Method for manufacturing silicon single crystal rod, silicon wafer, method for manufacturing silicon wafer, and crystal pulling furnace

Abstract

The invention provides a manufacturing method of a single crystal silicon rod, a silicon wafer, a manufacturing method of the silicon wafer and a crystal pulling furnace, and the manufacturing method comprises the steps: drawing the single crystal silicon rod in the crystal pulling furnace through a Czochralski method; in the crystal pulling furnace, first heat treatment is carried out on the single crystal silicon rod, the temperature range of the first heat treatment is 650-800 DEG C, and the lasting time range is 5-90 minutes; and in the crystal pulling furnace, second heat treatment is carried out on the single crystal silicon rod subjected to the first heat treatment, the temperature range of the second heat treatment is 100-300 DEG C, the duration time range is 10-60 minutes, the resistivity of the single crystal silicon rod subjected to the second heat treatment is larger than 1000 omega.cm, and the conduction type is P type.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the technical field of semiconductor processing, and in particular to a method for manufacturing a single crystal silicon rod, a silicon wafer and a method for manufacturing the same, and a crystal pulling furnace. BACKGROUND

[0002] As a core basic material in the manufacture of semiconductor devices, silicon wafers are widely used in the fields of integrated circuits, power devices, sensors, and photovoltaic components, etc. due to their excellent electrical properties, physical stability, and chemical stability.

[0003] With the rapid development of radio frequency communication, microwave devices, and high frequency and high power applications, devices have higher requirements for the electrical properties of silicon wafers. In particular, in the radio frequency field, high resistivity silicon wafers have gradually become a key basic material in order to effectively suppress parasitic effects, reduce signal transmission loss, and improve the overall performance of devices. The existing technology usually controls the doping concentration and optimizes the heat treatment process to regulate the resistivity of the silicon wafer.

[0004] However, the existing process still has significant deficiencies. On the one hand, for high resistance silicon wafers, oxygen donor annealing and low temperature heat treatment cannot be performed on each silicon wafer, because during the heat treatment process, the resistivity of the silicon wafer is easily reduced due to impurity contamination, affecting the effective resistivity of the device for use. On the other hand, heat treatment can also cause stress concentration points in the silicon wafer, which can cause chipping during subsequent grinding, polishing, and cleaning processes. SUMMARY

[0005] To solve the above problems, embodiments of the present disclosure provide a method for manufacturing a single crystal silicon rod, a silicon wafer and a method for manufacturing the same, and a crystal pulling furnace. The method for manufacturing a single crystal silicon rod continuously completes high temperature and low temperature heat treatment of the single crystal silicon rod in the crystal pulling furnace, avoids the cross contamination risk in the special heat treatment furnace, simplifies the process flow, and at the same time ensures that the resistivity of the single crystal silicon rod is greater than 1000Ω·cm and is uniform and stable, and the conductivity type is P type.

[0006] The technical solution of the present disclosure is implemented as follows: In a first aspect, the embodiments of the present disclosure provide a method for manufacturing a single crystal silicon rod, the manufacturing method comprising: In the crystal pulling furnace, a single crystal silicon rod is pulled by using the Czochralski method; In the crystal pulling furnace, the single crystal silicon rod is subjected to first heat treatment, the temperature range of the first heat treatment is 650-800℃, and the duration range is 5-90 minutes; In the crystal pulling furnace, the single crystal silicon rod after the first heat treatment is subjected to a second heat treatment, the temperature range of the second heat treatment is 100-300℃, and the duration range is 10-60 minutes, wherein the resistivity of the single crystal silicon rod after the second heat treatment is greater than 1000Ω·cm, and the conductivity type is P type.

[0007] In some optional examples, after the end of the first heat treatment and before the start of the second heat treatment, the manufacturing method further comprises: cooling the single crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment by using a cooling medium, the cooling medium comprising liquid nitrogen or liquid argon.

[0008] In some optional examples, after the end of the first heat treatment and before the start of the second heat treatment, the manufacturing method further comprises: cooling the single crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment by using a cooling medium, the cooling medium comprising liquid nitrogen or liquid argon.

[0009] In some optional examples, the crystal pulling furnace comprises a main furnace chamber and a sub-furnace chamber, and a temperature adjusting device is arranged in the sub-furnace chamber, wherein the temperature adjusting device is used to adjust the temperature in the sub-furnace chamber to perform the first heat treatment and the second heat treatment on the single crystal silicon rod in the sub-furnace chamber.

[0010] In some optional examples, the oxygen content of the single crystal silicon rod after the second heat treatment is less than 8ppma. In a second aspect, the embodiments of the present disclosure provide a manufacturing method of a silicon wafer, the manufacturing method comprising: cutting, grinding, polishing and cleaning a single crystal silicon rod made by the manufacturing method of the single crystal silicon rod according to the first aspect to obtain a silicon wafer.

[0011] In a third aspect, the embodiments of the present disclosure provide a silicon wafer, the silicon wafer being made by using the manufacturing method of the silicon wafer according to the second aspect, wherein the resistivity of the silicon wafer is greater than 1000Ω·cm, the conductivity type is P type, and the oxygen content is less than 8ppma. In a fourth aspect, the embodiments of the present disclosure provide a crystal pulling furnace for performing the manufacturing method of the single crystal silicon rod according to the first aspect.

[0012] In some optional examples, the crystal pulling furnace comprises a main furnace chamber, a sub-furnace chamber and a temperature adjusting device arranged in the sub-furnace chamber, the temperature adjusting device comprising a heater, wherein, the heater is used to perform a first heat treatment and a second heat treatment on a single crystal silicon rod, the temperature range of the first heat treatment is 650-800℃, and the temperature range of the second heat treatment is 100-300℃.

[0013] In some alternative examples, the temperature adjusting device further comprises a supply device for supplying a cooling medium, wherein, The supply device is configured to cool the single crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment at a cooling rate of no less than 15℃ / min by supplying the cooling medium to the auxiliary furnace chamber after the first heat treatment ends and before the second heat treatment starts.

[0014] The present disclosure provides a method for manufacturing a single crystal silicon rod, a silicon wafer and a method for manufacturing the same, and a crystal pulling furnace. The method for manufacturing a single crystal silicon rod is achieved by completing a series of process steps in a crystal pulling furnace. First, a single crystal silicon rod containing a dopant is pulled by using a Czochralski method, and the single crystal silicon rod is sequentially subjected to two-step heat treatment in the same crystal pulling furnace. First, a stable structure of oxygen polymer is destroyed by a first heat treatment step with a relatively high temperature, so that oxygen donor defects are removed. Then, a second heat treatment step with a lower temperature is used to further stabilize the carrier concentration, so as to ensure that the conductivity type of the single crystal silicon rod is P-type and the measured resistivity reaches and stabilizes in a high resistivity range of more than 1000Ω·cm. Since the heat treatment step is integrated in the crystal pulling furnace in the method for manufacturing a single crystal silicon rod, the risk of external contamination when the silicon rod is cut and then subjected to heat treatment in the conventional process is avoided, thereby effectively improving the stability of the high resistivity of the finished single crystal silicon. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A flow chart of the method for manufacturing a single crystal silicon rod provided by the embodiments of the present disclosure.

[0016] Figure 2 A schematic cross-sectional view of a conventional crystal pulling furnace.

[0017] Figure 3 A schematic cross-sectional view of a crystal pulling furnace provided by the embodiments of the present disclosure.

[0018] Figure 4 A partial cross-sectional view of Figure 3

[0019] Figure 5 A graph of the resistivity and oxygen content of a single crystal silicon rod manufactured by using the method for manufacturing a single crystal silicon rod provided by the embodiments of the present disclosure. DETAILED DESCRIPTION

[0020] The technical solutions in the present disclosure will be described clearly and completely below in combination with the drawings in the present disclosure.

[0021] ​In the conventional manufacturing process of high resistivity silicon wafers, after obtaining a single crystal silicon ingot, a plurality of processes such as cutting, heat treatment, grinding, polishing, cleaning, etc. are sequentially performed on the single crystal silicon ingot, and finally a silicon wafer meeting the electrical performance requirements is formed. In this manufacturing process, the control of impurities inside the silicon wafer, especially the distribution state of oxygen impurities, is a key factor affecting the stability and uniformity of the finished product resistivity.

[0022] Taking a single crystal silicon ingot grown by the Czochralski method (CZ method) as an example, a certain amount of oxygen impurities will inevitably be introduced during the growth process. These oxygen impurities mainly come from the reaction of the quartz crucible and molten silicon under high temperature conditions, and are usually in the form of interstitial oxygen (Oi) dissolved in the silicon crystal structure. This type of oxygen impurities is prone to aggregation or reaction during subsequent processing, forming oxygen precipitates or oxygen-related complex defects. These defects can introduce donor levels in the silicon crystal, releasing free carriers, thereby causing the effective resistivity of the silicon wafer to decrease, affecting its performance in high-frequency applications such as radio frequency and microwave. In addition, the oxygen precipitate core can also become a nucleation source for dislocations or slip dislocations, further causing local distortion of the crystal structure, not only weakening the mechanical strength of the silicon wafer, but also causing the dielectric loss to increase during device operation, affecting the electrical stability and consistency of the device.

[0023] In order to regulate the distribution of oxygen impurities and reduce defect formation, a high-temperature heat treatment process is usually introduced in the prior art to remove oxygen donor defects by controlling the heat treatment temperature and atmosphere conditions, thereby improving or stabilizing the effective resistivity of the silicon wafer, and also improving the integrity and defect density of the crystal. However, despite the widespread use of heat treatment processes, there are still many limitations in actual production, affecting the final quality of high resistivity silicon wafers.

[0024] Firstly, since the heat treatment equipment needs to be compatible with the processing needs of multiple types of silicon wafers, different types or doping conditions of silicon wafers are usually processed in the same furnace chamber, which has the risk of impurity cross-contamination. Doping agents such as boron, phosphorus, or metal ions such as iron, copper left on the inner wall of the furnace chamber can migrate to the surface or interior of the high resistivity silicon wafer under high temperature conditions, causing the surface or local impurity concentration of the silicon wafer to abnormally increase, and thus causing the problem of resistivity decrease. Moreover, the redistribution of oxygen during heat treatment is also a key influencing factor. If the heat treatment temperature and atmosphere are not reasonably controlled, it may cause changes in oxygen content, induce oxygen precipitates, oxygen donor type defects, etc., form local conductive channels, and destroy the uniformity of the overall resistivity of the silicon wafer.

[0025] In addition, high-temperature heat treatment has a potential adverse effect on the mechanical properties of the silicon wafer. After high-temperature heat treatment, the internal crystal structure of the silicon wafer can have problems such as residual stress release and micro-defect expansion, which can reduce the mechanical strength of the silicon wafer and significantly increase the risk of breakage during subsequent mechanical processing such as grinding, polishing, and cleaning, thereby affecting the yield of finished products and production efficiency.

[0026] In view of this, the embodiments of the present disclosure propose a method for manufacturing a single crystal silicon rod, a silicon wafer and a method for manufacturing the same, and a crystal pulling furnace. The method for manufacturing a single crystal silicon rod continuously completes high-temperature and low-temperature heat treatment of the single crystal silicon rod in the crystal pulling furnace, avoids the risk of cross-contamination in a special heat treatment furnace, simplifies the process flow, and ensures that the resistivity of the single crystal silicon rod is greater than 1000 Ω·cm and uniform and stable, and the conductivity type is P-type.

[0027] Referring to Figure 1 Some embodiments of the present disclosure propose a method for manufacturing a single crystal silicon rod. The method can include: S1, using a Czochralski method to pull a single crystal silicon rod in a crystal pulling furnace; S2, performing first heat treatment on the single crystal silicon rod in the crystal pulling furnace, the temperature range of the first heat treatment being 650-800°C, and the duration range being 5-90 minutes; S3, performing second heat treatment on the single crystal silicon rod after the first heat treatment in the crystal pulling furnace, the temperature range of the second heat treatment being 100-300°C, and the duration range being 10-60 minutes, wherein the resistivity of the single crystal silicon rod after the second heat treatment is greater than 1000 Ω·cm, and the conductivity type is P-type.

[0028] In this embodiment of the present disclosure, the above three steps of the proposed manufacturing method can be continuously completed in the same crystal pulling furnace, thereby reducing the impurity pollution that can be introduced during process switching, equipment replacement, and handling, and simplifying the manufacturing process. In addition, the single crystal silicon rod with a resistivity greater than 1000 Ω·cm and a conductivity type of P-type obtained through the manufacturing method can meet the strict requirements of high-frequency devices, radio frequency components, and the like for high-resistivity silicon materials.

[0029] Specifically, in step S1, a single crystal silicon rod S can be pulled in a crystal pulling furnace using a Czochralski method. In this process, first, high-purity polycrystalline silicon raw materials are loaded into a quartz crucible, and under high-temperature conditions, they are fully melted. Then, an oriented seed crystal is introduced, and by precisely controlling the pulling speed and the crystal rotation rate, the phase transition from the melt to the single crystal state is gradually realized, thereby growing a single crystal silicon rod S with a predetermined diameter, length, and crystal direction.

[0030] In order to make the drawn single crystal silicon rod have the required high resistivity and predetermined conductivity type, the doping scheme needs to be reasonably designed according to the conductivity characteristics of the polycrystalline silicon raw material during its growth. Specifically, the type and concentration of the dopant can be flexibly determined according to the background impurity level of the raw material, the target resistivity and the conductivity type. For example, if the raw material polycrystalline silicon has a relatively low background impurity concentration (close to intrinsic silicon), no dopant can be added, and an intrinsic high-resistivity single crystal silicon rod can be directly drawn; if the raw material contains a certain amount of donor impurities (such as phosphorus), in order to obtain P-type characteristics, a suitable amount of acceptor impurity - boron (B) needs to be introduced during the growth process to offset the background N-type doping and form a net P-type characteristic.

[0031] For high-resistivity silicon materials required by radio frequency components, high-frequency communication chips and other devices, P-type doping method can be preferably used, and boron (B) is typically selected as the doping element. As an example, the doping concentration of boron can be controlled in the range of less than 5×10 14 atoms / cm³. This doping concentration range helps to ensure that the conductivity type of the silicon rod is P-type while making its intrinsic resistivity as large as possible, for example, 1000 Ω·cm, while avoiding the problem of too much difference between the initial resistivity and the target resistivity caused by too high doping concentration, providing adjustable space for further improving the resistivity in subsequent process stages.

[0032] It should be noted that during the Czochralski process, the molten silicon liquid and the quartz crucible are in long-term contact at high temperature, and there is an unavoidable interfacial reaction, thereby introducing a certain amount of oxygen impurities. These oxygen impurities are mainly distributed in the form of interstitial oxygen in the crystal lattice structure of the single crystal silicon rod and are uniformly diffused throughout the silicon rod. Although interstitial oxygen is relatively stable at low temperatures, it is easy to migrate and accumulate in subsequent high-temperature processing or application environments, and may precipitate in the form of oxygen aggregates, oxygen precipitates or oxygen donor defects.

[0033] The above oxygen precipitates and oxygen donor defects not only can form electrical active centers in the crystal, which can release free carriers (electrons) at the donor level, causing the actual resistivity of the material to deviate from the theoretically expected value, but also can become the starting point of crystal structure defects, causing structural abnormalities such as micro-cracks and dislocations. Such defects can cause problems such as increased device leakage current and threshold drift in electrical performance, and can also cause local strength to decrease in subsequent slicing, polishing or other mechanical processing, affecting the yield and yield control.

[0034] Therefore, even if the type and concentration of the dopant are set according to the target resistivity during the single crystal pulling stage, the measured resistivity of the final obtained single crystal silicon rod can still deviate significantly from the expected value due to the migration and activation effect of oxygen impurities, which is one of the key factors limiting the improvement of material performance.

[0035] To suppress the above-mentioned adverse effects, the manufacturing method proposed by the embodiments of the present disclosure includes, after the completion of the single crystal silicon rod drawing, immediately performing steps S2 and S3, i.e., the first heat treatment step and the second heat treatment step, on the single crystal silicon rod in the crystal pulling furnace. The two steps are continued to be completed in the same crystal pulling furnace, reducing the risk of cross contamination of impurities caused by process transfer in the traditional process.

[0036] In step S2, the single crystal silicon rod S completed by drawing is subjected to the first heat treatment in the temperature range of 650-800°C in the crystal pulling furnace. The specific temperature of the first heat treatment can be reasonably selected and controlled according to the dopant concentration, oxygen impurity distribution and target resistivity requirement.

[0037] Specifically, under different doping schemes and oxygen impurity background conditions, the specific temperature of the first heat treatment can be reasonably set according to the actual target resistivity. For example, in the case of phosphorus (P) as the dopant, if the background phosphorus concentration in the used polycrystalline silicon raw material is less than 0.5 ppba, and the distribution concentration of oxygen impurities in the single crystal silicon rod is <6 ppma, in order to obtain a P-type characteristic single crystal silicon rod with a target resistivity >1000Ω·cm, the first heat treatment can be performed on the single crystal silicon rod in the crystal pulling furnace after the completion of the crystal pulling. At this time, the temperature range of the first heat treatment can be selected to be 700-770°C, and further preferably set to about 750°C.

