JP2013135018A - Light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element which prevents damages on a luminous region caused by an excessive load applied in bonding.SOLUTION: A light-emitting element comprises: a semiconductor light-emitting function layer formed on a substrate 11, in which a first semiconductor layer having a first conductivity type and a second semiconductor layer having a second conductivity type opposite to the first conductivity type are formed; and two electrodes 51, 52 used for energization for causing the semiconductor light-emitting function layer to emit light, and formed on a principal surface of the semiconductor light-emitting function layer on the side where the second semiconductor layer is formed. The second semiconductor layer is removed from the principal surface side immediately below pads of the two electrodes 51, 52 which are connected with the outside.

Description

The present invention relates to a structure of a light emitting element using a semiconductor layer as a constituent material.

  Light emitting elements (LEDs) are used for various purposes. For example, lighting equipment using this is expected to be replaced in the future because of low power consumption and low heat generation compared to conventional incandescent bulbs and fluorescent lamps. Here, the p-type semiconductor layer and the n-type semiconductor layer in the LED are usually formed by epitaxial growth, ion implantation, or the like. The light emitting element can emit light by passing a forward current of a pn junction between the electrode connected to the p side and the electrode connected to the n side.

  When a device is mounted on a mounting board, a so-called flip-chip connection method is adopted in which the mounting substrate and the element are connected by solder or the like, and electrical connection between the element is also made by this solder connection. There are many. The same applies to the light emitting element. In this case, the light emitting element is often configured to emit light to the side opposite to the substrate.

  In such a flip-chip connection method, bump balls are used in flip bonding, and an excessive load may be applied to the electrode connected to the p side and the electrode connected to the n side. Patent Document 1 discloses a technique for preventing damage to a light emitting region of a light emitting element due to an excessive load during such flip bonding.

FIG. 1 shows a light emitting device according to the prior art. In the nitride semiconductor light emitting device flip-bonded onto the lead pattern of the submount 200 via the bump ball 300, the substrate 101, and the buffer layer, the n-type nitride semiconductor layer 103, the active layer 105, and the p on the substrate. A light emitting structure in which a type nitride semiconductor layer 107 is sequentially formed, a transparent electrode 109, a p-type electrode 110a and an n-type electrode 110b formed on the light emitting structure, and a resultant structure in which the electrode is formed. A protective film 120 formed on the submount and exposing a surface of the electrode corresponding to a portion connected to the p-type lead pattern 201a and the n-type lead pattern 201b of the submount via a bump ball; and exposed through the protective film. And a lattice-shaped buffer film 130 formed on the surface of the electrode. The buffer film 130 has an effect of preventing the light emitting region of the light emitting element from being damaged by an excessive load exceeding the critical value of the bump ball.

However, although the conventional technology has the buffer film 130, it has an effect on the case where the buffer film 130 is not provided, but prevents the light emitting region of the light emitting element from being damaged by an excessive load exceeding the critical value of the bump ball. The point was not enough and was not optimal in terms of reliability.

Japanese Patent No. 4428716

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a light emitting element capable of preventing damage to a light emitting region due to an excessive load during bonding.

In order to solve the above problems, the present invention provides:
A semiconductor light emitting function in which a second semiconductor layer having a second conductivity type, which is a conductivity type opposite to the first conductivity type, is formed on a first semiconductor layer having a first conductivity type on a substrate. Layer, and two electrodes used for energization for causing the semiconductor light emitting functional layer to emit light are both formed on the main surface of the semiconductor light emitting functional layer on the side where the second semiconductor layer is formed. A first element formed so as to be connected to the first semiconductor layer at a position where the second semiconductor layer is removed from the main surface side at one end of the semiconductor light emitting functional layer. And a transparent electrode formed to extend from the other end side toward the one end portion on the surface of the second semiconductor layer, and formed at the other end portion. The second electrode is a pad portion connected to the outside and the first electrode The second semiconductor layer is removed from the main surface side immediately below the pad portion, and an insulating layer is interposed between the first electrode and the second electrode. The extending portion and the transparent electrode are connected.

It is possible to provide a light emitting element that prevents damage to a light emitting region due to an excessive load during bonding.

