KR20070056585A - Method of manufacturing iii-nitride compound semiconductor light emitting device - Google Patents

Abstract

A method for manufacturing a third group nitride semiconductor light emitting device is provided to acquire a uniform current density of device by using a vertical type electrode structure and to improve the efficiency of the device by removing a substrate. A plurality of nitride semiconductor layers(20) are formed on a substrate(10). A sacrificial layer(30) is grown on a portion between the nitride semiconductor layers. The plurality of nitride semiconductor layers are separated from the substrate by performing a photo chemical etching process on the sacrificial layer. At this time, the wavelength of light irradiated onto the sacrificial layer is properly controlled.

Description

METHODS OF MANUFACTURING III-NITRIDE COMPOUND SEMICONDUCTOR LIGHT EMITTING DEVICE

1 is a cross-sectional view showing an example of a conventional semiconductor light emitting device;

2 is a plan view of FIG.

3 is a conceptual diagram for a photochemical wet etching method;

4 is a cross-sectional view showing a method for manufacturing a group III nitride semiconductor light emitting device according to the present invention;

5 is a cross-sectional view of a group III nitride semiconductor light emitting device according to the present invention.

The present invention relates to a method for manufacturing a group III nitride semiconductor light emitting device, and more particularly, to a group III nitride semiconductor light emitting device having a vertical structure by removing a substrate and improving external quantum efficiency.

1 and 2 are cross-sectional views and plan views illustrating one example of a conventional semiconductor light emitting device, and a group III nitride semiconductor light emitting device is illustrated, and the semiconductor light emitting device is epitaxially grown on the substrate 100 and the substrate 100. (200), n-type nitride semiconductor layer 300 epitaxially grown on buffer layer 200, active layer 400 epitaxially grown on n-type nitride semiconductor layer 300, p-type nitride semiconductor epitaxially grown on active layer 400 The layer 500, the p-side electrode 600 formed on the p-type nitride semiconductor layer 500, the p-side bonding pad 700, the p-type nitride semiconductor layer 500 and the active layer formed on the p-side electrode 600. 400 includes an n-side electrode 800 formed on the n-type nitride semiconductor layer 301 exposed by mesa etching. The semiconductor light emitting device generates light in the active layer 400 through recombination of electrons and holes, and the generated light exits outside the semiconductor light emitting device to function as a light emitting device.

In general, in the case of a nitride semiconductor light emitting device, sapphire is mainly used as a substrate. Since sapphire does not conduct electricity, electrodes for supplying current are horizontally positioned. At this time, some of the light generated in the active layer escapes to the outside to affect the external quantum efficiency, but a large amount of light is trapped in the sapphire substrate and the nitride semiconductor layer is not being escaped by heat is being dissipated by heat. In addition, since current is applied in the horizontal direction, current density imbalance occurs in the light emitting device, which adversely affects the performance of the device.

Therefore, techniques for removing the sapphire substrate and manufacturing a high efficiency light emitting device having an electrode structure in the vertical direction have been studied. In general, a method using a laser is used to remove the sapphire substrate. When the laser is irradiated to the lower part of the sapphire substrate, the sapphire substrate does not absorb the laser light but transmits it as it is, but the nitride semiconductor layer absorbs the laser light to separate the group III element and the nitrogen element.

Gallium, the main group III element, maintains the liquid phase even at room temperature, so that the sapphire substrate and the nitride semiconductor layer are separated. However, in the method using a laser, high heat is generated when the laser is irradiated, which adversely affects the device, and also the nitride semiconductor layer is broken due to stress between the sapphire substrate and the nitride semiconductor layer.

The present invention is to solve the above problems, in order to emit more light generated in the active layer to the outside of the light emitting device to effectively remove the substrate through the photochemical wet etching method of manufacturing a group III nitride light emitting device of the vertical structure The purpose is to provide.

To this end, the present invention includes a plurality of nitride semiconductor layers which are grown on a substrate and have an active layer that generates light by recombination of electrons and holes, wherein the plurality of nitride semiconductor layers are formed separately from the substrate. In the method of manufacturing a semiconductor light emitting device,

A first step of growing a sacrificial layer between the substrate and the plurality of semiconductor layers; And,

The sacrificial layer is photochemically etched to separate the plurality of nitride semiconductor layers from the substrate. Provides a method of manufacturing a group III nitride semiconductor light emitting device comprising a.

In another aspect, the present invention is characterized in that the sacrificial layer is composed of Al _x In _y Ga _z N (0≤x≤1, 0 <y≤1, 0≤z≤1, x + y + z = 1) Provided is a method of manufacturing a group nitride semiconductor light emitting device.

In another aspect, the present invention provides a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the sacrificial layer further comprises a nitride semiconductor layer on the top and bottom.

