TWI839768B - A method for pulling a single crystal silicon rod - Google Patents

Abstract

The embodiment of the present invention discloses a method for pulling a single crystal silicon rod and a single crystal silicon rod, the method comprising: placing a set mass of polycrystalline silicon melt and a first preset mass of dopant in a quartz crucible, heating and melting to form a silicon melt, and then pulling a first single crystal silicon rod section of a first preset length; when the first single crystal silicon rod section is finished, a crystal with a horizontal shoulder grows at the tail of the first single crystal silicon rod section; after the first single crystal silicon rod section is lifted to the auxiliary furnace chamber for cooling, the dopant of a second preset mass is placed at the horizontal shoulder of the crystal; after the first single crystal silicon rod section is lowered so that the crystal is completely immersed in the remaining silicon melt and melted, a second single crystal silicon rod section of a second preset length is pulled.

Description

A method for pulling a single crystal silicon rod

The embodiment of the present invention belongs to the field of single crystal silicon rod manufacturing technology, and in particular to a single crystal silicon rod drawing method and a single crystal silicon rod.

Most single crystal silicon rods are made by the Czochralski method, also known as the Czochralski method. This method uses the principle of melt condensation crystallization drive. At the interface between solid and liquid, the melt temperature drops to produce a phase change from liquid to solid. In this method, the solid polycrystalline silicon melt is placed in a quartz crucible and heated to melt the polycrystalline silicon melt in the quartz crucible. After seeding, necking, shouldering, equalizing and finishing, the pulling of dislocation-free single crystal silicon rods is finally completed.

On the other hand, single crystal silicon rods can be divided into P-type single crystal silicon rods and N-type single crystal silicon rods according to the different dopants. In addition, taking P-type single crystal silicon rods as an example, according to the amount of dopant, P-type single crystal silicon rods can usually be divided into lightly doped P+ single crystal silicon rods and heavily doped P++ single crystal silicon rods. The current method of producing P-type single crystal silicon rods is to put the dopant boron and polycrystalline silicon melt into a quartz crucible at the same time and heat and melt them to change the characteristics of the single crystal silicon rod.

However, in actual production, customers often have different requirements, such as requiring only a specified length of lightly doped P+ single crystal silicon rod or heavily doped P++ single crystal silicon rod. In this case, if only a shorter length of lightly doped P+ single crystal silicon rod or heavily doped P++ single crystal silicon rod is pulled, the cost will increase, such as quartz crucible, production capacity, etc.; or if a longer length of lightly doped P+ single crystal silicon rod or heavily doped P++ single crystal silicon rod is still pulled, the part of the single crystal silicon rod that does not meet the customer's requirements will be wasted.

In view of this, the embodiment of the present invention is expected to provide a method for drawing a single crystal silicon rod and a single crystal silicon rod; it is possible to continuously draw two sections of single crystal silicon rods with different lengths, each containing lightly doped P+ and heavily doped P++, on the same single crystal silicon rod. The technical operation is simple, and the product requirements of different customers are met, thereby avoiding the waste of single crystal silicon rods and reducing production costs.

The technical solution of the embodiment of the present invention is implemented as follows:

In the first aspect, the embodiment of the present invention provides a method for pulling a single crystal silicon rod, the method comprising: placing a set mass of polycrystalline silicon melt and a first preset mass of dopant in a quartz crucible, heating and melting to form a silicon melt, and then pulling a first single crystal silicon rod section of a first preset length; when the first single crystal silicon rod section is finished, a crystal with a horizontal shoulder grows at the tail of the first single crystal silicon rod section; after the first single crystal silicon rod section is lifted to the auxiliary furnace chamber for cooling, the dopant of a second preset mass is placed at the horizontal shoulder of the crystal; after the first single crystal silicon rod section is lowered so that the crystal is completely immersed in the remaining silicon melt and melted, a second single crystal silicon rod section of a second preset length is pulled.

