Laser cutting apparatus and method based on dual spatial light modulator

Abstract

The application relates to a laser cutting device and method based on a double spatial light modulator, wherein a beam expander, a power attenuation module, a spatial light modulator one for loading a multi-focus phase map and a spatial light modulator two for loading an aberration correction phase map are sequentially arranged on an output light path of a laser; a first convex lens, a first mirror and a second convex lens are sequentially arranged on a light path between the spatial light modulator one and the spatial light modulator two; a third convex lens, a second mirror, a fourth convex lens and a third mirror are sequentially arranged on an output light path of the spatial light modulator two; and a machining objective is arranged on a reflected light path of the third mirror. A laser beam is phase-modulated by the spatial light modulator, focuses on a silicon wafer to generate a plurality of focal points, performs aberration correction, controls a phase map loaded by the spatial light modulator, generates a plurality of axial focal points; and a spot shaping technology of the spatial light modulator corrects a spherical aberration phenomenon caused by a refractive index mismatch in a hidden cutting process.

Description

Technical Field

[0001] This invention relates to a laser cutting device and processing method based on a dual spatial light modulator. Background Technology

[0002] In the semiconductor industry, semiconductor materials dominate and are widely used in products such as MEMS devices, memory modules, CPUs, and power devices. As die sizes and thicknesses decrease, traditional blade-based cutting equipment struggles to meet high-quality requirements due to excessive edge chipping. Laser stealth cutting technology, a non-contact processing method, focuses laser energy within the material to form a modified layer, thereby generating thermal stress cracks. By controlling crack propagation, it achieves highly efficient cutting with no surface scratches, no material loss, and a small heat-affected zone. Laser stealth cutting technology offers advantages such as high processing speed, high material utilization, good dicing quality, good consistency, and high automation, and is widely used in the cutting of brittle semiconductor materials such as silicon wafers.

[0003] Conventional laser stealth cutting technology employs a single-focusing method, where scanning at a single focal point generates the modified layer. For thick semiconductor materials, laser stealth cutting requires multiple scans with progressively increasing focal point positions, resulting in low processing efficiency. If multiple controllable focal points could be simultaneously focused within the material for cutting, the cutting efficiency could be significantly increased.

[0004] During laser stealth cutting, when the converged laser beam passes through the interface between an air medium and a material with different refractive indices, a strong spherical aberration occurs due to refractive index mismatch. This spherical aberration leads to significant focus shift, focal spot stretching, and distortion, and it becomes more pronounced with increasing processing depth. These phenomena negatively impact processing consistency, making aberration correction increasingly important in laser stealth cutting.

[0005] Spatial light modulators, as a new type of programmable optical device, can control the optical parameters such as amplitude, phase and polarization of laser beams. With the required optical path design, arbitrary light field intensity distribution can be obtained in the material processing area.

[0006] Chinese patent No. 201710721276.2 discloses a silicon-based MEMS wafer multi-focus laser cutting system and cutting method. As a multi-focus laser cutting method inside the wafer, it mainly forms multiple focal points through diffractive optical elements. The processing and shaping of diffractive optical elements are closely related to the number and spacing of focal points. If it is necessary to change the number and spacing of focal points, it is necessary to re-customize the diffractive optical elements and adjust the optical path, which makes the operation inconvenient.

[0007] Therefore, there is a need to develop laser processing equipment that improves the efficiency and consistency of internal cutting of semiconductor materials. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a laser cutting device and method based on a dual spatial light modulator, which aims to improve cutting efficiency and consistency.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] The laser cutting device based on dual spatial light modulators is characterized by the following: a beam expander, a power attenuation module, a spatial light modulator one for loading a multifocal phase map, and a spatial light modulator two for loading an aberration correction phase map are sequentially arranged on the output optical path of the laser; a first convex lens, a first reflecting mirror, and a second convex lens are sequentially arranged on the optical path between the spatial light modulator one and the spatial light modulator two; a third convex lens, a second reflecting mirror, a fourth convex lens, and a third reflecting mirror are sequentially arranged on the output optical path of the spatial light modulator two; and a processing objective lens is arranged on the reflected optical path of the third reflecting mirror.

