JPH05167100A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To prevent cracks from being generated in semiconductor layers 2-6 and prevent the life time of a light emitting element from decreasing. CONSTITUTION:A semiconductor light emitting element wherein on a semiconductor substrate 1, at least two layers of semiconductor layers 2-6 having different conductive types from each other are provided in the form of an island, and a protective layer 7 is deposited on the surface extending from the ones of the semiconductor layers 2-6 to the one of the semiconductor substrate 1, and further, a hole 7a, which is bored in the protective layer 7 deposited on the semiconductor layers 2-6, is used as the part for connecting the layers 2-6 with an electrode 8. The protective layer 7 is formed out of a silicon nitride film containing hydrogen element, and the hydrogen content is made to change in the protective layer 7.

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 particular, the present invention relates to a semiconductor light emitting device in which at least two semiconductor layers having different conductivity types are formed in an island shape on a semiconductor substrate.

[0002]

2. Description of the Related Art A conventional semiconductor light emitting device will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a conventional semiconductor light emitting device, wherein 1 is a semiconductor substrate made of, for example, silicon,
2 is a buffer layer made of gallium arsenide or the like, 3 is a first semiconductor layer made of aluminum gallium arsenide having the same conductivity type as that of the semiconductor substrate 1, 4 is aluminum gallium having an opposite conductivity type to the first semiconductor layer 3. A second semiconductor layer made of arsenic or the like, 5 is a third semiconductor layer made of aluminum gallium arsenide or the like in which the mixed crystal ratio of the semiconductor is changed to increase the band gap, and 6 is to make ohmic contact with the upper electrode 8. In addition, an ohmic contact layer made of gallium arsenide or the like containing a large amount of impurities of the opposite conductivity type, and 7 is a protective layer made of, for example, silicon nitride (SiNx). Protective layer 7 on ohmic contact layer 6
A hole 7a is formed in the hole, and the ohmic contact layer 6 and the upper electrode 8 are connected via the hole 7a. A lower electrode 9 for making ohmic contact with the semiconductor substrate 1 is provided on the back surface side of the semiconductor substrate 1. The semiconductor substrate 1 and the semiconductor layers 2 to
6, all single crystal.

The operation of the semiconductor light emitting device having such a structure will be described. When a voltage is applied in the forward bias direction with the upper electrode 8 being negative and the lower electrode 9 being positive, a second semiconductor layer 4 having a reverse conductivity type is provided. Minority carriers are injected from the first semiconductor layer 3 into the second semiconductor layer 4 and the first semiconductor layer 3
Carriers are recombined and emit light at the interface of the semiconductor junction portion on the second semiconductor layer 4 side, which is the interface. The emitted light passes through the third semiconductor layer 5, the ohmic contact layer 6, and the protective layer 7, and is extracted to the outside.

[0004]

In the conventional semiconductor light emitting device described above, a plurality of semiconductor layers 2 to 6 are deposited on the silicon substrate 1 by applying a predetermined temperature by the MOCVD method or the like. When a gallium arsenide layer is formed on the substrate, a tensile stress of about 10 ⁹ dyne / cm ² is generated. That is, a thickness of 2 μm on the silicon substrate 1.
When (2 × 10 ⁻⁴ cm) gallium arsenide layers 2 to 6 are deposited, the silicon substrate 1 and the gallium arsenide layers 2 to 6 are
10 ⁹ dyne / cm ² × (2 × 10 ^-4 cm) = 2 × 1
There is a problem that an absolute stress (total stress) of 0 ⁵ dyne / cm exists, cracks are generated in the thin gallium arsenide layers 2 to 6 and the life of the semiconductor light emitting device is shortened due to internal stress. Induce.

Therefore, when a protective layer 7 made of a silicon nitride film or the like formed by plasma CVD or the like is deposited on the gallium arsenide layers 2 to 6, the silicon nitride film 7 itself has a compressive stress. This compressive stress and the tensile stress of the above-described silicon substrate 1 and gallium arsenide layers 2 to 6 are offset to reduce the occurrence of cracking and the shortening of the device life. Since the silicon nitride film 7 is formed under the same conditions from the beginning to the end when forming, the above effect cannot be expected when a silicon nitride film having a small compressive stress is used as the protective layer 7. Further, when a silicon nitride film having a large compressive stress is used, excessive compressive stress is applied from the protective layer 7 to the gallium arsenide layers 2 to 6 to cause cracks. There is a problem that is very difficult.

[0006]

The semiconductor light emitting device according to the present invention has been made in order to solve the above-mentioned problems of the prior art, and is characterized in that it has a conductive type on a semiconductor substrate. Of at least two different semiconductor layers are provided in an island shape, a protective layer is deposited from the semiconductor layer to the semiconductor substrate, and a hole is formed in the protective layer on the semiconductor layer. In the semiconductor light emitting element used as the connecting portion, the protective layer is formed of a silicon nitride film containing a hydrogen element, and the content of the hydrogen element is changed in the protective layer. It is preferable that the content is gradually reduced toward the upper side of the protective layer.

