Laser grooving line light spot width control device and method

Abstract

The invention relates to the technical field of laser processing, in particular to a laser grooving line light spot width control device and method.The laser grooving line light spot width control device comprises a laser used for emitting laser beams; the slit is arranged on a light path of the laser beam, has a fixed physical slit width and is used for intercepting the laser beam, and the slit width of the slit is kept unchanged in the process of adjusting the width of the linear light spot; the imaging adjusting module is located on the light path behind the slit and used for conducting optical imaging on the slit to form a middle line light spot image with the variable width, and the imaging magnification of the imaging adjusting module is adjustable; the focusing module is located behind the imaging adjusting module and used for focusing the middle line light spot image to the surface of a workpiece to be machined, and a line light spot used for grooving is formed. According to the scheme, the energy utilization rate can be kept constant, meanwhile, accurate and continuous regulation and control of the linear light spot width are achieved, the diffraction effect is effectively restrained, and the grooving quality is improved.

Description

Technical Field

[0001] This application relates to the field of laser processing technology, and in particular to a device and method for controlling the laser grooving line spot width. Background Technology

[0002] In modern precision manufacturing, laser grooving and scribing technology is widely used in many fields, such as pre-treatment of semiconductor wafers for grooving, P1 / P2 / P3 scribing of solar cells, cutting of flat panel display (FPD) glass, and scribing separation of brittle materials such as ceramics or sapphire. In these applications, it is usually necessary to shape the circular Gaussian spot emitted by the laser into a focused linear spot with a specific width and a flat-top intensity distribution in order to efficiently and effectively form grooves or scribing lines on the material surface.

[0003] Currently, the existing technical solution in the industry uses a combination of a slit and a cylindrical lens. This involves using a mechanically adjustable slit to intercept the Gaussian incident beam, obtaining a portion of the beam with a relatively flat energy distribution and defining the width of the line spot. Subsequent optical elements, such as cylindrical lenses, then reshape and focus the beam. The biggest advantage of this solution is its low cost and the ability to easily achieve continuously adjustable width of the quasi-flat-top line spot.

[0004] However, this approach has an inherent and insurmountable drawback. Because the Gaussian beam emitted by the laser exhibits a distribution of energy that is strong at the center and weak at the edges, when the physical width of the slit is adjusted to meet the process requirements of different products, the total laser energy passing through the slit undergoes a drastic and nonlinear change. This results in extremely unstable power density acting on the workpiece, narrowing the process window, making the debugging process complex and time-consuming, and making it difficult to guarantee consistent processing results. In practical applications, it often occurs that after increasing the slit width, the energy in the newly added area is insufficient to reach the material's processing threshold, leading to a nonlinear problem where the actual groove width does not increase as expected. Furthermore, when processing fine, narrow grooves and adjusting the slit to a very narrow size (e.g., less than 0.3 mm), strong diffraction effects become unavoidable. This not only causes excessive beam divergence, easily exceeding the aperture of subsequent optical elements and causing energy loss, but also introduces high-frequency intensity oscillations and edge hotspots into the final focused spot, severely affecting the edge quality and bottom morphology of the groove.

[0005] Therefore, it is urgent to solve the problems of unstable energy utilization, process nonlinearity, severe diffraction effect, and difficulty in balancing cost and performance caused by directly adjusting the slit width in the existing technology. Summary of the Invention

[0006] The main objective of this application is to provide a laser grooving line spot width control device and method, which aims to solve the technical problems of unstable energy utilization, process nonlinearity, severe diffraction effect, and difficulty in balancing cost and performance caused by directly adjusting the slit width in the prior art.

[0007] To achieve the aforementioned objective, the first aspect of this application proposes a laser grooving line spot width control device, comprising: A laser, used to emit a laser beam; A slit is disposed in the optical path of the laser beam, has a fixed physical slit width, is used to intercept the laser beam, and the slit width remains unchanged during the process of adjusting the line spot width; An imaging adjustment module is located on the optical path after the slit and is used to perform optical imaging on the slit to form a centerline light spot image with variable width. The imaging magnification of the imaging adjustment module is adjustable. The focusing module, located after the imaging adjustment module, is used to focus the intermediate line spot image onto the surface of the workpiece to be processed, forming a line spot for grooving.

[0008] Furthermore, the imaging adjustment module includes at least one cylindrical lens, and the imaging magnification is changed by adjusting the object distance between the slit and the cylindrical lens.

[0009] Furthermore, the imaging adjustment module is a parfocal zoom cylindrical lens group, whose object plane and image plane remain in constant position during the zoom process, and the imaging magnification is continuously adjusted by changing the relative position between at least two lenses inside the parfocal zoom cylindrical lens group.

[0010] Furthermore, the focusing module includes a relay lens and a focusing objective lens arranged sequentially along the optical path propagation direction, used to relay and focus the centerline light spot image onto the workpiece surface.

