A surface treatment method for a semiconductor polycrystalline silicon material

Abstract

The application relates to a surface treatment method of semiconductor polycrystalline silicon material, which comprises the steps of machining, ultrasonic cleaning, first acid pickling, ultrasonic cleaning, grinding, ultrasonic cleaning, second acid pickling, ultrasonic cleaning, CMP polishing and ultrasonic cleaning. After polishing, the application can achieve very perfect mirror surface effect, and the crystal boundary and the grain position do not have obvious levelness. The area and density of the surface grains of the raw material are not strictly required. The application can eliminate the levelness between the crystal boundary and the grain position for the raw materials of semiconductor polycrystalline silicon materials with different grain densities, the finished product effect can meet the market demand of the mirror surface effect, the production cost is saved, and the practicability is high.

Description

Technical Field

[0001] This invention relates to a surface treatment method for semiconductor polycrystalline silicon materials, belonging to the field of semiconductor polycrystalline silicon material processing technology. Background Technology

[0002] Polycrystalline silicon is a form of elemental silicon. When molten elemental silicon solidifies under supercooled conditions, silicon atoms arrange themselves into many crystal nuclei in the form of a diamond lattice. If these crystal nuclei grow into grains with different crystal orientations, these grains combine to crystallize into polycrystalline silicon.

[0003] Currently, manufacturers of polycrystalline silicon materials use different crystal pulling processes, resulting in varying surface grain sizes (...). Figure 1 The surface area of ​​polycrystalline silicon varies, and due to differences in material density, the resistance of grains and grain boundaries to acid corrosion differs. After ultrasonic cleaning of polycrystalline silicon, the surface is etched using a mixture of hydrofluoric acid and nitric acid. Finally, after ultrasonic cleaning and CMP mechanical-chemical polishing, different materials exhibit varying degrees of layering at the grain boundaries (grain-to-grain interfaces) on their mirror-like surfaces. Figure 2 The grain boundary is lower than the grain position, and the lower the density of the material, the more obvious the sense of layering.

[0004] The grain size of polycrystalline silicon materials produced by different manufacturers is as follows: Figure 3 , Figure 4 As shown in the figure, there is a significant difference in grain size; the grain boundaries of small-grained polycrystalline silicon materials processed by conventional methods are very small or indistinct (see...). Figure 6 Large-grained polycrystalline silicon materials, after being processed using conventional methods, will have very distinct grain boundaries (see...). Figure 5 ).

[0005] The current standard process is as follows:

[0006] Machining → Ultrasonic cleaning → Fine grinding → Ultrasonic cleaning → Acid pickling → Ultrasonic cleaning → CMP polishing → Ultrasonic cleaning.

[0007] Based on this, the present invention is proposed. Summary of the Invention

[0008] This invention addresses the shortcomings of existing technologies by providing a surface treatment method for semiconductor polycrystalline silicon materials, the main process of which is as follows:

[0009] Machining → Ultrasonic cleaning → First pickling → Ultrasonic cleaning → Grinding → Ultrasonic cleaning → Second pickling → Ultrasonic cleaning → CMP polishing → Ultrasonic cleaning.

[0010] The specific technical solution is as follows:

[0011] A surface treatment method for semiconductor polycrystalline silicon material includes the following steps:

[0012] Step 1: Machining the semiconductor polycrystalline silicon material to obtain a preliminary blank; using machine tools to process all the shapes according to the product drawings, ensuring that the dimensions meet the drawing requirements.

[0013] Step 2: Perform ultrasonic cleaning on the surface of the blank. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the blank after one ultrasonic cleaning.

[0014] After machining, oil stains, metal impurities and other contaminants will remain on the surface of the machine tool. The surface needs to be cleaned. Ultrasonic cleaning in step two is effective.

[0015] Step 3: Pickle the preform after the first ultrasonic cleaning using a mixed strong acid to obtain a preform after one pickling. In this step, the mixed strong acid is used to clean the surface, which can improve the surface gloss and smoothness. The main purpose of this pickling is to pre-treat the structure other than the top and bottom planes (including inner and outer diameters, hole structure, etc.). During the pickling process, keep the product moving up and down. After pickling, quickly rinse it with deionized water. Each time, keep the product moving up and down for 30-60 seconds.

