CN103594583A - Flip-chip light emitting diode - Google Patents

Abstract

The invention provides a GaN-based flip-chip light-emitting diode, comprising: a sapphire substrate (1), an n-type GaN layer (2), an active layer (3), and a p-type GaN layer (4), located on the p-type GaN layer ( 4) An n-type electrode (9) and a p-type electrode (8) isolated by isolation grooves. A copper pillar (5) is formed in the isolation groove, and the n-type electrode (9) is electrically connected to the n-type GaN layer (2) through the copper pillar (5). The n-type electrode (9) and the p-type electrode (8) are welded to corresponding solder balls and bump electrodes (11) on the carrier substrate (10). The n-type electrode (9) and the p-type electrode (8) are equal in area and arranged symmetrically with respect to the isolation groove. The light-emitting diode proposed by the invention can greatly improve the luminous efficiency and product yield.

Description

A flip-chip light-emitting diode

technical field

The invention relates to the technical field of semiconductors, in particular to a GaN-based flip-chip light-emitting diode.

Background technique

The advantages of semiconductor light-emitting diodes are high luminous intensity, strong light directivity, low energy consumption, low manufacturing cost, etc., so their applications are becoming more and more extensive, especially in the trend of replacing incandescent and fluorescent lamps in lighting. The advantages of flip-chip light emitting diodes are excellent heat dissipation characteristics and high luminous efficiency. And in recent years, in order to improve the brightness of light-emitting diodes, light-emitting diodes with a vertical structure have been developed. Compared with light-emitting diodes with a front-mounted structure, that is, a mesa structure, the light-emitting diodes with a vertical structure have many advantages. The two electrodes of the vertical light-emitting diode are located on both sides of the light-emitting diode. Almost all the current flows vertically through the semiconductor epitaxial layer, and there is no current flowing laterally. Therefore, the current distribution is uniform and the heat generated is relatively small. And because the two electrodes of the vertical structure are on both sides, the light extraction process will not be blocked by the electrodes on the same side, and the light extraction efficiency is higher.

The structure of the more common GaN-based flip-chip light-emitting diodes is: a sapphire substrate, an n-type GaN layer formed on the sapphire substrate, an active layer formed on the n-type GaN layer, and an active layer formed on the active layer. For the p-type GaN layer, remove part of the p-type GaN layer and the active layer until the surface of the n-type GaN layer is exposed, thereby forming a platform structure GaN light-emitting diode, and the n-type electrode is formed on the exposed n-type GaN layer, while the p-type electrode is formed on the p-type GaN layer. The above-mentioned GaN-based flip-chip light emitting diode is arranged upside down on the carrier substrate, and the n-type electrode and the p-type electrode are respectively welded to solder balls or bump electrodes on the carrier substrate, thereby forming a flip-chip light-emitting diode. Light from the active layer is emitted from the sapphire substrate side. A light reflection layer can also be provided on the carrier substrate to increase the light reflectivity, or an n-type electrode or a p-type electrode can be formed as an electrode with a reflective function, so as to improve the light reflectivity.

However, the problem with the platform structure flip-chip light-emitting diode is that the p-type electrode and the n-type electrode are not on the same plane due to the height difference between the platform structures, so the p-type electrode and the n-type electrode are designed asymmetrically. It is likely to cause welding failure between the above-mentioned two electrodes and corresponding solder balls or bump electrodes on the carrier substrate during the subsequent welding process, thereby affecting product yield and electrical characteristics. Moreover, if there are differences in the area and shape of the electrodes, the light-emitting diode chip will be tilted during the soldering process, resulting in a decrease in product yield. Another problem with flip-chip GaN-based light-emitting diodes with a platform structure is that the light reflectivity cannot be significantly improved, even if the n-type electrode and the p-type electrode are formed as electrodes with high reflection function and light reflection is further formed on the carrier substrate. structure, the light reflectivity cannot be improved due to the loose bonding defect between the platform structure flip-chip GaN-based light-emitting diode and the carrier substrate, thereby reducing the luminous efficiency of the light-emitting diode.

