Regulation and control method for axial resistivity of doped monocrystalline silicon and single crystal furnace

Abstract

The invention discloses a method for regulating and controlling the axial resistivity of doped monocrystalline silicon and a single crystal furnace, and relates to the technical field of doped monocrystalline silicon, and the method comprises the following steps: adding a doping agent into molten silicon according to the amount required by the upper limit of the resistivity of monocrystalline silicon of a first specification as a first addition amount; drawing monocrystalline silicon of a first specification, obtaining the resistivity of the tail part of the monocrystalline silicon of the first specification, and determining the residual amount of a dopant in the molten silicon according to the resistivity of the tail part of the monocrystalline silicon, the mass of the residual molten silicon and the resistivity-doping concentration curve graph; determining the supplement amount of the dopant according to the doping amount required by the resistivity upper limit of the monocrystalline silicon of the second specification, the residual mass of the melt and the residual amount of the dopant in the molten silicon; and after the doping agent is added into the residual molten silicon according to the supplementary amount, drawing the monocrystalline silicon of the second specification. According to the method, the difference between the head resistivity and the tail resistivity of the doped monocrystalline silicon is reduced, namely, the uniformity of the axial resistivity of the doped monocrystalline silicon is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of doped monocrystalline silicon, in particular to a method for regulating axial resistivity of doped monocrystalline silicon and a single crystal furnace. BACKGROUND

[0002] Monocrystalline silicon is an important semiconductor material and is widely used in electronic devices. However, the electrical properties of intrinsic monocrystalline silicon are poor, and it is usually necessary to introduce specific impurity elements through doping to adjust its atomic structure and electronic properties, so as to obtain the required conductivity type and accurately control the resistivity. The doping process realizes directional regulation of the electrical properties of the material by controlling the impurity concentration, thereby optimizing the performance of the device, including forming a PN junction, regulating carrier transport, reducing resistance loss, improving voltage resistance, reducing parasitic capacitance, and setting the key operating voltage. The selection of resistivity is particularly critical, and a balance needs to be achieved between the on-state loss, voltage resistance performance, and response speed of the device. Common dopants and doping methods are as follows: pure boron is usually used to obtain P-type silicon by solid-phase doping / co-melting method, but the melting point of boron element is high and it is not easy to volatilize, and the resistivity distribution is significantly affected by the segregation effect; boron master alloy and phosphorus master alloy are also used for solid-phase doping / co-melting to form P-type and N-type silicon, respectively; pure phosphorus and pure arsenic are usually used for gas-phase doping to form N-type silicon, and such impurities are easy to volatilize and gasify at high temperatures, and the resistivity control is closely related to the process parameters; pure antimony is usually used for liquid-phase doping to achieve N-type silicon, and it is easy to liquefy and volatile at high temperatures.

[0003] With the market segmentation and the improvement of the performance requirements of terminal products, the resistivity range of the single crystal silicon substrate for devices is continuously narrowed; the resistivity of phosphorus-doped single crystal silicon is commonly 8-16 Ω·cm or 4-7 Ω·cm; the resistivity of heavily boron-doped single crystal silicon is commonly 0.012-0.015 Ω·cm or 0.0025-0.003 Ω·cm; for heavily doped single crystal silicon, the resistivity of the entire crystal rod can usually be brought within the target range by adjusting the crystal pulling process parameters. However, for lightly doped and pure boron heavily doped single crystal silicon, due to the obvious segregation effect of the doping elements, the resistivity cannot be controlled within a relatively narrow range by process adjustment. For example, the head-to-tail resistivity difference of lightly phosphorus-doped single crystal silicon can be up to 3.5-4 times, and the head-to-tail resistivity difference of pure boron or boron master alloy doped single crystal silicon can be up to 1.8-2 times, and the higher the resistivity, the greater the head-to-tail resistivity distribution range caused by segregation. SUMMARY In order to solve the problem of wide resistivity range in the prior art of doped monocrystalline silicon, the present application provides a method for regulating the axial resistivity of doped monocrystalline silicon and a single crystal furnace, which narrows the head-to-tail resistivity difference of doped monocrystalline silicon, i.e. improves the uniformity of the axial resistivity of doped monocrystalline silicon, and improves the effective output rate of single crystal products.

[0004] In order to achieve the above object, the present application adopts the following specific scheme: a method for controlling axial resistivity of doped single crystal silicon, comprising the following steps:

[0005] The dopant is added into the molten silicon as a first addition amount according to the required amount for the upper limit of the resistivity of the single crystal silicon of the first specification;

[0006] The single crystal silicon of the first specification is drawn, and the resistivity of the tail of the single crystal silicon of the first specification is obtained; the remaining amount of the dopant in the molten silicon is determined according to the resistivity of the tail of the single crystal silicon, the remaining mass of the molten silicon and a resistivity-doping concentration curve.

