Manufacturing methods for single-crystal silicon rods, silicon wafers and their manufacturing methods, and single-crystal furnaces.

Abstract

This disclosure provides a method for manufacturing a single-crystal silicon rod, a silicon wafer, the same method for manufacturing the wafer, and a single-crystal furnace. The manufacturing method includes: drawing a single-crystal silicon rod using the Czochralski method in a single-crystal furnace; subjecting the single-crystal silicon rod to a first heat treatment in the single-crystal furnace, wherein the temperature range of the first heat treatment is 650°C to 800°C and the duration ranges from 5 minutes to 90 minutes; and subjecting the single-crystal silicon rod after the first heat treatment to a second heat treatment in the single-crystal furnace, wherein the temperature range of the second heat treatment is 100°C to 300°C and the duration ranges from 10 minutes to 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.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202510968033.3, filed in China on July 14, 2025, the entire contents of which are incorporated herein by reference.

[0003] 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 a single-crystal furnace. Prior Technology

[0004] 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.

[0005] With the rapid development of radio frequency (RF) communications, microwave components, and high-frequency, high-power applications, higher requirements 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 component performance. Related technologies typically control the resistivity of silicon wafers by manipulating doping concentration and optimizing heat treatment processes.

[0006] However, significant shortcomings remain in the manufacturing process of related technologies. 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, thus reducing its effective resistivity and affecting the device's usability. 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

[0007] To address the aforementioned issues, this disclosure presents a method for manufacturing single-crystal silicon rods, silicon wafers, the same method for manufacturing silicon wafers, and a single-crystal furnace. This method for manufacturing single-crystal silicon rods avoids the risk of cross-contamination in dedicated heat treatment furnaces by continuously performing high-temperature and low-temperature heat treatments within the single-crystal furnace, simplifies the process flow, and ensures that the resistivity of the single-crystal silicon rods is greater than 1000 Ω·cm and is uniform and stable, with a P-type conductivity.

[0008] The technical solution disclosed herein is implemented as follows:

[0009] In a first aspect, the present disclosure provides a method for manufacturing a single-crystal silicon rod, the method comprising:

[0010] In a single crystal furnace, single-crystal silicon rods are drawn using the Czochralski method;

[0011] In the single crystal furnace, the single crystal silicon rod undergoes 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.

[0012] In the single crystal 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.

[0013] In some optional examples, 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.

[0014] 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 to cool the monocrystalline 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.

[0015] In some optional examples, the single crystal 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.

[0016] In some optional examples, the oxygen content of the monocrystalline silicon rod after the second heat treatment is less than 8 ppma.

[0017] Secondly, this disclosure provides a method for manufacturing a silicon wafer, the method comprising: cutting, grinding, polishing and cleaning a single-crystal silicon rod made by the method for manufacturing a single-crystal silicon rod according to the first aspect, to obtain a silicon wafer.

[0018] Thirdly, this disclosure provides a silicon wafer manufactured using a silicon wafer manufacturing method according to the second aspect, wherein the silicon wafer has a resistivity greater than 1000 Ω·cm, a P-type conductivity, and an oxygen content less than 8 ppma.

[0019] Fourthly, this disclosure provides a single-crystal furnace for performing a method for manufacturing a single-crystal silicon rod according to the first aspect.

[0020] In some optional examples, the single crystal 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, 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.

[0021] In some optional examples, 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 the cooling medium to the auxiliary furnace chamber after the first heat treatment is completed and before the second heat treatment begins.

[0022] This disclosure provides a method for manufacturing single-crystal silicon rods, silicon wafers, the same manufacturing method, and a single-crystal furnace. The method for manufacturing single-crystal silicon rods involves completing consecutive process steps within a single-crystal 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 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 single-crystal 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. Simple Explanation of the Diagram

[0023] Figure 1 is a flowchart of the manufacturing method of the single-crystal silicon rod provided in the present disclosure embodiment.

[0024] Figure 2 is a schematic cross-sectional view of a conventional single crystal furnace.

[0025] Figure 3 is a schematic cross-sectional view of the single crystal furnace provided in the embodiment of this disclosure.

[0026] Figure 4 is a partial cross-sectional view of Figure 3.

[0027] Figure 5 is a graph showing the resistivity versus oxygen content of a single-crystal silicon rod manufactured using the manufacturing method of the single-crystal silicon rod provided in this disclosure embodiment. Implementation

[0028] The technical solution disclosed herein will be clearly and completely described below with reference to the figures.

