A method, system, device and storage medium for suppressing laser delamination loss layer of a crystalline material

Abstract

The present application belongs to the technical field of semiconductor crystal material processing, and particularly relates to a method, system, device and storage medium for inhibiting laser stripping loss layer of crystal material. Before forming a stripping modification layer, the method pre-processes multiple circles of discrete laser traces at the edge of a crystal ingot to form a blocking layer, so that the width and depth of the blocking layer are matched with the edge transition zone, so as to inhibit the upward transition zone formed by the stripping laser at the edge, reduce the subsequent grinding removal amount, and improve the utilization rate and the wafer yield of the crystal material.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor crystal material processing technology, and particularly relates to a method, system, device and storage medium for suppressing laser lift-off loss layers in crystal materials. Background Technology

[0002] Crystal materials such as silicon carbide, gallium nitride, sapphire, and diamond possess characteristics such as high hardness, high thermal conductivity, wide bandgap, and high breakdown field strength, making them valuable for applications in power devices, radio frequency devices, optoelectronic devices, and high-temperature resistant devices. Taking silicon carbide crystal materials as an example, its ingot preparation cycle is long and material costs are high. Cutting and grinding losses during processing directly affect wafer yield and manufacturing costs. Therefore, how to reduce material loss while ensuring wafer flatness and subsequent epitaxial quality during ingot slicing has been a long-standing technical challenge in the field of crystal material processing.

[0003] Traditional wire cutting methods typically rely on diamond wire or slurry wire to mechanically slice crystal ingots, resulting in problems such as high kerf loss, long processing time, wire wear, and thick surface damage layers. To reduce cutting losses, laser-based internal resurfacing technology for crystal materials has emerged in recent years. This technology typically focuses a laser with a certain degree of transmittance at a predetermined depth inside the crystal ingot, forming a resurfacing layer, crack layer, or void layer within the crystal. Then, through mechanical force, thermal stress, ultrasound, or other external actions, the wafer is separated from the main crystal body along the resurfacing layer. Compared to traditional mechanical cutting, laser resurfacing technology helps reduce kerf loss, improves crystal ingot utilization, and enhances the processing efficiency of large-size wafers.

[0004] For example, prior art CN107790898A discloses a method for generating SiC wafers. This method involves positioning the focus point of a pulsed laser inside a SiC ingot. During the relative rotation and feeding process between the ingot and the focus point, multiple separation layers consisting of a modified layer and cracks extending along the c-plane are formed, thus generating a peeling surface. This document also proposes incorporating forward and reverse path movement during the peeling surface generation process, allowing the focus point to move from one end to the other and then trace back the already formed separation layers, thereby improving the productivity of SiC wafer peeling and the formation state of the peeling surface. This document indicates that the problem of unstable modified layer formation in the ingot end or edge regions has been addressed in laser processing, and attempts are being made to make the separation layers more stable through scanning path control.

[0005] For example, prior art CN115555736A discloses a method and apparatus for laser-based exfoliation of silicon carbide ingots. This method uses an ultrashort pulse laser to form a void modification layer and a crack modification layer above a predetermined depth layer on the silicon carbide ingot. Then, a short pulse laser is applied to the void modification region, causing the cracks to grow laterally and connect, thereby reducing the amount and length of cracks extending longitudinally along the silicon carbide ingot within the modification layer, and reducing cutting loss thickness. The key to this approach is the coordinated control of the void modification region and the crack modification region using different pulse lasers, maximizing the lateral extension of cracks to improve the quality of the exfoliated layer.

[0006] The aforementioned existing technologies all indicate that the core of laser ablation technology lies in controlling the formation location and propagation direction of the modified layer, crack layer, or void layer inside the crystal, enabling the wafer to be stably separated along the predetermined ablation surface. However, in actual processing, when the laser beam enters or approaches the edge region from the edge of the ingot, it is easily affected by factors such as the crystal edge morphology, refraction and scattering, local energy density changes, and changes in the propagation direction of the modified cracks. This can easily lead to the formation of a transition zone at the edge of the ingot that is inconsistent with the modified layer being ablated from the main body. This transition zone typically manifests as the modified layer climbing or extending relative to the predetermined ablation surface towards the upper surface of the ingot in the edge region, resulting in additional damaged areas at the edge of the ablated wafer or the edge of the remaining ingot.

[0007] For high-value crystalline materials, even if the radial width and height of the transition region are on the order of tens of micrometers, they will still translate into additional material removal during subsequent grinding, polishing, or planarization processes. To eliminate localized defects, steps, or crack residues caused by the edge transition region, it is usually necessary to increase the overall grinding allowance. However, increasing the overall grinding allowance not only reduces the number of wafers obtainable from the ingot but also increases the costs of grinding wheels, polishing consumables, and processing time. Especially for large-size silicon carbide ingots, where the requirements for wafer thickness and surface quality are high, localized transition damage in the edge region can further affect subsequent epitaxial growth, edge chamfering, and device manufacturing yield.

[0008] Based on existing publicly available technologies, CN107790898A primarily improves the formation state of the release layer through a reciprocating scanning method, while CN115555736A mainly controls the lateral connection of cracks through a void modification layer, a crack modification layer, and secondary laser action. Although the above solutions all help improve the stability of laser ablation or reduce longitudinal crack propagation, their control focus is still concentrated on the generation, connection, and ablation process of the main release layer. They do not address the problem of additional material loss caused by the transition zone at the ingot edge during subsequent grinding. Therefore, a technical solution is proposed to pre-treat a loss layer at a specific depth in the ingot edge before forming the main release modification layer.

[0009] Therefore, it is still necessary to propose a loss layer suppression method suitable for laser lift-off processing of crystal materials, so that the formation position and size of the transition zone at the edge of the ingot can be pre-controlled without significantly increasing the processing complexity, thereby suppressing the formation of an upward-climbing transition modification layer in the edge region by the subsequent lift-off laser, thus reducing the amount of grinding and polishing removed from the surface of the wafer or remaining ingot after lift-off, improving the utilization rate of crystal materials and the economy of the laser lift-off process. Summary of the Invention

[0010] The technical objective of this invention is to address the problem that an upward-growing laser transition zone easily forms at the edge of a crystal ingot during laser ablation, leading to increased removal volume and reduced material utilization in subsequent grinding and polishing. The invention provides a method to suppress the loss layer during laser ablation of crystal materials. This method involves pre-forming a blocking layer composed of multiple discrete laser dots at the edge of the ingot before forming the main ablation modification layer. This suppresses the propagation and modification expansion of the subsequent ablation laser in the edge region of the ingot, thereby reducing or avoiding the formation of the edge transition zone and lowering the additional processing losses after crystal sheet ablation.

[0011] Firstly, in order to achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0012] A method for suppressing the loss layer of a laser ablation layer in a crystal material, the method comprising the following steps:

[0013] S1, obtain the parameters of the transition zone formed at the edge of the crystal ingot when the crystal material ingot is laser-lifted without a blocking layer. The parameters of the transition zone include at least the width of the transition zone along the radial direction of the crystal ingot and the height of the transition zone along the thickness direction of the crystal ingot relative to the peeling modification layer.

[0014] S2, determine the width of the barrier layer along the radial direction of the ingot based on the width of the transition zone along the radial direction of the ingot, and determine the processing depth of the barrier layer based on the height of the transition zone relative to the peeling and modification layer along the thickness direction of the ingot, so that the processing depth of the barrier layer is located between the subsequent peeling and modification layer processing depth and the upper surface of the ingot.

