A method and system for combined pulsed laser cutting of semiconductor silicon material

Abstract

The application discloses a method and system for cutting semiconductor silicon material by combined pulse laser, and the method comprises the following steps: adopting nanosecond pulse laser to scan and irradiate a preset cutting path of a silicon wafer, and forming a preset notch on the preset cutting path of the silicon wafer; adopting millisecond pulse laser to scan and irradiate along the path of the preset notch, and generating brittle fracture of the silicon material along the preset notch through thermal stress generated by the millisecond pulse laser to complete the cutting. The application solves the problems of low efficiency, large thermal influence area and poor cutting quality of the single pulse laser cutting silicon wafer in the prior art.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material processing technology, and specifically to a method and system for cutting semiconductor silicon material using a combined pulsed laser. Background Technology

[0002] Silicon wafers, as one of the core substrate materials in semiconductor manufacturing, play an irreplaceable role in the fabrication of microelectronic devices. During the manufacturing process, silicon wafers need to be precisely diced into smaller wafers for use in integrated circuit manufacturing. However, traditional silicon wafer dicing methods mainly include diamond wheel cutting and laser cutting. While diamond wheel cutting is less expensive, it suffers from low cutting efficiency, susceptibility to microcracks at the cut edges, and rapid tool wear. Laser cutting, with its advantages of non-contact operation, high efficiency, and high precision, has become an important method for silicon wafer dicing.

[0003] Currently, laser cutting of silicon wafers mainly employs single-pulse lasers, such as nanosecond lasers, picosecond lasers, or femtosecond lasers. Nanosecond lasers offer high cutting efficiency, but their large heat-affected zone (HAZ) makes them prone to defects such as melting and microcracks at the cut edges. While picosecond and femtosecond lasers offer smaller HAZs and higher cutting quality, their expensive equipment and lower processing efficiency make them unsuitable for large-scale industrial production. Therefore, developing a laser cutting method for silicon wafers that combines high efficiency and high quality is of significant practical importance. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for cutting semiconductor silicon materials using combined pulsed lasers, so as to solve the problems of low efficiency, large heat-affected zone and poor cutting quality in the existing single-pulse laser cutting of silicon wafers.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for cutting semiconductor silicon material using a combined pulsed laser includes the following steps: S1: A nanosecond pulsed laser is used to scan and irradiate the preset cutting path of the silicon wafer to form a preset notch on the preset cutting path of the silicon wafer. S2: A millisecond pulsed laser is used to scan and irradiate along the path of the pre-set notch. The thermal stress generated by the millisecond pulsed laser induces brittle fracture of the silicon material along the pre-set notch, thus completing the cutting. The nanosecond pulse laser has a pulse width of 1 nanosecond to 100 nanoseconds, and the millisecond pulse laser has a pulse width of 1 millisecond to 100 milliseconds.

[0006] To optimize the above technical solution, the specific limitations also include: The nanosecond pulsed laser is focused by a cylindrical focusing lens to irradiate and form an ablation morphology, serving as a pre-set notch; the millisecond pulsed laser is focused by an optical focusing lens to form a circular spot.

[0007] Furthermore, the diameter of the light spot formed by focusing the millisecond pulse laser is 0.1mm to 10mm.

[0008] Preferably, the wavelength of the nanosecond pulsed laser is 1064 nm and the pulse energy is 10 mJ to 200 mJ; the wavelength of the millisecond pulsed laser is 1064 nm and the pulse energy is 0.1 J to 10 J.

[0009] Preferably, the direction of the pre-set notch and the scanning path direction of the millisecond pulse laser are both consistent with the crystal orientation of the silicon wafer.

[0010] Preferably, the depth of the pre-set notch is 2% to 10% of the thickness of the silicon wafer, and the width is 10 μm to 100 μm.

[0011] Furthermore, there is a time interval between the nanosecond pulse laser scan and the millisecond pulse laser scan.

[0012] Preferably, the thickness of the silicon wafer is 50μm to 1000μm.

