JPH01211989A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To improve the confinement effect of injection current and light, by a method wherein, after the overhang part of an insulating film on a rib is eliminated, II-VI compound semiconductor is buried. CONSTITUTION:A semiconductor substrate 101 has a clad layer 103, an active layer 104 and a clad layer 105, and a double hetero junction is stacked. On the substrate, an insulating film 107 is deposited, and resist 108 is spread. By patterning the resist 108 and using it as a mask, the insulating film 107 is subjected to etching. By using the insulating film 107 as a mask without eliminating the resist 108, etching is performed to form a rib. By etching the insulating film 107 between the resist 108 and the rib, the width of the insulating film 107 is made narrower than the stripe width of the rib. After the resist 108 is exfoliated, the epitaxial growth of II-VI compound semiconductor 109 is performed, and the semiconductor layer 109 is selectively eliminated. Thereby a semiconductor laser free from the leak of injection current and light can be manufactured with excellent yield.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a semiconductor laser.

[Conventional technology]

In conventional semiconductor lasers, when forming and embedding ribs, as shown in FIGS. 2(a) to (c), an insulating film, such as a silicon dioxide film, is deposited on a semiconductor substrate on which double heterojunctions are stacked. The silicon dioxide film is etched using the patterned resist as a mask.
Next, the resist is peeled off (a), and a II-Vl group compound semiconductor, such as zinc selenide, is epitaxially grown (b), and ribs are formed using the difference in etching speed between polycrystalline zinc selenide and single crystal zinc selenide. The zinc selenide on top was selectively removed.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, the insulating film on the live protrudes like a canopy, so when zinc selenide is epitaxially grown, polycrystalline and single-crystalline ff-Vl group compounds form in the shape shown in Figure 2(b). As the semiconductor layer grows, as a result, when selective etching is performed to remove the If-Vl group compound semiconductor layer on the rib, the etching progresses also along the sides of the rib as shown in FIG. 2(C), and the device When used as such, there is a problem in that injection current or light leakage occurs.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to manufacture a rib-embedded semiconductor laser with high yield without leakage of injection current or light.

[Means to solve the problem]

The method for manufacturing a semiconductor laser of the present invention includes the steps of depositing an insulating film on a semiconductor substrate laminated with a double heterojunction having a first cladding layer, an active layer, and a second cladding layer; a step of applying a resist; a step of patterning the resist and etching the insulating film using the resist as a mask; and a step of forming ribs by etching using the insulating film as a mask without removing the resist.
A step of etching the insulating film between the resist and the ribs to make the width of the insulating film thinner than the stripe width of the ribs, a step of epitaxially growing a ■-■ group compound semiconductor after stripping the resist, and a step of etching the If on the ribs. - selectively removing the Vl group compound semiconductor layer.

〔Example〕

Figure 1 shows an embodiment of the present invention, which differs from the conventional example in that after removing the protruding part of the insulating film used as a mask when forming the ribs, the ribs are formed using a -Vl group compound semiconductor. It is to embed.

Next, the manufacturing process will be explained using FIGS. 1(a) to 1(f). First, as shown in FIG. 1(a), a buffer layer 102, a first cladding layer 103, an active layer 104, a second cladding layer 1
05. A semiconductor substrate 101 on which contact layers 106 are sequentially laminated is prepared, and an insulating film, for example, a silicon dioxide film 107 is laminated on the entire surface of the contact layer 106. The deceptive silicon dioxide film was grown using atmospheric chemical vapor deposition (CVD) at 320-500°C, and the film thickness was 1000°C.
4. Next, a resist 108 of up to 3,000 layers is coated on the silicon dioxide film, and after patterning is performed by a photo process, the silicon dioxide layer 107 is etched using the resist as a mask until the contact layer 106 is exposed. Note that as the etchant, a hydrofluoric acid-ammonium fluoride based etchant is used. (FIG. 1(b)) After that, as shown in FIG. 1(c), the silicon dioxide layer 107
Using this as a mask, etching is performed to form ribs. In the deceptive etching, a sulfuric acid-based etchant is used, and the second cladding layer 106 is etched until a thickness of 0.1 to 0.4 .mu.m remains.

