A method of dyeing and sorting heavily doped silicon material

Abstract

The application provides a method for dyeing and sorting heavily doped silicon materials, comprising the following steps: S1: loading the silicon materials to be sorted into a high-temperature-resistant container, then placing the high-temperature-resistant container into a heating device and performing vacuumizing treatment; S2: introducing argon and oxygen into the heating device of step S1, then heating the silicon materials to be sorted loaded into the high-temperature-resistant container in step S1 through the heating device, raising the temperature to 100-300 DEG C, and performing heat preservation; S3: sorting the silicon materials after furnace cooling in step S2, sorting out blue-black silicon materials and light brown silicon materials in the silicon materials, thereby obtaining qualified silicon materials; wherein, P-type heavily doped silicon materials are blue-black, N-type heavily doped silicon materials are light brown, and the color of lightly doped silicon materials does not change. The method for dyeing and sorting heavily doped silicon materials can effectively dye and sort heavily doped silicon materials in silicon materials, and the application is environment-friendly, low in cost, suitable for large-scale industrial application, and has high commercial value.

Description

Technical Field

[0001] This invention relates to the field of silicon material processing and inspection, and more specifically, to a method for dyeing and sorting heavily doped silicon materials. Background Technology

[0002] With the development of the integrated circuit and photovoltaic industries, the demand for silicon raw materials is constantly increasing, and the quality requirements for silicon wafers are also becoming higher. In processing and recycling silicon fragments, in addition to removing impurities such as stones, metals, and fibers, it is also necessary to address the problem of silicon fragments mixed with high concentrations of P-type and N-type heavy dopants. Current sorting methods typically use instruments, but these instruments are costly, time-consuming, and inefficient, making them unsuitable for large-scale recycling of silicon fragments. Therefore, a more economical and efficient sorting method is urgently needed to solve this problem.

[0003] Chinese patent CN101021480A discloses a colorimetric method for detecting and sorting waste silicon. This method involves soaking the silicon material in a mixed acid solution to stain the heavily doped silicon, thereby achieving sorting of the heavily doped silicon. Chinese patent CN104624512A discloses a method for staining and sorting P-type and N-type heavily doped silicon. This method also requires preparing an etching solution using 55% hydrofluoric acid (11-13%), 70% nitric acid (950-1050%), and 85% phosphoric acid (9.5-10.5%). After soaking, the P-type and N-type heavily doped silicon are then stained and sorted. The operations described in these patents are environmentally unfriendly and have high sorting costs. They require strong acids such as hydrofluoric acid and nitric acid, and the processes are complex. Large-scale industrial application would also present significant challenges in subsequent processing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for dyeing and sorting heavily doped silicon materials, so as to solve the problems of high environmental pollution, high cost and complex process of sorting in the prior art, and to provide a method that can quickly sort P-type and N-type heavily doped silicon materials from qualified materials.

[0005] To address the above problems, this invention provides a method for dyeing and sorting heavily silicon-doped materials, comprising the following steps:

[0006] S1: The silicon material to be sorted is loaded into a high-temperature resistant container, then placed in a heating device and vacuumed.

[0007] S2: Argon and oxygen are introduced into the heating device of step S1, and then the silicon material to be sorted in the high-temperature resistant container in step S1 is heated to 100-300°C and kept at that temperature.

[0008] S3: The silicon material cooled in the furnace in step S2 is sorted to separate the blue-black silicon material and the light brown silicon material to obtain qualified silicon material; wherein, the P-type heavily doped silicon material is dyed blue-black, the N-type heavily doped silicon material is light brown, and the lightly doped silicon material has no color change.

[0009] Compared with the prior art, the present invention has at least the following technological advancements:

[0010] This invention provides a method for dyeing and sorting heavily doped silicon materials. Using this method, P-type and N-type heavily doped silicon materials can be quickly sorted based on their different types (low-concentration doping) and doping concentrations (high-concentration doping). Due to their different types, doping levels, and chemical potentials, these materials exhibit different oxidation rates under low-oxygen and low-temperature conditions. P-type and N-type heavily doped silicon materials are dyed different colors, thus improving sorting efficiency. This method eliminates the need for specialized sorting equipment, reducing production costs. It also overcomes the high pollution problem associated with pretreatment with strong acids before sorting in existing technologies. This invention provides an environmentally friendly method for dyeing and sorting heavily doped silicon materials, with simple operation steps, low requirements for reaction equipment, and high commercialization, industrialization, and promotion value.

