Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal
Reexamination Certificate
2001-02-28
2002-10-22
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
C438S042000, C372S045013, C372S046012, C257S094000
Reexamination Certificate
active
06468820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for fabricating a semiconductor laser emitting apparatus. More particularly, the present invention is concerned with a process for fabricating a semiconductor laser emitting apparatus which emits laser beams having two different wavelengths.
2. Description of the Related Art
A conventional process for fabricating a semiconductor laser emitting apparatus which emits laser beams having two different wavelengths is described below with reference to diagrammatic cross-sectional views of
FIGS. 2A
to
2
H illustrating the fabrication process.
As shown in
FIG. 2A
, on an n-type substrate
110
comprised of GaAs, a first n-type buffer layer
131
comprised of GaAs, a first n-type cladding layer
132
comprised of AlGaAs, a first active layer (having a multiple quantum well (MQW) structure having an oscillation wavelength of 780 nm)
133
, a first p-type cladding layer
134
comprised of AlGaAs, and a first p-type cap layer
135
comprised of GaAs are stacked on one another in this order by a metal organic vapor phase epitaxial growth (hereinafter, frequently referred to simply as “MOVPE”) method.
Then, as shown in
FIG. 2B
, a resist film (not shown) is formed so that it covers a region
121
in which a first semiconductor laser emitting device is to be formed (first semiconductor laser emitting device formation region
121
), and the layers of from the first p-type cap layer
135
to the first n-type cladding layer
132
, excluding the portion corresponding to the first semiconductor laser emitting device formation region
121
, are removed using the above resist film as-a mask by a wet etching process, such as a sulfuric acid system non-selective etching process and a hydrofluoric acid (HF) system selective etching process for AlGaAs, to thereby form, in the first semiconductor laser emitting device formation region
121
, a first laminate
123
in which the first p-type cap layer
135
, the first p-type cladding layer
134
, the first active layer
133
, and the first n-type cladding layer
132
are stacked on one another.
Subsequently, as shown in
FIG. 2C
, on the first n-type buffer layer
131
, a second n-type buffer layer
136
comprised of InGaP, a second n-type cladding layer
137
comprised of AlGaInP, a second active layer (having a multiple quantum well (MQW) structure having an oscillation wavelength of 650 nm)
138
, a second p-type cladding layer
139
comprised of AlGaInP, and a second p-type cap layer
140
comprised of GaAs are stacked on one another in this order by a MOVPE method so that they cover the first laminate
123
.
Then, as shown in
FIG. 2D
, a resist film (not shown) is formed so that it covers a region
122
in which a second semiconductor laser emitting device is to be formed (second semiconductor laser emitting device formation region
122
). The layers of from the second p-type cap layer
140
to the second n-type buffer layer
136
, excluding the portion corresponding to the second semiconductor laser emitting device formation region
122
, are removed using the above resist film as a mask by a wet etching process, such as a sulfuric acid system etching process for a cap layer and a phosphoric acid and hydrochloric acid system selective etching process for a quaternary-system compound semiconductor, and a hydrochloric acid system separation etching process, to thereby form, in the second semiconductor laser emitting device formation region
122
, a second laminate
124
in which the second n-type buffer layer
136
, the second n-type cladding layer
137
, the second active layer
138
, the second p-type cladding layer
139
, and the second p-type cap layer
140
are stacked on one another. As a result, the first laminate
123
and the second laminate
124
are separated from each other.
Subsequently, as shown in
FIG. 2E
, insulating films
125
are formed on the first laminate
123
and the second laminate
124
so that they cover portions which are to be current injection regions, and then, for forming a stripe structure which is to be a current constriction structure of a gain guide type, from surfaces of the first p-type cap layer
135
and the second p-type cap layer
140
to halfway portions of the first p-type cladding layer
134
and the second p-type cladding layer
139
are respectively processed in a ridge form in a certain depth of the first p-type cladding layer
134
and the second p-type cladding layer
139
by an etching process using the insulating films
125
as a mask.
Then, as shown in
FIG. 2F
, an n-type layer
141
comprised of, for example, GaAs is allowed to selectively grow on the compound semiconductor layer, so that it implants the portions etched in a ridge form in the first p-type cladding layer
134
and the second p-type cladding layer
139
.
Then, the insulating films
125
are removed by an etching process. Subsequently, as shown in
FIG. 2G
, a resist film (not shown) is formed so that it covers only the portions of the n-type layer
141
formed on the first laminate
123
and the second laminate
124
, and then, the n-type layer
141
is removed by an etching process using the above resist film as a mask so that the only portions of the n-type layer
141
on the first laminate
123
and the second laminate
124
remain.
Then, as shown in
FIG. 2H
, the resist film is removed. Further, a first p-type electrode
143
and a second p-type electrode
144
respectively connected to the first p-type cap layer
135
and the second p-type cap layer
140
are formed from, for example, a Ti/Pt/Au laminate, and an n-type electrode
151
connected to the n-type substrate
110
is formed from, for example, a AuGe/Ni/Au laminate.
However, in the step for separating the first semiconductor laser emitting device comprising the first laminate from the second semiconductor laser emitting device comprising the second laminate, an exposure step for a resist film which serves as a mask for etching is inevitably performed in a state such that the surface step of the layer directly under the resist film is large. Therefore, it has been difficult to achieve the patterning for resist with precision.
In addition, it is necessary that the step for separating the first semiconductor laser emitting device comprising the first laminate from the second semiconductor laser emitting device comprising the second laminate by an etching process, and the step for separating the n-type layer which constitutes the current constriction layer by an etching process be separately conducted in two different separation steps. Therefore, a burden on the process has been large.
SUMMARY OF THE INVENTION
The present invention is a process for fabricating a semiconductor laser emitting apparatus which has been made for solving the above-mentioned problems accompanying the prior art.
The process of the present invention is a process for fabricating a semiconductor laser emitting apparatus comprising a first semiconductor laser emitting device and a second semiconductor laser emitting device, which are formed on a substrate and respectively oscillate laser beams having different wavelengths, the process comprising the steps of: stacking on the substrate a compound semiconductor layer which constitutes the first semiconductor laser emitting device, to thereby form a first laminate; removing the first laminate so that the portion of the first laminate in a region in which the first semiconductor laser emitting device is to be formed remains; stacking on the substrate a compound semiconductor layer which constitutes the second semiconductor laser emitting device, to thereby form a second laminate; removing the second laminate formed on the first laminate, to thereby expose a surface of the first laminate to the outside and planarize a surface of the second laminate; forming current injection regions in a ridge form in the first and second laminates, respectively; selectively forming a current constriction layer on the portion of the first and second laminates other tha
Kananen, Esq. Ronald P.
Lee Calvin
Rader & Fishman & Grauer, PLLC
Smith Matthew
Sony Corporation
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