In another aspect, the present invention provides a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the sacrificial layer is etched by a photochemical selective etching method.

In another aspect, the present invention provides a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the sacrificial layer is controlled by etching the wavelength of the light irradiated during the photochemical selective etching.

In another aspect, the present invention provides a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the groove is formed by laser scribing, diamond scribing.

In another aspect, the present invention provides a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the upper and lower semiconductor layers of the sacrificial layer has a bandgap energy larger than the bandgap energy of the sacrificial layer.

In another aspect, the present invention provides a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the substrate is one selected from the group consisting of sapphire substrate, Si substrate, SiC substrate, and GaAs substrate.

For the understanding of the present invention, a photochemical wet etching method will be briefly described.

The photochemical wet etching method irradiates light from outside to generate electrons and holes in the semiconductor. At this time, the holes on the surface of the semiconductor are oxidized by chemical solutions such as KOH, NaOH, HCl, H ₃ PO ₄ , H ₂ SO _4, etc., which are later etched by the chemical solution.

Therefore, if light is not irradiated from the outside, electrons and holes are not generated in the semiconductor and etching does not occur. When the energy of light emitted from the outside is greater than or equal to the bandgap energy of the semiconductor, light is absorbed from the semiconductor to form electrons and holes, but when the energy of the light is smaller than the bandgap energy of the semiconductor, the light is absorbed. It is not transmitted.

Therefore, a large selectivity can be obtained by controlling the energy of light applied from the outside (wavelength in other words) and growing the semiconductor by appropriately combining the constituent materials of the semiconductor.

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

3 is a conceptual diagram of a photochemical wet etching method, in which a mercury lamp 1 is generally used as a UV light source. The light emitted from the mercury lamp 1 has various wavelengths, especially short wavelength components of 360 nm or less are the wavelength bands absorbed by GaN. Therefore, if the filter 2 which cuts off the wavelength below 360 nm sufficiently is used, electrons and holes will not be formed in GaN.

Also, In _x Ga _{1- x} N (0 <x≤1), which has a smaller bandgap energy than GaN, absorbs light of 360 nm or more to form electrons and holes, so that etching is rapidly performed by a photochemical wet etching method. Is done.

Therefore, when the wavelength control method is used in the photochemical wet etching, there is a very large etching selectivity between GaN and In _x Ga _1-x N (0 <x≤1).

4 is a cross-sectional view showing a method for manufacturing a group III nitride semiconductor light emitting device according to the present invention, and shows each step in detail. An undoped GaN layer 20 is grown on the sapphire substrate 10 and an In _x Ga _{1- x} N (0 <x≤1) layer 30 used as a sacrificial layer on the undoped GaN layer 20. Grow, and grow a GaN layer 40 doped with n-type impurities on the In _x Ga _{1- x} N (0 <x≤1) layer 30 used as a sacrificial layer, and GaN doped with n-type impurities On the layer 40, an active layer 50 in which electrons and holes meet to generate light is grown, and a GaN layer 60 doped with p-type impurities is grown on the active layer 50. In this case, the In _x Ga _{1- x} N (0 <x ≦ 1) layer 30 used as the sacrificial layer is etched and removed completely during the wet etching of the photochemical. The structure of the Group III nitride semiconductor light emitting device is for the embodiment of the present invention and the present invention is not limited to the above structure.

According to the following procedure, a vertical group III nitride semiconductor light emitting device having the substrate removed is manufactured.

In the first process, the p-side electrode 61 is formed on the GaN layer 60 doped with the p-type impurity. 4A is a cross-sectional view of a light emitting device in which the p-side electrode 61 is formed, and the p-side electrode 61 is nickel, gold, silver, chromium, titanium, platinum, palladium, rhodium, iridium, aluminum, tin, And one selected from the group consisting of ITO, ZnO, AgAl, copper indium oxide (CIO), indium, tantalum, copper, cobalt, iron, ruthenium, zirconium, tungsten, and molybdenum. After forming the p-side electrode 61, the GaN layer 60 doped with the p-type impurity, the active layer 50, and a portion of the GaN layer 40 doped with the n-type impurity are etched and removed.

In the second process, a protective film 70 for protecting the active layer 50 during photochemical wet etching is formed. The protective film 70 uses a material such as SiOx, SiNx, SiON, BCB, Polyimide, or the like. Then, the protective film 70 of the portion necessary for external connection of the p-side electrode 61 is removed.

In a third process, the seed metal layer 80 for the plating 90 is deposited on the substrate, followed by plating 90. FIG. 4C is a cross-sectional view of a device in which the protective film 70 and the plating 90 are formed. Metals used in the plating 90 include nickel, gold, silver, chromium, titanium, platinum, palladium, rhodium, iridium, Aluminum, tin, indium, tantalum, copper, cobalt, iron, ruthenium, zirconium, tungsten, molybdenum, PbSn, AuSn, or any combination thereof. At this time, the thickness of the final plating is not limited to the present invention, but considering the subsequent process, it is appropriate to have a thickness between 10μm and 150μm.