In the second aspect, an embodiment of the present invention provides a single crystal silicon rod, which is prepared according to the drawing method described in the first aspect.

The present invention provides a method for pulling a single crystal silicon rod and a single crystal silicon rod; through the pulling method, a first single crystal silicon rod section lightly doped with P+ can be pulled, and the length of the first single crystal silicon rod section can be controlled to be a first preset length. When the first single crystal silicon rod section is finished, a crystal with a horizontal shoulder is grown at its tail, and the dopant to be supplemented is placed at the horizontal shoulder of the crystal. The first single crystal silicon rod section is lowered so that the dopant to be supplemented is completely immersed in the remaining silicon melt. After being fully melted, the second single crystal silicon rod section heavily doped with P++ is pulled by the Czochralski method, and the growth length of the second single crystal silicon rod section can be controlled to be a second preset length, thereby continuously pulling the first single crystal silicon rod section and the second single crystal silicon rod section respectively containing lightly doped P+ and heavily doped P++ and having different lengths. The pulling method is simple and easy to operate, and the first single crystal silicon rod section and the second single crystal silicon rod section pulled can meet different product requirements, avoiding waste of single crystal silicon rods and reducing production costs.

1: Crystal pulling furnace

10: Auxiliary furnace room

20: Guide tube

30: Quartz crucible

40: Graphite heater

50: Main furnace room

60: Seed cable

70: Seed crystal

80: Pulling head

90: Winding shaft

901: Rope

MS: Silicon melt

S : Single crystal silicon rod

S ': Single crystal silicon rod

S ":Crystal

S ₁ : First single crystal silicon rod section

S ₂ : Second single crystal silicon rod section

S301-S304: Steps

Figure 1 is a schematic diagram of a crystal pulling furnace structure provided in an embodiment of the present invention.

Figure 2 is a schematic diagram of the structure of a single crystal silicon rod pulled in the conventional technical solution provided in an embodiment of the present invention.

Figure 3 is a schematic diagram of a single crystal silicon rod pulling method provided in an embodiment of the present invention.

Figure 4 is a schematic diagram of a structure for monitoring the growth length of a single crystal silicon rod provided in an embodiment of the present invention.

Figure 5 is a schematic diagram of the crystal structure of the first single crystal silicon rod segment tail growth provided by the embodiment of the present invention.

Figure 6 is a schematic diagram of placing dopants on the horizontal shoulder of a crystal provided in an embodiment of the present invention.

Figure 7 is a schematic diagram of a crystal provided in an embodiment of the present invention being completely immersed in silicon melt.

Figure 8 is a schematic diagram of the structure of a single crystal silicon rod provided in an embodiment of the present invention.

In order to help the review committee understand the technical features, content and advantages of the present invention and the effects it can achieve, the present invention is described in detail as follows with the attached drawings and appendices in the form of embodiments. The drawings used are only for illustration and auxiliary instructions, and may not be the true proportions and precise configurations after the implementation of the present invention. Therefore, the proportions and configurations of the attached drawings should not be interpreted to limit the scope of application of the present invention in actual implementation.

In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "left", "right", "top", "bottom", "inside", "outside" and the like indicate positions or location relationships based on the positions or location relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

See FIG. 1, which shows a schematic diagram of the structure 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 includes an auxiliary furnace chamber 10, a guide tube 20, a quartz crucible 30, and a graphite heater 40 distributed around the quartz crucible 30, which is located in the main furnace chamber 50. The polycrystalline silicon melt can be contained in the quartz crucible 30, and is heated and melted by the graphite heater 40 to form a silicon melt MS.

