Manufacturing method of laser

Abstract

The invention relates to the technical field of laser manufacturing, in particular to a manufacturing method of a laser. The manufacturing method of the laser provided by the invention comprises the following steps: providing a device substrate; comprising a target area to form a ridge-shaped structure; etching the device substrate, and forming a ridge-shaped structure in the target area; in the etching process, the ranges of the two sides of the target area of the device substrate are all etched to remove the same depth; forming a SiN protection layer, and covering the surface of the side, where the ridge-shaped structure is located, of the device substrate; forming a photoresist layer, at least filling all the space on the two sides of the ridge-shaped structure, and the height of the photoresist layer is not lower than that of the ridge-shaped structure; a first etching process: removing the SiN protection layer on the top surface of the ridge-shaped structure, and removing partial thickness of the photoresist layer on the two sides of the ridge-shaped structure at the same time; removing the residual photoresist layer; according to the invention, the problem that the two sides of the edge of the ridge-shaped waveguide of the 980nm single-mode high-power laser are easy to leak electricity can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of laser manufacturing, and in particular to a method for manufacturing a laser. Background Art

[0002] As the basis of high-capacity optical communication, the erbium-doped fiber amplifier (EDFA) can directly amplify the optical signal and is a key component for realizing the all-optical network. The all-fiber erbium-doped fiber amplifier (EDFA) is an important component of the long-distance (land and submarine) optical communication network. Long-distance optical communication systems must use low-loss single-mode optical fiber, and EDFA must also use single-mode 980 nm laser pumping to ensure the stable operation of the optical communication system. It is the core of EDFA and the core of the optical communication system. However, the core laser chips and devices of optical communication are still highly dependent on imports, so the production technology development of 980nm single-mode high-power lasers is very necessary.

[0003] In the prior art 980nm single-mode high-power laser manufacturing method, leakage is prone to occur on both sides of the waveguide structure edge of the ridge structure. This is because the silicon nitride protective layer on the surface of the ridge structure is offset when etching, so that the silicon nitride protective layer at the non-waveguide structure position on both sides of the ridge structure edge that should not be etched is incorrectly removed, and a conductive film layer is formed on the substrate surface at the non-waveguide structure position where the silicon nitride protective layer is removed in the subsequent film layer formation process, so that leakage occurs here.

[0004] Therefore, a solution is needed to solve the problem that leakage easily occurs on both sides of the waveguide edge of the ridge structure of the 980nm single-mode high-power laser. Summary of the invention

[0005] Therefore, the present invention provides a method for manufacturing a laser to solve the problem that leakage easily occurs on both sides of the waveguide edge of the ridge structure of a 980nm single-mode high-power laser.

[0006] In one aspect of the present invention: the present invention provides a method for manufacturing a laser, comprising the following steps: providing a device substrate; the device substrate includes a target area where a ridge structure is to be formed; etching the device substrate to form a ridge structure in the target area; during the etching process, the range on both sides of the target area of ​​the device substrate is all etched away to the same depth; forming a SiN protective layer, the SiN protective layer covers the surface of the device substrate on the side where the ridge structure is located; forming a photoresist layer, the photoresist layer at least fills all the space on both sides of the ridge structure, and the height of the photoresist layer is not less than the height of the ridge structure; a first etching process, removing the SiN protective layer on the top surface of the ridge structure, and simultaneously removing a portion of the thickness of the photoresist layer on both sides of the ridge structure; removing the remaining photoresist layer.

