internal pressure, the rotation of the silica glass crucible, the rotation of the single crystal, and the like.
In the above embodiment, the quartz glass crucible 3 is divided into 3 regions (33A, 33B, 33C) in the height direction, and the ratio T/T is set for each region, but in the present invention, the number of the regions is not limited and may be appropriately set.
In addition, instead of dividing into regions to set a specific ratio T/T, the ratio T/T may be changed slowly in the height direction of the quartz glass crucible 3.
The quartz glass crucible 3 has a double-layer structure of the opaque outer layer 3A and the transparent inner layer 3B, but the present invention is not limited to this configuration, and the number of layers is not limited as long as the inner layer is a transparent layer.
Moreover, in practicing the present invention, the following methods may be used in combination: a method using a heat insulating jig as disclosed in patent document 1, and a method of adjusting the amount of evaporation of SiO gas from a melt by the flow rate and pressure of inert gas as disclosed in patent document 2.
Examples
The method for producing a silicon single crystal according to the present invention will be further described with reference to examples.
(experiment 1)
In experiment 1, it was verified how it affects the oxygen concentration distribution in the pulling direction of the pulled silicon single crystal by varying the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the crucible wall in the crucible height direction.
In experiment 1, in the single crystal pulling apparatus having the structure described in the above embodiment, 350kg of raw material polycrystalline silicon was charged into a crucible, and a silicon single crystal having a diameter of 300mm was pulled. In order to suppress natural convection of the silicon melt, the magnetic beam density of the horizontal magnetic field applied in the pulling was set to 2500Gauss.
The flow rate of the inert gas was set to 90L/min, and the furnace internal pressure was set to 50torr.
The rotation speed of the crucible was set to 1rpm, and the rotation speed of the single crystal was set to 10rpm (the rotation directions were opposite to each other).
In example 1, example 2 and comparative example 1, the ratio T/T of the thickness T of the transparent inner layer 3B to the crucible wall thickness T shown in fig. 3 was set as shown in table 1.
In example 1, the ratio T/T of the quartz crucible was set under the condition of the pulling apparatus having a tendency that the upper oxygen concentration of the pulled single crystal was higher than the lower oxygen concentration.
In example 2, the ratio T/T of the quartz crucible was set under the condition of the pulling apparatus having a tendency that the upper oxygen concentration of the pulled single crystal was higher than the lower oxygen concentration.
In comparative example 1, the ratio T/T of the quartz crucible was not changed under the conditions of the pulling apparatus having a tendency that the upper oxygen concentration of the pulled single crystal was higher than the lower oxygen concentration.
The results of experiment 1 are shown in the graph of fig. 6. The vertical axis of the graph of FIG. 6 is the oxygen concentration (. Times.10) 18 /cm 3 ) The horizontal axis represents the curing rate. In addition, the deviation of the oxygen concentration in the axial direction of the single crystal pulled up according to the conditions of examples 1, 2 and comparative example 1 is shown in table 1.
(Table 1)
As shown in the graph of fig. 6, in example 1, the oxygen concentration at the initial stage of crystal pulling was suppressed, and a single crystal having a uniform oxygen concentration in the direction of the crystal growth axis was obtained at a low oxygen concentration. As shown in table 1, the variation in oxygen concentration was suppressed to 14%. In example 2, the oxygen concentration was increased in the later stage of crystal pulling, and a single crystal having a uniform oxygen concentration in the direction of the crystal growth axis was obtained at a high oxygen concentration. As shown in table 1, the variation in oxygen concentration was suppressed to 13%.
In comparative example 1, a single crystal having a higher oxygen concentration toward the upper portion of the crystal was obtained. As shown in table 1, the variation in oxygen concentration was as large as 30%.
From the results of this experiment 1, it was confirmed that: according to the present invention, the oxygen concentration can be controlled more uniformly in the crystal growth axis direction, and the variation in the oxygen concentration is suppressed to within 20%.
