KR20080100058A

KR20080100058A - Manufacturing method of light emitting diode

Info

Publication number: KR20080100058A
Application number: KR20070046143A
Authority: KR
Inventors: 이종희
Original assignee: (주)더리즈
Priority date: 2007-05-11
Filing date: 2007-05-11
Publication date: 2008-11-14
Also published as: KR100873187B1

Abstract

A method of manufacturing a light emitting diode is provide to fabricate a photoresist pattern used as the etching mask without the separate photomask and alignment process and to reduce the process time and process cost, and to prevent the element failure due to the misalignment generation between the electrode and the lower part semiconductor layer pattern. The manufacturing method of the light emitting diode is provided. A step is for forming the first semiconductor layer(110) and the second semiconductor layer(120) on the transparent substrate(100). A step is for forming the semi-transparent electrode(130) on the second semiconductor layer. A step is for coating the photoresist in the entire substrate having the electrode. A step is for irradiating the light ray for exposure to photoresist from the transparent substrate. A step is for selectively removing the exposed semiconductor.

Description

Manufacturing Method of Light Emitting Diode {MANUFACTURING METHOD OF LIGHT EMITTING DIODE}

1 is a perspective view schematically showing a structure of a general light emitting diode.

2A to 2F illustrate a process of patterning a semiconductor layer of a light emitting diode according to a conventional manufacturing method.

3A to 3B illustrate a process of patterning a semiconductor layer of a light emitting diode according to an embodiment of the present invention.

4 illustrates a state in which a series of processes for implementing a semiconductor diode device on a substrate are completed.

5 is a cross-sectional view for comparing a light emitting diode manufactured by a conventional method with a light emitting diode manufactured by an embodiment of the present invention.

The present invention relates to a method for manufacturing a light emitting diode, and more particularly, to a method for forming a semiconductor layer pattern of a light emitting diode.

BACKGROUND ART In general, light emitting diodes used as devices for emitting light have been spotlighted as next-generation lighting replacing incandescent bulbs or fluorescent lamps. In particular, as a blue light emitting diode using gallium nitride (GaN) has been developed, it is possible to realize all colors, and accordingly, demand in various fields is increasing. Light-emitting diodes are considered as next-generation national strategic items because they have the advantages of fast processing speed and low power consumption of semiconductors and environmentally friendly and high energy saving effect.

A general method for mass production of such light emitting diodes is as follows.

1 is a perspective view schematically showing a structure of a general light emitting diode. As shown in FIG. 1, the first semiconductor layer 11 is formed on the prepared substrate 10. The p-n junction surface 20 may be formed on the first semiconductor layer 11 by forming a second semiconductor layer 12 having a polarity opposite to that of the first semiconductor layer 11. That is, when the first semiconductor layer 11 is doped with p-type, the second semiconductor layer 12 doped with n-type is formed on the first semiconductor layer 11, and the first semiconductor layer 11 is n-type. When doped, the second semiconductor layer 12 doped in a p-type may be formed on the first semiconductor layer 11. The first metal electrode 14 is formed on the surface in contact with the second semiconductor layer 12 to flow current through the p-n junction surface 20 formed as described above. In this case, the current distribution transparent electrode 13 may be formed between the upper surface of the second semiconductor layer 12 and the first metal electrode 14 so that the current flows uniformly to the p-n junction surface 20. In addition, in order to form the second metal electrode 15, etching is performed from the second semiconductor layer 12 at the top of the device structure to a part of the first semiconductor layer 11 using a dry etching method. After etching, a pattern is formed using a photolithography process, and the second metal electrode 15 is formed using an electron beam deposition method. A pad (not shown) is then formed for wire contact with an external power source. When current flows through the first metal electrode 14 and the second metal electrode 15 of the light emitting diode manufactured as described above, light is emitted from the p-n junction surface.

In the process of manufacturing the light emitting diode device, a process of patterning to form the second metal electrode 15 after forming the first metal electrode 14 will be described in detail with reference to the drawings.

2A to 2F illustrate a process of selectively patterning a portion of the second semiconductor layer 12 and the first semiconductor layer 11 positioned below the first metal electrode by photolithography.

First, as shown in FIG. 2A, a transparent electrode 13 is formed on a substrate on which semiconductor layers such as the active layer 11a are formed, based on semiconductor layers 11 and 12 having different polarities. As shown in FIG. 2B, a photo-resist 30 is coated on the substrate on which the transparent electrode 13 is formed.

As shown in FIG. 2C, the photomask 40 is placed on the photoresist 30 and the ultraviolet rays 35 are irradiated thereon. Since the mask pattern 41 is formed in the photomask 40 to allow ultraviolet light to pass through only the portion where the transparent electrode 13 is placed, the photoresist 30 of the portion where the transparent electrode 13 is placed. Only UV light is selectively irradiated.

