High Voltage Semiconductor Device With Shallow-Trench Isolation
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Solution Overview
Problem
Conventional high voltage semiconductor devices require additional doping layers to achieve consistent threshold voltages, increasing costs and complexity.
Innovation Solution
The use of an epitaxial layer with specific doping types for low and high voltage wells, along with highly doping regions, forms a high voltage semiconductor device structure that eliminates the need for additional threshold voltage adjust layers by utilizing a highly doped well as the main body region and a lightly doped well as a supporting region, surrounded by a high voltage well, with a shallow-trench isolation structure and gate region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lightly doped well is used as body region to achieve high breakdown voltage, then breakdown voltage is improved, but threshold voltage becomes inconsistent with low voltage devices
Solution Approach 1:
The patent applies local quality by creating different doping regions within the same device structure. Specifically, it forms a first doped region (first conductivity type) in the second doped well (second conductivity type) at the source/body region, while maintaining a lightly doped high voltage well region. This localized doping variation allows the source/body region to exhibit low voltage characteristics (consistent threshold voltage) while the overall device maintains high breakdown voltage capability through the lightly doped high voltage well.
2Reliability
If additional threshold voltage adjust layer is added to ensure consistent threshold voltage, then threshold voltage consistency is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of multiple doped regions to achieve both threshold voltage adjustment and high breakdown voltage capability in a single integrated structure. Instead of adding separate threshold adjustment layers on top of a lightly doped well, the invention combines the threshold adjustment function into the well structure itself by forming a first doped region (first conductivity type) within the second doped well (second conductivity type). This merging eliminates the need for additional separate layers while maintaining both threshold consistency and high breakdown voltage.
Solution Approach 2:
The patent makes the doped well structure multi-functional by having it simultaneously serve as both the threshold voltage adjustment mechanism and the high breakdown voltage structure. The second doped well with the first doped region embedded in it performs dual functions: adjusting the threshold voltage to match low voltage devices while also providing the high breakdown voltage capability needed for high voltage operation. This eliminates the need for separate dedicated threshold adjustment layers.
3Reliability
If additional well with second doping type is added to achieve consistent threshold voltage without threshold adjust layer, then threshold voltage consistency is improved, but device complexity and cost still increase
Solution Approach 1:
The patent merges multiple doped regions into a single integrated well structure. Instead of creating separate first doped wells and second doped wells, the invention forms a first doped region (first conductivity type) within the second doped well (second conductivity type). This merging reduces the total number of discrete well structures from multiple separate wells to a single multi-functional well with embedded doped regions, thereby reducing device complexity and manufacturing cost while maintaining threshold voltage consistency.
Data Source
AI summary
The present disclosure discloses a high voltage semiconductor device and the associated methods of manufacturing. In one embodiment, the high voltage semiconductor device comprises: an epitaxial layer, a first low voltage well formed in the epitaxial layer; a second low voltage well formed in the epitaxial layer; a high voltage well formed in the epitaxial layer, wherein the second low voltage well is surrounded by the high voltage well; a first highly doping region formed in the first low voltage well; a second highly doping region and a third highly doping region formed in the second low voltage well, wherein the third highly doping region is adjacent to the second highly doping region; a field oxide formed in the epitaxial layer as a shallow-trench isolation structure; and a gate region formed on the epitaxial layer.