Contents of the invention

In view of this, the present invention proposes a GaN-based flip-chip light-emitting diode aimed at the problems of the prior art. By improving the structure and arrangement of the n-type electrode and the p-type electrode of the light-emitting diode, the electrical characteristics of the light-emitting diode can be improved, thereby effectively improving the luminous efficiency of the light-emitting diode.

The GaN-based flip-chip light-emitting diode proposed by the present invention includes:

carrying substrate (10);

Solder balls or bump electrodes (11) formed on the carrier substrate (10);

A flip-chip GaN-based light-emitting diode structure comprising:

Sapphire substrate (1);

An n-type GaN layer (2) formed on a sapphire substrate (1);

an active layer (3) formed on the n-type GaN layer (2);

a p-type GaN layer (4) formed on the active layer (3);

an n-type electrode (9) and a p-type electrode (8) formed on the p-type GaN layer (4);

an isolation groove formed between the n-type electrode (9) and the p-type electrode (8);

an insulating layer (6) formed on the sidewall of the isolation trench;

a copper column (5) formed in the isolation groove and electrically connected to the n-type electrode (9); and

The solder balls or bump electrodes (11) on the carrier substrate (10) are electrically connected to the n-type electrode (9) and the p-type electrode (8) respectively; the features are:

The n-type electrode (9) and the p-type electrode (8) are arranged symmetrically with respect to the isolation groove and the areas of the n-type electrode (9) and the p-type electrode (8) are equal, and the n-type electrode (9) and the p-type electrode (8) ) is at the same height and on the same surface as the surface electrically connected to the solder ball or bump electrode (11).

Description of drawings

Fig. 1 is the sectional view of GaN-based flip-chip light-emitting diode structure of the present invention;

FIG. 2 is a top view of the GaN-based flip-chip light-emitting diode structure shown in FIG. 1;

3 is a cross-sectional view of installing the GaN-based flip-chip light-emitting diode structure shown in FIG. 1 on a carrier substrate;

FIG. 4 is a cross-sectional view of a portion of the GaN-based flip-chip light emitting diode structure after removing the photoresist pattern.

Detailed ways

The GaN-based flip-chip light-emitting diode and its manufacturing method of the present invention will be described in detail below with reference to FIGS. 1-4 . For clarity, the various structures shown in the figures are not drawn to scale, and the present invention is not limited to the structures shown in the figures.

1. GaN-based flip-chip light-emitting diode structure and manufacturing method

As shown in Figure 1, the GaN-based flip-chip light-emitting diode of the present invention includes a GaN-based flip-chip light-emitting diode structure, which includes a sapphire substrate 1 for growing GaN-based epitaxial layers 2-4, and the substrate 1 is not limited to sapphire The substrate, and for example, may be a transparent substrate such as a ZnO substrate or a glass substrate. An n-type GaN layer 2 is formed on a sapphire substrate 1 , an active layer 3 is formed on the n-type GaN layer 2 , and a p-type GaN layer is formed on the active layer 3 .

As shown in FIG. 1-2, a photoresist (not shown) is formed on the p-type GaN layer 4, and the photoresist is developed, exposed, etc., so as to form a photoresist pattern (not shown), The photoresist pattern has rectangular openings near both sides of the central axis of the surface of the p-type GaN layer 4 (see the line of symmetry indicated by a dotted line in FIG. Equal distance, that is, the two long sides of the rectangular opening are symmetrical with respect to the central axis of the surface. The rectangular openings are used to form subsequent isolation grooves, while other parts of the photoresist pattern shield areas where n-type electrodes 9 and p-type electrodes 8 are to be formed later. Using the photoresist pattern as a mask, etch the p-type GaN layer 4, the active layer 3 and the n-type GaN layer 2 to form an isolation groove, the bottom of the isolation groove is located in the n-type GaN layer 2, that is, the isolation groove goes deep into the n-type GaN layer. In the GaN layer 2 , the distance between the bottom of the isolation groove and the surface of the n-type GaN layer 2 contacting the active layer 3 is 50 nm to 100 nm, preferably 70 nm. Moreover, the two long sides of the isolation groove in the top view of FIG. 2 are also parallel to the axis of symmetry and symmetrical with respect to the axis of symmetry.

