JPH0697709B2 - Method for manufacturing semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION [Outline] A V-Grooved-Substrate-buried-Laser, which is used as a light source of an optical communication system and is capable of high speed modulation, hereinafter referred to as VSB
(Referred to as a laser) for manufacturing a semiconductor light emitting device, wherein an active layer for emitting laser light is formed in a V-shaped groove having PN junctions formed on both sides, and a contact layer on the active layer of the V-shaped groove. A protective film serving as a mask for preventing crystal damage of the contact layer in a region facing the active layer on the contact layer in manufacturing a laser having a structure in which a portion of the upper insulating layer facing the active layer is opened. Are formed in advance. Next, an insulating film is formed over the contact layer including the protective film so that the crystal layer surface of the contact layer is not damaged.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, particularly a semiconductor light emitting device such as a VSB laser.

A semiconductor laser used as a light source of an optical communication system is required to be modulated at a higher speed, and therefore, semiconductor laser devices having various structures have been proposed.

FIG. 6 shows a cross-sectional structure of a VSB laser capable of such high speed modulation.

As shown in the figure, after a P-type InP crystal layer 2 is formed on an N-type indium-phosphorus (InP) substrate 1 and a V-shaped groove 4 is formed at a position where the active layer 3 of the substrate 1 is formed. , After the N-type InP crystal layer 5 is formed on the V-shaped groove 4 and the substrate,
In the V-shaped groove 4, a non-doped indium-gallium-arsenic-phosphorus (InGaAsP) crystal layer is formed as the active layer 3.

Further, after the P-type InP crystal layer 6 is formed on the substrate,
On top of that, P ⁺ InGaAs with high concentration of impurity atoms added
A crystal layer of P is formed as a contact layer 7, a silicon dioxide (SiO ₂ ) film 8 is formed thereon so as to define the V-shaped groove 4, and then an electrode 9 is formed through the SiO ₂ film 8. Has been formed.

An electrode 10 is also formed on the bottom of the substrate 1. In such a VSB laser, by applying a voltage between the electrodes 9 and 10, the light is confined and reflected in the active layer 3 of the heterostructure of the narrow region defined by the V-shaped groove 4 to reflect the element. At the same time as improving the luminous efficiency, the voltage applied to the active layer 3 is effectively applied to the active layer 3 by preventing the voltage applied to the active layer 3 from laterally shifting at the heterostructure PN junctions provided on both sides of the V-shaped groove 4. I am trying to do it.

Further, for the purpose of effectively applying a voltage to the active layer 3, the insulating film 8 made of a SiO ₂ film having the opening 11 at the position corresponding to the V-shaped groove 4 is formed as the contact layer 7 as described above.
An electrode 9 is formed on the substrate, and an electrode 9 is formed on the substrate via the insulating film 8.

By the way, in forming such a VSB laser element, it is required to increase the luminous efficiency of the laser element by forming the contact resistance between the electrode 9 and the contact layer 7 as low as possible. .

[Conventional technology]

When forming such a VSB laser, as shown in FIG. 1, the P-type InP crystal layer 2 is formed on the N-type indium-phosphorus (InP) substrate 1 by the liquid phase epitaxial growth method. . Further, after forming a V-shaped groove 4 on the substrate 1 where the active layer 3 is formed, an N-type In is formed on the V-shaped groove 4 and the substrate.
The crystal layer 5 of P is formed by the liquid phase epitaxial growth method.

Further, in the V-shaped groove 4, non-doped indium-gallium-
An arsenic-phosphorus (InGaAsP) crystal layer is formed as the active layer 3 by the liquid phase epitaxial growth method.

Further, a P-type InP crystal layer 6 is formed on the substrate by a liquid phase epitaxial method, and then a P ⁺ InGaAsP crystal layer to which impurity atoms are added at a high concentration is formed as a contact layer 7.

Further, a silicon dioxide (SiO ₂ ) film 8 is formed thereon by a sputtering method or the like, and a portion facing the V-shaped groove 4 is etched and opened by a photolithography method.

Further, an electrode 9 made of an alloy of titanium and gold is formed on the SiO ₂ film 8 by a sputtering method so as to come into contact with the opening 11 opened by etching.

[Problems to be solved by the invention]

However, such a conventional VSB laser device manufacturing method has a problem that the surface of the crystal layer of the contact layer 7 thereunder is damaged when the SiO ₂ film 8 is formed by the sputtering method.

Therefore, in the opening 11 where the SiO ₂ film 8 is etched, there is a problem that the electrode 9 formed thereon and the contact layer 7 are not sufficiently contacted, and a VSB laser having good characteristics cannot be obtained. There's a problem.

[Means for solving problems]

The present invention solves the above problems and provides a method for manufacturing a semiconductor light emitting device in which the crystal surface of the contact layer 7 in contact with the electrode 9 is not damaged and the electrode 9 and the contact layer 7 are in good contact. To aim.

The method for manufacturing a semiconductor light emitting device according to the present invention is directed to the contact layer 9
A protective film 21A made of a stripe-shaped compound semiconductor crystal layer is previously formed at a position facing the active layer 3 having the V-shaped groove 4 formed thereon.

Next, an insulating film 22 made of a SiO ₂ film is formed on the entire surface of the contact layer 7 having the protective film 21A, and then the insulating film 22 is etched until it becomes wider than the stripe width of the protective film 21A.

