KR20090121812A - Method of manufacturing an ultraviolet light emitting device - Google Patents

Abstract

PURPOSE: A method for manufacturing an ultraviolet light emitting device is provided to improve light extraction efficiency by manufacturing the vertical ultraviolet light emitting device. CONSTITUTION: A first conductive semiconductor layer(200), an active layer(300), and a second conductive semiconductor layer(400) are successively formed in an upper side of a first substrate(100). After a second conductive substrate is bonded in the upper side of the second conductive semiconductor layer, the first substrate is separated. A concavo-convex structure is formed in the upper side of the first conductive semiconductor layer separating the fist substrate. An electrode is formed in a part of the first conductive semiconductor layer. The first conductive semiconductor layer has the thickness of 4 to 20 nm.

Description

Method of manufacturing an ultraviolet light emitting device

The present invention relates to a method of manufacturing a light emitting device, and more particularly to a method of manufacturing a vertical ultraviolet light emitting device.

In general, nitrides such as GaN, AlN, InN, and the like have excellent thermal stability and have a direct transition type energy band structure, which has recently attracted much attention as a material for photoelectric devices in the blue and ultraviolet regions. In particular, GaN can be used in high-temperature high-power devices because the energy bandgap is very large at 3.4 eV at room temperature. In addition, GaN can control energy bandgap from 1.9eV (InN) to 3.4eV (GaN), 6.2eV (AlN) in combination with materials such as InN and AlN, and thus has a wide wavelength range from visible light to ultraviolet light. Because of this, the application of the optical device is a very large material.

Here, the ultraviolet light emitting element emits ultraviolet rays having a wavelength of approximately 400 nm or less. Ultraviolet rays are classified into long-wave UVA (400-320nm), medium-wave UVB (320-280nm), and short-wave or germicidal UVC (280nm or less) according to the effects on the human body and the environment. The ultraviolet light emitting device is used for antibacterial, antifouling, deodorizing or purifying by allowing the ultraviolet light to be emitted as it is. In addition, the ultraviolet light emitting element is also used as a light emitting device that emits white light by using a predetermined phosphor, for example, red, green, and blue light emitters.

UV light emitting devices are mainly manufactured by flip chip process. That is, an N-type GaN layer, an active layer having a quantum well structure, and a P-type GaN layer are stacked on the substrate to form a light emitting cell, and the light emitting cell is connected to a separate sub substrate. Here, an N-type electrode and a P-type electrode are formed on the sub-substrate, respectively, and the N-type GaN layer and the P-type GaN layer of the light emitting cell are formed on the N-type electrode and the P-type electrode of the sub substrate by the N-type solder and the P-type solder. Each is connected.

The ultraviolet light emitting device of the conventional flip chip structure has the advantage of high heat dissipation efficiency. However, in the ultraviolet light emitting device having a flip chip structure, a large amount of photons generated in the active layer does not escape to the outside of the light emitting device, and circulates inside, absorbs and disappears. That is, there is a problem that the light extraction efficiency (electricity energy) is converted to light energy and exits to the outside of the device is low.

The present invention provides a method for manufacturing an ultraviolet light emitting device that can improve light extraction efficiency.

The present invention provides a method for manufacturing an ultraviolet light emitting device that can improve the light extraction efficiency by manufacturing an ultraviolet light emitting device in a vertical type.

The present invention provides a method for manufacturing an ultraviolet light emitting device that can form a light emitting surface with an uneven structure to improve brightness and luminous efficiency.

According to one or more exemplary embodiments, a method of manufacturing an ultraviolet light emitting device includes sequentially forming a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on an upper surface of a first substrate; Bonding the conductive second substrate over the second conductive semiconductor layer and separating the first substrate; Forming a concave-convex structure on an upper surface of the first conductive semiconductor layer in which the first substrate is separated; And forming an electrode on at least a portion of the first conductivity type semiconductor layer, wherein the first conductivity type semiconductor layer is formed to a thickness of 4 to 20 nm.

The first conductive semiconductor layer formed on the first substrate includes an undoped semiconductor layer and a doped semiconductor layer.

The uneven structure is formed on the doped semiconductor layer by using a PEC (photoelectrochemical) etching process.

The active layer is formed of a multilayer structure in which an Al _x Ga _{1 - x} N (0 ≦ x ≦ 1) barrier layer and an Al _y Ga _{1 - y} N (0 ≦ _y ≦ 1) (x ≠ y) well layer are alternately stacked. It emits ultraviolet rays of 365 nm or less.

