Method and apparatus for high efficiency laser cutting of silicon carbide ingots

Abstract

The application discloses a method and device for high-efficiency laser cutting of a silicon carbide ingot, and relates to the technical field of semiconductor material laser processing and equipment. The method comprises the following steps: splitting a pulse laser into two beams, taking the first beam as a modification laser and taking the second beam as a heating laser after frequency conversion; delaying and combining the modification laser and the heating laser to realize coaxial and synchronous processing of the modification laser and the heating laser on the SiC ingot; focusing the modification laser inside the SiC ingot to perform modification processing, and forming a modification part and a crack area; focusing the heating laser inside the SiC ingot to apply thermal stress in a heating mode and control crack propagation; controlling the relative movement of the SiC ingot and the laser pulse to perform scanning processing according to a set path, and forming a modification layer and a crack connection layer; and peeling off a part of the SiC ingot to obtain a wafer by taking the modification layer and the crack connection layer as an interface. The application realizes the simultaneous spatial action of the modification laser and the heating laser on the SiC ingot, reduces processing time consumption and wafer peeling difficulty, and improves peeling quality.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material laser processing technology and equipment technology, and in particular, it is a method and apparatus for high-efficiency laser cutting of silicon carbide ingots. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Silicon carbide (SiC) is a new generation of semiconductor materials with a large bandgap, high temperature resistance, high pressure resistance, high radiation resistance, high thermal conductivity and high electron saturation velocity. It is particularly suitable for making high voltage, high temperature, high frequency, high power and radiation-resistant devices, and has a very broad application prospect in radio frequency communication, radar, satellite, power management, automotive electronics and industrial power electronics.

[0004] Semiconductor wafer substrate dicing technologies mainly include traditional mechanical dicing and laser dicing. For SiC materials, the mechanical dicing method involves winding diamond wire into parallel saws and cutting SiC ingots with specific crystal orientations at a certain speed to produce wafers. SiC has a Mohs hardness of 9.2–9.8, second only to diamond (Mohs hardness 10). During dicing, the kerf is wide and the cutting speed is slow. Taking 6-inch SiC as an example, cutting one ingot takes 110–120 hours, with a total thickness variation (TTV) of approximately 100 μm and a material loss rate of 40%–50%. Furthermore, sawing process parameters, bonded abrasive grain size, workpiece feed motion, and saw wire speed all affect the wire saw cutting accuracy, leading to severe surface damage to the wafers, increased processing difficulty, and reduced yield.

[0005] Laser processing is a non-contact processing technology that eliminates tool wear and cutting force on the workpiece. It boasts advantages such as high processing efficiency, ease of automation, good adaptability, and environmental friendliness, and is expected to bring breakthroughs in the quality, precision, and efficiency of SiC ingot slicing.

[0006] Laser processing of SiC ingots, currently reported common processes (such as invention patents CN115555736A and CN115555735A) involve first using a short-pulse ultrafast laser to focus and scan point-by-point within the SiC ingot at a specific depth. This modifies the SiC into amorphous Si and C, creating cracks that form modification points and regions. Then, a wider-pulse laser is used for a second scan, causing the cracks within the SiC to grow, expand, and connect, forming a modified layer. This allows for slicing of the SiC ingot. Compared to traditional multi-wire mechanical cutting methods, laser cutting offers advantages such as narrower kerfs, less waste, and non-contact cutting. However, current processes involve a two-stage process: first scanning to form the modified layer, then scanning again to heat the modified layer. This two-stage scanning process cannot achieve simultaneous scanning, resulting in drawbacks such as long processing time and low efficiency.

[0007] Furthermore, during the second scan, the ingot has cooled down. The ingot needs to absorb heat again and reach a certain threshold before the crack can grow and propagate. This means that the energy of the pulsed laser cannot be fully applied to the growth of the crack, which greatly affects the effect of crack growth and propagation. Therefore, it is necessary to reduce the scanning line spacing to achieve crack connection, which increases the processing time of the ingot and reduces the cutting efficiency. Summary of the Invention

[0008] The purpose of this invention is to provide a method and apparatus for high-efficiency laser cutting of silicon carbide ingots. It adopts a dual-wavelength laser coaxial synchronous single-processing mode, which realizes the simultaneous spatial interaction of the modification laser and the heating laser with the SiC ingot, reduces processing time and wafer stripping difficulty, improves stripping quality, and avoids the problem of low energy utilization of heating laser due to excessive time interval between two processing steps and material cooling in the secondary processing mode.

[0009] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0010] The first aspect of this invention provides a method for high-efficiency laser cutting of silicon carbide ingots.

