CN112436381A - High-speed DFB laser chip and manufacturing method thereof - Google Patents
High-speed DFB laser chip and manufacturing method thereof Download PDFInfo
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- CN112436381A CN112436381A CN202011347123.4A CN202011347123A CN112436381A CN 112436381 A CN112436381 A CN 112436381A CN 202011347123 A CN202011347123 A CN 202011347123A CN 112436381 A CN112436381 A CN 112436381A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/2004—Confining in the direction perpendicular to the layer structure
- H01S5/2018—Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/204—Strongly index guided structures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/2205—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers
- H01S5/2206—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers based on III-V materials
Abstract
The invention relates to a high-speed DFB laser chip and a manufacturing method thereof, which comprises the following steps: the method comprises the steps of growing a buffer layer, a lower limiting layer, a quantum well, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a P-InP cladding layer on a substrate in sequence, carrying out grating manufacturing, carrying out secondary epitaxial growth on a P-InP waveguide layer and an ohmic contact layer, then finishing ridge waveguide manufacturing and ridge upper injection window contact strip manufacturing, manufacturing strip electrodes on the contact strips, manufacturing BCB patterns on two sides of the ridge waveguides, etching the thickness of the BCB in a groove to be consistent with the height of the ridge waveguides, manufacturing circular electrodes on the BCB patterns, and connecting the strip electrodes. The invention not only effectively reduces various parasitic capacitances of the laser, satisfies the application of high-speed modulation, can reduce the ion bombardment damage to the ridge waveguide in the existing BCB etching process, and the pressure loss risk to the ridge waveguide in the later packaging process of the chip, improves the packaging yield, and simultaneously avoids the cavity surface damage caused by the photon heat accumulation of the cavity surface.
Description
Technical Field
The invention belongs to the technical field of high-speed optical communication chips, and particularly relates to a high-speed DFB laser chip and a manufacturing method thereof.
Background
With the continuous progress of information technology, people have higher and higher requirements on optical communication bandwidth, and the RC parameter f can be reduced by introducing a BCB (binary coded block bus) processc= 1/2 pi RC, thereby effectively reducing various parasitic capacitances of the laser and satisfying high-speed modulation application.
In the prior art, for the BCB fabrication of rwg (ridge waveguide) structure, generally, the BCB is used to fill all the trenches on both sides of the ridge waveguide, then ion etching is used to planarize the heights of the BCB and the ridge waveguide, and finally, a window electrical injection window is fabricated. Therefore, although the manufacturing method of the BCB adopting the RWG structure improves the modulation rate of the laser, the yield is not high and the market demand of the process temperature is not met.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a high-speed DFB laser chip and a manufacturing method thereof, which are used for improving the bandwidth capacity of the laser chip without influencing the heat dissipation characteristic of the laser in the application process, the planar BCB at the side of a ridge waveguide can reduce the damage risk in the later packaging process of the chip, and meanwhile, non-BCB areas at two sides of a cavity surface can avoid the cavity surface damage caused by the accumulation of photon heat at the cavity surface.
The technical scheme of the invention is realized as follows: the invention discloses a high-speed DFB laser chip which comprises a laser structure, wherein the laser structure grows on a substrate, the upper surface of the laser structure is provided with a ridge waveguide and grooves positioned on two sides of the ridge waveguide, the top layer of the ridge waveguide is provided with a first electrode, BCB graphs are arranged on two sides of the ridge waveguide, the thickness of the BCB positioned in the grooves is consistent with the height of the ridge waveguide, the BCB graphs are provided with a second electrode, and the second electrode is connected with the first electrode on the top layer of the ridge waveguide.
Further, the BCB patterns arranged on the two sides of the ridge waveguide include a first BCB coverage area located in the groove and a second BCB coverage area located outside the groove, the second BCB coverage area is located on the mesa on the two sides of the groove of the laser structure, and the second BCB coverage area is provided with a second electrode.
Furthermore, the size of the BCB graph along the length direction of the laser cavity is smaller than the length of the laser cavity, and areas which are not covered by the BCB are reserved on the two sides of the upper surface of the laser structure, close to the light-emitting end face and the backlight end face.