Next, as shown in Figure 1(d), the silicon dioxide 1B1107 protruding from the rib in a ridge shape was etched to remove the ridge-shaped part.The etchant used was the same as that used when patterning the silicon dioxide WA107 in Figure 1(b). The same hydrofluoric acid-ammonium fluoride type material as the one used was used, and the silicon dioxide film was 0.1 to 1.0
Etch until it retreats by μm.

Furthermore, the resist 108 is removed, and as shown in FIG.
[-Vl group compound semiconductor For example, the ribs are buried using zinc selenide as a current confinement layer, and the embedding is performed by organic chemical vapor deposition (MOCVD) using a dimethylzinc=diethylselenium adduct as a zinc source and the above adduct as a selenium source. In addition, hydrogen selenide is used for epitaxial growth at a growth temperature of 350 to 400°C. As a result, as shown in Figure 1(e), polycrystals of zinc selenide are formed on silicon dioxide, and selenium is formed on other parts. Single crystals of zinc oxide are stacked.

Finally, when zinc recryselide is etched with a sodium hydroxide etchant, polycrystalline zinc selenide on the ribs, which has a high etching rate, is selectively etched, and single-crystal zinc selenide is formed on both sides of the ribs. remain. Etching is performed until the silicon dioxide on the ribs is exposed.

As described above, in the semiconductor laser manufacturing method of this embodiment,
The rib-like portion of silicon dioxide on the ribs is removed before embedding with zinc selenide, so when the polycrystalline zinc selenide on the ribs is removed by etching after embedding, the sides of the ribs are not dug up. Compared to semiconductor lasers manufactured by conventional methods, this method has better current confinement and light confinement.

〔Effect of the invention〕

According to the method for manufacturing a semiconductor laser of the present invention, after filling the rib with the ■-■ group compound semiconductor, the ■
When removing the −■ group compound semiconductor, the ■−■ group compound semiconductor on the side surface of the rib is not etched even if selective etching is performed, and this improves the injection current and light confinement effect when used as a device. However, laser oscillation at a low threshold current value becomes possible and high external differential quantum efficiency can be obtained, and as a result, higher output and longer life of semiconductor lasers can be expected.

In addition, the II-Vl group compound semiconductor used as the buried layer has high thermal conductivity, so the fact that the ■-■ group compound semiconductor is in close contact with the rib means that the heat generated during laser oscillation is dissipated efficiently. This results in a long life and high reliability.

On the other hand, in the conventional technology, an FF-IV group compound semiconductor is epitaxially grown without removing the canopy part of the insulating film that overhangs from the rib, and a II-Vl group compound semiconductor layer on the rib is grown so that the sides of the lip are not dug after growth. In order to remove it, it is necessary to form a patterned mask on the II-Vl group compound semiconductor layer and perform etching, but this method increases the number of steps and requires alignment for the resist applied on an uneven surface. Therefore, the method for manufacturing a semiconductor laser has the effect of reducing the number of steps and greatly improving the yield.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(f) are sectional views showing the manufacturing process of an embodiment of the present invention, and FIGS. 2(a) to 2(c) are sectional views of the manufacturing process showing a conventional example. 101.201... Semiconductor substrate 102.202... Buffer layer 103.203... First cladding layer 104.204... Active layer 105.205... Second cladding layer 106.206... Contact layer 107.207...Silicon dioxide film 108...Resist 109.209...Buried layer of single crystal zinc selenide 110.210...Polycrystalline zinc selenide and above Applicant: Seiko Epson Agent Co., Ltd. Patent Attorney Tsutomu Mogami (1 other person) 6.

Claims (1)

[Claims] A step of depositing an insulating film on a semiconductor substrate laminated with a double heterojunction having a first cladding layer, an active layer, and a second cladding layer, a step of applying a resist on the above-mentioned insulating film, and a step of patterning the resist. a step of forming ribs by etching the insulating film using the insulating film as a mask without removing the resist; and a step of etching the insulating film between the resist and the ribs. It consists of a step of making the width thinner than the stripe width of the rib, a step of epitaxially growing the II-VI group compound semiconductor after removing the resist, and a step of selectively removing the II-VI group compound semiconductor layer on the rib. A method for manufacturing a semiconductor laser, characterized in that: