External gettering method, system and equipment for removing metal impurities in silicon wafer

Abstract

The embodiment of the invention relates to the technical field of silicon wafer processing, and discloses an external gettering method and system for removing metal impurities in a silicon wafer. Comprising the following steps: obtaining a silicon dioxide raw material, and preparing high-purity silicon dioxide sand by adopting a high-purity electromagnetic preparation method; performing sand blasting treatment on a silicon wafer by adopting the high-purity silicon dioxide sand material, and forming a damaged layer which is gradually increased from the center to the edge in a gradient manner on the surface of the silicon wafer; and carrying out thermodynamic electric multi-field coupling treatment on the gradient damage layer, gradually reducing the concentration of metal impurities in the silicon wafer body, and completing impurity removal treatment. The technical problem that high-efficiency silicon wafer impurity removal cannot be carried out in the prior art can be solved at least.

Description

Technical Field

[0001] The present application relates to the technical field of silicon wafer processing, and particularly to an external gettering method and system for removing metal impurities in a silicon wafer. Background Art

[0002] During the production and processing of silicon wafers, metal contamination is ubiquitous. For example, metal parts on processing equipment are contaminated, metal contamination in cleaning liquid medicine, metal ion contamination in etching solution during etching processing, etc. Metal ion impurities in silicon wafers will significantly reduce the minority carrier lifetime. High metal impurities will cause adverse effects such as micro-defects on the surface of epitaxial wafers and epitaxial self-doping, and will also cause serious adverse effects such as device failure at the device end.

[0003] Therefore, in order to remove metal impurities, various gettering methods are usually used to absorb metal contamination in silicon wafers after etching processing in the industry. In the external gettering process, Al2O3 particles are usually used to sandblast the back of the silicon wafer. Al 3+ ions are likely to cause new metal contamination on the surface of the silicon wafer. Or by controlling the removal amount during the etching process, a certain thickness of grinding mechanical damage layer is retained on the back of the silicon wafer to achieve the external gettering ability, but this process has strict requirements for the process conditions of etching and polishing.

[0004] Currently, there is an urgent need for a gettering method that does not introduce other metal contamination and is convenient for production and processing. Summary of the Invention

[0005] An object of the present application is to provide an external gettering method and system for removing metal impurities in a silicon wafer, at least to solve the technical problem that the prior art cannot efficiently remove impurities from silicon wafers.

[0006] To achieve the above object, some embodiments of the present application provide the following aspects:

[0007] In a first aspect, some embodiments of the present application further provide an external gettering method for removing metal impurities in a silicon wafer, including the following steps:

[0008] Obtain a silica raw material, and prepare high-purity silica sand by using a high-purity electromagnetic preparation method;

[0009] Use the high-purity silica sand to sandblast the silicon wafer to form a damage layer with a gradient increasing from the center to the edge on the surface of the silicon wafer;

[0010] Perform a multi-field coupling treatment of heat, electricity, and magnetism on the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body and complete the impurity removal treatment.

[0011] In a second aspect, some embodiments of the present application further provide an external gettering system for removing metal impurities in a silicon wafer, including: a high-purity silica sand preparation module, a gradient damage layer preparation module, and a silicon wafer impurity removal module;

[0012] The high-purity silica sand preparation module is used to obtain silica raw materials and prepare high-purity silica sand by using a high-purity electromagnetic preparation method;

[0013] The gradient damage layer preparation module is used to perform sandblasting on the silicon wafer with the high-purity silica sand to form a damage layer with a gradually increasing gradient from the center to the edge on the surface of the silicon wafer;

[0014] The silicon wafer impurity removal module is used to perform a thermoelectric multi-field coupling treatment on the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body and complete the impurity removal treatment.

[0015] In a third aspect, some embodiments of the present application further provide an electronic device, which includes: one or more processors; and a memory storing computer program instructions, and when the computer program instructions are executed, the processors execute the steps of the method described above.