[0029] In the conventional manufacturing process of high resistivity silicon wafers, after obtaining the 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.

[0030] Taking single-crystal silicon rods grown using the Czochralski method (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 charge 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.

[0031] To control the distribution of oxygen impurities and reduce defect formation, high-temperature heat treatment processes are commonly introduced in related 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.

[0032] 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 the high-resistivity silicon wafer 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.

[0033] 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 silicon 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.

[0034] In view of this, the present disclosure provides a method for manufacturing single-crystal silicon rods, silicon wafers and their manufacturing methods, and a single-crystal furnace. This method for manufacturing single-crystal silicon rods avoids the risk of cross-contamination in dedicated heat treatment furnaces by continuously performing high-temperature and low-temperature heat treatments within the single-crystal furnace, simplifies the process flow, and ensures that the resistivity of the single-crystal silicon rods is greater than 1000 Ω·cm and is uniform and stable, and that the conductivity type is P-type.

[0035] Referring to Figure 1, some embodiments disclosed herein present a method for manufacturing a single-crystal silicon rod. This manufacturing method may include:

[0036] S1. In a single crystal furnace, single crystal silicon rods are drawn using the Czochralski method;

[0037] S2. In a single-crystal furnace, the single-crystal silicon rod undergoes 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.

[0038] S3. In a single crystal 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.

[0039] In this disclosed embodiment, the three steps of the proposed manufacturing method can be completed continuously within the same single crystal 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 single-crystal silicon rods with a resistivity greater than 1000 Ω·cm and a P-type conductivity, which can meet the stringent requirements of high-frequency components, radio-frequency components, and other applications for high-resistivity silicon materials.

[0040] Specifically, in step S1, a single-crystal silicon rod S can be drawn in a single-crystal 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 into a single-crystal state is gradually realized, thereby growing a single-crystal silicon rod S with a predetermined diameter, length, and crystallization direction.

[0041] 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), then no dopant needs to be added, and an intrinsic high-resistivity single-crystal silicon rod can be directly pulled; 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) – needs to be introduced during the growth process to counteract the background N-type doping and form net P-type characteristics.

[0042] For high-resistivity silicon materials required for components such as radio frequency (RF) devices and high-frequency communication chips, p-type doping can be used, typically with boron (B) as the dopant element. As an example, the boron doping concentration can be controlled to be below 5 × 10¹⁴ atoms / cm³. This doping concentration range helps to ensure that the silicon rod has a p-type conductivity while maximizing its intrinsic resistivity to a target value, such as 1000 Ω·cm. It also avoids the problem of excessively high doping concentration leading to a large difference between the initial resistivity and the target resistivity, providing adjustable space for further resistivity improvements in subsequent process stages.

[0043] 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, potentially precipitating as oxygen aggregates, oxygen precipitates, or oxygen donor defects.

[0044] 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 electrical performance such as increased leakage current and threshold drift, and in mechanical performance, they can also lead to a decrease in localized strength during subsequent slicing, polishing, or other machining processes, affecting yield and quality control.

[0045] 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.

[0046] To mitigate the aforementioned adverse effects, the manufacturing method disclosed in this embodiment 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, within a single-crystal furnace. These two steps are completed within the same single-crystal furnace, reducing the risk of cross-contamination of impurities caused by process transfer in conventional processes.

[0047] In step S2, the pulled single-crystal silicon rod S undergoes a first heat treatment in a single-crystal 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.

[0048] 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 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 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 a single crystal furnace after crystal pulling. At this time, the temperature range of the first heat treatment can be selected as 700℃ to 770℃, and further, it can be set to approximately 750℃.

[0049] 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.

[0050] 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 the single-crystal silicon rod is equivalent to high-temperature annealing, which promotes the precipitation of some oxygen impurities within the silicon crystal and their loss of electroactivity, thereby reducing the oxygen donor density and increasing resistivity. Furthermore, the moderate high temperature also helps release localized stresses formed during silicon rod crystal growth, eliminates microscopic defects, and further improves the integrity and uniformity of the crystal structure.

[0051] Compared to technologies that use dedicated heat treatment furnaces to heat-treat silicon wafers obtained from cutting single-crystal silicon rods, in the embodiments disclosed herein, the first heat treatment step is completed directly in the single-crystal furnace, which is equivalent to in-situ heat treatment. Therefore, it eliminates the need for handling and unloading, reducing the risk of contamination of the surface and interior of the single-crystal silicon rod S by external impurities and / or impurities within the heat treatment furnace. Furthermore, the single-crystal furnace effectively provides a crystal environment that ensures high purity and high consistency.

