JPH03177088A - Method of manufacturing surface emitting semiconductor laser - Google Patents

Abstract

PURPOSE:To make it possible to form a very small section to be buried which has a small dependence upon crystal azimuth performance and remove etching mask completely by using a laminated layer body of an SiO2 film and a resist layer as a mask, and then carrying out chemical etching for GaAlAs and the SiO2 film. CONSTITUTION:A buffer layer 2, a first clad layer 3, an activity layer 4, a second clad layer 5, a cap layer 6, and a first mask layer 7 are formed continuously on a substrate 1. On the mask layer 7 there are formed an SiO2 film 8 and further a resist layer 9. The SiO2 film 8 excepting the area where the resist layer 9 is formed is removed by etching with an etchant for SiO2. Then, a lamination layer body of the SiO2 film 8 and the resist layer 9, which is used as a mask, is etched up to a section directly over the first clad layer 3 so that a round-shaped mesa section may be formed. Then, the first mask layer 7 is side-etched with a GaAlAs etchant and a non-reactive section 8a of the SiO2 film 8 is exposed. After that process is over, the SiO2 film 8 is etched and removed with the etchant for SiO2. During this operation, both the resist layer 9 and a reactant 10 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a surface-emitting semiconductor laser having a buried structure in which a buried portion is formed around a buried portion including an active region.

[Conventional technology]

In a manufacturing method of a surface-emitting semiconductor laser having a buried structure in which an active region is buried, there is a manufacturing method in which the active region is buried by selective liquid phase epitaxy (selective LPE method) using a GaA IAs thin film as a mask. It has been proposed (Japanese Patent Application No. 63-332066, etc.). FIG. 2 is a sectional view showing the main steps of such a manufacturing method. First, G
On the aAs substrate 21, a buffer layer 22.degree. first cladding layer 23. Active layer 24. 2nd cladding layer 25°crystal layer 2
6. A mask layer 27 made of a GaAlAs film is crystal-grown in this order, and a resist layer 28 is further patterned on the surface of the mask Jii 27 (FIG. 2(a)). By chemical etching using a sulfuric acid-based etchant using the resist layer 28 as a mask, etching is performed up to just above the first craft 123 to form a mesa portion (FIG. 2(b)). Then,
After removing the resist layer 28, the first current blocking layer 31. is removed by selective LPE using the mask layer 27 as a mask. After forming the second current blocking layer 32, the mask layer 27 is removed by etching. Then, a buried part A and a buried part B surrounding it are formed on the substrate 21 (second
Figure (C)). Thereafter, a reflecting mirror, electrodes, etc. are further formed to manufacture a surface emitting type semiconductor laser.

Also, unlike this manufacturing method, it is possible to use SiO□ film as a mask or active ion beam etching method (RI).
A method of forming an embedded part using the BE method has also been proposed (IEICE Spring National Conference, 1989, C-417). In this manufacturing method, after an active layer, a cladding layer, a cap layer, etc. are successively formed on a substrate, a SiOg film of a predetermined diameter is further formed, and the active layer is etched away by the RIBE method until a desired thickness remains. Thereafter, portions damaged by ion beam irradiation are removed by chemical etching, and a buried portion is formed by selective LPE using this SiOg film as a mask.

[Problem to be solved by the invention]

However, in the manufacturing method that uses a sulfuric acid-based etchant to form the buried part (mesa part), the etching is dependent on the crystal orientation, and the amount of side etching is large.
There is a problem that it is not possible to obtain an embedded part having a desired shape.

In addition, in the above-mentioned manufacturing method using the RIBE method, when chemical etching is performed, the 5i02 film is hardly etched, so the lower part thereof is side-etched, and there is a risk that the SiO□ film may be peeled off during cleaning after the etching process.
Furthermore, the ground layer, active layer, and camp layer that constitute the buried portion also lack uniformity. Therefore, in order to solve these difficulties, it is conceivable to further provide a GaAlAs film below the 5i02 film, which serves as a mask when performing the selective LPE method.

However, with the hydronic acid-based etchant for SiO□, S
When trying to remove the iO□ film, the SiO2 film and this G
Since it has reacted with the aA IAs film, it cannot be completely removed using an enchantment for SiO2.

Another possibility is to form the buried part by the RIBE method using a resist layer formed on the GaA IAs mask layer as a mask. cannot be completely removed. FIG. 3 is a cross-sectional view showing the state after irradiation with a reactive ion beam in such a manufacturing process, in which a degraded resist residue 29 remains on the GaAlAs mask layer 27. Therefore, there is a risk that the system used in the subsequent selective LPE method may be contaminated.

The present invention has been made in view of the above circumstances.
5ift as a mask when etching with IBE method
After forming the buried part by etching using the RIBE method using a laminated mask of the film and the resist layer, the GaA
Etching treatment with etchant for lAs + S + O
By continuing to perform the etching process using the etchant for No. 2 and removing the laminated mask, a highly accurate
It is an object of the present invention to provide a method for manufacturing a surface emitting semiconductor laser that can obtain a first mask layer made of a GaAlAs film and can miniaturize the active region.