[0015] S3, before forming the stripping and modification layer, the first laser is focused at the processing depth of the barrier layer, and the crystal material ingot is rotated around its own central axis to form the first ring of discrete laser dots on the edge of the ingot; then the first laser and the crystal material ingot are displaced relative to each other in the radial direction by a preset distance, and the crystal material ingot is rotated again to form the second ring of discrete laser dots. The above radial displacement and rotation dotting process is repeated until the last ring of discrete laser dots is formed.

[0016] As a further improvement, in step S1, the transition zone parameters are obtained in the following way: a test peeling modification layer is formed on a crystal material ingot of the same material, crystal orientation or batch according to a laser peeling process without a blocking layer, and the edge profile of the ingot is observed by microscopy, infrared imaging, confocal detection or cross-sectional contour detection to obtain the width of the transition zone along the radial direction of the ingot and the height of the transition zone along the thickness direction of the ingot relative to the peeling modification layer.

[0017] And / or, in step S2, the width of the barrier layer along the radial direction of the ingot is set according to the width of the transition region along the radial direction of the ingot, and the width of the barrier layer along the radial direction of the ingot is not less than the width of the transition region along the radial direction of the ingot.

[0018] And / or, in step S2, under the condition of improving the processing efficiency of the barrier layer, the width of the barrier layer along the radial direction of the ingot is more than 0.8 times the width of the transition zone along the radial direction of the ingot and less than the width of the transition zone along the radial direction of the ingot.

[0019] And / or, in step S2, the processing depth of the barrier layer is determined based on the processing depth of the stripped modified layer, the height of the transition zone relative to the stripped modified layer along the ingot thickness direction, and the depth matching coefficient, wherein the value of the depth matching coefficient ranges from 0.6 to 1.4.

[0020] As a further improvement, in step S3, the last ring of discrete laser dots is the ring of discrete laser dots closest to the center of the crystal ingot. Multiple rings of discrete laser dots together constitute a blocking layer located at the edge of the crystal ingot, and the width of the blocking layer along the radial direction of the crystal ingot is the difference between the radius of the crystal material ingot and the circumference of the last ring of discrete laser dots.

[0021] And / or, in step S3, the radius difference between the circumferences of two adjacent discrete laser dot marks is 1 micrometer to 200 micrometers, preferably 5 micrometers to 50 micrometers;

[0022] And / or, in step S3, the radius of the circumference of any discrete laser dot pattern is determined based on the radius of the crystal ingot, the number of the discrete laser dot pattern, and the radial displacement distance between two adjacent discrete laser dot patterns.

[0023] And / or, in step S3, the number of turns of the discrete laser dots is determined based on the width of the barrier layer along the radial direction of the ingot and the radial displacement distance, and is determined by rounding up the result of dividing the width of the barrier layer along the radial direction of the ingot by the radial displacement distance and then adding 1 turn.

[0024] And / or, in step S3, the discrete laser dots are spaced apart in the same circumferential direction, and unmodified crystal regions are retained between adjacent discrete laser dots, so that the barrier layer forms a discontinuous crack-type barrier structure, rather than forming a peeling crack that runs continuously along the circumferential direction.

[0025] As a further improvement, the method also includes:

[0026] S4, the second laser is focused to the depth of the stripping modification layer processing, and a stripping modification layer for stripping crystal sheets is formed inside the crystal material ingot;

[0027] S5, an external peeling action is applied to the crystal material ingot on which the peeling modification layer is formed, so that the crystal sheet is separated from the ingot body along the peeling modification layer.

[0028] As a further improvement, in step S3, the single pulse energy, repetition frequency, focused spot diameter and ingot rotation speed of the first laser are configured to form a localized modified region by a single discrete laser dot; in step S4, the single pulse energy or average power of the second laser is higher than that of the first laser, or the scanning overlap rate of the second laser is higher than that of the first laser, so as to form a continuous or quasi-continuous stripping modified layer that can be used to strip crystal sheets.

[0029] And / or, in step S4, the blocking layer is located on the edge propagation path of the stripped modification layer, and is used to absorb, scatter or interrupt the propagation of the second laser in the crystal ingot edge region, thereby inhibiting the stripped modification layer from climbing up the crystal ingot edge towards the upper surface of the crystal ingot to form a continuous transition zone.

[0030] And / or, when forming the stripping modification layer, the scanning path of the second laser covers the stripping area of ​​the main body of the ingot, and when it reaches the area where the edge barrier layer of the ingot is located, the effective energy density of the second laser in the edge region of the ingot is reduced by the barrier layer, so that the transition modification layer that rises continuously along the thickness direction is not formed in the edge region of the ingot.

[0031] And / or, after step S5, the process further includes grinding or polishing the surface of the stripped crystal sheet or the surface of the remaining crystal ingot; wherein, since the barrier layer inhibits the formation of the transition zone at the edge of the crystal ingot, the amount removed by grinding or polishing is less than the amount required to remove the transition zone under conditions where no barrier layer is provided.

[0032] As a further improvement, the crystal material ingot is a silicon carbide ingot, a sapphire ingot, a gallium nitride ingot, a diamond ingot, or other wide bandgap crystal material ingots that are transparent to the second laser.

[0033] In a second aspect, the present invention also provides a system for suppressing laser ablation loss layers in crystal materials, for performing the method, the system comprising:

[0034] The crystal ingot support and rotation mechanism is used to support the crystal material ingot and rotate the crystal material ingot around its own central axis.

[0035] A radial displacement mechanism is used to displace the laser focusing position relative to the crystal material ingot by a preset distance in the radial direction;

[0036] A laser processing mechanism is used to form multiple discrete laser dots at the depth of the barrier layer and to form a stripped modified layer at the depth of the stripped modified layer.

[0037] A depth adjustment mechanism is used to adjust the focusing depth of the first laser and the second laser.

[0038] The control module is used to determine the width of the barrier layer, the processing depth of the barrier layer, and the number of discrete laser dot rings based on the width of the transition zone along the radial direction of the ingot, the height of the transition zone along the thickness direction of the ingot relative to the stripped modified layer, the ingot radius, and the radial displacement distance. It also controls the coordinated operation of the ingot bearing rotation mechanism, the radial displacement mechanism, the laser processing mechanism, and the depth adjustment mechanism.

[0039] As a further improvement, the system also includes a detection module, which is used to acquire an image or cross-sectional profile of the transition zone at the edge of the ingot, and output the width of the transition zone along the radial direction of the ingot and the height of the transition zone along the thickness direction of the ingot relative to the stripping modification layer; the control module automatically generates barrier layer processing parameters based on the width of the transition zone along the radial direction of the ingot and the height of the transition zone along the thickness direction of the ingot relative to the stripping modification layer output by the detection module.

[0040] Thirdly, the present invention also provides an electronic device, including a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method described above.

[0041] Fourthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0042] This invention sets the barrier layer processing depth between the peeling and modification layer processing depth and the upper surface of the ingot, and ensures that the barrier layer covers or substantially covers the formation range of the edge transition zone along the radial direction of the ingot. This barrier layer can block, scatter, absorb, or interrupt laser energy, modification cracks, or damage propagation paths during subsequent peeling and modification layer processing, thereby inhibiting the peeling and modification layer from climbing upwards in the ingot edge region to form a continuous transition zone. Compared with direct laser peeling, this invention can reduce the abnormal damage height and radial damage width at the edges of crystal wafers or remaining ingots, reduce the additional grinding and polishing allowance required to eliminate the edge transition zone, thereby reducing the consumption of grinding wheels and polishing consumables, increasing the number of wafers obtainable from a single ingot, and improving crystal material utilization. Simultaneously, the barrier layer is formed using a laser dotting method with rotating the ingot and radially displacing it in circles. The process path is clear, easily integrated with existing laser peeling equipment, and does not require changes to the basic processing method of the main peeling and modification layer, thus exhibiting good process compatibility and industrialization value. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of laser stripping of a crystal ingot.

