JPH11251635A - Semiconductor element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the development of lattice defect due to the thermal cracking of the second layer during the growing step of the third layer, by a method wherein the third layer made of a GaN base compound semiconductor capable of being grown at lower temperature than SiC is grown on upper part of the second layer (active layer). SOLUTION: A semiconductor element composed of the first clad layer 2 made of p type SiC, an active layer 3 made of In(1-x) Gax N (0<=X<1), the second clad layer 4 made of n type Al'(1-y) Gay N (0<=Y<=1) successively laminated on a SiC substrate 1 is provided with an n type electrode in thickness exceeding 2 μm on the second clad layer 4. In such a constitution, the development of lattice defect due to the thermal cracking of the active layer 3 in the growing step of the clad layer 4 can be avoided by growing an n type clad layer 4 capable of low temperature growing on the upper part of the active layer 3. Besides, the n type electrode fills the role of a shock absorbing layer, so that the layers lower than the n type electrode may be turned into the thin films hardly having the crack due to the difference in lattice constants.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art GaN-based and SiC-based materials are attracting attention as materials suitable for blue light emission, and various techniques are currently proposed.

[0003] For example, in JP-A-8-64910,
As shown in FIG. 4A, an n-type SiC cladding layer 11, an InGaN active layer 12, a p-type S
An iC cladding layer 13 is sequentially stacked, an Al electrode 14 is formed in the upper center of the p-type SiC cladding layer 13, and a Ni electrode 15 is formed in the lower center of the n-type SiC substrate 10. Structure A) has been proposed.

[0004] Further, the same publication discloses, as its prior art,
As shown in FIG. 4B, on the sapphire substrate 20, A
lGaN buffer layer 21, n-type GaN layer 22, n-type Al
GaN cladding layer 23, InGaN active layer 24, p-type A
An lGaN cladding layer 25, a p-type GaN layer 26, and a p-type transparent electrode 27 are sequentially stacked. Further, a p-type electrode 28 is provided on the p-type transparent electrode 27, and an n-type electrode 29 is provided on a part of the n-type GaN layer 22. A semiconductor element capable of emitting blue light (hereinafter, referred to as a conventional structure B) formed with a blue light is also disclosed.

[0005]

In the conventional structure A, a p-type SiC grown at a high temperature (1400 to 1500 ° C.) is formed on the InGaN active layer 12 grown at a low temperature (about 800 ° C.).
Since the cladding layer 13 is grown, N in the InGaN active layer 12 is easily released during the growth of the p-type SiC cladding layer 13 and lattice defects are likely to occur, so that good crystals cannot be obtained, and device characteristics are deteriorated. There are issues.

In the conventional structure B, p-type GaN
When the layer 26 and the p-type AlGaN cladding layer 25 are formed, post-processing such as annealing and electron beam irradiation is required after growing the acceptor-added layer, and thus there is a problem that the manufacturing process is complicated. Although a p-type layer can be obtained by such a post-treatment, the specific resistance is as high as several ohm-cm, and a sufficiently low-resistance p-type layer cannot be obtained. It is necessary to provide the electrode 27 separately, and there is a problem that the manufacturing process is complicated. Generally, it is necessary to form the transparent electrode 27 by forming a light-shielding metal material so as to be thin enough to transmit light, so that a high controllability is required in a process for forming the transparent electrode 27. There is.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and has a basic feature that a first layer made of p-type SiC, In _(1-X) Ga _X N (0 ≦ X <1) and a third layer made of an n-type GaN-based compound semiconductor are sequentially stacked, and an n layer having a thickness of 2 μ or more is formed on the third layer.
That is, it is configured to include a mold electrode.

Thus, in the film forming process, In
An n-type GaN-based third layer capable of growing at a lower temperature than the SiC layer (growth temperature: 1400 to 1500 ° C.) is formed on the second layer made of _(1-X) Ga _X N (0 ≦ X <1). Layer (growth temperature:
To grow the 1100 ° C.), it is possible to prevent occurrence of lattice defects due to thermal decomposition of the second layer of _{In (1-X) Ga X} N.

In addition, since the n-type electrode having a thickness of 2 μm or more is provided on the third layer, the n-type electrode functions as a shock absorbing layer for effectively absorbing the shock applied at the time of wire bonding. The layer below the electrode can be maintained as a thin film in which cracks due to a difference in lattice constant do not easily occur. Further, when the thickness of the n-type GaN-based compound semiconductor layer under the n-type electrode is increased to function as a shock absorbing layer, the film formation takes a long time. This can be performed in a short time, and the manufacturing time can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to a semiconductor device suitable for blue light emission shown in FIG.

