JP2000269586A - Manufacture of light transmit-receive module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a semiconductor laser and a photodiode in the same substrate by providing an etching stop layer inside an upper multilayer film reflection mirror layer of a region used as a photodiode and etching a region which is used as a photodiode until a surface of the stop layer is exposed. SOLUTION: In a surface light emission type semiconductor laser 52, a buffer layer 11 is provided on a substrate 10, and an n-type lower multilayer reflection mirror layer 12 is provided on the buffer layer 11. A first spacer layer 14, an i-type quantum well active layer 16 and a second spacer layer 18 are laminated thereon and an active layer 30 is formed. An etching stop layer 26 is provided between a first upper multilayer film reflection mirror layer 24 and a second upper multilayer film reflection mirror layer 27 on the active layer 30. A region which is used as a photodiode 54 is etched until a surface of the etching stop layer 26 is exposed.

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 an optical transmission / reception module for optical transmission used in various optical communication equipment fields, and more particularly, to a method for forming a surface emitting semiconductor laser and a photodiode on the same semiconductor substrate. The present invention relates to a method for manufacturing an optical transceiver module.

[0002]

2. Description of the Related Art Hitherto, in optical communication, a semiconductor laser for transmission and a photodiode for reception have been basically manufactured separately. However, from the viewpoint of cost reduction and miniaturization by simplifying the manufacturing process, it has been studied to use a semiconductor laser and a photodiode formed on the same semiconductor substrate.

For example, JP-A-5-218581 and JP-A-2
-65538 proposes an optical transceiver module in which a part of a semiconductor laser device functions as a photodiode. However, no specific production method was disclosed.

An example in which a multilayer mirror on the surface of a commercially available surface-emitting laser is thinly etched by etching several pairs with an ion beam to evaluate the characteristics as a light receiving element (Milan Dragas)
et.al., IEEE LEOS '98 Conference Proceeding Nara, T
uE7, p107-108, 1998), but the method of cutting a multilayer mirror with an ion beam was not practical from the viewpoint of equipment and productivity.

Also, GGOrtizet.al., Electronics Lett
ers, Vol.32, No.13, p1205-1207, 1996, after crystal growth of a surface emitting semiconductor laser device, the reflection mirror composed of a multilayer film is removed by etching one by one with a chemical. Has been proposed. However, the multilayer film once formed in this way is one by one.
The manufacturing method of removing about 20 times of etching alternately by Al _0.15 Ga _0.85 As and Al _0.93 Ga _0.07 As is not a realistic manufacturing method in practical use.

As described above, an optical transceiver module in which a semiconductor laser and a photodiode are formed on the same semiconductor substrate is expected to be put to practical use from the viewpoint of cost reduction and size reduction by simplifying the manufacturing process. At present, a practical manufacturing method has not been established yet.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to form a surface-emitting type semiconductor laser and a photodiode on the same semiconductor substrate. An object of the present invention is to provide a simple manufacturing method of an optical transceiver module.

[0008]

As a result of intensive studies, the present inventor has found that the above means can be solved by the following means.

That is, a method of manufacturing an optical transceiver module according to the present invention is a method of manufacturing an optical transceiver module in which a surface-emitting type semiconductor laser and a photodiode are formed on the same semiconductor substrate. An active region including a film reflection mirror layer, an active layer in which a quantum well is formed,
And an upper multilayer reflection mirror layer forming a resonator structure together with the lower multilayer reflection mirror layer, and the upper multilayer reflection mirror in a region used as a photodiode when the upper multilayer reflection mirror layer is provided. It is characterized by including a laminating step of providing an etching stop layer inside the mirror layer, and an etching step of etching a region used as the photodiode until the surface of the etching stop layer is exposed.

When a surface emitting semiconductor laser and a photodiode are formed on the same semiconductor substrate to form an optical transceiver module, the surface emitting semiconductor laser side has a reflectance of, for example, 9%.
The mirror is used as a surface-emitting type semiconductor laser while maintaining a mirror characteristic of high efficiency of 9.5% or more, and the mirror layer on the photodiode side is thinned by etching to lower the performance of the mirror so as to function as a photodiode.

