High-reliability DFB laser and preparation method thereof

Abstract

The invention discloses a high-reliability DFB laser and a preparation method thereof, and relates to the field of lasers. The DFB laser comprises a substrate, a bottom electrode, a first epitaxial layer, a second epitaxial layer, a passivation layer, a top electrode and a dielectric film. The second epitaxial layer comprises a body part and at least one ridge waveguide structure, and an isolation groove for exposing the first epitaxial layer is arranged between the body part and the ridge waveguide structure; the passivation layer covers the surface of the body part, the surface and the side wall of the ridge waveguide structure and the side wall and the bottom wall of the isolation groove; the top electrode covers the ridge waveguide structure and the side wall and the bottom wall of the isolation groove, and at least partially extends to the surface of the body part; the dielectric film covers the ridge waveguide structure; the top surface of the dielectric film is higher than the top surface of the top electrode, and the hardness of the dielectric film is greater than that of the top electrode. According to the invention, the yield of the DFB laser can be improved, and the reliability of the DFB laser can be improved.

Description

Technical Field

[0001] The present invention relates to the field of lasers, and in particular to a high-reliability DFB laser and a preparation method thereof. Background Art

[0002] There is basically no significant difference in height between the table of a traditional DFB laser and the ridge waveguide structure. The surface of the ridge waveguide structure is Au, which is very soft. During end-face optical coating and subsequent testing and sorting, it is easy for the strip and nozzle to crush the ridge waveguide. The crushing of the ridge waveguide will also cause certain reliability risks, so the AOI will select it for scrapping, affecting the final actual output yield. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a high-reliability DFB laser and a preparation method thereof, which can improve the yield and reliability of the DFB laser.

[0004] In order to solve the above technical problems, the present invention provides a high-reliability DFB laser, which includes:

[0005] a substrate comprising opposing first and second surfaces;

[0006] a bottom electrode disposed on the second surface of the substrate;

[0007] a first epitaxial layer disposed on the first surface;

[0008] a second epitaxial layer disposed on the first epitaxial layer; the second epitaxial layer comprising a body portion and at least one ridge waveguide structure, an isolation trench exposing the first epitaxial layer being disposed between the body portion and the ridge waveguide structure;

[0009] a passivation layer covering a surface of the body portion, a surface and sidewalls of the ridge waveguide structure, and sidewalls and a bottom wall of the isolation trench;

[0010] a top electrode covering the passivation layer on the ridge waveguide structure, the passivation layer on the sidewalls and bottom wall of the isolation trench, and at least partially extending onto the passivation layer on the surface of the body portion; the top electrode electrically contacts the ridge waveguide structure through an opening provided in the passivation layer; and

[0011] A dielectric film covers the top electrode above the ridge waveguide structure; a top surface of the dielectric film is higher than a top surface of the top electrode, and a hardness of the dielectric film is greater than a hardness of the top electrode.

[0012] As an improvement of the above technical solution, the dielectric film also covers the bottom wall and the top electrode above the side wall of the isolation trench;

[0013] and the dielectric film at least partially extends onto the surface of the main body;

[0014] An extension distance of the dielectric film on the surface of the body portion is smaller than an extension distance of the top electrode on the surface of the body portion, so that at least a portion of the top electrode is exposed outside the dielectric film.

[0015] As an improvement of the above technical solution, the film stress of the dielectric film is ≤200 MPa.

[0016] As an improvement of the above technical solution, the dielectric film includes a first silicon oxide film and a silicon nitride film stacked in sequence; the thickness of the dielectric film is 500nm to 700nm;

[0017] A ratio of a thickness of the first silicon oxide film to a thickness of the silicon nitride film is 1:1 to 1:5.

[0018] As an improvement of the above technical solution, the dielectric film includes a second silicon oxide film and a silicon oxynitride film stacked in sequence; the thickness of the dielectric film is 500nm to 700nm;

[0019] A ratio of a thickness of the second silicon oxide film to a thickness of the silicon oxynitride film is 1:1 to 1:3.

