Patterned AlN Substrate Structure to Prevent Epitaxial Wafer Warping
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Solution Overview
Problem
Deep ultraviolet LED chips face issues with warping and low efficiency due to epitaxial wafers grown on AlN single crystals, making mass production challenging.
Innovation Solution
A patterned substrate with grooves in the AlN layer and optional dielectric layer is introduced, reducing stress and preventing warping, and combined with annealing to improve crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an epitaxial structure is directly grown on an AlN single crystal, then the LED chip production process is simplified, but the epitaxial wafer warps easily and it is difficult to guarantee efficiency and yield of mass production
Solution Approach 1:
The AlN single crystal substrate is segmented into multiple independent AlN layers separated by grooves. This segmentation allows each AlN layer to independently support the epitaxial structure without transmitting stress across the entire substrate, preventing warping while maintaining process simplicity.
Solution Approach 2:
The grooves act as intermediary elements between the base plate and the epitaxial structure. By introducing these grooves, stress is distributed and managed, serving as a mediator that prevents direct stress transmission that would cause warping, thus improving reliability without significantly complicating the production process.
2Length of stationary object
If the substrate is thinned to reduce stress, then the device size is reduced, but the substrate may fracture during the thinning process
Solution Approach 1:
The substrate is divided into multiple thin AlN layers separated by grooves. This segmentation allows the substrate to be effectively thinned while maintaining strength, as each individual layer remains thin enough to be flexible yet is supported by the segmented structure, preventing fracture during thinning processes.
Solution Approach 2:
The grooves create local variations in the substrate structure, providing different mechanical properties in different regions. The areas with grooves have reduced stress concentration, allowing the substrate to be thinned safely in these regions while maintaining overall structural integrity.
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 solution prevents warping and fractures, enhances crystal quality, and improves the efficiency and yield of deep ultraviolet LED production.
Implementation Method 1
stress in a thinning process of the substrate is reduced
Implementation Method 2
an epitaxial structure grown subsequently is prevented from warping
Data Source
AI summary
Disclosed are a patterned substrate, a semiconductor device and a nanotube structure. The patterned substrate includes, in a vertical direction, a base plate and an AlN layer that are sequentially stacked. The patterned substrate includes, in the vertical direction, a first surface and a second surface that are oppositely arranged, a bottom surface of the base plate is the first surface of the patterned substrate, the second surface of the patterned substrate is a patterned surface, the second surface is provided with a plurality of grooves that are independent of each other in a horizontal direction and are arranged in an array, and at least part of the base plate is left below each of the plurality of grooves. According to the patterned substrate in the present application, a structure of the AlN layer is changed, so that an epitaxial structure grown subsequently is prevented from warping.