Nitride Semiconductor Strain Suppression Layer Warpage Control
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Solution Overview
Problem
The formation of nitride semiconductor elements on silicon substrates using conventional GaN/AlN stacked superlattice layers faces challenges with warpage and substrate fractures, particularly on large-diameter substrates, leading to low yield and productivity issues in power devices.
Innovation Solution
A strain suppression layer is introduced, comprising a first nitride semiconductor layer, a second nitride semiconductor layer with a smaller lattice constant, and a superlattice layer with an average lattice constant between the two, to balance compressive and tensile strain, reducing warpage and increasing the distance between the operation layer and the substrate for enhanced dielectric strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large-diameter Si substrate is used to reduce cost and improve productivity, then substrate cost decreases and productivity increases, but warpage and substrate fractures increase leading to low yield
Solution Approach 1:
The patent divides the strain suppression function into multiple discrete layers: a first spacer layer (GaN), a second spacer layer (AlN), and a superlattice layer with alternating GaN and AlN layers. Each layer segment contributes differently to strain management, allowing the system to handle large-diameter substrates without excessive warpage while maintaining high yield.
Solution Approach 2:
The patent changes the lattice constant parameter by using different nitride semiconductor materials with varying composition ratios. The first spacer layer uses GaN with a larger lattice constant, the second spacer layer uses AlN with a smaller lattice constant, and the superlattice layer uses alternating layers with average lattice constants between the two extremes. This parameter variation enables effective strain suppression on large-diameter Si substrates.
2Stability of the object's composition
If a GaN/AlN stacked superlattice layer is used to suppress strain, then warpage is reduced, but the structure complexity increases
Solution Approach 1:
The strain suppression layer is segmented into three distinct structural components: a first spacer layer, a second spacer layer, and a superlattice layer. This segmentation allows each component to perform its specific function while maintaining overall structural stability and controlling warpage effectively.
Solution Approach 2:
The patent introduces an intermediate layer between the Si substrate and the operation layer that acts as a mediator to manage strain. This intermediate layer includes the spacer layers and superlattice layer, which collectively mediate the strain between the Si substrate and the nitride semiconductor operation layer, reducing warpage without excessive complexity.
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
This configuration effectively reduces warpage and substrate fractures, allowing for the use of large-diameter silicon substrates, improves dielectric strength, and increases productivity, making nitride semiconductor elements suitable for power devices.
Implementation Method 1
a first spacer layer made of a first nitride semiconductor, a second spacer layer formed on and in contact with the first spacer layer, the second spacer layer being made of a second nitride semiconductor smaller in lattice constant than the first nitride semiconductor, and a superlattice layer formed on and in contact with the second spacer layer, the superlattice layer having first layers made of a third nitride semiconductor and second layers made of a fourth nitride semiconductor smaller in lattice constant than the third nitride semiconductor stacked alternately on top of one another
Implementation Method 2
highly concentrated two-dimensional electron gas (2DEG) is generated at the heterointerface between aluminum gallium nitride (AlGaN) and GaN due to the piezoelectric effect
Data Source
AI summary
A nitride semiconductor element includes: a strain suppression layer formed on a silicon substrate via an initial layer; and an operation layer formed on the strain suppression layer. The strain suppression layer includes a first spacer layer, a second spacer layer formed on and in contact with the first spacer layer, and a superlattice layer formed on and in contact with the second spacer layer. The first spacer layer is larger in lattice constant than the second spacer layer. The superlattice layer has first layers and second layers smaller in lattice constant than the first layers stacked alternately on top of one another. The average lattice constant of the superlattice layer is smaller than the lattice constant of the first spacer layer and larger than the lattice constant of the second spacer layer.