[0044] Figure 2 This is a schematic diagram of the transition zone at the edge of the crystal ingot.

[0045] Figure 3 This is a schematic diagram showing the location where the barrier layer is formed.

[0046] Figure 4 This is a schematic diagram of the barrier layer at the edge of the crystal ingot.

[0047] Figure 5 This is a schematic diagram illustrating how the barrier layer prevents the formation of a transition zone.

[0048] Figure 6 This is a schematic diagram of the barrier layer processing.

[0049] Figure 7 This is a flowchart of a method for suppressing the loss layer of a crystal material through laser ablation.

[0050] Figure 8 This is a block diagram of a laser ablation loss layer suppression system for crystal materials.

[0051] Figure 9 This is a comparison chart of the transition zone width under different processes.

[0052] Figure 10 This is a comparison chart of film output rate and material utilization rate. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are only used to illustrate the technical solution of the present invention and should not be construed as limiting the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make adaptive adjustments to the specific parameters according to the type of crystal material, ingot size, laser wavelength, pulse width, processing depth, and peeling process requirements.

[0054] The crystal material ingot referred to in this invention can be a silicon carbide ingot, a sapphire ingot, a gallium nitride ingot, a diamond ingot, or other crystal material ingots capable of forming a release layer through internal laser modification. The following description uses a silicon carbide ingot as an example, but this invention is not limited to silicon carbide ingots.

[0055] I. Terminology Explanation

[0056] "Exfoliation modification layer" refers to a layered structure formed by focusing a laser at a predetermined depth inside a crystal ingot, causing localized modification, voids, cracks, or stress concentration areas in the crystal material near the laser focal point. The exfoliation modification layer is used to guide the separation of crystal flakes from the main ingot body during subsequent external exfoliation.

[0057] The "transition zone" refers to the abnormal damage area formed at the edge of the ingot during laser ablation, caused by factors such as light propagation state, edge refraction and scattering, changes in energy density, or changes in crack propagation direction. This damage causes the laser-induced modified layer to rise or shift relative to the main ablation modified layer towards the upper surface of the ingot. The transition zone is typically located at the edge of the ingot and has a width along the radial direction of the ingot. It has a high degree of separation relative to the stripped modified layer along the thickness direction of the ingot. .

[0058] A "barrier layer" refers to a localized refining structure formed pre-formed in the ingot edge region before the formation of the main stripping refining layer, used to suppress the formation of the edge transition zone. The barrier layer preferably consists of multiple rings of discrete laser dots, arranged sequentially from the outer edge of the ingot towards the center. The barrier layer is not used for direct stripping of the crystal sheet, but rather to restrict laser propagation, energy distribution, or refining propagation path as the subsequent stripping laser approaches the ingot edge, thereby reducing the upward climb of the stripped refining layer at the edge.

[0059] "Discrete laser spot" refers to a point-like, speckled, or short-range modified region formed locally within a crystalline material by a laser pulse. Adjacent discrete laser spots on the same circumference can retain unmodified crystalline regions, preventing the formation of a continuous circumferential crack ring.

[0060] "Barrier layer processing depth" refers to the depth of the laser focal point from the upper surface of the ingot when the barrier layer is formed, denoted as... "Deepness of peeling off the modified layer" refers to the depth of the laser focal point from the upper surface of the ingot when the main peeling modified layer is formed, denoted as . In this invention, the barrier layer processing depth Located at the processing depth of the stripped and modified layer Between the ingot and the top surface, the barrier layer is closer to the top surface of the ingot than the stripping modification layer.

[0061] "Radial displacement distance" refers to the distance along the radial direction of the ingot between the circumferences of two adjacent discrete laser dot marks, denoted as... .

[0062] II. System Structure

[0063] like Figure 8 As shown, the crystal material laser ablation loss layer suppression system of the present invention includes a crystal ingot bearing rotation mechanism, a radial displacement mechanism, a laser processing mechanism, a depth adjustment mechanism, a detection module, and a control module.

[0064] The ingot-bearing rotation mechanism is used to clamp or support crystal material ingots and rotate them around their central axis. The ingot-bearing rotation mechanism may include a vacuum adsorption stage, a mechanical clamping stage, a hydrostatic support stage, a rotating spindle, an angle encoder, and a speed control unit. To ensure uniform distribution of discrete laser dots along the circumference, the rotating spindle preferably has an angle feedback function, allowing the control module to control the circumferential spacing of the dots based on the laser pulse frequency and the ingot's rotation speed.

[0065] The radial displacement mechanism is used to create a relative displacement between the laser focusing position and the crystal ingot along the radial direction of the ingot. This radial displacement mechanism can be achieved by moving the laser processing head, moving the ingot support platform, or both in a coordinated manner. After each complete rotation of discrete laser dot processing, the radial displacement mechanism moves according to a set radial displacement distance. The laser focus is moved inward relative to the center of the ingot, thereby forming the next ring of discrete laser dots.

[0066] The laser processing mechanism outputs a first laser and a second laser. The first laser forms a barrier layer at the edge of the ingot, and the second laser forms a stripping modification layer inside the ingot. The first and second lasers can be output from the same laser under different parameter conditions, or they can be output from different lasers. The processing objective of the first laser is to form localized, discrete modification dots; therefore, its energy, pulse frequency, focal size, and dot overlap can be configured to avoid forming continuous, through-crack stripping. The processing objective of the second laser is to form a stripping modification layer that can guide the stripping of the crystal sheet; therefore, its scanning path, energy density, and dot overlap can be configured to form continuous or quasi-continuous layered modification regions.

[0067] The depth adjustment mechanism is used to adjust the focusing depth of the laser focus within the crystal ingot. The depth adjustment mechanism may include a lifting platform, an objective lens axis adjustment mechanism, a dynamic focusing lens group, or a laser optical path focus adjustment unit. The control module adjusts the focus based on the processing depth of the barrier layer. and the depth of stripping and modification layer processing They control the focal positions of the first and second lasers respectively.

[0068] The detection module is used to acquire images, cross-sectional profiles, modified layer heights, or edge damage information after wafer peeling from the transition zone at the ingot edge. The detection module may include a microscopic imaging device, an infrared transmission imaging device, a confocal imaging device, an optical profilometer, a cross-sectional observation device, or other detection devices capable of identifying the size of the transition zone. The detection module can be configured as an offline detection module or integrated with a laser processing system to form an online or quasi-online detection unit.

[0069] The control module is used to determine the width of the transition zone. Transition zone height Ingot radius Radial displacement distance Depth of stripping and modification layer processing Parameters such as these determine the width of the barrier layer. Barrier layer processing depth Number of discrete laser dot rings And the radius position of each discrete laser dot, and control the coordinated work of each actuator.

[0070] III. Overall Method Flow

[0071] like Figure 7 As shown, the method of the present invention includes: obtaining transition zone parameters; determining barrier layer parameters; forming a multi-ring discrete laser dot-type barrier layer at the edge of the ingot; forming a main body peeling modification layer; applying an external peeling action to separate the crystal sheet from the main body of the ingot; and grinding or polishing the peeled surface if necessary.

