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

Abstract

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

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor processing technology, and in particular to a method for manufacturing single-crystal silicon rods, silicon wafers and their manufacturing methods, and crystal pulling furnaces. Background Technology

[0002] Silicon wafers, as a core material in semiconductor device manufacturing, are widely used in integrated circuits, power devices, sensors, and photovoltaic modules due to their excellent electrical properties, physical stability, and chemical stability.

[0003] With the rapid development of radio frequency (RF) communication, microwave devices, and high-frequency, high-power applications, higher demands are being placed on the electrical performance of silicon wafers. Especially in the RF field, high-resistivity silicon wafers are gradually becoming a key basic material for effectively suppressing parasitic effects, reducing signal transmission loss, and improving overall device performance. Existing technologies typically control the resistivity of silicon wafers by adjusting the doping concentration and optimizing the thermal processing.

[0004] However, existing processes still have significant shortcomings. On the one hand, for high-resistivity silicon wafers, it is impossible to perform oxygen donor annealing and low-temperature heat treatment on every wafer, because during heat treatment, the resistivity of the silicon wafer is easily contaminated by impurities and decreases, affecting the effective resistivity of the device. On the other hand, heat treatment may also create stress concentration points on the silicon wafer, leading to fragmentation during subsequent grinding, polishing, and cleaning processes. Summary of the Invention

[0005] To address the aforementioned issues, this disclosure provides a method for manufacturing a single-crystal silicon rod, a silicon wafer, the same method, and a crystal pulling furnace. This method for manufacturing a single-crystal silicon rod continuously performs high-temperature and low-temperature heat treatments within the crystal pulling furnace, avoiding the risk of cross-contamination in dedicated heat treatment furnaces, simplifying the process flow, and ensuring that the resistivity of the single-crystal silicon rod is greater than 1000 Ω·cm and is uniform and stable, with a P-type conductivity.

[0006] The technical solution disclosed herein is implemented as follows: In a first aspect, embodiments of this disclosure provide a method for manufacturing a single-crystal silicon rod, the method comprising: In a crystal pulling furnace, single-crystal silicon rods are pulled using the Czochralski method; In the crystal pulling furnace, the single crystal silicon rod is subjected to a first heat treatment, the temperature range of which is 650°C to 800°C and the duration range of which is 5 minutes to 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°C to 300°C, and the duration ranges from 10 minutes to 60 minutes. 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.

[0007] In some optional examples, after the first heat treatment ends and before the second heat treatment begins, the manufacturing method further includes: cooling the single-crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment using a cooling medium, the cooling medium including liquid nitrogen or liquid argon.

[0008] In some optional examples, after the first heat treatment is completed and before the second heat treatment begins, the manufacturing method further includes a cooling process of 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 rate of not less than 15°C / min.

[0009] In some optional examples, the crystal pulling furnace includes a main furnace chamber and an auxiliary furnace chamber, wherein a temperature control device is provided in the auxiliary furnace chamber, wherein the temperature control device is used to adjust the temperature in the auxiliary furnace chamber to perform the first heat treatment and the second heat treatment on the single crystal silicon rod in the auxiliary furnace chamber.

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

[0011] Thirdly, embodiments of this disclosure provide a silicon wafer manufactured using a silicon wafer manufacturing method according to the second aspect, wherein the resistivity of the silicon wafer is greater than 1000 Ω·cm, the conductivity type is P-type, and the oxygen content is less than 8 ppma. Fourthly, embodiments of this disclosure provide a crystal pulling furnace for performing a method for manufacturing a single-crystal silicon rod according to the first aspect.

[0012] In some optional examples, the crystal pulling furnace includes a main furnace chamber, an auxiliary furnace chamber, and a temperature control device disposed in the auxiliary furnace chamber, the temperature control device including a heater, wherein, The heater is used to perform a first heat treatment and a second heat treatment on the single crystal silicon rod. The temperature range of the first heat treatment is 650°C to 800°C, and the temperature range of the second heat treatment is 100°C to 300°C.

[0013] In some optional examples, the temperature control device further includes a supply device for supplying the 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 rate of not less than 15°C / min by supplying cooling medium to the auxiliary furnace chamber after the first heat treatment is completed and before the second heat treatment begins.

[0014] This disclosure provides a method for manufacturing a single-crystal silicon rod, a silicon wafer, the same method, and a crystal pulling furnace. The method for manufacturing the single-crystal silicon rod involves continuous process steps within a crystal pulling furnace. First, a doped single-crystal silicon rod is pulled using the Czochralski method, and then the single-crystal silicon rod undergoes a two-step heat treatment within the same furnace. First, a relatively high-temperature heat treatment step disrupts the stable structure of the oxygen polymer, thereby removing oxygen donor defects. Subsequently, a lower-temperature heat treatment step further stabilizes the carrier concentration, ensuring that the single-crystal silicon rod has a P-type conductivity and that the measured resistivity reaches and stabilizes within a high resistivity range greater than 1000 Ω·cm. Because this method integrates the heat treatment steps within the crystal pulling furnace, it avoids the external contamination risks associated with cutting the silicon rod before heat treatment in traditional processes, thus effectively improving the stability of the high resistivity of the finished single-crystal silicon. Attached Figure Description

[0015] Figure 1 A flowchart illustrating a method for manufacturing a single-crystal silicon rod according to an embodiment of this disclosure.