In this semiconductor device, a p-type clad layer 2 made of a p-type SiC single crystal and a p-type
Single-layer active layer 3 made of n _(1-X) Ga _X N (0 ≦ X <1), n _- type clad made of single crystal of n-type Al _(1-Y) Ga _Y N (0 ≦ Y ≦ 1) It has a structure in which the layers 4 are sequentially laminated.

An n-type electrode 5 made of a laminate of Ti and Al is formed on the n-type cladding layer 4, and an S-type electrode 5 is formed on the back surface of the substrate 1.
A p-type electrode 6 made of a laminate of i, Al and Au is formed.

Although the thickness of the n-type electrode is generally set to about 0.5 μm, conventionally, even if the n-type electrode has such a thickness, a relatively large thickness is provided between the n-type electrode and the active layer. Since the film layer was interposed, it could function as a shock absorbing layer for absorbing the shock applied to the active layer during wire bonding. Here, for example, the thickness of the n-type AlGaN cladding layer 4 is 0.5 μm
This is necessary. However, if the n-type AlGaN cladding layer 4 is formed to a thickness of 0.5 μm or more necessary to function as a shock absorbing layer, cracks are generated due to accumulation of stress due to a difference in lattice constant with the layer below the layer. This causes a problem that the device characteristics are easily deteriorated. In addition, when a semiconductor layer such as the n-type AlGaN cladding layer 4 is formed into a thick film as a shock absorbing layer, there is a problem that the time required for the film formation becomes long and the manufacturing efficiency is reduced.

Therefore, the n-type electrode 5 has a thickness of 2 μm or more based on the experimental results shown in FIG. 2, and functions as a shock absorbing layer for absorbing the shock applied to the active layer during wire bonding. It has a thick film structure so that it can be used.

That is, except that only the thickness of the GaN-based compound semiconductor layer (typified by the cladding layer 4) interposed between the active layer and the n-type electrode is 0.1 μm and 0.2 μm, For each type of element, the thickness of the n-type electrode was changed from 0.5 μm to 3.0 μm in steps of 0.5 μm, and after wire bonding by the ball bonding method was performed under the same conditions, continuous energization was performed for 1000 hours. An experiment was performed to determine the ratio of the number of elements whose emission luminance was reduced by 70% or more from the beginning. As a result, characteristics as shown in FIG. 2 were obtained. As is clear from these characteristics, for both of the two types of devices, the device characteristics are improved when the thickness of the n-type electrode exceeds 2.0 μm, and when the thickness exceeds 2.5 μm, the device characteristics are significantly improved. It can be seen that it is planned. Therefore, the thickness of the n-type electrode is preferably set to 2.0 μm or more, and more preferably to 2.5 μm or more.

FIG. 3 shows the physical property constants of various materials constituting each layer. The SiC material used in this embodiment includes 6H
There are various polymorphs such as -SiC, 4H-SiC, and 2H-SiC, each having a different physical property constant. Also In
The physical property constants of the ternary mixed crystal material of _(1-X) Ga _X N, Al _(1-Y) Ga _Y N are values between the respective binary materials. Further, in the double hetero structure of this embodiment, the band gap energy of the p-type cladding layer 2 and the n-type cladding layer 4 needs to be higher than that of the active layer 3.

In the semiconductor device of this embodiment, for example, when emitting blue light, the Ga ratio of the active layer 3 is set to 0.6.
It is preferable that the thickness is about 0.8 and the film thickness is about 500 angstroms. In order to efficiently emit light in such an active layer 3, it is preferable to increase the band gap difference between the active layer 3 and each of the cladding layers 2 and 4. Therefore, the p-type cladding layer 2 has a thickness of 1.0
On the other hand, the n-type cladding layer 4 has a Ga ratio of about 0.8 to 0.9 and a thickness of about 2 μm.
N _- type Al _(1-Y) Ga _Y N having a thickness of about 0.1 to 0.2 μm
(0 ≦ Y ≦ 1).

Next, a method of manufacturing the above semiconductor device will be described below.