[0011] A method for high-efficiency laser cutting of silicon carbide ingots includes the following steps:

[0012] The pulsed laser emitted by the laser source is split into two beams according to a set ratio. The first beam is used as the quality modification laser, and the second beam is used as the heating laser after frequency conversion.

[0013] A phase delay and combination technique is used to combine the modifying laser and the heating laser to achieve coaxial and synchronous processing of SiC ingots. The modifying laser is focused inside the SiC ingot at a set depth to perform the modification process, and finally forms a modified part and a crack zone near the focal point of the modifying laser. The heating laser is focused at the same depth as the modifying laser and applies thermal stress inside the SiC ingot by heating to control crack propagation.

[0014] The relative movement of the SiC ingot and the laser pulse is controlled, and scanning processing is performed according to the set path to form a modified layer and a crack bonding layer at a set depth.

[0015] Using the modified layer and the crack-connecting layer as the interface, a portion of the SiC ingot is peeled off to obtain a wafer.

[0016] Preferably, the pulsed laser energy of the modification laser is such that it reaches the damage threshold of the SiC ingot, causing internal modification of the SiC ingot. The pulse width of the modification laser is 100 fs to 100 ns, and the single pulse energy is 10 to 100 μJ.

[0017] Preferably, the second laser beam is phase-matched using a nonlinear crystal to achieve frequency doubling and obtain the heating laser. The wavelength of the heating laser is a wavelength with a high absorption rate for single-crystal silicon carbide, and the wavelength of the heating laser is preferably 532nm.

[0018] Preferably, the modified laser and the heating laser are subjected to a phase delay and fusion technique to achieve coaxial and synchronous processing of SiC ingots by the modified laser and the heating laser, specifically as follows:

[0019] First, achieve synchronization between the modification laser and the heating laser:

[0020] The modified laser is reflected by multiple mirrors, and the position of the mirrors in the delay line is adjusted to change the transmission optical path of the modified laser, ultimately achieving synchronous processing with the heating laser.

[0021] Then, the coaxiality of the modified laser and the heating laser was achieved:

[0022] The modified laser, synchronized with the heating laser, is combined with the heating laser using a dichroic mirror to achieve coaxial processing of the modified laser and the heating laser.

[0023] Preferably, the set depth is 100-700 μm below the upper surface of the SiC ingot.

[0024] Preferably, the modified layer is composed of a plurality of modified parts, and the crack-connecting layer is formed by the interconnection of the crack regions near each modified part.

[0025] Preferably, the relative movement of the SiC ingot and the laser pulse is controlled to achieve a Z-shaped scanning path, in which the distance between adjacent modified parts on the Y-axis is 10-60 μm and the distance between adjacent scanning parts on the X-axis is 10-400 μm.

[0026] Preferably, the SiC wafer is peeled off by applying external tension, torque, or ultrasonic vibration.

[0027] A second aspect of the present invention provides an apparatus for high-efficiency laser cutting of silicon carbide ingots.

[0028] A high-efficiency laser cutting device for silicon carbide ingots includes a laser source module, a beam splitting module, a frequency conversion module, a coaxial synchronization processing module, and a motion module, wherein:

[0029] The laser source module is used to generate pulsed laser;

[0030] The beam splitting module is used to split the pulsed laser into two laser beams, wherein the first laser beam is used as the quality-modifying laser, and the second laser beam is fed into the frequency conversion module.

[0031] The frequency conversion module is used to convert the frequency of the second laser beam through nonlinear optical effects to obtain a heating laser.

[0032] The coaxial synchronous processing module is used to achieve synchronization and coaxiality between the modification laser and the heating laser, resulting in a combined laser beam, which is then used to perform simultaneous spatial processing on the SiC ingot.

[0033] The motion module is used to control the relative motion between the combined laser beam and the SiC ingot, so that the combined laser beam can complete the scanning and processing of the ingot at a set depth and along a set path.

[0034] Preferably, the coaxial synchronization processing module includes a dual-beam synchronization processing system and a beam combining module. The dual-beam synchronization processing system includes multiple reflectors. The dual-beam synchronization processing system is used to adjust the position of the reflectors in the delay line, change the transmission optical path of the modified laser, and achieve synchronous processing with the heating laser. The beam combining module is used to combine the modified laser, which is synchronized with the heating laser, with the heating laser.

[0035] The present invention has the following beneficial effects:

[0036] 1. This invention provides a method and apparatus for high-efficiency laser cutting of silicon carbide ingots. It adopts a dual-wavelength beam coaxial synchronous single-pass processing, avoiding the problems of long processing time and low efficiency caused by traditional secondary laser processing. It realizes the synchronous generation and propagation of internal cracks in SiC, resulting in better crack propagation effect and better crack connection effect. The good crack connection effect reduces the difficulty of peeling between ingot and wafer. The morphology of the wafer surface after peeling is more uniform, the peeling difficulty is reduced, and the peeling quality is improved. At the same time, the laser scanning line spacing can be further increased to improve processing efficiency.