It can be understood that the structure of the crystal pulling furnace 1 also includes a seed crystal cable 60, which can be used to pull a standard single crystal silicon rod S ' containing a dopant. M mass of polycrystalline silicon melt and m ' of a certain mass of dopant are loaded into the quartz crucible 30. When the quartz crucible 30 is heated to melt the polycrystalline silicon melt and the dopant to form a silicon melt MS and the temperature of the silicon melt MS is stabilized, the seed crystal 70 is lowered to the solid-liquid interface of the silicon melt MS through the seed crystal cable 60 and the processes of seeding, necking, shouldering, isodiametric growth and finishing are started, and finally a standard single crystal silicon rod S of a certain length can be obtained. ', for example, taking the current standard single crystal silicon rod S ' with a diameter of 12 inches as an example, when 400 kg of polycrystalline silicon melt and a certain mass of dopant boron are added to the quartz crucible 30, a standard single crystal silicon rod S ' with a length of about 2 meters can be drawn, and it can be understood that for the standard single crystal silicon rod S ', the doping amount contained in each part is consistent. The drawn standard single crystal silicon rod S ' is shown in FIG2.

It should be noted that a pulling head 80 connected to the seed crystal cable 60 is also provided at the top of the crystal pulling furnace 1. The pulling head 80 is mainly used to realize the rotation and lifting of the seed crystal 70, and can record the displacement of the seed crystal and other data.

It can be understood that the crystal pulling furnace 1 shown in FIG1 may also include other structures not shown in FIG1 , such as a crucible lifting device, etc., which are not specifically described in the embodiment of the present invention.

Based on the crystal pulling furnace 1, referring to FIG. 3, a method for pulling a single crystal silicon rod S provided by an embodiment of the present invention is shown, the method comprising: S301: placing a set mass of polycrystalline silicon melt and a first preset mass of dopant in a quartz crucible and heating and melting them to form a silicon melt, and then pulling a first single crystal silicon rod section of a first preset length; S302: when the first single crystal silicon rod section is finished, A crystal with a horizontal shoulder grows at the tail of the first single crystal silicon rod segment; S303: After the first single crystal silicon rod segment is lifted to the auxiliary furnace chamber for cooling, the second preset mass of the dopant is placed on the horizontal shoulder of the crystal; S304: After the first single crystal silicon rod segment is lowered so that the crystal is completely immersed in the remaining silicon melt and melted, a second single crystal silicon rod segment with a second preset length is pulled.

It should be noted that after adding a first preset mass of dopant boron to a set mass of polycrystalline silicon melt and melting to form a silicon melt, the first single crystal silicon rod segment lightly doped with P+ can be pulled by the Czochralski method. After the first single crystal silicon rod segment is pulled, a supplementary dopant is added to the remaining silicon melt to pull a second single crystal silicon rod segment heavily doped with P++. Therefore, the second preset mass of the dopant in step S303 represents the mass of the dopant boron that needs to be supplemented later.

According to the technical solution shown in FIG3, a first single crystal silicon rod section of a first preset length lightly doped with P+ is first pulled, and a crystal with a horizontal shoulder is grown at the end of the first single crystal silicon rod section. Before pulling the second single crystal silicon rod section, the first single crystal silicon rod section is lifted to the auxiliary furnace chamber for cooling, and the dopant of the second preset mass to be supplemented is placed at the horizontal shoulder of the crystal. After the crystal at the tail of the first single crystal silicon rod section is completely immersed in the remaining silicon melt and fully melted, the second single crystal silicon rod section heavily doped with P++ can be pulled by the CZ method.

For the technical solution shown in FIG. 3 , in some examples, after placing a set mass of polycrystalline silicon melt and a first preset mass of a dopant in a quartz crucible and heating and melting to form a silicon melt, a first single crystal silicon rod section with a first preset length is pulled, including: obtaining a first preset mass m ₁ of the dopant when the mass M of the polycrystalline silicon melt is constant; adding the polycrystalline silicon melt with the mass M and the dopant with the first preset mass m ₁ into a quartz crucible and heating and melting to form a silicon melt, pulling the first single crystal silicon rod section S ₁ by a Czochralski method, and monitoring the growth length of the first single crystal silicon rod section S ₁ in the isodiametric growth stage; when the first single crystal silicon rod section S When the growth length of the first single crystal silicon rod segment _S1 reaches _the first preset length L1 , the finishing process is performed on _the first single crystal silicon rod segment S1 .

