KR101205831B1 - Semiconductor light emitting device and manufacturing method of the same - Google Patents

Abstract

A vertical structure semiconductor light emitting device having a current blocking layer that does not degrade the brightness of the device, and a method of manufacturing the same. A semiconductor light emitting device according to the present invention comprises a conductive substrate; A current blocking layer formed on the conductive substrate using at least one highly reflective metal selected from the group consisting of Al, Cr, Ti, and V; A plurality of p-type electrodes formed on both sides of the current blocking layer; A p-type semiconductor layer, an active layer, and an n-type semiconductor layer sequentially stacked on the p-type electrode and the current blocking layer; And an n-type electrode formed on the n-type semiconductor layer.

Description

Semiconductor light emitting device and method of manufacturing the same {Semiconductor light emitting device and manufacturing method of the same}

The present invention relates to a method for manufacturing a semiconductor light emitting device, and more particularly, to a method for manufacturing a vertical structure semiconductor light emitting device.

A semiconductor light emitting device such as a light emitting diode (LED) is one of solid state electronic devices that convert current into light, and typically includes an active layer of a semiconductor material interposed between a p-type semiconductor layer and an n-type semiconductor layer. When a driving current is applied across the p-type semiconductor layer and the n-type semiconductor layer in the semiconductor light emitting device, electrons and holes are injected into the active layer from the p-type semiconductor layer and the n-type semiconductor layer. The injected electrons and holes are recombined in the active layer to generate light.

In general, the semiconductor light emitting device is a nitride group III-V group having an Al _x In _y Ga _(1-xy) N composition formula, where 0≤x≤1, 0≤y≤1, 0≤x + y≤1 Although it is manufactured with a semiconductor compound, it becomes a device which can produce short wavelength light (ultraviolet light-green light), especially blue light. However, since the nitride compound semiconductor is manufactured by using an insulating substrate such as a sapphire substrate or a silicon carbide (SiC) substrate that satisfies the lattice matching condition for crystal growth, the p-type semiconductor layer and n Two electrodes connected to the semiconductor semiconductor layer have a planar structure in which they are arranged almost horizontally on the upper surface of the light emitting structure.

However, when the n-type electrode and the p-type electrode are arranged almost horizontally on the upper surface of the light emitting structure, the light emitting area is reduced, the luminance is decreased, and current spreading is not smooth, causing reliability problems vulnerable to electrostatic discharge (ESD). . In addition, there is a problem that the yield is reduced by reducing the number of chips on the same wafer. In addition, there is a limit in reducing the chip size, and furthermore, since the sapphire substrate has poor thermal conductivity, heat generated during high-power driving is not sufficiently discharged, thereby limiting device performance.

In order to solve this problem, a laser lift off method for separating the sapphire substrate and the nitride compound semiconductor layer part by decomposing the interface between the sapphire substrate and the nitride compound compound semiconductor layer using the high-density energy of the high power laser. To manufacture a semiconductor light emitting device having a vertical structure.

1 is a vertical structure fabricated by forming a nitride compound semiconductor layer composed of an n-type semiconductor layer, an active layer and a p-type semiconductor layer on a sapphire substrate, and then separating the sapphire substrate by a laser lift-off method and attaching a support conductive substrate. It is sectional drawing which shows a semiconductor light emitting element.

Referring to FIG. 1, a conventional vertical structure semiconductor light emitting device 10 includes a metal layer 35, a p-type semiconductor layer 25, an active layer 20, and an n-type semiconductor layer 15 on a conductive substrate 40. The n-type electrode 45 is formed on the n-type semiconductor layer 15 upper surface. When a driving current is applied across the p-type semiconductor layer 25 and the n-type semiconductor layer 15, electrons and holes are injected into the active layer 20 from the p-type semiconductor layer 25 and the n-type semiconductor layer 15. . The injected electrons and holes recombine in the active layer 20 to generate light.

