A method for regulating laser precision machining of a silicon carbide surface

Abstract

The application discloses a kind of laser precision machining silicon carbide surface regulation and control method, by testing the ablation area after laser processing silicon carbide surface and corresponding Raman spectrum change, the carbonization effect of silicon carbide surface after laser processing and ablation boundary are calibrated, in combination with spatial resolution method obtains the related threshold value of the surface carbonization and ablation of various silicon carbide crystals under different parameters laser irradiation, and can be according to ablation and carbonization processing size demand, obtains corresponding incident laser energy density and incident laser light intensity, to realize laser precision, controllable processing various silicon carbide surface ablation and carbonization size, improve processing precision and quality, can be according to demand to realize the precision machining of different demand, provide reliable processing scheme for expanding the application of silicon carbide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor material processing, in particular to a method for regulating and controlling laser precision machining of a silicon carbide surface. BACKGROUND

[0002] As a representative of the third generation semiconductor, compared with the second generation semiconductor such as gallium arsenide, silicon carbide crystal has more excellent optical performance, larger band gap, higher breakdown threshold and higher thermal conductivity, and has been widely used in aerospace, new energy vehicles and semiconductor chip fields. However, the hardness of silicon carbide is only lower than that of diamond, which belongs to a standard hard and brittle material, which brings great challenges to the precision machining of its surface. At the same time, for the preparation of some precision components and special functional surfaces, high-precision machining is required, therefore, precise and controllable silicon carbide surface machining has become a problem to be solved in the expansion of silicon carbide applications. As a typical ultra-short and ultra-fast laser, picosecond and femtosecond laser not only has high peak light intensity, but also can realize cutting, drilling and other machining of any material, and due to its extremely short pulse width, it will not introduce thermal effects during machining of the material, which belongs to a typical "cold" machining, therefore, it has become one of the important technical means for precision machining of silicon carbide.

[0003] However, there is a carbonization phenomenon in the process of laser machining of the silicon carbide surface, that is, in the process of destroying the chemical bond of silicon carbide by laser, carbon atoms will be gathered and precipitated to realize carbonization. For different application scenarios of silicon carbide material, the size and proportion of carbonization are different, and the existing laser machining means does not have a precise and reliable method for regulating and controlling carbonization of silicon carbide. At the same time, the regulation and control precision of the ablation size of silicon carbide crystal is increasingly required. Therefore, it is urgent to invent a precise regulation and control machining method for ablation and carbonization of different silicon carbide materials, which provides a basis for expanding the physical nature of silicon carbide and expanding the application of silicon carbide material. SUMMARY

[0004] Therefore, the present application provides a method for regulating and controlling laser precision machining of a silicon carbide surface, which masters the boundary conditions of the ablation diameter and the carbonization gray value intensity by online measurement of the laser ablation area and the carbonization Raman spectrum distribution, and combines the spatial energy resolution test method to determine the ablation threshold and carbonization threshold of silicon carbide with different properties, and also realizes precise regulation and control of different ablation sizes and carbonization sizes of silicon carbide crystal. The present application not only determines the physical process of ultra-short pulse laser machining of the silicon carbide surface, but also provides a basis for precise regulation and control of silicon carbide surface modification machining.

[0005] The present application provides a method for regulating and controlling laser precision machining of a silicon carbide surface, which comprises the following steps:

[0006] S1, the pulsed laser emitted by the Gaussian pulsed laser passes sequentially through an energy attenuator, a spatial light modulator, a sampling mirror, a first reflecting mirror, a second reflecting mirror, a third reflecting mirror, and a focusing system mounted on a Z-axis displacement platform, irradiating the silicon carbide surface. The silicon carbide surface is set on the XY-axis displacement platform. The two beams split off by the sampling mirror are collected and recorded by an energy meter and a beam quality analyzer, respectively, to monitor the energy and spot size of the main optical path in real time.

