SiC Trench Gate MOSFET Pillar Field Spreading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vertical trench MOSFETs using silicon carbide experience premature breakdown due to electric field concentration at the gate, resulting in a breakdown voltage lower than the intrinsic threshold voltage, which is inadequate for large-sized and high-capacity applications.
Innovation Solution
The semiconductor device incorporates p-type pillar regions disposed below and spaced apart from trenches in the silicon carbide substrate, spreading the electric field concentration to the junction between the pillar regions and the epitaxial layer, thereby enhancing the breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a vertical trench MOSFET structure is used, then high current capacity and high-speed switching characteristics are achieved, but electric field concentration at the gate bottom causes premature breakdown and reduces breakdown voltage
Solution Approach 1:
The patent introduces p-type pillar regions with specific doping concentrations (1×10^16 to 1×10^18 atoms/cm³) located at the bottom corners of the trench gate, creating localized regions with different electrical properties. These pillar regions modify the electric field distribution locally at critical stress points without changing the overall MOSFET structure, thereby reducing electric field concentration and preventing premature breakdown while maintaining high current capacity.
Solution Approach 2:
The p-type pillar regions are formed during the epitaxial growth process before final device fabrication, preemptively addressing the electric field concentration issue. By incorporating these pillar regions into the semiconductor structure during manufacturing, the design proactively prevents breakdown problems rather than attempting to address them after device operation begins.
2Speed
If the trench gate structure is used to improve switching characteristics, then high-speed operation is achieved, but oxide film breakdown occurs due to electric field concentration
Solution Approach 1:
The p-type pillar regions are strategically positioned at the bottom corners of the trench gate where electric field concentration occurs. These localized doped regions create potential wells that redistribute the electric field, reducing peak field strength at the oxide film interface and preventing breakdown while preserving the high-speed switching characteristics of the trench gate structure.
3Reliability
If silicon carbide material is used instead of silicon, then higher breakdown voltage and higher current capacity are achieved, but manufacturing complexity increases
Solution Approach 1:
The p-type pillar regions are integrated into the existing silicon carbide MOSFET fabrication process during the epitaxial growth stage. By combining the formation of pillar regions with the standard layer deposition process, the patent avoids adding separate manufacturing steps, thereby maintaining high breakdown voltage benefits while minimizing increases in manufacturing 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
The solution significantly increases the breakdown voltage by approximately 27% compared to conventional vertical trench MOSFETs, making it suitable for high-power applications.
Implementation Method 1
a breakdown occurs which can damage an oxide film due to an electric field concentration effect by which an electric field is concentrated at the bottom of a gate
Implementation Method 2
forming a first p type pillar region by first epitaxial growth on the exposed part of the first surface of the n+ type silicon carbide substrate; removing the buffer layer pattern, and then forming an n− type epitaxial layer by second epitaxial growth on the first p type pillar region
Data Source
AI summary
The present inventive concept has been made in an effort to improve the breakdown voltage of a silicon carbide MOSFET using a trench gate.A semiconductor device according to the present inventive concept includes a p type pillar region disposed below the trench, spaced apart from the trench or a first p type pillar region and a second p type pillar region disposed below the trench and corresponding to two corners of the trench.