[0016] Compared with the related art, in the solution provided by the embodiments of the present application,

[0017] (1) In the present invention, high-purity SiO2 powder is used for sandblasting processing, and the metal content in the sand is strictly controlled to avoid introducing new metal contamination on the surface of the silicon wafer;

[0018] (2) In the present invention, by controlling parameters such as sandblasting pressure, nozzle swing speed, and sandblasting range, micro-damage with a uniform density is formed on the back surface of the silicon wafer to achieve the gettering effect, and at the same time, serious mechanical damage to the surface of the silicon wafer is not caused, reducing the impact on subsequent processing procedures. The processing method is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] One or more embodiments are illustrated by way of example in the accompanying drawings, and these exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, and the drawings in the figures do not constitute a proportional limitation.

[0020] Figure 1 It is a schematic flowchart of an external gettering method for removing metal impurities in a silicon wafer according to the first embodiment of the present application;

[0021] Figure 2 It is a schematic diagram of the process of sandblasting and forming micro-damage of an external gettering method for removing metal impurities in a silicon wafer according to the first embodiment of the present application;

[0022] Figure 3 Schematic structural diagram of an external gettering system for removing metal impurities in a silicon wafer according to the second embodiment of the present application;

[0023] Figure 4 Schematic structural diagram of an electronic device according to the present application. Specific embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0025] First embodiment

[0026] The first embodiment of the present application relates to an external gettering method for removing metal impurities in a silicon wafer. As Figure 1 shown, the method may include the following steps:

[0027] S101. Obtain silica raw materials and prepare high-purity silica sand by a high-purity electromagnetic preparation method.

[0028] In this embodiment, gaseous HF is used to chemically react with the metal impurities on the surface of the sand to strip the metal contaminants adsorbed on the surface of the SiO2 particles. This embodiment ensures that the metal content of the sand is less than 5 ppb through a chemical-physical combined process, providing high-purity silica sand for subsequent sandblasting.

[0029] Specifically, this embodiment uses HF vapor-phase etching to establish a surface metal stripping kinetic equation by obtaining sand parameters and HF vapor parameters, specifically:

[0030]

[0031] where C M is the metal impurity concentration per unit area, k ads is the adsorption rate constant, S BET is the specific surface area of the sand. The silica raw materials are repeatedly ground and pressed by ball milling to prepare fine silica raw material sand for increasing the specific surface area, P HF is the partial pressure of HF vapor, D eff is the effective diffusion coefficient of metal atoms in the SiO2 layer, and t is the time.

[0032] During the reaction process, this embodiment determines the critical etching depth during the etching process to effectively avoid sand grain breakage caused by over-etching, specifically:

[0033]

[0034] Among them, d crit is the critical etching depth, is the surface energy of SiO2, is the elastic modulus, ν is the Poisson's ratio, σ y is the yield strength, is the initial metal content, is the target metal content.

[0035] In this embodiment, when d crit <200 nm, the breakage rate of the abrasive is <0.1%.

[0036] After the etching is completed, there may be metal impurities that have not been removed. Therefore, for the metal impurities that have not been removed, this embodiment realizes the separation of magnetic foreign matters by using the electromagnetic separation method, and uses the magnetic difference between the metal impurities and SiO2 to achieve physical separation in a strong electromagnetic field.

[0037] The sand grains in this embodiment obtain surface charges in the ionization region, specifically:

[0038]

[0039] Among them, Z eff is the effective charge number, which characterizes the actual number of electrons carried on the surface of the sand grains and is determined by the surface chemical state. e is the elementary charge, ε r is the relative permittivity of SiO2, ε0 is the permittivity of vacuum, r is the radius of the sand grains, E corona is the corona electric field strength.

