JPH0621565A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To provide the manufacturing method of a buried type semiconductor laser wherein an etching stop layer is formed on a mesa bottom surface, irregularity in an etching surface are little, and etching control is easy. CONSTITUTION:On an N-InP substrate 11, an N-InP buffer layer 12 is formed, and thereon an N-InGaAsP etching stop layer 13 is formed. Thereon the following are epitaxially grown in order; a first N-InP clad layer 14, a P-InGaAsP active layer 15, and a second P-InP clad layer 16. An etching mask 17 is formed on the layer 16. The second clad layer 16 is eliminated by using first corrosive liquid. The etching mask 17 and the left second clad layer 16 are used as masks, and the active layer 15 is eliminated by using second corrosive liquid. The left active layer 15 is used as a mask, and the first clad layer 14 is etched as far as the etching stop layer 13 by using the first corrosive liquid. Thereby mesa structure is 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 a mesa structure in the process of manufacturing an embedded semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, a manufacturing process for producing a semiconductor laser has been described in "Semiconductor Laser and Optical Integrated Circuit", edited by Yasuharu Suematsu, published by Ohmsha Co., Ltd., April 25, 1984.
Issued p. 446-p. 449 were disclosed. 2A to 2D are cross-sectional views of manufacturing steps of such a conventional embedded semiconductor laser.

First, as shown in FIG. 2A, a DH (double hetero) structure wafer is formed by a normal epitaxial growth technique (LPE, OM-VPE). That is, the n-InP clad layer 2, the p-InGaAsP active layer 3, and the p-InP clad layer 4 are sequentially stacked on the n-InP substrate 1. Next, as shown in FIG.
A SiO ₂ film is deposited by CVD, and a SiO ₂ stripe mask 5 is formed in the <011> direction by photolithography.

Next, as shown in FIG. 2C, a portion other than the SiO ₂ stripe mask 5 is removed by Br / methanol etching to form a mesa stripe. Next, as shown in FIG. 2D, after formation of the mesas and stripes, with the SiO ₂ stripe mask 5 remaining, p
The -InP block layer 6 and the n-InP block layer 7 are epitaxially grown. InP does not grow epitaxially on the stripe due to the selective growth property.

Finally, as shown in FIG. 2 (e), SiO
₂ Stripe mask 5 is removed, p-InP layer 8, p-
The InGaAsP contact layer 9 is epitaxially grown, and the crystal growth of the BH laser is completed.

[0006]

However, in the conventional method for manufacturing a buried semiconductor laser described above, it is difficult to control the etching depth, and the etching with Br / methanol is diffusion-controlled, so that the in-plane surface of the wafer is There was a drawback that the variation was large. Further, even in the case of forming BH using a hydrochloric acid-based etchant, there is a problem that the etching bottom surface is rough although the in-plane variation is small.

The present invention utilizes the selective growth of a hydrochloric acid type etchant in order to eliminate the above-mentioned in-plane variation in etching and poor controllability, and has an etching stop layer on the bottom surface of a mesa. It is an object of the present invention to provide a method for manufacturing an embedded semiconductor laser with a small variation and easy etching control.

[0008]

In order to achieve the above object, the present invention provides a method of manufacturing an embedded semiconductor laser, including a step of forming a buffer layer on a semiconductor substrate, and an etching stop layer on the buffer layer. Forming a first cladding layer on the etching stop layer by epitaxial growth, forming an active layer on the first cladding layer, and forming a second cladding layer on the active layer by epitaxial growth. Forming a clad layer, a step of forming an etching mask on the second clad layer, a step of removing the second clad layer with a first etchant, the etching mask and the remaining second clad layer. Removing the active layer with a second etchant using the clad layer as a mask, and using the remaining active layer as a mask. Etching the first cladding layer to the insulating layer with a first etchant to form a mesa structure, forming current blocking layers by epitaxial growth on both sides of the etching mask, and after removing the etching mask The step of forming the InP layer and the contact layer by epitaxial growth is performed.