First, as a first step, a p-type clad layer 2 made of a p-type SiC single crystal is formed on a p-type SiC single crystal substrate 1.
Is grown using a CVD (Chemical Vapor Deposition) method. Specifically, SiH ₄ is injected at a flow rate of 0.5 CC / min and C ₃ H ₈ is injected at a flow rate of 0.3 CC / min.
Heat to ° C. Also, TMA [trimethylaluminum: (C
H ₃ ) ₃ Al] is injected at a flow rate of 0.06 CC / min. In the present embodiment, the (0001) plane is used as the growth plane of the p-type SiC substrate 1. However, a so-called off-angle plane that is inclined by 10 ° or less from the low index plane of the crystal may be used.

Next, as a second step, an InGaN active layer 3 is grown by MOCVD (metal organic chemical vapor deposition). Specifically, TMI [trimethyl indium: (CH ₃ ) ₃ In] was supplied at a flow rate of 15 μmol / min and TEG.
[Triethylgallium: (C ₂ H ₅ ) ₃ Ga] was added at a flow rate of 0.1%.
7 μmol / min and NH ₃ are injected at a flow rate of 2.0 l / min, and the substrate temperature is heated to 800 ° C. to grow the InGaN layer 3.

Next, as a third step, an n-type AlGaN cladding layer 4 is grown by MOCVD. Specifically, TMA is injected at a flow rate of 4.0 μmol / min, TMG at a flow rate of 27 μmol / min, and NH 3 at a flow rate of 2.0 l / min, and the substrate temperature is heated to 1100 ° C. Also, S
In order to add i, SiH ₄ is injected as a dopant gas at a flow rate of 1.5 nmol / min.

Next, as a fourth step, the n-type cladding layer 4 is formed.
On top, an n-type electrode 5 made of a laminate of Ti and Al is deposited to a thickness of 2.0 μm or more using a vapor deposition or sputtering device.
Preferably, after forming a film having a thickness of 2.5 μm or more, a patterning process is performed, if necessary, into a desired shape such as a circle.

Finally, as a fifth step, a p-type electrode 6 made of a laminate of Si, Al and Au is formed on the back surface of the substrate 1 to a thickness of about 1.0 μm using a vapor deposition or sputtering apparatus. After that, a patterning process is performed, if necessary, into a desired shape such as a circle.

As described above, since the AlGaN cladding layer 4 that can be grown at a lower temperature than SiC is grown on the InGaN active layer 3, the InGaN active layer 3 has a lattice defect during the growth of the AlGaN cladding layer 4. The risk of occurrence can be reduced.

According to the structure of the above embodiment, since the GaN-based compound cladding layer 4 is of the n-type, the specific resistance is smaller than that of the conventional structure B in which the GaN-based layer is of the p-type. This eliminates the need for post-processing such as annealing or electron beam irradiation for p-type as in the case of the conventional structure B, thereby reducing the number of manufacturing steps.

Further, since the GaN-based compound cladding layer 4 is of the n-type and has a lower specific resistance value than that of the p-type, the formation of a transparent electrode as in the conventional structure B is unnecessary.
Since the process for forming the transparent electrode is unnecessary, the number of constituent members and the number of manufacturing steps can be reduced.

In addition, since the n-type electrode 5 having a thickness of 2 μm or more is provided, the n-type electrode 5 functions as a shock absorbing layer for effectively absorbing the shock applied during wire bonding.
The layer under the mold electrode 5 can be maintained as a thin film in which cracks due to a difference in lattice constant are less likely to occur. Also,
As compared with the film formation time of the n-type GaN-based compound semiconductor layer 4, n
Since the time required for forming the mold electrode 5 is only about a fraction, the time required for forming the layer functioning as the shock absorbing layer can be significantly reduced, and the manufacturing time can be reduced.

In the above embodiment, the n-type electrode 5 is made of T
Although a laminated body of i and Al was used, the n-type electrode 5 can use a combination of other materials.
A laminate of l and Si, a laminate of Al and Cu, and the like can also be used.

Further, in the above embodiment, the case where the active layer 3 has a single-layer structure is described, but a multi-layered active layer can be used as the active layer 3. That is, as the active layer 3,
At least I is disposed so as to be in contact with the cladding layers 2 and 4.
a plurality of first InGaN layers 3a made of n _(1-X1) Ga _X1 N (0 <X1 <1) single crystal; and a first InGaN layer 3a
At least one or more In
_{A (1-X2)} Ga _X2 N (0 ≦ X2 <X1 <1) multi-layer active layer (multi-quantum well structure layer) structure composed of a multi-layer film in which second InGaN layers 3b composed of single crystals are alternately stacked is used. May be.

