Vertical MOSFET High-Resistance Drift Region for Trench Gate Breakdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vertical MOSFETs, the concentration of electric fields at the bottom corner of trench gate electrodes leads to breakdown and degradation of the gate insulating film, resulting in irreversible avalanche breakdown, which limits the device's reuse.
Innovation Solution
Incorporating a high resistance region with a higher resistance value than the drift region, positioned below the gate insulating film, to protect the insulating film from breakdown and enhance the device's reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively thick insulating film is provided to the bottom portion of the trench to prevent breakdown, then the reliability of the gate insulating film is improved, but the device complexity increases and manufacturing precision requirements are worsened
Solution Approach 1:
The patent applies local quality by creating a high resistance region specifically at the bottom corner of the trench where electric field concentration occurs. This region has different electrical properties (higher resistance) compared to the surrounding drift region, providing localized protection against breakdown without requiring a uniformly thick insulating film throughout the entire trench bottom.
Solution Approach 2:
The patent changes the electrical parameter (resistance) of the semiconductor material at the critical bottom corner region by adjusting impurity concentration. This parameter change creates a high resistance region that naturally reduces electric field concentration, replacing the need for geometric changes in insulating film thickness.
2Reliability
If a thick insulating film is provided at the trench bottom to prevent breakdown, then the gate insulating film protection is improved, but the manufacturing precision requirements are worsened
Solution Approach 1:
Instead of requiring precise control of insulating film thickness across the entire trench bottom, the patent applies local quality by modifying the semiconductor material properties only at the critical bottom corner region. This approach eliminates the need for complex multi-layer or variable-thickness insulating film structures that would be difficult to manufacture.
Solution Approach 2:
The patent replaces the mechanical/geometric solution (varying insulating film thickness) with an electrical solution (modifying resistance properties through impurity concentration). This substitution simplifies the manufacturing process by using standard semiconductor doping techniques rather than requiring complex film deposition and thickness control.
3Reliability
If the high resistance region is positioned directly below the gate insulating film, then the protection effect is maximized, but the device complexity increases
Solution Approach 1:
The patent applies local quality by creating a high resistance region with specific spatial characteristics - broader than the trench opening and positioned at the bottom corner. This localized modification provides maximum protection where electric field concentration occurs most severely, while maintaining simplicity in the overall device structure.
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 high resistance region effectively prevents irreversible breakdown, allowing for improved switching performance and extended device lifespan by reducing the risk of gate insulating film degradation.
Implementation Method 1
if a high voltage is applied between a source and a drain of a gate when the gate is turned off, an electric field is concentrated
Implementation Method 2
since the avalanche breakdown generated in the insulating film is an irreversible breakdown phenomenon
Implementation Method 3
A resistance value per unit length of the high resistance region may be higher than that of the drift region
Data Source
AI summary
A vertical MOSFET having a compound semiconductor layer is provided, the vertical MOSFET comprising a gate electrode, a gate insulating film provided between the gate electrode and the compound semiconductor layer, a drift region provided directly in contact with at least a part of the gate insulating film and being a part of the compound semiconductor layer, and a high resistance region provided at least in the drift region, is positioned below at least a part of the gate insulating film, and has a higher resistance value per unit length than that of the drift region.