Method for cleaving semiconductor elements and method for manufacturing

Abstract

The application belongs to the technical field of semiconductor optoelectronic device process, and relates to a cleaving method and a manufacturing method of a semiconductor element. The cleaving process of the semiconductor element comprises a laser hidden cutting scribe line stage and a cavity surface cleaving stage; a picosecond pulse laser hidden cutting technology is used to focus laser spots to different height positions away from a semiconductor surface in a substrate thickness direction, to form a plurality of preset cutting metamorphic points, similar preset cutting metamorphic points are interconnected through crack traces, a hidden cutting mode in the substrate thickness direction is repeated in a parallel cavity surface direction, and finally an ideal cleaving separation groove is obtained in the semiconductor substrate. Compared with a laser surface cutting and a traditional diamond mechanical cleaving scheme, the cleaving method of the semiconductor element of the application can accurately form a cleaving separation groove in the substrate crystal by using a picosecond pulse laser, avoid pollution of the cavity surface by cutting debris in the process of laser surface opening and diamond cleaving, reduce the failure probability of the cavity surface COD, and prolong the service life.

Description

Technical Field

[0001] This invention relates to a cleavage method and manufacturing method for semiconductor elements, belonging to the field of semiconductor optoelectronic device technology. Background Technology

[0002] Gallium nitride (GaN) lasers are the optimal choice for blue and green light sources in laser display's three primary colors, possessing significant application value and broad market prospects in laser lighting and display, optical information storage, quantum technology, underwater communication, metal welding, and laser additive manufacturing. Existing high-power GaN lasers mostly employ an active region emission mode with edge emission, utilizing the natural cleavage surface of the semiconductor crystal as a reflecting surface to form a FP resonant cavity, where self-excited oscillation occurs, thus achieving light emission from the cavity's end face. Therefore, the quality of the cleaved GaN cavity surface directly affects the device's threshold current, output power, operational stability, and lifetime.

[0003] In the fabrication of GaN-based laser chips, the formation of smooth and parallel reflective surfaces is crucial. Therefore, cavity cleavage is a vital process technique, typically employing classic diamond scribing and cutting methods to create separation grooves followed by pressure cutting. However, experience shows that the cleavage results on c-plane GaN substrates still exhibit crystallographic defects. These defects can act as initiation points for wafer breakage and can cause the extended cleavage planes to deviate from their ideal planar shape; for example, small-area, high-density steps can easily appear on the cavity surface. Furthermore, GaN-based laser epitaxial structures often contain AlGaN layers, which are under high tensile stress when coherently grown on c-plane GaN substrates. Consequently, severe wafer bending and cracks frequently appear in the epitaxial layers, hindering precise dicing.

[0004] In recent years, with the development of laser cutting technology, a technique using laser irradiation to form separation grooves has been proposed to replace diamond scribing and cutting methods. However, in the scheme of melting the wafer by irradiating the surface with a high-energy laser, the generation of GaN debris and the spatter during the subsequent cleaving process can contaminate the laser's natural cleavage cavity surface, leading to catastrophic optical damage (COD) and ultimately device failure. Furthermore, material deformation occurs in the secondary solidification region of the surface, and the increased defects reduce the device's luminous brightness. To address this, short-pulse laser processing has been proposed, but this technique cannot completely avoid the performance degradation caused by cavity contamination and defects. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned technical challenges and meet the needs of industrial production by innovatively developing an optimal fabrication method for laser components. This method utilizes a novel laser slicing technique to repeatedly focus high-energy picosecond pulsed lasers onto the interior of GaN and other substrates (avoiding the high-stress regions of epitaxial structures). This creates specific alteration points and cracks at designated locations, with the cracks linking adjacent alteration points. Under the premise that laser-induced damage does not affect the electro-optical performance of the device, ideal cleavage separation grooves are obtained within the GaN and other substrates. Combined with mechanical cleaving, this ultimately achieves efficient fabrication of the laser's reflective cavity surface, improving cleavage quality and success rate, further enhancing the laser's stability, reliability, and operational lifespan, and providing technical support for its industrialization feasibility.

[0006] The technical solution adopted in this invention is as follows:

[0007] A cleaving method for a semiconductor device includes a laser scribe stage and a cavity surface cleaving stage;

[0008] The laser hidden cutting and scribing stage includes: using picosecond pulsed laser hidden cutting technology, focusing the laser spot to different height positions from the semiconductor surface in the thickness direction of the semiconductor substrate to form multiple preset cutting and alteration points, and connecting the preset cutting and alteration points with similar points through cracks; repeating the hidden cutting mode in the thickness direction of the substrate in the direction parallel to the cavity surface, and finally obtaining a cleavage separation groove inside the semiconductor substrate;

[0009] The cavity surface cleavage stage includes: splitting the semiconductor substrate along the cleavage separation groove with the assistance of mechanical splitting force to complete the cavity surface cleavage.