[0007] S2, the computer adjusts the incident laser energy E0 through an attenuator, irradiating the ablation area of ​​the silicon carbide surface with single-pulse lasers of different energies. Based on the spot area S0 irradiated onto the silicon carbide surface, the laser energy density φ0 irradiated onto the silicon carbide surface is obtained. C =E0 / S0;

[0008] After single-pulse laser irradiation, the XY-axis displacement platform is controlled by a computer to irradiate other ablation areas on the silicon carbide surface with lasers of different energy densities. The ablation diameter D of the silicon carbide surface is measured using a CCD camera. At the same time, the ablation area of ​​silicon carbide is irradiated with a coaxial Raman spectroscopy excitation source, and the Raman spectrum at different locations in the ablation area is recorded using a Raman spectroscopy collection module.

[0009] S3, the ablation threshold φ of different ablation regions on the silicon carbide surface under the laser wavelength and pulse width parameters is obtained by fitting according to Formula I. th ω0 is the radius at the focal point of the ablation region.

[0010]

[0011] This allows us to obtain the ablation threshold φ for different silicon carbide surfaces. th Furthermore, based on requirements, the corresponding laser energy density φ0 relationship required to achieve different ablation diameters D can be obtained;

[0012] S4. Using Raman spectroscopy, the Raman peak distribution under different laser energy densities φ0 was measured. It was found that two characteristic carbonized Raman peaks (D band (1350 cm⁻¹) and G band (1590 cm⁻¹)) appeared near the center of the laser spot, and the gray intensity of these characteristic Raman peaks varied with the distance from the center of the laser spot. Therefore, based on the spatial energy distribution characteristics of Gaussian lasers, combined with the incident peak intensity I₀ = φ₀ / τ, where τ is the distance r from the center of the laser spot where the characteristic peak disappears and the focal spot radius ω₀, the carbonization threshold I at the location where the characteristic peak gray intensity is zero can be calculated according to Formula II. carbonation I0 is the incident peak light intensity, τ is the incident laser pulse width, and I0 = φ0 / τ.

[0013]

[0014] The carbonization threshold I of different silicon carbide surfaces was obtained. carbonation The corresponding ablation diameter D and the corresponding incident peak light intensity I0.

[0015] Furthermore, the laser is a picosecond or femtosecond ultrashort pulse laser.

[0016] Furthermore, the silicon carbide surface is high-purity or doped silicon carbide with any doping concentration.

[0017] Furthermore, the spatial light modulator adjusts the incident laser spot to a spatially Gaussian distributed Gaussian spot.

[0018] Furthermore, since the CCD camera is set at an angle θ to the laser-irradiated silicon carbide surface, the resulting laser ablation and carbonization area will be elliptical. Therefore, the radius r of the major axis of this ellipse needs to be adjusted. l Multiplying by the tangent function of the placement angle θ, we obtain the radius r of the actual ablation or carbonization region, r = r l ×tanθ, find the mean, r l The major axis radius of the ellipse is captured by the CCD camera to show the actual ablation or carbonization area.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention, through online measurement of the ablation dimensions of laser-induced silicon carbide surfaces, establishes the correspondence between the peak energy density of the incident laser and the diameter of the ablation area, and fits the boundary conditions for ultrashort pulse laser-induced silicon carbide surface ablation, thus determining the ablation threshold φ for different silicon carbide crystal surfaces. th And the peak energy density φ0 required for each ablation size D, thereby achieving precise adjustment of the ablation size of different silicon carbide materials;

[0021] 2. This invention utilizes Raman spectroscopy to perform Raman spectral scanning measurements on the ablation and carbonization of silicon carbide crystal surfaces induced by ultrashort pulse lasers. This yields the characteristic peaks (D band (1350 cm⁻¹) and G band (1590 cm⁻¹)) of ultrashort pulse laser-induced silicon carbide crystal carbonization. Simultaneously, the relationship between the carbonization characteristic peaks and their distance from the laser spot center is analyzed. Combined with Gaussian beam spatial energy resolution, the carbonization threshold of the silicon carbide crystal surface is determined. Furthermore, based on relevant rules, the required carbonization size of the silicon carbide crystal surface can be precisely and controllably prepared, providing a solution for precision processing of silicon carbide surfaces in different fields and for different needs.

