JPH05283817A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To realize the manufacture of a semiconductor laser which has limited side etching, and can make slim and deep mesa grooves. CONSTITUTION:A buffer layer 2, block layers 3, 4, and a mask layer are crystallized and made to grow on a P-InP crystal substrate 1 where the projected part is formed. The projected part is etched by HC1, and mesa-forming grooves 12 are made. After that, an arrow-head type groove 13 is made, and the mask layer is eliminated. Then, a clad layer 5, an active layer 6, a clad layer 7, and a cap layer 8 are buried and made to grow. After forming an insulating film, a stripe-type electrical window is opened, and a p-type electrode 10 and an n-type electrode 11 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor laser suitable for use as a light source for high speed optical communication.

[0002]

2. Description of the Related Art In a semiconductor laser, it has been considered to reduce the parasitic capacitance of an element (chip) of the semiconductor laser in order to realize high-speed response characteristics with short rise and fall times. As a method thereof, for example, on both sides of an optical waveguide of a semiconductor laser, a mesa forming groove is formed in parallel,
The method of forming mesas is commonly used.

FIG. 6 is a sectional view of an example of a conventional semiconductor laser. In the figure, 1 is a p-InP single crystal substrate and 2 is a p-InP substrate.
InP buffer layer, 3 is n-InP block layer, 4 is p
-InP block layer, 5 is p-InP clad layer, 6 is InGaAsP active layer, 7 is n-InP clad layer, 8
Is an n-InGaAsP cap layer, 9 is a SiNx insulating film, 10 is a p-electrode, 11 is an n-electrode, 12 is a mesa formation groove,
Reference numeral 13 is an arrow head type groove.

A method of manufacturing the conventional semiconductor laser shown in FIG. 6 will be described. First, p-InP single crystal substrate 1
The p-InP buffer layer 2, the n-InP block layer 3, and the p-InP block layer 4 are epitaxially grown thereon by liquid phase growth. Next, the arrow head type groove 13 is formed by etching in a portion corresponding to the top of the mesa.
Further, four layers of the p-InP clad layer 5, the InGaAsP active layer 6, the n-InP clad layer 7, and the n-InGaAsP cap layer 8 are embedded and grown by liquid phase growth. Then, on both sides of the arrow head type groove 13 produced previously, the mesa forming groove 12 deeper than the active layer 6 is dug to form a mesa. After forming the SiNx insulating film 9, a stripe type current window is opened on the waveguide, and the p electrode 1 is formed on both sides of p and n.
The 0 and n electrodes 11 are deposited. Then, the semiconductor laser device is completed by cleaving and separating into individual chips.

Since the wafer of embedded growth is relatively small, the mesa forming groove 12 is formed in each small wafer, and a process for forming a large substrate is performed once by a method such as etching rather than forming a mesa. Forming mesas in (1) is also useful in reducing manufacturing costs, and this method has been used conventionally.

In the conventional manufacturing method as described above, the mesa forming groove 12 is dug and the mesa is formed after all the crystals have been manufactured. Therefore, in order to dig the mesa formation groove 12, it is necessary to etch a plurality of different layers, and therefore, an etchant such as Brmethanol, which causes an excessively large side etching, must be used. .. As a result, the bonding pad for wire bonding or the top of the mesa becomes very small, which makes it difficult to perform wire bonding and window opening of the current window. If a small acid for side etching is used instead of Br-methanol, it must be etched several times by various kinds of etchants due to the difference in etching characteristics of each layer. Further, there is a problem in the residual property of the acid used for the device.

Further, after the production of all the crystals,
In the case of forming a mesa forming groove for forming a mesa, the waveguide after completion of the buried growth cannot be seen from above and the surface of the cap layer is flat, so that the location of the waveguide can be easily identified. Not stick. However, in order to open a current window in the SiNx insulating film and to form two grooves for forming a mesa by the conventional method, it is necessary to grasp the exact location of the waveguide. Therefore, conventionally, the guideline had to be prepared on the back side of the substrate at the position of the waveguide.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is little side etching, the bonding pad and the top of the mesa do not become small, and the residue of the acid used as an etchant on the element does not pose a problem, and the mesa can be easily formed. It is an object of the present invention to provide a method for manufacturing a semiconductor laser capable of forming a formation groove.

