KR100764450B1 - Flip chip type nitride semiconductor light emitting diode - Google Patents

Abstract

A flip chip type nitride semiconductor light emitting device is provided to decrease the generation of failure by restraining the delamination between an ohmic contact layer and a metal barrier layer using a delamination restraining layer. A flip chip type nitride semiconductor light emitting device includes a transparent substrate(11), an N type nitride semiconductor layer(13) on the transparent substrate, an active layer(14) on the N type nitride semiconductor layer, a P type nitride semiconductor layer(15) on the active layer, a high reflection type ohmic contact layer(21) on the P type nitride semiconductor layer, a delamination restraining layer, a metal barrier layer, and a P side bonding electrode. The delamination restraining layer(22) is formed on the high reflection type ohmic contact layer. The delamination restraining layer is composed of a metal film and a metal oxide layer on the metal film. The metal barrier layer(23) is formed on the delamination restraining layer. The P side bonding electrode(17) is formed on one portion of the metal barrier layer.

Description

Flip chip type nitride semiconductor light emitting device {FLIP CHIP TYPE NITRIDE SEMICONDUCTOR LIGHT EMITTING DIODE}

1 is a side cross-sectional view showing a flip chip nitride light emitting device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion indicated by A in the p-side electrode structure of FIG.

3A and 3B are optical micrographs for comparing defect rates of p-side electrode peeling between a conventional flip chip type nitride semiconductor light emitting device and a flip chip type nitride semiconductor light emitting device according to the present invention, respectively.

<Code Description of Main Parts of Drawing>

10: flip chip nitride semiconductor light emitting device 11: sapphire substrate

12: buffer layer 13: n-type nitride semiconductor layer

14: active layer 15: p-type nitride semiconductor layer

21: highly reflective ohmic contact layer 22: peeling inhibiting layer

22a, 22b: metal layer and metal oxide film 23: metal barrier layer

16, 17: n-side electrode, p-side bonding electrode P: peeling area

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a flip chip nitride semiconductor light emitting device having reduced defect rate by suppressing peeling of a p-side electrode portion.

Recently, a nitride semiconductor light emitting device is a light emitting device for obtaining light in a blue or green wavelength band, and has an Al _x In _y Ga _(1-xy) N composition formula (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). The nitride semiconductor crystal is grown on a nitride single crystal growth substrate such as a sapphire substrate in consideration of lattice matching. Here, since the sapphire substrate is an electrically insulating substrate, the final nitride semiconductor light emitting device has a structure in which the p-side electrode and the n-side electrode are formed on the same surface.

Due to these structural features, nitride semiconductor light emitting devices are being actively developed in a form suitable for flip chip structures.

Looking at the conventional flip chip type nitride semiconductor light emitting device, since the sapphire substrate mainly used as the substrate for nitride growth is light-transmissive, it can be used as a light emitting surface.

In addition, the electrode of the flip chip type nitride semiconductor light emitting device, particularly the p-side electrode, may form an ohmic contact with the p-type nitride semiconductor layer, and may reflect light emitted from the active layer toward the light emitting surface. It is required to have a high reflectance. Accordingly, the p-side electrode structure may include an ohmic contact layer having a high reflectance formed on the p-type nitride semiconductor layer and a metal barrier layer for preventing diffusion of the ohmic contact layer component.

However, in general, the adhesion force between the Ag employed as the ohmic contact layer and the TiW employed as the metal barrier layer is weak due to internal stress. Accordingly, the ohmic contact layer may be easily peeled off, thereby adversely affecting the performance and reliability of the flip chip type nitride semiconductor light emitting device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide a flip chip type nitride semiconductor light emitting device having a low defect rate by improving the p-side electrode structure such that peeling of the ohmic contact layer and the metal barrier layer is suppressed. .

In order to achieve the above technical problem, the present invention,

A transmissive substrate for nitride single crystal growth, an n-type nitride semiconductor layer formed on the translucent substrate, an active layer formed on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer, and the p-type A peeling suppression layer comprising a highly reflective ohmic contact layer formed on the nitride semiconductor layer, a metal layer formed on the highly reflective ohmic contact layer, and a metal oxide film formed on the metal layer, a metal barrier layer formed on the peeling suppression layer; Provided is a flip chip type nitride semiconductor light emitting device including a p-side bonding electrode formed on one region of the metal barrier layer.

The term " flip chip type nitride semiconductor light emitting device " used in the present invention means a light emitting device employed in a light emitting device having a flip chip structure, and a surface on which a p-side electrode and an n-side electrode are formed is mounted on a substrate of the light emitting device. The light emitting element which becomes a surface.

