KR100767697B1 - Fabrication Method for Semiconductor Laser Diode - Google Patents

Abstract

The present invention provides a method for manufacturing a semiconductor laser diode, an n-type nitride semiconductor layer, a first cladding layer, a first waveguide layer, an active layer, a second waveguide layer, a second cladding layer, a p-type nitride semiconductor on a substrate Sequentially forming the layers; Etching the p-type nitride semiconductor layer, the second cladding layer, the second waveguide layer, the active layer, the first waveguide layer, and the first cladding layer to expose a portion of the n-type nitride semiconductor layer; Etching a portion of the second clad layer such that a predetermined region of the second clad layer has a protruding region; Sputtering the entire surface including the protruding region to form a protective film, and heat treatment and plasma treatment in a gas atmosphere mixed with oxygen; And forming an n-contact layer and a p-contact layer so as to be connected to the n-type nitride semiconductor layer and the protruding region, respectively, by sputtering the protective layer and using heat treatment or plasma in the gas atmosphere. The heat treatment is performed to compensate for the oxygen deficiency in the passivation layer by the etching process and the sputtering process to prevent leakage of current into the second clad layer, thereby improving electrical characteristics of the semiconductor laser diode.

Plasma, sputtering

Description

Fabrication Method for Semiconductor Laser Diode

1A to 1G are cross-sectional views of a semiconductor laser diode manufacturing process according to the prior art.

Figure 2a to 2g is a cross-sectional view of the semiconductor laser diode manufacturing process according to the present invention.

* Explanation of symbols for main parts of the drawings

delete

delete

delete

delete

delete

delete

101: sapphire substrate 102: n-GaN

103: n-AlGaN cladding layer 104: n-GaN waveguide layer

105: active layer 106: p-GaN waveguide layer

107: p-AlGaN cladding layer 108: p-GaN

109: protective film 110: n-contact                 

111: p-contact

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a blue semiconductor laser diode, and more particularly, to a method for reducing leakage current flowing toward a p-clad and improving electrical characteristics of a semiconductor laser diode.

Looking at the manufacturing process of a semiconductor laser diode (LD: Laser Diode) using the MOCVD method according to the prior art as follows.

As shown in Fig. 1A, n-GaN (2), n-AlGaN cladding layer (3), n-GaN waveguide layer (waveguide) 4: active layer (5), p-GaN on sapphire substrate (1) The waveguide layer 6, the p-AlGaN cladding layer 7, and the p-GaN 8 are sequentially formed.

Subsequently, after forming a mesa pattern with a photoresist (PR) mask, a mesa is formed by etching until the n-GaN 2 is exposed by a dry etching method as shown in FIG. 1B.

After the mesa process, a ridge pattern is formed with a PR mask, and then a p-GaN waveguide layer 6 and a p-AlGaN cladding layer are dry-etched until a part of the p-GaN waveguide layer 6 is exposed. (7), p-GaN (8) is etched to form a ridge as shown in Fig. 1C.

When the mesa and ridge forming processes are completed, as shown in FIG. 1D, after forming a predetermined pattern with a PR mask, a metal material 9 for contact with the electrode is coated on the n-GaN 2.

Then, as shown in FIG. 1E, the PR is lifted off to remove the n-contact 9 to form an alloy in an N ₂ atmosphere.

Subsequently, as shown in FIG. 1F, the protective film 10 is deposited by a sputtering method, a predetermined pattern is formed using a PR mask, and the deposited protective film 10 is wet-etched to open the n-contact 9.

After the deposited protective film 10 is alloyed in an N ₂ atmosphere, the protective film 10 on the ridge is finally removed by wet etching, and the p-contact 11 for contact with the electrode is shown in FIG. 1G. Form as
However, the semiconductor laser diode manufacturing method according to the related art described above has the following problems.
The plasma process is required three times during the semiconductor laser diode forming process. The more plasma processes are applied, the more adversely affects the characteristics of the device such as leakage current generated in the p-clad layer. Attempts were made to mitigate the damage of the device by heat treatment.
However, since the alloy is not easy for a long time due to the alloy and n-contact in the N ₂ atmosphere, the pinhole density of the protective film is increased and the degree of porosity is increased to prevent the proper function of the protective film, so that leakage current is leaked to a place other than the ridge. There is a drawback of current flow.

delete

delete

delete

Accordingly, the present invention has been made to solve the above problems, to provide a method for manufacturing a semiconductor laser diode with improved performance by preventing leakage current due to pinholes and porosity of the protective film and reducing the characteristic degradation and improving the electrical properties. There is a purpose.

Features of the semiconductor laser diode manufacturing method according to the present invention for achieving the above object is an n-type nitride semiconductor layer, the first cladding layer, the first waveguide layer, the active layer, the second waveguide layer, the second clad on the substrate Sequentially forming a layer, a p-type nitride semiconductor layer; Etching the p-type nitride semiconductor layer, the second cladding layer, the second waveguide layer, the active layer, the first waveguide layer, and the first cladding layer to expose a portion of the n-type nitride semiconductor layer; Etching a portion of the second clad layer such that a predetermined region of the second clad layer has a protruding region; Forming a protective film by sputtering on the entire surface including the protruding region, and heat treatment in a gas atmosphere in which oxygen is mixed; And forming an n-contact layer and a p-contact layer to be connected to the n-type nitride semiconductor layer and the protruding region, respectively.

The second clad layer is formed by sputtering the passivation layer, followed by heat treatment using plasma in the gas atmosphere, or by further adding a plasma process to compensate for oxygen deficiency in the passivation layer by the etching process and the sputtering process. This prevents leakage of current and improves the electrical characteristics of the semiconductor laser diode.                     