Furthermore, metal covering layers are respectively arranged on two sides of the bottom of the ridge waveguide, and form a first electrode together with the metal covering layers on the top layer of the ridge waveguide, and the first electrode extends along the length direction of the ridge waveguide to form a strip-shaped electrode. The metal covering layers on two sides of the bottom of the ridge waveguide are arranged on the bottom wall of the groove and connected with the side wall of the ridge waveguide, namely the width of the first electrode is widened.
The invention can only make the bar electrode on the top layer of the ridge waveguide, also can suitably widen the width of the bar electrode, and set up the metal covering layer on both sides of the bottom of the ridge waveguide.
Further, the cross section of the groove is in a trapezoid shape with a narrow upper part and a wide lower part; the cross section of the ridge waveguide is a trapezoid with a wide upper part and a narrow lower part. The RWG structure ridge waveguide is inverted, so that the threshold value can be reduced, and the bandwidth can be improved.
Further, the laser structure comprises a buffer layer, a lower limiting layer, a quantum well layer, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a P-InP cladding layer which are sequentially grown from bottom to top on the substrate; and a secondary epitaxial layer is arranged on the P-InP cladding layer and comprises an InP waveguide layer and an ohmic contact layer from bottom to top. The cladding layer and the waveguide layer are both made of InP, and the two layers are combined together after secondary epitaxy to form the InP waveguide layer. The P-InP cladding is arranged on the top after one-time epitaxy, so that the cladding is called as a cladding, the cladding mainly plays a role of protecting a grating layer InGaAsP, a layer of thin InP is arranged on the cladding from MO every time, firstly, air is isolated, and secondly, the burying quality is better when quaternary materials below InP are decomposed in the cooling process and the cladding is buried in the second epitaxy thickness later. The P-InP waveguide layer is an optical field requirement, improving the vertical divergence angle.
The first transition layer and the second transition layer are made of InP materials. The first transition layer can improve the growth quality and avoid the poor growth effect of the quaternary corrosion stop layer directly grown on the limiting layer; the second transition layer is used for preventing the etching stop layer from being etched when the grating is etched, so that the etching stop layer is not used; the corrosion stop layer is of a quaternary InGaAsP structure, when ridge waveguides are manufactured, when the ridge waveguides are corroded by mixed liquid of phosphoric acid and hydrogen peroxide, the corrosion stop layer is selective corrosive liquid, quaternary InGaAsP cannot be corroded, if the corrosion stop layer is not provided, the corrosion stop layer is directly arranged on the quantum well and the upper limit layer, and the corrosion stop layer is not good for an active area.
Non-grating areas are reserved on two sides of the grating layer, which are close to the light-emitting end face and the backlight end face. The purpose of this design is to avoid the grating region being cut when the back fringes are cleaved, which causes random disorder of the refractive index and affects the wavelength.
The invention also discloses a manufacturing method of the high-speed DFB laser chip, which comprises the following steps:
growing a first epitaxial structure on a substrate to form a wafer A;
carrying out grating manufacturing on the wafer A to form a wafer B;
after the grating is manufactured, a second epitaxial structure is epitaxially grown on the wafer B for the second time to form a wafer C;
manufacturing a ridge waveguide structure on the wafer C to form a wafer D, wherein grooves are formed between the two sides of the ridge waveguide and the table top;
manufacturing an electricity injection window contact strip on the top layer of the ridge waveguide of the wafer D to form a wafer E;
finishing the first electrode manufacturing on the contact strip of the power injection window of the wafer E to form a wafer F;
manufacturing BCB patterns on two sides of a ridge waveguide of a wafer F to form a wafer with the BCB patterns, and etching the wafer with the BCB patterns until a structural wafer G with the thickness of the BCB in the groove consistent with the height of the ridge waveguide is formed;
and manufacturing a second electrode on the BCB pattern and connecting the second electrode with the first electrode.
Further, growing a first epitaxial structure on the substrate, comprising:
sequentially growing a buffer layer, a lower limiting layer, a quantum well, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a cladding layer on a substrate;
non-grating areas are reserved on two sides of the grating layer, which are close to the light-emitting end face and the backlight end face;
after the grating is manufactured, a second epitaxial structure is continuously grown on the wafer B in a secondary epitaxial growth mode, and the method comprises the following steps: a waveguide layer and an ohmic contact layer are epitaxially grown on the wafer B for the second time;
and manufacturing a ridge waveguide structure on the wafer C, wherein the manufacturing comprises the following steps: and forming a photoetching pattern on the surface of the wafer C, etching the ohmic contact layer through a dry process to form a straight-platform ridge waveguide structure, and etching the waveguide layer to the corrosion stop layer at the bottom through a wet process to form an inverted-platform ridge waveguide structure between the two grooves.