[0052] After the first heat treatment, step S3, a second heat treatment at a temperature range of 100°C to 300°C, is performed on the single-crystal silicon rod that has undergone the first heat treatment. The second heat treatment is completed in a single-crystal 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.

[0053] In some embodiments disclosed herein, the two-step heat treatment process for the single-crystal 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 single-crystal silicon rod can stably obtain high resistivity characteristics.

[0054] Specifically, in some embodiments disclosed herein, 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 optional embodiment disclosed herein, the duration of the first heat treatment can be set within the range of 10 to 60 minutes.

[0055] 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.

[0056] In some other embodiments disclosed herein, 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 an equilibrium state 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 optional embodiment disclosed herein, the duration of the second heat treatment can be set within the range of 20 to 40 minutes.

[0057] 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 >3000 Ω·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℃.

[0058] 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 carrier concentration stabilization process and optimize the overall process rhythm.

[0059] After high-temperature annealing, the concentration distribution of electrons and holes in single-crystal silicon rods (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 a 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.

[0060] After undergoing the two heat treatment steps S1 and S2, the single-crystal silicon rod S possesses high resistivity characteristics, especially with a measured resistivity greater than 1000 Ω·cm and a P-type conductivity, meeting the performance requirements of high-frequency, radio frequency, and power components for high-resistivity substrate materials.

[0061] This disclosure provides a method for manufacturing a single-crystal silicon rod. The method involves completing a series of process steps in a single-crystal 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 first heat treatment step eliminates oxygen donor defects; subsequently, a lower-temperature second 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 single-crystal 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.

[0062] In the embodiments disclosed herein, 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.

[0063] 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 disclosed herein, the cooling step can be limited to a cooling rate of not less than 15°C / min.

[0064] 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.

[0065] Moreover, this cooling step also plays a positive role in improving the mechanical properties of the single-crystal silicon rod S. Because single-crystal 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 thermal stress release process may lead to local lattice distortion, dislocation propagation, or even the induction of microcracks. However, by adopting a reasonable rapid cooling process, thermal stress can be released uniformly, reducing the level of residual stress, thereby effectively improving the mechanical strength of the single-crystal silicon rod and reducing the risk of damage or fragmentation during subsequent processing such as cutting, grinding, and polishing.

[0066] In addition, controlling the cooling rate to above 15℃ / min also has good process efficiency advantages, 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.

[0067] To achieve the aforementioned cooling rate control, in some embodiments disclosed herein, 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.

[0068] In the embodiments disclosed herein, in order to achieve precise temperature control of the single crystal silicon rod throughout the first heat treatment, cooling treatment and second heat treatment processes, and to further improve the stability and controllability of the process, in the case where the single crystal 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 single crystal silicon rod pulled in the main furnace chamber.

[0069] 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:

[0070] First, because the auxiliary furnace chamber is relatively independent, its internal environment is easier to control, avoiding the impact of high-temperature disturbances or contamination introduced by the main furnace chamber during crystal pulling on the heat treatment process, thus 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.

[0071] The temperature control device in the auxiliary furnace chamber may include components such as a heater 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.

[0072] The temperature control device in the auxiliary furnace chamber ensures that the three-step process of 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 single crystal 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.

[0073] To implement the manufacturing method proposed in the above embodiments of this disclosure, some embodiments of this disclosure also propose a single crystal furnace 10, which includes a temperature control device 1. The single crystal furnace 10 will be described in detail below with reference to the drawings.

[0074] Figure 2 illustrates a conventional single-crystal furnace 10. Specifically, the single-crystal furnace 10 may include a main furnace chamber 11 and an auxiliary furnace chamber 12 arranged vertically, wherein the auxiliary furnace chamber 12 is located directly above the main furnace chamber 11 and communicates with it. The main furnace chamber 11 mainly includes a quartz crucible 20, a graphite crucible 30, and a heating module 40. The quartz crucible 20 can be used to contain solid polycrystalline silicon raw material in the initial stage of pulling the single-crystal silicon rod S. The graphite crucible 30 can be 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.

[0075] When using the single crystal furnace 10, the polycrystalline silicon raw material of the set quality 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 silicon melt.