Subsequently, an insulating layer 6, which may be silicon dioxide, silicon nitride, etc., is formed on the bottom and sidewalls of the isolation trench. Moreover, an insulating layer 6 is also formed on the sidewall of the rectangular opening of the photoresist pattern.

Subsequently, metal Cu is deposited in the isolation groove, so that it fills up the isolation groove and the rectangular opening of the photoresist pattern until it covers the surface of the photoresist pattern. Subsequently, metal Cu covering the surface of the photoresist pattern is removed by etching, CMP, or the like. Subsequently, the photoresist pattern is removed to expose the p-type GaN layer 4, as shown in FIG. 4 . Copper pillars 5 are thus formed, which protrude to a height of 100 nm to 150 nm, preferably 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, above the surface of the p-type GaN layer 4 . And the sidewall of the copper pillar 5 has an insulating layer 6 .

Subsequently, the p-type electrode 8 of AlCu alloy is deposited on the left side of the copper pillar 5, that is, the left side of the symmetry axis described in FIG. The height of the AlCu alloy layer on the surface of the p-type GaN layer 4 is then thinned by methods such as CMP or etching until its thickness is the same as the height of the copper pillar 5 protruding from the surface of the p-type GaN layer 4, thus forming a p-type GaN layer. Type electrode 8, the thickness of p-type electrode 8 is 100nm to 150nm, preferably 110nm, 120nm, 130nm, 140nm, 150nm.

Subsequently, an aluminum oxide insulating layer 7 with a thickness of 30 nm to 50 nm is deposited on the right side of the copper pillar 5, that is, on the right side of the symmetry axis described in FIG. A part of the insulating layer 6 on the right side of the axis of symmetry described in FIG. 2 . Subsequent deposition material is an n-type electrode 9 of AlCu alloy until it is flush with the surface of the copper pillar 5, thereby forming an n-type electrode 9, the thickness of the n-type electrode 9 is 70nm to 100nm, preferably 75nm, 80nm, 85nm, 90nm, 100nm. It should be noted here that since the aluminum oxide insulating layer 7 is used as the etching stop layer and a part of the insulating layer 6 of the copper column 5 located on the right side of the axis of symmetry described in FIG. 2 is removed, the height of the removed part of the insulating layer 6 corresponds to The thickness of the n-type electrode 9 is 70nm to 100nm. Therefore, the subsequently formed n-type electrode 9 is directly in contact with the copper pillar 5, thereby forming a conductive path from the n-type electrode 9 to the copper pillar 5 to the n-type GaN layer, so that the n-type electrode 9 is electrically connected to the n-type GaN layer through the copper pillar 5 .

So far, a GaN-based flip-chip light-emitting diode structure has been formed, in which, as shown in FIG. The electrode 9 and the p-type electrode 8 are symmetrical with respect to the isolation groove, and the shape and area of the n-type electrode 9 and the p-type electrode 8 are the same. The total area of the n-type electrode 9 and the p-type electrode 8 accounts for 70%-90% of the surface area of the p-type GaN layer 4, preferably 75%, 80%, 85%. And the isolation groove accounts for 10%-30% of the surface area of the p-type GaN layer 4 , preferably 15%, 20%, 25%.