It is sectional drawing which shows the conventional semiconductor light-emitting device roughly. It is sectional drawing which shows the light emitting element which concerns on Example 1 of this invention. It is the figure which has arrange | positioned the light emitting element which concerns on Example 1 of this invention on the mounting board | substrate. It is the figure which has arrange | positioned the light emitting element which concerns on Example 2 of this invention on the mounting board | substrate.

Next, embodiments of the present invention will be specifically described with reference to the drawings. In addition, embodiment shown here is an example and this invention is not the meaning limited to embodiment shown here.

FIG. 2 shows a cross-sectional view of the light emitting device according to Example 1 of the present invention. As shown in FIG. 2, the semiconductor layer 20 is formed on the substrate 11. The semiconductor layer 20 includes an n-type GaN layer (hereinafter abbreviated as n-type layer) 21, an MQW (Multi Quantum Well) layer 23, and a p-type GaN layer (hereinafter abbreviated as p-type layer) 22 from the substrate 11 side. Has a laminated structure. The main light emitting layer in this configuration is the MQW layer 23. As the substrate 11, for example, an insulating material capable of heteroepitaxially growing GaN thereon can be used, such as sapphire.
In the region on one end (right end in FIG. 2) side of the semiconductor layer 20, the p-type layer 22 and the MQW layer 23 are partially removed, and similarly, the p-side electrode 51 connected to the outside The p-type layer 22 and the MQW layer 23 are partially removed also in the region immediately below the pad portion. A transparent electrode 30, an insulating layer 40, a p-side electrode (anode) 51, and an n-side electrode (cathode) 52 are formed on the semiconductor layer 20.

The n-type layer 21, the MQW layer 23, and the p-type layer 22 in the semiconductor layer 20 can be epitaxially grown on the substrate 11 by an MBE (Molecular Beam Epitaxy) method or an MOCVD (Metal Organic Chemical Vapor Deposition) method. The n-type layer 21 is appropriately doped with an impurity serving as a donor, and the p-type layer 22 is appropriately doped with an impurity serving as an acceptor. The thickness of the n-type layer 21 can be set to, for example, 5.0 μm, and the thickness of the p-type layer 22 can be set to, for example, about 0.2 μm. Further, the MQW layer 23 has a structure in which a plurality of InGaN and GaN thin films having a thickness of, for example, several nm to several tens of nm are stacked, and each layer of InGaN and GaN is epitaxially grown in the same manner as the n-type layer 21 and the p-type layer 22. It is formed.

The transparent electrode 30 is made of, for example, ITO (Indium-Tin-Oxide) or ZnO (Zinc-Oxide) as a material that can make ohmic contact with the p-type layer 22 and is transparent to light emitted from the semiconductor layer 20. Is done. In addition, in order to improve the ohmic property and adhesion between the p-type layer 22 and the like, a thin titanium (Ti) layer or nickel (Ni) layer is inserted between them so that light is sufficiently transmitted. You can also. The patterning of the transparent electrode 30 is performed by an etching method or by forming a mask such as a photoresist other than a desired portion, forming the transparent electrode material on the entire surface, and then removing the mask later. Any method of removing the transparent electrode material other than the above (lift-off method) can be used.

The insulating layer 40 is made of a material that has sufficient insulating properties and is transparent to the light emitted from the semiconductor layer 20, and is made of, for example, silicon oxide (SiO ₂ ).
In the region on one end (right end in FIG. 2) side of the semiconductor layer 20, an opening is formed in the insulating layer 40, and the exposed n-type layer 21 and the n-side electrode 52 are connected. Also, a plurality of openings are formed between the p-side electrode 51 and the n-side electrode 52 formed at the other end portion (left end portion in FIG. 2) of the semiconductor layer 20, and the p-side extends in the direction of the n-side electrode 52. The extending part of the electrode 51 and the transparent electrode 30 are connected.
The insulating layer 40 can be formed with good coverage even at the stepped portion shown in FIG. 2 by using, for example, a CVD (Chemical Vapor Deposition) method. The patterning is performed by an etching method.

The p-side electrode 51 is made of a highly conductive metal such as gold (Au). The n-side electrode 52 is made of a material that can make ohmic contact with the n-type layer 21. The p-side electrode 51 and the n-side electrode 52 can be patterned in the same manner as the patterning of the transparent electrode 30.

