Image Sensor Contact Via Alignment and Resistance Reduction
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Solution Overview
Problem
Image sensors face challenges in enhancing reliability due to misalignment and increased resistance between contacts and vias, which affect the performance and efficiency of the device.
Innovation Solution
The image sensor design incorporates a substrate with a photoelectric conversion element, a via penetrating through the substrate, and a contact extending into the via, with strategically stacked insulating films and varying slope profiles to secure misalignment margins and reduce resistance, including a contact with different slope profiles and dimensions to optimize electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact is disposed on a substrate to connect with a via, then electrical connectivity is achieved, but misalignment between the contact and via occurs leading to reliability issues
Solution Approach 1:
The patent applies beforehand cushioning by designing the contact to extend beyond the sidewalls of the via, creating an overlapping region. This geometric configuration provides a misalignment margin that compensates for potential positioning errors during manufacturing, ensuring reliable electrical connectivity even when alignment is not perfect.
2Reliability
If the width of a contact is increased to reduce resistance, then electrical resistance between contact and lower electrode decreases, but device area increases
Solution Approach 1:
The patent transitions from a two-dimensional contact layout to a three-dimensional configuration by having the contact extend vertically beyond the via sidewalls. This dimensional change increases the effective contact area and reduces resistance without requiring a larger footprint on the substrate plane, thus maintaining compact device area while improving electrical connectivity.
3Reliability
If a contact extends into a via to reduce resistance, then resistance between contact and via decreases, but manufacturing complexity increases
Solution Approach 1:
The patent segments the contact structure into distinct functional regions: a first portion extending beyond the via sidewalls to ensure misalignment tolerance, a second portion within the via to reduce resistance, and a third portion connecting to the lower electrode. This segmentation allows each region to be optimized independently while simplifying the overall manufacturing process through standardized formation steps.
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 enhances the reliability and performance of the image sensor by ensuring proper alignment and reducing electrical resistance, leading to improved signal conversion and processing capabilities.
Implementation Method 1
Each of the pixels may include a photodiode (PD). The photodiode may function to convert incident light into electrical signals.
Data Source
AI summary
An image sensor includes a substrate having a photoelectric conversion element therein, a first via extending into a first surface of the substrate such that a first upper surface of the first via is exposed adjacent the first surface of the substrate, a second upper surface of the first via extending away from the first surface of the substrate, first to third insulating films sequentially stacked on the first surface of the substrate, and a contact extending through the first to third insulating films and into the second upper surface of the first via. The contact includes a first portion within the first via, a second portion in the first insulating film, a third portion in the second insulating film, and a fourth portion in the third insulating film.