[0022] 3. This invention can achieve precise and controllable surface ablation and carbonization processing for any silicon carbide crystal material with different properties, materials, sizes, and functions, and has high applicability. Attached Figure Description

[0023] Figure 1 This is a flowchart of laser precision machining of silicon carbide surfaces provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the structure for laser precision machining of silicon carbide surfaces provided in an embodiment of the present invention;

[0025] Figure 3 This is a block diagram of the control principle of the computer provided in an embodiment of the present invention;

[0026] Figure 4 This is a graph showing the relationship between incident laser energy density and ablation diameter provided in an embodiment of the present invention;

[0027] Figure 5 These are the characteristic Raman peaks of carbonization measured by Raman spectroscopy provided in the embodiments of the present invention;

[0028] Figure 6 This is a characteristic peak distribution diagram of ablation damage points obtained by Raman spectroscopy testing provided in an embodiment of the present invention;

[0029] Figure 7 This is a threshold test diagram showing that the carbonization characteristic peak is "zero" obtained by Raman spectroscopy testing according to an embodiment of the present invention;

[0030] In the figure: 1. Laser, 2. Attenuator, 3. Spatial light modulator, 4. Beam splitter, 5. Energy meter, 6. Beam quality analyzer, 7. First mirror, 8. Second mirror, 9. Third mirror, 10. Z-axis displacement platform, 11. Focusing system, 12. Silicon carbide crystal, 13. XY-axis displacement platform, 14. CCD camera, 15. Raman excitation source, 16. Raman laser mirror, 17. Raman spectrometer, 18. Raman spectrometer mirror, 19. Computer. Detailed Implementation

[0031] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. A flowchart of the laser precision machining of silicon carbide surfaces provided in the embodiments is shown below. Figure 1 As shown.

[0032] This invention provides a method for controlling the laser precision machining of silicon carbide surfaces, characterized by comprising the following steps:

[0033] S1, the pulsed laser emitted by the Gaussian pulsed laser 1 passes sequentially through the energy attenuator 2, spatial light modulator 3, sampling mirror 4, first reflector 7, second reflector 8, third reflector 9, and focusing system 11 mounted on the Z-axis displacement platform 10, irradiating the silicon carbide surface 12. A schematic diagram of the structure for laser precision machining of the silicon carbide surface provided in this embodiment is shown below. Figure 2As shown. The silicon carbide 12 surface is set on the XY axis displacement platform. The two beams of light split from the sampling mirror are collected and recorded by the energy meter 5 and the beam quality analyzer 6, respectively, to monitor the energy and spot size of the main optical path in real time; the control principle of the computer provided in the embodiment is as follows. Figure 3 As shown.

[0034] S2, the computer 15 adjusts the incident laser energy E0 through the attenuator 2, and irradiates the ablation area of ​​the silicon carbide surface 12 with single-pulse lasers of different energies. Based on the spot area S0 irradiated to the silicon carbide surface 12, the laser energy density φ0 irradiated to the silicon carbide surface 12 is obtained. The laser energy density φ0 = E0 / S0.

[0035] After single-pulse laser irradiation, the XY axis displacement platform 13 is controlled by computer 15 to irradiate other ablation areas of silicon carbide surface 12 with lasers of different energy densities. The ablation diameter D of silicon carbide surface is measured by CCD camera 14. At the same time, the ablation area of ​​silicon carbide 12 is irradiated by coaxial Raman spectroscopy excitation light source 15, and the Raman spectrum at different positions of the ablation area is recorded by Raman spectroscopy collection module 17.

[0036] S3, according to Formula I, the ablation threshold φ of 12 different ablation regions on the silicon carbide surface under this laser wavelength and pulse width parameter condition is obtained by fitting. th ω0 is the radius at the focal point of the ablation region.

[0037]

[0038] This allows us to obtain the ablation threshold φ for different silicon carbide surfaces. th Furthermore, the corresponding laser energy density φ0 relationship required to achieve different ablation diameters D can be obtained according to the requirements; the incident laser energy density and ablation diameter provided in the embodiment are as follows: Figure 4 As shown.

