An electronic grade silicon material cleaning device and method

Abstract

The present application relates to the technical field of polysilicon production, and particularly relates to an electronic-grade silicon material cleaning device and method, which comprises a first acid washing tank, a second acid washing tank, a third acid washing tank and a rectifying device, the rectifying device returns separated nitric acid to the first acid washing tank, hydrofluoric acid and water flow into the second acid washing tank, the rectifying device separates and circulates the acid liquid in the first acid washing tank, a first detection device detects the concentration of the nitric acid in the first acid washing tank, the flow of the nitric acid supplement port of the first acid washing tank is controlled according to the detection result, a second detection device detects the concentration of the hydrofluoric acid in the second acid washing tank, the flow of the nitric acid supplement in the first acid washing tank is controlled, so that the descending gradient of the nitric acid in the first acid washing tank and the ascending gradient of the hydrofluoric acid in the second acid washing tank are kept in an optimal range, which is helpful to control the effective concentration of the acid liquid, the concentration of the hydrofluoric acid in the second acid washing tank is increased, which is helpful to exert the etching capacity, improve the cleaning efficiency, reduce the use amount of the acid liquid and reduce the cost.

Description

Technical Field

[0001] This invention relates to the field of polysilicon production technology, specifically to an electronic-grade silicon material cleaning device and method. Background Technology

[0002] Electronic-grade polysilicon is a major raw material in the semiconductor industry. Silicon-based semiconductors are still the most widely used semiconductor materials and play a huge role in modern industry. Electronic-grade polysilicon is mostly produced using a modified Siemens process. The produced silicon rods need to be crushed into small pieces of silicon material of appropriate particle size and then cleaned to remove impurities that may be attached to the surface, in order to meet the downstream requirements for high-quality single crystal pulling. The mainstream process for cleaning silicon material is to use a mixed solution of nitric acid and hydrofluoric acid for etching. The silicon blocks are placed in an acid pickling basket and then placed in an acid pickling tank for surface etching. This production is batch production, with each batch of silicon material having a fixed weight, and multiple batches are taken in turn to enter the acid pickling tank for cleaning.

[0003] In the initial preparation of the mixed acid solution, high-purity nitric acid and high-purity hydrofluoric acid are mixed in a certain proportion using saturated solutions. However, after a period of production, the ratio of nitric acid to hydrofluoric acid in the acid solution changes due to the reaction between the acid and the silicon material. At the same time, the reaction produces water, which leads to a decrease in the effective concentration of the acid. This causes problems for the cleaning of silicon material in the second half of the batch.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides an electronic-grade silicon cleaning apparatus and method, thereby effectively solving the problems pointed out in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An electronic-grade silicon cleaning device, comprising:

[0008] The first pickling tank, the second pickling tank, and the third pickling tank are set up in sequence;

[0009] A distillation device is provided between the first pickling tank and the second pickling tank. The inlet of the distillation device is connected to the first pickling tank and is used to distill and separate nitric acid, hydrofluoric acid and water from the acid solution in the first pickling tank.

[0010] The first outlet of the distillation unit is connected to the first pickling tank, and is used to return the distilled nitric acid to the first pickling tank.

[0011] The second outlet of the distillation apparatus is connected to the second pickling tank, and is used to allow the distilled hydrofluoric acid and water to flow into the second pickling tank.

[0012] The first pickling tank is equipped with a first detection device for detecting the concentration of nitric acid in the first pickling tank, and the second pickling tank is equipped with a second detection device for detecting the concentration of hydrofluoric acid in the second pickling tank.

[0013] The first pickling tank is equipped with a nitric acid replenishment port that is connected to the first detection device.

[0014] Furthermore, the distillation apparatus is a distillation column.

[0015] The present invention also includes a method for cleaning electronic-grade silicon material, used in the electronic-grade silicon material cleaning apparatus described above, comprising:

[0016] The pickling solutions in the first pickling tank, the second pickling tank, and the third pickling tank are mixed in a specific ratio. The pickling solutions include hydrofluoric acid and nitric acid, wherein the ratio of hydrofluoric acid to nitric acid in the first pickling tank, the second pickling tank, and the third pickling tank gradually decreases.

[0017] The silicon material is sequentially placed into the first pickling tank, the second pickling tank, and the third pickling tank for pickling.

