A semiconductor laser and a method for manufacturing the same

Abstract

The present invention provides a semiconductor laser and a method for manufacturing the same. The method for manufacturing the semiconductor laser includes: forming a semiconductor structure, the semiconductor structure including a substrate, an epitaxial layer located on one side surface of the substrate, a plurality of ridge waveguides arranged in parallel and spaced apart on the side surface of the epitaxial layer facing away from the substrate, an insulating layer covering at least the side walls of the ridge waveguides, and a first electrode layer covering at least the insulating layer; a cleavage region is formed between adjacent ridge waveguides, and the insulating layer and the first electrode layer both extend to the cleavage region; removing the first electrode layer and the insulating layer located in the cleavage region; performing a first cleavage on the semiconductor structure along the cleavage region to obtain a plurality of bars. By removing the first electrode layer and the insulating layer located in the cleavage region before the first cleavage, it is ensured that the bars have flat first and second cleavage surfaces, thereby ensuring that the front and rear cavity surfaces of the resonant cavity are parallel to each other, and finally ensuring the light-emitting performance of the semiconductor laser.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, and particularly to a semiconductor laser and a method for manufacturing the same. Background Art

[0002] A semiconductor laser is a semiconductor device that uses semiconductor materials to generate laser light. The working principle of a semiconductor laser is as follows: When a semiconductor light-emitting material is excited, electron-hole pairs are generated and undergo transitions between energy bands, achieving population inversion of non-equilibrium carriers. Then, they oscillate and feedback in a resonant cavity, ultimately realizing the function of laser emission. Currently, the most widely used semiconductor lasers are those with a Fabry-Perot resonant cavity. The manufacturing process generally includes: forming a semiconductor structure, which includes a substrate, an epitaxial layer on one side surface of the substrate, a plurality of ridge waveguides arranged in parallel and spaced apart on the side surface of the epitaxial layer facing away from the substrate, an insulating layer covering at least the sidewalls of the ridge waveguides, and a first electrode layer covering at least the insulating layer. A cleavage region is formed between adjacent ridge waveguides, and both the insulating layer and the first electrode layer extend to the cleavage region. The substrate, epitaxial layer, and ridge waveguides form an epitaxial wafer, and the first electrode layer is a metal layer; a second electrode layer is formed on the side of the epitaxial layer facing away from the P electrode; a first cleavage is performed along the cleavage region to obtain a bar, which has a first cleavage surface and a second cleavage surface arranged oppositely; a reflective film and an antireflection film are respectively formed on the first cleavage surface and the second cleavage surface of the bar to form a resonant cavity; a second cleavage is performed on the bar to obtain a semiconductor laser, and the direction of the second cleavage is perpendicular to the direction of the first cleavage. Generally, the first cleavage step includes: forming a shallow scratch in the cleavage region and using a dicing machine to dice along the scratch.

[0003] However, since the metal layer and the insulating layer are arranged in a polycrystalline orientation, while the epitaxial wafer is arranged in a single-crystalline orientation, and the cleavage directions of the insulating layer and the metal layer are inconsistent with the cleavage direction of the epitaxial wafer, the cleavage direction of the epitaxial wafer during the first cleavage is affected by the cleavage directions of the insulating layer and the metal layer, resulting in an inability to obtain a flat front cavity surface and / or rear cavity surface. Even water ripples may appear on the front cavity surface and / or rear cavity surface, causing the front cavity surface and the rear cavity surface of the semiconductor laser to be not completely parallel, affecting the resonant effect of the resonant cavity, and further affecting the light-emitting performance of the semiconductor laser. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the metal layer and the insulating layer on the P surface affect the structure of the laser resonant cavity during cleavage and reduce the light-emitting performance of the semiconductor laser in the prior art, thereby providing a method for manufacturing a semiconductor laser.

