Light-emitting diode structure and method for manufacturing the same
A light-emitting diode (LED) structure and a method for manufacturing the LED structure are disclosed for promoting the recognition rate of LED chips, wherein a roughness degree of the surface under a first electrode pad of a first conductivity type is made similar to that of the surface under a second electrode pad of a second conductivity type, so that the luster shown from the first electrode pad can be similar to that from the second electrode pad, thus resolving the poor recognition problem of wire-bonding machines caused by different lusters from the first and second electrode pads.
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The present application is based on, and claims priority from, Taiwan Application Serial Number 95150037, filed Dec. 29, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety.
FIELD OF THE INVENTIONThe present invention relates to a light-emitting diode (LED) structure and a method for manufacturing the same, and more particularly, to a LED structure and its manufacturing method for promoting the LED chip recognition rate.
BACKGROUND OF THE INVENTIONReferring to
After a LED structure is formed, it is desirable to perform the subsequent processes of die bonding and wire bonding. The die bonding or wire bonding process mainly uses an image comparison and recognition method to select a LED chip matching a predetermined reference image. At this point, in the conventional LED structure, due to the etching process, the surface roughness of the epitaxial layers (the p-type confining layer 140 and the transparent electrode layer 150) under the p-type electrode pad 160 is different from that of the epitaxial layers (the n-type confining layer 120) under the n-type electrode pad 170, and thus the light scattering and reflected intensities of the p-type electrode pad 160 are inconsistent with those of the n-type electrode pad 170, thus lowering the image recognition rate, leading to the increase of downtime ratio, further causing the occurrence of abnormalities or the decrease of production, and resulting in rough surface textures.
The conventional skill adopts the method of adjusting etch parameters to make the surface roughnesses of the epitaxial layers under these two electrode pads as similar as possible. However, the respective conditions are different for each product lot, so that the conventional method of adjusting the etch parameters is significantly limited and it is difficult to make the surface roughnesses of the epitaxial layers under these two electrode pads reach the same level, thus causing recognition difficulty in the processes of die bonding and wire bonding. Moreover, this conventional skill has to adjust the etch parameter for each individual product lot, and thus is not suitable for use in mass production.
SUMMARY OF THE INVENTIONAn aspect of the present invention is to provide a LED structure and a method for manufacturing the same, thereby making the epitaxial layers under two electrode pads have similar surface roughnesses for forming two electrode pads of similar lusters, thus promoting the image recognition rate and accuracy in the processes of die bonding and wire bonding, further increasing the overall production, decreasing the amount of inferior products, and improving the problem of rough surface textures.
According to an embodiment of the present invention, the LED structure includes a substrate, a first confining layer having a first electrical property, a light-emitting epitaxial structure disposed on a first portion of the first confining layer, a protrusive structure disposed on a second portion of the first confining layer, a n-type electrode pad covering the protrusive structure, and a p-type electrode pad disposed on a second confining layer having a second electrical property. The first confining layer is disposed on the substrate. The light-emitting epitaxial structure includes an active layer disposed on the first portion of the confining layer, and the second confining layer disposed on the active layer, wherein the first electrical property is opposite to the second electrical property. The protrusive structure is spaced from the light-emitting epitaxial structure by a predetermined gap exposing the first confining layer. The material layers forming the protrusive structure are substantially equivalent to the material layers forming the light-emitting epitaxial structure with respect to the material species and arrangement sequence, and the thickness of the material layers forming the protrusive structure is smaller than or equal to the thickness of the material layers forming the light-emitting epitaxial structure. The n-type electrode pad is electrically connected to the first confining layer.
According to an embodiment of the present invention, in a method for manufacturing a light-emitting diode structure, a substrate is provided. Then, a first confining layer having a first electrical property is formed on the substrate. Thereafter, an active layer is formed on the confining layer, and a second confining layer having a second electrical property is formed on the active layer, wherein the first electrical property is opposite to the second electrical property. Then, a photoresist layer is coated on a surface of the second confining layer, wherein the photoresist layer has a predetermined gap. Thereafter, a step is performed for etching the second confining layer and the active layer along the predetermined gap by using the photoresist layer as a mask, and then the photoresist layer is removed so as to form a light-emitting epitaxial structure and a protrusive structure. Then, a n-type electrode pad is fabricated to cover the protrusive structure, wherein the n-type electrode pad is electrically connected to the first confining layer. Thereafter, a p-type electrode pad is formed on a top surface of the light-emitting epitaxial structure.
According to another embodiment of the present invention, the LED structure further comprises a buffer layer disposed between the substrate and the first confining layer.
According to another embodiment of the present invention, the LED structure further comprises a low-temperature buffer layer disposed on the substrate, and a high-temperature buffer layer disposed on the low-temperature buffer layer.
According to another embodiment of the present invention, the LED structure further comprises transparent electrode layers disposed on a top surface of the light-emitting epitaxial structure and on a top surface of the protrusive structure.
According to another embodiment of the present invention, the first electrical property is n type, and the second electrical property is p type.
The foregoing aspects and many of the attendant advantages of this invention are more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
An embodiment of the present invention shown hereinafter is used to resolve the problem of poor image recognition and rough surface textures caused by different levels of surface roughness of the epitaxial layers under two respective electrode pads. The embodiment of the present invention reserves a complete epitaxial structure (protrusive structure) in the area under a n-type electrode pad, and the protrusive structure is substantially equivalent to a light-emitting epitaxial structure under a p-type electrode pad, wherein the thickness of the material layers forming the protrusive structure is smaller than or equal to the thickness of the material layers forming the light-emitting epitaxial structure, thereby making the surface roughnesses of the epitaxial layers under these two electrode pads as similar as possible, thus resolving the problem of rough surface textures. Moreover, a portion of the n-type electrode pad directly contacts a n-type epitaxial layer so as to assure that no change would occur in the electrical properties of the LED. In order to make the illustration of the present invention more explicit, the following description is provided with reference to
As shown in
Thereafter, such as shown in
It can be known from
Further, the protrusive structure also can be composed of a plurality of protrusive structure units.
