SiC Power Device Fabrication via Substrate Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The development of silicon carbide power devices, particularly n-channel IGBTs, is hindered by the poor quality and conductivity of 4H silicon carbide p-type substrates, which limit their ability to operate at high blocking voltages and are prone to conduction losses, whereas p-channel IGBTs face challenges in achieving low on-resistance and high blocking voltage.
Innovation Solution
A method is developed to fabricate silicon carbide power devices by forming a p-type silicon carbide epitaxial layer on an n-type substrate, partially removing the n-type substrate to expose the p-type epitaxial layer, and creating an ohmic contact on the p-type layer, thereby reducing the disadvantages associated with using a p-type substrate, and forming an n-channel silicon carbide DMOSFET structure that converts to an n-channel IGBT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type silicon carbide substrate is used to fabricate n-channel IGBTs, then the device structure can be formed, but the poor quality and conductivity of the substrate limit the blocking voltage capability and increase conduction losses
Solution Approach 1:
The patent extracts and removes the problematic n-type substrate material while preserving the functional p-type epitaxial layer. The n-type substrate is selectively removed through the formed openings to expose the p-type layer, eliminating the substrate quality limitations while maintaining the device structure.
Solution Approach 2:
The device is segmented into distinct functional layers with different conductivity types. The p-type epitaxial layer is separated from the n-type substrate through selective removal, allowing each layer to perform its optimal function without the constraints of the other.
2Reliability
If a p-channel IGBT structure is used, then the blocking voltage can be achieved, but the on-resistance cannot be reduced to low levels
Solution Approach 1:
Instead of using a p-channel structure with p-type substrate, the patent inverts the approach by using an n-channel structure with p-type epitaxial layer formed on n-type substrate. This inversion allows achieving low on-resistance characteristics of n-channel devices while maintaining high blocking voltage capability through the p-n junction configuration.
3Ease of manufacture
If the n-type substrate is completely removed, then the p-type epitaxial layer can be exposed, but the device loses structural support and cannot be fabricated
Solution Approach 1:
The patent applies partial removal of the n-type substrate rather than complete removal. Openings are formed to expose the p-type epitaxial layer in specific regions where contact is needed, while the majority of the substrate remains to provide structural support for the device.
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 enables the production of n-channel silicon carbide IGBTs with lower on-resistance and higher blocking voltage capabilities compared to p-channel counterparts, suitable for high voltage applications, and improves the yield and attractiveness of silicon carbide power devices in electronic systems.
Implementation Method 1
The n-type silicon carbide substrate is partially removed, so as to expose the p-type silicon carbide epitaxial layer
Implementation Method 2
An ohmic contact is formed on at least some of the p-type silicon carbide epitaxial layer that is exposed
Data Source
Figure 1A~1G
Figure 2A~2G
Figure 3A~3G
AI summary
A silicon carbide power device is fabricated by forming a p-type silicon carbide epitaxial layer on an n-type silicon carbide substrate, and forming a silicon carbide power device structure on the p-type silicon carbide epitaxial layer. The n-type silicon carbide substrate is at least partially removed, so as to expose the p-type silicon carbide epitaxial layer. An ohmic contact is formed on at least some of the p-type silicon carbide epitaxial layer that is exposed. By at least partially removing the n-type silicon carbide substrate and forming an ohmic contact on the p-type silicon carbide epitaxial layer, the disadvantages of using a p-type substrate may be reduced or eliminated. Related structures are also described.