[0010] Furthermore, the wavelength of the picosecond pulsed laser is 1064nm for P-plane cutting or 532nm or 355nm for N-plane cutting.

[0011] Furthermore, the distance between the preset cutting modification point closest to the P-type semiconductor surface in the substrate thickness direction and the P-type semiconductor surface is not less than 20 μm.

[0012] Furthermore, the hidden cutting mode in the parallel cavity surface direction is either a periodic skip hidden cutting mode for cutting the P-face or a continuous hidden cutting mode for cutting the N-face.

[0013] Furthermore, the periodic skip hidden cutting mode for P-plane cutting generates a first cleavage line in the direction parallel to the cavity surface and a second cleavage line in the direction of substrate thickness.

[0014] A method for manufacturing a gallium nitride-based semiconductor device includes the following steps:

[0015] 1) The ridge structure and P-side electrode of the GaN-based laser were fabricated on a GaN epitaxial wafer by photolithography, etching and coating processes to obtain the sample;

[0016] 2) Spin-coat a photolithographic protective film on the P-side of the sample, fix the wafer onto a ceramic or sapphire tray using a waxing device, and perform mechanical thinning, rough grinding, fine grinding and polishing steps on the back side of the GaN wafer to obtain a thinned GaN sample.

[0017] 3) After the thinned GaN sample was cleaned with N-methylpyrrolidone, ethanol and deionized water, the N-side GaN was subjected to ICP etching, N-electrode evaporation and electrode metal fusion steps.

[0018] 4) Using picosecond pulsed laser cleaving technology, the laser spot is focused at different heights from the P-type GaN surface in the substrate thickness direction to form no less than two preset cutting transformation points. The preset cutting transformation points that are close to each other are connected by cracks. The above-mentioned substrate thickness direction cleaving mode is repeated in the parallel cavity surface direction. Finally, an ideal cleaving separation groove is obtained inside the GaN substrate. Then, with the assistance of a cleaving machine, the substrate is cleaved along the cleaving separation groove to complete the cavity surface cleaving of the bar.

[0019] 5) The complete fabrication process of the GaN-based laser chip is completed by performing cavity surface coating, single-tube scratching, and testing and sorting steps on the cleaved bar strips.

[0020] Furthermore, the surface of the sample described in step 1) is covered with a SiO2 insulating layer except for the ridge structure region.

[0021] Furthermore, the thickness of the thinned GaN sample in step 2) is less than 150 μm.

[0022] Furthermore, the distance between the preset cutting and alteration point on the outermost edge of the corresponding ridge structure and the outermost edge of the corresponding ridge structure in the direction parallel to the cavity surface is not less than 10 μm.

[0023] The present invention also provides a gallium nitride-based semiconductor device manufactured according to the above method.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) This method uses picosecond pulse laser hidden cutting technology to overcome the difficulty of poor cutting accuracy caused by the deviation of the cavity surface cleavage line from the ideal preset trajectory due to crystal defects of GaN and other substrates in traditional diamond mechanical cleavage. It also solves the problem of the formation of harmful cracks in the high strain epitaxial layer in the cleavage guide groove region caused by mechanical pressure at the diamond tip. It often presents a high-density stepped structure distribution. The picosecond pulse laser hidden cutting technology route is conducive to obtaining high-quality reflective cavity surfaces, especially in the ridge light-emitting region.

[0026] (2) To address the problem of slight deviation between the cleavage cavity surface and the actual material crystal orientation in traditional cleavage processes, picosecond pulsed laser hidden cutting technology can correct the crystal orientation deviation. After pulsed laser processing, the cleavage dividing lines formed by the different Z values ​​in the Y direction are precisely located inside the cleavage guide groove structure. Then, the cleavage dividing lines with different Z values ​​are connected by cracks to form a cleavage separation groove, which enhances the cleavage guidance, improves the yield of cavity surface cleavage, and extends the device's working life.

[0027] (3) Compared with laser surface cutting and traditional diamond mechanical cleaving, this method uses picosecond pulsed laser to precisely form cleavage separation grooves in the substrate crystal, avoiding contamination of the cavity surface by cutting debris during laser surface cutting and diamond cleaving, reducing the probability of COD failure of the cavity surface, and improving the working life.

[0028] (4) This method can stably achieve laser cavity surface cleavage and perform efficient single-chip cutting, saving manufacturing costs and improving production efficiency. Attached Figure Description

[0029] Figure 1 This is a top-view plan view of the P-side illustrating the main steps of the implementation method.