[0007] The manufacturing method of the laser provided by the present invention completely removes the device substrate on both sides of the ridge structure while forming the ridge structure, and in the subsequent steps, fills the partial space with a photoresist layer. In this way, the top surface of the device substrate forms a distribution state of photoresist layer-ridge structure-photoresist layer, and the subsequent steps directly etch one side of the top surface of the ridge structure of the device substrate, so as to realize the self-alignment of the SiN protective layer on the top surface of the ridge structure in the target area, without the need to use a special graphical mask, and even more without the need to calibrate the mask, which is simple and convenient, avoiding the process difficulties of the high-precision photolithography overlay process, and has high precision, which can avoid the problem of etching offset caused by mask offset, thereby causing the part of the SiN protective layer that should not be removed to be removed by mistake; ensure that the SiN protective layer structure on both sides of the ridge structure is complete, and avoid the situation of causing leakage. Therefore, the manufactured device will not have leakage.

[0008] Optionally, before forming the SiN protective layer, the method further includes: forming a SiO2 protective layer, the SiO2 protective layer covering the surface of the device substrate on the side where the ridge structure is located; and forming the SiN protective layer on the surface of the SiO2 protective layer facing away from the device substrate.

[0009] The laser manufacturing method provided by the present invention forms a SiO2 protective layer before forming a SiN protective layer, so that the SiO2 protective layer can be used as an etching stop layer during the etching process of the SiN protective layer to prevent over-etching of the SiN protective layer.

[0010] Optionally, after removing the remaining photoresist layer, the method further includes: a second etching process to remove the SiO2 protective layer on the top surface of the ridge structure and simultaneously remove a partial thickness of the SiN protective layer.

[0011] The manufacturing method of the laser provided by the present invention removes the SiO2 protective layer exposed by the first etching process through the second etching process. Similar to the first etching process, there are only SiN protective layer and SiO2 protective layer on one side of the ridge structure of the device substrate, so etching from this side will only etch these two layers, thereby achieving self-alignment of the SiO2 protective layer in the target area.

[0012] Optionally, the photoresist layer is formed only on two sides of the ridge structure, and the height of the photoresist layer is the same as the height of the ridge structure.

[0013] The laser manufacturing method provided by the present invention can realize that the top surface of the formed photoresist layer is flush with the top surface of the ridge structure by controlling the step conditions during the process of forming the photoresist layer, and then directly etches the SiN protective layer on the top surface of the ridge structure, making the subsequent etching process faster and more convenient.

[0014] Optionally, the height of the photoresist layer is higher than the height of the ridge structure, and the photoresist layer also covers the top surface of the ridge structure; in the first etching process, the photoresist layer covering the top surface of the ridge structure is first removed in one etching step, and then the SiN protective layer on the top surface of the ridge structure is etched.

[0015] The laser manufacturing method provided by the present invention can make the photoresist layer cover the surface of the ridge structure during the photoresist layer formation process. The photoresist layer formed in this way has loose process conditions and is easy to form. The steps of forming the photoresist layer are simple and convenient.

[0016] Optionally, the first etching process is a reactive ion etching process; the etching gas is CHF3:O2:AR=10:1:2; the chamber pressure is 20Pa~30Pa; and the power is 150W~200W. Optionally, the height of the ridge structure is 1 μm to 1.2 μm; the thickness of the SiN protective layer is 200 nm; and the thickness of the SiO2 protective layer is 50 nm.

[0017] Optionally, the second etching process is a reactive ion etching process; the etching gas is CHF3:O2:AR=7:1:17; the chamber pressure is 15Pa~20Pa; and the power is 170W~210W. Optionally, after the first etching process, it also includes: forming a top surface seed metal layer, the top surface seed metal layer covers the surface of the device substrate on the side where the ridge structure is located; electroplating on the surface of the top surface seed metal layer to form a top surface metal layer; thinning the thickness of the device substrate on the opposite side of the ridge structure; and forming a bottom surface metal layer on the opposite side of the device substrate on the ridge structure.