2. Connection between carrier substrate and GaN-based flip-chip light-emitting diode structure

Firstly, a carrier substrate 10 is provided on which solder balls or bump electrodes 11 are formed, and then the GaN flip-chip light emitting diode structure is soldered on the carrier substrate 10, wherein the n-type electrode 9 and the p-type electrode 8 are respectively connected to the corresponding solder balls or The bump electrodes 11 are welded to form a GaN-based flip-chip light emitting diode. And because the material of the n-type electrode 9 and the p-type electrode 8 is AlCu, it can provide a light reflection function, and since the total area of the n-type electrode 9 and the p-type electrode 8 accounts for 70% of the surface area of the p-type GaN layer 4- 90%, so most of the light can be reflected to the side of the sapphire substrate 1, thereby improving the luminous efficiency. And because the n-type electrode 9 and the p-type electrode 8 have the same shape and equal area, and are electrically connected with the solder ball or the bump electrode (11) at the same height and on the same surface, so there will be no damage during the soldering process. The LED chips are tilted to improve product yield.

So far, the above description has explained in detail the structure and manufacturing method of the GaN flip-chip light-emitting diode of the present invention. Compared with the light-emitting diode produced by the existing method, the light-emitting diode proposed by the present invention can greatly improve the luminous efficiency and product yield. . The embodiments described above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Those skilled in the art can make any modifications to the present invention without departing from the spirit of the present invention, and the protection scope of the present invention is defined by the appended claims.

Claims (7)

1. a GaN based flip-chip light-emitting diode, comprising:

Bearing substrate (10);

Be formed at soldered ball or salient pole (11) on bearing substrate (10);

Upside-down mounting GaN based light-emitting diode structure, it comprises:

Sapphire Substrate (1);

Be formed on the N-shaped GaN layer (2) in Sapphire Substrate (1);

Be formed on the active layer (3) on N-shaped GaN layer (2);

Be formed on the p-type GaN layer (4) on active layer (3);

Be formed on N-shaped electrode (9) and p-type electrode (8) on p-type GaN layer (4);

Be formed on the isolation channel between N-shaped electrode (9) and p-type electrode (8);

Be formed on the insulating barrier (6) on ditch non-intercommunicating cells lateral wall;

Be formed in isolation channel and the copper post (5) being electrically connected to N-shaped electrode (9); And

Soldered ball or salient pole (11) on bearing substrate (10) are electrically connected to N-shaped electrode (9) and p-type electrode (8) respectively.

2. GaN based flip-chip light-emitting diode according to claim 1, is characterised in that:

N-shaped electrode (9) and p-type electrode (8) are symmetrical arranged with respect to isolation channel and the area of N-shaped electrode (9) and p-type electrode (8) equates, and the apparent height of N-shaped electrode (9) and p-type electrode (8) and soldered ball or salient pole (11) electrical connection is identical and on same surface.

3. GaN based flip-chip light-emitting diode according to claim 2, is characterised in that:

Between N-shaped electrode (9) and p-type GaN layer (4), have alumina insulating layer (7), its thickness is 30nm to 50nm, and the thickness of N-shaped electrode (9) is 70nm to 100nm, preferred 75nm, 80nm, 85nm, 90nm, 100nm.

4. GaN based flip-chip light-emitting diode according to claim 3, is characterised in that: the surperficial height that copper post (5) protrudes from p-type GaN layer (4) is 100nm to 150nm, and the thickness of p-type electrode (8) is 100nm to 150nm, preferred 110nm, 120nm, 130nm, 140nm, 150nm.

5. GaN based flip-chip light-emitting diode according to claim 4, is characterised in that: N-shaped electrode (9) is identical with the surperficial height of the gross thickness of alumina insulating layer (7) and the thickness of p-type electrode (8) and the outstanding p-type GaN layer 4 of copper post (5).

6. GaN based flip-chip light-emitting diode according to claim 5, be characterised in that: the gross area of N-shaped electrode (9) and p-type electrode (8) accounts for the 70%-90% of the surface area of p-type GaN layer (4), and isolation channel accounts for the 10%-30% of the surface area of p-type GaN layer (4).

7. GaN based flip-chip light-emitting diode according to claim 6, be characterised in that: N-shaped electrode (9) directly contacts with copper post (5), thereby form N-shaped electrode (9) to the conductive path of N-shaped GaN layer (2), N-shaped electrode (9) is electrically connected to N-shaped GaN layer (2) by copper post (5).

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