(experiment 2)
In experiment 2, under the condition of the pulling apparatus having a tendency that the upper oxygen concentration of the pulled single crystal is lower than the lower oxygen concentration, the ratio T/T of the thickness T of the transparent inner layer of the quartz crucible to the thickness T of the crucible wall was varied in the crucible height direction, and the variation in the oxygen concentration in the height direction of the pulled single crystal was verified. The conditions for single crystal pulling were the same as in experiment 1.
The ratio T/T of the upper, middle, and lower portions of the crucible in examples 3, 4 and comparative example 2, and the deviation of the oxygen concentration in the axial direction of the single crystal pulled according to these conditions are shown in Table 2.
In addition, the graph of fig. 7 shows the variation of the single crystal oxygen concentration in examples 3, 4 and comparative example 2. In the graph of FIG. 7, the vertical axis represents oxygen concentration (. Times.10) 18 /cm 3 ) The horizontal axis represents the curing rate.
(Table 2)
As shown in the graph of fig. 7 and table 2, in examples 3 and 4, by setting the ratio T/T of the upper portion of the crucible to be larger than that of the lower portion of the crucible, the deviation of the oxygen concentration distribution in the pulling-up axis direction of the single crystal was suppressed to a small level (10% or less).
On the other hand, in comparative example 2, the ratio T/T of the thickness of the transparent inner layer was set to be substantially constant in the crucible height direction, but the upper oxygen concentration of the pulled single crystal was lower than that of the lower portion (similar to the base), and as a result, the variation in the oxygen concentration became larger (22%).
(experiment 3)
In experiment 3, a suitable range of the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the crucible wall was verified. Whether or not the crystal is suitable is determined based on the dislocation rate of the crystal and the magnitude of the temperature change.
Table 3 shows conditions, i.e., the ratio T/T, and dislocation rate of the resulting crystals and the amount of change in temperature of the melt in examples 5 to 7 and comparative examples 3 to 6. In examples 5 to 7 and comparative examples 3 to 6 of experiment 3, the ratio T/T was set so as to make the oxygen concentration distribution in the pulling axis direction of the pulled single crystal uniform. Other conditions were the same as in experiment 1.
(Table 3)
As shown in Table 3, good results were obtained with dislocation ratios of 10% or less and temperature changes of.+ -. 3 ℃ at the ratios T/T set in examples 5 to 7.
On the other hand, when there is a portion having a ratio T/T lower than 0.05 as in comparative examples 3 and 4, bubbles in the opaque layer are exposed, fine quartz particles are generated, and the dislocation rate increases.
In addition, in the case where there is a portion having a ratio T/T of 0.80 or more as in comparative examples 5 and 6, uniform diffusion of heat by the opaque outer layer becomes insufficient, and it becomes difficult to control the temperature, and the amount of change in the temperature of the silicon melt increases.
From this result, it was confirmed that: it is desirable that the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the crucible wall be in the range of greater than 0.05 and less than 0.80.
Symbol description
1: a single crystal pulling device;
2: a carbon base;
3: quartz glass crucible (crucible);
4: an intermediate heater;
6: a wire rod;
7: a radiation shield;
8: a magnetic field applying electromagnetic coil;
9: a lifting mechanism;
10: a furnace body;
11: a computer;
11a: a storage device;
11b: an arithmetic control device;
14: a rotation driving part;
15: a lifting driving part;
c: a silicon single crystal;
m: a silicon melt;
c1: a shoulder;
c2: a straight cylinder part.
Claims (3)
1. A method for producing a silicon single crystal, characterized by: a method for producing a silicon single crystal by pulling up a silicon single crystal from a silicon melt contained in a quartz glass crucible by the Czochralski method using the quartz glass crucible,
wherein the quartz glass crucible for pulling the silicon single crystal is a double-layer structure comprising an opaque outer layer and a transparent inner layer,
the ratio T/T of the thickness T of the transparent inner layer to the sidewall thickness T of the quartz glass crucible from the upper portion to the lower portion of the sidewall of the quartz glass crucible is determined based on the tendency of the oxygen concentration in the growth axis direction of the silicon single crystal to be pulled in advance,
and the ratio T/T is in the range of more than 0.05 and less than 0.8 from the upper part to the lower part of the side wall of the quartz glass crucible,
when the silicon single crystal pulled in advance is pulled under the pulling conditions, the deviation of the oxygen concentration in the crystal growth axis direction of the pulled silicon single crystal is within 20%.
