JP3268990B2 - Method for manufacturing semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a light source for an optical information processing system such as a CD (compact disk) player, MD (mini disk) player, DVD (digital video disk) player, or information storage device of a computer. More particularly, the present invention relates to a method for manufacturing a semiconductor laser device characterized by a method for forming an end face reflection protective film formed on a light emitting surface of a semiconductor laser device.

[0002]

2. Description of the Related Art In recent years, the demand for semiconductor lasers used for pickups for CDs and MDs has been increasing more and more, and a semiconductor laser device having small variations in characteristics and excellent reliability has been demanded. In addition, the demand for semiconductor laser devices is expected to continue to increase in the future, such as the commercialization of CD-ROMs or DVDs as information storage devices for computers.

[0003] In order to improve the functions of these products, the characteristics of the semiconductor laser device used as the light source of the optical information processing system are required to further reduce the current and increase the output. In order to supply such high-quality semiconductor lasers at low cost, mass production with high yield is required.

Conventionally, in a practical semiconductor laser device, a single layer film of silicon nitride, alumina, silicon, Al _{x Gal x} As crystal thin film or a laminated film thereof is provided on an end face of the semiconductor laser device as a light emitting surface. By forming, the light reflectance of the end face is adjusted to a desired value, the laser characteristics such as the threshold current and the operating current are improved, and the deterioration and destruction of the light emitting surface are prevented, and the long-term reliability of the semiconductor laser element is prevented. Is secured.

As described above, it is necessary to form an end face reflection protective film on the light emitting surface of the semiconductor laser device. However, since it is necessary to form an end face reflection protective film on the end face of each element, the end face reflection protection is performed on the wafer as it is. It is impossible to form a protective film.
For this reason, it is necessary to divide the wafer into bar-shaped wafers having a laser resonator length or to divide the wafer into individual laser chips before forming the end face reflection protective film.

As a conventional example of a method for forming such an end face reflection protective film, for example, Hiroshi Momoki, "Low Cost of Semiconductor Laser", Optics, Vol. 24, No. 5, 1995.
295, page 295 (hereinafter referred to as a first conventional example).

In the first conventional example, as shown in FIG.
The laser chip 211 is die-bonded to the special stem 212, and the wire bonding to the electrode is completed.
A method is adopted in which a reflection protective film is formed on the end face by introducing the protective film into a protective film forming machine every 12 minutes. In the figure, reference numeral 213 denotes a heat sink, 214 denotes a submount, and 215 denotes a PIN.
-PD, 216 are leads (L), 217 are leads (G), and 218 are leads (PD).

As another method for forming an end face reflection protective film, there is a method previously proposed by the present applicant in Japanese Patent Application No. 7-231778 (hereinafter referred to as a second conventional example).

In the second conventional example, as shown in FIG.
The laser bars 233 cleaved to the length of the laser resonator are arranged on a tray, and an end face reflection protective film 232 is formed on the electrodes on both side surfaces of the bars and the upper surface of the bars by a method such as P-CVD. The removal method is adopted. Note that reference numeral 241 in the figure denotes a reaction electrode,
3 is a reactive gas species.

In the first and second prior art examples, both end face reflection protective films are formed simultaneously on both side faces, so that one side face serving as a light emitting front face and the other side face serving as a light emitting rear face are provided. It is only possible to form a symmetric end face reflection protective film having the same light reflectance on the side face. In the case of a laser having a relatively low output, an element using the symmetric end face reflection protective film is often manufactured in order to reduce the manufacturing cost.

However, when a semiconductor laser device having higher performance than low-current operation or high-output operation is demanded, it cannot be often realized by using the symmetrical end-face reflection protective film. It is necessary to obtain a laser element having desired characteristics by using an asymmetric end face reflection protective film having different light reflectivities between the light emitting surface and the light emitting surface.

FIG. 9 shows a conventional example of a method for forming such an asymmetrical end face reflection protective film (hereinafter referred to as a third conventional example).

In the third conventional example, FIGS. 9 (a) and 9 (b)
As shown in FIG. 7, the bar-shaped wafer 201 cleaved to the length of the laser resonator is stacked in the groove 203 of the jig 202 in the thickness direction, and is fixed to the jig 202 and exposed from the jig 202. For example, a method is employed in which the jig 202 is inverted on the cleavage plane 205 by, for example, electron beam evaporation or the like, and end face reflection protective films are separately formed on the light emitting front surface and the light emitting rear surface. Note that reference numeral 204 in the drawing is a partition member.