[0018] Start the distillation apparatus to distill and circulate the acid solution in the first pickling tank;

[0019] The concentration of nitric acid in the first pickling tank is detected by the first detection device, and the feed rate of nitric acid replenishment port is controlled according to the detection results.

[0020] The concentration of hydrofluoric acid in the second pickling tank is detected by the second detection device, and the ratio of the decreasing gradient of nitric acid concentration in the first pickling tank to the increasing gradient of hydrofluoric acid concentration in the second pickling tank is controlled within a set range.

[0021] Furthermore, the hydrofluoric acid and nitric acid ratios in the first pickling tank, the second pickling tank, and the third pickling tank are 1:5~1:15, 1:20~1:40, and 1:40~1:100, respectively.

[0022] Furthermore, the silicon material stays in the first pickling tank, the second pickling tank, and the third pickling tank for 100 to 500 seconds respectively.

[0023] Furthermore, the ratio of the decreasing gradient of nitric acid concentration in the first pickling tank to the increasing gradient of hydrofluoric acid concentration in the second pickling tank is controlled to be 1:1.3 to 1:1.5.

[0024] Furthermore, the feed rate at the inlet of the distillation unit is 0.1~0.3L / min.

[0025] Furthermore, the volume of the first pickling tank, the second pickling tank, and the third pickling tank is 50~300L.

[0026] Furthermore, a pump is provided between the inlet of the distillation apparatus and the first pickling tank for pumping the acid solution in the first pickling tank into the distillation apparatus.

[0027] Furthermore, the nitric acid replenishment port of the first pickling tank is equipped with a control valve, which is connected to the first detection device.

[0028] The technical solution of this invention achieves the following technical effects: A distillation device is provided between the first and second pickling tanks, which are a first pickling tank, a second pickling tank, and a third pickling tank. The separated nitric acid is returned to the first pickling tank, while hydrofluoric acid and water flow into the second pickling tank. The distillation device separates and circulates the acid solution in the first pickling tank. A first detection device detects the nitric acid concentration in the first pickling tank and controls the flow rate of the nitric acid replenishment port in the first pickling tank. A second detection device detects the hydrofluoric acid concentration in the second pickling tank. By controlling the flow rate of the replenished nitric acid in the first pickling tank, the descending gradient of nitric acid in the first pickling tank and the ascending gradient of hydrofluoric acid in the second pickling tank are kept within the optimal range. This helps control the effective concentration of the acid solution. The increased hydrofluoric acid concentration in the second pickling tank is beneficial for the etching ability, improving cleaning efficiency, reducing acid consumption, and lowering costs. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of an electronic-grade silicon material cleaning device;

[0031] Figure 2 This is a flowchart of a method for cleaning electronic-grade silicon material.

[0032] Reference numerals in the attached drawings: 1. First pickling tank; 2. Second pickling tank; 3. Third pickling tank; 4. Distillation apparatus; 5. First detection device; 6. Second detection device. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] like Figure 1 As shown: An electronic-grade silicon cleaning device, comprising:

[0036] The first pickling tank 1, the second pickling tank 2, and the third pickling tank 3 are set up in sequence. The concentration of acid in the third pickling tank 3 is lower than that in the first pickling tank 1 and the second pickling tank 2, so that the pickling process is relatively gentle and improves the appearance and color of the silicon material.

[0037] A distillation device 4 is provided between the first pickling tank 1 and the second pickling tank 2. The inlet of the distillation device 4 is connected to the first pickling tank 1 and is used to distill and separate nitric acid, hydrofluoric acid and water from the acid solution in the first pickling tank 1.

[0038] The first outlet of the distillation unit 4 is connected to the first pickling tank 1, which is used to return the distilled nitric acid to the first pickling tank 1;

[0039] The second outlet of the distillation apparatus 4 is connected to the second pickling tank 2, and is used to flow the distilled hydrofluoric acid and water into the second pickling tank 2; specifically, the acid solution in the first pickling tank 1 is distilled and circulated through the distillation apparatus 4.

[0040] The first pickling tank 1 is equipped with a first detection device 5 for detecting the concentration of nitric acid in the first pickling tank 1, and the second pickling tank 2 is equipped with a second detection device 6 for detecting the concentration of hydrofluoric acid in the second pickling tank 2.