[0009]

According to the present invention, as shown in FIG. 1, in an embedded semiconductor laser manufacturing method, an n-InP substrate 1 is used.
1. An n-InP buffer layer 12 is formed on the
An n-InGaAsP etching stop layer 13 is formed on the nP buffer layer 12. A first n-InP cladding layer 14 is formed on the n-InGaAsP etching stop layer 13 by epitaxial growth, a p-InGaAsP active layer 15 is formed on the first n-InP cladding layer 14, and the p- A second p-InP clad layer 16 is formed on the InGaAsP active layer 15 by epitaxial growth, and the second p-InP clad layer 16 is formed.
An etching mask 17 is formed thereon, the second p-InP clad layer 16 is removed with a first etchant, and the second etchant is used with the etching mask and the remaining second p-InP clad layer as a mask. p-I
The nGaAsP active layer 15 is removed, and the remaining p-InGa is removed.
Using the AsP active layer as a mask, the n-InGaAsP etching stop layer 13 is first etched by the first etchant.
Then, the n-InP clad layer 14 is etched to form a mesa structure.

Further, the current block layers 18 and 19 are formed on both sides of the etching mask by epitaxial growth. After removing the etching mask, the InP layer 20 and the contact layer 21 are formed by epitaxial growth. In particular, the n-InGaAsP layer 13 is grown under the p-InGaAsP active layer 15 as an etching stop layer. Next, the SiO ₂ mask 17 is formed, and the first
P-InG is a hydrochloric acid-based etchant
Second p-InP clad layer 1 on aAsP active layer 15
Remove 6.

Next, the p-InGaAsP active layer 15 is removed with a second etchant, sulfuric acid / hydrogen peroxide, or Br / methanol. Next, the p-InGaAsP active layer 1
5 as a mask until the etching stop layer 13
The first n- in the hydrochloric acid-based etchant that is
The InP clad layer 14 is etched to form a mesa structure for a buried semiconductor laser.

Therefore, the InP, InGaAsP-based embedded semiconductor laser can be manufactured with good controllability.

[0013]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a manufacturing process of an embedded semiconductor laser showing an embodiment of the present invention. First, as shown in FIG. 1A, a double hetero structure is crystal-grown. The growth method at this time is preferably a method with a small in-plane variation in thickness (for example, vapor phase growth is preferable to liquid phase growth). That is, on the n-InP substrate 11, n-
An InP buffer layer (about 0.5 μm) 12 is formed, and then an n-InGaAsP etching stop layer (about 0.1 μm) 13 is formed on the buffer layer 12. A first n-InP clad layer (about 1.5 μm) 14 is formed on the stop layer 13, a p-InGaAsP active layer (about 0.1 μm) 15 is formed on the stop layer 13, and a second p-InP layer is formed on the p-InGaAsP active layer 15 (about 0.1 μm).
A clad layer (about 0.5 μm) 16 is sequentially laminated.

Next, as shown in FIG. 1 (b), SiO ₂
The mask 17 is formed in the <011> crystal axis direction by photolithography. Next, as shown in FIG. 1C, using the SiO ₂ mask 17, the p-InP cladding layer 16 is removed with a cooled hydrochloric acid-based etchant that is the first etchant. In this case, since side etching is performed, the width of the active layer can be controlled.

Next, as shown in FIG. 1D, SiO ₂
Using the mask 17 and the remaining p-InP clad layer 16 as a mask, p- with a second etchant, sulfuric acid / hydrogen peroxide.
The InGaAsP active layer 15 is etched. InP is also etched by sulfuric acid / hydrogen peroxide, but since the etching rate is large and different from InGaAsP, it can be considered that InP is hardly etched. [InP sulfuric acid / hydrogen peroxide (5
Etching rate at 0 ° C) is about 0.1 μm / min
And about 1 μm / min for InGaAsP. ] Then, as shown in FIG.
Using the iO ₂ mask 17, the remaining p-InP clad layer 16 and the remaining p-InGaAsP active layer 15 as a mask, a hydrochloric acid-based etchant, which is a first etchant, is used to etch n-I.
n-InP up to nGaAsP etching stop layer 13
The clad layer 14 is removed. At this time, p-InGaAs
It is known that the side etching hardly enters under the P active layer 15.