[0040] After the electric field is applied, the motion of the charged sand grains conforms to the electromagnetic field motion equation. Based on this equation, the motion trajectory of the charged sand grains is determined, so as to identify the sand grains and realize the physical separation of magnetic foreign matters. The separation trajectory is specifically:

[0041]

[0042] Among them, m is the mass of the sand grains, v x is the horizontal carrier gas velocity, specifically the main gas flow velocity for transporting the sand grains through the shunt chamber. B z is the vertical magnetic field component, which can generate a Lorentz force in the vertical direction. v z is the vertical velocity component, the velocity caused by gravitational sedimentation. B x is the horizontal magnetic field component, C D is the air resistance coefficient, ρ air is the air density, v y is the lateral velocity, which reflects the deviation degree of the impurity particles.

[0043] Subsequently, in this embodiment, the surface annealing treatment is performed on the separated silica sand material to repair the surface defects caused during the etching process, and the high-purity silica sand material is prepared.

[0044] Specifically, the surface defect healing rate method adopted in this embodiment is specifically as follows:

[0045]

[0046] Among them, N defect is the surface defect density, specifically including structures such as microcracks and dangling bonds. k0 is the pre-exponential factor, which is related to the lattice vibration frequency of SiO2. E a is the activation energy, k is the Boltzmann constant, T is the annealing temperature, S v is the specific surface area, is the oxygen concentration.

[0047] During the annealing process, the surface roughness of the sand grains changes as follows:

[0048]

[0049] Among them, ΔR a is the roughness change amount, is the arithmetic mean of the roughness, R a0 is the initial roughness, specifically the surface state after chemical etching. k heal is the healing coefficient, t1 is the annealing time, α is the thermal expansion coefficient, σ thermal is the thermal stress, is the elastic modulus.

[0050] By controlling the annealing temperature and annealing time, ΔR a is reduced. At the same time, by controlling the heating rate, the cracking of the sand grains caused by thermal stress is avoided, so as to ensure that the sand grains will not be broken during sandblasting.

[0051] S102. Sandblast the silicon wafer with the high-purity silica sand material to form a damage layer with a gradient increasing from the center to the edge on the surface of the silicon wafer.

[0052] In this embodiment, by actually sandblasting the silicon wafer, a damage layer with a gradient increasing from the center to the edge is formed on the back surface of the silicon wafer, so as to achieve high-density capture sites (>3×10 5 / cm 2 ) to adsorb metal impurities, the surface roughness <0.4 μm (to avoid affecting subsequent epitaxial growth), and the radial stress gradient (to drive the directional migration of impurities).

[0053] In this embodiment, through precise motion control, the sandblasting head scans the surface of the silicon wafer along a specific path, forming an impact dot matrix with a gradient distribution, providing an optimized capture trap distribution for metal impurities, thereby solving the problem of uneven damage distribution in traditional sandblasting.

[0054] Specifically, this embodiment uses a spiral progressive trajectory for scanning. Specifically, it is sparse in the center: the starting point is located at the center of the silicon wafer, the initial scanning radius is small, and the number of impacts per unit area is small; it is dense at the edge: as time goes by, the scanning radius increases exponentially, and the impact density in the edge area is higher.

[0055] As Figure 2 shown, the specific process is as follows: Prepare a mortar with a fixed specific gravity for sandblasting on the surface of the silicon wafer to form a fine back damage layer. The sand particle size is 1000 mesh - 3000 mesh. The sand is mixed with water to form a mortar, and the specific gravity of the mortar is 1 - 1.5 g / cm³.

[0056] Secondly, the silicon wafer moves on the conveyor belt at a fixed conveyor speed, generating relative motion with the nozzle, enabling uniform sandblasting operation of the silicon wafer in the direction parallel to the belt. At the same time, different conveyor belt speeds can meet different damage strength requirements. The conveyor speed of the belt is 0.5 - 2 m / min.

[0057] Then, the BSD nozzle swings in the direction perpendicular to the running direction of the belt at a certain speed and sandblasting pressure, enabling uniform sandblasting operation of the silicon wafer in the direction perpendicular to the belt. At the same time, different nozzle swing frequencies and sandblasting pressures can meet different damage strength requirements. The nozzle swing frequency is 60 - 80 times / min, and the sandblasting pressure is 0.5 - 3 Kg / cm². The swing center of the nozzle coincides with the conveyor center of the silicon wafer on the belt.