[0016] Figure 2 This is 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 in an embodiment of this disclosure.

[0018] Figure 4 for Figure 3 Partial cross-sectional view.

[0019] Figure 5 A graph showing the resistivity versus oxygen content of a single-crystal silicon rod manufactured using the manufacturing method for single-crystal silicon rods provided in this disclosure. Detailed Implementation

[0020] The technical solutions in this disclosure will now be clearly and completely described with reference to the accompanying drawings.

[0021] In the conventional manufacturing process of high resistivity silicon wafers, after obtaining a single-crystal silicon rod, multiple processes such as cutting, heat treatment, grinding, polishing, and cleaning are sequentially performed on the single-crystal silicon rod to finally form a silicon wafer that meets the electrical performance requirements. In this manufacturing process, the control of impurities inside the silicon wafer, especially the distribution of oxygen impurities, is the core factor affecting the resistivity stability and uniformity of the finished product.

[0022] Taking single-crystal silicon rods grown using the Czochralski (CZ) method as an example, a certain amount of oxygen impurities are inevitably introduced during the growth process. These oxygen impurities mainly originate from the reaction between the quartz crucible and molten silicon under high-temperature conditions, and are usually dissolved in the silicon crystal structure as interstitial oxygen (Oi). These oxygen impurities are prone to aggregation or reaction during subsequent processing, forming oxygen precipitates or oxygen-related composite defects. These defects introduce donor levels into the silicon crystal, releasing free carriers, thereby reducing the effective resistivity of the silicon wafer and affecting its performance in high-frequency applications such as radio frequency and microwave. Furthermore, oxygen precipitate nuclei can also become nucleation sources for dislocations or slip dislocations, further inducing local distortions in the crystal structure. This not only weakens the mechanical strength of the silicon wafer but also increases dielectric loss during device operation, affecting the electrical stability and consistency of the device.

[0023] To control the distribution of oxygen impurities and reduce defect formation, high-temperature heat treatment processes are commonly introduced in existing technologies. By controlling the heat treatment temperature and atmosphere conditions, oxygen donor defects are removed, thereby increasing or stabilizing the effective resistivity of the silicon wafer, while also improving crystal integrity and defect density. However, despite the widespread adoption of heat treatment processes, they still have many limitations in actual production, affecting the final quality of high-resistivity silicon wafers.

[0024] First, because heat treatment equipment needs to be compatible with the processing requirements of various types of silicon wafers, different types or doping conditions of silicon wafers are usually processed in the same furnace cavity, posing a risk of cross-contamination of impurities. Dopants such as boron and phosphorus, or metal ions such as iron and copper, remaining on the inner wall of the furnace cavity may migrate to the surface or interior of high-resistivity silicon wafers under high-temperature conditions, leading to an abnormally high concentration of impurities on the surface or in localized areas of the silicon wafer, thereby causing a decrease in resistivity. Moreover, oxygen redistribution during heat treatment is also a key influencing factor. If the heat treatment temperature and atmosphere are not properly controlled, it may lead to changes in oxygen content, inducing oxygen precipitation, oxygen donor defects, etc., forming localized conductive channels and disrupting the uniformity of the overall resistivity of the silicon wafer.

[0025] Furthermore, high-temperature heat treatment has potential adverse effects on the mechanical properties of silicon wafers. After high-temperature heat treatment, the silicon wafer's crystal structure may experience residual stress release and micro-defect propagation, leading to a decrease in the wafer's mechanical strength. This significantly increases the risk of fragmentation during subsequent machining processes such as grinding, polishing, and cleaning, affecting finished product yield and production efficiency.

[0026] In view of this, embodiments of this disclosure provide a method for manufacturing a single-crystal silicon rod, a silicon wafer, the same method for manufacturing the same, and a crystal pulling furnace. This method for manufacturing a single-crystal silicon rod continuously performs high-temperature and low-temperature heat treatments on the single-crystal silicon rod within the crystal pulling furnace, avoiding the risk of cross-contamination in dedicated heat treatment furnaces, simplifying the process flow, and ensuring that the resistivity of the single-crystal silicon rod is greater than 1000 Ω·cm and is uniform and stable, and that the conductivity type is P-type.

[0027] See Figure 1 Some embodiments of this disclosure provide a method for manufacturing a single-crystal silicon rod. This manufacturing method may include: S1. In a crystal pulling furnace, single-crystal silicon rods are pulled using the Czochralski method; S2. In a crystal pulling furnace, the single crystal silicon rod is subjected to a first heat treatment. The temperature range of the first heat treatment is 650°C to 800°C, and the duration ranges from 5 minutes to 90 minutes. S3. In a 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℃ to 300℃, and the duration ranges from 10 minutes to 60 minutes. 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.

