Shielded Stacked-Die Image Sensor Interconnects
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Solution Overview
Problem
Conventional stacked-die image sensors experience parasitic capacitive coupling and electrical crosstalk between adjacent conductive interconnects, leading to image artifacts and degraded image quality.
Innovation Solution
The implementation of an isolation structure between interconnect elements within a pixel or between adjacent pixels, using shielding structures formed from conductive materials like copper, aluminum, or gold, to reduce parasitic coupling and cross-talk in split-pixel architecture image sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive interconnects are placed adjacent to each other in stacked-die image sensors, then electrical connection between dies is achieved, but parasitic capacitive coupling and electrical crosstalk occur between adjacent interconnects
Solution Approach 1:
A shielding structure made of conductive material is positioned between adjacent conductive interconnects to act as an intermediary element. This shielding structure blocks parasitic capacitive coupling and electrical crosstalk between the interconnects, allowing them to be placed in close proximity while maintaining signal integrity. The shielding structure effectively mediates the electromagnetic interaction between adjacent interconnects.
Solution Approach 2:
The shielding structure is selectively positioned only between adjacent conductive interconnects where parasitic coupling occurs, rather than throughout the entire device. This localized approach provides targeted protection against crosstalk while minimizing the overall complexity and material usage. The shielding is applied specifically where needed to address the harmful capacitive coupling.
2Object-generated harmful factors
If shielding structures are added between conductive interconnects, then electrical crosstalk is reduced, but device complexity increases
Solution Approach 1:
The shielding structure serves as a simple intermediary element that can be integrated into existing interconnect architectures. By using conductive material that can be deposited using standard semiconductor fabrication processes, the shielding adds minimal complexity while effectively blocking crosstalk. The shielding structure acts as a straightforward mediator between adjacent interconnects.
3Area of stationary object
If conductive interconnects are placed in close proximity, then device area is reduced, but image quality degrades due to electrical crosstalk
Solution Approach 1:
The shielding structure enables close placement of conductive interconnects by blocking the parasitic capacitive coupling that would otherwise cause image artifacts. This allows the device to maintain a compact form factor while preserving image quality. The shielding acts as a mediator that permits dense interconnect spacing without sacrificing imaging performance.
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 solution effectively minimizes electrical crosstalk and enhances image quality by preventing unwanted interactions between adjacent coupling structures, thereby improving the performance of stacked-die image sensors.
Implementation Method 1
parasitic capacitive coupling may occur between adjacent conductive interconnects, thereby causing electrical crosstalk
Data Source
AI summary
A stacked-die image sensor may be provided with an array of image pixels. The stacked-die image sensor may include at least first and second integrated circuit dies stacked on top of one another. Some of the pixel circuitry in each pixel may be formed in the first integrated circuit die and some of the pixel circuitry in each pixel may be formed in the second integrated circuit die. Coupling structures such as conductive pads may electrically couple the pixel circuitry in the first integrated circuit die to the pixel circuitry in the second integrated circuit die. A shielding structure may partially or completely surround each conductive pad to reduce parasitic capacitive coupling between adjacent conductive pads. The shielding structure may be a metal wire coupled to a ground voltage. The shielding structure may extend between columns of image pixels and/or between rows of image pixels.