Color Filter Integration in Inter-Metal Dielectric Layers
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Solution Overview
Problem
Image sensors face reduced optical performance and increased crosstalk due to the large distance between color filters and micro lenses, which degrades imaging efficiency when the backend thickness of the substrate is thinned for optical light path reduction.
Innovation Solution
The integration of a color filter within the inter-metal-dielectric layers of the image sensor, vertically aligned with the image-sensing region, reduces the optical path and enhances imaging efficiency by minimizing light diffraction and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the backend thickness of the substrate is thinned down for optical light path reduction, then optical performance is improved, but crosstalk increases
Solution Approach 1:
The color filter is moved from a planar position above the substrate to a vertical integration within the inter-metal-dielectric layers, changing the spatial dimension of light filtering. This vertical integration shortens the optical path length while maintaining effective color separation, thereby improving optical performance without increasing crosstalk.
Solution Approach 2:
The color filter is nested within the existing inter-metal-dielectric layer structure of the image sensor. By embedding the color filter material within the IMD layers during the fabrication process, the filter becomes an integral part of the sensor stack, reducing the overall optical path distance between the color filter and the photodetector while maintaining structural integrity.
2Productivity
If the distance between color filter and micro lens is reduced, then imaging efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The color filter formation process is merged with the existing inter-metal-dielectric layer fabrication process. By depositing color filter material within the IMD layers using standard semiconductor manufacturing techniques, the color filter and interconnect structure become a unified integrated component, reducing manufacturing steps and complexity while achieving shorter optical path distance.
3Reliability
If the color filter is integrated within inter-metal-dielectric layers, then quantum efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The color filter material is deposited selectively within specific regions of the inter-metal-dielectric layers corresponding to the pixel array locations. This localized integration ensures that the color filter is precisely positioned over each photodetector without requiring high-precision alignment across the entire wafer, as the filter formation occurs during standard IMD deposition processes already localized to pixel regions.
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 improves quantum efficiency and sensitivity while reducing crosstalk, leading to enhanced imaging performance and ease of implementation across various image sensor generations.
Implementation Method 1
a color filter formed in at least one of the IMD layers and overlying the image sensor
Data Source
AI summary
The present disclosure provides various embodiments of an image sensor device. An exemplary image sensor device includes an image sensing region disposed in a substrate; a multilayer interconnection structure disposed over the substrate; and a color filter formed in the multilayer interconnection structure and aligned with the image sensing region. The color filter has a length and a width, where the length is greater than the width.