[0058] Finally, the nozzle and the belt move simultaneously, enabling the nozzle to fully cover the entire back of the silicon wafer and forming micro - damages with a uniform density on the back of the silicon wafer. Among them, Figure 2 (a) is a schematic diagram of the movement of the sandblasting head and the belt, Figure 2 (b) is a schematic diagram of the movement trajectory of the sandblasting head on the surface of the silicon wafer.

[0059] During the scanning process, the specific motion equation of the sandblasting head constructed in this embodiment is as follows:

[0060]

[0061] Among them, R is the radius of the silicon wafer, β is the mirror expansion coefficient, ω is the angular velocity, φ0 is the initial phase, v p is the axial feed speed, a p is the acceleration, r(t) is the radial motion equation, θ(t) is the angular motion equation, and z(t) is the axial motion equation.

[0062] Meanwhile, in this embodiment, by precisely controlling the density and depth of damage points per unit area, the gettering ability and surface integrity are balanced, and micro-damage points are formed by controlling the impact energy of a single sand grain.

[0063] In this embodiment, the moving direction of the sand grains is at an angle of 60°, and the lateral stress on the surface is reduced by oblique impact, and the energy of its vertical component penetrates deep into the lattice.

[0064] Specifically, the density control during the impact process in this embodiment is as follows:

[0065]

[0066] where N d is the damage density, η is the kinetic energy conversion efficiency, ρ 砂 is the density of SiO2, vn is the normal impact velocity, θ is the incident angle, E c is the lattice breaking energy, d nozzle is the nozzle diameter, P is the sandblasting pressure, A scan is the scanning area.

[0067] The depth control is as follows:

[0068]

[0069] where K IC is the silicon fracture toughness, H v is the Vickers hardness of silicon, m is the mass of a single sand grain, d dam is the damage depth, and r is the radius of the sand grain.

[0070] During the sandblasting process, damage points are formed by controlling the sandblasting impact energy. The specific impact energy is:

[0071]

[0072] where E trans is the effective transmitted energy, e is the restitution coefficient, m1 is the mass of the sand grain, m2 is the effective mass of silicon, E pl is the plastic dissipation energy.

[0073] After the sandblasting is completed, a three-dimensional stress gradient from the surface to the inside and from the center to the edge is established inside the silicon wafer, including the center area, the transition area, and the edge area. Specifically, the constructed gradient control is as follows:

[0074]

[0075] where α is the gradient coefficient, is the damage density gradient. By controlling v pand β to control obtaining high gradients and low gradients, thereby forming a gradient damage layer.

[0076] S103. Perform a multi-field coupling treatment of heat, electricity, and mechanics on the gradient damage layer, gradually reduce the metal impurity concentration in the silicon wafer body, and complete the impurity removal treatment.

[0077] In this embodiment, the formed gradient damage layer is transformed into an efficient "gettering trap", and through the synergistic action of the three fields of heat, force, and electricity, the following can be achieved: reducing the metal impurity concentration in the silicon wafer body to <5×10 10 atoms / cm 3 , permanently fixing metal impurities within the damage points (preventing re-release), and shortening the process time to 45 minutes (120 minutes for the traditional process).

[0078] First of all, in this embodiment, the diffusion ability of metal impurities is activated, and a matching temperature gradient is established based on the damage gradient, thereby avoiding warping of the silicon wafer caused by thermal stress.

[0079] The specific temperature field equation constructed in this embodiment is as follows:

[0080]

[0081] Among them, T(r,z) is the temperature field, T0 is the reference temperature of the center surface, ΔT max is the maximum temperature difference between the edge and the center of the silicon wafer, z is the depth coordinate, δ is the temperature attenuation depth constant, T1 is the absolute temperature, and τ get is the capture time constant of the damage point.