Forming a photoetching pattern on the surface of the wafer C, wherein the photoetching pattern comprises the following steps: growing a mask layer on the surface of the wafer C, and forming a strip-shaped SiO layer after photoresist-homogenizing alignment, RIE mask layer etching and photoresist removal2The ridge waveguide of the mask pattern.
Because the material of the ohmic contact is InGaAs, the solution for corroding the waveguide layer is selective corrosive liquid, and the InGaAs is not corroded, the ohmic contact is etched through by a dry method to be corroded, and then the ohmic contact is corroded by a wet method until the stop layer stops.
Furthermore, the size of the BCB graph along the length direction of the laser cavity is smaller than the length of the laser cavity, and areas which are not covered by the BCB are reserved on the two sides of the upper surface of the laser structure, close to the light-emitting end face and the backlight end face.
Further, the cross section of the groove is in a trapezoid shape with a narrow upper part and a wide lower part; the cross section of the ridge waveguide is a trapezoid with a wide upper part and a narrow lower part.
The grating is a rectangular grating and is formed by low-temperature RIE etching after exposure by adopting a holographic laser system. If in 250um single family chip, the length of grating along the cavity length direction is 230um, 10um non-grating area is left in the light-emitting and backlight direction respectively, avoiding the random spectrum disorder caused by cavity surface cleavage.
Furthermore, the manufacturing method of the contact strip of the injection window on the ridge strip is a common partial exposure method in the industry, and a layer of SiO with the thickness of 300-2After the dielectric film is formed, the top electricity injection window of the ridge waveguide is opened, and the complete SiO is still remained in other areas2And (6) covering.
Further, the strip-shaped electrodes are manufactured after the contact strips are manufactured and before the BCB patterns are manufactured. The manufacturing method is completed by adopting a negative glue process, the central line of the strip electrode is superposed with the central line of the ridge waveguide, after the magnetron sputtering P-surface gold plating is completed, the top layer of the ridge waveguide realizes complete gold coverage, the two sides of the bottom of the ridge waveguide are covered by gold with the width of 0.5-2um, the sputtering material is titanium platinum, and ohmic contact of an injection area is formed.
Furthermore, the size of the BCB graph is 200um x 100um, the BCB graph is located on two sides of the ridge waveguide, the center line of the BCB graph is overlapped with the center line of the ridge waveguide, and 25um non-BCB areas are reserved in the light emitting direction and the backlight direction respectively.
Furthermore, the manufacturing method of the contact strip of the electricity injection window on the ridge strip is a common under-exposure mode in the industry, the electricity injection window above the ridge waveguide is opened, and the side surfaces of the electricity injection window are all made of an electric insulating material SiO2And (6) covering.
Furthermore, the second electrode is a circular electrode, and the size of the circular electrode pattern is 90um by 90um, and the circular electrode pattern is connected with the strip-shaped electrode, namely the first electrode.
