Regulation and control method for laser precision machining of silicon carbide surface

Abstract

The invention discloses a method for regulating and controlling a silicon carbide surface subjected to laser precision machining, which comprises the following steps of: calibrating a carbonization effect and an ablation boundary of the silicon carbide surface subjected to laser machining by testing an ablation area and a corresponding Raman spectrum change after the silicon carbide surface is subjected to laser machining; in combination with a spatial resolution method, related thresholds for inducing surface carbonization and ablation of various silicon carbide crystals under irradiation of lasers with different parameters are obtained, and corresponding incident laser energy density and incident laser light intensity can be obtained according to ablation and carbonization processing size requirements. Therefore, laser precise and controllable machining of various silicon carbide surface ablation and carbonization sizes is achieved, the machining precision and quality are improved, precise machining of different requirements can be achieved according to the requirements, and a reliable machining scheme is provided for expanding application of silicon carbide.

Description

Technical Field

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

[0002] As a representative of the third generation of semiconductors, silicon carbide crystals have advantages over second generation semiconductors such as gallium arsenide, such as better optical properties, larger bandgap width, higher breakdown threshold and higher thermal conductivity. They have been widely used in aerospace, new energy vehicles and semiconductor chips. However, the hardness of silicon carbide is only lower than that of diamond, and it is a standard hard and brittle material, which brings huge challenges to its surface precision processing. At the same time, the preparation of some precision components and special functional surfaces requires high-precision processing. Therefore, the precise and controllable realization of silicon carbide surface processing has become an urgent problem to be solved in the extended application of silicon carbide. Picosecond and femtosecond lasers are typical ultrashort and ultrafast lasers. They not only have high peak light intensity, but can also realize cutting and drilling of any material. At the same time, due to their extremely short pulse width, no thermal effect will be introduced during the material processing process. They are typical "cold" processing, so they have become one of the important technical means in the application of precision processing of silicon carbide.

[0003] However, there is a carbonization phenomenon during the laser processing of the silicon carbide surface, that is, in the process of laser destroying the chemical bonds of silicon carbide, carbon atoms will gather and precipitate, thereby achieving carbonization. For different application scenarios of silicon carbide materials, the size and proportion of carbonization requirements are different, and the existing laser processing methods do not have a precise and reliable method for regulating the carbide of silicon carbide. At the same time, the requirements for the control accuracy of the ablation size of silicon carbide crystals are increasing. Therefore, it is urgent to invent a precision control processing method for the ablation and carbonization of different silicon carbide materials, which provides a basis for expanding the understanding of the physical nature of silicon carbide and expanding the application of silicon carbide materials. Summary of the invention

[0004] In view of this, the present invention provides a method for regulating the surface of silicon carbide by laser precision machining. By online measuring the laser ablation area and the distribution of the carbonization Raman spectrum, the boundary conditions of the ablation diameter and the intensity of the carbonization grayscale value are mastered, and the ablation threshold and carbonization threshold of silicon carbide with different properties are explored in combination with the spatial energy resolution test method. At the same time, the precise regulation of different ablation sizes and carbonization sizes of silicon carbide crystals can also be achieved. The present invention not only explores the physical process of ultrashort pulse laser machining of silicon carbide surfaces, but also provides a basis for precise regulation of silicon carbide surface modification processing.

[0005] The present invention provides a method for regulating and controlling the surface of silicon carbide by laser precision machining, which is characterized by comprising the following steps:

[0006] S1, the pulse laser emitted by the Gaussian pulse laser passes through the energy attenuator, spatial light modulator, sampling mirror, first reflector, second reflector, third reflector and focusing system mounted on the Z-axis displacement platform in sequence, irradiating the silicon carbide surface, the silicon carbide surface is set on the XY-axis displacement platform, and the two beams of light separated by the sampling mirror are collected and recorded by the energy meter and beam quality analyzer respectively, and the energy and spot size of the main light path are monitored in real time;

[0007] S2, the computer uses the attenuator to measure the incident laser energy E 0 Adjust the ablation area on the silicon carbide surface by single pulse laser irradiation with different energies, and adjust the spot area S irradiated to the silicon carbide surface. 0 , the laser energy density φ irradiated to the silicon carbide surface is obtained 0 , laser energy density φ C =E 0 / S 0 ;

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

[0009] S3, according to formula I, the ablation threshold φ of different ablation areas on the silicon carbide surface under the conditions of laser wavelength and pulse width parameters is obtained th ,ω 0 is the radius of the focal point of the ablation area,

