Two-Step Field Plate High-Voltage Transistors
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Solution Overview
Problem
High-voltage transistors face challenges in achieving high breakdown voltages and low on-resistances, which are essential for high-voltage applications but are not adequately addressed by existing technologies.
Innovation Solution
The implementation of a two-step field plate structure in high-voltage transistor devices, where a first film and a second film are used to create a field plate configuration that optimizes the electric field distribution, allowing for higher breakdown voltages while reducing on-resistance, without the need for additional masks in the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional field plate structure is used, then the breakdown voltage is limited, but the on-resistance increases
Solution Approach 1:
The field plate structure is segmented into two distinct films with different thicknesses. The first film has a greater thickness extending from the gate electrode toward the drain region, while the second film has a lesser thickness extending from the first film toward the drain region. This segmentation allows different regions of the field plate to perform different functions: the thicker first film provides higher breakdown voltage near the gate, while the thinner second film reduces on-resistance near the drain, thereby resolving the contradiction between breakdown voltage and on-resistance.
Solution Approach 2:
Different regions of the field plate are given different local properties through the two-film structure. The first film region (with greater thickness) is optimized for electric field control and breakdown voltage near the gate electrode, while the second film region (with lesser thickness) is optimized for reducing on-resistance near the drain region. This local differentiation of properties allows simultaneous optimization of both breakdown voltage and on-resistance in their respective regions.
2Strength
If the field plate thickness is increased to improve breakdown voltage, then the on-resistance increases
Solution Approach 1:
Rather than using a single thick field plate that would increase on-resistance, the structure is segmented into two films of different thicknesses. The first film provides the necessary thickness for breakdown voltage near the gate, while the second film tapers toward the drain to reduce on-resistance. This segmentation resolves the contradiction by allowing thickness variation within the field plate structure itself.
Solution Approach 2:
The field plate structure transitions from a one-dimensional uniform thickness to a two-dimensional varying thickness profile through the combination of two films. The first film establishes a baseline thickness, while the second film adds or subtracts thickness in specific regions to create a graded thickness profile that optimizes both breakdown voltage and on-resistance simultaneously.
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 breakdown voltage and reduces on-resistance, optimizing the performance of high-voltage transistor devices for various applications, including high-frequency switching and DC operations, while maintaining compatibility with standard semiconductor manufacturing processes.
Implementation Method 1
a first film and a second film are used to create a field plate configuration that optimizes the electric field distribution, allowing for higher breakdown voltages while reducing on-resistance
Data Source
AI summary
High-voltage transistor devices with two-step field plate structures and methods of fabricating the transistor devices are provided. An example high voltage transistor device includes: a gate electrode disposed over a substrate between a source region and a drain region, a first film laterally extending from over the gate electrode to over a drift region laterally arranged between the gate electrode and the drain region, a second film laterally extending over a portion of the drift region adjacent to the drain region and away from the gate electrode, and a field plate laterally extending from over the first film to over the second film. A first thickness vertically from a top surface of the gate electrode to a bottom surface of the field plate is smaller than a second thickness vertically from a top surface of the portion of the drift region to the bottom surface of the field plate.