The invention has at least the following beneficial effects: the method comprises the step of sequentially growing an N-InP buffer layer, an AlGaInAs lower limiting layer, a multi-layer compressive strain AlGaInAs quantum well layer, an AlGaInAs upper limiting layer, a first P-InP transition layer, a P-InGaAsP corrosion stop layer, a second P-InP transition layer, a P-InGaAsP grating layer and a P-InP cladding layer on an N-InP substrate. And after grating manufacture, carrying out secondary epitaxial growth on the P-InP waveguide layer and the InGaAs ohmic contact layer. And then, manufacturing a ridge waveguide structure, a chip cleavage area and an electricity injection window contact strip on the ridge strip. After finishing the manufacture of the window contact strip, finishing the manufacture of a strip electrode and the manufacture of BCB graphs on two sides of the ridge waveguide on the contact strip, wherein the size of the cavity length direction of the BCB graphs is smaller than the cavity length, non-BCB areas with certain distances are reserved in the light emitting direction and the backlight direction, the thickness of the BCB is consistent with the height of the ridge waveguide after being etched,the effect of a planar ridge waveguide structure is achieved, after BCB graph manufacturing is completed, circular electrode manufacturing is completed on the BCB graph, the BCB graph is connected with a strip electrode, and the graph manufacturing is completed through a conventional ultraviolet exposure alignment means. The RWG structure and the BCB process are adopted for manufacturing the laser chip, so that the RC parameter f can be reducedcAnd the design of the pattern of the power injection window, the strip electrode and the BCB can reduce the ion bombardment damage to the ridge waveguide in the existing BCB etching process and the pressure loss risk to the ridge waveguide in the later packaging process of the chip, improve the packaging yield and simultaneously avoid the cavity surface damage caused by the photon heat accumulation of the cavity surface.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 schematically shows a structural diagram of a high-speed DFB laser chip according to an embodiment of the present application;
FIG. 2 schematically illustrates a top view of a high speed DFB laser chip according to an embodiment of the present application;
fig. 3 schematically shows a flow chart of a method for fabricating a high speed DFB laser chip according to an embodiment of the present application.
In the figure, 1 is a ridge waveguide, 2 is a groove, 3 is a mesa, 4 is a second electrode, 5 is a first electrode, and 6 is BCB.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 and 2, an embodiment of the present invention provides a high-speed DFB laser chip, including a laser structure, where the laser structure is grown on a substrate, a ridge waveguide and grooves located on two sides of the ridge waveguide are disposed on an upper surface of the laser structure, a first electrode is disposed on a top layer of the ridge waveguide, BCB patterns are disposed on two sides of the ridge waveguide, a thickness of the BCB located in the grooves is consistent with a height of the ridge waveguide, a second electrode is disposed on the BCB patterns, and the second electrode is connected to the first electrode on the top layer of the ridge waveguide.
Further, the BCB patterns arranged on the two sides of the ridge waveguide include a first BCB coverage area located in the groove and a second BCB coverage area located outside the groove, the second BCB coverage area is located on the mesa on the two sides of the groove of the laser structure, and the second BCB coverage area is provided with a second electrode.
BCB patterns arranged on two sides of the ridge waveguide are symmetrically arranged along the central line of the top layer of the ridge waveguide.
Furthermore, the size of the BCB graph along the length direction of the laser cavity is smaller than the length of the laser cavity, and areas which are not covered by the BCB are reserved on the two sides of the upper surface of the laser structure, close to the light-emitting end face and the backlight end face.
Furthermore, metal covering layers are respectively arranged on two sides of the bottom of the ridge waveguide, and form a first electrode together with the metal covering layers on the top layer of the ridge waveguide, and the first electrode extends along the length direction of the ridge waveguide to form a strip-shaped electrode. The metal covering layers on two sides of the bottom of the ridge waveguide are arranged on the bottom wall of the groove and connected with the side wall of the ridge waveguide. The metal covering layers on the two sides of the bottom of the ridge waveguide are symmetrically arranged along the central line of the top layer of the ridge waveguide.
Further, the cross section of the groove is a trapezoid with a narrow upper part and a wide lower part (the upper bottom of the trapezoid is shorter than the lower bottom); the cross section of the ridge waveguide is a trapezoid with a wide upper part and a narrow lower part (the upper bottom of the trapezoid is longer than the lower bottom).
Further, the laser structure comprises a buffer layer, a lower limiting layer, a quantum well layer, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a cladding layer which are sequentially grown from bottom to top on the substrate; and a secondary epitaxial layer is arranged on the cladding layer and comprises a waveguide layer and an ohmic contact layer from bottom to top. The above epitaxial structure growth of the present embodiment is all completed by MOCVD.
Non-grating areas are reserved on two sides of the grating layer, which are close to the light-emitting end face and the backlight end face.
