LDMOS Transistor Uniform Channel Impurity Distribution
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Solution Overview
Problem
Conventional LDMOS transistors have a non-uniform channel impurity concentration, which limits device integration due to a graded junction, preventing the reduction of channel length.
Innovation Solution
The LDMOS transistor features a source region surrounded by a first impurity region and additional impurity regions on either side of the channel, ensuring a uniform impurity distribution, thereby reducing channel length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a graded junction is used in conventional LDMOS transistors, then breakdown voltage is maintained, but channel length cannot be reduced due to non-uniform impurity concentration
Solution Approach 1:
The patent applies local quality by creating distinct impurity concentration zones: a first impurity region with higher concentration surrounding the source region, and a second impurity region with lower concentration adjacent to the drift region. This spatial variation in impurity concentration allows the channel to achieve uniform effective doping where needed while maintaining overall breakdown voltage characteristics.
Solution Approach 2:
The channel impurity distribution is segmented into multiple regions with different impurity concentrations. The first impurity region (higher concentration) and second impurity region (lower concentration) are spatially separated, allowing independent optimization of channel uniformity and breakdown voltage without requiring a continuous graded junction.
2Productivity
If channel length is reduced for device integration, then device integration improves, but breakdown voltage becomes insufficient with non-uniform impurity distribution
Solution Approach 1:
The patent changes the impurity concentration parameters by introducing a dual-region structure with distinct concentration levels. The first impurity region has higher concentration to ensure sufficient breakdown voltage, while the second impurity region has lower concentration to maintain uniform channel characteristics, enabling short channel operation without sacrificing reliability.
Data Source
AI summary
A lateral DMOS transistor having a uniform distribution of channel impurity concentration includes a drift region of a first conductivity; a body of a second conductivity, the body being disposed in the drift region and has a channel thereon; and a source region of the first conductivity, the source region being disposed within the body and having an upper region surrounded by a first impurity region of the first conductivity.