[0038] For example, in the case of boron (B) as the dopant, if the boron doping concentration is <0.5 ppba, and the distribution concentration of oxygen impurities in the single crystal silicon rod is <6 ppma, in order to realize a high-resistivity P-type single crystal silicon rod with a target resistivity >3000Ω·cm, the temperature range of the first heat treatment can be set to 680-760°C, and further selected to be about 740°C.

[0039] The first heat treatment step is performed to remove oxygen donor defects. This is because the presence of oxygen donor defects can cause the release of free carriers, resulting in a local increase in carrier concentration and thus a decrease in resistivity. The first heat treatment of the single crystal silicon rod is equivalent to high-temperature annealing to promote the precipitation of part of the oxygen impurities in the silicon crystal and lose electrical activity, thereby achieving the effect of reducing the oxygen donor density and improving the resistivity. In addition, moderate high temperature also helps to release the local stress formed during the growth of the silicon rod crystal and eliminate micro defects, further improving the crystal structure integrity and uniformity.

[0040] Compared with the prior art of heat treatment of a silicon wafer obtained by cutting a single crystal silicon rod using a dedicated heat treatment furnace, in the embodiments of the present disclosure, the first heat treatment step is directly completed in the crystal pulling furnace, i.e., the heat treatment is performed in situ, so that the handling and unloading steps can be omitted, and the risk of contamination of the surface and interior of the single crystal silicon rod S by external impurities and / or impurities in the heat treatment furnace can be reduced. Moreover, the crystal pulling furnace actually provides a crystal environment that can ensure high purity and high consistency.

[0041] After the first heat treatment is completed, the single crystal silicon rod that has undergone the first heat treatment is subjected to a second heat treatment at a temperature ranging from 100°C to 300°C, i.e., step S3. The second heat treatment is also continued in the crystal pulling furnace. The temperature of the second heat treatment is set to be significantly lower than that of the first heat treatment, so as to achieve a carrier stabilization process.

[0042] In some embodiments of the present disclosure, the two-step heat treatment steps for the single crystal silicon rod S are not only reasonably selected in terms of temperature setting, but also optimized in terms of the duration of each heat treatment step, so as to ensure that the final single crystal silicon rod can stably obtain a high resistivity characteristic.

[0043] Specifically, in some embodiments of the present disclosure, the duration of the first heat treatment can be set in the range of 5 minutes to 90 minutes. As described above, the main purpose of the first heat treatment is to eliminate oxygen donor defects. Based on this, if the duration of the first heat treatment is too short, the diffusion and precipitation process of oxygen impurities in the crystal can not be sufficient, which is likely to result in residual oxygen donor defects and affect the high resistivity stability of the single crystal silicon rod; and if the duration is too long, the thermal stress inside the crystal structure can be intensified, the risk of dislocation or slip dislocation can be increased, and the mechanical stability of the subsequent process can be adversely affected. Therefore, by controlling the duration in the range of 5 minutes to 90 minutes, the sufficiency of the oxygen precipitation effect and the integrity of the crystal structure can be considered, and the resistivity stability of the single crystal silicon rod can be ensured. In further preferred embodiments of the present disclosure, the duration of the first heat treatment can be set in the range of 10 minutes to 60 minutes.

[0044] The temperature of the second heat treatment is preferably reasonably determined and selected based on the temperature and time settings of the first heat treatment, the type and concentration of the dopant, the target resistivity level, and other process parameters.

[0045] In some embodiments of the present disclosure, the duration of the second heat treatment can be set in the range of 10 minutes to 60 minutes. As set forth above, the main role of the second heat treatment is to promote the stability of the carrier concentration in a lower temperature environment, so that the holes and electrons of the monocrystalline silicon rod reach a balanced state. Based on this, if the heat treatment time is insufficient, the carrier concentration is difficult to effectively stabilize in the crystal, thereby causing the resistivity test results to fluctuate, reducing the consistency of the finished product; and if the time is too long, the production efficiency is reduced, and the effect on the final crystal performance improvement is limited. Therefore, selecting a time interval of 10 minutes to 60 minutes can improve the process efficiency and reduce the cost on the premise of ensuring the uniformity of the electrical performance. In further preferred embodiments of the present disclosure, the duration of the second heat treatment can be set in the range of 20 minutes to 40 minutes.

[0046] For example, under the condition that the first heat treatment temperature is 700°C, the duration is 45 min, the dopant is boron, and the target resistivity is >3000Ω·cm, to achieve the stabilization of the carrier and the uniform improvement of the resistivity, the second heat treatment temperature can be set in the range of 180°C to 220°C, for example, it can be 190°C.

[0047] In another case, if the first heat treatment temperature is set to 750°C, the duration is 30 min, and the doping concentration is relatively high, the temperature of the second heat treatment can be appropriately increased, such as being set in the range of 190°C to 240°C, for example, it can be 210°C, to accelerate the process of stabilizing the carrier concentration and optimize the overall process rhythm.

[0048] After the monocrystalline silicon rod S undergoes high-temperature annealing, the concentration distribution of electrons and holes fluctuates to some extent, especially in P-type high-resistance silicon single crystals, the hole concentration is low, and if the free electron migration speed is too fast, it will affect the stability and measurement consistency of the final resistivity of the monocrystalline silicon rod S. The second heat treatment of the monocrystalline silicon rod S can also be referred to as a low-temperature heat treatment step, which is used to effectively alleviate the carrier migration effect caused by heat treatment, so that the hole and electron concentrations tend to be balanced, the resistivity is stabilized, and the conductivity type of the finished silicon rod is accurately P-type.