In the manufacturing method of the present invention, an isomer film (for example, AlAs having a different Al and Ga concentration from the multilayer film of the upper reflection mirror) is provided inside the upper multilayer reflection mirror layer of the laminated body as an etching stop layer. Film), the upper multilayer reflective mirror layer on the surface emitting laser side is protected by a mask, and only the upper multilayer reflective mirror layer on the photodiode side is etched once before the etching stop layer. Can be cut down.

With such a simple structure, an optical transceiver module in which a surface-emitting type semiconductor laser and a photodiode are formed on the same semiconductor substrate can be manufactured. Modules can be manufactured at low cost.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing an optical transceiver module according to the present invention will be described in detail, taking the optical transceiver module shown in FIG. 1 as an example.

The optical transceiver module 50 shown in FIG. 1 has a surface-emitting type semiconductor laser 52 and a photodiode 54 on an n-type GaAs substrate 10 provided with an n-side electrode 28 on the back surface.
Are formed. Surface emitting semiconductor laser 52
The photodiode 54 and the n-type GaAs substrate 10 form a mesa 53 and a mesa 55 which are independent of each other, except that the n-type GaAs substrate 10 and an n-type lower multilayer reflective mirror layer 12 described later are partially shared.

The surface-emitting type semiconductor laser 52 uses the above-mentioned n-type G
GaAsn doped with Se on an aAs substrate 10
A buffer layer 11 is provided. An n-type Al _0.9 Ga _0.1 As film having a thickness of λ / (4n _r ) (λ: oscillation wavelength, n _r : refractive index of a medium) is provided on the upper layer of the buffer layer 11. λ / (4
n _r ) n-type Al _0.3 Ga _0.7 As film
An n-type lower multilayer reflection mirror layer 12 doped with Se and stacked for about a period is provided.

The first spacer layer 1 made of n-type Al _0.6 Ga _0.4 As is formed on the upper layer of the n-type lower multilayer reflection mirror layer 12.
4 is further provided on the first spacer layer 14, and four layers of undoped Al _0.3 Ga _0.7 As having a thickness of 5 nm are provided.
Undoped Al _0.11 Ga with a barrier film and three layers having a thickness of 8 nm
_An i-type quantum well active layer 16 including a quantum well layer having a configuration in which _0.89 As films are alternately stacked is provided. Further, on the upper layer of the i-type quantum well active layer 16, p-type Al _0.6 Ga _0.4
A second spacer layer 18 made of As is provided.
The active layer 30 is formed by sandwiching the i-type quantum well active layer 16 between the spacer layer 14 and the second spacer layer 18.

The upper layer of the second spacer layer 18 has a thickness λ /
A p-type AlAs selective oxidation layer 22 doped with (4n _r ) Mg is provided. p-type AlAs selective oxidation layer 2
2 is a p-type Al _0.9 Ga _0.1 layer having a thickness of λ / (4n _r ).
As film and p-type Al _0.3 Ga _0.7 As of thickness λ / (4n _r )
A p-type first upper multilayer reflection mirror layer 24 doped with C by alternately laminating the film with the film for 20 periods is provided, and a thickness λ / ( 4
A p-type AlAs etching stop layer 26 doped with _nr ) Mg is provided. On the upper layer of the etching stop layer 26, a p-type Al _0.9 G layer having a thickness of λ / (4n _r ) is formed.
a _0.1 As layer and a p-type Al _{0. 3} Ga _0.7 thickness λ / (4n _r)
A p-type second upper multilayer reflective mirror layer 27 doped with C by alternately laminating As films for 10 periods is provided, and the upper layer of the p-type second upper multilayer reflective mirror layer 27 is doped with C. A p-type GaAs contact layer 29 is provided.

The AlAs selective oxidation layer 22 and the etching stop layer 26 are composed of an Al _0.9 Ga _0.1 As film and an Al _0.3 Ga _0.7 As film whose Al composition constitutes a multilayer reflection mirror layer.
The film is set higher than the film, and is adjusted to be easily oxidized by heat treatment in a steam atmosphere. This Al
An oxidized region 21 is provided on the periphery of the As selective oxidation layer 22, and an oxidized region 2 is provided on the periphery of the etching stop layer 26.
5 are provided.