[0014]

However, in the third conventional example, a plurality of bar-shaped wafers 201 are mounted on a jig 202.
Is necessary, and since this step is performed by a troublesome manual operation, automation is difficult. For this reason, the manufacturing efficiency is reduced, the manufacturing cost of the semiconductor laser element is increased, and it is necessary to form the reflection protection film twice separately on the cleaved surface with a time interval. Since it is difficult to avoid an oxide film or other attached matter on the side surface, there is a problem that it is difficult to reduce the reliability of the semiconductor laser device and to stabilize the manufacturing conditions.

The present invention has been made in view of such circumstances, and provides a method of manufacturing a semiconductor laser device which can improve the manufacturing efficiency of a semiconductor laser device having an asymmetrical end-face reflection protective film and reduce the cost. The purpose is to:

Another object of the present invention is to provide a method of manufacturing a semiconductor laser device which can prevent a decrease in the reliability of the semiconductor laser device and stabilize the manufacturing conditions.

[0017]

According to a method of manufacturing a semiconductor laser device of the present invention, an asymmetrical end face having different light reflectivities on a light emitting front surface and a light emitting surface is provided on a light emitting surface of a semiconductor laser device using a compound semiconductor. In a method of manufacturing a semiconductor laser device including a step of forming a reflection protective film , a low refractive index film is provided on both side surfaces of a semiconductor laser device bar having a two-cavity length.
A first step of forming a multilayer film composed of a high-refractive-index film, a second step of dividing the two- cavity-length semiconductor laser element bar into two one-laser-length semiconductor laser element bars, Of the multilayer film on both sides of the semiconductor laser element bar
Third step of forming the same film of the same material as the outermost film
In the first step, the outermost layer of the multilayer film
Is thinned by the thickness of the film formed in the third step.
It is characterized by forming
The above object is achieved.

Preferably, the first step and the third step
The process is performed by a plasma CVD method, a low pressure CVD method, a normal pressure CVD method, or a sputtering method.

Preferably, at least one of silicon nitride, silicon dioxide and alumina is used as the low refractive index film in the multilayer film , and at least one of polycrystalline silicon and amorphous silicon is used as the high refractive index film. Used.

The principle and operation of the method for manufacturing a semiconductor laser device according to the present invention will be described below with reference to FIG.

First, as shown in FIG.
A plurality of laser bar-shaped wafers 100 having a length W102 corresponding to two laser resonator lengths are set on 01. In addition,
The upper surface of the laser bar-shaped wafer 100 is an electrode surface 104.

Subsequently, as shown in FIG. 2B, both side surfaces of a bar-shaped wafer 100 having two laser resonator lengths (a laser bar-shaped wafer having one resonator length) are formed by, for example, P-CVD. The same end face reflection protective film 105 is formed on 103). End face reflection protection film 1 formed at this time
05 may be a single layer film or a multilayer film.

Subsequently, the bar-shaped wafer 100 is divided into two to form a bar-shaped wafer 106 having a length W107 corresponding to one resonator length. By this step, the end face reflection protection film 105 formed in the above-described step is formed on one side of the bar-shaped wafer 106 for one resonator length, and the end face reflection protection film is formed on the other side. A bar-shaped wafer having an uncleaved face that has just been cleaved is obtained (FIG. 1).
(C)).

Next, the same end face reflection protective film 108 is formed on both side surfaces of the bar-shaped wafer 106 (FIG. 1D).
reference). The end face reflection protective film formed at this time may be a single layer film or a multilayer film.

According to the above process, the laminated film of the end face reflection protection films 105 and 108 formed on the first and second times is formed on one side surface of the bar-shaped wafer 106 for one laser resonator length. On the side surface, only the end face reflection protection film 108 formed at the second time is formed. As a result, a bar-shaped wafer having a laser resonator length on which an asymmetric end face reflection protective film is formed is obtained.

By adjusting the thickness and structure of the end face reflection protective film in each step and setting the light reflectance of the finally obtained asymmetric end face reflection protection film to a desired value, a desired asymmetric light A laser bar-shaped wafer having a reflectance can be obtained.

In the above steps, the electrodes 10 other than those on both sides are formed.
Since unnecessary protection films are also formed on the substrate 3, these are finally removed by etching to form a laser bar-shaped wafer 109 having an asymmetrical end face reflection protection film only on both side surfaces.
(See FIG. 1 (e)).

According to the present invention including the above steps, the formation of the asymmetric end face reflection protection film on the light emitting surface of the bar-shaped wafer of the semiconductor laser device is performed in the first and second conventional examples. It can be obtained by a method suitable for mass production, such as P-CVD or sputtering, which was impossible.

