Fabrication method of light emitting diode incorporating substrate surface treatment by laser and light emitting diode fabricated thereby
View Patent ↗The present invention relates to a fabrication method of LEDs incorporating a step of surface-treating a substrate by a laser and an LED fabricated by such a fabrication method. The present invention can use a laser in order to implement finer surface treatment to an LED substrate over the prior art. As a result, the invention can improve the light extraction efficiency of an LED while protecting the substrate from chronic problems of the prior art such as stress or defects induced from chemical etching and/or physical polishing.
1. A method of fabricating Light Emitting Diodes (LEDs), comprising the steps of:
preparing a substrate having opposite first and second sides;
directing a laser beam onto the first side of the substrate to form a first finely roughened structure on the first side of said substrate;
forming an n-doped semiconductor layer, an active layer and a p-semiconductor layer in the recited order on the first finely roughened structure of the first side of the substrate to obtain a resultant structure;
mesa-etching the resultant structure to expose a partial area of the n-doped semiconductor layer;
forming a p-electrode on the p-doped semiconductor layer and an n-electrode on the exposed area of the n-doped semiconductor layer;
polishing the second side of the substrate to reduce the thickness of the substrate after the step of forming the p-electrode and the n-electrode; and
directing a laser beam onto the second side of the substrate to form a second finely roughened structure on the second side of said substrate.
2. The method of claim 1 , wherein the first finely roughened structure is formed by
loading the substrate on a movable pedestal with the first side thereof facing upward,
moving the movable pedestal at a predetermined rate,
emitting the laser beam from a laser source, and
opening a shutter on the path of the laser beam between the laser source and the substrate to form a groove at the movement of the pedestal to a predetermined pitch.
3. The method of claim 1 , wherein the first finely roughened structure is formed by
loading the substrate on a movable pedestal with the first side thereof facing upward,
placing a mask having a number of holes matching the roughened structure above the substrate, and
directing the laser beam from a laser source through the holes of the mask onto the first side of said substrate.
4. The method of claim 1 , wherein the first finely roughened structure is formed by
loading the substrate on a movable pedestal with the first side thereof facing upward, and
moving the pedestal while directing the laser beam onto the first side of the substrate, the laser beam having a diameter less than a width of a groove formed by said laser beam in the first finely roughened structure.
5. The method of claim 1 , wherein the first finely roughened structure is formed by
loading the substrate on a pedestal with the first side thereof facing upward, and
directing the laser beam emitted by a laser source onto the first side of the substrate while moving the laser source, the laser beam having a diameter less than a width of a groove formed by said laser beam in the roughened structure.
6. The method of claim 1 , wherein the substrate is one selected from the group consisting of a sapphire substrate, a SiC substrate, an oxide substrate, and a carbide substrate.
7. The method of claim 1 , wherein the second finely roughened structure is formed after said polishing step.
8. The method of claim 1 , wherein the laser beam that forms the first finely roughened structure is directed substantially perpendicular to the plane of said substrate.
9. The method of claim 1 , wherein the laser beam that forms the second finely roughened structure is directed substantially perpendicular to the plane of said substrate.