[0016] Step 4: Perform ultrasonic cleaning on the initial pickling blank. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the initial cleaned blank after a second ultrasonic cleaning. After pickling, acid stains will remain on the surface of the product, which need to be neutralized by ultrasonic cleaning.

[0017] Step 5: Grind the initial blank after the second ultrasonic cleaning to obtain a blank. Since the upper and lower surfaces after machine processing need to remove the saw marks and surface damage caused by slicing, this invention has found through multiple experiments that grinding is the best way to remove them. It can effectively improve the warpage, flatness and parallelism of polycrystalline silicon, and achieve a fine grinding process before polishing.

[0018] Step 6: Perform ultrasonic cleaning on the surface of the blank. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the blank after three ultrasonic cleanings. The residual suspending agent, metal impurities, abrasive and other contaminants after grinding and processing need to be ultrasonically cleaned on the surface.

[0019] Step 7: The blank after three ultrasonic cleanings is pickled with a fine-washing acid to obtain a blank after a second pickling. The second pickling uses the fine-washing acid to further enhance the removal of abrasive and other impurities from the surface. Due to the differences in corrosion resistance between grain boundaries and grains, the ratio and type of fine-washing acid have a significant impact on the final polished texture. In this invention, by adding acetic acid to the fine-washing acid and adjusting and optimizing the acid solution ratio, the surface treatment effect can be improved.

[0020] Step 8: Perform ultrasonic cleaning on the blank after the second pickling. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the blank after three ultrasonic cleanings. Since acid stains will remain on the product surface after the fine pickling acid cleaning, ultrasonic cleaning is required to neutralize the residual acid on the surface.

[0021] Step 9: Perform double-sided mirror polishing on the blank after three ultrasonic cleanings to obtain the polished blank.

[0022] Step 10: Perform ultrasonic cleaning on the polished blank. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the finished product. If there is residual polishing solution on the surface after polishing, ultrasonic cleaning is required.

[0023] As an improvement to the above technical solution, in step two, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes.

[0024] Rinse at least three times with deionized water at a temperature of 50-60°C, rinse for 2 minutes at an ultrasonic frequency of 40 kHz, and rinse for 2 minutes at an ultrasonic frequency of 80 kHz.

[0025] The drying temperature is 100℃, and the drying time is 10 to 30 minutes;

[0026] As an improvement to the above technical solution, in step four, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes.

[0027] Rinse at least three times with deionized water at a temperature of 50-60°C, rinse for 2 minutes at an ultrasonic frequency of 40 kHz, and rinse for 2 minutes at an ultrasonic frequency of 80 kHz.

[0028] The drying temperature is 100℃ and the drying time is 10 to 30 minutes.

[0029] As an improvement to the above technical solution, in step three, the mixed strong acid contains HF and HNO3, with the mass fraction of HF in the mixed strong acid being 5% to 8% and the mass fraction of HNO3 in the mixed strong acid being 50-60%; the pickling time is 30 to 60 seconds, and after pickling, it is rinsed in deionized water at least twice.

[0030] As an improvement to the above technical solution, in step five, the amount of material removed by grinding is 50-60 μm, the grinding equipment is a double-sided grinding machine, the grinding disc is made of cast iron, the abrasive is 1000-1500 mesh alumina, and the grinding time is 30-60 min.

[0031] As an improvement to the above technical solution, in step seven, the washing acid contains HF, HNO3, and CH3COOH. The mass fraction of HF in the washing acid is 1-2%, the mass fraction of HNO3 in the washing acid is 10-20%, and the mass fraction of CH3COOH in the washing acid is 1-5%. The washing time is 30-60 seconds. After the washing is completed, the product is rinsed in deionized water at least twice. During the washing process, the product needs to be agitated up and down for 30-60 seconds.

[0032] As an improvement to the above technical solution, in step seven, the mass ratio of HF, HNO3, and CH3COOH in the washing acid is 3:30:5. Too much or too little CH3COOH will affect the final polished mirror surface; the grain boundaries are visible to the naked eye.