[0011] As a preferred embodiment, in step S1, the silicon material is semiconductor or photovoltaic silicon scrap.

[0012] The method for dyeing and sorting heavily doped silicon material according to the present invention can be applied to the sorting of broken silicon material for semiconductors or photovoltaics in industry, and reduces the sorting cost.

[0013] As a preferred embodiment, in step S1, the high-temperature resistant container is a crucible, and the heating device is a vacuum furnace.

[0014] The use of a crucible to hold the silicon material to be sorted protects the silicon material compared to directly heating it, and the vacuum furnace facilitates the vacuuming of the reaction environment.

[0015] As a preferred embodiment, in step S2, the heating device must maintain an oxygen concentration of less than 10% during heating.

[0016] By controlling the oxygen concentration inside the heating device, the oxidation of silicon material can be better controlled, preventing excessive oxidation caused by excessive oxygen concentration and thus avoiding economic losses.

[0017] As a preferred embodiment, in step S2, the heating rate is 1-5°C.

[0018] As a preferred embodiment, in step S2, the temperature for heat preservation is 150°C.

[0019] As a preferred embodiment, in step S2, the heat preservation time is 0.5-2 hours.

[0020] In the present invention, a method for dyeing and sorting heavily doped silicon material addresses the issue that excessively high heating temperatures or rapid heating rates during the heating and holding process can negatively impact the silicon material surface. Excessive heating rates and temperatures can cause severe oxidation of all silicon material surfaces, turning them white, and may even lead to significant oxidation of qualified silicon material (non-heavily doped), resulting in economic losses. Conversely, excessively slow heating rates and low holding temperatures can also result in minimal surface changes in the heavily doped silicon material, making sorting impossible. Therefore, it is crucial to control the heating rate and time within the aforementioned range and to maintain these conditions within the preferred range. This allows for effective sorting of heavily doped silicon material while ensuring that qualified silicon material is not subjected to excessive surface oxidation.

[0021] The principle of the dyeing and sorting method for heavily silicon-doped materials of the present invention is as follows:

[0022] When silicon contains impurities, its electrochemical potential and surface activity differ, with heavily doped silicon exhibiting a higher electrochemical potential than lightly doped silicon. In a low-oxygen, low-temperature environment, low-concentration doped fragmented silicon and heavily doped silicon undergo selective oxidation during thermal oxidation. The heavily doped silicon reacts faster, preferentially forming a SiO2 film on its surface. As the SiO2 film thickens, the silicon surface color changes accordingly. Furthermore, because the types of impurities in the P-type and N-type silicon differ in heavily doped silicon, their electrochemical potentials also differ, resulting in different oxidation rates. The reacted P-type and N-type silicon exhibit different colors: the SiO2 film of heavily doped P-type silicon appears bluish-black, while that of heavily doped N-type silicon appears yellowish-brown. Lightly doped silicon shows no color change, making them easily distinguishable. Attached Figure Description

[0023] Figure 1 This is a color difference diagram between heavily doped silicon and lightly doped silicon after the silicon material reaction in an embodiment of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention discloses a method for dyeing and sorting heavily silicon-doped materials, comprising the following steps:

[0026] S1: The silicon material to be sorted is loaded into a high-temperature resistant container, then placed in a heating device and vacuumed.

[0027] S2: Argon and oxygen are introduced into the heating device of step S1, and then the silicon material to be sorted in the high-temperature resistant container in step S1 is heated to 100-300°C and kept at that temperature.

[0028] S3: The silicon material cooled in the furnace in step S2 is sorted to separate the blue-black silicon material and the light brown silicon material to obtain qualified silicon material; wherein, the P-type heavily doped silicon material is dyed blue-black, the N-type heavily doped silicon material is light brown, and the lightly doped silicon material has no color change.

[0029] Preferably, in step S1, the silicon material is semiconductor or photovoltaic silicon scrap.

[0030] Preferably, in step S1, the high-temperature resistant container is a crucible, and the heating device is a vacuum furnace.

[0031] Preferably, in step S2, the heating device needs to maintain an oxygen concentration of less than 10% during heating.

