阅读说明：本技术 一种新型脊形波导结构及制作方法 (Novel ridge waveguide structure and manufacturing method ) 是由 黄永光 王宝军 张瑞康 朱洪亮 于 2019-08-31 设计创作，主要内容包括：本发明提出了一种新型脊形波导结构及制作方法,具体的制作方法包括以下步骤,S1,在激光器结构材料上制作波导掩膜条；S2,利用腐蚀液I,腐蚀掉波导掩膜条外侧的重掺杂顶接触层；S3,利用腐蚀液II,在InP覆盖包层上腐蚀出倒台结构,所述倒台结构的高度为InP覆盖包层厚度的2/3~4/5；S4,利用腐蚀液III,在剩余的InP覆盖包层上腐蚀出直台结构；S5,除去波导掩膜条。本发明通过改变倒台脊形波导的结构,保持了倒台结构相对于直台结构的主要优点,既提高了注入电流的汇聚和钳制作用,又消除了倒台底部的锐角,解决了绝缘介质膜和电极金属膜层在倒台底颈部易断裂而造成器件失效的问题。(The invention provides a novel ridge waveguide structure and a manufacturing method thereof, and the specific manufacturing method comprises the following steps of S1, manufacturing a waveguide mask strip on a laser structure material, S2, corroding a heavily doped top contact layer on the outer side of the waveguide mask strip by using a corrosive liquid I, S3, corroding a reversed platform structure on an InP covering cladding layer by using a corrosive liquid II, wherein the height of the reversed platform structure is 2/3 ~ 4/5 of the thickness of the covering cladding layer, S4, corroding a straight platform structure on the residual InP covering cladding layer by using a corrosive liquid III, and S5, removing the waveguide mask strip.)

1. A manufacturing method of a novel ridge waveguide structure is characterized by comprising the following steps:

s1, manufacturing a waveguide mask strip (7) on the laser structural material;

s2, etching off the heavily doped top contact layer (6) on the outer side of the waveguide mask strip (7) by using the etching solution I;

s3, etching a reversed mesa structure (8) on the InP cladding layer (5) by using an etching solution II, wherein the height of the reversed mesa structure (8) is 2/3 ~ 4/5 of the thickness of the InP cladding layer (5);

s4, etching a straight platform structure (9) on the residual InP covering cladding layer (5) by using the etching solution III;

s5, removing the waveguide mask strip (7).

2. A method for fabricating a novel ridge waveguide structure according to claim 1, wherein in step S1, the laser structure material is a fabry-perot laser or a dfb laser structure material, and the laser structure material comprises an InP buffer layer (2), an MQW active layer (3), a grating and filling layer and an etch stop layer (4), an InP capping cladding layer (5) and a heavily doped top contact layer (6) sequentially grown on an InP (100) plane substrate (1).

3. A method for fabricating a novel ridge waveguide structure according to claim 2, wherein the substrate (1) is doped n-type or p-type; the InP buffer layer (2) comprises a far-field reduction layer; the MQW active layer (3) comprises a lower separate confinement layer, an MQW layer and an upper separate confinement layer; the doping types of the layers below the MQW layer are the same as that of the substrate (1), and the doping types of the layers above the MQW layer are opposite to that of the substrate (1); the lower and upper respective confinement layers are doped or undoped; the quantum well number of the MQW layer is two wells to ten wells, and the material of the multiple quantum wells is InGaAlAs or InGaAsP.

4. A method for fabricating a novel ridge waveguide structure as claimed in claim 1, 2 or 3, whereinIn step S1, the waveguide mask stripes (7) are arranged along<011>The direction is consistent with that of the ridge waveguide, and the waveguide mask strip (7) is made of SiO₂、Si₃N₄Or a photoresist.

5. A method for fabricating a novel ridge waveguide structure according to claim 4, wherein in step S2, the material of the heavily doped top contact layer (6) comprises InGaAsP and InGaAs; the corrosive liquid I is sulfuric acid selective corrosive liquid which comprises H₂SO₄、H₂O₂And H₂O, and the selective etching solution of sulfuric acid has higher etching rate to the heavily doped top contact layer (6) than to the InP cladding layer (5).

