Power MOSFET Gate-Source ESD Diode with Body Ring Leakage Control
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Solution Overview
Problem
Power MOSFETs face challenges in protecting against electrostatic discharge (ESD) and maintaining breakdown voltage, as existing ESD diode structures can lead to leakage and damage, particularly in high-voltage applications.
Innovation Solution
A power MOSFET design incorporating a gate-source ESD diode structure with a breakdown voltage enhancement and leakage prevention structure, featuring a body ring structure underneath the ESD diode to disperse electric fields and reduce peak electric fields, thereby enhancing breakdown voltage and preventing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a back-to-back ESD diode structure is connected between gate and source to protect against electrostatic discharge, then gate protection from ESD is improved, but leakage current increases and breakdown voltage decreases
Solution Approach 1:
A body ring structure is introduced as an intermediary element between the ESD diode and the substrate. This body ring acts as a mediator that redistributes the electric field, preventing direct high-field stress on the ESD diode while providing a controlled path for leakage current, thereby reducing overall leakage while maintaining ESD protection capability
Solution Approach 2:
The patent applies different doping concentrations and structural configurations to different regions: the body ring has specific doping levels distinct from the substrate and ESD diode regions. This local differentiation allows the body ring to locally manage electric field distribution and leakage current paths without affecting the overall ESD protection function
2Reliability
If a back-to-back ESD diode structure is connected between gate and source to protect against electrostatic discharge, then gate protection from ESD is improved, but breakdown voltage decreases
Solution Approach 1:
The body ring structure serves as an intermediary that decouples the ESD diode from direct interaction with the substrate's high-voltage stress. By positioning the body ring between the ESD diode and substrate, it mediates the electric field distribution, allowing the ESD diode to provide protection while the body ring maintains the overall breakdown voltage through controlled field distribution
Solution Approach 2:
The invention transitions from a two-dimensional planar structure to a three-dimensional structure by adding the body ring that extends vertically and laterally. This dimensional addition creates multiple electric field paths and distribution zones, allowing simultaneous optimization of ESD protection and breakdown voltage characteristics through spatial field management
3Reliability
If the ESD diode structure is implemented as an array of doped p and n+ regions to create low breakdown voltage for clamping, then ESD clamping capability is improved, but leakage current increases
Solution Approach 1:
The body ring structure acts as an intermediary that intercepts and redistributes leakage current before it reaches the ESD diode array. This mediator function allows the ESD diodes to maintain their low breakdown voltage for effective clamping while the body ring manages the leakage current paths, reducing the net leakage effect
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 proposed design effectively protects against ESD and improves breakdown voltage and leakage prevention in power MOSFETs, ensuring reliable operation in high-voltage applications.
Implementation Method 1
a body ring structure underneath the ESD diode to disperse electric fields and reduce peak electric fields
Implementation Method 2
the p-n+structure is a common configuration for ESD protection diodes. The p-n+structure helps create a structure having a low breakdown voltage, making the ESD diode structure suitable for clamping and diverting the excess voltage during an ESD event
Data Source
AI summary
A method includes growing an epitaxial layer over a substrate, forming a plurality of gates in the epitaxial layer, forming a breakdown voltage enhancement and leakage prevention structure in the epitaxial layer comprising a body ring structure, forming a source and a body region in the epitaxial layer, forming an interlayer dielectric layer over the epitaxial layer, forming a gate-source Electrostatic Discharge (ESD) diode structure in the interlayer dielectric layer, forming a source contact connected to the source, and a first terminal of the gate-source ESD diode structure, forming a gate contact connected to the plurality of gates and a second terminal of the gate-source ESD diode structure, and forming a drain contact underneath the substrate.