Further, an insulating film 32 is provided on the side surface of the mesa 53, and a p-side electrode 34 is provided on the p-type GaAs contact layer 29 provided on the uppermost layer.

The photodiode 54 has the same structure as the surface emitting semiconductor laser up to the etching stop layer 26, and a p-type GaAs contact layer 36 doped with C is provided on the etching stop layer 26. The insulating film 32 is provided on the side surface of the mesa 55, and the p-type GaAs contact layer 36 provided on the uppermost layer is
A side electrode 40 is provided.

Hereinafter, a manufacturing process of the optical transceiver module having the above configuration will be described with reference to FIGS.

As shown in FIG. 2, an n-type GaAs substrate 10
GaAsn buffer layer 1 doped with Se
1, an n-type lower multilayer reflection mirror layer 12, an n-type first spacer layer 14 and a p-type second spacer layer 18, sandwiching the quantum well active layer 16 between the active layer 30 and the p-type A
1As selective oxidation layer 22, p-type first upper multilayer reflection mirror layer 24, p-type AlAs etching stop layer 26
And a p-type second upper multilayer reflection mirror layer 27 are sequentially formed by lamination using a semiconductor crystal growth technique such as a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method (lamination). Process).

Next, as shown in FIG.
After depositing a silicon-based insulating film on the entire surface of the
Finally, a surface-emitting semiconductor using photolithography technology
The upper surface of each mesa of the body laser 52 and the photodiode 54
A photoresist is formed in a region to be formed. This is a mask
And wet etching (etchant: H_TwoSO_FourAnd H_TwoO _Two
And water) until the side surface of the selective oxidation layer 22 is exposed.
And the mesa 53 of the surface-emitting type semiconductor laser 52
And a mesa 55 of the photodiode 54 (mesa formation).
Process).

Thereafter, the AlAs film serving as the selective oxidation layer 22 is selectively oxidized by heating at 430 ° C. for about 10 minutes in a quartz tube filled with water vapor. As a result, as shown in FIG. 4, the p-type AlAs selective oxidation layer 22 exposed on the side surfaces of the mesas 53 and the mesas 55 and the p-type AlA
The s etching stop layer 26 is gradually oxidized from the outer peripheral portion toward the inner portion to form an oxidized region 21 and an oxidized region 25 (selective oxidation step).

Next, a photoresist is formed on the upper surface of the mesa 53. Using this as a mask, wet etching (etchant: H ₂ SO ₄ , H ₂ O _2, and water) is performed on the entire surface,
The mesa 55 of the photodiode 54 is etched until the surface of the etching stop layer 26 is exposed. The oxidized region 25 is formed in the outer peripheral portion of the etching stop layer 26, and the non-oxidized region does not contain Ga. Therefore, the selectivity can be set to be considerably large, and the etching stop layer 26 functions as an etching stop layer. As shown in FIG. 4, only the p-type second upper multilayer reflection mirror layer 27 of the mesa 55 of the photodiode 54 can be removed by one etching (etching step).

Thereafter, the side surfaces of the mesas 53 and the mesas 55 are covered with the insulating film 32, and the upper surface of the mesas of the surface-emitting type semiconductor laser 52 is p-type GaAs having a thickness of about 20 nm by MOCVD.
A contact layer 29 is formed, and subsequently, a p-side electrode 34 made of Cr / Au and having a thickness of about 300 nm and having an opening 20a for emitting light is formed by photolithography. On the upper surface of the mesa of the photodiode 54, p-type GaAs having a thickness of about 20 nm is formed by MOCVD.
forming an s-contact layer 36, and then using a photolithography technique, an opening 20b for emitting light.
Is formed, and a p-side electrode 40 of about 300 nm in thickness made of Cr / Au is formed. Finally, an n-side electrode 28 is formed on the entire back surface of the GaAs substrate 10 to obtain an optical transceiver module having the configuration shown in FIG.

As described above, according to the manufacturing method of the present invention, an etching stop layer is previously provided inside the simultaneously formed laminate, and the upper multilayer reflection mirror layer on the surface emitting laser side is masked. With a simple configuration of protection, only the upper multilayer reflective mirror layer on the photodiode side can be removed by a single etching, and a manufacturing process for forming a surface emitting semiconductor laser and a photodiode on the same semiconductor substrate. Is more simplified. Thereby, the optical transceiver module can be manufactured at low cost.