With this configuration, the p-side electrode 51 is connected to the p-type layer 22 via the transparent electrode 30, and the n-side electrode 52 is directly connected to the n-type layer 21. Thus, by applying a positive voltage to the p-side electrode 51 and a negative voltage to the n-side electrode 52, the light emitting layer (mainly the MQW layer 23) in the semiconductor layer 20 can emit light.

What is characteristic here is that the p-side electrode 51 includes a pad portion connected to the outside and an extending portion extending in the direction of the n-side electrode 52, but the transparent electrode 30, even in the region immediately below the pad portion of the p-side electrode 51, That is, the p-type layer 22 and the MQW layer 23 are partially removed. Since a pn junction is not formed in a region immediately below the pad portion of the p-side electrode 51, even if an excessive load is applied to the pad portion of the p-side electrode 51 during flip bonding as shown in FIG. Since the light emitting region is not affected by the load, damage to the light emitting region can be prevented.

FIG. 4 is a diagram in which a light emitting device according to Example 2 of the present invention is arranged on a mounting substrate. In the first embodiment, the p-type layer 22 and the MQW layer 23 are partially removed in the region immediately below the pad portion of the p-side electrode 51, but in the second embodiment, the n-type layer 21 is also formed on the substrate 11. The difference is that it is removed until it reaches. Other structures are the same as those of the light emitting device according to Example 1.
Since the semiconductor layer 20 itself is not formed in the region immediately below the pad portion of the p-side electrode 51, even if an excessive load is applied to the pad portion of the p-side electrode 51 during flip bonding, the light emitting region of the light emitting element It is possible to further increase the suppression of damage to the light emitting region without being affected by the load.

Although the present invention has been described by way of example as described above, it should not be understood that the discussion and drawings that form part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.
In the description of the embodiment already described, the example in which the semiconductor layer 20 in the region immediately below the pad portion of the p-side electrode 51 is partially removed has been shown, but the semiconductor layer 20 in the region immediately below the pad portion of the n-side electrode 52 has been shown. Is removed within a range in which the n-side electrode 52 and the n-type layer 21 can be connected, so that not only the p-side electrode 51 but also an excessive load is applied to the n-side electrode 52 during flip bonding. It is possible to suppress damage to the light emitting region.
Further, in this embodiment, an example of a flip type has been shown, but a light emitting element that is not a flip type also has a similar structure, so that, for example, an excessive amount is applied to the p-side electrode and the n-side electrode during wire bonding or the like. Obviously, even when a load is applied, damage to the light emitting region of the light emitting element can be prevented.
As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

11 Semiconductor substrate 20 Semiconductor layer 21 n-type GaN layer 22 p-type GaN layer 23 MQW layer 30 Transparent electrode 40 Insulating layer 51 p-side electrode 52 n-side electrode 60 Mounting substrate 70 Wiring 80 Solder (conducting bump ball)

Claims (3)

A semiconductor light emitting function in which a second semiconductor layer having a second conductivity type, which is a conductivity type opposite to the first conductivity type, is formed on a first semiconductor layer having a first conductivity type on a substrate. Layer, and two electrodes used for energization for causing the semiconductor light emitting functional layer to emit light are both formed on the main surface of the semiconductor light emitting functional layer on the side where the second semiconductor layer is formed. A first element formed so as to be connected to the first semiconductor layer at a position where the second semiconductor layer is removed from the main surface side at one end of the semiconductor light emitting functional layer. And a transparent electrode formed to extend from the other end side toward the one end portion on the surface of the second semiconductor layer, and formed at the other end portion. The second electrode is connected to the pad portion connected to the outside and the first electrode. An extension portion extending toward the surface, the second semiconductor layer is removed from the main surface side immediately below the pad portion, and an insulating layer is interposed between the first electrode and the second electrode. The extending portion and the transparent electrode are connected to each other.   Further, the first semiconductor layer is removed from the main surface side together with the second semiconductor layer immediately below the pad portion of the second electrode formed at the other end portion. The light emitting device according to claim 1. 3. The device according to claim 1, wherein the first semiconductor layer is made of an n-type nitride semiconductor, and the second semiconductor layer is made of a p-type nitride semiconductor. 4. Light emitting element.

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