[0033] As an improvement to the above technical solution, in step nine, the polishing equipment is a CMP mechanical-chemical double-sided polishing machine, the polishing liquid is a silica polishing liquid, the mass fraction of silica in the polishing liquid is 1% to 3%, and the polishing time is 1 to 2 hours.

[0034] As an improvement to the above technical solution, in step six, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60°C, and the cleaning is performed at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes.

[0035] Rinse at least three times with deionized water at a temperature of 50-60°C, rinse for 2 minutes at an ultrasonic frequency of 40 kHz, and rinse for 2 minutes at an ultrasonic frequency of 80 kHz.

[0036] The drying temperature is 100℃ and the drying time is 10 to 30 minutes.

[0037] As an improvement to the above technical solution, in step eight, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60°C, and the cleaning is performed at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes.

[0038] Rinse at least three times with deionized water at a temperature of 50-60°C, rinse for 2 minutes at an ultrasonic frequency of 40 kHz, and rinse for 2 minutes at an ultrasonic frequency of 80 kHz.

[0039] The drying temperature is 100℃ and the drying time is 10 to 30 minutes.

[0040] As an improvement to the above technical solution, in step ten, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when cleaning with the alkaline cleaning agent is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes.

[0041] Rinse at least three times with deionized water at a temperature of 50-60°C, rinse for 2 minutes at an ultrasonic frequency of 40 kHz, and rinse for 2 minutes at an ultrasonic frequency of 80 kHz.

[0042] The drying temperature is 100℃ and the drying time is 10 to 30 minutes.

[0043] In this invention, regardless of the preceding steps (such as machining, initial pickling, grinding, secondary pickling, or CMP polishing), the same ultrasonic cleaning process can be used. The process parameters, alkaline cleaning agent, and two ultrasonic cleaning cycles at different frequencies all contribute to effective cleaning. In particular, rinsing at 40kHz and 80kHz ultrasonic frequencies separately during the ultrasonic cleaning process yields better results than rinsing solely at 80kHz.

[0044] In this invention, taking step ten as an example, after multiple experiments, it was found that rinsing at an ultrasonic frequency of 20kHz alone resulted in a greater than 10% chance (more than 2 out of 20 tests resulted in cracks) of corrosion voids in the semiconductor polycrystalline silicon material, and a greater than 5‰ chance of cracks, with crack lengths even exceeding 3cm. Rinsing at an ultrasonic frequency of 30kHz alone resulted in a greater than 3% chance of corrosion voids in the semiconductor polycrystalline silicon material, and a greater than 1‰ chance of cracks, with crack lengths not exceeding 1cm. Rinsing at ultrasonic frequencies of 40kHz and 80kHz alone did not result in corrosion voids or cracks in the semiconductor polycrystalline silicon material. Cleaning at only 40kHz typically required more than 16 minutes to achieve a clean result; cleaning at only 80kHz typically required more than 20 minutes to achieve a clean result.

[0045] In addition, in step seven, if CH3COOH in the washing acid is replaced with gluconic acid or citric acid, the cleaning effect is not as good as that of the present invention, and it cannot eliminate the sense of hierarchy between grain boundaries and grain positions.

[0046] The beneficial effects of this invention are:

[0047] 1. By using the above method in this invention, a very perfect mirror effect can be achieved after polishing, and there is no obvious sense of layering at the grain boundaries and grain positions.

[0048] 2. This invention does not impose stringent requirements on the area and density of the grains on the surface of the raw materials. Using this invention, in actual production processing, the layering between grain boundaries and grain positions can be eliminated for semiconductor polycrystalline silicon materials with different grain densities. The finished product can meet the market demand for a mirror-like finish, greatly saving production costs.

[0049] 3. The processing steps of this invention generally do not require producers to introduce new equipment, nor do they require separate time to retrain operators on new equipment processes. Furthermore, the adjusted and optimized process flow can meet production requirements, thus this invention has high practicality. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the grains and grain boundaries on the surface of existing polycrystalline silicon materials;

[0051] Figure 2 This is a magnified image of the actual object showing the location of the grain boundaries;

[0052] Figure 3 This is a surface image of a large-grain polycrystalline silicon material.