Thereafter, as shown in FIG. 2D, when development is performed using a development solution, only the photoresist of the portion to which ultraviolet rays are irradiated is selectively removed. In this case, the photoresist 30a that is selectively removed and remains is formed in a form including the transparent electrode 13, as shown in the drawing, and therefore, is generally larger in size than the transparent electrode. The reason for this is that a margin should be provided in consideration of misalignment that may occur in the photolithography process, that is, misalignment between the existing patterned layer and the newly formed layer. This space is disadvantageous in terms of density since it eventually results in unnecessary area.

When the dry etching process is performed using the photoresist 30a that is selectively removed and remains as an etching mask, only the semiconductor layer positioned below the transparent electrode 13 is selectively removed as shown in FIG. 2E.

Finally, as shown in FIG. 2F, the remaining photoresist 30a is removed using a chemical solvent.

When the semiconductor layer under the electrode is patterned by such a conventional photolithography process, a separate photomask and alignment are required to form a pattern of the photoresist used as an etching mask, and further, misalignment is prevented. It requires extra space.

The present invention is to solve the above problems, in the patterning of the semiconductor layer of the lower part of the electrode, without a separate photomask and alignment operation, the pattern of the photoresist used as an etching mask can be formed in the electroluminescent device An object of the present invention is to provide a method for producing the same.

Another object of the present invention is to maximize the effective area of the EL device, thereby increasing the manufacturing yield of the device.

In order to achieve the above technical problem, a method of manufacturing a light emitting diode according to the present invention includes: forming a semiconductor layer on a transparent substrate with respect to a predetermined exposure light ray; Forming an electrode opaque to the exposure light beam on the semiconductor layer; Applying a photoresist to the entire surface of the substrate on which the electrode is formed; Irradiating the exposure light beam toward the photoresist from the transparent substrate side; Developing the photoresist to expose the semiconductor layer only in an area except for a portion where the opaque electrode is formed; It provides a method of manufacturing a light emitting diode comprising the step of selectively removing the exposed semiconductor layer.

The method may further include making the opaque electrode transparent by using a heat treatment process after selectively removing the exposed semiconductor layer. Here, the opaque electrode may be made of a material that changes transparent through a heat treatment process, in particular, a material containing InSn.

The said exposure light ray can be an ultraviolet-ray.

The semiconductor layer includes a first semiconductor layer doped with an n-type or p-type impurity and a second semiconductor layer positioned on the first semiconductor layer and doped with an impurity having a polarity opposite to that of the first semiconductor layer. It may be formed of a plurality of layers, wherein the step of selectively removing the exposed semiconductor layer is to remove all of the second semiconductor layer in the thickness direction of the exposed semiconductor layer, and remove only part of the first semiconductor layer in the thickness direction It can be done. The method may further include forming a lower electrode on the partially removed first semiconductor layer.

The transparent substrate may include any one of sapphire, zinc oxide (ZnO), and silicon carbide (SiC), and the semiconductor layer may include any one of GaN, ZnSe, SiC, and AlGaInN.

Hereinafter, a method of manufacturing a light emitting diode according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, area, plate, etc. is over another part, this includes not only the part directly above the other part but also another part in the middle. On the contrary, when a part is just above another part, it means that there is no other part in the middle.

First, as shown in FIG. 3A, the first semiconductor layer 110 and the second semiconductor layer 120 are stacked on the substrate 100 through which exposure light rays such as ultraviolet rays can pass. In an embodiment, a sapphire substrate, a zinc oxide (ZnO) substrate, a silicon carbide (SiC) substrate, or the like may be used as the substrate 100. In particular, the sapphire substrate is excellent in transparency to ultraviolet rays.

Gallium nitride (GaN) -based, ZnSe-based, SiC-based, or AlGaInN-based semiconductors may be used as the first semiconductor layer 110 and the second semiconductor layer 120. The first semiconductor layer 110 may be doped with a p-type or n-type, and the second semiconductor layer 120 may be doped with a polarity opposite to that of the first semiconductor layer 110 to form a p-n junction surface. An active layer 115 may be provided between the first semiconductor layer 110 and the second semiconductor layer 120, and a buffer layer (not shown) may be provided at an interface between the layers. The first semiconductor layer 110, the second semiconductor layer 120, the active layer 115, and the buffer layer disposed therebetween are all formed of the same series or similar series of semiconductor materials, and reduce process cost and time. In addition to the purpose for the purpose of utilizing the inherent characteristics of the thin film, it is preferable that it is formed of a thin film of several μm or less.

An electrode 130 that is opaque to the exposure light ray is formed on the second semiconductor layer 120. The electrode forming process may be formed in the form of a direct electrode on top of the semiconductor layer using a vacuum deposition method using a direct mask, in a more general manner, the electrode material is formed on the semiconductor layer through deposition After that, a method of patterning the desired shape through a photolithography process may be used. Such electrodes are advantageous in that their thickness is larger within the process range possible in terms of maximizing the conductive properties.