[0037] 2. The laser-processed ingot wafer generation system of the present invention can be roughly divided into four parts: a laser source system, a frequency conversion system, a coaxial synchronous processing system, and a motion control system. Compared with traditional SiC ingot laser wafer lift-off devices, the present invention uses only one laser source and achieves dual-wavelength pulse generation through frequency conversion technology, greatly reducing the cost of the device. In addition, the device achieves precise synchronous processing of SiC ingots with dual pulses through delay lines, and achieves coaxial focusing processing of dual-wavelength pulses through beam combining. Compared with traditional two-stage processing devices, the crack propagation and connection effect is better, the lifting force required is smaller, the wafer morphology obtained by lifting is more uniform, and the lifting quality is better. At the same time, the scanning line spacing can be set larger, the processing time is further shortened, and the processing efficiency is improved.

[0038] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A schematic diagram showing the modification and crack growth and propagation process after the modifying laser and heating laser are focused inside the SiC ingot.

[0041] Figure 2 A schematic diagram of the laser "unidirectional zigzag" scanning processing path;

[0042] Figure 3 A schematic diagram of the laser "bidirectional zigzag" scanning processing path;

[0043] Figure 4 This is a schematic diagram of the processing results using a dual-wavelength beam.

[0044] Figure 5 Diagram of a laser cutting device for SiC ingots;

[0045] Figure 6a A photograph of the upper surface of the SiC sample after laser slicing and peeling;

[0046] Figure 6b This is a photograph of the lower surface of the SiC sample after laser slicing and peeling.

[0047] The attached diagram lists the components represented by each number as follows:

[0048] SiC ingot 100, setting position 101, upper surface of SiC material 102, modified part 103, crack 104, modified laser 105, heating laser 106, laser source module 200, beam splitting module 300, frequency conversion module 400, dual beam synchronous processing system 500, beam combining module 600, coaxial synchronous processing module 700, beam focusing module 800, motion module 900. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] This invention provides a method and apparatus for high-efficiency laser cutting of silicon carbide ingots. The laser cutting method employs a dual-wavelength laser coaxial synchronous single-pass processing mode. Under single-source conditions, dual-wavelength laser output is achieved through frequency conversion technology. Simultaneously, a coaxial synchronization system enables simultaneous spatial and temporal interaction between the modification laser and the heating laser with the SiC ingot. Compared to the traditional two-stage processing mode of modification followed by heating, the single-pass processing mode significantly reduces processing time. Furthermore, the dual-wavelength coaxial synchronous processing avoids the problem of reduced heating laser energy utilization due to material cooling caused by excessively long processing intervals in the two-stage processing mode. During crack formation, thermal stress is applied by the incident heating laser to control the crack propagation mode, improving the crack connection effect between adjacent modified sections, reducing wafer peeling difficulty, and improving peeling quality. Moreover, the good crack connection effect allows for increasing the laser scanning spacing, further improving processing efficiency.

[0051] A method for high-efficiency laser cutting of silicon carbide ingots includes the following steps:

[0052] The pulsed laser emitted by the laser source is split into two beams according to a set ratio. The first beam is used as the quality modification laser, and the second beam is used as the heating laser after frequency conversion.

[0053] A phase delay and combination technique is used to combine the modifying laser and the heating laser to achieve coaxial and synchronous processing of SiC ingots. The modifying laser is focused inside the SiC ingot at a set depth to perform the modification process, and finally forms a modified part and a crack zone near the focal point of the modifying laser. The heating laser is focused at the same depth as the modifying laser and applies thermal stress inside the SiC ingot by heating to control crack propagation.

[0054] The relative movement of the SiC ingot and the laser pulse is controlled, and scanning processing is performed according to the set path to form a modified layer and a crack bonding layer at a set depth.

[0055] Using the modified layer and the crack-connecting layer as the interface, a portion of the SiC ingot is peeled off to obtain a wafer.

[0056] Furthermore, the pulsed laser energy of the modified laser is such that it reaches the damage threshold of the SiC ingot, causing internal modification of the SiC ingot. The pulse width of the modified laser is 100 fs to 100 ns, and the single pulse energy is 10 to 100 μJ.

[0057] Furthermore, the second laser beam is phase-matched using a nonlinear crystal to achieve frequency doubling and obtain a heating laser. The wavelength of the heating laser is a wavelength with a high absorption rate for single-crystal silicon carbide, and the wavelength of the heating laser is preferably 532nm.

