Power MOSFET Gate-Source ESD Diode with Body Ring Isolation
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Solution Overview
Problem
Power MOSFETs, particularly vertical power MOSFETs, are vulnerable to electrostatic discharge (ESD) damage due to excessive gate voltage, leading to breakdown and potential damage, and existing ESD protection structures do not adequately enhance breakdown voltage or prevent leakage.
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 improve breakdown voltage while reducing 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 from ESD, then gate protection from electrostatic discharge is improved, but breakdown voltage is reduced and leakage increases
Solution Approach 1:
A body ring structure is introduced as an intermediary element between the ESD diode and the substrate. This body ring structure acts as a mediator that disperses the electric field, preventing direct concentration of high electric fields that would cause breakdown. The body ring structure includes a first body ring region and a second body ring region with different doping types, creating a gradual transition zone that maintains ESD protection while preserving breakdown voltage characteristics.
Solution Approach 2:
The patent applies local quality by creating a body ring structure with spatially varying doping characteristics. The first body ring region has a first doping type while the second body ring region has a second doping type opposite to the first. This local variation in doping quality allows the structure to provide ESD protection in specific areas while maintaining high breakdown voltage in other areas, resolving the contradiction between protection and voltage handling capability.
2Reliability
If a back-to-back ESD diode structure is connected between gate and source to protect from ESD, then gate protection from electrostatic discharge is improved, but leakage current increases
Solution Approach 1:
The body ring structure serves as an intermediary that intercepts and disperses electric field lines before they can create direct leakage paths between the ESD diode terminals. By introducing this intermediate structure with controlled doping, the patent reduces the formation of high-field regions that would otherwise generate leakage current, while still maintaining the ESD protection function.
Solution Approach 2:
The body ring structure with alternating doping types creates localized regions that control charge distribution. The first body ring region with first doping type and the second body ring region with second doping type work together to locally manage electric field distribution, reducing leakage in critical areas while preserving ESD clamping functionality in other areas.
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 design effectively protects the MOSFET from ESD by enhancing breakdown voltage and minimizing leakage, ensuring reliable operation under high voltage and current conditions.
Implementation Method 1
a breakdown voltage enhancement and leakage prevention structure formed underneath the gate-source ESD diode structure
Implementation Method 2
the gate of a vertical power MOSFET is a crucial element. Excessive voltage at the gate relative to the source can lead to breakdown and damage. To protect the gate of the vertical power MOSFET from ESD, a back-to-back ESD diode structure may be connected between the gate and source terminals
Data Source
AI summary
An apparatus includes a drain and a source on opposing sides of an epitaxial layer, a body region and a plurality of gates formed in the epitaxial layer, an interlayer dielectric layer over the epitaxial layer, a gate-source electrostatic discharge (ESD) diode in the interlayer dielectric layer, a source contact connected to the source and a first terminal of the gate-source ESD diode structure, a gate contact connected to the plurality of gates and a second terminal of the gate-source ESD diode structure, a drain contact on opposing sides of the epitaxial layer of the source contact, a breakdown voltage enhancement and leakage prevention structure formed underneath the gate-source ESD diode structure, wherein the breakdown voltage enhancement and leakage prevention structure comprises a body ring structure.