Back-Side Illumination Photosite Reset via Deep Isolation Trenches
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Solution Overview
Problem
Back-side illumination imaging devices lack a suitable draining zone for resetting photogenerated charges, as the substrate is removed during fabrication, making existing resetting methods incompatible with this configuration.
Innovation Solution
A method involving deep isolation trenches with electrically conductive internal parts is used to recombine photogenerated charges with charges of opposite polarity, eliminating the need for a draining layer by applying potential differences between these trenches and the semiconductor region, and using a transistor to regenerate and displace charges for recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the substrate is removed during fabrication to enable back-side illumination, then quantum efficiency is improved, but the ability to use the substrate as a draining zone for resetting photogenerated charges is lost
Solution Approach 1:
The patent introduces deep isolation trenches with conductive fillings as intermediary structures to perform the resetting function. These trenches, filled with conductive material and doped semiconductor regions, act as mediators to collect and drain photogenerated charges from the photosite, replacing the substrate's original draining function while preserving back-side illumination capability.
Solution Approach 2:
The patent transitions from using the substrate (horizontal/directional draining) to using vertical deep isolation trenches for charge draining. By creating trenches that extend deeply into the semiconductor region and filling them with conductive material, the draining function is moved to a different spatial dimension (vertical depth), enabling charge collection without requiring a removed substrate.
2Adaptability or versatility
If deep isolation trenches with conductive fillings are introduced for resetting, then resetting capability is improved, but device complexity increases
Solution Approach 1:
The deep isolation trenches serve multiple functions simultaneously: they provide electrical isolation between adjacent photosites, enable resetting of photogenerated charges through their conductive fillings, and contribute to charge collection. By making the isolation trenches multi-functional, the patent avoids adding separate dedicated resetting structures, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the isolation function and the resetting function into a single structural element (the deep isolation trenches with conductive fillings). Instead of having separate isolation structures and separate resetting mechanisms, the conductive-filled trenches perform both roles, reducing overall device complexity.
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
Enables effective resetting of photogenerated charges through recombination without a draining layer, enhancing the functionality of back-side illumination imaging devices by maintaining charge accumulation and isolation capabilities.
Implementation Method 1
the dissociation of the charges takes place by photoelectric effect
Implementation Method 2
The creation may comprise the application of a potential difference between the semiconductor region and the electrically conductive internal part of the at least one deep isolation trench
Data Source
AI summary
A method of resetting a photosite is disclosed. Photogenerated charges accumulated in the photosite are reset by recombining the photogenerated charges with charges of opposite polarity.