[0018] Optionally, the step of providing a device substrate includes: providing a semiconductor substrate layer; sequentially forming a lower functional layer, a quantum well layer and an upper functional layer on one side of the semiconductor substrate layer; and forming a ridge structure on one side of the upper functional layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1a It is a schematic diagram of an ideal state after the SiN protective layer on the top surface is removed after the ridge structure is etched to form the ridge structure in the prior art 980nm single-mode high-power laser. Figure 1bIt is a top view of an ideal state after the SiN protective layer on the top surface is removed after the ridge structure is etched to form the ridge structure in the prior art 980nm single-mode high-power laser. Figure 1c It is a top view showing a step of removing the SiN protective layer on the top surface after etching to form the ridge structure of a 980nm single-mode high-power laser in the prior art, where the step is offset; Figure 2 This is a schematic diagram of a state in which a device substrate is etched to form a ridge structure in a method for manufacturing a laser according to an embodiment of the present invention; Figure 3 It is a schematic top view of a method for manufacturing a laser according to an embodiment of the present invention, after the SiN protective layer on the top surface of the ridge structure is removed; Figure 4 This is a schematic diagram of a state after a SiN protective layer is formed in a method for manufacturing a laser according to an embodiment of the present invention; Figure 5a A schematic diagram of forming a photoresist layer in a method for manufacturing a laser according to an embodiment of the present invention; Figure 5b A schematic diagram of forming a photoresist layer in a method for manufacturing a laser according to another embodiment of the present invention; Figure 6 A schematic diagram of a first etching process in a method for manufacturing a laser according to an embodiment of the present invention; Figure 7 A schematic diagram of a second etching process in a method for manufacturing a laser according to an embodiment of the present invention; Figure 8 It is a schematic diagram of forming a top metal seed layer and a top metal layer in a method for manufacturing a laser according to an embodiment of the present invention; Fig. 9 A schematic diagram of forming a bottom metal layer in a method for manufacturing a laser according to an embodiment of the present invention; Fig.10 Schematic diagram of the core process of a method for manufacturing a laser according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] refer to Figure 1aIn the process of forming a 980nm single-mode high-power laser formed by the prior art, a device substrate is provided, and the device substrate includes a substrate layer and a lower functional layer 100, a quantum well layer 200 and an upper functional layer 300; the lower functional layer 100 includes at least a lower cladding layer and a lower waveguide layer; the upper functional layer 300 includes at least an upper waveguide layer and an upper cladding layer, and a GaAs doped layer above the upper cladding layer. A groove G is etched on one side of the functional layer 300 on the device substrate to form a ridge structure R in the middle of the groove G; then a SiN protective layer 400 is formed on the surface of the device substrate; then the SiN protective layer 400 on the top surface of the ridge structure R is etched away by a precise photolithography overlay process to expose the GaAs doped layer in the ridge structure R, so as to continue to form subsequent metal layers. The ideal situation in this process is as follows Figure 1a and Figure 1b As shown, the SiN protective layer 400 on the surface of the ridge structure R is precisely etched away. In the actual process, the etching accuracy is usually about 2μm over 4μm, and the accuracy is very high. It is very easy to deviate from the angle, which may cause the following Figure 1c The situation shown in the figure causes the SiN on both sides of the edge of the original ridge structure R to be incorrectly removed, such as Figure 1c The circle in the middle corresponds to Figure 1a The circles on both sides of the circuit make this part of the GaAs doped layer incorrectly exposed, and after the subsequent conductive metal layer is formed, electrical contact will be formed at these locations, resulting in leakage.

[0022] It should be noted that Figure 1c In order to clearly show the deflection, a larger deflection angle is used. In the actual process, there may not be such a large angle, but it will still cause the above situation. The angle in the figure is only for illustration and is not the actual deflection angle that must occur.

[0023] Therefore, a solution is needed to solve the problem that leakage easily occurs on both sides of the waveguide edge of the ridge structure of the above-mentioned 980nm single-mode high-power laser.

[0024] The invention provides a method for manufacturing a laser to solve the problem that leakage easily occurs on both sides of the waveguide edge of a ridge structure of a 980nm single-mode high-power laser.