In the fourth step, the back surface of the sapphire substrate 10 is polished. The final thickness after polishing of the sapphire substrate 10 preferably has a value between 10 μm and 100 μm. If the final thickness is less than 10μm has a disadvantage that the substrate is broken in a subsequent process, if the final thickness is more than 100μm it is difficult to cut the sapphire substrate 10 by the scribing method is a subsequent process.

In a fifth process, the groove 100 is formed by scribing to the final chip size for efficient chemical supply. 4D is a cross-sectional view in which the groove 100 is formed on the rear surface of the polished sapphire substrate 10, and scribing may use a laser or a diamond scribing method. In the present invention, a laser is used, and the scribing thickness is scribed up to the sacrificial layer 30. The groove 100 of the process is not limited to the photochemical wet etching method but may be applied to other wet etching methods to enable a smooth supply of the chemical to remove the substrate.

In a sixth step, photochemical wet etching is performed. At this time, the emitted light is filtered by the filter is in the GaN layer is not etched electrons and holes not formed sacrificial layer of In _x Ga ₁ is electron-hole _-x N (0 <x≤1) layer 30 Formed and etched. It is also possible to increase the etching rate by biasing the sample. Figure 4 (E) shows the cross section of the device with the sapphire substrate removed.

In a seventh process, when the sapphire substrate is removed through photochemical wet etching, the GaN layer 40 doped with n-type impurities is exposed, and the n-side electrode 41 is formed on the surface of the n-type impurity-doped GaN layer 40. To form. The n-side electrode 41 is selected from the group consisting of nickel, gold, silver, chromium, titanium, platinum, palladium, rhodium, iridium, aluminum, tin, indium, tantalum, copper, cobalt, iron, ruthenium, zirconium, tungsten and molybdenum Consisting of any one or combination thereof.

In an eighth process, the rough surface 200 is formed on a portion where the n-side electrode 41 is not formed in order to increase the external quantum efficiency. Photochemical method is used to form the rough surface 200 and the wavelength of light irradiated from the outside to form electrons and holes in the GaN layer 40 doped with n-type impurities in contact with the n-side electrode 41 To the filter. After the formation of the rough surface 200, the device is separated using a laser or sawing to manufacture each chip. 4F shows a cross section of the light emitting element in which the n-side electrode 41 and the rough surface 200 are formed.

5 is a cross-sectional view of a group III nitride semiconductor light emitting device according to the present invention, showing a group III nitride semiconductor light emitting device having a vertical structure manufactured by the above process.

The above process is an embodiment according to the present invention, and it is understood that slight modification of the epi structure, addition or subtraction of additional epi layers, addition and deletion of other imposing processes are also included in the present invention.

According to the present invention, the electrode structure in the vertical direction can be formed to make the current density inside the device uniform.

In addition, according to the present invention, it is possible to implement a Group III nitride semiconductor light emitting device having a high efficiency by removing the substrate.

Claims (7)

Fabrication of a Group III nitride semiconductor light emitting device comprising: a plurality of nitride semiconductor layers grown on a substrate, the nitride semiconductor layer having an active layer generating light by recombination of electrons and holes, wherein the plurality of nitride semiconductor layers are separated from the substrate; In the method, A first step of growing a sacrificial layer between the substrate and the plurality of semiconductor layers; And, And a second step in which the sacrificial layer is photochemically etched to separate the plurality of nitride semiconductor layers from the substrate. The method of claim 1, In the first step, the sacrificial layer has a single layer or other composition composed of Al _x In _y Ga _z N (0 ≦ x ≦ 1, 0 <y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) and Al Group III-nitride semiconductor light-emitting device, characterized in that it has a laminated structure consisting of _x In _y Ga _z N (0≤x≤1, 0 <y≤1, 0≤z≤1, x + y + z = 1). Method of preparation. The method of claim 1, In the first step, the sacrificial layer further comprises a nitride semiconductor layer in contact with the upper and lower portions. The method of claim 1, wherein the sacrificial layer is etched by controlling the wavelength of light irradiated during photochemical selective etching. The method of claim 1, In the second step, the substrate is a method of manufacturing a group III nitride semiconductor light emitting device, characterized in that the groove is formed by laser scribing, diamond scribing. 4. The method of claim 3, wherein the nitride semiconductor layer in contact with the upper and lower portions of the sacrificial layer has a bandgap energy greater than the bandgap energy of the sacrificial layer. The method of claim 1, wherein the substrate is one selected from the group consisting of sapphire substrate, Si substrate, SiC substrate, and GaAs substrate.

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