A method for manufacturing a semiconductor laser

Abstract

The present application belongs to the technical field of semiconductor optoelectronic device process, and relates to a manufacturing method of a semiconductor laser, which can realize beam shaping of a semiconductor laser element. The present application innovatively adopts a selected-area microprocessing technology to realize a selected-area optical limiting microstructure of a laser cavity surface through wafer pretreatment before cleaving of the cavity surface, eliminate cavity surface light emission, and improve beam quality. The greatest advantage of the present application is that the preparation of the selected-area optical limiting microstructure is completed before cleaving of the cavity surface, which can avoid cavity surface pollution and solve the far-field "square window" problem, improve product performance and production yield, and provide reliable technical support for commercial application.

Description

Technical Field

[0001] This invention relates to a method for fabricating semiconductor laser light, belonging to the field of semiconductor optoelectronic device technology. Background Technology

[0002] Gallium nitride (GaN)-based semiconductor 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 GaN lasers mostly employ an active region emission mode with edge emission, utilizing the natural cleavage planes of the substrate crystal as reflective surfaces to form a FP resonant cavity, where self-excited oscillation occurs, thereby achieving laser emission from the cavity end face. Multilayer cavity surface films are a crucial component of the laser cavity surface, effectively preventing oxidation during device operation and improving environmental stability. They also reduce the device's operating current and extend its lifespan by altering the reflectivity of the emission cavity surface. The cavity surface of an ideal edge-emitting semiconductor laser consists of a pair of parallel natural cleavage planes of a crystal, with flat and smooth surfaces. Due to the abrupt change in refractive index at the interface between the laser material and the operating environment, spontaneously emitted light is effectively reflected at the cleavage planes. After multiple reflections, self-excited oscillation occurs, ultimately resulting in laser emission. Cavity surface mount technology (CSMT) can effectively control the selection of laser threshold, emission direction, and frequency through reflectivity modulation. CSMT can also effectively passivate interface dangling bonds and defects caused by the cavity surface cleavage process, reducing cavity surface loss and improving device performance and lifetime. However, during lasing, due to imperfect waveguide confinement in the chip thickness direction, lasing light leakage into the substrate becomes the source of cavity surface luminescence. Furthermore, there is a refractive index difference between the cavity surface mount, GaN, and the operating environment, especially at the interface between the cavity surface mount and the environment (typically air, with a refractive index of 1), which easily forms a strong waveguide confinement effect. This causes waveguide leakage light to be confined within the cavity surface mount and air interface, ultimately resulting in luminescence from the entire cavity surface.

[0003] An ideal laser beam, shaped by an optical system, achieves a desired far-field pattern and is widely used in laser illumination, laser display, laser ranging, and laser marking devices. However, with surface-emitting laser beams (SELs), stray light appears in the optical control system (i.e., the far-field image of the emitting cavity surface after collimation and focusing), affecting the optical shaping effect and leading to a decrease in beam quality. For example, in laser marking applications, after optical collimation and focusing, the laser beam converges onto a cylindrical lens (or a Powell prism) to form a high-brightness, recognizable linear far-field pattern, used for marking in fields such as machinery manufacturing, precision instrument production, metallurgical cutting, and architectural decoration. Laser beams carrying SLEs inevitably generate stray light in the optical shaping system, presenting a "square window" image of the cavity surface shape in the far field, severely affecting beam quality and reducing equipment accuracy and reliability. To solve the problem of SLEs, it is necessary to break the waveguide confinement of the cavity surface film while maintaining the epitaxial growth, eliminating SLEs and improving beam quality. To address this issue, one approach is to focus on the cavity surface film, utilizing the "shadowing" effect to selectively deposit absorbing materials within designated areas, thereby reducing cavity surface emission and improving beam quality (see Japanese Patent: JP2020-129653 (P2020-129653A)). This patented solution requires secondary bar arrangement of the laser bar and secondary selective coating of the cavity surface to achieve the "shadowing" effect, increasing the fabrication process and coating difficulty. This process can easily cause secondary contamination and damage to the cavity surface, reducing production efficiency and yield. Furthermore, the coating equipment must have good deposition directionality to limit the lateral diffusion of the secondary-grown absorber film on the cavity surface, ensuring the accuracy of the selective coating. Alternatively, another approach is to focus on the laser cavity surface itself, selectively microfabricating materials in the emission-restricting areas. The fabrication of these selective microstructures increases optical confinement capabilities and disrupts the waveguide confinement capabilities of the cavity surface film, thus resolving cavity surface emission and improving laser beam quality. Summary of the Invention