[0007] The replenishment amount of the dopant is determined according to the required doping amount for the upper limit of the resistivity of the single crystal silicon of the second specification, the remaining mass of the melt and the remaining amount of the dopant in the molten silicon;

[0008] After the dopant is added into the remaining molten silicon according to the replenishment amount, the single crystal silicon of the second specification is drawn.

[0009] As an optimization scheme of the above method for controlling axial resistivity of doped single crystal silicon, the resistivity of the first specification is greater than the resistivity of the second specification.

[0010] A single crystal furnace, comprising a furnace body and a furnace cover, a hot field assembly, a heater, a graphite crucible and a support shaft for supporting the graphite crucible are arranged in the furnace body, a quartz crucible for containing molten silicon is arranged in the graphite crucible, the hot field assembly comprises a heat shield unit and a heat preservation unit located above the graphite crucible; the heat shield unit comprises an inner shield and an outer shield which are coaxially arranged and the bottom end of the inner shield can extend into the quartz crucible, the inner shield gradually shrinks in diameter from top to bottom, the top end of the outer shield overlaps the top end of the inner shield, the bottom end of the outer shield is bent towards the inner shield to form a bent portion, the end of the bent portion away from the outer shield overlaps the bottom end of the inner shield, so that a closed annular cavity is formed between the outer shield and the inner shield, and the annular cavity is filled with heat preservation material; the heat preservation unit comprises an inner container which is sleeved outside the heater, and the annular gap between the inner container and the inner wall of the furnace body is filled with heat preservation material to form a heat preservation layer; a doping assembly is arranged on the furnace cover, the doping assembly comprises a doping pipe and a storage pipe, one end of the doping pipe extends into the furnace body and is located above the quartz crucible, the other end of the doping pipe extends out of the furnace body and is connected with the storage pipe through a ball valve, and the end of the storage pipe away from the doping pipe is provided with a sealing plate which can close the end.

[0011] As an optimization scheme of the above single crystal furnace, the heater comprises a heating section and support legs for fixing the heating section to the bottom electrode of the furnace body, the height of the heating section is 1 / 2-2 / 3 of the height of the quartz crucible, and the distance between the bottom end of the heating section and the bottom wall of the furnace body is 500 mm.

[0012] As another optimization scheme of the above single crystal furnace, the doping pipe comprises a first pipe section located in the furnace body and a second pipe section located outside the furnace body, the first pipe section and the second pipe section are connected through a first flange, and the first flange is sealingly and fixedly connected with the furnace cover.

[0013] As another optimization scheme of the above single crystal furnace, the first pipe section comprises a first part, a second part and a third part which are integrally connected, the first part is a straight pipe, the second part and the third part are arc-shaped pipes, the axis of the second part is convex downward and tangent to the axis of the first part, and the axis of the third part is convex upward and tangent to the axis of the second part, so that a buffer zone is formed at the connection between the second part and the third part.

[0014] As another optimization scheme of the above single crystal furnace, the radius of the axis of the second part is 90 mm, and the radius of the axis of the third part is 145 mm.

[0015] As another optimization scheme of the above single crystal furnace, the heat preservation layer comprises an upper heat preservation layer, a middle heat preservation layer and a lower heat preservation layer arranged from top to bottom, the thickness of the middle heat preservation layer is the same as the thickness of the lower heat preservation layer, and the thickness of the upper heat preservation layer is 65 mm less than the thickness of the middle heat preservation layer.

[0016] As another optimization scheme of the above single crystal furnace, the distance between the outer side wall of the upper heat preservation layer and the lower heat preservation layer and the inner side wall of the furnace body is 90 mm and 25 mm.

[0017] Compared with the prior art, the present application has the following beneficial effects: the present application provides a method for controlling the axial resistivity of doped single crystal silicon and a single crystal furnace, wherein the first addition amount of the dopant is determined according to the required amount of the upper limit of the resistivity of the first specification single crystal silicon, after the first specification single crystal silicon is drawn, the required replenishment amount of the dopant to the remaining molten silicon is determined according to the resistivity of the tail part of the drawn first specification single crystal silicon, the remaining mass of the molten silicon and the required amount of the upper limit of the resistivity of the second specification single crystal silicon, and then the second specification single crystal silicon is drawn, thereby narrowing the resistivity range of the single crystal rod drawn in the same furnace and improving the effective output rate of the single crystal product. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic view of a single crystal furnace;

[0019] Figure 2 is a sectional view of a single crystal furnace;

[0020] Figure 3 is a schematic view of a furnace cover of a single crystal furnace;

[0021] Figure 4 is a sectional view of a furnace cover of a single crystal furnace;

[0022] Figure 5 is a top view of a single crystal furnace;

[0023] Figure 6 is a schematic view of the structure of the doping device;

[0024] Figure 7 is a sectional view of the doping device;

[0025] Figure 8 is a graph of resistivity-doping concentration;

