JP2959493B2 - Semiconductor light emitting device - Google Patents

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 in which the deposition of a semiconductor such as an AlGaAs element on the surface of an electrode containing Au is prevented, and the wire bonding property is improved.

[0002]

2. Description of the Related Art As an electrode for a compound semiconductor, for example, AlGaAs, an electrode formed by forming an AuGeNi layer on the lower side and an Au layer on the upper side is known. Here, the lower AuGeN
The i-layer is a metal layer for ohmic contact for contacting and making ohmic contact with the AlGaAs semiconductor region, and the upper Au layer is a metal layer for wire bonding for wire-bonding a fine lead wire made of gold. By the way, in this type of electrode, Al or the like in the AlGaAs semiconductor region may diffuse to the electrode surface (Au layer surface) and precipitate during heat treatment after the electrode formation. Deposition of such a metal on the electrode surface is a problem other than Al. Particularly, deposition of Al on the electrode surface
An oxide film is formed, and the reliability of wire bonding, that is, wire bondability is reduced, which is a problem.

[0003]

In order to solve this problem, for example, Japanese Unexamined Patent Publication No. Hei 4-109677 discloses Au.
An electrode structure in which a TiN (titanium nitride) layer and a Ti (titanium) layer are interposed between a GeNi layer and an Au layer is disclosed. According to such an electrode structure, the TiN layer prevents the deposition of Al or the like on the electrode surface, and the Ti layer improves the bondability between the TiN layer and the Au layer, thereby improving wire bondability and preventing electrode peeling. It was believed that a highly reliable electrode that achieved both prevention was obtained. However, in practice, both improvement in wire bondability and prevention of electrode peeling have not been achieved to a sufficiently satisfactory level, and there remains a problem in practicality.

Accordingly, an object of the present invention is to provide a semiconductor light emitting device capable of preventing the deposition of a semiconductor on an Au-containing electrode and improving the wire bonding property.

[0005]

In order to solve the above-mentioned problems and to achieve the above-mentioned object, the present invention provides a method for manufacturing a semiconductor device, comprising the steps of:
Is formed by sequentially laminating a first layer containing Ti, second and third layers made of TiN, and a fourth layer made of Au, and the N (nitrogen) of the second layer is formed. Content is third
In which the N content is higher than the N content of the layer. In addition, as shown in claim 2, the content of N in the second layer is 50 to 70 atm%,
It is desirable that the content of the third layer is 10 to 30 atm%. Further, the thickness of the second layer is set to 0.1.
3 to 0.5 μm (3000 to 5000 angstroms), and the thickness of the third layer is 0.01 to 0.03 μm (10
0 to 300 angstroms).

[0006]

According to the present invention, since the second and third layers made of TiN having different N contents are provided, the semiconductor can be transferred to the fourth layer made of Au (gold). Not only can improve the reliability of wire bonding by favorably preventing precipitation, but also can improve the mutual adhesion of each layer. Thereby, a highly reliable semiconductor light emitting device can be obtained.

[0007]

Next, a semiconductor light emitting device (light emitting diode) according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the semiconductor light emitting device of this embodiment has a p-type GaAs substrate layer 1, a p-type GaAs buffer layer 2, a p-type AlGaInP cladding layer 3, an AlGaInP
Active layer 4, n-type AlGaInP cladding layer 5, p-type Al
A compound semiconductor substrate 8 in which a GaInP current blocking layer 6 and an n-type AlGaAs contact layer 7 are laminated; a cathode electrode 9 formed in contact with the contact layer 7 on one main surface of the substrate 8; 8 and an anode electrode 10 formed so as to be in contact with the substrate layer 1 on the other main surface. Here, a fine lead wire 11 made of Au (gold) is wire-bonded to the upper surface of the cathode electrode 9.

