A temporary storage system for electronic grade polysilicon materials

Abstract

The present invention discloses a temporary storage system for electronic-grade polysilicon materials, including several storage structures and a high-purity water system; the box cover of the storage structure is placed on the top of the silicon material box, the two sides of the silicon material box are respectively connected with an inlet pipe and an overflow pipe, the side of the silicon material box is connected with a drain pipe, and the inlet pipe, the overflow pipe and the drain pipe are all provided with silicon material box pipeline electric control valves; the high-purity water system includes an inlet main pipe, the inlet main pipe is connected with several inlet branch pipes, the return main pipe is connected with several return branch pipes, the inlet branch pipes and the return branch pipes are respectively provided with branch pipe electric control valves, a storage structure is arranged between a pair of inlet branch pipes and return branch pipes, the inlet branch pipe is connected to the inlet pipe through a quick connector, and the return branch pipe is respectively connected to the overflow pipe and the drain pipe through a quick connector. Advantages: Prevent silicon rods or silicon materials from being polluted by the environment during transportation and storage. Prevent silicon rods or silicon materials from causing an increase in surface impurity content.

Description

Technical Field

[0001] The invention relates to the field of cleaning technology, and in particular to an electronic-grade polysilicon material temporary storage system. Background Art

[0002] Solar-grade polysilicon has a purity of 99.9999%, while the purity of electronic-grade polysilicon is required to reach 99.999999999%. Therefore, compared to photovoltaic polysilicon, electronic-grade polysilicon must go through a silicon block cleaning process after crushing, sorting, and temporary storage to remove impurities adsorbed on the surface of the silicon blocks so that they meet the requirements of the integrated circuit industry.

[0003] The main sources of impurities on the surface of electronic-grade polysilicon are: 1. During the reduction and dismantling process, the silicon rods are exposed to the hall environment, and impurities in the air adhere to the surface of the silicon rods; 2. During the silicon rod crushing process, the crushing tools contact the silicon blocks and become contaminated with impurities; 3. The crushed silicon blocks have hidden cracks and tiny gaps that are invisible to the naked eye. During the transportation and storage process, impurities in the air or impurities brought by other tools will diffuse into the hidden cracks and gaps, and have a certain depth.

[0004] Most of the impurities can be removed through the subsequent silicon block cleaning process, that is, by etching the silicon block surface with mixed acid to peel off the surface, but the etching thickness is much smaller than the depth of the crack gap, and the impurities in it are difficult to remove. Increasing the etching depth to remove deep impurities will greatly increase silicon material loss, increase acid consumption, and reduce production efficiency. Therefore, how to effectively solve the impurities in impurity cracks and gaps is the top priority to ensure the quality requirements of electronic-grade polysilicon. Reducing the entry of impurities into the cracks and gaps of silicon blocks can effectively reduce the difficulty of subsequent cleaning, reduce cleaning costs, and improve product quality.

[0005] In actual production, it is found that the silicon material of polysilicon can be effectively sealed in the transportation and temporary storage process after crushing and before cleaning, which can reduce the impurity content on the surface and even in the cracks and gaps. The current electronic-grade polysilicon mainly uses silicon material boxes (pallet boxes) to store and transport silicon rods. The silicon material boxes are mostly made of low-pressure high-density polyethylene for one-time injection molding. They can be operated in four directions by mechanical or manual forklifts. They are easy to store, stackable, and can be equipped with wheels. The silicon material box only has the functions of temporary storage and transportation, and does not take into account the equipment and facilities for impurity contamination during transportation and temporary storage. Summary of the invention

[0006] The object of the present invention is to provide an electronic-grade polysilicon material temporary storage system.