Further, since the step of arranging the bars, which is required in the third conventional example of forming the asymmetrical end face reflection protective film, becomes unnecessary, the mass production in the automation step which has been difficult in the past becomes easy.

Therefore, according to the present invention, a high-performance semiconductor laser device can be manufactured efficiently, and the cost can be greatly reduced.

In the third conventional example, since the end face reflection protective film is formed on each of the side faces of the laser bar-shaped wafer obtained by cleavage, the side face on which the end face reflection protection film is formed later. In some cases, it is difficult to avoid the attachment of an oxide film or other deposits, which may affect the reliability. However, according to the method of the present invention, the end face reflection protective film is immediately formed on the side surface obtained by cleavage. Therefore, the reliability of the semiconductor laser device can be greatly improved.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

(Embodiment 1) FIG. 2 shows Embodiment 1 of a semiconductor laser device manufactured by the method of the present invention, in which an asymmetric end face reflection protective film is formed on a light emitting surface. However, FIG. 2 shows a state of the bar-shaped wafer 62.

The semiconductor laser device of the first embodiment is made of Al
This is a GaAs-based semiconductor laser device in which the Al composition ratio of the active layer is set to about 0.13 to 0.14 and the Al composition ratio of the cladding layer is set to about 0.45 to 0.6. The mixed crystal ratio can be arbitrarily set as long as both layers are 0 or more and the Al mixed crystal ratio of the cladding layer is in a range larger than that of the active layer.

In the semiconductor laser device of the first embodiment, silicon nitride (the layer thickness λ / 2: λ is the wavelength of the emitted light, and the reflectance is 3) is used as an end surface reflection protective film on the light emitting surface of the light emitting surface 63.
0%) as an end-face reflection protective film on the light emitting rear surface.
Three-layer film composed of silicon nitride / amorphous silicon / silicon nitride (layer thicknesses λ / 4, λ / 4, λ / 2, reflectance: 7)
4%).

As described in the principle of the present invention, a λ / 4, λ / 4 film is first grown on both sides of a semiconductor laser bar having a two-cavity length, and the bar is divided into two parts. An asymmetric end face reflection protection film is formed by growing a λ / 2 film on both side surfaces of the semiconductor laser bar having one resonator length. This semiconductor laser device is grown by metal organic chemical vapor deposition (MOCVD), and its manufacturing process will be described below.

First, a substrate 51 made of an n-type GaAs substrate
A buffer layer 52 of Se-doped n-type GaAs having a thickness of 2 μm and a Se-doped n-type Al _0.5 G having a thickness of 1 μm are formed thereon.
a Lower clad layer 53 of _0.5 As, thickness 0.06 μm
m, an active layer 54 of Al _0.14 Ga _0.86 As, a 0.24 μm thick Zn-doped upper cladding layer 55 of Al _0.5 Ga _0.5 As, and a 0.6 μm thick Se-doped n.
A current blocking layer 56 of type GaAs is sequentially grown.

Next, as shown in FIG. 2, stripe-shaped grooves (upper width 4 μm) penetrate current block layer 56.
m) 57 is formed by etching.

Then, as shown in FIG. 2, the Mg-doped p-type Al _0.5 Ga _0.5 As having a thickness of 1 μm outside the stripe groove is used.
The contact layer 59 made of Mg-doped p-type GaAs having a thickness of 50 μm and the
liquid phase epitaxy liquid layer growth method)
It grows sequentially by the method.

Subsequently, the high-resistance layer near the surface of the contact layer 59 is removed by using, for example, a technique such as etching or mechanical polishing. Finally, for example, Au-Zn or Au-
A p electrode 60 made of Ge or the like is formed on the surface of the contact layer 59, and an n electrode 61 is formed on the back surface of the substrate 63.

Next, the bar-shaped wafer 62 is cleaved perpendicular to the direction of the stripes at intervals of 360 μm to obtain a bar-shaped wafer having two resonator lengths (resonator length: 180 μm).

Next, an end-face reflection protection film is formed on the cleavage plane of the two-cavity long bar corresponding to the light emission rear surface. Embodiment 1
Used a silicon nitride / amorphous silicon laminated film as an end face reflection protective film. The P-CVD method was used to form these end face reflection protective films.

More specifically, bar-shaped wafers each having a length of two resonators are arranged on a tray with the electrode surfaces up and down, and the bar-shaped wafers together with the trays are introduced into a P-CVD apparatus, and P-CVDs are formed on both sides as cleavage planes. -Forming an end face reflection protective film by a CVD method.
In the first embodiment, silane (Si
A high-frequency discharge plasma CVD method using H ₄ ) and ammonia (NH ₃ ) was used.