[0049] After undergoing the above two heat treatment steps S1 and S2, the monocrystalline silicon rod S has a high resistivity characteristic, especially the measured resistivity is greater than 1000Ω·cm and the conductivity type is P-type, which meets the performance requirements of high-frequency, radio frequency and power devices for high-resistivity substrate materials.

[0050] Some embodiments of the present disclosure provide a method for manufacturing a single crystal silicon rod. The method is accomplished by performing continuous process steps in a crystal pulling furnace, first pulling a single crystal silicon rod containing dopants by using a Czochralski method, and then sequentially performing two-step heat treatment on the single crystal silicon rod in the same crystal pulling furnace. First, by the first heat treatment step with a relatively high temperature, elimination of oxygen donor defects is performed; then, by the second heat treatment step with a lower temperature, further stabilization of the carrier concentration is performed to ensure that the measured resistivity of the single crystal silicon rod reaches and stabilizes in a high resistivity range of greater than 1000 Ω·cm. Since the manufacturing method integrates the heat treatment steps in the crystal pulling furnace, it avoids the external contamination risk faced in the conventional process when the silicon rod is cut and then heat treated, thereby effectively improving the stability of the high resistivity of the finished single crystal silicon.

[0051] In embodiments of the present disclosure, in order to further improve the resistivity uniformity and stability of the single crystal silicon rod S, while taking into account the efficiency and reliability of the process, a cooling step, which can also be referred to as a cooling-down step, is further provided between the end of the first heat treatment and the beginning of the second heat treatment.

[0052] Specifically, after completing the first heat treatment, the single crystal silicon rod S needs to be cooled down from the higher temperature range of the first heat treatment to a lower temperature range suitable for performing the second heat treatment. To this end, in some embodiments of the present disclosure, the cooling step can be limited to cooling down at a cooling rate of not less than 15 ℃ / min.

[0053] The setting of this cooling rate has multiple considerations. First, if the cooling rate is too slow, the single crystal silicon rod S stays in the sensitive temperature range of 400 ℃-450 ℃ for a long time, which is easy to cause the re-generation of oxygen donor defects. In this temperature range, the oxygen impurities in the silicon crystal are highly active, which is easy to re-aggregate and form oxygen donor defects, thereby causing the local carrier concentration to abnormally increase, affecting the uniformity and stability of the overall resistivity of the silicon rod. By controlling the cooling rate to be above 15 ℃ / min, the residence time of the single crystal silicon rod S in this temperature range can be effectively shortened, and the elimination of the influence of oxygen donor defects is ensured from the source, so that the silicon rod has a high resistivity characteristic of greater than 1000 Ω·cm.

[0054] Moreover, this cooling step also has a positive effect on improving the mechanical properties of the single crystal silicon rod S. Since the single crystal silicon rod S is prone to form thermal stress accumulation during high-temperature heat treatment, if the cooling rate is too slow or the cooling process is not uniform, the thermal stress release process can cause local lattice distortion, dislocation expansion, or even induce micro-cracks. By using a reasonable rapid cooling process, the thermal stress can be uniformly released, and the residual stress level can be reduced, thereby effectively improving the mechanical strength of the single crystal silicon rod and reducing the risk of damage or fragmentation during subsequent cutting, grinding, polishing and other processing procedures.

[0055] In addition, the cooling rate is controlled to be greater than or equal to 15 ℃ / min, which has good process efficiency advantage, can significantly shorten the time between the first heat treatment and the second heat treatment, optimize the production rhythm, and meet the demand of large-scale industrial production.

[0056] To achieve the above-mentioned cooling rate control, in some embodiments of the present disclosure, cooling medium can be used for auxiliary cooling. Specifically, the cooling medium includes but is not limited to liquid nitrogen, liquid argon. These cooling media have lower temperature and excellent heat exchange efficiency, so that the single crystal silicon rod can be rapidly cooled from high temperature to the temperature range required for the second heat treatment, without introducing impurity contamination, meeting the clean process requirement in semiconductor manufacturing. In addition, according to specific production conditions, liquid nitrogen or liquid argon can be used in combination with a cooling water system, an inert gas circulation or a heat exchange device to flexibly regulate the cooling rate and temperature uniformity, so as to simultaneously improve the stability and mechanical properties of the electrical properties.

[0057] In the embodiments of the present disclosure, in order to achieve precise temperature control of the single crystal silicon rod during the whole process of the first heat treatment, cooling treatment and second heat treatment, and further improve the stability and controllability of the process, in the case that the crystal pulling furnace includes a main furnace chamber and a secondary furnace chamber, a temperature regulating device can be configured in the secondary furnace chamber to perform subsequent treatment on the single crystal silicon rod pulled in the main furnace chamber.

[0058] Specifically, the main furnace chamber is used to complete the Czochralski growth process of the single crystal silicon rod, and the secondary furnace chamber is used to perform subsequent heat treatment and cooling process. The heat treatment and cooling steps are performed in the secondary furnace chamber, which has many advantages: Firstly, since the secondary furnace chamber is relatively independent, its internal environment is easier to control, which can avoid the influence of high temperature disturbance or pollution introduced by the main furnace chamber during the crystal pulling process on the heat treatment process, and ensure the uniformity and stability of the heat treatment temperature. Moreover, the space of the secondary furnace chamber can be used for heat treatment only, which can reduce the risk of cross contamination and improve the purity and consistency of the high resistivity silicon rod product.