6. A method for fabricating a novel ridge waveguide structure according to claim 1 or 5, wherein in step S3, the etching solution II is a selective etching solution containing HBr and H₃PO₄And H₂O, the corrosion rate of the hydrobromic acid selective etching solution to the InP (100) surface is higher than that to the InP (111) surface, and the corrosion rate of the hydrobromic acid selective etching solution to the InP is higher than that to the InGaAsP and the InGaAs; the thickness of the InP covering cladding (5) is consistent with the height of the ridge waveguide, and the thickness of the InP covering cladding (5) is 1.5-2.0 micrometers; the included angle between the corrosion side surface of the inverted platform structure (8) along the direction of the waveguide mask strip (7) and the corrosion bottom plane is an acute angle, and the acute angle is 50-60 degrees.

7. A method for fabricating a novel ridge waveguide structure according to claim 6, wherein in step S4, said etching solution III is a hydrochloric acid etching solution including Hcl and H₃PO₄And H₂O, and the corrosion rate of the hydrochloric acid corrosion solution to InP is higher than that to InGaAsP and InGaAs; the included angle between the corrosion side surface of the straight platform structure (9) along the direction of the waveguide mask strip (7) and the corrosion bottom plane is close to a right angle, and the included angle is85-95 degrees.

8. A novel ridge waveguide structure is characterized by comprising an inverted platform structure (8) at the upper part and a straight platform structure (9) at the lower part, wherein the longitudinal section of the inverted platform structure (8) is inverted trapezoid, and the inverted platform structure (8) is arranged at the lower part of a heavily doped top contact layer (6); the straight platform structure (9) is arranged on the grating and filling layer and the etching stop layer (4), and the upper part of the straight platform structure (9) is correspondingly connected with the lower part of the inverted platform structure (8); the sum of the height of the inverted mesa structure (8) and the height of the straight mesa structure (9) is equal to the thickness of the InP covering cladding layer (5).

9. The novel ridge waveguide structure of claim 8, wherein the height of the inverted mesa structure (8) is 2/3 ~ 4/5 a of the thickness of the InP cladding layer (5).

10. An active device of a novel ridge waveguide structure, wherein the active device is fabricated by the novel ridge waveguide structure of claim 8 or 9.

Technical Field

The invention belongs to the field of manufacturing of III-V family photoelectronic device chips, and particularly relates to a novel ridge waveguide structure and a manufacturing method thereof.

Background

In the manufacturing process of InP (indium phosphide) -based optoelectronic device chips, the ridge waveguide structure is simple to manufacture, high in process uniformity and repeatability, suitable for large-scale batch production and one of the mainstream methods for manufacturing active waveguides and passive waveguides. In the waveguide fabrication of active devices such as lasers, amplifiers, modulators, etc., particularly active devices made of InGaAlAs (indium gallium aluminum arsenide)/InP MQW (multiple quantum well) materials containing Al (aluminum), device chip manufacturers commonly use ridge waveguide structures to fabricate chips in order to avoid the problem of Al oxidation during the fabrication of buried heterojunction waveguide structures. However, most device chips employ a ridge waveguide structure with vertical sidewalls (k.y.liou, et al., appl. phys. lett., 1991, vol.59(26), pp.3381-3383), i.e., the top and bottom widths of the ridge waveguide strip are very close (called "straight mesa structure"). Limited by the requirements of the laser transmission base transverse mode light emission, the ridge waveguide strip can only be limited within the narrow strip range with the width less than or equal to 3 microns, so that the photoetching alignment process is high in difficulty, and the device performance improvement is limited.