[0020] As an improvement of the above technical solution, it further includes an adhesion layer, which is provided below the dielectric film;

[0021] The adhesion layer is a Ti layer, a Cr layer or a TiW layer, and has a thickness of 10 nm to 30 nm.

[0022] As an improvement of the above technical solution, the adhesion layer is a Ti layer with a thickness of 10nm to 20nm;

[0023] The film stress of the dielectric film is ≤100 MPa.

[0024] As an improvement of the above technical solution, the first epitaxial layer includes a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper confinement layer, a grating layer and an etching stop layer sequentially stacked on the first surface;

[0025] The second epitaxial layer includes an InP cladding layer and a contact layer sequentially stacked on the first epitaxial layer.

[0026] Accordingly, the present invention also discloses a method for preparing a high-reliability DFB laser, which is used to prepare the above-mentioned high-reliability DFB laser, and comprises:

[0027] forming a first epitaxial layer and a second epitaxial layer on the first surface of the substrate;

[0028] Etching the second epitaxial layer to form an isolation trench exposing the first epitaxial layer, thereby obtaining a first intermediate body; wherein the isolation trench separates the second epitaxial layer into a main body portion and at least one ridge waveguide structure;

[0029] forming a passivation layer on the first intermediate body, and forming an opening in the passivation layer above the ridge waveguide structure to obtain a second intermediate body;

[0030] forming a top electrode to obtain a third intermediate;

[0031] forming a dielectric film on the surface of the third intermediate and patterning the film;

[0032] A bottom electrode is formed on the second surface of the substrate.

[0033] As an improvement of the above technical solution, the step of forming a dielectric film on the surface of the third intermediate and patterning the film includes:

[0034] forming an adhesion layer on the surface of the third intermediate;

[0035] forming a dielectric film on the surface of the adhesion layer;

[0036] The dielectric film and the adhesion layer are etched to pattern both.

[0037] The implementation of the present invention has the following beneficial effects:

[0038] A high-reliability DFB laser according to one embodiment of the present invention includes a substrate, a bottom electrode, a first epitaxial layer, a second epitaxial layer, a passivation layer, a top electrode, and a dielectric film. The second epitaxial layer includes a body portion and at least one ridge waveguide structure, with an isolation trench exposing the first epitaxial layer between the body portion and the ridge waveguide structure. The passivation layer covers the surface of the body portion, the surface and sidewalls of the ridge waveguide structure, and the sidewalls and bottom wall of the isolation trench. The top electrode covers the passivation layer on the ridge waveguide structure, the passivation layer on the sidewalls and bottom wall of the isolation trench, and at least partially extends onto the passivation layer on the surface of the body portion. The dielectric film covers the top electrode above the ridge waveguide structure. The top surface of the dielectric film is higher than the top surface of the top electrode, and the dielectric film has a greater hardness than the top electrode. This dielectric film effectively prevents damage and scratches to the ridge waveguide structure caused by the strip and the nozzle during subsequent operations, effectively improving the yield rate and enhancing the reliability of the DFB laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1 is a schematic structural diagram of a high-reliability DFB laser according to an embodiment of the present invention;

[0040] Figure 2 1 is a schematic structural diagram of a substrate, a first epitaxial layer, and a second epitaxial layer in one embodiment of the present invention;

[0041] Figure 3 This is a schematic structural diagram of the first intermediate obtained after step S2 in one embodiment of the present invention;

[0042] Figure 4 This is a schematic structural diagram of the second intermediate obtained after step S3 in one embodiment of the present invention;

[0043] Figure 5 This is a schematic structural diagram of the third intermediate obtained after step S4 in one embodiment of the present invention;