[0004] The purpose of this invention is to innovatively propose a semiconductor laser manufacturing method that addresses the aforementioned technical challenges and meets the needs of industrial production, enabling beam shaping of semiconductor laser components. This method innovatively employs selective area micromachining (SIM) technology. Before cavity surface cleaving, a selective optical confinement microstructure is created on the laser cavity surface through wafer preprocessing, eliminating cavity surface emission, resolving the far-field "square window" problem, and improving beam quality. The greatest advantage of this invention is that the selective optical confinement microstructure is fabricated before cavity surface cleaving, avoiding cavity surface contamination and resolving the far-field "square window" problem, thus improving product performance and production yield, and providing reliable technical support for commercial applications.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for manufacturing a semiconductor laser, comprising the following steps, using a thermally oxidized cavity surface selective region (CFR) approach to fabricate a selective optical confinement microstructure:

[0007] Step 1: Deposit a SiO2 layer on the laser epitaxial wafer, where SiO2 serves as an antioxidant protective layer.

[0008] Step 2: Define the thermal oxidation region on the surface of the epitaxial wafer using photolithography, and transfer the photolithographically defined pattern to the SiO2 layer using an etching process. The area not covered by SiO2 is the thermal oxidation region.

[0009] Step 3: The epitaxial wafer defined by SiO2 pattern is oxidized by thermal oxidation process. Finally, the patterned modified region is obtained in the wafer thickness direction through surface thermal oxygen diffusion effect, which completes the preparation of selected area optical confinement microstructure.

[0010] Step 4: The SiO2 anti-oxidation protective layer is removed by etching. The laser ridge structure and P-side electrode are fabricated through photolithography, etching, and coating processes. The sample surface is covered with SiO2 insulating layer except for the ridge window structure area.

[0011] Step 5: 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 of the back side of the substrate wafer to finally obtain a thinned wafer sample with a thickness of <150μm.

[0012] Step 6: Perform cavity surface cleavage, cavity surface coating, single-tube cleaving, testing and sorting on the thinned wafer to complete the complete fabrication process of the semiconductor laser chip.

[0013] A method for manufacturing a semiconductor laser, comprising the following steps, using ion implantation to fabricate a selected-area optical confinement microstructure:

[0014] Step 1: Deposit a SiO2 layer on the laser epitaxial wafer, where SiO2 serves as an ion implantation protective layer.

[0015] Step 2: Define the ion implantation region on the surface of the epitaxial wafer using photolithography, and transfer the photolithographically defined pattern to the SiO2 layer using an etching process. The area not covered by SiO2 is the ion implantation region.

[0016] Step 3: Selective ion implantation is performed on the SiO2 patterned epitaxial wafer. Finally, patterned modified regions are obtained in the wafer thickness direction through surface ion implantation, thus completing the fabrication of the selected optical confinement microstructure.

[0017] Step 4: The SiO2 ion implantation protective layer is removed by etching. The laser ridge structure and P-side electrode are fabricated by photolithography, etching, and coating processes. Except for the ridge window structure area, the sample surface is covered by a SiO2 insulating layer.

[0018] Step 5: 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 of the back side of the substrate wafer to finally obtain a thinned wafer sample with a thickness of <150μm.