[0030] Figure 2 yes Figure 1 AA line profile diagram.

[0031] Figure 3 This is a top-view schematic diagram from the N side illustrating the main steps of the implementation method.

[0032] Figure 4 yes Figure 3 BB line profile diagram.

[0033] Figure 5 The morphology of the cleavage cavity surface and the LIV characteristic curves of the method of the present invention, as well as the corresponding reference embodiment results, are shown.

[0034] Figure 6 This is a schematic diagram illustrating the main principle of the modified implementation method.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1- Ridge structure; 2- Cleavage-guided structure (Y direction); 3- Modified point (located inside the GaN substrate, with its highest point at a distance h ≥ 20 μm from the P-plane gallium nitride surface); 4- Single-tube cleavage groove (X direction); 5- P-plane electrode; 6- Preset cleavage line (located in region 2); 7- Mesa structure; 8- P-plane insulating layer; 9- Crack; 10- Region inside the GaN substrate interacting with the pulsed laser, F is the laser focus; 11- N-plane electrode; 12- m-plane cleavage crystal orientation of GaN; θ- Angle between cleavage crystal orientation 12 and preset cleavage line 6; l- Lateral period; L- Bar length; a and b are respectively Z min The deterioration points at both ends of the value. Detailed Implementation

[0037] The cleavage and manufacturing methods for semiconductor devices of the present invention are applicable not only to GaN crystal materials but also to other crystal materials. The specific implementation of the method of the present invention will be described below primarily using GaN as an example.

[0038] The semiconductor device manufacturing method of this invention specifically includes processes such as picosecond pulsed laser cleaving and mechanically assisted cavity surface cleaving. First, a high-energy picosecond pulsed laser is repeatedly focused onto the interior of a GaN substrate using laser cleaving technology, forming specific altered points and cracks in designated areas. These cracks connect adjacent altered points, creating ideal cleavage separation grooves within the GaN substrate, thus completing the cleaving process. This is then combined with subsequent mechanically assisted cavity surface cleaving to obtain the reflecting cavity surface of the GaN laser. Furthermore, this method effectively suppresses errors in the cleavage cavity surface and cleavage crystal orientation during the manufacturing process, improving the cleavage yield. To further illustrate the technical means and effects employed by this invention to achieve its intended purpose, the embodiments of the method are described in detail below with reference to the accompanying drawings. This invention is not limited to the following embodiments and examples; various modifications can be made without departing from the main technical concept of this invention.

[0039] Figure 1 This is a top plan view of the P-side, which is a key step in the manufacturing method of the semiconductor element according to this embodiment. Figure 2 yes Figure 1 AA line profile diagram.

[0040] First, the picosecond pulse hidden cleaving system aligns the wafer to be processed with the P-plane facing upwards. Then, it focuses the laser beam inside the GaN substrate within the cleavage guide structure 2 region along the Y-direction. The specific position of the laser focus F is as follows: Figure 2As shown, the following conditions should be met: In the Z direction, the distance h from the highest point of the laser focus to the surface of the P-plane GaN should be ≥20μm, preferably h=30μm; the distance from the lowest point of the laser focus to the bottom surface of the N-plane GaN should be greater than 5μm, preferably 10μm-15μm; In the Y direction, the distance d from the outermost point in the cleavage guiding structure 2 region to the ridge edge should be ≥10μm, preferably d=20μm; Ensure that the coverage area of ​​the metamorphic point 3 and the corresponding crack 9 does not extend to the emitting area of ​​the laser, and is confined to the laser action area 10.

[0041] In the Y and Z processing directions, the distance between adjacent metamorphic points 3 is greater than the diameter of the laser focus. The metamorphic points 3 are connected to each other through cracks 9. However, the generated cracks do not occur in the specified direction. Cracks that extend to other directions may occur. High-precision cleavage cavity surfaces can be achieved by at least making the cracks that connect adjacent metamorphic points occur.

[0042] Along the Y-direction, a predetermined cleavage line 6 is formed on a surface with the same Z value. Under the above conditions, the laser focus F is focused into the GaN substrate, and continuous dot cutting is performed. Multiple adjacent metamorphic points 3 are formed along the predetermined cleavage line 6 and are interconnected by cracks 9. Their extension range is limited to the laser action area 10.

[0043] In the Y direction, the cleavage line formed by the adjacent metamorphic point 3 and the crack 9 is the first cleavage line, and the crack is the first crack.

[0044] Along the Z direction, at the same Y value, considering the damage range of the laser effect, the laser focus F is focused on different Z value heights in the GaN substrate, and continuous dot cutting is performed. Multiple adjacent altered points 3 are formed along the same Y value and are interconnected through cracks 9. Their expansion range is limited to the laser effect area 10.

