JP2000183400A - Iii nitride compound semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element of high brightness and durability and to simplify the configuration of an electrode. SOLUTION: In a flip-chip III nitride compound semiconductor light-emitting element, a multiplex thick-film positive electrode 120 which connected to a p-type semiconductor layer, reflects light toward a sapphire substrate side comprises, a first metal layer 11 comprising rhodium(Rh), platinum(Pt), or an alloy of them, a second metal layer 112 of gold (Au), and a third metal layer 113 of titanium(Ti) or chromium(Cr). Thus, a positive electrode of high reflectivity is provided. The multiplex thick-film positive electrode 120 does not corrode with infiltration of water content, etc., for superior durability. Thus, a region a which covers a protective layer 130 is less, the configuration of electrode is simplified, providing a light-emitting element which requires no wire bonding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip-chip type light emitting device in which a layer made of a group III nitride compound semiconductor is laminated on a substrate, and more particularly to a flip-chip type light emitting device having a high luminous intensity and a low driving voltage. Related to the element.

[0002]

2. Description of the Related Art FIG.
10 shows a sectional view. 101 is a sapphire substrate, 102
Is an AlN buffer layer, 103 is an n-type GaN layer, 104 is a light-emitting layer, 105 is a p-type AlGaN layer, 106 is a p-type GaN layer, 1
91 is a positive electrode, 130 is a protective film, and 140 is a negative electrode. Further, a thick positive electrode 191 connected to the p-type layer 106 is conventionally formed of, for example, nickel (Ni) or cobalt (Co).
It is formed of a metal layer having a thickness of 3000 mm.

FIG. 6 is a cross-sectional view of a light emitting device 920 having a transparent metal thin film electrode and a pad electrode as positive electrodes.
The stacked structure of the group III nitride-based semiconductor has a light emitting element 91 shown in FIG.
0, but the translucent metal thin film electrode 192 and the pad electrode 193 are positive electrodes. Light emitting device 92 in FIG.
Reference numeral 0 denotes that the metal thin-film electrode 192 is translucent. Therefore, in order to form a flip-chip light-emitting element, light transmitted through the metal thin-film electrode 192 needs to be reflected in a desired direction by an external member covering the light-emitting element. is there.

[0004]

In the flip chip type light emitting element 910 shown in FIG. 5, in order to sufficiently reflect the light emitted from the light emitting layer 104 toward the sapphire substrate 101, a normal flip chip type light emitting element 910 is used. As the electrode 120, a thick metal electrode is used. However, in the prior art,
Nickel (Ni) or cobalt (Co) is applied to this thick film positive electrode 120.
Since the metal was used, the wavelength is 380nm ~ 550nm
The amount of reflected (blue-violet, blue, green) visible light was not sufficient, and a sufficient luminous intensity as a light-emitting element could not be secured.
Further, in the light emitting element 920 of FIG. 6, light was absorbed by the metal thin film electrode 192 to a considerable extent, and the efficiency of the light emitting element was not favorable.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a light emitting element having high luminous intensity and high durability. Another purpose is to form a high-reflectance and high-durability thick-film electrode,
An object of the present invention is to provide a light emitting element which does not require wire bonding by simplifying the configuration of an electrode portion of the light emitting element.

[0006]

In order to solve the above-mentioned problems, the following means are effective. That is, the first means is a flip-chip type light emitting element in which a layer made of a group III nitride compound semiconductor is laminated on a substrate, and is formed on a p-type semiconductor layer so as to cover most of the element. In a group III nitride compound semiconductor light emitting device having a multi-thick film positive electrode that reflects light to the substrate side, the first metal layer in contact with the p-type semiconductor layer is rhodium (Rh), platinum (Pt), or Characterized in that it is formed from an alloy containing at least one kind of metal.

A second means is the first means, wherein the thickness of the first metal layer is 0.01 to 5 μm. The thickness of the first metal layer is preferably 0.02 to 2 μm, and more preferably 0.05 to 1 μm.

The third means is characterized in that a second metal layer made of gold (Au) is formed on the first metal layer as described above. In the fourth means, the thickness of the second metal layer is set to 0.
It is 1 to 5 μm. The thickness of the second metal layer is preferably 0.2 to 3 μm, more preferably 0.5 to 2 μm
It is.

