LDMOS Drain Well Zoning for Breakdown Voltage and Kirk Effect
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Solution Overview
Problem
LDMOS devices face challenges with reduced breakdown voltage and increased susceptibility to the Kirk effect due to shrinking device dimensions, which affects switching speed and current handling capabilities.
Innovation Solution
Incorporating multiple concentration zones in the drain well of LDMOS devices, with varying dopant concentrations and depths, and optimizing the implant angles and depths during the doping process to maintain a smaller channel length while enhancing breakdown voltage and resistance to the Kirk effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device dimensions are shrunk to improve integration density, then productivity is improved, but breakdown voltage decreases and susceptibility to Kirk effect increases
Solution Approach 1:
The drain well is segmented into multiple zones with different dopant concentrations. The first zone has a first dopant concentration and the second zone has a second dopant concentration different from the first, creating distinct regions that collectively maintain high breakdown voltage while allowing compact device dimensions for high integration density.
Solution Approach 2:
Different regions of the drain well are assigned different dopant concentrations tailored to their specific functional requirements. The first zone and second zone have locally optimized dopant concentrations to achieve both high breakdown voltage in critical regions and compact overall device size for high integration density.
2Productivity
If device dimensions are shrunk to improve integration density, then productivity is improved, but susceptibility to Kirk effect increases
Solution Approach 1:
The drain well is divided into multiple zones with different dopant concentrations to mitigate the Kirk effect. By segmenting the drain well structure, the patent reduces carrier saturation and minimizes the Kirk effect while maintaining small device dimensions for high integration density.
Solution Approach 2:
Specific zones within the drain well are locally optimized with appropriate dopant concentrations to resist the Kirk effect. The first zone and second zone have tailored dopant profiles that prevent carrier saturation locally, reducing overall Kirk effect susceptibility while enabling compact device design.
3Reliability
If multiple concentration zones are incorporated to increase breakdown voltage, then reliability is improved, but device complexity increases
Solution Approach 1:
The drain well is segmented into zones with different dopant concentrations achieved through sequential implantation processes. While this creates multiple zones for high breakdown voltage, the segmented approach allows systematic control of each zone's properties.
Solution Approach 2:
The patent employs parameter changes in the doping process, varying implantation angles and depths to create different dopant concentration zones. By changing implantation parameters (angle, depth, concentration), the patent achieves multiple zones with tailored properties while managing process complexity through systematic parameter variation.
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 approach effectively increases the breakdown voltage and reduces the Kirk effect, enabling faster switching times and improved current handling without carrier saturation, thus enhancing the performance of LDMOS devices.
Implementation Method 1
a first doped zone is formed by implanting dopant atoms along a first implant vector at a first implant angle to a first depth
Data Source
AI summary
A method of making an integrated circuit includes forming a drift region in a substrate, the drift region having a first dopant type; forming a drain well in the drift region, the drain well having the first dopant type. The drain well includes a first zone with a first concentration of the first dopant and a second zone having a second concentration of the first dopant different from the first concentration of the first dopant. The method further includes forming a source well in the substrate, the source well having a second dopant type opposite from the first dopant type, the source well being adjacent to the drift region in the substrate. The method includes forming a gate electrode over a top surface of the substrate over the drift region and the source well, and being laterally separated from the drain well. The method includes forming a drain low-density doped (LDD) region in the second zone of the drain well.