JP2000124502A - Semiconductor light-emitting element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element which is manufactured, by a method wherein firstly the deterioration of the characteristics of the element in the production process of the element is prevented from being generated, and secondly the production process is simplified to be able to maintain highly the yield of the manufacture of the element. SOLUTION: In a semiconductor light-emitting element of a structure, wherein the element has first and second conductivity type layers 3 and 5, a light- transmitting electrode 6 is formed on the surface of the layer 5, a pad electrode 7 is formed on the upper part of the film 6, a current stopping layer 29 is formed under the lower part of the electrode 7, and a protective film 19 is provided on the electrode 6. The layer 29 and the film 19 are used when one part of the layer 5 is removed, and by using the layer 29 and the film 19 as remaining etching masks flaws are prevented from being cut in the electrode 6 in the production process of the element and at the same time, a process of forming the film 19 for the electrode 6 and an insulative film for the layer 29 directly under the electrode 7, and a process of forming an insulative film for the etching masks are performed in the same process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device used for an optical device such as a light emitting diode and a method for manufacturing the same, and more particularly to a semiconductor light emitting device having a pad electrode for wire bonding and a light transmitting electrode.

[0002]

2. Description of the Related Art In recent years, development of a high-luminance semiconductor light emitting device using a Group 3-5 compound semiconductor has been advanced. In particular, the visible light emitting device using a gallium nitride-based compound semiconductor has made remarkable progress, and the development in the field of blue and green light emitting diodes is progressing rapidly.

In a light emitting device using a gallium nitride-based compound semiconductor, a p-type layer has a higher resistivity than other devices using a Group 3-5 compound semiconductor, and an insulating substrate such as sapphire is used. Due to restrictions such as use, pad electrodes for p and n-side wire bonding are formed on one surface side of the substrate, and furthermore, a translucent ultra-thin electrode is spread over almost the entire surface of the semiconductor layer. This is a general structure. With such a structure, the size of the light emitting element is reduced and the light emission output is improved.

In the light-emitting element having the above-described light-transmitting electrode, of the light generated under the pad electrode formed on the light-transmitting electrode, the light directed to the pad electrode is blocked by the pad electrode. As a result, there is a problem that the luminous efficiency is suppressed low because the light-transmitting electrode is not extracted to the outside from the surface side. In order to improve this, by forming an insulating or high-resistance current blocking layer such as silicon oxide below the pad electrode, the current component flowing immediately below the pad electrode is reduced, and light emission blocked by the pad electrode is reduced. A structure that improves luminous efficiency has been proposed. A light emitting device having such a structure is disclosed in, for example,
No. 68, and has a structure as shown in FIG.

In FIG. 3, a substrate 5 made of sapphire
1, a buffer layer 52, an n-type layer 53, and a light emitting layer 5
4 and a p-type layer 55 are formed.
A translucent electrode 56 is formed on the surface of the mold layer 55, and a pad electrode 57 for bonding is formed on the electrode 56. An insulating layer 69 made of silicon oxide is formed in a part of the p-type layer 55 and immediately below the pad electrode 57.

Since the light-transmitting electrode 56 is formed so thin as to transmit light as described above, the light-transmitting electrode 56 is easily damaged in the middle of the production line. In the gallium nitride based compound semiconductor light emitting device as shown in FIG.
6 is almost a light emitting region, so that if the translucent electrode 56 is damaged, a current partially flows,
There has been a problem in that the production yield is reduced because uniform light emission cannot be obtained or the light emission intensity decreases. Therefore, a method has been proposed in which a light-transmitting film such as silicon oxide is formed on the surface of the light-transmitting electrode 56 and this is used as a protective film to prevent the light-transmitting electrode from being damaged. Such a method is disclosed in, for example, JP-A-7-94783.

[0007]

As described above, in a light emitting device using a light transmitting electrode, a technique of forming a current blocking layer immediately below a pad electrode formed on the light transmitting electrode, a light transmitting electrode, and the like. The use of a translucent electrode to reduce the luminous efficiency and the production yield due to the use of a technique for forming a protective film on the substrate have been improved. However, in the manufacture of a gallium nitride-based compound semiconductor light emitting device employing such a technique, an etching process for exposing the surface of the n-type layer, a mask forming process, and the like, and an insulating film for a current blocking layer are formed. It is necessary to go through several times, such as a film forming process by a CVD method or the like for forming a protective film or a photolithography process for patterning, which causes a problem that the manufacturing process becomes very complicated. In such a case, there is a problem that the ultra-thin electrode 56 is easily damaged when the wafer is handled in each step, and as a result, the production yield of the semiconductor light emitting device is reduced.

