Patterned Sapphire Substrate Manufacturing Method

Abstract

A patterned sapphire substrate manufacturing method uses two-section dip etching procedure to improve the lateral etching rate at each etching position, so as to produce a concave-convex pattern composed of a plurality of triangular pyramid structures protruded from a surface onto an upper surface of a sapphire substrate, such that less planar area of the sapphire substrate surface will remain, and a mixed solution of sulfuric acid and phosphoric acid is used in a first dip etching step, and pure phosphoric acid or a mixed solution of sulfuric acid and phosphoric acid is used in a second dip etching step for etching the sapphire substrate to control the inclination of each triangular pyramid structure precisely, and providing a better light extraction rate for later manufactured light emitting diodes.

Description

BACKGROUND OF THE INVENTION(a) Field of the InventionThe present invention relates to a method of patternizing a sapphire substrate surface, and more particularly to an etching method of producing concave-convex patterns onto a sapphire substrate surface effectively up to the manufacturing quality.(b) Description of the Related ArtIn general, a light emitting diode comprises a substrate, a first semiconductor layer, an electrode, a light emitting layer, a second semiconductor layer, an ohmic contact layer, and another electrode, wherein the first semiconductor layer, light emitting layer, second semiconductor layer, ohmic contact layer and electrodes are installed sequentially on the substrate, and the light emitting layer is just covered onto a portion of the first semiconductor layer, and the electrodes are installed onto the first semiconductor layer not covered by the light emitting layer.Sapphire or silicon carbide (SiC) is usually used as a substrate for performing a direct ep...

AI Technical Summary

Benefits of technology

The present invention provides a method for manufacturing a patterned sapphire substrate with improved manufacturing quality. By using a wet etching process, a concave-convex pattern with triangular pyramid structures can be produced on the sapphire substrate surface. This method controls the inclination of each triangular pyramid structure precisely, which helps improving the yield rate of producing devices on the surface of the sapphire substrate at later processes. Additionally, a mixed solution of sulfuric acid and phosphoric acid is used in the first dip etching step, and a pure phosphoric acid or a mixed solution of sulfuric acid and phosphoric acid is used in the second dip etching step for etching the sapphire substrate to control the inclination of each triangular pyramid structure precisely, which helps improving the light extraction rate of the light emitting diode manufactured at a later process.

Problems solved by technology

Since the epitaxial growing surface of the substrate is in a planar shape, its misalignment defect is extended to quantum wells and the crystalline quality is affected when the epitaxy is performed directly on the plane.

Such result only affects the yield rate of the fabricated devices, but also reduces the light emitting efficiency and the electron mobility, and fails to produce light emitting diodes with a higher light emitting efficiency.

Although the aforementioned method can improve the light extraction efficiency by roughening the sapphire substrate surface, the sapphire substrate surface is damaged easily due to a composition change and a lattice distortion occurred at the sapphire substrate surface and caused by ion bombardments occurred during the roughening process.

Furthermore, some mask materials or reacting ions are sputtered and subsided into a certain depth from the substrate surface during the process, so that the quality of epitaxial layer formed at a later stage will be affected.

Similarly, the lattice structure of the sapphire substrate surface is damaged in the mechanical polishing process, and thus the quality of semiconductor layer grown at a later stage will be affected, and the internal quantum efficiency will be lowered.

Therefore, we are unable to predict necessary conditions from a single parameter condition during the process of perceiving the patterned sapphire substrate manufacturing method, but we can do the evaluations indirectly in the complicated manufacturing process to learn the necessary conditions.

Images