[0005] The present invention provides a method for manufacturing a semiconductor laser, comprising: forming a semiconductor structure, the semiconductor structure including a substrate, an epitaxial layer located on one side surface of the substrate, a plurality of ridge waveguides arranged in parallel and spaced apart on one side surface of the epitaxial layer facing away from the substrate, an insulating layer covering at least the side walls of the ridge waveguides, and a first electrode layer covering at least the insulating layer; a cleavage region is formed between adjacent ridge waveguides, and both the insulating layer and the first electrode layer extend to the cleavage region; removing the first electrode layer and the insulating layer located in the cleavage region; performing a first cleavage on the semiconductor structure along the cleavage region to obtain a plurality of bars, the bars having a first cleavage surface and a second cleavage surface arranged in parallel and opposite to each other.

[0006] Optionally, the step of removing the first electrode layer and the insulating layer located in the cleavage region includes: forming a first mask layer on one side surface of the first electrode layer facing away from the epitaxial layer, the first mask layer exposing the first electrode layer located in the cleavage region; using a wet etching process and / or a plasma cleaning process to remove the first electrode layer and the insulating layer located in the cleavage region; after removing the first electrode layer and the insulating layer located in the cleavage region, removing the first mask layer.

[0007] Optionally, the first electrode layer includes a Ti layer, a Pt layer, and an Au layer stacked in sequence, the Ti layer being located on one side of the insulating layer facing away from the epitaxial layer; the insulating layer is made of silicon oxide or silicon nitride. The step of removing the first electrode layer and the insulating layer located in the cleavage region includes: using a wet etching process to remove the Au layer located in the cleavage region; after removing the Au layer located in the cleavage region, using a plasma cleaning process to remove the Pt layer located in the cleavage region; after removing the Pt layer located in the cleavage region, using a wet etching process to remove the Ti layer and the insulating layer located in the cleavage region.

[0008] Optionally, an iodine solution of potassium iodide is used to etch the Au layer located in the cleavage region.

[0009] Optionally, the mass ratio of the iodine solution of potassium iodide is I 2 ∶KI∶H 2 O=(40g - 80g):(100g - 150g):100g, and the etching time is 60s to 180s.

[0010] Optionally, the process parameters for using a plasma cleaning process to remove the Pt layer located in the cleavage region include: the flow rate of the inert gas is 30sccm to 35sccm, the radio frequency power is 60W to 80W, the vacuum degree is 3.0×10 -3 Pa to 5.0×10 - 3 Pa, and the removal time is 10min to 20min.

[0011] Optionally, a buffered oxide etchant is used to etch the Ti layer and the insulating layer located in the cleavage region, and the etching time is 45 s to 55 s.

[0012] Optionally, after removing the first electrode layer and the insulating layer located in the cleavage region, before performing the first cleavage along the cleavage region, it further includes: forming a second electrode layer on the surface of the substrate facing away from the epitaxial layer.

[0013] Optionally, after performing the first cleavage on the semiconductor structure along the cleavage region to obtain a plurality of bar strips, it further includes: forming a reflective film on the first cleavage surface and an antireflection film on the second cleavage surface; after forming the reflective film and the antireflection film on the bar strips, performing a second cleavage along the cleavage region perpendicular to the first cleavage surface and the second cleavage surface to obtain a plurality of semiconductor lasers.

[0014] The present invention also provides a semiconductor laser, which is prepared by using the preparation method of the semiconductor laser.

[0015] The technical solution of the present invention has the following advantages:

[0016] 1. In the preparation method of the semiconductor laser provided by the present invention, since the first electrode layer and the insulating layer located in the cleavage region are removed before performing the first cleavage on the semiconductor structure along the cleavage region, when performing the first cleavage, the cracking directions of the epitaxial layer and the ridge waveguide are split in one direction and are not affected by the insulating layer and the metal layer, ensuring that the bar strip has a flat first cleavage surface and a flat second cleavage surface, thereby ensuring that the front cavity surface and the rear cavity surface of the resonant cavity are parallel to each other, and further ensuring the light emission performance of the semiconductor laser. At the same time, removing the first electrode layer and the insulating layer located in the cleavage region before performing the first cleavage facilitates the first cleavage, is beneficial to reducing the wear degree of the cleavage knife, and prolongs the service life of the cleavage knife.

