LDMOS Drift Region Impurity Gradient for On-Resistance Trade-off
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Solution Overview
Problem
LDMOS transistors face a trade-off between low on resistance and sufficient breakdown voltage, with existing solutions increasing on resistance when attempting to improve breakdown voltage, and vice versa.
Innovation Solution
The implementation of a semiconductor device with a drift diffusion region having a higher impurity concentration in the surface region than the substrate inner region, combined with a trench-based insulating film structure, reduces on resistance while maintaining a sufficient breakdown voltage by altering the carrier path and electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick oxide film is formed by LOCOS between the drain region and the end portion of the gate electrode to offset the gate electrode end portion from the drain region, then the breakdown voltage is improved, but the on resistance increases
Solution Approach 1:
The patent applies local quality by creating a drift diffusion region with non-uniform impurity concentration distribution. The surface region has higher impurity concentration than the substrate inner region, optimizing different zones for different functions: the high-concentration surface region reduces on-resistance while the overall drift diffusion structure maintains breakdown voltage.
Solution Approach 2:
The patent changes the impurity concentration parameter within the drift diffusion region. By implanting impurities to create a surface region with higher concentration than the substrate inner region, the patent optimizes the electrical characteristics to achieve both low on-resistance and sufficient breakdown voltage.
2Loss of energy
If the channel resistance component is decreased to reduce on resistance, then the on resistance is reduced, but the breakdown voltage decreases
Solution Approach 1:
The patent creates different impurity concentration zones within the drift diffusion region. The surface region has higher impurity concentration to reduce channel resistance and on-resistance, while the substrate inner region maintains lower concentration to support breakdown voltage requirements.
Solution Approach 2:
The patent transitions from uniform impurity distribution to a vertically stratified impurity concentration profile within the drift diffusion region. This dimensional change in impurity distribution allows simultaneous optimization of on-resistance (surface region) and breakdown voltage (substrate inner region).
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 effectively reduces the on resistance of the semiconductor device while preventing a decrease in breakdown voltage, making it suitable for high-power applications.
Implementation Method 1
a drift diffusion region (10) formed in an upper portion of the semiconductor substrate (1), wherein the drift diffusion region (10) includes a surface region formed on a substrate inner region and below the gate electrode (5) and containing an impurity at a higher concentration than that of the substrate inner region
Implementation Method 2
reduces on resistance while maintaining a sufficient breakdown voltage by altering the carrier path and electric field concentration
Data Source
AI summary
A semiconductor device includes a drift diffusion region of a first conductivity type, a body diffusion region of a second conductivity type, a source diffusion region of the first conductivity type, an insulating film buried in a trench formed in an upper portion of the drift diffusion region and spaced apart from the body diffusion region, a drain diffusion region of the first conductivity type formed in an upper portion of the drift diffusion region and adjacent to the insulating film on the opposite side of the insulating film from the source diffusion region, and a gate electrode formed on a portion of the body diffusion region, the drift diffusion region, and a portion of the insulating film. The drift diffusion region includes a substrate inner region, and a surface region containing an impurity of the first conductivity type at a higher concentration than that of the substrate inner region.