JP2004288679A - Method of manufacturing visible semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when the conventional method of manufacturing visible semiconductor laser is used, undesirable projecting and recessed parts 13a are produced on the surface of a block layer 8 and worsen the flatness of the surface of an upper electrode 10 and produce erroneous chip recognition, by causing level fluctuation in the reflected light to a camera during the course of chip recognition in removing an etching mask 12 by dry etching. <P>SOLUTION: A method of manufacturing visible semiconductor laser 101 includes a step of forming a lower clad layer 3, an active layer 4, and a first upper clad layer 5 on an n-type GaAs substrate 2; a step of forming the etching mask 12 used for forming the first upper clad layer 5 in a mesa-shape; and a step of forming a mesa section 7 by partially etching off the first upper clad layer 5. The method also includes a step of forming the block layer 8 so as to embed the mesa section 7, a step of covering the surface of the block layer 8 with a protective coating film 102 composed of a photoresist film, and a step of removing the etching mask 12 by dry etching. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a visible light semiconductor laser, and more particularly, to a method for manufacturing a visible light semiconductor laser having good surface flatness.
[0002]
[Prior art]
FIG. 4 is a perspective view of an example of a conventional visible light semiconductor laser.
[0003]
The conventional visible light semiconductor laser 1 comprises an n-type GaAs substrate 2, a lower cladding layer 3 of n-type AlGaInP, an active layer 4 of GaInP / AlGaInP 4, and a first upper cladding layer of p-type AlGaInP. 5, an etching stopper layer 6 made of p-type GaInP, a second upper cladding layer 7 made of p-type AlGaInP in a mesa shape, and a block made of n-type GaAs formed so as to bury the second upper cladding layer 7. A layer 8, a contact layer 9 made of p-type GaAs formed on the upper surface of the second upper cladding layer 7 and the upper surface of the block layer 8, an upper electrode 10 formed thereon, and a lower portion formed on the back surface of the n-type GaAs substrate 2. And an electrode 11.
[0004]
Here, of the surface of the upper electrode 10, the region directly above the second upper cladding layer 7 is flat, but the surface of the other region 10 a (the region surrounded by a broken line in the drawing) has a fine uneven shape. It has become. The reason is described in the following description of the manufacturing method.
[0005]
FIGS. 5 and 6 show an example of a method for manufacturing the conventional visible light semiconductor laser 1. 5 and 6 are sectional views showing the order of steps.
[0006]
First, as shown in FIG. 5A, a lower cladding layer 3 made of n-type AlGaInP, an active layer 4 made of GaInP / AlGaInP, and a first upper cladding layer made of p-type AlGaInP are formed on an n-type GaAs substrate 2. 5, an etching stopper layer 6 made of p-type GaInP and a second upper cladding layer 7a made of p-type AlGaInP are sequentially formed by metal organic chemical vapor deposition, and then formed on the upper surface of the second upper cladding layer 7a along the waveguide direction. An etching mask 12 made of a striped silicon oxide film is formed using a CVD method and a photolithography method.
[0007]
Next, as shown in FIG. 5B, the second upper cladding layer is etched down to the etching stopper layer 6 using the etching mask 12 to form the second upper cladding layer 7 having a mesa shape.
[0008]
Next, as shown in FIG. 5C, the second upper cladding layer 7 having the mesa shape is buried by the selective epitaxial growth method using the etching mask 12 so that the second upper cladding layer 7 is opposite in conductivity to the second upper cladding layer 7. A block layer 8 of n-type GaAs is grown.
[0009]
Next, as shown in FIG. 5D, the unnecessary etching mask is removed by dry etching (for example, reactive ion etching; RIE). Here, in the reactive ion etching (RIE), since the ionized etching species is vigorously accelerated and strikes the surface to be processed, when removing the etching mask, the etching species collides with the surface of the block layer 8 and the block layer 8 is removed. Undesired asperities 13a were generated on the surface of No. 8.
[0010]
Next, as shown in FIG. 6E, a contact layer 9 made of p-type GaAs is grown on the upper surface of the second upper cladding layer 7 and the upper surface of the block layer 8 by metal organic chemical vapor deposition. Here, the irregularities 13 formed on the surface of the block layer 8 are also reflected on the contact layer 9 formed thereon, and undesired irregularities 13b are formed on the surface of the contact layer 9 except for the portion directly above the second upper cladding layer 7. Was caused.