[0019] Step 6: Perform cavity surface cleavage, cavity surface coating, single-tube cleaving, testing and sorting on the thinned wafer to complete the complete fabrication process of the semiconductor laser chip.

[0020] A method for manufacturing a semiconductor laser, comprising the following steps, using laser-modified cavity surface selected region (CBS) to prepare a selected region optical confinement microstructure:

[0021] Step 1: Polish the substrate surface of the laser epitaxial wafer using grinding and polishing technology to obtain a smooth and transparent epitaxial substrate.

[0022] Step 2: On the transparent substrate side, a patterned modified region is obtained in the wafer thickness direction by laser irradiation modification technology, which completes the preparation of the selected area optical confinement microstructure.

[0023] Step 3: On the front side of the epitaxial wafer, the laser ridge structure and P-side electrode are fabricated through photolithography, etching, and coating processes. Except for the ridge window structure area, the sample surface is covered with a SiO2 insulating layer.

[0024] Step 4: 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 of the back side of the substrate wafer to finally obtain a thinned wafer sample with a thickness of <150μm.

[0025] Step 5: Perform cavity surface cleavage, cavity surface coating, single-tube cleaving, testing and sorting on the thinned wafer to complete the complete fabrication process of the semiconductor laser chip.

[0026] The beneficial effects of this invention are:

[0027] This method innovatively achieves precise fabrication of selected microstructures on the cavity surface of semiconductor lasers through wafer surface treatment. These selected microstructures enhance optical confinement capabilities and disrupt the waveguide confinement of the cavity surface film, thus solving the cavity surface emission problem and improving laser beam quality. Firstly, the greatest advantage of this invention is that the fabrication of the selected microstructures is performed before laser processing. Micro- and nano-fabrication techniques are cleverly used to prefabricate the microstructures onto a designated area of ​​the laser cavity surface via the surface of the laser epitaxial wafer, achieving effective cavity surface emission confinement. This completely avoids contamination and damage to the laser cavity surface, reduces processing difficulty, and significantly improves laser performance and yield. Secondly, the fabrication of the selected microstructures is achieved through precise prefabrication on the laser cavity surface via the wafer surface. This fabrication process is simple, efficient, and compatible with semiconductor processing procedures, requiring no additional investment in production equipment, making it suitable for industrial-scale promotion and practical. Attached Figure Description

[0028] Figure 1 This is a process diagram showing the fabrication of laser devices using methods 1 and 2;

[0029] Figure 2 This is a process diagram of fabricating laser devices using method 3;

[0030] Figure 3 This is a schematic diagram of the cavity surface structure of the laser fabricated using methods 1 and 2;

[0031] Figure 4 This is a schematic diagram of the cavity surface structure of the laser prepared using method 3;

[0032] Figure 5 This is a three-dimensional structural diagram of the semiconductor laser prepared according to the present invention. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0034] Example 1:

[0035] A method for manufacturing a semiconductor laser involves fabricating a selected-area optical confinement microstructure using a thermally oxidized cavity surface selective region method. The process flow is as follows: Figure 1 As shown, it includes the following steps:

[0036] Step 1: Deposit a silicon oxide (SiO2) layer on the laser epitaxial wafer, where SiO2 serves as an antioxidant protective layer. The thickness of the SiO2 layer is 2-5 μm, and in this embodiment, the thickness of the SiO2 layer is 3 μm.

[0037] Step 2: Define the thermal oxidation region on the surface of the epitaxial wafer using photolithography, and transfer the photolithographically defined pattern to the SiO2 layer using an etching process. The area not covered by SiO2 is the thermal oxidation region, where the width b of the SiO2 mask is 30 μm.

[0038] Step 3: Using a thermal oxidation process, the treated epitaxial wafer is placed in an oxidation furnace at a temperature of 800-1200℃ (1000℃ in this embodiment) and an oxidation time of 1-5 hours (3 hours in this embodiment). The SiO2 pattern-defined epitaxial wafer is oxidized, and finally, a patterned modified region is obtained in the wafer thickness direction through the surface thermal oxygen diffusion effect, thus completing the fabrication of the selected area optical confinement microstructure.