[0007]

With the above-mentioned structure, the silicon nitride film forming the protective layer has a compressive stress which varies in each region within the layer.
Therefore, sufficient compressive stress can be applied to at least two semiconductor layers formed on the semiconductor substrate without applying sudden compressive stress, and thus cracks occur in the semiconductor layer or the life of the light emitting element is shortened. Is prevented.

[0008]

EXAMPLES Examples of the present invention will be described in detail below. Since the structure itself of the semiconductor light emitting device according to the present invention is the same as the conventional semiconductor light emitting device shown in FIG. 1, the manufacturing method will be mainly described with reference to FIG.

In the semiconductor light emitting device according to the present invention, as the semiconductor substrate 1, for example, a single crystal silicon substrate cut off by 2 ° off from the (100) plane to the (001) plane is used, and from antimony (Sb) or the like. 10 ¹⁹
A semiconductor substrate containing about pcs / cm ³ is used.

On the semiconductor substrate 1, a buffer layer 2 containing one conductivity type, for example, n-type impurities is formed. The buffer layer 2 is made of, for example, a III-V group compound semiconductor film such as GaAs. This buffer layer 2 is made of silicon (Si)
About 10 ¹⁸ donors / cm ³ are formed and are formed to a thickness of about 1 to 1.5 μm by the MOCVD method that appropriately adopts the two-step growth method or the thermal cycle method. That is, M
After heating the inside of the OCVD device once at 900 to 1000 ° C., the temperature is lowered to 400 to 450 ° C. and TMGa gas, AsH ₃
Gas and a GaAs film is grown by the MOCVD method using SiH ₄ gas which is an impurity element source for semiconductors, and the temperature is raised to 600 to 650 ° C. to grow the GaAs film (two-step growth method), and then 300 to 900. The temperature is raised and lowered at ℃ (thermal cycle method) to generate internal stress due to the difference in thermal expansion coefficient, and the silicon substrate 1 and the GaAs layer 2
Are formed so as to reduce the misfit transition due to the difference in the lattice constants of.

A first semiconductor layer 3 containing an impurity of one conductivity type is formed on the buffer layer 2. The first semiconductor layer 3 is made of, for example, Al _x Ga ₁ -x As, and contains about 10 ¹⁷ donors / cm ^{3 of} silicon or the like. The first semiconductor layer 3 made of Al _X Ga _1-X As or the like is formed by the MOCVD method using TMAl gas, TMGa gas, AsH ₃ gas, and SiH ₄ gas as an impurity element for semiconductor, and The mixed crystal ratio X is
For example, it is set to 0.3 or 0.65.

A second semiconductor layer 4 is formed on the first semiconductor layer 3.
To form. The second semiconductor layer 4 is made of, for example, Al _y G.
a _1-y As made such, opposite conductivity type, for example, zinc as a p-type semiconductor impurity (Zn) acceptor 10 ^17, such as
Includes about 1 piece / cm ³ . The second semiconductor layer 4 made of Al _y Ga _1-y As or the like is TMAl gas, TMG.
The mixed crystal ratio y of Al is, for example, 0.3 in order to emit light having a wavelength of about 700 nm, which is formed by the MOCVD method using a gas, AsH ₃ gas, and DMZn gas serving as an impurity element source for semiconductors. Is set to. The first semiconductor layer 3 and the second semiconductor layer 4 described above form a semiconductor junction portion and a light emitting portion.

A third semiconductor layer 5 is formed on the second semiconductor layer 4.
To form. This third semiconductor layer 5 is made of, for example, Al _z G
It is made of a _1-z As or the like and has a thickness of about 1 μm. The third semiconductor layer 5 made of Al _z Ga _1-z As or the like is also used for the TMAl gas, TMGa gas, AsH ₃ gas,
And an MOCVD method using DMZn gas which is an impurity element source for semiconductors having an opposite conductivity type, for example, p-type. Al _z Ga _1-z As of the third semiconductor layer 5
The mixed crystal ratio z of Al is set to, for example, z = 0.65 in order to increase the band gap.

An ohmic contact layer 6 containing a large amount of impurities of opposite conductivity type is formed on the third semiconductor layer 5.
The ohmic contact layer 6 is made of, for example, a III-V group compound semiconductor such as GaAs, and has a high concentration of a reverse conductivity type impurity such as zinc (Zn) in order to make an ohmic contact with the upper electrode 7.

The buffer layer 2, the first to third semiconductor layers 3, 4, 5 and the ohmic contact layer 6 on the semiconductor substrate 1 are formed in an island shape by etching or the like so as to form the contour shape of the light emitting element. To do.

