Preparation method of black silicon
By using two induced processing methods of focused and negatively defocused laser beams in the preparation of black silicon, micron- and nanometer-scale light-trapping structures are formed, which solves the problems of complex equipment and the use of dangerous chemicals in the existing technology and achieves efficient and safe black silicon preparation.
Patent Information
- Application Number
- CN202211154718.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-21
- Publication Date
- 2025-09-23
- Estimated Expiration
- 2042-09-21
AI Technical Summary
The existing black silicon preparation method requires complex laser processing equipment and uses hazardous chemicals, which makes the operation complicated and makes it difficult to achieve efficient and safe micro-nanostructure preparation.
A focused and negatively defocused laser beam is used to form micron- and nanometer-scale light-trapping structures on the surface of silicon-based materials. Through two induced processing steps, the material protection requirements are reduced, and a larger light spot is used to clean impurity accumulation, thereby improving processing efficiency.
It has achieved the efficient and safe formation of micron- and nanometer-scale light-trapping structures on the surface of silicon-based materials, with a light absorption rate of more than 93%, simplifying the laser processing process.
Smart Images
Figure CN115415664B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing black silicon. Background Art
[0002] There are many ways to prepare black silicon surfaces, including sol-gel methods, electronic etching, wet etching, dry etching, and laser processing. Laser processing can meet the requirements for arbitrary and controllable processing structures, as well as the high-precision processing structures. Secondly, laser processing has the advantages of being programmable, suitable for large-area processing, and environmentally friendly. In addition, laser processing has structural designability, which is conducive to the design and subsequent preparation of anti-reflection structure surfaces. Currently, there are two main laser processing methods for preparing silicon-based light-trapping structures: one is the "black silicon" technology, in which a pulsed laser directly scans the silicon-based material in a sulfur-based atmosphere (SF6, H2S, etc.) to produce a spike micron structure; the other is to irradiate the silicon-based material with a pulsed laser through a liquid environment (distilled water, sulfuric acid solution, etc.) to produce a columnar structure. However, both methods have drawbacks such as complex operation, complex laser equipment, and the presence of hazardous chemicals. Summary of the Invention
[0003] The method for preparing black silicon provided by the present invention can reduce the requirements for material protection during laser processing and reduce the use of hazardous chemicals.
[0004] The present invention provides a method for preparing black silicon, comprising:
[0005] After completing the induction processing of the previous processing path, the laser beam is focused to form a first light spot on the surface of the current processing path to perform the first induction processing on the current processing path, so that the surface of the current processing path forms a micron-level structure;
[0006] After the first induced processing is completed, the laser beam is used to form a second spot on the surface of the current processing path in a negative defocused manner to perform a second induced processing on the current processing path, so that the surface of the current processing path forms a nanoscale structure.
[0007] Optionally, a diameter of the second light spot is 1.15-2.5 times the diameter of the first light spot.
[0008] Optionally, the diameter of the first light spot is 40-60 μm, and the diameter of the second light spot is 70-100 μm.
[0009] Optionally, the distance between the previous processing path and the current processing path is 1 / 3-3 / 4 times the diameter of the first light spot.
[0010] Optionally, the distance between the previous processing path and the current processing path is 20-30 μm.
[0011] Optionally, the energy density of the first light spot is 0.7-2 J / cm 2 The energy density of the second spot is 0.3-0.5J / cm 2 .
[0012] Optionally, the laser output power used in the first induced processing and the second induced processing is 2-10W, the frequency is 200-400KHz, the pulse wavelength is less than 650nm, and the pulse width is less than 10ns.
[0013] Optionally, the current path includes multiple processing points, and during the first induced processing and the second induced processing, each processing point is processed using a light spot formed by 300-700 pulses.
[0014] Optionally, the number of pulses at each processing point during the second induced processing is greater than the number of pulses at each processing point during the first induced processing.
[0015] Optionally, during the first induction processing and the second induction processing, the material to be processed is set in an air atmosphere.
[0016] In the technical solution provided by the present invention, a focusing method is adopted during the first induction processing to form a first light spot with high energy density on the surface of the material to be processed, and a micron-level light-trapping structure is processed. A defocusing method is adopted during the second induction processing to form a second light spot with low energy density on the surface of the material to be processed, and a nanometer-level light-trapping structure is further formed on the surface of the micron-level light-trapping structure, thereby further improving the light absorption capacity of black silicon. At the same time, by adopting the technical solution provided by the present invention, when a larger second light spot is used for the second induction processing of the current processing path, the impurity accumulation of the next processing path is cleaned, thereby reducing the protection requirements of the material to be processed during the laser processing and improving the processing efficiency. The black silicon prepared by the technical solution of the present invention has a cone structure with a height of 3-10μm and a light absorption rate of more than 93% in the 400nm-2.5μm spectral range. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a flow chart of a method for preparing black silicon according to an embodiment of the present invention;
[0018] Figure 2 This is a scanning electron microscope photograph of black silicon prepared by the method for preparing black silicon according to another embodiment of the present invention. DETAILED DESCRIPTION
[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings 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 making creative efforts shall fall within the scope of protection of the present invention.