[0072] The key difference between this invention and conventional laser lift-off processes lies in the fact that, instead of simply adjusting the scanning path of the main lift-off laser to improve the lift-off layer, a barrier layer is constructed within a specific depth range at the ingot edge before the formation of the main lift-off modified layer. This barrier layer is located on the path where subsequent lift-off lasers might propagate abnormally or undergo modified uptake in the edge region, thus pre-constraining laser energy transfer and modified expansion in the edge region. Therefore, this invention can target and suppress the "edge transition zone," a localized problem that leads to additional grinding losses, without significantly altering the processing method of the main lift-off modified layer.

[0073] (I) Step S1: Obtaining transition zone parameters

[0074] In step S1, the parameters of the transition region formed at the edge of the crystal ingot during laser ablation without a barrier layer are first obtained. The transition region parameters include at least the width of the transition region along the radial direction of the ingot. And the height of the transition zone along the ingot thickness direction relative to the stripped modified layer .

[0075] In one implementation, a test ingot of the same material, crystal orientation, diameter, or batch as the ingot to be processed can be selected, and the peeling modification layer processing depth can be determined according to the planned specifications. Trial processing without a blocking layer was performed using laser wavelength, pulse width, scanning speed, and scanning path. After the trial processing, cross-sectional samples were prepared from the edge region of the ingot, and the morphology of the edge transition zone was obtained through microscopy, infrared transmission imaging, confocal microscopy, or optical contour detection. Figure 2 As shown, the transition zone shifts upwards or rises relative to the main stripped modified layer, and its width in the radial direction is defined as... Its maximum height or representative height relative to the main stripped modified layer is defined as .

[0076] In another implementation, transition zone parameters can be determined based on historical processing data. For example, for the same type of ingot, the same peeling depth, and the same laser processing equipment, if an edge transition zone database has been established, the control module can directly call the database entries that match the current ingot. and When historical data fluctuates, a statistically safe parameter can be selected, such as taking the larger width from multiple test results. The larger height from multiple test results is taken as... This is to ensure that the subsequent barrier layer can cover most or all of the transition zone formation area.

[0077] This invention does not arbitrarily perform laser pretreatment at the edge of the ingot, but rather uses the actual size of the edge transition zone as the basis for the barrier layer design. This is achieved by quantifying the parameters of the transition zone... and The radial coverage and processing depth of the subsequent barrier layer can be matched with the formation area of ​​the transition zone, thereby avoiding insufficient suppression due to an excessively narrow barrier layer, and also avoiding unnecessary processing damage due to an excessively wide or deep barrier layer.

[0078] (II) Step S2: Determining the parameters of the barrier layer

[0079] In step S2, based on the width of the transition zone Determine the width of the barrier layer along the radial direction of the ingot. And according to the height of the transition zone Determine the processing depth of the barrier layer This increases the processing depth of the barrier layer. Located at the processing depth of the stripped and modified layer Between and the upper surface of the ingot.

[0080] Barrier layer width It is an important parameter affecting the suppression effect of the edge transition region. For example Figure 3 and Figure 4 As shown, the barrier layer extends from the outer edge of the ingot towards the center, and its radial width is used to cover areas where the stripping laser is prone to abnormal propagation, refraction, scattering, or alteration at the edge. When the width of the barrier layer... Not less than the width of the transition zone At this time, the barrier layer can cover the main formation range of the transition zone, which is suitable for scenarios with high requirements for control of grinding removal, high requirements for wafer edge quality, or high cost of ingot materials.

[0081] The width of the barrier layer can meet the following requirements:

[0082] ;

[0083] In the formula, The width of the barrier layer along the radial direction of the ingot; The width of the transition zone formed in the ingot radial direction without a barrier layer is defined.

[0084] In another embodiment, to improve processing efficiency, the width of the barrier layer... It can also be slightly smaller than the width of the transition zone. At this point, the barrier layer preferentially covers the outer edge region of the transition zone where the damage height is large and has a significant impact on the amount of damage removed by subsequent grinding. This implementation is suitable for scenarios where subsequent minor edge trimming is permissible, or where the ingot edge chamfering process can remove some residual transition damage. Preferably, the barrier layer width... The width of the transition zone can be set. The range is 80% to 100%. This 80% to 100% range is based on process experience and does not require specific numbers to be defined as independent mathematical symbols; those skilled in the art can adjust it according to the ingot diameter, peeling depth, and transition zone morphology.

[0085] Barrier layer processing depth The determination of the depth of the barrier layer is one of the most significant technical contributions of this invention. If the barrier layer processing depth is too shallow, the barrier layer may only act near the upper surface of the ingot, making it difficult to effectively interfere with the process of the lift-off laser climbing upwards from the lift-off modification layer in the edge region; if the barrier layer processing depth is too deep, the barrier layer may approach or interfere with the main lift-off modification layer, affecting the separation of the crystal wafer along the predetermined lift-off surface. Therefore, this invention determines the depth of the barrier layer processing depth. Located at the processing depth of the stripped and modified layer Between the ingot's upper surface and the ingot's lower surface, and to make the depth difference between the two equal to the height of the transition zone. correspond.

[0086] In a preferred embodiment, the processing depth of the barrier layer and the processing depth of the stripped modified layer satisfy the following:

[0087] ;

[0088] In the formula, The depth of the barrier layer processing; The depth of the stripping and modification layer processing; The height of the transition zone relative to the stripped modified layer along the thickness direction of the ingot; It is the depth matching coefficient, used to adjust the degree of matching between the barrier layer and the height of the transition zone according to different crystal materials, laser energy, edge morphology and safety margin.

[0089] When laser-induced cracks in crystalline materials have a strong tendency to propagate upwards, the laser size can be appropriately increased. This allows the barrier layer to be closer to the upper region of the transition zone; when the barrier layer poses a risk of interfering with the main stripping layer, it can be appropriately reduced. This allows the barrier layer to be positioned closer to the adjacent area above the main stripped modified layer. This is achieved by setting a depth matching coefficient. The present invention can balance the effect of suppressing the transition zone and the integrity of the main peel layer.

[0090] Step S2 establishes the correspondence between "transition zone parameters and barrier layer parameters". Existing conventional laser ablation processes mainly focus on the formation depth, crack connection, and ablation strength of the ablation modified layer itself. However, this invention treats the edge transition zone as an independent control object, through... , , , and The relationship between these parameters makes the blocking layer a directional suppression structure targeting the edge loss layer. This parameter matching relationship means that the present invention is no longer simply adding a laser processing step, but rather forming a laser preprocessing method adapted to the size and position of the edge transition region.

[0091] (III) Step S3: Multi-ring discrete laser dot-type blocking layer processing

[0092] Step S3 does not involve forming a continuous cutting groove at the edge of the ingot, nor does it involve forming a complete annular crack. Instead, it involves forming multiple discrete laser dots at a specific depth, which together constitute a barrier layer. This barrier layer should have sufficient ability to block laser propagation or interrupt the modification path, while also not prematurely causing unintended peeling between the crystal sheet and the main ingot.

[0093] Specifically, before the main peeling and modification layer is formed, the first laser is focused at the processing depth of the barrier layer. The crystal ingot is rotated around its central axis. A first laser pulses at a predetermined frequency at the edge of the ingot, creating a first ring of discrete laser dots along its edge as the ingot rotates. These discrete laser dots are preferably positioned close to the outer edge of the ingot to preferentially interfere with the propagation of subsequent stripping lasers in the outermost edge region.

[0094] After completing the first circle of discrete laser dots, the first laser and the crystal ingot are displaced relative to each other in the radial direction. This relative displacement can be achieved by radially moving the laser focus or by radially moving the ingot support platform. After the displacement is complete, the crystal ingot is rotated again around its central axis, and a second ring of discrete laser dots is formed by the first laser. The process of "rotation dotting—radial displacement—re-rotation dotting" is repeated until the second ring of discrete laser dots is formed. Discrete laser dots in a circle. The discrete laser dot ring is the ring of dots closest to the center of the ingot, and multiple rings of dots together form a barrier layer extending from the edge of the ingot towards the center of the ingot.