[0053] Figure 4 This is a physical image of the surface of a small-grained polycrystalline silicon material;

[0054] Figure 5 A surface finish image of large-grain polycrystalline silicon material after processing using conventional techniques;

[0055] Figure 6 A surface effect diagram of small-grained polycrystalline silicon material after processing using conventional processes;

[0056] Figure 7 The image shows the surface effect of polycrystalline silicon material after applying the surface treatment method of Example 1.

[0057] Figure 8 The formula for the fine washing acid is shown in the surface effect diagram of the polycrystalline silicon material after processing, corresponding to Formula 1.

[0058] Figure 9 The formula for the fine washing acid is shown in the surface effect diagram of the polycrystalline silicon material after processing, corresponding to Formula 2.

[0059] Figure 10 The formula for the fine washing acid is shown in the surface effect diagram of the polycrystalline silicon material after processing, corresponding to Formula 3.

[0060] Figure 11The formula for the fine washing acid is shown in the surface effect diagram of the polycrystalline silicon material after processing, corresponding to Formula 4.

[0061] Figure 12 The image shows the surface effect of the polycrystalline silicon material after applying the surface treatment method of Example 1.

[0062] Figure 13 The image shows the surface effect of the polycrystalline silicon material after applying the surface treatment method of Experiment Example 2. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0064] Example 1

[0065] 1) Obtain a blank by mechanically processing semiconductor polycrystalline silicon material.

[0066] 2) The surface of the billet is ultrasonically cleaned first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a billet after one ultrasonic cleaning. The alkaline cleaning agent is a 7.5% potassium hydroxide solution. The cleaning temperature is 55±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The billet is then rinsed at least three times with deionized water at 55±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0067] 3) The initial blank after ultrasonic cleaning is pickled with a mixed strong acid to obtain a initial blank after pickling; the mixed strong acid contains HF and HNO3, the mass fraction of HF in the mixed strong acid is 6.5%, and the mass fraction of HNO3 in the mixed strong acid is 55%; the pickling time is 40s, and after pickling, it is rinsed in deionized water at least twice.

[0068] 4) The initial pickled billet is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a billet after a second ultrasonic cleaning. The alkaline cleaning agent is a 7.5% potassium hydroxide solution. The cleaning temperature is 55±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The billet is then rinsed at least three times with deionized water at 55±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0069] 5) Grind the initial blank after the second ultrasonic cleaning to obtain a blank; the amount of material removed by grinding is 50-60μm. The grinding equipment is a double-sided grinding machine, the grinding disc is made of cast iron, the abrasive is 1200 mesh alumina, and the grinding time is 40min.

[0070] 6) The surface of the blank is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a blank after three ultrasonic cleanings. The alkaline cleaning agent is a 7.5% potassium hydroxide solution. The cleaning temperature is 55±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blank is then rinsed at least three times with deionized water at 55±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0071] 7) The blank after three ultrasonic cleanings is pickled with a fine pickling acid to obtain a blank after two picklings. The fine pickling acid contains HF, HNO3, and CH3COOH. The mass fraction of HF in the fine pickling acid is 1.5%, the mass fraction of HNO3 in the fine pickling acid is 15%, and the mass fraction of CH3COOH in the fine pickling acid is 2.5%. The pickling time is 40 seconds. After pickling, the blank is rinsed in deionized water at least twice.

[0072] 8) The blanks after the second pickling are ultrasonically cleaned. First, they are cleaned with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain blanks after three ultrasonic cleanings. The alkaline cleaning agent is a 7.5% potassium hydroxide solution. The temperature for cleaning with the alkaline cleaning agent is 55±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blanks are then rinsed at least three times with deionized water at 55±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0073] 9) The blank after three ultrasonic cleanings is subjected to double-sided mirror polishing to obtain the polished blank. The polishing equipment is a CMP mechanical and chemical double-sided polishing machine, the polishing liquid is a silica polishing liquid with a silica mass fraction of 2%, and the polishing time is 1.5h.

[0074] 10) The polished blank is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain the finished product. The alkaline cleaning agent is a 7.5% potassium hydroxide solution. The cleaning temperature is 55±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blank is then rinsed at least three times with deionized water at 55±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0075] The final product obtained in this embodiment achieves a very perfect mirror effect, and there is no obvious sense of layering at the grain boundaries and grain positions, such as Figure 7 As shown.

