JP2003008055A - Method for manufacturing semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor light emitting device having a thin electrode such as a mesh electrode on a part of a light emitting surface, the method having high luminous efficiency and between a semiconductor and an electrode. To provide a method for manufacturing a semiconductor light emitting device having a low contact resistance. When a surface of a semiconductor light emitting device is subjected to a surface roughening treatment, a coating film made of a resist is formed so as to cover an outer surface of an upper electrode on a semiconductor surface in a coating film forming step. Therefore, when the roughening process is performed by etching in the roughening process,
Even if the semiconductor light emitting element 10 has a thin upper electrode 24 such as a mesh electrode in a part of the semiconductor light emitting device, a portion of the semiconductor surface immediately below the upper electrode 24 is removed without eroding the semiconductor surface in contact with the upper electrode 24. The semiconductor light emitting device 10 having high luminous efficiency and low contact resistance between the semiconductor and the upper electrode 24 because a large number of minute projections can be formed in other regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor light emitting device.

[0002]

2. Description of the Related Art In recent years, light emitting diodes have been widely used in optical communication and display devices. Such a light emitting diode is generally constructed by using a semiconductor light emitting element in which semiconductor layers including a light emitting layer are sequentially stacked on a semiconductor substrate by a method such as MOCVD (Metal Organic Chemical Vapor Deposition). One type of such semiconductor light emitting device is a light emitting surface on which an electrode is partially provided, an active layer which is provided in parallel with the light emitting surface and generates light, and the light is emitted toward the lower side of the active layer. There is known a surface-emitting type semiconductor light emitting device that includes a reflective layer or the like that reflects the emitted light toward the light emitting surface, and emits the light generated from the active layer from the light emitting surface.

One of the methods for improving the light emission output of such a semiconductor light emitting device is a method generally called roughening treatment (texture treatment). This is a method of increasing the light extraction efficiency from the light emitting surface by roughening the surface of the semiconductor light emitting element, that is, forming a large number of minute protrusions on the semiconductor surface. The surface of the semiconductor is eroded by being dipped in the etching solution, and a large number of minute projections are formed on the surface of the semiconductor including the light emitting surface, so that the light extraction efficiency from the light emitting surface can be improved.

[Problems to be Solved by the Invention]

By the way, in such a semiconductor light emitting device, a surface in which the density of the current flowing in the light emitting portion is made uniform by crossing a thin linear electrode such as a mesh on the light emitting surface, and the light output is increased. Light emitting devices are known. However, if the semiconductor light emitting device having such a thin electrode is subjected to the surface roughening treatment as described above, the light output may be increased, but at the same time, the required voltage may be increased. Was becoming.

The inventor has found that the cause of this problem is
When the surface of the semiconductor light-emitting device was roughened, it was thought that the etching solution might penetrate from the outside of the electrode to the bottom of the electrode and slightly corrode the semiconductor surface in contact with the electrode. . That is, when the contact area between the electrode formed on the semiconductor surface and the semiconductor surface is sufficient, such a problem does not occur, but, for example, a mesh electrode in which linear electrodes with a width of 30 μm or less intersect When it is formed, when the semiconductor surface is subjected to a surface roughening treatment, even the semiconductor surface in contact with the electrode is eroded by the etching solution and the side portion of the electrode is floated. I thought that the contact resistance increased and the optical output increased as a result, but at the same time, the required voltage also increased.

The present invention has been made from such a background, and an object thereof is a method for manufacturing a semiconductor light emitting device having a thin electrode such as a mesh electrode on a part of a light emitting surface, An object of the present invention is to provide a method for manufacturing a semiconductor light emitting device having high luminous efficiency and low contact resistance between a semiconductor and an electrode.

[0007]

In order to achieve the above object, the gist of the present invention is a method for manufacturing a semiconductor light emitting device in which an electrode is formed on a part of a light emitting surface. A coating film forming step of forming a coating film with a resist so as to cover the outer surface of the electrode formed on the surface, and etching the surface of the semiconductor light emitting element with the coating film formed. And a surface roughening treatment step of forming a large number of minute projections on a region of the surface of the semiconductor light emitting device excluding a portion immediately below the electrode.

[0008]

According to the present invention, when the surface of the semiconductor light emitting device is roughened, the surface of the semiconductor is covered with a resist so as to cover the outer surface of the electrode on the surface of the semiconductor in the coating film forming step. Since the film is formed, when roughening treatment is performed by etching in the roughening treatment step,
Even if the semiconductor light-emitting element has a thin electrode such as a mesh-shaped electrode on a part of the light-emitting surface, the etching solution penetrates under the electrode from the outer side of the electrode without corroding the semiconductor surface in contact with the electrode. Since a large number of minute protrusions can be formed in a region other than a portion directly below the electrode on the semiconductor surface, it is possible to provide a semiconductor light emitting device having high luminous efficiency and low contact resistance between the semiconductor and the electrode. it can.

