Shared-Transistor Image Sensor Layout for Reduced Contact Area
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Solution Overview
Problem
The existing image capturing devices, such as CMOS, have a configuration where photoelectric transducers and pixel transistors are on the same semiconductor substrate, leading to an increased substrate area due to the high number of contacts required for wiring connections, which is not effectively reduced.
Innovation Solution
An image sensor design where photoelectric transducers and pixel transistors are on separate substrates, with shared pixel transistors and a reduced number of contacts through a specific wiring configuration that aggregates multiple elements onto a single contact, thereby minimizing the substrate area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If photoelectric transducers and pixel transistors are disposed on the same semiconductor substrate, then the device structure is simplified, but the substrate area increases due to the high number of contacts required for wiring connections
Solution Approach 1:
The patent divides the device into two separate substrates: a first substrate containing photoelectric transducers and a second substrate containing pixel transistors. This segmentation allows each substrate to be optimized independently, reducing the number of contacts required on each substrate while maintaining functional integration through the stacked configuration.
Solution Approach 2:
The patent transitions from a planar two-dimensional layout to a three-dimensional stacked configuration. By stacking the first substrate with photoelectric transducers and the second substrate with pixel transistors vertically, the device reduces the footprint area while maintaining the necessary functional connections through vertical inter-substrate wiring.
2Area of stationary object
If multiple photoelectric transducers share one pixel transistor on separate substrates, then the substrate area is reduced, but the number of wiring contacts increases
Solution Approach 1:
The patent merges multiple first elements (photoelectric transducer connections) into a single shared second element (pixel transistor) through the second wiring. This consolidation reduces the number of separate wiring paths and contacts required, as multiple photoelectric transducers can be connected to a single pixel transistor via the aggregated second wiring structure.
Solution Approach 2:
The second wiring structure is designed to serve multiple functions: it connects multiple first elements to the shared second element, aggregates signal paths, and reduces the overall number of contacts required. This multi-functional wiring approach efficiently handles the connections between the photoelectric transducers and the shared pixel transistor.
3Productivity
If individually stacked substrates are used with shared pixel transistors, then photoelectric conversion efficiency is improved, but the mounting area increases due to multiple contacts
Solution Approach 1:
The patent employs a three-dimensional stacked configuration where the first substrate with photoelectric transducers is vertically stacked with the second substrate containing shared pixel transistors. This vertical arrangement improves photoelectric conversion efficiency by optimizing the photoelectric transducer layout while reducing the horizontal mounting area through efficient vertical inter-substrate connections.
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 effectively reduces the substrate area and improves photoelectric conversion efficiency by minimizing transistor noise and increasing pixel density, while maintaining the same chip size.
Implementation Method 1
a first semiconductor substrate having a pixel region and a second semiconductor substrate having a logic circuit are stacked on top of each other... a photoelectric transducer and a pixel transistor, both disposed on the same semiconductor substrate. The pixel transistor reads out an electric signal corresponding to the amount of light received by the photoelectric transducer
Data Source
AI summary
A first substrate having a plurality of photoelectric transducers formed on the first substrate, a second substrate having a pixel transistor for each of sets of two or more of the photoelectric transducers as a constituent unit, the pixel transistor being shared by the set and formed on the second substrate, and a second wiring which is connected to a first wiring formed on the second substrate via one contact, and is connected to a plurality of first elements, the first wiring leading to a second element shared by a plurality of first elements among a plurality of elements formed on the first substrate, each of the plurality of first elements being formed for each of the photoelectric transducers are included.