2. The method for producing a silicon single crystal according to claim 1, wherein: as a tendency of the oxygen concentration in the growth axis direction of the pulled silicon single crystal, there is a tendency that the oxygen concentration in the upper portion of the pulled silicon single crystal is lower than the oxygen concentration in the lower portion, and in the silica glass crucible used for the single crystal pulling condition, the ratio T/T in the upper portion of the silica glass crucible is set to be larger than the ratio T/T in the lower portion of the silica glass crucible.
3. The method for producing a silicon single crystal according to claim 1, wherein: the quartz glass crucible is divided into a plurality of regions from the upper part to the lower part of the side wall of the quartz glass crucible, and the ratio T/T of the thickness T of the transparent inner layer to the thickness T of the side wall of the quartz glass crucible is adjusted for each of the plurality of regions.
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| JP2019203916A JP2021075425A (en) | 2019-11-11 | 2019-11-11 | Method for manufacturing silicon single crystal |
| JP2019-203916 | 2019-11-11 | ||
| PCT/JP2020/032354 WO2021095324A1 (en) | 2019-11-11 | 2020-08-27 | Method for producing silicon single crystal |
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| JP (1) | JP2021075425A (en) |
| CN (1) | CN114616361B (en) |
| DE (1) | DE112020005532T5 (en) |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004106247A1 (en) * | 2003-05-30 | 2004-12-09 | Shin-Etsu Quartz Products Co., Ltd. | Quartz glass crucible for pulling up silicon single crystal |
| CN101624721A (en) * | 2008-07-10 | 2010-01-13 | 日本超精石英株式会社 | Quartz glass crucible and silicon single crystal pulling method using same |
| CN101857969A (en) * | 2009-04-02 | 2010-10-13 | 日本超精石英株式会社 | Vitreous silica crucible for pulling silicon single crystal |
| JP2013538179A (en) * | 2010-09-21 | 2013-10-10 | ヘレウス・クアルツグラース・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング・ウント・コンパニー・コマンディット・ゲゼルシャフト | Method for producing a quartz glass crucible with a transparent inner layer made of synthetic quartz glass |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2606046B2 (en) | 1992-04-16 | 1997-04-30 | 住友金属工業株式会社 | Control method of single crystal oxygen concentration during single crystal pulling |
| TW554093B (en) | 2000-02-28 | 2003-09-21 | Shinetsu Handotai Kk | Method for preparing silicon single crystal and silicon single crystal |
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- 2020-08-27 WO PCT/JP2020/032354 patent/WO2021095324A1/en active Application Filing
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004106247A1 (en) * | 2003-05-30 | 2004-12-09 | Shin-Etsu Quartz Products Co., Ltd. | Quartz glass crucible for pulling up silicon single crystal |
| CN101624721A (en) * | 2008-07-10 | 2010-01-13 | 日本超精石英株式会社 | Quartz glass crucible and silicon single crystal pulling method using same |
| CN101857969A (en) * | 2009-04-02 | 2010-10-13 | 日本超精石英株式会社 | Vitreous silica crucible for pulling silicon single crystal |
| JP2013538179A (en) * | 2010-09-21 | 2013-10-10 | ヘレウス・クアルツグラース・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング・ウント・コンパニー・コマンディット・ゲゼルシャフト | Method for producing a quartz glass crucible with a transparent inner layer made of synthetic quartz glass |
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| JP2021075425A (en) | 2021-05-20 |
| TW202132633A (en) | 2021-09-01 |
| CN114616361A (en) | 2022-06-10 |
| DE112020005532T5 (en) | 2022-09-01 |
| WO2021095324A1 (en) | 2021-05-20 |
| TWI784314B (en) | 2022-11-21 |
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