The problem to be solved in the present invention is to firstly prevent an electrode formed on the surface of a semiconductor layer from being damaged, and secondly to simplify a manufacturing process, thereby providing a semiconductor light emitting device having a high manufacturing yield and a semiconductor light emitting device having the same. It is to provide a manufacturing method.

[0009]

Means for Solving the Problems The inventors of the present invention have repeatedly studied improvements to prevent the electrodes formed on the surface of the semiconductor layer from being damaged and to simplify the manufacturing process. As a result, by forming an insulating film on the surface of the electrode immediately after the formation of the electrode on the surface of the semiconductor layer, the problem of damaging the electrode in the manufacturing process is eliminated. And that the remaining etching mask is used as a protective film for the translucent electrode and a current blocking layer immediately below the pad electrode, thereby simplifying the manufacturing process and consequently significantly improving the manufacturing yield.

That is, the present invention has a first conductivity type layer and a second conductivity type layer laminated on a substrate, and the second conductivity type layer exposes the surface of the first conductivity type layer. A light-transmitting electrode is formed on the surface of the second conductivity type layer, a pad electrode is formed on the light-transmitting electrode, and a current-blocking electrode is formed below the pad electrode. In a semiconductor light emitting device having an insulating film formed thereon and a protective insulating film provided on a light-transmitting electrode, the current blocking insulating film and the protective insulating film are formed of the second conductivity type layer. It is characterized by being a remaining etching mask used when removing a part of the etching mask, a protective film for protecting the surface of the translucent electrode and a current blocking layer immediately below the pad electrode, Also, the manufacturing process can be simplified.

Further, the present invention provides a method of forming a light-transmitting electrode on a surface of a second conductive type layer having a laminated structure in which a first conductive type layer and a second conductive type layer are sequentially provided on a substrate. And a second step of forming an insulating film on the electrode following the first step, and etching a part of the second conductivity type layer using the insulating film as a mask. A third step of removing the surface of the first conductivity type layer to expose the surface of the first conductivity type layer, a fourth step of removing a part of the mask and exposing a part of the surface of the light transmitting electrode, A fifth step of forming a pad electrode so as to be in contact with the light-transmitting electrode exposed in the step and to cover a part of the mask, in order. According to such a manufacturing method, the electrode may be damaged when the wafer is handled in the manufacturing process. In addition, it is possible to prevent a decrease in light emission intensity, and furthermore, to form an insulating film used as an etching mask, a protective film for an electrode, and an insulating film used as a current blocking layer immediately below a pad electrode in the same step. Can be simplified.

[0012]

The invention according to claim 1 of the present invention has a first conductivity type layer and a second conductivity type layer laminated on a substrate, wherein the second conductivity type layer is A part is removed to expose the surface of the first conductivity type layer, a light-transmitting electrode is formed on the surface of the second conductivity type layer, and a pad electrode is formed on the light-transmitting electrode. A semiconductor light emitting device having a current blocking insulating film formed below the pad electrode and including a protective insulating film on the light transmitting electrode, wherein the current blocking insulating film and the protective insulating film are The film is characterized by being a remaining etching mask used when removing a part of the second conductivity type layer, the second conductivity type for exposing the surface of the first conductivity type layer An etching mask for removing a part of the mold layer and a transparent electrode formed on the surface of the semiconductor layer; The insulating film used as a protective film is also used to form an insulating film for an etching mask and a protective film for a light-transmitting electrode and an insulating film for a current blocking layer immediately below a pad electrode. And the film can be performed in the same process, which simplifies the manufacturing process and has the effect of preventing the light-transmitting electrode from being damaged in the manufacturing process.

According to a second aspect of the present invention, the surface of the second conductivity type layer having a laminated structure in which a first conductivity type layer and a second conductivity type layer are sequentially provided on a substrate is provided. A first step of forming an electrode, a second step of forming an insulating film on the translucent electrode following the first step, and a second step of using the insulating film as a mask. A third step of exposing a part of the conductive type layer by etching to expose a surface of the first conductive type layer, and removing a part of the mask to expose a part of a surface of the translucent electrode; And a fifth step of forming a pad electrode so as to be in contact with the light-transmitting electrode exposed in the fourth step and to cover a part of the mask. A method of manufacturing a semiconductor light emitting device, wherein an insulating film is formed continuously after a process of forming an electrode. By providing the step, it is possible to prevent the light-transmitting electrode from being damaged in the manufacturing process after the formation of the insulating film, and to form the insulating film used as an etching mask, the protective film of the electrode, and the part immediately below the pad electrode. And an insulating film used as a current blocking layer can be formed in the same step.