In other words, the protective film deposited by sputtering is changed to an atmosphere of oxygen mixed gas, and the heat treatment is rapidly performed to prevent pinholes and porosity of the protective film, thereby improving the electrical characteristics of the semiconductor laser diode, and the damage caused by dry etching and sputtering. Can be minimized.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

A preferred embodiment of the semiconductor laser diode manufacturing method according to the present invention will be described with reference to the accompanying drawings.

First, as shown in FIG. 2A, an n-GaN 102, an n-AlGaN cladding layer 103, an n-GaN waveguide layer 104, an active layer 105, and p− are formed on a sapphire substrate 101. The GaN waveguide layer 106, the p-AlGaN cladding layer 107, and the p-GaN 108 are sequentially formed using epitaxy.

Subsequently, after forming a mesa pattern with a photoresist (hereinafter, PR) mask, a mesa is formed by etching until the n-GaN 102 is exposed by a dry etching method as shown in FIG. 2B.

After the mesa process, a ridge pattern is formed using a PR mask, and then p-GaN waveguide layer 106 and p-AlGaN cladding layer are dry-etched until a part of the p-GaN waveguide layer 106 is exposed. 107 and p-GaN 108 are etched to form ridges as shown in Fig. 2C.

When the mesa and ridge forming processes are completed, as shown in FIG. 2D, a protective film 109 is formed of an oxide film such as SiO ₂ by a sputtering method, and a post process is performed.

There are three methods listed below for the post process.

First, heat treatment at a temperature of 100 ℃ ~ 800 ℃ in the furnace (furnace) in the atmosphere of oxygen (1 ~ 70%) and nitrogen mixed.

Second, heat treatment at a temperature of 100 ℃ ~ 800 ℃ using a plasma in an atmosphere of oxygen (1 ~ 70%), nitrogen, argon mixed or mixed atmosphere of oxygen and argon.

Third, after the heat treatment in the atmosphere mixed with oxygen (1 ~ 70%) and nitrogen, heat treatment at a temperature of 100 ℃ ~ 800 ℃ using a plasma.

In order to obtain a protective film without pinholes or porosity, a substrate temperature of 100 ° C to 800 ° C is required during the deposition of the protective film. However, since the substrate temperature cannot be raised due to equipment problems, the post process as described above is necessary.

Such a post process reduces the leakage current by compensating for oxygen deficiency in the protective film. That is, since the leakage current density is greatly influenced by the heat treatment temperature and the atmosphere, the leakage current density is decreased by the post-treatment process due to the reduction of defects at the interface and the trap density.

In addition, since the reactivity of the oxygen molecules is very weak and the heat treatment time is very short, it is not very effective to fill the oxygen deficiency while the oxygen molecules are diffused. Likewise, the use of plasma is effective in compensating for oxygen deficiency.                     

The protective film also serves as a diffusion mask or plays an important role in protecting the PN junctions in particular.

The protective film stabilizes the electrical properties of the junction, increases the reliability of the packaged device and prevents scratches in subsequent processes by forming a protective film after the metal pattern is deposited.

Subsequently, as shown in FIG. 2E, after forming a PR of a predetermined pattern, the protective layer 109 formed on the n-GaN 102 is wet-etched and removed to expose the n-GaN 102. The metal material 110 for contact with the electrode is coated on the n-GaN 102.

The PR is then lifted off and removed to form an n-contact 110 as shown in FIG. 2F and then alloyed in an N ₂ atmosphere.

Subsequently, a predetermined pattern is formed using a PR mask to remove the protective layer 109 formed on the ridge by wet etching, and then a p-contact 111 for contact with the electrode is formed as shown in FIG. 2G.

The method of manufacturing a semiconductor laser diode according to the present invention as described above has the following effects.

After dry etching, it can effectively protect rough surfaces, reduce leakage current, and reduce plasma damage during sputtering, improving device properties.

The protective film SiO ₂ deposited by sputtering is intended to improve electrical properties while minimizing the damage caused by dry etching and sputtering by changing the temperature and atmosphere of rapid heat treatment.

Accordingly, by improving the quality of the protective film, a semiconductor laser diode having good characteristics can be produced.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (5)

Forming an n-type nitride semiconductor layer, a first cladding layer, a first waveguide layer, an active layer, a second waveguide layer, a second cladding layer, and a p-type nitride semiconductor layer sequentially on the substrate; Etching the p-type nitride semiconductor layer, the second cladding layer, the second waveguide layer, the active layer, the first waveguide layer, and the first cladding layer to expose a portion of the n-type nitride semiconductor layer; Etching a portion of the second clad layer to a predetermined depth such that a predetermined region of the second clad layer has a protruding region; Sputtering the entire surface including the protruding region to form a protective film and heat-treating in an oxygen mixed gas atmosphere; And forming an n-contact layer and a p-contact layer so as to be connected to the n-type nitride semiconductor layer and the protruding region, respectively. The method of claim 1, The oxygen mixed gas atmosphere is a semiconductor laser diode manufacturing method, characterized in that any one of the atmosphere mixed oxygen and nitrogen, the atmosphere mixed oxygen and argon, the atmosphere mixed oxygen, nitrogen, argon. The method of claim 1, The content of the oxygen is a semiconductor laser diode manufacturing method, characterized in that 1 to 70%. delete The method of claim 1, The heat treatment is a semiconductor laser diode manufacturing method, characterized in that at a temperature of 100 ℃ ~ 800 ℃.

Images