Method for drawing silicon single crystal rod and silicon single crystal rod
阅读说明：本技术 一种单晶硅棒的拉制方法及单晶硅棒 (Method for drawing silicon single crystal rod and silicon single crystal rod ) 是由 孙介楠 于 2021-07-07 设计创作，主要内容包括：本发明实施例公开了一种单晶硅棒的拉制方法及单晶硅棒,所述方法包括：将设定质量的多晶硅熔料和第一预设质量的掺杂剂放置于石英坩埚中加热熔化形成硅熔液后,拉制第一预设长度的第一单晶硅棒节；当所述第一单晶硅棒节收尾时,在所述第一单晶硅棒节的尾部生长出带水平肩部的晶体；提升所述第一单晶硅棒节至副炉室冷却后,将第二预设质量的所述掺杂剂放置在所述晶体的水平肩部处；通过下降所述第一单晶硅棒节使所述晶体完全浸入剩余的所述硅熔液中并熔化后,拉制第二预设长度的第二单晶硅棒节。(The embodiment of the invention discloses a method for drawing a single crystal silicon rod and the single crystal silicon rod, wherein the method comprises the following steps: placing a polycrystalline silicon molten material with set mass and a dopant with first preset mass in a quartz crucible, heating and melting to form silicon melt, and drawing a first monocrystalline silicon rod section with first preset length; when the first monocrystalline silicon rod section is ended, growing a crystal with a horizontal shoulder at the tail part of the first monocrystalline silicon rod section; lifting the first monocrystalline silicon bar section to a secondary furnace chamber for cooling, and then placing a second preset mass of the dopant at a horizontal shoulder of the crystal; after the crystal is completely immersed and melted in the remaining silicon melt by lowering the first single crystal silicon rod segment, a second single crystal silicon rod segment of a second predetermined length is pulled.)
1. A method for pulling a single crystal silicon rod, the method comprising:
placing a polycrystalline silicon molten material with set mass and a dopant with first preset mass in a quartz crucible, heating and melting to form silicon melt, and drawing a first monocrystalline silicon rod section with first preset length;
when the first monocrystalline silicon rod section is ended, growing a crystal with a horizontal shoulder at the tail part of the first monocrystalline silicon rod section;
lifting the first monocrystalline silicon bar section to a secondary furnace chamber for cooling, and then placing a second preset mass of the dopant at a horizontal shoulder of the crystal;
after the crystal is completely immersed and melted in the remaining silicon melt by lowering the first single crystal silicon rod segment, a second single crystal silicon rod segment of a second predetermined length is pulled.
2. The method of claim 1, wherein drawing a first single crystal silicon rod segment of a first predetermined length after placing a set mass of polycrystalline silicon melt and a first predetermined mass of dopant in a quartz crucible and heating and melting to form a silicon melt comprises:
under the condition that the mass M of the polycrystalline silicon molten material is constant, acquiring a first preset mass M of the dopant1；
Melting the polysilicon with mass M and a first preset mass M1The dopant is added into a quartz crucible to be heated and melted to form silicon melt, and then the first monocrystalline silicon rod section S is drawn by adopting a Czochralski method1And monitoring the first monocrystalline silicon segment S in the isometric growth stage1The growth length of (a);
when the first monocrystalline silicon rod section S1Up to the first preset length L1While aligning the first monocrystalline silicon rod section S1And carrying out ending procedure operation.
3. The method of claim 2, wherein the obtaining of the first predetermined mass M of the dopant is performed under a condition that the mass M of the polysilicon frit is constant1The method comprises the following steps:
obtaining a first preset mass m of the dopant by calculation of formula (1)1：
Wherein ρ 'represents the resistivity of the reference single crystal silicon rod S'; m 'represents the mass of the dopant in the reference single crystal silicon rod S'; rho1Represents the first monocrystalline silicon segment S1Of (c) is measured.
4. The method of claim 2 wherein the step of melting the polysilicon of mass M and a first predetermined mass M1The dopant is added into a quartz crucible to be heated and melted to form silicon melt, and then the first monocrystalline silicon rod section S is drawn by adopting a Czochralski method1And monitoring the first monocrystalline silicon segment S in the isometric growth stage1Comprises:
pulling the first monocrystalline silicon segment S by a Czochralski method1In the process, the first monocrystalline silicon rod section S is determined by monitoring the rising distance of the seed crystal cable in the equal-diameter growth stage1The growth length of (2).
5. The method of claim 1 wherein growing a crystal with a horizontal shoulder at the tail of the first monocrystalline silicon segment as the first monocrystalline silicon segment is terminated comprises:
at the first monocrystalline silicon rod section S1At the final stage of ending, the first monocrystalline silicon rod section S is accelerated1The rising speed of the crystal is increased, and the seeding and necking processes are carried out;
when the first monocrystalline silicon rod section S1After a section of thin neck grows out of the tail part of the neck, shoulder-putting operation is carried out, so that a horizontal shoulder grows out of the tail end of the thin neck;
after the horizontal shoulder is grown, a rapid ending process operation is carried out to form a first monocrystalline silicon rod section S1Grows a crystal S "with a horizontal shoulder.
6. The method of claim 1 wherein said lifting said first monocrystalline silicon segment to a sub-furnace chamber after cooling places a second predetermined mass of said dopant at a horizontal shoulder of said crystal, comprising:
by lifting a seed crystal cable to make the first monocrystalline silicon rod section S1After moving to a sub-furnace chamber and cooling, placing the second predetermined mass of the dopant at a horizontal shoulder of the crystal.
7. Method according to claim 6, characterized in that said second preset mass m2The calculation method of (2) comprises:
according to the first monocrystalline silicon rod section S1The first monocrystalline silicon rod section S is obtained by calculation1Mass ofWherein D is1Represents the first monocrystalline silicon segment S1λ represents the density of the first monocrystalline silicon rod segment;
according to the first monocrystalline silicon rod section S1Mass M of1Calculating to obtain the mass M of the residual silicon melt in the quartz crucible2＝M-M1；
According to the formula (2), the first monocrystalline silicon rod section S is obtained by derivation calculation1Of the dopant contained in (1)1'：
Wherein a represents a segregation coefficient of the dopant in the silicon melt; m is1"represents the mass of the dopant contained in the remaining silicon melt, and m1”＝m1-m1'；
Calculating to obtain the second monocrystalline silicon rod section S when the mass of the polycrystalline silicon is M according to the formula (3)2Corresponding doping amount m2'：
Where ρ is2Represents the second silicon single crystal bar segment S2The resistivity of (a);
according to the formula (4), the mass M is obtained by calculation2Of the dopant contained in the silicon melt of (1)2”：
According to the doping amount m2"and doping amount m in the remaining silicon melt1", calculating to obtain a second preset mass m of said dopant to be replenished2＝m2”-m1”。
8. The method of claim 1 wherein drawing a second predetermined length of a second single crystal silicon rod segment after said crystal has been fully immersed and melted in the remaining silicon melt by lowering said first single crystal silicon rod segment comprises:
lowering the first monocrystalline silicon segment S1After the dopant deposited on the crystal is completely immersed in the remaining silicon melt and melted, the second single-crystal silicon rod segment S is pulled by the Czochralski method2And monitoring the second monocrystalline silicon bar section S in the equal-diameter growth stage2The growth length of (a);
when the second monocrystalline silicon rod section S2Is the second preset length L2While aligning the second monocrystalline silicon rod section S2And carrying out ending procedure operation.
9. The method of claim 8 wherein said lowering said first monocrystalline silicon segment S1After the dopant deposited on the crystal is completely immersed in the remaining silicon melt and melted, the second single-crystal silicon rod segment S is pulled by the Czochralski method2And monitoring the second monocrystalline silicon bar section S in the equal-diameter growth stage2Comprises:
pulling the second monocrystalline silicon segment S by a Czochralski method2In the process, the second monocrystalline silicon rod section S is determined by monitoring the rising distance of the seed crystal cable in the equal-diameter growth stage2The growth length of (2).
10. A single crystal silicon rod, characterized in that it is prepared according to the pulling method of any one of claims 1 to 9.
Technical Field
The embodiment of the invention relates to the technical field of manufacturing of single crystal silicon rods, in particular to a method for drawing a single crystal silicon rod and the single crystal silicon rod.
