Vertical MOSFET Well Doping Gradient for Electric Field Crowding
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Solution Overview
Problem
The reduction of cell size in vertical oriented semiconductor devices, such as MOSFETs, is limited by manufacturing accuracy and space between body implants, leading to challenges in achieving a balance between conduction performance, electric parasitics, and device robustness.
Innovation Solution
The implementation of a lateral doping gradient with monotonic decreasing doping concentration in well regions, achieved through multiple masking steps during the manufacturing process, to reduce electric field crowding and enhance device robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cell size is reduced to increase channel density, then conduction performance is improved, but manufacturing accuracy requirements increase and space between body implants decreases
Solution Approach 1:
The patent applies local quality by creating a lateral doping gradient within the well regions, where the doping concentration varies monotonically decreasing from a first lateral end towards a second lateral end facing the current-accommodating region. This local variation in doping concentration allows optimization of electric field distribution in specific areas without requiring uniform changes across the entire device structure, thereby enabling reduced cell size while maintaining manufacturability.
Solution Approach 2:
The patent implements parameter changes by introducing a lateral doping gradient as a continuous variation in doping concentration rather than uniform doping. This parameter change in the doping profile allows for better control of electric field crowding and reduces the need for excessive spacing between body implants, enabling higher channel density while maintaining acceptable manufacturing precision requirements.
2Productivity
If cell size is reduced to increase channel density, then conduction performance is improved, but device robustness deteriorates due to increased electric field crowding
Solution Approach 1:
The lateral doping gradient creates local quality variations where the doping concentration is higher at the first lateral end and decreases towards the second lateral end facing the current-accommodating region. This local differentiation in doping concentration specifically addresses electric field crowding at critical interfaces while maintaining optimal conditions for conduction in the channel region, thereby improving device robustness without sacrificing conduction performance.
Solution Approach 2:
By changing the doping concentration parameter spatially across the well region, the patent effectively manages electric field distribution. The monotonic decreasing doping concentration from one lateral end to the other reduces electric field crowding at corners and interfaces, enhancing device robustness while allowing reduced cell size for improved conduction performance.
3Productivity
If space between body implants is reduced to increase cell density, then channel density is improved, but electric field crowding increases leading to reduced device robustness
Solution Approach 1:
The patent applies local quality by implementing a lateral doping gradient specifically in the well regions adjacent to the current-accommodating region. The doping concentration varies locally from higher at the first lateral end to lower at the second lateral end, creating optimized electric field distribution at critical interfaces where field crowding occurs, allowing reduced spacing between body implants without excessive field crowding.
Solution Approach 2:
The patent uses parameter changes in the doping concentration profile to mitigate electric field crowding effects. The monotonic decreasing lateral doping concentration in the well regions modifies the electric field distribution, reducing field crowding at corners and interfaces, thereby enabling reduced spacing between body implants while maintaining device robustness.
Data Source
AI summary
A vertical oriented semiconductor device is provided. The semiconductor device includes a semiconductor body having a first major surface, the semiconductor device includes a current-accommodating region of a first conductivity type, well regions of a second conductivity type, at or near the first major surface, the second conductivity type opposite to the first conductivity type, the well regions laterally adjacent sides of the current-accommodating region, the well regions having a first depth into the semiconductor body, a substrate region, provided at a second major surface vertically opposite to the first major surface, the substrate region being of the first conductivity type, and at least one of the well regions has a lateral doping gradient with monotonic decreasing doping concentration, from a higher doping concentration at a first lateral end of the well regions towards a lower doping concentration at a second, opposite, lateral end thereof facing the current-accommodating region.