Further, the fifth means is the second means as described above.
A third metal layer made of titanium (Ti) or chromium (Cr) is formed on the metal layer. Further, the sixth means is characterized in that the thickness of the third metal layer is 5 to 1000 °. The thickness of the third metal layer is desirably 10 to 500 °,
More preferably, it is 15 to 100 °. By the above means,
The above problem can be solved.

[0010]

[Action and effect of the invention] Rhodium (Rh) and platinum (Pt)
Is a metal (0.6 <R <1.0) having a very large light reflectance R with respect to visible light having a wavelength of 380 nm to 550 nm (blue violet, blue, and green).
Therefore, by using these metals or an alloy containing at least one of these metals as the first metal layer in contact with the p-layer of the multi-thick film positive electrode, reflection of these visible light by the electrode can be achieved. The amount can be made sufficiently large, so that a sufficient light emission intensity as a light emitting element can be secured.

In addition, since the above metals or alloys have low contact resistance with the p-type semiconductor layer due to a large work function and the like, the use of these metals simultaneously realizes a light emitting element with a low driving voltage. be able to. In addition, since the above-mentioned metals are noble metals or platinum group elements, the use of these metals improves the corrosion resistance against moisture and the like, and also has the effect of forming a highly reliable electrode.

The thickness of the first metal layer is 0.01 μm or more,
μm or less is good. When this film thickness is 0.01 μm or less, the film thickness is too thin, and the transmitted light that is not reflected is generated.
This is not preferable because it takes a lot of time to form the electrodes.

By providing the second metal layer made of gold (Au), a thick positive electrode can be obtained without increasing the resistance of the positive electrode. In addition, although gold (Au) is a metal having a large light reflectance R, although not as large as rhodium (Rh) or platinum (Pt), the function of the first metal layer can be supplemented also in this regard. The thickness of the second metal layer is desirably 0.1 μm or more and 5 μm or less. When the thickness is less than 0.1 μm, the thickness is too thin and the effect is small.When the thickness is 5 μm or more, a large amount of time is required for forming an electrode. Unnecessarily thickening is not preferred.

Further, by providing a third metal layer made of titanium (Ti) or chromium (Cr), for example, a silicon oxide film (SiO ₂ ) is provided between the positive electrode and the negative electrode arranged on the opposite side of the substrate surface. When an insulating layer made of a silicon nitride film (SiN _x ) or polyimide is provided, peeling of the insulating layer from the positive electrode can be suppressed. This can prevent a short circuit from occurring due to the bump material when forming a bump in a processing step described later. The thickness of the third thin film metal layer is 5 mm or more, 1
000 良 い or less is good. If the thickness is less than 5 mm, the thickness is too thin to obtain a strong adhesion with the insulating layer,
If it is more than 1000 mm, it is not preferable because strong adhesion to a connecting member such as a bump material or a gold ball cannot be obtained.

The multi-thick film positive electrode formed as described above has a high light reflectivity and a high durability against penetration of moisture and the like, so that the protective layer can be simplified, and as a result, wire bonding can be performed. It is also possible to connect to an external electrode without using.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. Note that the present invention is not limited to the following embodiments.

(First Embodiment) FIG. 1 is a schematic sectional view of a flip-chip type semiconductor light emitting device 100 according to the present invention. Aluminum nitride on sapphire substrate 101
A buffer layer 102 having a thickness of about 200 ° made of (AlN) is provided, and a buffer layer 102 made of GaN doped with silicon (Si) is formed thereon.
A high carrier concentration n ⁺ layer 103 of 4.0 μm is formed. A light emitting layer 104 having a multiple quantum well structure (MQW) made of GaN and Ga _0.8 In _0.2 N is formed on the layer 103. On the light emitting layer 104, a p-type layer 105 made of magnesium (Mg) doped Al _0.15 Ga _0.85 N and having a thickness of about 600 ° is formed. Further, on the p-type layer 105, a p-type layer 106 made of magnesium (Mg) -doped GaN and having a thickness of about 1500 ° is formed.

On the p-type layer 106, a multi-thick film electrode 120 formed by metal deposition, and on the n ⁺ layer 103, a negative electrode 1
40 are formed. The multi-thick film electrode 120 includes a first metal layer 111 and a first metal layer 111 bonded to the p-type layer 106.
2 has a three-layer structure of a second metal layer 112 formed on the top of the first metal layer 112 and a third metal layer 113 formed on the second metal layer 112.