[0026] Fig. 1 is a furnace body, 2, inner container 201, upper inner container, 202, support ring, 203, lower inner container, 204, bottom inner container, 205, top ring, 3, furnace cover, 301, observation hole, 4, outer screen, 5, inner screen, 6, annular cavity, 7, first flange, 8, first pipe section, 801, first part, 802, second part, 803, third part, 9, second pipe section, 10, sealing plate, 11, impurity storage pipe, 12, ball valve, 13, heater, 1301, heating section, 1302, support leg, 14, doping pipe, 15, insulation layer, 1501, upper insulation layer, 1502, middle insulation layer, 1503, lower insulation layer, 1504, bottom insulation layer. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be further described in detail below in combination with specific embodiments. The parts not described and disclosed in detail in the following embodiments of the present application should be understood as the prior art known or should be known by those skilled in the art.

[0028] Embodiment 1

[0029] A method for regulating the axial resistivity of doped single crystal silicon, comprising the following steps:

[0030] The dopant is added into the molten silicon according to the required amount for the upper limit of the resistivity of the first specification single crystal silicon as the first addition amount; the quartz crucible of the single crystal furnace is charged according to the maximum charging capacity, and the dopant is put into the quartz crucible, and the amount of the dopant is the first addition amount, and the dopant is co-melted with the polycrystalline material in the quartz crucible.

[0031] The first specification single crystal silicon is drawn, and the resistivity of the tail of the first specification single crystal silicon is obtained, and the remaining amount of the dopant in the molten silicon is determined according to the resistivity of the tail of the single crystal silicon, the remaining mass of the molten silicon and the resistivity-doping concentration graph; in this embodiment, the first specification single crystal silicon is drawn according to the process of evacuation-leakage-pressure melting-stable-crystal drawing, and the specific process is the prior art, which will not be described here.

[0032] The replenishment amount of the dopant is determined according to the required doping amount for the upper limit of the resistivity of the second specification single crystal silicon, the remaining mass of the melt and the remaining amount of the dopant in the molten silicon;

[0033] After the dopant is added into the molten silicon according to the supplementary amount, single crystal silicon of the second specification is drawn according to the process of dopant melting-stabilization-crystal pulling-shoulder transfer-equal diameter-end cooling.

[0034] In this embodiment, the resistivity of the first specification is greater than the resistivity of the second specification.

[0035] Example 2

[0036] A single crystal furnace, as shown in Figure 1 and Figure 2 , comprises a furnace body 1 and a furnace cover 3, the furnace body 1 is provided with a thermal field assembly, a heater 13, a graphite crucible and a support shaft for supporting the graphite crucible, a quartz crucible for containing molten silicon is arranged in the graphite crucible, and the thermal field assembly comprises a heat shield unit and a heat preservation unit located above the graphite crucible; the heat shield unit comprises an inner shield 5 and an outer shield 4 which are coaxially arranged and the bottom end of which can extend into the quartz crucible, the inner shield 5 is gradually reduced in diameter from top to bottom and is fixedly connected with the furnace body 1, and the connection mode of the two is the prior art which will not be described here. The top end of the outer shield 4 overlaps the top end of the inner shield 5, specifically, the top end of the outer shield 4 is coaxially fixedly connected with a connecting ring, and the top end of the connecting ring is sealingly fixedly connected with the inner shield 5. The bottom end of the outer shield 4 is bent towards the inner shield 5 to form a bent portion, and the end of the bent portion away from the outer shield 4 overlaps the bottom end of the inner shield 5, so that a closed annular cavity 6 is formed between the outer shield 4 and the inner shield 5, and the annular cavity 6 is filled with heat preservation material.

[0037] The heat preservation unit comprises an inner container 2 which is sleeved outside the heater 13, and an annular gap is formed between the inner container 2 and the inner wall of the furnace body 1, and the annular gap is filled with heat preservation material to form a heat preservation layer 15. The inner container 2 comprises a side inner container coaxial with the furnace body 1 and a bottom inner container 204 parallel to the bottom wall of the furnace body 1. Among them, the side inner container is a two-section structure, comprising an upper side inner container 201 and a lower side inner container 203, the top end of the lower side inner container 203 is located above the top end of the heater 13, the diameter of the lower side inner container 203 is greater than the diameter of the upper side inner container 201, and the outer side wall of the upper side inner container 201 is flush with the outer side wall of the heater 13; the top end of the lower side inner container 203 overlaps a support ring 202, and the bottom end of the upper side inner container 201 overlaps the upper surface of the support ring 202. The outer edge of the bottom inner container 204 is flush with the outer side wall of the lower side inner container 203, the bottom end of the lower side inner container 203 overlaps the upper surface of the bottom inner container 204, and the bottom inner container 204 is filled with heat preservation material between the bottom wall to form a bottom heat preservation layer 1504.

