Fe-Ni Electrode Layer for Thermal Stress-Resistant Semiconductor Bonding
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Solution Overview
Problem
Existing semiconductor devices face issues with thermal expansion differences between semiconductor materials and conductors, leading to stress, deformation, and potential damage due to thermal fatigue, particularly in high-power devices, which existing Fe—Ni alloy metal solutions do not adequately address in terms of electrical conductivity, thermal conductivity, and cost.
Innovation Solution
Coating an Fe—Ni alloy metal layer directly or indirectly onto the electrodes of semiconductor elements, connecting them to conductors through this layer, with controlled thermal expansion coefficients to alleviate stress and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as conductor material, then electrical conductivity and thermal conductivity are improved, but thermal expansion difference with semiconductor causes stress and damage
Solution Approach 1:
An Fe-Ni alloy metal layer is introduced as an intermediary between the semiconductor element and the copper conductor. This intermediate layer has a thermal expansion coefficient that matches the semiconductor, thereby mediating the thermal expansion difference and preventing stress concentration at the interface while maintaining electrical conductivity through the copper connection.
Solution Approach 2:
The invention uses a composite structure consisting of the semiconductor element, the Fe-Ni alloy metal layer, and the copper conductor. This composite material approach combines materials with different properties: the Fe-Ni alloy provides thermal expansion matching, while the copper provides high electrical and thermal conductivity, achieving a balance of multiple requirements.
2Object-affected harmful factors
If Fe—Ni alloy metal layer is used to match thermal expansion coefficient, then thermal stress is reduced, but electrical conductivity and thermal conductivity are lower than copper
Solution Approach 1:
The Fe-Ni alloy metal layer is applied locally only at the interface between the semiconductor and the copper conductor, rather than throughout the entire conductor structure. This localized application allows the Fe-Ni alloy to provide thermal expansion matching where it is most needed (at the interface), while the bulk copper material maintains its superior electrical and thermal conductivity properties.
3Object-affected harmful factors
If ceramic substrates with thermal expansion coefficient close to Si are used, then thermal expansion difference is suppressed, but cost increases significantly
Solution Approach 1:
Instead of using expensive ceramic substrates, the invention employs a thin Fe-Ni alloy metal layer deposited on conventional, cost-effective substrate materials. This approach achieves the same thermal expansion matching function at a fraction of the cost, making the solution economically viable for mass production while maintaining the protective function against thermal stress.
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 Fe—Ni alloy metal layer effectively reduces thermal stress, preventing deformation and damage to semiconductor elements by matching thermal expansion coefficients, while maintaining low electrical resistance and cost-effectiveness.
Implementation Method 1
the difference in thermal expansion of the objects to be connected is suppressed by an Fe—Ni alloy metal layer
Data Source
AI summary
The purpose of this invention is to provide a semiconductor device that prevents defects in semiconductor elements caused by differences in thermal expansion and maintains low electrical resistance by directly or indirectly laminating an Fe—Ni alloy metal layer onto the front-surface or back-surface electrodes of the semiconductor element. In this invention, an Fe—Ni alloy metal layer is directly or indirectly applied on the surface electrodes of the semiconductor element, and the semiconductor element is connected to a conductor through the Fe—Ni alloy metal layer. Depending on the application, the Ni content of the Fe—Ni alloy metal layer is set within the range of 36% to 45% by weight, and the thickness of the Fe—Ni alloy metal layer is set within the range of 2 μm to 20 μm.