Group III Nitride LED Substrate Triangular Convexity
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Solution Overview
Problem
Existing methods for manufacturing Group III nitride semiconductor light-emitting elements face challenges in achieving high internal quantum efficiency and light extraction efficiency due to deformation or deficiency of convex portions on the substrate, leading to reduced light-emitting properties and external appearance issues.
Innovation Solution
A method involving the formation of convex portions on a sapphire substrate using a stepper exposure method with a polygonal reticle, where the convex portions are arranged in an isosceles or equilateral triangular shape, and the substrate is processed to prevent linear convex portions and crystal defects, enhancing the crystallinity and light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If concavity and convexity are formed in the light extraction surface by mechanical or chemical processing, then light extraction efficiency is improved, but damage is caused to the light-emitting layer and internal quantum efficiency decreases
Solution Approach 1:
Instead of forming concavity and convexity on the light extraction surface (top surface), the invention forms them on the light incident surface (bottom surface) where the substrate is located. This inversion of the processing location avoids damaging the light-emitting layer while still achieving light scattering effects to improve extraction efficiency.
Solution Approach 2:
The invention introduces a resin layer as an intermediary between the convex portions on the substrate and the light-emitting layer. This resin layer with refractive index between 1.4 and 1.7 acts as a mediator that enables light scattering without causing mechanical damage to the delicate light-emitting layer, thus resolving the contradiction between improving light extraction and maintaining internal quantum efficiency.
2Manufacturing precision
If concavity and convexity are formed on the substrate surface, then light extraction efficiency is improved, but deformation or deficiency of convex portions occurs leading to reduced productivity
Solution Approach 1:
The invention replaces mechanical or chemical processing methods with a photolithography-based approach using a reticle and stepper exposure method. This allows precise formation of convex portions through photoresist patterning and etching, avoiding deformation and deficiency issues while maintaining high productivity through standardized semiconductor manufacturing processes.
Solution Approach 2:
The invention specifies precise parameter ranges for the convex portions (height h: 0.05-1.0 μm, base width d1: 0.05-1.5 μm, distance d2: 0.5-5.0 times d1) and the resin layer (thickness t1: 0.01-0.5 μm, refractive index: 1.4-1.7) to ensure optimal performance while preventing deformation. These controlled parameters enable consistent manufacturing with high yield.
3Ease of manufacture
If linear convex portions are formed on the substrate, then manufacturing is simplified, but crystal defects occur and external appearance deteriorates
Solution Approach 1:
The invention uses a reticle with asymmetric positioning of convex portion patterns, specifically arranging them in triangular or other non-linear configurations rather than simple linear arrays. This asymmetric arrangement prevents the formation of linear convex portions that cause crystal defects, while still maintaining ease of manufacture through standardized reticle design and photolithography processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in high internal quantum efficiency and light extraction efficiency, improving light-emitting properties and external appearance while maintaining high productivity, leading to the production of Group III nitride semiconductor light-emitting elements with excellent performance.
Implementation Method 1
a patterning process of sequentially forming mask patterns in respective regions of the flat surface using a polygonal reticle having two pairs of parallel opposing ends in a plan view by a stepper exposure method
Implementation Method 2
an etching process of forming the plurality of convex portions by etching the flat surface using the mask patterns
Implementation Method 3
an epitaxial process of epitaxially growing the Group III nitride semiconductor on the main surface of the substrate so as to cover the flat surface and the convex portions
Data Source
AI summary
A method for manufacturing a Group III nitride semiconductor light-emitting element of the invention includes a substrate-processing process of forming a main surface including a flat surface and a convex portion 13 on the substrate 10, an epitaxial process of epitaxially growing an underlying layer on the main surface of the substrate 10 so as to cover the flat surface and the convex portion 13, and an LED lamination process of forming an LED structure by epitaxially growing a Group III nitride semiconductor. In the substrate-processing process, mask patterns 15 are sequentially formed in respective regions R1 and R2 of the flat surface using a polygonal reticle 51 having two pairs of parallel opposing ends in a plan view, by a stepper exposure method, and then the flat surface is etched to dispose and form three arbitrary convex portions 13, which are arranged to be adjacent to each other, in an isosceles triangular shape in a plan view.