[0011] Furthermore, in the aforementioned laser cutting device based on a dual spatial light modulator, the laser is a near-infrared laser, a green laser, or an ultraviolet laser with a pulse width of nanosecond, picosecond, or femtosecond.

[0012] Furthermore, in the aforementioned laser cutting device based on a dual spatial light modulator, the laser is a near-infrared laser with a wavelength of 1064nm or 1080nm, or a green laser with a wavelength of 532nm or 515nm, or an ultraviolet laser with a wavelength of 355nm or 343nm.

[0013] Furthermore, in the aforementioned laser cutting device based on a dual spatial light modulator, the laser is a laser with a continuously adjustable emission frequency between 10 and 100 kHz, an adjustable average power between 0 and 10 W, and a repetition frequency between 10 and 100 kHz.

[0014] Furthermore, in the aforementioned laser cutting device based on dual spatial light modulators, the first spatial light modulator and the second spatial light modulator are spatial light modulators with wavelengths of 300nm to 1100nm and a pixel count of over 300,000.

[0015] Furthermore, in the aforementioned laser cutting device based on a dual spatial light modulator, the focal length of the first convex lens is the same as that of the second convex lens.

[0016] This invention relates to a laser cutting method based on dual spatial light modulators. The laser output from the laser is magnified and collimated by a beam expander. A power attenuation module adjusts the laser power so that the laser power density incident on spatial light modulator one is below its threshold. Spatial light modulator one loads a multi-focal phase map and reflects and transmits the laser. A first reflecting mirror changes the optical path transmission direction. A first convex lens and a second convex lens form a 4f system to transmit the image to spatial light modulator two. Spatial light modulator two loads an aberration-corrected phase map. A second and third reflecting mirror change the optical path transmission direction. A third convex lens and a fourth convex lens form a 4f system to reduce the laser beam and transmit the image, ensuring the laser beam passes completely through the aperture of the processing objective. The laser output from the processing objective generates multiple axial focal points along the beam propagation direction within the processed material and performs aberration correction, thus achieving the cutting of the processed material.

[0017] Furthermore, in the aforementioned laser cutting method based on dual spatial light modulators, multiple focal points are generated within the semiconductor material and aberration correction is performed by loading an axial multifocal phase map into spatial light modulator one and an aberration correction phase map into spatial light modulator two. The number and spacing of the focal points are controlled by loading different phase maps, and aberration correction is controlled by the aberration correction phase map.

[0018] Furthermore, in the aforementioned laser cutting method based on dual spatial light modulators, a multi-focal phase map is loaded by the spatial light modulator. After the laser beam is focused by the processing objective lens, multiple focal points are generated before and after the focal plane. The number and spacing of the focal points are adjusted by different phase maps. Aberration correction phase maps at different depths are loaded by the spatial light modulator to correct the phenomenon of focal spot stretching and poor focusing caused by refractive index mismatch at different processing depths.

[0019] Compared with the prior art, the present invention has significant advantages and beneficial effects, specifically reflected in the following aspects:

[0020] ①This invention generates multiple focal points and performs aberration correction inside a semiconductor material by loading an axial multifocal phase map and an aberration correction phase map through a spatial light modulator. The number and spacing of the focal points are controlled by loading different phase maps, and the aberration correction is controlled by the aberration correction phase map.

[0021] ② By loading an axial multifocal phase map and an aberration correction phase map using a spatial light modulator, multiple focal points are generated inside the semiconductor material and aberration correction is performed. The number and spacing of the focal points are controlled by loading different phase maps, and aberration correction is controlled by the aberration correction phase map. The controllable axial multifocal points generated by the spatial light modulator are used for stealth cutting of semiconductor materials, which greatly improves the stealth cutting efficiency of semiconductor materials and can be extended to the precision processing of brittle semiconductor materials such as silicon wafers, gallium arsenide, indium phosphide, and gallium nitride, as well as glass materials.

[0022] ③ By using the spot shaping technology of spatial light modulator, the spherical aberration caused by refractive index mismatch during the hidden cutting process of semiconductor materials can be corrected, which helps to improve the consistency and processing quality of the hidden cutting of semiconductor materials.

