Method for preparing single crystal silicon surface lattice structure by nanosecond laser irradiation

Abstract

The present invention relates to a method for preparing a lattice structure on the surface of single crystal silicon by nanosecond laser irradiation, and belongs to the field of micro-nano processing of material surfaces. The method comprises the following steps: ultrasonically cleaning the single crystal silicon in anhydrous ethanol and acetone in sequence; focusing the laser on the surface of the single crystal silicon, irradiating the surface of the single crystal silicon with nanosecond laser in an air environment with set laser irradiation parameters, and inducing the formation of a lattice structure on the surface of the single crystal silicon by utilizing the plasma etching effect induced by the laser irradiation and the change in the surface tension of the single crystal silicon caused by the laser irradiation. In addition, based on the difference in temperature accumulation under different laser pulse repetition frequencies, the controllable preparation of an ordered or disordered lattice structure on the surface of the single crystal silicon can be achieved. The present invention has the advantages of simple process flow and green environmental protection, and has potential application value in the fields of micro-nano optics, semiconductor industry, photovoltaic solar cells, etc.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano processing of material surfaces, and in particular to a method for preparing a single-crystal silicon surface lattice structure by nanosecond pulse laser irradiation, and has potential application value in the fields of micro-nano optics, semiconductor industry, photovoltaic solar cells, etc. Background Art

[0002] With its unique physical properties such as wear resistance, high temperature resistance, and easy doping, single crystal silicon has become a hot material in high-tech fields such as photovoltaic power generation systems, sensor technology, electronic products, and optical devices. Studies have shown that by preparing special surface micro-nano structures on the surface of single crystal silicon, its surface wettability, anti-reflection and other functional properties can be effectively regulated. Nevertheless, from the perspective of processing and preparation, how to develop new methods for efficient and controllable preparation of large-area micro-nano structures on the surface of single crystal silicon has become a technical problem that limits the widespread application of single crystal silicon.

[0003] As an efficient, environmentally friendly and flexible non-contact processing method, laser processing has become an effective means of micro-processing the surface of materials with the development of short / ultra-short pulse laser processing technology. For example, in 2017 "Optical Material" Vol. 72, 508-512 (Direct fabrication of cone array microstructure on monocrystalline silicon surface by femtosecond laser texturing), Quanji Wang et al. successfully obtained a quasi-uniform cone array microstructure on the surface of single-crystal silicon by femtosecond laser irradiation. However, the process flow of femtosecond laser processing is complicated and the cost is high. In contrast, the use of nanosecond laser processing can reduce the processing cost to a certain extent while ensuring the processing efficiency and processing quality. Therefore, it is undoubtedly more appropriate to use this method to realize the preparation of micro-nanostructures on the surface of single-crystal silicon. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a lattice structure on the surface of single-crystal silicon by nanosecond pulse laser irradiation, so as to solve the above-mentioned problems existing in the prior art. The present invention utilizes the plasma etching effect induced by laser irradiation and the resulting change in the surface tension of single-crystal silicon to induce the formation of a lattice structure on the surface of single-crystal silicon. In addition, based on the difference in temperature accumulation under different laser pulse repetition frequencies, the controllable preparation of ordered or disordered lattice structures on the surface of single-crystal silicon can be achieved. The present invention has the advantages of simple process flow and green environmental protection, and has potential application value in the fields of micro-nano optics, semiconductor industry, photovoltaic solar cells, etc. The above-mentioned purpose of the present invention is achieved by the following technical solutions:

[0005] A method for preparing a single crystal silicon surface lattice structure by nanosecond pulse laser irradiation, characterized in that it comprises the following steps:

[0006] (1) ultrasonically cleaning the single crystal silicon sample with anhydrous ethanol and acetone in sequence, and air-drying at room temperature to obtain a clean single crystal silicon sample;

[0007] (2) The laser is focused onto the surface of single crystal silicon, and the plasma etching effect induced by laser irradiation and the resulting change in the surface tension of the single crystal silicon are utilized to prepare a lattice structure on the surface of the single crystal silicon by adjusting the laser irradiation parameters. In addition, based on the difference in temperature accumulation under different laser pulse repetition frequencies, an ordered or disordered lattice structure is prepared on the surface of the single crystal silicon, and an ordered or disordered large-area lattice structure is further obtained by performing multi-line scanning.