[0010]

[0011] From this, the ablation threshold φ of different silicon carbide surfaces can be obtained th , and the corresponding laser energy density φ required to achieve different ablation diameters D can be obtained according to the requirements 0 relation;

[0012] S4, using Raman spectroscopy, different laser energy densities φ 0 The Raman peak distribution under irradiation was measured and 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 light spot, and the gray value intensity of the characteristic Raman peaks changed with the distance from the center of the light spot. 0 =φ 0 / τ, τ is the distance r from the coordinate where the characteristic peak of the incident laser pulse width disappears to the center of the spot and the focal spot radius ω 0 , calculate the carbonization threshold I at the position where the characteristic peak gray value intensity is zero according to formula II carbonation , I 0 is the incident peak light intensity, τ is the incident laser pulse width, I 0 =φ 0 / τ,

[0013]

[0014] Obtain the carbonization threshold I of different silicon carbide surfaces carbonation The corresponding ablation diameter D and the corresponding incident peak light intensity I 0 .

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

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

[0017] Furthermore, the spatial light modulator adjusts the incident laser spot to be a Gaussian spot with spatial Gaussian distribution.

[0018] Furthermore, the CCD camera is set at an angle θ to the laser-irradiated silicon carbide surface, so the laser ablation and carbonization area obtained by the camera will appear elliptical. The radius r of the major axis of the ellipse needs to be l Multiply by the tangent function of the placement angle θ to obtain the radius r of the actual ablation or carbonization area, r = r l × tanθ, find the center, r l The major axis radius of the ellipse of the actual ablation or carbonization area is captured by the CCD camera.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention measures the laser-induced silicon carbide surface ablation size online, sorts out the corresponding relationship between the incident laser peak energy density and the ablation area diameter, and fits the boundary conditions of ultrashort pulse laser-induced silicon carbide surface ablation, that is, grasps the ablation threshold φ of different silicon carbide crystal surfaces. th And the peak energy density φ required for each ablation size D 0 , thus achieving precise adjustment of the ablation size of different silicon carbide materials;

[0021] 2. The present invention uses Raman spectroscopy to measure the ultrashort pulse laser induced ablation and carbonization of silicon carbide crystal surface by Raman spectroscopy scanning, and obtains the characteristic peaks (D band (1350cm-1) and G band (1590cm-1)) of ultrashort pulse laser induced carbonization of silicon carbide crystal. At the same time, the relationship between the characteristic peaks of carbonization and the distance from the center of the light spot is sorted out, and the carbonization threshold of the silicon carbide crystal surface is found out by combining the Gaussian beam spatial energy resolution method. In addition, the carbonization size required for the surface of the silicon carbide crystal can be precisely and controllably prepared according to relevant rules, providing solutions for the precision processing of silicon carbide surfaces in different fields and with different needs.

[0022] 3. The present invention can realize precise and controllable surface ablation and carbonization processing for any silicon carbide crystal material with different properties, different materials, different sizes, different functions, etc., and has high applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of laser precision machining of silicon carbide surface provided by an embodiment of the present invention;

[0024] Figure 2 It is a schematic diagram of the structure of the laser precision machining of silicon carbide surface provided by an embodiment of the present invention;

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

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

[0027] Figure 5 is a carbonization characteristic Raman peak measured by the Raman spectrum provided by the embodiment of the present invention;

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

[0029] Figure 7 This is a threshold test diagram of a carbonization characteristic peak of "zero" obtained by a Raman spectrum test provided by an embodiment of the present invention;

[0030] In the figure, 1. laser, 2. attenuator, 3. spatial light modulator, 4. spectroscope, 5. energy meter, 6. beam quality analyzer, 7. first reflector, 8. second reflector, 9. third reflector, 10. Z-axis displacement platform, 11. focusing system, 12. silicon carbide crystal, 13. XY-axis displacement platform, 14. CCD camera, 15. Raman excitation light source, 16. Raman laser reflector, 17. Raman spectrum analyzer, 18. Raman spectrum reflector, 19. computer. DETAILED DESCRIPTION

[0031] In order to better understand the technical solution of the present invention, the following is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. The flowchart of the laser precision machining of silicon carbide surface provided in the embodiment is as follows: Figure 1 shown.