其中，ρ'表示基準單晶矽棒S'的電阻率；m'表示基準單晶矽棒S'中該摻雜劑的質量；ρ ₁表示該第一單晶矽棒節S ₁的電阻率。 For the above example, in some possible implementations, when the mass M of the polycrystalline silicon melt is constant, obtaining the first preset mass m ₁ of the dopant includes: calculating the first preset mass m ₁ of the dopant through equation (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 '; ρ ₁ represents _the resistivity of the first single crystal silicon rod section S1 .

For the above technical solution, before the specific implementation of the present invention, a reference single crystal silicon rod S ' as shown in FIG. 2 is pre-pulled based on the crystal pulling furnace 1, wherein the mass of the polycrystalline silicon melt added when pulling the reference single crystal silicon rod S ' is also M , and the mass of the dopant boron added is m ', so that the resistivity ρ' of the reference single crystal silicon rod S ' can be obtained through testing. The specific resistivity ρ ' testing method is not specifically described in the embodiment of the present invention.

When the resistivity ρ ' of the reference single crystal silicon rod S ' is obtained through testing, the first preset mass m1 of the dopant boron that needs to be added to the polycrystalline silicon melt of mass M when pulling the first lightly P+ doped single crystal silicon rod section _S1 can be calculated by equation ( ₁ ).

It should be noted that, in the embodiment of the present invention, _the first single crystal silicon rod _section S1 is drawn according to product requirements, so its resistivity ρ1 is known.

For the above example, in some possible implementations, after the polycrystalline silicon melt with a mass M and the dopant with _a first preset mass m1 are added to a quartz crucible and heated and melted to form a silicon melt, the first single crystal silicon rod section S1 is pulled by the Czochralski method _, and the growth length of the first single crystal silicon rod section S1 is monitored in the _isodiametric growth stage, including: when the first single crystal silicon rod section S1 is pulled by the Czochralski method, the growth length of _the first single crystal silicon rod section S1 is determined by monitoring the rising distance _of the seed crystal cable in the isodiametric growth stage.

It can be understood that, as shown in FIG1 , when the first single crystal silicon rod section S1 is prepared by using the crystal pulling furnace ₁ , 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 surface of the silicon melt by the pulling head 80 and the seeding process and the like are performed. When the seeding is completed and the neck begins to grow, the seed crystal 70 gradually rises with the rise of the seed crystal cable 60. Therefore, it can be understood that in the isodiametric growth stage, the rising distance of the seed crystal cable 60 can be used to represent the growth length of _the first single crystal silicon rod section S1 .

It should be noted that the distance that the seed cable 60 rises can be obtained through the displacement data in the pulling head 80.

也能夠控制第一單晶矽棒節S ₁的生長長度。 In some implementations of the present invention, as shown in FIG. 4 , the end of the seed cable 60 may also be connected to the rope 901 on the winding shaft 90. In the isodiametric growth stage, the growth length of the first single crystal silicon rod segment S1 is determined by monitoring the distance the rope 901 moves. Specifically, the distance l = _πdn moved by the rope 901 is obtained by the number of turns n wound around the winding shaft 90 and the diameter d of the winding shaft 90 when the rope 901 moves. Of course, when the first preset length _L1 of the first single crystal silicon rod segment S1 is known, the number of turns n wound around the winding shaft 90 by the rope ₉₀₁ is monitored.

The growth length of _the first single crystal silicon rod section S1 can also be controlled.

Of course, monitoring the growth length of the first single crystal silicon rod section S1 is not limited to the above method. For example, an industrial camera may be installed in the observation window (not shown) of the crystal pulling furnace ₁ to monitor the growth status and growth length of _the first single crystal silicon rod section S1 in real time.