The peeling suppression layer employed in the present invention includes a metal oxide film having a strong adhesion and functions to suppress peeling of the highly reflective ohmic contact layer and the metal barrier layer. In this case, the metal oxide film is preferably formed by oxidizing the metal constituting the metal layer, the metal layer may be made of a material selected from the group consisting of Ni, Ti, Cr, Al, Ph, V.

In order to prevent the metal oxide film from lowering the operating voltage Vf of the chipped nitride semiconductor light emitting device in consideration of low electrical conductivity, the thickness of the peeling suppression layer may be 3 to 1000 kW, and The metal oxide film may have a thickness of 3 to 100 kPa. In this case, in the case where the metal layer is Ni, even if the metal oxide film becomes thick, there is no significant effect on the electrical conductivity. In the case of Al, the metal oxide film is preferably formed to have a thickness of about several tens of micrometers or less.

The highly reflective ohmic contact layer employable in the present invention may be made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof.

More specifically, the highly reflective ohmic contact layer is formed of a first layer of a material selected from the group consisting of Ni, Pd, Ir, Pt, and Zn and a material selected from the group consisting of Ag and Al formed on the first layer. It may be composed of a second layer made up. Alternatively, the highly reflective ohmic contact layer may include a first layer made of Ni, a second layer made of Ag formed on the first layer, and a third layer made of Pt formed on the second layer. have.

In an embodiment in which the highly reflective ohmic contact layer is composed of two or three layers, the thickness of the first layer is 3 to 50 GPa, the thickness of the second layer is 1000 to 10000 GPa, and the thickness of the third layer is 100 to It is preferable that it is 500 Hz.

In another embodiment of the present invention, the highly reflective ohmic contact layer comprises Ag,

The metal barrier layer may be formed to surround the entire highly reflective ohmic contact layer. In this case, the peeling suppression layer may also be formed to surround the entire highly reflective ohmic contact layer for an adhesion effect.

The metal barrier layer may be formed of a tungsten (W) alloy, and more preferably, the metal barrier layer may be formed of TiW or Ti / TiW.

In another embodiment of the present invention,

A light-transmissive substrate for nitride single crystal growth, an n-type nitride semiconductor layer formed on the light-transmissive substrate, an active layer formed on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer, and the p-type nitride On the highly reflective ohmic contact layer formed on the semiconductor layer and the highly reflective ohmic contact layer, a peeling suppression layer made of a metal oxide film and a metal barrier layer formed on the peeling suppression layer and one region of the metal barrier layer Provided is a flip chip type nitride semiconductor light emitting device including a p-side bonding electrode. In the previous embodiment, all of the metal layers included in the peeling suppression layer are oxidized, and the peeling suppression layer corresponds to the metal oxide film only. In this case, it is preferable that the said metal oxide film has a thickness of 3-100 kPa similarly to the above-mentioned case comprised with a metal layer and a metal oxide film.

Hereinafter, each component of the nitride semiconductor light emitting device of the present invention will be described in more detail.

p-type and n-type nitride semiconductor layers

The p-type and n-type nitride semiconductor layers are single crystals having an Al _x In _y Ga _(1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. Organic metal vapor deposition (MOCVD), molecular beam growth (MBE) and hybrid vapor deposition (HVPE) and the like. Representative nitride semiconductor layers are GaN, AlGaN, GaInN.

The p-type nitride semiconductor layer may include impurities such as Mg, Zn, and Be, and the n-type nitride semiconductor layer may include impurities such as Si, Ge, Se, Te, and C. In general, a buffer layer may be formed between the substrate and the n-type nitride semiconductor layer. Typical buffer layers include low temperature nucleus growth layers such as AlN or GaN.

Active layer

The active layer employed in the present invention may be a layer for emitting blue green light (about 350-550 nm wavelength range), and is composed of an undoped nitride semiconductor layer having a single or multiple quantum well structure. Like the p-type or n-type nitride semiconductor layer, the active layer may be grown by organometallic vapor deposition (MOCVD), molecular beam growth (MBE) and hybrid vapor deposition (HVPE).

Highly reflective ohmic contact layer

The highly reflective ohmic contact layer employed in the present invention is formed of a material having a high reflectance in consideration of the structural aspects of the flip chip type nitride semiconductor light emitting device while reducing contact resistance with a p-type nitride semiconductor layer having a relatively high energy band gap. To be required.

