JPH06152062A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To acquire highly accurate laser diode edge face of easy wafer process. CONSTITUTION:An LD edge face groove 6 is first formed by dry etching in an epitaxial wafer after crystal formation, and the groove 6 is filled with dissimilar semiconductor material 13. After electrode formation process is finished, the dissimilar material 13 inside the groove is removed and an LD edge face 6 is formed. Thereby, edge face formation process becomes easy, and a highly accurate LD edge face of good flatness and less damage can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser, and more particularly to a method for forming an end face of a semiconductor laser and a functional element including the semiconductor laser.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a conventional method for forming an end face of a semiconductor laser by cleavage. In the conventional end face formation of a semiconductor laser, a crystal plane 51 is formed after a wafer process is completed, especially after an electrode is formed. For example, a laser end face, that is, an end face mirror of a laser resonator is formed by cleaving the wafer along the {110} face in a wafer having a (100) face. In addition, not only cleavage but also wet etching or dry etching was used to form the laser facet to obtain the crystal face.

FIGS. 5 and 6 show, for example, Microelectronic.
It is a figure which shows the method of forming the laser end surface by the conventional dry etching shown by Engineering 9 (1989) p485-p489. In FIG. 5, 1 is a substrate, 2 is an active layer, 3
Is the upper cladding layer. 4 is a surface electrode formed on the upper clad layer 3, 5 is Au plating on each surface electrode 4,
Reference numeral 6 denotes a groove formed by dry etching in the region between the surface electrodes 4 and corresponds to the end face of the laser diode (LD).

Further, in FIG. 6, reference numeral 21 is a hard bake resist, 22 is an insulating film made of SiO or SiN, 23 is a resist, and 24 is a multilayer mask composed of the hard bake resist 21, the insulating film 22 and the resist 23. Is.

Next, the manufacturing method will be described. In FIG. 5, a buffer layer, a lower clad layer (not shown), an active layer 2, and an upper clad layer 3 are formed on the substrate 1 by MOCVD.
Lamination growth is performed by a vapor phase growth method such as a (Metal Organic Chemical Vapor Deposition) method or an MBE (Molecular Beam Epitaxy) method (FIG. 5 (a)). Depending on the structure of the LD,
A waveguide or ridge having a width of several μm is formed, and then the waveguide or ridge is embedded in a block layer to grow a contact layer. Here, since the detailed structure changes depending on the LD structure, the structure is simply DH (Double Heter) in FIG.
ostructure) structure.

Next, a surface electrode 4 is formed on the wafer surface,
Further, Au plating 5 for wire bond is formed (FIG. 5).
(b)). Next, as shown in FIG. 6, a multilayer resist 24 including a hard bake resist 21, an insulating film 22, and a resist 23 is applied on the surface of the wafer. This multilayer resist structure 2
4, the uppermost layer resist 23 becomes almost flat,
The mask pattern for forming the end face is transferred to the resist 23.

Next, using this resist 23 as a mask, C
The insulating film 22 and the hard bake resist 21 are etched by the RIE method using F4 and O2 gas to complete the end face forming mask.

Finally, using Cl 2 / Ar gas, CAI
By etching the semiconductor layers 1, 2 and 3 by the BE (Chemically Ion Beam Etching) method, a vertical and flat etching end face 6 can be formed, and that portion can be used as a laser end face (FIG. 5 (c )).

[0009]

In the conventional laser end face forming method by etching as described above, in order to prevent the end face from being contaminated, after the step of forming the electrode made of the surface electrode 4 and the Au plating 5 is completed, Finally, it was necessary to form the end face. Therefore, it was not possible to form a uniform resist pattern with a single-layer resist due to the influence of the step of the Au plated portion 5. Here, since the shape of the mask reflects the shape of the end face at the time of etching, the mask needs to have a uniform shape. Therefore, conventionally, the mask shape is made uniform by flattening the final resist 23 by the multilayer resist structure 24.
However, in this multilayer resist structure 24, it is necessary to provide the intermediate layer 22 in order to prevent the resist from being mixed, the number of times of resist coating and baking is increased, and further, the intermediate layer 22 and the hard bake resist layer 21. There is a problem that the process becomes very complicated as compared with the single-layer resist mask because it is necessary to separately etch.

Further, even if the multi-layer resist is used as described above, the influence of the step difference cannot be completely removed.
After all, there was a problem that it was difficult to obtain a uniform shape.

The present invention has been made in order to solve the above problems. It is possible to easily form an end face by etching without using a multi-layer resist structure, and the flatness of the end face of etching is also achieved. Provided is a method for manufacturing a semiconductor laser, which can be improved and which can obtain a laser end face equivalent to an LD end face formed by cleaving without being contaminated on the end face and without affecting the device characteristics and device life of the LD. The purpose is to do.