[0028] In this embodiment of the present disclosure, the three steps of the proposed manufacturing method can be completed continuously within the same crystal pulling furnace, thereby reducing impurity contamination that may be introduced during process switching, equipment replacement, and handling, and simplifying the manufacturing process. Furthermore, this manufacturing method ultimately yields a single-crystal silicon rod with a resistivity greater than 1000 Ω·cm and a P-type conductivity, which can meet the stringent requirements of high-frequency devices, radio frequency components, and other applications 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 the Czochralski method. In this process, high-purity polycrystalline silicon raw material is first loaded into a quartz crucible and fully melted under high temperature conditions. Then, a seed crystal that has undergone orientation treatment is introduced, and by precisely controlling the pulling speed and crystal rotation rate, the phase transformation of the melt to the single-crystal state is gradually realized, thereby growing a single-crystal silicon rod S with a predetermined diameter, length, and crystallization direction.

[0030] To ensure that the pulled single-crystal silicon rod possesses the required high resistivity and predetermined conductivity type, a doping scheme must be rationally designed during its growth process based on the conductivity characteristics of the polycrystalline silicon raw material used. Specifically, the type and concentration of dopant can be flexibly determined according to the background impurity level, target resistivity, and conductivity type of the raw material. For example, if the raw polycrystalline silicon has a low background impurity concentration (close to intrinsic silicon), an intrinsic high-resistivity single-crystal silicon rod can be directly pulled without adding dopant; if the raw material contains a certain amount of donor impurities (such as phosphorus), then to obtain P-type characteristics, an appropriate amount of acceptor impurity—boron (B)—must be introduced during the growth process to counteract the background N-type doping and form net P-type characteristics.

[0031] For high-resistivity silicon materials required in devices such as radio frequency components and high-frequency communication chips, P-type doping is preferred, with boron (B) typically chosen as the dopant element. As an example, the boron doping concentration can be controlled to be below 5 × 10⁻⁶. 14 Within the range of atoms / cm³, this doping concentration range helps to ensure that the silicon rod is P-type conductive while making its intrinsic resistivity as high as possible, such as 1000 Ω·cm. At the same time, it avoids the problem of excessive difference between the initial resistivity and the target resistivity caused by excessively high doping concentration, and provides adjustable space for further increasing the resistivity in subsequent process stages.

[0032] It is important to note that during the Czochralski crystal pulling process, the molten silicon and the quartz crucible are in prolonged contact at high temperatures, inevitably leading to interfacial reactions and the introduction of oxygen impurities. These oxygen impurities are mainly distributed as interstitial oxygen within the crystal lattice structure of the single-crystal silicon rod, exhibiting a uniform diffusion throughout the rod. Although interstitial oxygen is relatively stable at low temperatures, it is prone to migration and enrichment during subsequent high-temperature processing or application environments, and may precipitate as oxygen aggregates, oxygen deposits, or oxygen donor defects.

[0033] The aforementioned oxygen precipitation and oxygen donor defects can not only form electrically active centers within the crystal, whose donor levels can release free charge carriers (electrons), causing the actual resistivity of the material to deviate from the theoretically expected value, but also become the starting point for crystal structure defects, inducing structural anomalies such as microcracks and dislocations. These defects can cause problems in device performance such as increased leakage current and threshold drift, and in mechanical performance, they may lead to a decrease in local strength during subsequent slicing, polishing, or other machining processes, affecting yield and quality control.

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

[0035] To mitigate the aforementioned adverse effects, the manufacturing method proposed in this disclosure includes performing steps S2 and S3, namely a first heat treatment step and a second heat treatment step, on the single crystal silicon rod immediately after the single crystal silicon rod is pulled in a crystal pulling furnace. These two steps are completed within the same crystal pulling furnace, reducing the risk of cross-contamination of impurities caused by process transfer in conventional processes.

[0036] In step S2, the pulled single-crystal silicon rod S undergoes a first heat treatment in a crystal pulling furnace at a temperature ranging from 650°C to 800°C. 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 requirements.

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

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

[0039] The first heat treatment step is performed to remove oxygen donor defects. This is because the presence of oxygen donor defects triggers the release of free charge carriers, leading to a localized increase in carrier concentration and thus reducing resistivity. Performing the first heat treatment on a single-crystal silicon rod is equivalent to high-temperature annealing, which causes some oxygen impurities to precipitate within the silicon crystal and lose their electroactivity, thereby reducing the oxygen donor density and increasing resistivity. Furthermore, moderately high temperatures also help release localized stresses formed during silicon rod crystal growth, eliminate microscopic defects, and further improve the integrity and uniformity of the crystal structure.