[0045] In the Z direction, the cleavage line formed by adjacent metamorphic points 3 and cracks 9 is the second cleavage line, and the crack is the second crack. The first and second cleavage lines and their corresponding first and second cracks constitute the actual cleavage action region. For processing periodic chip structures with laser beams incident on the P-plane, the laser action region is not continuous. The damage caused by laser irradiation in the ridge region 1 must be considered. Even without energy focusing, it will affect performance. Therefore, laser slicing is required on the P-plane to achieve a skip-cutting mode, avoiding the ridge luminous region.

[0046] Within the laser-acting region 10, the formation order of the preset metamorphic points 3 can be arbitrarily arranged. Preferably, the first cleavage line and the first crack are formed first along the Y direction in the same Z-value contour plane. More preferably, the first cleavage line and the first crack are formed first along the Y direction in the plane with the smallest Z-value contour plane. Even more preferably, the first cleavage line is formed unidirectionally from the edge to the center, i.e., from a to b or from b to a. Figure 2 As shown in the figure, a second cleavage line and a second crack are then formed.

[0047] At the laser beam focusing point, a metamorphic point forms, further generating compressive stress in its vicinity, leading to the formation of cracks. The expansion and connection range of these cracks are linearly related to the laser energy and also to the distance between adjacent metamorphic points; that is, the higher the energy, the wider the crack range. However, if the distance between adjacent metamorphic points is too large, exceeding the crack range, the adjacent metamorphic points cannot connect smoothly. It is important to note that there is a maximum processing energy value for the laser. Exceeding this limit will cause rapid decomposition of the action point region inside the GaN substrate, resulting in the rapid expansion and cracking of the generated N2, causing permanent damage to the device. If the distance between adjacent metamorphic points is too small, the compressive stress generated at the previous laser beam focusing point and the compressive stress generated by the subsequent laser beam irradiation will cancel each other out in the overlapping area, reducing the range of compressive stress and preventing adjacent metamorphic points from connecting smoothly through cracks. A preferred metamorphic point distance is 5μm-10μm, and more preferably 8μm. Furthermore, the laser energy varies on surfaces with different Z values, the purpose of which is also to control compressive stress and cutting damage, ultimately achieving ideal cavity surface cleavage. Preferably, the energy is at the minimum Z value, i.e., Z... min At this point, the maximum laser energy is used. As the Z value increases (the laser point of action is close to the luminous region of the P-surface), the laser energy gradually decreases to ensure that the distance h between the action area and the P-surface is ≥ 20 μm. Where Z... min The high energy at the beginning and end ensures sufficient compressive stress and longer cracks connecting adjacent metamorphic points to generate cleavage lines. As Z increases, the energy gradually decreases, correspondingly reducing the spacing between metamorphic points to protect the luminescent area and achieve cavity surface cleavage. Further optimization involves a laser energy variation from high to low and then back to high as Z increases. This optimized scheme, while ensuring the luminescent area remains unaffected, allows for more precise control of compressive stress and reduces the number of metamorphic points, avoiding the mutual cancellation effect of compressive stress between preceding and following metamorphic points, thus improving cleavage efficiency. The high energy at the beginning and end ensures the direction of compressive stress transmission and reduces the number of metamorphic points, facilitating the natural cleavage process. The decrease in energy during the middle process allows for the interconnection of adjacent metamorphic points within a small range, ensuring material stability during high-energy cutting and maintaining the directionality of compressive stress transmission, efficiently generating cavity surface cleavage lines. Therefore, there are important optimal values ​​for laser beam irradiation energy, frequency, pulse width, and the location and sequence of metamorphic point generation, enabling precise formation of metamorphic points and cracks to achieve controllable cavity surface cleavage.

[0048] For GaN substrates, the wavelength of the cleaved pulsed laser needs to be smaller than the bandgap width of GaN, meaning the GaN substrate is transparent and has no absorption for the processing laser wavelength. This invention uses a 1064nm picosecond pulsed laser, but is not limited to this implementation method and example. The processing laser can be selected based on the optical bandgap characteristics of the cleaved material according to the above rules. Regarding the laser irradiation energy, specifically, the single pulse energy is in the range of 0.5μJ to 5μJ, preferably 0.6μJ-2μJ, more preferably 0.4μJ-1.6μJ. The frequency is 20kHz to 200kHz, preferably 50kHz to 100kHz. Regarding the pulse width, to prevent degradation absorption on non-focused surfaces during processing, the pulse width is continuously adjustable from 100-300ps. Regarding the spacing of the degradation points generated during processing, the processing laser generally generates degradation points at equal intervals within the laser action region 10 inside the GaN substrate along the preset cleavage line 6, ensuring that the degradation points are at least within the expansion range of the crack 9 it generates. Specifically, the preferred distance between the processed and altered points is 1-5 times the diameter of the processed and altered points, and more preferably the distance is 2-3 times.