[0082] In this embodiment, the edge temperature of the silicon wafer (850 °C) > the center temperature (650 °C). Compared with the damage degree, by having a higher surface temperature than the internal temperature, impurities are driven to migrate towards the surface.

[0083] Subsequently, in this embodiment, a stress-driven method is adopted, and the residual stress field generated during the construction of the damage layer is used to drive the metal impurities to migrate directionally towards the high-stress region, that is, the damage point.

[0084] The constructed diffusion kinetic equation is:

[0085]

[0086] Among them, D0 is the intrinsic diffusion coefficient of the metal in silicon, E a is the diffusion activation energy, σ is the residual stress, V * is the activation volume, C is the local concentration of metal impurities in the silicon lattice, and T1 is the absolute temperature.

[0087] Subsequently, an electric field is applied to the surface of the silicon wafer, and the charged characteristics of metal impurities are utilized (such as Fe +)Enhance the enrichment of the targeted damage points.

[0088] Specifically, the constructed electric field control equation is:

[0089]

[0090] Wherein, is the impurity ion current density, q is the ion charge, μ is the Fe + mobility, n is the impurity concentration, is the external electric field strength, ψ is the stress potential, and D is the diffusion coefficient.

[0091] After the metal impurities are enriched, the captured metal impurities are converted into stable compounds to prevent re-release in subsequent processes. The specific chemical equation is:

[0092] Meanwhile, in this embodiment, by constructing an SIMS online monitoring model and monitoring the metal concentration distribution in real time, the thermal-mechanical-electric parameters are dynamically optimized. The constructed model is specifically:

[0093]

[0094] Wherein, I Fe + is the Fe + ion signal intensity, σ ion is the Fe ionization cross section, η is the transmission efficiency, Δz is the sampling depth resolution, and C Fe is the iron atom concentration at the monitoring point.

[0095] Through this embodiment, high-purity silica sandblasting is used to replace traditional alumina, thereby eliminating metal contamination from the source. Meanwhile, in this embodiment, a gradient damage layer is constructed and the combined action of multiple physical fields is designed, so as to effectively improve the removal speed and efficiency of metal impurities, effectively improve the production capacity, and shorten the process time.

[0096] The step division of the above various methods is only for clear description. When implemented, they can be combined into one step or some steps can be split into multiple steps. As long as the same logical relationship is included, they are all within the protection scope of this patent; adding insignificant modifications to the algorithm or process or introducing insignificant designs, but not changing the core design of its algorithm and process are all within the protection scope of this patent.

[0097] Second Embodiment

[0098] The second embodiment of this application relates to an external gettering system for removing metal impurities in a silicon wafer, including: a high-purity silica sand material preparation module 1, a gradient damage layer preparation module 2, and a silicon wafer impurity removal module 3;

[0099] The high-purity silica sand preparation module 1 is used to obtain silica raw materials and prepare high-purity silica sand by using a high-purity electromagnetic preparation method;

[0100] The gradient damage layer preparation module 2 is used to perform sandblasting treatment on the silicon wafer with the high-purity silica sand to form a damage layer with a gradually increasing gradient from the center to the edge on the surface of the silicon wafer;

[0101] The silicon wafer impurity removal module 3 is used to perform thermoelectric multi-field coupling treatment on the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body and complete the impurity removal treatment.

[0102] It is not difficult to find that this embodiment is a system embodiment corresponding to the first embodiment, and this embodiment can be implemented in cooperation with the first embodiment. The relevant technical details mentioned in the first embodiment are still valid in this embodiment. To avoid repetition, they will not be elaborated here. Correspondingly, the relevant technical details mentioned in this embodiment can also be applied in the first embodiment.

[0103] It is worth mentioning that each module involved in this embodiment is a logical module. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, to highlight the innovative part of this application, units that are not closely related to solving the technical problems proposed in this application are not introduced in this embodiment, but this does not mean that there are no other units in this embodiment.