[0038] In the embodiment, the heat preservation layer includes an upper heat preservation layer 1501, a middle heat preservation layer 1502 and a lower heat preservation layer 1503 arranged from top to bottom, the thickness of the middle heat preservation layer 1502 is the same as that of the lower heat preservation layer 1503, and the thickness of the upper heat preservation layer 1501 is 65 mm less than that of the middle heat preservation layer 1502. The top end of the upper heat preservation layer 1501 is 342 mm higher than the top end of the lower inner container 203. The top end of the upper inner container 201 is overlapped with a top ring 205, a top plate is arranged above the top ring 205, and the top plate is filled with heat preservation material to form a top heat preservation layer between the top ring 205. The edge of the top heat preservation layer is located between the edge of the middle heat preservation layer 1502 and the edge of the upper heat preservation layer 1501.

[0039] In the embodiment, the bottom end of the inner screen 5 and the outer screen 4 is located at the center height of the upper inner container 201. The distance between the outer side wall of the upper heat preservation layer 1501 and the lower heat preservation layer 1503 and the inner side wall of the furnace body 1 is 90 mm and 25 mm.

[0040] A doping assembly is arranged on the furnace cover 3, and the doping assembly includes a doping pipe 14 and a storage pipe 11. One end of the doping pipe 14 extends into the furnace body 1 and is located above the quartz crucible. The other end of the doping pipe 14 extends out of the furnace body 1 and is connected with the storage pipe 11 through a ball valve 12. The end of the storage pipe 11 away from the doping pipe 14 is provided with a sealing plate 10 capable of sealing the end.

[0041] The doping pipe 14 has an S-shaped structure. The doping pipe 14 includes a first pipe segment 8 located in the furnace body 1 and a second pipe segment 9 located outside the furnace body 1. The first pipe segment 8 and the second pipe segment 9 are connected through a first flange 7. The first flange 7 is in sealing and fixed connection with the furnace cover 3. A through hole is formed in the furnace cover 3 for the first pipe segment 8 to pass through. The first flange 7 is in bolted connection with the furnace cover 3. The first pipe segment 8 includes a first part 801, a second part 802 and a third part 803 which are integrally connected. The first part is a straight pipe. The second part and the third part are arc-shaped pipes. The axis of the second part protrudes downward and is tangent to the axis of the first part. The axis of the third part protrudes upward and is tangent to the axis of the second part. The connecting part of the second part and the third part forms a buffer zone. Specifically, the radius of the axis of the second part is 90 mm, and the center is located at the upper left side of the first part. The radius of the axis of the third part is 145 mm, and the center is located at the lower right side of the first part. Thus, the first pipe segment 8 has a parabolic structure. The bottom end of the first pipe segment 8 is flush with the top end of the inner screen 5. In the embodiment, the doping pipe 14 is arranged in combination with the structure of the furnace cover. The structure of the doping pipe 14 can ensure that the outlet of the doping pipe 14 extends to the center. The lower end of the third part 803 faces the molten silicon in the quartz crucible. The space provided by the third part 803 does not interfere with the upper limit of the heat screen. When the dopant is added, the dopant slides along the wall of the doping pipe 14 by gravity potential. The potential is maximum at the tangent position of the second part 802 and the third part 803, so the dopant can continue to slide into the molten silicon and play a buffering role.

[0042] The connection between the second tube segment 9 and the dopant storage tube 11 is a vacuum flange connection. Before drawing the second specification single crystal silicon, the dopant is placed in the dopant storage tube 11, and the dopant storage tube is closed by the sealing plate 10. The ball valve 12 is opened to allow the dopant to enter the quartz crucible. After the molten mixture is uniformly mixed, the second specification single crystal silicon is drawn.

[0043] In this embodiment, the dopant tube 14 and the dopant storage tube 11 are both high-purity transparent quartz, and the sealing plate 10 is polished stainless steel. The inner surface of the sealing plate 10 is coated with a layer of Si or SiO2 by PVD / CVD.

[0044] The heater 13 includes a heating segment 1301 and support legs 1302 for fixing the heating segment 1301 to the bottom electrode of the furnace body 1. The height of the heating segment 1301 is 1 / 2 to 2 / 3 of the height of the quartz crucible, and the distance between the bottom end of the heating segment 1301 and the bottom wall of the furnace body is 500 mm.

[0045] In this embodiment, an observation hole 301 is formed in the furnace cover 3, and the opening of the observation hole 301 is sealed with glass.

[0046] Embodiment 3

[0047] A method for controlling the axial resistivity of doped single crystal silicon, the dopant being a boron master alloy, the first specification single crystal silicon having a size of 8 inches and a resistivity of 95-70 Ω·cm, and the second specification single crystal silicon having a size of 8 inches and a resistivity of 15-8 Ω·cm. The first loading amount is 140 kg, and no secondary loading is considered. The dopant master alloy used has the same characteristics. The method comprises the following steps:

[0048] A single crystal furnace as described in Embodiment 2 is used. The quartz crucible is loaded according to the maximum loading amount. The dopant is added to the quartz crucible as the first addition amount according to the amount required for the upper limit of the resistivity of the first specification single crystal silicon, and is co-melted with the polycrystalline material in the quartz crucible.