[0039] Step 4: The SiO2 anti-oxidation protective layer is removed by etching. The laser ridge structure and P-side electrode are fabricated through photolithography, etching, and coating processes. The sample surface is covered with SiO2 insulating layer except for the ridge window structure area.

[0040] Step 5: 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 of the back side of the substrate wafer to finally obtain a thinned wafer sample with a thickness of <150μm.

[0041] Step 6: The thinned wafer undergoes cavity surface cleaving, cavity surface coating, single-tube dicing, testing, and sorting to complete the full fabrication process of the semiconductor laser chip. The three-dimensional structure of the semiconductor laser fabricated in this embodiment is as follows: Figure 5 As shown.

[0042] In this embodiment, the ridge width 'a' of the laser chip is 10 μm, the width 'c' of the diffusion region is 10 μm, and 'b' = 'a' + 2c'. Figure 3 As shown, the reserved diffusion areas on both sides of the ridge can effectively reduce the impact of diffusion during the thermal oxidation process on the light-emitting point of the cavity surface below the ridge of the laser chip.

[0043] Example 2:

[0044] A method for manufacturing a semiconductor laser involves fabricating a selected-area optical confinement microstructure using ion implantation with a cavity surface selected region (CSP). The process flow is as follows: Figure 1 As shown, it includes the following steps:

[0045] Step 1: Deposit a silicon oxide (SiO2) layer on the laser epitaxial wafer, wherein SiO2 serves as an ion implantation protective layer. The thickness of the SiO2 layer is 100-1000 nm, and in this embodiment, the thickness of the SiO2 layer is 300 nm.

[0046] Step 2: Define the ion implantation region on the surface of the epitaxial wafer using photolithography, and transfer the photolithographically defined pattern to the SiO2 layer using an etching process. The area not covered by SiO2 is the ion implantation region, where the SiO2 mask width b is 30 μm.

[0047] Step 3: Using ion implantation, the processed epitaxial wafer is placed in an ion implantation device, heated to 100°C, and argon ions are implanted at an energy of 30 keV. Selective ion implantation is performed on the SiO2 patterned epitaxial wafer. Finally, a patterned modified region is obtained in the wafer thickness direction through surface ion implantation, thus completing the fabrication of the selected optical confinement microstructure.

[0048] Step 4: The SiO2 ion implantation protective layer is removed by etching. The laser ridge structure and P-side electrode are fabricated by photolithography, etching, and coating processes. Except for the ridge window structure area, the sample surface is covered by a SiO2 insulating layer.

[0049] Step 5: 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 of the back side of the substrate wafer to finally obtain a thinned wafer sample with a thickness of <150μm.

[0050] Step 6: Perform cavity surface cleavage, cavity surface coating, single-tube dicing, testing and sorting, etc. on the thinned wafer to complete the complete fabrication process of the semiconductor laser chip.

[0051] In this embodiment, the ridge width 'a' of the laser chip is 10 μm, the width 'c' of the diffusion region is 10 μm, and 'b' = 'a' + 2c'. Figure 3 As shown, the pre-reserved diffusion areas on both sides of the ridge can effectively reduce the impact of diffusion during the ion implantation process on the light-emitting point of the cavity surface below the ridge of the laser chip.

[0052] Example 3:

[0053] A method for manufacturing a semiconductor laser involves fabricating a selected-area optical confinement microstructure using laser-modified cavity surface area selection (CSBI). The process flow is as follows: Figure 2 As shown, it includes the following steps:

[0054] Step 1: Polish the substrate surface of the laser epitaxial wafer using grinding and polishing technology to obtain a smooth and transparent epitaxial substrate.

