Chip Bonding Electrode Layout for Thermal Expansion Matching
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Solution Overview
Problem
Existing semiconductor devices face bonding defects due to uneven expansion of metal pads during heat treatment, leading to gaps and reduced bonding quality between chips.
Innovation Solution
The semiconductor device design features a first electrode with a thinner thickness and larger planar area than the second electrode at the bonding interface, ensuring the volume of the first electrode is 80% to 120% of the second electrode's volume, which enhances the bonding characteristics by matching the expansion of both electrodes during heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If electrodes of different thicknesses are bonded together, then bonding area is increased, but uneven expansion during heat treatment causes gaps and bonding defects
Solution Approach 1:
The patent applies local quality by creating an asymmetric electrode structure where the first electrode has a different thickness profile compared to the second electrode. Specifically, the first electrode includes a first region with greater thickness and a second region with lesser thickness, allowing different portions to expand at different rates during heat treatment, thereby compensating for the inherent expansion differences between dissimilar electrodes while maintaining large bonding area.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the thickness dimensions of the first electrode's different regions. The first region is designed with a thickness parameter that allows it to expand more during heat treatment, compensating for the smaller initial bonding area contribution, while the second region's reduced thickness parameter allows it to expand less, matching the second electrode's expansion characteristics. This parameter optimization ensures uniform overall expansion.
2Strength
If electrode thickness is increased to improve bonding strength, then bonding strength is improved, but expansion uniformity during heat treatment deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the first electrode into distinct functional regions: a first region with greater thickness designed to provide bonding strength and a second region with lesser thickness designed to control expansion characteristics. This segmentation allows each region to fulfill its specific function while collectively achieving both bonding strength and expansion uniformity that would be impossible with a uniform thickness electrode.
Solution Approach 2:
The patent employs asymmetry by designing the first electrode with non-uniform thickness distribution, where the first region has greater thickness than the second region. This asymmetric structure is deliberately created to balance the competing requirements of bonding strength (requiring greater thickness) and expansion uniformity (requiring thinner portions), allowing the electrode to satisfy both conditions simultaneously through its asymmetric geometry.
3Reliability
If electrodes of different materials are used, then electrical conductivity is improved, but thermal expansion mismatch causes bonding defects
Solution Approach 1:
The patent applies local quality by creating spatial variation in the first electrode's thickness, with the first region having greater thickness and the second region having lesser thickness. This local variation in geometric properties compensates for the thermal expansion mismatch that arises from using different materials, allowing the structure to accommodate differential expansion while maintaining electrical connectivity.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the thickness parameters of the first electrode's different regions. The first region's greater thickness parameter and the second region's lesser thickness parameter are specifically designed to counterbalance the thermal expansion differences between dissimilar electrode materials, ensuring that the overall expansion remains uniform despite material differences.
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 design effectively prevents bonding defects and improves the bonding quality between chips by ensuring the first electrode's volume is within the specified range, ensuring better electrical connectivity and reliability.
Implementation Method 1
the volume of the first electrode is 80% to 120% of the second electrode's volume, which enhances the bonding characteristics by matching the expansion of both electrodes during heat treatment
Data Source
AI summary
According to one embodiment, a semiconductor device includes a first chip with a first electrode and a second electrode and a second chip with a third electrode and a fourth electrode. The first and second chips are bonded to each other with the first electrode contacting the third electrode and the second electrode contacting the fourth electrode. A thickness of the first electrode in a first direction perpendicular to a bonding interface between the first chip and the second chip is less than a thickness of the second electrode in the first direction. A planar area of the first electrode at the bonding interface is greater than a planar area of the second electrode at the bonding interface.