[0058] Furthermore, a phase delay and merging technique is applied to the modified laser and the heating laser to achieve coaxial and synchronous processing of SiC ingots by the modified laser and the heating laser, specifically as follows:

[0059] First, achieve synchronization between the modification laser and the heating laser:

[0060] The modified laser is reflected by multiple mirrors, and the position of the mirrors in the delay line is adjusted to change the transmission optical path of the modified laser, ultimately achieving synchronous processing with the heating laser.

[0061] Then, the coaxiality of the modified laser and the heating laser was achieved:

[0062] The modified laser, synchronized with the heating laser, is combined with the heating laser using a dichroic mirror to achieve coaxial processing of the modified laser and the heating laser.

[0063] Furthermore, the set depth is 100–700 μm below the upper surface of the SiC ingot.

[0064] Furthermore, the modified layer is composed of multiple modified parts, and the crack-connecting layer is formed by the interconnection of the crack regions near each modified part.

[0065] Furthermore, by controlling the relative movement of the SiC ingot and the laser pulse, the scanning path is made into a Z-shaped path, in which the distance between adjacent modified parts on the Y-axis is 10-60 μm and the distance between adjacent scanning parts on the X-axis is 10-400 μm.

[0066] Furthermore, SiC wafers can be peeled off by applying external tension, torque, or ultrasonic vibration.

[0067] A high-efficiency laser cutting device for silicon carbide ingots includes a laser source module, a beam splitting module, a frequency conversion module, a coaxial synchronization processing module, and a motion module, wherein:

[0068] The laser source module is used to generate pulsed laser;

[0069] The beam splitting module is used to split the pulsed laser into two laser beams, wherein the first laser beam is used as the quality-modifying laser, and the second laser beam is fed into the frequency conversion module.

[0070] The frequency conversion module is used to convert the frequency of the second laser beam through nonlinear optical effects to obtain a heating laser.

[0071] The coaxial synchronous processing module is used to achieve synchronization and coaxiality between the modification laser and the heating laser, resulting in a combined laser beam, which is then used to perform simultaneous spatial processing on the SiC ingot.

[0072] The motion module is used to control the relative motion between the combined laser beam and the SiC ingot, so that the combined laser beam can complete the scanning and processing of the ingot at a set depth and along a set path.

[0073] Furthermore, the coaxial synchronization processing module includes a dual-beam synchronization processing system and a beam combining module. The dual-beam synchronization processing system includes multiple reflectors. The dual-beam synchronization processing system is used to adjust the position of the reflectors in the delay line, change the transmission optical path of the modified laser, and achieve synchronous processing with the heating laser. The beam combining module is used to combine the modified laser, which is synchronized with the heating laser, with the heating laser.

[0074] Example 1:

[0075] Please see Figure 1-4 As shown, to facilitate understanding of the high-efficiency laser cutting method for SiC ingots provided in this embodiment of the invention, the application scenario of the laser cutting method provided in this embodiment of the invention is first described below. This laser cutting method is applied in the process of peeling SiC ingots to obtain SiC wafers. The following description, in conjunction with the attached... Figure 1-4 The method for achieving high-efficiency laser cutting of SiC ingots is described in detail.

[0076] In the embodiments described below, the relevant parameters of the experiment are as follows:

[0077] Modification laser wavelength: 1064nm;

[0078] Modified laser pulse width: 200ps;

[0079] Modified laser repetition frequency: 10kHz;

[0080] Heating laser wavelength: 532nm;

[0081] Heating laser pulse width: 200ps;

[0082] Heating laser repetition frequency: 10kHz;

[0083] Single pulse energy: 10 μJ;

[0084] Beam focusing module: 50×, NA=0.65 objective lens;

[0085] Y-axis scanning interval: 50μm;

[0086] X-axis scanning interval: 200μm.

[0087] A method for achieving high-efficiency laser cutting of silicon carbide ingots includes:

[0088] Provide and fix the SiC ingot to be sliced;

[0089] The pulsed laser emitted by the laser source is split into two beams. One beam is used as a modifying laser and is directly focused inside the ingot to set a depth for modifying. The other beam is frequency-converted and used as a heating laser to apply thermal stress inside the ingot to control crack propagation.

