Stacked Image Sensor Pad-Via Structure for Dark Current Uniformity
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Solution Overview
Problem
In solid-state imaging apparatuses with stacked semiconductor substrates, noise due to differences in dark current between electrode pads and dummy pads reduces image quality, primarily caused by uneven hydrogen supply to pixel circuits.
Innovation Solution
The implementation of a configuration where vias connect both electrode and dummy pads to ensure uniform hydrogen supply across the substrate, stabilizing the electrical characteristics and reducing dark current variations by bonding hydrogen-terminating atoms like hydrogen to the bonding surface, thereby equalizing the dark current across all pixel circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If dummy pads are bonded to improve bonding strength, then bonding strength is improved, but dark current uniformity deteriorates
Solution Approach 1:
The patent applies different via configurations to different pad regions. Electrode pads have vias connected to both upper and lower wiring layers, while dummy pads have vias connected only to the lower wiring layer. This local differentiation ensures uniform hydrogen supply to pixel circuits above electrode pads while preventing excessive hydrogen supply to pixel circuits above dummy pads, thereby maintaining dark current uniformity while preserving bonding strength benefits.
2Manufacturing precision
If vias connect both electrode and dummy pads to ensure uniform hydrogen supply, then dark current uniformity is improved, but device complexity increases
Solution Approach 1:
The patent segments the via connections into two distinct types: vias connecting electrode pads to both upper and lower wiring layers, and vias connecting dummy pads only to the lower wiring layer. This segmentation allows precise control over hydrogen supply paths, ensuring uniform dark current characteristics while maintaining a systematic and manageable via configuration that does not excessively increase device complexity.
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 enhances image quality by minimizing noise and improving the uniformity of dark current, leading to better image data with reduced streaking and improved overall performance.
Implementation Method 1
bonding hydrogen-terminating atoms like hydrogen to the bonding surface
Data Source
AI summary
There is provided an image sensor including a first substrate including a plurality of pixels and a plurality of vertical signal lines and a plurality of first wiring layers and a second substrate including a plurality of second wiring layers. The first and second substrates are secured together between the pluralities of first and second wiring layers. First pads are provided between one of the plurality of first wiring layers and one of the plurality of second wiring layers and second pads are provided between another of the plurality of first wiring layers and another of the plurality of second wiring layers. First vias and second vias connect the first pads and the one of the plurality of first wiring layers and the one of the plurality of second wiring layers together.