Ultrafast laser welding method for transparent hard and brittle material and semiconductor heterogeneous material

Abstract

The invention relates to an ultrafast laser welding method for a transparent hard and brittle material and a semiconductor heterogeneous material. The transparent hard and brittle material and the semiconductor heterogeneous material are assembled in a clamp according to an optical contact state; and ultrafast laser welding parameters are set, an ultrafast laser is adopted to emit laser beams, the laser beams penetrate through the transparent hard and brittle material to act on the interface between the transparent hard and brittle material and the semiconductor material, and scanning welding is completed. Compared with the prior art, the ultrafast laser interlayer-free direct connection technology of the heterogeneous transparent hard and brittle material and the semiconductor material is provided for the first time, thermal stress concentration is avoided by optimizing the scanning path, effective connection of the transparent hard and brittle material and the semiconductor material is successfully achieved, and a high-strength and high-precision connection joint is formed. Compared with a traditional connection technology, the method does not need high temperature, an intermediate layer or an external load, is simple and convenient to operate, has a narrow heat affected zone, and is suitable for the precise manufacturing field of MEMS packaging and the like.

Description

Technical Field

[0001] This invention relates to the field of ultrafast laser processing materials technology, and in particular to a method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials. Background Technology

[0002] Microelectromechanical systems (MEMS), as a core field integrating microelectronics and precision mechanics, pushes miniaturized devices to new dimensions of high intelligence and high functional density by integrating mechanical sensing, signal processing, and environmental interaction functions. Typical applications include key devices such as pressure / temperature sensors, accelerometers, gyroscopes, and chemical sensors, and their miniaturization advantages have allowed them to penetrate cutting-edge fields such as biomedicine, environmental monitoring, and smart terminals. In MEMS manufacturing systems, semiconductor materials, due to their wide bandgap semiconductor properties, high thermal conductivity, and excellent mechanical strength, become the core structural materials, while transparent, rigid, and brittle materials, with their three-dimensional heterogeneous integration capabilities, chemical stability, and optical transparency, become ideal media for packaging.

[0003] Reliable bonding between these materials is a key technological challenge in constructing multifunctional MEMS devices. However, current traditional bonding processes, such as anodic bonding, adhesive bonding, and solid-state bonding, generally face bottlenecks such as interface cracks caused by thermal stress mismatch, organic degassing contamination, photo-aging, and material selectivity limitations, which severely restrict the long-term stability and large-scale production of devices. Developing novel heterogeneous material bonding technologies to achieve low-heat-loss, high-strength, transparent, hard, and brittle material-semiconductor bonding has become a key breakthrough in promoting the development of MEMS towards smaller scales and higher reliability.

[0004] Ultrafast laser welding technology, with its core advantages of high processing precision, zone selectivity, small heat-affected zone, no need for an intermediate layer, and safety and pollution-free operation, has demonstrated significant technological advantages in the field of precision welding. Therefore, ultrafast lasers offer new possibilities for efficient and reliable bonding between transparent, hard, and brittle materials and semiconductor materials.

[0005] Patent publication number CN118455710A discloses an adaptive ultrashort pulse laser welding joint stress relief method. This method achieves high-quality welding between hard and brittle materials by adding a flexible thin film between them, maintaining a suitable gap and ultimately obtaining a shear strength of 29.94 MPa. While this method alleviates joint stress by introducing an intermediate layer, the fabrication process for this flexible thin film is complex and time-consuming, making it unsuitable for mass production in actual industrial settings. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art, such as low connection strength between transparent hard and brittle materials and semiconductor heteromaterials, and poor bonding ability due to interface cracks. This invention provides a method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials. By optimizing the laser scanning path, the invention successfully achieves effective connection between transparent hard and brittle materials and semiconductor materials, forming a high-strength and high-precision connection joint. This is a new, highly reliable, and highly efficient method for connecting transparent hard and brittle materials and semiconductor materials.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for ultrafast laser welding of a transparent, hard, and brittle material and a semiconductor heterostructure involves assembling the two materials in an optically contacted state within a fixture. Ultrafast laser welding parameters are set, and an ultrafast laser beam is emitted, penetrating the transparent, hard, and brittle material and acting on its interface with the semiconductor material to complete the scanning welding. After passing through the transparent, hard, and brittle material layer, the laser beam is absorbed by the semiconductor material, heating its surface and causing thermal conduction. This leads to the melting, mixing, and cooling of the transparent and semiconductor materials, forming a stable connection. The joint strength is enhanced through a metallurgical-mechanical anchoring mechanism. Mechanical anchoring refers to the physical bond formed after the molten transparent, hard, and brittle material enters the micropores on the surface of the semiconductor material and solidifies. Metallurgical bonding refers to the formation of atomic-level bonds at the material interface through atomic diffusion or a melt-solidification process, achieving a dense connection without an interface layer.