[0044] In the figure: 100 is the substrate, 110 is the first surface, 120 is the second surface, 200 is the bottom electrode, 300 is the first epitaxial layer, 301 is the buffer layer, 302 is the lower confinement layer, 303 is the lower waveguide layer, 304 is the active layer, 305 is the upper waveguide layer, 306 is the upper confinement layer, 307 is the transition layer, 308 is the grating layer, 309 is the grating buried layer, 310 is the etching stop layer, 400 is the second epitaxial layer, 410 is the ridge waveguide structure, 420 is the main body, 430 is the isolation groove, 411 is the InP cladding layer, 412 is the contact layer, 413 is the barrier gradient layer, 500 is the passivation layer, 510 is the opening, 600 is the top electrode, 700 is the dielectric film, and 800 is the adhesion layer. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0046] See also Figure 1 and Figure 2 As a first aspect of the present invention, the present invention provides a DFB laser, which includes a substrate 100, a bottom electrode 200, a first epitaxial layer 300, a second epitaxial layer 400, a passivation layer 500, a top electrode 600, and a dielectric film 700. Specifically, in the thickness direction of the substrate (i.e., the vertical direction), the substrate 100 includes a first surface 110 and a second surface 120 opposite to each other, and the bottom electrode 200 is disposed on the second surface 120. The first epitaxial layer 300 is disposed on the first surface 110, and the second epitaxial layer 400 is disposed on the first epitaxial layer 300. See Figures 3 to 5Along a horizontal direction perpendicular to the thickness of the substrate, the second epitaxial layer 400 includes a body portion 420 and at least one ridge waveguide structure 410. An isolation trench 430 is provided between the body portion 420 and the ridge waveguide structure 410, exposing the first epitaxial layer 300. A passivation layer 500 covers the surface of the body portion 420, the surface and sidewalls of the ridge waveguide structure 410, and the sidewalls and bottom walls of the isolation trench 430. The passivation layer 500 located above the ridge waveguide structure 410 defines an opening 510 that exposes the ridge waveguide structure 410. A top electrode 600 covers the passivation layer 500 on the ridge waveguide structure 410 and the sidewalls and bottom walls of the isolation trench 430, and extends at least partially onto the passivation layer 500 on the surface of the body portion 420. The top electrode 600 electrically contacts the ridge waveguide structure 410 through the opening 510. The dielectric film 700 covers the top electrode 600 above the ridge waveguide structure 410. The top surface of the dielectric film 700 is higher than the top surface of the top electrode 600, and the dielectric film 700 has a greater hardness than the top electrode 600. This structure effectively prevents the DFB laser from damaging the ridge waveguide structure 410 and the second epitaxial layer 400 by the sliver and the nozzle during subsequent placement of the sliver. This improves the yield and reliability of the DFB laser.

[0047] Specifically, in some embodiments, the substrate 100 is an InP substrate, which is conductive. More specifically, the substrate 100 is an N-type InP doped with Si, and its doping concentration is 8×10 17 cm -3 ~1×10 18 cm -3 .

[0048] Specifically, in some embodiments, the first epitaxial layer 300 includes, but is not limited to, a waveguide layer, an active layer, and a grating layer commonly found in the art. Preferably, in some embodiments, the first epitaxial layer 300 includes a buffer layer 301, a lower confinement layer 302, a lower waveguide layer 303, an active layer 304, an upper waveguide layer 305, an upper confinement layer 306, a transition layer 307, a grating layer 308, a grating buried layer 309, and an etch-stop layer 310, stacked sequentially on the first surface 110.

[0049] Specifically, in some embodiments, the buffer layer 301 may be an N-type InP layer, but is not limited thereto. The thickness of the buffer layer 301 is 0.5 μm to 2 μm, and its doping concentration is 1×10 16 cm -3 ~5×10 17 cm -3 .

[0050] Specifically, in some embodiments, the lower confinement layer 302 is an N-type AlInAs layer with a thickness of 50 nm to 300 nm and a gradient band gap, and can limit the diffusion of carriers and light toward the substrate 100 .