[0041] The first pickling tank 1 is equipped with a nitric acid replenishment port connected to the first detection device 5. Specifically, based on the online detection results of the first detection device 5, the flow rate of nitric acid replenished through the nitric acid replenishment port is controlled so that the gradient of the decrease in nitric acid concentration in the first pickling tank 1 and the gradient of the increase in hydrofluoric acid concentration in the second pickling tank 2 are kept within a certain range. This helps to adjust the etching ability and maintain the stability of the cleaning effect.

[0042] In this embodiment, because 70% saturated nitric acid and 49% saturated hydrofluoric acid are used in the initial acid solution preparation, and water is generated during the etching of silicon, the concentration of nitric acid in the first pickling tank 1 decreases. Even if saturated nitric acid is added at the replenishment port, it is impossible to raise the overall concentration to the initial saturated state. Therefore, simply adding saturated nitric acid at the replenishment port will still reduce the concentration of nitric acid in the first pickling tank 1, which still causes problems for the subsequent batches of silicon cleaning. Therefore, this invention provides a distillation device 4 between the first pickling tank 1 and the second pickling tank 2. The distillation device 4 distills part of the nitric acid in the first pickling tank 1. The acid solution is distilled to separate nitric acid, hydrofluoric acid, and water. The separated nitric acid is returned to the first pickling tank 1, which helps to slow down the decrease in nitric acid concentration in the first pickling tank 1. The separated hydrofluoric acid and water flow into the second pickling tank 2, which helps to increase the concentration of hydrofluoric acid in the second pickling tank 2. The increased concentration of hydrofluoric acid in the second pickling tank 2 is conducive to the etching ability and improves the cleaning efficiency. By controlling the flow rate of nitric acid replenished in the first pickling tank 1, the decrease in nitric acid in the first pickling tank 1 and the increase in hydrofluoric acid in the second pickling tank 2 are kept within the optimal range, which helps to control the effective concentration of the acid solution and improve the cleaning efficiency and cleaning effect.

[0043] The system comprises a first pickling tank 1, a second pickling tank 2, and a third pickling tank 3. A distillation unit 4 is installed between the first and second pickling tanks 1 and 2. The distillation unit 4 returns the separated nitric acid to the first pickling tank 1, while hydrofluoric acid and water flow into the second pickling tank 2. The distillation unit 4 separates and circulates the acid solution in the first pickling tank 1. A first detection device 5 detects the concentration of nitric acid in the first pickling tank 1 and controls the flow rate of the nitric acid replenishment port in the first pickling tank 1. A second detection device 6 detects the concentration of hydrofluoric acid in the second pickling tank 2. By controlling the flow rate of nitric acid replenished in the first pickling tank 1, the decreasing gradient of nitric acid in the first pickling tank 1 and the increasing gradient of hydrofluoric acid in the second pickling tank 2 are kept within the optimal range. This helps to control the effective concentration of the acid solution. The increasing concentration of hydrofluoric acid in the second pickling tank 2 is beneficial to the etching ability, improves cleaning efficiency, reduces the amount of acid used, and reduces costs.

[0044] As a preferred embodiment of the above, the distillation device 4 is a distillation column. Specifically, the distillation column is made of stainless steel lined with PTFE or PVDF material, uses atmospheric pressure distillation, and has multiple trays inside for the distillation separation of nitric acid, hydrofluoric acid and water. The theoretical number of trays is 15-30, the reflux ratio is 3-6, and the top temperature is 110-118 degrees Celsius.

[0045] like Figure 2 As shown, the present invention also includes an electronic-grade silicon cleaning method for use in the electronic-grade silicon cleaning apparatus described above, comprising:

[0046] S10: The pickling solutions in the first pickling tank 1, the second pickling tank 2, and the third pickling tank 3 are prepared in a specific ratio. The pickling solutions include hydrofluoric acid and nitric acid. The ratio of hydrofluoric acid to nitric acid in the first pickling tank 1, the second pickling tank 2, and the third pickling tank 3 gradually decreases. In this step, as the pickling tanks progress, the concentration of hydrofluoric acid and nitric acid in the cleaning solution gradually decreases, which can reduce the corrosive effect on the silicon material surface, make the cleaning process more gentle, and help protect the quality of the silicon material surface.

[0047] S20: The silicon material is sequentially placed into the first pickling tank 1, the second pickling tank 2 and the third pickling tank 3 for pickling; and left for a certain period of time in each tank. This step, through continuous multiple cleaning processes, thoroughly removes various contaminants from the surface of the silicon material, ensuring the cleanliness of the surface.

