Semiconductor Device with Parallel JFETs and Series MOSFET for Low Ron
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Solution Overview
Problem
High voltage semiconductor devices, such as LDMOS, face a trade-off between high breakdown voltage and low on-state resistance (Ron), where improving one typically compromises the other.
Innovation Solution
A semiconductor device is designed by connecting multiple junction gate field-effect transistors (JFETs) in parallel with a metal-oxide-semiconductor field-effect transistor (MOSFET) in series, allowing for a high breakdown voltage while maintaining a low on-state resistance (Ron) by leveraging the pinch-off effect in JFETs at high drain voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the breakdown voltage is increased to meet high voltage device specifications, then the breakdown voltage is improved, but the on-state resistance (Ron) increases and deteriorates
Solution Approach 1:
The device is segmented into two distinct transistor types: JFETs connected in parallel for low-voltage operation with low Ron, and a MOSFET in series for high-voltage operation with high breakdown voltage. This segmentation allows each transistor type to optimize its performance for its specific voltage range, resolving the contradiction between low Ron and high breakdown voltage that plagues single-transistor designs
Solution Approach 2:
The device dynamically switches between JFET-dominated conduction at low drain voltages (where parallel JFETs provide low Ron) and MOSFET-dominated conduction at high drain voltages (where the series MOSFET provides high breakdown voltage). This dynamic behavior enables the device to simultaneously achieve low on-state resistance and high breakdown voltage by adapting its conduction path based on operating conditions
2Reliability
If multiple JFETs are connected in parallel to reduce on-state resistance, then the on-state resistance is improved, but the breakdown voltage decreases and deteriorates
Solution Approach 1:
The device segments the low-voltage current-carrying function (handled by parallel JFETs for low Ron) from the high-voltage blocking function (handled by series MOSFET for high breakdown voltage). This functional segmentation allows the parallel JFET configuration to provide low on-state resistance without being constrained by the breakdown voltage limitations that would affect a pure parallel JFET device
Solution Approach 2:
The series-connected MOSFET acts as an intermediary that protects the parallel JFETs from high-voltage stress. The MOSFET's high breakdown voltage capability allows it to block high voltages while the parallel JFETs handle low-voltage conduction, enabling the parallel JFET configuration to achieve low Ron without sacrificing overall device breakdown voltage
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 semiconductor device achieves a balance between high breakdown voltage and low Ron, enhancing its efficiency and reliability by acting as a parallel resistance at low drain voltages and increasing breakdown voltage at high voltages.
Implementation Method 1
when the drain voltage is high, since a pinch-off effect in the JFETs shares most of the voltage drop, the breakdown voltage of the semiconductor device provided in the embodiments of the invention is increased
Data Source
AI summary
A semiconductor device including a substrate, a metal-oxide-semiconductor field-effect transistor (MOSFET), and a plurality of junction gate field-effect transistors (JFETs) connected in parallel is provided. The MOSFET is disposed on a substrate. The MOSFET includes a source region, a drain region, and a gate structure disposed between the source region and the drain region. The JFETs and the MOSFET are connected in series. Each of the JFETs laterally extends between the source region and the drain region.