[0040] Compared to existing technologies that use dedicated heat treatment furnaces to heat-treat silicon wafers obtained from cutting monocrystalline silicon rods, in the embodiments of this disclosure, the first heat treatment step is completed directly in the crystal pulling furnace, which is equivalent to in-situ heat treatment. Therefore, the handling and loading / unloading process can be eliminated, reducing the risk of contamination of the surface and interior of the monocrystalline silicon rod S by external impurities and / or impurities within the heat treatment furnace. Moreover, the crystal pulling furnace also provides a crystal environment that ensures high purity and high consistency.

[0041] After the first heat treatment, the single-crystal silicon rod that has undergone the first heat treatment is then subjected to step S3, namely a second heat treatment at a temperature range of 100°C to 300°C, which is completed in a crystal pulling furnace. The temperature of the second heat treatment is set to be significantly lower than that of the first heat treatment to achieve carrier stabilization.

[0042] In some embodiments of this disclosure, the two-step heat treatment process for the monocrystalline silicon rod S is not only rationally selected in terms of temperature setting, but also optimized and controlled in terms of the duration of each heat treatment step, so as to ensure that the final monocrystalline silicon rod can stably obtain high resistivity characteristics.

[0043] Specifically, in some embodiments of this disclosure, the duration of the first heat treatment can be set within the range of 5 to 90 minutes. As explained above, the main purpose of the first heat treatment is to eliminate oxygen donor defects. Therefore, if the duration of the first heat treatment is too short, the diffusion and precipitation process of oxygen impurities within the crystal may be insufficient, which can easily lead to residual oxygen donor defects and affect the high resistivity stability of the single-crystal silicon rod. Conversely, if the duration is too long, it may exacerbate the thermal stress within the crystal structure, increasing the risk of dislocations or slip dislocations, thereby adversely affecting the mechanical stability of subsequent processes. Therefore, by controlling the duration within the range of 5 to 90 minutes, the sufficiency of the oxygen precipitation effect and the integrity of the crystal structure can be balanced, ensuring a stable increase in the resistivity of the single-crystal silicon rod. In a further preferred embodiment of this disclosure, the duration of the first heat treatment can be set within the range of 10 to 60 minutes.

[0044] The temperature setting for the second heat treatment should be reasonably estimated and selected based on the temperature and time settings of the first heat treatment, the type and concentration of dopant, the target resistivity level, and other pre-process parameters.

[0045] In some other embodiments of this disclosure, the duration of the second heat treatment can be set within the range of 10 to 60 minutes. As explained above, the main function of the second heat treatment is to stabilize the carrier concentration at a lower temperature, thereby achieving a balance between holes and electrons in the single-crystal silicon rod. Therefore, if the heat treatment time is insufficient, the carrier concentration will be difficult to stabilize effectively within the crystal, leading to fluctuations in resistivity test results and reduced product consistency; while excessively long treatment times will reduce production efficiency and have limited impact on improving the final crystal performance. Therefore, selecting a time range of 10 to 60 minutes can improve process efficiency and reduce costs while ensuring electrical performance uniformity. In a further preferred embodiment of this disclosure, the duration of the second heat treatment can be set within the range of 20 to 40 minutes.

[0046] For example, under the conditions of a first heat treatment temperature of 700℃, a duration of 45 min, boron as the dopant, and a target resistivity >3000Ω·cm, in order to achieve carrier stabilization and uniform increase in resistivity, the second heat treatment temperature can be set in the range of 180℃ to 220℃, for example, 190℃.

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

[0048] After high-temperature annealing, the concentration distribution of electrons and holes in the single-crystal silicon rod S fluctuates, especially in p-type high-resistivity silicon single crystals where the hole concentration is low. If the migration speed of free electrons is too fast, it will affect the stability and measurement consistency of the final resistivity of the single-crystal silicon rod S. The second heat treatment of the single-crystal silicon rod S, also known as the low-temperature heat treatment step, is used to effectively alleviate the carrier migration effect caused by heat treatment, so that the hole and electron concentrations tend to be balanced, stabilize the resistivity, and ensure that the conductivity type of the finished silicon rod is accurately p-type.

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

[0050] Some embodiments of this disclosure provide a method for manufacturing a single-crystal silicon rod. This method involves performing consecutive process steps in a crystal pulling furnace. First, a doped single-crystal silicon rod is pulled using the Czochralski method, and then the single-crystal silicon rod undergoes a two-step heat treatment sequentially within the same furnace. First, a relatively high-temperature heat treatment step eliminates oxygen donor defects; subsequently, a lower-temperature heat treatment step further stabilizes the carrier concentration, ensuring that the measured resistivity of the single-crystal silicon rod reaches and stabilizes within a high resistivity range greater than 1000 Ω·cm. Because this manufacturing method integrates the heat treatment steps within the crystal pulling furnace, it avoids the external contamination risks associated with cutting the silicon rod before heat treatment in traditional processes, thereby effectively improving the stability of the high resistivity of the finished single-crystal silicon.