[0048] S30: Start the distillation unit 4 to distill and circulate the acid in the first pickling tank 1; specifically, through distillation circulation, the acid in the first pickling tank 1 can be recovered and reused, which helps to reduce the waste of acid, improve the utilization efficiency of acid, and reduce the cost of the cleaning process.

[0049] S40: The concentration of nitric acid in the first pickling tank 1 is detected by the first detection device 5, and the feed rate of the nitric acid replenishment port is controlled according to the detection result. This step realizes the feedback mechanism, realizes the automatic monitoring and control of the concentration of nitric acid solution in the first pickling tank 1, improves production efficiency and consistency, accurately controls the feed rate of nitric acid replenishment port, and ensures that the concentration of nitric acid solution is always within the required range.

[0050] S50: The second detection device 6 detects the concentration of hydrofluoric acid in the second pickling tank 2 and controls the ratio of the decreasing gradient of nitric acid concentration in the first pickling tank 1 to the increasing gradient of hydrofluoric acid concentration in the second pickling tank 2 within a set range. Specifically, when the decreasing gradient of nitric acid concentration in the first pickling tank 1 is too large, the flow rate of the nitric acid replenishment port is increased; conversely, the flow rate of the nitric acid replenishment port is decreased. This makes the decreasing gradient of nitric acid concentration in the first pickling tank 1 and the increasing gradient of hydrofluoric acid concentration in the second pickling tank 2 controllable, improving cleaning efficiency, increasing production efficiency, and reducing costs.

[0051] By controlling the flow rate of nitric acid replenishment port in the first pickling tank 1, the ratio of the decreasing gradient of nitric acid concentration in the first pickling tank 1 to the increasing gradient of hydrofluoric acid concentration in the second pickling tank 2 is kept within a set range. This ensures that the concentration changes of different pickling solutions are relatively balanced during the pickling process, thereby improving the stability and controllability of the process, maintaining the stability of the cleaning effect, improving cleaning efficiency, reducing the amount of acid used, and reducing costs.

[0052] If the surface color does not meet the requirements, the remaining acid in the pickling tank is completely drained, and then new acid is added to start a new cleaning cycle.

[0053] As a preferred embodiment of the above embodiments, the hydrofluoric acid and nitric acid ratios in the first pickling tank 1, the second pickling tank 2, and the third pickling tank 3 are 1:5~1:15, 1:20~1:40, and 1:40~1:100, respectively. Specifically, by precisely controlling the ratios of hydrofluoric acid and nitric acid in different pickling tanks, a more accurate, efficient, and safe cleaning process can be achieved, meeting the special requirements for cleaning electronic-grade silicon materials and improving product quality and process stability.

[0054] In this embodiment, the silicon material stays in the first pickling tank 1, the second pickling tank 2, and the third pickling tank 3 for 100 to 500 seconds respectively. This step provides sufficient time for the silicon material to stay, ensuring that the cleaning agent reacts fully with the surface contaminants, thoroughly removing impurities and contaminants from the surface of the silicon material. This helps to improve cleaning efficiency and reduce the risk of residues in subsequent process steps.

[0055] Specifically, the ratio of the decreasing gradient of nitric acid concentration in the first pickling tank 1 to the increasing gradient of hydrofluoric acid concentration in the second pickling tank 2 is controlled to be 1:1.3 to 1:1.5. This step, by precisely controlling the changing ratio of nitric acid and hydrofluoric acid concentrations, optimizes the chemical reaction during the cleaning process, ensuring more effective cleaning of different contaminants on the silicon surface and improving the cleaning effect. On the other hand, the acid solution ratio remains relatively stable, avoiding process fluctuations caused by excessive concentration changes, thus improving the stability of the cleaning process and enhancing cleaning efficiency and quality.

[0056] As a preferred embodiment of the above, the feed rate at the inlet of the distillation unit 4 is 0.1~0.3L / min. By reasonably setting the feed rate, the acid solution is efficiently fractionated in the distillation unit 4 to remove impurities and impure substances, thereby improving cleaning efficiency and reducing residue.

[0057] In this embodiment, the volumes of the first pickling tank 1, the second pickling tank 2, and the third pickling tank 3 are 50~300L, which can flexibly adapt to different production scales, save resources, improve cleaning efficiency, reduce process interruptions, and improve consistency, thereby optimizing the process flow of electronic-grade silicon material cleaning.

