JPH11220167A - Semiconductor light-emitting device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device, wherein uniformizing of the attitude of light-emitting elements causes stable light-orientation property and less molding processes leads to improved productivity. SOLUTION: A semiconductor light-emitting element 1 of flip-chip type is mounted on a Zener diode 7 for electrostatic protection, and p-side and n-side electrodes 3 and 2 of the semiconductor light-emitting element 1 are connected for conduction, to electrodes 7b and 7a of the Zener diode 7, with a surface of a side opposite to the mounting surface side as a main light extracting surface. Here, the p-side and p-side electrodes 3 and 2 are formed on the surfaces of a p-type layer 1c and n-type layer 1b of the semiconductor light-emitting element 1, respectively, and depending on the thickness of these electrodes 3 and 2, a gap with out shorting interference among the semiconductor light- emitting element 1, the mounting surface, and its electrode is formed.

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 semiconductor light-emitting device using a gallium nitride compound used for an optical device such as a blue light-emitting diode, and more particularly to an improvement in light distribution. The present invention relates to a semiconductor light emitting device and a method for manufacturing the same.

[0002]

2. Description of the Related Art GaN, GaAlN, InGaN and I
In the production of gallium nitride based semiconductors such as nAlGaN, insulating sapphire is generally used as a crystal substrate for growing a semiconductor film on the surface. When an insulating crystal substrate such as sapphire is used, electrodes cannot be provided from the crystal substrate side, so that the p and n electrodes provided on the semiconductor layer are formed on one surface facing the crystal substrate. become.

For example, a light-emitting device using a GaN-based compound semiconductor uses a sapphire substrate as an insulating substrate, and forms an n-type layer and a p-type layer on the upper surface thereof by metal organic chemical vapor deposition to form a p-type layer. Etch part of the layer to n
The basic configuration is that the mold layer is exposed and an n-side electrode and a p-side electrode are formed on each of the n-type layer and the p-type layer. If the p-side electrode is a transparent electrode, bonding pads are formed on these p-side and n-side electrodes, respectively, and wire-bonded to a lead frame or a substrate.

On the other hand, in a flip-chip type semiconductor light emitting device in which light is extracted from the sapphire substrate,
A configuration is adopted in which micro-bumps are formed on each of the p-side and n-side electrodes without the side electrodes being transparent electrodes, and these micro-bumps are connected to the p-side and n-side of the substrate or lead frame. .

FIG. 3 is a longitudinal sectional view schematically showing an LED lamp using a flip-chip type semiconductor light emitting device.

In FIG. 1, a light-emitting element 1 includes, for example, a GaN buffer layer, an n-type GaN layer, an InGaN active layer, and a p-type AlGa on a surface of an insulating transparent sapphire substrate 1a.
An N layer and a p-type GaN layer are sequentially stacked, and an InGaN active layer is used as a light emitting layer. An n-side electrode 20 is formed on the upper surface of the n-type GaN layer, and a p-side electrode 30 is formed on the upper surface of the p-type GaN layer by vapor deposition. Have micro bumps 4 and 5, respectively.

A mount 6a of the lead frame 6 on which the light emitting element 1 is mounted is provided with a zener diode 7 as an electrostatic protection element in order to prevent external destruction of the light emitting element 1 by preventing static electricity from being applied thereto. The Zener diode 7 is bonded and fixed to a mount 6a with a conductive Ag paste 8, and has p-side and n-side electrodes 7a and 7b formed on the upper surface thereof.

The light emitting element 1 is mounted on the Zener diode 7 with the sapphire substrate 1a facing upward, and the n-side and p-side micro bumps 4 and 5 are respectively joined to the electrodes 7a and 7b of the Zener diode 7. In this way, electrical conduction is achieved. And lead frame 6
The entire light emitting element 1 including the upper end portion is sealed with the epoxy resin 9 to form an LED lamp having the shape shown in the figure.

When the light emitting element 1 is energized, the InGaN active layer in the semiconductor laminated film becomes a light emitting layer, and light from this light emitting layer travels in both directions of the sapphire substrate 1a and the p-side electrode 30. By forming the p-side electrode 30 as a reflection type laminated film that does not transmit light, this surface can be used as a main light extraction surface with maximum light emission luminance from the upper surface of the sapphire substrate 1a.