Here, the opaque electrode 130 may be a metal-based or oxide-based common electrode material. In the light emitting diode manufactured according to the embodiment of the present invention, in order to increase the luminous efficiency, it is preferable to form the electrode located on the upper portion of the second semiconductor layer 120 transparently. Therefore, it is desirable to ultimately convert the opaque electrode 130 formed above into a transparent electrode. That is, although the electrode 130 located on the upper portion of the second semiconductor layer 120 is formed of an opaque electrode due to the structural characteristics of the embodiment according to the present invention, which will be described later, a subsequent process requiring an opaque electrode is required. After this is completed, it is preferable to convert the opaque electrode 130 into a transparent electrode using a separate process. For this purpose, a metal made of a metal material of tin (Sn), indium (In), or titanium (Ti) or a combination thereof, such as an indium-tin (In-Sn) combination, or the like is first used as an opaque electrode, In a subsequent process, a method of oxidizing them and converting them into oxide-based transparent electrodes may be applied. This subsequent process will be described in detail later.

3B, the photoresist 300 is coated on the entire upper surface of the second semiconductor layer 120 on which the opaque electrode 130 is formed. The photoresist 300 may be a positive photoresist in which only a portion exposed to ultraviolet rays is dissolved and removed when developing with a developer after an exposure process.

Subsequently, as shown in FIG. 3C, the substrate 100 is turned upside down and irradiated with light 350 for exposure such as ultraviolet rays through the substrate 100. As described above, the substrate 100 is transparent to the light for exposure, and since the semiconductor layers 110, 115, and 120 positioned above the substrate are relatively thin, which is less than a few μm, ultraviolet light is emitted to the substrate 100. And the first semiconductor layer 110 and the second semiconductor layer 120 to reach the photoresist 300. However, the opaque electrode 130 is formed of a non-transmissive to light reflective material such as metal does not transmit ultraviolet light. Therefore, only the photoresist 300b of the portion where the electrode is not exposed is exposed, and the photoresist 300a of the portion where the electrode is formed is not exposed. In this case, the substrate 100 may not be turned upside down, and an exposure method may be used in which a light source for exposure is positioned below the substrate and irradiated with ultraviolet rays toward the photoresist.

After the exposure process shown in Figure 3c is similar to the process of the existing invention. That is, when the selectively exposed light emitting diode substrate is developed by immersing it in a developer, as shown in FIG. 3D, only the photoresist 300a positioned above the portion where the electrode 130 is formed remains, leaving the remaining photo. The resist portion (300b of FIG. 3C) is removed. As described above, since the photoresist uses a positive photoresist in which only portions exposed to ultraviolet rays are melted and removed by a developer, the remaining photoresist except for the photoresist 300a positioned on the opaque electrode 130 is removed. The portion 300b causes a chemical reaction with the exposure light such as ultraviolet rays, and the photoresist corresponding to the chemical reaction portion is dissolved and removed by the developer. As a result, the upper surface of the second semiconductor layer 120 except for the portion where the opaque electrode 130 is formed is exposed without being covered with the photoresist.

When the photoresist 300a formed as a pattern is used as an etch mask, the semiconductor layers 110, 115, and 120 of the exposed portions are selectively removed in the thickness direction, thereby forming a state illustrated in FIG. 3E. That is, the semiconductor layer under the portion not covered with the photoresist 300a is vertically removed by using an anisotropic etching method such as a reactive ion etching (RIE) method or a plasma etching method. In this etching process, all of the second semiconductor layer 120 and the active layer 115 under the exposed portion are removed in the thickness direction, and only a portion of the first semiconductor layer 110 is removed in the thickness direction so as to be formed on the substrate 100. It will remain with thickness.

When the etching process is completed, the photoresist 300a used as an etching mask is removed with a chemical solvent. After etching of the semiconductor layer is completed, a state in which the photoresist is removed is illustrated in FIG. 3F.

Thereafter, the opaque electrode 130 may be made transparent by using a heat treatment process. A material such as indium tin (In-Sn), which is used as the material of the opaque electrode 130, is heat treated in an oxygen atmosphere to form an oxide electrode through an oxidation reaction. In particular, in the case of the indium-tin combination, it is converted into indium-tin oxide (ITO) through an oxidation reaction. As is well known to those skilled in the art, indium tin oxide is used as a transparent electrode in semiconductor processes. That is, in a semiconductor device requiring a high light transmittance such as a light emitting element, it is used as a thin light electrode having a high light transmittance formed on the surface of an insulating material having a high light transmittance.