[0051] In the embodiments of this 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 process, is provided between the end of the first heat treatment and the start of the second heat treatment.

[0052] Specifically, after the first heat treatment is completed, the single-crystal silicon rod S needs to be cooled from the higher temperature range of the first heat treatment to a lower temperature range suitable for performing the second heat treatment. Therefore, in some embodiments of this disclosure, the cooling step can be limited to a cooling rate of not less than 15°C / min.

[0053] The setting of this cooling rate is based on several considerations. First, if the cooling rate is too slow, the single-crystal silicon rod S will remain in the sensitive temperature range of 400℃~450℃ for an extended period, which can easily lead to the regeneration of oxygen donor defects. Within this temperature range, oxygen impurities in the silicon crystal are highly reactive and easily re-aggregate to form oxygen donor defects, thereby causing an abnormal increase in local carrier concentration and affecting the uniformity and stability of the overall resistivity of the silicon rod. By controlling the cooling rate to above 15℃ / min, the residence time of the single-crystal silicon rod S in this temperature range can be effectively shortened, eliminating the influence of oxygen donor defects and ensuring that the silicon rod has a high resistivity greater than 1000 Ω·cm from the source.

[0054] Furthermore, this cooling step also plays a positive role in improving the mechanical properties of the monocrystalline silicon rod S. Because monocrystalline silicon rod S is prone to thermal stress accumulation during high-temperature heat treatment, if the cooling rate is too slow or the cooling process is not uniformly controlled, the release of thermal stress may lead to localized lattice distortion, dislocation propagation, or even the induction of microcracks. However, by employing a reasonable rapid cooling process, thermal stress can be released uniformly, reducing the residual stress level, thereby effectively improving the mechanical strength of the monocrystalline silicon rod and reducing the risk of damage or fragmentation during subsequent processing steps such as cutting, grinding, and polishing.

[0055] In addition, controlling the cooling rate to above 15℃ / min also has the advantage of good process efficiency, which can significantly shorten the time between the first heat treatment and the second heat treatment, optimize the production rhythm, and meet the needs of large-scale industrial production.

[0056] To achieve the aforementioned cooling rate control, in some embodiments of this disclosure, a cooling medium can be introduced to assist in cooling. Specifically, the cooling medium includes, but is not limited to, liquid nitrogen and liquid argon. These cooling media have low temperatures and excellent heat exchange efficiency, thus enabling rapid cooling of the single-crystal silicon rod from a high temperature to the temperature range required for the second heat treatment without introducing impurities, meeting the clean process requirements in semiconductor manufacturing. Furthermore, depending on specific production conditions, liquid nitrogen or liquid argon can be used in conjunction with a cooling water system, inert gas circulation, or heat exchange device to flexibly control the cooling rate and temperature uniformity, thereby achieving a stable improvement in both electrical and mechanical properties.

[0057] In the embodiments of this disclosure, in order to achieve precise temperature control of the monocrystalline silicon rod throughout the first heat treatment, cooling treatment and second heat treatment process, and to further improve the stability and controllability of the process, when the crystal pulling furnace includes a main furnace chamber and an auxiliary furnace chamber, a temperature regulating device can be configured in the auxiliary furnace chamber to perform subsequent processing on the monocrystalline silicon rod pulled in the main furnace chamber.

[0058] Specifically, the main furnace chamber is used to complete the Czochralski growth process of single-crystal silicon rods, while the auxiliary furnace chamber undertakes the subsequent heat treatment and cooling processes. Setting the heat treatment and cooling steps in the auxiliary furnace chamber has several advantages: First, because the auxiliary furnace chamber is relatively independent, its internal environment is easier to control. This avoids the impact of high-temperature disturbances or contamination introduced by the main furnace chamber during crystal pulling on the heat treatment process, ensuring the uniformity and stability of the heat treatment temperature. Furthermore, the auxiliary furnace chamber space can be dedicated to heat treatment, reducing the risk of cross-contamination and improving the purity and consistency of high-resistivity silicon rod products.

[0059] The temperature control device in the auxiliary furnace chamber can include components such as heaters and a cooling gas supply system, used to dynamically adjust the temperature parameters of the auxiliary furnace chamber. Specifically, the heater can achieve the high-temperature conditions required for the first heat treatment, controlling the temperature within the range of 650℃ to 800℃, and maintaining temperature stability during the heat treatment process. The cooling gas supply system is used to assist in the cooling stage, controlling the cooling rate to reach no less than 15℃ / min, quickly reducing the temperature to the low-temperature range suitable for the second heat treatment. For further cooling requirements, a liquid nitrogen or liquid argon supply system can be optionally added to improve cooling efficiency and temperature control accuracy.