[0076] Example 2

[0077] 1) Obtain a blank by mechanically processing semiconductor polycrystalline silicon material.

[0078] 2) The surface of the billet is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a billet after one ultrasonic cleaning. The alkaline cleaning agent is a 10% potassium hydroxide solution. The cleaning temperature is 60±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The billet is then rinsed at least three times with deionized water at 60±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 10 minutes.

[0079] 3) The initial blank after ultrasonic cleaning is pickled with a mixed strong acid to obtain a pickled initial blank; the mixed strong acid contains HF and HNO3, the mass fraction of HF in the mixed strong acid is 8%, and the mass fraction of HNO3 in the mixed strong acid is 50%; the pickling time is 30s, and after pickling, it is rinsed in deionized water at least twice.

[0080] 4) The initial pickled billet is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a billet after a second ultrasonic cleaning. The alkaline cleaning agent is a 10% potassium hydroxide solution. The cleaning temperature is 60±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The billet is then rinsed at least three times with deionized water at 60±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0081] 5) Grind the initial blank after the second ultrasonic cleaning to obtain a blank; the amount of material removed by grinding is 50-60μm. The grinding equipment is a double-sided grinding machine, the grinding disc is made of cast iron, the abrasive is 1500 mesh alumina, and the grinding time is 30min.

[0082] 6) The surface of the blank is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a blank after three ultrasonic cleanings. The alkaline cleaning agent is a 10% potassium hydroxide solution. The cleaning temperature is 60±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blank is then rinsed at least three times with deionized water at 60±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0083] 7) The blank after three ultrasonic cleanings is pickled with a fine pickling acid to obtain a blank after two picklings. The fine pickling acid contains HF, HNO3, and CH3COOH. The mass fraction of HF in the fine pickling acid is 2%, the mass fraction of HNO3 in the fine pickling acid is 10%, and the mass fraction of CH3COOH in the fine pickling acid is 1%. The pickling time is 60s. After pickling, the blank is rinsed in deionized water at least twice.

[0084] 8) The blanks after the second pickling are ultrasonically cleaned. First, they are cleaned with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain blanks after three ultrasonic cleanings. The alkaline cleaning agent is a 10% potassium hydroxide solution. The temperature for cleaning with the alkaline cleaning agent is 60±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blanks are then rinsed at least three times with deionized water at 60±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0085] 9) The blank after three ultrasonic cleanings is subjected to double-sided mirror polishing to obtain the polished blank. The polishing equipment is a CMP mechanical and chemical double-sided polishing machine, the polishing liquid is a silica polishing liquid with a silica mass fraction of 3%, and the polishing time is 1 hour.

[0086] 10) The polished blank is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain the finished product. The alkaline cleaning agent is a 10% potassium hydroxide solution. The cleaning temperature is 60±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blank is then rinsed at least three times with deionized water at 60±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0087] Example 3

[0088] 1) Obtain a blank by mechanically processing semiconductor polycrystalline silicon material.

[0089] 2) The surface of the billet is ultrasonically cleaned first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a billet after one ultrasonic cleaning. The alkaline cleaning agent is a 5% potassium hydroxide solution. The cleaning temperature is 50±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The billet is then rinsed at least three times with deionized water at 50±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 30 minutes.

[0090] 3) The initial blank after ultrasonic cleaning is pickled with a mixed strong acid to obtain a pickled initial blank; the mixed strong acid contains HF and HNO3, the mass fraction of HF in the mixed strong acid is 5%, and the mass fraction of HNO3 in the mixed strong acid is 60%; the pickling time is 60s, and after pickling, it is rinsed in deionized water at least twice.

[0091] 4) The initial pickled billet is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a billet after a second ultrasonic cleaning. The alkaline cleaning agent is a 5% potassium hydroxide solution. The cleaning temperature is 50±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The billet is then rinsed at least three times with deionized water at 50±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 30 minutes.

[0092] 5) Grind the initial blank after the second ultrasonic cleaning to obtain a blank; the amount of material removed by grinding is 50-60μm. The grinding equipment is a double-sided grinding machine, the grinding disc is made of cast iron, the abrasive is 1000 mesh alumina, and the grinding time is 60min.