[0049] Inside the GaN substrate, the volume of the laser-acting region 10 is larger than the actual area affected by laser cutting along the Y and Z directions, ensuring the non-destructive characteristics of the cleaved cavity surface. The fundamental principle of picosecond pulse hidden cavity surface technology is to generate metamorphic points within the substrate material through laser irradiation under the aforementioned laser processing constraints, within a laser-acting region that does not affect device emission along the substrate's crystal orientation. Simultaneously, the compressive stress around these metamorphic points induces cracks in the substrate. These cracks from adjacent metamorphic points interconnect, ultimately creating cleavage planes parallel to the cleavage crystal orientation within the substrate. With the assistance of mechanical cleaving, the laser cavity surface is cleaved, resulting in a smooth and flat cavity surface in the emission region. The extent of the cracks can be adjusted by the compressive stress, preferably at a location deeper inside the substrate away from the P-plane. Specifically, this can be controlled by parameters such as the wavelength, irradiation energy, frequency, pulse width, processing feed rate, and the location and sequence of metamorphic point generation.

[0050] The control of compressive stress can be achieved by processing the wavelength of the pulsed laser. The shorter the laser emission wavelength, the greater the energy absorbed by the processed material, the shallower its penetration depth into the substrate, and the closer the crack is to the incident surface of the laser processing. Considering the impact of absorption on the luminescence performance of the non-focused region, processing can be performed on the N-side, which is far from the luminescent active region. Figure 3 As shown. Short-wavelength lasers can reduce processing energy and decrease spatter in the processing area.

[0051] The control of compressive stress can also be achieved by adjusting the laser processing energy, frequency, and pulse width. With the processing laser frequency and pulse width constant, higher energy results in a larger damage range at the point of application. Energy has a maximum value for different materials, preventing rapid material decomposition and cracking. With a fixed energy and pulse width, a higher frequency results in a larger processing damage range; similarly, a larger pulse width increases the damage range. Both pulse frequency and pulse width have extreme values ​​and must be coordinated with laser energy to control the range of compressive stress, avoiding the overlap and cancellation of stress at two points of application, thus achieving rapid cleavage of the semiconductor laser cavity surface.

[0052] Precise control is required for the laser processing feed rate, the location and sequence of degradation points. A faster feed rate results in a shorter time spent at the processing point, leading to a smaller crack range and less damage, and vice versa. Stress tends to concentrate on the laser irradiation side, facilitating crack formation from the processing point to the substrate surface. Therefore, there is an optimal solution for the location and sequence of degradation point formation, which directly relates to the crack formation direction, i.e., the direction of compressive stress. By controlling the compressive stress introduced by laser irradiation, the direction and range of cracks within the GaN substrate can be adjusted, and external mechanical forces can be used to achieve perfect cavity cleavage in the GaN laser.

[0053] The cleavage surface can be obtained using either a periodic skip cleavage mode or a continuous cleavage mode, which can be selected based on the surface properties of the workpiece. If the cleavage laser is focused through the material's luminescent region, considering the damage to the material in the luminescent region caused by the unfocused beam, a periodic skip cleavage mode should be chosen to avoid the effective luminescent region. Figure 2 As shown. Conversely, if the hidden-cut laser is focused without passing through the material's luminescent region, then continuous hidden-cutting mode can be selected without considering laser irradiation damage to the material, such as... Figure 4 As shown. Specific processing details are described in the embodiments. This invention is not limited to specific implementation methods and embodiments, and various modifications can be made without departing from the main technical principles of this invention. Furthermore, it is not limited to GaN materials; the cleavage of other crystal materials is also applicable to this patent.

[0054] Example 1

[0055] A method for manufacturing a semiconductor device includes the following steps:

[0056] Step 1: The ridge structure and P-side electrode of the GaN-based laser are fabricated on the GaN epitaxial wafer through photolithography, etching and coating processes. The sample surface is covered with SiO2 insulating layer except for the ridge window structure area.

[0057] Step 2: Spin-coat the P-side of the sample with a photolithographic protective film, fix the wafer onto a ceramic tray using a waxing device, and perform mechanical thinning, rough grinding, fine grinding and polishing on the back side of the GaN wafer to finally obtain a GaN sample with a thickness of <150μm.

[0058] Step 3: After the wax-thinned sample is cleaned with N-methylpyrrolidone (NMP, 80℃), ethanol, and deionized water, the N-side GaN is subjected to ICP etching, N-electrode evaporation, and electrode metal fusion.

