Source Trench Implants Reduce On-Resistance in Power Semiconductors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional trench type power semiconductor devices face challenges in reducing on-state resistance and output capacitance without compromising reverse voltage blocking capability, as increasing source trench depth improves breakdown voltage but increases on-state resistance, and impact ionization at the semiconductor-dielectric interface leads to leakage and breakdown degradation.
Innovation Solution
The implementation of source and termination trench implants of a second conductivity type in the drift region below the trenches, which reduces on-state resistance and output capacitance while maintaining high breakdown voltage by creating a p-n junction that shields the source-to-drain overlap and moves impact ionization away from the dielectric interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the source trench depth is increased to improve breakdown voltage, then the reverse voltage blocking capability is improved, but the on-state resistance increases
Solution Approach 1:
The patent introduces a termination trench implant of opposite conductivity type at the bottom of the source trench, creating a p-n junction that modifies the electric field distribution. This parameter change allows the breakdown voltage to be enhanced through the implant structure rather than solely through increased trench depth, thereby avoiding the penalty of increased on-state resistance that would result from deeper trenches.
2Strength
If the source trench depth is increased to improve breakdown voltage, then the reverse voltage blocking capability is improved, but the output capacitance increases
Solution Approach 1:
The termination trench implant creates a p-n junction that reduces the source-to-drain overlap capacitance by modifying the depletion region characteristics. This allows breakdown voltage improvement through the implant mechanism rather than increased trench depth, thereby avoiding the increase in output capacitance that would result from deeper trenches and larger overlap areas.
3Ease of manufacture
If conventional trench structure is used, then manufacturing is simpler, but impact ionization occurs at the semiconductor-dielectric interface causing leakage and breakdown degradation
Solution Approach 1:
The termination trench implant acts as an intermediary structure at the bottom of the source trench, creating a p-n junction that serves as a buffer zone. This intermediary structure absorbs and redistributes the impact ionization effects away from the vulnerable semiconductor-dielectric interface, preventing the harmful effects of interface damage while maintaining the overall trench structure.
Solution Approach 2:
The patent converts the potentially harmful impact ionization effects into a beneficial mechanism by using the implant-created p-n junction to deliberately control and redirect the high-field regions. The impact ionization that would normally damage the interface is instead channeled through the controlled p-n junction structure, transforming a harmful effect into a protective mechanism that enhances device reliability.
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 on-state resistance by 1% and output capacitance by 10-25% while increasing breakdown voltage by 5%, enhancing the stability and reliability of the power semiconductor device by making it less sensitive to trench depth variations and reducing impact ionization at the dielectric interface.
Implementation Method 1
The implementation of source and termination trench implants of a second conductivity type in the drift region below the trenches, which reduces on-state resistance and output capacitance while maintaining high breakdown voltage by creating a p-n junction that shields the source-to-drain overlap
Implementation Method 2
impact ionization mainly occurs along the bottom and sidewalls of the source trench causing damage at the semiconductor-dielectric interface, which may lead to an increase in drain-to-source leakage and/or breakdown voltage degradation
Data Source
AI summary
A power semiconductor device is disclosed. The power semiconductor device includes a source region in a body region, a gate trench adjacent to the source region, and a source trench electrically coupled to the source region. The source trench includes a source trench conductive filler surrounded by a source trench dielectric liner, and extends into a drift region. The power semiconductor device includes a source trench implant below the source trench and a drain region below the drift region, where the source trench implant has a conductivity type opposite that of the drift region. The power semiconductor device may also include a termination trench adjacent to the source trench, where the termination trench includes a termination trench conductive filler surrounded by a termination trench dielectric liner. The power semiconductor device may also include a termination trench implant below the termination trench.