[0060] The temperature control device in the auxiliary furnace chamber ensures that the three processes of the first heat treatment, cooling treatment, and second heat treatment can be completed continuously and stably within the auxiliary furnace chamber through precise temperature regulation. This eliminates the need to transfer the monocrystalline silicon rods to external dedicated heat treatment equipment, reducing the risk of mechanical damage or contamination to the silicon rod surface during handling and helping to control the production rhythm.

[0061] To implement the manufacturing method proposed in the above embodiments of this disclosure, some embodiments of this disclosure also provide a crystal pulling furnace 10, which includes a temperature control device 1. The crystal pulling furnace 10 will be described in detail below with reference to the accompanying drawings.

[0062] Figure 2 The diagram illustrates a conventional crystal pulling furnace 10. Specifically, the crystal pulling furnace 10 may include a main furnace chamber 11 and a secondary furnace chamber 12 arranged vertically, wherein the secondary furnace chamber 12 is located directly above and communicates with the main furnace chamber 11. The main furnace chamber 11 mainly includes a quartz crucible 20, a graphite crucible 30, and a heating module 40. The quartz crucible 20 is used to contain solid polycrystalline silicon raw material in the initial stage of pulling the crystal ingot S. The graphite crucible 30 is arranged around the quartz crucible 20 to provide support for the quartz crucible 20 during the heating of the polycrystalline silicon raw material. The heating module 40 is disposed on the outer periphery of the quartz crucible 20.

[0063] When using the crystal pulling furnace 10, the polycrystalline silicon raw material of a set mass is first placed in the quartz crucible 20. 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 may also include a seed crystal cable 50, a crystal rod pulling device 60, and a crucible lifting device 70. The seed crystal cable 50 is positioned above the quartz crucible 20. After the polycrystalline silicon raw material in the quartz crucible 20 melts to form a silicon melt and the temperature of the solid-liquid interface stabilizes, the crystal rod pulling device 60 controls the seed crystal cable 50 to descend to the solid-liquid interface of the silicon melt and begin processes such as crystal pulling, necking, shoulder formation, constant diameter growth, and tailing, ultimately pulling a crystal rod S of a certain length. The crucible lifting device 70 is located 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] To meet the requirement of continuous heat treatment of single-crystal silicon rods in the embodiments of this disclosure, the inventors made improvements to the conventional crystal pulling furnace, such as... Figure 3 As shown, a temperature control device 1 was added to the auxiliary furnace chamber 12, thus forming an improved crystal pulling furnace 10.

[0066] Specifically, during the pulling process, the monocrystalline silicon rod S gradually leaves the melting zone of the main furnace chamber 11 and gradually enters the auxiliary furnace chamber 12. After pulling is complete, the rod pulling device 60 completely pulls the monocrystalline silicon rod S into the auxiliary furnace chamber 12 and suspends it inside, avoiding direct contact with the bottom of the auxiliary furnace chamber. Within the auxiliary furnace chamber 12, the monocrystalline silicon rod S can directly complete subsequent heat treatment steps without needing to be transferred.

[0067] like Figure 3 and Figure 4 As shown, the auxiliary furnace chamber 12 is equipped with a temperature control device 1, which includes a heater 121 arranged around the circumferential wall of the auxiliary furnace chamber and a cooling supply device 122. 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 monocrystalline silicon rod S remains within the set process temperature range at different temperature stages. The supply device 122 is located at the top of the auxiliary furnace chamber 12 or other suitable positions, with one end connected to the interior of the auxiliary furnace chamber through a supply port, and the other end connected to a cooling medium source. The supply device 122 can introduce cooling medium into the auxiliary furnace chamber for rapid cooling of the monocrystalline silicon rod S after the first heat treatment. Suitable cooling media may include cryogenic media such as liquid nitrogen and liquid argon, which have efficient heat exchange characteristics and help to achieve precise control of the cooling rate.

[0068] By using the heater 121 and the supply device 122 in the temperature control device 1 together, the temperature in the auxiliary furnace chamber 12 can be dynamically adjusted, so that the single crystal silicon rod S can directly complete the first heat treatment, cooling treatment and second heat treatment in the auxiliary furnace chamber after the pulling is completed. This eliminates the steps of handling and converter, reduces the risk of silicon rod being contaminated by impurities and mechanically damaged during handling, and further ensures the temperature stability and uniformity of the heat treatment process. This provides further assurance for obtaining high-performance single crystal silicon rods with resistivity greater than 1000 Ω·cm and controlled oxygen content.

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

[0070] Specifically, as explained above, oxygen impurities, as a key intrinsic impurity in single-crystal silicon materials, mainly originate from the high-temperature reaction between the quartz crucible and molten silicon during the Czochralski growth process. Oxygen impurities typically exist in the form of interstitial oxygen, and their content directly affects the electrical properties of the silicon rod and the stability of subsequent processing. Excessive oxygen content can easily induce oxygen precipitation, oxygen donor defects, or microstructural defects during subsequent heat treatment or device use, thereby reducing the effective resistivity and resistivity uniformity of the material, creating localized conductive channels, and even leading to a decrease in device reliability.