[0007] The present invention is implemented by the following technical solutions:

[0008] An electronic grade polysilicon material temporary storage system, comprising a plurality of storage structures and a high-purity water system;

[0009] The storage structure comprises a silicon material box body and a box cover, wherein the box cover is placed on the top of the silicon material box body, a water inlet pipe and an overflow pipe are connected to both sides of the upper half of the silicon material box body, and a drainage pipe is connected to the side of the lower half of the silicon material box body, and a silicon material box pipeline electric control valve is provided on the water inlet pipe, the overflow pipe and the drainage pipe;

[0010] The high-purity water system includes an inlet main pipe, a return main pipe, an inlet branch pipe, and a return branch pipe. The inlet main pipe is connected to a plurality of the inlet branch pipes, and the return main pipe is connected to a plurality of the return branch pipes. The inlet branch pipes and the return branch pipes are respectively provided with branch pipe electric-controlled valves. A storage structure is arranged between a pair of the inlet branch pipes and the return branch pipes. The inlet branch pipe is connected to the inlet pipe through a quick connector, and the return branch pipe is respectively connected to the overflow pipe and the drain pipe through a quick connector.

[0011] Preferably, a plurality of supporting legs distributed in a matrix are fixed to the bottom of the silicon material box.

[0012] Preferably, a controller is further included, and the controller is electrically connected to the silicon material box pipeline electric control valve and the branch pipe electric control valve respectively.

[0013] Preferably, it also includes an electronic flow meter, which is arranged on the return water branch pipe between the overflow pipe and the drain pipe; the signal transmission end of the electronic flow meter is connected to the signal receiving end of the controller.

[0014] Preferably, a conductivity meter is further included, and a monitoring probe of the conductivity meter passes through the box cover and is placed in the silicon material box; a signal transmission end of the conductivity meter is connected to a signal receiving end of the controller.

[0015] Advantages of the present invention: The present invention realizes high-purity water liquid sealing of silicon materials or silicon rods through the water inlet, overflow and outlet settings of the silicon material box, in conjunction with a high-purity water system, which can prevent electronic-grade polysilicon from being polluted by the environment during storage and transportation, and reduce the workload of subsequent cleaning processes. The high-purity water liquid seal can effectively prevent air impurities from entering cracks and gaps, thereby effectively controlling the depth of impurity diffusion into the silicon block, allowing the impurities to remain on the surface at a shallower level, and reducing the etching thickness when mixed acid etching is used in the subsequent cleaning process.

[0016] By reducing the etching thickness, the cleaning time and cleaning process can be reduced, and production efficiency can be improved; reducing the etching thickness can increase the yield rate; by avoiding pollution, quality risks can be reduced; the amount of acid used can be reduced, reducing production costs; reducing waste acid treatment, which is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 It is a structural schematic diagram of the storage structure of the present invention.

[0020] Figure 3 It is a control block diagram of the present invention.

[0021] In the figure: storage structure 1, silicon material box body 1.1, box cover 1.2, water inlet pipe 1.3, overflow pipe 1.4, drain pipe 1.5, silicon material box pipeline electric control valve 1.6, high-purity water system 2, water inlet main pipe 2.1, return water main pipe 2.2, water inlet branch pipe 2.3, return water branch pipe 2.4, branch pipe electric control valve 2.5, support leg 3, controller 4, electronic flow meter 5, conductivity meter 6. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 , Figure 2 , Figure 3 As shown, an electronic grade polysilicon material temporary storage system includes a plurality of storage structures 1 and a high-purity water system 2;

[0025] The storage structure 1 includes a silicon material box 1.1 and a box cover 1.2. The silicon material box 1.1 and the box cover 1.2 are preferably made of low-pressure high-density polyethylene (HDPE) material and are injection molded in one step. They are acid-resistant, alkali-resistant, leak-proof, impact-resistant, and have high strength. The box cover 1.2 is placed on the top of the silicon material box 1.1. By opening the box cover 1.2, silicon rods or silicon materials can be placed inside the silicon material box 1.1. A water level scale line is provided near the top of the silicon material box 1.1, and the height of the silicon rods or silicon materials should be lower than the water level scale line. The upper half of the silicon material box 1.1 is connected to a water inlet pipe 1.3 and an overflow pipe 1.4 on both sides, and the lower half of the silicon material box 1.1 is connected to a drain pipe 1.5 on the side. The water inlet pipe 1.3, the overflow pipe 1.4, and the drain pipe 1.5 are all provided with a silicon material box pipeline electric control valve 1.6.

