Vertical Trench Gate MOSFET Shield Electrode Design
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Solution Overview
Problem
Designing and manufacturing high-density MOSFET devices that achieve low specific on-resistance, optimum switching performance, support voltage scaling, and are cost-effective remains a challenge in semiconductor technology.
Innovation Solution
The method involves forming a semiconductor device with a trench gate structure, using a combination of dielectric and conductive layers to optimize trench dimensions and layer thicknesses, and employing specific etching and deposition techniques to reduce on-resistance and enhance switching performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If device cells are densely packed to increase current carrying capability and reduce on-resistance, then specific on-resistance is reduced, but manufacturing complexity and difficulty increase
Solution Approach 1:
The device is divided into multiple trench gate structures that extend vertically through the semiconductor substrate. Each trench gate acts as an independent cell with its own gate electrode, source region, and drain region. This segmentation allows for high-density packing while maintaining manufacturability through standardized repeating units.
Solution Approach 2:
The invention transitions from planar device architecture to vertical trench gate architecture. The gate electrodes extend downward from the major surface into the substrate, utilizing the vertical dimension to increase device density. This dimensional change allows more device cells to be packed into the same footprint area, reducing specific on-resistance without proportionally increasing manufacturing complexity.
2Productivity
If trench gate structures are used to increase device density, then current carrying capability increases, but manufacturing difficulty increases
Solution Approach 1:
The gate dielectric layer is formed on the trench sidewalls before depositing the gate electrode material. This preliminary formation of the insulating layer simplifies subsequent processing steps and ensures proper electrical isolation is established before conductor deposition, making the overall manufacturing process more manageable despite the vertical structure complexity.
Solution Approach 2:
The gate dielectric layer serves as an intermediary between the gate electrode and the semiconductor substrate. This intermediate layer facilitates the complex trench gate structure by providing electrical isolation and enabling the vertical configuration without direct contact between the gate conductor and the active semiconductor regions, thereby simplifying the manufacturing sequence.
3Area of stationary object
If vertical current flow is implemented in trench gate devices, then device cell density increases, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the geometric parameters of the device structure by introducing vertical trench gates with controlled depth and width. The trench dimensions, gate dielectric thickness, and electrode positioning are precisely controlled through parameter optimization. This allows high device cell density to be achieved while maintaining manufacturable precision levels through standardized dimensional specifications.
Data Source
AI summary
In one embodiment, a vertical insulated-gate field effect transistor includes a shield electrode formed in trench structure within a semiconductor material. A gate electrode is isolated from the semiconductor material using gate insulating layers. Before the shield electrode is formed, spacer layers can be used form shield insulating layers along portions of the trench structure. The shield insulating layers are thicker than the gate insulating layers. In another embodiment, the shield insulating layers have variable thickness.