[0011] Furthermore, it also includes a beam expander disposed between the laser and the slit for expanding and collimating the laser beam.

[0012] Furthermore, the fixed slit width of the slit is 0.5 mm to 2 mm.

[0013] The second aspect of this application proposes a method for controlling the laser grooving line spot width, including: A laser beam is emitted from a laser and passed through a slit with a fixed physical width, and the width of the slit remains unchanged during subsequent adjustments. The slit is optically imaged using an imaging adjustment module to form a centerline spot image with variable width; Adjust the imaging magnification of the imaging adjustment module to change the width of the midline spot image; The adjustable-width centerline spot image is focused onto the surface of the workpiece to be processed for laser grooving.

[0014] Furthermore, the adjustment of the imaging magnification is achieved by controlling the object distance between the slit and the imaging adjustment module.

[0015] Furthermore, the imaging adjustment module is a parfocal variable magnification cylindrical lens group. The adjustment of the imaging magnification is achieved by changing the relative positions of the lenses inside the parfocal variable magnification cylindrical lens group, and the positions of the object plane and the image plane of the parfocal variable magnification cylindrical lens group remain unchanged throughout the adjustment process.

[0016] Furthermore, before the step of using the imaging adjustment module to perform optical imaging on the slit to form a midline spot image, the method further includes: using a beam expander to expand and collimate the laser beam.

[0017] Beneficial effects This solution effectively decouples the energy interception function from the line spot width adjustment function by employing a structural design that combines a fixed-width slit with a subsequent adjustable imaging module. Specifically, the physical slit width remains constant during processing, ensuring a constant energy transmittance of the laser beam as it passes through the slit. This fundamentally avoids the drastic power density fluctuations caused by slit width changes in traditional adjustable slit solutions, significantly improving process stability and repeatability. Simultaneously, the line spot width no longer depends on the physical size of the slit but is achieved by scaling the slit image through the magnification of the imaging module. This results in excellent linearity and predictability in line width adjustment, greatly simplifying the process debugging process. Furthermore, when the system allows for spot width adjustment without using an excessively narrow fixed slit, it effectively reduces the risk of slit damage due to blocking excessively high laser power density, extending its service life. It also effectively suppresses strong diffraction effects, reducing undesirable phenomena such as intensity oscillations and edge hotspots in the final spot, thereby improving processing quality. Attached Figure Description

[0018] Figure 1 This is a schematic block diagram of a laser grooving line spot width control device according to an embodiment of this application; Figure 2 This is a schematic diagram of the optical path in the X direction according to an embodiment of this application; Figure 3 This is a schematic diagram of the optical path in the Y direction according to an embodiment of this application; Figure 4This is a simulation diagram of line spots with widths of nearly 80 μm and nearly 20 μm achieved by adjusting the total magnification in one embodiment of this application, as well as the square distribution of the electric field intensity in the width direction; Figure 5 This is a flowchart illustrating a laser grooving line spot width control method according to an embodiment of this application; Among them, 10 is the laser; 20 is the beam expander; 30 is the slit; 40 is the imaging adjustment module; 50 is the focusing module; 51 is the first relay lens; 52 is the second relay lens; 60 is the workpiece to be processed; and 70 is the stage. The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] Those skilled in the art will understand that, unless explicitly stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of features, integers, steps, operations, elements, modules, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, modules, components, and / or groups thereof. It should be understood that when an element is referred to as “connected” or “coupled” to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein may include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any modules and all combinations of one or more associated listed items.

[0021] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this solution pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0022] Reference Figure 1In one embodiment, this application proposes a laser grooving line spot width control device, characterized in that it includes: a laser 10 for emitting a laser beam; a slit 30 disposed in the optical path of the laser beam, having a fixed physical slit width for intercepting the laser beam, and the slit width of the slit 30 remains unchanged during the adjustment of the line spot width; an imaging adjustment module 40 located in the optical path after the slit 30, for optically imaging the slit 30 to form a variable-width intermediate line spot image, wherein the imaging magnification of the imaging adjustment module 40 is adjustable; and a focusing module 50 located after the imaging adjustment module 40, for focusing the intermediate line spot image onto the surface of the workpiece 60 to be processed, forming a line spot for grooving.

[0023] In this embodiment, laser 10 serves as the light source, providing the initial laser beam. Its selection depends on the specific processing material and process requirements. For example, when grooving a low-k material on a workpiece 60 (e.g., a semiconductor wafer) placed on a stage 70, a 355nm ultraviolet nanosecond, picosecond, or femtosecond laser 10 can be selected. This not only utilizes the "cold processing" characteristic to reduce the heat-affected zone but also improves processing accuracy. The beam emitted from laser 10 is typically a circular spot with a Gaussian energy distribution.