[0095] The width of the barrier layer can be determined by the ingot radius and the radius of the innermost dot pattern:

[0096] ;

[0097] In the formula, The width of the barrier layer along the radial direction of the ingot; Let be the radius of the crystal ingot; For the first The radius of the circle containing the discrete laser dot pattern.

[0098] For the The radius of the circle containing a discrete laser dot can be expressed as:

[0099] ;

[0100] In the formula, For the first The radius of the circle containing the discrete laser dots; Let be the radius of the crystal ingot; This refers to the lap number sequence. It represents the radial displacement distance between two adjacent discrete laser dot patterns.

[0101] In one embodiment, the radius difference between the circumferences of two adjacent discrete laser dot marks is 1 μm to 200 μm, preferably 5 μm to 50 μm. A smaller radial displacement distance can increase the radial coverage density of the barrier layer, which is suitable for ingots with a large transition zone height or obvious laser edge propagation anomalies; a larger radial displacement distance can reduce the number of processing turns and improve the processing efficiency of the barrier layer, which is suitable for scenarios with a shallow transition zone or relatively relaxed requirements for subsequent grinding allowance.

[0102] The number of rings of discrete laser dots can be determined based on the width of the blocking layer and the radial displacement distance:

[0103] ;

[0104] In the formula, The number of revolutions of the discrete laser dots; The width of the barrier layer along the radial direction of the ingot; This represents the radial displacement distance between two adjacent discrete laser dot rings. This represents the function for rounding up.

[0105] The spacing between the dots along the same circumferential direction can be controlled by the ingot rotation speed and the repetition frequency of the first laser pulse. If the dot spacing is too large, there may be too many unmodified regions in the blocking layer along the circumference, which may cause the subsequent stripping laser to form a transition zone at some angular positions. If the dot spacing is too small, the dots may connect along the circumference to form a continuous crack ring, thereby weakening the mechanical stability of the ingot edge. Therefore, it is preferable to retain unmodified crystal regions between adjacent discrete laser dots, while ensuring that the dot density is sufficient to change the energy propagation conditions of the subsequent stripping laser in the edge region.

[0106] In one embodiment, the single-pulse energy of the first laser is set below the energy required to form the bulk stripping remodeling layer, or by reducing the dot overlap rate, it forms only localized remodeling regions without creating a continuous stripping surface. The first laser does not cut the ingot, but rather forms multiple localized remodeling points. These localized remodeling points are arranged in multiple rings in space, which can scatter, absorb, and refract disturbances, release localized stress, or interrupt crack propagation of the subsequent second laser. Thus, when the second laser approaches the edge of the ingot, its tendency to continue forming a continuous transition zone upwards in the edge region is suppressed.

[0107] Step S3 forms a barrier layer specifically targeting the edge transition zone through a structural combination of "depth shallower than the peeling modifier layer, multiple radially distributed rings, and circumferentially discrete rather than continuously continuous" patterns. If only a single ring of dots is formed, its radial coverage is limited; if continuous annular cracks are formed, edge strength may be compromised and the peeling path affected; if the barrier layer is at the same depth as the peeling modifier layer, it may become mixed with the main peeling layer, failing to effectively suppress the upward-climbing transition zone. This invention, through the spatial combination of multiple discrete rings of dots, enables the barrier layer to cover the main formation area of ​​the edge transition zone while avoiding the formation of excessively continuous crack structures, thus achieving a balance between suppressing the loss layer and ensuring peeling stability.

[0108] (iv) Step S4: Peeling off the modified layer and the function of the barrier layer

[0109] In step S4, the second laser is focused to the depth of the stripping modified layer. The first laser forms a stripping modification layer inside the crystalline ingot for separating the crystal flakes. The second laser can form a continuous or quasi-continuous modification layer inside the ingot according to a preset scanning path. This stripping modification layer can consist of modification zones, void zones, crack zones, or stress concentration zones, and its main function is to guide the crystal flakes to separate along a predetermined depth when subsequent external forces are applied.

[0110] In conventional processes without a barrier layer, when the second laser scans to the edge region of the ingot, the laser energy may propagate unexpectedly at the edge due to the ingot boundary conditions. This causes the modified layer to gradually rise from the depth where the modified layer was removed towards the upper surface of the ingot. This transition zone becomes an abnormally damaged area at the wafer edge or on the surface of the remaining ingot after peeling, requiring increased grinding and polishing to eliminate it.

[0111] In this invention, since a barrier layer has been pre-formed in step S3, when the second laser approaches the edge of the ingot, the barrier layer is located on the propagation path or the modified extension path where it may form a rising transition zone. The discrete laser dots in the barrier layer have already modified the local crystal structure. These modified dots can change the local optical transmittance, refractive state, thermal stress distribution, or crack propagation conditions, thereby reducing the effective energy density of the second laser in the edge region or interrupting the upward continuous extension path of the modified layer.

[0112] Therefore, in step S4, the barrier layer and the stripping modification layer are not simply superimposed, but have a functional division of labor: the stripping modification layer is used to achieve crystal wafer separation, and the barrier layer is used to control the abnormal expansion of the stripping modification layer in the edge region. Through this functional division of labor, the main stripping layer can maintain its original processing efficiency and stripping capability, while the edge transition zone is limited to a small area or is essentially eliminated.

[0113] (V) Step S5: Crystal wafer peeling and subsequent processing

[0114] In step S5, an external peeling action is applied to the crystal material ingot with the peeling modification layer, causing the crystal wafers to separate from the ingot body along the peeling modification layer. The external peeling action can be mechanical tension, wedging force, vacuum adsorption tension, thermal stress, ultrasonic vibration, or a combination thereof. The specific form of the peeling action can be determined based on the thickness of the crystal material, the strength of the peeling modification layer, and the wafer size.

[0115] After stripping, the surfaces of the crystal wafers and the remaining ingots can be ground, polished, or planarized. Without a barrier layer, the edge transition zone is quite high, often requiring increased overall grinding and removal to obtain a smooth, defect-free wafer. This invention uses a barrier layer to suppress the formation of the edge transition zone, reducing the height and radial width of abnormal edge damage after stripping, thereby reducing the subsequent grinding and polishing allowance.

[0116] Without this invention, the grinding reference typically needs to cover the highest damage position in the edge transition zone, resulting in the removal of a significant amount of material from the entire crystal wafer or the remaining ingot surface. With this invention, the edge transition zone is suppressed, and the grinding reference can be closer to the plane where the main exfoliated modified layer is located, thus reducing the amount of material removed. This effect is particularly pronounced for high-value crystal materials such as silicon carbide, increasing the number of wafers obtainable from a single ingot, reducing the consumption of grinding wheels and polishing consumables, and improving the economics of laser lift-off processes. IV. Specific Implementation Examples

[0118] (a) Test subjects, equipment and testing methods

[0119] This application example uses a 4H-SiC ingot as the test object. The ingot has an outer diameter of 150 mm, a thickness of 20 mm, and a crystal orientation typical of power device substrates. The experiment employs a picosecond laser processing device with internal focusing capabilities. The device includes an ingot-supporting rotation mechanism, a radial displacement mechanism, a laser focusing depth adjustment mechanism, a control module, and a microscopic inspection module. The ingot is fixed to the supporting rotation mechanism and rotates around its central axis. The laser focusing depth is controlled by the depth adjustment mechanism, and the radial position is controlled by the radial displacement mechanism.