[0059] The temperature regulating device in the secondary furnace chamber can include a heater, a cooling gas supply system and the like, which are used to dynamically adjust the temperature parameters of the secondary furnace chamber. Specifically, the heater can achieve the high temperature condition required for the first heat treatment, control the temperature in the range of 650-800 ℃, and maintain the temperature stability during the heat treatment process. The cooling gas supply system is used to assist in achieving the cooling treatment stage, control the cooling rate to be not less than 15 ℃ / min, and rapidly reduce the temperature to a low temperature range suitable for the second heat treatment. For further cooling requirement, a liquid nitrogen or liquid argon supply system can also be selected to improve the cooling efficiency and temperature control accuracy.

[0060] The temperature adjusting device in the auxiliary furnace chamber ensures that the first heat treatment, the cooling treatment and the second heat treatment can be continuously and stably completed in the auxiliary furnace chamber through accurate adjustment of the temperature. In this way, the step of transferring the single crystal silicon rod to an external special heat treatment equipment is omitted, which not only reduces the risk of mechanical damage or pollution of the surface of the silicon rod in the handling process, but also helps to control the production rhythm.

[0061] In order to realize the manufacturing method proposed in the above-mentioned embodiments of the present disclosure, some embodiments of the present disclosure also propose a crystal pulling furnace 10 comprising the temperature adjusting device 1. The crystal pulling furnace 10 will be specifically described below in combination with the drawings.

[0062] Figure 2 A conventional crystal pulling furnace 10 is shown in FIG. 1. Specifically, the crystal pulling furnace 10 can comprise a main furnace chamber 11 and an auxiliary furnace chamber 12 arranged in a top-bottom manner, wherein the auxiliary furnace chamber 12 is located directly above the main furnace chamber 11 and communicates with the main furnace chamber 11. The main furnace chamber 11 mainly comprises a quartz crucible 20, a graphite crucible 30 and a heating module 40. The quartz crucible 20 can be used to contain the solid polycrystalline silicon raw material in the initial stage of pulling the crystal rod S. The graphite crucible 30 can be arranged around the quartz crucible 20 to provide support for the quartz crucible 20 during heating of the polycrystalline silicon raw material. The heating module 40 is arranged at the outer periphery of the quartz crucible 20.

[0063] In use of the crystal pulling furnace 10, a polycrystalline silicon raw material with a certain mass is first placed in the quartz crucible 20, and then the polycrystalline silicon raw material in the quartz crucible 20 is heated and melted by the heating module 40 to form a silicon melt.

[0064] The crystal pulling furnace 10 can further comprise a seed cable 50, a crystal rod pulling device 60 and a crucible lifting device 70. The seed cable 50 is arranged above the quartz crucible 20, and is used to control the seed cable 50 to lower the seed crystal to the solid-liquid interface of the silicon melt and start the processes of seeding, necking, shoulder forming, diameter growth and tailing, etc. by the crystal rod pulling device 60 after the polycrystalline silicon raw material in the quartz crucible 20 is melted to form a silicon melt and the temperature of the solid-liquid interface is stable, so as to finally pull a crystal rod S with a certain length. The crucible lifting device 70 is arranged at the bottom of the graphite crucible 30 and is used to drive the lifting and rotation of the quartz crucible 20 during the pulling of the single crystal silicon rod S.

[0065] In order to meet the needs of continuous heat treatment of the single crystal silicon rod in the embodiments of the present disclosure, the inventors have improved the conventional crystal pulling furnace, as shown in FIG. 2, a temperature adjusting device 1 is additionally arranged in the auxiliary furnace chamber 12, thereby forming an improved crystal pulling furnace 10. Figure 3

[0066] ​Specifically, the single crystal silicon rod S gradually leaves the melting zone of the main furnace chamber 11 and gradually enters the auxiliary furnace chamber 12 during the pulling process. After the pulling is completed, the crystal rod pulling device 60 completely pulls the single crystal silicon rod S to the auxiliary furnace chamber 12 and suspends it in the auxiliary furnace chamber to avoid direct contact with the bottom of the auxiliary furnace chamber. In the auxiliary furnace chamber 12, the single crystal silicon rod S can directly complete the subsequent heat treatment steps without being transferred.

[0067] As shown in Figure 3 and Figure 4 The auxiliary furnace chamber 12 is provided with a temperature adjusting device 1, which includes a heater 121 arranged around the circumferential wall of the auxiliary furnace chamber and a supply device 122 for cooling. The heater 121 is used to regulate the temperature conditions in the auxiliary furnace chamber 12 during the first and second heat treatment stages, respectively, to ensure that the single crystal silicon rod S remains within the set process temperature range at different temperature stages. The supply device 122 is provided at the top or other suitable position of the auxiliary furnace chamber 12, one end of which is communicated with the inside of the auxiliary furnace chamber through a supply port, and the other end is connected to a cooling medium source. The supply device 122 can introduce cooling medium into the auxiliary furnace chamber for rapid cooling of the single crystal silicon rod S after the first heat treatment. The suitable cooling medium can include liquid nitrogen, liquid argon and other low-temperature media, which have high heat exchange characteristics and help to achieve precise control of the cooling rate.

[0068] Through the cooperation of the heater 121 and the supply device 122 in the temperature adjusting device 1, dynamic adjustment of the temperature in the auxiliary furnace chamber 12 can be achieved, so that the single crystal silicon rod S can directly complete the continuous operation of the first heat treatment, cooling treatment and second heat treatment in the auxiliary furnace chamber after the pulling is completed. The steps of handling, transferring and the like are omitted, the risk of impurity pollution and mechanical damage of the silicon rod during handling is reduced, the temperature stability and uniformity of the heat treatment process are further ensured, and further protection is provided for obtaining a high-performance single crystal silicon rod with a resistivity greater than 1000 Ω·cm and controlled oxygen content.

[0069] In some embodiments of the present disclosure, in order to further ensure the stability of the high resistivity performance of the single crystal silicon rod and reduce the risk of defects caused by oxygen impurities, it is particularly limited that the oxygen content of the single crystal silicon rod is less than 8ppma after the second heat treatment is completed.