In the manufacture of such an LED lamp, in order to electrically connect the micro bumps 4 and 5 and the electrodes 7a and 7b and fix the light emitting element 1 on the Zener diode 7, for example, a conductive adhesive is used. It is necessary to use a bonding agent or join by ultrasonic heating and pressure bonding. In the case of the ultrasonic heating and compression bonding method, ultrasonic waves are applied while heating and applying a load with the tips of the micro bumps 4 and 5 abutting against the surfaces of the electrodes 7a and 7b. Joining by melting and solidification is performed.

[0011]

SUMMARY OF THE INVENTION Micro bumps 4, 5
The function of (1) is to provide a clearance between the lower surface of the light emitting element 1 and the upper surface of the Zener diode 7 in addition to the conductive connection between the electrodes 7a and 7b, thereby providing a clearance between the light emitting element 1 and the Zener diode 7. Is to prevent short-circuiting. Therefore, it is necessary to form the micro bumps 4 and 5 so as to have a certain height dimension, and in a normal case, the length is about 50 μm.

However, the method of forming the micro-bumps 4 and 5 on the n-side electrode 20 and the p-side electrode 30 is to make the tip of the Au wire spherical and press this part on the electrode, and to apply the spherical portion by ultrasonic waves and heat. After welding on the electrode while crushing
The u-wire is pulled and cut at its trunk, and is often called a stud bump because of its molding method. In such a stud bump, for example, the height dimension, ie, n
Variations are likely to occur in the protruding lengths from the side and p-side electrodes. Therefore, in the example of the light emitting element 1 shown in FIG.
The lengths of the micro bumps 4 and 5 may be irregular.

If the lengths of the micro bumps 4 and 5 are not uniform as described above, the posture of the light emitting element 1 is inclined when the light emitting element 1 is mounted on the Zener diode 7 and pressure-bonded. For example, if the micro-bump 4 is shorter than the other micro-bump 5, the light-emitting element 1 has a downward-sloping posture and the light-emitting layer also has the same posture. Therefore, if the micro bumps 4 and 5 are not aligned, the direction of the light emitting element 1 will be variously changed. In the case of a panel or the like in which a large number of LED lamps are arranged, the light distribution from each light emitting element 1 will be different. Loses uniformity,
This has an undesirable effect on the displayed image.

Although the micro bumps 4 and 5 themselves sufficiently contribute to preventing a short circuit between the light emitting element 1 and the Zener diode 7, it is necessary to form the micro bumps 4 and 5 for each light emitting element 1. There is. Therefore, a step of adding the micro bumps 4 and 5 is required for a primary product in which the n-side electrode 20 and the p-side electrode 30 are formed by a metal deposition method, which hinders improvement in productivity and yield.

As described above, in the conventional bonding structure using the microbumps on the mounting surface side of the light emitting element, the light distribution property is deteriorated due to the disturbance of the attitude of the light emitting element, and expensive Au for forming the microbump is consumed. There is a problem of doing it.

The problem to be solved in the present invention is to provide a semiconductor light emitting device which can stabilize the light distribution by uniformizing the posture of the light emitting element, reduce the number of molding steps, and improve the productivity. .

[0017]

According to the present invention, a flip-chip type semiconductor light emitting device is mounted on a mounting surface of a substrate such as a substrate or a lead frame, and p-side and n-side electrodes of the semiconductor light emitting device are mounted. In a GaN-based semiconductor light emitting device which is electrically connected to a corresponding electrode on the surface side and has a surface opposite to the mounting surface side as a main light extraction surface, the p-side and n-side electrodes are connected to the semiconductor light-emitting element. A metal-deposited film is formed on each surface of the p-type layer and the n-type layer, and the thickness of these electrodes makes it possible to form a gap without short-circuit interference between the semiconductor light emitting element, the mounting surface, and the electrodes. It is characterized by.

In such a configuration, the gap formed by the p-side and n-side electrodes of the light-emitting element can be used to prevent short-circuit interference between the light-emitting element and the mounting surface without forming the microbump. Is formed by a metal vapor-deposited film, the thickness of the light-emitting element can be made uniform, and the posture of the light-emitting element can be made uniform.

