Vertically Stacked Light Sensors for Multi-Wavelength Imaging
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Solution Overview
Problem
Current image sensor technologies require multiple chips for sensing different wavelength ranges, leading to increased fabrication costs and a larger lateral footprint due to the need for separate CMOS image sensors for visible and infrared light, which are not efficiently integrated.
Innovation Solution
A stacked integrated chip (IC) structure is developed, where a first IC chip with visible light sensors is vertically stacked over a second IC chip with infrared light sensors, both sharing a common lens structure and interconnects, using silicon for visible light and germanium for infrared light absorption, reducing lateral footprint and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate chips are used for sensing different wavelength ranges, then each sensor can be optimized for its specific wavelength, but the lateral footprint and fabrication costs increase
Solution Approach 1:
The patent transitions from a lateral arrangement of multiple separate chips to a vertical stacking configuration. Different wavelength sensors (visible, NIR, SWIR) are stacked in the vertical dimension rather than arranged side-by-side in the lateral plane. This dimensional change allows multiple sensors to coexist in a compact footprint while maintaining individual optimization for their respective wavelength ranges through separate substrate and sensor designs.
Solution Approach 2:
The patent combines multiple previously separate chips into a single integrated stacked structure. The visible light sensor chip, NIR sensor chip, and SWIR sensor chip are merged through vertical stacking with shared packaging and interconnect structures. This merging reduces the overall lateral footprint while preserving the specialized sensing capabilities of each wavelength range through material-specific sensor designs.
2Measurement precision
If multiple separate chips are used for sensing different wavelength ranges, then each sensor can be optimized for its specific wavelength, but fabrication costs increase
Solution Approach 1:
The patent merges multiple separate fabrication processes into a more integrated manufacturing flow. While each sensor chip retains its specialized material composition (silicon for visible, InGaAs for NIR, HgCdTe for SWIR), the stacked configuration allows for shared packaging, interconnect structures, and system-level integration. This reduces overall fabrication costs by eliminating redundant packaging and interconnection components that would be required for separate chips.
3Area of stationary object
If vertically stacked light sensors are used, then lateral footprint and fabrication costs are reduced, but integration complexity increases
Solution Approach 1:
The patent segments the integrated sensor system into distinct functional modules stacked vertically. Each wavelength sensor (visible, NIR, SWIR) remains as a separate sensor chip with its own optimized substrate and sensor array. This segmentation allows each module to be independently designed, fabricated, and tested using established processes for that specific wavelength range, while the vertical stacking provides a systematic integration framework that manages complexity through modular assembly.
4Productivity
If vertically stacked light sensors are used, then device density is increased, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates preliminary alignment features during the fabrication of individual sensor chips. Alignment marks, mechanical interlocks, and registration structures are built into each chip before stacking. This preliminary preparation ensures that when chips are stacked vertically, they can be precisely aligned without requiring ultra-precision assembly equipment. The alignment features are designed into the chips themselves, enabling high device density while maintaining manufacturability through standard precision assembly processes.
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 configuration allows efficient sensing of multiple wavelength ranges while minimizing fabrication costs and increasing device density by vertically integrating visible and infrared light sensors within a single chip structure.
Implementation Method 1
a first substrate comprising a first semiconductor material; a first light sensor disposed within the first substrate, wherein the first light sensor is configured to absorb electromagnetic radiation within a first wavelength range
Implementation Method 2
an absorption structure underlying the first substrate and comprising a second semiconductor material different from the first semiconductor material. The second light sensor is disposed within the absorption structure
Data Source
AI summary
Various embodiments of the present disclosure are directed towards a semiconductor structure including a first substrate comprising a first semiconductor material. A first light sensor is disposed within the first substrate. The first light sensor is configured to absorb electromagnetic radiation within a first wavelength range. A second light sensor is disposed within an absorption structure underlying the first substrate. The second light sensor is configured to absorb electromagnetic radiation within a second wavelength range different from the first wavelength range. The absorption structure underlies the first light sensor and comprises a second semiconductor material different from the first semiconductor material.