Stacked Image Sensor Shared Diffusion Regions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional stacked image sensors face increased cost and complexity due to per-pixel interconnects between photosensitive elements and circuitry, which negatively impacts performance.
Innovation Solution
Implementing shared diffusion regions in the sensor wafer, where photosensitive elements are interconnected through shared floating diffusion regions and inter-wafer interconnects, reducing the need for individual pixel connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If per-pixel interconnects are used between sensor wafer and circuit wafer, then each pixel can be individually connected to circuitry, but manufacturing cost and device complexity significantly increase
Solution Approach 1:
Multiple photodiodes share a common floating diffusion region and common interconnect structure. Instead of providing separate interconnects for each pixel, the patent merges the connection path for multiple pixels through shared diffusion regions, thereby reducing the total number of interconnects and simplifying the overall device structure while maintaining functional connectivity.
Solution Approach 2:
The shared floating diffusion region serves multiple functions: it acts as the charge collection node for multiple photodiodes simultaneously, and serves as a common connection point that interfaces with the underlying circuit wafer. This multi-functional design reduces the number of specialized components needed in the sensor structure.
2Reliability
If per-pixel interconnects are implemented, then complete signal routing is achieved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple signal paths into a shared interconnect structure through common floating diffusion regions. This merging approach reduces the total number of interconnects that need to be fabricated and connected between wafers, directly lowering manufacturing complexity and cost while still achieving complete signal routing for all pixels through the shared infrastructure.
3Device complexity
If shared diffusion regions are used, then interconnect complexity is reduced, but photosensitive element density in array positions decreases
Solution Approach 1:
The patent extracts the floating diffusion region from the traditional pixel location and places it in a separate shared position outside the main photodiode array. This extraction allows photodiodes to occupy their optimal positions for light sensitivity while the diffusion region is relocated to serve multiple pixels without competing for the same spatial resources, thus maintaining high photosensitive element density while achieving shared connectivity.
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 simplifies the manufacturing of stacked image sensors, reduces cost and complexity, and enhances performance by leveraging sparse CFA patterns for improved light sensitivity and simplified image processing.
Implementation Method 1
The sensor wafer comprises a plurality of photodiodes or other photosensitive elements arranged in respective positions of a two-dimensional array of positions
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A CMOS image sensor (100) or other type of image sensor comprises a sensor wafer (106) and an underlying circuit wafer (108) The sensor wafer comprises a plurality of photosensitive elements (Al, A3, B4, C2, Dl, D3) arranged in respective positions of a two-dimensional array of positions in which a subset of the array positions do not include photosensitive elements but instead include diffusion regions (103A,103D) each of which is shared by two or more of the photosensitive elements. The sensor wafer is interconnected with the circuit wafer utilizing a plurality of inter-wafer interconnects (104A,104D) coupled to respective ones of the shared diffusion regions in respective ones of the array positions that do not include photosensitive elements. The image sensor may be implemented in a digital camera or other type of image capture device.