[0104] In addition, some embodiments of this application also provide an electronic device. The electronic device can be various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and so on. The electronic device can also be various forms of mobile devices, such as personal digital processors, cellular phones, smart phones, wearable devices, and other similar computing devices.

[0105] The electronic device includes: one or more processors; and a memory storing computer program instructions, and when the computer program instructions are executed, the processors execute the steps of the method provided in any one or more of the above embodiments. Figure 4 An exemplary structural diagram of the electronic device is disclosed. As Figure 4As shown, the electronic device includes: one or more processors 1101, a memory 1102, and interfaces for connecting the components, including a high-speed interface and a low-speed interface. Each component is interconnected using different buses and can be mounted on a common motherboard or otherwise mounted as required. The processor can process instructions executed within the electronic device, including instructions stored in the memory or on the memory to display graphical information of a GUI on an external input / output device (such as a display device coupled to the interface). In some other embodiments, if needed, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple electronic devices can be connected, with each device providing part of the necessary operations (such as an array of servers, a set of blade servers, or a multi-processor system). Among them, the components, their connections and relationships, and their functions shown herein are only examples and are not intended to limit the implementation of the present application described and / or claimed herein.

[0106] The electronic device may further include: an input device 1103 and an output device 1104. The processor 1101, the memory 1102, the input device 1103, and the output device 1104 can be connected via a bus or other means. Figure 4 Taking connection via a bus as an example.

[0107] The input device 1103 can receive input digital or character information and generate key signal inputs related to the user settings and function controls of the electronic device, such as input devices like a touch screen, a keypad, a mouse, a trackpad, a touchpad, a pointing stick, one or more mouse buttons, a trackball, a joystick, etc. The output device 1104 can include a display device, an auxiliary lighting device (such as an LED), and a haptic feedback device (such as a vibration motor), etc. The display device can include, but is not limited to, a liquid crystal display (LCD), a light emitting diode (LED) display, and a plasma display. In some embodiments, the display device can be a touch screen.

[0108] To provide interaction with the user, the electronic device can be a computer. The computer has: a display device for displaying information to the user (such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and a pointing device (such as a mouse or a trackball), through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (such as visual feedback, auditory feedback, or haptic feedback); and inputs from the user can be received in any form (including sound input, voice input, or haptic input).

[0109] In the embodiments of the present application, a computer program / instruction is stored on a computer-readable medium. When the computer program / instruction is executed by a processor, the steps of the method provided in any one or more of the above embodiments are implemented. The computer-readable medium may be included in the electronic device described in the above embodiments; or it may exist separately without being assembled into the device. The above computer-readable medium carries one or more computer-readable instructions.

[0110] The memory 1102 can be used as a non-transitory computer-readable storage medium, and can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules. By running the non-transitory software programs, instructions, and modules stored in the memory 1102, the processor 1101 executes various functional applications and data processing of the server, so as to implement the program instructions / modules corresponding to the method provided in any one or more of the above embodiments of the present application.

[0111] The memory 1102 may include a program storage area and a data storage area. Among them, the program storage area may store an operating system and application programs required for at least one function; the data storage area may store data created according to the use of the electronic device, etc. In addition, the memory 1102 may include a high-speed random access memory, and may also include a non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state storage devices. In some embodiments, the memory 1102 may optionally include a memory remotely set relative to the processor 1101, and these remote memories may be connected to the electronic device through a network. Examples of the above network include but are not limited to the Internet, an enterprise intranet, a local area network, a mobile communication network, and combinations thereof.

[0112] It should be noted that the computer-readable medium described in the present application may be a computer-readable signal medium, a computer-readable storage medium, or any combination of the two. The computer-readable medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples of the computer-readable storage medium may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present application, the computer-readable medium may be any tangible medium that contains or stores a program, and the program can be used by or combined with an instruction execution system, apparatus, or device.

[0113] A computer-readable medium includes permanent and non-permanent, removable and non-removable media and can implement information storage by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device.

[0114] Computer program code for performing the operations of this application can be written in one or more programming languages or combinations thereof. The programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., by using an Internet service provider to connect through the Internet).

