LDMOS Trench Insulation Field Plates for Breakdown Voltage
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Solution Overview
Problem
Lateral double diffused MOS (LDMOS) transistors face a trade-off between drain junction breakdown voltage and on-resistance, where improving one characteristic typically degrades the other, limiting the electrical performance of high voltage integrated devices.
Innovation Solution
The integration of trench insulation field plates and metal field plates in a semiconductor device structure, which includes recessed regions for the metal field plates and a gate stack extending over the trench insulation field plate, helps to enhance the drain junction breakdown voltage while maintaining low on-resistance by controlling carrier accumulation and electric field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentration of the drift region is reduced or the drift length is increased to improve drain junction breakdown voltage, then the drain junction breakdown voltage is improved, but the on-resistance increases and current drivability is degraded
Solution Approach 1:
The patent introduces a field plate structure with specific doping regions (first and second doping regions) that create localized electric field modulation. The field plate is positioned adjacent to the drain region with controlled doping concentrations that differ from both the drift region and drain region, creating a gradient structure that locally optimizes electric field distribution to reduce peak fields at the drain junction while maintaining lower resistance paths in other areas.
Solution Approach 2:
The patent employs a composite doping structure combining multiple doping regions with different concentrations and types (n-type and p-type dopants) within the field plate and surrounding areas. This composite approach creates a multi-layered doping profile that simultaneously achieves high breakdown voltage through field spreading and acceptable on-resistance through optimized carrier concentration distribution.
2Object-generated harmful factors
If the doping concentration of the drift region is increased or the drift length is decreased to reduce on-resistance and improve current drivability, then the on-resistance is reduced and current drivability is improved, but the drain junction breakdown voltage is lowered
Solution Approach 1:
The field plate structure with differentiated doping regions creates localized electric field control that allows the drift region to maintain higher doping concentrations for low on-resistance while the field plate area provides localized field spreading to ensure adequate breakdown voltage. The first and second doping regions adjacent to the drain create a transition zone that manages the electric field peak without requiring the entire drift region to have low doping.
Solution Approach 2:
The field plate acts as an intermediary structure between the high-field drain junction and the lower-field drift region. By introducing controlled doping regions within the field plate, it mediates the electric field distribution, allowing the drift region to operate at higher doping levels for low resistance while the field plate absorbs the field peak through its structured doping profile.
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 improves the drain junction breakdown voltage and current drivability of the high voltage integrated devices without significantly increasing on-resistance, effectively addressing the trade-off between these two critical parameters.
Implementation Method 1
a metal field plate disposed over the trench insulation field plate and filling the recessed region
Implementation Method 2
a gate insulation layer provided over the channel region and extending over the drift region and over the trench insulation field plate, and a gate electrode disposed over the gate insulation layer
Data Source
AI summary
A high voltage integrated device includes a source region and a drain region disposed in a semiconductor layer and spaced apart from each other, a drift region disposed in the semiconductor layer and surrounding the drain region, a channel region defined in the semiconductor layer and between the source region and the drift region, a trench insulation field plate disposed in the drift region, a recessed region provided in the trench isolation field plate, a metal field plate disposed over the trench insulation field plate, and filling the recessed region, a gate insulation layer provided over the channel region and extending over the drift region and over the trench insulation field plate, and a gate electrode disposed over the gate insulation layer.