[0013] This invention also proposes a system for combined pulsed laser cutting of semiconductor silicon materials, comprising: Nanosecond pulsed lasers are used to generate lasers with pulse widths ranging from 1 nanosecond to 100 nanoseconds. Millisecond pulsed lasers are used to generate lasers with pulse widths ranging from 1 millisecond to 100 milliseconds. A timer is used to control nanosecond pulse lasers and millisecond pulse lasers to operate at certain time intervals. A focusing optical system is used to guide and focus the lasers emitted by the nanosecond pulse laser and the millisecond pulse laser to the corresponding processing positions on the silicon wafer, respectively. A three-dimensional moving platform for fixing and moving the silicon wafer; The computer control system is electrically connected to the nanosecond pulse laser, the millisecond pulse laser, and the three-dimensional moving platform, and is used to control the laser emission timing, parameters, and the motion path of the three-dimensional moving platform.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a method and system for cutting semiconductor silicon material using combined pulsed lasers. A high-peak-power nanosecond pulsed laser scans a silicon wafer along a predetermined cutting path, forming a pre-defined notch with controllable depth and precise width on or inside the material surface. Then, a low-energy-density millisecond pulsed laser scans and irradiates along the path of the pre-defined notch to complete the cutting. The sequential synergy of the nanosecond and millisecond pulsed lasers overcomes the inherent problems of low cutting efficiency with a single nanosecond laser and poor cutting quality with a single millisecond laser.

[0015] This invention utilizes a nanosecond laser to pre-define a precise notch, followed by a millisecond laser to precisely drive the cutting path with thermal stress, resulting in accurate cutting path control and excellent cut perpendicularity. Simultaneously, the low-energy millisecond laser avoids material melting and recasting, minimizing the heat-affected zone on the cut sidewalls, reducing chipping size, and lowering surface roughness. This achieves superior processing accuracy and surface quality, meeting the cutting track quality requirements of high-end semiconductor chips and reducing subsequent processing steps.

[0016] The nanosecond and millisecond pulsed lasers used in this invention are mature, relatively low-cost industrial-grade lasers. Compared with picosecond and femtosecond ultrafast laser systems, they achieve similar or better cutting quality while offering advantages in equipment and maintenance costs. Furthermore, this invention is applicable to silicon wafers with thicknesses ranging from 50μm to 1000μm and can be adapted to materials of different thicknesses and crystal orientations by adjusting the laser parameters, demonstrating strong practicality. Attached Figure Description

[0017] Figure 1 : Schematic diagram of the device for cutting semiconductor silicon material using combined pulsed laser according to the present invention.

[0018] Figure 2 : A schematic diagram of the method for cutting semiconductor silicon material using combined pulsed laser according to the present invention.

[0019] Figure 3 : Schematic diagram of the pre-set notch formed by nanosecond pulsed laser scanning according to the present invention.

[0020] Figure 4 : Schematic diagram of the result of cutting silicon wafers using the method of the present invention.

[0021] Figure 5 : A schematic diagram showing the result of cutting the silicon wafer with a deviation angle between the direction of the pre-set notch and the crystal orientation of the silicon wafer.

[0022] Among them: 1-delay unit, 2-nanosecond pulse laser, 3-millisecond pulse laser, 4-energy meter, 5-beam splitter, 6-reflector, 7-attenuator, 8-optical focusing lens, 9-half-glass slide, 10-polarizing beam splitter, 11-cylindrical focusing lens, 12-three-dimensional moving platform, 13-computer system, 14-silicon wafer, 15-preset notch, 16-millisecond pulse laser. Detailed Implementation

[0023] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0024] In one embodiment of the present invention, a method for cutting semiconductor silicon material using a combined pulsed laser is provided, the method comprising the following steps: A silicon wafer 14 to be cut is provided, and the silicon wafer 14 is fixed on the three-dimensional moving platform 12; A nanosecond pulsed laser is used to scan and irradiate the preset cutting path of the silicon wafer 14, forming a preset notch 15 on the preset cutting path of the silicon wafer 14. A millisecond pulse laser 16 is used to scan and irradiate along the path of a pre-set notch 15. The thermal stress generated by the millisecond pulse laser 16 induces brittle fracture of the silicon material along the pre-set notch 15, thus completing the cutting.

[0025] In this process, a nanosecond pulsed laser, focused by a cylindrical focusing lens 11, irradiates the working surface, forming a linear ablation morphology that serves as a pre-set notch 15. The extension direction of the pre-set notch 15 is parallel to the scanning path direction of the millisecond pulsed laser 16 and to a specific crystal orientation of the silicon wafer 14, thereby utilizing crystal anisotropy to obtain a straighter cutting surface with less edge chipping. The depth of the pre-set notch is 2% to 10% of the thickness of the silicon wafer 14, and the width is 10 μm to 100 μm.