The uneven structure of the first conductive semiconductor layer is formed to a height of about 0.7 to 2㎛.

The doped semiconductor layer is thicker than the undoped semiconductor layer.

According to the present invention, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer are sequentially formed on an insulating substrate, and then a conductive substrate is bonded to the upper portion of the P-type semiconductor layer, and the insulating substrate is separated, and then the upper portion of the N-type semiconductor layer is removed. It is formed in an uneven structure to manufacture a vertical ultraviolet light emitting device.

By manufacturing the ultraviolet light emitting device in the vertical manner as described above it is possible to improve the light extraction efficiency compared to the conventional flip chip structure. In addition, by forming the light emitting surface, for example, the upper portion of the N-type semiconductor layer in a concave-convex structure, brightness and luminous efficiency can be improved. The heat dissipation effect can also be improved by constructing the ultraviolet light emitting element vertically.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and 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 for clarity, and like reference numerals designate like elements.

1 is a cross-sectional view of a vertical ultraviolet light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, a vertical UV light emitting device according to an exemplary embodiment may include a plurality of semiconductor layers sequentially formed on an upper surface of the substrate 100, that is, a P-type semiconductor layer 200, an active layer 300, and an N-type. The semiconductor layer 400 may further include a first electrode 500 formed on the N-type semiconductor layer 400 and a second electrode 600 formed on the substrate 100. In addition, the semiconductor device may further include a reflective layer 250 formed between the substrate 100 and the P-type semiconductor layer 200.

Substrate 100 may be a substrate having a conductive property, such as silicon, germanium, GaAs doped with impurities.

As the P-type semiconductor layer 200, a GaN layer in which P-type impurities are injected is preferably used as a layer for supplying holes to the active layer 300, and more preferably, an AlGaN layer in which P-type impurities are injected. Without being limited to this, various semiconductor material layers may be used. For example, AlInGaN may be used. In addition, the P-type semiconductor layer 200 may be formed of a multilayer film.

The active layer 300 has a predetermined band gap and is a region where quantum wells are made to recombine electrons and holes, and is preferably formed using AlGaN. In this case, since the emission wavelength generated by the combination of the electrons and the holes is changed according to the type of the material forming the active layer 300, it is preferable to adjust the semiconductor material included in the active layer 300 according to the target wavelength. According to an embodiment of the present invention, the active layer 300 may emit Al _x Ga _{1 - x} N (0 ≦ x ≦ 1) barrier layer and Al _y Ga _1-y N ( 0 ≦ y ≦ 1) (x ≠ y) A well layer is formed in a multilayer structure in which alternating layers are stacked. At this time, the Al content of the barrier layer is higher than the Al content of the well layer. In addition, GaN may be used as the well layer. In this case, the AlGaN barrier layer and the GaN well layer may be formed in multiple layers by repeating the inflow and interruption of the Al source.

The N-type semiconductor layer 400 is a layer for supplying electrons to the active layer 300, it is preferable to use an AlGaN layer doped with N-type impurities, without being limited to this may be a material layer of various semiconductor properties. For example, GaN can be used. In addition, the N-type semiconductor layer 400 may be formed of a multilayer film. The N-type semiconductor layer 400 may be formed by stacking an undoped semiconductor layer and a doped semiconductor layer. That is, the N-type semiconductor layer 400 is formed by stacking an undoped semiconductor layer and a doped semiconductor layer from the top of the active layer 300, and the doped semiconductor layer is formed thicker than the undoped semiconductor layer. In addition, the N-type semiconductor layer 400 forms a top, that is, a doped semiconductor layer in an uneven structure to improve the light emission effect. That is, when the N-type semiconductor layer 400 is formed in the concave-convex structure, high brightness and luminous efficiency can be obtained because photons are not reflected by various angles and escape to the outside. The uneven structure may be formed by using a photoelectrochemical (PEC) etching process, and the thickness may be about 0.7 to 2 μm. If the uneven structure is lower than 0.7 mu m, light cannot be extracted, and it is difficult to form the process at 2 mu m or more. In addition, the N-type semiconductor layer 400 may be leaked downward along the valley between the uneven structure when forming the uneven structure, the thickness to secure the height of the uneven structure while preventing the leakage, for example 4 It is formed in the thickness of about -20 micrometers, Preferably it is formed in the thickness of about 4-10 micrometers. When the N-type semiconductor layer 400 is formed to a thickness of 4㎛ or less may leak along the valley between the uneven structure, when formed to a thickness of 20㎛ or more there is a problem that light extraction is difficult. Meanwhile, an N-type cladding layer (not shown) may be further formed between the active layer 300 and the N-type semiconductor layer 400, and the N-type cladding layer may be formed using GaN, AlGaN, or InGaN.

