Direct Wafer-Bonded SiC-Si Layers for Low-Defect Power Devices
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Solution Overview
Problem
The formation of semiconductor devices with SiC substrates is challenged by high defect densities and lattice mismatch issues, leading to stress and strain at heterointerfaces, which affect reliability and increase manufacturing costs, particularly in applications requiring radiation hardness and high breakdown voltage.
Innovation Solution
A method involving the creation of a sacrificial heteroepitaxy interface with inverted pyramids and micropillars to confine defects to sacrificial layers, followed by removal of these layers, resulting in a nearly defect-free SiC substrate using direct wafer bonding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If SiC layer is formed on Si substrate through heteroepitaxy, then high breakdown voltage and high power density are achieved, but defect density increases due to lattice mismatch and CTE difference
Solution Approach 1:
The invention segments the SiC layer into multiple thin epitaxial layers grown on patterned Si substrates with inverted pyramids or micropillars. This segmentation allows defects to be confined to specific regions and removed selectively, while maintaining the high breakdown voltage characteristics of SiC.
Solution Approach 2:
The invention extracts and removes the defective regions (inverted pyramids or micropillars) from the SiC structure after epitaxial growth. By selectively removing these sacrificial structures, defects are eliminated while preserving the high-quality SiC semiconductor regions.
2Reliability
If heteroepitaxy is used to grow SiC on Si substrate, then high breakdown voltage devices are enabled, but stress and strain occur at the heterointerface
Solution Approach 1:
The inverted pyramids or micropillars serve as intermediary structures during the epitaxial growth process. These sacrificial structures manage the stress and strain at the heterointerface during growth, and are subsequently removed to eliminate residual stress in the final device structure.
Solution Approach 2:
The invention changes the physical and geometric parameters of the Si substrate by creating inverted pyramids or micropillars with specific dimensions and patterns. This parameter modification alters the stress distribution during epitaxial growth, enabling high-quality SiC layer formation.
3Ease of manufacture
If conventional heteroepitaxy processes are used, then SiC layers can be grown, but manufacturing costs increase due to defect reduction requirements
Solution Approach 1:
The inverted pyramids or micropillars are designed as disposable sacrificial structures that are removed after serving their purpose during epitaxial growth. This approach uses inexpensive temporary structures to enable the growth of high-quality SiC layers, reducing overall manufacturing costs.
Solution Approach 2:
The invention discards the defective sacrificial structures (inverted pyramids or micropillars) after they have fulfilled their function of enabling high-quality epitaxial growth. This selective discarding eliminates defects while preserving the valuable SiC semiconductor material.
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 approach reduces defect density and manufacturing costs while enhancing the reliability and radiation hardness of SiC substrates, enabling the production of high-breakdown voltage semiconductor devices suitable for aerospace and other demanding applications.
Implementation Method 1
forming the SiC layer on a Si layer produces a heterointerface between two dissimilar materials
Implementation Method 2
method of direct wafer bonding between semiconductor layers
Data Source
AI summary
A semiconductor device has a substrate made of a first semiconductor material. The first semiconductor material is silicon carbide. A first semiconductor layer made of the first semiconductor material is disposed over the substrate. A second semiconductor layer made of a second semiconductor material dissimilar from the first semiconductor material is disposed over the first semiconductor layer. The first semiconductor material is substantially defect-free silicon carbide, and the second semiconductor material is silicon. A semiconductor device is formed in the second semiconductor layer. The semiconductor device can be a power MOSFET, diode, insulated gate bipolar transistor, cluster trench insulated gate bipolar transistor, and thyristor. The second semiconductor layer with the electrical component provides a first portion of a breakdown voltage for the semiconductor device and the first semiconductor layer and substrate provide a second portion of the breakdown voltage for the semiconductor device.