[0009]

According to a first aspect of the present invention, in a method for manufacturing a semiconductor laser having a mesa forming groove on both sides of an active region, a convex portion is formed at a position where the mesa forming groove is formed. The invention is characterized in that the formed substrate is used, and after forming a predetermined layer on the substrate, the mesa forming groove is formed by etching the convex portion. In a method of manufacturing a semiconductor laser having mesa forming grooves on both sides of an active region, after forming arrowhead-shaped grooves or V-shaped grooves on a semiconductor wafer on which a block layer is formed and forming mesa forming grooves on both sides thereof, It is characterized by performing buried growth.

In a method of manufacturing a semiconductor laser in which an arrow head type groove or a V-shaped groove is formed in a block layer wafer and then an active layer is embedded and grown, a substrate is made to have irregularities and the block is formed on the substrate. It is possible to grow a layer, form a groove for forming a mesa by etching, form an arrow head type groove or a V-shaped groove, and perform embedded growth.

[0011]

According to the first aspect of the present invention, in the method of manufacturing a semiconductor laser having the mesa forming grooves on both sides of the active region, the convex portion is previously formed on the substrate at a position where the mesa forming groove is formed. , A predetermined layer is formed on the substrate, and then a groove for forming a mesa can be formed by etching the convex portion of the substrate, so that one kind of etchant with less residual property is used. It is possible,
Side etching is small, and it is possible to form a thin and deep mesa forming groove.

According to the second aspect of the invention, in the method of manufacturing a semiconductor laser having the mesa forming grooves on both sides of the active region, the semiconductor wafer at the stage where the block layer is formed,
By forming the groove, it is possible to use one kind of etchant having a low residual property, and it is possible to form a thin and deep mesa forming groove with small side etching.

[0013]

1 is a sectional view of an embodiment of a semiconductor laser manufactured by the manufacturing method of the present invention. 2 to 5 are process diagrams of one embodiment of the manufacturing method of the present invention. In the figure, the same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. Reference numeral 14 is a convex portion, and 15 is an InGaAsP mask layer.

In this embodiment, like the conventional example described in FIG. 6, the present invention is applied to the manufacture of an end face light emitting diode having an arrow head type groove, and a mesa formed on both sides of an active region is formed. The mesa is formed by the groove.

A method of manufacturing the semiconductor laser of FIG. 1 will be described. P-In thicker than the required substrate
A P single crystal substrate 1 is used. SiN on this (100) plane
An x film is formed, and SiN is formed along the <011> direction of the crystal.
The x film is etched into stripes. The SiNx film serves as a mask during etching. The portion where the SiNx film remains corresponds to a position which will later become a mesa formation groove.

Using HCl + 2HNO ₃ as an etchant, the p-InP single crystal substrate 1 is etched. After the etching is completed, the SiNx film is removed (FIG. 2). Through this step, the p-InP single crystal substrate 1 in which the convex portion 14 is formed at the position to be the mesa formation groove can be manufactured. Convex part 1
4 corresponds to a portion to be a mesa forming groove later.

The p-InP buffer layer 2, the n-InP block layer 3, and the p-InP block layer 4 are epitaxially grown by liquid crystal growth on the p-InP single crystal substrate 1 on which the convex portions are formed. On top of that, InGaA
Crystals of the sP mask layer 15 are grown (FIG. 3).

Etching is performed using HCl as an etchant. As a result, the convex portion formed on the p-InP single crystal substrate 1 is etched, and the mesa forming groove 12 is formed. Side etching in this etching is small, and the manufactured mesa forming groove 12 is slightly expanded downward.

A resist is applied to the formed mesa forming groove 12, the InGaAsP mask layer 15 is patterned, and the arrow head type groove 1 is formed on the top of the mesa by etching.
3 is produced. Then, resist and InGaAsP
The mask layer 15 is removed (FIG. 4). HC is the etchant
1 can be used, but other etchants may be used.

P-InP clad layer 5, InGaA
sP active layer 6, n-InP clad layer 7, n-InGa
Four layers of AsP cap layer 8 are embedded and grown (FIG. 5).

After forming the SiNx insulating film 9 on the n-InGaAsP cap layer 8, a stripe type current window is opened on the waveguide (on the arrow head type groove 13), and the p electrode 10 is formed.
Then, the n-electrode 11 is formed and cleaved into individual chips (FIG. 1). The semiconductor laser is completed by the above procedure.

