Nitride Semiconductor Multi-Layer Substrate Warp Control
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Solution Overview
Problem
Conventional semiconductor multi-layer substrates face challenges in controlling warp without increasing crack density when the active layer thickness is increased to enhance withstand voltage, leading to increased production costs and leakage currents.
Innovation Solution
A semiconductor multi-layer substrate is designed with a Si substrate, a first warp control layer made of nitride semiconductor, and a second warp control layer with a lower increase in warp per unit thickness, allowing for a thicker active layer to reduce electric field stress and prevent crack formation, while maintaining low production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the active layer thickness is increased to enhance withstand voltage, then the withstand voltage is improved, but the crack density increases
Solution Approach 1:
The buffer layer is segmented into multiple sub-layers with different functions: a first buffer layer for initial warp control and a second buffer layer for refined warp adjustment. This segmentation allows independent optimization of each layer's thickness and composition to control overall warp while supporting thicker active layers without cracks
Solution Approach 2:
The patent changes the composition parameters of the buffer layers, specifically using AlGaN with varying Al compositions (higher Al content in the first buffer layer, lower Al content in the second buffer layer). This parameter variation enables precise control of thermal expansion coefficients and stress distribution, allowing thicker active layers to be grown without exceeding warp thresholds that cause cracking
2Strength
If the active layer thickness is increased to enhance withstand voltage, then the withstand voltage is improved, but the production cost increases
Solution Approach 1:
By changing the Al composition parameters in the buffer layers and optimizing their thickness ratios, the patent achieves effective warp control that enables thicker active layers to be grown in a single batch process. This eliminates the need for multiple batch growths or complex post-growth warp correction steps, thereby reducing production costs while maintaining high withstand voltage
3Strength
If the active layer thickness is increased to enhance withstand voltage, then the withstand voltage is improved, but the leakage current increases
Solution Approach 1:
The segmented buffer layer structure with different Al compositions creates optimized stress distribution and defect management throughout the layer stack. This segmentation prevents the formation of large-scale defects that would increase leakage current, while still allowing the active layer to be thick enough for high withstand voltage operation
Solution Approach 2:
By precisely controlling the Al composition parameters in each buffer layer, the patent optimizes the thermal and mechanical properties of the structure. This parameter optimization reduces thermally-induced leakage paths and defect formation, enabling thick active layers to achieve both high withstand voltage and low leakage current
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 effectively reduces current leakage and crack density, enabling increased active layer thickness without increasing production costs, thus enhancing the semiconductor device's withstand voltage and stability.
Implementation Method 1
a first warp control layer made of a nitride semiconductor grown on the substrate and imparting a predetermined warp to the substrate
Implementation Method 2
a second warp control layer made of a nitride semiconductor, grown on the first warp control layer, of which amount of an increase in a warp per a unit thickness is smaller than an amount of increase the warp per a unit thickness of the first warp control layer
Data Source
AI summary
A semiconductor multi-layer substrate includes a substrate made of Si and a multi-layer semiconductor layer. The multi-layer semiconductor layer includes an active layer made of a nitride semiconductor, a first warp control layer being formed between the substrate and the active layer and giving a predetermined warp to the substrate, and a second warp control layer made of a nitride semiconductor of which amount of an increase in a warp per a unit thickness is smaller than an amount of increase in the warp per a unit thickness of the first warp control layer. A total thickness of the multi-layer semiconductor layer is equal to or larger than 4 μm.