[0051] Specifically, in some embodiments, the lower waveguide layer 303 is an undoped AlGaInAs layer, whose refractive index and bandgap vary linearly. Specifically, from the active layer 304 to the lower confinement layer 302, the bandgap of the lower waveguide layer 303 increases, while the refractive index decreases. This allows the lower waveguide layer 303 to function as an optical waveguide and carrier confinement layer. The thickness of the lower waveguide layer 303 ranges from 50 nm to 200 nm.

[0052] Specifically, in some embodiments, the active layer 304 is a periodic structure formed by alternating AlGaInAs well layers and AlGaInAs barrier layers, with a period number of 4 to 10. The thickness of the AlGaInAs well layers is 5 nm to 10 nm, and the thickness of the AlGaInAs barrier layers is 10 nm to 20 nm.

[0053] Specifically, in some embodiments, the upper waveguide layer 305 is an undoped AlGaInAs layer that is symmetrical with the lower waveguide layer 303, meaning its refractive index and bandgap vary linearly. Specifically, from the active layer 304 to the upper confinement layer 306, the bandgap of the upper waveguide layer 305 increases, while its refractive index decreases. This allows the upper waveguide layer 305 to function as an optical waveguide and carrier confinement layer.

[0054] Specifically, in some embodiments, upper confinement layer 306 is a p-type AlInAs layer with a thickness of 50 nm to 300 nm and a gradient bandgap. Upper confinement layer 306 can enhance the bandgap matching between upper waveguide layer 305 and subsequent layers, strengthen carrier confinement, and enhance light confinement.

[0055] Specifically, in some embodiments, the transition layer 307 is a non-doped InP layer with a thickness of 5 nm to 15 nm.

[0056] Specifically, in some embodiments, the grating layer 308 is a non-doped InGaAsP layer with a thickness of 30 nm to 50 nm, and the grating structure is formed by photolithography and etching.

[0057] Specifically, in some embodiments, the grating buried layer 309 is an InP layer with a thickness of 50 nm to 200 nm.

[0058] Specifically, in some embodiments, the etching stop layer 310 is a P-type InGaAsP layer, which can protect the grating layer 308 from being corroded during the etching process of the ridge waveguide structure 410. The thickness of the etching stop layer 310 is 30nm to 50nm, and its doping concentration is 5×10 17 cm -3 ~5×10 18 cm -3 .

[0059] Specifically, in some embodiments, the second epitaxial layer 400 includes an InP cladding layer 411 and a contact layer 412 , but is not limited thereto.

[0060] The InP cladding layer 411 is a P-type InP layer with a thickness of 1.5 μm to 2 μm and a doping concentration of 5×10 16 cm -3 ~5×10 17 cm -3 The InP cladding layer 411 can further limit the lateral diffusion of carriers and also reduce the leakage rate.

[0061] The contact layer 412 is a P-type InGaAs layer with a thickness of 80 nm to 300 nm and a doping concentration of 1×10 19 cm -3 ~5×10 19 cm -3 The contact layer 412 can reduce the electrode contact resistance and optimize the photoelectric conversion efficiency.

[0062] Preferably, in some embodiments, the second epitaxial layer 400 further includes a barrier graded layer 413, which is provided between the InP cladding layer 411 and the contact layer 412. The barrier graded layer 413 is a P-type InGaAsP layer with a thickness of 30 nm to 50 nm, a wavelength of 1300 nm or 1500 nm, and a doping concentration of 1×10 16 cm -3 ~1×10 17 cm -3 The barrier gradient layer 413 can optimize the carrier injection efficiency and improve the electro-optical conversion efficiency; at the same time, it can also adjust the lateral distribution of the light field and suppress the lasing of high-order transverse modes.

[0063] Specifically, in some embodiments, the passivation layer 500 is made of one or more of silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide, but is not limited thereto. The thickness of the passivation layer 500 is 100 nm to 800 nm. Preferably, in some embodiments, the passivation layer 500 is a silicon oxide layer with a thickness of 200 nm to 500 nm.