[0049] The first specification single crystal silicon is drawn. The doping calculation is performed according to the upper limit resistivity of 95 Ω·cm of the first specification single crystal silicon. The corresponding concentration is about 1.37×10 14 atoms / cm 3 , the effective segregation coefficient, and the control of the weight of the drawn crystal. A total of 68 kg is drawn, and the resistivity of the tail of the first specification single crystal silicon is 71.5 Ω·cm, corresponding to a concentration of about 1.82×10 14 atoms / cm 3 ; according to the resistivity of the tail of the single crystal silicon, the remaining mass of the molten silicon is 72 kg, and the resistivity-doping concentration curve (the target resistivity is 15 Ω·cm, and the corresponding concentration is about 8.76×10 14 atoms / cm 3) to determine the remaining dopant concentration in the molten silicon; to calculate the amount of additional doping required by subtracting the amount of dopant concentration remaining in the melt from the amount of doping concentration corresponding to the target resistivity of the second specification single crystal silicon; the calculation is mainly based on the formula m (pure dopant mass) = C (dopant concentration) x m (melt mass) x M (molar mass of dopant) / (p (density of molten silicon) x NA (Avogadro's number)), and then combined with the concentration of the doping element in the specific master alloy to calculate the actual weight.

[0050] The amount of dopant required for the upper limit of the resistivity of the second specification single crystal silicon is 13.029 g, and the amount of dopant supplement is 10.308 g.

[0051] The dopant is preloaded into the storage tube according to the supplement amount, and is closed by the sealing plate. Before drawing the second specification single crystal silicon, the ball valve is opened, the dopant in the storage tube slides into the doping tube under the action of gravitational potential energy, and falls into the molten silicon along the first part, the second part and the third part, is stabilized after melting, and then the second specification single crystal silicon is drawn.

[0052] In this embodiment, the ball valve is closed and the sealing plate is opened during the process of the dopant entering the storage tube. After the addition of the dopant is completed, the sealing plate is closed. At this time, there will be a small amount of air in the doping tube. A branch connecting pipe and a control valve can be installed on the side wall of the doping tube to solve the problem of external vacuumization, which is not shown in the figure. Moreover, the pressure of the single crystal furnace production system is usually 1E3~5E4 pa, and a certain amount of argon flow is continuously introduced and extracted. The amount of dopant is measured in "grams". Therefore, the relative volume of the doping tube is small, and the air contained in the small doping tube has little effect on the crystal pulling. The amount of air is not more than the amount of impurity volatiles in the furnace body.

[0053] Example 4

[0054] A method for controlling the axial resistivity of doped single crystal silicon, the dopant is boron master alloy, the first specification single crystal silicon has a size of 8 inches and a resistivity of 95-70 Ω·cm, the second specification single crystal silicon has a size of 6 inches and a resistivity of 50-25 Ω·cm, the first loading amount is 140 kg, and the second loading is not considered. The characteristics of the dopant master alloy used are the same. The method comprises the following steps:

[0055] A single crystal furnace as described in Example 2 is used, a quartz crucible is loaded according to the maximum loading amount, and the dopant is added to the quartz crucible according to the amount required for the upper limit of the resistivity of the first specification single crystal silicon as the first addition amount, and is co-melted with the polycrystalline material in the quartz crucible.

[0056] The first specification single crystal silicon is drawn, and the doping calculation is performed according to the upper limit resistivity of the first specification single crystal silicon, which is 95 Ω·cm. The corresponding concentration is about 1.37 x 10 14 atoms / cm 3, combined with the effective segregation coefficient and the control of the weight of the pulled crystal, a 68 kg crystal was pulled, and the resistivity of the tail of the first specification single crystal silicon was 70.8 Ω·cm, corresponding to a concentration of about 1.84×10 14 atoms / cm 3 ; the remaining doping amount in the molten silicon was determined according to the resistivity of the tail of the single crystal silicon, the remaining mass of the molten silicon 72 kg, and the resistivity-doping concentration curve; the second specification was calculated according to the doping of 50 Ω·cm, corresponding to a concentration of about 2.61×10 14 atoms / cm 3 ; the amount of doping required for the second specification single crystal silicon resistivity upper limit was calculated by subtracting the doping amount of the remaining dopant concentration in the melt from the doping amount of the second specification single crystal silicon target resistivity corresponding to the doping concentration.

[0057] The amount of dopant required for the upper limit of the resistivity of the second specification single crystal silicon was 3.882 g, and the amount of dopant to be supplemented was 1.161 g.