A specific example of an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a structure of a semiconductor light emitting device according to one embodiment of the present invention. In FIG. 1, on a substrate 1 made of sapphire, a buffer layer 2, an n-type layer 3, a light-emitting layer 4, and a p-type layer 5 made of a gallium nitride-based compound semiconductor are sequentially laminated. Then, a part of the p-type layer 5 and the light emitting layer 4 is removed by dry etching such as a reactive ion etching (RIE) method, and an n-side electrode 8 is formed on the exposed surface of the n-type layer 3. On the p-type layer 5, a translucent electrode 6 is formed. Above the light transmitting electrode 6, a pad electrode 7 electrically connected to the light transmitting electrode 6 is formed. n
The side electrode 8 is made of aluminum (Al) or titanium (Ti).
And the like. The translucent electrode 6 can be made of a metal material such as Au, Ni, Pt, Ti, or a conductive material such as ITO, and can be formed by an evaporation method, a sputtering method, or the like. The thickness of the translucent electrode 6 varies depending on the material. For example, when Au or Ni is used, the thickness is preferably in the range of 0.005 μm to 0.02 μm. Further, for example, by performing a heat treatment at a temperature of 400 ° C. or more, the light transmittance can be improved. For the pad electrode 7, a metal material such as Au, Ni, Pt, or Ti can be used.

A protective film 19 made of an insulating film is formed on the translucent electrode 6, and a current blocking layer 29 made of the insulating film is formed on a part of the p-type layer 5 directly below the pad electrode 7. Are formed. In the protective film 19 and the current blocking layer 29 made of these insulating films, the etching mask used for removing a part of the p-type layer 5 and the light emitting layer 4 by dry etching remains, and the same process is performed. Is formed. As described above, the formation of the insulating film used for the protective film 19 and the current blocking layer 29 is performed by also using the etching mask used for the dry etching, the protective film for the translucent electrode 6 and the current blocking layer immediately below the pad electrode 7. Since the process is performed in three steps, the manufacturing process is simplified, and the frequency of handling the wafer is reduced. Therefore, a decrease in yield due to wafer handling can be suppressed, and the overall manufacturing yield can be improved.

The formation of the insulating film is performed continuously after the formation of the light-transmitting electrode 6, so that the ultra-thin light-transmitting electrode 6 is covered with the protective film 19 in the subsequent steps. Since there is almost no exposure, the light-transmitting electrode 6 is less likely to be damaged in the manufacturing process.
Deterioration of the light-emitting characteristics due to scratches of the light-emitting element is greatly suppressed, and the production yield of the light-emitting element is greatly improved.

The material of the protective film 19 and the current blocking layer 29 must have a light-transmitting property and an insulating property, and must be a material capable of obtaining a large etching selectivity with a gallium nitride-based compound semiconductor in dry etching. Specifically, Si
O ₂ , TiO ₂ , Al ₂ O ₃ , SiN and the like can be preferably used.

FIG. 2 shows a light transmitting electrode 6 on the surface of the p-type layer 5.
FIG. 5 is a schematic view sequentially showing the steps from the formation of a film to a partial opening of a protective film 19. These figures are schematic diagrams relating to only one element in the wafer, and in actuality, the manufacturing is performed as a wafer in which the elements shown in the figure are repeatedly formed two-dimensionally.

First, a wafer prepared by sequentially laminating a buffer layer 2, an n-type layer 3, a light-emitting layer 4, and a p-type layer 5 on a sapphire substrate 1 is prepared, as shown in FIG. 2 (a). Next, an electrode 6 having an extremely thin translucency is formed in a desired shape on the surface of the p-type layer 5 by using a vapor deposition method and photolithography.

Next, a protective film 9 made of SiO ₂ having an insulating property is deposited on the translucent electrode 6 by a CVD method, and patterned into a desired shape by photolithography as shown in FIG. 2B. .

After the patterning of the protective film 9, the p-type layer 5 and a part of the light emitting layer 4 are removed by RIE using the protective film 9 as an etching mask as shown in FIG. Then, the surface of n-type layer 3 is exposed, and a part of protective film 9 used as an etching mask is left.