After that, the protective film 21A is etched, and then the electrode 24 is formed on the insulating film 22 having the opening 23 that is etched wider than the stripe width of the protective film 21A.

[Action]

According to the method for manufacturing a semiconductor light emitting device of the present invention, a protective film 21A made of a compound semiconductor crystal is previously formed in a contact region where the electrode 24 and the contact layer 7 are in contact with each other, and the protective film 21A is used to insulate the contact layer 7 from the insulation. The contact layer 7 is not damaged when the film 22 is formed.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1 to 5 are sectional views showing a method of manufacturing a semiconductor light emitting device of the present invention in the order of steps.

First, as shown in FIG. 1, N-type indium-phosphorus (In
P) A P-type Inp crystal layer 2 is formed on a substrate 1 by a liquid phase epitaxial growth method.

Further, a V-shaped groove 4 is formed on the substrate 1 at a position where the active layer 3 is formed by photolithography and etching, and then an N-type Inp crystal layer 5 is formed on the V-shaped groove 4 and the substrate by liquid phase epitaxial growth. Form by method.

Further, in the V-shaped groove 4, non-doped indium-gallium-
An arsenic-phosphorus (InGaAsP) crystal layer is formed as the active layer 3 by the liquid phase epitaxial growth method.

In this case, the same In layer as that of the active layer 3 is formed in the portions other than the V-shaped groove 4.
A GaAsP crystal layer is formed, but since it is extremely thin, no problem occurs.

Further, a P-type InP crystal layer 6 is formed on the substrate by a liquid phase epitaxial method, and then a P ⁺ InGaAsP crystal layer to which impurity atoms are added at a high concentration is formed as a contact layer 7.

On top of that, a P-type Inp to be a protective film 21 for etching is formed.
Is formed on the entire surface of the substrate by a liquid phase epitaxial growth method so as to have a thickness of about 0.3 μm.

Then, as shown in FIG. 2, the protective film 21 is etched by using a photolithography method and an aqueous solution of hydrochloric acid (HCl), and is processed and shaped to have a stripe width of about 5 μm to form a protective film 21A. .

This dimension is formed slightly smaller than the width dimension of the active layer 3 formed in the V-shaped groove 4.

Next, as shown in FIG. 3, an insulating film 22 made of a SiO ₂ film is formed on the contact layer 7 including the protective film 21A thus patterned by a sputtering method.

Further, as shown in FIG. 4, the insulating film 22 is formed by photolithography and an etching solution mainly containing hydrofluoric acid (HF) to a width of 5 μm from both end portions A of the protective film 21A in the lateral direction. An etching opening is formed in a wide dimension that spreads to some extent.

By doing this, the contact layer 7 on the bottom of the protective film 21A is formed.
Is not damaged by the step of forming the insulating film 22 by the sputtering method, and therefore the crystal layer in the contact region where the contact layer and the electrode are in contact is not damaged.

Then, as shown in FIG. 5, an insulating film 22 having an opening 23 etched wider than the stripe width of the protective film 21A.
A semiconductor light emitting device according to the method of the present invention can be obtained by forming an electrode 24 of an alloy of titanium-gold on the top by sputtering.

In this embodiment, the VSB laser is used as an example for explanation.
The method of the present invention can also be applied to the manufacture of semiconductor light emitting devices other than VSB lasers.

〔The invention's effect〕

As described above, according to the method of the present invention, since the protective film is formed on the contact layer, the crystal damage of the contact layer is not observed due to the sputtering step when the insulating layer is attached, There is an effect that a semiconductor light emitting device having a good property that the layer and the electrode are in good contact can be obtained.

[Brief description of drawings]

1 to 5 are sectional views showing a method of manufacturing a semiconductor light emitting device according to the present invention in the order of steps, and FIG. 6 is a sectional view for explaining the structure of a conventional semiconductor light emitting device and its manufacturing method. is there. In the figure, 1 is an N-type InP substrate, 2 is a P-type InP crystal layer, 3 is an active layer, 4
Is a V-shaped groove, 5 is an N-type InP crystal layer, 6 is a P-type InP crystal layer, 7
Is a contact layer, 21 and 21A are protective films, 22 is an insulating film, 23 is an opening, 24 is an electrode, and A is a side end of the protective film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Naoki Kono, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Yoshiyuki Kuwahara, 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa, Fujitsu Limited ( 56) References JP-A-61-502434 (JP, A)

Claims (1)

[Claims] 1. A compound semiconductor crystal layer (2,5,6) having different conductivity types is provided on a compound semiconductor substrate (1), and an active layer (3) is provided, and the crystal layer (2,5,6) is provided. ), A contact layer (7) is formed thereon, and an insulating film (8) having an opening formed on the opposing region of the active layer (3) is formed, and then an electrode (9) is formed.
In the manufacture of a device for forming a film, a stripe-shaped protective film (21A) made of a compound semiconductor crystal is previously formed on the contact layer (7), and then on the contact layer (7) including the protective film (21A). An insulating film (22) is formed on the insulating film (22), the insulating film (22) is etched wider than the stripe width of the protective film (21A), and then the protective film (21A) is removed to form a film on the insulating film (22). A method for manufacturing a semiconductor light emitting device, comprising forming an electrode (24).