[0023] ④ For thicker semiconductor materials (>300μm), traditional hidden cutting methods require 5 to 6 cuts at a processing speed of around 300mm / s, while the present invention requires only 1 to 2 cuts at a processing speed of >500mm / s;

[0024] ⑤ By loading a multi-focal phase map through a spatial light modulator, the laser beam generates multiple focal points before and after the processing objective lens. The number and spacing of the focal points can be adjusted by different phase maps. By loading aberration correction phase maps at different depths through a spatial light modulator, the phenomenon of focal spot stretching and poor focusing caused by refractive index mismatch at different processing depths can be corrected, thereby improving processing consistency.

[0025] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing specific embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 : Schematic diagram of the optical path structure of the device of the present invention;

[0028] Figure 2 Aberration correction diagram;

[0029] Figure 3 : Schematic diagram of a dual-focal hidden section;

[0030] Figure 4 Image showing the effect of dual-focus hidden cutting and aberration correction on a silicon wafer;

[0031] Figure 5 Schematic diagram of a three-focal hidden section;

[0032] Figure 6 : Trifocal hidden section and aberration correction effect diagram of silicon wafer. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, directional and ordinal terms are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] like Figure 1 As shown, in a laser cutting device based on dual spatial light modulators, a beam expander 2, a power attenuation module 3, a spatial light modulator 4 for loading a multifocal phase map, and a spatial light modulator 8 for loading an aberration correction phase map are sequentially arranged on the output optical path of the laser 1. A first convex lens 5, a first reflecting mirror 6, and a second convex lens 7 are sequentially arranged on the optical path between the spatial light modulator 4 and the spatial light modulator 8. A third convex lens 9, a second reflecting mirror 10, a fourth convex lens 11, and a third reflecting mirror 12 are sequentially arranged on the output optical path of the spatial light modulator 8. A processing objective lens 13 is arranged on the reflected optical path of the third reflecting mirror 12.

[0036] The laser 1 emits a near-infrared, green, or ultraviolet laser with a pulse width of nanosecond, picosecond, or femtosecond. Preferably, the emitted laser wavelength is 1064nm or 1080nm, or the green laser wavelength is 532nm or 515nm, or the ultraviolet laser wavelength is 355nm or 343nm. The emitted laser frequency is continuously adjustable between 10 and 100kHz, the average power is adjustable between 0 and 10W, and the repetition frequency is between 10 and 100kHz.

[0037] Spatial light modulator 1-4 and spatial light modulator 2-8 are spatial light modulators with wavelengths of 300nm to 1100nm and a pixel count of over 300,000.

[0038] The focal length of the first convex lens 5 is the same as the focal length of the second convex lens 7.

[0039] When used for cutting, the laser output from laser 1 is magnified and collimated by beam expander 2 to cover the effective window of spatial light modulator as much as possible. Power attenuation module 3 adjusts the laser power so that the laser power density incident on spatial light modulator 4 is lower than its threshold to prevent damage. Spatial light modulator 4 loads a multi-focal phase map and reflects and transmits the laser. First reflector 6 changes the direction of light path transmission. First convex lens 5 and second convex lens 7 form a 4f system to transmit the image to spatial light modulator 8. Spatial light modulator 8 loads an aberration correction phase map. Second reflector 10 and third reflector 12 change the direction of light path transmission. Third convex lens 9 and fourth convex lens 11 form a 4f system to shrink the laser spot and transmit the image, so that the laser beam passes completely through the aperture of processing objective lens 13. The laser output from processing objective lens 13 generates multiple axial focal points along the beam propagation direction inside the processed material 14 and performs aberration correction to achieve cutting of the processed material.

[0040] By loading an axial multifocal phase map using spatial light modulator 4 and an aberration correction phase map using spatial light modulator 8, multiple focal points are generated inside the semiconductor material and aberration correction is performed. The number and spacing of the focal points are controlled by loading different phase maps, and aberration correction is controlled by the aberration correction phase map.