[0064] Specifically, in some embodiments, the top electrode 600 is a stacked structure formed of metals such as Ti, Pt, Au, Ag, Cr, and Ni, but is not limited thereto. Preferably, in some embodiments, the top electrode 600 includes a Ti layer, a Pt layer, and an Au layer stacked in sequence, wherein the thickness of the Ti layer is 10 nm to 100 nm, the thickness of the Pt layer is 50 nm to 100 nm, and the thickness of the Au layer is 800 nm to 1500 nm.

[0065] Specifically, in some embodiments, dielectric film 700 can be made of one or more of, but not limited to, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, or hafnium oxide. Dielectric films 700 made of these materials have a high hardness, effectively preventing damage to the DFB laser during subsequent optical coating and testing. The thickness of dielectric film 700 is 400 nm to 1000 nm, preferably 500 nm to 700 nm.

[0066] Specifically, the dielectric film 700 may only cover the top surface of the ridge waveguide structure 410, effectively preventing damage to the ridge waveguide structure 410, but is not limited thereto. Preferably, in some embodiments, the dielectric film 700 also covers the bottom and sidewalls of the isolation trench 430, and the dielectric film 700 at least partially extends onto the surface of the body portion 420. Based on this structure, the area of ​​the dielectric film 700 can be increased, optimizing its support function and further reducing damage. Furthermore, based on this structure, the extension distance of the dielectric film 700 on the surface of the body portion 420 is less than the extension distance of the top electrode 600 on the surface of the body portion 420, thereby exposing at least a portion of the top electrode 600 outside the dielectric film 700, thereby enabling subsequent electrical connection between the DFB laser and other devices.

[0067] Specifically, in some embodiments, the bottom electrode 200 may be made of one or more of Pt, Au, Ti, Cu, Ag, TiW, and AuGe, but is not limited thereto. Preferably, in some embodiments, the bottom electrode 200 includes an AuGe alloy layer, a Pt layer, a first Au layer, a Ti layer, and a second Au layer sequentially stacked on the second surface 120, wherein the AuGe alloy layer can optimize the ohmic contact with the substrate 100, the Pt layer is mainly used to block metal diffusion, the first Au layer and the second Au layer are mainly used to reduce resistance and improve current transmission, and the Ti layer can enhance adhesion. Specifically, the thickness of the AuGe alloy layer is 50nm to 200nm, the thickness of the Pt layer is 50nm to 100nm, the thickness of the first Au layer is 100nm to 300nm, the thickness of the Ti layer is 10nm to 50nm, and the thickness of the second Au layer is 150nm to 300nm.

[0068] Preferably, in some embodiments, the dielectric film 700 includes a first silicon oxide film and a silicon nitride film stacked sequentially from the second surface to the first surface. This dual-layer structure allows the thin-layer stress of the dielectric film 700 to be adjusted to ≤200 MPa, thereby effectively preventing the dielectric film 700 from shedding due to excessive stress between the top electrode 600 and the dielectric film 700, further improving yield and reliability. Specifically, in this embodiment, the ratio of the thickness of the first silicon oxide film to the thickness of the silicon nitride film is 1:(1-5). It should be noted that when the silicon oxide film or silicon nitride film alone is used as the dielectric film 700, its internal stress can reach over 300 MPa.

[0069] Preferably, in some other embodiments, the dielectric film 700 includes a second silicon oxide film and a silicon oxynitride film stacked sequentially from the second surface to the first surface. This dual-layer structure allows for adjustment of the dielectric film 700's sheet stress, ensuring that the sheet stress is ≤ 200 MPa. This effectively prevents shedding of the dielectric film 700 due to excessive stress between the top electrode 600 and the dielectric film 700, further improving yield and reliability. Specifically, in this embodiment, the ratio of the thickness of the second silicon oxide film to the thickness of the silicon oxynitride film is 1:(1-3).