Such a vertical structure semiconductor light emitting device has a thick thickness of the n-type semiconductor layer 15 as compared to the horizontal structure, but the current spreads well, but similar to that of the n-type electrode in order to realize high brightness and high power LED device by more uniformly distributing photons. There is a need for a current blocking layer (CBL) for pattern-depositing a type insulator onto a p-type semiconductor layer.

2 is a cross-sectional view for each process for explaining a method of manufacturing a conventional semiconductor light emitting device employing a SiO ₂ current blocking layer.

Referring to FIG. 2A, first, an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are sequentially grown on a semiconductor substrate 5 to form a light emitting structure 30, and then on the light emitting structure 30. SiO ₂ film 31 is formed. According to FIG. 2B, an ohmic metal 32 is deposited on a portion of the SiO ₂ film 31 and then heat-treated. Next, referring to FIG. 2C, the SiO ₂ film 31 on both sides of the ohmic metal 32 is removed by etching. After forming the seed metal layer 33 over the SiO ₂ film 31 and the ohmic metal 32 with reference to FIG. 2 (d), the conductive substrate 40 is formed on the seed metal layer 33 with reference to FIG. 2 (e). To form. Next, the semiconductor substrate 5 is removed as shown in FIG. 2 (f) by a laser lift-off process. Then, the concave-convex 42 is formed on the upper surface of the light emitting structure 30 with reference to FIG. 2 (g), and separated by chips as shown in FIG. Next, an n-type electrode 45 is formed on the upper surface of the light emitting structure 30 with reference to FIG. 2 (i).

A Si ₃ N ₄ film may be used instead of the SiO ₂ film 31 as a current blocking layer, but a SiO ₂ film or Si ₃ N ₄ film formed by depositing on a surface of a p-type semiconductor layer is generated in a quantum well of the light emitting structure 30. Absorption or scattering a portion of the light to reduce the brightness of the device. In addition, an additional photolithography process and dry or wet etching are required to form a current blocking layer pattern, which is complicated.

In order to solve this problem, the use of the Bragg reflective film which has a high reflectivity characteristic is proposed. However, in this structure, oxides must be multi-laminated and a patterning process is still required, which increases the process cost.

An object of the present invention is to provide a semiconductor light emitting device having a current blocking layer that does not lower the brightness of the device.

Another object of the present invention is to provide a method of manufacturing a semiconductor light emitting device in which the process is simplified by reducing the number of photolithography and etching processes in forming a current blocking layer.

The semiconductor light emitting device according to the present invention for solving the above problems is a conductive substrate; A current blocking layer formed on the conductive substrate using at least one highly reflective metal selected from the group consisting of Al, Cr, Ti, and V; A plurality of p-type electrodes formed on both sides of the current blocking layer; A p-type semiconductor layer, an active layer, and an n-type semiconductor layer sequentially stacked on the p-type electrode and the current blocking layer; And an n-type electrode formed on the n-type semiconductor layer.

In a preferred embodiment, the current blocking layer is made of Al. The current blocking layer forms a Schottky junction with the p-type semiconductor layer. The current blocking layer is not heat treated. The current blocking layer has the same pattern as the n-type electrode.

In the method of manufacturing a semiconductor light emitting device according to the present invention for solving the above-mentioned other problems, an n-type semiconductor layer, an active layer and a p-type semiconductor layer are sequentially grown on a semiconductor substrate, and then an ohmic metal on the p-type semiconductor layer. After the deposition, a plurality of p-type electrodes are formed by heat treatment. At least one highly reflective metal selected from the group consisting of Al, Cr, Ti and V is formed between at least the p-type electrode to form a current blocking layer. Then, a conductive substrate is formed on the p-type electrode and the current blocking layer, and the semiconductor substrate is removed. An n-type electrode is formed on the n-type semiconductor layer.

In the present invention, the current blocking layer is formed on the entire surface of the p-type electrode and the semiconductor substrate without a photolithography process and an etching process. The forming of the conductive substrate may include forming a seed metal layer over the current blocking layer; And forming a conductive material on the seed metal layer by any one of plating, deposition, and sputtering, or attaching the conductive substrate to the current blocking layer through a wafer bonding process.