Background
Single crystal silicon rods are mostly produced by the Czochralski (Czochralski) method, also referred to as the Czochralski method. The method uses the principle of condensation crystallization driving of melt, and at the interface of solid and liquid, the phase change from liquid to solid is generated due to the temperature drop of the melt. In the method, the solid polycrystalline silicon melt is placed in a quartz crucible and heated to melt the polycrystalline silicon melt in the quartz crucible, and then the dislocation-free silicon single crystal rod is finally pulled through the processes of seeding, necking, shouldering, diameter equalization, ending and the like.
On the other hand, the silicon single crystal rod may be classified into a P-type silicon single crystal rod and an N-type silicon single crystal rod according to the difference of the dopant. In addition, taking a P-type single crystal silicon rod as an example, the P-type single crystal silicon rod can be further divided into a lightly doped P + single crystal silicon rod and a heavily doped P + + single crystal silicon rod according to the content of the dopant. The existing method for producing the P-type single crystal silicon rod is to put boron as a dopant and a polycrystalline silicon melt into a quartz crucible at the same time for heating and melting so as to change the characteristics of the single crystal silicon rod.
However, in actual production, customers often make different demands, for example, only a specified length of a lightly doped P + single crystal silicon rod or a heavily doped P + + single crystal silicon rod is needed, in which case, if only a short length of the lightly doped P + single crystal silicon rod or the heavily doped P + + single crystal silicon rod is pulled, costs such as a quartz crucible, productivity, etc. may be increased; or if a long length of lightly doped P + single crystal silicon rod or heavily doped P + + single crystal silicon rod is still being pulled, the portion of the single crystal silicon rod that is not in customer demand is wasted.
Disclosure of Invention
In view of the above, embodiments of the present invention are intended to provide a method for pulling a single crystal silicon rod and a single crystal silicon rod; the continuous drawing method can realize that two sections of monocrystalline silicon rod sections which respectively contain lightly doped P + and heavily doped P + + and have different lengths are continuously drawn on the same monocrystalline silicon rod, has simple process operation, meets the product requirements of different customers, avoids the waste of the monocrystalline silicon rod, and reduces the production cost.
The technical scheme of the embodiment of the invention is realized as follows:
in a first aspect, an embodiment of the present invention provides a method for pulling a single crystal silicon rod, where the method includes:
placing a polycrystalline silicon molten material with set mass and a dopant with first preset mass in a quartz crucible, heating and melting to form silicon melt, and drawing a first monocrystalline silicon rod section with first preset length;
when the first monocrystalline silicon rod section is ended, growing a crystal with a horizontal shoulder at the tail part of the first monocrystalline silicon rod section;
lifting the first monocrystalline silicon bar section to a secondary furnace chamber for cooling, and then placing a second preset mass of the dopant at a horizontal shoulder of the crystal;
after the crystal is completely immersed and melted in the remaining silicon melt by lowering the first single crystal silicon rod segment, a second single crystal silicon rod segment of a second predetermined length is pulled.
In a second aspect, the embodiment of the present invention provides a single crystal silicon rod, which is prepared according to the drawing method of the first aspect.
The embodiment of the invention provides a method for drawing a single crystal silicon rod and the single crystal silicon rod; by the drawing method, a first monocrystalline silicon rod section which is lightly doped with P + can be drawn firstly, the length of the first monocrystalline silicon rod section can be controlled to be a first preset length, a crystal which contains a horizontal shoulder part grows at the tail part of the first monocrystalline silicon rod section when the first monocrystalline silicon rod section is closed, a dopant which needs to be supplemented subsequently is placed at the horizontal shoulder part of the crystal, the first monocrystalline silicon rod section is descended to ensure that the dopant which needs to be supplemented is completely immersed in the residual silicon melt and is fully melted, a second monocrystalline silicon rod section which is heavily doped with P + + is drawn by adopting a Czochralski method, the growth length of the second monocrystalline silicon rod section can be controlled to be a second preset length, so that a first monocrystalline silicon rod section and a second monocrystalline silicon rod section which respectively contain the lightly doped P + and the heavily doped P + + and have different lengths are obtained by continuous drawing, the drawing method is simple and easy to operate, and the first monocrystalline silicon rod section and the second monocrystalline silicon rod section which are drawn can meet different product requirements, the waste of the silicon single crystal rod is avoided, and the production cost is reduced.
Drawings
FIG. 1 is a schematic view of a crystal pulling furnace according to an embodiment of the present invention.