[0017] 2. In the preparation method of the semiconductor laser provided by the present invention, the Au layer located in the cleavage region is removed by a wet etching process, the Pt layer located in the cleavage region is removed by a plasma cleaning process, and the Ti layer and the insulating layer located in the cleavage region are removed by a wet etching process, which can avoid damaging the epitaxial layer and there is no residue when removing the first electrode layer and the insulating layer located in the cleavage region.

[0018] 3. In the semiconductor laser provided by the present invention, the front cavity surface and the rear cavity surface of the resonant cavity are parallel to each other, and further ensure the light emission performance of the semiconductor laser. Description of the Drawings

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 Process flow chart of the preparation method of the semiconductor laser provided by the embodiment of the present invention;

[0021] Figures 2 to 16 Schematic structural diagram during the preparation process of the semiconductor laser provided by the embodiment of the present invention;

[0022] Description of reference numerals:

[0023] 1 - Substrate; 2 - Initial epitaxial layer; 21 - Lower confinement layer; 22 - Lower waveguide layer; 23 - Active layer; 24 - Upper waveguide layer; 25 - Upper confinement layer; 26 - Cap layer; 27 - Epitaxial layer; 28 - Ridge waveguide; 29 - Cleavage region; 3 - Second mask layer; 4 - Initial insulating layer; 41 - Insulating layer; 42 - Electron injection window; 5 - Third mask layer; 6 - First electrode layer; 7 - First mask layer; 8 - Second electrode layer; 9 - Bar. Specific embodiments

[0024] The following will clearly and completely describe the technical solutions of the present invention with reference to the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0026] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] See Figure 1 , this embodiment provides a preparation method of a semiconductor laser, including:

[0028] S1. Form a semiconductor structure, which includes a substrate, an epitaxial layer located on one side surface of the substrate, a plurality of ridge waveguides arranged in parallel and spaced apart on the side surface of the epitaxial layer facing away from the substrate, an insulating layer covering at least the side walls of the ridge waveguides, and a first electrode layer covering at least the insulating layer; a cleavage region is formed between adjacent ridge waveguides, and both the insulating layer and the first electrode layer extend to the cleavage region;

[0029] S2. Remove the first electrode layer and the insulating layer located in the cleavage region;

[0030] S3. Perform a first cleavage on the semiconductor structure along the cleavage region to obtain a plurality of bars, and the bars have a first cleavage surface and a second cleavage surface that are parallel and oppositely arranged.

[0031] In the preparation method of the above semiconductor laser, since the first electrode layer and the insulating layer in the cleavage region are removed before performing the first cleavage on the semiconductor structure along the cleavage region, when the first cleavage is performed, the cracking directions of the epitaxial layer and the ridge waveguides crack in one direction and are not affected by the insulating layer and the metal layer, ensuring that the bars have flat first and second cleavage surfaces, thereby ensuring that the front cavity surface and the rear cavity surface of the resonant cavity are parallel to each other, and further ensuring the light-emitting performance of the semiconductor laser.

[0032] It should be understood that the presence of the first electrode layer and the insulating layer makes it necessary to perform cleavage at a low speed and a relatively high knife pressure, which will wear the cleavage knife. By removing the first electrode layer and the insulating layer in the cleavage region before performing the first cleavage, the preparation method of the above semiconductor laser facilitates the first cleavage, is beneficial to reducing the wear degree of the cleavage knife, prolongs the service life of the cleavage knife, and thus reduces the use cost of the cleavage knife.