The growth conditions were as follows: substrate temperature 300 ° C., silane flow rate 100 SCCM, ammonia flow rate 200 SCC.
M, a growth pressure of 1 Torr, a high frequency power of 30 W and a growth of about 8 minutes to form a silicon nitride film of about 110 nm,
Subsequently, a substrate temperature of 300 ° C., a silane flow rate of 150 SCCM,
An amorphous silicon film having a thickness of about 57 nm was grown under the conditions of a growth pressure of 1 Torr and a high frequency power of 20 W for about 4 minutes.

Next, the bar-shaped wafers are taken out from the P-CVD apparatus, and each bar-shaped wafer is divided into two so as to form two bars each having a resonator length of 180 μm. Then, these bar-shaped wafers are arranged on a tray, and the bar-shaped wafers together with the
-Introduce into a CVD apparatus, and form an end face reflection protection film by P-CVD on the side surface on which the silicon nitride / amorphous silicon laminated film is formed and the newly formed cleavage surface. In the first embodiment, a silicon nitride film of about 220 nm was grown under the same growth conditions as above for about 16 minutes.

Next, unnecessary protective films adhering to the upper and lower electrodes are removed. In order to remove an unnecessary protective film, the side surface of the laser bar is protected with a resist, and the unnecessary protective film on the electrode is removed by etching with a hydrofluoric-nitric acid-based etchant.

The semiconductor laser device according to the first embodiment can be manufactured by dividing the laser bar-shaped wafer having the end face reflection protective film formed by the above process into individual chips and mounting the chips on a stem.

It was confirmed that the semiconductor laser device manufactured by this method also had practically no problematic reliability of 50,000 hours or more like the semiconductor laser device manufactured by the third conventional example. Further, it was confirmed that the yield in manufacturing a laser chip could be improved to 1.3 times that of the third conventional example, and that the process time could be significantly reduced.

(Embodiment 2) FIG. 3 shows Embodiment 2 of a semiconductor laser device manufactured by the method of the present invention, in which an asymmetric end face reflection protective film is formed on a light emitting surface. However, FIG. 3 shows a state of the bar-shaped wafer 30.

The semiconductor laser device of the second embodiment is also made of AlG
This is an aAs-based semiconductor laser device in which the Al composition ratio of the active layer is set to about 0.13 to 0.14 and the Al composition ratio of the cladding layer is set to about 0.45 to 0.6. The mixed crystal ratio can be arbitrarily set as long as both layers are 0 or more and the Al mixed crystal ratio of the cladding layer is in a range larger than that of the active layer.

In the second embodiment, silicon nitride (layer thickness) is used as an end-face reflection protection film on the light exit surface 31 on the light exit front surface.
[lambda] / 5: [lambda] is the wavelength of the emitted light, reflectivity: 6%), and is composed of silicon nitride / amorphous silicon / silicon nitride / amorphous silicon / silicon nitride as an end surface reflection protective film on the light emitting surface. Layer film (each layer thickness λ / 4, λ / 4, λ /
4, λ / 4, λ / 2 reflectance: 90%).

In the second embodiment, first, λ / 4, λ / 4,
An asymmetric end face is obtained by growing a λ / 4, λ / 4, (λ / 2−λ / 5) film, and growing λ / 5 films on both side surfaces of a semiconductor laser bar of one resonator length obtained by dividing the bar into two. A reflective protective film was formed.

The semiconductor laser device according to the second embodiment has a VSIS (V-cha) grown by the LPE method.
nnnl substrate inner str
(ipe) type, and its manufacturing process will be described below.

First, an n-type GaAs layer 22 is laminated on a p-type GaAs substrate 21 to a thickness of about 1 μm by the LPE method.
A V-groove is formed in the n-type GaAs layer 22 by photolithography and etching up to the substrate 21.

Next, in the second liquid layer growth step, p-type Al _0.45 Ga _0.55 0.2 μm thick (the portion other than the V-groove) is formed.
As clad layer 23, p-type Al _{0.14 having} a thickness of 0.06 μm
Ga _0.86 As active layer 24, 1 μm thick n-type Al _0.45 G
a _0.55 As clad layer 25 and 3 μm thick n-type Ga
As cap layers 26 are sequentially laminated.

After growing the wafer having this structure, a p-electrode 27 and an n-electrode 28 made of, for example, Au-Zn or Au-Ge are formed on the upper and lower surfaces of the semiconductor laser device.

