PTC Fuse Layer on Source Electrode for Over-Current Protection
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Solution Overview
Problem
Existing power device protection methods, such as fusible links and positive temperature coefficient (PTC) materials, face limitations in high voltage applications, including increased cost, damage to active regions, and non-reresettable fuses, as well as challenges in achieving effective over-current protection without compromising system performance.
Innovation Solution
A new configuration where a PTC fuse protection layer is applied to the source connection of active devices, providing feedback voltage to automatically turn off the transistor during over-current conditions, thereby minimizing parasitic resistance and expanding voltage ranges while allowing for resettable protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fusible links such as metal fuse or polysilicon fuse are placed in the interconnect pattern before the bond pads, then over-current protection is provided, but the die size increases and manufacturing cost increases
Solution Approach 1:
The patent combines the protective function with the existing source electrode structure by forming the PTC material directly on the source electrode, eliminating the need for separate fusible links and reducing die size while maintaining over-current protection
Solution Approach 2:
The source electrode serves dual functions: as the electrical connection terminal and as the substrate for the PTC protective material, allowing one structure to perform multiple functions and reduce overall device complexity
2Reliability
If multiple fuses and pads are used for very high current application, then over-current protection is improved, but the die size increases causing unfavorable cost impacts
Solution Approach 1:
The protective function is merged into the source electrode structure itself, eliminating the need for multiple separate fuses and pads, thereby reducing manufacturing complexity and cost while providing adequate protection for high current applications
3Reliability
If PTC materials are used for over-current protection, then re-settable protection is achieved, but self-heating requires special mounting to avoid heat sink that could reduce protection effectiveness
Solution Approach 1:
The PTC material is formed directly on the source electrode, merging the protective element with the electrical connection structure, which eliminates special mounting requirements and heat sink considerations while maintaining re-settable protection functionality
4Reliability
If higher resistance is used in PTC materials to achieve better protection through self-heating, then over-current protection effectiveness is improved, but system performance is negatively impacted
Solution Approach 1:
The PTC material is applied locally on the source electrode where it is needed for protection, rather than using high resistance throughout the entire current path, allowing effective local protection while minimizing overall energy loss and maintaining system performance
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 power devices from over-current conditions across various voltage ratings with minimal increase in parasitic resistance and manufacturing costs, ensuring reliable and efficient operation.
Implementation Method 1
an over current protection layer composed of a material having a resistance with a positive temperature coefficient (PTC)
Implementation Method 2
self-heating is usually required to increase the temperature and that requires an I.sup.2R drop within the device
Data Source
AI summary
A vertical semiconductor power device includes a top surface and a bottom surface of a semiconductor substrate constituting a vertical current path for conducting a current there through. The semiconductor power device further includes an over current protection layer composed of a material having a resistance with a positive temperature coefficient (PTC) and the over current protection layer constituting as a part of the vertical current path connected to a source electrode and providing a feedback voltage a gate electrode of the vertical semiconductor power device for limiting a current passing there through for protecting the semiconductor power device at any voltage.