[0032] The present invention provides a method for regulating and controlling the surface of silicon carbide by laser precision machining, which is characterized by comprising the following steps:

[0033] S1, the pulse laser emitted by the Gaussian pulse laser 1 passes through the energy attenuator 2, the spatial light modulator 3, the sampling mirror 4, the first reflector 7, the second reflector 8, the third reflector 9 and the focusing system 11 mounted on the Z-axis displacement platform 10 in sequence, and irradiates the silicon carbide surface 12. The structural schematic diagram of the laser precision machining of the silicon carbide surface provided in the embodiment is shown in Figure 2 The surface of silicon carbide 12 is set on the XY axis displacement platform, and the two beams of light separated by the sampling mirror 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 light path are monitored in real time; the control principle of the computer provided in the embodiment is as follows Figure 3 shown.

[0034] S2, the computer 15 uses the attenuator 2 to measure the incident laser energy E 0 Adjustment is performed to irradiate the ablation area of ​​the silicon carbide surface 12 with single pulse lasers of different energies, and the spot area S irradiated to the silicon carbide surface 12 is adjusted. 0 , the laser energy density φ irradiated to the silicon carbide surface 12 is obtained 0 , laser energy density φ 0 =E 0 / S 0 ;

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

[0036] S3, according to formula I, the ablation threshold φ of different ablation areas on the silicon carbide surface 12 under the conditions of laser wavelength and pulse width parameters is obtained th ,ω 0 is the radius of the focal point of the ablation area,

[0037]

[0038] From this, the ablation threshold φ of different silicon carbide surfaces can be obtainedth , and the corresponding laser energy density φ required to achieve different ablation diameters D can be obtained according to the requirements 0 Relationship; the incident laser energy density and ablation diameter provided in the embodiment are as follows Figure 4 shown.

[0039] S4, using Raman spectroscopy, different laser energy densities φ 0 The Raman peak distribution under irradiation was measured and 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 light spot, and the gray value intensity of the characteristic Raman peaks changed with the distance from the center of the light spot. 0 =φ 0 / τ, τ is the distance r from the coordinate where the characteristic peak of the incident laser pulse width disappears to the center of the spot and the focal spot radius ω 0 , calculate the carbonization threshold I at the position where the characteristic peak gray value intensity is zero according to formula II carbonation , I 0 is the incident peak light intensity, τ is the incident laser pulse width, I 0 =φ 0 / τ,

[0040]

[0041] Obtain the carbonization threshold I of different silicon carbide surfaces carbonation The corresponding ablation diameter D and the corresponding incident peak light intensity I 0 The carbonization characteristic Raman peaks measured by Raman spectroscopy provided in the embodiment are as follows: Figure 5 The characteristic peak distribution diagram of the Raman spectrum test ablation damage point provided in the embodiment is shown in FIG. Figure 6 The threshold test diagram of the carbonization characteristic peak obtained by the Raman spectrum test provided in the embodiment is as follows: Figure 7 shown.

[0042] Furthermore, the 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 be a Gaussian spot with spatial Gaussian distribution.

[0045] Furthermore, the CCD camera 14 is set at an angle θ to the laser-irradiated silicon carbide surface 12, so the laser ablation and carbonization area obtained by the camera will appear elliptical. The radius r of the major axis of the ellipse needs to be lMultiply by the tangent function of the placement angle θ to obtain the radius r of the actual ablation or carbonization area, r = r l × tanθ, find the center, r l The CCD camera takes a picture of the major axis radius of the ellipse of the actual ablation or carbonization area.

[0046] Example 1

[0047] In this embodiment, laser 1 is a 305fs-1.4ps adjustable ultrashort pulse laser, and a 20x magnification lens is selected as the focusing system, with a focal radius ω 0 5μm(1 / e 2 ); the silicon carbide crystal 12 is a doped silicon carbide crystal; the CCD camera 14 has a pixel of 1980*1080 and is placed at an inclination angle θ, 35°, and the Raman excitation light source 15 is a 532nm laser;

[0048] Arrangement of different incident laser energy densities φ 0 Under irradiation, the relationship between the ablation diameter D of high-purity silicon carbide crystal and doped silicon carbide crystal is found to satisfy ln(φ 0 ) and D 2 The ablation threshold φ of the silicon carbide surface 12 under different laser wavelength and pulse width parameters can be obtained by fitting the following formula: th ,ω 0 is the radius at the focus:

[0049]

[0050] From this, the ablation threshold φ of different silicon carbide surfaces can be obtained th The ablation thresholds of pulse widths of 305fs, 600fs, 900fs, and 1.4ps are 0.51J / cm 2 , 0.98J / cm 2 , 1.50J / cm 2 and 2.02 J / cm 2 And according to the needs, the incident peak energy density φ corresponding to the required ablation diameter D can be obtained 0 .