The conditions of the heat treatment process for the formation of the indium-tin oxide is a temperature of 400 ~ 700 degrees, the atmosphere mixed with nitrogen or nitrogen and oxygen, the heat treatment time is about 10 seconds to 10 minutes, the heat treatment process is completed pattern formation Thereafter, it is possible to proceed at any stage after the photoresist used as the etch mask is removed.

The lower electrode 150 is formed on the semiconductor layer partially removed in the process, and the upper electrode 140 is formed on the opaque electrode 130 to cross the semiconductor layers 110, 115, and 120 in the thickness direction. Complete the structure through which current can flow.

The upper electrode 140, which serves as a pad electrode connected to an external power source, is formed of a material having excellent conductivity and excellent adhesion properties with the lower layer, regardless of whether the transparent electrode is transparent or not.

As described above, an exposure process for pattern formation is performed using an opaque electrode, and then the opaque electrode is converted into a transparent electrode, whereby the manufacturing process can be performed without loss of light emission efficiency and current distribution of the light emitting diode. have.

The electroluminescent device thus manufactured can maximize the effective area of the area that actually generates light.

In FIG. 5, (a) is a cross sectional view of a light emitting diode manufactured by a conventional method, and (b) is a sectional view of a light emitting diode manufactured by an embodiment of the present invention. The effective area of the light emitting diode is substantially coincident with the effective areas of the transparent electrodes 13 and 130 on the semiconductor layer, as indicated by the dotted lines in FIG. 5. That is, unlike the light emitting diode of Fig. (A) in which a clearance gap is prepared between the transparent electrode and the semiconductor layers 12 and 120 in preparation for misalignment in photomask operation, the light emitting diode of the embodiment of the present invention In this case, since there is no need to provide a clearance gap for misalignment as described above, the area corresponding to the clearance gap is gained.

When the effective area of the light emitting diode is increased by 8% by the manufacturing method according to the above embodiment, it was confirmed that the light intensity of the light emitting diode element is detected to be more than 5%.

In the above, the present invention has been described with reference to the presently considered embodiments, but the present invention should not be understood as being limited to the above embodiments. Rather, it should be construed as including all modifications of the range which are easily changed by those skilled in the art from the above-described embodiment of the present invention and considered equivalent.

According to the exemplary embodiment of the present invention, in the operation of patterning the semiconductor layer under the electrode after the formation of the upper electrode, the photoresist used as an etching mask can be patterned without a separate photomask and alignment operation. Compared to the process, process time and process cost can be reduced, and device defects due to misalignment between the electrode and the lower semiconductor layer pattern can be prevented.

In addition, it is possible to maximize the effective area of the EL device, thereby increasing the manufacturing yield by reducing the size of the device.

Claims

Forming a semiconductor layer on a substrate that is transparent to light for exposure;

Forming an electrode opaque to the exposure light beam on the semiconductor layer;

Applying a photoresist to the entire surface of the substrate on which the electrode is formed;

Irradiating the exposure light beam toward the photoresist from the transparent substrate side;

Developing the photoresist to expose the semiconductor layer only in an area except for a portion where the opaque electrode is formed;

Selectively removing the exposed semiconductor layer.

The method of claim 1,

After selectively removing the exposed semiconductor layer,

The method of manufacturing a light emitting diode further comprising the step of making the opaque electrode transparent by using a heat treatment process.

The method of claim 2,

The opaque electrode is a method of manufacturing a light emitting diode, characterized in that made of a material that changes transparent through the heat treatment process.

The method of claim 3,

The opaque electrode is a method of manufacturing a light emitting diode, characterized in that made of a material containing indium-tin (In-Sn).

The method of claim 1,

The light emitting diode is a manufacturing method of a light emitting diode, characterized in that the ultraviolet.

The method of claim 1,

The semiconductor layer is formed of a plurality of layers including a first semiconductor layer doped with an n-type or p-type impurity, and a second semiconductor layer positioned on the first semiconductor layer,

And the second semiconductor layer is doped with an impurity having a polarity opposite to that of the first semiconductor layer.

The method of claim 6,

Selectively removing the exposed semiconductor layer is characterized in that all of the second semiconductor layer of the exposed semiconductor layer is removed in the thickness direction, only a portion of the first semiconductor layer in the thickness direction,

And forming a lower electrode on the partially removed first semiconductor layer.

The method of claim 1,

The transparent substrate is a manufacturing method of a light emitting diode comprising any one of sapphire, zinc oxide (ZnO), silicon carbide (SiC).

The method of claim 1,

The semiconductor layer is a manufacturing method of a light emitting diode, characterized in that any one of GaN, ZnSe, SiC, AlGaInN.

The method of claim 4, wherein

The heat treatment step is carried out under the conditions of 400 to 700 ℃ temperature, nitrogen atmosphere or atmosphere mixed with nitrogen and oxygen, and heat treatment time of 10 seconds to 10 minutes.