[0058] The dopant was preloaded into the storage tube according to the supplement amount, and was closed by the sealing plate. Before pulling the second specification single crystal silicon, the ball valve was opened, the dopant in the storage tube slid down to the doping tube under the action of gravitational potential energy, and fell into the molten silicon along the first part, the second part and the third part, was melted and stabilized, and then the second specification single crystal silicon was pulled.

[0059] In this embodiment, the dopant enters the storage tube, the ball valve is closed and the sealing plate is opened for dopant addition, and the sealing plate is closed after the addition is completed. At this time, there will be a small amount of air in the doping tube. A branch connecting pipe and a control valve can be installed on the side wall of the doping tube to solve the problem of external air extraction. The pressure of the single crystal furnace production system is usually 1E3-5E4 pa, and a certain amount of argon flow is continuously introduced and extracted. The amount of dopant is also measured in "grams". Therefore, the relative volume of the doping tube is small, and the air contained in the small doping tube has little effect on the pulling of the crystal. The amount of air is not more than the amount of impurity volatilization in the furnace body.

[0060] Example 5

[0061] A method for controlling the axial resistivity of doped single crystal silicon, the dopant is boron master alloy, the first specification single crystal silicon size is 6 inches, the resistivity is 95-70 Ω·cm, the second specification size is 6 inches, the resistivity is 20-10 Ω·cm, the first loading amount is 140 kg, and the second loading is not considered. The characteristics of the dopant master alloy used are the same. The method comprises the following steps:

[0062] A single crystal furnace as described in Example 2 is used, a quartz crucible is loaded according to the maximum loading amount, and the dopant is added to the quartz crucible according to the amount required for the upper limit of the resistivity of the first specification single crystal silicon as the first addition amount, and is co-melted with the polycrystalline material in the quartz crucible.

[0063] The first specification single crystal silicon is drawn, and the doping calculation is performed according to the upper limit resistivity 95Ω·cm of the first specification single crystal silicon, and the corresponding concentration is about 1.37×10 14 atoms / cm 3 The effective segregation coefficient and the control of the weight of the drawn crystal are combined, 66kg is drawn, and the resistivity of the tail of the first specification single crystal silicon is 71.2Ω·cm, and the corresponding concentration is about 1.83×10 14 atoms / cm 3 The remaining doping amount in the molten silicon is determined according to the resistivity of the single crystal silicon tail, the remaining mass of the molten silicon 74kg, and the resistivity-doping concentration curve; the second specification is calculated according to the doping concentration of 20Ω·cm, and the corresponding concentration is about 6.55×10 14 atoms / cm 3 The second specification single crystal silicon target resistivity corresponding to the doping concentration is subtracted from the remaining doping agent concentration in the melt, and the amount of the second specification single crystal silicon resistivity upper limit required for doping is calculated.

[0064] The amount of the second specification single crystal silicon resistivity upper limit required for doping is 10.012g, and the supplement amount of the dopant is 7.169g.

[0065] The dopant is preloaded into the storage pipe according to the supplement amount, and is closed by the sealing plate. Before drawing the second specification single crystal silicon, the ball valve is opened, the dopant in the storage pipe slides to the doping pipe under the action of gravitational potential energy, and falls into the molten silicon along the first part, the second part and the third part, is melted and stabilized, and then the second specification single crystal silicon is drawn.

[0066] In this embodiment, the dopant enters the storage pipe, the ball valve is closed and the sealing plate is opened for dopant addition, and the sealing plate is closed after the addition is completed. At this time, there will be a small amount of air in the doping pipe. A branch connecting pipe and a control valve can be installed on the side wall of the doping pipe to solve the problem by external evacuation. The pressure of the single crystal furnace production system is usually 1E3-5E4pa, and a certain amount of argon flow is continuously introduced and extracted. The dopant is also measured in "grams", so the relative volume of the doping pipe is small, and the air contained in the small doping pipe has little effect on the drawn crystal. The amount is also not more than the impurity volatiles in the furnace body.

[0067] Example 6

[0068] A method for controlling the axial resistivity of doped single crystal silicon, the dopant is pure boron, the first specification single crystal silicon has a size of 6 inches and a resistivity of 0.015-0.012Ω·cm, the second specification has a size of 6 inches and a resistivity of 0.003-0.002Ω·cm, and the first loading amount is 140kg, without considering secondary feeding. The method comprises the following steps:

[0069] The single crystal furnace described in Example 2 was used, the quartz crucible was charged according to the maximum loading capacity, the dopant was added into the quartz crucible according to the amount required for the upper limit of the first specification single crystal silicon resistivity as the first addition amount, and was co-melted with the polycrystalline material in the quartz crucible.