[0020] An embodiment of the present invention provides a method for preparing black silicon, comprising:
[0021] Step 100, after completing the induction processing of the previous processing path, focusing the laser beam to form a first spot on the surface of the current processing path, so as to perform the first induction processing on the current processing path, so that the surface of the current processing path forms a micron-scale structure;
[0022] In some embodiments, the surface of the material to be processed will be divided into multiple processing paths, and the multiple processing paths will be processed using the same processing method. In this embodiment, the processing method of the current processing path is described. The laser beam forms a first light spot on the surface of the current processing path in a focused manner, which means that the focal position of the laser is set on the surface of the material to be processed. Since the surface of the material to be processed usually has slight undulations, in order to reduce the movement of the follower head of the laser during the processing process, the corner point of the laser beam can be set at the average height of the surface of the material to be processed. In this way, the follower head does not need to follow in the height direction. During the processing, the distance between the surface of the material to be processed and the laser changes minimally. Even if there are slight undulations on the surface of the material to be processed, the energy density change of the light spot is within the allowable range.
[0023] Step 200, after the first induced processing is completed, the laser beam is formed into a second spot on the surface of the current processing path in a negative defocus manner to perform a second induced processing on the current processing path, so that the surface of the current processing path forms a nanoscale structure.
[0024] In some embodiments, negative defocus means that the focus of the laser beam is above the surface of the material to be processed, and positive defocus means that the focus of the laser beam is below the surface of the material to be processed, that is, the focus is inside the material to be processed. By adopting the defocusing method, the size of the second light spot formed on the surface of the material to be processed can be made larger. At the same time, the energy density of the second light spot is lower, which is conducive to the formation of a smaller nanoscale structure on the surface of the micron-scale structure. Although the positive defocusing method can also form a second light spot with a larger size and lower energy density, since the positive defocusing method causes the focus to be located inside the material to be processed, the higher energy at the focus will form cracks inside the material, causing the material to be cut. Therefore, the negative defocusing method is adopted in this embodiment instead of the positive defocusing method.
[0025] In the technical solution provided by the embodiment of the present invention, a focusing method is adopted during the first induction processing to form a first light spot with high energy density on the surface of the material to be processed, and a micron-level light-trapping structure is processed. A defocusing method is adopted during the second induction processing to form a second light spot with low energy density on the surface of the material to be processed, and a nanometer-level light-trapping structure is further formed on the surface of the micron-level light-trapping structure, thereby further improving the light absorption capacity of black silicon. At the same time, by adopting the technical solution provided by the embodiment of the present invention, when a larger second light spot is used for the second induction processing of the current processing path, the impurity accumulation of the next processing path is cleaned, thereby reducing the protection requirements of the material to be processed during the laser processing and improving the processing efficiency. The black silicon prepared by the technical solution of the embodiment of the present invention has a cone structure with a height of 3-10μm and a light absorption rate of more than 93% in the 400nm-2.5μm spectral range.
[0026] As an optional embodiment, the diameter of the second light spot is 1.15-2.5 times the diameter of the first light spot. In some embodiments, during the first induced processing of the first light spot, impurities will inevitably accumulate in the area outside the current processing path. In this embodiment, the diameter of the second light spot is set to 1.15-2.5 times the diameter of the first light spot, which can clean up the adjacent area outside the current processing path, thereby reducing the impact of accumulated impurities on the processing of the next processing path. As a preferred embodiment, the diameter of the first light spot is 40-60μm, and the diameter of the second light spot is 70-100μm.
[0027] As an optional embodiment, the distance between the previous processing path and the current processing path is 1 / 3-3 / 4 times the diameter of the first light spot. In some embodiments, since Gaussian spots are usually used for processing materials, the energy of the Gaussian spots is mainly concentrated around the central area. In order to improve the distribution uniformity of the micron-level structure, in this embodiment, the distance between the previous processing path and the current processing path is 1 / 3-3 / 4 times the diameter of the first light spot. At the same time, the smaller processing path spacing can also ensure that the second light spot covers the next processing path adjacent to the current processing path. Thus, while the current path is being induced for the second time, the next processing path is cleaned. As a preferred embodiment, the distance between the previous processing path and the current processing path is 20-30μm.