[0011]
Next, as shown in FIG. 6F, an upper electrode 10 is formed on the contact layer 9 by an evaporation method, and a lower electrode 11 is formed on the back surface of the n-type GaAs substrate 2. Here, the unevenness 13 generated on the surface of the block layer 8 is also reflected on the surface of the upper electrode 10 via the contact layer 9, and undesired on the surface of the upper electrode 10 except for the portion directly above the second upper clad layer 7. The unevenness 13c is caused.
[0012]
As described above, the visible light semiconductor laser 1 having the current confinement structure is completed.
[0013]
In the above description, the configuration including the etching stopper layer 6 used when forming the second upper cladding layer 7a in a mesa shape has been described, but the etching stopper layer 6 is not formed and the second upper cladding layer 7a is formed. A configuration in which etching is removed halfway may be used.
(For example, see Non-Patent Document 1.)
[0014]
[Non-patent document 1]
Hiroshi Kobe, “Introduction to Semiconductor Laser Technology”, published by the Industrial Research Institute, April 20, 2001, p. 110, FIG. 7.6
[Problems to be solved by the invention]
[0015]
As described above, in the conventional method for manufacturing a visible light semiconductor laser, when the etching mask 12 is removed by dry etching (for example, reactive ion etching; RIE), undesired irregularities 13 a are formed on the surface of the block layer 8. What happened was inevitable. The unevenness 13a is also reflected on the surface of the upper electrode 10 via the contact layer 9, and the unevenness of the flatness of the surface of the upper electrode 10 causes a camera (not shown) to recognize a chip in an assembling process. This caused variations in the level of the reflected light, causing chip recognition errors.
[0016]
An object of the present invention is to provide a method of manufacturing a visible light semiconductor laser in which undesired irregularities do not occur on the surface of a block layer when an etching mask used to form an upper clad layer in a mesa shape is removed by dry etching. It is to provide.
[0017]
The method for manufacturing a visible light semiconductor laser according to the present invention includes:
Forming at least a lower cladding layer, an active layer, and an upper cladding layer on the semiconductor substrate,
A step of forming an etching mask for forming the upper cladding layer in a mesa shape,
A step of forming a mesa by etching away a part of the upper cladding layer using an etching mask;
A step of forming a block layer so as to bury the mesa portion,
A step of covering the surface of the block layer with a protective film for dry etching,
A step of removing the etching mask by dry etching;
And a method for manufacturing a visible light semiconductor laser.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a perspective view of an example of the visible light semiconductor laser of the present invention. The same parts as those in FIG. 4 are denoted by the same reference numerals.
[0019]
The visible light semiconductor laser 101 of the present invention comprises a lower cladding layer 3 of n-type AlGaInP formed sequentially on an n-type GaAs substrate 2, an active layer 4 of GaInP / AlGaInP, and a first upper cladding of p-type AlGaInP. A layer 5, an etching stopper layer 6 made of p-type GaInP, a second upper cladding layer 7 made of p-type AlGaInP having a mesa shape, and n-type GaAs formed so as to bury the second upper cladding layer 7; A block layer 8, a contact layer 9 made of p-type GaAs formed on the upper surface of the second upper cladding layer 7 and the upper surface of the block layer 8, an upper electrode 10 formed thereon, and a back surface of the n-type GaAs substrate 2 were formed. And the lower electrode 11.
[0020]
That is, the structure is exactly the same as that of the conventional visible light semiconductor laser 1, but is seen in a specific region 10 a (the region surrounded by a broken line in the figure) on the surface of the upper electrode 10 of the conventional visible light semiconductor laser 1. The entire surface is flat without fine irregularities. The reason is described in the following description of the manufacturing method.
[0021]
2 and 3 show an example of a method for manufacturing the visible light semiconductor laser 101 of the present invention. 2 and 3 are sectional views showing the order of the steps. The same parts as those in FIGS. 5 and 6 are denoted by the same reference numerals.
[0022]
First, as shown in FIG. 2A, a lower cladding layer 3 made of n-type AlGaInP, an active layer 4 made of GaInP / AlGaInP, and a first upper cladding layer made of p-type AlGaInP are formed on an n-type GaAs substrate 2. 5, an etching stopper layer 6 made of p-type GaInP and a second upper cladding layer 7a made of p-type AlGaInP are sequentially formed by metal organic chemical vapor deposition, and then formed on the upper surface of the second upper cladding layer 7a along the waveguide direction. An etching mask 12 made of a striped silicon oxide film is formed using a CVD method and a photolithography method.