[0024] Subsequently, the laser beam enters the beam expander 20. The beam expander 20 serves three purposes: first, it enlarges the original, relatively small laser spot to reduce the laser power density on the surface of subsequent optical components, preventing optical damage and improving the system's stability and lifespan at high power; second, it collimates the laser beam, ensuring it enters the subsequent system in a nearly parallel state, providing a basis for precise optical transformation; third, by adjusting the beam expansion ratio, the diameter of the spot incident on the fixed slit 30 can be controlled, providing an additional degree of freedom for adjusting energy utilization to some extent. The beam expander 20 consists of a focal-free system composed of multiple internal lenses, and its expansion factor can be adjusted between 2 and 10 times. After expansion, the laser beam diameter (defined by 1 / e² intensity) reaches 2 mm to 10 mm.

[0025] The collimated and expanded laser beam is incident on a key component of this design—the fixed slit 30. Unlike the prior art, which uses a variable-width slit 30 to directly control the line spot width, the slit 30 in this design has a preset physical slit width that remains unchanged during processing. In this embodiment, the width of the slit 30 can be selected as any fixed value between 0.5 mm and 2 mm. The slit width direction of the slit 30 is defined as the X-direction. The core objective of this design is to completely decouple the physical process of energy interception from the size adjustment process. Since both the energy distribution (Gaussian distribution) of the incident spot and the physical width of the slit 30 are fixed, the percentage of laser energy passing through the slit 30 (i.e., energy utilization) becomes an inherent constant of the system. This fundamentally solves the problem of drastic energy fluctuations caused by adjusting the width of the slit 30 in the prior art. The plane containing the fixed slit 30 is optically precisely defined as the initial object plane in the X-direction.

[0026] When the slit 30 confines the incident Gaussian beam in the X direction (the direction of the line spot width), a diffraction effect occurs. According to the single-slit diffraction formula... ,in When the intensity distribution is the first principal maximum, . Let be the diffraction angle, and D be the width of slit 30. Using a relatively wide slit 30, such as 0.5 mm or more, significantly reduces the diffraction angle (inversely proportional to the slit width). This allows subsequent components to receive more high-frequency diffracted light, effectively suppressing high-frequency intensity oscillations and edge hotspots in the final line spot. Simultaneously, the wider slit width also reduces the power density at the edge of slit 30, decreasing the risk of thermal damage and extending component lifespan.

[0027] The light beam passing through the fixed slit 30 enters the imaging adjustment module 40. The core function of this module is to perform the first optical imaging of the fixed slit 30, which acts as the "object," forming a continuously adjustable intermediate image with a magnification of Mpre. In a basic embodiment, the intermediate imaging zoom module can be composed of a single or fixed combination of cylindrical lenses. By changing the relative distance (i.e., object distance u) between the fixed slit 30 and the cylindrical lens group, the magnification can be adjusted according to the Gaussian imaging formula 1 / u + 1 / v = 1 / f and the magnification formula M = -v / u. However, according to the imaging formula, a change in object distance u inevitably leads to a corresponding change in image distance v. Therefore, in this embodiment, in order to obtain a clear final image after changing the magnification, it is necessary to mechanically adjust the position of the subsequent focusing system to track the drift of the intermediate image plane.

[0028] Reference Figure 4As shown, this figure illustrates the simulation results of achieving different line spot widths by adjusting the total magnification in one embodiment of this application, as well as the square distribution of the electric field intensity along the corresponding width direction. Specifically, it includes four sub-figures: The top left image shows a simulated linear spot formed when the total magnification is relatively large (e.g., M_total≈0.05). Its width is about 80μm, presenting a relatively long and wide linear spot with a relatively uniform energy distribution.

[0029] The upper right figure shows the square distribution curve of the electric field intensity in the width direction (X direction) of the 80μm line spot, which shows the energy distribution trend along the line width direction. The overall distribution is flat-topped with a slight decrease at the edges, indicating good energy uniformity.

[0030] The lower left image shows a simulated line spot formed when the total magnification is relatively small (e.g., M_total≈0.0125). Its width is about 20μm, the line width is significantly narrowed, but it still maintains a clear linear outline.

[0031] The lower right figure shows the square distribution curve of the electric field intensity in the width direction of the 20μm line spot, which shows a steeper edge and higher energy concentration, while still maintaining a near-rectangular flat-top characteristic.

[0032] like Figure 4 As shown, by adjusting the magnification of the imaging adjustment module, the system can continuously control the line spot width from approximately 20 μm to 80 μm. When the total magnification is high, a line spot with a width of approximately 80 μm is formed, with a near-flat-topped square distribution of the electric field intensity along its width direction, indicating uniform energy. When the magnification decreases, the line spot width shrinks to approximately 20 μm, while still maintaining good energy distribution characteristics and sharp edges. This demonstrates that the device can achieve high-precision and highly consistent line width adjustment without changing the slit width, meeting different process requirements.