[0058] A pump is installed between the inlet of the distillation device 4 and the first pickling tank 1 to pump the acid solution in the first pickling tank 1 into the distillation device 4, thereby achieving precise control of the acid flow rate, reducing acid waste, improving cleaning consistency and distillation effect, and thus optimizing the process flow of electronic-grade silicon material cleaning.

[0059] As a preferred embodiment of the above embodiment, the nitric acid replenishment port of the first pickling tank 1 is equipped with a control valve, which is connected to the first detection device 5 to realize the automated control of the nitric acid replenishment process. The first detection device 5 can monitor the concentration or level of nitric acid in the pickling tank. When the concentration is lower than or the level drops to a certain level, the detection device will send a signal to the control valve to automatically open the nitric acid replenishment port, thereby realizing timely replenishment of nitric acid, maintaining the appropriate concentration and level of nitric acid in the pickling tank, realizing the automated control of the nitric acid replenishment process, accurately controlling the nitric acid concentration, saving resources, and improving safety.

[0060] This method enables the continuous production of high-purity electronic-grade polycrystalline silicon, with a surface metal content of 20-50 pptw. It delays the deterioration of silicon surface color by 80%-120%. Traditional processes typically require 900 minutes of continuous cleaning before the silicon exhibits poor cleaning performance, while this new method extends the cleaning time to 1620-1980 minutes, extending the single-cycle cleaning period and effectively improving production efficiency. It also reduces acid consumption. This method offers high production efficiency, low cost, and extremely high purity, meeting the needs of semiconductor customers.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for cleaning electronic grade silicon material, the method comprising: The apparatus used in the method includes: ​ The first pickling tank, the second pickling tank, and the third pickling tank are set up in sequence; A distillation device is provided between the first pickling tank and the second pickling tank. The inlet of the distillation device is connected to the first pickling tank and is used to distill and separate nitric acid, hydrofluoric acid and water from the acid solution in the first pickling tank. The first outlet of the distillation unit is connected to the first pickling tank, and is used to return the distilled nitric acid to the first pickling tank. The second outlet of the distillation apparatus is connected to the second pickling tank, and is used to allow the distilled hydrofluoric acid and water to flow into the second pickling tank. The first pickling tank is equipped with a first detection device for detecting the concentration of nitric acid in the first pickling tank, and the second pickling tank is equipped with a second detection device for detecting the concentration of hydrofluoric acid in the second pickling tank. The first pickling tank is equipped with a nitric acid replenishment port connected to the first detection device; The steps of the method include: The pickling solutions in the first pickling tank, the second pickling tank, and the third pickling tank are mixed in a specific ratio. The pickling solutions include hydrofluoric acid and nitric acid, wherein the ratio of hydrofluoric acid to nitric acid in the first pickling tank, the second pickling tank, and the third pickling tank gradually decreases. The silicon material is sequentially placed into the first pickling tank, the second pickling tank, and the third pickling tank for pickling. Start the distillation apparatus to distill and circulate the acid solution in the first pickling tank; The concentration of nitric acid in the first pickling tank is detected by the first detection device, and the feed rate of nitric acid replenishment port is controlled according to the detection results. The concentration of hydrofluoric acid in the second pickling tank is detected by the second detection device, and the ratio of the decreasing gradient of nitric acid concentration in the first pickling tank to the increasing gradient of hydrofluoric acid concentration in the second pickling tank is controlled within a set range, wherein the increasing gradient ratio is 1:1.3 to 1:1.

5.

2. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. The distillation apparatus is a distillation column.

3. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. The hydrofluoric acid and nitric acid ratios in the first pickling tank, the second pickling tank, and the third pickling tank are 1:5~1:15, 1:20~1:40, and 1:40~1:100, respectively.

4. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. The silicon material stays in the first pickling tank, the second pickling tank, and the third pickling tank for 100 to 500 seconds, respectively.

5. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. The feed rate at the inlet of the distillation unit is 0.1~0.3L / min.

6. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. The volume of the first pickling tank, the second pickling tank, and the third pickling tank is 50~300L.

7. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. A pump is provided between the inlet of the distillation apparatus and the first pickling tank to pump the acid solution in the first pickling tank into the distillation apparatus.

8. The method of claim 1, wherein the electronic grade silicon material is cleaned by the method. The first pickling tank has a nitric acid replenishment port equipped with a control valve, which is connected to the first detection device.

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