[0120] The experiments were divided into Comparative Example 1 and Examples 1 to 4. Comparative Example 1 used a conventional laser ablation method, i.e., without setting an edge barrier layer, directly forming the ablation modification layer at a predetermined ablation depth. Examples 1 to 4 all used the method of the present invention, i.e., first processing a barrier layer composed of multiple discrete laser dots at a predetermined depth at the edge of the ingot, then forming the main ablation modification layer and performing ablation.

[0121] To ensure the comparability of the comparison results, the comparative example and the embodiment used the same ingot batch, the same main body peel-off modification layer depth, the same second laser processing parameters, and the same peeling method. The only difference was whether an edge barrier layer was processed before the formation of the main body peel-off modification layer, and the width of the barrier layer. Radial displacement distance The parameters are different.

[0122] The detection method for the edge transition zone is as follows: After peeling, 12 detection points are selected at intervals along the edge of the wafer. A cross-sectional sample is prepared at the edge of the peeled surface, and the morphology of the edge modified layer is observed using a confocal microscope and infrared transmission microscopy. Using the plane containing the main peeled modified layer as a reference plane, the maximum height of the edge modified layer relative to this reference plane and rising towards the upper surface of the ingot is measured and recorded as the transition zone height. The width of the abnormal rise region along the radial direction of the ingot is measured and recorded as the transition zone width. Each group of experiments measured 12 locations, and the average and maximum values ​​were used as evaluation indicators.

[0123] The testing method for grinding removal is as follows: After peeling, the wafer surface is planarized by grinding until the edge transition zone, residual cracks, and abnormal modification traces are basically eliminated, and the flatness requirements before subsequent polishing are met. The minimum grinding removal amount required to achieve the same surface quality is recorded. Grinding wheel wear is calculated by the change in the outer diameter of the grinding wheel before and after grinding and the amount of dressing compensation. Material utilization is evaluated by the number of wafers available from the same ingot and the remaining usable thickness.

[0124] (ii) Comparative Example 1: Conventional laser ablation test without a barrier layer

[0125] Comparative Example 1 was performed using a conventional laser ablation method. For example... Figure 1 As shown, a second laser is focused at a predetermined depth inside the ingot to form a main body peeling and modification layer; then, an external peeling force is applied to separate the crystal sheet from the main body of the ingot along the peeling and modification layer. This comparative example was not performed. Figures 3 to 6 The edge barrier layer processing is shown.

[0126] The test results showed that a distinct laser transition zone was formed at the edge of the crystal ingot. For example... Figure 2 As shown, the main exfoliated modified layer no longer remains straight near the edge of the ingot, but gradually rises towards the upper surface of the ingot. After exfoliation, this transition zone exhibits localized step-like damage and residual oblique cracks at the edge. Statistics from 12 detection points show that the average width of the transition zone is 63.8 μm, with a maximum width of 88.6 μm; the average height of the transition zone is 27.4 μm, with a maximum height of 41.2 μm.

[0127] To eliminate the aforementioned edge transition zone, Comparative Example 1 required an increased overall removal amount during subsequent polishing. In the experiment, when the polishing removal amount was less than 48 μm, abnormal edge modification traces were still visible at some detection points; when the polishing removal amount reached approximately 56 μm, the edge transition damage was essentially eliminated. Therefore, the effective polishing removal amount for Comparative Example 1 was recorded as 56 μm. This result indicates that, without a barrier layer, although the main body stripping of the modification layer can achieve wafer separation, the ingot edge transition zone significantly increases subsequent polishing losses.

[0128] (III) Example 1: Laser peeling test where the width of the barrier layer covers the width of the transition zone

[0129] Example 1 was implemented using the method of the present invention. Based on the edge transition zone parameters obtained in Comparative Example 1, the average width of the transition zone without a barrier layer was used as the basis for the barrier layer design, and the width of the barrier layer was set accordingly. The main area covered by the transition zone. Depth of the barrier layer processing. Setting the processing depth of the main body stripping and modification layer Between the ingot and the upper surface, so that the barrier layer is located Figure 3 On the rising path of the edge transition zone shown.

[0130] During barrier layer processing, such as Figure 6 As shown, the first laser is focused at a specified depth at the edge of the ingot, and the ingot-supporting rotation mechanism is activated to rotate the ingot around its central axis, forming the first ring of discrete laser dots; then the laser focus and the ingot are displaced relative to each other in the radial direction. Continue rotating the ingot to form a second ring of discrete laser dots; repeat the above steps until the second ring is formed. Discrete laser dots in multiple loops. Figure 4 The edge barrier layer shown.

[0131] In Example 1, the width of the barrier layer satisfies:

[0132] ;

[0133] In the formula, The width of the barrier layer along the radial direction of the ingot; The radius of the crystal ingot is the ingot radius of the crystalline material. For the first The radius of the circle containing the discrete laser dot pattern.

[0134] At the same time, make Not less than the average width of the transition zone measured in Comparative Example 1 This ensures that the barrier layer covers the main formation area of ​​the transition zone at the edge of the ingot. The radial displacement distance between two adjacent discrete laser dot rings... The size is set to 20μm, and the dots are distributed at intervals along the circumference. Unmodified crystal regions are retained between adjacent dots to avoid the formation of continuous circumferential cracks.

[0135] After the barrier layer is processed, the second laser is focused to the depth of the stripping and modification layer processing. This forms the main exfoliation modified layer. Since the barrier layer is located on the propagation path of the exfoliation laser, which may form a transition zone at the edge of the ingot, when the second laser approaches the edge of the ingot, the discrete modified points in the barrier layer scatter, absorb, or locally interrupt the propagation of the laser energy, while also restricting the continuous upward propagation of the crack, so that the main exfoliation modified layer remains closer to the predetermined exfoliation plane at the edge.

[0136] In Example 1, the transition zone at the ingot edge was significantly reduced, and the main exfoliated modified layer did not show a clear continuous upward climb at the edge. Statistical results from 12 detection points showed that the average width of the transition zone decreased to 14.6 μm, with a maximum width of 23.9 μm; the average height of the transition zone decreased to 6.8 μm, with a maximum height of 11.5 μm. Compared to Comparative Example 1, the average width of the transition zone decreased by approximately 77.1%, and the average height of the transition zone decreased by approximately 75.2%.

[0137] In Example 1, the subsequent grinding removal amount was 24 μm, which was sufficient to essentially eliminate residual modification traces at the edge and achieve the same surface quality requirements as Comparative Example 1. Compared to 56 μm in Comparative Example 1, the grinding removal amount was reduced by 32 μm, a decrease of approximately 57.1%. This result demonstrates that the present invention, by pre-forming a barrier layer at the ingot edge, can effectively suppress the formation of the laser ablation edge transition zone and significantly reduce subsequent grinding losses.

[0138] (V) Example 2: Efficiency optimization test with barrier layer width slightly smaller than transition zone width

[0139] Example 2 was used to verify the barrier layer width while improving processing efficiency. Slightly smaller than the width of the transition zone Even so, a good loss layer suppression effect can still be obtained. The processing parameters of the main body peeling modified layer in Example 2 are the same as those in Example 1, the difference being that the width of the barrier layer is... The radial displacement distance is set to approximately 85% of the average width of the transition zone measured in Comparative Example 1. It remains at 20μm.

[0140] Because the barrier layer is slightly narrower, it primarily covers the area from the outermost edge of the ingot to the main damage height in the transition zone, without completely covering the inner boundary of the transition zone. This configuration helps reduce the number of barrier layer dot rings and processing time, making it suitable for situations where subsequent edge chamfering or light grinding can remove a small amount of residual damage.