[0070] Specifically, as explained above, oxygen impurities, as a key intrinsic impurity in single crystal silicon material, mainly come from the high-temperature reaction between quartz crucible and molten silicon during the Czochralski growth process. Oxygen impurities usually exist in the form of interstitial oxygen, and their content directly affects the electrical properties and subsequent processing stability of the silicon rod. Too high oxygen content is easy to induce oxygen precipitation, oxygen donor defects or microstructure defects during subsequent heat treatment or device use, thereby reducing the effective resistivity and resistivity uniformity of the material, inducing local conductive channels, and even causing device reliability to decrease.

[0071] By introducing the two-step heat treatment process in the manufacturing method, first in the first heat treatment stage, the diffusion and uniform distribution of oxygen impurities are promoted by high temperature, effectively eliminating oxygen donor defects and avoiding their aggregation to form a carrier supply source. Subsequently, through the second heat treatment stage, the hole and electron distribution in the crystal structure is further stabilized at a lower temperature, inhibiting the active reaction of oxygen impurities, and ensuring that the final single crystal silicon rod has an oxygen content of less than 8 ppma. In further preferred embodiments of the present disclosure, the oxygen content of the single crystal silicon rod can be controlled to be less than 6 ppma.

[0072] Through the manufacturing method provided by the embodiments of the present disclosure, two forms of single crystal silicon semiconductor structures can be obtained: on the one hand, a single crystal silicon rod subjected to two-step heat treatment can be directly obtained; on the other hand, by further performing processing steps such as cutting, grinding, polishing and cleaning on the single crystal silicon rod, a silicon wafer meeting the requirements of high-performance applications can also be prepared.

[0073] Especially noteworthy is that the manufacturing method of the present disclosure effectively controls the oxygen content distribution in the single crystal silicon rod, removes oxygen donor defects, and reduces the level of internal residual stress through the two-step heat treatment continuously performed in the crystal pulling furnace. This process significantly improves the resistivity uniformity and mechanical stability of the single crystal silicon rod, and improves the controllability and yield of the subsequent processing process from the source.

[0074] Therefore, in the subsequent cutting, grinding and polishing processes, the single crystal silicon rod exhibits high mechanical damage resistance, and the fragment rate is significantly reduced. Moreover, the final obtained silicon wafer not only has excellent electrical properties, especially a resistivity greater than 1000 Ω·cm and an oxygen content less than 8 ppma, but also meets the strict requirements of material electrical properties and reliability in the fields of radio frequency devices, high frequency applications and the like.

[0075] To further verify the characteristics of the single crystal silicon rod obtained by the manufacturing method of the present disclosure, Figure 5 The central resistivity and central oxygen content distribution data along the length direction are shown in the graph.

[0076] The graph shows two key material properties of a single crystal silicon ingot along its length direction (X-axis represented by “Ingot position (cm)”: center resistivity (Center Resistivity) and center oxygen content (Center Oxygen). The left Y-axis represents resistivity in ohm-cm (ohm-cm) ranging from 0 to 9000 ohm-cm, and the right Y-axis represents oxygen content in nppma (nppma) ranging from 0 to 7 nppma. The black solid line with square data points represents “Center Resistivity”, and the gray solid line with circular data points represents “Center Oxygen”. In terms of data trend, the center resistivity gradually increases as the ingot position increases. Specifically, at the beginning of the ingot (about 1.5 cm), the resistivity is about 6352 ohm-cm; in the middle (about 5.5 cm), the resistivity slightly increases to 6511 ohm-cm; and then at the end of the ingot (about 9.5 cm), the resistivity significantly increases to 7721 ohm-cm. At the same time, the center oxygen content shows a trend of first slightly decreasing and then significantly increasing. At the beginning of the ingot (about 1.5 cm), the oxygen content is about 4.851 nppma; in the middle (about 5.5 cm), the oxygen content slightly decreases to 4.048 nppma; and at the end of the ingot (about 9.5 cm), the oxygen content significantly increases to 5.910 nppma.

[0077] Examples and Comparative Examples In order to verify the effectiveness of the manufacturing method provided by the embodiments of the present disclosure on the electrical properties of single crystal silicon ingots, multiple groups of examples were designed. These examples all use the crystal pulling furnace with a temperature adjusting device provided by the above-mentioned embodiments of the present disclosure, and use the Czochralski method to prepare single crystal silicon ingots containing dopants, and complete the subsequent two-step heat treatment process in the crystal pulling furnace.

[0078] Example A1 The finished single crystal silicon ingot was pulled into the auxiliary furnace chamber, and the first heat treatment was performed at a temperature of 750°C for a duration of 60 minutes. Then, it was cooled to 150°C at a cooling rate of 15°C / min, and the second heat treatment was continued at a temperature of 150°C for a duration of 60 minutes. After the treatment, the silicon ingot was cut and polished to obtain silicon wafers with uniform resistivity, and the test value was greater than 3000Ω·cm, and the oxygen content was less than 8ppma.

[0079] Example A2 The first heat treatment temperature is set at 750°C for 45 minutes; the cooling rate is 15°C / min, and the cooling medium is liquid nitrogen. The second heat treatment temperature is set at 210°C for 20 minutes. The final silicon wafer has a uniform resistivity of greater than 7000 Ω-cm, and an oxygen content of less than 5 ppma.

[0080] <Example A3> The first heat treatment temperature is set at 750°C for 30 minutes; the cooling rate is 15°C / min, and the cooling medium is liquid nitrogen. The second heat treatment temperature is set at 210°C for 20 minutes. The final silicon wafer has a uniform resistivity of greater than 7000 Ω-cm, and an oxygen content of less than 5 ppma.