The first metal layer 111 is a metal layer made of rhodium (Rh) or platinum (Pt) having a thickness of about 0.3 μm and joined to the p-type layer 106. The second metal layer 112 has a thickness of about 1.2
A metal layer made of μm gold (Au). The third metal layer 113 is a metal layer made of titanium (Ti) having a thickness of about 30 °.

The negative electrode 140 having a two-layer structure has a thickness of about 175 °.
Is formed by sequentially laminating a vanadium (V) layer 141 and an aluminum (Al) layer 142 having a thickness of about 1.8 μm from a part of the high carrier concentration n ⁺ layer 103 which is partially exposed.

The thus formed multi-thick film positive electrode 12
Protective film 13 made of a SiO ₂ film between
0 is formed. The protective layer 130 is formed by etching the side surface of the light emitting layer 104, the side surface of the p-type layer 105, and the side surface and the upper surface of the p-type layer 106, which are exposed by etching from the n ⁺ layer 103 exposed to form the negative electrode 140. Part of the first metal layer 111, side surfaces of the second metal layer 112, the third metal layer 11
3 is partially covered. Protective film 1 made of SiO ₂ film
The thickness of the portion covering the third metal layer 113 is 0.5 μm.

As described above, the multi-thick positive electrode 120 is composed of the first metal layer made of rhodium (Rh) or platinum (Pt), the second metal layer made of gold (Au), and the third metal layer made of titanium (Ti). The luminous intensity of the light-emitting element 100 composed of a metal layer was measured and compared with the conventional light-emitting element 910. The results are shown in FIG. From this, it was possible to improve the luminous intensity by about 60% to 90% according to the present invention as compared with the light emitting device 910 according to the prior art.

Next, the change over time in the luminous intensity of the light emitting element 100 was measured and compared with the conventional light emitting element 910. The results are shown in FIG. From here, the light emitting device 910 according to the prior art
The light-emitting intensity of the light-emitting element 100 of the present invention decreases to 80% of the initial light-emitting intensity after 100 hours and to 70% of the initial light-emitting intensity after 100 hours.
%, And after 100 hours, a luminous intensity of 90% of the initial luminous intensity could be maintained. That is, according to the present invention, a light-emitting element with significantly improved durability as compared with the conventional light-emitting element 910 can be obtained.

(Application Example) The flip-chip type light emitting device 100 having such a configuration has a high luminous intensity and a high durability, can largely omit the protective layer 130, and has a positive electrode when connected to an external electrode. A large area can be used for both the negative electrode and the negative electrode. FIG. 4 is a plan view of a light emitting device 200 which is a specific application example of the light emitting device 100 according to the present invention. The light emitting device 200 of FIG.
The configuration is almost the same as that of 00, and the same reference numerals are described.
The light emitting element 200 has a negative electrode of 40% or more of the upper surface area.
Since the above can be a positive electrode, the connection with the external electrode is not limited to wire bonding. As an example, bumps can be formed with solder or the like, or gold balls can be formed directly on the positive and negative electrodes, and the device can be inverted and directly connected to a circuit board.

In the above embodiment, the multiple thick film positive electrodes 120
Was about 1.5 μm, but the multiple thick film positive electrode 120
May have a thickness of 0.11 μm or more and 10 μm or less. If the thickness of the multi-thick positive electrode 120 is less than 0.11 μm, light cannot be sufficiently reflected, and strong adhesion to a connecting member such as a bump material or a gold ball cannot be obtained. On the other hand, 10
If it exceeds μm, the deposition time and the material are unnecessarily increased, and the production cost is inferior.

Further, in the above embodiment, the thickness of the first metal layer was 0.3 μm, but the thickness of the first metal layer was 0.01 to 0.01 μm.
If it is 5 μm, the effect is exhibited. The thickness of the first metal layer is preferably 0.02 to 2 μm, more preferably 0.05 to 1 μm.
μm. If the first metal layer 111 is too thin, light reflection will be insufficient. If it is too thick, the deposition time and material will be unnecessarily long, and the production cost will be poor.