[0026] High-purity water is injected into the material box 1.1 from the water inlet pipe 1.3 until it overflows from the overflow pipe 1.4, so that the high-purity water covers the silicon rods or silicon materials. The silicon rods or silicon materials are sealed with high-purity water to avoid contamination by impurities and facilitate storage; the silicon material box pipeline electric control valve 1.6 can open and close the water inlet pipe 1.3, the overflow pipe 1.4 and the drain pipe 1.5 to avoid water leakage when closed, which is convenient for transportation; after use, the sealed high-purity water can be discharged through the drain pipe 1.5.

[0027] A plurality of support legs 3 arranged in a matrix are fixed to the bottom of the silicon material box 1.1. The support legs 3 are arranged to form front, back and both sides to be transparent, so as to facilitate four-way operation by mechanical or manual forklifts.

[0028] The high-purity water system 2 includes an inlet main pipeline 2.1, a return water main pipeline 2.2, an inlet branch pipeline 2.3, and a return water branch pipeline 2.4. The inlet main pipeline 2.1 is connected to a plurality of inlet branch pipelines 2.3, and the return water main pipeline 2.2 is connected to a plurality of return water branch pipelines 2.4. The inlet branch pipelines 2.3 and the return water branch pipelines 2.4 are respectively provided with branch pipe electric control valves 2.5. A storage structure 1 is set between a pair of inlet branch pipelines 2.3 and the return water branch pipelines 2.4. The inlet branch pipeline 2.3 is connected to the inlet pipe 1.3 through a quick connector, and the return water branch pipeline 2.4 is respectively connected to the overflow pipe 1.4 and the drain pipe 1.5 through a quick connector.

[0029] When high-purity water is connected or stored, multiple storage structures 1 can be directly connected to the water inlet main pipe 2.1 and the water return main pipe 2.2, and each storage structure 1 is placed between a pair of water inlet branch pipes 2.3 and a water return branch pipe 2.4; the branch pipe electric control valve 2.5 is opened, and the high-purity water of the water inlet main pipe 2.1 is injected into the silicon material box 1.1 from the water inlet pipe 1.3 through the water inlet branch pipe 2.3, and the high-purity water overflowing from the overflow pipe 1.4 and the high-purity water discharged from the drain pipe 1.5 both flow from the return branch pipe 2.4 to the return main pipe 2.2; when the high-purity water in the silicon material box 1.1 reaches the water level requirement, the branch pipe electric control valve 2.5 can be closed.

[0030] It also includes a controller 4, which is electrically connected to the silicon material box pipeline electric control valve 1.6 and the branch pipe electric control valve 2.5 respectively. The controller 4 is a PLC controller that can control the switching of the silicon material box pipeline electric control valve 1.6 and the branch pipe electric control valve 2.5.

[0031] It also includes an electronic flow meter 5, which is arranged on the return water branch pipe 2.4 between the overflow pipe 1.4 and the drain pipe 1.5; the signal transmission end of the electronic flow meter 5 is connected to the signal receiving end of the controller 4, and the electronic flow meter 5 detects whether there is high water overflow in the overflow pipe 1.4. If water overflows, the signal is sent to the controller 4, and then the silicon material box pipeline electric control valve 1.6 and the branch pipe electric control valve 2.5 are controlled to close, thereby realizing automatic control.

[0032] In order to ensure that the high-purity water is always effectively sealed to isolate impurities, the high-purity water can be regularly replenished and replaced in the silicon material box 1.1 to ensure the purity of the high-purity water and avoid the high-purity water being polluted by the environment and then contaminating the silicon blocks and silicon materials sealed by ultrapure water. The hourly water replenishment volume L=K*X*V. K is the environmental pollution coefficient, that is, the environmental particle size is detected by a particle size detector, and the environment is graded according to the number of particles N with a particle size of 0.1um to 5.0um in the test results, which are divided into 100 levels (N<3500), 1000 levels (N<35000), and 10000 levels (N<350000), and the coefficients correspond to 1, 2, and 3 respectively; X is the coefficient corresponding to the product grade, the first, second, and third levels (according to the purity classification of industry standards), and the coefficients correspond to 1, 0.5, and 0.25 respectively; V is the effective volume of the silicon material box. For example: the environmental particle size N=35000, the first-level product, its water replenishment volume L=2*1*V.