[0009]

According to another aspect of the present invention, preferably, in the method for manufacturing a semiconductor light emitting device, a resist pattern for obtaining a desired electrode shape on a surface of an electrode material layer fixed on the surface of the semiconductor light emitting device. And a step of forming an electrode having a desired pattern by removing a portion of the electrode material layer exposed from the resist pattern formed by the patterning step by etching. In the covering film forming step, the resist left on the electrode is caused to flow by heating so as to cover the outer surface of the electrode formed in the electrode forming step, thereby forming a covering film of the resist. By doing so, the resist patterned on the electrode surface to form an electrode having a desired shape is not removed, but the resist is heated to flow and the end face is sagged, so that the electrode on the semiconductor light emitting element surface Since the resist coating film is formed on the outer side surface, it is possible to efficiently and economically provide a semiconductor light emitting device having high luminous efficiency and low contact resistance between a semiconductor and an electrode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the drawings used in the following description, the dimensional ratios of the respective parts are not necessarily drawn accurately.

FIG. 1A is a diagram showing the structure of a semiconductor light emitting device 10 which is an embodiment of the present invention. Such a semiconductor light emitting device 10 is a multilayer film in which, for example, 30 pairs of n-AlGaAs / AlAs semiconductors are laminated on a substrate 12 which is an n-GaAs semiconductor by using, for example, MOCVD (Metal Organic Chemical Vapor Deposition) method. Reflective layer 14, n-AlGaAs
The first clad layer 16 which is a semiconductor, the active layer 18 which is a p-GaAs semiconductor, and the second layer which is a p-AlGaAs semiconductor
A clad layer 20 and a cap layer 22 which is a p-GaAs semiconductor are sequentially laminated, and an upper electrode 24 made of AuZn / Au eutectic is provided on the cap layer 22 to form a substrate 12.
Lower electrode 2 made of AuGe / Ni / Au eutectic on the lower surface of the
6 are formed by vapor deposition or sputtering. In the semiconductor light emitting device 10 of the present embodiment, the first cladding layer 16, the active layer 18, and the second cladding layer 20 form a double hetero structure, and light is emitted from the active layer 18. Further, in FIG. 1, the first cladding layer 1
6, a portion of the active layer 18, the second cladding layer 20, and the cap layer 22 surrounded by a dotted line is doped with an impurity such as H ⁺ by using, for example, an ion implantation apparatus, and has a high resistance current confinement region. It is A.

The semiconductor light emitting device 1 having the above structure
At 0, when a pn forward current is applied between the upper electrode 24 and the lower electrode 26, light is generated by recombination of electrons and holes in the active layer 18, and the light is generated. Is emitted from the light emitting surface 28 of the. Here, FIG. 1B is a view of the semiconductor light emitting element 10 as viewed from the direction perpendicular to the light emitting surface 28. The upper electrode 24 is
On the light emitting surface 28, for example, a mesh shape in which lines having a width of 5 μm intersect is formed, and in the other regions, it is formed so as to cover the entire surface. The region A other than the light emitting surface 28 has a high resistance due to the implantation of H ⁺ ions from the upper surface of the cap layer 22 to a depth that does not reach the lower surface of the first cladding layer 16, and is located in a place other than the light emitting portion. Since it is difficult for the current to flow, the light extraction efficiency is improved and a high light output can be obtained.

The semiconductor light emitting device 10 as described above is manufactured, for example, in the following steps. First, for example, MO
An epitaxial wafer is manufactured by sequentially growing crystals from the multilayer reflective layer 14 to the cap layer 22 on the substrate 12 by the CVD method. Next, an ion implantation mask is formed at a position which becomes a light emitting portion of the cap layer 22, and H ⁺ ions are implanted into a region other than the light emitting portion to form a current confinement region A. On the cap layer 22 of the semiconductor wafer thus manufactured, the electrode material layer to be the upper electrode 24 is fixed on one surface by vapor deposition or sputtering. Subsequently, a resist pattern for obtaining a desired electrode shape is formed on the surface of the fixed electrode material layer, and then etching is performed to form an upper electrode 24 having a desired shape.

Subsequently, the surface of the semiconductor is roughened in order to increase the luminous efficiency of the semiconductor light emitting device 10. This roughening treatment is one of the methods for increasing the efficiency of extracting light from the light emitting surface 28 to the outside.
0 in nitric acid-based etching solution for a predetermined time (several seconds to several tens of seconds)
By immersing, a large number of minute protrusions are formed on the semiconductor surface including the light emitting surface 28, so that the light emitting efficiency of the semiconductor light emitting device 10 is improved. FIG. 2 is a diagram showing a light emitting surface 28 of the semiconductor light emitting device 10 in which a large number of minute protrusions are formed in a region other than the portion directly below the upper electrode 24. A sufficient contact area is provided between the upper electrode 24 and the semiconductor surface,
At the same time, in order to increase the light emission efficiency of the light emitting surface 28, it is preferable to form a large number of minute projections in a region other than the portion directly below the upper electrode 24 on the light emitting surface 28 as shown in this figure.

Here, according to the conventional method, the upper electrode 2
4 was formed, and after the resist patterned to form the upper electrode 24 having a desired shape was removed, roughening treatment of the semiconductor surface was performed. In this case, the etching solution not only roughens the surface of the semiconductor that does not come into contact with the upper electrode 24 by roughening, but also penetrates below the upper electrode 24 from the outer side of the upper electrode 24 to reach the upper electrode 24. Even the contacting semiconductor surface is slightly corroded. Here, when the contact area between the upper electrode 24 fixed to the semiconductor surface and the semiconductor surface is sufficient, that is, the upper electrode 24 formed around the light emitting surface 28 as shown in FIG. 3A is considered. If this is the case, this is not a problem. However, when a linear electrode having a width of 30 μm or less, for example, a mesh-shaped upper electrode 24 in which linear electrodes having a width of 5 μm intersect as in this embodiment is formed, the semiconductor surface is roughened by etching. At this time, even the semiconductor surface in contact with the upper electrode 24 is eroded by the etching solution, so that the side portions of the upper electrode 24 are floated as shown in FIG. Although the contact resistance with and the light output increases as a result, the required voltage also increases at the same time. In particular, since a nitric acid-based etching solution having a strong oxidizing action is generally used for roughening the semiconductor surface, such a problem tends to occur even if the etching is performed for a short time such as several seconds to several tens of seconds. .

In this embodiment, in order to solve this problem, the semiconductor surface is roughened by using an etching technique in the step shown in FIG. First, in the patterning step P1, a pattern of the resist 30 for obtaining a desired electrode shape is formed on the surface of the electrode material layer fixed on the semiconductor surface. FIG. 5A shows this state. Then, the electrode forming step P2
In FIG. 5, as shown in FIG. 5B, the electrode material layer is etched to form the upper electrode 24 having a desired pattern. Then, in the coating film forming step P3, the semiconductor wafer is baked on the upper electrode 24 after the etching by baking in a temperature range of 150 to 200 ° C. for 10 minutes to 3 hours, preferably 30 minutes to 1 hour. The resist 30 thus formed is caused to flow and the end surface is sagged, so that FIG.
As shown in (c), a coating film of this resist 30 is formed so as to cover the outer surface of the upper electrode 24. Then, in the roughening treatment step P4, as shown in FIG. 5D, the semiconductor surface is etched in a state where the coating film of the resist 30 is formed, and the semiconductor surface of the semiconductor surface immediately below the upper electrode 24 is etched. A large number of minute protrusions are formed in other regions except the portion, and in the subsequent step, the coating film of the resist 30 is removed as shown in FIG.

As described above, in this embodiment, when the surface of the semiconductor light emitting device 10 is roughened, the coating film forming step P is performed.
Since the coating film of the resist 30 is formed so as to cover the outer surface of the upper electrode 24 on the semiconductor surface in 3, the light emitting surface when the roughening treatment is performed by etching in the roughening treatment step P4. Even in the semiconductor light emitting device 10 having a thin upper electrode 24 such as a mesh-shaped electrode in a part of 28, the etching liquid penetrates under the upper electrode 24 from the outer portion of the upper electrode 24 to form the upper electrode 24. Since a large number of minute protrusions can be formed in a region other than a portion directly below the upper electrode 24 on the semiconductor surface without eroding the contacting semiconductor surface, the luminous efficiency is high and the semiconductor and the upper electrode 24 are It is possible to provide the semiconductor light emitting device 10 having low contact resistance between them.

Further, in this embodiment, the resist 30 used for patterning the surface of the electrode material layer for forming the upper electrode 24 having a desired shape is not removed, but the resist 30 is fluidized by heating. Since the coating film of the resist 30 is formed on the outer surface of the upper electrode 24 on the semiconductor surface by sagging the end face, the luminous efficiency is high efficiently and economically, and the space between the semiconductor and the upper electrode 24 is high. It is possible to provide the semiconductor light emitting device 10 having a low contact resistance.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention is not limited to this embodiment and can be implemented in other modes.

For example, in the above embodiment, p-G
The semiconductor light emitting device 10 having the light emitting layer of the double hetero structure having the aAs semiconductor as the active layer 18 has been described, but the present invention is, for example, AlGaAs, InGaN, InGaA.
The same can be applied to a semiconductor light emitting device having a double hetero structure light emitting layer having an active layer of s, InGaAsP, InGaAlP, or the like, or a light emitting layer having a multiple quantum structure. Further, for the substrate 12, other materials such as InP and sapphire may be used.