Fig. 2 is a schematic view of a structure of a single crystal silicon rod pulled in a conventional technical scheme provided by an embodiment of the invention.
Fig. 3 is a schematic flow chart of a method for pulling a single crystal silicon rod according to an embodiment of the present invention.
Fig. 4 is a schematic view of a structure for monitoring the growth length of a single crystal silicon rod according to an embodiment of the present invention.
FIG. 5 is a schematic crystal structure of a first single crystal silicon ingot tail growth according to an embodiment of the present invention.
FIG. 6 is a schematic diagram of horizontal shoulder placement of dopants in a crystal according to an embodiment of the present invention.
FIG. 7 is a schematic view of a crystal fully immersed in a silicon melt according to an embodiment of the present invention.
Fig. 8 is a schematic structural view of a single crystal silicon rod according to an embodiment of the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Referring to fig. 1, which shows a schematic structural diagram of a crystal pulling furnace 1 capable of implementing the technical solution of the embodiment of the present invention, as shown in fig. 1, the crystal pulling furnace 1 comprises a sub-furnace chamber 10, a draft tube 20, a quartz crucible 30 and a graphite heater 40 distributed around the quartz crucible 30, and is located in a main furnace chamber 50, and a polycrystalline silicon melt can be contained in the quartz crucible 30 and heated and melted by the graphite heater 40 to form a silicon melt MS.
It can be understood that the crystal pulling furnace 1 further comprises a seed cable 60, which can be used for loading M mass of polysilicon melt and M ' mass of dopant into the quartz crucible 30 when pulling the reference single crystal silicon rod S ' containing dopant, when the quartz crucible 30 is heated to melt the polysilicon melt and the dopant to form a silicon melt MS and the temperature of the silicon melt MS is stable, the seed cable 60 lowers the seed 70 to the solid-liquid interface of the silicon melt MS and starts the processes of seeding, necking, shouldering, isodiametric growth, ending and the like, so as to finally obtain a reference single crystal silicon rod S ' with a certain length, for example, taking the current reference single crystal silicon rod S ' with a diameter of 12 inches as an example, when 400 kg of polysilicon melt and a certain mass of dopant boron are added into the quartz crucible 30, the reference single crystal silicon rod S ' with a length of about 2 meters can be pulled, and it is understood that the reference single crystal silicon rod S' contains the same amount of doping at each portion thereof. The reference single crystal silicon rod S' after being pulled is shown in fig. 2.
A pulling head 80 connected to the seed crystal cable 60 is further provided at the uppermost portion of the furnace body of the crystal pulling furnace 1, and the pulling head 80 is mainly used for rotating and lifting the seed crystal 70 and recording data such as the displacement of the seed crystal.
It is understood that other structures not shown in FIG. 1, such as a crucible lifting device, etc., may be included in the crystal pulling furnace 1 shown in FIG. 1, and embodiments of the present invention are not specifically illustrated.
Referring to fig. 3, a crystal pulling furnace 1 is provided, which illustrates a method for pulling a single crystal silicon rod S according to an embodiment of the present invention, the method including:
s301, placing a polycrystalline silicon molten material with set mass and a dopant with first preset mass in a quartz crucible, heating and melting to form silicon molten liquid, and drawing a first monocrystalline silicon rod section with first preset length;
s302, when the first monocrystalline silicon rod section is ended, growing a crystal with a horizontal shoulder at the tail part of the first monocrystalline silicon rod section;
s303, lifting the first monocrystalline silicon rod section to a secondary furnace chamber for cooling, and then placing the dopant with a second preset mass at the horizontal shoulder of the crystal;
s304, lowering the first monocrystalline silicon rod segment to enable the crystal to be completely immersed into the residual silicon melt and melted, and then drawing a second monocrystalline silicon rod segment with a second preset length.
It should be noted that, after adding a first predetermined mass of boron dopant into a polysilicon melt with a predetermined mass and melting the mixture to form a silicon melt, the first silicon single crystal rod segment lightly doped with P + can be obtained by pulling according to the czochralski method, and after the first silicon single crystal rod segment is pulled, a supplementary dopant is added into the remaining silicon melt to obtain a second silicon single crystal rod segment heavily doped with P + +, so that the second predetermined mass of the dopant in step S303 represents the mass of boron dopant to be subsequently supplemented.