[0033] Furthermore, to overcome the image plane drift problem in the basic implementation described above, in a preferred embodiment, the imaging zoom module employs a parfocal zoom cylindrical lens group. The function of this module is to maintain the fixed positions of its object plane (i.e., the fixed slit 30 position) and the final intermediate image plane while achieving continuous adjustment of the imaging magnification Mpre. In this embodiment, the zoom magnification of the parfocal zoom cylindrical lens group is Mpre = 0.25X to 1X. The parfocal zoom cylindrical lens group consists of multiple cylindrical lenses, all with their cylindrical axes parallel to the Y-axis. Functionally, they can be divided into at least two cooperating lens groups: a zoom group, which is the core driving unit for realizing the zoom function; its position change is mainly used to change the overall effective focal length of the entire module, thereby directly changing the imaging magnification; and a compensation group, whose motion trajectory is strictly coupled with the zoom group through a precise mechanical linkage structure, performing nonlinear cooperative displacement to accurately compensate for image plane drift caused by zoom.

[0034] Furthermore, to achieve independent control of the beams in both the X and Y directions, a Y-direction cylindrical lens with its cylindrical axis orthogonal to the aforementioned cylindrical lens (i.e., parallel to the X-axis) is integrated within or immediately after this module. This lens only affects the collimated beam in the Y direction (the diffraction-limited direction of the line spot), causing it to diverge and form a virtual image point in the Y direction. A key aspect of its optical design is ensuring that the plane of the formed Y-direction virtual image point precisely coincides with the aforementioned intermediate image plane in the X direction. This coincident plane provides a unified, coplanar, conjugate object plane for subsequent optical systems.

[0035] Furthermore, the Y-direction cylindrical lens and the relay lens form a focal-free system in the Y direction, expanding the beam in the Y direction. This step is necessary because the scaling factor in the X direction is limited, restricting the physical width of the slit 30. Simultaneously, considering energy utilization, the diameter of the beam incident on the slit 30 should not exceed six times the width of the slit 30. The energy utilization can be expressed by the formula... The calculation is performed, where η is the energy transmittance, erf(x) is the error function, which is the analytical solution function of the Gaussian function integral, and Dnorm is the normalized slit width 30, i.e., the slit width D divided by the incident light spot radius. When the energy transmittance is greater than 30%, the width of slit 30 is not less than 0.4 times the beam radius. Therefore, the beam diameter in the Y direction is smaller than the incident beam diameter of the maximum numerical aperture of the final focusing lens. The beam in the Y direction is expanded separately to meet the requirement of the maximum numerical aperture of the final focusing lens. In one embodiment, the width of slit 30 is 1 mm, and the incident beam diameter is 5 mm. A focal-free system in the Y direction is formed by the cylindrical lens and the relay lens in the module, and the beam in the Y direction is expanded by 2 times, so that the beam diameter becomes 10 mm, which meets the incident beam diameter requirement of the maximum numerical aperture of the subsequent focusing lens.

[0036] After being processed by the module, the light beam emitted from the fixed "conjugate plane" enters the focusing system consisting of a relay lens, namely the first relay lens 51, and a focusing objective, namely the second relay lens 52. Specifically, the focusing module 50 includes a first relay lens 51 and a second relay lens 52, wherein the second relay lens 52 serves as a focusing objective and is used to focus the light beam onto the surface of the workpiece.

[0037] In one embodiment, the conjugate plane is disposed on the front focal plane of the first relay lens 51 of the focusing system, hence the name telescope focusing system. The telescope focusing system "images" in the X direction and "focuses" in the Y direction. The system processes beams in both directions simultaneously: for the X direction, the system acts as a relay telescope, clearly imaging the intermediate image on the "conjugate plane" onto the rear focal plane of the second relay lens 52 with a constant reduction magnification Mtele = f52 / f51 (where f51 is the focal length of the first relay lens 51 and f52 is the focal length of the second relay lens 52), forming the final image. The total magnification of the system is Mtotal = Mpre. Mtele is entirely controlled by the magnification Mpre of the variable-magnification cylindrical lens group. For the Y direction, the diverging beam emanating from the "conjugate object plane" becomes collimated after passing through the first relay lens 51 and is finally focused on the back focal plane of the second relay lens 52. Because the "objects" in the X and Y directions originate from the same plane, their "images" must also fall on the same plane.

[0038] Since the Y-direction is an uncut Gaussian beam, while the X-direction is a cut-off beam with relatively flat energy, after focusing by the telescope focusing system, a diffraction-limited focused beam is formed in the Y-direction at the image / focal plane, and a scaled-down, flat-top beam with a specific width in the X-direction, thus forming a linear spot. In this embodiment, the focused flat-top linear spot, after one or more scans, creates a 20-80 μm groove on the semiconductor wafer surface. The groove bottom is flat, and the groove walls are vertical, indicating that the control device and method for this linear spot have a significant beneficial effect on improving the quality of the linear spot and the process quality of the grooving.

