Image Sensor Pad Noise Reduction via TSV Segmentation
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Solution Overview
Problem
Image sensors face issues with noise and parasitic capacitance in the pad area due to light reflection and absorption, leading to reduced sensitivity and crosstalk, particularly in backside illuminated (BSI) sensors where metal line layers are not formed over the light incident surface.
Innovation Solution
The implementation of through silicon vias (TSVs) that penetrate the substrate and are formed at both sides of the pad in a first direction, or omnidirectionally surround the pad, to reduce parasitic capacitance and noise by creating a floated state that prevents coupling between the pad and the substrate, thereby minimizing capacitance and noise introduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pad area is formed in a BSI image sensor substrate, then electrical connection is achieved, but parasitic capacitance and noise increase due to coupling between the pad and substrate
Solution Approach 1:
The substrate area under the pad is segmented into multiple regions by forming TSVs that divide the continuous substrate into isolated sections. This segmentation prevents the pad from coupling with a large continuous substrate area, thereby reducing parasitic capacitance while maintaining electrical connection functionality.
Solution Approach 2:
The harmful coupling effect between the pad and substrate is extracted by removing electrical continuity in specific regions through TSV formation. The TSVs create isolation zones that extract the parasitic capacitance pathway while preserving the necessary pad functionality for electrical connection.
2Adaptability or versatility
If the pad area is enlarged to accommodate more connections, then device functionality improves, but noise and parasitic capacitance increase
Solution Approach 1:
By segmenting the substrate under the pad area with TSVs, the patent enables larger pad areas to be used without proportionally increasing noise. Each segmented region acts as an isolated electrical zone, allowing multiple pad connections to be accommodated while maintaining low noise levels through the isolation effect.
3Adaptability or versatility
If metal line layers are added to improve circuit functionality, then device capability improves, but light reflection and absorption increase reducing sensitivity
Solution Approach 1:
The patent moves the metal line layers from the light-receiving surface to the backside of the substrate, changing the dimensional arrangement. This allows metal lines to be positioned in a different spatial dimension (behind the light path) where they do not interfere with light sensitivity, while still providing necessary circuit functionality through the substrate.
Data Source
AI summary
An image sensor device is disclosed, which blocks noise of a pad region. The image sensor device includes a substrate including a first surface and a second surface that are arranged to face each other, a pad disposed over the first surface of the substrate, and a through silicon via (TSV) formed to penetrate the substrate, and disposed at both sides of the pad in a first direction.