[0051] This example uses 532nm laser as the excitation light source to test different laser peak light intensities I 0 The Raman spectra of ablation and carbonization induced by the laser were found to have two characteristic Raman peaks of carbonization (D band (1350cm-1) and G band (1590cm-1)) near the center of the light spot, and the gray value intensity of the characteristic Raman peaks changed with the distance from the center of the light spot. 0 =φ0 / τ, τ is the incident laser pulse width) The coordinate distance from the center of the spot where the characteristic peak disappears (r) and the focal spot radius (ω 0 ), the threshold light intensity at the position where the characteristic peak disappears (the gray value intensity of the characteristic peak is zero), that is, the carbonization threshold, can be calculated according to the following formula:

[0052] It can be obtained that when the doped silicon carbide surface is irradiated with a 305fs pulse width laser, the gray value of the characteristic peak of silicon carbide is the average value of "zero", that is, the carbonization threshold (I carbonation ) is 2.17*10 12 W / cm 2 And according to the needs, the incident peak light intensity (I 0 );

[0053] Silicon carbide crystals have excellent physical properties and are widely used in aerospace, semiconductor chips, new energy vehicles and many other fields. However, silicon carbide crystals are hard and brittle materials, which are difficult to process. Existing surface processing is often based on laser processing. With the continuous expansion of the application field of silicon carbide, the requirements for its processing accuracy are also increasing. There are no reports on the ablation and carbonization control technology of the silicon carbide crystal surface. In response to this problem, this patent proposes a control method for laser precision processing of silicon carbide surfaces, which improves the processing accuracy of various silicon carbide surfaces and provides assistance for the application of silicon carbide crystals in new fields such as micro-nano components and quantum communications.

[0054] The present invention is described in detail above in combination with specific implementation methods and exemplary examples. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments; the above description cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, the technical solution of the present invention and its implementation methods may be subjected to a variety of equivalent substitutions, modifications or improvements, all of which fall within the scope of the present invention; the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for controlling the surface of silicon carbide by laser precision machining, characterized in that: The specific steps include: S1, the pulse laser emitted by the Gaussian pulse laser (1) passes through the energy attenuator (2), the spatial light modulator (3), the sampling mirror (4), the first reflector (7), the second reflector (8), the third reflector (9) and the focusing system (11) mounted on the Z-axis displacement platform (10) in sequence, and irradiates the silicon carbide surface (12), wherein the silicon carbide surface (12) is arranged on the XY-axis displacement platform (13), and the two beams of light separated by the sampling mirror (4) are respectively collected and recorded by the energy meter (5) and the beam quality analyzer (6), so as to monitor the energy and spot size of the main light path in real time; S2, the computer (15) adjusts the incident laser energy E0 through the attenuator (2), performs single pulse laser irradiation of different energies on the ablation area of ​​the silicon carbide surface (12), and obtains the laser energy density φ0 irradiated to the silicon carbide surface (12) according to the spot area S0 irradiated to the silicon carbide surface (12), and the laser energy density φ0 = E0 / S0; After the single-pulse laser irradiation, the XY-axis displacement platform (13) is controlled by a computer (15) to irradiate the ablation area at other positions of the silicon carbide surface (12) with lasers of different energy densities, and a CCD camera (14) is used to measure the ablation diameter D of the silicon carbide surface (12), and at the same time, a coaxial Raman spectrum excitation light source (15) is used to irradiate the ablation area of ​​the silicon carbide (12), and a Raman spectrum collection module (17) is used to record the Raman spectra at different positions of the ablation area; S3, according to formula I, the ablation threshold φ of different ablation areas of the silicon carbide surface (12) is obtained by fitting th , ω0 is the radius of the focal point of the ablation area, The corresponding laser energy density φ0 relationship required to achieve different ablation diameters D is obtained; S4, using Raman spectroscopy, calculate the carbonization threshold I at the position 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, I0=φ0 / τ, Obtain the carbonization threshold I of different silicon carbide surfaces carbonation The corresponding ablation diameter D and the corresponding incident peak light intensity I0.

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

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

5. A control method for laser precision machining of silicon carbide surface according to claim 1, characterized in that: The CCD camera (14) is arranged at an angle θ with the silicon carbide surface (12) irradiated by the laser, and the radius r of the actual ablation or carbonization area is obtained, r=r l × tanθ, find the center, r l The CCD camera (14) is used to photograph the major axis radius of the ellipse of the actual ablation or carbonization area.

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