[0059] Step 4: The Φ2-inch wafer is initially cut into regular rectangles of specified length using laser cutting technology, followed by cavity surface cleaving. Picosecond pulsed laser cleaving technology is used to focus laser spots at different heights from the P-type GaN surface along the substrate thickness (Z) direction, forming preset cleaving points. The focal point closest to the P-type GaN surface should be greater than 20 μm. To ensure that the cleaving points and cracks (proportional to the laser energy, with a crack range of 5-20 μm) do not propagate to the light-emitting region of the device, especially the light-emitting quantum well region (about 0.5-1 μm from the P-type GaN surface), multiple gradient cleaving points are interconnected through the propagation of adjacent cracks. The above cleaving mode in the Z direction is repeated in the parallel cavity surface (Y) direction to finally obtain an ideal cleavage separation groove inside the GaN substrate. The Y direction can be either a periodic skip cleaving mode (avoiding the ridge light-emitting region) or a conventional continuous cleaving mode. The mode selection varies depending on the target. Subsequently, the cavity surface cleavage of the bar is completed with the assistance of a cleaving machine.

[0060] Step 5: Perform cavity surface coating, single-tube cleaving (forming single-tube cleaving groove 4), testing and sorting on the cleaved bar to complete the complete fabrication process of the GaN-based laser chip.

[0061] Example 2

[0062] A GaN wafer with an epitaxial laser structure and a thickness of 400±50μm is mechanically thinned and polished to obtain a GaN wafer with a thickness of 80μm-150μm. In this embodiment, the preferred thickness is 90μm, and the N-face electrode is fabricated, ensuring precise alignment with the P-face facing upwards in the laser slicing system. A picosecond pulsed laser is focused onto the laser action region 10 inside the GaN wafer through the surface of the cleavage guide structure 2. First, on a contour surface with a Z value of 15μm (Z=0 for N-type surfaces), a single pulse energy of 1.4μJ, a frequency of 50kHz, a laser energy of 50mW, and a cutting speed of 400mm / s are used. Starting at point b, altered points are generated unidirectionally along the Y-axis (AA is a preset cleavage line) at 8μm intervals, ending at point a. These altered points are connected by the first cracks to form the first cleavage line. Then, the Z values ​​are sequentially adjusted to 25.2μm, 30.6μm, and 49.5μm. The laser energies for the 57.6μm and 57.6μm lasers are set to 40mW, 40mW, 50mW, and 60mW, respectively, while other parameters remain constant. Starting from point b on each contour surface, altered points are generated along the Y-axis at 8μm intervals until point a. A first crack is generated in the Y-direction, connecting to form a first cleavage line, and a second crack is generated in the Z-direction, connecting to form a second cleavage line. Within the laser-acting region 10, a cleavage surface composed of the first and second cleavage lines is formed. By repeating the above processing steps on the periodically varying region 2, cleavage dividing lines for laser cavity surface cleavage are eventually periodically formed in the Y-axis direction inside the GaN wafer, as shown below. Figure 1 and Figure 2 As shown. With the assistance of a mechanical splitting force, a smooth and flat laser reflector cavity surface is obtained in the emitting region, as... Figure 5 As shown in Figure 5a, in comparison with mechanical cleavage cavity surfaces ( Figure 5 In section 5b), the laser-cut cavity surface has the same surface morphology in the non-laser processing area and the mechanically cleaved cavity surface. This is the most fundamental guarantee for similar electro-optical performance. Figure 5 As shown in Figures 5c and 5d, the processing area is precisely controlled within the GaN substrate and the pulsed laser interaction area 10, effectively controlling the cavity surface damage range and ensuring normal laser operation. This solves the problem of secondary contamination of the cavity surface by debris falling off during laser surface cutting and mechanical cleaving, avoids COD problems caused by cavity surface impurity absorption, and increases the device's lifespan and stability.

