SiC MOSFET with Integrated Schottky Diode via Shared Openings
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Solution Overview
Problem
Silicon carbide (SiC) MOSFETs face challenges with high turn-on voltage and switching losses due to wide bandgap, and the integration of a Schottky diode requires additional manufacturing steps and design tolerances, affecting yield and performance.
Innovation Solution
A SiC MOSFET device is integrated with a Schottky diode without an additional mask, featuring separately arranged source and junction openings, and a metal layer structure that forms Ohmic and Schottky contacts, avoiding shorting and improving manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a Schottky diode is externally co-packaged with SiC MOSFET, then switching speed is increased and switching loss is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the Schottky diode and MOSFET into a single integrated device structure. The source opening and junction opening share the same opening structure, allowing the Schottky contact and MOSFET source contact to be formed simultaneously without additional masks or process steps. This integration eliminates the need for external co-packaging while maintaining the performance benefits of having both components in one device.
Solution Approach 2:
The opening structure serves multiple functions: it acts as both the source opening for the MOSFET and the junction opening for the Schottky diode. The same opening is used to form both the Ohmic contact (MOSFET source) and the Schottky contact, making the structure multi-functional and eliminating redundant manufacturing steps.
2Ease of manufacture
If source metal and Schottky metal are adjacent requiring additional layers, then individual fabrication is achieved, but manufacturing process complexity and design rule tolerances increase
Solution Approach 1:
The patent combines the source opening and junction opening into a single opening structure. The first metal layer forms both the MOSFET source contact and the Schottky contact through the same opening, eliminating the need for separate metal layers and additional fabrication steps for individual component fabrication.
Solution Approach 2:
The single opening structure serves dual purposes: it provides the source contact for the MOSFET and the junction contact for the Schottky diode. This multi-functional approach simplifies the manufacturing process by reducing the number of lithography masks and metal deposition steps required.
3Reliability
If greater tolerances are reserved to prevent source metal contact to drift layer, then leakage current is avoided, but effective gate width and current density are reduced
Solution Approach 1:
The patent applies different metal layers with different properties in different locations within the same opening. The first metal layer forms Ohmic contacts with the n+ and p+ regions, while the second metal layer forms the Schottky contact with the drift layer. This local differentiation allows precise control of electrical properties in different regions, preventing leakage while maintaining current density.
Solution Approach 2:
The contact structure is segmented into multiple metal layers: the first metal layer for Ohmic contacts and the second metal layer for the Schottky contact. This segmentation allows independent optimization of each contact type and prevents unwanted electrical interactions between the source metal and drift layer.
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 integration enhances manufacturing yield and reduces switching losses by avoiding shorting issues and optimizing contact formation, leading to improved performance and efficiency in SiC MOSFETs.
Implementation Method 1
The first metal layer is disposed at a bottom of the source openings to form an Ohmic contact with the surface portion of the n+ region and the p+ region
Implementation Method 2
The second metal layer includes a first portion and a second portion. The first portion covers the junction openings and the source openings, is in contact and electrically connected with the first metal layer, and forms a Schottky contact with the surface portion of the JFET region
Data Source
AI summary
A silicon carbide (SiC) semiconductor device having a metal oxide semiconductor field effect transistor (MOSFET) and integrated with an anti-parallelly connected Schottky diode includes: a substrate, an n-drift layer, a plurality of doped regions, a gate dielectric layer, a gate electrode, an inter-layer dielectric layer, a plurality of source openings, a plurality of junction openings, a plurality of gate openings, a first metal layer and a second metal layer. The second metal layer at the junction openings forms the Schottky diode.