Although HCl is used as an etchant in the above manufacturing process, HCl is suitable for the present invention because it has less residual properties and less side etching than Br methanol or the like. Further, the InGaAsP mask layer 15 used as a mask during etching may be made of another substance as long as it serves as a mask for the etchant.

Arrowhead groove 13 in the manufacturing process
The forming step of can also be performed in the same step as the mesa forming groove 12 in. However, in this embodiment, the mesa forming groove 12 has a longer etching time. Therefore,
First, the etching of the mesa forming groove 12 is started, and when the part of the mesa forming groove 12 is formed, the etching is interrupted and the InGaAsP mask layer 15 is patterned for the arrow head type groove 13. After that, etching may be performed again to continuously form the mesa forming groove 12 after the interruption, and simultaneously form the arrow head type groove.

The etching for forming the mesa forming groove 12 can also be performed after the embedded growth step. For example, at the stage where the n-InGaAsP cap layer 8 is formed, a resist may be applied to etch the convex portions. Also in this method, the mesa forming groove 12 is
Since the convex portion is formed by etching, a thin and deep mesa forming groove can be formed.

In the above-mentioned embodiment, the substrate having the convex portion is used, but after the buffer layer and the block layer are formed using the substrate having no convex portion, as described in the manufacturing process, In the step (1), that is, in the case of forming the mesa formation groove and the mesa groove, the single crystal substrate, the buffer layer, and the block layer can be formed of the same material, so that one kind of etchant can be used. Further, since HCl, which has a small side etching, can be used, it is possible to form a deep mesa forming groove having a narrow groove width as in the above-described embodiment.

In the above-mentioned embodiments, the materials used for the respective layers constituting the semiconductor laser such as the block layer, the clad layer, the active layer and the cap layer are not limited to the above-mentioned materials, and other suitable materials are used. Needless to say, even if the above method is used, the production method of the present invention can be applied.

Although the p-type substrate is used as the base in the above-described embodiments, a semiconductor laser based on the n-type substrate is manufactured by changing the p-type of each layer to n-type and n-type to p-type. be able to.

Further, although the above-described embodiments have been described with respect to the case where the present invention is applied to the arrow head type end face light emitting diode, the present invention can be applied to other types of end face light emitting diodes. Is clear.

[0029]

As is apparent from the above description, according to the present invention, a convex portion is provided on a substrate in advance, a predetermined layer is formed, and then a groove for forming a mesa is formed by etching. By doing so, there is an effect that the groove width is narrow, a deep groove can be formed, and the width of the mesa portion is not significantly narrowed. Therefore, compared with the conventional method of forming a groove for forming a mesa using Br methanol or the like, when a chip of the same size is manufactured, the size of a bonding pad for wire bonding can be increased, Bonding becomes easy. Similarly, when the stripe type current window is opened on the waveguide of the SiNx insulating film, the processing becomes easy.

Further, when etching the groove for forming the mesa, an acid such as HCl, which has a low residual property and a small side etching, can be used, so that the above-mentioned effect can be further enhanced. It also solves problems such as persistence.

Furthermore, the guideline on the back side of the substrate, which was conventionally required to grasp the exact location of the waveguide, is not necessary by applying the present invention, and the process for producing the guideline on the back side of the substrate can be omitted. There is also the effect.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a semiconductor laser manufactured by a manufacturing method of the present invention.

[Figure 2]

FIG. 5 is a process drawing of an example of the manufacturing method of the present invention.

FIG. 6 is a sectional view of a conventional semiconductor laser.

[Explanation of symbols]

 1 p-InP single crystal substrate 2 p-InP buffer layer 3 n-InP block layer 4 p-InP block layer 5 p-InP clad layer 6 InGaAsP active layer 7 n-InP clad layer 8 n-InGaAsP cap layer 9 SiNx insulation Film 10 p electrode 11 n electrode 12 mesa forming groove 13 arrow head type groove 14 convex portion 15 InGaAsP mask layer

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor laser having a mesa forming groove on both sides of an active region, wherein a substrate having a convex portion formed at a position where the mesa forming groove is formed is used, and a predetermined layer is formed on the substrate. And then forming the mesa forming groove by etching the convex portion. 2. A method of manufacturing a semiconductor laser having mesa forming grooves on both sides of an active region, wherein arrowhead-shaped grooves or V-shaped grooves are formed on a semiconductor wafer on which a block layer is formed, and mesa forming grooves are formed on both sides thereof. A method for manufacturing a semiconductor laser, which comprises performing buried growth after the formation.