In the present invention, a current blocking layer is formed using a highly reflective metal such as Al having a reflectance of 80% or more. Al has a Schottky characteristic in a metal contact with a p-type semiconductor layer such as p-GaN and has a reflectance of 80% or more in the blue wavelength region. The use of such a highly reflective metal as a current blocking layer improves current spreading and at the same time maintains the characteristics of the high reflective film, thereby improving light output. Therefore, a high brightness, high output vertical LED element can be manufactured.

According to the present invention, an additional photolithography process and an etching process are not necessary when forming a current blocking layer using a highly reflective metal. This simplifies the process and reduces production costs.

1 is a cross-sectional view showing a vertical structure semiconductor light emitting device according to the prior art.
2 is a cross-sectional view for each process for explaining a method of manufacturing a conventional semiconductor light emitting device employing a SiO ₂ current blocking layer.
3 is a cross-sectional view showing a semiconductor light emitting device according to the present invention.
4 is a cross-sectional view showing another semiconductor light emitting device according to the present invention.
5 is a cross-sectional view showing still another semiconductor light emitting device according to the present invention.
6 is a cross-sectional view illustrating processes according to an embodiment of the method of manufacturing a semiconductor light emitting device according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments make the disclosure of the present invention complete, and the scope of the invention to those skilled in the art. It is provided for complete information. In the drawings, the thickness of layers, films, panels, regions, etc., may be exaggerated or exaggerated for clarity.

3 is a cross-sectional view showing a semiconductor light emitting device according to the present invention.

Referring to FIG. 3, the semiconductor light emitting device 100 includes a conductive substrate 140, a p-type electrode 132 formed on the conductive substrate 140, a current blocking layer 133, and a p-type semiconductor sequentially formed thereon. The layer 125, the active layer 120, the n-type semiconductor layer 115, and the n-type electrode 145 are included.

The conductive substrate 140 may be made of a material selected from the group consisting of Si, Cu, Ni, Au, W, and Ti, and according to the selected material, the p-type electrode 132 and the current may be formed by a process such as plating, deposition, and sputtering. It may be formed directly on the blocking layer 133. Here, in the embodiment, the example in which the conductive substrate 140 is attached through a wafer bonding process is not limited thereto. A bonding metal layer made of a eutectic alloy mainly containing Au and Sn is formed on the p-type electrode 132. It may further be deposited and attached by means of pressurization / heating.

The p-type semiconductor layer 125, the active layer 120, and the n-type semiconductor layer 115 are light emitting structures 130. The n-type semiconductor layer 115, the active layer 120, and the p-type semiconductor layer 125 have an In _X Al _Y Ga _1-XY N composition formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). It may be made of a semiconductor material having. More specifically, the n-type semiconductor layer 115 may be formed of a GaN layer or a GaN / AlGaN layer doped with n-type impurities, for example, Si, Ge, Sn, Te or C, etc. Is used, and preferably Si is mainly used. The p-type semiconductor layer 125 may be formed of a GaN layer or a GaN / AlGaN layer doped with p-type impurities. For example, Mg, Zn, Be, or the like may be used as the p-type impurity. Mainly uses Mg. The active layer 120 is a layer for generating and emitting light, and is generally formed by forming a multi-quantum well with an InGaN layer as a well and a GaN layer as a wall layer. The active layer 120 may be composed of one quantum well layer or a double hetero structure.

The light emitting structure 130 may have a side surface spaced apart from an edge of the p-type electrode 132. The light emitting structure 130 may be formed such that a side surface thereof is inclined with respect to the conductive substrate 140. The semiconductor light emitting device 100 may further include a passivation film (not shown) to cover side surfaces of the light emitting structure.

The light emitting structure 130 may have an unevenness 142 on an upper surface thereof. The rough surface by the uneven surface 142 is very easy to extract the light by lowering the incident angle of the photon incident in the air from the nitride compound semiconductor layer below the critical angle.

