Semiconductor Package Conductive Section for MOSFET On-Resistance
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Solution Overview
Problem
Semiconductor packages face challenges in reducing the on-resistance of MOSFETs, particularly due to limitations in backside metallization and wafer thickness, which affect heat transfer and electrical coupling between MOSFETs.
Innovation Solution
Incorporating a prefabricated electrically conductive section, such as copper, between two or more MOSFETs, coupled to the back metal using materials like silver sintering paste, to reduce on-resistance and enhance electrical coupling, with a thickness between 25 microns to 125 microns, allowing for independent formation from the back metal during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backside metallization is applied through evaporation or sputtering, then solder attachment and heat transfer are improved, but on-resistance of MOSFETs cannot be sufficiently reduced
Solution Approach 1:
The backside metallization is segmented into two distinct functional layers: a back metal layer (Ti/Ni/Ag alloy) for solder attachment and heat transfer, and a separate electrically conductive section (copper, aluminum, or silver) for reducing on-resistance. This segmentation allows each layer to be optimized independently for its specific function without compromising the other.
Solution Approach 2:
The back metal layer serves as an intermediary between the semiconductor die and the electrically conductive section. It provides both mechanical attachment (for solder) and thermal conduction, while the electrically conductive section provides the low-resistance electrical path. This intermediary structure resolves the conflict between mechanical/thermal requirements and electrical performance requirements.
2Temperature
If wafer thickness is reduced, then heat transfer efficiency is improved, but structural integrity and electrical coupling are compromised
Solution Approach 1:
The patent employs composite material structures at multiple levels: the back metal uses a Ti/Ni/Ag alloy composite for optimized mechanical and thermal properties, while the electrically conductive section uses pure copper, aluminum, or silver. The combination of thin wafer with these composite materials maintains structural integrity while enabling efficient heat transfer through the thin profile.
3Ease of manufacture
If electrically conductive section is formed independently from back metal, then manufacturing flexibility is improved, but process complexity increases
Solution Approach 1:
The electrically conductive section is prepared as a prefabricated element before being attached to the semiconductor die. This preliminary preparation allows for independent optimization of the conductive section's properties (material selection, thickness, geometry) without affecting the die fabrication process. The pre-formed conductive sections are then attached using standard bonding techniques, integrating the complex functionality without significantly complicating the overall manufacturing flow.
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 lowers the on-resistance of MOSFETs by up to 30% and improves heat dissipation, while allowing for flexible manufacturing methods like punching and stamping, optimizing the thickness for reduced resistivity and increased efficiency.
Implementation Method 1
the electrically conductive section may be coupled to the back metal and may be configured to electrically couple the two or more MOSFETs together during operation of the two or more MOSFETs
Implementation Method 2
Backside metallization often helps with solder attachment and application of heat transfer devices in semiconductor die packages
Data Source
AI summary
Implementations of semiconductor packages may include: a prefabricated electrically conductive section; two or more metal oxide semiconductor field effect transistors (MOSFET) physically coupled together; and a back metal coupled to the two or more MOSFETs; wherein the electrically conductive section may be coupled to the back metal and may be configured to electrically couple the two or more MOSFETs together during operation of the two or more MOSFETs.