[0008] Furthermore, in step (1), the surface roughness of the single crystal silicon is 4 nm, the ultrasonic cleaning temperature is 50° C., and the cleaning time is 5 minutes.

[0009] Furthermore, the laser irradiation parameters in step (2) are: laser wavelength of 1064 nm, pulse width of 7 ns, repetition frequency of 300-600 kHz, spot diameter of 43 μm, laser energy density of 0.539 J / cm 2 , the scanning speed is 1-6 mm / s, the number of scans is 1, and the laser energy distribution is Gaussian distribution. A disordered lattice structure is obtained when the repetition frequency is 600 kHz, and an ordered lattice structure is obtained when the repetition frequency is 300, 400, and 500 kHz.

[0010] Furthermore, the overlap rate between adjacent scanning lines of the multi-line scanning in step (2) is 0-20%.

[0011] Furthermore, the characteristic period of the ordered lattice structure on the surface of the single crystal silicon described in step (2) is 1.05 μm.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The plasma etching effect induced by laser irradiation and the change in the surface tension of single-crystal silicon caused by laser irradiation are used to induce the formation of a lattice structure on the surface of single-crystal silicon. In addition, based on the difference in temperature accumulation under different laser pulse repetition frequencies, the controllable preparation of an ordered or disordered lattice structure on the surface of single-crystal silicon can be achieved. The present invention has the advantages of simple process flow and green environmental protection, and has potential application value in the fields of micro-nano optics, semiconductor industry, photovoltaic solar cells, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The illustrative examples of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0015] Figure 1 In the embodiment of the present invention, the laser repetition frequency is 600 Hz and the laser energy density is 0.539 J / cm 2 Scanning electron microscope laser image of the disordered lattice structure on the surface of single-crystalline silicon prepared by nanosecond laser irradiation;

[0016] Figure 2 In the embodiment of the present invention, the repetition frequency is 500 Hz and the laser energy density is 0.539 J / cm 2 Scanning electron microscope image of the ordered lattice structure on the surface of single-crystalline silicon prepared by nanosecond laser irradiation;

[0017] Figure 3 In the embodiment of the present invention, the laser repetition frequency is 400 Hz and the laser energy density is 0.539 J / cm 2 Scanning electron microscope image of the ordered lattice structure on the surface of single-crystalline silicon prepared by nanosecond laser irradiation;

[0018] Figure 4 In the embodiment of the present invention, the laser repetition frequency is 300 Hz and the laser energy density is 0.539 J / cm 2 Scanning electron microscope image of the ordered lattice structure on the surface of single-crystalline silicon prepared by nanosecond laser irradiation;

[0019] Figure 5 In the embodiment of the present invention, the laser repetition frequency is 600 Hz and the laser energy density is 0.539 J / cm 2 , a scanning electron microscope image of a large area disordered lattice structure on the surface of single crystal silicon prepared by nanosecond laser irradiation with an overlap rate of 0% between adjacent scan lines;

[0020] Figure 6 In the embodiment of the present invention, the laser repetition frequency is 500 Hz and the laser energy density is 0.539 J / cm 2 , a scanning electron microscope image of a large area ordered lattice structure on the surface of single crystal silicon prepared by nanosecond laser irradiation with an overlap rate of 0% between adjacent scan lines; DETAILED DESCRIPTION

[0021] The details and specific implementation methods of the present invention are further described below in conjunction with the accompanying drawings.