[0028] As an optional embodiment, the energy density of the first light spot is 0.7-2 J / cm 2 The energy density of the second spot is 0.3-0.5J / cm 2 In some embodiments, the energy density of the second light spot is much smaller than the energy density of the first light spot, which is conducive to forming a nanoscale structure on the surface of the microscale structure.
[0029] As an optional implementation, the laser output power used in the first induced processing and the second induced processing is 2-10W, the frequency is 200-400KHz, the pulse wavelength is less than 650nm, and the pulse width is less than 10ns.
[0030] As an optional embodiment, the current path includes multiple processing points. During the first and second induction processing, each processing point is processed using a spot formed by 300-700 pulses. In some embodiments, laser light is typically output in pulse form, i.e., laser light is output upon receipt of each pulse. In this embodiment, each processing point remains at a fixed position for 300-700 pulses, resulting in each processing point being processed by a spot formed by 300-700 pulses.
[0031] As an optional embodiment, the number of pulses at each processing point during the second induced processing is greater than the number of pulses at each processing point during the first induced processing. In some embodiments, the second induced processing uses lower energy and a greater number of pulses, which is beneficial for uniform distribution of the thermal field and for forming small and uniformly distributed nanoscale structures on the surface of the microscale structure.
[0032] As an optional embodiment, the material to be processed is placed in an air atmosphere during both the first and second induction processes. In some embodiments, the size of the second spot is larger than that of the first spot. During the second induction process of the current processing path, impurity accumulation in the next processing path will be cleared. Thus, the embodiment can achieve processing in an air atmosphere, without the need for a sulfur-based atmosphere (SF6, H2S, etc.) or a liquid environment (distilled water, sulfuric acid solution, etc.) for protection.
[0033] An exemplary embodiment of the present invention is provided below to illustrate the technical solution of the present invention:
[0034] This embodiment provides a method for rapidly fabricating large-area micron-nanometer black silicon structures. An ultrafast laser with a wavelength of 532 nm and a pulse width of 500 fs is used to process a silicon wafer area. The processing line spacing is 30 μm. For each processing line, the first scan uses a spot diameter of 50 μm and a spot density of 1 J / cm. 2 The number of single-point repeated spots is 500; the second scan uses a spot diameter of 80μm and a spot density of 0.3J / cm 2 , the number of single point repeated spots is 700. After all the processing is completed, the morphology of the light trapping structure is observed using a scanning electron microscope, such as Figure 2 In the magnified image, nanoscale structures can be seen growing on the conical microstructures.
[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.
Claims
1. A method for preparing black silicon, characterized in that: include: After completing the induction processing of the previous processing path, the laser beam is focused to form a first light spot on the surface of the current processing path to perform the first induction processing on the current processing path, so that the surface of the current processing path forms a micron-level structure; After the first induced processing is completed, the laser beam is used to form a second spot on the surface of the current processing path in a negative defocusing manner, so as to perform a second induced processing on the current processing path, so that the surface of the current processing path forms a nanoscale structure; Among them, when the second light spot induces the second processing of the current processing path, the impurities accumulated in the next processing path are cleaned; The diameter of the second light spot is 1.15-2.5 times the diameter of the first light spot; the energy density of the first light spot is 0.7-2 J / cm 2 The energy density of the second spot is 0.3-0.5J / cm 2 .
2. The method according to claim 1, characterized in that The diameter of the first light spot is 40-60 μm, and the diameter of the second light spot is 70-100 μm.
3. The method according to claim 1, characterized in that The distance between the previous processing path and the current processing path is 1 / 3-3 / 4 times the diameter of the first light spot.
4. The method according to claim 3, characterized in that The distance between the previous processing path and the current processing path is 20-30 μm.
5. The method according to claim 1, wherein The laser output power used in the first induction processing and the second induction processing is 2-10W, the frequency is 200-400KHz, the pulse wavelength is less than 650nm, and the pulse width is less than 10ns.
6. The method according to claim 1, wherein The current processing path includes multiple processing points. During the first induced processing and the second induced processing, each processing point is processed using a light spot formed by 300-700 pulses.
7. The method according to claim 1, characterized in that The number of pulses at each processing point during the second induced processing is greater than the number of pulses at each processing point during the first induced processing.
8. The method according to claim 1, characterized in that During the first induction process and the second induction process, the material to be processed is placed in an air atmosphere.
Citation Information
Patent Citations
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