The first electrode 500 and the second electrode 600 are formed in a single layer or multiple layers using a metal material such as Ti, Cr, Au, Al, or an alloy thereof. For example, it may be formed of a stacked structure of Ti and Al or a stacked structure of Ti and Au. The first electrode 500 is formed on the N-type semiconductor layer 400 having an uneven structure, and the second electrode 600 is formed on the substrate 100. That is, when the first electrode 500 is formed in the undoped semiconductor layer of the N-type semiconductor layer 400, the ohmic contact is not easy, so the first electrode 500 is the doped semiconductor of the N-type semiconductor layer 400. It is formed on the uneven structure formed in the layer.

The reflective layer 250 is bonded to the substrate 100 using the conductive adhesive layer 260. The reflective layer 250 is a layer for improving the effective luminance toward the upper surface of the device, and may be formed of a metal having high reflectance. For example, the reflective layer 250 may be formed using Au, Ni, Ag, Al, and alloys thereof.

The conductive adhesive layer 260 may be an alloy that can be used for flip chip bonding, and it is preferable to use a material having a low melting point of about 200 to 300 ° C. and capable of being bonded at low temperatures. For example, the conductive adhesive layer 260 may use a material including at least one of Au—Sn, Sn, In, Au-Ag, and Pb-Sn.

Meanwhile, the above-described material layers may include metal organic chemical vapor deposition (MOCVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and molecular beam growth method. (Molecular Beam Epitaxy; MBE), hydride vapor phase growth (Hydride Vapor Phase Epitaxy; HVPE) and the like formed using a variety of deposition or growth methods.

In the above embodiment, an uneven structure is formed on the light exit surface, that is, the upper portion of the N-type semiconductor layer 400. However, when the substrate 100 is bonded to the N-type semiconductor layer 400 and the light exit surface is the P-type semiconductor layer 200, an uneven structure may be formed on the P-type semiconductor layer 200.

The manufacturing method of the ultraviolet light emitting device according to the exemplary embodiment of the present invention configured as described above will be described with reference to FIGS. 2 (a) to 2 (d).

Referring to FIG. 2A, an N-type semiconductor layer 400, an active layer 300, and a P-type semiconductor layer 200 are sequentially formed on an insulating substrate, for example, a sapphire substrate 10.

The N-type semiconductor layer 400 may be formed of an AlGaN layer doped with N-type impurities and an AlGaN layer doped with impurities. For this purpose, trimethaluminum (TMAl) as an aluminum source, trimethylgallium (TMGa) as a gallium source, and ammonia (NH ₃ ) as a nitrogen source are introduced at a temperature of about 900 to 1000 ° C, and SiH ₄ as an N-type impurity. Or inflow and interruption of SiH ₆ to form a silicon doped AlGaN layer and an undoped AlGaN layer. Meanwhile, the sapphire substrate 10 may be nitrided after thermal cleaning the sapphire substrate 10 before the N-type semiconductor layer 400 is formed on the sapphire substrate 10. The thermal cleaning process is carried out at a temperature of 950-1050 ° C. or slightly higher. After performing the thermal cleaning, a nitrogen source such as ammonia (NH ₃ ) is introduced at a temperature of 700 to 1000 ° C. to nitride the surface of the sapphire substrate 10. Nitriding is a process for facilitating the formation of a nitride film and is selectively performed according to a system or growth conditions.

The active layer 300 is formed on the N-type semiconductor layer 400, and the active layer 40 is formed of, for example, a multi quantum well structure (MQW) composed of an AlGaN layer. That is, the active layer is formed in a structure in which a plurality of AlGaN barriers and AlGaN wells are stacked. To this end, the AlGaN layer is formed by introducing TMAl as an aluminum source, TMGa as a gallium source, and ammonia (NH ₃ ) as a nitrogen source at a temperature of 700 to 850 ° C. At this time, the Al content of the AlGaN barrier and the AlGaN well is changed differently by changing the inflow amount of the Al source. The Al content of the barrier is controlled to be higher than the Al content of the well. In addition, the well may be formed of GaN. In this case, the active layer 400 is formed in a structure in which a plurality of AlGaN barriers and GaN wells are stacked by repeating inflow and interruption of Al.