[0039] Reference Figure 2This figure illustrates the optical shaping process of the laser beam in the X-direction (i.e., the direction of the line spot width). The beam first passes through a fixed slit 30, whose physical slit width remains constant, intercepting only a portion of the incident Gaussian beam to form an "object" with a near-flat-top energy distribution. Subsequently, the beam enters the imaging adjustment module 40, which consists of cylindrical lenses, to optically image the slit, forming an intermediate line spot image with an adjustable width. This intermediate image is further transmitted to a focusing system composed of a first relay lens 51 and a second relay lens 52, ultimately forming a line spot of the desired width on the workpiece surface. Since the X-direction is restricted by the slit, the imaging process is an "imaging-relay" structure, enabling precise control of the line width.

[0040] Reference Figure 3 This figure illustrates the processing path of the laser beam in the Y-direction (i.e., the length direction of the line spot, the diffraction-limited direction). In this direction, the beam is not truncated by the slit, maintaining its original Gaussian distribution. The beam directly enters the Y-direction cylindrical lens 40 in the imaging adjustment module. This lens is a negative lens or a diverging lens, causing the beam to diverge and form a virtual image point in the Y-direction. Subsequently, the beam is collimated by the first relay lens 51 and focused by the second relay lens 52, forming a diffraction-limited focal point on the workpiece surface. This path achieves beam expansion and focusing in the Y-direction, ensuring high energy density and sharp edges of the line spot along its length.

[0041] The two schematic diagrams show that the X and Y orthogonal directions are controlled independently in this scheme. The X direction achieves linewidth adjustment through a fixed slit and variable magnification imaging; the Y direction achieves diffraction-limited focusing through unfocused beam expansion and focusing. The two coincide at the conjugate plane, ensuring that a high-quality line spot with controllable width and good focusing in the length direction is formed on the surface of the workpiece, which is suitable for high-precision laser grooving applications.

[0042] In summary, this embodiment, through a series of precise optical designs, enables accurate, linear, and parfocal adjustment of the line spot width while maintaining constant energy utilization. It not only addresses the core pain points of the prior art but also, by employing a relatively wide fixed slit 30, suppresses strong diffraction effects at the source, improving the quality of the final spot. This provides an ideal solution for high-precision laser grooving applications that combines high performance, high stability, and reasonable cost.

[0043] In one embodiment, the imaging adjustment module 40 includes at least one cylindrical lens, and the imaging magnification is changed by adjusting the object distance between the slit 30 and the cylindrical lens.

[0044] In this embodiment, the imaging adjustment module 40 is composed of one or more cylindrical lenses, with their cylindrical axes parallel to the Y direction, and only performs imaging processing on the beam in the X direction. The slit 30, acting as the object, is located in front of the cylindrical lens. The object distance is denoted as u, the image distance as v, and the lens focal length as f, satisfying the Gaussian imaging formula 1 / u + 1 / v = 1 / f, with an imaging magnification M = -v / u. By adjusting the relative distance between the slit 30 and the cylindrical lens (i.e., changing the object distance u) through a precision displacement mechanism, the magnification can be continuously adjusted, thereby changing the width of the midline light spot image.

[0045] This structure is suitable for applications requiring high system integration flexibility and allowing for coordinated position adjustments to the subsequent focusing module 50. For example, in laboratory R&D or small-batch pilot production environments, the object distance can be fine-tuned manually or electrically to quickly verify the process effects under different linewidths. Because this solution has a small number of optical components and a simple structure, it is easy to debug and maintain, making it practically valuable in cost-sensitive applications or those with low magnification frequencies.

[0046] In one embodiment, the imaging adjustment module 40 is a parfocal zoom cylindrical lens group, whose object plane and image plane remain in constant position during the zoom process, and the imaging magnification is continuously adjusted by changing the relative position between at least two lenses inside the parfocal zoom cylindrical lens group.

[0047] In this embodiment, the imaging adjustment module 40 employs a parfocal zoom cylindrical lens group with a zoom range of 0.25X to 1X. This lens group consists of multiple cylindrical lenses and includes at least two functional lens groups: one is a zoom group, which moves along the optical axis to change the effective focal length of the system, thereby directly adjusting the imaging magnification; the other is a compensation group, whose motion trajectory is strictly coupled with the zoom group through an internal mechanical cam structure to perform nonlinear cooperative displacement, used to precisely compensate for image plane drift caused by zoom.