[0023]
Next, as shown in FIG. 2B, the second upper cladding layer 7a is removed by etching using the etching mask 12 to the etching stopper layer 6, thereby forming a mesa-shaped second upper cladding layer 7.
[0024]
Next, as shown in FIG. 2C, the second upper cladding layer 7 and the second upper cladding layer 7 are buried in the mesa shape by the selective epitaxial growth method using the etching mask 12. A block layer 8 of n-type GaAs is grown.
[0025]
Next, as shown in FIG. 2D, a protective film 102 made of a photoresist film covering the block layer 8 is formed by opening the etching mask 12 by photolithography. The protective film 102, which is a feature of the present invention, serves to protect the block layer 8 from etching damage when the etching mask 12 is later removed by dry etching (for example, reactive ion etching; RIE). do.
[0026]
Next, as shown in FIG. 3E, the unnecessary etching mask is removed by reactive ion etching (RIE). Here, in the reactive ion etching (RIE), since the ionized etching species is vigorously accelerated and hits the surface to be processed, when the etching mask is removed, the etching species collides also with the surface of the protective film 102, and the protective species is protected. The unevenness 13 d is generated on the surface of the coating 102, but the underlying block layer 8 remains flat because it is protected by the protective coating 102.
[0027]
Next, as shown in FIG. 3F, after removing the protective film 102, a contact layer 9 made of p-type GaAs is formed on the upper surface of the second upper cladding layer 7 and the upper surface of the block layer 8 by metal organic chemical vapor deposition. To grow. Here, since the surface of the block layer 8 has good flatness, the surface of the contact layer 9 formed thereon also has good flatness.
[0028]
Next, as shown in FIG. 3G, an upper electrode 10 is formed on the contact layer 9 by evaporation, and a lower electrode 11 is formed on the back surface of the n-type GaAs substrate 2. Here, since the surface of the contact layer 9 has good flatness, the surface of the upper electrode 10 formed thereon also has good flatness.
[0029]
As described above, the visible light semiconductor laser 101 having the current confinement structure is completed.
[0030]
In the above description, the configuration including the etching stopper layer 6 used when forming the second upper cladding layer 7a in a mesa shape has been described, but the etching stopper layer 6 is not formed and the second upper cladding layer 7a is formed. A configuration in which etching is removed halfway may be used.
[0031]
Further, the protective film 102 of the block layer 8 is not limited to the photoresist film, but the photoresist film is suitable because it can be easily formed and removed.
[0032]
【The invention's effect】
According to the method for manufacturing a visible light semiconductor laser of the present invention, when the etching mask used to etch the upper cladding layer into a mesa shape is removed by dry etching, a protective film is formed to protect the surface of the block layer from etching damage. Therefore, undesired irregularities are not caused on the surface of the block layer, and as a result, the flatness of the upper electrode surface is also good.
[Brief description of the drawings]
FIG. 1 is a perspective view of an example of a visible light semiconductor laser of the present invention. FIG. 2 is a cross-sectional view of an example of a method of manufacturing a visible light semiconductor laser of the present invention. FIG. FIG. 4 is a perspective view of an example of a conventional visible light semiconductor laser. FIG. 5 is a cross-sectional view of an example of a method of manufacturing a conventional visible light semiconductor laser. FIG. 6 is a method of manufacturing a conventional visible light semiconductor laser. Sectional view of one example
DESCRIPTION OF SYMBOLS 1 Conventional visible light semiconductor laser 2 GaAs substrate 3 Lower cladding layer 4 Active layer 5 First upper cladding layer 6 Etching stopper layer 7 Second upper cladding layer 7a having a mesa shape Second upper cladding layer 8 Block layer 9 Contact layer 10 Upper electrode 10a Irregular area 11 of upper electrode 10 Lower electrode 12 Etching masks 13a, 13b, 13c Irregularity 101 Visible light semiconductor laser 102 of the present invention Protective coating

Claims (2)

Forming at least a lower cladding layer, an active layer, and an upper cladding layer on the semiconductor substrate,
Forming an etching mask for forming the upper cladding layer in a mesa shape;
Forming a mesa portion by etching away a part of the upper cladding layer using the etching mask;
Forming a block layer so as to bury the mesa portion,
Covering the surface of the block layer with a protective film for dry etching,
Removing the etching mask by dry etching;
A method for manufacturing a visible light semiconductor laser, comprising: The method according to claim 1, wherein the protective film is a photoresist film.

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