[0070] Preferably, in some embodiments, the DFB laser further includes an adhesion layer 800 disposed beneath the dielectric film 700. The adhesion layer 800 can further enhance the adhesion between the top electrode 600 and the dielectric film 700, preventing the dielectric film 700 from falling off, thereby further improving reliability and yield. Specifically, the adhesion layer 800 is a Ti layer, a Cr layer, or a TiW layer, and has a thickness of 10 nm to 30 nm.

[0071] More preferably, in some embodiments, adhesion layer 800 is a Ti layer with a thickness of 10 nm to 20 nm. The Ti layer can better adjust the thin layer stress of dielectric film 700 to ≤ 100 MPa. Furthermore, the Ti layer can be etched with the same etching medium as dielectric film 700, improving production efficiency.

[0072] Accordingly, as a second aspect of the present invention, the present invention further provides a method for preparing a high-reliability DFB laser, which is used to prepare the above-mentioned high-reliability DFB laser, and comprises the following steps:

[0073] S1, forming a first epitaxial layer and a second epitaxial layer on a first surface of a substrate;

[0074] Specifically, in some embodiments, the first epitaxial layer 300 and the second epitaxial layer 400 may be sequentially grown on the first surface 110 by MOCVD, PVD, etc., but the present invention is not limited thereto.

[0075] S2, etching the second epitaxial layer to form an isolation trench exposing the first epitaxial layer, thereby obtaining a first intermediate;

[0076] Specifically, in some embodiments, a mask layer is first formed on the second epitaxial layer 400, and then patterned, and then the isolation trench 430 is formed by a wet etching or dry etching process, see Figure 3 The isolation trench 430 separates the second epitaxial layer 400 into the body portion 420 and the at least one ridge waveguide structure 410, but is not limited thereto. Specifically, the mask layer is a photoresist layer or a SiO2 layer, but is not limited thereto.

[0077] S3, forming a passivation layer on the first intermediate, and forming an opening in the passivation layer above the ridge waveguide structure to obtain a second intermediate;

[0078] Specifically, the passivation layer 500 can be grown by methods such as MOCVD and PECVD, but is not limited thereto. Preferably, in some embodiments, a silicon oxide layer is grown by PECVD as the passivation layer 500. Specifically, the process parameters for growing the silicon oxide layer by PECVD include: RF power of 50W to 100W, chamber pressure of 60Pa to 100Pa, reaction gases of a first mixed gas and N2O, a flow ratio of the first mixed gas to N2O of 1:3 to 1:5, a total flow rate of the reaction gas of 1000sccm to 1500sccm, and a temperature of the first intermediate during deposition of 200°C to 350°C; wherein the first mixed gas is a mixed gas of SiH4 and N2, and the proportion of SiH4 in the first mixed gas is 3vol% to 10vol%, preferably 5vol%.

[0079] See also Figure 4 After the passivation layer 500 is prepared, it is photolithographically etched to form an opening 510 exposing the contact layer 412 on the top of the ridge waveguide structure 410 .

[0080] S4, forming a top electrode to obtain a third intermediate;

[0081] Specifically, the top electrode 600 can be formed by electron beam evaporation or PVD, but is not limited thereto. Preferably, in some embodiments, a photoresist layer is first formed, exposed and developed for patterning, and then the top electrode 600 is formed. The photoresist layer and the top electrode 600 thereon are then removed by a peeling process to achieve patterning of the top electrode 600, but is not limited thereto. The coverage area of ​​the top electrode 600 is as follows: Figure 5 shown.

[0082] S5, forming a dielectric film on the surface of the third intermediate and patterning it;

[0083] Specifically, the dielectric film 700 may be grown by PECVD, PVD, or MOCVD, but is not limited thereto, and then patterned by photolithography and etching processes, but is not limited thereto.