[0048] When the operator adjusts the magnification, the zoom group and the compensation group synchronously execute preset linkage movements, ensuring that the positions of the object plane (i.e., the location of slit 30) and the intermediate image plane remain fixed throughout the zoom process. This design internalizes the complex image plane tracking problem within the module, eliminating the need for external adjustments to the subsequent optical path.

[0049] This structure is suitable for industrial online production scenarios with high requirements for processing stability, repeatability, and response speed. For example, when performing high-speed dicing on a 60-inch semiconductor wafer, the linewidth needs to be switched within seconds and the focus position must not shift. The parfocal zoom cylindrical lens group can ensure that the intermediate image is always clearly located on the same conjugate plane after each zoom, thereby ensuring the consistency of grooving quality.

[0050] In one embodiment, the focusing module 50 includes a relay lens and a focusing objective lens arranged sequentially along the optical path propagation direction, for relaying and focusing the centerline light spot image onto the workpiece surface.

[0051] In this configuration, the focusing module 50 consists of a first relay lens 51 and a second relay lens 52 arranged sequentially along the optical path to form a telescope focusing system. The conjugate object plane of this system (i.e., the plane that coincides with the intermediate image plane in the X direction and the virtual image point plane in the Y direction) is set at the front focal plane of the first relay lens 51.

[0052] In the X direction, the system acts as a relay telescope, clearly imaging the midline spot image on the conjugate plane at a constant reduction magnification Mtele=f52 / f51 (where f51 is the focal length of the first relay lens 51 and f52 is the focal length of the second relay lens 52) onto the back focal plane of the second relay lens 52. In the Y direction, the diverging beam emitted from the conjugate plane is collimated by the first relay lens 51 and then focused onto the same back focal plane by the second relay lens 52.

[0053] Since the "objects" in the X and Y directions originate from the same conjugate object plane, their "images" must fall on the same physical plane, thus forming a high-quality line spot on the surface of the workpiece 60 (such as a solar cell substrate or glass panel) with a scaled, flat-top distribution in the X direction and diffraction-limited focusing in the Y direction. This dual-lens structure effectively corrects aberrations, ensuring that the line spot has uniform energy and sharp edges along its length, meeting the requirements for micron-level precision grooving.

[0054] In one embodiment, a beam expander 20 is also included, disposed between the laser 10 and the slit 30, for expanding and collimating the laser beam.

[0055] In this embodiment, the beam expander 20 is a focalless system composed of multiple optical lenses, positioned in the optical path between the laser 10 and the slit 30. Its beam expansion factor can be continuously adjusted within the range of 2 to 10 times, achieved by changing the relative positions of the internal lenses. After beam expansion, the laser beam diameter (defined according to 1 / e² intensity) reaches 2 mm to 10 mm.

[0056] The beam expander 20 has three functions: First, it expands the beam diameter to reduce the laser power density on the surface of subsequent optical elements (especially slit 30), prevents thermal damage, and improves the long-term operational reliability of the system under high average power. Second, it collimates the original diverging beam to output a nearly parallel beam, providing stable input conditions for spatial interception of slit 30 and subsequent imaging. Third, by adjusting the beam expansion ratio, the size of the light spot incident on slit 30 can be controlled, thereby fine-tuning the energy transmittance under the premise of fixed slit width of slit 30, providing additional degrees of freedom for process optimization.

[0057] For example, when the workpiece 60 to be processed is a brittle ceramic material, higher pulse energy is required, and a smaller beam expander ratio (such as 2×) can be selected to retain more energy; while when processing heat-sensitive polymer films, a larger beam expander ratio (such as 8×) can be used to reduce power density and avoid ablation. Therefore, the beam expander 20 enhances the device's adaptability to different materials and process windows.

[0058] In one embodiment, the fixed slit width of the slit 30 is 0.5 mm to 2 mm.

[0059] In this embodiment, the slit width of the slit 30 can be selected as a fixed value within the range of 0.5 mm to 2 mm and remains unchanged throughout the entire processing. The selection of this range is based on two considerations: energy utilization and diffraction effect suppression.

[0060] Regarding energy utilization efficiency, when the laser beam has a Gaussian distribution, the percentage of energy passing through the slit 30 (i.e., energy transmittance η) can be expressed by the formula... The calculation is performed using η, where η is the energy transmittance, erf(x) is the error function (an analytical solution of the Gaussian integral), and Dnorm is the normalized slit width (D), which is the slit width D divided by the incident light spot radius W0. Experiments show that when η is greater than 30%, D ≥ 0.4W0 is required, meaning the slit width should not be too small, otherwise the effective power will be insufficient. Regarding the diffraction effect, according to the single-slit diffraction theory, the diffraction angle... (λ is the laser wavelength). When D is less than 0.5 mm, θ increases significantly, causing beam divergence, loss of high-frequency components, and intensity oscillations and edge hotspots in the focused spot. However, when D is not less than 0.5 mm, θ is small enough that the subsequent optical system can effectively collect most of the diffracted light, thus obtaining a smooth line spot profile.