On the basis of a straight platform structure, researchers use a wet method to select an etching solution to manufacture an inverted platform-shaped ridge waveguide structure laser chip (M, Aoki, et al, IEEE Photonics technology letters, 1995, Vol.7 (1), PP.13-15) with an InP (111) surface on the side wall, wherein the top width W of a ridge waveguide strip is wider than the width W of a bottom neck (abbreviated as inverted platform structure), and an acute angle theta is formed between the side surface and a bottom plane of the inverted platform structure, as shown in FIG. 1, W is the width of the top of the ridge waveguide strip, W is the width of the bottom of the ridge waveguide strip, H is the height of the ridge waveguide, and theta is an included angle between an etched side surface and an etched bottom plane along the direction of a waveguide mask strip. The structure of falling the platform compares in straight platform structure has following characteristics: 1. for the laser with the same ridge width w and the same cavity length, the ohmic contact area of the inverted platform structure is larger than that of the straight platform structure; 2. the width w of the bottom of the inverted platform structure is not limited by the contact of a top electrode and photoetching alignment, and can be less than or equal to 2 micrometers; 3. the inverted platform structure has stronger convergence and clamping effects on the current injected into the top of the ridge, and the transverse expansion and leakage current of the straight platform structure are weakened. The characteristics make the inverted platform structure have outstanding advantages in the aspects of reducing the contact impedance of the laser, reducing the threshold current characteristic of the laser and the like, so that the inverted platform structure is particularly suitable for manufacturing high-temperature high-power and high-speed active devices.

However, in the actual chip manufacturing process, the acute angle θ formed at the bottom of the inverted platform often brings a series of problems to the subsequent dielectric film growth process and metal film covering process, such as the thin film on the side wall of the inverted platform, the uneven film at the shadow under the ridge eave, and especially the film crack easily occurs at the acute angle at the bottom of the inverted platform, which seriously affects the device characteristics and reduces the yield.

Disclosure of Invention

Aiming at the problems that the existing inverted platform structure is easy to generate film layer fracture and the yield is low, the invention provides a novel inverted platform ridge-shaped waveguide structure and a manufacturing method thereof, and solves the problem that a dielectric film and a metal film layer are easy to fracture at the bottom neck of an inverted platform.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a manufacturing method of a novel ridge waveguide structure comprises the following steps:

s1, manufacturing waveguide mask strips on the laser structural material;

s2, corroding the heavily doped top contact layer on the outer side of the waveguide mask strip by using corrosive liquid I;

s3, etching a reversed mesa structure on the InP covering cladding layer by using an etching solution II, wherein the height of the reversed mesa structure is 2/3 ~ 4/5 of the thickness of the InP covering cladding layer;

s4, etching a straight platform structure on the residual InP covering cladding by using the etching solution III;

s5, removing the waveguide mask strips.

In step S1, the laser structure material is a fabry-perot laser or a dfb laser structure material, and the laser structure material includes an InP buffer layer, an MQW active layer, a grating and filling layer, an etching stop layer, an InP cladding layer, and a heavily doped top contact layer, which are sequentially grown on an InP (100) substrate.

The substrate is doped in an n type or a p type; the InP buffer layer comprises a far-field reduction layer; the MQW active layer comprises a lower separate confinement layer, an MQW layer and an upper separate confinement layer; the doping types of the layers below the MQW layer are the same as those of the substrate, and the doping types of the layers above the MQW layer are opposite to those of the substrate; the upper and lower separate confinement layers are doped or undoped; the quantum wells of the MQW layer are two wells to ten wells, and the MQW material is InGaAlAs (indium gallium aluminum arsenide) or InGaAsP (indium gallium arsenic phosphide).

In step S1, the waveguide mask stripes<011>The direction of the waveguide mask strip is consistent with that of the ridge waveguide, and the waveguide mask strip is made of SiO₂(silicon dioxide), Si₃N₄(silicon nitride) or photoresist.

In step S2, the material of the heavily doped top contact layer includes InGaAsP and InGaAs (indium gallium arsenide); the corrosive liquid I is sulfuric acid selective corrosive liquid which comprises H₂SO₄(sulfuric acid), H₂O₂(hydrogen peroxide solution) and H₂O (water), and the sulfuric acid selective etching solution has a higher etching rate for the heavily doped top contact layer than for the InP clad layer.

