Photoconductor-on-Active Pixel Fabrication via Selective Layer Removal
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Solution Overview
Problem
In the fabrication of photoconductor-on-active pixel devices, existing methods face challenges in exposing photo sensing devices to light without obstruction from opaque active devices and interconnects, which affects the efficiency of image sensors.
Innovation Solution
A method involving the deposition of conductive and dielectric layers, capping layers, and the formation of radiation absorbing layers on exposed portions, along with the creation of conductive pads and interconnects, allows for the exposure of photo sensing devices to light while maintaining the integrity of active devices and interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photo sensing devices are formed over active devices to allow light exposure, then light exposure efficiency is improved, but the complexity of the fabrication process increases due to multiple layer depositions and removal steps
Solution Approach 1:
The fabrication process is segmented into distinct stages: forming conductive layers with capping layers, selective removal to create pads and interconnects, depositing additional dielectric and capping layers, and finally forming radiation absorbing layers on specific exposed portions. Each segment addresses a specific structural requirement, allowing the photo sensing devices to be exposed to light while maintaining the integrity of active devices and interconnects through controlled layer removal and deposition.
2Reliability
If multiple layers are deposited and removed to create conductive pads and interconnects, then the functionality of active devices is maintained, but the manufacturing time and process steps increase
Solution Approach 1:
Capping layers are deposited over conductive layers before the conductive layers are removed to form pads and interconnects. This preliminary action protects the conductive structures during subsequent processing steps and ensures that the conductive patterns are formed accurately. The capping layers are later removed selectively to expose the conductive portions, ensuring proper device functionality while following a systematic fabrication sequence that manages manufacturing time.
Solution Approach 2:
The fabrication process utilizes multiple vertical layers (conductive layers, capping layers, dielectric layers, radiation absorbing layers) stacked in the thickness dimension. By working in this vertical dimension and selectively removing portions of layers at different heights, the process creates the three-dimensional structure of pads and interconnects while maintaining control over the fabrication sequence and reducing the number of lateral processing steps required.
3Use of energy by moving object
If radiation absorbing layers are formed on exposed portions of dielectric layers and conductive pads, then light absorption efficiency is enhanced, but the number of fabrication steps increases
Solution Approach 1:
Radiation absorbing layers are formed selectively on exposed portions of dielectric layers and conductive pads rather than uniformly across the entire surface. This local quality approach ensures that radiation absorption is enhanced precisely where needed - in the photo sensing device regions - while avoiding unnecessary material deposition on other areas. The selective formation is achieved through the prior selective removal of layers, creating a targeted structure that improves light absorption efficiency without requiring additional comprehensive fabrication 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 approach enables efficient light absorption by photoconductor layers, enhancing the performance of image sensors by ensuring unobstructed exposure to radiation while maintaining the functionality of active devices and interconnects.
Implementation Method 1
enables efficient light absorption by photoconductor layers
Data Source
AI summary
A design structure embodied in a machine readable medium used in a design process includes a first dielectric layer disposed on an intermediary layer, a first conductive pad portion and a first interconnect portion disposed on the first dielectric layer, a second dielectric layer disposed on the first dielectric layer, a first capping layer disposed on the first interconnect portion and a portion of the first conductive pad portion, a second capping layer disposed on the first capping layer and a portion of the second dielectric layer, an n-type doped silicon layer disposed on the second capping layer and the first conductive pad portion, an intrinsic silicon layer disposed on the n-type doped silicon layer, and a p-type doped silicon layer disposed on the intrinsic silicon layer.