The thickness range of the BCB of the table board outside the groove is 3-5um, the thickness range of the BCB inside the groove is 2-2.3um, and is consistent with the depth of the ridge waveguide, namely the height of the BCB inside the groove is flush with the ridge waveguide. Of course, the thickness of the BCB of the mesa outside the groove and the thickness of the BCB inside the groove are not limited to the above embodiments, and may be set according to the need, fig. 1 only illustrates the structure of the laser, and the actual thickness of each layer is set according to the need, which may not be in accordance with the scale illustrated in the figure. The BCB pattern structure is formed by exposing photosensitive BCB twice, wherein 1 exposure is complete exposure of the table-board BCB outside the groove, 2 exposures are partial exposure of the BCB in the groove, and RIE is used for etching the surface of the BCB after development and solidification so that the thickness of the BCB in the groove is consistent with the depth of the ridge waveguide.
Referring to fig. 1 to 3, the present invention also discloses a method for manufacturing a high-speed DFB laser chip, comprising the following steps:
growing a first epitaxial structure on a substrate to form a wafer A;
carrying out grating manufacturing on the wafer A to form a wafer B;
after the grating is manufactured, a second epitaxial structure is epitaxially grown on the wafer B for the second time to form a wafer C;
manufacturing a ridge waveguide structure on the wafer C to form a wafer D, wherein grooves are formed between the two sides of the ridge waveguide and the table top;
manufacturing an electricity injection window contact strip on the top layer of the ridge waveguide of the wafer D to form a wafer E;
manufacturing a first electrode on the contact strip of the power injection window of the wafer E to form a wafer F;
manufacturing BCB patterns on two sides of a ridge waveguide of a wafer F to form a wafer with the BCB patterns, and etching the wafer with the BCB patterns until a structural wafer G with the thickness of the BCB in the groove consistent with the height of the ridge waveguide is formed;
and manufacturing a second electrode on the BCB pattern and connecting the second electrode with the first electrode.
Further, growing a first epitaxial structure on the substrate, comprising:
sequentially growing a buffer layer, a lower limiting layer, a quantum well, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a cladding layer on a substrate;
non-grating areas are reserved on two sides of the grating layer, which are close to the light-emitting end face and the backlight end face;
after the grating is manufactured, a second epitaxial structure is continuously grown on the wafer B in a secondary epitaxial growth mode, and the method comprises the following steps: a waveguide layer and an ohmic contact layer are epitaxially grown on the wafer B for the second time;
and manufacturing a ridge waveguide structure on the wafer C, wherein the manufacturing comprises the following steps: and forming a photoetching pattern on the surface of the wafer C, etching the ohmic contact layer through a dry process after the photoetching pattern is finished, and etching the waveguide layer to the corrosion stop layer at the bottom through a wet process to form a ridge waveguide structure between the two grooves.
Forming a photoetching pattern on the surface of the wafer C, wherein the photoetching pattern comprises the following steps: growing a mask layer on the surface of the wafer C, and forming a strip-shaped SiO layer after photoresist-homogenizing alignment, RIE mask layer etching and photoresist removal2The ridge waveguide of the mask pattern.
Furthermore, the size of the BCB graph along the length direction of the laser cavity is smaller than the length of the laser cavity, and areas which are not covered by the BCB are reserved on the two sides of the upper surface of the laser structure, close to the light-emitting end face and the backlight end face.
Further, the cross section of the groove is in a trapezoid shape with a narrow upper part and a wide lower part; the cross section of the ridge waveguide is a trapezoid with a wide upper part and a narrow lower part.
The width of the ridge waveguide of the present embodiment ranges from 2 to 2.5 um; the width L1 of each groove on both sides of the ridge waveguide ranges from 15um to 20 um; the first electrode width L2 ranges from 3-6.5 um. The invention is not limited to the above-described embodiments.