[0022] A method for preparing a single crystal silicon surface lattice structure by nanosecond pulse laser irradiation, characterized in that it comprises the following steps:

[0023] (1) ultrasonically cleaning the single crystal silicon sample with anhydrous ethanol and acetone in sequence, and air-drying at room temperature to obtain a clean single crystal silicon sample;

[0024] (2) The laser is focused onto the surface of single crystal silicon, and the plasma etching effect induced by laser irradiation and the resulting change in the surface tension of the single crystal silicon are utilized to prepare a lattice structure on the surface of the single crystal silicon by adjusting the laser irradiation parameters. In addition, based on the difference in temperature accumulation under different laser pulse repetition frequencies, an ordered or disordered lattice structure is prepared on the surface of the single crystal silicon, and an ordered or disordered large-area lattice structure is further obtained by performing multi-line scanning.

[0025] Furthermore, in step (1), the surface roughness of the single crystal silicon is 4 nm, the ultrasonic cleaning temperature is 50° C., and the cleaning time is 5 minutes.

[0026] Furthermore, the laser irradiation parameters in step (2) are: laser wavelength of 1064 nm, pulse width of 7 ns, repetition frequency of 300-600 kHz, spot diameter of 43 μm, laser energy density of 0.539 J / cm 2 , the scanning speed is 1-6 mm / s, the number of scans is 1, and the laser energy distribution is Gaussian distribution. A disordered lattice structure is obtained when the repetition frequency is 600 kHz, and an ordered lattice structure is obtained when the repetition frequency is 300, 400, and 500 kHz.

[0027] Furthermore, the overlap rate between adjacent scanning lines of the multi-line scanning in step (2) is 0-20%.

[0028] Furthermore, the characteristic period of the ordered lattice structure on the surface of the single crystal silicon described in step (2) is 1.05 μm.

[0029] It can be seen from the test results that, using the method proposed by the present invention, an ordered or disordered lattice structure can be quickly and efficiently prepared on the surface of single crystal silicon by nanosecond pulse laser irradiation in an air environment, wherein the characteristic period of the ordered lattice structure is 1.05 μm. In addition, an ordered or disordered large-area lattice structure can be obtained by multi-line scanning. The present invention has potential application value in the fields of micro-nano optics, semiconductor industry, photovoltaic solar cells, etc.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made to the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a single crystal silicon surface lattice structure by nanosecond laser irradiation, characterized in that: The following steps are involved: (1) The single crystal silicon sample is ultrasonically cleaned with anhydrous ethanol and acetone in sequence, and air-dried at room temperature to obtain a clean single crystal silicon sample; (2) focusing the laser onto the surface of single crystal silicon, utilizing the plasma etching effect induced by laser irradiation and the change in surface tension of single crystal silicon caused by laser irradiation, and preparing a lattice structure by nanosecond laser irradiation of the single crystal silicon surface in an air environment by adjusting the laser irradiation parameters. In addition, based on the difference in temperature accumulation under different laser pulse repetition frequencies, an ordered or disordered lattice structure is prepared on the surface of single crystal silicon, and further an ordered or disordered large-area lattice structure is obtained by performing multi-line scanning. The laser irradiation parameters are: pulse width of 7 ns, repetition frequency of 300-600 kHz, spot diameter of 43 μm, and laser energy density of 0.539 J / cm 2 , the scanning speed is 1~6mm / s, the number of scans is 1, the laser energy distribution is Gaussian distribution, wherein a disordered lattice structure is obtained when the repetition frequency is 600kHz, and an ordered lattice structure is obtained when the repetition frequency is 300, 400, and 500kHz, the characteristic period of the ordered lattice structure on the surface of the single crystal silicon is 1.05μm, and the overlap rate between adjacent scanning lines of the multi-line scanning is 0~20%.

2. The method for preparing a single crystal silicon surface lattice structure by nanosecond laser irradiation according to claim 1, characterized in that: The surface roughness of the single crystal silicon in step (1) is 4 nm, the ultrasonic cleaning temperature is 50° C., and the cleaning time is 5 minutes.

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