[0008] Furthermore, the transparent hard and brittle material is selected from at least one of transparent glass materials, single crystal materials, or transparent ceramic materials.

[0009] Furthermore, the transparent glass material includes soda-lime glass, quartz glass, borosilicate glass, or aluminosilicate glass; The single-crystal materials include sapphire (Al2O3 single crystal) or diamond (C single crystal); The transparent ceramic materials include spinel (MgAl2O4) or transparent zirconia ceramics.

[0010] Furthermore, the semiconductor material includes at least one of silicon, germanium, gallium arsenide, or silicon carbide.

[0011] Furthermore, the ultrafast laser is a femtosecond laser or a picosecond laser.

[0012] Furthermore, the ultrafast laser welding parameters include at least one of the following: defocusing amount, laser power, repetition frequency, scanning speed, pulse width, scanning interval, number of scans, or scanning path.

[0013] Furthermore, the ultrafast laser has a wavelength of 1030 nm, a defocus of 0 μm, a laser power of 1-7 W, a repetition rate of 200 kHz-1.2 MHz, a scanning speed of 1-25 mm / s, a pulse width of 300 fs-8 ps, a scanning spacing of 40-100 μm, and 1-3 scans. The 0 μm defocus indicates that the ultrafast laser's focus is precisely and without deviation set at the interface between the transparent, hard, and brittle material and the semiconductor material. This ensures that the laser energy is used most efficiently to create a welding effect at the heterogeneous interface, while minimizing thermal damage to the transparent material itself.

[0014] Furthermore, the scanning path is an outer circle with an inner grid path. The outer circle is circular to restrict heat diffusion, and the interior is filled with a grid with a grid spacing of 40-100 μm and an outer circle diameter of 3-5 mm.

[0015] Furthermore, before assembling the transparent hard and brittle material and the semiconductor material in an optical contact state in the fixture, the transparent hard and brittle material and the semiconductor material are pretreated, the pretreatment including ultrasonic cleaning and drying, so as to keep the material surface clean.

[0016] Furthermore, the ultrasonic cleaning method is as follows: the material is placed in anhydrous ethanol and ultrasonically cleaned for 10-15 minutes; Furthermore, after washing, remove it with tweezers and blow it dry.

[0017] Furthermore, when the transparent hard and brittle material and the semiconductor material are assembled, the semiconductor material is on the bottom and the transparent hard and brittle material is on top.

[0018] Furthermore, the fixture is used to press the transparent hard and brittle material and the semiconductor material to the interface to form Newton's rings, and fix them on the three-dimensional moving platform of the ultrafast laser processing system.

[0019] Furthermore, after welding, the microstructure and elemental distribution of the interface are characterized by scanning electron microscopy and energy dispersive spectroscopy, and / or the sealing performance is tested by red ink immersion method.

[0020] Compared with the prior art, the present invention has the following advantages: (1) A method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials is proposed for the first time in this invention, which is original. This invention achieves high-quality connection between transparent hard and brittle materials and semiconductor materials without destroying the light transmittance of transparent hard and brittle materials by utilizing the nonlinear light absorption effect of femtosecond / picosecond pulsed lasers.

[0021] (2) The present invention uses ultrafast laser to achieve reliable connection between transparent hard and brittle materials and semiconductor materials. The reason is that ultrafast laser is an ultrashort pulse laser with extremely high instantaneous power. When the ultrafast laser is focused on the interface between the transparent hard and brittle material and the semiconductor material, the energy density near the focal point will exceed the ablation threshold of the material, causing the material to ionize and generate plasma. The plasma heats the nearby material and melts it, ultimately achieving local fusion of the transparent hard and brittle material and the semiconductor material.

[0022] (3) The present invention can avoid the stress problem at the joint between transparent hard and brittle materials and semiconductor materials. This is because the average power of ultrafast laser is extremely small, the heat input is extremely small, and the heating is localized with a small heat-affected zone, allowing for selective processing. Therefore, neither transparent hard and brittle materials nor semiconductor materials experience overall expansion and contraction, thus avoiding stress problems caused by differences in thermal expansion coefficients. Therefore, compared with anodic bonding, adhesive bonding, direct bonding, and other methods, the present invention is suitable for connecting precision devices to meet the production needs of MEMS devices.

[0023] (4) This invention achieves good sealing performance by optimizing the laser scanning path and selecting a scanning path with an outer circle and an inner grid. This is because, under the same laser welding parameters, rectangular welding deposits more energy at the corners, resulting in greater stress at the corners. This uneven stress can easily cause the glass to crack at the corners, making it impossible to maintain good sealing performance for a long time. In contrast, circular welding samples have good uniformity and can achieve a uniform stress distribution along the weld path. The inner grid filling method can increase the welding area and reduce stress generation compared to the U-shaped pattern, thereby improving the mechanical properties of the joint.