In step S3, the etching solution II is a selective etching solution of hydrobromic acid, and the selective etching solution of hydrobromic acid includes HBr (hydrobromic acid), H₃PO₄(phosphoric acid) and H₂O, the corrosion rate of the hydrobromic acid selective etching solution to the InP (100) surface is higher than that to the InP (111) surface, and the corrosion rate of the hydrobromic acid selective etching solution to the InP is higher than that to the InGaAsP and the InGaAs; the thickness of the InP covering cladding is consistent with the height of the ridge waveguide, and the thickness of the InP covering cladding is 1.5-2.0 microns; the included angle between the corrosion side surface of the inverted platform structure along the direction of the waveguide mask strip and the corrosion bottom plane is an acute angle, and the angle of the acute angle is 50-60 degrees.

In step S4, the etching solution III is a hydrochloric acid etching solution, and the hydrochloric acid etching solution includes Hcl (hydrochloric acid) and H₃PO₄And H₂O, and the corrosion rate of the hydrochloric acid corrosion solution to InP is higher than that to InGaAsP and InGaAs; the straight platform structure means that an included angle between the corrosion side surface and the corrosion bottom plane along the direction of the waveguide mask strip is close to a right angle, and the included angle is 85-95 degrees.

A novel ridge waveguide structure comprises an inverted platform structure on the upper portion and a straight platform structure on the lower portion, wherein the longitudinal section of the inverted platform structure is inverted trapezoid, the inverted platform structure is arranged on the lower portion of a heavy doping top contact layer, the straight platform structure is arranged on a grating, a filling layer and an etching stop layer, the upper portion of the straight platform structure is correspondingly connected with the lower portion of the inverted platform structure, the sum of the height of the inverted platform structure and the height of the straight platform structure is equal to the thickness of an InP covering cladding layer, and the height of the inverted platform structure is 2/3 ~ 4/5 of the thickness of the InP covering cladding layer.

An active device of a novel ridge waveguide structure, which is fabricated by the novel ridge waveguide structure of claim 8 or 9.

The invention has the beneficial effects that:

the invention changes the structure of the inverted platform ridge waveguide through a simple thought and a simple corrosion operation process, keeps the main advantages of the inverted platform structure relative to a straight platform structure, improves the convergence and clamping effects of injected current, eliminates an acute angle at the bottom of the inverted platform, solves the problem that an insulating dielectric film and an electrode metal film layer are easy to break at the neck part of the inverted platform bottom in the subsequent process to cause device failure, and obviously improves the manufacturing yield of active device chips.

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 is a schematic cross-sectional view of an inverted ridge waveguide structure in the prior art.

FIG. 2 is a schematic structural diagram of a laser structural material according to the present invention.

Fig. 3 is a schematic structural diagram of waveguide mask stripes fabricated on a laser structural material.

Fig. 4 is a schematic diagram of a state where the heavily doped top contact layer outside the waveguide mask stripes is etched away.

FIG. 5 is a schematic view showing a state where a reverse mesa structure is etched.

FIG. 6 is a schematic view showing a state where a mesa structure is etched.

Fig. 7 is a schematic view of a state after removing the waveguide mask stripes.

Fig. 8 is a schematic cross-sectional view of a single ridge waveguide laser fabricated on an n-InP substrate using the present invention.

Fig. 9 is a schematic cross-sectional view of a double-trench ridge waveguide laser fabricated on an n-InP substrate using the present invention.

Fig. 10 is a schematic cross-sectional view of a double trench ridge waveguide laser fabricated on a p-InP substrate using the present invention.

In the figure, 1 is a substrate, 2 is an InP buffer layer, 3 is an MQW active layer, 4 is a grating and filling layer and an etching stop layer, 5 is an InP covering cladding layer, 6 is a heavily doped top contact layer, 7 is a waveguide mask strip, 8 is an inverted mesa structure, and 9 is a straight mesa structure.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.