Image Sensor Pixel Structure With Vertical Signal Channel
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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 pixel unit design incorporates a protection layer, a gate dielectric layer, and a conductive layer to 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
1Area of moving object
If conventional pixel unit design is used, then manufacturing process is simple, but light-sensitive element area occupancy is limited and quantum efficiency is reduced
Solution Approach 1:
The patent introduces a vertical channel structure extending from the light-sensitive element through the protection layer and gate dielectric layer to the conductive layer. This three-dimensional charge transmission path allows the light-sensitive element to occupy larger horizontal area while maintaining efficient electrical connection, resolving the contradiction between area occupancy and structural complexity
Solution Approach 2:
The patent introduces intermediate layers (protection layer, gate dielectric layer) and a conductive layer as mediators between the light-sensitive element and peripheral circuits. These intermediary structures enable the light-sensitive element to expand in area while maintaining electrical connection through the vertical channel, solving the contradiction between area expansion and connection efficiency
2Measurement precision
If light-sensitive element area is increased to improve quantum efficiency, then signal transmission distance increases and transmission efficiency deteriorates
Solution Approach 1:
The patent transitions from horizontal signal transmission to vertical channel transmission. The vertical channel provides a direct, short transmission path from the light-sensitive element through the protection layer and gate dielectric layer to the conductive layer, eliminating the problem of increased transmission distance that would result from larger light-sensitive element areas
Solution Approach 2:
The patent segments the signal transmission path into distinct vertical layers (light-sensitive element, protection layer, gate dielectric layer, conductive layer), with each layer optimized for its specific function. This segmentation allows the light-sensitive element to be large for high quantum efficiency while the vertical channel maintains short transmission distance for high transmission efficiency
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 increasing the overall performance of the image sensor.
Implementation Method 1
a gate dielectric layer and a conductive layer are sequentially disposed on the light-sensitive element and surround the post structure, thereby forming a vertical gate structure on the light-sensitive element
Data Source
AI summary
A method for fabricating an image sensor is provided. The method includes forming a first light-sensitive pixel unit and a second light-sensitive pixel unit neighboring the first light-sensitive pixel unit in a sensor wafer, and bonding the sensor wafer to a circuit wafer. Forming the first light-sensitive pixel unit and the second light-sensitive pixel unit includes forming a first light-sensitive element and a second light-sensitive element in the sensor wafer; and forming a first source contact over the first light-sensitive element and a second source contact over the second light-sensitive element. Bonding the sensor wafer to the circuit wafer is performed such that a first pixel circuit of the circuit wafer is electrically connected to the first source contact, and a second pixel circuit of the circuit wafer is electrically connected to the second source contact.