[0090] The modification laser and heating laser are synchronously processed by a coaxial synchronous processing system to achieve simultaneous modification and heating of the SiC ingot. The modification laser is focused on a predetermined depth layer inside the ingot. After the modification laser is applied, a series of processes such as energy absorption, energy transfer, phase transformation, deformation, and fragmentation occur inside the ingot, ultimately forming a modified part and a crack zone near the focal point of the modification laser. The heating laser is focused in the region near the predetermined depth layer. The heating laser is absorbed by the ingot and converted into heat energy, which then causes thermal expansion and generates thermal stress to affect crack propagation. The crack propagation and connection effect is better. Since the heating laser corresponds to the absorption band of the SiC ingot, the energy is absorbed more uniformly by the ingot, and there are no problems with modification or thermal damage.

[0091] Specifically, in this embodiment, ultrafast lasers are used to generate dual-wavelength pulsed lasers of infrared and green light through frequency conversion technology. Then, through phase delay and combining technology, the two wavelength laser pulses are coaxially and synchronously processed into SiC ingots.

[0092] Infrared pulsed laser light is focused onto a predetermined depth layer inside a silicon carbide ingot. At the laser focal point within this layer, laser-modified points, modified regions, and crack zones are formed from the inside out. The modified points are similar in size to the laser spot, while the modified regions primarily consist of amorphous C and amorphous Si. This is mainly due to the ultrafast non-thermal melting process induced by the ultrafast laser pulse acting on the material. Bound charge carriers in the silicon carbide break free from their covalent bonds and are excited into free electrons. The electron clouds forming covalent bonds in the C and Si atoms no longer overlap, and the covalent bonds are broken. The crack zone is mainly caused by the deformation of the material after laser action, generating internal stress waves. Under the influence of these stress waves, cracks form in the material.

[0093] When a green pulsed laser is focused at a predetermined depth along the same axis as an infrared pulsed laser on SiC, the material absorbs the laser energy, creating internal thermal stress. Simultaneously, cracks in the SiC are generated and further propagated under this thermal stress.

[0094] The dual-wavelength pulsed laser is controlled to scan at a set depth layer to form a modified layer and a crack propagation zone layer at that depth. The modified layer consists of multiple modified parts, and the crack propagation zone layer is composed of interconnected crack regions formed point by point.

[0095] like Figure 1 , Figure 4 As shown, at the designated position 101 of the SiC ingot 100, the modifying laser and the heating laser are combined into a combined laser beam to process the SiC ingot 100. The combined laser beam enters from the upper end face 102 of the SiC material and reaches the designated position 101. After processing by the modifying laser 105, a modified part 103 and a crack 104 are formed. Under the combined action of the heating laser 106, the crack 104 continues to expand and connect, forming a crack propagation zone.

[0096] By controlling a three-axis motion platform, the relative movement between the SiC ingot and the laser pulse is achieved, enabling the dual-wavelength laser pulse to scan and process along a specified path at a set depth, thereby forming a modified layer and a crack-connecting layer at the set depth. The modified layer is composed of multiple modified portions, and the crack-connecting layer is formed by the interconnection of crack regions near each modified portion.

[0097] Using the modified layer and the crack-connecting layer as an interface, a portion of the SiC ingot is peeled off to obtain a wafer.

[0098] The wavelength of the modifying laser is a wavelength with high transmittance to single-crystal silicon carbide, and the pulse width of the modifying laser is 200 ps, ​​the single pulse energy is 10 μJ, and the pulse laser energy should reach the damage threshold to cause internal modification of the silicon carbide ingot material. A pulse width and pulse energy that can achieve the same effect are also acceptable.

[0099] The wavelength of the heating laser is a wavelength with a high absorption rate for single-crystal silicon carbide.

[0100] The set depth is 100-700 μm below the upper surface of the SiC ingot.

[0101] The three-axis motion platform is controlled to achieve a zigzag scanning path. The speed of the motion platform is controlled to achieve a spacing of 50 μm between adjacent modified parts on the Y-axis and a spacing of 200 μm between adjacent scans on the X-axis. Scanning paths and spacing that achieve similar effects are also acceptable.

[0102] In summary, the SiC wafer peeling method provided in this embodiment employs two pulsed laser wavelengths that interact with SiC simultaneously. Compared to traditional laser ingot cutting methods, this saves time on secondary laser processing and improves processing efficiency. Furthermore, compared to the traditional method of modifying the material before heating to promote crack propagation, this method allows for simultaneous crack propagation during crack initiation, resulting in better crack propagation and connection.

