Image Sensor Cavity Fabrication for Light Penetration
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Solution Overview
Problem
Miniaturization of MOS image sensors leads to reduced photosensitivity due to low light penetration through dielectric and diffusion barrier layers, and the plasma etch process damages the photoelectric transformation device, increasing dark levels in output signals.
Innovation Solution
A method of forming a cavity that penetrates multi-layer interlayer dielectric and diffusion barrier layers on the photoelectric transformation device, followed by heat or UV treatments to repair damage and increase light penetration, which can include filling the cavity with a light penetration material and forming a color filter and microlens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a plasma etch process is used to form a cavity penetrating the dielectric and diffusion barrier layers, then light penetration to the photoelectric transformation device is improved, but damage to the photoelectric transformation device increases causing higher dark levels in output signals
Solution Approach 1:
The patent applies thermal annealing and UV irradiation treatments to repair the damage caused by the plasma etch process. The thermal treatment heals the damaged photoelectric transformation device, while UV irradiation removes trapped charges, thereby converting the harmful effects of plasma etching into beneficial repair processes that reduce dark levels while maintaining the light penetration improvement from cavity formation
Solution Approach 2:
The patent changes the physical and chemical parameters of the photoelectric transformation device through thermal annealing (temperature parameter) and UV irradiation (energy parameter) to repair damage. These parameter changes restore the device performance and reduce dark levels without compromising the structural benefits of the cavity for light penetration
2Reliability
If multi-layer interlayer dielectric layers and diffusion barrier layers are formed on the photoelectric transformation device, then device functionality and protection are improved, but light penetration ratio decreases reducing photosensitivity
Solution Approach 1:
The patent segments the multi-layer dielectric structure by forming a cavity that penetrates through the interlayer dielectric and diffusion barrier layers. This segmentation creates a light transmission path through the otherwise opaque layered structure, allowing incident light to reach the photoelectric transformation device while the layers remain intact for device protection and functionality
Solution Approach 2:
The patent introduces a vertical dimension by forming a cavity that penetrates through the horizontal layers. This dimensional change creates a three-dimensional light transmission path through the multi-layer structure, enabling light to pass through the dielectric and barrier layers via the cavity while maintaining their protective functions
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
The method reduces the dark level of output signals by enhancing light penetration and repairing damage caused by the etching process, resulting in improved photosensitivity and signal quality.
Implementation Method 1
A heat treatment is performed on the substrate on which the cavity is formed
Implementation Method 2
A UV treatment is performed on the substrate on which the cavity is formed
Implementation Method 3
a photoelectric transformation device which absorbs incident light and accumulates corresponding charge
Data Source
AI summary
A method of fabricating an image sensor includes forming a photoelectric transformation device on a substrate and forming a dielectric layer structure on the substrate. The dielectric layer structure includes multi-layer interlayer dielectric layers and multi-layer metal interconnections which are located between the multi-layer interlayer dielectric layers. A cavity which penetrates the multi-layer interlayer dielectric layers on the photoelectric transformation device is formed. A heat treatment is performed on the substrate on which the cavity is formed.