[0026] There is a time interval between the nanosecond pulsed laser scan and the millisecond pulsed laser 16 scan, which realize different physical mechanisms in steps. The nanosecond pulsed laser is responsible for the precision manufacturing of initial defects, while the millisecond pulsed laser 16 is responsible for providing controllable thermal stress.

[0027] The thickness of silicon wafer 14 is 50μm~1000μm, which is suitable for common silicon wafer 14 thickness specifications in the semiconductor industry.

[0028] This invention also proposes a combined pulsed laser cutting system for semiconductor silicon materials, the specific structure of which is as follows: Figure 1 As shown, it includes: a delay unit 1, a nanosecond pulse laser 2, a millisecond pulse laser 3, a focusing optical system, a three-dimensional moving platform 12, and a computer system 13.

[0029] Delay unit 1 is used to control the nanosecond pulse laser 2 and the millisecond pulse laser 3 to work at certain time intervals to ensure the process sequence.

[0030] Nanosecond pulsed laser 2 is used to emit nanosecond pulsed lasers of the required wavelength. It adopts a solid-state pulsed laser with an output wavelength of 1064nm. The pulse width can be adjusted in the range of 1ns to 100ns, and the single pulse energy adjustment range is 10mJ to 200mJ. Other types of pulsed lasers, such as carbon dioxide lasers and laser diode arrays, can also be used.

[0031] The millisecond pulse laser 3 is used to emit millisecond pulse laser 16 of the required wavelength. It adopts a solid-state pulse laser with an output wavelength of 1064nm. The pulse width can be adjusted in the range of 1ms to 100ms, the single pulse energy adjustment range is 0.1J to 10J, and the repetition frequency is 10Hz. Other types of pulse lasers can also be used.

[0032] A focusing optical system is used to guide and focus the lasers emitted by the nanosecond pulse laser 2 and the millisecond pulse laser 3 onto the corresponding processing positions on the silicon wafer 14, respectively. It includes a cylindrical focusing lens 11 for shaping and focusing the nanosecond pulse laser beam, an optical focusing lens 8 for focusing the millisecond pulse laser 16, and a series of beam splitters 5, mirrors 6, attenuators 7, optical focusing lenses 8, half-glass slides 9, and polarizing beam splitters 10. Furthermore, a laser energy meter 4 is included to monitor and measure the output energy of the laser in real time, ensuring the stability and repeatability of the processing. After focusing by the cylindrical lens, the laser irradiates the working surface, forming a linear ablation morphology; the millisecond pulse laser 16, after focusing, forms a circular spot with a diameter of 0.1 mm to 10 mm. The nanosecond pulse laser uses a smaller spot width to obtain a high-precision pre-set notch 15, while the low-energy millisecond pulse laser 16 uses a larger spot diameter to improve scanning efficiency and thermal stress uniformity.

[0033] Among them, beam splitter 5 is used to split nanosecond pulse laser and millisecond pulse laser 16; reflector 6 is used to change the direction of nanosecond pulse laser and millisecond pulse laser 16; attenuator 7 is used to attenuate the energy of millisecond pulse laser 16; optical focusing lens 8 is used to focus millisecond pulse laser 16; 1 / 2 glass plate 9 and polarizing beam splitter prism 10 are used to adjust the energy of nanosecond pulse laser.

[0034] A three-dimensional moving platform 12 is used to fix and move the silicon wafer 14.

[0035] The computer control system is electrically connected to the nanosecond pulse laser 2, the millisecond pulse laser 3, and the three-dimensional moving platform 12, and is used to control the laser emission timing, parameters, and the motion path of the three-dimensional moving platform 12.

[0036] To further understand the technical solution of the present invention, a detailed description is provided in conjunction with specific embodiments: Example 1 The method for cutting semiconductor silicon material using combined pulsed laser provided by the present invention is used to pyrolyze and cut a single crystal silicon wafer 14.

[0037] Adopting such Figure 1 The experimental setup for combined pulsed lasers is shown. Millisecond pulsed laser 3 is an Nd:YAG laser with an output wavelength of 1064 nm and an adjustable pulse width; nanosecond pulsed laser 2 has an output wavelength of 1064 nm and a pulse width of 7 ns.