Further, it was confirmed that the optical transceiver module manufactured by this method can achieve an external quantum efficiency of 85%.

Further, the manufacturing method of the present invention can be applied to the manufacture of an optical transceiver module in which elements are two-dimensionally integrated. For example, as shown in FIG. ) And the photodiode (PD) can be formed in any arrangement. Therefore, linking with a transmission medium such as an optical fiber becomes easy, and application to a large-capacity communication technology by spatial multiplexing becomes possible.

The method of manufacturing an optical transceiver module having a specific configuration has been described above. However, the configuration of the optical transceiver module is only an example, and the manufacturing method of the present invention is not limited to the above-described method.
As long as the device is a device that forms a vertical resonator by using a plurality of multilayer film reflection mirrors, the device can be applied without much depending on the device configuration.

In this embodiment, the p-type AlAs film is used as the etching stop layer. However, the present invention is not limited to this, and the etching ratio of the upper multilayer reflection mirror layer to other layers can be improved during etching. As long as the lattice constant is matched and a large stress does not occur in the multilayer film of the reflection mirror layer and the film thickness can be made an integral multiple of a quarter wavelength, even if it is formed from other materials, Good.

Although the characteristics of the surface-emitting type semiconductor laser element are not particularly mentioned, the surface-emitting type semiconductor laser has a configuration including an etching stop layer and has a highly efficient mirror characteristic (for example, 99.5% or more). It is necessary to be able to obtain.

Further, it is preferable that the thickness of the P-type multilayer reflection mirror layer on the photodiode side is such that the photodiode characteristics can be optimized.

In the present embodiment, the current confinement layer is formed by selective oxidation of the AlAs film. However, the present invention is not limited to this. The current confinement layer may be formed by a method using proton implantation.

In this embodiment, a GaAs substrate is used. However, the substrate material is not limited to this, and a general compound semiconductor can be used. Further, in the present embodiment, the bonding example in which NIPPP′-P is formed from the substrate side has been described.
The joining method is not limited to this, and a joining structure such as NIPPP'-P "or NIPPP '(M is a metal) may be used.

According to the present invention, there is provided a simpler method for manufacturing an optical transceiver module in which a surface emitting semiconductor laser and a photodiode are formed on the same semiconductor substrate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an optical transceiver module to which the manufacturing method of the present invention can be applied.

FIG. 2 is a process chart for explaining the manufacturing method of the present invention.

FIG. 3 is a process chart for explaining the manufacturing method of the present invention.

FIG. 4 is a process chart for explaining the manufacturing method of the present invention.

FIG. 5 is a plan view of an array type optical transceiver module in which light emitting and receiving elements are arbitrarily arranged.

[Explanation of symbols]

 Reference Signs List 10 GaAs substrate 12 Lower multilayer reflective mirror layer 11 Buffer layer 14 First spacer layer 16 Quantum well active layer 18 Second spacer layer 21, 25 Oxidized area 22 Selective oxidation layer 24 First upper multilayer reflective mirror layer 26 Etch stop layer 27 second upper multilayer reflective mirror layer 28 n-side electrode 29 contact layer 30 active layer 32 insulating film 34 p-side electrode 36 contact layer 38 insulating film 40 p-side electrode 50 optical transceiver module 52 surface emitting semiconductor laser 53, 55 mesa 54 Photodiode

Claims (1)

[Claims] 1. A method of manufacturing an optical transceiver module in which a surface emitting semiconductor laser and a photodiode are formed on the same semiconductor substrate, wherein a lower multilayer reflective mirror layer and a quantum well are formed on the semiconductor substrate. An active region including an active layer, and an upper multilayer reflection mirror layer constituting a resonator structure together with the lower multilayer reflection mirror layer are provided in order, and used as a photodiode when the upper multilayer reflection mirror layer is provided. Manufacturing an optical transceiver module, comprising: a laminating step of providing an etching stop layer inside the upper multilayer reflective mirror layer in a region; and an etching step of etching a region used as the photodiode until the surface of the etching stop layer is exposed. Method.