[0084] Preferably, in some embodiments, a first silicon oxide layer and a silicon nitride layer are sequentially grown by PECVD to form the dielectric film 700. Specifically, the process parameters for PECVD growth of the first silicon oxide film include: an RF power of 50W to 100W, a chamber pressure of 60Pa to 100Pa, reactant gases of the second mixed gas and N2O, a flow ratio of the second mixed gas to N2O of 1:3 to 1:5, a total reactant gas flow of 1000sccm to 1500sccm, and a temperature of the third intermediate during deposition of 200°C to 350°C. The second mixed gas is a mixture of SiH4 and N2, with the proportion of SiH4 in the second mixed gas being 3% to 10% by volume, preferably 5% by volume. The process parameters for growing silicon nitride film by PECVD include: RF power of 100W~200W, chamber pressure of 80Pa~150Pa, reaction gas is a third mixed gas, NH3 and He, the flow rate of the third mixed gas is 280sccm~360sccm, the flow rate of NH3 is 10sccm~30sccm, the flow rate of He is 200sccm~400sccm, and the flow ratio of SiH4 to NH3 is 1:1~1:2; the temperature of the third intermediate during deposition is 200℃~350℃; wherein, the third mixed gas is a mixed gas of SiH4 and N2, and the proportion of SiH4 in the third mixed gas is 3vol%~10vol%, preferably 5vol%.

[0085] Preferably, in other embodiments, a second silicon oxide film and a silicon oxynitride film are sequentially grown by PECVD to serve as the dielectric film 700. Specifically, the process parameters for PECVD growth of the second silicon oxide film include: an RF power of 50W to 100W, a chamber pressure of 60Pa to 100Pa, reactant gases of a fourth mixed gas and N2O, a flow ratio of the fourth mixed gas to N2O of 1:3 to 1:5, a total reactant gas flow of 1000sccm to 1500sccm, and a temperature of the third intermediate during deposition of 200°C to 350°C. The fourth mixed gas is a mixture of SiH4 and N2, with the proportion of SiH4 in the fourth mixed gas being 3% to 10% by volume, preferably 5% by volume. The process parameters for growing silicon oxynitride films by PECVD include: RF power of 100W to 200W, chamber pressure of 70Pa to 120Pa, reactant gases consisting of a fifth mixed gas, N2O, NH3, and He, a flow ratio of the fifth mixed gas to N2O, NH3, and He of (15-22):1:(25-35):(3-10), a total reactant gas flow of 1000sccm to 1500sccm, and a temperature of the third intermediate during deposition of 250°C to 350°C. The fifth mixed gas is a mixture of SiH4 and N2, with SiH4 accounting for 3% to 10% by volume.

[0086] Specifically, after the dielectric film 700 is grown, the dielectric film 700 in a predetermined area is removed by a photolithography and etching process, but the present invention is not limited thereto.

[0087] Preferably, in some embodiments, step S5 includes:

[0088] S51: forming an adhesion layer on the surface of the third intermediate;

[0089] Specifically, the adhesion layer 800 may be formed by an electron beam evaporation process or a PVD process, but is not limited thereto. Preferably, in some embodiments, a Ti layer is evaporated as the adhesion layer 800 .

[0090] S52: forming a dielectric film 700 on the surface of the adhesion layer 800;

[0091] S53: etching the dielectric film 700 and the adhesion layer 800 to pattern them.

[0092] Specifically, the dielectric film 700 and the adhesion layer 800 may be etched in steps, but the present invention is not limited thereto. S6. Form a bottom electrode on the second surface of the substrate.

[0093] Specifically, the bottom electrode 200 may be formed by an electron beam evaporation process or PVD, but is not limited thereto.

[0094] Preferably, in some embodiments, before forming the bottom electrode 200 , the substrate 100 is thinned.

[0095] Preferably, in some embodiments, after forming the bottom electrode 200 , the wafer is subjected to bar dissociation, end-face optical coating, cutting to form chips, and sorting to obtain a finished DFB laser, but the present invention is not limited thereto.

