Multi-Substrate Image Sensor Wiring for Dense Pixel Integration
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Solution Overview
Problem
Current image sensors face challenges in increasing integration density and efficiently arranging wirings due to limited degrees of freedom in space for connecting source follower, select, and reset transistors.
Innovation Solution
A vertically integrated image sensor design with multiple substrates, including a pixel region, connection region, and pad region, featuring advanced wiring structures and adhesion pads to enhance electrical signal transfer and increase integration density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional planar image sensor structure is used, then the manufacturing process is simpler, but the integration density is limited and wiring arrangement flexibility is reduced
Solution Approach 1:
The patent transitions from a conventional planar (2D) image sensor structure to a three-dimensional stacked structure with multiple substrates arranged vertically. The first substrate contains pixel regions and connection regions, while the second substrate is stacked above it to provide additional wiring layers and functional regions. This vertical stacking enables higher integration density by utilizing the third dimension (height) for wiring arrangement and component placement, effectively increasing the degrees of freedom for connecting transistors and reducing wiring congestion in the planar direction.
2Reliability
If more wirings are added to connect transistors, then the electrical signal transfer is improved, but the space for wiring arrangement becomes more constrained
Solution Approach 1:
The patent utilizes vertical stacking of substrates to create multiple wiring layers in the height direction. The first substrate provides initial wiring layers, while the second substrate stacked above it introduces additional wiring planes. This three-dimensional wiring architecture allows electrical signals to be transferred through multiple vertical and horizontal pathways, improving signal transfer reliability without confining all wirings to a single planar layer, thereby alleviating space constraints.
Solution Approach 2:
The patent divides the image sensor into multiple functional substrates: the first substrate contains pixel regions with photodetectors and initial wiring, while the second substrate provides additional wiring layers and connection regions. This segmentation allows different substrates to specialize in different functions, with the first substrate focusing on light sensing and the second substrate focusing on complex wiring and transistor connections, thereby improving overall wiring efficiency and signal transfer.
3Manufacturing precision
If the substrate area is increased to accommodate more components, then the integration density improves, but the overall sensor size increases
Solution Approach 1:
The patent achieves higher integration density by stacking substrates vertically rather than expanding the planar area. The first substrate contains essential pixel regions, while the second substrate is stacked above it to provide additional wiring and connection functionality. This vertical integration allows more components and wiring to be packed into the same footprint area, increasing integration density without proportionally increasing the overall sensor size.
Data Source
AI summary
An image sensor includes a first substrate having a first transistor integrated therein, and a first plurality of wiring structures on the first substrate. The first plurality of wiring structures include a first wiring structure electrically connected to the first transistor. A second substrate extends on the first plurality of wiring structures, and has a second transistor integrated therein, which is electrically connected to a second wiring structure within the first plurality of wiring structures. A second plurality of wiring structures extend on the second substrate. A third substrate is provided on the second plurality of wiring structures. A microlens extends on a light receiving surface of the third substrate. A light sensing element extends within the third substrate. A transfer gate (TG) extends into a portion of the third substrate, extends adjacent the light sensing element, and is electrically connected to a first wiring structure within the second plurality of wiring structures. A floating diffusion (FD) region extends within the third substrate and adjacent the TG. The FD region is electrically connected to a second wiring structure within the second plurality of wiring structures.