Next, the width 750 is perpendicular to the direction of the stripe.
μm (resonator length: 375 μm) at wafer intervals, ie, FIG.
Is cleaved to obtain a bar-shaped wafer having a length of two resonators.

Next, an end-face reflection protection film is formed on the cleavage plane of the two-cavity long bar corresponding to the rear surface of the light emission. Embodiment 2
In this example, a five-layer laminated film composed of silicon nitride / amorphous silicon / silicon nitride / amorphous silicon / silicon nitride was used as an end face reflection protection film. The P-CVD method was used to form these end face reflection protective films.

Specifically, the bar-shaped wafers are arranged on a tray with the electrode surfaces up and down, and the bar-shaped wafers are
It is introduced into a VD apparatus, and an end face reflection protective film is formed on both side faces, which are cleavage planes, by a P-CVD method. In the second embodiment, a high frequency discharge plasma CVD method using silane and ammonia as source gases is used.

The growth conditions are the same as those in the first embodiment, a silicon nitride film of about 110 nm is grown by growing for about 8 minutes, an amorphous silicon film of about 57 nm is grown by growing for about 4 minutes, and further about 8 minutes. Growth of about 110 nm of silicon nitride film, followed by about 4 minutes of growth of about 57 nm.
After successively growing four layers of amorphous silicon films each having a thickness of about 4 nm, a silicon nitride film having a thickness of about 176 nm was finally grown by growing about 12.8 minutes.

Next, a bar-shaped wafer having a length of two resonators is placed on a PC
The bar-shaped wafer is taken out from the VD device and each bar-shaped wafer is divided into two so as to form two bar-shaped wafers each having one resonator length of 375 μm.
Then, these bar-shaped wafers were arranged in a tray, and the bar-shaped wafers together with the tray were introduced into a P-CVD apparatus, and a silicon nitride / amorphous silicon / silicon nitride / amorphous silicon / silicon nitride laminated film was formed. An end surface reflection protection film is formed on the side surface and the newly formed cleavage surface by the P-CVD method. In the second embodiment, a silicon nitride film having a thickness of about 54 nm is grown under the same growth conditions as in the first embodiment by about 3.9 minutes.

Next, unnecessary protective films adhering to the upper and lower electrodes are removed. In Embodiment 2, in order to remove an unnecessary protective film, a reactive ion etching method using CF ₄ gas and O ₂ gas was used.

Next, the laser bar-shaped wafer having the silicon nitride / amorphous silicon laminated film adhered thereon is arranged on the reaction electrode of the reactive ion etching apparatus with the front electrode facing upward. Then, dry etching is performed under the conditions of a CF ₄ gas flow rate of 50 SCCM, an O ₂ gas flow rate of 150 SCCM, a gas pressure of 0.1 Torr, and a high frequency power of 100 W.

In the reactive ion etching apparatus, the substrate is placed on the cathode side electrode, and gaseous raw ions contributing to the etching reaction are accelerated in the direction toward the electrode.
Only silicon nitride and amorphous silicon on the front electrode are removed by etching, and the silicon nitride film on the light emitting surface is hardly etched. In addition, a gold electrode (n
Under the present etching conditions, only the silicon nitride and the amorphous silicon on the gold electrode are removed by etching, since only the etching rate of the silicon nitride and the amorphous silicon is 1/10 or less of that of the silicon nitride and the amorphous silicon. It is easy to stop etching at the gold electrode. In the second embodiment, only the silicon nitride and amorphous silicon films on the gold electrodes are removed by dry etching by etching for about 6 minutes.

Next, the laser bar-shaped wafer is turned upside down,
Silicon nitride on the aluminum electrode (formed on the p-electrode 27) on the back surface by the same process as above;
The amorphous silicon film is removed by dry etching. Under the present etching conditions, aluminum, which is the back electrode, has an etching rate of 1/30 or less as compared with the silicon nitride and amorphous silicon films, so that it is easier to stop the etching on the aluminum electrode. Embodiment 2
Then, only the silicon nitride and amorphous silicon films on the aluminum electrode were dry-etched and removed by etching for about 3 minutes.

By the above-mentioned two anisotropic dry etching steps, the silicon nitride film on the front surface of the light emitting surface is reduced to about 54
The silicon nitride film on the upper surface after light emission is slightly etched from
Were slightly removed by etching to about 220 nm.

The semiconductor laser device of the second embodiment can be manufactured by dividing the laser bar-shaped wafer having the end face reflection protective film formed by the above process into individual chips and mounting the chips on a stem.