[0096] The above is a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A high-reliability DFB laser, characterized in that: include: a substrate comprising opposing first and second surfaces; a bottom electrode disposed on the second surface of the substrate; a first epitaxial layer disposed on the first surface; a second epitaxial layer disposed on the first epitaxial layer; the second epitaxial layer comprising a body portion and at least one ridge waveguide structure, an isolation trench exposing the first epitaxial layer being disposed between the body portion and the ridge waveguide structure; a passivation layer covering a surface of the body portion, a surface and sidewalls of the ridge waveguide structure, and sidewalls and a bottom wall of the isolation trench; a top electrode covering the passivation layer on the ridge waveguide structure, the passivation layer on the sidewalls and bottom wall of the isolation trench, and at least partially extending onto the passivation layer on the surface of the body portion; The top electrode is in electrical contact with the ridge waveguide structure through an opening provided in the passivation layer; as well as A dielectric film covers the top electrode above the ridge waveguide structure; a top surface of the dielectric film is higher than a top surface of the top electrode, and a hardness of the dielectric film is greater than a hardness of the top electrode.

2. The high-reliability DFB laser according to claim 1, wherein: The dielectric film also covers the bottom wall and the top electrode above the side wall of the isolation trench; and the dielectric film at least partially extends onto the surface of the main body; An extension distance of the dielectric film on the surface of the body portion is smaller than an extension distance of the top electrode on the surface of the body portion, so that at least a portion of the top electrode is exposed outside the dielectric film.

3. The high-reliability DFB laser according to claim 1, wherein: The film stress of the dielectric film is ≤200 MPa.

4. The high-reliability DFB laser according to claim 3, wherein: The dielectric film includes a first silicon oxide film and a silicon nitride film stacked in sequence; the thickness of the dielectric film is 500nm to 700nm; A ratio of a thickness of the first silicon oxide film to a thickness of the silicon nitride film is 1:1 to 1:

5.

5. The high-reliability DFB laser according to claim 3, wherein: The dielectric film includes a second silicon oxide film and a silicon oxynitride film stacked in sequence; the thickness of the dielectric film is 500nm to 700nm; A ratio of a thickness of the second silicon oxide film to a thickness of the silicon oxynitride film is 1:1 to 1:

3.

6. The high-reliability DFB laser according to any one of claims 1 to 5, characterized in that: Also included is an adhesion layer, which is disposed below the dielectric film; The adhesion layer is a Ti layer, a Cr layer or a TiW layer, and has a thickness of 10 nm to 30 nm.

7. The high-reliability DFB laser according to claim 6, characterized in that: The adhesion layer is a Ti layer with a thickness of 10nm to 20nm; The film stress of the dielectric film is ≤100 MPa.

8. The high-reliability DFB laser according to claim 1, wherein: The first epitaxial layer includes a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper confinement layer, a grating layer and an etching stop layer sequentially stacked on the first surface; The second epitaxial layer includes an InP cladding layer and a contact layer sequentially stacked on the first epitaxial layer.

9. A method for preparing a high-reliability DFB laser, for preparing the high-reliability DFB laser according to any one of claims 1 to 8, characterized in that: include: forming a first epitaxial layer and a second epitaxial layer on the first surface of the substrate; Etching the second epitaxial layer to form an isolation trench exposing the first epitaxial layer, thereby obtaining a first intermediate body; wherein the isolation trench separates the second epitaxial layer into a main body portion and at least one ridge waveguide structure; forming a passivation layer on the first intermediate body, and forming an opening in the passivation layer above the ridge waveguide structure to obtain a second intermediate body; forming a top electrode to obtain a third intermediate; forming a dielectric film on the surface of the third intermediate and patterning the film; A bottom electrode is formed on the second surface of the substrate.

10. The method for preparing a high-reliability DFB laser according to claim 9, wherein: The step of forming a dielectric film on the surface of the third intermediate and patterning the film comprises: forming an adhesion layer on the surface of the third intermediate; forming a dielectric film on the surface of the adhesion layer; The dielectric film and the adhesion layer are etched to pattern both.

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