[0024] (5) The present invention can effectively connect glass and silicon carbide transparent hard and brittle materials at room temperature without the need for high temperature, intermediate layer, external load and external voltage, etc. It has the advantages of simple operation, fast connection speed and high joint yield.

[0025] (6) The present invention connects transparent hard and brittle materials with large differences in thermophysical properties to semiconductor materials. The joint strength can reach 33.1 MPa, which significantly improves the mechanical properties compared with traditional connection technologies (anodic bonding, adhesive bonding). Attached Figure Description

[0026] Figure 1 The diagram shows the laser optical path (a), glass and silicon carbide sample (b), and scanning path (c) of the glass-silicon carbide ultrafast laser welding in Embodiment 1 of the present invention. Figure 2The image shows the elemental distribution of the joint formed by ultrafast laser welding of glass and silicon carbide in Embodiment 1 of the present invention. (a) Typical microstructure of glass-silicon carbide joint welded by femtosecond laser, (b)-(e) EDS analysis of the interface. Figure 3 The sealing test results of the joint formed by glass-silicon carbide ultrafast laser welding in the embodiments of the present invention are (a) 0h, (b) 12h, (c) 24h, and (d) 168h. Figure 4 The following are schematic diagrams of the scanning paths for glass-silicon carbide ultrafast laser welding in Comparative Examples 1 to 3 of the present invention: (a) Comparative Example 1, (b) Comparative Example 2, and (c) Comparative Example 3.

[0027] Explanation of markings in the diagram: 1-Laser emitter, 2-Beam expander, 3-First reflector, 4-Second reflector, 5-Third reflector, 6-Fourth reflector, 7-Galvanometer, 71-Camera, 72-Camera light source, 8-Glass and silicon carbide sample, 81-Glass, 82-Silicon carbide, 9-Laser moving platform. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0029] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0030] Example 1 A method for ultrafast laser welding of a transparent, hard, and brittle material and a semiconductor heteromaterial includes the following steps: (1) In this embodiment, the transparent and brittle material is 15 mm × 15 mm × 0.7 mm glass 81 (Corning high-aluminum high-transparency glass), and the semiconductor material is 15 mm × 15 mm × 0.5 mm silicon carbide 82. The glass 81 and silicon carbide 82 are further pretreated by immersing them in anhydrous ethanol and ultrasonically cleaning them for 15 minutes. After ultrasonic cleaning, they are removed with tweezers and dried to keep the surfaces of the glass 81 and silicon carbide 82 clean.

[0031] (2) Place the cleaned glass 81 and silicon carbide 82 on a special tooling fixture and clamp them in the following order: silicon carbide 82 at the bottom and glass 81 at the top. While clamping, apply an upward pressure from the bottom until the contact surfaces of glass 81 and silicon carbide 82 reach optical contact and Newton's rings are observed to form. During the clamping and pressure application process, pay attention to the condition of the materials to avoid damage.

[0032] (3) Place the clamped glass and silicon carbide sample 8 on the laser moving platform 9, open the platform moving software, set the platform parameters, locate the camera focus, move the platform under the camera for positioning, and position it at the center of the Newton's rings. After positioning, move the platform under the laser galvanometer. The welding parameters are set as follows: wavelength is 1030nm, focus position is 0 μm, laser power is 5.85W, repetition frequency is 200kHz, scanning speed is 10mm / s, pulse width is 300fs, scanning interval is 100μm, and the number of scans is 1. The ultrafast laser is a femtosecond laser. The scanning path is an outer circle filled with a grid inside. The outer circle is circular to restrict heat diffusion, and the inside is filled with a grid with a grid spacing of 100μm and an outer circle diameter of 4mm. See details. Figure 1 The laser emitted by laser emitter 1 first passes through beam expander 2, then through first reflector 3, second reflector 4, third reflector 5, and fourth reflector 6 as shown in the diagram, and finally through galvanometer 7 to emit pulsed laser light, which reaches the glass and silicon carbide sample 8. During or after processing, the camera light source 72 is activated to provide optimal illumination for the target area. Subsequently, the camera 71 is activated to capture an image of the glass and silicon carbide sample 8.

[0033] (4) After setting the parameters, start the ultrafast laser, click Start Processing, and perform selective scanning welding. The laser beam is absorbed by the semiconductor material after passing through the transparent hard and brittle material layer, and heats the surface of the semiconductor material, causing it to generate heat conduction. As a result, the transparent material and the semiconductor material melt, mix and cool to form a solid connection.

