Trench Gate MOSFET Shielding Structure for Breakdown and Low JFET Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional trench gate MOSFETs fail to fully meet the requirements of power electronic applications in terms of on-state resistance, breakdown voltage, and reliability due to limitations in electric field shielding and current spreading.
Innovation Solution
A semiconductor device with a heavily doped region of reduced width positioned directly below the trench gate, acting as an electric field shielding structure, and a current spreading layer with a laterally gradual doping concentration surrounding the trench and heavily doped region, to enhance breakdown voltage and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional trench gate MOSFET structure is used, then the element size is reduced and parasitic capacitance is reduced, but the breakdown voltage and reliability are insufficient
Solution Approach 1:
The patent applies local quality by creating a heavily doped region with specific doping concentration directly below the trench gate, and a current spreading layer with gradually varying doping concentration surrounding the trench bottom. This localized doping structure provides enhanced electric field shielding and current spreading exactly where needed, improving breakdown voltage and reliability without increasing overall element size.
Solution Approach 2:
The patent changes the doping concentration parameter by implementing a heavily doped region with high doping concentration directly below the trench gate, and a current spreading layer with gradually varying doping concentration. This parameter change optimizes the electric field distribution and current spreading characteristics, thereby improving breakdown voltage while maintaining the compact trench structure.
2Reliability
If a heavily doped region with width equal to trench width is used, then electric field shielding is improved, but junction field effect transistor resistance increases
Solution Approach 1:
The patent applies local quality by creating a heavily doped region with width smaller than the trench width, positioned directly below the trench gate. This localized heavy doping provides effective electric field shielding at the critical region under the gate, while the reduced width minimizes the formation of junction field effect transistors at the sidewalls, thereby reducing the associated resistance.
Solution Approach 2:
The patent inverts the conventional approach by making the heavily doped region narrower than the trench width rather than equal to it. This inverted design counterintuitively improves performance by reducing junction field effect transistor resistance at the sidewalls while maintaining effective electric field shielding through the heavily doped region directly below the gate.
3Ease of manufacture
If current spreading layer with uniform doping concentration is used, then manufacturing is simplified, but breakdown voltage is reduced due to high electric field intensity at trench gate bottom
Solution Approach 1:
The patent changes the doping concentration parameter by implementing a current spreading layer with gradually varying doping concentration rather than uniform doping. The doping concentration increases from the heavily doped region outward, which effectively reduces the electric field intensity at the trench gate bottom and improves breakdown voltage, while the gradual variation is achieved through controlled ion implantation processes.
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 effectively reduces the electric field intensity at the trench gate, improving breakdown voltage and reliability while minimizing junction field effect transistor (JFET) resistance, thereby enhancing the overall performance of the semiconductor device.
Implementation Method 1
a heavily doped region is disposed directly below a trench gate to be an electric field shielding structure
Implementation Method 2
a current spreading layer is disposed to surround the bottom of the trench and the heavily doped region. The current spreading layer has a laterally gradual doping concentration
Data Source
AI summary
A semiconductor device includes a trench in a substrate, a gate electrode in the trench, a source contact region on a first surface of the substrate, a drain contact region on a second surface of the substrate, a heavily doped region directly below the trench, and a current spreading layer in the substrate to surround the bottom of the trench and the heavily doped region. The heavily doped region has a first conductivity type, and the width of the heavily doped region is smaller than the width of the trench in a first direction. The current spreading layer has a second conductivity type and a gradual doping concentration that is gradually increased along the first direction from the heavily doped region to the outside of the current spreading layer.