[0032] Preferably, in step S2, the heating rate is 1-5°C.

[0033] Preferably, in step S2, the temperature for heat preservation is 150°C.

[0034] Preferably, the heat preservation time is 0.5-2 hours.

[0035] The following embodiments, in conjunction with the above-mentioned data range, provide a further explanation of the present invention:

[0036] Example 1:

[0037] This embodiment discloses a method for dyeing and sorting heavily silicon-doped materials, including the following steps:

[0038] S1: Place the semiconductor or photovoltaic silicon scraps that need to be sorted into a high-temperature resistant crucible, then put it into a heating furnace and evacuate it;

[0039] S2: Heat the silicon fragments in the vacuum furnace from step S1. Before heating, introduce argon and oxygen, with the oxygen concentration being less than 10%. The heating rate is 3 degrees Celsius / minute, and the temperature is raised to 150 degrees Celsius. The temperature is held for 1 hour, and then cooled with the furnace to allow the silicon fragments to undergo an oxidation reaction with the oxygen.

[0040] When silicon contains impurities, its electrochemical potential and surface activity differ, with heavily doped silicon exhibiting a higher electrochemical potential than lightly doped silicon. In a low-oxygen, low-temperature environment, low-concentration doped fragmented silicon and heavily doped silicon undergo selective oxidation reactions during thermal oxidation. The heavily doped silicon reacts faster, preferentially forming a SiO2 film on its surface. The color of the silicon surface changes with the thickness of the SiO2 film, thus altering the silicon's color. Furthermore, because the types of P-type and N-type impurities in the heavily doped silicon differ, their electrochemical potentials also differ, resulting in different oxidation rates.

[0041] The reacted P-type and N-type silicon materials exhibit different colors. The heavily doped P-type silicon material is blue-black, the heavily doped N-type silicon material is light brown, while the lightly doped silicon material shows no color change.

[0042] S3: After the reaction of the broken silicon material in step S2 is completed, the blue-black P-type heavy doped silicon material and the light brown N-type heavy doped silicon material in the broken silicon material are sorted out to obtain qualified silicon material.

[0043] Example 2:

[0044] This embodiment discloses a method for dyeing and sorting heavily silicon-doped materials, including the following steps:

[0045] S1: Place the semiconductor or photovoltaic silicon scraps that need to be sorted into a high-temperature resistant crucible, then put it into a heating furnace and evacuate it;

[0046] S2: Heat the silicon fragments in the vacuum furnace from step S1. Before heating, introduce argon and oxygen, with the oxygen concentration being less than 10%. The heating rate is 5 degrees Celsius / minute, and the temperature is raised to 300 degrees Celsius. The temperature is held for 2 hours, and then cooled with the furnace to allow the silicon fragments to undergo an oxidation reaction with the oxygen.

[0047] When silicon contains impurities, its electrochemical potential and surface activity differ, with heavily doped silicon exhibiting a higher electrochemical potential than lightly doped silicon. In a low-oxygen, low-temperature environment, low-concentration doped fragmented silicon and heavily doped silicon undergo selective oxidation reactions during thermal oxidation. The heavily doped silicon reacts faster, preferentially forming a SiO2 film on its surface. The color of the silicon surface changes with the thickness of the SiO2 film, thus altering the silicon's color. Furthermore, because the types of P-type and N-type impurities in the heavily doped silicon differ, their electrochemical potentials also differ, resulting in different oxidation rates.

[0048] The reacted P-type and N-type silicon materials exhibit different colors. The heavily doped P-type silicon material is blue-black, the heavily doped N-type silicon material is light brown, while the lightly doped silicon material shows no color change.

[0049] S3: After the reaction of the broken silicon material in step S2 is completed, the blue-black P-type heavy doped silicon material and the light brown N-type heavy doped silicon material in the broken silicon material are sorted out to obtain qualified silicon material.

[0050] Example 3:

[0051] This embodiment discloses a method for dyeing and sorting heavily silicon-doped materials, including the following steps:

[0052] S1: Place the semiconductor or photovoltaic silicon scraps that need to be sorted into a high-temperature resistant crucible, then put it into a heating furnace and evacuate it;

[0053] S2: Heat the silicon fragments in the vacuum furnace from step S1. Before heating, introduce argon and oxygen, with the oxygen concentration being less than 10%. The heating rate is 1 degree / minute, and the temperature is raised to 100 degrees. The temperature is held for 0.5 hours, and then cooled with the furnace to allow the silicon fragments to undergo an oxidation reaction with the oxygen.