By the technical scheme shown in FIG. 3, a second monocrystalline silicon rod section heavily doped with P + + can be obtained by pulling a first monocrystalline silicon rod section lightly doped with P + and growing a crystal with a horizontal shoulder when the first monocrystalline silicon rod section is terminated, lifting the first monocrystalline silicon rod section to a sub-furnace chamber for cooling before pulling a second monocrystalline silicon rod section, placing a dopant with a second preset mass to be supplemented at the horizontal shoulder of the crystal, and completely immersing the crystal from the first monocrystalline silicon rod section to the tail part into the remaining silicon melt and fully melting the crystal.
For the solution shown in fig. 3, in some examples, after placing the polysilicon melt of the set mass and the dopant of the first preset mass in the quartz crucible and heating and melting the polysilicon melt to form the silicon melt, the pulling the first single crystal silicon rod segment of the first preset length includes:
under the condition that the mass M of the polycrystalline silicon molten material is constant, acquiring a first preset mass M of the dopant1；
Melting the polysilicon with mass M and a first preset mass M1The dopant is added into a quartz crucible to be heated and melted to form silicon melt, and then the first monocrystalline silicon rod section S is drawn by adopting a Czochralski method1And monitoring the first monocrystalline silicon segment S in the isometric growth stage1The growth length of (a);
when the first monocrystalline silicon rod section S1Up to the first preset length L1While aligning the first monocrystalline silicon rod section S1And carrying out ending procedure operation.
For the above example, in some possible implementations, the obtaining of the first preset mass M of the dopant is performed under a condition that the mass M of the polysilicon frit is constant1The method comprises the following steps:
the dopant is obtained by calculation of formula (1)First predetermined mass m1：
Wherein ρ 'represents the resistivity of the reference single crystal silicon rod S'; m 'represents the mass of the dopant in the reference single crystal silicon rod S'; rho1Represents the first monocrystalline silicon segment S1Of (c) is measured.
For the above technical solution, before the implementation of the present invention, a reference single crystal silicon rod S 'as shown in fig. 2 is drawn in advance based on the crystal pulling furnace apparatus 1, wherein the mass of the polysilicon melt fed when the reference single crystal silicon rod S' is drawn is also M, and the mass of the added dopant boron is M ', so that the resistivity ρ' of the reference single crystal silicon rod S 'can be obtained through a test, and a test method of the specific resistivity ρ' is not specifically described in the embodiments of the present invention.
Under the condition that the resistivity rho 'of the reference monocrystalline silicon rod S' is obtained through the test, the first monocrystalline silicon rod section S of the drawn lightly doped P + can be obtained through the calculation of the formula (1)1A first predetermined mass M of boron dopant to be added to the M-mass polysilicon melt1。
In the embodiment of the present invention, the first monocrystalline silicon segment S1Is drawn according to the requirements of the product, and therefore its resistivity ρ1Are known.
For the above example, in some possible implementations, the polysilicon frit material of mass M and a first predetermined mass M1The dopant is added into a quartz crucible to be heated and melted to form silicon melt, and then the first monocrystalline silicon rod section S is drawn by adopting a Czochralski method1And monitoring the first monocrystalline silicon segment S in the isometric growth stage1Comprises:
pulling the first monocrystalline silicon segment S by a Czochralski method1In the process, the first monocrystalline silicon rod section S is determined by monitoring the rising distance of the seed crystal cable in the equal-diameter growth stage1The growth length of (2).
Can be used forUnderstandably, as shown in FIG. 1, a first monocrystalline silicon segment S is prepared using crystal pulling furnace 11In the meantime, after the polycrystalline silicon melt is melted and the temperature of the silicon melt MS is stabilized, the seed crystal 70 is lowered to the liquid level of the silicon melt by the pulling head 80 and the process operations such as seeding are performed, and when the seeding is completed and the growth of the narrow neck is started, the seed crystal 70 gradually rises along with the rise of the seed crystal cable 60. Thus, it will be appreciated that the distance that seed cable 60 rises during the isometric growth stage can be used to characterize first single crystal silicon rod segment S1The growth length of (2).
Note that the distance by which the seed cable 60 rises can be obtained from the displacement data in the pulling head 80.