In the light emitting diode of this embodiment, the structure of the cathode electrode 9 is different from that of the conventional one, and the semiconductor substrate 8 and the anode electrode 10 are the same as those of the conventional example. For this reason,
The semiconductor substrate 8 and the like may have another structure, for example, a structure in which the current blocking layer 6 is omitted. As shown in FIG. 2, the cathode electrode 9 is formed on the AlGaAs contact layer 7 which is a compound semiconductor region, as an AuGeNi layer 12 as a first layer for ohmic contact, and as a second layer mainly functioning as a diffusion barrier layer. TiN layer 13
In addition, a TiN layer 14 as a third layer mainly functioning to improve adhesion and an Au layer 15 as a fourth layer for wire bonding are sequentially laminated.
Here, the TiN layer 13 and the TiN layer 14 are not the same metal layer, but have different composition ratios of Ti and N. That is, the TiN layer 13 mainly functioning as a diffusion barrier layer
Is a N-rich layer in which the content of Ti is larger than the content of Ti. On the other hand, the TiN layer 14, which mainly functions to improve the adhesion between the TiN layer 13 and the Au layer 15, is a Ti-rich layer in which the content of Ti in the layer is larger than the content of N.

An example of the N content of the TiN layers 13 and 14 is as follows. TiN layer 13: 50 to 70 atm% TiN layer 14: 10 to 30 atm%

Next, a preferred method of forming the cathode electrode 9 will be described. First, AuG is formed on the upper surface of the contact layer 7.
eNi is deposited to a thickness of 0.4 to 0.6 μm (4
000-6000 angstroms). Next, a TiN layer 13 is formed on the AuGeNi layer 12 by a method of depositing Ti in an N ₂ atmosphere, that is, a reactive deposition method. The degree of vacuum and the rate of vapor deposition at the time of vapor deposition are, for example, on the order of 10 ^-5 torr and 3 to 5 angstroms / sec. The TiN layer 13 has a thickness of 0.3 to
It is formed to a thickness of 0.5 μm. The TiN layer 13 is a Ti film rich in N because Ti is deposited in a relatively N-rich atmosphere. Whether the atmosphere is N-rich or N-poor can be controlled by controlling the degree of vacuum in the vapor deposition apparatus when forming the TiN layer. That is, if the degree of vacuum is reduced, N becomes rich, and if the degree of vacuum is increased, N becomes poor. Therefore, when the TiN layer 14 is formed next on the upper surface of the TiN layer 13, the EB (electron beam) vapor deposition is performed with a higher degree of vacuum in the vapor deposition apparatus (10 ^-6 torr order) than when the TiN layer 13 is formed. By doing. TiN
The layer 14 is formed to a thickness of 0.01 to 0.03 μm. Finally, Au is EB-deposited on the upper surface of the TiN layer 14 to a thickness of 1.5 to 1.7 μm to complete the electrode 9. This AuGe
The formation from the Ni layer 12 to the Au layer 15 is performed in a continuous series of vapor deposition steps. The TiN layer 13 and the TiN layer 1
As described above, the control of the Ti and N contents in No. 4 can be performed by controlling the degree of vacuum at the time of vapor deposition, but can also be performed by controlling the flow rate of N ₂ into the vapor deposition apparatus (vapor deposition tank).

The function (action) of each layer of the above-mentioned cathode electrode 9 is as follows. The AuGeNi layer 12 is an ohmic contact layer for obtaining an ohmic contact with the contact layer 7 as in the conventional example. AlGaAs
Since a natural oxide film is formed on the surface of the contact layer 7 made of s, Ni is added to destroy the natural oxide film. Ni is used to form a thermally stable alloy with the group V element, that is, to promote the reaction between AuGe and AlGaAs, thereby realizing a highly reliable ohmic contact.