[0093] 6) The surface of the blank is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain a blank after three ultrasonic cleanings. The alkaline cleaning agent is a 5% potassium hydroxide solution. The cleaning temperature is 50±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blank is then rinsed at least three times with deionized water at 50±2℃, rinsing at 40kHz for 2 minutes, and then rinsing at 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0094] 7) The blank after three ultrasonic cleanings is pickled with a fine pickling acid to obtain a blank after two picklings. The fine pickling acid contains HF, HNO3, and CH3COOH. The mass fraction of HF in the fine pickling acid is 1%, the mass fraction of HNO3 in the fine pickling acid is 20%, and the mass fraction of CH3COOH in the fine pickling acid is 5%. The pickling time is 30 seconds. After pickling, the blank is rinsed in deionized water at least twice.

[0095] 8) The blanks after the second pickling are ultrasonically cleaned. First, they are cleaned with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain blanks after three ultrasonic cleanings. The alkaline cleaning agent is a 5% potassium hydroxide solution. The temperature for cleaning with the alkaline cleaning agent is 50±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blanks are then rinsed at least three times with deionized water at 50±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0096] 9) The blank after three ultrasonic cleanings is subjected to double-sided mirror polishing to obtain the polished blank. The polishing equipment is a CMP mechanical and chemical double-sided polishing machine, the polishing liquid is a silica polishing liquid with a silica mass fraction of 1%, and the polishing time is 2 hours.

[0097] 10) The polished blank is ultrasonically cleaned, first with an alkaline cleaning agent, then rinsed with deionized water, and finally dried to obtain the finished product. The alkaline cleaning agent is a 5% potassium hydroxide solution. The cleaning temperature is 50±2℃, and the ultrasonic frequency is 40kHz for 5 minutes, followed by 80kHz for 5 minutes. The blank is then rinsed at least three times with deionized water at 50±2℃, 40kHz for 2 minutes, and 80kHz for 2 minutes. The drying temperature is 100℃, and the drying time is 20 minutes.

[0098] Example 4

[0099] The proportion of CH3COOH in the washing acid in Example 1 was changed, while other conditions remained unchanged. The final surface effect of the polycrystalline silicon material after processing is shown in Table 1.

[0100] Table 1

[0101] HF concentration / % <![CDATA[HNO3 concentration / %]]> <![CDATA[CH3COOH concentration / %]]> Surface finish after processing Formula 1 1.5 15 0.1 See Figure 8 Formula 2 1.5 15 1 See Figure 9 Formula 3 1.5 15 5 See Figure 10 Formula 4 1.5 15 10 See Figure 11

[0102] Verification showed that, under constant concentration conditions, the best results were achieved when the concentration of acetic acid was between 1% and 5%, resulting in almost invisible grain boundaries on the final polished mirror surface.

[0103] Experimental Example 1

[0104] Compared to Example 1, this example only differs in that CH3COOH in the washing acid is replaced with gluconic acid; all other conditions remain unchanged. The final surface finish of the polycrystalline silicon material after processing is as follows. Figure 12 As shown.