A protective layer 7 is formed on the semiconductor substrate 1 and the plurality of island-shaped semiconductor layers 2 to 6. The protective layer 7 is formed of, for example, a silicon nitride film (SiN _x ) in which the content of hydrogen element gradually decreases toward the upper side of the layer. The silicon nitride film containing the hydrogen element is formed of, for example, silane gas (SiH ₄ ), ammonia gas (NH ₃ ),
And a plasma CVD method using hydrogen gas (H ₂ ). In this case, for example, the flow rate of silane gas is set to 14 s
ccm, the flow rate of ammonia gas is set to 123 sccm, the flow rate of hydrogen gas is set to 73 to 173 sccm, and the like.
It is formed at a speed of about 150 to 200Å / min using a high frequency power source of 00W. The content of hydrogen element in the silicon nitride film 7 can be changed by gradually changing the flow rate of hydrogen gas. In the semiconductor light emitting device according to the present invention, since the plurality of semiconductor layers 2 to 6 are formed on the semiconductor substrate 1 in an island shape, the protective layer 7 may be relatively thin and can be formed to a thickness of about 5000Å. , Semiconductor substrate 1
And the tensile stress of the semiconductor layers 2 to 6 can be offset.

FIG. 2 shows the relationship between the flow rate of hydrogen gas and the internal stress of the silicon nitride film when forming the silicon nitride film 7. The silicon nitride film shown in FIG. 2 has a silane gas flow rate of 14 sccm and an ammonia gas flow rate of 123 s.
Set to ccm and use high frequency power of 300W, 1
It was formed at a speed of 70Å / min. As is clear from FIG. 2, when the flow rate of hydrogen is 73 sccm, the silicon nitride film has an internal stress of -1 × 10 ⁹ dyne / cm ² , and when the flow rate of hydrogen is 123 sccm, the silicon nitride film is When the hydrogen has a flow rate of 173 sccm, the silicon nitride film has an internal stress of -3 × 10 ⁸ dyne / cm ^{2 and} an internal stress of -1 × 10 ⁷ dyne / cm ² . That is, the compressive stress increases as the flow rate of hydrogen decreases. Therefore, when the silicon nitride film 7 is formed by gradually reducing the flow rate of hydrogen, the tensile stress of the gallium arsenide films 2 to 6 can be completely canceled without giving a sharp impact to the gallium arsenide films 2 to 6. Then, the silicon nitride film 7 can be formed. Note that if the flow rate of hydrogen gas is gradually reduced, the content of hydrogen element in the silicon nitride film is also gradually reduced.

Further, as described above, the silicon nitride film 7
It is not limited to the case where the content of the hydrogen element in the layer gradually decreases toward the upper side of the layer, but it may be gradually decreased toward the upper side of the layer. May be provided alternately.

As shown in FIG. 1, a hole 7a is formed in the protective layer 7 on the ohmic contact layer 6, and an upper electrode 8 is formed in the hole 7a. Further, the lower electrode 9 is formed on the back surface side of the semiconductor substrate 1. The upper electrode 8 and the lower electrode 9 are made of Ag, Ag / Zn, Au / Cr, or the like, and are formed to a thickness of about 5000Å by a vapor deposition method or the like. In the present invention, a plurality of semiconductor layers including the buffer layer 2, the first semiconductor layer 3, the second semiconductor layer 4, the third semiconductor layer 5, and the ohmic contact layer 6 are provided, but the present invention is not limited to this example. However, it is sufficient that there are at least two semiconductor layers capable of forming a semiconductor junction. Further, a hole may be provided in the protective layer 7 on the semiconductor substrate 1 and the lower electrode 9 may be formed on the front surface side of the semiconductor substrate 1.

[0020]

As described above, according to the semiconductor light emitting device of the present invention, at least two semiconductor layers having different conductivity types are provided in an island shape on a semiconductor substrate, and the semiconductor layer is formed on the semiconductor substrate. While depositing a protective layer over the, to provide a hole in the protective layer on the semiconductor layer, in the semiconductor light-emitting device using the hole as a connection portion with an electrode, the protective layer,
Since the silicon nitride film containing a hydrogen element was formed and the content of this hydrogen element was changed in the protective layer, the compressive stress of the silicon nitride film forming the protective layer changes in each region of the layer. Therefore, sudden compressive stress is not applied to at least two semiconductor layers formed on the semiconductor substrate, and thus cracks in the semiconductor layer and shortening of the life of the light emitting element are prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a semiconductor light emitting device.

FIG. 2 is a diagram showing a relationship between a flow rate of hydrogen gas and internal stress when forming a silicon nitride film.

[Explanation of symbols]

1 ... Semiconductor substrate, 2-6 semiconductor layers, 7 ... Protective layer, 8, 9 ... Electrodes.

Claims (2)

[Claims] 1. At least two semiconductor layers having different conductivity types are provided in an island shape on a semiconductor substrate, a protective layer is deposited from the semiconductor layer to the semiconductor substrate, and the protective layer is provided on the semiconductor layer. In the semiconductor light emitting element having a hole provided in, and using the hole as a connection portion with an electrode, the protective layer is formed of a silicon nitride film containing a hydrogen element,
A semiconductor light-emitting device characterized in that the content of the hydrogen element is changed in the protective layer. 2. The semiconductor light emitting device according to claim 1, wherein the content of the hydrogen element is gradually reduced toward the upper side of the protective layer.