[0103] Example 2:

[0104] This embodiment provides a high-efficiency laser cutting apparatus for silicon carbide ingots. The apparatus includes a laser source, a modification laser system, a heating laser system, a phase delay and beam combining system, a motion platform, and a stripping system. The laser source generates an ultrafast laser with a specific pulse width. The modification laser system provides infrared modification pulse lasers and focuses the laser beam at a predetermined depth on the SiC ingot, creating a modified portion and a crack region at that depth. The heating laser system generates a green pulse heating laser beam and focuses it at a predetermined depth on the SiC ingot, further expanding and connecting the crack region. The phase delay and beam combining system enables the modification and heating pulses to process the ingot material coaxially and synchronously. The motion platform can precisely move the ingot material in three dimensions, achieving a scanning effect of the laser beam focus at the predetermined depth, forming the modification layer and the crack propagation layer. The stripping system uses the cracked modification layer as an interface to strip specific portions of the silicon carbide ingot material to produce wafers.

[0105] Compared to traditional SiC ingot laser lift-off wafer devices, this solution uses only a single laser source and achieves dual-wavelength pulse generation through frequency conversion technology, significantly reducing device costs. Furthermore, this device achieves precise synchronous processing of SiC ingots using delay lines, and achieves coaxial focusing processing of dual-wavelength pulses through beam combining. Compared to traditional two-stage processing devices, it results in better crack propagation and connection, requires less tensile force for lift-off, produces more uniform wafer morphology, and achieves better lift-off quality. Simultaneously, the scanning line spacing can be set larger, further shortening processing time and improving processing efficiency.

[0106] A high-efficiency laser cutting device for silicon carbide ingots, reference Figure 5 The device comprises five parts: a laser source module 200, a frequency conversion module 400, a coaxial synchronization processing module 700, a motion module 900, and a stripping module.

[0107] The laser source module 200 generates the fundamental frequency light for the modification laser 105 and the heating laser 106; the frequency conversion module 400 generates the 532nm heating laser 106 through frequency doubling; the coaxial synchronous processing module 700 enables the simultaneous spatial processing of the SiC ingot 100 by the modification laser 105 and the heating laser 106; the motion module 900 has X, Y, and Z-axis three-axis coordinated adjustment functions to control the relative motion between the laser beam and the SiC ingot material 100, realizing the laser scanning processing of the ingot 100. The following is a detailed description of each step in conjunction with the accompanying drawings.

[0108] Usage process:

[0109] The first step involves providing a SiC ingot 100 to be processed and fixing it onto the surface of the motion module 900. In this embodiment, it is fixed by suction cup adsorption, but other methods that achieve the same adsorption effect can also be used.

[0110] The second step is to obtain the modified laser 105 and the heating laser 106. The laser source 200 emits a 1064nm pulsed laser with a pulse width of 200ps. Other pulse widths that meet the requirements are also acceptable. After passing through the beam splitting module 300, the beam is split into two beams in a 1:1 ratio. Other beam splitting ratios that meet the requirements are also acceptable.

[0111] Beam 1 is converted into a 532nm wavelength heating laser 106 by the frequency conversion module 400, and beam 2 is a 1064nm refining laser 105. In this embodiment, the pulse energy is set to 10μJ, but other pulse energies that can cause internal refining cracks in the SiC ingot 100 can also be used.

[0112] The third step is to set the focusing depth 101 of the laser inside the SiC ingot 100. By controlling the Z-axis of the three-axis motion system 900, the relative distance between the beam focusing module 800 and the SiC ingot 100 is adjusted, thereby achieving focused modification of the laser at a specific depth inside the SiC ingot 100. In this embodiment, the focusing depth 101 of the laser inside the SiC ingot 100 is 400 μm. The focusing depth 101 is determined by the wafer thickness that the implementer ultimately wants to obtain; therefore, other focusing depths are also possible.

[0113] The fourth step involves adjusting the coaxial synchronization processing module 700 to achieve coaxial synchronous processing of the two beams. By adjusting the positions of the two reflectors in the delay line on the stepper motor, the transmission optical path of the modified laser 105 is changed, ultimately achieving synchronous processing with the heating laser 106. A dichroic mirror is an excellent beam splitter and combiner, capable of reflecting a laser of a specific wavelength 1 and transmitting a laser of a specific wavelength 2. In the described embodiment, the core component of the beam combining module 600 is a dichroic mirror. By adjusting the dichroic mirror and other reflectors in the optical path, the modified laser 105 and the heating laser 106 are combined, ultimately achieving coaxial processing of the two beams.

[0114] The fifth step is the scanning and processing of the SiC ingot by the dual-wavelength beam. By controlling the X and Y axes of the three-axis motion module 900, the SiC ingot 100 and the combined pulse laser move relative to each other in the XY plane. By setting the scanning path, the beam is processed at a specified depth 101 inside the ingot material 100, and finally a modified layer and crack bonding layer are formed at the specified depth layer 101.