[0038] The sample is an N-type (100) crystal orientation single crystal silicon wafer 14 with a thickness of 500 μm and a polished surface.

[0039] The two laser beams are coaxially confocal through a focusing optical system, and the spot radius of the millisecond pulse laser 16 is 1.5 mm. The silicon wafer 14 is driven by the three-dimensional moving platform 12 and moves at a constant speed.

[0040] The specific process parameters are set as follows: Nanosecond pulsed laser parameters: pulse width is 7ns, single pulse energy is 45.5mJ.

[0041] Millisecond pulsed laser 16 parameters: pulse width set to 1ms, single pulse energy to 4.2J, single pulse energy density to 59.4J / cm².

[0042] Timing and motion parameters: For the same processing point on the preset cutting path, the cutting speed is set to 4 mm / s before the millisecond pulse laser 16 irradiates the nanosecond pulse laser.

[0043] The specific steps are as follows: A nanosecond pulsed laser is used to scan and irradiate along a preset cutting path of a single-crystal silicon wafer 14. The high peak power of the nanosecond pulsed laser achieves precise ablation on the material surface, forming a pre-set notch 15 with controllable depth and clear contour. Figure 3 As shown; The direction of the pre-set notch 15 and the scanning path direction of the millisecond pulse laser are both consistent with the crystal orientation of the silicon wafer; After the nanosecond pulse laser completes its function at that position, a certain delay is followed by a millisecond pulse laser 16 scanning and irradiating along the same path using a pre-set notch 15. Figure 2 As shown. The low energy density and long pulse width of the millisecond pulsed laser 16 irradiates and generates a uniform thermal stress field. This stress is precisely concentrated at the tip of the pre-set notch 15, inducing brittle fracture of the silicon material along the lattice direction of this notch, thereby achieving clean cutting across the entire thickness. After cutting, as shown... Figure 4 As shown.

[0044] After cutting, the morphology was found to be a uniform, continuous ablation groove with a width of approximately 190 μm. The groove edges were smooth with no obvious slag accumulation. The cracks propagated strictly along the preset cutting path with a deviation angle ≤3°. The edge roughness (Ra) was less than 0.62 μm, and the width of the heat-affected zone was ≤80 μm. This method achieved efficient and high-precision pyrolysis cutting.

[0045] Example 2 The difference between this embodiment and Embodiment 1 is that only the energy density of the millisecond pulse laser 16 is adjusted, in order to illustrate the core influence of the energy density of the millisecond pulse laser 16 on the cutting effect, especially its effect on the damage radius and melting depth.

[0046] The apparatus, materials, and basic parameters are the same as in Example 1, with a fixed nanosecond pulse laser energy and a cutting speed of 4 mm / s. The single-pulse energy of the millisecond pulse laser 16 is changed to achieve energy densities of 40.0 J / cm² and 87.7 J / cm², respectively.

[0047] When the energy density of the millisecond pulse laser 16 is 40.0 J / cm² (single pulse energy is 2.8 J), its cutting edge is smooth and the heat-affected zone is smaller than that of Example 1; When the energy density of the millisecond pulse laser 16 is 87.7 J / cm² (single pulse energy is 6.2 J), the melting depth is about 0.9 μm, the damage radius is about 9.0 μm, a slight melting and resolidification layer appears at the cutting edge, and the heat-affected zone is larger than that in Example 1.

[0048] This embodiment illustrates that the damage radius and melting depth mainly depend on the energy density of the millisecond pulsed laser 16. Excellent cutting results can be obtained when the energy density is in the range of 40.0 J / cm² to 59.4 J / cm², while excessive energy will lead to aggravated thermal damage.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that only a single millisecond pulse laser 16 is used to cut the silicon wafer 14.

[0050] Turn off nanosecond pulse laser 2 and use only millisecond pulse laser 3 with the following parameters: energy density 87.7 J / cm², pulse width 1 ms, and cutting speed 4 mm / s.

[0051] After dicing, inspection revealed a large molten zone on silicon wafer 14, averaging approximately 8.2 mm². Material was primarily removed through melting and vaporization, resulting in a wide and irregular kerf. Crack propagation was chaotic and uncontrollable, with an average deviation from the preset path angle of 15°–22°. The diced edges exhibited a noticeable recast layer and numerous microcracks, with a heat-affected zone width of 120–150 μm and a melting depth exceeding 1.1 μm.