In some implementations of the invention, as shown in FIG. 4, the end of seed crystal cable 60 may also be connected to a cable 901 on spool 90, and the first monocrystalline silicon rod segment S is determined during the isometric growth phase by monitoring the distance traveled around cable 9011The length of growth of (1), specifically, the distance l that the rope 901 moves is pi dn obtained by the number of turns n of the rope 901 wound on the winding shaft 90 when moving and the diameter d of the winding shaft 90; of course, in the first monocrystalline silicon segment S1First preset length L1By monitoring the number of turns of rope 901 wound on spool 80, as is knownCan also control the first monocrystalline silicon bar section S1The growth length of (2).
Of course, for the first monocrystalline silicon segment S1The monitoring of the growth length is not limited to the above-mentioned method, and for example, an industrial camera or the like may be installed in an observation window (not shown) of the crystal pulling furnace 1 to monitor the first silicon single crystal ingot S in real time1The growth state and the growth length of (c).
As can be appreciated, during the isometric growth phase, when seed cable 60 is moved a distance l equal to first monocrystalline silicon segment S1First preset length L1Then, the first monocrystalline silicon segment S can be carried out1And (4) ending the process.
For the solution shown in fig. 3, in some examples, growing a crystal with a horizontal shoulder at the tail of the first monocrystalline silicon segment as the first monocrystalline silicon segment is terminated includes:
at the first monocrystalline silicon rod section S1At the final stage of ending, the first monocrystalline silicon rod section S is accelerated1The rising speed of the crystal is increased, and the seeding and necking processes are carried out;
when the first monocrystalline silicon rod section S1After a section of thin neck grows out of the tail part of the neck, shoulder-putting operation is carried out, so that a horizontal shoulder grows out of the tail end of the thin neck;
after the horizontal shoulder is grown, a rapid ending process operation is carried out to form a first monocrystalline silicon rod section S1Grows a crystal S "with a horizontal shoulder.
Understandably, in the first monocrystalline silicon segment S1At the final stage of ending, the first monocrystalline silicon rod section S can be accelerated1And performing a necking operation on the first monocrystalline silicon segment S1The first monocrystalline silicon rod section S can be formed by growing a section of thin neck at the conical tail end, shouldering and rapidly ending1As shown in FIG. 5, and the crystal S' has a first single crystal silicon rod S1The same horizontal shoulder.
For the solution shown in fig. 3, in some examples, said lifting said first monocrystalline silicon segment to a sub-furnace chamber after cooling, placing a second predetermined mass of said dopant at a horizontal shoulder of said crystal, comprises:
by lifting a seed crystal cable to make the first monocrystalline silicon rod section S1After moving to a sub-furnace chamber and cooling, placing the second predetermined mass of the dopant at a horizontal shoulder of the crystal.
Understandably, as shown in FIG. 6, when the first monocrystalline silicon segment S1When the furnace is lifted to the auxiliary furnace chamber and after cooling, the mass prepared in advance can be set to a second preset mass m by a charging device in the crystal pulling furnace 12Is placed in the horizontal shoulder of the crystal S "(shown as a black circle).
For the above example, in some possible implementations, the second preset mass m2The calculation method of (2) comprises:
according to the first monocrystalline silicon rod section S1The first monocrystalline silicon rod section S is obtained by calculation1Mass ofWherein D is1Represents the first monocrystalline silicon segment S1λ represents the density of the first monocrystalline silicon rod segment;
according to the first monocrystalline silicon rod section S1Mass M of1Calculating to obtain the mass M of the residual silicon melt in the quartz crucible2＝M-M1；
According to the formula (2), the first monocrystalline silicon rod section S is obtained by derivation calculation1Of the dopant contained in (1)1'：
Wherein a represents a segregation coefficient of the dopant in the silicon melt; m is1"represents the mass of the dopant contained in the remaining silicon melt, and m1”＝m1-m1'；
Calculating to obtain the second monocrystalline silicon rod section S when the mass of the polycrystalline silicon is M according to the formula (3)2Corresponding doping amount m2'：
Where ρ is2Represents the second silicon single crystal bar segment S2The resistivity of (a);
according to the formula (4), the mass M is obtained by calculation2Of the dopant contained in the silicon melt of (1)2”：
According to the doping amount m2"and doping amount m in the remaining silicon melt1", calculating to obtain a second preset mass m of said dopant to be replenished2＝m2”-m1”。
Note that since the segregation coefficient is the solubility of impurities in the solid phase/the solubility of impurities in the liquid phase, and the segregation coefficient of boron as a dopant in the silicon melt is generally 0.3, it can be derived by the inverse of the equations (2), (3) and (4): when the mass M of the remaining silicon melt is known2Then, a second monocrystalline silicon bar section S heavily doped with P + + is prepared2Mass m of boron as dopant required2", so as to depend on the mass m of dopant already contained in the remaining silicon melt1", calculating to obtain a second predetermined mass m of dopant to be replenished2。
It should be noted that, in the embodiment of the present invention, the second monocrystalline silicon segment S2Is drawn according to the requirements of the product, and therefore its resistivity ρ2Are known.