[0071] By introducing the aforementioned two-step heat treatment process into the manufacturing method, in the first heat treatment stage, high temperature promotes the diffusion and uniform distribution of oxygen impurities, effectively eliminating oxygen donor defects and preventing their aggregation to form carrier supply sources. Subsequently, in the second heat treatment stage, the distribution of holes and electrons in the crystal structure is further stabilized at a lower temperature, suppressing the active reaction of oxygen impurities and ensuring that the oxygen content of the final single-crystal silicon rod is controlled below 8 ppma. In a further preferred embodiment of this disclosure, the oxygen content of the single-crystal silicon rod can be controlled below 6 ppma.

[0072] The manufacturing method provided in this disclosure can obtain two forms of single-crystal silicon semiconductor structures: on the one hand, a single-crystal silicon rod that has undergone 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 that meets the requirements of high-performance applications can also be prepared.

[0073] Of particular note is that the manufacturing method disclosed herein, through a two-step heat treatment performed continuously within a crystal pulling furnace, effectively controls the oxygen content distribution in the monocrystalline silicon rod, removes oxygen donor defects, and reduces the level of internal residual stress. This process significantly improves the resistivity uniformity and mechanical stability of the monocrystalline silicon rod, thereby improving the controllability of subsequent processing and the yield of the finished product from the source.

[0074] Therefore, during the subsequent cutting, grinding, and polishing processes, the single-crystal silicon rod exhibits high resistance to mechanical damage, and the fragmentation rate is significantly reduced. Moreover, the resulting silicon wafer not only possesses excellent electrical properties, especially a resistivity greater than 1000 Ω·cm and an oxygen content less than 8 ppma, but also meets the stringent requirements for material electrical performance and reliability in fields such as radio frequency devices and high-frequency applications.

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

[0076] This graph illustrates two key material properties of a single-crystal silicon ingot along its length (the X-axis, represented by "Ingot position (cm)"): center resistivity and center oxygen content. The left Y-axis represents resistivity in ohm-cm, ranging from 0 to 9000 ohm-cm. The right Y-axis represents oxygen content in parts per million atoms (nppma), ranging from 0 to 7 nppma. The black solid line with square data points represents "center resistivity," while the gray solid line with circular data points represents "center oxygen content." In terms of trends, center resistivity gradually increases with increasing ingot position. Specifically, at the beginning of the crystal rod (approximately 1.5 cm), the resistivity is approximately 6352 ohm-cm; in the middle (approximately 5.5 cm), the resistivity increases slightly to 6511 ohm-cm; subsequently, at the end of the crystal rod (approximately 9.5 cm), the resistivity increases significantly, reaching 7721 ohm-cm. Simultaneously, the oxygen content in the center shows a trend of first slightly decreasing and then significantly increasing. At the beginning of the crystal rod (approximately 1.5 cm), the oxygen content is approximately 4.851 nppma; in the middle (approximately 5.5 cm), the oxygen content decreases slightly to 4.048 nppma; while at the end of the crystal rod (approximately 9.5 cm), the oxygen content significantly rebounds, reaching 5.910 nppma.

[0077] Examples and Comparative Examples To verify the effectiveness of the manufacturing method provided in this disclosure for the electrical properties of single-crystal silicon rods, multiple sets of embodiments were designed. These embodiments all utilize the crystal pulling furnace with a temperature control device provided in the above embodiments of this disclosure, and employ the Czochralski method to prepare doped single-crystal silicon rods, completing the subsequent two-step heat treatment process within the crystal pulling furnace.

[0078] <Example A1> The drawn single-crystal silicon ingot was pulled into the auxiliary furnace chamber and subjected to the first heat treatment at 750℃ for 60 minutes. It was then cooled to 150℃ at a cooling rate of 15℃ / min, and a second heat treatment was performed at 150℃ for 60 minutes. After treatment, the silicon ingot was cut and ground to obtain silicon wafers with uniform resistivity (greater than 3000 Ω·cm) and an oxygen content of less than 8 ppma.

[0079] <Example A2> The first heat treatment temperature was set at 750℃ for 45 minutes, with a cooling rate of 15℃ / min and liquid argon as the cooling medium. The second heat treatment temperature was set at 180℃ for 40 minutes. The final wafer exhibited uniform resistivity, with a measured value greater than 5000 Ω·cm and an oxygen content less than 6 ppma.

[0080] <Example A3> The first heat treatment temperature was set at 750℃ for 30 minutes; the cooling rate was 15℃ / min, and liquid nitrogen was used as the cooling medium. The second heat treatment temperature was set at 210℃ for 20 minutes. The final wafer exhibited uniform resistivity, with a measured value greater than 7000 Ω·cm, and an oxygen content less than 5 ppma.