Further, according to the manufacturing method of the present invention, the p-side electrode and the n-side electrode are set at 300 to 35 with respect to the corresponding electrodes on the mounting surface side.
The semiconductor light emitting device is bonded to the mounting surface by heating and pressing in a temperature atmosphere of 0 ° C.

In this manufacturing method, the heating temperature is set to 300 to 3
By setting the temperature to 50 ° C., it is possible to perform stable bonding between the electrodes by Au—Sn eutectic without causing abnormalities such as deterioration of characteristics and appearance discoloration to the GaN-based LED which is a light emitting element. it can.

[0021]

According to the first aspect of the present invention, a flip-chip type semiconductor light emitting device is mounted on a mounting surface of a substrate such as a substrate or a lead frame.
And the n-side electrode is electrically connected to the corresponding electrode on the mounting surface side, and the surface opposite to the mounting surface side is used as a main light extraction surface.
In an aN-based semiconductor light-emitting device, the p-side and n-side electrodes are formed by metal deposition films on respective surfaces of a p-type layer and an n-type layer of the semiconductor light-emitting element, and the thickness of these electrodes varies depending on the thickness of the semiconductor. It is possible to form a gap without short-circuit interference between the light emitting element and the mounting surface and its electrodes.
The gap formed by the n-side and n-side electrodes can be used to prevent short-circuit interference between the light-emitting element and the mounting surface side, and has the effect of making the thickness of the electrode uniform and the posture of the light-emitting element uniform. .

According to a second aspect of the present invention, there is provided the semiconductor light emitting device according to the first aspect, wherein the p-side and n-side electrodes have a thickness of 10 to 20 μm. Has the effect of reliably preventing short-circuit interference between the device and the mounting surface.

According to a third aspect of the present invention, the p-side and n-side electrodes are each a laminated film of Ti and Au, and the corresponding electrodes on the mounting surface side are an alloy of Au and Sn. The semiconductor light emitting device according to the above, wherein Ti is a material for enhancing the adhesion of Au, and Au is an alloy of Au and Sn for the electrode of the substrate or the lead frame, so that Au at the time of thermocompression bonding is used.
Has the effect of lowering the eutectic temperature with

According to a fourth aspect of the present invention, there is provided an electrostatic protection element mounted on the substrate and electrically connected to the substrate, and the semiconductor light emitting element is provided on the p-side and n-side electrodes on the electrostatic protection element. The semiconductor light emitting device according to any one of claims 1 to 3, wherein the semiconductor light emitting device is mounted and bonded as a relationship having opposite polarities.
This has the effect that the electrostatic protection element prevents electrostatic breakdown of the semiconductor light emitting element.

According to a fifth aspect of the present invention, there is provided a method for manufacturing a semiconductor light emitting device according to any one of the first to fourth aspects, wherein
Side and n-side electrodes are 3
This is a method for manufacturing a semiconductor light emitting device in which a semiconductor light emitting element is bonded to a mounting surface by heat-pressing in a temperature atmosphere of 00 to 350 ° C. This has the effect that a stable joining by Au-Sn eutectic can be performed between the electrodes without causing abnormalities in the above.

Hereinafter, a specific example of the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged view of a main part of a semiconductor light emitting device according to an embodiment of the present invention, and FIG. 2 is a perspective view of a light emitting element. The configuration of the light emitting element is the same as that of the conventional example except for the shapes of the n-side and p-side electrodes, and the zener diode is also the same. Detailed description is omitted.

In FIG. 2, the light emitting element 1 has an n-type layer 1b and a p-type layer 1c formed on the upper surface of a sapphire substrate 1a, and an n-side electrode is formed on the upper surface of each of the n-type layer 1b and the p-type layer 1c. 2 and a p-side electrode 3 are formed. By forming a silver-white light reflection film 1d made of a laminated film of, for example, Ni and Pt or a laminated film of Sb and Pt on the surface of the p-type layer 1c, light from the light emitting layer is reflected by the light reflection film 1d. Is reflected in the direction of the sapphire substrate 1a, so that the lower surface of the sapphire substrate 1a can be used as a main light extraction surface.