[0076] The single crystal furnace 10 may further 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 initiates processes such as crystal introduction, necking, shoulder formation, constant diameter growth, and tailing, ultimately pulling a single crystal silicon 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.

[0077] To meet the requirement of continuous heat treatment of single-crystal silicon rods in this disclosed embodiment, the inventors made improvements to the conventional single-crystal furnace. As shown in Figure 3, a temperature control device 1 was added to the auxiliary furnace chamber 12, thus forming the improved single-crystal furnace 10.

[0078] Specifically, during the pulling process, 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. After pulling is completed, the rod pulling device 60 completely pulls the single-crystal silicon rod S into the auxiliary furnace chamber 12 and suspends it inside the auxiliary furnace chamber 12, avoiding direct contact with the bottom of the auxiliary furnace chamber 12. Inside the auxiliary furnace chamber 12, the single-crystal silicon rod S can directly complete the subsequent heat treatment steps without needing to be transferred.

[0079] As shown in Figures 3 and 4, 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 12 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 single crystal 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 12 via 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 12 for rapid cooling of the single crystal silicon rod S after the first heat treatment. Suitable cooling media may include cryogenic media such as liquid nitrogen and liquid argon, which have high heat exchange characteristics and help to achieve precise control of the cooling rate.

[0080] 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. This allows the single crystal silicon rod S to undergo continuous operation of the first heat treatment, cooling treatment and second heat treatment directly in the auxiliary furnace chamber 12 after pulling. This eliminates the need for handling and converter steps, reducing the risk of contamination and mechanical damage to the silicon rod during handling. It further ensures the temperature stability and uniformity of the heat treatment process, providing further assurance for obtaining high-performance single crystal silicon rods with resistivity greater than 1000 Ω·cm and controlled oxygen content.

[0081] In some embodiments disclosed herein, 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, the oxygen content of the monocrystalline silicon rod is specifically limited to less than 8 ppma after the second heat treatment is completed.

[0082] 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 component use, thereby reducing the effective resistivity and resistivity uniformity of the material, creating localized conductive channels, and even leading to a decrease in component reliability.

[0083] 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, a lower temperature is used to further stabilize the distribution of holes and electrons in the crystal structure, suppressing the active reactions of oxygen impurities and ensuring that the oxygen content of the final single-crystal silicon rod is controlled below 8 ppma. In a further optional embodiment disclosed herein, the oxygen content of the single-crystal silicon rod can be controlled below 6 ppma.

[0084] The manufacturing method provided in this disclosed embodiment can obtain two forms of single-crystal silicon semiconductor structure: on the one hand, a single-crystal silicon rod after 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, silicon wafers that meet the requirements of high-performance applications can also be prepared.

[0085] Of particular note is that the manufacturing method disclosed herein, through a two-step heat treatment performed continuously in a single-crystal furnace, effectively controls the oxygen content distribution in the single-crystal 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 single-crystal silicon rod, thereby improving the controllability of subsequent processing and the yield of finished products from the source.

[0086] 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 components and high-frequency applications.

[0087] To further verify the characteristics of the single-crystal silicon rod obtained by the manufacturing method disclosed in this paper, Figure 5 shows the distribution data of its central resistivity and central oxygen content along the length direction as a curve.

[0088] This graph illustrates two key material properties of a single-crystal silicon rod 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 rod 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 increases significantly, reaching 5.910 nppma.

[0089] Examples and Comparative Examples

[0090] 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 single-crystal furnace with a temperature control device provided in the above-described 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 single-crystal furnace.

[0091] <Example A1>

[0092] The drawn single-crystal silicon rods were pulled into the auxiliary furnace chamber and subjected to the first heat treatment at 750°C for 60 minutes. They were then cooled to 150°C at a rate of 15°C / min and subjected to the second heat treatment at 150°C for 60 minutes. After treatment, the silicon rods were cut and ground to obtain silicon wafers with uniform resistivity (greater than 3000 Ω·cm) and an oxygen content of less than 8 ppma.

[0093] <Example A2>

[0094] 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 resulting wafer exhibited uniform resistivity, with a measured value greater than 5000 Ω·cm and an oxygen content less than 6 ppma.

[0095] <Example A3>

[0096] 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.

[0097] <Example A4>

[0098] 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.

[0099] <Example A5>

[0100] The drawn single-crystal silicon rods were pulled into the auxiliary furnace chamber and subjected to the first heat treatment at 650°C for 90 minutes. They were then cooled to 100°C at a rate of 15°C / min and subjected to the second heat treatment at 100°C for 60 minutes. After treatment, the silicon rods were cut and ground to obtain silicon wafers with uniform resistivity (greater than 1000 Ω·cm) and an oxygen content of less than 8 ppma.