[0081] <Example A4> The first heat treatment temperature is set at 750°C for 15 minutes; the cooling rate is 15°C / min, and the cooling medium is liquid nitrogen. The second heat treatment temperature is set at 240°C for 10 minutes. The final silicon wafer has a uniform resistivity of greater than 7000 Ω-cm, and an oxygen content of less than 4 ppma.

[0082] <Example A5> The finished single crystal silicon rod is pulled into the secondary furnace chamber, and the first heat treatment is performed at a temperature of 650°C for 90 minutes. Subsequently, the cooling rate is 15°C / min to 100°C, and the second heat treatment is performed at a temperature of 100°C for 60 minutes. After the treatment is completed, the silicon rod is cut and polished to obtain a silicon wafer with a uniform resistivity of greater than 1000 Ω-cm, and an oxygen content of less than 8 ppma.

[0083] <Example A6> The finished single crystal silicon rod is pulled into the secondary furnace chamber, and the first heat treatment is performed at a temperature of 800°C for 5 minutes. Subsequently, the cooling rate is 20°C / min to 300°C, and the second heat treatment is performed at a temperature of 300°C for 10 minutes. After the treatment is completed, the silicon rod is cut and polished to obtain a silicon wafer with a uniform resistivity of greater than 5000 Ω-cm, and an oxygen content of less than 5 ppma.

[0084] <Comparative Example> The comparative experiment uses a conventional method. First, a single crystal silicon rod is obtained by using a conventional crystal pulling furnace through the Czochralski method. Then, the single crystal silicon rod is cut into a silicon wafer, and the wafer is transported to a special heat treatment furnace for annealing treatment. The annealing conditions are consistent with the existing high-resistance wafer manufacturing process. After detection, the resistivity of the obtained silicon wafer is very uneven. Compared with the examples, the resistivity uniformity of the silicon wafer of this comparative example is poor, there are low resistivity areas in some parts, and the oxygen content is high.

[0085] For specific comparison, please refer to Table 1 below.

[0086] Table 1

[0087] As can be seen from the experimental data of the above Examples A1 to A6, the manufacturing method of the present disclosure can eliminate oxygen donor defects by integrating two-step heat treatment and cooling in the crystal pulling furnace, and obtain a silicon wafer with a resistivity greater than 1000 Ω·cm, a P-type conductivity, and an oxygen content less than 8 ppma, and has good resistivity uniformity and mechanical stability. The comparative examples use a traditional heat treatment method, which has problems such as cross contamination, poor oxygen content control, and unstable resistivity, further verifying the significant advantages of the scheme of the present disclosure.

[0088] It should be noted that the technical solutions disclosed in the present disclosure can be combined arbitrarily without conflict.

[0089] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of producing a single crystal silicon ingot, characterized by, The manufacturing method comprises: drawing a single crystal silicon rod in a crystal pulling furnace by using a Czochralski method; performing a first heat treatment on the single crystal silicon rod in the crystal pulling furnace, the first heat treatment having a temperature range of 650-800℃ and a duration range of 5-90 minutes; performing a second heat treatment on the single crystal silicon rod after the first heat treatment in the crystal pulling furnace, the second heat treatment having a temperature range of 100-300℃ and a duration range of 10-60 minutes, wherein the single crystal silicon rod after the second heat treatment has a resistivity greater than 1000Ω·cm and a P-type conductivity.

2. The method of producing a single crystal silicon ingot according to claim 1, wherein After the first heat treatment ends and before the second heat treatment starts, the manufacturing method further comprises cooling the single crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment by using a cooling medium, the cooling medium comprising liquid nitrogen or liquid argon.

3. The method of producing a single crystal silicon ingot according to claim 1 or 2, characterized by After the first heat treatment ends and before the second heat treatment starts, the manufacturing method further comprises a cooling process for cooling the single crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment at a cooling speed no less than 15℃ / min.

4. The method of producing a single crystal silicon ingot according to claim 1 or 2, characterized by The crystal pulling furnace comprises a main furnace chamber and a sub-furnace chamber, and a temperature adjusting device is arranged in the sub-furnace chamber, wherein the temperature adjusting device is used to adjust the temperature in the sub-furnace chamber to perform the first heat treatment and the second heat treatment on the single crystal silicon rod in the sub-furnace chamber.

5. The method of producing a single crystal silicon ingot according to claim 1 or 2, wherein The single crystal silicon rod after the second heat treatment has an oxygen content less than 8ppma.

6. A method for manufacturing a silicon wafer, characterized by, The manufacturing method comprises cutting, grinding, polishing and cleaning the single crystal silicon rod manufactured by the manufacturing method of the single crystal silicon rod according to any one of claims 1-5 to obtain a silicon wafer.

7. A silicon wafer, characterized by, The silicon wafer is manufactured by using the manufacturing method of the silicon wafer according to claim 6, wherein the silicon wafer has a resistivity greater than 1000Ω·cm, a P-type conductivity and an oxygen content less than 8ppma.

8. A crystal pulling furnace characterized by comprising: The crystal pulling furnace is used to perform the manufacturing method of the single crystal silicon rod according to any one of claims 1-5.

9. The crystal pulling furnace of claim 8 wherein, The crystal pulling furnace comprises a main furnace chamber, a sub-furnace chamber and a temperature adjusting device arranged in the sub-furnace chamber, the temperature adjusting device comprising a heater, wherein, the heater is used to perform a first heat treatment and a second heat treatment on a single crystal silicon rod, the first heat treatment having a temperature range of 650-800℃ and the second heat treatment having a temperature range of 100-300℃.

10. The crystal pulling furnace of claim 9 wherein, The temperature adjusting device further comprises a supply device for supplying a cooling medium, wherein the supply device is used to cool the single crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment at a cooling speed no less than 15℃ / min by supplying the cooling medium to the sub-furnace chamber after the first heat treatment ends and before the second heat treatment starts.

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