Stacked Image Sensor Bonding Pad Layout for Reliable Interconnects
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Solution Overview
Problem
Current image sensors face challenges in minimizing size and enhancing processing speed, particularly in stacked structures, which affects their performance in applications requiring high integration and rapid signal conversion.
Innovation Solution
The image sensor design involves direct bonding of stacked upper and lower structures with specific bonding pad configurations, including varying widths and thicknesses, to optimize electrical connections and reduce stress at bonding surfaces, thereby improving bonding reliability and processing speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If stacked structures are used to enhance integration, then device complexity is reduced and functionality is improved, but manufacturing precision and bonding reliability become more difficult to achieve
Solution Approach 1:
The bonding pads are designed with non-uniform thickness, where the first bonding pad has a first thickness and the second bonding pad has a second thickness different from the first. This local variation in thickness distributes stress differently across the bonding interface, improving bonding reliability at specific critical locations while maintaining overall structural integrity.
Solution Approach 2:
The bonding pads are designed with asymmetric geometry, where the first bonding pad has different dimensions (width and thickness) compared to the second bonding pad. This asymmetric design optimizes the stress distribution and electrical connection properties at the bonding interface, addressing the challenges of stacked structure manufacturing.
2Reliability
If bonding pad dimensions are increased to improve bonding reliability, then connection strength is enhanced, but device area increases
Solution Approach 1:
Instead of uniformly increasing the size of all bonding pads, the invention applies local quality enhancement by varying the thickness of specific bonding pads. The first bonding pad has a first thickness while the second bonding pad has a second thickness, allowing optimized stress distribution and bonding reliability without proportionally increasing the overall device area.
Solution Approach 2:
The invention moves from two-dimensional area scaling to three-dimensional thickness variation. By adjusting the thickness dimension of bonding pads rather than only their planar area, the design achieves improved bonding reliability while maintaining compact device footprint.
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 enables miniaturization and enhanced image processing speed, addressing the limitations of existing image sensors by ensuring reliable electrical connections and efficient signal conversion in high-integration applications.
Implementation Method 1
a first lower bonding pad directly connected to the first upper bonding pad
Implementation Method 2
a first substrate having a photoelectric converter
Data Source
AI summary
An image sensor includes a first substrate structure, which includes a first substrate having a photoelectric converter and a first wiring structure therein. The first wiring structure includes upper connection wiring, which is electrically connected to the photoelectric converter, a first upper bonding pad and a second upper bonding pad. A second substrate structure is provided, which includes a second substrate and a second wiring structure bonded to the first wiring structure. The second wiring structure includes: lower connection wiring, which is electrically connected to the upper connection wiring, a first lower bonding pad, which is directly connected to the first upper bonding pad, and a second lower bonding pad, which is directly connected to the second upper bonding pad. A width of the first upper bonding pad is unequal to a width of the second upper bonding pad, and a thickness of the first upper bonding pad is unequal to a thickness of the second upper bonding pad.