After the etching of the p-type layer 5, a part of the remaining protective film 9 is opened by photolithography and wet etching using a diluted hydrofluoric acid solution, and as shown in FIG. While exposing the surface of the electrode 6,
A part of the protective film 9 is used as the current blocking layer 29, and at the same time, the remaining protective film 9 is used as the protective film 19 of the translucent electrode 6. At this time,
The thickness of the current blocking layer 29 and the thickness of the protective film 19 are adjusted separately by forming a mask such as a resist by photolithography on one of them, or simultaneously without forming a mask.
It can also be adjusted by using wet etching or the like. The protective film 19 and the current blocking layer 29 do not need to be completely separated from each other, and are transparent so that the translucent electrode 6 and the pad electrode 7 formed immediately above the current blocking layer 29 are electrically connected. It is only necessary that the light electrode 6 is exposed.

Thereafter, the pad electrode 7 and the n-side electrode 8 are respectively formed on the current blocking layer 29 and the exposed surface of the n-type layer 3 in the same step or separate steps by vapor deposition and photolithography. Let it form. Then, the elements are separated into chips as shown in FIG. 1 by scribing or dicing.

As described above, since the protective film 9 is continuously formed on the light-transmitting electrode 6 after forming the extremely thin light-transmitting electrode 6, the light-transmitting electrode 6 is formed in a subsequent step. Since the light-transmitting electrode 6 is hardly exposed, and thus the light-transmitting electrode 6 is hardly damaged, it is possible to suppress a decrease in manufacturing yield due to deterioration of the light-transmitting electrode 6.

In the above embodiment, a light emitting device having a double hetero junction structure in which an n-type layer, a light-emitting layer, and a p-type layer are sequentially stacked, and a method of manufacturing the same have been described.
The same effect can be obtained even in the case of a homo-junction structure or a single hetero-junction structure in which a p-type layer and a p-type layer are directly bonded, or in a structure in which the order of lamination of an n-type layer and a p-type layer is reversed. Can be

In the above embodiment, a light emitting element using a gallium nitride-based compound semiconductor has been described. However, a light emitting element using a compound semiconductor such as GaAlAs or InGaAlP deviates from the concept of the present invention. It is possible to apply within the range that does not.

[0027]

According to the first aspect of the present invention, an insulating film used as a protective film for a light-transmitting electrode formed on the surface of a semiconductor layer and a current blocking layer formed immediately below a pad electrode;
By also serving as a mask for etching the semiconductor layer, the formation of an insulating film for an etching mask, the formation of an insulating film for a current blocking layer immediately below the protective film of the translucent electrode and the pad electrode, Can be performed in the same step, the manufacturing process is simplified, and it is possible to prevent the light-transmitting electrode from being damaged in the manufacturing process. As a result, it is possible to manufacture a light-emitting element having high reliability and improved luminous efficiency with a high production yield.

According to the second aspect of the present invention, the method further comprises the step of forming a protective film continuously after the step of forming an electrode on the surface of the semiconductor layer. In addition to preventing the electrode from being damaged, the insulating film used as an etching mask and the insulating film used as a protective film for the electrode and a current blocking layer immediately below the pad electrode can be formed in the same step. Therefore, it is possible to manufacture a semiconductor light emitting device with improved luminous efficiency without deterioration of device characteristics with a high production yield. Further, since the manufacturing process is simplified, the semiconductor light emitting device can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a gallium nitride-based compound semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a manufacturing process of the semiconductor light emitting device according to one embodiment of the present invention.

FIG. 3 is a sectional view showing the structure of a conventional semiconductor light emitting device.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 buffer layer 3 n-type layer 4 light-emitting layer 5 p-type layer 6 electrode 7 pad electrode 8 n-side electrode 9, 19 protective film 29 current blocking layer

Claims (2)

[Claims] A first conductivity type layer and a second conductivity type layer laminated on a substrate, wherein the second conductivity type layer is partially formed to expose a surface of the first conductivity type layer. Has been removed,
A light-transmitting electrode is formed on a surface of the second conductivity type layer, a pad electrode is formed on the light-transmitting electrode, and a current blocking insulating film is formed on a lower part of the pad electrode; In a semiconductor light emitting device having a protective insulating film on a conductive electrode, the current blocking insulating film and the protective insulating film are used when a part of the second conductivity type layer is removed. A semiconductor light emitting device, characterized in that the etching mask is a remaining etching mask. 2. A first step of forming a light-transmissive electrode on the surface of the second conductivity type layer having a stacked structure including a first conductivity type layer and a second conductivity type layer in this order on a substrate; A second step of forming an insulating film on the translucent electrode following the first step, and removing a portion of the second conductivity type layer by etching using the insulating film as a mask A third step of exposing the surface of the first conductivity type layer to expose a part of the surface of the light-transmissive electrode by removing a part of the mask; and A fifth step of forming a pad electrode so as to be in contact with the light-transmitting electrode exposed in the step and to cover an upper part of the mask.