[0105] Experimental Example 2

[0106] Compared to Example 1, this example only differs in that CH3COOH in the washing acid is replaced with citric acid; all other conditions remain unchanged. The final surface finish of the polycrystalline silicon material after processing is as follows: Figure 13 As shown.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A surface treatment method for semiconductor polycrystalline silicon material, characterized in that... Includes the following steps: Step 1: Machining the semiconductor polycrystalline silicon material to obtain a preliminary blank; Step 2: Perform ultrasonic cleaning on the surface of the blank. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the blank after one ultrasonic cleaning. Step 3: Pickling the preform after one ultrasonic cleaning with a mixed strong acid to obtain a preform after one pickling. Step 4: Perform ultrasonic cleaning on the billet after the first pickling. First, clean it with an alkaline cleaning agent, then rinse it with deionized water, and finally dry it to obtain the billet after the second ultrasonic cleaning. Step 5: Grind the blank after the second ultrasonic cleaning to obtain a rough blank; Step 6: Perform ultrasonic cleaning on the surface of the blank. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the blank after three ultrasonic cleanings. Step 7: Use fine pickling acid to pickle the blank after three ultrasonic cleanings to obtain a blank after two picklings. Step 8: Perform ultrasonic cleaning on the blank after the second pickling. First, clean with an alkaline cleaning agent, then rinse with deionized water, and finally dry to obtain the blank after three ultrasonic cleanings. Step 9: Perform double-sided mirror polishing on the blank after three ultrasonic cleanings to obtain the polished blank. Step 10: Perform ultrasonic cleaning on the polished blank. First, clean it with an alkaline cleaning agent, then rinse it with deionized water, and finally dry it to obtain the finished product. In step three, the mixed strong acid contains HF and HNO3, with the mass fraction of HF in the mixed strong acid being 5%~8% and the mass fraction of HNO3 in the mixed strong acid being 50-60%; the pickling time is 30~60s, and after pickling, it is rinsed in deionized water at least twice; In step five, the amount of material removed by grinding is 50~60μm. The grinding equipment is a double-sided grinding machine, the grinding disc is made of cast iron, the abrasive is 1000-1500 mesh alumina, and the grinding time is 30~60min. In step seven, the washing acid contains HF, HNO3, and CH3COOH. The mass fraction of HF in the washing acid is 1-2%, the mass fraction of HNO3 in the washing acid is 10-20%, and the mass fraction of CH3COOH in the washing acid is 1-5%. The washing time is 30-60 seconds. After the washing is completed, the acid is rinsed in deionized water at least twice. In step nine, the polishing equipment is a CMP mechanical-chemical double-sided polishing machine, the polishing slurry is a silica polishing slurry with a silica mass fraction of 1% to 3%, and the polishing time is 1 to 2 hours.

2. The surface treatment method for semiconductor polycrystalline silicon material according to claim 1, characterized in that: In step two, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes. Rinse at least three times with deionized water at a temperature of 50-60℃, rinse for 2 minutes at an ultrasonic frequency of 40kHz, and rinse for 2 minutes at an ultrasonic frequency of 80kHz. The drying temperature is 100℃, and the drying time is 10~30min; And / or, In step four, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes. Rinse at least three times with deionized water at a temperature of 50-60℃, rinse for 2 minutes at an ultrasonic frequency of 40kHz, and rinse for 2 minutes at an ultrasonic frequency of 80kHz. The drying temperature is 100℃ and the drying time is 10~30min.

3. The surface treatment method for semiconductor polycrystalline silicon material according to claim 1, characterized in that: In step seven, the mass ratio of HF, HNO3, and CH3COOH in the washing acid is 3:30:

5.

4. The surface treatment method for semiconductor polycrystalline silicon material according to claim 1, characterized in that: In step six, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature for cleaning with the alkaline cleaning agent is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes. Rinse at least three times with deionized water at a temperature of 50-60℃, rinse for 2 minutes at an ultrasonic frequency of 40kHz, and rinse for 2 minutes at an ultrasonic frequency of 80kHz. The drying temperature is 100℃ and the drying time is 10~30min.

5. The surface treatment method for semiconductor polycrystalline silicon material according to claim 1, characterized in that: In step eight, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes. Rinse at least three times with deionized water at a temperature of 50-60℃, rinse for 2 minutes at an ultrasonic frequency of 40kHz, and rinse for 2 minutes at an ultrasonic frequency of 80kHz. The drying temperature is 100℃ and the drying time is 10~30min.

6. The surface treatment method for semiconductor polycrystalline silicon material according to claim 1, characterized in that: In step ten, the alkaline cleaning agent is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 5-10%. The temperature when using the alkaline cleaning agent for cleaning is 50-60℃, and the cleaning is carried out at an ultrasonic frequency of 40kHz for 5 minutes and at an ultrasonic frequency of 80kHz for 5 minutes. Rinse at least three times with deionized water at a temperature of 50-60℃, rinse for 2 minutes at an ultrasonic frequency of 40kHz, and rinse for 2 minutes at an ultrasonic frequency of 80kHz. The drying temperature is 100℃ and the drying time is 10~30min.

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