Field Electrode Transistor Voltage Blocking On-Resistance
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Solution Overview
Problem
Transistor devices, particularly MOS transistors, face a trade-off between on-resistance and voltage blocking capability, where increasing doping concentration or reducing the length of the drift region to decrease on-resistance compromises voltage blocking capability, necessitating an innovative design to enhance voltage blocking without increasing on-resistance.
Innovation Solution
Incorporating a field electrode arrangement adjacent the drift region, dielectrically insulated from both the drift and body regions, with varying widths and dielectric thicknesses to optimize voltage blocking while minimizing on-resistance, allowing for a reduced size and increased doping concentration in the drift region without compromising voltage blocking capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentration of the drift region is increased or the length is decreased to reduce on-resistance, then the on-resistance decreases, but the voltage blocking capability decreases
Solution Approach 1:
The patent divides the drift region into multiple segments by introducing field electrodes at different positions along the drift region. These field electrodes create separate electric field zones that collectively enhance voltage blocking capability while allowing each segment to contribute to current conduction, thereby reducing overall on-resistance without compromising voltage blocking.
Solution Approach 2:
The patent transitions from a one-dimensional drift region structure to a multi-dimensional structure by adding field electrodes that extend in the lateral direction. This dimensional expansion allows the electric field to be distributed and controlled in multiple directions, enabling simultaneous optimization of voltage blocking (vertical dimension) and on-resistance (lateral dimension) through the varying width configuration of field electrodes.
2Reliability
If a field electrode arrangement with larger width adjacent to drift region and smaller width adjacent to body region is used, then voltage blocking capability is enhanced, but device complexity increases
Solution Approach 1:
The patent applies local quality by configuring field electrodes with varying widths at different locations: larger width adjacent to the drift region where voltage blocking is most critical, and smaller width adjacent to the body region where space is constrained. This localized optimization enhances voltage blocking capability exactly where needed while minimizing unnecessary structural complexity in other regions.
Solution Approach 2:
The patent employs asymmetric field electrode design where the width of field electrodes varies along their length, being larger near the drift region and smaller near the body region. This asymmetric configuration optimizes the electric field distribution to enhance voltage blocking capability while avoiding the complexity of symmetric designs, achieving better performance with reduced structural complexity.
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 field electrode arrangement effectively enhances voltage blocking capability while reducing on-resistance, enabling a more compact transistor design with improved performance and increased transistor cell density in a given area.
Implementation Method 1
The field electrode arrangement includes a field electrode, and a field electrode dielectric. The field electrode dielectric dielectrically insulates the field electrode at least from the drift region.
Implementation Method 2
a gate electrode adjacent the body region, and dielectrically insulated from the body region by a gate dielectric
Data Source
AI summary
A method for forming a transistor device includes forming a field electrode arrangement by forming a trench in a first surface of a semiconductor body, forming a protection layer on sidewalls of the trench in an upper trench section, forming a dielectric layer on a bottom of the trench and on sidewall sections uncovered by the protection layer, and forming a field electrode at least on the dielectric layer. The method further includes forming a gate electrode and a gate electrode dielectric horizontally spaced apart from the field electrode arrangement with respect to the first surface, forming a body region adjacent the gate electrode and dielectrically insulated from the gate electrode by the gate dielectric, and forming a source region in the body region.