Multi-Zone Drain Well LDMOS for Breakdown Voltage and Kirk Effect
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Solution Overview
Problem
LDMOS devices face challenges in maintaining high breakdown voltage and resistance to the Kirk effect due to shrinking device dimensions, which lead to faster switching times but decreased breakdown voltages and increased susceptibility to base pushout.
Innovation Solution
The implementation of a drain well with multiple concentration zones of dopant, where the dopant concentration gradually increases from the first zone to the fourth zone, helps maintain a smaller channel length while preserving breakdown voltage. This design also increases the separation between dopant zones at the substrate surface, enhancing resistance to the Kirk effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If device dimensions are shrunk to achieve faster switching times, then switching speed is improved, but breakdown voltage decreases and susceptibility to base pushout increases
Solution Approach 1:
The drain well is divided into multiple concentration zones (first, second, third, and fourth zones) with different dopant concentrations. This segmentation allows each zone to serve a specific function: the first zone maintains breakdown voltage, while subsequent zones with increasing concentrations resist base pushout and enable faster switching, thus resolving the contradiction between switching speed and breakdown voltage
Solution Approach 2:
Different regions of the drain well are given different dopant concentrations tailored to their specific functions. The first zone has lower concentration for high breakdown voltage, while later zones have progressively higher concentrations for resistance to base pushout and optimized switching characteristics, allowing simultaneous optimization of both switching speed and breakdown voltage
2Speed
If device dimensions are shrunk to achieve faster switching times, then switching speed is improved, but susceptibility to base pushout increases
Solution Approach 1:
The drain well is segmented into multiple zones where the second, third, and fourth zones have progressively higher dopant concentrations than the first zone. This segmentation creates a gradient that specifically addresses base pushout in the high-current region while maintaining fast switching, resolving the contradiction between switching speed and base pushout susceptibility
Solution Approach 2:
The dopant concentration parameter is changed progressively across different zones of the drain well. By increasing the dopant concentration from the first zone through the fourth zone, the patent creates a concentration gradient that enhances resistance to base pushout while maintaining fast switching times, thus resolving the technical contradiction
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
The multi-zone dopant structure in the drain well effectively maintains high breakdown voltage and reduces the impact of the Kirk effect, allowing for higher current handling without carrier saturation, thus improving the overall performance and reliability of LDMOS devices.
Implementation Method 1
a drain well with multiple concentration zones of dopant, where the dopant concentration gradually increases from the first zone to the fourth zone
Data Source
AI summary
An integrated circuit includes a drain in a substrate, wherein the drain comprising a doped drain well. The doped drain well includes a first zone, wherein the first zone has a first concentration of a first dopant; and a second zone, wherein the second zone has a second concentration of the first dopant, a top-most surface of the first zone is coplanar with a top-most surface of the second zone, and the first concentration is different from the second concentration. The integrated circuit further includes a gate electrode over the substrate, the gate electrode being separated from each of the first zone and the second zone in a direction parallel to a top surface of the substrate by a distance greater than 0.