[0115] In this embodiment, the set scanning path is as follows: Figure 2 and Figure 3 As shown, the distance between adjacent modified parts on the Y-axis is 50 μm, and the distance between adjacent scans on the X-axis is 200 μm. Scanning paths and distances that can achieve similar effects are also acceptable. Figure 2 The image shows a "unidirectional zigzag" scanning path. During the processing, the combined laser beam scans and processes the SiC material along this path at a certain repetition frequency. The laser beam expands upward and downward at both ends of the path in the Y-axis direction to ensure that the laser can process the SiC material at a uniform speed in the Y-axis processing section. While expanding upward and downward, the laser beam moves in the X-axis direction at a 200μm interval to form the next scanning path in the Y-axis direction. Figure 3 The image shows a "bidirectional zigzag" scanning path, which differs from a "unidirectional zigzag" scanning path. When the laser scans along this path, it scans back and forth twice along the same scanning path in the Y-axis direction, and moves in the X-axis direction during upward expansion.

[0116] After the dual-wavelength beam scans inside SiC, the modified layer and crack-connecting layer significantly reduce the crystal bonding strength on both sides of the layer at the set depth. By applying external tension, torque, ultrasonic vibration, etc., the SiC wafer can be peeled off, and the peeling effect is significantly improved. The final processing result is shown in Figure 6. Figure 6a This is a photograph of the upper surface of the SiC sample after laser slicing and peeling. Figure 6b This is a photograph of the lower surface of the SiC sample after laser slicing and peeling.

[0117] The picosecond laser generated by the laser source 200 is split into two paths after passing through the beam splitting module 300. One path is used as the modification laser 105 to directly process the SiC ingot 100 after passing through the objective lens. The other path is used as the heating laser 106 to expand the modification crack after passing through the frequency conversion module 400.

[0118] For the modified laser 105, after passing through the beam focusing module 800, the modified laser 105 passes through the upper surface 102 of the ingot and is focused at a predetermined position 101 inside SiC. Due to the extremely high peak power of the modified laser 105, nonlinear processes such as multiphoton absorption, tunneling ionization, and avalanche ionization occur in the region near the laser beam waist, exciting the electronic system of SiC. After the electronic system is excited, some electrons continuously transfer their energy to the lattice through electron-phonon coupling, and the temperature of the lattice continuously increases. Eventually, the electron-lattice system reaches equilibrium, and the lattice system undergoes thermal phase transition processes such as melting and vaporization after reaching a certain temperature. In addition, some electrons in the electronic system escape, causing non-thermal phase transition processes such as Coulomb explosion and electrostatic ablation in SiC. After the phase transition, a modified part 103 is finally formed. Due to the phase transition process, a gradient distribution of tensile stress exists inside the material, forming a stress wave. After reaching a certain damage threshold, a crack 104 is formed near the modified part. In this embodiment, a 50× objective lens with a numerical aperture of 0.65 is used as the beam focusing module 800 shaping and refining laser 105. The laser has a long focal depth, and only a very small area near the beam waist reaches the SiC refining threshold. The remaining areas cannot be refining due to the low laser energy. Ultimately, this results in a small amount of grinding and polishing after the wafer is peeled off, reducing material waste and increasing the number of wafer slices.

[0119] For laser frequency conversion technology, the fundamental frequency light emitted by the laser source 200 passes through a nonlinear crystal (taking LBO and KTP crystals as examples, but not limited to LBO and KTP crystals) and, after satisfying the phase matching condition, achieves frequency doubling to obtain a 532nm heating laser. For laser frequency conversion technology, the fundamental frequency light emitted by the laser source 200 passes through the frequency conversion module 400. Under certain phase matching conditions, various frequency conversions can be achieved. In this embodiment, the 532nm heating laser is obtained through the frequency conversion module 400. Because SiC material has a high absorption rate for 532nm laser, the heating laser 106 is absorbed and converted into heat energy. This low energy portion will not cause secondary modification of the SiC material or damage to the ingot surface caused by the heat-affected zone. Since this energy is injected into the SiC material when cracks are formed inside, the internal cracks are further extended under the thermal stress generated by the thermal expansion of the material. This results in better crack connection near different modified parts, which is beneficial for reducing the final peeling difficulty and improving the peeling morphology quality.

[0120] For the dual-beam synchronous processing system 500, since the two beams travel through different optical paths, they cannot be simultaneously incident on the upper surface 102 of the SiC material. By designing a dual-beam synchronous system composed of delay lines and adjusting a certain beam propagation distance, three processing modes can be realized respectively: pre-modification laser-post-heating laser, pre-heating laser-post-modification laser, and modification laser-heating laser synchronous processing. After comparison, the modification laser-heating laser synchronous mode injects energy into silicon carbide during the formation of phase transformation cracks in the material, so that the crack propagation effect is optimal.