[0101] <Example A6>

[0102] The drawn single-crystal silicon rods were pulled into the auxiliary furnace chamber and subjected to the first heat treatment at 800℃ for 5 minutes. They were 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 rods were cut and ground to obtain silicon wafers with uniform resistivity (greater than 5000 Ω·cm) and an oxygen content of less than 5 ppma.

[0103] <Comparative>

[0104] The comparative experiment employed a conventional method. First, single-crystal silicon rods were drawn using the Czochralski method in a conventional single-crystal 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 high-resistivity wafer manufacturing processes in related technologies. Detection revealed highly non-uniform resistivity in the resulting silicon wafers. Compared to the example, the resistivity uniformity of this comparative silicon wafer was poorer, with localized low-resistivity regions and a higher oxygen content.

[0105] For a detailed comparison, please refer to Table 1 below. Table 1 First heat treatment temperature (°C) First heat treatment time (min) Cooling rate (℃ / min) Second heat treatment temperature (°C) Second heat treatment time (min) Silicon rod resistivity (Ω·cm) Oxygen content (ppma) Example A1 750 60 15 150 60 >3000 <8 Example A2 750 45 15 180 40 >5000 <6 Example A3 750 30 15 210 20 >7000 <5 Example A4 750 15 15 240 10 >7000 <4 Example A5 650 90 15 100 60 >1000 <8 Example A6 800 5 20 300 10 >5000 <5 Comparative Example - - - - - Unstable -

[0106] As can be seen from the experimental data of embodiments A1 to A6 above, the manufacturing method disclosed herein, by integrating two-step heat treatment and cooling in a single crystal furnace, can eliminate oxygen donor defects and obtain silicon wafers with a resistivity greater than 1000 Ω·cm, P-type conductivity, and oxygen content less than 8 ppma, exhibiting good resistivity uniformity and mechanical stability. In contrast, the comparative example using a traditional heat treatment method suffers from cross-contamination, poor oxygen content control, and unstable resistivity, further validating the significant advantages of the disclosed solution.

[0107] It should be noted that the technical solutions described in this disclosure can be combined arbitrarily as long as they do not conflict.

[0108] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by a person skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the scope of protection of the claims.

[0109] 10: Single Crystal Furnace 11: Main furnace chamber 12: Auxiliary furnace chamber 1: Temperature control device 121: Heater 122: Supply device 20: Quartz crucible 30: Graphite crucible 40: Heating Module 50: Seed Crystal Cable 60: Crystal rod pulling device 70: Crucible lifting device S: Monocrystalline silicon rod S1: Single-crystal silicon rods are produced in a single-crystal furnace using the Czochralski method. S2: In a single-crystal furnace, the single-crystal silicon rod undergoes 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 single-crystal 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 1000 Ω·cm, and the conductivity type is P-type.

Claims

1. A method for manufacturing a single-crystal silicon rod, the method comprising: In a single crystal furnace, a single crystal silicon rod is drawn using the Czochralski method. In the single crystal furnace, the single crystal silicon rod undergoes a first heat treatment at a temperature ranging from 650°C to 800°C for a duration ranging from 5 minutes to 90 minutes. In the single crystal furnace, the single crystal silicon rod after the first heat treatment undergoes a second heat treatment at a temperature ranging from 100°C to 300°C for a duration ranging 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 its conductivity is P-type.

2. A method for manufacturing a single-crystal silicon rod as described in claim 1, wherein, 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. A method for manufacturing a single-crystal silicon rod as described in claim 1 or 2, wherein, 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. A method for manufacturing a single-crystal silicon rod as described in claim 1 or 2, wherein, The single crystal furnace includes a main furnace chamber and an auxiliary furnace chamber. 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.

5. A method for manufacturing a single-crystal silicon rod as described in claim 1 or 2, wherein, 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, the method comprising: A single-crystal silicon rod made by any of the methods described in claims 1 to 5 is cut, ground, polished, and cleaned to obtain a silicon wafer.

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

8. A single crystal furnace for performing a method of manufacturing a single crystal silicon rod as described in any one of claims 1 to 5.

9. The single crystal furnace as described in claim 8, wherein, The single crystal 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, 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.

10. The single crystal furnace as described in claim 9, wherein, 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.

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