Field Electrode Trench Geometry for Semiconductor On-Resistance
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Solution Overview
Problem
Power transistors in automotive and industrial electronics face a challenge in achieving a balance between low area-specific on-resistance and high voltage blocking capability, with existing technologies experiencing voltage overshoot and switching losses due to dynamic avalanche effects.
Innovation Solution
The semiconductor device incorporates a field electrode in a field plate trench with a specific extension length and resistivity range, coupled to a source terminal via a contact plug with matching resistivity, which reduces area-specific on-resistance and controls voltage overshoot by using a high resistive material for the field plate without causing homogeneous potential transfer issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If charge compensation using an isolated field-plate or field-electrode is used to reduce area-specific on-resistance, then area-specific on-resistance is reduced, but output charge increases causing voltage overshoot at fast switching
Solution Approach 1:
The field plate trench is designed with non-uniform dimensions where the extension length in the first direction (parallel to main surface) is less than double the extension length in the second direction, and specifically more than half of the second direction's length. This creates localized field distribution that reduces charge compensation effects while maintaining voltage blocking capability, thereby reducing both on-resistance and voltage overshoot simultaneously
Solution Approach 2:
The patent specifies precise dimensional parameters for the field plate trench: the extension length in the first direction is constrained to be less than double and more than half of the extension length in the second direction. By controlling these geometric parameters, the field distribution and charge compensation are optimized to resolve the contradiction between low on-resistance and reduced voltage overshoot
2Length of stationary object
If higher doping of the drift region is used to reduce area-specific on-resistance, then area-specific on-resistance is reduced, but output charge increases causing voltage overshoot
Solution Approach 1:
Instead of uniformly increasing drift region doping, the patent applies localized field control through the anisotropic field plate trench structure. This local field management allows reduced doping levels while maintaining voltage blocking, thereby reducing on-resistance without the harmful side effect of increased output charge and voltage overshoot
Solution Approach 2:
The patent changes the geometric parameters of the field plate trench (extension length ratio between first and second directions) to optimize the electric field distribution. This parameter optimization allows the drift region to operate at lower doping levels while still achieving low on-resistance and controlled switching behavior
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 design reduces switching losses, avoids dynamic avalanche effects, and enables higher switching frequencies while maintaining high voltage blocking capability, thereby improving the trade-off between on-resistance and switching behavior.
Implementation Method 1
The field electrode is insulated from an adjacent drift zone by means of a field dielectric layer
Implementation Method 2
a field plate material of the field electrode has a resistivity in a range from 10^5 to 10^-1 Ohm·cm
Implementation Method 3
The contact plug comprises a contact material having a resistivity in a range from 10^5 to 10^-1 Ohm·cm
Data Source
AI summary
A semiconductor device is manufactured by forming a gate electrode adjacent to a body region in a semiconductor substrate, forming a field plate trench in a main surface of the substrate, the field plate trench having an extension length in a first direction parallel to the main surface, and forming a field electrode and a field dielectric layer in the field plate trench so that the field electrode is insulated from an adjacent drift zone by the field dielectric layer. The extension length of the field plate trench in the first direction is less than double an extension length of the field electrode in a second direction that is perpendicular to the first direction and is parallel to the main surface. The extension length in the first direction is more than half the extension length in the second direction.