[0041] By loading a multi-focal phase map using a spatial light modulator, the laser beam generates multiple focal points before and after the processing objective lens. The number and spacing of these focal points are adjusted using different phase maps. Aberration correction phase maps at different depths are loaded using a spatial light modulator to correct focal spot stretching and poor focusing caused by refractive index mismatch at different processing depths, thereby improving processing consistency.

[0042] like Figure 2 As shown, during laser stealth cutting, when the converged laser beam passes through the interface between an air medium and a material with different refractive indices, a strong spherical aberration occurs due to refractive index mismatch. Spherical aberration leads to significant focus shift, focal spot stretching, and distortion, and it becomes more pronounced with increasing processing depth. To compensate for spherical aberration caused by refractive index mismatch, this invention loads an aberration correction phase map onto a spatial light modulator to modulate the phase field of the incident light, thereby compensating for spherical aberration.

[0043] The specific formula for spherical aberration compensation is as follows: Phase modulation of the laser focus projected onto the material to be processed.

[0044]

[0045] Where λ is the laser wavelength, ρ is the normalized pupil radius of the emitted laser, and d nomLet n1 = 1 be the refractive index of air, n2 be the refractive index of the material to be processed, NA be the numerical aperture of the femtosecond laser exiting objective, and φ be the spherical aberration corrected phase. Substituting the parameters, the aberration corrected phase map can be calculated using MATLAB or Python software, with a resolution of 1920×1080 and a depth of 8.

[0046] like Figure 3 The illustrated dual-focal hidden section shows a beam that undergoes phase modulation via a spatial light modulator and, after passing through a 4f system, reaches the processing objective and is focused inside the silicon wafer to generate two focal points. Aberration correction is then performed. By controlling the phase map loaded onto the spatial light modulator, two axial focal points can be generated. The focal distance can be adjusted using the phase map. Figure 4 The image shown illustrates the effect of dual-focus hidden cutting and aberration correction on a silicon wafer.

[0047] like Figure 5 The diagram illustrates a three-focal hidden beam. The beam undergoes phase modulation via a spatial light modulator and, after passing through a 4f system, reaches the processing objective and is focused inside the silicon wafer, generating three focal points. By controlling the phase map loaded onto the spatial light modulator, three axial focal points can be generated. The focal point spacing can be adjusted using the phase map. Figure 6 The image shows a hidden three-focal section on a silicon wafer and the aberration correction effect.

[0048] On one hand, the laser beam undergoes phase modulation via a spatial light modulator and, after passing through a 4f system, reaches the processing objective lens and is focused inside the silicon wafer to generate multiple focal points. Aberration correction is then performed, and multiple axial focal points are generated by controlling the phase map loaded onto the spatial light modulator; the focal point spacing can be adjusted using the phase map. On the other hand, the spot shaping technology of the spatial light modulator corrects spherical aberration caused by refractive index mismatch during the silicon wafer dicing process, thus improving the consistency and processing quality of the silicon wafer dicing.

[0049] In summary, this invention generates multiple focal points and performs aberration correction within a semiconductor material by loading an axial multifocal phase map and an aberration correction phase map using a spatial light modulator. The number and spacing of the focal points are controlled by loading different phase maps, and the aberration correction is controlled by the aberration correction phase map.

[0050] Using spatial light modulators to generate controllable axial multifocals for stealth cutting of semiconductor materials significantly improves the efficiency of stealth cutting of semiconductor materials and can be extended to the precision processing of brittle semiconductor materials such as silicon wafers, gallium arsenide, indium phosphide, and gallium nitride, as well as glass materials.

[0051] The spot shaping technology of spatial light modulator can be used to correct the spherical aberration caused by refractive index mismatch during the hidden cutting process of semiconductor materials, which helps to improve the consistency and processing quality of the hidden cutting of semiconductor materials.

[0052] For thicker semiconductor materials (>300μm), traditional hidden cutting methods require 5 to 6 cuts at a processing speed of around 300mm / s, while the present invention requires only 1 to 2 cuts at a processing speed of >500mm / s.