Of course, it is understood that in the embodiment of the present invention, a weighing device (not shown) may also be provided at the pull head 80 to obtain the first monocrystalline silicon segment S1Mass M of1Further according to the first monocrystalline silicon bar section S1Mass M of1Obtaining the mass M of the silicon melt remaining in the quartz crucible2And when the mass of the silicon melt is M2While drawing the second monocrystalline silicon rod section S heavily doped with P ++2Mass m of boron as dopant2", ultimately obtaining a second predetermined mass m of said dopant to be replenished2。
With respect to the solution shown in FIG. 3, in some examples, said pulling a second predetermined length of a second single crystal silicon rod segment after said crystal has been completely immersed and melted in the remaining silicon melt by lowering said first single crystal silicon rod segment comprises:
lowering the first single crystalSilicon rod segment S1After the dopant deposited on the crystal is completely immersed in the remaining silicon melt and melted, the second single-crystal silicon rod segment S is pulled by the Czochralski method2And monitoring the second monocrystalline silicon bar section S in the equal-diameter growth stage2The growth length of (a);
when the second monocrystalline silicon rod section S2Is the second preset length L2While aligning the second monocrystalline silicon rod section S2And carrying out ending procedure operation.
Understandably, as shown in FIG. 7, the first monocrystalline silicon segment S "is lowered by placing boron, which is a dopant to be replenished, in the horizontal shoulder of crystal S ″1Until the entire crystal S ", including its horizontal shoulder, is completely immersed in the remaining silicon melt and melted and the temperature of the silicon melt is stabilized, the process steps of the Czochralski method can be followed: the operations of seeding, necking, shouldering, equal-diameter growth and ending are carried out on the first monocrystalline silicon rod section S1Is continuously drawn to obtain a second preset length L2Second monocrystalline silicon segment S2And the second monocrystalline silicon segment S2The doping type of the doped layer is heavily doped P + +.
As can be appreciated, after crystal S "is melted in its entirety into the remaining silicon melt, a second single crystal silicon rod segment S is pulled by the Czochralski method2While the first monocrystalline silicon bar section S1The seeding can be carried out, and the process operations of necking, shouldering, equal-diameter growth and ending can be completed on the basis of the seeding operation.
For the above example, in some possible implementations, the lowering the first monocrystalline silicon segment S1After the dopant deposited on the crystal is completely immersed in the remaining silicon melt and melted, the second single-crystal silicon rod segment S is pulled by the Czochralski method2And monitoring the second monocrystalline silicon bar section S in the equal-diameter growth stage2Comprises:
pulling the second monocrystalline silicon segment S by a Czochralski method2In the process, the second monocrystalline silicon rod section S is determined by monitoring the rising distance of the seed crystal cable in the equal-diameter growth stage2The growth length of (2).
Referring to fig. 8, a single crystal silicon rod S provided by an embodiment of the present invention is shown, which is prepared according to the pulling method of the foregoing technical solution.
As can be seen from FIG. 8, the single crystal silicon rod S obtained by pulling according to the example of the present invention includes a first predetermined length L1The first monocrystalline silicon rod section S of light doped P +1And a length of a first preset length L2The second monocrystalline silicon rod section S heavily doped with P ++2The method can meet different requirements of different customers, and reduces the waste of production cost.
It can be understood that by using the pulling method provided by the embodiment of the invention, the single crystal silicon rod S can also comprise a plurality of sections of single crystal silicon rods with different doping amounts and different lengths.
It should be noted that: the technical schemes described in the embodiments of the present invention can be combined arbitrarily without conflict.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
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