Further, in the above-mentioned embodiment, the current confinement structure was formed by implanting H ⁺ ions in order to obtain a high light output, but this may not necessarily be formed, and p- Other current constriction structures such as an n-inversion region may be formed.

Further, in the above-described embodiment, FIG.
Although the semiconductor light emitting device 10 in which the thin mesh-shaped upper electrode 24 is formed on the light emitting surface 28 as shown in (b) has been described, the present invention is not limited to this, and, for example, as shown in FIG. A thin annular upper electrode 24 on the light emitting surface 28.
It can be widely used for the semiconductor light emitting element 10 in which the thin linear upper electrode 24 is partially formed on the light emitting surface 28, such as the semiconductor light emitting element 10 formed by combining the above and the linear upper electrode 24.

Further, in the above-mentioned embodiment, the light emitting surface 2
Mesh-shaped upper electrode 2 with 5 μm wide lines crossing 8
4 is formed, the present invention is preferably used for the semiconductor light emitting device 10 in which the upper electrode 24 having a width dimension of 30 μm or less is formed, and particularly, the width dimension of 5 μm or less. It is also used for the semiconductor light emitting device 10 on which the upper electrode 24 is formed. Further, if necessary, it can be used for the semiconductor light emitting device 10 in which the upper electrode 24 having a width dimension of 30 μm or more is formed.

Further, in the above-described embodiment, when forming a large number of minute protrusions on the semiconductor surface by etching, the resist 30 patterned on the surface of the electrode material layer is removed to form the upper electrode 24 having a desired shape. Without,
The resist 30 was made to flow by heating and the end face was sagged to form a coating film of the resist 30 on the outer surface of the upper electrode 24 on the semiconductor surface. However, the upper electrode 24 having a desired shape is formed. Therefore, after removing the resist 30 patterned on the surface of the electrode material layer, a resist coating film may be formed on the outer surface of the upper electrode 24 on the semiconductor surface by using, for example, a photolithography technique.

Further, in the above-described embodiment, the upper electrode 24 is formed by etching the electrode material layer fixed on the semiconductor surface by vapor deposition or sputtering. For example, it may be formed by another process different from the process of etching the portion exposed from the resist 30 such as lift-off.

Further, in the above-mentioned embodiment, the nitric acid-based etching solution was used for the roughening treatment of the semiconductor surface, but if the etching solution is capable of suitably roughening the surface of the semiconductor light emitting element 10, nitric acid is used. It does not need to be a system etching solution.

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a semiconductor light emitting device according to an embodiment of the present invention and a state as viewed from a direction vertically above a light emitting surface.

FIG. 2 is a diagram showing a light emitting surface of a semiconductor light emitting element in which a large number of minute protrusions are formed in a region other than a portion immediately below an electrode.

FIG. 3 is a diagram showing a top surface of a semiconductor light emitting device in which a semiconductor surface is roughened by a conventional technique using an etching technique.

FIG. 4 is a process chart showing a step of subjecting a semiconductor surface to a roughening treatment using an etching technique according to the present invention.

FIG. 5 is a diagram illustrating a step of subjecting a contact layer to a surface roughening treatment using an etching technique according to the present invention.

FIG. 6 shows a semiconductor light emitting device according to another embodiment of the present invention,
It is a figure which shows a mode seen from the perpendicular upper direction with respect to a light emitting surface.

[Explanation of symbols]

10: Semiconductor light emitting element 24: Upper electrode 28: Light emitting surface 30: Resist

Claims (2)

[Claims] 1. A method for manufacturing a semiconductor light emitting device having an electrode formed on a part of a light emitting surface, wherein a resist coating film is formed so as to cover an outer surface of the electrode formed on the light emitting surface. A step of forming a coating film to be formed, and the surface of the semiconductor light emitting element is etched in a state where the coating film is formed, and a large number of areas are formed on the surface of the semiconductor light emitting element except for a portion immediately below the electrode. A method for manufacturing a semiconductor light emitting device, comprising: a roughening treatment step of forming minute protrusions. 2. The method for manufacturing a semiconductor light emitting device, comprising: a patterning step of forming a resist pattern for obtaining a desired electrode shape on the surface of an electrode material layer fixed on the surface of the semiconductor light emitting element; An electrode forming step of forming an electrode having a desired pattern shape by removing a portion of the material layer exposed from the resist pattern formed by the patterning step by etching, wherein the coating film forming step comprises forming the electrode. The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the coating film of the resist is formed by flowing the resist left on the electrode by heating so as to cover the outer surface of the electrode formed by the process. .