It can be understood that, in the isodiametric growth stage, when the moving distance l of the seed crystal cable ₆₀ is equal to the first preset length L1 _of the first single crystal silicon rod section S1 , the finishing process of the _first single crystal silicon rod section S1 can be performed.

For the technical solution shown in FIG3 , in some examples, when the first single crystal silicon rod section is finished, a crystal with a horizontal shoulder is grown at the tail of the first single crystal silicon rod section, including: at the end of the first single crystal silicon rod section S1 being finished, accelerating the _rising speed of the first single crystal silicon rod section S1 _, and performing seeding and neck shrinking process operations; after a thin neck is _grown at the tail of the first single crystal silicon rod section S1 , performing a shoulder release operation so that a horizontal shoulder is grown at the end of the thin neck; after the horizontal shoulder is grown, performing a rapid finishing process operation to grow a crystal S " with a horizontal shoulder at the tail of the first _single crystal silicon rod section S1 .

It can be understood that at the end of the tailing of the first single crystal silicon rod section S1 , _the lifting speed of the first single crystal silicon rod section S1 can be accelerated and a necking operation can be performed to grow a thin neck at the conical end of the _first single crystal silicon rod section S1 _. After the shoulder release and rapid tailing process operations, a crystal S " can be grown at the tail of _the first single crystal silicon rod section S1 , as shown in Figure 5, and the crystal S " has the same horizontal shoulder as _the first single crystal silicon rod S1 .

For the technical solution shown in FIG. 3 , in some examples, after the first single crystal silicon rod segment is lifted to the auxiliary furnace chamber for cooling, the second preset mass of the dopant is placed at the horizontal shoulder of the crystal, including: lifting the seed crystal cable so that the first single crystal silicon rod segment S1 is moved to the auxiliary furnace chamber and cooled _, and then the second preset mass of the dopant is placed at the horizontal shoulder of the crystal.

，其中，D ₁表示該第一單晶矽棒節S ₁的直徑，λ表示該第一單晶矽棒節的密度；根據該第一單晶矽棒節S ₁的質量M ₁，計算獲得該石英坩堝中剩餘矽熔液的質量M ₂=M-M ₁；根據式(2)，推導計算得到該第一單晶矽棒節S ₁中包含的該摻雜劑的質量m ₁'：

其中，a表示該摻雜劑在該矽熔液中的分凝係數；m ₁"表示該剩餘矽熔液中包含的該摻雜劑的質量，且m ₁"=m ₁-m ₁'；根據式(3)，計算獲得當多晶矽質量為M時該第二單晶矽棒節S ₂對應的摻雜量m ₂'：

其中，ρ ₂表示該第二單晶矽棒節S ₂的電阻率；根據式(4)，計算獲得質量為M ₂的矽熔液中包含的該摻雜劑的質量m ₂"：

根據該摻雜量m ₂"以及該剩餘矽熔液中的摻雜量m ₁"，計算獲得需要補充的該摻雜劑的第二預設質量m ₂=m ₂"-m ₁"。 It can be understood that, as shown in FIG6 , when the first single crystal silicon rod section S ₁ is lifted to the auxiliary furnace chamber and cooled, the pre-prepared dopant boron (shown as a black circle in the figure) with a second preset mass m ₂ can be placed on the horizontal shoulder of the crystal S ″ through the feeding device in the crystal pulling furnace 1. For the above example, in some possible implementations, the calculation method of the second preset mass m ₂ includes: calculating the mass of the first single crystal silicon rod section S ₁ according to the size parameters of the first single crystal silicon rod section S ₁

, wherein D ₁ represents the diameter of the first single crystal silicon rod section S ₁ , λ represents the density of the first single crystal silicon rod section; according to the mass M ₁ of the first single crystal silicon rod section S ₁ , the mass M ₂ = M - M ₁ of the remaining silicon melt in the quartz crucible is calculated; according to formula (2), the mass m ₁ ' of the dopant contained in the first single crystal silicon rod section S ₁ is derived and calculated:

Wherein, a represents the segregation coefficient of the dopant in the silicon melt; m ₁ "represents the mass of the dopant contained in the remaining silicon melt, and m ₁ "= m ₁ - m ₁ '; According to formula (3), the doping amount m ₂ ' corresponding to the second single crystal silicon rod section S ₂ when the mass of polycrystalline silicon is M is calculated:

Wherein, ρ ₂ represents the resistivity of the second single crystal silicon rod section S ₂ ; according to formula (4), the mass m ₂ "of the dopant contained in the silicon melt with a mass of M ₂ is calculated:

According to the doping amount m ₂ "and the doping amount m ₁ " in the remaining silicon melt, a second preset mass m ₂ = m ₂ "- m ₁ " of the dopant that needs to be supplemented is calculated.

It should be noted that the segregation coefficient = solubility of impurities in the solid phase / solubility of impurities in the liquid phase, and the segregation coefficient of the dopant boron in the silicon melt is generally 0.3. Therefore, through equations (2), (3) and (4), it can be reversely deduced that: when the mass M2 of the remaining silicon melt is known, the mass m2 _" of the dopant boron required to prepare the second single crystal silicon rod section S2 heavily doped with P++ is obtained, and then the second preset mass m2 _of the dopant that needs to be supplemented is calculated based on the mass m1 _{" of} the dopant already contained in the remaining silicon melt _.

It should be noted that, in the embodiment of the present invention, _the second single crystal silicon rod _section S2 is drawn according to product requirements, so its resistivity ρ2 is known.

Of course, it can be understood that in the specific embodiment of the present invention, a weighing device (not shown in the figure) can also be set at the pulling head 80 to obtain the mass M1 _{of the} first single crystal silicon rod section S1 , and then obtain the mass M2 of the silicon melt remaining in the quartz crucible according to the mass M1 _{of the} first single crystal silicon rod section S1 , and when the mass of the silicon melt is M2 , the mass m2 _" of the dopant boron required when pulling the _second single crystal silicon rod section S2 heavily doped with P ₊₊ , _and finally obtain the second preset mass m2 of the dopant that needs to be supplemented _.

For the technical solution shown in FIG3 , in some examples, the first single crystal silicon rod section is lowered so that the crystal is completely immersed in the remaining silicon melt and melted, and then _the second single crystal silicon rod section of the second preset length is pulled, including: lowering the first single crystal silicon rod section S1 so that the dopant placed on the crystal is completely immersed in the remaining silicon melt and melted, and then the second single crystal silicon rod section S2 is pulled by the Czochralski method, and the growth length of the second single crystal silicon rod section S2 is monitored in the isodiametric growth stage; when the growth length of the second single crystal silicon rod section S2 _{is the second} preset length L2 _, the second single crystal silicon rod section S2 _is subjected to a finishing process.

It can be understood that, as shown in FIG7 , after the dopant boron to be supplemented is placed on the horizontal shoulder of the crystal S _″ , the first single crystal silicon rod segment S1 is lowered until 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 second single crystal silicon rod segment _S2 with a second preset length L2 can be continuously pulled at the tail of the first single crystal silicon rod segment S1 according to the process steps of the Czochralski method: seeding-neck shrinkage-shoulder release-equal diameter growth-finishing operations, and the doping type of the second single crystal silicon rod segment S2 _{is heavily} doped P ₊₊ .

It can be understood that after the crystal S ″ is entirely melted into the remaining silicon melt, when _the second single crystal silicon rod section S2 is pulled by the _Czochralski method, the first single crystal silicon rod section S1 can be seeded, thereby completing the necking, shouldering, isodiametric growth and finishing process operations based on the seeding operation.