[0070] The first specification single crystal silicon was drawn, and the doping calculation was performed according to the upper limit resistivity of 0.015 Ω·cm of the first specification single crystal silicon, and the corresponding concentration was about 4.25×10 18 atoms / cm 3 , in combination with the effective segregation coefficient and the control of the weight of the drawn crystal, 70 kg was drawn, and the resistivity of the tail of the first specification single crystal silicon was 0.012 Ω·cm, and the corresponding concentration was about 6.03×10 18 atoms / cm 3 ; the remaining doping amount in the molten silicon was determined according to the resistivity of the tail of the single crystal silicon, the remaining mass of the molten silicon of 70 kg, and the resistivity-doping concentration curve; the second specification was calculated according to 0.003 Ω·cm, and the corresponding concentration was about 3.73×10 19 atoms / cm 3 ; the amount of the second doping was calculated by subtracting the doping amount of the remaining dopant concentration in the melt from the doping amount corresponding to the target resistivity of the second specification single crystal silicon;

[0071] The amount of the dopant required for the upper limit of the second specification single crystal silicon resistivity was 20.50 g, and the replenishment amount of the dopant was 17.16 g.

[0072] The dopant was pre-charged into the dopant storage pipe according to the replenishment amount, and was closed by the sealing plate. Before the second specification single crystal silicon was drawn, the ball valve was opened, the dopant in the dopant storage pipe slid down to the doping pipe under the action of the gravitational potential energy, and fell into the molten silicon along the first part, the second part and the third part, was melted and stabilized, and then the second specification single crystal silicon was drawn.

[0073] In this example, the ball valve was closed and the sealing plate was opened for dopant addition during the process of the dopant entering the dopant storage pipe, and the sealing plate was closed after the addition was completed. At this time, there was a small amount of air in the doping pipe. A branch connecting pipe and a control valve can be installed on the side wall of the doping pipe to solve the problem by external evacuation, which is not shown in the figure. Moreover, the pressure of the single crystal furnace production system is usually 1E3~5E4 pa, and a certain amount of argon flow is continuously introduced and extracted. The amount of the dopant is also measured in “grams”, so the relative volume of the doping pipe is small, and the air contained in the small doping pipe has little effect on the drawn crystal. The amount of the air is also less than the amount of impurity volatiles in the furnace body.

[0074] Example 7

[0075] A method for controlling axial resistivity of doped single crystal silicon, the dopant is a phosphorus master alloy, the first specification single crystal silicon has a size of 6 inches and a resistivity of 7-4 Ω·cm, the second specification single crystal silicon has a size of 6 inches and a resistivity of 3-1.5 Ω·cm, the first loading amount is 120 kg, no secondary loading is considered, and the dopant master alloys used have the same characteristics. The method comprises the following steps:

[0076] A single crystal furnace as described in Example 2 is used, a quartz crucible is loaded according to the maximum loading amount, the dopant is added into the quartz crucible according to the amount required for the upper limit of the resistivity of the first specification single crystal silicon as the first addition amount, and the dopant is co-melted with the polycrystalline material in the quartz crucible.

[0077] The first specification single crystal silicon is drawn, the doping calculation is performed according to the upper limit resistivity 7 Ω·cm of the first specification single crystal silicon, the corresponding concentration is about 6.34×10 14 atoms / cm 3 , the effective segregation coefficient and the control of the weight of the drawn crystal are combined, 46 kg is drawn, and the resistivity of the tail of the first specification single crystal silicon is 4.15 Ω·cm, the corresponding concentration is about 1.08×10 15 atoms / cm 3 ; the residual doping amount in the molten silicon is determined according to the resistivity of the tail of the single crystal silicon, the residual mass 74 kg of the molten silicon, and the resistivity-doping concentration curve; the second specification is calculated according to the doping calculation of 3 Ω·cm, the corresponding concentration is about 1.52×10 15 atoms / cm 3 ; the amount of the second specification single crystal silicon target resistivity corresponding to the doping concentration is subtracted from the amount of the residual dopant concentration in the melt to calculate the amount of the second doping;

[0078] The amount of the dopant required for the upper limit of the resistivity of the second specification single crystal silicon is 5.766 g, and the supplement amount of the dopant is 1.669 g.

[0079] The dopant is preloaded into the dopant storage pipe according to the supplement amount, and is closed by a sealing plate, before the second specification single crystal silicon is drawn, the ball valve is opened, the dopant in the dopant storage pipe slides to the doping pipe under the action of the gravitational potential energy, and falls into the molten silicon along the first part, the second part and the third part, is melted and then is stabilized, and then the second specification single crystal silicon is drawn.

[0080] In this embodiment, the dopant enters the storage pipe, the ball valve is closed and the sealing plate is opened for adding the dopant, and after the addition is completed, the sealing plate is closed. At this time, there is a small amount of air in the dopant pipe. A branch connecting pipe and a control valve can be installed on the side wall of the dopant pipe, and the problem can be solved by external evacuation. The production system of the single crystal furnace is usually under a pressure of 1E3-5E4 pa, and a certain amount of argon flow is continuously introduced and extracted. The amount of the dopant is also measured in "grams". Therefore, the relative volume of the dopant pipe is small, and the air contained in the small dopant pipe basically has no effect on crystal pulling. The amount is also not more than the amount of impurity volatiles in the furnace body.