[0033] Specifically, the covering area of the insulating layer includes the side walls of the ridge waveguides and the cleavage region; the covering area of the first electrode layer includes the top surface of the ridge waveguides and the surface of the insulating layer. The following Figures 2 - 16 Describe the preparation method of the semiconductor laser clearly and completely.

[0034] See Figure 2 , provide the substrate 1. Specifically, the substrate 1 has a first surface and a second surface arranged oppositely, and the material of the substrate 1 is GaAs. In other embodiments, the substrate 1 can be other materials.

[0035] See Figure 3, an initial epitaxial layer 2 is prepared; specifically, the steps of preparing the initial epitaxial layer 2 include: according to the required laser wavelength, a plurality of functional layers are sequentially grown on the first surface of the substrate 1, and the functional layers include: a lower confinement layer 21, a lower waveguide layer 22, an active layer 23, an upper waveguide layer 24, an upper confinement layer 25, and a cap layer 26, and one side of the lower confinement layer 21 facing away from the lower waveguide layer 22 is in contact with the first surface of the substrate 1. Specifically, the process of growing the functional layers on the substrate 1 includes but is not limited to metal-organic chemical vapor deposition (MOCVD) process and molecular beam epitaxy (MBE) process.

[0036] See Figure 4 , a patterned second mask layer 3 is formed on the surface of the initial epitaxial layer 2 facing away from the substrate 1. Specifically, the steps of forming the patterned second mask layer 3 include: using a spin coater, a layer of photoresist is uniformly coated on the surface of the initial epitaxial layer 2 facing away from the substrate 1 as an initial mask layer, and then the initial mask layer is exposed according to the requirements of the ridge waveguide structure design, and then developed. The photoresist in the pre-formed ridge waveguide region is retained, while the photoresist in the cleavage region is removed to obtain the second mask layer 3.

[0037] See Figure 5 , the initial epitaxial layer 2 is etched to remove a part of the thickness of the upper waveguide layer 24, so as to form the epitaxial layer 27 and a plurality of ridge waveguides 28 arranged in parallel and spaced apart, and the cleavage region 29 is between adjacent ridge waveguides 28.

[0038] See Figure 6 , the second mask layer 3 on the surface of the ridge waveguide 28 is removed.

[0039] See Figure 7 , an initial insulating layer 4 covering the ridge waveguide 28 and the cleavage region 29 is formed; the initial insulating layer 4 is formed by plasma enhanced chemical vapor deposition (PECVD) method or electron beam evaporation method. The material of the insulating layer is silicon oxide or silicon nitride.

[0040] See Figure 8 , a third mask layer 5 covering the initial insulating layer 4 is formed, and the third mask layer 5 exposes the initial insulating layer 4 above the ridge waveguide 28.

[0041] See Figure 9 , the initial insulating layer 4 above the ridge waveguide 28 is etched to form an electron injection window 42, so as to obtain the insulating layer 41.

[0042] See Figure 10, remove the third mask layer 5.

[0043] Refer to Figure 11 , form a first electrode layer 6 on the side of the insulating layer 41 facing away from the epitaxial layer 27, and the first electrode layer 6 covers the insulating layer 41 and the electron injection window 42. Specifically, the process of forming the first electrode layer 6 includes, but is not limited to, PECVD process or vacuum evaporation process. The first electrode layer 6 includes a Ti layer, a Pt layer, and an Au layer stacked in sequence, and the Ti layer covers the insulating layer 41 and the electron injection window 42.