[0061] Therefore, limiting the slit width to between 0.5 mm and 2 mm can effectively suppress diffraction while ensuring sufficient energy. For example, when grooving the low-k dielectric layer of a 60-bit semiconductor wafer, a 1.0 mm slit width, combined with a 5 mm incident light spot, satisfies both η>30% and controls the diffraction angle to the milliradian level, ultimately creating high-quality grooves with a width of 20–80 μm and a wall perpendicularity better than ±2° on the wafer surface. This slit width range has been verified through grooving experiments on various materials (including silicon, sapphire, and ITO glass), demonstrating broad process applicability.

[0062] Reference Figure 2 In one embodiment, this application also proposes a distributed wireless terminal signal shielding method, using a coverage unit in the system described in any of the above claims, characterized by comprising the following steps: S1. A laser beam is emitted using a laser 10, and the laser beam passes through a slit 30 with a fixed physical width, and the width of the slit 30 remains unchanged during subsequent adjustments. S2. The imaging adjustment module 40 is used to perform optical imaging on the slit 30 to form a centerline light spot image with variable width. S3. Adjust the imaging magnification of the imaging adjustment module 40 to change the width of the midline light spot image; S4. Focus the adjustable width centerline spot image onto the surface of the workpiece 60 to be processed, and perform laser grooving.

[0063] As described in step S1, firstly, a laser beam with a Gaussian energy distribution is emitted using laser 10 and passed through a slit 30 with a fixed physical width. Throughout the entire processing and adjustment process, the width of the slit 30 remains constant. The key to this design is decoupling the energy extraction process from the subsequent linewidth adjustment process—since both the incident light spot and the width of the slit 30 are fixed values, the proportion of laser energy passing through the slit 30 is constant, thus avoiding the energy fluctuation problem caused by width changes in traditional adjustable slits 30, providing a foundation for stable processing.

[0064] As described in step S2, the imaging adjustment module 40 then performs optical imaging on the slit 30. The slit 30 serves as an optical "object," and the imaging adjustment module 40 forms a midline spot image in the downstream optical path. This midline image exhibits a flat-top energy distribution in the X direction (i.e., the opening direction of the slit 30), and its width is determined by both the physical dimensions of the slit 30 and the imaging magnification. Since the width of the slit 30 is fixed, the width variation of the midline image depends entirely on the magnification capability of the imaging adjustment module 40, thereby achieving separation between linewidth control and energy stability.

[0065] As described in step S3, the width of the central line spot image is then dynamically changed by adjusting the imaging magnification of the imaging adjustment module 40. This magnification can be achieved in two ways: first, by adjusting the object distance between the slit 30 and the cylindrical lens, suitable for scenarios with high tolerance for system complexity; second, by using a parfocal variable magnification cylindrical lens group, where the magnification is continuously adjusted without changing the positions of the object plane and image plane through the coordinated movement of the internal lenses, suitable for high-speed, high-precision industrial online processing. Regardless of the method used, continuous and precise adjustment of the line spot width can be achieved.

[0066] As described in step S4, the adjusted width of the center line spot image is finally sent to the focusing module 50. After relay and focusing processing, it is precisely projected onto the surface of the workpiece 60 (such as a semiconductor wafer, glass substrate, etc.) to form the final line spot for grooving. This line spot is a diffraction-limited focal point in the Y direction and a scaled-down, flat-top distribution in the X direction, exhibiting a high-quality linear shape overall. Through single or multiple scans, precision grooves with a width of 20–80 μm, a flat bottom, and vertical walls can be created on the workpiece surface, significantly improving the consistency and processing quality of laser grooving.

[0067] In summary, this method, by combining a fixed slit 30 with variable imaging, achieves flexible and precise control of the line spot width while ensuring constant energy utilization, effectively solving the technical problem of coexisting energy fluctuations and strong diffraction in traditional schemes.

[0068] In one embodiment, the adjustment of the imaging magnification is achieved by controlling the object distance between the slit 30 and the imaging adjustment module 40.

[0069] In this embodiment, the imaging magnification is adjusted by changing the object distance between the slit 30 and the imaging adjustment module 40. Specifically, the imaging adjustment module 40 includes at least one cylindrical lens, and the slit 30 is located in front of the cylindrical lens as an optical object. According to the principle of geometrical optics imaging, when the distance between the slit 30 and the cylindrical lens (i.e., the object distance) changes, the position and size of the intermediate image also change accordingly. By adjusting this object distance through a precision displacement mechanism, the imaging magnification can be continuously adjusted, thereby changing the width of the intermediate line spot image. This method has a simple structure and is suitable for applications with low system complexity requirements or where subsequent focusing modules 50 can be used for tracking focus.