The p-type electrode 132 is formed on both sides of the current blocking layer 133. The p-type electrode 132 is responsible for not only an ohmic contact function with the conductive substrate 140 but also a function of an electrode for hole injection. The p-type electrode 135 may be formed of one or more multilayer films including an ohmic metal selected from the group consisting of Ag, Ni, Rh, Pd, Ir, Ru, Mg, Zn, Pt, and Au.

The current blocking layer 133 is formed between the p-type electrode 132 using at least one metal selected from the group consisting of Al, Cr, Ti, and V, which are highly reflective metals. Preferably, the current blocking layer 133 is made of Al. Al has a reflectance of 80% or more. The current blocking layer 133 and the p-type electrode 132 have different materials so that a current can flow toward the p-type electrode 132. The current blocking layer 133 is schottky bonded with the p-type semiconductor layer 125 and is not heat treated. The current blocking layer 133 has the same pattern as the n-type electrode 145. The current blocking layer 133 reflects photons that emit light toward the current blocking layer 133 and intentionally blocks specific paths through which current flows, thereby improving current diffusion efficiency to implement high output, high brightness vertical GaN LEDs. In addition, to improve current spreading while maintaining high reflective film characteristics, absorbing or scattering a part of light generated from a quantum well, such as a SiO ₂ film or a Si ₃ N ₄ film, which is used as a current blocking layer, to reduce the luminance of a device. There is no improvement in light output.

4 is a cross-sectional view showing another semiconductor light emitting device according to the present invention.

Referring to FIG. 4, the semiconductor light emitting device 100 ′ includes a conductive substrate 140, a p-type electrode 132, a current blocking layer 133 ′, and a p-type semiconductor layer 125 formed on the conductive substrate 140. ), An active layer 120, an n-type semiconductor layer 115, and an n-type electrode 145.

In the semiconductor light emitting device 100 described with reference to FIG. 3, a current blocking layer 133 is formed between the p-type electrodes 132. In contrast, in the semiconductor light emitting device 100 ′, the current blocking layer 133 ′ is formed not only between the p-type electrode 132 but also between the conductive substrate 140 under the p-type electrode 132.

5 is a cross-sectional view showing still another semiconductor light emitting device according to the present invention. The semiconductor light emitting device 100 ″ has a metal seed layer or a bonding metal layer 134 between the current blocking layer 133 ′ and the conductive substrate 140 as compared with the semiconductor light emitting device 100 ′ described with reference to FIG. 4. It includes more.

6 is a cross-sectional view illustrating processes according to an embodiment of the method of manufacturing a semiconductor light emitting device according to the present invention. Here, a conventional vertical structure nitride III-V semiconductor compound semiconductor light emitting device manufacturing method is manufactured in plural using a predetermined wafer, Figure 6 shows a method for manufacturing only one light emitting device for convenience of description Doing.

First, as shown in FIG. 6A, the n-type semiconductor layer, the active layer, and the p-type semiconductor layer are sequentially grown on the semiconductor substrate 110 to form the light emitting structure 130, and then the light emitting structure 130. P-type electrode 132 is formed.

 The semiconductor substrate 110 is a substrate suitable for growing a nitride semiconductor single crystal, and may be formed of SiC, zinc oxide (ZnO), gallium nitride (GaN), and aluminum nitride (AlN) in addition to sapphire. have. The n-type semiconductor layer 115, the active layer 120, and the p-type semiconductor layer 125 are formed of the nitride-based III-V semiconductor compound as mentioned above, and are grown through a deposition process such as MOCVD, MBE, or HVPE. Let's do it. The p-type electrode 132 is formed by depositing an ohmic metal as described above on the p-type semiconductor layer 125 and then performing heat treatment (RTA).