[0054] When silicon contains impurities, its electrochemical potential and surface activity differ, with heavily doped silicon exhibiting a higher electrochemical potential than lightly doped silicon. In a low-oxygen, low-temperature environment, low-concentration doped fragmented silicon and heavily doped silicon undergo selective oxidation reactions during thermal oxidation. The heavily doped silicon reacts faster, preferentially forming a SiO2 film on its surface. The color of the silicon surface changes with the thickness of the SiO2 film, thus altering the silicon's color. Furthermore, because the types of P-type and N-type impurities in the heavily doped silicon differ, their electrochemical potentials also differ, resulting in different oxidation rates.

[0055] The reacted P-type and N-type silicon materials exhibit different colors. The heavily doped P-type silicon material is blue-black, the heavily doped N-type silicon material is light brown, while the lightly doped silicon material shows no color change.

[0056] S3: After the reaction of the broken silicon material in step S2 is completed, the blue-black P-type heavy doped silicon material and the light brown N-type heavy doped silicon material in the broken silicon material are sorted out to obtain qualified silicon material.

[0057] The sorting results of Examples 1-3 of the present invention were measured, and the sorting rate was >98%.

[0058] The reacted silicon fragments are sorted using an automatic sorting machine. Based on image processing and pattern recognition technology, the sorting machine can identify colored areas in the silicon and separate them from the normal areas, quickly separating silicon fragments of different colors. Sorting rate = weight of sorted heavily doped silicon / actual weight of heavily doped silicon contained in the silicon. Figure 1The reaction of the crushed silicon material showed a significant color difference between the heavily doped and lightly doped silicon materials. The sorting results of the heavily doped silicon materials in Examples 1-3 are shown in the table below. The silicon materials to be sorted in Examples 1-3 were from different batches, and there were differences in the P-type and N-type heavily doped silicon materials contained within them.

[0059] Example 1 36.1％ 63.2％ 99.3％ Example 2 56.5％ 42.6％ 99.1％ Example 3 23.6％ 75.2％ 98.8％

[0060] In summary, the above embodiments further demonstrate that the method for dyeing and sorting heavily doped silicon material of the present invention provides an environmentally friendly silicon material sorting method. Furthermore, the present invention has a high sorting rate, requires no complex operations or equipment, and possesses high commercial and industrial value, making it suitable for large-scale promotion and utilization.

[0061] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for dyeing and sorting heavily silicon-doped materials, characterized in that: Includes the following steps: S1: The silicon material to be sorted is loaded into a high-temperature resistant container, then placed in a heating device and vacuumed; S2: Argon and oxygen are introduced into the heating device of step S1, and then the silicon material to be sorted in the high-temperature resistant container of step S1 is heated to 100-300℃ and kept at that temperature, and then cooled in the furnace; S3: The silicon material after being cooled in the furnace in step S2 is sorted to separate the blue-black silicon material and the light brown silicon material, thereby obtaining qualified silicon material; wherein, P-type heavily doped silicon material is dyed blue-black, N-type heavily doped silicon material is light brown, and lightly doped silicon material has no color change; In step S2, the heating device must maintain an oxygen concentration of less than 10% during heating.

2. The method for dyeing and sorting heavily silicon-doped materials according to claim 1, characterized in that: In step S1, the silicon material is shredded silicon material for semiconductors or photovoltaics.

3. The method for dyeing and sorting heavily silicon-doped materials according to claim 1, characterized in that: In step S1, the high-temperature resistant container is a crucible, and the heating device is a vacuum furnace.

4. The method for dyeing and sorting heavily silicon-doped materials according to claim 1, characterized in that: In step S2, the heating rate is 1-5°C / minute.

5. The method for dyeing and sorting heavily silicon-doped materials according to claim 1, characterized in that: In step S2, the insulation temperature is 150°C.

6. The method for dyeing and sorting heavily silicon-doped materials according to claim 1, characterized in that: In step S2, the heat preservation time is 0.5-2 hours.

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