[0034] (5) The joint formed by ultrafast laser connection of glass 81 and silicon carbide 82 was tested for shear strength using a tensile testing machine with a shearing speed of 5 mm / min, and the maximum joint strength was 33 MPa.

[0035] The cross-section and fracture surface after tensile shearing were analyzed, and the results were as follows ( Figure 2The study found that the effective connection between glass 81 and silicon carbide 82 was attributed to the synergistic effect of metallurgical bonding and mechanical anchoring, specifically manifested as significant elemental diffusion and the formation of a mixed layer approximately 1 μm thick. The joint strength was enhanced through a metallurgical bonding and mechanical anchoring mechanism. Mechanical anchoring refers to the physical bonding formed after molten, transparent, hard, and brittle materials enter the micropores on the surface of semiconductor materials and solidify. Metallurgical bonding refers to the formation of atomic-level bonds at the material interface through atomic diffusion or melt-solidification processes, achieving a dense connection without an interface layer.

[0036] The sealing performance of glass 81 and silicon carbide 82 was tested by immersion in red ink, and the results were as follows ( Figure 3 It was found that the sealing performance of glass 81 and silicon carbide 82 can be maintained for 168 hours without leakage.

[0037] Comparative Example 1 Compared to Example 1, most aspects were the same, except for the scanning path, which was adjusted to a concentric circle path, welding from the outside in, with a line spacing of 100 μm. The welded sample was subjected to mechanical property testing, and the mechanical strength was found to be 15.52 MPa.

[0038] Comparative Example 2 Compared to Example 1, most aspects were the same, except for the scanning path, which was adjusted to a zigzag path, with the scanning direction determined by the shape of the welding area, and the line spacing being 100 μm. The welded sample was subjected to mechanical property testing, yielding a mechanical strength of 16.19 MPa.

[0039] Comparative Example 3 Compared to Example 1, most aspects were the same, except for the scanning path, which was adjusted to a grid path, scanning along mutually perpendicular directions with a line spacing of 100 μm. The welded sample was subjected to mechanical property testing, yielding a mechanical strength of 17.67 MPa.

[0040] Analysis of Comparative Examples 1-3 shows that when the welding path is concentric circle, zigzag, or grid, the surface of the welded samples all show cracks of varying degrees and the mechanical properties are only a few tens of megapascals.

[0041] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for ultrafast laser welding of a transparent, hard, and brittle material and a semiconductor heteromaterial, characterized in that, The transparent hard and brittle material and the semiconductor material are assembled in a fixture in an optical contact state; the ultrafast laser welding parameters are set, and an ultrafast laser emits a laser beam that passes through the transparent hard and brittle material and acts on the interface between it and the semiconductor material to complete the scanning welding.

2. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 1, characterized in that, The transparent hard and brittle material is selected from at least one of transparent glass materials, single crystal materials, or transparent ceramic materials.

3. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 2, characterized in that, The transparent glass materials include soda-lime glass, quartz glass, borosilicate glass, or aluminosilicate glass; The single-crystal materials include sapphire or diamond; The transparent ceramic materials include spinel or transparent zirconia ceramics.

4. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 1, characterized in that, The semiconductor material includes at least one of silicon, germanium, gallium arsenide, or silicon carbide.

5. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 1, characterized in that, The ultrafast laser welding parameters include at least one of the following: defocusing amount, laser power, repetition frequency, scanning speed, pulse width, scanning interval, number of scans, or scanning path.

6. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 5, characterized in that, The ultrafast laser has a wavelength of 1030 nm, a defocus of 0 μm, a laser power of 1-7 W, a repetition frequency of 200 kHz-1.2 MHz, a scanning speed of 1-25 mm / s, a pulse width of 300 fs-8 ps, a scanning interval of 40-100 μm, and a scanning number of 1-3 times.

7. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 5, characterized in that, The scanning path is an outer circle with an inner grid path. The outer circle is circular to restrict heat diffusion, and the inside is filled with a grid with a grid spacing of 40-100 μm and an outer circle diameter of 3-5 mm.

8. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 1, characterized in that, Before assembling the transparent hard and brittle material and the semiconductor material in an optical contact state in the fixture, the transparent hard and brittle material and the semiconductor material are pretreated, the pretreatment including ultrasonic cleaning and drying.

9. The method for ultrafast laser welding of transparent hard and brittle materials and semiconductor heteromaterials according to claim 1, characterized in that, When the transparent hard and brittle material and the semiconductor material are assembled, the semiconductor material is at the bottom and the transparent hard and brittle material is at the top.

10. The method for ultrafast laser welding of a transparent, hard, and brittle material and a semiconductor heteromaterial according to claim 1, characterized in that, The clamp is used to press the transparent, hard, and brittle material and the semiconductor material to the interface to form Newton's rings.

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