[0115] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. For example, an application-specific integrated circuit (ASIC), a general-purpose computer, or any other similar hardware device can be used. In some embodiments, the software program of this application can be executed by a processor to implement the above steps or functions. Similarly, the software program of this application (including related data structures) can be stored in a computer-readable recording medium, such as a RAM memory, a magnetic or optical drive, or a floppy disk and similar devices. Additionally, some steps or functions of this application can be implemented by hardware, for example, as a circuit that cooperates with a processor to execute each step or function.

[0116] The computer program product provided by the embodiments of the present application includes one or more computer programs / instructions. When the computer programs / instructions are executed by a processor, they wholly or partially generate the processes or functions described in the embodiments of the present application. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server or a data center that includes one or more integrated available media. The available medium may be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid state disk (SSD)), etc.

[0117] The flowcharts or block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of devices, methods, and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, as well as the combination of blocks in the block diagram and / or flowchart, may be implemented by a dedicated hardware-based system for performing the specified functions or operations, or by a combination of dedicated hardware and computer instructions.

[0118] The scope of the present application is defined by the appended claims rather than the above description. Therefore, all changes that fall within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be construed as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. The multiple elements or devices recited in the apparatus claims may also be implemented by one element or device through software or hardware. The words "first", "second", etc. are only used for distinguishing descriptions and do not represent any specific order, nor can they be understood as indicating or implying relative importance..

[0119] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily make changes or substitutions, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims, and the above embodiments should be regarded as exemplary and non-restrictive.

Claims

1. An external gettering method for removing metal impurities in a silicon wafer, characterized in that, It includes the following steps: Obtain silica raw materials and prepare high-purity silica sand by using a high-purity electromagnetic preparation method; Perform sandblasting treatment on the silicon wafer with the high-purity silica sand to form a damage layer with a gradually increasing gradient from the center to the edge on the surface of the silicon wafer; Perform a thermoelectric multi-field coupling treatment on the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body and complete the impurity removal treatment.

2. The external gettering method for removing metal impurities in a silicon wafer according to claim 1, wherein The process of obtaining silica raw materials and preparing high-purity silica sand by using a high-purity electromagnetic preparation method is as follows: Etch the silica raw materials with HF vapor, construct a surface metal stripping kinetic equation, and strip the metal impurities existing in the silica during the etching process based on the equation; Construct a charged sand grain motion equation, utilize the magnetic difference between the metal impurities and silica, and perform electromagnetic separation on the stripped raw materials in a strong electromagnetic field to complete the secondary separation of the metal impurities and silica; Perform a surface annealing treatment on the separated silica sand to repair the surface defects caused during the etching process and prepare high-purity silica sand.

3. The external gettering method for removing metal impurities in a silicon wafer according to claim 2, characterized in that, The process of etching the silica raw materials with HF vapor, constructing a surface metal stripping kinetic equation, and stripping the metal impurities existing in the silica during the etching process based on the equation is as follows: Use ball milling to repeatedly grind and press the silica raw materials to prepare fine silica raw material sand, and at the same time prepare HF vapor with a concentration of 6.5 vol%; Obtain sand material parameters and HF vapor parameters to construct a surface metal kinetic equation, and based on the equation, perform an etching reaction on the HF vapor flow and the fine silica raw material sand, control the etching process by calculating the critical etching depth, generate volatile metal oxides, and complete the metal impurity stripping.

4. The external gettering method for removing metal impurities in a silicon wafer according to claim 2, characterized in that, The surface metal kinetic equation is: Among them, C M is the metal impurity concentration per unit area, k ads is the adsorption rate constant, S BET is the specific surface area of the sand. The silica raw material is repeatedly ground and pressed by ball milling to prepare fine silica sand for increasing the specific surface area. P HF is the partial pressure of HF vapor, D eff is the effective diffusion coefficient of metal atoms in the SiO2 layer, and t is the time.