[0141] The experimental results show that Example 2 can still significantly suppress the edge transition zone. The average width of the transition zone is 22.8 μm, and the maximum width is 35.4 μm; the average height of the transition zone is 9.7 μm, and the maximum height is 15.8 μm. The subsequent grinding removal amount is 29 μm. Compared with Comparative Example 1, the average height of the transition zone in Example 2 is reduced by approximately 64.6%, and the grinding removal amount is reduced by approximately 48.2%. Compared with Example 1, the suppression effect of Example 2 is slightly weaker, but the barrier layer processing time is shortened by approximately 18.5%.

[0142] The results demonstrate that when high production cycle time is required, the width of the barrier layer can be appropriately reduced to cover the main damage area of ​​the transition zone, while still achieving a significant edge loss suppression effect. This embodiment... Slightly smaller The parameter range demonstrates that the width of the barrier layer in this invention is not limited to being mechanically equal to or greater than the width of the transition zone, but can be adaptively set according to processing efficiency and quality requirements.

[0143] (vi) Example 3: Experiment on the effect of radial displacement distance on the barrier layer effect

[0144] Example 3 was used to verify the radial displacement distance between two adjacent discrete laser dot patterns. The effect on the suppression effect of the barrier layer. The width of the barrier layer was maintained during the experiment. Barrier layer processing depth , Main body stripping and modification layer processing depth The parameters of the first and second lasers are basically the same, with only minor adjustments. .

[0145] The experiment was set up with three groups: Group 1 10μm, second group 20μm, third group The thickness is 50 μm. All three groups used multiple discrete laser dots to form the blocking layer, with the dots spaced apart along the circumference to avoid forming continuous annular cracks.

[0146] The experimental results are shown in the table below.

[0147]

[0148] As can be seen from the data in the table, when When the diameter is 10 μm, the radial density of the barrier layer is high, resulting in the best suppression effect in the transition region, but the processing time is long; when... At a size of 20 μm, a relatively good balance is struck between the suppression effect and the processing efficiency; when When the diameter is increased to 50 μm, the processing time of the barrier layer is shortened, but due to the increased radial spacing between adjacent dotted rings, the barrier effect of the local area on the subsequent stripping laser is weakened, and the average height of the transition zone increases to 13.9 μm.

[0149] This result proves that the radial displacement distance It is an important parameter affecting the suppression effect of the barrier layer. With Increasing the radius reduces the barrier layer processing time, but increases the residual height of the edge transition zone. Therefore, in actual processes, it is preferable to set the radius difference between two adjacent rings within the range of 5μm to 50μm, and select the specific value according to the ingot material, transition zone height, and production line cycle time.

[0150] (vii) Example 4: Test of matching coefficient for different barrier layer depths

[0151] Example 4 is used to verify the processing depth of the barrier layer. Processing depth of the stripped modified layer The matching relationship between them. Based on the aforementioned transition zone height. The depth of the barrier layer processing is determined according to the following formula:

[0152] ;

[0153] In the formula, The depth of the barrier layer processing; The depth of the stripping and modification layer processing; The height of the transition zone relative to the stripped modified layer under conditions where no barrier layer is set; is the depth matching coefficient.

[0154] The experiment was set up separately. The values ​​are 0.6, 1.0, and 1.4. Other process parameters remain consistent, including the barrier layer width. Radial displacement distance First laser dot parameters and second laser stripping parameters.

[0155] The experimental results are shown in the table below.

[0156]

[0157] As can be seen from the data in the table, when When the value is 1.0, the barrier layer depth matches the main climbing path of the transition zone well, the average height of the transition zone is the lowest, and the amount of material removed by grinding is minimal. When When the value is 0.6, the barrier layer is closer to the stripped modified layer. Although it can provide a barrier effect, its coverage of the upper climbing path of the transition zone is slightly insufficient; when When the depth matching coefficient is 1.4, the barrier layer is closer to the upper surface of the ingot, which has a suppressive effect on the upper damage path, but the local edge microcracks increase slightly. Therefore, the depth matching coefficient is preferably set in the range of 0.6 to 1.4 according to the crystal material and laser parameters, and more preferably close to 1.0.

[0158] This embodiment demonstrates that the present invention does not simply form dots at arbitrary shallow locations, but rather makes the depth of the barrier layer and the height of the transition zone... This parameter relationship allows the blocking layer to be positioned more accurately along the transition zone formation path, thereby improving the suppression effect.

[0159] (viii) Summary of experimental data

[0160] In order to comprehensively evaluate the technical effects of the present invention, the main results of Comparative Example 1 and Examples 1 to 4 are summarized as follows.

[0161]

[0162] Based on the above data and Figure 9 As can be seen, compared with Comparative Example 1 without a blocking layer, the average height of the edge transition zone in Example 1 decreased from 27.4 μm to 6.8 μm, the average width of the transition zone decreased from 63.8 μm to 14.6 μm, and the amount of material removed by grinding decreased from 56 μm to 24 μm. These results demonstrate that the present invention can significantly suppress the formation of the laser transition zone at the ingot edge and reduce subsequent grinding and polishing losses.

[0163] (ix) Calculation of film output rate improvement

[0164] To further illustrate the impact of this invention on the utilization rate of crystal materials, calculations were performed using continuous wafer fabrication from the same SiC ingot as an example. It was assumed that after each peeling to obtain a crystal wafer, grinding and polishing were required to remove damage to the peeling surface. In Comparative Example 1, 56 μm needed to be removed by grinding to eliminate the edge transition zone; in Example 1, because the barrier layer inhibited the formation of the transition zone, the amount removed by grinding was reduced to 24 μm. Both methods reduced grinding loss by 32 μm per wafer.

[0165] Taking the continuous peeling of 100 wafers as an example, the cumulative thickness reduction achieved by Example 1 compared to Comparative Example 1 is as follows:

[0166] ;

[0167] In the formula, For the cumulative savings in crystal material thickness; This refers to the number of wafers that are continuously stripped. This represents the amount of material removed during single-piece grinding in the comparative example. The amount removed by grinding a single piece in the example is the amount removed.

[0168] Substituting the above experimental data, when continuously peeling off 100 wafers, the cumulative thickness saved is approximately 3.2 mm. For high-value SiC ingots, this thickness can be converted into additional usable wafer thickness or remaining processable ingot thickness, thereby improving ingot material utilization. This calculation is consistent with... Figure 10 The relationship between the amount of material removed by grinding and the number of sheets produced is consistent.

[0169] The above experimental results show that the present invention, by pre-forming a barrier layer composed of multiple discrete laser dots at the edge of the crystal ingot, reduces the width of the barrier layer. With transition zone width Match and make the barrier layer processing depth Processing depth of the stripped modified layer and transition zone height This matching technology can effectively suppress the formation of transition zones at the edges of crystal ingots during laser ablation.

[0170] Compared with conventional laser stripping methods without a barrier layer, the present invention achieves at least the following technical effects: First, it significantly reduces the height and width of the transition zone at the edge of the ingot; second, it reduces the amount of grinding and polishing required to remove abnormal edge damage after stripping; third, it reduces the consumption of grinding wheels and polishing consumables; fourth, it improves the effective material utilization rate and theoretical wafer yield of the same ingot; and fifth, the barrier layer processing can be achieved by adding an edge pretreatment procedure to existing laser stripping equipment, resulting in good process compatibility.