For the above example, in some possible implementations, _after the first single crystal silicon rod section S1 is lowered so that the dopant placed on the crystal is completely immersed in the remaining silicon melt and melted, the second single crystal silicon rod section S2 is pulled by the Czochralski method, and the growth length of the second single crystal silicon rod section _S2 is monitored in the isodiametric growth stage, including: when the second single crystal silicon rod section S2 is pulled by _the Czochralski method, the growth length of _the second single crystal silicon rod section S2 is determined by monitoring the rising distance _of the seed crystal cable in the isodiametric growth stage.

Referring to FIG. 8 , it shows a single crystal silicon rod S provided by an embodiment of the present invention. The single crystal silicon rod S is prepared according to the drawing method described in the aforementioned technical solution.

As can be seen from FIG8 , the single crystal silicon rod S pulled by the embodiment of the present invention includes a first single crystal silicon rod section S1 lightly doped with P ₊ having a first preset length L1 and a second single crystal silicon rod section S2 heavily doped with P ₊₊ having _a first preset length L2 , which can meet the _different needs of different customers and reduce the waste of production costs.

It can be understood that by adopting the drawing method provided in the embodiment of the present invention, it is also possible to realize that the same single crystal silicon rod S includes multiple single crystal silicon rod sections with different doping amounts and different lengths.

It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict. The above are only the preferred embodiments of the present invention and are not used to limit the scope of implementation of the present invention. If the present invention is modified or replaced equivalently without departing from the spirit and scope of the present invention, it should be covered by the protection scope of the patent application of the present invention.

1: Crystal pulling furnace

10: Auxiliary furnace room

20: Guide tube

30: Quartz crucible

40: Graphite heater

50: Main furnace room

60: Seed cable

70: Seed crystal

80: Pulling head

MS: Silicon melt

S ': Single crystal silicon rod

Claims (7)

A method for pulling a single crystal silicon rod comprises: placing a set mass of polycrystalline silicon melt and a first preset mass of dopant in a quartz crucible, heating and melting to form a silicon melt, and then pulling a first single crystal silicon rod section of a first preset length; when the first single crystal silicon rod section is finished, growing a crystal with a horizontal shoulder at the tail of the first single crystal silicon rod section; lifting the first single crystal silicon rod After the first single crystal silicon rod section is cooled in the auxiliary furnace chamber, the second preset mass of the dopant is placed at the horizontal shoulder of the crystal; the first single crystal silicon rod section is lowered to make the crystal completely immersed in the remaining silicon melt and melted, and then a second single crystal silicon rod section of a second preset length is pulled; wherein the calculation method of the second preset mass includes: obtaining the mass M1 of the first single crystal silicon rod section by a weighing method; according to the mass M1 _of the first single crystal silicon rod section, calculating the mass M2 = M _- M1 of the _remaining silicon melt in the quartz crucible; _according to the following formula, calculating the mass m1 ' of the dopant contained in the _first single crystal silicon rod section:

wherein a represents the segregation coefficient of the dopant in the silicon melt; m ₁ "represents the mass of the dopant contained in the residual silicon melt, and m ₁ "= m ₁ - m ₁ '; m ₁ represents the first preset mass, and m ₁ 'represents the mass of the dopant in a reference single crystal silicon rod; wherein, when the mass M of the polycrystalline silicon melt is constant, obtaining the first preset mass m ₁ of the dopant comprises: obtaining the first preset mass m ₁ of the dopant by calculating through formula (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 '; ρ ₁ represents the resistivity of the first single crystal silicon rod section S ₁ ; according to the following formula, the doping amount m ₂ ' corresponding to the second single crystal silicon rod section is calculated when the mass of polycrystalline silicon is M :

Wherein, ρ ₂ represents the resistivity of the second single crystal silicon rod section; the mass m ₂ " of the dopant contained in the silicon melt having a mass of M ₂ is calculated according to the following formula:

