Semiconductor Drain Region with High-Concentration Corner for Reliability
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Solution Overview
Problem
Existing semiconductor devices with shallow trench isolation (STI) insulating films suffer from hot-carrier degradation due to high drain current density near the corner portions, leading to instability in threshold voltage and drain current, which compromises long-term reliability and increases on-resistance.
Innovation Solution
A semiconductor device design featuring a trench with a thick insulating film and a high-concentration drain region, where the impurity concentration is higher in regions away from the corner portions, reducing the drain electric field and on-resistance while maintaining high breakdown voltage, by forming a second drain drift-region with a higher impurity concentration than the first drain drift-region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick insulating film is formed on the drain drift-region to extend its length and achieve higher drain breakdown voltage, then the drain breakdown voltage is improved, but hot-carrier degradation occurs near the corner portion of the insulating film leading to instability in threshold voltage and drain current
Solution Approach 1:
The patent applies local quality by forming a high-concentration drain region specifically at the corner portion of the thick insulating film, while maintaining a low-concentration drain drift-region in other areas. This localized high impurity concentration counteracts the electric field concentration at the corner, suppressing hot-carrier generation and preventing threshold voltage shifts without compromising the overall drain breakdown voltage.
Solution Approach 2:
The patent changes the impurity concentration parameter spatially within the drain region. By creating a high-concentration drain region with significantly higher impurity concentration than the surrounding low-concentration drain drift-region, the patent modifies the electric field distribution to prevent hot-carrier degradation while maintaining the necessary breakdown voltage characteristics.
2Reliability
If the impurity concentration of the drain drift-region is reduced to relax the drain electric field and suppress hot-carrier generation, then hot-carrier degradation is suppressed, but the drain resistance increases making it difficult to reduce on-resistance
Solution Approach 1:
The patent applies local quality by creating a high-concentration drain region with high impurity concentration at the corner portion of the thick insulating film. This localized high-concentration region provides low resistance at the critical area where hot-carrier degradation occurs, while the surrounding low-concentration drain drift-region maintains relaxed electric field conditions to suppress hot-carrier generation overall.
Solution Approach 2:
The high-concentration drain region acts as an intermediary between the thick insulating film and the low-concentration drain drift-region. It mediates the electric field distribution by providing a transition zone that prevents excessive field concentration at the corner while maintaining low resistance, thus balancing both reliability and energy loss considerations.
Data Source
AI summary
A semiconductor device (1) includes a drain region (14) of a first conductivity type which includes a high-concentration drain region (14a), a first drain drift-region (14b), and a second drain drift-region (14c) of the first conductivity type, a source region (15) of the first conductivity type, a body region (16) of a second conductivity type, a gate insulating film (12), a gate electrode (13), and an STI insulating film (11) formed on the drain region (14). The second drain drift-region (14c) is formed from a first position (11f) of the STI insulating film (11) which is away from a first corner portion (11a) by a distance (x1) in a direction of a second corner portion (11b).