[0025] The invention provides a method for manufacturing a laser, comprising the following steps: providing a device substrate; the device substrate comprises a target area to be formed with a ridge structure; etching the device substrate to form a ridge structure in the target area; during the etching process, the ranges on both sides of the target area of ​​the device substrate are all etched away to the same depth; forming a SiN protective layer, the SiN protective layer covers the surface of the side of the device substrate where the ridge structure is located; forming a photoresist layer, the photoresist layer at least fills all the spaces on both sides of the ridge structure, and the height of the photoresist layer is not less than the height of the ridge structure; a first etching process, removing the SiN protective layer on the top surface of the ridge structure, and simultaneously removing a portion of the thickness of the photoresist layer on both sides of the ridge structure; and removing the remaining photoresist layer.

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0027] Example 1 refer to Figure 2-Figure 9 , and combined Fig.10 The present invention provides a method for manufacturing a laser, comprising the following steps: Providing a device substrate; the device substrate includes a target area where a ridge structure is to be formed; refer to Figure 2 , etching the device substrate to form a ridge structure R in the target area; during the etching process, the areas on both sides of the target area of ​​the device substrate are all etched away to the same depth; refer to Figure 4 , forming a SiN protective layer 400, wherein the SiN protective layer 400 covers the surface of the device substrate on the side where the ridge structure is located; refer to Figure 5a or Figure 5b , forming a photoresist layer 500, the photoresist layer 500 at least fills all the spaces on both sides of the ridge structure R, and the height of the photoresist layer 500 is not less than the height of the ridge structure R; refer to Figure 6 , a first etching process, removing the SiN protective layer 400 on the top surface of the ridge structure R, and removing a portion of the photoresist layer 500 on both sides of the ridge structure; The remaining photoresist layer 500 is removed.

[0028] The manufacturing method of the laser provided in this embodiment completely removes the device substrate on both sides of the ridge structure R while forming the ridge structure R. In the subsequent steps, the photoresist layer 500 is used to fill the space. In this way, the top surface of the device substrate forms a distribution state of photoresist layer 500-ridge structure R-photoresist layer 500. In the subsequent steps, the top surface side of the ridge structure R of the device substrate is directly etched to achieve self-alignment of the SiN protective layer 400 on the top surface of the ridge structure R. There is no need to use a special graphic mask, and there is no need to calibrate the mask. It is simple and convenient, avoiding the process difficulties of high-precision photolithography overlay process, and has high precision. It can avoid the problem of etching offset caused by mask offset, thereby causing the part of the SiN protective layer 400 that should not be removed to be removed by mistake; it ensures that the SiN protective layer 400 on both sides of the ridge structure R is structurally intact, avoiding the situation of causing leakage. Therefore, the manufactured device will not have leakage. This can solve the problem that leakage easily occurs on both sides of the waveguide edge of the ridge structure of the 980nm single-mode high-power laser. The laser manufactured by the laser manufacturing method provided in this embodiment can be applicable to the 980nm single-mode high-power laser.

[0029] Specifically, refer to Figure 3 The top view of the device substrate after removing the photoresist layer 500 is shown in FIG. Figure 3 As shown. The ridge structure area in the middle exposes the top surface of the GaAs doped layer in the upper functional layer 300, and the device substrate surface on the side is covered by the SiN protective layer 400. The ridge structure R includes a first waveguide segment R1 on the high reflection side, a third waveguide segment R3 on the light output side, and a second waveguide segment R2 connecting the first waveguide segment R1 and the third waveguide segment R3. The width dimension of the first waveguide segment R1 is smaller than the width dimension of the third waveguide segment R3, the width dimension of the second waveguide segment R2 gradually expands from the first waveguide segment R1 to the third waveguide segment R3, and the width dimension of the second waveguide segment R2 expands from the width dimension of the first waveguide segment R1 to the width dimension of the third waveguide segment R3.

