JP2710248B2 - Manufacturing method of semiconductor laser - Google Patents

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 which is a main component of a communication system.

[0002]

2. Description of the Related Art With the advancement of optical communication technology, its application field is rapidly expanding from backbone transmission systems to subscriber systems, LAN data links, and other systems. Since semiconductor lasers used in these fields are used in various environments and in large quantities, they are required to be excellent in environmental performance and low in price, and active research and development are being carried out. As a method for producing such a high-performance and low-cost device, a laser in which a buried layer is formed by a metal organic chemical vapor deposition (MOVPE) method having excellent uniformity and controllability has attracted attention.

In the formation of a buried layer using metalorganic vapor phase epitaxy, the mesa shape is processed by wet etching, but side etching occurs in which the crystal under the mask is etched. Therefore, it is difficult to control the width of the active layer, and the uniformity and reproducibility are not good. On the other hand, if the mesa etching is performed by dry etching, the width of the active layer can be easily controlled because side etching hardly occurs, and processing can be performed uniformly and with good reproducibility within the wafer surface. Realization of a laser is desired.

[0004]

However, it is widely known that a damage layer is formed on the bottom and side surfaces by dry etching, and in the above-described conventional method, damage is left in the buried layer, and the reliability of the laser element is reduced. It is feared that it will decrease and crystal defects in the buried layer will increase.

The damaged layer can be removed by wet etching. However, since the adhesion between the dielectric film and the InP cladding layer is good, the InP layer has an inverted mesa shape near the mask.

FIG. 6 is a sectional view for explaining a main part of a vertical mesa having an inverted mesa shape by a conventional semiconductor laser manufacturing method. FIG. 7 is a cross-sectional view illustrating abnormal growth of an inverted mesa shape by a conventional semiconductor laser manufacturing method.

For this reason, there is a problem that the crystal of the buried layer is deteriorated or a space is formed. Also, depending on the embedding conditions, the orientation of the projections is affected by the plane orientation, and the projections 1
There was a problem that something like 8 could be done.

The present invention has been made in view of the above points, and provides a method of manufacturing a semiconductor laser, which is a main component of a communication system, which is excellent in uniformity and controllability and does not cause damage to crystals. The purpose is to do.

[0009]

According to the present invention, there is provided a method for manufacturing a semiconductor laser having a buried structure, which is formed on an InP substrate of a first conductivity type. And an InGaAs layer or I
forming a cap layer made of an nGaAsP layer;
A step of processing the semiconductor substrate into a mesa shape by dry etching using the dielectric film processed in a stripe shape as a mask; a step of removing the damaged layer formed by the dry etching by wet etching; Forming a current confinement layer comprising a two-conductivity-type InP current block layer and a first-conductivity-type InP current block layer; and forming the dielectric film and the InGaAs layer or I
a step of selectively etching and removing the nGaAsP layer; and a step of forming a second conductivity type InP layer on the substrate by a vapor phase growth method.

Alternatively , the current confinement is caused by the above-mentioned second conductivity type In.
P current block layer and first conductivity type InP current block
Instead of the current confinement structure consisting of
It is characterized by being a current confinement layer composed of a lock layer.

[0011]

Since the cap layer made of InGaAs or InGaAsP is inserted between the InP clad layer and the dielectric film, the cap layer is etched earlier than the InP clad layer even if wet etching is performed on the vertical mesa after dry etching. Therefore, the InP layer does not have an inverted mesa shape. In addition, since the removal of the damage layer is performed by etching of 0.2 μm or less, high uniformity and controllability obtained by dry etching are not lost. Even after the buried growth by the MOVPE method, a space that cannot be buried is generated,
The crystallinity does not deteriorate. Thus, according to the present invention, in-plane uniformity, reproducibility is high, the width of the active layer is easily controlled, and the damaged layer of dry etching is removed.
In addition, a good buried layer can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIGS. 1 to 5 are cross-sectional views for explaining a main part of a method of manufacturing a buried semiconductor laser on an n-InP substrate according to the present invention in the order of steps.

First step: M is placed on the n-type InP substrate 1
The n-type InP cladding layer 2 and the InGa
A layer including an AsP active layer 3 and a p-type InP cladding layer 4 is formed, and InGaAs is further formed on the p-type InP cladding layer 4.
An s cap layer 5 is formed (FIG. 1).

Second step: SiO ₂ film 6 on semiconductor substrate 1 by thermal CVD using SiH ₄ gas and oxygen gas
Is formed and processed into a strite pattern by photolithography and reactive ion etching using CF ₄ , and the resist is removed (FIG. 1).