[0171] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

[0172] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0173] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0174] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0175] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0176] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0177] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0178] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

Claims

1. A method for suppressing laser ablation loss layers in crystal materials, characterized in that, The method includes the following steps: S1, obtain the parameters of the transition zone formed at the edge of the crystal ingot when the crystal material ingot is laser-lifted without a blocking layer. The parameters of the transition zone include at least the width of the transition zone along the radial direction of the crystal ingot and the height of the transition zone along the thickness direction of the crystal ingot relative to the peeling modification layer. S2, determine the width of the barrier layer along the radial direction of the ingot based on the width of the transition zone along the radial direction of the ingot, and determine the processing depth of the barrier layer based on the height of the transition zone relative to the peeling and modification layer along the thickness direction of the ingot, so that the processing depth of the barrier layer is located between the subsequent peeling and modification layer processing depth and the upper surface of the ingot. S3, before forming the stripping and modification layer, the first laser is focused at the processing depth of the barrier layer, and the crystal material ingot is rotated around its own central axis to form the first ring of discrete laser dots on the edge of the ingot; then the first laser and the crystal material ingot are displaced relative to each other in the radial direction by a preset distance, and the crystal material ingot is rotated again to form the second ring of discrete laser dots. The above radial displacement and rotation dotting process is repeated until the last ring of discrete laser dots is formed.

2. The method for suppressing laser ablation loss layer of crystal materials according to claim 1, characterized in that, In step S1, the transition zone parameters are obtained as follows: a test peeling modification layer is formed on a crystal ingot of the same material, crystal orientation, or batch according to a laser peeling process without a blocking layer. The edge profile of the crystal ingot is observed under a microscope, infrared imaging, confocal detection, or cross-sectional contour detection to obtain the width of the transition zone along the radial direction of the crystal ingot and the height of the transition zone along the thickness direction of the crystal ingot relative to the peeling modification layer. And / or, in step S2, the width of the barrier layer along the radial direction of the ingot is set according to the width of the transition region along the radial direction of the ingot, and the width of the barrier layer along the radial direction of the ingot is not less than the width of the transition region along the radial direction of the ingot. And / or, in step S2, under the condition of improving the processing efficiency of the barrier layer, the width of the barrier layer along the radial direction of the ingot is more than 0.8 times the width of the transition zone along the radial direction of the ingot and less than the width of the transition zone along the radial direction of the ingot. And / or, in step S2, the processing depth of the barrier layer is determined based on the processing depth of the stripped modified layer, the height of the transition zone relative to the stripped modified layer along the ingot thickness direction, and the depth matching coefficient, wherein the value of the depth matching coefficient ranges from 0.6 to 1.

4.

3. The method for suppressing laser ablation loss layer of crystal materials according to claim 1, characterized in that, In step S3, the last ring of discrete laser dots is the ring of discrete laser dots closest to the center of the crystal ingot. Multiple rings of discrete laser dots together form a blocking layer located at the edge of the crystal ingot, and the width of the blocking layer along the radial direction of the crystal ingot is the difference between the radius of the crystal material ingot and the circumference of the last ring of discrete laser dots. And / or, in step S3, the radius difference between the circumferences of two adjacent discrete laser dot marks is 1 micrometer to 200 micrometers, preferably 5 micrometers to 50 micrometers; And / or, in step S3, the radius of the circumference of any discrete laser dot pattern is determined based on the radius of the crystal ingot, the number of the discrete laser dot pattern, and the radial displacement distance between two adjacent discrete laser dot patterns. And / or, in step S3, the number of turns of the discrete laser dots is determined based on the width of the barrier layer along the radial direction of the ingot and the radial displacement distance, and is determined by rounding up the result of dividing the width of the barrier layer along the radial direction of the ingot by the radial displacement distance and then adding 1 turn. And / or, in step S3, the discrete laser dots are spaced apart in the same circumferential direction, and unmodified crystal regions are retained between adjacent discrete laser dots, so that the barrier layer forms a discontinuous crack-type barrier structure, rather than forming a peeling crack that runs continuously along the circumferential direction.

4. The method for suppressing laser ablation loss layer of crystal materials according to claim 1, characterized in that, The method also includes: S4, the second laser is focused to the depth of the stripping modification layer processing, and a stripping modification layer for stripping crystal sheets is formed inside the crystal material ingot; S5, an external peeling action is applied to the crystal material ingot on which the peeling modification layer is formed, so that the crystal sheet is separated from the ingot body along the peeling modification layer.

5. The method for suppressing laser ablation loss layer of crystal materials according to claim 4, characterized in that, In step S3, the single-pulse energy, repetition frequency, focused spot diameter, and ingot rotation speed of the first laser are configured to form a localized modified region by a single discrete laser dot; in step S4, the single-pulse energy or average power of the second laser is higher than that of the first laser, or the scanning overlap rate of the second laser is higher than that of the first laser, so as to form a continuous or quasi-continuous stripping modified layer that can be used to strip crystal wafers. And / or, in step S4, the blocking layer is located on the edge propagation path of the stripped modification layer, and is used to absorb, scatter or interrupt the propagation of the second laser in the crystal ingot edge region, thereby inhibiting the stripped modification layer from climbing up the crystal ingot edge towards the upper surface of the crystal ingot to form a continuous transition zone. And / or, when forming the stripping modification layer, the scanning path of the second laser covers the stripping area of ​​the main body of the ingot, and when it reaches the area where the edge barrier layer of the ingot is located, the effective energy density of the second laser in the edge region of the ingot is reduced by the barrier layer, so that the transition modification layer that rises continuously along the thickness direction is not formed in the edge region of the ingot. And / or, after step S5, the process further includes grinding or polishing the surface of the stripped crystal sheet or the surface of the remaining crystal ingot; wherein, since the barrier layer inhibits the formation of the transition zone at the edge of the crystal ingot, the amount removed by grinding or polishing is less than the amount required to remove the transition zone under conditions where no barrier layer is provided.

6. The method for suppressing laser ablation loss layer of crystal materials according to any one of claims 1 to 5, characterized in that, The crystal material ingot is a silicon carbide ingot, a sapphire ingot, a gallium nitride ingot, a diamond ingot, or other wide-bandgap crystal material ingots that are transparent to the second laser.

7. A system for suppressing laser ablation loss layers in crystal materials, characterized in that, The system for performing the method according to any one of claims 1 to 6, the system comprising: The crystal ingot support and rotation mechanism is used to support the crystal material ingot and rotate the crystal material ingot around its own central axis. A radial displacement mechanism is used to displace the laser focusing position relative to the crystal material ingot by a preset distance in the radial direction; A laser processing mechanism is used to form multiple discrete laser dots at the depth of the barrier layer and to form a stripped modified layer at the depth of the stripped modified layer. A depth adjustment mechanism is used to adjust the focusing depth of the first laser and the second laser. The control module is used to determine the width of the barrier layer, the processing depth of the barrier layer, and the number of discrete laser dot rings based on the width of the transition zone along the radial direction of the ingot, the height of the transition zone along the thickness direction of the ingot relative to the stripped modified layer, the ingot radius, and the radial displacement distance. It also controls the coordinated operation of the ingot bearing rotation mechanism, the radial displacement mechanism, the laser processing mechanism, and the depth adjustment mechanism.

8. The system for suppressing laser lift-off loss layer of crystal materials according to claim 7, characterized in that, The system also includes a detection module, which is used to acquire an image or cross-sectional profile of the transition zone at the edge of the ingot, and output the width of the transition zone along the radial direction of the ingot and the height of the transition zone along the thickness direction of the ingot relative to the stripping modification layer; the control module automatically generates barrier layer processing parameters based on the width of the transition zone along the radial direction of the ingot and the height of the transition zone along the thickness direction of the ingot relative to the stripping modification layer output by the detection module.

9. An electronic device, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method according to any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1 to 6.

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