Further, if necessary, an n-type GaN layer may be stacked as a cap layer on the n-type AlGaN cladding layer 4 and an n-type electrode may be formed on the cap layer. The driving voltage of the element can be reduced by improving the ohmic characteristics with the electrode (the contact resistance of the electrode is small).

Further, in the above embodiment, a p-type SiC cladding layer, an active layer, an n-type Al _(1-Y) Ga _Y N
(0 ≦ Y ≦ 1) The configuration in which the clad layers are sequentially stacked has been described. However, an n-type SiC clad layer, an active layer, and a p-type GaN-based compound semiconductor layer (clad layer) are sequentially stacked on an n-type SiC substrate. In this case, the same effect as in the above embodiment can be obtained. However, the p-type GaN-based compound semiconductor layer has n
Since the resistance is higher than that of the GaN type, a structure for obtaining a uniform current distribution at the joint surface such as formation of a transparent electrode is separately required.

In the case where a p-type SiC cladding layer, an active layer, and an n-type GaN-based compound semiconductor layer (cladding layer) are sequentially laminated on an n-type or i-type (high-resistance) SiC substrate, the above-described embodiment will be described. The same effect can be obtained. However, since the p-type electrode cannot be provided on the SiC substrate, the conventional structure B
(In this case, the formation of a transparent electrode is unnecessary because the n-type GaN-based cladding layer has a low resistance.)

Although the above embodiment has been described by taking a light emitting diode as an example, the present invention can be applied to other semiconductor elements such as a light receiving element and a semiconductor laser.

[0034]

According to the present invention, the semiconductor device of the present invention comprises In _(1-X) Ga _X
A third layer (Al _(1-Y) Ga _Y N ( ₎ made of a GaN-based compound semiconductor that can be grown at a lower temperature than SiC on the second layer (active layer) made of N (0 ≦ X <1) Since the cladding layer (0 ≦ Y ≦ 1) is grown, lattice defects due to thermal decomposition of the second layer during growth of the third layer can be avoided. In addition, since the n-type electrode having a film thickness of 2 μm or more is provided on the third layer, the n-type electrode functions as a shock absorbing layer for effectively absorbing the shock applied at the time of wire bonding. The lower layer can be maintained as a thin film in which cracks due to a difference in lattice constant do not easily occur. Further, when the thickness of the n-type GaN-based compound semiconductor layer under the n-type electrode is increased to function as a shock absorbing layer, the film formation takes a long time. This can be performed in a short time, and the manufacturing time can be reduced.

As described above, according to the present invention, a high-quality semiconductor device having high luminous efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a semiconductor device according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between electrode thickness and device characteristics after wire-bonding.

FIG. 3 is a view showing physical property constants of various materials used for a semiconductor device in an example of the present invention.

FIGS. 4A and 4B are views showing a structure of a semiconductor device according to a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 p-type SiC substrate 2 p-type SiC cladding layer 3 InGaN active layer 4 n-type AlGaN cladding layer 5 n-type electrode 6 p-type electrode

Claims (3)

[Claims] 1. A first layer made of p-type SiC, In
_(1-X) Second layer made of Ga _X N (0 ≦ X <1), n-type G
a third layer made of an aN-based compound semiconductor, the second layer being sequentially stacked, and having a thickness of 2 μm on the third layer.
A semiconductor device comprising the above n-type electrode. 2. The method according to claim 1, wherein a first type of p-type SiC is formed on a SiC substrate.
Cladding layer, an active layer composed of In _{(1- X)} Ga _X N (0 ≦ X <1), and a second cladding layer composed of n-type Al _(1-Y) Ga _Y N (0 ≦ Y ≦ 1) Are stacked in this order, wherein n having a thickness of 2 μm or more is formed on the second cladding layer.
A semiconductor element comprising a mold electrode. 3. A first step of forming a clad layer made of p-type SiC on a SiC substrate by a CVD growth method, and forming an In _(1-X) Ga _X N (0 ≦ X <1 ₎ on the clad layer. A) forming an active layer of MOCVD growth method, and n-type Al _(1-Y) Ga _Y N (0 ≦ Y ≦
A third step of forming a cladding layer made of 1) by MOCVD growth, and n-type Al _(1-Y) Ga _Y N (0 ≦ Y ≦
1) A method for manufacturing a semiconductor device, comprising a fourth step of forming an n-type electrode having a thickness of 2 μm or more on a cladding layer by vapor deposition or sputtering.