According to the doping amount m ₂ "and the doping amount m ₁ " in the remaining silicon melt, a second preset mass m ₂ = m ₂ "- m ₁ " of the dopant that needs to be supplemented is calculated. The method for pulling a single crystal silicon rod as claimed in claim 1, wherein the polycrystalline silicon melt of a set mass and the dopant of a first preset mass are placed in a quartz crucible and heated to melt to form a silicon melt, and then a first single crystal silicon rod section of a first preset length is pulled, comprising: obtaining a first preset mass m1 of the dopant when the mass M of the polycrystalline silicon melt is _constant ; adding the polycrystalline silicon melt of mass M and the _dopant of the first preset mass m1 into a quartz crucible and heating to melt to form a silicon melt, and then pulling the first single crystal silicon rod section S1 by a Czochralski method, and monitoring the growth length of the first single crystal silicon rod section S1 in the isodiametric _growth stage; when the first single crystal silicon rod section _S1 is When the growth length of the first single crystal silicon rod segment _S1 reaches _the first preset length L1 , the finishing process is performed on _the first single crystal silicon rod segment S1 . A method for pulling a _single crystal silicon rod as described in claim 1, wherein the polycrystalline silicon melt of mass M and the dopant of first preset mass m1 are added to a quartz crucible and heated to melt to form a silicon melt, and then the first single crystal silicon rod section S1 is pulled by the Czochralski method, and the growth length of the first single crystal silicon rod section S1 _is monitored in the isodiametric growth stage, including: when the first single crystal silicon rod section S1 is pulled by the _Czochralski method _, the growth length of the first single crystal silicon rod section S1 is determined by monitoring the rising distance of the seed crystal cable in the _isodiametric growth stage. A method for pulling a single crystal silicon rod as described in claim 1, wherein when the first single crystal silicon rod section is terminated, a crystal _with a horizontal shoulder is grown at the tail of the first single crystal silicon rod section, comprising: at the end of the termination of the first single crystal silicon rod section S1 , accelerating _the rising speed of the first single crystal silicon rod section S1 _, and performing seeding and neck shrinking process operations; after a thin neck is grown at the tail of the first single crystal silicon rod section S1 , performing a shoulder release operation so that a horizontal shoulder is grown at the end of the thin neck; after the horizontal shoulder is grown, performing a rapid termination process operation to grow a crystal S _" with a horizontal shoulder at the tail of the first single crystal silicon rod section S1 . A method for pulling a single crystal silicon rod as described in claim 1, wherein after the first single crystal silicon rod segment S1 is lifted to the auxiliary furnace chamber for cooling, the second preset mass of the dopant is placed on the horizontal shoulder of the crystal, comprising: lifting the seed crystal cable so that the first single crystal silicon rod segment S1 is moved to the auxiliary furnace chamber and cooled, and then _the second preset mass of the dopant is placed on the horizontal shoulder of the crystal. A method for pulling a single crystal silicon rod as described in claim 1, wherein the first single crystal silicon rod section is lowered so that the crystal is _completely immersed in the remaining silicon melt and melted, and then a second single crystal silicon rod section of a second preset length is pulled, comprising: lowering the first single crystal silicon rod section S1 so that the dopant placed on the crystal is completely immersed in the remaining silicon melt and melted, and then using the _Czochralski method to pull the second single crystal silicon rod section S2 , and monitoring the growth length of the second single crystal silicon rod section S2 during the isodiametric growth stage; when the growth length of the second single crystal silicon rod section _S2 is the second preset length L2 , performing _a finishing process operation on _{the second} single crystal silicon rod section S2 . A method for pulling a single crystal silicon rod as described in claim 6, wherein the first single crystal silicon rod section S1 is _lowered so that the dopant placed on the crystal is completely immersed in the remaining silicon melt and melted, and then the second single crystal silicon rod section S2 is pulled by the Czochralski method, and the growth length of the second single crystal silicon rod section S2 is monitored during the isodiametric _growth stage, including: when the second single crystal silicon rod section _S2 is pulled by the Czochralski method, the growth length of _the second single crystal silicon rod section S2 is determined by monitoring the rising distance of the seed crystal cable during _the isodiametric growth stage.