[0055] Step 2: A patterned modification region is obtained along the thickness direction of the laser epitaxial wafer on the transparent substrate side using laser irradiation modification technology, thus completing the fabrication of the selected area optical confinement microstructure. A 1064nm picosecond pulsed laser is used for laser irradiation modification, with a single pulse energy of 1.4μJ, a frequency of 50kHz, and a laser energy set to 50mW. A fixed-point focused beam with a step size of 5μm is used, passing over a target ridge with a width a of 8μm and pre-reserved extension regions c on both sides of the ridge with a width of 10μm. The laser energy decreases by 5mW sequentially in the direction of decreasing distance from the active region of the laser epitaxial wafer until the fixed-point focused beam reaches the top surface of the laser epitaxial wafer. Figure 4 As shown in (a).

[0056] Step 3: The laser ridge structure and P-side electrode are fabricated through photolithography, etching, and coating processes. Except for the ridge window structure area, the sample surface is covered with a SiO2 insulating layer.

[0057] Step 4: 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 of the back side of the substrate wafer to finally obtain a thinned wafer sample with a thickness of <150μm.

[0058] Step 5: Perform cavity surface cleavage, cavity surface coating, single-tube dicing, testing and sorting, etc. on the thinned wafer to complete the complete fabrication process of the semiconductor laser chip.

[0059] Example 4:

[0060] In step 2, a 1064nm picosecond pulsed laser is used, with a single pulse energy of 1.4μJ, a frequency of 50kHz, and a laser energy set to 50mW. A fixed-point focused beam with a step size of 5μm is employed. The laser energy decreases by 5mW sequentially along the direction of decreasing distance from the active region of the laser epitaxial wafer until the focused beam stops at a distance d of 20μm from the top surface of the laser epitaxial wafer. Figure 4 As shown in (b). Everything else is the same as in Example 3.

[0061] Example 5:

[0062] In step 2, a 1064nm picosecond pulsed laser is used, with a single pulse energy of 1.4μJ, a frequency of 50kHz, and a laser energy set to 50mW. A fixed-point focused beam with a step size of 5μm is employed. The laser energy decreases by 5mW sequentially in the direction of decreasing distance from the active region of the laser epitaxial wafer, until the fixed-point focused beams on both sides of the laser ridge stop at a distance d of 20μm from the top surface of the laser epitaxial wafer, and the closest fixed-point focused beam below the laser ridge stops at a distance e of 25μm from the top surface of the laser epitaxial wafer. Figure 4As shown in (c), everything else is the same as in Example 4.

[0063] The semiconductor laser manufacturing method of the present invention, by designing the preparation of the cavity surface selected area microstructure before the laser process cleaving, cleverly uses micro-nano processing technology to prefabricate the specified area of ​​the laser cavity surface on the surface of the laser epitaxial wafer, thereby achieving effective cavity surface emission restriction. It completely avoids contamination and damage to the laser cavity surface, reduces the process difficulty, and greatly improves the performance and yield of the laser.

[0064] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and to implement it accordingly. Those skilled in the art will understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification; the scope of protection of the present invention is defined by the claims.

Claims

1. A method for manufacturing a semiconductor laser, characterized in that, Includes the following steps: A SiO2 layer is deposited on the epitaxial wafer of a laser, wherein SiO2 serves as an antioxidant protective layer; Thermally oxidized regions are defined on the surface of a laser epitaxial wafer using photolithography, and the photolithographically defined pattern is transferred to the SiO2 layer through an etching process. The areas not covered by SiO2 are thermally oxidized regions. The epitaxial wafer with SiO2 pattern definition is oxidized by thermal oxidation process. The patterned modified region is obtained in the wafer thickness direction through surface thermal oxygen diffusion effect, and the selected area optical confinement microstructure is prepared. The SiO2 antioxidant protective layer was removed by etching, and the laser ridge structure and P-side electrode were prepared by photolithography, etching and coating processes. Except for the ridge window structure area, the surface was covered by a SiO2 insulating layer. The substrate wafer undergoes back-side mechanical thinning, rough grinding, fine grinding, and polishing steps to obtain a thinned wafer; The semiconductor laser chip is fabricated by performing cavity surface cleavage, cavity surface coating, single-tube cleaving, and testing and sorting steps on the thinned wafer.