In order to satisfy such conditions of contact resistance improvement and high reflectance, the highly reflective ohmic contact layer is formed of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. It may be formed of, and preferably has a reflectance of 70% or more.

Further, preferably, the highly reflective ohmic contact layer is formed from a first layer made of a material selected from the group consisting of Ni, Pd, Ir, Pt, and Zn and selected from the group consisting of Ag and Al formed on the first layer. It may be composed of a second layer made of a material, and alternatively, a first layer made of Ni, a second layer made of Ag formed on the first layer, and a third layer made of Pt formed on the second layer. It may be configured as.

The highly reflective ohmic contact layer having a two-layer or three-layer structure has a high reflectance so that the thickness of the first layer is in the range of 3 to 50 GPa, and the thickness of the second layer is in the range of 1000 to 10,000 Pa. It is preferable to form the thickness in the range of 100 to 500 Pa.

The highly reflective ohmic contact layer is formed by a conventional deposition method or a sputtering process, and may be heat-treated at a temperature of about 400 to 900 ° C. to improve the properties of the ohmic contact layer.

Peeling Inhibition Layer

The peeling suppression layer employed in the present invention forms a metal oxide film having a strong adhesion and functions to suppress peeling of the highly reflective ohmic contact layer and the metal barrier layer. The metal oxide layer may be formed by oxidizing a metal forming a metal layer formed on the highly reflective ohmic contact layer. In this case, the metal layer may be made of a material selected from the group consisting of Ni, Ti, Cr, Al, Ph, and V, most preferably Ni. However, according to the embodiment, the peeling suppression layer may be made of only the metal oxide film by oxidizing the entire metal layer, not the structure of the metal layer and the metal oxide film.

The metal layer constituting the release inhibitory layer may be formed by a deposition method or a sputtering process, which is a conventional metal layer growth method, and then a metal oxide film may be formed by heat treatment in a state where a metal layer is formed on the highly reflective ohmic contact layer. . In this case, the heat treatment of the highly reflective ohmic contact layer may be performed together with the heat treatment in the metal oxide film formation process, thereby simplifying the heat treatment process.

Metal barrier layer

The metal barrier layer employed in the present invention is formed in the region of the highly reflective ohmic contact layer in which the p-side bonding electrode is to be formed, and is fused at the interface between the bonding electrode material and the ohmic contact layer material so that the characteristics of the ohmic contact layer (especially, reflectance and contact It is adopted as a layer to prevent the degradation of resistance). This metal barrier layer may be made of TiW or Ti / TiW.

In addition, the metal barrier layer may be formed to the side of the highly reflective ohmic contact layer, according to the embodiment. In particular, this embodiment has the advantage that the leakage current due to the migration of Ag can be effectively prevented when the highly reflective ohmic contact layer contains Ag.

Furthermore, the metal barrier layer having a predetermined reflectance may serve to assist the reflection role of the highly reflective ohmic contact layer.

The metal barrier layer is formed by a conventional deposition method or a sputtering process like other electrodes, and may be heat treated for several tens of seconds to several minutes at a temperature of about 300 ° C. to improve adhesion.

p side Bonding electrode

The bonding electrode constituting the p-side electrode structure together with the highly reflective ohmic contact layer, the peeling suppression layer, and the metal barrier layer is the outermost electrode layer to be mounted on the lead through the conductive bump in the flip chip structure, and generally contains Au or Au. It is made of one alloy.

The p-side bonding electrode may be formed by a deposition method or a sputtering process, which is a conventional metal layer growth method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a side cross-sectional view showing a flip chip nitride light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, the flip chip nitride semiconductor light emitting device 10 according to the present embodiment includes a nitride semiconductor growth substrate 11 such as a sapphire substrate, a buffer layer 12 sequentially stacked on an upper surface thereof, and an n-type nitride semiconductor. A layer 13, an active layer 14 and a p-type nitride semiconductor layer 15 are included. In addition, the n-side electrode 17 of the flip chip type nitride semiconductor light emitting device 10 is formed on the upper surface of the n-type nitride semiconductor layer 13 exposed through mesa etching.

The p-side electrode structure employed in the nitride semiconductor light emitting device 10 includes a highly reflective ohmic contact layer 21, a peeling suppression layer 22, a metal barrier layer 23, and a p-side bonding electrode 17. In this case, the highly reflective ohmic contact layer 21 is formed on the p-type nitride semiconductor layer 15.