[0044] Refer to Figures 12 - 13 , remove the first electrode layer 6 and the insulating layer 41 located in the cleavage region 29. Specifically, the steps of removing the first electrode layer 6 and the insulating layer 41 located in the cleavage region 29 include:

[0045] Refer to Figure 12 , form a first mask layer 7 on the surface of the first electrode layer 6 facing away from the epitaxial layer 27, and the first mask layer 7 exposes the cleavage region 29;

[0046] Refer to Figure 13 , use a wet etching process and / or a plasma cleaning process to remove the first electrode layer 6 and the insulating layer 41 located in the cleavage region 29. Specifically, use a wet etching process to remove the Au layer located in the cleavage region 29; after removing the Au layer located in the cleavage region 29, use a plasma cleaning process to remove the Pt layer located in the cleavage region 29; after removing the Pt layer located in the cleavage region 29, use a wet etching process to remove the Ti layer and the insulating layer 41 located in the cleavage region 29. The above method can remove the first electrode layer 6 and the insulating layer 41 located in the cleavage region 29 while avoiding damage to the epitaxial layer and without residue.

[0047] Further, use an iodine solution of potassium iodide to etch the Au layer located in the cleavage region 29. Among them, the mass ratio of the iodine solution of potassium iodide is I 2 ∶KI∶H 2 O=(40g - 80g):(100g - 150g):100g, and the etching time is 50s - 100s; it should be understood that the greater the concentration of I 2 , the shorter the etching time; preferably, the mass ratio of the iodine solution of potassium iodide is I 2 ∶KI∶DI = 65g:115g:100g, and the etching time is 55s - 65s.

[0048] Further, the process parameters for removing the Pt layer located in the cleavage region 29 by using a plasma cleaning process include: the flow rate of the inert gas is 30 sccm to 35 sccm, the radio frequency power is 60 W to 80 W, the vacuum degree is 3.0×10 -3 Pa to 5.0×10 -3 Pa, and the removal time is 10 min to 20 min. Exemplarily, the flow rate of the inert gas is 32 sccm, the radio frequency power is 70 W, the vacuum degree is 4.0×10 -3 Pa, and the removal time is 15 min; wherein, the inert gas includes but is not limited to argon.

[0049] Further, a buffered oxide etchant is used to etch the Ti layer and the insulating layer 41 located in the cleavage region 29, and the etching time is 45 s to 55 s. Specifically, the buffered oxide etchant (BOE, Buffered Oxide Etch) is a liquid obtained by mixing 49% hydrofluoric acid and 40% NHF 4 solution in a certain volume ratio, wherein the solvent of the solution is preferably deionized water. Preferably, HF (49%): NHF 4 (40%) = 1:6. In other embodiments, a buffered hydrofluoric acid (BHF) solution may also be used to etch the Ti layer and the insulating layer 41 in the cleavage region 29.

[0050] See Figure 14 , after removing the first electrode layer 6 and the insulating layer 41 located in the cleavage region 29, the first mask layer 7 is removed.

[0051] See Figure 15 , the side of the substrate 1 facing away from the epitaxial layer 27 is thinned, and a second electrode layer 8 is formed on the thinned surface. The process for forming the first electrode layer 6 includes but is not limited to PECVD process or vacuum evaporation process. One of the first electrode layer 6 and the second electrode layer 8 is a P electrode, and the other is an N electrode. Preferably, the first electrode layer 6 is a P electrode, and the second electrode layer 8 is an N electrode.

[0052] See Figure 16 , the semiconductor structure is first cleaved along the cleavage region 29 to obtain a plurality of bars 9, and the bars 9 have a first cleavage plane and a second cleavage plane that are parallel and oppositely arranged, and the first cleavage plane and the second cleavage plane are parallel to the extending direction of the bars 9.

[0053] Further, after the semiconductor structure is first cleaved along the cleavage region 29 to obtain a plurality of bars 9, it further includes: forming a reflective film on the first cleavage plane and an antireflection film on the second cleavage plane to obtain a complete resonant cavity.

[0054] Further, after forming the reflective film and the antireflection film on the bar 9, a second cleavage is performed in a direction perpendicular to the first cleavage plane and the second cleavage plane to obtain a plurality of semiconductor lasers.