[Means to solve the problem]

A method for manufacturing a surface-emitting semiconductor laser according to the present invention includes a method for manufacturing a surface-emitting semiconductor laser in which a buried portion is formed around a buried portion including an active region. a step of forming a first mask layer made of a GaAlAs film in this order; a step of patterning a second mask layer made of laminating a SiOg film and a resist layer on the first mask layer; forming the buried portion by removing a portion of the stacked body and the first mask layer by a reactive ion beam etching method using the layer as a mask; and removing a portion of the first mask layer using an etchant for GaAlAs. After removing the peripheral edge of the second film, the second film is chemically etched.
The method is characterized by comprising a step of removing a mask layer, and a step of forming the buried portion by selective liquid phase epitaxy using the first mask layer as a mask.

[Effect]

In the method for manufacturing a surface emitting semiconductor laser of the present invention,
As a mask in the RIBE method, a laminate (second mask N) of a Sin film and a resist layer is used.

Then, GaA IAs only at the periphery of the mesa
The first mask layer made of a film reacts with the Sin film. Next, an etching process is performed using an etchant for GaAlAs. Then, the first mask layer is side etched to expose unreacted portions of the Si0g film. Therefore, Si
The second mask layer can be completely removed by etching the Si0g film using an etchant for n. It is therefore possible to obtain a first mask layer free of residues.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a cross-sectional view showing the steps of a method for manufacturing a surface-emitting semiconductor laser according to the present invention. First, a buffer layer 2. First cladding layer 3. Active layer 4, second cladding layer 5. Cap layer 6. Ga+-XA1. As film (X≧
0.3) is continuously grown. Next, electron beam evaporation (EB) is applied onto the first mask layer 7.
Using a vapor deposition method, a SiO2 film 8 (film thickness: ~0.2 μm) was deposited.
), and then a resist layer 9 is formed thereon in a pattern with a diameter of 5 μm (FIG. 1(a)).

The SiO□ film 8 other than the resist layer 9 is
It is removed by etching with a suitable etchant such as BHF (FIG. 1(b)). Next, RIB is performed using the stacked body (second mask layer) of the SiO2 film 8 and the resist layer 9 as a mask.
Using the E method, this grown layer is etched to just above the first cladding layer 3 to form a circular mesa portion.

At this time, at the end of the 5ift film 8, Sing and GaAl
The reactant 10 with As (first mask layer 7) has a width of 0.2
It is generated over a range of less than μm (Fig. 1(C)).

GaAlAs etchant e.g. H2SO4: Hz (
h: H2O=t:S:S solution (30°C), about 3
Etch for seconds. Then, the first mask layer 7 is side-etched by about 0.3 μm, and the 5i02 film 8
The unreacted portion 8a of is exposed (FIG. 1(d)). next,
SiO□ with an etchant for SiO□ e.g. BHF
The film 8 is removed by etching. At this time, the resist layer 9 and the reactant 10 are also removed (FIG. 1(e)).

By selective LPE method using the first mask layer 7 as a mask,
First current blocking layer 11. After growing the second current blocking layer 12 to define the buried portion, the first mask layer 7 is removed by etching to define the buried portion. A flattening layer 13° and a semiconductor multilayer film reflecting mirror 14 are placed on the buried portion and the buried portion.
．． Contact layer 15. Electrodes 16 are formed in this order.

Finally, after removing the substrate 1 by etching to form an exit window 17, a dielectric multilayer reflector 18 is formed on the exposed lower surface of the buffer layer 2, and an electrode 19 is formed on the lower surface of the remaining substrate l. to manufacture a surface-emitting semiconductor laser (see Figure 1 (')
). Note that the light output is taken out from the substrate 1 side as shown by the white arrow.

The manufacturing process described above is an example of the manufacturing method of the present invention, and the mesa shape of the buried part is formed using the RIBE method, and the selective LPE method using a mask layer made of GaAlAs is performed. The present invention can be applied to manufacturing a surface emitting type semiconductor laser having any configuration as long as the method is for manufacturing a surface emitting type semiconductor laser by embedding the active layer.

〔Effect of the invention〕

In the manufacturing method of the present invention, a mesa portion is shaped by the RIBE method using a laminate of a Si0g film and a resist layer as a mask,
Then chemical etching on GaAlAs.

Since chemical etching is performed on SiO□, it is possible to form a minute buried portion with little dependence on crystal orientation, and the etching mask can be completely removed.

As a result, the active region can be miniaturized with good stability, and the threshold current can be reduced. Further, since there is no etching mask residue, a good surface-emitting semiconductor laser without any impurities can be manufactured, and the yield is improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the steps of a method for manufacturing a surface-emitting semiconductor laser according to the present invention, FIG. 2 is a cross-sectional view showing the steps of a conventional method for manufacturing a surface-emitting semiconductor laser, and FIG. FIG. 3 is a cross-sectional view showing a part of a process of a conventional method for manufacturing a surface-emitting semiconductor laser.

Claims (1)

[Claims] 1. A method for manufacturing a surface-emitting semiconductor laser in which a buried portion is formed around a buried portion including an active region, comprising: a first layer comprising a laminate and a GaAlAs film constituting the buried portion; a step of forming a mask layer in this order; a step of patterning a second mask layer formed by laminating a SiO_2 film and a resist layer on the first mask layer; and a step of forming a mask layer using the second mask layer as a mask. forming the buried portion by removing a portion of the stacked body and the first mask layer by active ion beam etching; and removing a peripheral portion of the first mask layer using an etchant for GaAlAs. and then chemically etching the SiO_2 film to remove the second mask layer, and forming the buried portion by selective liquid phase growth using the first mask layer as a mask. A method for manufacturing a surface-emitting semiconductor laser.