Grounded Metal Shield for BSI Image Sensors
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Solution Overview
Problem
Backside Illumination (BSI) image sensor chips face issues with accumulated charges in the metal shield structure, leading to image saturation in bright environments due to ungrounded metal shields, which affect the accuracy and quality of captured images.
Innovation Solution
A grounded metal shield structure is formed by creating metal plugs that electrically connect the metal shield to the semiconductor substrate, preventing charge accumulation and ensuring proper grounding, thereby eliminating the adverse effects on image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metal shield structure is used in BSI image sensor chips, then light shielding and electrical interference protection are improved, but charge accumulation occurs leading to image saturation
Solution Approach 1:
The patent extracts the harmful accumulated charges from the metal shield by creating conductive pathways (via holes with conductive material) that connect the metal shield to the semiconductor substrate, allowing charges to be removed and discharged, thus preventing image saturation while maintaining the shielding function
Solution Approach 2:
The patent introduces an intermediary conductive structure (via holes filled with conductive material) between the metal shield and the semiconductor substrate to provide a charge discharge pathway, enabling the metal shield to maintain its shielding function without charge accumulation
2Ease of manufacture
If ungrounded metal shields are used, then manufacturing simplicity is maintained, but image quality deteriorates due to charge accumulation
Solution Approach 1:
The patent segments the metal shield structure into isolated regions surrounded by dielectric material, with selective via holes created in specific areas to provide charge discharge pathways, allowing the shield to maintain manufacturing simplicity while improving image quality through targeted grounding
3Object-affected harmful factors
If metal shields are added to BSI image sensor chips, then electromagnetic shielding is improved, but device complexity increases
Solution Approach 1:
The patent merges the metal shield structure with the existing semiconductor substrate and dielectric layers, integrating the shielding function into the chip architecture rather than adding it as a separate component, thus improving electromagnetic shielding while minimizing increases in 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
The grounded metal shield structure effectively prevents image saturation, enhancing the accuracy and quality of images captured by BSI image sensor chips, especially in bright environments, by ensuring that accumulated charges are conducted away from the sensitive areas.
Implementation Method 1
a metal plug is formed through the dielectric layer. The metal plug is in contact with the metal shield and the semiconductor substrate
Data Source
AI summary
A device includes a semiconductor substrate having a front side and a backside. A photo-sensitive device is disposed on the front side of the semiconductor substrate. A dielectric layer is disposed on the backside of the semiconductor substrate, wherein the dielectric layer is over a back surface of the semiconductor substrate. A metal shield is over the dielectric layer and overlapping the photo-sensitive device. A metal plug penetrates through the dielectric layer, wherein the metal plug electrically couples the metal shield to the semiconductor substrate.