The embodiment provides a specific embodiment of a manufacturing method of a high-speed DFB laser chip, which comprises the following specific steps:
s1, growing a structure wafer A which is sequentially provided with an N-InP substrate, an N-InP buffer layer, an AlGaInAs lower limiting layer, a multi-layer compressive strain AlGaInAs quantum well, an AlGaInAs upper limiting layer, a P-InP transition layer 1, a P-InGaAsP corrosion stop layer, a P-InP transition layer 2, a P-InGaAsP grating layer and a P-InP cladding layer from bottom to top by using MOCVD;
s2, cleaning the surface of a wafer A by organic acetone, uniformly attaching S18 series thin glue, sequentially exposing non-grating areas of 10um in the light emitting and backlight directions, carrying out interference exposure of a holographic laser, developing, baking, further controlling the thickness of the grating glue within a certain range by using a plasma photoresist remover, and then carrying out RIE (reactive ion etching) low-damage grating etching with the etching depth ranging from 40 nm to 60nm, wherein the thickness of the grating glue corresponds to the sum of the thicknesses of a P-InP cladding layer and a P-InGaAsP grating layer;
s3, performing surface treatment on the structure wafer B after grating etching by using KOH alkaline solution, further removing polymer residues possibly generated in the etching process, and then performing MOCVD secondary epitaxial growth, wherein the growth materials and the sequence are a P-InP waveguide layer and a P + -InGaAs ohmic contact layer in sequence;
s4, growing 200nmSiO after the surface treatment of the structure wafer C after the secondary epitaxy is carried out by diluting HF2Mask layer, which is formed by photoresist alignment, RIE mask layer etching and KOH alkaline solution photoresist removal2Etching a P + -InGaAs ohmic contact layer and a P-InP waveguide layer by a RIE dry etching mask, forming a straight-platform ridge waveguide structure within the etching depth range of 500-600nm, then corroding the straight-platform ridge waveguide structure by using a diluted solution of phosphoric acid, hydrogen peroxide and water to form an inverted-platform ridge waveguide within the depth range of 2-2.3um (specifically 2.1um in the embodiment, the width of each groove on the two sides of the ridge waveguide is 15 um), finally removing a mask layer on the surface of the ridge waveguide by using a mixed solution BOE of ammonium fluoride and hydrofluoric acid, and regrowing a passivation layer of 300nm to form a structure wafer D;
s5, etching SiO by photoetching2Removing a passivation layer above the ridge waveguide, and forming a structure wafer E with an injection window after removing the surface mask photoresist by using KOH alkaline solution;
s6, uniformly attaching AZ5214 negative glue on the surface of a wafer E, exposing for 5S for 1 time, baking, reversing, carrying out full exposure for 35S for 2 times, developing photoresist on the surface of the wafer E to form a strip-shaped electrode pattern, placing the wafer E in a measurement and control sputtering machine, plating a layer of titanium platinum with the total thickness of 200nm, and ultrasonically stripping and removing the photoresist with acetone to form a wafer F with a strip-shaped electrode;
s7, uniformly attaching an AP3000 reinforcing agent to the surface of a wafer F, baking the wafer F on a hot plate at 110 ℃ for 30S after glue is uniformly applied, cooling the wafer F for 3min at room temperature after baking is finished, uniformly attaching a BCB photoresist at a glue-applying rotating speed of 3000R, performing forward baking at 65 ℃ for 1min to obtain 30S, performing full exposure on a table BCB and partial exposure on the BCB in a groove, performing forward baking at 55 ℃ for 1min, performing development and post baking at 100 ℃ for 1min, curing to obtain a wafer with a BCB pattern, performing curing at 300 ℃ for 1h, performing ion etching on the wafer in RIE equipment, and performing multiple step etching on the etching gas by using mixed gas of CHF3 and O2 until a structural wafer G with the BCB thickness consistent with the ridge waveguide height is formed;
s8, uniformly attaching AZ5214 negative glue on the surface of the structural wafer G, exposing for 5S for 1 time, baking and reversing, carrying out full exposure for 35S for 2 times, developing photoresist on the surface of the wafer E to form a circular electrode pattern, placing the wafer E in a measurement and control sputtering machine, plating a layer of gold with the total thickness of 300nm, and ultrasonically stripping and removing the photoresist with acetone to form the wafer H with the circular electrode.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A high speed DFB laser chip, comprising: including the laser instrument structure, the upper surface of shown laser instrument structure is equipped with ridge waveguide and is located the recess of ridge waveguide both sides, be equipped with first electrode on the ridge waveguide top layer, ridge waveguide both sides set up the BCB figure, and the BCB thickness that is located the recess is highly uniform with ridge waveguide, is provided with the second electrode on the BCB figure, and the second electrode is connected with the first electrode on the ridge waveguide top layer.
2. A high speed DFB laser chip as claimed in claim 1 wherein: the BCB patterns arranged on two sides of the ridge waveguide comprise a first BCB coverage area located in the groove and a second BCB coverage area located outside the groove, the second BCB coverage area is located on the table top on two sides of the groove of the laser structure, and a second electrode is arranged on the second BCB coverage area.