2. The method according to claim 1, characterized in that, The thickness of the SiO2 layer is 2-5 μm.

3. The method according to claim 1, characterized in that, The temperature of the thermal oxidation process is 800-1200℃, and the oxidation time is 1-5h.

4. The method according to claim 1, characterized in that, Diffusion regions are reserved on both sides of the ridge of the laser chip to reduce the impact of diffusion during the thermal oxidation process on the light-emitting point of the cavity surface below the ridge.

5. A method for manufacturing a semiconductor laser, characterized in that, Includes the following steps: A SiO2 layer is deposited on the epitaxial wafer of a laser, wherein SiO2 serves as an ion implantation protective layer; Ion implantation regions are defined on the surface of a laser epitaxial wafer using photolithography, and the photolithographically defined pattern is transferred to the SiO2 layer by etching. The areas not covered by SiO2 are the ion implantation regions. Selective ion implantation was performed on a SiO2 patterned epitaxial wafer. By surface ion implantation, patterned modified regions were obtained in the wafer thickness direction, thus completing the fabrication of selected optical confinement microstructures. The SiO2 ion implantation protective layer was removed by etching, and the laser ridge structure and P-side electrode were prepared by photolithography, etching and coating processes. The surface was covered with SiO2 insulating layer except for the ridge window structure area. The substrate wafer undergoes back-side mechanical thinning, rough grinding, fine grinding, and polishing steps to obtain a thinned wafer; The semiconductor laser chip is fabricated by performing cavity surface cleavage, cavity surface coating, single-tube cleaving, and testing and sorting steps on the thinned wafer.

6. The method according to claim 5, characterized in that, The thickness of the SiO2 layer is 100-1000 nm.

7. The method according to claim 5, characterized in that, Diffusion regions are reserved on both sides of the ridge of the laser chip to reduce the impact of diffusion during ion implantation on the light emission point of the cavity surface below the ridge.

8. A method for manufacturing a semiconductor laser, characterized in that, Includes the following steps: The substrate surface of the laser epitaxial wafer is polished using grinding and polishing technology to obtain a smooth and transparent epitaxial substrate. Patterned modification regions were obtained in the wafer thickness direction by laser irradiation modification technology on the transparent substrate side, thus completing the fabrication of selected area optical confinement microstructures; The laser ridge structure and P-side electrode were fabricated by photolithography, etching and coating processes. Except for the ridge window structure area, the surface was covered by a SiO2 insulating layer. The substrate wafer undergoes back-side mechanical thinning, rough grinding, fine grinding, and polishing steps to obtain a thinned wafer; The semiconductor laser chip is fabricated by performing cavity surface cleavage, cavity surface coating, single-tube cleaving, and testing and sorting steps on the thinned wafer.

9. The method according to claim 8, characterized in that, The selected optical confinement microstructures obtained by the laser irradiation modification technique include the following three types: As the distance from the laser beam to the active region of the laser epitaxial wafer decreases, the laser energy decreases sequentially until the focused beam reaches the top surface of the laser epitaxial wafer. The laser energy of the focused beam decreases sequentially in the direction of decreasing distance from the active region of the laser epitaxial wafer until it stops at a distance d of 20 μm from the top surface of the laser epitaxial wafer. The laser energy of the fixed-point focused beam decreases sequentially in the direction of decreasing distance from the active region of the laser epitaxial wafer until the fixed-point focused beams on both sides of the laser ridge stop at a distance d of 20 μm from the top surface of the laser epitaxial wafer, and the nearest fixed-point focused beam below the laser ridge stops at a distance e of 25 μm from the top surface of the laser epitaxial wafer.

10. A semiconductor laser manufactured by the method according to any one of claims 1 to 9.

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