Next, referring to FIG. 6 (b), at least one highly reflective metal selected from the group consisting of Al, Cr, Ti, and V is formed between at least the p-type electrode 132 to form a current blocking layer 133 ′. . In the case where a highly reflective metal is formed only between the p-type electrodes 132 using a mask or the like, the current blocking layer 133 of the semiconductor light emitting device 100 described with reference to FIG. 3 can be formed. As shown in FIG. The current blocking layer 133 ′ may be formed when the highly reflective metal is formed on the electrode 132 and on the semiconductor substrate 110. In either case, the process proceeds without the photolithography process and the etching process, which are conventionally performed in forming the current blocking layer.

Next, as shown in FIG. 6C, the conductive substrate 140 is formed on the p-type electrode 132 and the current blocking layer 133 ′. The conductive substrate 140 is an element included in the final semiconductor light emitting device 100 ″, and serves as a support for supporting the light emitting structure 130. In particular, the semiconductor substrate 110 is removed by a laser lift-off process. By attaching the conductive substrate 140, the light emitting structure having a relatively thin thickness can be more easily handled.

In this case, the conductive substrate 140 may directly attach the conductive substrate and the current blocking layer 133 ′ through a wafer bonding process. However, the conductive substrate 140 may be formed through the seed metal layer or the bonding metal layer 134. The conductive substrate 140 may be formed of a material selected from the group consisting of Si, Cu, Ni, Au, W, and Ti. The conductive substrate 140 may be formed on the current blocking layer 133 ′ by a process such as plating, deposition, and sputtering according to the selected material. The seed metal layer 134 may be directly formed of a conductive material. Alternatively, the bonding metal layer 134 made of a eutectic alloy containing Au and Sn as a main component may be attached by pressing / heating.

Next, the semiconductor substrate 110 is removed as shown in Fig. 6D by the laser lift-off process. The semiconductor substrate 110 is separated along the interface between the n-type semiconductor layer 115 and the semiconductor substrate 110 by irradiating a laser, for example, a KrF laser having a wavelength of 248 nm on the back surface of the semiconductor substrate 110. As a result, the n-type semiconductor layer 115 is exposed to the outside. A chemical lift off process may be used instead of the laser lift off process. In the case of using the chemical lift-off process, a sacrificial layer (not shown) may be further provided between the semiconductor substrate 110 and the light emitting structure 130 by wet etching, and an etchant may be selectively removed. The semiconductor substrate 110 is separated.

Then, by using the KOH solution with reference to Figure 6 (e) to generate a roughness so that the concave-convex 142 is formed on the upper surface of the light emitting structure (130). FIG. 6 (f) shows a process of separating chips for each chip, and the n-type electrode 145 is formed on the upper surface of the light emitting structure 130 with reference to FIG. 6 (g). In this case, the n-type electrode 145 is formed on the current blocking layer 133 ′ such that the current blocking layer 133 ′ has the same pattern as the n-type electrode 145.

According to the manufacturing method of the present invention, when forming a current blocking layer using a highly reflective metal, a pattern process for etching is not required, and an etching process is also not necessary. This simplifies the process and reduces production costs.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the technology to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

Claims (8)

delete delete delete delete Sequentially growing an n-type semiconductor layer, an active layer, and a p-type semiconductor layer on the semiconductor substrate;
Depositing an ohmic metal on the p-type semiconductor layer and then performing heat treatment to form a plurality of p-type electrodes;
Forming at least one highly reflective metal selected from the group consisting of Al, Cr, Ti, and V between at least the p-type electrode to form a current blocking layer;
Forming a conductive substrate on the p-type electrode and the current blocking layer;
Removing the semiconductor substrate from the resultant product on which the conductive substrate is formed; And
Forming an n-type electrode on the n-type semiconductor layer,
And the current blocking layer is formed on the entire surface of the p-type electrode and the semiconductor substrate without a photolithography process and an etching process. delete The method of claim 5, wherein the forming of the conductive substrate,
Forming a seed metal layer over the current blocking layer; And
Forming a conductive material on the seed metal layer by any one of plating, deposition and sputtering process. The method of claim 5, wherein the forming of the conductive substrate,
And attaching a conductive substrate to the current blocking layer through a wafer bonding process.

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