[0030] In a specific embodiment, the width of the device substrate is 400 μm and the length is 3000 μm; the width of the first waveguide segment R1 is 4 μm and the length is 1000 μm; the width of the second waveguide segment R2 gradually increases from 4 μm to 7 μm and the length is 500 μm; the width of the third waveguide segment R3 is 7 μm and the length is 1500 μm.

[0031] For further reference, Figure 4In some embodiments, before forming the SiN protective layer 400, the method further includes: forming a SiO2 protective layer 600, the SiO2 protective layer 600 covering the surface of the device substrate on the side where the ridge structure is located; the SiN protective layer 400 is formed on the surface of the SiO2 protective layer 600 facing away from the device substrate. After removing the SiN protective layer 400 on the top surface of the ridge structure R, the SiO2 protective layer 600 on the top surface of the ridge structure R is removed to expose the GaAs doped layer in the ridge structure R.

[0032] In the laser manufacturing method provided in this embodiment, a SiO2 protective layer 600 is first formed before forming the SiN protective layer 400. In this way, the SiO2 protective layer 600 can be used as an etching stop layer during the etching process of the SiN protective layer 400 to prevent over-etching of the SiN protective layer 400.

[0033] For further reference, Figure 7 After removing the remaining photoresist layer, the method further includes: a second etching process to remove the SiO2 protective layer 600 on the top surface of the ridge structure R, and simultaneously remove a portion of the thickness of the SiN protective layer 400. The SiO2 protective layer 600 on the top surface of the ridge structure R exposed after the first etching process is removed by the second etching process, so that the GaAs doped layer in the ridge structure R is exposed, so as to subsequently form a current injection window. At the same time, a portion of the thickness of the SiN protective layer 400 is removed in this process.

[0034] The manufacturing method of the laser provided in this embodiment removes the SiO2 protective layer exposed by the first etching process through the second etching process. Similar to the first etching process, there are only SiN protective layer and SiO2 protective layer on one side of the ridge structure of the device substrate, so etching from this side will only etch these two layers, thereby achieving self-alignment of the SiO2 protective layer in the target area.

[0035] For further reference, Figure 5a In some embodiments, the photoresist layer 500 is only formed on both sides of the ridge structure R, and the height of the photoresist layer 500 is the same as the height of the ridge structure R.

[0036] The manufacturing method of the laser provided in this embodiment can achieve that the top surface of the formed photoresist layer 500 is flush with the top surface of the ridge structure by controlling the step conditions during the formation of the photoresist layer 500, and then directly etches the SiN protective layer 400 on the top surface of the ridge structure, making the subsequent etching process faster and more convenient.

[0037] For further reference, Figure 5bIn some embodiments, the height of the photoresist layer 500 is higher than the height of the ridge structure, and the photoresist layer 500 also covers the top surface of the ridge structure; in the first etching process, the photoresist layer 500 covering the top surface of the ridge structure is first removed in one etching step, and then the SiN protective layer 400 on the top surface of the ridge structure is etched.

[0038] The laser manufacturing method provided in this embodiment can make the photoresist layer 500 cover the surface of the ridge structure during the formation of the photoresist layer 500. The photoresist layer 500 formed in this way has loose process conditions and is easy to form, and the formation steps of the photoresist layer 500 are simple.

[0039] For further reference, Figure 6 In the first etching process, the top surface of the device substrate with the ridge structure R is etched, and the SiN protective layer 400 on the top surface of the ridge structure R and the photoresist layer 500 on the side are etched simultaneously. Since there are only the photoresist layer 500 and the SiN protective layer on the top surface of the ridge structure R on this side, only these two parts will be etched, which forms a self-alignment of the etching steps. In addition, the etching speed of the photoresist layer 500 is relatively fast. At the same time, since the thickness of the SiN protective layer 400 on the top surface of the ridge structure R is much thinner than the photoresist layer 500, when the etching of the SiN protective layer 400 on the top surface of the ridge structure R is completed, there is still a portion of the photoresist layer 500 remaining, and the SiN protective layer 400 below the photoresist layer 500, that is, the SiN protective layer 400 on the side of the ridge structure will not be etched, and the SiN protective layer 400 here will not be etched through, so the GaAs doped layer in the upper functional layer 300 that should not be exposed on the side of the ridge structure R will not be exposed, so there will be no leakage problem. In addition, in the method of this embodiment, a SiO2 protective layer 600 is formed as a stop layer for etching insurance, which further avoids the risk of over-etching and exposing the GaAs doped layer.