In the above embodiment, the thickness of the second metal layer was 1.2 μm, but the thickness of the second metal layer was 0.1 to 5 μm.
If it is μm, the effect is exhibited. The thickness of the second metal layer 112 is preferably 0.2 to 3 μm, more preferably 0.5 to 3 μm.
22 μm. If the second metal layer 112 is too thin, it cannot compensate for the light reflection of the first metal layer 111, and it will not be possible to obtain strong adhesion with a connection member such as a bump material or a gold ball. On the other hand, if the thickness is too large, the negative electrode 140 needs to be balanced, and both the second metal layer 112 and the negative electrode 140 require more deposition time and material than necessary, which is not preferable.

In the above embodiment, the thickness of the third metal layer was 30 °, but the thickness of the third metal layer was 5 to 1000 °.
If Å, the effect is exhibited. The thickness of the third metal layer 112 is preferably 10 to 500 °, more preferably 15 to 1 °.
00Å. If the third metal layer 113 is too thin, the adhesion to the protective layer deteriorates, and if it is too thick, the resistance value increases, which is not preferable.

In the above embodiment, titanium (Ti) was used as the third metal layer.
(Cr) may be used.

Further, the structure of each layer of the light emitting element in the above embodiment is a physical or chemical structure when forming each layer, and thereafter, in order to obtain stronger adhesion, It goes without saying that a solid solution or a compound is formed between the layers by a physical or chemical treatment such as a heat treatment for the purpose of lowering the resistance value.

In the above embodiment, the light emitting device 100
Although the light emitting layer 104 has an MQW structure, it may have an SQW structure or a homojunction structure. Further, the group III nitride compound semiconductor layer forming the light emitting device of the present invention has a mixed crystal ratio of 4
_{Ternary, binary} , Al _x Ga _y In _{1 -xy} N (0 ≦ x ≦ 1, 0 ≦ y ≦
1, 0 ≦ x + y ≦ 1). The p-type impurities include magnesium (Mg), beryllium (Be), and zinc (Zn).
And the like can be used.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a flip-chip type semiconductor light emitting device 100 according to the present invention.

FIG. 2 shows flip-chip type semiconductor light emitting devices 100 and 9;
FIG. 10 is a table showing the luminous intensity of No. 10.

FIG. 3 shows flip-chip type semiconductor light emitting devices 100 and 9;
FIG. 10 is a table showing changes with time in the luminous intensity of light emission of No. 10;

FIG. 4 is a plan view of a flip-chip type semiconductor light emitting device 200 according to the present invention.

FIG. 5 is a schematic cross-sectional view of a flip-chip type semiconductor light emitting device 910.

FIG. 6 is a schematic cross-sectional view of a light-emitting element 920 having a transparent thin-film electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 ... Sapphire substrate 102 ... Buffer layer made of AlN 103 ... N ⁺ layer made of GaN 104 ... Emitting layer 105 ... P-type layer made of AlGaN 106 ... P-type layer made of GaN 111 ... First metal layer 112 ... Second metal Layer 113 Third metal layer 120 Multi-layer thick positive electrode 130 Protective film 140 Negative electrode 191, 192, 193 Metal layer forming positive electrode of conventional light emitting device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA04 CA02 CA04 CA05 CA13 CA34 CA40 CA57 CA83 CA85 CA92 CB15 DA09

Claims (6)

[Claims] 1. A flip-chip type light-emitting element in which a layer made of a group III nitride compound semiconductor is laminated on a substrate, wherein light is formed on a p-type semiconductor layer so as to cover most of the light. Having a multiple thick-film positive electrode that reflects to the substrate side
In the group III nitride compound semiconductor light emitting device, the first metal layer in contact with the p-type semiconductor layer of the multi-thick film positive electrode is rhodium (Rh), platinum (Pt), or at least one of these metals. A group III nitride compound semiconductor light-emitting device characterized by being formed from an alloy containing the compound. 2. The group III nitride compound semiconductor light emitting device according to claim 1, wherein said first metal layer has a thickness of 0.01 to 5 μm. 3. The group III nitride compound semiconductor light emitting device according to claim 1, wherein a second metal layer made of gold (Au) is formed on the first metal layer. . 4. The group III nitride compound semiconductor light emitting device according to claim 3, wherein said second metal layer has a thickness of 0.1 to 5 μm. 5. The semiconductor device according to claim 1, wherein a third metal layer made of titanium (Ti) or chromium (Cr) is formed on the second metal layer. III-nitride-based compound semiconductor light emitting device. 6. The group III nitride compound semiconductor light emitting device according to claim 5, wherein the thickness of the third metal layer is 5 to 1000 °.