In addition, in the present embodiment, the peeling suppression layer 22 includes a metal layer 22a formed on the highly reflective ohmic contact layer 21 and a metal oxide film 22b formed on the metal layer 22a. The metal barrier layer 23 is formed on the metal oxide film 22b. In this case, as shown in FIG. 1, the peeling suppression layer 22 and the metal barrier layer 23 have a structure formed to surround not only the upper surface of the highly reflective ohmic contact layer 21 but also the side surfaces thereof. In general, the metal barrier layer 23 may be expected to serve as a barrier to prevent mixing of Au components at the interface between the p-side bonding electrode 39b and the highly reflective ohmic contact layer 35. Furthermore, in this embodiment, the function of preventing the element of the highly reflective ohmic contact layer 21 from moving and generating a leakage current can also be expected. In particular, the present embodiment can have a great effect when the highly reflective ohmic contact layer 21 containing Ag having high mobility is used.

On the other hand, the highly reflective ohmic contact layer 21 preferably has a reflectance of 70% or more, and forms an ohmic contact with the p-type nitride semiconductor layer 15. The highly reflective ohmic contact layer 21 may be formed of at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. have. Preferably the highly reflective ohmic contact layer 21 is Ni / Ag, Zn / Ag, Ni / Al, Zn / Al, Pd / Ag, Pd / Al, Ir / Ag. It may be formed of Ir / Au, Pt / Ag, Pt / Al or Ni / Ag / Pt.

Fig. 2 shows an enlarged view of a portion indicated by A in the p-side electrode structure.

Referring to FIG. 2, as described above, the metal oxide film 22b can lower the electrical conductivity to increase the operating voltage. Preferably, the metal oxide film 22b has an appropriate thickness within a range that does not excessively reduce the peeling inhibiting effect and the electrical conductivity. Can be determined. In this case, the thickness t1 of the peeling inhibiting layer may be 3 to 1000 kPa, and the thickness t2 of the metal oxide film is 3 to 100 kPa.

On the other hand, although not shown, the peeling suppression layer 22 may be made of a metal oxide film only, likewise, the metal oxide film preferably has a thickness of 3 ~ 100 3.

Experiments were performed to compare the characteristics of the flip chip-type nitride semiconductor light emitting device according to the present invention and the conventional flip chip-type nitride semiconductor light emitting device through the Examples and Comparative Examples performed as follows.

(Example)

First, after the sapphire substrate was placed in a chamber for the MOCVD process, a GaN cryogenic nucleus growth layer was grown as a buffer layer. Subsequently, in order to provide a blue light emitting device on the buffer layer, an n-type nitride semiconductor layer composed of an n-type GaN layer and an n-type AlGaN layer, a multi-quantum well structure active layer composed of an InGaN / GaN layer, and a p-type GaN layer A type nitride semiconductor layer was formed.

Next, after forming a highly reflective ohmic contact layer on the p-type nitride semiconductor layer, it was heat-treated at about 500 ℃. As the highly reflective ohmic contact layer of this embodiment, a Ni / Ag / Pt structure was used, and each thickness was 5 mW, 2500 mW, and 300 mW.

Subsequently, a peeling suppression layer was formed on the upper surface of the p-type nitride semiconductor layer so as to surround the upper surface and the side surfaces of the highly reflective ohmic contact layer. The peeling inhibiting layer may be obtained by forming a metal oxide film by heat treatment at about 500 ° C. for 2 minutes after forming the metal layer. Ni was used as the metal layer of this example, and the thickness was set to 30 kPa. In addition, NiOx, which is a metal oxide film formed by heat treatment, was made to have a thickness of 15 kPa. Thus, both the Ni layer and the NiOx layer had a thickness of 15 kPa.

Subsequently, a metal barrier layer was formed on the peeling suppression layer so as to surround the top surface and the side surfaces of the highly reflective ohmic contact layer, and then heat-treated at about 350 ° C. A TiW layer was formed as the metal barrier layer of this embodiment. Next, a flip chip type nitride light emitting device was prepared by forming a p-side bonding electrode and an n-side electrode including Au.

(Comparative Example)

In this comparative example, a flip chip-type nitride semiconductor light emitting device was manufactured under the same materials and conditions as in the above example, except that a peel barrier layer was formed, and a metal barrier layer was directly formed on the upper surface of the highly reflective ohmic contact layer.

As described above, the appearance defect rate due to the p-side electrode peeling was investigated for the flip chip type nitride semiconductor light emitting device manufactured through the Examples and Comparative Examples. 3A and 3B are optical micrographs for describing appearance defects of flip chip-type nitride semiconductor light emitting devices according to an embodiment and a comparative example, respectively.