[0040] Further, in some embodiments, the first etching process is a reactive ion etching process (RIE); the etching gas is CHF3:O2:AR=10:1:2; the chamber pressure is 20Pa~30Pa; the power is 150W~200W. RIE etching can have good anisotropic etching, the covered part will definitely not be etched, and the uncovered position will be fully etched. Conventional etching, such as wet etching, is isotropic etching and does not have good directionality. It will etch laterally while etching downward, resulting in an expansion of the lateral size, which is not as expected. If the above conditions exceed the upper or lower limit, the etching selectivity and the shape of the etched ridge structure will not meet expectations. When the conditions are within the above range, the best etching selectivity can be obtained, and the best ridge structure morphology can be obtained.

[0041] Furthermore, in some embodiments, the height of the ridge structure is 1 μm to 1.2 μm. If the height of the ridge structure is less than 1 μm, it will affect the single-mode characteristics and the mode will be insufficiently restricted; if the etching exceeds 1.2 μm, it will be too deep and too close to the quantum well, which will increase the loss and affect the single-mode output power.

[0042] In a specific embodiment, the height of the ridge structure is 1.2 μm; the thickness of the SiN protection layer 400 is 200 nm; and the thickness of the SiO 2 protection layer 600 is 50 nm.

[0043] Further, in some embodiments, the second etching process is a reactive ion etching process; the etching gas is CHF3:O2:AR=7:1:17; the chamber pressure is 15Pa~20Pa; the power is 170W~210W. If the above conditions exceed the upper or lower limit, the etching selectivity and the shape of the etched ridge structure will not meet expectations. When the conditions are within the above range, the best etching selectivity can be obtained, and the best ridge structure morphology can be obtained.

[0044] Further, the step of providing a device substrate includes: providing a semiconductor substrate layer; A lower functional layer 100, a quantum well layer 200 and an upper functional layer 300 are sequentially formed on one side of the semiconductor substrate layer; a ridge structure R is formed on one side of the upper functional layer 300. The lower functional layer 100 includes at least a lower cladding layer and a lower waveguide layer; the upper functional layer 300 includes at least an upper waveguide layer and an upper cladding layer, and a GaAs doping layer on the upper cladding layer.

[0045] For further reference, Figure 8 , after the first etching process (or after the second etching process, if any), further comprising: Forming a top seed metal layer 700, the top seed metal layer 700 covers the surface of the device substrate on the side where the ridge structure R is located; Electroplating the top metal layer 800 on the surface of the top seed metal layer 700; For further reference, Fig. 9 , also includes: Reducing the thickness of the device substrate on the side opposite to the ridge structure R (i.e., the thickness of the semiconductor substrate layer); A bottom metal layer 900 is formed on the opposite side of the device substrate where the ridge structure R is formed.

[0046] At this point, the formation of the 980nm single-mode high-power laser is completed.

[0047] A specific implementation process is as follows: A device substrate is provided, including: A hard mask SiO2 silicon oxide layer of about 200 nm is grown on the entire surface of one side of the GaAs doped layer of the upper functional layer 300 of the device substrate, mainly to provide an etching basis for subsequent steps.