[0081] <Example A4> The first heat treatment temperature was set at 750℃ for 15 minutes; the cooling rate was 15℃ / min, and liquid nitrogen was used as the cooling medium. The second heat treatment temperature was set at 240℃ for 10 minutes. The final wafer exhibited uniform resistivity, with a measured value greater than 7000 Ω·cm and an oxygen content less than 4 ppma.

[0082] <Example A5> The drawn single-crystal silicon ingot was pulled into the auxiliary furnace chamber and subjected to the first heat treatment at 650℃ for 90 minutes. It was then cooled to 100℃ at a cooling rate of 15℃ / min, and a second heat treatment was performed at 100℃ for 60 minutes. After treatment, the silicon ingot was cut and ground to obtain silicon wafers with uniform resistivity (greater than 1000 Ω·cm) and an oxygen content of less than 8 ppma.

[0083] <Example A6> The drawn single-crystal silicon ingot is pulled into the auxiliary furnace chamber and subjected to the first heat treatment at 800℃ for 5 minutes. It is then cooled to 300℃ at a rate of 20℃ / min, followed by a second heat treatment at 300℃ for 10 minutes. After treatment, the silicon ingot is cut and ground to obtain silicon wafers with uniform resistivity (greater than 5000 Ω·cm) and an oxygen content of less than 5 ppma.

[0084] <Comparative> The comparative experiment employed a conventional method. First, single-crystal silicon rods were drawn using the Czochralski method in a conventional crystal pulling furnace. These rods were then diced into silicon wafers, which were subsequently transferred to a dedicated heat treatment furnace for annealing. The annealing conditions were consistent with existing high-resistivity wafer manufacturing processes. Testing revealed highly non-uniform resistivity in the resulting silicon wafers. Compared to the example, this comparative silicon wafer exhibited poor resistivity uniformity, with localized low-resistivity regions and a higher oxygen content.

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

[0086] Table 1

[0087] The experimental data from embodiments A1 to A6 above demonstrate that the manufacturing method of this disclosure, by integrating two-step heat treatment and cooling within a crystal pulling furnace, can eliminate oxygen donor defects, obtaining silicon wafers with a resistivity greater than 1000 Ω·cm, P-type conductivity, and an oxygen content less than 8 ppma, and exhibiting good resistivity uniformity and mechanical stability. In contrast, the comparative example using traditional heat treatment methods suffers from cross-contamination, poor oxygen content control, and unstable resistivity, further validating the significant advantages of the solution disclosed herein.

[0088] It should be noted that the technical solutions described in this disclosure can be combined arbitrarily as long as they do not conflict.

[0089] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for manufacturing a single-crystal silicon rod, characterized in that, The manufacturing method includes: In a crystal pulling furnace, single-crystal silicon rods are pulled using the Czochralski method; In the crystal pulling furnace, the single crystal silicon rod is subjected to a first heat treatment, the temperature range of which is 650°C to 800°C and the duration range of which is 5 minutes to 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°C to 300°C, and the duration ranges from 10 minutes to 60 minutes. 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.

2. The method for manufacturing a single-crystal silicon rod according to claim 1, characterized in that, After the first heat treatment is completed and before the second heat treatment begins, the manufacturing method further includes: cooling the single-crystal silicon rod from the temperature of the first heat treatment to the temperature of the second heat treatment using a cooling medium, the cooling medium including liquid nitrogen or liquid argon.

3. The method for manufacturing a single-crystal silicon rod according to claim 1 or 2, characterized in that, After the first heat treatment is completed and before the second heat treatment begins, the manufacturing method further includes a cooling process of 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 rate of not less than 15°C / min.

4. The method for manufacturing a single-crystal silicon rod according to claim 1 or 2, characterized in that, The crystal pulling furnace includes a main furnace chamber and an auxiliary furnace chamber. The auxiliary furnace chamber is equipped with a temperature control device, which is used to adjust the temperature in the auxiliary furnace chamber to perform the first heat treatment and the second heat treatment on the single crystal silicon rod in the auxiliary furnace chamber.

5. The method for manufacturing a single-crystal silicon rod according to claim 1 or 2, characterized in that, The oxygen content of the single-crystal silicon rod after the second heat treatment is less than 8 ppma.

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

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

8. A crystal pulling furnace, characterized in that, The crystal pulling furnace is used to perform the method for manufacturing single-crystal silicon rods according to any one of claims 1 to 5.

9. The crystal pulling furnace according to claim 8, characterized in that, The crystal pulling furnace includes a main furnace chamber, an auxiliary furnace chamber, and a temperature control device disposed in the auxiliary furnace chamber. The temperature control device includes a heater. The heater is used to perform a first heat treatment and a second heat treatment on the single crystal silicon rod. The temperature range of the first heat treatment is 650°C to 800°C, and the temperature range of the second heat treatment is 100°C to 300°C.

10. The crystal pulling furnace according to claim 9, characterized in that, The temperature control device further includes 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 rate of not less than 15°C / min by supplying a cooling medium to the auxiliary furnace chamber after the first heat treatment is completed and before the second heat treatment begins.

Images