The n-side electrode 2 and the p-side electrode 3 are, for example,
It is formed by an evaporation method using an alloy of i and Au as a material, and has a height of about 10 to 20 μm. Then, when the bottom surface of the sapphire substrate 1a is positioned on a horizontal plane, the heights of the upper end surfaces of the n-side and p-side electrodes 2 and 3 are exactly the same and are formed so as to be included in the same plane. . Such a molding can be performed with high precision by a vapor deposition method using a metal, and the n-side and p-side electrodes 2 are formed.
3 can be formed as a smooth and uniform plane.

The p formed on the upper surface of the Zener diode 7
As the metal material of the side and n-side electrodes 7a and 7b, an alloy of Au and Sn is preferable since the n-side and p-side electrodes 2 and 3 of the light emitting element 1 are joined by a heat compression method.
In this case, the optimal ratio of Au to Sn is Au: Sn =
(3: 9) to (3:11), and the electrodes 7a, 7b
Is preferably about 5 μm.

The light emitting element 1 has a structure similar to that of the conventional structure.
The sapphire substrate 1a is mounted on the top surface of the Zener diode 7 as shown in FIG. At this time, the n-side electrode 2 and the p-side electrode 3 are directly joined to the p-side and n-side electrodes 7a and 7b of the Zener diode 7 by a heat compression method.

The electrodes 2 and 3 on the n-side and p-side of the light-emitting element 1 and the electrodes 7 a and
Bonding with 7b may be performed if the heating temperature is in the range of 300 to 350 ° C. and the pressing force is in the range of about 10 g to 20 g. Under such conditions, the eutectic of Au and Sn proceeds uniformly on the surfaces of the n-side and p-side electrodes 2 and 3, and therefore n
The joint end surfaces of the side and p-side electrodes 2 and 3 are prevented from being deformed into, for example, an arc-shaped convex surface, and the posture of the light emitting element 1 can be prevented from tilting. In this temperature range,
Heat compression bonding can be performed without deteriorating the characteristics of the GaN-based LED that is a light emitting element.

Here, the thickness of the p-side and n-side electrodes in the conventional GaN-based compound semiconductor light emitting device is about 1 to 2 μm, and therefore, in the present invention, the thickness of the p-side and n-side electrodes 2 and 3 is The size is about 10 times larger than the conventional structure. The thickness of the micro-bumps 4 and 5 shown in the conventional example is about 30 μm, and has a sufficient thickness to keep a space between the light-emitting element 1 and the Zener diode 7 to prevent a short circuit.

On the other hand, in the present invention, the n-side electrode 2 is
When the thickness is 0 μm and the thickness of the p-side electrode 3 is 10 μm, the gap of 10 μm can be secured by the p-side electrode 3 at a minimum, although it is smaller than the gap formed by the conventional micro bumps 4 and 5. If the gap is about 10 μm, contact between the light emitting element 1 and the Zener diode 7 can be avoided, and the problem of short circuit does not occur.

The n-side and p-side electrodes 2 and 3 of the light-emitting element 1 made of an alloy of Ti and Au are heat-pressed to the electrodes 7a and 7b of a zener diode 7 made of an alloy of Au and Sn. In this case, the eutectic bonding of Au and Sn can be uniformly performed at a relatively low temperature of 300 ° C. to 350 ° C., and the bonding strength with the light reflection film 1d can be maintained strongly by Ti.

In the above arrangement, the n-side and p-side electrodes 2 and 3 formed on the light emitting element 1 by metal vapor deposition can be manufactured with high precision in the length up to the junction end face with the Zener diode 7. When the light-emitting elements 1 are joined to the surfaces of the light-emitting elements 1a and 7b, the inclination of the light-emitting element 1 is prevented. Also, by forming the joint end surfaces of the n-side and p-side electrodes 2 and 3 as uniform flat surfaces, proper joining to the electrodes 7a and 7b becomes possible, and the inclination of the light emitting element 1 is further improved. Can be eliminated.

Furthermore, by setting the load conditions of heat and pressure by the thermocompression bonding within a range in which the joint end surfaces of the n-side and p-side electrodes 2 and 3 do not swell and deform in the protruding direction, for example. The flatness of the joining ends of the electrodes 2 and 3 can be kept high.