[0048] refer to Figure 2 , etching the device substrate to form a ridge structure R in the target area, including: First, a Ridge (ridge structure R) pattern is formed by photolithography, and RIE (Reactive Ion Etching) reactive ion etching transfers the pattern from the photoresist to the above-grown SiO2 hard mask. Then the photoresist is removed and cleaned, followed by dry etching to a depth of 1.2μm, and the pattern is transferred from the SiO2 hard mask to the GaAs doped layer. The Mark and Ridge (ridge structure R) formed in this step are mainly used to provide lateral refractive index steps and control current injection. Among them, the Mark and Ridge (ridge structure R) etching width are etched away except for the ridge in the middle. The part sandwiched in the middle is the Mark and Ridge (ridge structure R). The size of the Ridge (ridge structure R) from the HR high reflective surface to the AR light-emitting surface is: 1000μm×4μm (first waveguide segment R1) ~ 500μm×4μm-7μm (second waveguide segment R2) ~ 1500μm×7μm (third waveguide segment R3). After etching, BOE wet etching is performed for 40 seconds to remove the SiO2 hard mask remaining on the device substrate and expose the highly doped GaAs layer underneath.

[0049] refer to Figure 4 , forming a SiO2 protective layer 600, and then forming a SiN protective layer 400 on the surface of the SiO2 protective layer 600. The thickness of the SiO2 protective layer 600 is 50nm, and the thickness of the SiN protective layer 400 is 200nm. The two protective layers serve as protective layers for the GaAs doped layer, forming current insulation and physical protection, and providing a film layer structure for the subsequent current injection window.

[0050] refer to Figure 5a or Figure 5b , directly spin-coating the photoresist, allowing the photoresist to cover the entire device substrate to form a photoresist layer 500, and controlling the thickness of the photoresist to be flush with the surface of the SiN protective layer 400 or exceed a certain height of the SiN protective layer 400, and the excess height does not exceed 200nm.

[0051] refer to Figure 6, the first etching process is performed, and a reactive ion etching process is used to etch the surface of the device substrate on the side where the ridge structure R is formed. In this step, the etching gas is CHF3:O2:AR=10:1:2; the chamber pressure is 20Pa; and the power is 150W. The SiN protective layer 400 on the top surface of the ridge structure R and the photoresist layer 500 on the side are etched simultaneously. Since there are only the photoresist layer 500 and the SiN protective layer on the top surface of the ridge structure R on this side, only these two parts will be etched, which forms a self-alignment of the etching step. In addition, the etching speed of the photoresist layer 500 is relatively fast. At the same time, since the thickness of the SiN protective layer 400 on the top surface of the ridge structure R is much thinner than the photoresist layer 500, when the etching of the SiN protective layer 400 on the top surface of the ridge structure R is completed, there is still a portion of the photoresist layer 500 remaining, and the SiN protective layer 400 below the photoresist layer 500, that is, the SiN protective layer 400 on the side of the ridge structure will not be etched, and the SiN protective layer 400 here will not be etched through, so the GaAs doped layer on the side of the ridge structure R that should not be exposed will not be exposed, so there will be no leakage problem. In addition, in the method of this embodiment, a SiO2 protective layer 600 is formed as a stop layer for etching insurance, which further avoids the risk of over-etching and exposing the GaAs doped layer.

[0052] refer to Figure 7 The second etching process is also a reactive ion etching process, with the etching gas being CHF3:O2:AR=7:1:17; the chamber pressure being 15Pa; and the power being 170W. The SiO2 protective layer 600 on the top surface of the ridge structure R is removed, and a portion of the thickness of the SiN protective layer 400 is removed at the same time. Similar to the first etching process, there are only the SiN protective layer 400 and the SiO2 protective layer 600 on one side of the ridge structure R of the device substrate, so etching from this side will only etch these two layers, thereby achieving self-alignment of the SiO2 protective layer 600 in the target area. The SiO2 protective layer 600 on the top surface of the ridge structure R is removed to expose the GaAs doped layer in the ridge structure R so as to subsequently form a current injection window. At the same time, a portion of the thickness of the SiN protective layer 400 is removed in this process.