[0070] In one embodiment, the imaging adjustment module 40 is a parfocal zoom cylindrical lens group. The adjustment of the imaging magnification is achieved by changing the relative positions of the lenses inside the parfocal zoom cylindrical lens group, and the positions of the object plane and the image plane of the parfocal zoom cylindrical lens group remain unchanged throughout the adjustment process.

[0071] In this embodiment, the imaging adjustment module 40 employs a parfocal zoom cylindrical lens group, which internally contains at least two lens groups movable along the optical axis: a zoom group and a compensation group. When adjusting the imaging magnification, the relative positions between these two lens groups are changed through a drive mechanism, thereby adjusting the effective focal length of the system and achieving continuous changes in magnification. Crucially, the motion trajectories of the zoom group and the compensation group are precisely designed and tightly coupled (e.g., through internal mechanical cam linkage), ensuring that regardless of the magnification adjustment, the position of the object plane where the slit 30 is located and the formed intermediate image plane in space remain constant. This parfocal characteristic avoids image plane drift and eliminates the need for subsequent optical path focusing adjustments, making it suitable for high-precision, high-speed linewidth switching industrial laser processing scenarios.

[0072] In one embodiment, before the step of using the imaging adjustment module 40 to perform optical imaging on the slit 30 to form a midline spot image, the method further includes: using the beam expander 20 to expand and collimate the laser beam.

[0073] In this embodiment, before optically imaging the slit 30 using the imaging adjustment module 40 to form the centerline spot image, the laser beam first passes through a beam expander 20. This beam expander 20 is positioned between the laser 10 and the slit 30 to expand the original small-diameter beam output from the laser 10, increasing its diameter to 2mm to 10mm (defined by 1 / e² intensity). Simultaneously, it collimates the beam, making it nearly parallel light incident on subsequent optical elements. This process not only reduces the power density of the beam on the surface of elements such as the slit 30, preventing optical damage and improving the system's stability and lifespan under high-power operation, but also provides additional degrees of freedom for optimizing energy utilization by controlling the spot size incident on the slit 30, thus laying the foundation for subsequent stable and high-quality line spot formation.

[0074] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method 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, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0075] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A laser grooving line spot width control device, characterized in that, include: A laser, used to emit a laser beam; A slit is disposed in the optical path of the laser beam, has a fixed physical slit width, is used to intercept the laser beam, and the slit width remains unchanged during the process of adjusting the line spot width; An imaging adjustment module is located on the optical path after the slit and is used to perform optical imaging on the slit to form a centerline light spot image with variable width. The imaging magnification of the imaging adjustment module is adjustable. The focusing module, located after the imaging adjustment module, is used to focus the intermediate line spot image onto the surface of the workpiece to be processed, forming a line spot for grooving.

2. The apparatus according to claim 1, characterized in that, The imaging adjustment module includes at least one cylindrical lens, and the imaging magnification is changed by adjusting the object distance between the slit and the cylindrical lens.

3. The apparatus according to claim 1, characterized in that, The imaging adjustment module is a parfocal zoom cylindrical lens group, whose object plane and image plane remain in constant position during the zoom process. The imaging magnification is continuously adjusted by changing the relative position between at least two lenses inside the parfocal zoom cylindrical lens group.

4. The apparatus according to claim 1, characterized in that, The focusing module includes a relay lens and a focusing objective lens arranged sequentially along the optical path propagation direction, used to relay and focus the centerline light spot image onto the surface of the workpiece.

5. The apparatus according to claim 1, characterized in that, It also includes a beam expander, disposed between the laser and the slit, for expanding and collimating the laser beam.

6. The apparatus according to claim 1, characterized in that, The fixed slit width of the slit is 0.5 mm to 2 mm.

7. A method for controlling the laser grooving line spot width, characterized in that, include: A laser beam is emitted from a laser and passed through a slit with a fixed physical width, and the width of the slit remains unchanged during subsequent adjustments. The slit is optically imaged using an imaging adjustment module to form a centerline spot image with variable width; Adjust the imaging magnification of the imaging adjustment module to change the width of the midline spot image; The adjustable-width centerline spot image is focused onto the surface of the workpiece to be processed for laser grooving.

8. The method according to claim 7, characterized in that, The magnification of the imaging is adjusted by controlling the object distance between the slit and the imaging adjustment module.

9. The method according to claim 7, characterized in that, The imaging adjustment module is a parfocal zoom cylindrical lens group. The magnification of the image is adjusted by changing the relative positions of the lenses inside the parfocal zoom cylindrical lens group. Throughout the adjustment process, the positions of the object plane and the image plane of the parfocal zoom cylindrical lens group remain unchanged.

10. The method according to claim 7, characterized in that, Before the step of using the imaging adjustment module to perform optical imaging on the slit to form a midline spot image, the method further includes: using a beam expander to expand and collimate the laser beam.

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