It was confirmed that the semiconductor laser device manufactured by this method also had practically no problematic reliability of 50,000 hours or more like the semiconductor laser device manufactured by the third conventional example. In addition, it was confirmed that the yield in manufacturing the laser chip was 1.5 times that of the third conventional example, and that the process time could be significantly reduced.

(Embodiment 3) FIGS. 4 to 6 show Embodiment 3 of the present invention. 4 to 6 show a series of manufacturing steps of the AlGaP-based semiconductor laser device according to the third embodiment in three parts.

Also in the semiconductor laser device of the third embodiment, the Al composition ratio of the active layer and the cladding layer can be arbitrarily set as in the first and second embodiments.

In the semiconductor laser device of the third embodiment, silicon nitride (layer thickness λ / 2: λ is the wavelength of the emitted light: 30%) is used as the end surface reflection protective film on the light emitting front surface, and the light emitting rear surface is formed. Silicon nitride / amorphous silicon / silicon nitride / amorphous silicon /
Five-layer film made of silicon nitride (each layer thickness λ / 4, λ /
4, λ / 4, λ / 4, λ / 2 reflectivity: 90%).

In the third embodiment, first, λ / 4, λ / 4,
λ / 4 and λ / 4 films were grown, and λ / 2 films were grown on both side surfaces of a semiconductor laser bar having a resonator length obtained by dividing the bar into two, thereby forming an asymmetric end face reflection protective film.

The semiconductor laser device according to the third embodiment is grown by molecular beam epitaxy (MBE method). First, an outline of the structure will be described with reference to FIG. 4 (a)-(d), FIG. 5 (e)-
The manufacturing process will be described with reference to (i) and FIGS.

As shown in FIG. 6 (m), this semiconductor laser device has a first conductivity type GaAs buffer layer 2, a first conductivity type GaInP buffer layer 3, a first conductivity type GaAs buffer layer 3 on a first conductivity type GaAs substrate 1. AlGaInP first cladding layer 4, G
aInP active layer 5, second conductivity type AlGaInP second cladding layer 6, GaInP etching stop layer 7, second conductivity type AlGaInP third cladding layer 8, second conductivity type Ga
The InP intermediate layer 9 and the second conductivity type GaAs contact layer 10 are stacked in this order from the substrate 1 side. AlG
Striped mesas (4 μm in width) are formed in the aInP third cladding layer 8, GaInP intermediate layer 9 and GaAs contact layer 10.

Then, the first conductivity type GaAs current element layer 11 is formed so as to bury the stripe-shaped mesas. Electrodes 12 and 1 are provided on the GaAs contact layer 10 and the GaAs current element layer 11 and on the back surface of the substrate 1, respectively.
3 are formed.

Next, the manufacturing process will be described. First,
As shown in FIG. 4A, a first conductivity type GaAs buffer layer 2 (0.5 μm thick) is formed on a first conductivity type GaAs substrate 1.
m), a first conductivity type AlGaInP first cladding layer 4 (thickness 1 μm), a GaInP active layer 5 (thickness 0.08 μm).
m), second conductivity type AlGaInP second cladding layer 6 (thickness 0.3 μm), GaInP etching stop layer 7
(Thickness: 8 nm), the second conductivity type AlGaInP third cladding layer 8 (thickness: 0.5 μm), the second conductivity type GaInP intermediate layer 9 (thickness: 0.05 μm), and the second conductivity type GaAs contact layer 10 (thickness: Substrate 0.5 in this order.
From the side, it grows by MBE method.

Next, an Al ₂ O ₃ film 14 is formed on the GaAs contact layer 10 by an electron beam evaporation method to a thickness of 300 to 600 nm.
Is deposited with a film thickness of At this time, the substrate temperature is 300 to 350
In the range of ° C. Then, a stripe-shaped resist pattern 17 having a width of 4 μm is formed on the Al ₂ O ₃ film 14 (see FIG. 4A).

Thereafter, as shown in FIG. 4B, the Al ₂ O ₃ film 14 is etched in a striped shape by hot phosphoric acid, and then, as shown in FIG. Remove. And FIG.
As shown in FIG. 1D, the GaAs contact layer 10 is etched in a stripe shape using an Al ₂ O ₃ film as a mask and an ammonia-based or sulfuric acid-based GaAs selective etchant.

Further, as shown in FIG. 5E, a halfway portion of the GaInP intermediate layer 9 and the AlGaInP third cladding layer 8 is etched in a stripe shape using a hydrochloric acid-based or bromine-based etchant. Next, as shown in FIG. 5F, the Al ₂ O ₃ film 14 is etched using a hydrofluoric acid-based etchant, and the GaAs contact layer 10 and the GaInP
The eaves of the Al ₂ O ₃ film 14 generated when the intermediate layer 9 and the AlGaInP third cladding layer 8 are partially etched are removed.