[0055] This embodiment also provides a semiconductor laser, which is prepared by using the preparation method of the above semiconductor laser. The front cavity surface and the rear cavity surface of the resonant cavity are parallel to each other, thereby ensuring the light-emitting performance of the semiconductor laser.

[0056] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for fabricating a semiconductor laser, characterized in that, comprising: forming a semiconductor structure, the semiconductor structure including a substrate, an epitaxial layer on one side surface of the substrate, a plurality of ridge waveguides arranged in parallel and spaced apart on the side surface of the epitaxial layer facing away from the substrate, an insulating layer covering at least the sidewalls of the ridge waveguides, and a first electrode layer covering at least the insulating layer; a cleavage region is formed between adjacent ridge waveguides, and the insulating layer and the first electrode layer both extend to the cleavage region; forming a first mask layer on the side surface of the first electrode layer facing away from the epitaxial layer, the first mask layer exposing the first electrode layer located in the cleavage region; removing the first electrode layer and the insulating layer located in the cleavage region by using a wet etching process and / or a plasma cleaning process; after removing the first electrode layer and the insulating layer located in the cleavage region, removing the first mask layer; performing a first cleavage on the semiconductor structure along the cleavage region to obtain a plurality of bars, the bars having a first cleavage surface and a second cleavage surface arranged in parallel and opposite to each other.

2. The method for fabricating a semiconductor laser according to claim 1, characterized in that, the first electrode layer includes a Ti layer, a Pt layer, and an Au layer stacked in sequence, the Ti layer being on the side of the insulating layer facing away from the epitaxial layer; the insulating layer is made of silicon oxide or silicon nitride; the step of removing the first electrode layer and the insulating layer located in the cleavage region includes: removing the Au layer located in the cleavage region by using a wet etching process; after removing the Au layer located in the cleavage region, removing the Pt layer located in the cleavage region by using a plasma cleaning process; after removing the Pt layer located in the cleavage region, removing the Ti layer and the insulating layer located in the cleavage region by using a wet etching process.

3. The method for fabricating a semiconductor laser according to claim 2, characterized in that, using an iodine solution of potassium iodide to etch the Au layer located in the cleavage region.

4. The method for fabricating a semiconductor laser according to claim 3, characterized in that, The mass ratio of the iodine solution of potassium iodide is I 2 ∶KI∶H 2 O=(40 g - 80 g):(100 g - 150 g):100 g, and the etching time is 50 s to 100 s.

5. The method for fabricating a semiconductor laser according to claim 2, characterized in that, The process parameters for removing the Pt layer located in the cleavage region by using the plasma cleaning process include: the flow rate of the inert gas is 30 sccm to 35 sccm, the radio frequency power is 60 W to 80 W, the vacuum degree is 3.0×10 -3 Pa to 5.0×10 -3 Pa, and the removal time is 10 min to 20 min.

6. The method for fabricating a semiconductor laser according to claim 2, characterized in that, using a buffered oxide etchant to etch the Ti layer and the insulating layer located in the cleavage region, and the etching time is 45 s to 55 s.

7. The method for fabricating a semiconductor laser according to any one of claims 1-6, characterized in that, after removing the first electrode layer and the insulating layer located in the cleavage region and before performing the first cleavage along the cleavage region, further comprising: forming a second electrode layer on the side surface of the substrate facing away from the epitaxial layer.

8. The method for fabricating a semiconductor laser according to claim 1, characterized in that, after performing the first cleavage on the semiconductor structure along the cleavage region to obtain a plurality of bars, further comprising: forming a reflective film on the first cleavage surface and forming an antireflection film on the second cleavage surface; After forming the reflective film and the antireflection film on the bar, a second cleavage is performed in a direction perpendicular to the first cleavage plane and the second cleavage plane to obtain a plurality of semiconductor lasers.

9. A semiconductor laser, characterized in that, it is prepared by using the preparation method of the semiconductor laser according to any one of claims 1-8.

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