Referring to FIG. 3A, in the flip chip type nitride semiconductor light emitting device according to the comparative example, as shown by a dotted line, a peeling phenomenon P occurs between the highly reflective ohmic contact layer and the metal barrier layer. It was about 10%.

On the contrary, referring to FIG. 3B, in the flip chip type nitride semiconductor light emitting device according to the present embodiment, the peeling phenomenon as shown in FIG. 3A was not observed, and accordingly, it was confirmed that the defective rate was nearly 0%.

On the other hand, even in the flip chip type nitride semiconductor light emitting device according to the embodiment, it was confirmed that the electrical characteristics such as the operating voltage is almost the same as compared with the case of not using the peeling inhibiting layer.

The above-described embodiments and the accompanying drawings are merely illustrative of preferred embodiments, and the present invention is intended to be limited by the appended claims. In addition, it will be apparent to those skilled in the art that the present invention may be substituted, modified, and changed in various forms without departing from the technical spirit of the present invention described in the claims.

As described above, according to the present invention, the peeling of the p-side electrode structure can be reduced by employing a peeling suppression layer capable of bringing the high reflective ohmic contact layer and the metal barrier into close contact with the p-side electrode structure. As a result, the defect rate of the flip chip type nitride semiconductor light emitting device according to the present invention can be reduced, and high luminous efficiency and reliability can be expected.

Claims (15)

Translucent substrates for nitride single crystal growth; An n-type nitride semiconductor layer formed on the light transmissive substrate; An active layer formed on the n-type nitride semiconductor layer; A p-type nitride semiconductor layer formed on the active layer; A highly reflective ohmic contact layer formed on the p-type nitride semiconductor layer; A peeling suppression layer having a metal layer formed on said highly reflective ohmic contact layer and a metal oxide film formed on said metal layer; A metal barrier layer formed on the release inhibitory layer; And And a p-side bonding electrode formed on one region of the metal barrier layer. The method of claim 1, The metal oxide film is a flip chip type nitride semiconductor light emitting device, characterized in that the metal constituting the metal layer is formed by oxidation. The method of claim 2, The metal layer is a flip chip nitride semiconductor light emitting device, characterized in that made of a material selected from the group consisting of Ni, Ti, Cr, Al, Ph, V. The method of claim 1, The peel-inhibiting layer has a thickness of 3 ~ 1000 GPa flip chip type nitride semiconductor light emitting device. The method of claim 1, The metal oxide film has a thickness of 3 ~ 100 GPa flip chip type nitride semiconductor light emitting device. The method of claim 1, The highly reflective ohmic contact layer includes at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. Flip chip nitride semiconductor light emitting device. The method of claim 1, The highly reflective ohmic contact layer is a first layer made of a material selected from the group consisting of Ni, Pd, Ir, Pt, and Zn and a second layer formed on the first layer and made of a material selected from the group consisting of Ag and Al. Flip chip type nitride semiconductor light emitting device comprising a. The method of claim 1, The highly reflective ohmic contact layer includes a first layer made of Ni, a second layer made of Ag formed on the first layer, and a third layer made of Pt formed on the second layer. Flip chip nitride semiconductor light emitting device. The method of claim 8, The thickness of the first layer is 3 to 50 GPa, the thickness of the second layer is 1000 to 10000 GPa, and the thickness of the third layer is 100 to 500 GPa. The method of claim 1, The highly reflective ohmic contact layer has Ag, And the metal barrier layer is formed so as to surround the entire highly reflective ohmic contact layer. The method of claim 10, The peeling suppression layer is a flip chip nitride semiconductor light emitting device, characterized in that formed to surround the entire highly reflective ohmic contact layer. The method of claim 1, And the metal barrier layer is formed of a tungsten (W) -based alloy. The method of claim 12, And the metal barrier layer is formed of TiW or Ti / TiW. Translucent substrates for nitride single crystal growth; An n-type nitride semiconductor layer formed on the light transmissive substrate; An active layer formed on the n-type nitride semiconductor layer; A p-type nitride semiconductor layer formed on the active layer; A highly reflective ohmic contact layer formed on the p-type nitride semiconductor layer; A peeling suppression layer formed on the highly reflective ohmic contact layer and formed of a metal oxide film; A metal barrier layer formed on the release inhibitory layer; And And a p-side bonding electrode formed on one region of the metal barrier layer. The method of claim 14, The metal oxide film has a thickness of 3 ~ 100 GPa flip chip type nitride semiconductor light emitting device.

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