Then, a sulfuric acid type or phosphoric acid type AlG
As shown in FIG. 5 (g), the AlGaInP third cladding layer 8 is etched in a stripe shape using an aInP selective etchant, and the GaInP etching stop layer 7 is formed.
Repeat until is exposed.

Next, as shown in FIG. 5H, a GaAs current blocking layer 11 of a first conductivity type (thickness 1.05 μm) is grown by MBE. At this time, the substrate temperature is adjusted to 500 to 5 while irradiating a sufficient amount of As molecular beam before the growth.
Raise the temperature to 80 ° C, wait for about 5 minutes, and
Clean the surface. As a result, the GaAs polycrystal 15 grows on the Al ₂ O ₃ film 14.

Next, as shown in FIG. 5I, a resist 18 is applied by a spinner. At this time, as shown in FIG. 5I, a resist 1 is formed on the GaAs current blocking layer 11.
8 is applied, but the resist 18 is hardly applied on the GaAs polycrystalline stripe 15. Thereafter, the entire surface of the resist 18 is ashed with O ₃ -UV, and FIG.
As shown in (j), only the GaAs current blocking layer 11 is coated with the resist 18.

Next, as shown in FIG. 6K, the GaAs polycrystal 15 is removed with a sulfuric acid-based etchant. At this time, the Al ₂ O ₃ film 14 functions as an etch stop layer. Thereafter, as shown in FIG. 6 (l), the resist 18 is entirely removed using an asher. And then H
The Al ₂ O ₃ film 14 is removed by an F-based etchant.

Finally, by forming electrodes 12 and 13 on the upper surface of the laminated structure thus formed and the back surface of the substrate 1, a semiconductor laser of a refractive index guided type as shown in FIG. An element is manufactured.

Next, the width of 100 is perpendicular to the direction of the stripe.
By cleaving the wafer at intervals of 0 μm (resonator length: 500 μm), a bar-shaped wafer having two resonator lengths is obtained.

Next, an end-face reflection protective film is formed on the cleavage plane of the two-cavity long bar corresponding to the rear surface of the light emission. Embodiment 3
Used a four-layer laminated film composed of silicon nitride / amorphous silicon / silicon nitride / amorphous silicon as an end face reflection protective film. To form these end face reflection protective films, P-
The CVD method was used.

Next, the bar-shaped wafers are arranged on a tray with the electrode surfaces up and down, and the bar-shaped wafers together with the trays are introduced into a P-CVD apparatus. To form In the third embodiment, a high frequency discharge plasma CVD method using silane and ammonia as source gases is used. The growth conditions are Embodiment 1.
About 92n with about 6.7 minutes growth under the same conditions as
m of silicon nitride film, followed by about 3.3 minutes of growth of about 48 nm of amorphous silicon film, and of about 6.7 minutes of growth of about 92 nm of silicon nitride, followed by about 3.3 minutes. As a result, four layers of about 48 nm amorphous silicon film were sequentially grown.

Next, the bar-shaped wafers are taken out of the P-CVD apparatus, and each bar-shaped wafer is divided into two so that two bar-shaped wafers each having one resonator length of 500 μm are formed. Then, these bar-shaped wafers are arranged in a tray, and the bar-shaped wafers together with the tray are introduced into a P-CVD apparatus, and a side surface on which a silicon nitride / amorphous silicon / silicon nitride / amorphous silicon laminated film is formed; P-CVD with newly formed cleavage plane
The end face reflection protective film is formed by the method. In the third embodiment, a silicon nitride film having a thickness of about 183 nm was grown under the same growth conditions as above for 13.3 minutes.

Finally, the unnecessary protective film on the electrode is removed by the same method as shown in the first and second embodiments.

The semiconductor laser device of the third embodiment can be manufactured by dividing the laser bar-shaped wafer having the end face reflection protection film formed by the above process into individual chips and mounting the chips on a stem.

It was confirmed that the semiconductor laser device manufactured by this method also had practically no problematic reliability of 50,000 hours or more, similarly to the semiconductor laser device manufactured by the third conventional example. Further, it was confirmed that the yield in manufacturing a laser chip could be improved to 1.3 times that of the third conventional example, and that the process time could be significantly reduced.

[0092]

According to the present invention described above, the bar arranging step which is necessary in the third conventional example is not required, and mass production in the automation step which has been difficult in the prior art is facilitated.
The time required for forming the end face reflection protective film when manufacturing a semiconductor laser device having an asymmetric end face reflection protection film and having excellent characteristics can be greatly reduced.