Accordingly, the light emitting element 1 can be bonded to the zener diode 7 in a correct posture, and even a display panel having a large number of light emitting elements 1 can reproduce a clear image excellent in light distribution. it can.

In the above embodiment, an example is shown in which the light emitting element is mounted on a Zener diode. However, it goes without saying that the present invention can be applied to a case where the light emitting element is mounted on a lead frame or a substrate.

[0039]

According to the first aspect of the present invention, the thicker p-side and n-side electrodes are also used to form a gap for preventing interference short-circuit, so that the step of forming a micro-bump as in the prior art is performed. And the production yield can be improved. Also,
Since the electrodes are formed of a metal vapor-deposited film, the thickness of the electrodes and the accuracy of the joint end surface can be maintained at a high level, and an assembly in which the posture of the light emitting element is not disturbed is possible.

According to the second aspect of the invention, by setting the thickness of the p-side and n-side electrodes to 10 to 20 μm, a short circuit between the light emitting element and the mounting surface can be reliably prevented.

According to the third aspect of the present invention, the material of the p-side and n-side electrodes is a laminated film of Ti and Au, so that the adhesion strength to the light emitting element and the Au and S on the substrate or the lead frame side are formed.
Thermocompression bonding can be performed at a relatively low temperature with an electrode made of an alloy of n and the production yield is improved.

According to the fourth aspect of the present invention, by providing the electrostatic protection element, the electrostatic breakdown voltage of the GaN-based semiconductor light emitting element having a low electrostatic breakdown voltage can be increased, and the electrostatic breakdown due to an overcurrent or the like can be prevented. .

According to the fifth aspect of the present invention, the heating temperature is set to 300 ° C.
By setting the temperature to 350 ° C., a stable junction can be obtained between the electrodes by uniform eutectic of Au and Sn without deteriorating the characteristics of the GaN-based light emitting device.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of the present invention, and is a view showing a state in which a light emitting element is heated and pressed on a Zener diode on a mount portion.

FIG. 2 is a perspective view showing an outline of a light emitting element.

FIG. 3 shows a conventional L-type chip having a flip-chip type light emitting element.
Schematic vertical sectional view of an ED lamp

[Explanation of symbols]

 Reference Signs List 1 light emitting element 1a sapphire substrate 1b n-type layer 1c p-type layer 1d light reflection film 2 n-side electrode 3 p-side electrode 4,5 microbump 6 lead frame 6a mounting part 7 Zener diode 7a, 7b electrode 8 Ag paste 9 epoxy resin

Claims (5)

[Claims] 1. A flip-chip type semiconductor light emitting device is mounted on a mounting surface of a substrate such as a substrate or a lead frame, and p-side and n-side electrodes of the semiconductor light emitting device are connected to corresponding electrodes on the mounting surface side. In the GaN-based semiconductor light-emitting device, wherein the surface opposite to the mounting surface side is a main light extraction surface, the p-side and n-side electrodes are connected to the p-type layer and the n-type layer of the semiconductor light-emitting element. A semiconductor light emitting device which is formed on each surface by a metal vapor deposition film, and which can form a gap without short-circuit interference between the semiconductor light emitting element and the mounting surface and its electrodes by the thickness of these electrodes. 2. The thickness of the p-side and n-side electrodes is 10 to
2. The semiconductor light emitting device according to claim 1, wherein the thickness is 20 μm. 3. The p-side and n-side electrodes are each made of Ti.
3. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is a stacked film of Au and Au, and the corresponding electrode on the mounting surface side is an alloy of Au and Sn. 4. An electrostatic protection element is mounted on the substrate and is electrically connected to the substrate, and the semiconductor light emitting element is placed on the electrostatic protection element such that p-side and n-side electrodes have opposite polarities. 4. The semiconductor light emitting device according to claim 1, wherein the device is mounted and joined. 5. The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the p-side electrode and the n-side electrode are disposed at a temperature of 300 to 350 ° C. with respect to a corresponding electrode on a mounting surface side. A method for manufacturing a semiconductor light-emitting device in which a semiconductor light-emitting element is bonded to a mounting surface by thermocompression bonding in a temperature atmosphere.