Therefore, in the above process, if there is no in-plane variation in the layer thickness, the in-plane variation is almost determined by the etching variation of the hydrochloric acid etchant and the mask width variation. The hydrochloric acid-based etchant is reaction-controlled, and the in-plane variation is much smaller than that of the diffusion-controlled Br / methanol-based etchant. In addition, the roughness of the bottom surface does not exist because of the etching stop layer. At this time, the shape of the mesa is, as shown in FIG. 1 (e), a substantially rectangular shape (Retangular Mesa;
RM).

Next, as shown in FIG. 1F, p-In
A current block layer composed of the P block layer 18 and the n-InP block layer 19 is formed. Finally, as shown in FIG. 1G, the SiO ₂ mask 17 is removed and the p-InP layer 2 is formed.
0, the p-InGaAsP contact layer 21 is epitaxially grown, and the crystal growth of the BH laser is completed.

The present invention is not limited to the above embodiments, and various modifications can be made within the spirit of the present invention, which are not excluded from the scope of the present invention.

[0019]

As described above in detail, according to the present invention, the etching is stopped by the etching stop layer by the etching using the selective etchant of the first etchant and the second etchant. Is determined by the epitaxially grown first cladding layer on the etch stop layer.

Therefore, if a growth method with a small in-plane variation is used as the epitaxial growth method, the in-plane variation of the mesa height is small and the etching control is easy.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufacturing process of an embedded semiconductor laser showing an embodiment of the present invention.

FIG. 2 is a sectional view of a manufacturing process of a conventional embedded semiconductor laser.

[Explanation of symbols]

11 n-InP substrate 12 n-InP buffer layer 13 n-InGaAsP etching stop layer 14 n-InP clad layer 15 n-InGaAsP active layer 16 p-InP clad layer 17 SiO ₂ mask 18 p-InP block layer 19 n-InP Block layer 20 p-InP layer 21 p-InGaAsP contact layer

Claims (4)

[Claims] 1. A method for manufacturing an embedded semiconductor laser, comprising: (a) forming a buffer layer on a semiconductor substrate; (b) forming an etching stop layer on the buffer layer; and (c) A step of forming a first clad layer on the etching stop layer by epitaxial growth, (d) a step of forming an active layer on the first clad layer, and (e) a second step of epitaxial growth on the active layer. A step of forming a clad layer, (f) a step of forming an etching mask on the second clad layer, and (g) a step of removing the second clad layer with a first etchant using the etching mask. And (h) removing the active layer with a second etchant using the etching mask and the remaining second cladding layer as a mask, and (i) Using the remaining active layer as a mask, etching the first cladding layer to the etching stop layer with a first etchant to form a mesa structure, and (j) forming a current blocking layer on both sides of the etching mask by epitaxial growth. A method of manufacturing a semiconductor laser, which comprises the step of forming and (k) the step of forming the InP layer and the contact layer by epitaxial growth after removing the etching mask. 2. The method of manufacturing a semiconductor laser according to claim 1, wherein the active layer is an InGaAsP layer, the etching mask is a SiO ₂ mask, and the etching stop layer is an InGaAsP layer. 3. The first etchant etches only the InP layer and not the InGaAsP layer, or the etching rate of the InP layer is sufficiently higher than the etching rate of the InGaAsP layer. A method for manufacturing the semiconductor laser described. 4. The second etchant is the InGa.
The method of manufacturing a semiconductor laser according to claim 2, wherein only the AsP layer is etched and the InP layer is not etched, or the etching rate of the InGaAsP layer is sufficiently higher than the etching rate of the InP layer.