[0052] Compared with Example 1, the material removal efficiency of the single millisecond pulse laser 3 is improved, but it causes severe thermal damage to the silicon wafer 14 and results in low cutting quality.

[0053] Comparative Example 2 The difference between this comparative example and Example 1 is that the direction in which the nanosecond pulse laser forms the pre-set notch 15 is deviated from the crystal orientation of the silicon wafer 14 by a certain angle.

[0054] After cutting, as follows Figure 5 As shown, when the directional deviation angle of the pre-set notch 15 is small, the initial crack path will have a significant directional change, rapidly returning from the defect direction to the crystal orientation of the silicon wafer 14, forming a hook-shaped crack initiation mark; if the angle is too large, the initiation will produce multi-source cracks or even breakage.

[0055] The present invention provides a method for cutting semiconductor silicon material using a combined pulsed laser. By employing a combination of nanosecond pulsed lasers and millisecond pulsed lasers 16, energy density matching, and pulse delay time control, the method combines the nanosecond pulsed laser and the millisecond pulsed laser 16 to produce a significant synergistic effect. Compared with cutting with a single millisecond pulsed laser 16, the present invention improves cutting quality while ensuring cutting efficiency, and maximizes the synergistic effect by optimizing the delay time.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for cutting semiconductor silicon material using a combined pulsed laser, characterized in that, Includes the following steps: S1: A nanosecond pulsed laser is used to scan and irradiate the preset cutting path of the silicon wafer to form a preset notch on the preset cutting path of the silicon wafer. S2: A millisecond pulsed laser is used to scan and irradiate along the path of the pre-set notch. The thermal stress generated by the millisecond pulsed laser induces brittle fracture of the silicon material along the pre-set notch, thus completing the cutting. The nanosecond pulse laser has a pulse width of 1 nanosecond to 100 nanoseconds, and the millisecond pulse laser has a pulse width of 1 millisecond to 100 milliseconds.

2. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 1, characterized in that: The nanosecond pulsed laser is focused by a cylindrical focusing lens to irradiate and form an ablation morphology, serving as a pre-set notch; the millisecond pulsed laser is focused by an optical focusing lens to form a circular spot.

3. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 2, characterized in that: The diameter of the light spot formed by focusing the millisecond pulse laser is 0.1mm to 10mm.

4. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 1, characterized in that: The nanosecond pulsed laser has a wavelength of 1064 nm and a pulse energy of 10 mJ to 200 mJ; the millisecond pulsed laser has a wavelength of 1064 nm and a pulse energy of 0.1 J to 10 J.

5. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 1, characterized in that: The direction of the pre-set notch and the scanning path direction of the millisecond pulse laser are both consistent with the crystal orientation of the silicon wafer.

6. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 1, characterized in that: The depth of the pre-set notch is 2% to 10% of the thickness of the silicon wafer, and the width is 10 μm to 100 μm.

7. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 1, characterized in that: There is a time interval between the nanosecond pulse laser scan and the millisecond pulse laser scan.

8. The method for cutting semiconductor silicon material using a combined pulsed laser according to claim 1, characterized in that: The thickness of the silicon wafer is 50μm to 1000μm.

9. A system for performing the method of any one of claims 1-8 combined with pulsed laser cutting of semiconductor silicon material, characterized in that, include: Nanosecond pulsed lasers are used to generate lasers with pulse widths ranging from 1 nanosecond to 100 nanoseconds. Millisecond pulsed lasers are used to generate lasers with pulse widths ranging from 1 millisecond to 100 milliseconds. A timer is used to control nanosecond pulse lasers and millisecond pulse lasers to operate at certain time intervals. A focusing optical system is used to guide and focus the lasers emitted by the nanosecond pulse laser and the millisecond pulse laser to the corresponding processing positions on the silicon wafer, respectively. A three-dimensional moving platform for fixing and moving the silicon wafer; The computer control system is electrically connected to the nanosecond pulse laser, the millisecond pulse laser, and the three-dimensional moving platform, and is used to control the laser emission timing, parameters, and the motion path of the three-dimensional moving platform.

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