[0033] It also includes a conductivity meter 6, the monitoring probe of the conductivity meter 6 passes through the box cover 1.2 and is placed in the silicon material box 1.1, and the monitoring probe of the conductivity meter 6 extends into the high-purity water. The conductivity meter 6 automatically detects the conductivity in the silicon material box 1.1 regularly. When the conductivity is higher than 0.065μS / cm, the silicon material box pipeline electric control valve 1.6 and the branch pipe electric control valve 2.5 are opened to replenish fresh high-purity water, which is another way to ensure the purity of the high-purity water; the signal transmission end of the conductivity meter 6 is connected to the signal receiving end of the controller 4. When the conductivity meter 6 detects that the conductivity increases, the signal is given to the controller 4 to control the silicon material box pipeline electric control valve 1.6 and the branch pipe electric control valve 2.5 to open, replenish fresh high-purity water, realize automatic control of water replenishment, and ensure the effect of the water seal.

[0034] Working principle:

[0035] The storage structure 1 is placed between a pair of water inlet branch pipes 2.3 and a water return branch pipe 2.4; the branch pipe electric control valve 2.5 and the silicon material box pipe electric control valve 1.6 are opened, and the high-purity water of the water inlet main pipe 2.1 is injected into the silicon material box 1.1 from the water inlet pipe 1.3 through the water inlet branch pipe 2.3 until it overflows from the overflow pipe 1.4, so that the high-purity water covers the silicon rods or silicon materials, and the branch pipe electric control valve 2.5 and the silicon material box pipe electric control valve 1.6 are closed, and the silicon rods or silicon materials are sealed with high-purity water to avoid contamination by impurities, which is conducive to storage;

[0036] The water inlet pipe 1.3, the overflow pipe 1.4 and the drain pipe 1.5 are closed through the silicon material box pipeline electric control valve 1.6 to avoid water leakage, and the silicon material box body 1.1 is taken away separately to facilitate transportation.

[0037] The high-purity water overflowing from the overflow pipe 1.4 and the high-purity water discharged from the drain pipe 1.5 both flow from the return water branch pipe 2.4 to the return water main pipe 2.2.

[0038] The present invention can prevent electronic-grade polysilicon from being polluted by the environment during storage and transportation by sealing silicon materials or silicon rods with high-purity water, thereby reducing the workload of subsequent cleaning processes. The high-purity water seal can effectively prevent air impurities from entering crack gaps, thereby effectively controlling the depth of impurity diffusion into the silicon block, allowing the impurities to remain on the surface at a shallower level, and reducing the etching thickness when mixed acid etching is used in the subsequent cleaning process.

[0039] By reducing the etching thickness, the cleaning time and cleaning process can be reduced, and production efficiency can be improved; reducing the etching thickness can increase the yield rate; by avoiding pollution, quality risks can be reduced; the amount of acid used can be reduced, reducing production costs; reducing waste acid treatment, which is more environmentally friendly.

[0040] The experimental process of this embodiment is selected:

[0041] Storage structure 1: Silicon material box 1.1 Outer diameter 1300*1300*800mm, inner diameter 1200*1200*700mm. Dynamic load 2.3-2.5T, static load 5-5.5T, box material is HDPE. Scale line position: 680mm upward from the bottom of the box.

[0042] High-purity water system 2: The diameter of the inlet branch pipe 2.3 and the return branch pipe 2.4 is DN25, the diameter of the inlet main pipe 2.1 and the return main pipe 2.2 is DN50, the material is PTFE, and the water pressure is 0.03-0.05 MPa.

[0043] The silicon blocks (silicon rods / silicon materials) used in this embodiment are all products of the same silicon rod produced in the same reduction furnace at the same time, that is, the surface impurities of the original body are basically the same. The crushing method is the same, and the manual crushing method is adopted. Samples Z1-Z9 are silicon blocks stored conventionally, and S1-S9 are silicon blocks stored by this method. The sizes of the silicon blocks are all controlled within 25-50 mm. They are all first-class products. The particle size of the storage environment (particle size of 0.1um to 5.0um) is 3500 < N < 35000, and the environmental coefficient is 2.

