Patent Application
20150228861
The present application relates to a method of manufacturing a light-emitting device with a rough surface to improve the reliability thereof.
Generally, the top surface of a light-emitting diode is roughened to reduce total reflection and improve the light extraction efficiency. The process of roughening the top surface includes dry etching and wet etching. Dry etching could control the roughening region precisely, but the cost is higher. The cost of wet etching is lower, but the top surface under the bonding pad is usually laterally etched during the process of wet etching and causes the peeling of the bonding pad easily.
As
A method for manufacturing a light-emitting device, comprising steps of: providing a semiconductor stack; forming an first conductive oxide layer on the semiconductor stack, wherein first conductive oxide layer has a top surface opposite to the semiconductor stack, and the top surface comprises a first region and a second region; forming a first layer contacting the first region of the top surface, wherein the first layer comprises a metal material; providing a first solution; forming a second layer by a reaction between the first solution, the first layer and the first conductive oxide layer; and removing the second layer to reveal the first region.
a to 2f show a method of roughening an oxide layer of a light-emitting device according to first embodiment;
a to 3c show the top view of the patterned metal layer;
a to 4c show the top view of the second oxide layer.
Exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings hereafter. The following embodiments are given by way of illustration to help those skilled in the art fully understand the spirit of the present application. Hence, it should be noted that the present application is not limited to the embodiments herein and can be realized by various forms. Further, the drawings are not precise scale and components may be exaggerated in view of width, height, length, etc. Herein, the similar or identical reference numerals will denote the similar or identical components throughout the drawings.
a to 2f show a method of roughening an oxide layer of a vertical type light-emitting device.
The materials of the first semiconductor layer 12, the active layer 10, and the second semiconductor layer 11 comprise group III-V compound semiconductor, such as gallium phosphide (GaP), gallium arsenide (GaAs), or gallium nitride (GaN). The first semiconductor layer 12, the second semiconductor layer 11, or the active layer 10 may be formed by a known epitaxy method such as metallic-organic chemical vapor deposition (MOCVD) method, a molecular beam epitaxy (MBE) method, or a hydride vapor phase epitaxy (HVPE) method.
The material of the first oxide layer 2a comprises transparent conductive oxide material, such as indium tin oxide (ITO), cadmium tin oxide (CTO), antimony tin oxide, indium zinc oxide (IZO), zinc aluminum oxide, zinc oxide, and zinc tin oxide. The first oxide layer 2a is doped with a first impurity, wherein the first impurity comprises Sn, In, Al, Cd, or W. The first oxide layer 2a has a first transparency which depends on the concentration of the first impurity and the thickness of the first oxide layer 2a, and the first transparency is greater than 80% in the embodiment. The first oxide layer 2a is used for spreading the electrical current from the first pad 21. The first oxide layer 2a has a predetermined thickness such as smaller than 3000 angstroms and can be formed by a evaporation deposition method under chamber conditions of around room temperature, N2 ambient environment, and a pressure between 1×10−4 Torr and 1×10−2 Torr, or preferably around 5×10−3 Torr.
The first pad 3 and the second pad 9 are used for conducting an electrical current into the light-emitting device 100. Each of the first pad 3 and the second pad 9 comprises a bonding portion (not shown) for wire bonding and a conducting portion (not shown) for ohmically contacting the first oxide layer 2a or the substrate 8. In other embodiment, the first pad 3 or the second pad 9 further comprises a mirror portion for reflecting a light emitted from the active layer 10 or an adhesion layer for increasing the adhesion between the first pad 3 and the first oxide layer 2a or between the second pad 9 and the substrate 8.
b to 2e show a process of roughening a pattern region of the top surface 21 without damaging the first pad 3.
c shows the step of providing a first solution 101 and immersing the light-emitting device 100 in the first solution 101. The first solution 101 triggers a chemical reaction of the patterned metal layer 4 and the first oxide layer 2a, such as reduction-oxidation reaction, to dope a second impurity into the first oxide layer 2a to form a second layer 41 on the first region 211 of the top surface 21, as shown in
e shows the step of removing the second layer 41 to reveal the first region 211 by using a second solution, wherein the second solution comprises buffered oxide etching solution (BOE) or phosphoric acid. The BOE is a mixture of a buffering agent, such as the mixture of ammonium fluoride (NH4F) and hydrofluoric acid (HF). The first region 211 is rougher than the second region 212. The top view of the pattern of the first region 211 is the same as the pattern of the patterned metal layer 4 showed in
f shows the step of forming a second oxide layer 2b on the first region 211. The material of the second oxide layer 2b can be the same as or different from that of the first oxide layer 2a. The second oxide layer 2b comprises transparent conductive oxide material, such as indium tin oxide (ITO), cadmium tin oxide (CTO), antimony tin oxide, indium zinc oxide (IZO), zinc aluminum oxide, zinc oxide, and zinc tin oxide. The second oxide layer 2b is used for enhancing the lateral conduction of the electrical current in the first oxide layer 2a in the first region 211. The second oxide layer 2b comprises a second top surface 23, and the first region 211 is rougher than the second top surface 23, but the second top surface 23 is still rougher than the second region 212.
The foregoing description of preferred and other embodiments in the present disclosure is not intended to limit or restrict the scope or applicability of the inventive concepts conceived by the Applicant. In exchange for disclosing the inventive concepts contained herein, the Applicant desires all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