[0063] Comparative Example

[0064] A GaN wafer with an epitaxial laser structure and a thickness of 400±50μm was mechanically thinned and polished to obtain a GaN wafer with a thickness of 80μm-150μm. In this embodiment, the preferred thickness is 90μm. The N-face electrode was then fabricated, and the wafer was precisely aligned with the P-face facing upwards in a mechanical cleaving system. A diamond cleaving tool was used to scribing a 400μm line from the center of region 2 towards the wafer edge along the Y-direction. The scribing speed was 1000μm / s, the weight was 15g, the scribing depth was 50μm, and the angle was in the range of 40-60°. After a cleaving process with cleaving parameters of 1.2N cleaving tool load, 60μm / s cleaving speed, and 30μm indentation, a smooth cavity surface was obtained. The cavity surface morphology and electro-optic properties are as follows: Figure 5 As shown. Compared to the method of this invention, firstly, diamond scribing acts on the wafer surface, generating surface debris during processing and increasing the probability of surface-mount COD; secondly, diamond scribing needs to act on the wafer surface for a certain distance, inevitably damaging the ridge structure of the scribing area, leading to chip failure in the scribing area and increasing material costs; thirdly, diamond scribing cleavage is a process in which a cleavage initiation point is marked by external force against a specific crystal orientation parallel to the cleavage crystal, and the wafer naturally cleaves along the crystal orientation at the point of failure under the assistance of mechanical splitting force. If there are large defects or special processing structures in the crystal near the natural cleavage line, stacking faults will occur on the cleavage plane along the cleavage crystal orientation, resulting in a non-mirror cleavage plane and reducing device performance; fourthly, regarding the deviation between the scribing direction and the actual wafer crystal orientation, such as... Figure 6 As shown, the solution of this invention can be effectively corrected, improving the cavity surface quality and increasing the device yield.

[0065] Example 3

[0066] A GaN wafer with an epitaxial laser structure and a thickness of 400±50μm is mechanically thinned and polished to obtain a GaN wafer with a thickness of 80μm-150μm. In this embodiment, the preferred thickness is 90μm. The N-face patterned electrode is then fabricated, and the N-face is precisely aligned in the laser slicing system. A picosecond pulsed laser is focused through the back side of region 2 onto the 10-laser action area inside the GaN wafer. First, on a contour surface with a Z value of -50μm (Z=0 for N-type surfaces), a single pulse energy of 1.4μJ, a frequency of 50kHz, a laser energy of 50mW, and a cutting speed of 400mm / s are applied. The slicing proceeds unidirectionally along the Y-axis (BB preset cleavage line), starting from one edge of the wafer, generating altered particles at 5μm intervals, and ending at the opposite edge. The resulting first cracks connect to form the first cleavage line. Figure 3As shown; the Z value is adjusted in sequence to -30μm, -25μm, and -15μm, and the corresponding laser energies are set to 40mW, 40mW, and 60mW respectively. Other parameters remain unchanged. Starting from one edge of the wafer at each contour surface, along the Y-axis unidirectionally, with a step size of 5μm, metamorphic points are generated at intervals and scribed through to the opposite edge end, forming the first cleavage line connected by the first crack in the Y direction and the second cleavage line connected by the second crack in the Z direction. A cleavage plane composed of the first cleavage line and the second cleavage line is formed within the laser action area 10, as Figure 4 shown. Finally, a cleavage dividing line for laser cavity surface cleavage is formed in the Y-axis direction inside the GaN wafer, and a smooth and flat laser reflection cavity surface of the light-emitting area is obtained with the assistance of mechanical cleavage external force.

[0067] Example 4

[0068] Regarding the micro deviation of the crystal orientation between the cleavage cavity surface and the actual material in the diamond tool mechanical cleavage solution, the picosecond pulsed laser stealth dicing technology can achieve the correction of the crystal orientation deviation in the periodic skip cutting mode, as Figure 6 shown. The included angle θ between the actual crystal orientation 12 of the crystal and the preset cleavage line 6 (ideally θ = 0 ° ), the chip period is l, and the bar length is L. When using a diamond tool for cleavage, an external force destroys and marks the cleavage starting point. With the assistance of mechanical cleavage external force, it naturally cracks along the crystal orientation 12 of the wafer at the damage point. Since θ ≠ 0 ° , then at the length L, the maximum deviation in the X direction between the preset cleavage line and the cleavage cavity surface is L·tanθ, resulting in the cleavage cavity surface deviating from the 2 cleavage guiding structures, causing cleavage cavity surface cleavage failure and increasing the loss of the laser, making it unable to lasing. The pulsed laser stealth dicing technology can achieve the correction of the crystal orientation deviation in the periodic skip cutting mode. Periodic skip stealth dicing reduces the cleavage action distance L compared to the diamond tool cleavage solution. The maximum deviation in the X direction is l·tanθ (l << L). Due to the short action distance, the deviation between the preset cleavage line and the cleavage cavity surface in the X direction is reduced. After pulsed laser treatment, the metamorphic points at different Z values in the Y direction and the cleavage dividing lines composed of them are precisely inside the cleavage guiding groove structure. Then, the cleavage dividing lines at different Z value heights are connected by cracks to form a cleavage separation groove, enhancing the cleavage directivity, improving the yield of cavity surface cleavage, and increasing the device working life.