The aforementioned material species and types applied to the respective material layers are merely used as examples for explanation, and the present invention is not limited thereto.
As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrated of the present invention rather than limiting of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.
Claims
1. A light-emitting diode (LED) structure comprising:
- a substrate;
- a first confining layer having a first electrical property, wherein the first confining layer is disposed on the substrate;
- a light-emitting epitaxial structure disposed on a first portion of the first confining layer, wherein the light-emitting epitaxial structure comprises; an active layer disposed on the first portion of the confining layer; and a second confining layer having a second electrical property, wherein the second confining layer is disposed on the active layer, and the first electrical property is opposite to the second electrical property;
- a protrusive structure disposed on a second portion of the first confining layer, wherein the protrusive structure is spaced from the light-emitting epitaxial structure by a predetermined gap exposing the first confining layer, and the material layers forming the protrusive structure are substantially equivalent to the material layers forming the light-emitting epitaxial structure with respect to material species and arrangement sequence, and a thickness of the material layers forming the protrusive structure is smaller than or equal to a thickness of the material layers forming the light-emitting epitaxial structure;
- a n-type electrode pad covering the protrusive structure, wherein the n-type electrode pad is electrically connected to the first confining layer; and
- a p-type electrode pad disposed on the second confining layer.
2. The light-emitting diode structure according to claim 1, further comprising:
- a buffer layer disposed between the substrate and the first confining layer.
3. The light-emitting diode structure according to claim 2, wherein the buffer layer further comprises:
- a low-temperature buffer layer disposed on the substrate; and
- a high-temperature buffer layer disposed on the low-temperature buffer layer.
4. The light-emitting diode structure according to claim 1, wherein the material forming the substrate is selected from the group consisting of sapphire, ZnO, LiGaO2, spinel, SiC, GaN and silicon.
5. The light-emitting diode structure according to claim 1, wherein the first electrical property is n type, and the second electrical property is p type.
6. The light-emitting diode structure according to claim 1, wherein the protrusive structure is composed of a plurality of protrusive structure units.
7. The light-emitting diode structure according to claim 1, further comprising:
- a transparent electrode layer disposed on a top surface of the light-emitting epitaxial structure, wherein the p-type electrode pad is disposed on the transparent electrode layer.
8. The light-emitting diode structure according to claim 1, further comprising
- a transparent electrode layer disposed on a top surface of the protrusive structure, wherein the n-type electrode pad covers the protrusive structure and the transparent electrode layer.
9. A method for manufacturing a light-emitting diode structure, comprising:
- providing a substrate;
- forming a first confining layer having a first electrical property on the substrate;
- forming an active layer on the confining layer;
- forming a second confining layer having a second electrical property on the active layer, wherein the first electrical property is opposite to the second electrical property;
- coating a photoresist layer on a surface of the second confining layer, wherein the photoresist layer has a predetermined gap;
- etching the second confining layer and the active layer along the predetermined gap by using the photoresist layer as a mask;
- removing the photoresist layer, thereby forming a light-emitting epitaxial structure and a protrusive structure;
- fabricating a n-type electrode pad covering the protrusive structure, wherein the n-type electrode pad is electrically connected to the first confining layer; and
- fabricating a p-type electrode pad on a top surface of the light-emitting epitaxial structure.
10. The method according to claim 9, further comprising:
- forming a buffer layer between the substrate and the first confining layer.
11. The method according to claim 9, further comprising:
- respectively forming a low-temperature buffer layer and a high-temperature buffer layer between the substrate and the first confining layer, wherein the low-temperature buffer layer is disposed on the substrate, and the high-temperature buffer layer is disposed on the low-temperature buffer layer.
12. The method according to claim 9, wherein the material forming the substrate is selected from the group consisting of sapphire, ZnO, LiGaO2, spinel, SiC, GaN and silicon.
13. The method according to claim 9, wherein the first electrical property is n type, and the second electrical property is p type.
14. The method according to claim 9, wherein the protrusive structure is composed of a plurality of protrusive structure units.
15. The method according to claim 9, further comprising:
- forming a transparent electrode layer on a top surface of the light-emitting epitaxial structure; and
- forming the p-type electrode pad on the transparent electrode layer.
16. The method according to claim 9, further comprising:
- forming a transparent electrode layer on a top surface of the protrusive structure; and
- forming the n-type electrode pad covering the protrusive structure and the transparent electrode layer.
Type: Application
Filed: Jan 30, 2007
Publication Date: Jul 3, 2008
Applicant: Epitech Technology Corporation (Tainan County)
Inventors: Cheng-Ta Kuo (Hsinchu City), Kuo-Hui Yu (Chia Yi Hsien), Chao-Hsing Chen (Xinying City), Tsun-Kai Ko (Yuanlin Town), Chi-Ming Huang (Xinshi Shiang), Shih-Wei Yeh (Guanmiau shiang), Chien-Kai Chung (Xinhua Town)
Application Number: 11/699,942
International Classification: H01L 33/00 (20060101); H01L 21/00 (20060101);