[0081] The above description of disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of controlling the axial resistivity of doped single crystal silicon, comprising: The method comprises the following steps: ​ The dopant is added into the molten silicon as a first amount according to the upper limit of the resistivity of the first specification single crystal silicon; The first specification single crystal silicon is drawn, and the resistivity of the tail of the first specification single crystal silicon is obtained; the remaining amount of the dopant in the molten silicon is determined according to the resistivity of the tail of the single crystal silicon, the remaining mass of the molten silicon and a resistivity-dopant concentration curve; The replenishment amount of the dopant is determined according to the required doping amount of the upper limit of the resistivity of the second specification single crystal silicon, the remaining mass of the melt and the remaining amount of the dopant in the molten silicon; After the dopant is added into the remaining molten silicon according to the replenishment amount, the second specification single crystal silicon is drawn.

2. The method of claim 1, wherein the axial resistivity of the doped single crystal silicon is controlled by: The resistivity of the first specification is greater than that of the second specification. ​ 3. A single crystal furnace comprising a furnace body (1) and a furnace cover (3), the furnace body (1) being provided with a hot zone assembly, a heater (13), a graphite crucible and a support shaft for supporting the graphite crucible, the graphite crucible being provided with a quartz crucible for containing molten silicon, characterized in that: The hot field assembly comprises a heat shield unit and a heat preservation unit located above the graphite crucible; The heat shield unit comprises an inner shield (5) and an outer shield (4) which are coaxially arranged and the bottom ends of which can extend into the quartz crucible; the inner shield (5) is gradually tapered from top to bottom; the top end of the outer shield (4) is overlapped with the top end of the inner shield (5); the bottom end of the outer shield (4) is bent to form a bent portion toward the inner shield (5); the end of the bent portion away from the outer shield (4) is overlapped with the bottom end of the inner shield (5), so that a closed annular cavity (6) is formed between the outer shield (4) and the inner shield (5), and the annular cavity (6) is filled with heat preservation material; The heat preservation unit comprises an inner container (2) sleeved outside the heater (13); the inner container (2) and the inner wall of the furnace body (1) have an annular gap therebetween, and the annular gap is filled with heat preservation material to form a heat preservation layer (15); the furnace cover (3) is provided with a doping assembly, which comprises a doping pipe (14) and a storage pipe (11); one end of the doping pipe (14) extends into the furnace body (1) and is located above the quartz crucible; the other end of the doping pipe (14) extends out of the furnace body (1) and is connected with the storage pipe (11) through a ball valve (12); the end of the storage pipe (11) away from the doping pipe (14) is provided with a sealing plate (10) capable of sealing the same.

4. A single crystal furnace as claimed in claim 3, wherein: The heater (13) comprises a heating section (1301) and support legs (1302) for fixing the heating section (1301) to the bottom electrode of the furnace body (1); the height of the heating section (1301) is 1 / 2-2 / 3 of the height of the quartz crucible; the distance between the bottom end of the heating section and the bottom wall of the furnace body is 500 mm.

5. A single crystal furnace as claimed in claim 3, wherein: The doping pipe (14) comprises a first pipe section (8) located in the furnace body (1) and a second pipe section (9) located outside the furnace body (1); the first pipe section (8) and the second pipe section (9) are connected through a first flange (7); the first flange (7) is sealingly and fixedly connected with the furnace cover (3).

6. A single crystal furnace as claimed in claim 5, wherein: The first pipe section (8) comprises a first part (801), a second part (802) and a third part (803) which are integrally connected; the first part (801) is a straight pipe; the second part (802) and the third part (803) are arc-shaped pipes; the axis of the second part (802) protrudes downward and is tangent to the axis of the first part (801); the axis of the third part (803) protrudes upward and is tangent to the axis of the second part (802), so that a buffer zone is formed at the connection between the second part (802) and the third part (803).

7. A single crystal furnace as claimed in claim 6, wherein: The radius of the axis of the second part (802) is 90 mm, and the radius of the axis of the third part (803) is 145 mm.

8. A single crystal furnace as claimed in claim 3, wherein: The heat preservation layer (15) comprises an upper heat preservation layer (1501), a middle heat preservation layer (1502) and a lower heat preservation layer (1503) arranged from top to bottom, the thickness of the middle heat preservation layer (1502) and the thickness of the lower heat preservation layer (1503) are the same, and the thickness of the upper heat preservation layer (1501) is 65 mm less than the thickness of the middle heat preservation layer (1502).

9. A single crystal furnace as claimed in claim 8, wherein: The distance between the outer side wall of the upper heat preservation layer (1501) and the lower heat preservation layer (1503) and the inner side wall of the furnace body (1) is 90 mm and 25 mm.

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