Membrane Bridge Nitride Semiconductor Structure for Crack Relief
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Solution Overview
Problem
Nitride semiconductor devices face challenges with high dislocation density and cracking due to lattice mismatch and thermal expansion coefficient differences when grown on silicon substrates, and etching processes lead to leakage currents and property deterioration.
Innovation Solution
A method involving the formation of a sacrificial layer pattern on a substrate, followed by a membrane bridge that is crystallized to match the substrate's crystal structure, allowing a nitride semiconductor layer to be grown with reduced defects and stress relief through cavities and controlled stress application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a nitride semiconductor layer is grown on a silicon substrate, then thermal conductivity is improved and large-diameter film growth is enabled, but dislocation density increases and cracks occur due to lattice mismatch and thermal expansion coefficient differences
Solution Approach 1:
A membrane bridge structure is introduced as an intermediary layer between the silicon substrate and the nitride semiconductor layer. This membrane bridge comprises a first region and a second region that independently contact the substrate, creating a compliant structure that mediates the mechanical and thermal stresses. The membrane bridge reduces dislocation density and prevents cracks by accommodating the lattice mismatch and thermal expansion coefficient differences between the silicon substrate and nitride semiconductor layer.
Solution Approach 2:
The membrane bridge structure changes the mechanical parameters of the system by introducing a compliant layer with different stiffness characteristics. The first and second regions of the membrane bridge create a stress-distributing structure that modifies the stress field distribution, reducing the concentration of dislocations and preventing crack formation while maintaining thermal conductivity benefits.
2Length of moving object
If a nitride semiconductor layer is etched to manufacture small-size devices, then device miniaturization is achieved, but leakage current increases and semiconductor properties deteriorate due to etching damage
Solution Approach 1:
The membrane bridge structure is formed in advance before the nitride semiconductor layer is grown. This preliminary structure provides a pre-configured stress-management system that prevents etching-induced damage from propagating into the bulk material. The membrane bridge acts as a buffer that protects the semiconductor layer during subsequent etching processes, maintaining electrical properties even after miniaturization.
3Ease of manufacture
If a sapphire substrate is used for nitride-based semiconductor devices, then electrical conductivity and manufacturing ease are improved, but cost increases and warpage occurs at high temperature due to low thermal conductivity
Solution Approach 1:
The membrane bridge serves as an intermediary structure that combines the advantages of both sapphire and silicon substrates. By using a thin membrane structure with regions independently contacting the substrate, it achieves the manufacturing ease and electrical properties of sapphire while the underlying silicon substrate provides high thermal conductivity to prevent warpage at high temperatures.
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 reduces defect density, prevents cracking, and maintains high-quality semiconductor properties by growing the nitride semiconductor layer on a compliant membrane bridge, enhancing current injection efficiency and reducing line defects.
Implementation Method 1
crystallizing the membrane bridge such that the membrane bridge and the substrate have a same crystal structure
Implementation Method 2
removing the sacrificial layer pattern from the substrate to form a plurality of cavities defined by the substrate and the membrane bridge
Implementation Method 3
growing a nitride semiconductor layer on the crystallized membrane bridge
Data Source
AI summary
Provided are a semiconductor structure and a method of manufacturing the same. The semiconductor structure includes a substrate, a membrane bridge that defines, with the substrate, a plurality of cavities, and a nitride semiconductor layer arranged on the membrane bridge. The membrane bridge and the substrate have the same crystal structure. The membrane bridge has an upper surface with a constant height with respect to a surface of the substrate.