5. The external gettering method for removing metal impurities in a silicon wafer according to claim 1, characterized in that, The process of performing sandblasting treatment on the silicon wafer with the high-purity silica sand to form a damage layer with a gradually increasing gradient from the center to the edge on the surface of the silicon wafer is as follows: Through precise motion control, use a sandblasting head to scan the surface of the silicon wafer along a specific path for sandblasting. During the sandblasting process, control the depth per unit area, damage density, and the impact energy of a single sand grain to form bowl-shaped micro-damage points in the silicon lattice; Construct a sandblasting head motion equation, and based on the equation, continuously adjust the sandblasting path of the sandblasting head to form an impact dot matrix with a gradient distribution on the surface of the silicon wafer; Based on the impact dot matrix and the micro-damage points, establish a three-dimensional stress gradient damage layer from the surface to the inside and from the center to the edge inside the silicon wafer.

6. The external gettering method for removing metal impurities in a silicon wafer according to claim 5, wherein, The depth per unit area is: Among them, K IC is the silicon fracture toughness, H v is the silicon Vickers hardness, m is the mass of a single abrasive grain, d dam is the damage depth, r is the abrasive grain radius, v n is the normal impact velocity; The damage density is: Among them, N d is the damage density, η is the kinetic energy conversion efficiency, ρ 砂 is the density of SiO2, v n is the normal impact velocity, θ is the incident angle, E c is the lattice damage energy, d nozzle is the nozzle diameter, P is the sandblasting pressure, A scan is the scanning area; The impact energy is: Among them, E trans For effective energy transfer, e is the restitution coefficient, m1 is the mass of the sand grain, m2 is the effective mass of silicon, and E pl Plastic dissipation energy.

7. The external gettering method for removing metal impurities in a silicon wafer according to claim 1, characterized in that, The process of performing a thermoelectric multi-field coupling treatment on the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body and complete the impurity removal treatment is as follows: Based on the gradient damage layer, establish a matching temperature gradient, construct a temperature field equation, and drive the metal impurities to migrate towards the surface based on the temperature field equation; Through the residual stress field generated during the formation process of the gradient damage layer, construct a stress-driven diffusion model to drive the metal impurities to migrate directionally towards the damage points; Apply an electric field to the back side of the silicon wafer, and utilize the charged characteristics of metal impurities to enhance the enrichment degree of metal impurities towards the damage points; Capture the metal impurities at the damage points, convert the captured metal impurities into stable compounds, achieve the annihilation and passivation of impurities, and complete the impurity removal process.

8. The external gettering method for removing metal impurities in a silicon wafer according to claim 7, characterized in that, The thermoelectric multi-field coupling treatment of the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body, and the completion of the impurity removal process further includes: By constructing an SIMS online monitoring model, the metal concentration distribution is monitored in real time, and the temperature field equation, stress-driven diffusion model, and the electric field parameters are dynamically optimized based on the metal concentration values.

9. An external gettering system for removing metal impurities in a silicon wafer, which is used to implement the external gettering method for removing metal impurities in a silicon wafer as described in any one of claims 1-8, characterized in that Including: A high-purity silica sand preparation module (1), a gradient damage layer preparation module (2), and a silicon wafer impurity removal module (3); The high-purity silica sand preparation module (1) is used to obtain silica raw materials and prepare high-purity silica sand by using a high-purity electromagnetic preparation method; The gradient damage layer preparation module (2) is used to perform sandblasting treatment on the silicon wafer with the high-purity silica sand to form a damage layer with a gradually increasing gradient from the center to the edge on the silicon wafer surface; The silicon wafer impurity removal module (3) is used to perform thermoelectric multi-field coupling treatment on the gradient damage layer to gradually reduce the metal impurity concentration in the silicon wafer body and complete the impurity removal process.

10. An electronic device, characterized in that, The electronic device includes: One or more processors; and A memory storing computer program instructions, which when executed cause the processor to execute the steps of the method according to any one of claims 1 to 8.

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