LDMOS Second Region Impurity Profile for Breakdown Voltage
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Solution Overview
Problem
The on-state breakdown voltage of LDMOS transistors in semiconductor devices is limited due to the insufficient suppression of potential rise in the well region, leading to reduced on-state resistance and operational efficiency.
Innovation Solution
The semiconductor device incorporates a second epitaxial layer with a second region having a higher impurity concentration, positioned closer to the buried region, which extends to avoid the lower portion of the drain region, thereby suppressing the potential rise and enhancing the on-state breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the second region is located farther from the first surface than the first region, then the manufacturing process is simplified, but the potential rise of the well region cannot be sufficiently suppressed
Solution Approach 1:
The patent applies local quality by creating the second region with higher impurity concentration specifically in the area beneath the source region, while maintaining lower impurity concentration in other areas. This localized high impurity concentration optimally suppresses the potential rise of the well region without requiring complex overall structural changes, thus resolving the contradiction between manufacturing simplicity and potential suppression capability.
Solution Approach 2:
The patent changes the impurity concentration parameter by introducing the second region with higher impurity concentration than the first region. This parameter change enables effective suppression of the well region potential rise while maintaining a relatively simple structural configuration, thereby resolving the contradiction between ease of manufacture and reliability.
2Reliability
If the impurity concentration of the second region is increased, then the on-state breakdown voltage is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by concentrating the high impurity concentration in the second region specifically beneath the source region, rather than uniformly throughout the structure. This localized approach achieves the necessary on-state breakdown voltage improvement while limiting the scope of precision control requirements to a specific area, thus resolving the contradiction between reliability and manufacturing precision.
3Reliability
If the second region extends below the source region, then the potential rise suppression is enhanced, but the device complexity increases
Solution Approach 1:
The patent applies local quality by extending the second region with higher impurity concentration specifically beneath the source region where it is most needed for suppressing well region potential rise. This targeted approach enhances potential suppression while avoiding unnecessary complexity in other areas of the device, thus resolving the contradiction between reliability and device complexity.
Data Source
AI summary
A semiconductor device includes a semiconductor substrate including a first epitaxial layer having a first surface and a second surface, a second epitaxial layer, a buried region formed across the first epitaxial layer and the second epitaxial layer, and a gate electrode. The second epitaxial layer includes a drain region, a source region, a body region, a drift region, a first region, and a second region. The first region is formed below at least the drain region. The second region has first and second ends in a channel length direction. The first end is located between the body region and the drain region in the channel length direction. The second region extends from the first end toward the second end such that the second end extends below at least the source region. An impurity concentration of the second region is greater than an impurity concentration of the first region.