[0053] By loading a multi-focal phase map using a spatial light modulator, the laser beam is focused by the processing objective lens to generate multiple focal points before and after the focal plane. The number and spacing of the focal points can be adjusted by different phase maps.

[0054] By loading aberration correction phase maps at different depths using a spatial light modulator, phenomena such as focal spot stretching and poor focusing caused by refractive index mismatch at different processing depths can be corrected, thereby improving processing consistency.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0056] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A laser cutting device based on a dual spatial light modulator, characterized in that: A beam expander (2), a power attenuation module (3), a spatial light modulator (4) for loading a multifocal phase map, and a spatial light modulator (8) for loading an aberration correction phase map are arranged sequentially on the output optical path of the laser (1). A first convex lens (5), a first reflector (6), and a second convex lens (7) are arranged sequentially on the optical path between the spatial light modulator (4) and the spatial light modulator (8). A third convex lens (9), a second reflector (10), a fourth convex lens (11), and a third reflector (12) are arranged sequentially on the output optical path of the spatial light modulator (8). A processing objective lens (13) is arranged on the reflected optical path of the third reflector (12). The spatial light modulator one (4) and spatial light modulator two (8) are spatial light modulators with wavelengths of 300 nm to 1100 nm and a pixel count of more than 300,000.

2. The laser cutting device based on a dual spatial light modulator according to claim 1, characterized in that: The laser (1) is a near-infrared laser, a green laser, or an ultraviolet laser with a pulse width of nanosecond, picosecond, or femtosecond.

3. The laser cutting apparatus based on a dual spatial light modulator according to claim 1 or 2, characterized in that: The laser (1) is a near-infrared laser with a wavelength of 1064 nm or 1080 nm, or a green laser with a wavelength of 532 nm or 515 nm, or an ultraviolet laser with a wavelength of 355 nm or 343 nm.

4. The laser cutting apparatus based on a dual spatial light modulator according to claim 1 or 2, characterized in that: The laser (1) is a laser whose emission frequency is continuously adjustable between 10 and 100 kHz, whose average power is adjustable between 0 and 10 W, and whose repetition frequency is between 10 and 100 kHz.

5. The laser cutting device based on a dual spatial light modulator according to claim 1, characterized in that: The focal length of the first convex lens (5) is the same as that of the second convex lens (7).

6. A laser cutting method based on a dual spatial light modulator using the apparatus of claim 1, characterized in that: The laser output from the laser (1) is magnified and collimated by the beam expander (2). The power attenuation module (3) adjusts the laser power so that the laser power density incident on the first spatial light modulator (4) is lower than its threshold. The first spatial light modulator (4) loads a multi-focal phase map and reflects and transmits the laser. The first reflector (6) changes the direction of optical path transmission. The first convex lens (5) and the second convex lens (7) form a 4f system to transmit the image to the second spatial light modulator (8). The second spatial light modulator (8) loads an aberration correction phase map. The second reflector (10) and the third reflector (12) change the direction of optical path transmission. The third convex lens (9) and the fourth convex lens (11) form a 4f system to shrink the laser spot and transmit the image so that the laser beam passes completely through the aperture of the processing objective (13). The laser output from the processing objective (13) generates multiple axial focal points along the beam propagation direction inside the processed material (14) and performs aberration correction to achieve the cutting of the processed material.

7. The laser cutting method based on a dual spatial light modulator according to claim 6, characterized in that: By loading an axial multifocal phase map through spatial light modulator one (4) and an aberration correction phase map through spatial light modulator two (8), multiple focal points are generated inside the semiconductor material and aberration correction is performed. The number and spacing of focal points are controlled by loading different phase maps, and aberration correction is controlled by the aberration correction phase map.

8. The laser cutting method based on a dual spatial light modulator according to claim 6, characterized in that: By loading a multifocal phase map using a spatial light modulator, the laser beam generates multiple focal points before and after being focused by the processing objective lens. The number and spacing of these focal points are adjusted using different phase maps. Aberration correction phase maps at different depths are loaded using a spatial light modulator to correct the phenomenon of focal spot stretching and poor focusing caused by refractive index mismatch at different processing depths.

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