3. A high speed DFB laser chip as claimed in claim 1 or 2 wherein: the size of the BCB graph along the length direction of the laser cavity is smaller than the length of the laser cavity, and areas which are not covered by the BCB are reserved on the two sides of the upper surface of the laser structure, which are close to the light-emitting end face and the backlight end face.
4. A high speed DFB laser chip as claimed in claim 1 wherein: and metal covering layers are respectively arranged on two sides of the bottom of the ridge waveguide and form a first electrode together with the metal covering layer on the top layer of the ridge waveguide, and the first electrode extends along the length direction of the ridge waveguide to form a strip electrode.
5. A high speed DFB laser chip as claimed in claim 1 wherein: the cross section of the groove is in a trapezoid shape with a narrow upper part and a wide lower part; the cross section of the ridge waveguide is a trapezoid with a wide upper part and a narrow lower part.
6. A high speed DFB laser chip as in claim 1 or 5 wherein: the laser structure comprises a buffer layer, a lower limiting layer, a quantum well layer, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a cladding layer which are sequentially grown from bottom to top on a substrate; a secondary epitaxial layer is arranged on the cladding layer, and the secondary epitaxial layer comprises a waveguide layer and an ohmic contact layer from bottom to top;
the cladding layer and the waveguide layer are both made of InP, and the two layers are subjected to secondary epitaxy and then combined together to form an InP waveguide layer;
non-grating areas are reserved on two sides of the grating layer, which are close to the light-emitting end face and the backlight end face.
7. A manufacturing method of a high-speed DFB laser chip is characterized by comprising the following steps:
growing a first epitaxial structure on a substrate to form a wafer A;
carrying out grating manufacturing on the wafer A to form a wafer B;
after the grating is manufactured, a second epitaxial structure is epitaxially grown on the wafer B for the second time to form a wafer C;
manufacturing a ridge waveguide structure on the wafer C to form a wafer D, wherein grooves are formed between the two sides of the ridge waveguide and the table top;
manufacturing an electricity injection window contact strip on the top layer of the ridge waveguide of the wafer D to form a wafer E;
finishing the first electrode manufacturing on the contact strip of the power injection window of the wafer E to form a wafer F;
manufacturing BCB patterns on two sides of a ridge waveguide of a wafer F to form a wafer with the BCB patterns, and etching the wafer with the BCB patterns until a structural wafer G with the thickness of the BCB in the groove consistent with the height of the ridge waveguide is formed;
and manufacturing a second electrode on the BCB pattern and connecting the second electrode with the first electrode.
8. A method of fabricating a high speed DFB laser chip as claimed in claim 7 wherein: growing a first epitaxial structure on a substrate, comprising:
sequentially growing a buffer layer, a lower limiting layer, a quantum well, an upper limiting layer, a first transition layer, an etching stop layer, a second transition layer, a grating layer and a cladding layer on a substrate;
non-grating areas are reserved on two sides of the grating layer, which are close to the light-emitting end face and the backlight end face;
after the grating is manufactured, a second epitaxial structure is continuously grown on the wafer B in a secondary epitaxial growth mode, and the method comprises the following steps: a waveguide layer and an ohmic contact layer are epitaxially grown on the wafer B for the second time;
and manufacturing a ridge waveguide structure on the wafer C, wherein the manufacturing comprises the following steps: and forming a photoetching pattern on the surface of the wafer C, etching the ohmic contact layer through a dry process to form a straight-platform ridge waveguide structure, and etching the waveguide layer to the corrosion stop layer at the bottom through a wet process to form an inverted-platform ridge waveguide structure between the two grooves.
9. A method of fabricating a high speed DFB laser chip as claimed in claim 7 or 8 wherein: the size of the BCB graph along the length direction of the laser cavity is smaller than the length of the laser cavity, and areas which are not covered by the BCB are reserved on the two sides of the upper surface of the laser structure, which are close to the light-emitting end face and the backlight end face.
10. A method of fabricating a high speed DFB laser chip as claimed in claim 7 or 8 wherein: the cross section of the groove is in a trapezoid shape with a narrow upper part and a wide lower part; the cross section of the ridge waveguide is a trapezoid with a wide upper part and a narrow lower part.
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