[0069] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. Those of ordinary skill in the art can understand that without departing from the spirit and scope of the present invention, various substitutions, changes, and modifications are possible. The present invention should not be limited to the content disclosed in the embodiments of this specification, and the protection scope of the present invention shall be defined by the scope defined in the claims.

Claims

1. A method for cleaving gallium nitride-based semiconductor devices, characterized in that, This includes the laser-guided scribing stage and the cavity surface cleavage stage; The laser hidden cutting and scribing stage includes: using picosecond pulsed laser hidden cutting technology, focusing the laser spot to different height positions from the semiconductor surface in the thickness direction of the semiconductor substrate to form multiple preset cutting and alteration points, and connecting the preset cutting and alteration points with similar points through cracks; repeating the hidden cutting mode in the thickness direction of the substrate in the direction parallel to the cavity surface, and finally obtaining a cleavage separation groove inside the semiconductor substrate; The cavity surface cleavage stage includes: splitting the semiconductor substrate along the cleavage separation groove with the assistance of mechanical splitting force to complete the cavity surface cleavage; The hidden cutting mode in the parallel cavity surface direction is either a periodic skip hidden cutting mode for P-plane cutting or a continuous hidden cutting mode for N-plane cutting, and the wavelength of the picosecond pulse laser is 1064nm for P-plane cutting or 532nm or 355nm for N-plane cutting. The distance between the preset cutting metamorphic points is 1-5 times the diameter of the preset cutting metamorphic points, and the spacing between the preset cutting metamorphic points is 5μm-10μm; During the laser scribe process, the laser energy decreases or increases again as the substrate thickness increases.

2. The cleavage method for a gallium nitride-based semiconductor device according to claim 1, characterized in that, The distance between the preset cutting modification point closest to the P-type semiconductor surface in the thickness direction of the substrate and the P-type semiconductor surface is not less than 20 μm.

3. The cleavage method for a gallium nitride-based semiconductor device according to claim 1, characterized in that, The periodic skip hidden cutting mode for P-plane cutting generates a first cleavage line in the direction parallel to the cavity surface and a second cleavage line in the direction of substrate thickness.

4. A method for manufacturing a gallium nitride-based semiconductor device, characterized in that, Includes the following steps: 1) The ridge structure and P-side electrode of the GaN-based laser were fabricated on a GaN epitaxial wafer by photolithography, etching and coating processes to obtain the sample; 2) Spin-coat a photolithographic protective film on the P-side of the sample, fix the wafer onto a ceramic or sapphire tray using a waxing device, and perform mechanical thinning, rough grinding, fine grinding and polishing steps on the back side of the GaN wafer to obtain a thinned GaN sample. 3) After the thinned GaN sample was cleaned with N-methylpyrrolidone, ethanol and deionized water, the N-side GaN was subjected to ICP etching, N-electrode evaporation and electrode metal fusion steps. 4) Picosecond pulsed laser scriber technology is used to focus a laser spot at different heights from the P-type GaN surface along the substrate thickness direction, forming at least two preset scriber points. Closely adjacent preset scriber points are interconnected by cracks. The above-mentioned substrate thickness direction scriber pattern is repeated in the parallel cavity plane direction, ultimately obtaining an ideal cleavage separation groove inside the GaN substrate. Then, with the assistance of a dicing machine, the substrate is cleaved along the cleavage separation groove to complete the cavity surface cleavage of the bar. The scriber pattern in the parallel cavity plane direction is either a periodic skip scriber pattern for P-face scriber or a continuous scriber pattern for N-face scriber. The wavelength of the picosecond pulsed laser is 1064nm for P-face scriber or 532nm or 355nm for N-face scriber. The distance between the preset scriber points is 1-5 times the diameter of the preset scriber point, and the spacing between the preset scriber points is 5μm-10μm. During the laser scriber scribing stage, the laser energy decreases or increases again as the substrate thickness increases. 5) The complete fabrication process of the GaN-based laser chip is completed by performing cavity surface coating, single-tube cleaving, and testing and sorting steps on the cleaved bar strips.

5. The method for manufacturing a gallium nitride-based semiconductor device according to claim 4, characterized in that, Step 1) The surface of the sample, except for the ridge structure area, is covered with a SiO2 insulating layer.

6. The method for manufacturing a gallium nitride-based semiconductor device according to claim 4, characterized in that, Step 2) The thickness of the thinned GaN sample is less than 150 μm.

7. The method for manufacturing a gallium nitride-based semiconductor device according to claim 4, characterized in that, The distance between the preset cutting and alteration point on the outermost edge of the corresponding ridge structure and the outermost edge of the corresponding ridge structure in the direction parallel to the cavity surface is not less than 10 μm.

8. A gallium nitride-based semiconductor device manufactured by the method according to any one of claims 4-7.

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