[0044] Detection method:

[0045] C: Determination of carbon and oxygen content in silicon single crystal - Low temperature Fourier transform infrared spectroscopy method in GBT35306-2017

[0046] Donor-acceptor impurities: Determination of group III and V impurity contents in silicon single crystal - Low temperature Fourier transform infrared spectroscopy method in GBT24581-2022

[0047] Surface metals: Determination of surface metal impurities in polysilicon by inductively coupled plasma mass spectrometry with acid leaching in GB∕T24582-2009

[0048] Cleaning (acid pickling) process:

[0049] Adopt the process flow of high-purity water rinsing (resistivity after cleaning is 8-10 MΩ / cm) - alkali washing - high-purity water rinsing (resistivity after cleaning is 8-10 MΩ / cm) - etching with mixed acid (nitric acid plus hydrofluoric acid) - high-purity water rinsing (resistivity after cleaning is 8-10 MΩ / cm) - drying. The cleaning cycle is determined according to different etching thicknesses. In this comparative example 1, it is not cleaned. In comparative example 2, the cleaning cycle is 180 s, and in comparative example 3, the cleaning cycle is 360 s.

[0050]

[0051] After comparison, the surface metal impurities of the silicon blocks stored by this method are much lower than those stored conventionally.

[0052] Using the same crushing, transportation, and cleaning methods, for the silicon blocks isolated by high-purity water liquid seal and the silicon blocks stored conventionally, when the cleaning etching thickness is 20μm, the difference is not significant; when not cleaned or the etching depth is small, the quality of the conventionally stored ones does not meet the standard, while the quality of the silicon blocks stored by this method meets the standard. Therefore, this method can greatly reduce the etching thickness, save costs, and improve efficiency.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electronic grade polysilicon material temporary storage system, characterized in that: Includes several storage structures and high purity water systems; The storage structure comprises a silicon material box body and a box cover, wherein the box cover is placed on the top of the silicon material box body, a water inlet pipe and an overflow pipe are connected to both sides of the upper half of the silicon material box body, and a drainage pipe is connected to the side of the lower half of the silicon material box body, and a silicon material box pipeline electric control valve is provided on the water inlet pipe, the overflow pipe and the drainage pipe; Open the box cover, and place silicon rods or silicon materials into the silicon material box. A water level mark is provided near the top of the silicon material box, and the height of the silicon rods or silicon materials should be lower than the water level mark. Injecting high-purity water into the silicon material box from the water inlet pipe until it overflows from the overflow pipe, so that the high-purity water covers the silicon rods or silicon materials, and the silicon rods or silicon materials are water-sealed by the high-purity water; The high-purity water system comprises an inlet main pipe, a return main pipe, an inlet branch pipe, and a return branch pipe. The inlet main pipe is connected with a plurality of inlet branch pipes, and the return main pipe is connected with a plurality of return branch pipes. The inlet branch pipes and the return branch pipes are respectively provided with branch pipe electric control valves. A storage structure is provided between a pair of the inlet branch pipes and the return branch pipes. The inlet branch pipes are connected to the inlet pipes through quick connectors, and the return branch pipes are respectively connected with the overflow pipe and the drain pipe through quick connectors. It also includes a conductivity meter for detecting the purity of high-purity water in the silicon material box, and a monitoring probe of the conductivity meter passes through the box cover and is placed in the silicon material box; It also includes a controller, which is electrically connected to the silicon material box pipeline electric control valve and the branch pipe electric control valve respectively, and the signal transmission end of the conductivity meter is connected to the signal receiving end of the controller.

2. The electronic grade polysilicon material temporary storage system according to claim 1, characterized in that: A plurality of supporting legs distributed in a matrix are fixed on the bottom of the silicon material box.

3. The electronic grade polysilicon material temporary storage system according to claim 2, characterized in that: It also includes an electronic flowmeter, which is arranged on the return water branch pipe between the overflow pipe and the drain pipe; the signal transmission end of the electronic flowmeter is connected to the signal receiving end of the controller.

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