After the active layer 300 is formed, a gallium source, a nitrogen source, and an aluminum source are introduced in a state where the temperature is maintained at 900 to 1100 ° C to form a P-type AlGaN layer as the P-type semiconductor layer 200.

Referring to FIG. 2B, the reflective layer 250 is formed on the P-type semiconductor layer 200. The reflective layer 250 is formed to improve the effective luminance of the light emitting device, and may be formed using a metal having high reflectance, for example, Au, Ni, Ag, Al, and an alloy thereof. In addition, the reflective layer 250 may form an ohmic contact with other single crystal structures to smoothly conduct current in the vertical direction. The reflective layer 250 can be formed using a conventional sputtering apparatus. The substrate 100 is bonded to the reflective layer 250 using the conductive adhesive layer 260. The substrate 100 may be a conductive substrate that is conductive by doping with impurities. After the conductive adhesive layer 260 is formed on the reflective layer 250, the substrate 100 may be bonded to each other. The conductive adhesive layer 260 may be formed on the substrate 100, and then the substrate 100 and the reflective layer 250 may be formed. You may join.

Referring to FIG. 2C, the sapphire substrate 10 is removed after adhering the substrate 100. The sapphire substrate 10 may be removed by laser melting, mechanical polishing, chemical etching, or the like. However, since the sapphire substrate 100 is very solid as a hexahedral crystal structure of aluminum oxide (Al 2 O 3), the process cost or time may be increased when using a mechanical polishing or chemical etching process. Therefore, a method of separating using mainly the difference of the thermal coefficient of expansion (TCE) of the sapphire substrate 10 and the GaN light emitting structure is mainly used. This representative method is a separation method using a laser beam.

Referring to FIG. 2 (d), the concave-convex structure is formed on the doped semiconductor layer, that is, on the exposed N-type semiconductor layer 400 by removing the Gaffer substrate 10. The uneven structure is formed to a thickness of about 0.7 to 2㎛ using a PEC etching process. By forming the uneven structure, high brightness and luminous efficiency can be obtained because the photons escape to the outside without being reflected by various angle surfaces. Thereafter, the first electrode 500 and the second electrode 600 are formed on the N-type semiconductor layer 400 and the substrate 100.

In addition, triethylgallium (TEGa) may be used as the source of gallium in addition to trimethylgallium (TMGa), and triethylaluminum (TEAl) and trimethyl in addition to trimethyaluminum (TMAl) as the aluminum source. Trimethylaminealuminum (TMAAl) or dimethylethylaminealuminum (DMEAAl) may be used. The nitrogen source may be monomethylhydrazine (MMHy) or dimethylhydrazine (DMHy) in addition to ammonia (NH ₃ ).

Although the technical spirit of the present invention has been described in detail according to the above embodiment, it should be noted that the above embodiment is for the purpose of description and not for the purpose of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

1 is a cross-sectional view of a light emitting device according to an embodiment of the present invention.

2 (a) to 2 (d) is a process flow chart for explaining a method of manufacturing a light emitting device according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100 substrate 200 P-type semiconductor layer

300: active layer 400: N-type semiconductor layer

500: first electrode 600: second electrode

250: reflective layer 260: conductive adhesive layer

Claims (6)

Sequentially forming a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer on the first substrate; Bonding the conductive second substrate over the second conductive semiconductor layer and separating the first substrate; Forming a concave-convex structure on an upper surface of the first conductive semiconductor layer in which the first substrate is separated; And Forming an electrode on at least a portion of the first conductivity type semiconductor layer, The first conductive semiconductor layer is a manufacturing method of the ultraviolet light emitting device to form a thickness of 4 to 20nm. The method of claim 1, wherein the first conductive semiconductor layer formed on the first substrate comprises a doped semiconductor layer and an undoped semiconductor layer. The method of claim 2, wherein the uneven structure is formed on the doped semiconductor layer by using a PEC (photoelectrochemical) etching process. 2. The active layer of claim 1, wherein an Al _x Ga _{1 - x} N (0 ≦ x ≦ 1) barrier layer and an Al _y Ga _{1 - y} N (0 ≦ _y ≦ 1) (x ≠ y) well layer are alternately stacked. A method of manufacturing an ultraviolet light emitting device, which is formed in a multilayered structure to emit ultraviolet rays of 365 nm or less. The method of claim 1, wherein the uneven structure of the first conductive semiconductor layer is formed to a height of about 0.7 to 2 μm. The method of claim 1, wherein the doped semiconductor layer is thicker than the undoped semiconductor layer.

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