Image Sensor Through-Passage Isolation Against Metal Diffusion
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Solution Overview
Problem
Current image sensor fabrication methods face challenges in preventing metal diffusion from conductive fillings into the semiconductor substrate, which can lead to contamination and affect device performance, while also requiring effective passivation and mutual isolation between pixels.
Innovation Solution
The solution involves a semiconductor substrate with through-passages and dielectric anti-diffusion layers that prevent metal diffusion, comprising interior and back dielectric layers made of silicon oxide, with conductive fillings of doped polysilicon and tungsten, and additional metal layers in local cavities, ensuring isolation and passivation of internal interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal fillings are used in through-passages for electrical connections, then electrical conductivity is improved, but metal diffusion into the semiconductor substrate causes contamination and performance degradation
Solution Approach 1:
A dielectric anti-diffusion layer is introduced as an intermediary between the metal filling and the semiconductor substrate. This layer physically separates the two materials, allowing electrical connectivity through the metal filling while preventing harmful metal atoms from diffusing into the substrate and degrading device performance.
Solution Approach 2:
The through-passage structure is segmented into distinct functional zones: a first portion containing the metal filling for electrical conduction, and a second portion containing the dielectric anti-diffusion layer for contamination prevention. This segmentation allows each material to perform its specific function without interfering negatively with the other.
2Reliability
If through-passages are formed in the substrate for electrical connections, then electrical connectivity is improved, but the substrate structure becomes more complex and vulnerable to contamination
Solution Approach 1:
The through-passage is divided into functionally distinct portions: a first portion for electrical conduction and a second portion for anti-diffusion protection. This segmentation enables the structure to achieve both electrical connectivity and contamination prevention without requiring entirely new architectural approaches.
Solution Approach 2:
The dielectric anti-diffusion layer serves multiple functions simultaneously: it acts as a diffusion barrier to prevent metal contamination, provides structural support within the through-passage, and maintains the integrity of the substrate architecture. This multi-functionality reduces the need for additional separate components.
3Reliability
If anti-diffusion layers are added to prevent metal contamination, then substrate integrity is improved, but the device structure and fabrication process become more complex
Solution Approach 1:
The dielectric anti-diffusion layer is integrated into the existing through-passage structure, merging the anti-diffusion function with the electrical connection pathway. This integration approach allows the anti-diffusion protection to be achieved without adding entirely separate structural elements, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The dielectric anti-diffusion layer serves as an intermediary element that is strategically placed within the through-passage structure. Rather than adding complex external protection systems, this intermediary layer provides substrate integrity protection through a relatively simple integrated structure that fits within the existing architectural framework.
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 approach effectively prevents metal contamination, achieves mutual isolation between pixels, and enhances the performance of image sensors by maintaining the integrity of the semiconductor material and optimizing light sensing capabilities.
Implementation Method 1
dielectric layers for anti-diffusion of the metal of the fillings into the semiconductor substrate wafer
Data Source
AI summary
An electronic device includes a substrate semiconductor wafer with semiconductor portions separated from one another by through-passages. Electronic circuits and a dielectric layer with a network of electrical connections are formed at a front face of the substrate semiconductor wafer. Electrically conductive fillings are contained within the through-passages and are connected to the network of electrical connections. Interior dielectric layers for anti-diffusion protection are provided in the through-passages between the electrically conductive fillings and the semiconductor portions. Back side dielectric layers are joined to the interior dielectric layers.