[0121] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0122] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of high efficiency laser cutting of silicon carbide ingot, characterized by, The method comprises the following steps: The pulsed laser emitted by the laser source is split into two beams according to a set ratio, the first beam is used as a modification laser, and the second beam is used as a heating laser after frequency conversion; The modification laser and the heating laser are phase delayed and combined to realize coaxial and synchronous processing of the SiC crystal ingot by the modification laser and the heating laser; wherein the modification laser is focused at a set depth inside the SiC crystal ingot for modification processing, and finally a modification part and a crack zone are formed near the focal point of the modification laser; the heating laser is focused at the same depth as the modification laser to apply thermal stress in a heating manner inside the SiC crystal ingot to control crack propagation; The relative movement of the SiC crystal ingot and the laser pulse is controlled to scan and process according to a set path to form a modification layer and a crack connection layer at a set depth; A part of the SiC crystal ingot is peeled off to obtain a wafer by taking the modification layer and the crack connection layer as an interface; The pulsed laser energy of the modification laser reaches the damage threshold of the SiC crystal ingot, so that modification occurs inside the SiC crystal ingot, the pulse width of the modification laser is 100 fs-100 ns, and the single pulse energy is 10-100 muJ; The second beam of laser is phase matched through a nonlinear crystal to realize frequency doubling to obtain the heating laser, and the wavelength of the heating laser is a wavelength with high absorption rate for single crystal silicon carbide; The modification laser and the heating laser are phase delayed and combined to realize coaxial and synchronous processing of the SiC crystal ingot by the modification laser and the heating laser, specifically: Firstly, the synchronization of the modification laser and the heating laser is realized: The delay line is composed of a mirror and a high-precision stepping motor, the position of the mirror in the delay line is adjusted, the transmission optical path of the modification laser is changed, and finally the synchronous processing with the heating laser is realized; Then, the coaxiality of the modification laser and the heating laser is realized: The modification laser synchronized with the heating laser is combined with the heating laser through a dichroic mirror to realize coaxial processing of the modification laser and the heating laser.

2. The method of high efficiency laser cutting of silicon carbide ingot according to claim 1, wherein, The wavelength of the heating laser is 532 nm.

3. The method of high efficiency laser cutting of silicon carbide ingot as claimed in claim 1, wherein, The set depth is 100-700 mu m below the upper end surface of the SiC crystal ingot.

4. The method of high efficiency laser cutting of silicon carbide ingot according to claim 1, wherein, The modification layer is composed of a plurality of modification parts, and the crack connection layer is formed by the crack zones near each modification part.

5. The method of high efficiency laser cutting of silicon carbide ingot as claimed in claim 1, wherein, The relative movement of the SiC crystal ingot and the laser pulse is controlled to realize a scanning path in the shape of a Chinese character, and the distance between adjacent modification parts in the Y-axis of the Chinese character-shaped path is 10-60 mu m, and the distance between adjacent scanning in the X-axis is 10-400 mu m.

6. The method of high efficiency laser cutting of silicon carbide ingot as claimed in claim 1, wherein, The peeling of the SiC wafer is realized by applying external tension, torsion and ultrasonic vibration.

7. The method for high-efficiency laser cutting of a silicon carbide crystal ingot according to claim 1 uses a device for high-efficiency laser cutting of a silicon carbide crystal ingot, which comprises a laser source module, a beam splitting module, a frequency conversion module, a coaxial synchronous processing module and a motion module, wherein: The laser source module is used to generate pulsed laser; The beam splitting module is used to split the pulsed laser into two beams, of which the first beam is used as a modification laser, and the second beam is input into the frequency conversion module; The frequency conversion module is used to convert the second beam of laser through nonlinear optical effect to obtain a heating laser; The coaxial synchronous processing module is used for realizing synchronization and coaxiality of the modification laser and the heating laser, obtaining a combined laser, and simultaneously and spatially processing the SiC crystal ingot by using the combined laser; The motion module is used for controlling relative motion of the combined laser and the SiC crystal ingot, and realizing scanning processing of the combined laser on the crystal ingot according to a set path at a set depth.

8. The method of high efficiency laser cutting of silicon carbide ingot as claimed in claim 7, wherein, The coaxial synchronous processing module comprises a double-beam synchronous processing system and a combined module, the double-beam synchronous processing system comprises a plurality of reflecting mirrors, wherein the double-beam synchronous processing system is used for adjusting positions of the reflecting mirrors in a delay line, changing a transmission optical path of the modification laser, and realizing synchronous processing with the heating laser; and the combined module is used for combining the modification laser synchronized with the heating laser and the heating laser.

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