[0039] S4. Using Raman spectroscopy, the Raman peak distribution under different laser energy densities φ0 was measured. It was found that two characteristic carbonized Raman peaks (D band (1350 cm⁻¹) and G band (1590 cm⁻¹)) appeared near the center of the laser spot, and the gray intensity of these characteristic Raman peaks varied with the distance from the center of the laser spot. Therefore, based on the spatial energy distribution characteristics of Gaussian lasers, combined with the incident peak intensity I₀ = φ₀ / τ, where τ is the distance r from the center of the laser spot where the characteristic peak disappears and the focal spot radius ω₀, the carbonization threshold I at the location where the characteristic peak gray intensity is zero can be calculated according to Formula II. carbonation I0 is the incident peak light intensity, τ is the incident laser pulse width, and I0 = φ0 / τ.

[0040]

[0041] The carbonization threshold I of different silicon carbide surfaces was obtained. carbonation The corresponding ablation diameter D and the corresponding incident peak light intensity I0. The Raman spectra of the example provided show the characteristic Raman peaks of carbonization as follows: Figure 5 As shown in the example, the characteristic peak distribution diagram of the ablation damage points obtained by Raman spectroscopy is as follows. Figure 6 As shown in the figure. The threshold test diagram of the carbonization characteristic peak obtained by Raman spectroscopy provided in the example is shown in the figure. Figure 7 As shown.

[0042] Furthermore, laser 1 is a picosecond or femtosecond ultrashort pulse laser.

[0043] Furthermore, the silicon carbide surface 12 is high-purity or doped silicon carbide with any doping concentration.

[0044] Furthermore, the spatial light modulator 3 adjusts the incident laser spot to a spatially Gaussian distributed Gaussian spot.

[0045] Furthermore, the CCD camera 14 is set at an angle θ to the laser-irradiated silicon carbide surface 12. Therefore, the laser-ablated and carbonized area captured will appear elliptical. The radius r of the major axis of the ellipse needs to be adjusted. l Multiplying by the tangent function of the placement angle θ, we obtain the radius r of the actual ablation or carbonization region, r = r l ×tanθ, find the mean, r l The major axis radius of the ellipse in the actual ablation or carbonization area was captured by the CCD camera in 14 shots.

[0046] Example 1

[0047] In this embodiment, laser 1 is a 305fs-1.4ps adjustable ultrashort pulse laser, and a 20x magnifying lens is selected as the focusing system, with a focal radius ω0 of 5μm (1 / e 2 ); Silicon carbide crystal 12 is a doped silicon carbide crystal; CCD camera 14 has a pixel resolution of 1980*1080 and is placed at an angle of θ, 35°; Raman excitation source 15 is a 532nm laser.

[0048] By analyzing the relationship between the ablation diameter D of high-purity silicon carbide crystals and doped silicon carbide crystals under irradiation with different incident laser energy densities φ0, it was found that both satisfy ln(φ0) and D. 2 The ablation threshold φ of silicon carbide surface 12 under different laser wavelengths and pulse width parameters can be obtained by fitting the following formula. th ω0 is the radius at the focus:

[0049]

[0050] This allows us to obtain the ablation threshold φ for different silicon carbide surfaces. th The ablation thresholds for pulse widths of 305 fs, 600 fs, 900 fs, and 1.4 ps were 0.51 J / cm², respectively. 2 0.98J / cm 2 1.50 J / cm 2 and 2.02J / cm 2 Furthermore, the incident peak energy density φ0 corresponding to the required ablation diameter D can be obtained according to the requirements.

[0051] This embodiment uses a 532nm laser as the excitation source to test the Raman spectra of ablation and carbonization induced by different laser peak intensities I0. It was found that two characteristic Raman peaks of carbonization (D band (1350cm⁻¹) and G band (1590cm⁻¹)) appeared near the center of the laser spot, and the grayscale intensity of these characteristic Raman peaks varied with the distance from the center of the laser spot. Therefore, based on the spatial energy distribution characteristics of the Gaussian laser, combined with the distance (r) from the center of the laser spot to the coordinates where the characteristic peak disappears (I0 = φ0 / τ, where τ is the incident laser pulse width) and the radius of the focal spot (ω0), the threshold intensity at the location where the characteristic peak disappears (where the grayscale intensity of the characteristic peak is zero), i.e., the carbonization threshold, can be calculated using the following formula:

[0052] Therefore, the average value of the characteristic peak grayscale value of silicon carbide with a value of "zero" under 305 fs pulse width laser irradiation can be obtained, which is the carbonization threshold (I0). carbonation The value is 2.17 * 10. 12 W / cm 2 Furthermore, the incident peak light intensity (I0) corresponding to the required ablation diameter (D) can be obtained according to the requirements.