[0012]

In the method of manufacturing a semiconductor laser according to the present invention, an end face is formed on a wafer after crystal growth, and a groove formed thereby is selected with a different semiconductor material different from the epitaxial wafer material. By embedding and flattening it, the electrode is formed, and finally the groove is formed again by the selective etchant.

Further, according to the present invention, the heterogeneous semiconductor material is selectively embedded by a vapor phase epitaxy method using a dry etching mask for forming a laser end face.

Further, according to the present invention, the groove is filled with a material different from the semiconductor substrate material such as SOG or polyimide resin.

Further, according to the present invention, the above-mentioned different materials are applied by spin coating and hard-baked to fill the grooves.

Further, according to the present invention, the end face is protected by an insulating film and then the groove is selectively filled with a different material.

Further, according to the present invention, the dissimilar material is removed by selective etching after the electrode forming step.

[0018]

In the present invention, since the end face forming groove is formed directly on the epitaxial wafer after crystal growth, since the wafer is flat, the single layer resist can be used as a mask, and thus the uniform resist can be formed. Side wall (end face) of the groove where the mask is obtained and formed by etching
Also becomes flat. Further, by selectively filling the groove with a different material, the end face can be protected and the wafer becomes flat even in the subsequent electrode forming process, so that the processing accuracy can be improved.

Further, since the material buried in the groove can be easily removed by the selective etchant, it is possible to finally obtain a uniform and flat LD end face.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Example 1. FIG. 1 is a diagram showing a flow of a method for manufacturing a semiconductor laser according to an embodiment of the present invention.
Is a semiconductor substrate made of GaAs or InP, 2 is an active layer, 3 is an upper cladding layer, 6 is an LD end face forming groove formed by dry etching, 11 is an insulating film serving as an etching mask, and 13 is a heterogeneous semiconductor material.

Next, the process flow of this manufacturing method will be described. First, on an n-GaAs substrate 1, an n-GaAs buffer layer, an n-AlGaAs lower clad layer (both not shown), an undoped active layer 2 having a bulk or QW (quantum well) structure, and a p-AlGaAs upper clad layer. Three
Are crystal-grown by a vapor phase growth method such as MOCVD or MBE. In general, since the layer structure differs depending on the LD structure, only the DH structure is shown in FIG. Further, depending on the structure of the LD, in order to efficiently perform current injection, a ridge having a width of several μm is formed in the DH structure portion, both sides are filled with a current block layer, and finally p-GaAs is formed.
A contact layer (not shown) is grown.

Thus, the crystal growth for producing the LD is completed. Next, as shown in FIG. 1 (a), an insulating film 11 of SiO2 or the like, which serves as an etching mask, is formed on the epitaxial wafer after the crystal growth is completed, and an LD end face forming groove 6 is formed thereon by a single layer resist. A resist mask (not shown) for forming is prepared. A positive type resist is used as the single-layer resist, and the resist pattern is formed by exposure using a stepper or the like. Furthermore, C
By etching the insulating film 11 by RIE using F4 as a gas and removing the resist by plasma ashing with O2 gas, the etching mask 11 shown in FIG. 1A can be formed.

Next, the RIE method using Cl 2 gas,
RIBE (Reactive Ion Beam Etching) method or CAI
By dry etching such as BE method, a groove 6 having a width of several μm to several tens of μm is formed with a depth of about 5 μm so that the groove bottom passes through the active layer 2 and reaches the substrate 1. After forming the groove 6, the insulating film 11 is used as a selective growth mask, and the inside of the groove 6 is selectively grown again with a different semiconductor material 13 such as GaInP or AlGaInP (FIG. 1B).

Next, the insulating film 11 is removed by wet etching with an HF-based etchant to form the surface electrode 4,
Further, Au plating 5 for wire bonding is formed (FIG. 1 (c)).

Next, the wafer is polished to a thickness of about 100 μm to form the back electrode 7. Finally, GaAs (or AlGaAs) which is an epitaxial wafer material and GaInP (or AlGa) which is a heterogeneous semiconductor material embedded therein.
When only the GaInP (or AlGaInP) embedded layer 13 is selectively etched using a selective etchant that selectively etches InP), as shown in FIG. 1 (d), it has a clean end face and has flatness ( The LD end surface 6 having excellent flatness can be formed.

In Example 1 as described above, since the end face forming groove is formed directly on the epitaxial wafer after crystal growth, since the wafer is flat, the single layer resist can be used for forming the mask, and thus the uniform resist can be formed. Even when the semiconductor layer is etched with a different mask, that is, the flat insulating film 11 and the resist for etching the same is also a flat resist, or a resist in place of the insulating film 11, the semiconductor layer is flat and uniform. A resist mask can be obtained, and the side walls (end faces) of the grooves formed by etching can be flat. Further, since the groove is selectively filled with the heterogeneous semiconductor material 13, the end face 6 can be protected even in the subsequent electrode forming process, and the wafer can be flattened accordingly, so that the processing accuracy of the surface electrode 4 and the like is improved. can do. Further, since the material 13 embedded in the groove can be easily removed by the selective etchant, the LD end surface 6 which is uniform, flat and highly reliable can be finally obtained.