[0053] refer to Figure 8 , providing a conductive path for subsequent electroplating metal deposition, and also forming electrical contact with the exposed highly doped GaAs layer, a photolithography is performed to form an electroplating pattern of the top seed metal layer 700, and then a metal of target thickness is deposited to form a top metal layer 800. The top metal layer 800 serves as the P-side metal layer of the laser.

[0054] Final Reference Fig. 9, the thickness of the device substrate opposite to the ridge structure R (i.e., the thickness of the semiconductor substrate layer) is reduced; a bottom metal layer 900 is formed on the device substrate opposite to the ridge structure R. The bottom metal layer 900 serves as the N-side metal layer of the laser.

[0055] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for manufacturing a laser, characterized in that: The following steps are involved: Providing a device substrate; the device substrate includes a target area where a ridge structure is to be formed; Etching the device substrate to form a ridge structure in the target area; during the etching process, both sides of the target area of ​​the device substrate are etched away to the same depth; forming a SiN protective layer, wherein the SiN protective layer covers the surface of the device substrate on the side where the ridge structure is located; forming a photoresist layer, wherein the photoresist layer at least fills all the space on both sides of the ridge structure, and the height of the photoresist layer is not less than the height of the ridge structure; A first etching process is used to remove the SiN protective layer on the top surface of the ridge structure and simultaneously remove a portion of the thickness of the photoresist layer on both sides of the ridge structure; The remaining photoresist layer is removed.

2. The method for manufacturing a laser according to claim 1, characterized in that: Before forming the SiN protective layer, the method further includes: forming a SiO2 protective layer, wherein the SiO2 protective layer covers the surface of the device substrate on the side where the ridge structure is located; The SiN protective layer is formed on the surface of the SiO2 protective layer facing away from the device substrate.

3. The method for manufacturing a laser according to claim 2, characterized in that: After removing the remaining photoresist layer, the method further comprises: The second etching process removes the SiO2 protective layer on the top surface of the ridge structure and removes a portion of the SiN protective layer.

4. The method for manufacturing a laser according to claim 1, characterized in that: The photoresist layer is only formed on two sides of the ridge structure, and the height of the photoresist layer is the same as the height of the ridge structure.

5. The method for manufacturing a laser according to claim 1, characterized in that: The height of the photoresist layer is higher than the height of the ridge structure, and the photoresist layer also covers the top surface of the ridge structure; In the first etching process, the photoresist layer covering the top surface of the ridge structure is first removed in one etching step, and then the SiN protective layer on the top surface of the ridge structure is etched.

6. The method for manufacturing a laser according to claim 1, characterized in that: The first etching process is a reactive ion etching process; The etching gas is CHF3:O2:AR=10:1:2; The chamber pressure is 20Pa~30Pa; The power is 150W~200W.

7. The method for manufacturing a laser according to claim 3, characterized in that: The height of the ridge structure is 1 μm to 1.2 μm; The thickness of the SiN protective layer is 200 nm; The thickness of the SiO2 protective layer is 50nm.

8. The method for manufacturing a laser according to claim 7, characterized in that: The second etching process is a reactive ion etching process; The etching gas is CHF3:O2:AR=7:1:17; The chamber pressure is 15Pa~20Pa; The power is 170W~210W.

9. The method for manufacturing a laser according to claim 1, characterized in that: After the first etching process, the method further includes: forming a top surface seed metal layer, wherein the top surface seed metal layer covers the surface of the device substrate on the side where the ridge structure is located; Electroplating the surface of the top seed metal layer to form a top metal layer; Thinning the thickness of the device substrate on the side opposite to the side where the ridge structure is formed; A bottom metal layer is formed on the opposite side of the device substrate where the ridge structure is formed.

10. The method for manufacturing a laser according to claim 1, characterized in that: The step of providing a device substrate comprises: providing a semiconductor substrate layer; Sequentially forming a lower functional layer, a quantum well layer and an upper functional layer on one side of the semiconductor substrate layer; The ridge structure is formed on one side of the upper functional layer.

Images