Power MOSFET Gate-Source ESD Diode Structure for Breakdown Control
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Solution Overview
Problem
Existing power MOSFETs face challenges in protecting the gate from electrostatic discharge (ESD) while maintaining high breakdown voltage and preventing leakage.
Innovation Solution
The implementation of a power MOSFET with a gate-source ESD diode structure and a breakdown voltage enhancement and leakage prevention structure, which includes an epitaxial layer, a plurality of gates, a body region, and a body ring structure underneath the gate-source ESD diode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a back-to-back ESD diode structure is connected between gate and source to protect the gate from ESD, then gate protection is improved, but breakdown voltage decreases and leakage increases
Solution Approach 1:
The ESD protection structure is segmented into multiple p-n+ diode pairs arranged in series between gate and source. Each diode pair consists of a p-type region and an n+ region, creating multiple breakdown stages that distribute the ESD protection function while maintaining higher overall breakdown voltage compared to a single diode structure.
Solution Approach 2:
The patent introduces a body ring structure with specific doping concentration and geometry positioned underneath the ESD diode structure. This localized structure modifies the electric field distribution specifically in the region beneath the ESD diodes, enhancing breakdown voltage and reducing leakage current without affecting the overall ESD protection function.
2Reliability
If a back-to-back ESD diode structure is connected between gate and source to protect the gate from ESD, then gate protection is improved, but leakage current increases
Solution Approach 1:
The body ring structure with optimized doping concentration (1e16 to 1e18 atoms/cm³) is positioned directly underneath the ESD diode structure. This localized modification creates a potential well that confines carriers and reduces leakage current paths without compromising the ESD clamping function.
Solution Approach 2:
The body ring structure acts as an intermediary layer between the ESD diodes and the substrate. It mediates the electric field distribution and carrier flow, providing a controlled path that reduces leakage while maintaining ESD protection capability.
3Reliability
If a body ring structure is added underneath the gate-source ESD diode structure to enhance breakdown voltage and reduce leakage, then device performance is improved, but device complexity increases
Solution Approach 1:
The body ring structure is merged with the existing ESD diode fabrication process. The same ion implantation or diffusion steps that create the ESD diode regions also form the body ring structure underneath, combining multiple functions into a single integrated structure rather than adding separate components.
Solution Approach 2:
The body ring structure serves multiple functions simultaneously: it enhances breakdown voltage, reduces leakage current, and provides mechanical support. This multi-functionality reduces the need for additional separate structures, offsetting the complexity increase with functional consolidation.
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 effectively protects the gate from ESD, enhances breakdown voltage, and reduces leakage, thereby improving the overall performance and reliability of the power MOSFET.
Implementation Method 1
The input/output terminals of the vertical power MOSFET must be protected from electrostatic discharge (ESD) voltages
Implementation Method 2
a back-to-back ESD diode structure may be connected between the gate and source terminals of the vertical power MOSFET
Implementation Method 3
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
Implementation Method 4
When a control voltage is applied to the gate a power MOSFET and the control voltage is greater than the threshold of the power MOSFET, a conductive channel is established between the drain and the source of the power MOSFET
Data Source
AI summary
An apparatus includes a drain and a source on opposing sides of an epitaxial layer, a plurality of gates formed in the epitaxial layer, a source contact connected to the source, a gate contact connected to the plurality of gates, a gate-source electrostatic discharge (ESD) diode connected between the gate contact and the source contact, and a breakdown voltage enhancement and leakage prevention structure formed underneath the gate-source ESD diode structure.