Third step: The n-InP cladding layer is etched by reactive ion etching (RIE) using chlorine gas to form a vertical mesa (FIG. 2).

Fourth step: The surface of the vertical mesa is reduced to 0.1 μm or more by an etchant obtained by dissolving bromine in methanol.
Etching is performed by 0.2 μm to remove the damaged layer (FIG. 3).

Fifth step: A p-InP current block layer and an n-InP current block layer are formed by selective growth by MOVPE using the SiO ₂ film 6 as a mask (FIG. 4).

Sixth step: The SiO ₂ film 6 is removed using buffered hydrofluoric acid, and sulfuric acid: hydrogen peroxide: water is used in a ratio of 1:
After selectively etching the InGaAs layer 3 with a 1: 5 etchant, a second n-type layer is formed by MOVPE.
An InP buried layer and a p-InGaAsP contact layer are formed (FIG. 5).

Seventh step: An electrode is formed and cut into chips.

The light etching method used in the present invention is not limited to reactive ion etching (RIE), but reactive ion beam etching (RIBE) can also be used. Further, the gas to be used is not limited to chlorine gas, and argon gas may be added to chlorine gas, and gas containing methane or ethane gas may be used. In the above embodiment, an n-InP substrate is used, but a p-InP substrate may be used. Further, the present invention can be applied to other current confinement structures, and is effective even when the current confinement structure portion is a high-resistance InP layer.

[0022]

As described above, according to the present invention, since the mesa shape is formed by dry etching, the width of the active layer can be accurately controlled, and the damage layer of dry etching can be removed. And an excellent effect that a good buried layer can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating one step of a method for manufacturing a buried semiconductor laser on an n-InP substrate according to the present invention.

FIG. 2 is a cross-sectional view illustrating one step of a method of manufacturing a buried semiconductor laser on an n-InP substrate according to the present invention.

FIG. 3 is a cross-sectional view illustrating one step of a method for manufacturing a buried semiconductor laser on an n-InP substrate according to the present invention.

FIG. 4 is a cross-sectional view illustrating one step of a method for manufacturing a buried semiconductor laser on an n-InP substrate according to the present invention.

FIG. 5 is a cross-sectional view illustrating one step of a method of manufacturing a buried semiconductor laser on an n-InP substrate according to the present invention.

FIG. 6 is a cross-sectional view illustrating a main part of a vertical mesa having an inverted mesa shape by a conventional semiconductor laser manufacturing method.

FIG. 7 is a cross-sectional view illustrating abnormal growth of an inverted mesa shape by a conventional semiconductor laser manufacturing method.

[Explanation of symbols]

Reference Signs List 1 n-InP substrate 2 n-InP cladding layer 3 active layer 4 p-InP cladding layer 5 InGaAs cap layer 6 SiO ₂ film 7 p-InP current blocking layer 8 n-InP current blocking layer 9 p-InP burying layer 10 p -InGaAsP contact layer 11 n-InP substrate 12 n-InP cladding layer 13 active layer 14 p-InP cladding layer 15 SiO ₂ film 16 p-InP current blocking layer 17 n-InP current blocking layer 18 projections

Claims (2)

(57) [Claims] A first conductive type InP substrate formed on the first conductive type InP substrate;
In a method for manufacturing a semiconductor laser having a buried structure,
Forming a Dablo heterojunction including an active layer, forming a cap layer composed of an InGaAs layer or an InGaAsP layer following the dabloheterojunction, and performing dry etching using the dielectric film processed into a stripe as a mask. Processing the semiconductor substrate into a mesa shape; removing the damaged layer formed by the dry etching by wet etching; and performing a second conductivity type InP current blocking layer and a first conductivity type InP current block by a vapor deposition method. Forming a current confinement layer composed of a layer, selectively etching and removing the dielectric film and the InGaAs layer or the InGaAsP layer, and forming a second conductivity type In on the substrate by a vapor growth method.
Forming a P layer. 2. The method according to claim 1, wherein the first conductive type InP substrate is formed on a first conductive type InP substrate.
In a method for manufacturing a semiconductor laser having a buried structure,
Forming a Dablo heterojunction including an active layer;
An InGaAs layer or
Step of forming a cap layer composed of an InGaAsP layer
With the dielectric film processed into a stripe as a mask.
Processing the semiconductor substrate into a mesa shape by light etching
Process and the damage layer formed by the dry etching
Removing by wet etching and vapor phase growth
Current constriction consisting of high resistance InP current block layer
Forming a layer, the dielectric film and the InGa
Selectively etch As layer or InGaAsP layer
And removing the second by vapor phase epitaxy on the substrate.
Forming a conductive type InP layer .