Super-junction Trench MOSFET with Split Gate and Thick Oxide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Super-junction trench MOSFETs face manufacturing yield instability due to dopant re-diffusion issues and charge imbalance, particularly at lower bias voltages, which complicates the fabrication process and increases costs, and existing solutions do not effectively address these challenges.
Innovation Solution
A super-junction trench MOSFET design featuring a single epitaxial layer with split gate electrodes and a thick oxide layer to minimize charge imbalance, using a single type of gate trenches and reducing the complexity of the fabrication process, thereby enhancing manufacturing capability and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional super-junction trench MOSFET uses p type and n type column structures arranged in parallel, then breakdown voltage and specific Rds are improved, but manufacturing yield becomes unstable due to dopant re-diffusion and charge imbalance
Solution Approach 1:
The patent extracts and eliminates the problematic p type column structure from the super-junction design. Instead of using both p type and n type columns in parallel, the invention uses only n type columns with a modified single-poly gate structure, removing the source of dopant re-diffusion issues and charge imbalance while maintaining the super-junction effect through alternative means
Solution Approach 2:
The patent inverts the conventional approach by using a single-poly gate structure with selective doping rather than dual-poly gates with both p and n columns. The gate structure is modified to achieve the desired electrical characteristics without requiring the problematic column arrangement, effectively solving the manufacturing yield issue
2Reliability
If the column structure width is narrowed to reduce specific Rds, then Rds performance is improved, but charge imbalance and dopant re-diffusion issues become more pronounced
Solution Approach 1:
The patent removes the p type columns that cause charge imbalance issues. By using only n type columns with a modified gate structure, the invention achieves low specific Rds without the sensitivity to charge imbalance that plagues narrower column designs in conventional super-junction devices
Solution Approach 2:
The patent changes the gate structure parameters and doping configuration to achieve the desired electrical characteristics. By modifying the single-poly gate structure and doping profile, the invention maintains low specific Rds performance without requiring narrow column widths that would exacerbate charge imbalance issues
3Reliability
If dual-poly gate structures with thick oxides are used to reduce charge imbalance, then charge balance is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The patent extracts and eliminates the need for dual-poly gate structures by achieving charge balance through a modified single-poly gate design. This simplifies the device structure and reduces fabrication complexity while maintaining the charge balance benefits
Solution Approach 2:
The patent merges the functions of multiple gate polysilicon layers into a single-poly gate structure with modified doping and geometry. This consolidation achieves the same electrical performance with reduced structural complexity and lower fabrication costs
4Reliability
If multiple epitaxial layers with different doping concentrations are used, then breakdown voltage is improved, but fabrication process complexity increases
Solution Approach 1:
The patent achieves high breakdown voltage by optimizing the doping concentration and profile within a single epitaxial layer rather than using multiple layers. This approach maintains the electrical performance benefits while significantly simplifying the fabrication process
Data Source
AI summary
A super-junction trench MOSFET with Resurf Stepped Oxide and split gate electrodes is disclosed. The inventive structure can apply additional freedom for better optimization of device performance and manufacturing capability by tuning thick oxide thickness to minimize influence of charge imbalance, trapped charges, etc. Furthermore, the fabrication method can be implemented more reliably with lower cost.