The second N-rich TiN layer 13 functions as a diffusion barrier layer for preventing the AlGaAs element decomposed by the heat treatment from depositing on the electrode surface. Since N is richer than Ti in the layer, the layer is denser than TiN in which N is poorer than Ti, and effectively diffuses the thermally decomposed element to the electrode surface. To prevent. The content of N in the TiN layer 13 is 50 to
Preferably, it is 70 atm%. N content is 50at
If it is less than m%, the effect as a diffusion barrier layer is reduced. If the N content exceeds 70 atm%, interlayer adhesion becomes insufficient and electrical connection is hindered. Note that N exists not only in the form of Ti-N but also as an interstitial impurity. TiN layer 1
It is desirable that the thickness of 3 is 0.3 to 0.5 μm.
When the thickness is less than 0.3 μm, the layer strength is reduced and the effect as a diffusion barrier layer is reduced. If the thickness of the TiN layer 13 exceeds 0.5 μm, cracks or the like may occur, which may cause an electrical or thermal trouble.

The third Ti-rich TiN layer 14 is made of Ti
This is a layer for improving the adhesion (adhesion) between the N layer 13 and the Au layer 15. Here, since N is contained in the layer in a layer lower than Ti, the layer exhibits better characteristics as a layer for improving adhesion as compared with a conventional electrode structure composed of only Ti. That is, in the layer composed of only Ti, since Ti reacts strongly with Au, if it is formed thickly, Ti precipitates on the Au surface,
Wire bonder damage is impaired. On the other hand, if the Ti layer is formed too thin, the adhesion cannot be sufficiently improved, and the diffusion barrier effect of the AlGaAs element by the Ti layer is impaired. In this embodiment, since N is contained in the layer, the reaction of Ti with the Au layer is suppressed, and Ti is deposited on the upper surface of the Au layer 15 even when the layer is formed with a thickness of 0.01 to 0.03 μm. Nothing. For this reason, the effect of improving the adhesion can be obtained at a high level, and the effect of preventing the diffusion of the AlGaAs element can be obtained in combination with the TiN layer 13. It is desirable that the content of N in the TiN layer 14 is 10 to 30 atm%. TiN
If the N content of the layer 14 is less than 10 atm%, it reacts too strongly with Au in the upper layer. The N content of the TiN layer 14 is 30 atm%.
When the ratio exceeds, the reaction with Au in the upper layer is reduced, so that delamination tends to occur. In addition, the thickness of the TiN layer 14 is set to 0.1.
It is desirable that the thickness be from 0.01 to 0.03 μm. TiN layer 1
When the thickness of No. 4 is less than 0.01 μm, it becomes difficult to control the film thickness and the adhesiveness to Au of the upper layer is reduced. TiN layer 14
When the thickness exceeds 0.03 μm, the reaction with Au in the upper layer due to the heat treatment increases due to the Ti-rich layer, the surface condition of the electrode (Au) deteriorates, and the wire bonding property (W / B property) decreases. affect.

The fourth Au layer 15 is made of A
It is a metal layer for wire bonding for wire bonding a u thin wire. In this embodiment, the TiN layer 1 is mainly used.
3, the diffusion and deposition of the AlGaAs element on the electrode surface are also prevented by the TiN layer 14, so that a high level of wire bondability is achieved.

[0015]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The compound semiconductor in the semiconductor substrate 8 can be various semiconductors other than the examples. Further, the number of layers in the semiconductor substrate 8 can be increased or decreased. (2) The shape and the like of the electrodes 9 and 10 can be changed. (3) The conductivity type of each layer of the semiconductor substrate 8 can be reversed so that 9 is an anode and 10 is a cathode.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a part of FIG. 1 in detail.

[Explanation of symbols]

 12 first layer 13 second layer 14 third layer 15 fourth layer

Claims (3)

(57) [Claims] An electrode is formed on a semiconductor region by sequentially stacking a first layer containing Au, second and third layers made of TiN, and a fourth layer made of Au. ,
A semiconductor light-emitting device, wherein the N content of the second layer is higher than the N content of the third layer. 2. The N content of the second layer is 50 to 70.
atm%, and the content of N in the third layer is 10 to 30 atm.
%. 3. The thickness of the second layer is 0.3 to 0.5 μm.
3. The semiconductor light emitting device according to claim 1, wherein the thickness of the third layer is 0.01 to 0.03 μm.