Image Sensor Pad Structure for Tungsten Oxidation and Step Defects
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Solution Overview
Problem
The manufacturing of CMOS image sensors faces issues with structural integrity due to tungsten oxidation and the formation of steps between silicon and tungsten in the pad region, which affects the performance and reliability of the image sensor.
Innovation Solution
The image sensor design incorporates a substrate structure with a penetrating conductive material layer that extends into both the upper and lower substrates, minimizing exposure of tungsten and reducing the step defect by using a second conductive material layer that surrounds the sidewall of the first conductive material layer, thereby simplifying the pad region structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten is deposited in the CIS pad region, then electrical connectivity is improved, but tungsten oxidation occurs and structural integrity decreases
Solution Approach 1:
The patent uses a composite structure consisting of a first conductive material layer (tungsten) and a second conductive material layer (aluminum or copper) stacked together. The tungsten layer provides low resistance and high reliability for electrical connectivity, while the aluminum or copper layer protects the tungsten from oxidation and environmental damage, thus maintaining structural integrity.
2Reliability
If tungsten is deposited in the CIS pad region, then electrical connectivity is improved, but step defects are generated between silicon and tungsten
Solution Approach 1:
The stacked composite structure of tungsten and aluminum/copper layers creates a more gradual transition at the interface with silicon, reducing the height difference and minimizing step defects. The softer aluminum or copper layer can better conform to the substrate surface, reducing folding profiles on overlying films.
Solution Approach 2:
The patent changes the material parameters by introducing a second conductive material layer with different physical properties (softer, more ductile) that can better accommodate the interface with silicon, thereby reducing step defects and folding profiles while maintaining electrical connectivity.
3Ease of manufacture
If a simple pad region structure is used, then manufacturing is simplified, but structural integrity and defect reduction are insufficient
Solution Approach 1:
The patent employs a composite material structure with two conductive layers that can be deposited using standard commercial CMOS manufacturing processes. This approach maintains ease of manufacture while significantly improving structural integrity and reducing defects compared to single-layer structures.
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 enhances the structural integrity and performance of the image sensor by reducing defects and simplifying the pad region structure, leading to improved reliability and efficiency in converting light energy into electrical signals.
Implementation Method 1
an ALO capping on tungsten (W) may be deposited in the CIS pad region
Data Source
AI summary
An image sensor includes a substrate structure including a sensor array region and a pad region adjacent to the sensor array region. The substrate structure includes a first substrate structure and a second substrate structure. The first substrate structure is on the second substrate structure. The image sensor includes a penetrating structure including a first conductive material layer and a second conductive material layer in at least a portion of the first substrate structure. The second conductive material layer is electrically connected to the first conductive material layer and extends into the first substrate structure.