[0053] Silicon carbide crystals possess excellent physical properties and are widely used in aerospace, semiconductor chips, and new energy vehicles. However, silicon carbide crystals are hard and brittle materials, making them difficult to process, and current surface processing methods primarily rely on laser processing. As the application fields of silicon carbide continue to expand, the requirements for its processing precision are also increasing. Currently, there are no reports on ablation and carbonization control technologies for silicon carbide crystal surfaces. This patent addresses this issue by proposing a method for controlling the laser precision processing of silicon carbide surfaces, improving the processing precision of various silicon carbide surfaces, and providing assistance for the application of silicon carbide crystals in emerging fields such as micro-nano components and quantum communication.

[0054] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments; the above descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present invention without departing from the spirit and scope of the present invention, and all such modifications and improvements fall within the scope of the present invention; the scope of protection of the present invention is determined by the appended claims.

Claims

1. A method for controlling the laser precision machining of silicon carbide surfaces, characterized in that, Specifically, the following steps are included: S1, the pulsed laser emitted by the Gaussian pulsed laser (1) passes sequentially through the energy attenuator (2), spatial light modulator (3), sampling mirror (4), first reflector (7), second reflector (8), third reflector (9) and focusing system (11) mounted on the Z-axis displacement platform (10) to irradiate the silicon carbide surface (12), the silicon carbide surface (12) is set on the XY-axis displacement platform (13), the two beams of light split by the sampling mirror (4) are collected and recorded by the energy meter (5) and the beam quality analyzer (6) respectively, and the energy and spot size of the main optical path are monitored in real time; S2, the computer (15) adjusts the incident laser energy E0 through the attenuator (2) and irradiates the ablation area of ​​the silicon carbide surface (12) with single-pulse lasers of different energies. Based on the spot area S0 irradiated to the silicon carbide surface (12), the laser energy density φ0 irradiated to the silicon carbide surface (12) is obtained. The laser energy density φ0 = E0 / S0. After single-pulse laser irradiation, the XY axis displacement platform (13) is controlled by computer (15) to irradiate other ablation areas of the silicon carbide surface (12) with lasers of different energy densities. The ablation diameter D of the silicon carbide surface (12) is measured by CCD camera (14). At the same time, the ablation area of ​​the silicon carbide is irradiated by coaxial Raman spectroscopy excitation source (15), and the Raman spectrum at different positions of the ablation area is recorded by Raman spectroscopy collection module (17). S3, the ablation threshold φ of different ablation regions on the silicon carbide surface (12) is obtained by fitting according to Formula I. th ω0 is the radius at the focal point of the ablation region. The corresponding laser energy density φ0 required to achieve different ablation diameters D is obtained; S4. Using Raman spectroscopy, calculate the carbonization threshold I at the location where the characteristic peak gray value intensity is zero according to Formula II. carbonation I0 is the incident peak light intensity, τ is the incident laser pulse width, and I0 = φ0 / τ. The carbonization threshold I of different silicon carbide surfaces was obtained. carbonation The corresponding ablation diameter D and the corresponding incident peak light intensity I0.

2. The method for controlling the laser precision machining of silicon carbide surfaces according to claim 1, characterized in that, The laser (1) is a picosecond or femtosecond ultrashort pulse laser.

3. The method for controlling the laser precision machining of silicon carbide surfaces according to claim 1, characterized in that, The silicon carbide surface (12) is high-purity or doped silicon carbide with any doping concentration.

4. A method for controlling the laser precision machining of silicon carbide surfaces according to claim 1, characterized in that, The spatial light modulator (3) adjusts the incident laser spot to a Gaussian spot with a spatial Gaussian distribution.

5. A method for controlling the laser precision machining of silicon carbide surfaces according to claim 1, characterized in that, The CCD camera (14) is set at an angle θ to the laser-irradiated silicon carbide surface (12) to obtain the radius r of the actual ablation or carbonization region, r = r l ×tanθ, find the mean, r l The CCD camera (14) captures the elliptical major axis radius of the actual ablation or carbonization region.

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