Example 2. In the first embodiment described above, the example in which the heterogeneous semiconductor material 13 is directly selectively grown in the groove by using the insulating mask 11 for forming a groove is shown. However, as shown in the second embodiment in FIG. The insulating film 12 having a thickness of λ / 2n (λ: LD wavelength, n: refractive index) or the like may be formed and then filled with the heterogeneous semiconductor material 13. in this case,
The insulating film 12 is formed as a passivation film that protects the end surface 6.

In the second embodiment, the same effect as that of the above-described embodiment can be obtained, and the laser end face 6 can be protected more than in the first embodiment.

Example 3. Further, in FIGS. 1 and 2 showing Examples 1 and 2 above, the material to be buried in the groove is different semiconductor material 13 different from the epitaxial wafer material, and the groove is flattened by the selective growth. As shown in Example 3 of FIG. 3, SOG (Spin on Glas
s) or polyimide resin or the like 14 may be embedded by spin coating or the like, flattened by hard baking, and removed after the electrode forming process is completed, as in the first and second embodiments.

In the third embodiment, the same effect as that of the first embodiment can be obtained. Example 4. Further, as in the fourth embodiment shown in FIG. 4, after forming the passivation film 12 on the laser end face as in the second embodiment shown in FIG. 2, the groove may be filled with SOG, resin or the like 14. . Example 4
In, the effect similar to that of the above-described second embodiment can be obtained.

[0031]

As described above, according to the method of manufacturing a semiconductor laser of the present invention, the groove for the LD end face is formed in the epitaxial wafer after crystal growth.
A uniform etching mask can be easily formed by a single-layer resist process, and a flat LD end face can be formed. Further, by filling the inside of the groove with a different semiconductor material or different material after the groove is formed and flattening the surface, the electrode forming process can be easily performed even if the groove is formed prior to the electrode formation, and the end face is There is an effect that the LD end face can be formed without being contaminated.

Further, by protecting the sidewall of the groove with an insulating layer before filling the inside of the groove with a different material, the insulating film can be used not only as a passivation film for the LD, but also when removing the different material. There is an effect that it becomes a pollution prevention layer and a more reliable LD end face can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a process flow of a method for manufacturing a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a diagram showing a process flow of a method for manufacturing a semiconductor laser according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a process flow of a method for manufacturing a semiconductor laser according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a process flow of a method for manufacturing a semiconductor laser according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a process flow of a conventional semiconductor laser end face forming method.

FIG. 6 is a diagram showing a method for forming a conventional end face forming mask.

FIG. 7 is a diagram showing another conventional method for forming an LD end face.

[Description of Reference Signs] 1 semiconductor substrate 2 active layer 3 upper cladding layer 4 front surface electrode 5 Au plating 6 LD end face etching groove 7 back surface electrode 11 insulating film 12 insulating film 13 different semiconductor material 14 SOG or polyimide resin 21 resist 22 insulating film 23 Resist 51 Cleaved Surface

Claims (7)

[Claims] 1. A method of manufacturing a semiconductor laser including a step of forming a laser end face by dry etching, the step of crystal-growing an epitaxial wafer having a semiconductor layer constituting a laser including a semiconductor active layer, and the step of: A step of forming a laser end face by dry etching, a step of filling the groove formed by the laser end face forming step with a desired material, and then forming an electrode on a region other than the laser end face forming part of the epitaxial wafer. A method of manufacturing a semiconductor laser, comprising: 2. The method for manufacturing a semiconductor laser according to claim 1, wherein the step of filling the groove is performed by filling with a semiconductor material different from a semiconductor substrate material. 3. The method for manufacturing a semiconductor laser according to claim 2, wherein in the step of burying the heterogeneous semiconductor material, a mask for dry etching for forming the laser end face is used to selectively bury by a vapor phase epitaxy method. A method for manufacturing a semiconductor laser, comprising: 4. The method for manufacturing a semiconductor laser according to claim 1, wherein the step of filling the groove is performed by filling with a material different from a semiconductor substrate material such as SOG or polyimide resin. 5. The method for manufacturing a semiconductor laser according to claim 4, wherein the different material is applied by spin coating, and the groove is filled by hard baking. 6. The method for manufacturing a semiconductor laser according to claim 2, further comprising protecting the laser end face formed by the dry etching with an insulating film before filling the groove with the different material. A method for manufacturing a characteristic semiconductor laser. 7. The method of manufacturing a semiconductor laser according to claim 2, wherein the different material is removed by selective etching after the electrode forming step.