In addition, according to the method of the present invention, since the end face reflection protective film can be formed immediately on the side face obtained by cleavage, it is possible to prevent an oxide film and other deposits from sticking.
As a result, the reliability of the semiconductor laser device can be greatly improved. Further, the yield in the production of laser chips can be improved.

As a result, high-performance semiconductor lasers for use in pickups for CDs, MDs and DVDs or information storage devices for computers can be supplied at low cost, and the spread of these products can be further accelerated.

[Brief description of the drawings]

FIG. 1 is a process chart showing the principle of a method for manufacturing a semiconductor laser device of the present invention.

FIG. 2 is a perspective view of a bar-shaped wafer, showing Embodiment 1 of the semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device of the present invention.

FIG. 3 is a perspective view of a bar-shaped wafer, showing a second embodiment of a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device of the present invention.

FIG. 4 is a process chart showing a part of the manufacturing process of the semiconductor laser device according to Embodiment 3 of the present invention;

FIG. 5 is a process diagram showing a part of the manufacturing process of the semiconductor laser device according to the third embodiment of the present invention after FIG. 4;

FIG. 6 is a process chart showing a manufacturing process of the semiconductor laser device according to the third embodiment of the present invention after FIG. 5;

FIG. 7 is a perspective view showing a first conventional example of a method for manufacturing a semiconductor laser device.

FIG. 8 is a sectional view showing a second conventional example of a method for manufacturing a semiconductor laser device.

FIG. 9 is a process chart showing a third conventional example of a method for manufacturing a semiconductor laser device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st conductivity type GaAs substrate 2 1st conductivity type GaAs buffer layer 3 1st conductivity type GaInP buffer layer 4 1st conductivity type AlGaInP 1st clad layer 5 GaInP active layer 6 2nd conductivity type AlGaInP 2nd clad layer 7 GaInP etching Stop layer 8 Second conductivity type AlGaInP third cladding layer 9 Second conductivity type GaInP intermediate layer 10 Second conductivity type GaAs contact layer 11 First conductivity type GaAs current element layer 12, 13 Electrode 14 Al ₂ O ₃ film 15 GaAs layer Crystal 21 p-type GaAs substrate 22 n-type GaAs layer 23 p-type Al0.45Ga0.55As cladding layer 24 p-type Al0.14Ga0.86As active layer 25 n-type Al0.45Ga0.55As cladding layer 26 n-type GaAs cap layer 27 p electrode 28 n-electrode 30 bar-shaped wafer 31 Light emitting surface 51 n-type GaAs substrate 52 buffer layer 53 lower cladding layer 54 active layer 55 upper cladding layer 56 current blocking layer 57 stripe-shaped groove 58 cladding layer 58 59 contact layer 60 p electrode 61 n electrode 62 bar-shaped wafer 63 light Emission surface 100 Bar-shaped wafer 101 Tray W102 2 Resonator length 103 Light emission surface 104 Electrode surface 105 End reflection protective film formed in the first step 106 One resonator having end reflection protection film formed only on one emission surface Long bar-shaped wafer WI07 1 Resonator length 108 Edge reflection protective film formed in the second step 109 Bar-shaped wafer on which asymmetric edge reflection protective film is formed

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A method of manufacturing a semiconductor laser device, comprising the step of forming, on a light emitting surface of a semiconductor laser device using a compound semiconductor, an asymmetric end face reflection protective film having different light reflectivities on a light emitting front surface and a light emitting rear surface. The method comprises: on both sides of a semiconductor laser device bar having a two cavity length ,
The forming a multilayer film comprising a low refractive index film and the high refractive index film
A first step, a second step of dividing the semiconductor laser element bar of the second resonator length 1 cavity length semiconductor laser element bars two, on both sides of the semiconductor laser element bar of the one resonator length, wherein
Form the same film of the same material as the outermost film of the multilayer film
A third step, wherein in the first step, the outermost film of the multilayer
It should be thinner by the thickness of the film formed in the process.
And a method for manufacturing a semiconductor laser device. 2. The method according to claim 1, wherein the first and third steps are performed by a plasma CVD method, a low pressure CVD method, a normal pressure CVD method, or a sputtering method. 3. The multilayer film according to claim 1, wherein at least one of silicon nitride, silicon dioxide and alumina is used as a low refractive index film, and at least one of polycrystalline silicon and amorphous silicon is used as a high refractive index film. 3. The method for manufacturing a semiconductor laser device according to claim 1.