Shield Gate Trench MOSFET Field Plate Layout for Lateral Depletion
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Solution Overview
Problem
Existing SGT MOSFET devices with a left-right structure face challenges in enhancing depletion capability of the shielding structure with respect to the drift region close to the channel region when reversely biased, particularly due to the complexity of achieving a uniform electric field distribution and high substrate resistance.
Innovation Solution
The introduction of a second field plate conductive material layer filling a first top sub-trench between the source and gate conductive material layers, with a depth greater than the gate conductive material layer, enhances lateral depletion of the drift region close to the channel, improving depletion capability and reducing specific on-resistance without increasing process complexity or costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shielding dielectric layer with varying thickness is used to enhance depletion capability, then the depletion capability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the geometric parameters of the field plate conductive material layer, specifically making its depth greater than that of the gate conductive material layer. This parameter modification enables the field plate to extend deeper into the drift region, enhancing lateral depletion capability without requiring a complex varying thickness shielding dielectric layer structure.
Solution Approach 2:
The patent introduces a vertical dimension element by making the field plate conductive material layer deeper than the gate conductive material layer. This depth difference creates a three-dimensional configuration that enhances the depletion region extension into the drift region, achieving improved depletion capability through dimensional modification rather than complex lateral structure variations.
2Reliability
If the depth of field plate conductive material layer is increased to enhance lateral depletion, then depletion capability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary action by forming the field plate conductive material layer to a predetermined depth that is greater than the gate conductive material layer depth before final device assembly. This pre-established depth relationship ensures that the lateral depletion capability is enhanced from the outset, and the etching process can be controlled to achieve the required depth differential without excessive precision requirements during subsequent manufacturing steps.
3Stability of the object's composition
If a second field plate conductive material layer is added to improve electric field distribution, then electric field uniformity improves, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the field plate function with the existing gate trench structure by forming the field plate conductive material layer within the same gate trench. This consolidation approach allows the field plate to be integrated into the existing manufacturing process flow, achieving improved electric field distribution uniformity without significantly increasing manufacturing process complexity.
Solution Approach 2:
The field plate conductive material layer serves multiple functions: it acts as a shielding structure, extends the depletion region laterally, and improves electric field distribution uniformity. By making this single structural element multi-functional, the patent achieves multiple performance improvements without proportionally increasing device complexity or manufacturing steps.
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 configuration enhances the depletion capability of the drift region near the channel, leading to a more uniform electric field distribution, improved withstand voltage, and reduced specific on-resistance, while simplifying the manufacturing process by eliminating the need for a shielding dielectric layer with varying thickness.
Implementation Method 1
The source field plate and the drift region are laterally depleted, so as to greatly increase the doping concentration of the drift region without reducing the breakdown voltage
Implementation Method 2
The source conductive material layer and the gate conductive material layer are isolated from each other by a gate dielectric layer provided therebetween
Data Source
AI summary
The present application provides an SGT MOSFET device, a gate structure of which is a left-right structure, wherein a second field plate conductive material layer with a depth greater than that of a gate conductive material layer is formed between a source conductive material layer and the gate conductive material layer. When the device is reversely biased, depletion capability with respect to the drift region at a side close to a channel region is enhanced due to the feature that a spacing between the second field plate conductive material layer and the drift region is less than a spacing between the source conductive material layer and the drift region. The present application further provides a method for manufacturing an SGT MOSFET device.