Image Sensor Pixel Structure With Vertical Signal Channels
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Solution Overview
Problem
Conventional image sensors face challenges in achieving high quantum efficiency and full well capacity due to limitations in the design of pixel units, which restrict the area occupancy by light-sensitive elements and affect signal transmission efficiency.
Innovation Solution
The proposed solution involves a pixel unit design with a semiconductor substrate, a light-sensitive element, a protection layer, and a gate dielectric layer, where the protection layer and conductive layer induce a channel for upward signal transmission, allowing the light-sensitive element to occupy a larger area and improve quantum efficiency by enabling efficient electrical signal transmission to peripheral circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pixel unit design uses conventional structures, then the manufacturing process is simpler, but the light-sensitive element area occupancy is reduced, lowering quantum efficiency
Solution Approach 1:
The patent transitions from planar signal transmission to vertical three-dimensional signal transmission by inducing channels in the light-sensitive element that extend upward through the pixel structure. This dimensional change allows the light-sensitive element to maintain large area occupancy while efficiently transmitting signals to peripheral circuits located at different vertical levels, thereby improving quantum efficiency without excessive structural complexity
Solution Approach 2:
The patent introduces induced channels as intermediary pathways within the light-sensitive element that facilitate signal transmission from the photoelectric conversion region upward to peripheral circuits. These channels act as mediators that enable efficient signal transport without requiring direct lateral connections, allowing larger light-sensitive element area while maintaining electrical connectivity
2Manufacturing precision
If the light-sensitive element occupies larger area, then quantum efficiency improves, but signal transmission efficiency may be affected
Solution Approach 1:
The patent resolves this contradiction by establishing vertical transmission channels that extend upward through the light-sensitive element. This three-dimensional approach allows the light-sensitive element to occupy maximum planar area for high quantum efficiency while the vertical channels provide efficient signal transmission pathways to peripheral circuits, decoupling area occupancy from transmission efficiency
Solution Approach 2:
The patent segments the signal transmission function from the photoelectric conversion area by creating dedicated vertical channels within the light-sensitive element. These segmented channels provide specialized pathways for signal transport, allowing the majority of the element area to be dedicated to light sensitivity while specific regions facilitate efficient signal transmission to peripheral circuits
3Device complexity
If conventional pixel design is used, then device complexity is lower, but dark current reduction and signal transmission are compromised
Solution Approach 1:
The patent introduces induced channels as intermediary structures that mediate between the photoelectric conversion region and peripheral circuits. These channels provide controlled pathways that reduce dark current by confining carrier movement to specific regions while maintaining signal transmission quality, achieving improved reliability without excessive structural complexity
Solution Approach 2:
The patent applies local quality by creating induced channels with specific electrical properties in targeted regions of the light-sensitive element. These localized channels have enhanced carrier confinement and transmission properties, improving signal quality and reducing dark current in critical areas while maintaining simpler structures in other regions
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 design enhances quantum efficiency and full well capacity by allowing the light-sensitive element to cover a larger pixel area, improving signal transmission and reducing dark current, thereby optimizing image sensor performance.
Implementation Method 1
The sensing wafer includes pixel units for converting various types of photo energy of light into electrical signals
Implementation Method 2
the protection layer and conductive layer induce a channel for upward signal transmission
Data Source
AI summary
A method for fabricating an image sensor is provided. The method includes doping a bottom portion of a semiconductor substrate with a first dopant to form a light-sensitive element in the bottom portion of the semiconductor substrate; etching a top portion of the semiconductor substrate to form a post structure on the light-sensitive element; forming a gate structure on at least one sidewall of the post structure, wherein the gate structure exposes a first part of the bottom portion of the semiconductor substrate; doping the exposed first part of the bottom portion of the semiconductor substrate with a second dopant to form a pinning layer on the light-sensitive element, wherein the second dopant has a conductivity type opposite that of the first dopant; and forming a contact on the post structure.