Stacked Pixel Semiconductor Capacitor With 3D Trench Electrodes
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Solution Overview
Problem
Existing image sensors face challenges in increasing the full well capacity (FWC) of photodetectors without compromising the area available for metal routing in the interconnect structure, which affects device scaling and density.
Innovation Solution
The image sensor design incorporates a semiconductor capacitor with increased capacitance, where the capacitor is disposed on the second substrate of the second IC die, allowing for protrusions in trenches to increase the area between the capacitor electrodes without expanding the lateral footprint, thus enhancing FWC without reducing pixel transistor area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitor is disposed within the interconnect structure of the first IC die, then the FWC of photodetectors is increased, but the area available for metal routing is reduced
Solution Approach 1:
The pixel circuit is divided across two separate IC dies: the first IC die contains the photodetectors and some circuit elements, while the second IC die contains the capacitors and other circuit elements. This segmentation allows the capacitor to be formed on the back surface of the second IC die without occupying routing area on the first IC die, thereby resolving the contradiction between increasing FWC and maintaining metal routing area.
2Quantity of substance
If the lateral footprint of the capacitor is increased to increase capacitance, then the FWC is improved, but the pixel transistor area is reduced
Solution Approach 1:
The capacitor is formed by utilizing the vertical dimension through protrusions that extend into trenches on the back surface of the second IC die. This three-dimensional configuration increases the effective capacitance area without expanding the lateral footprint, allowing high capacitance values while maintaining sufficient area for pixel transistors and other circuit elements.
3Quantity of substance
If the capacitor is disposed on the first IC die, then the FWC is increased, but the device density and scaling are compromised
Solution Approach 1:
By segmenting the pixel circuit across two IC dies and placing the capacitor on the back surface of the second IC die, the design enables higher device density on each individual die. The capacitor does not occupy valuable routing or transistor area, allowing for more efficient packing of circuit elements and improved scalability.
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 increases the FWC of photodetectors, improves device density, and simplifies metal routing, reducing design complexity and fabrication costs while facilitating device scaling.
Implementation Method 1
a semiconductor capacitor with increased capacitance, where the capacitor is disposed on the second substrate of the second IC die, allowing for protrusions in trenches to increase the area between the capacitor electrodes
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an image sensor including a first integrated circuit (IC) die stacked with a second IC die. The first IC die includes a plurality of photodetectors disposed within a first substrate. The second IC die includes a plurality of pixel transistors and a semiconductor capacitor disposed on a second substrate. The semiconductor capacitor includes a first capacitor electrode, a capacitor dielectric layer, and a doped capacitor region. The first capacitor electrode overlies the second substrate and comprises a protrusion disposed in the second substrate. The capacitor dielectric layer is disposed between the first capacitor electrode and the second substrate. The doped capacitor region is disposed within the second substrate and underlies the first capacitor electrode. The plurality of photodetectors, the plurality of pixel transistors, and the semiconductor capacitor define a pixel.