Near-Infrared Sensor Plasmonic Coupling for Thin CMOS Integration
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Solution Overview
Problem
Integrating near infrared light sensors with CMOS image sensors is challenging due to low absorption of near infrared light by silicon-based materials, leading to low quantum efficiency, and existing solutions like thickening the silicon base or adding germanium increase complexity and thickness.
Innovation Solution
Incorporating a surface plasmon polariton structure at the light-receiving surface of near infrared light detectors using existing CMOS manufacturing steps, with embedded gratings and metal grids tuned to resonate at the infrared wavelength, enhancing optical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the silicon base is thickened to improve near infrared light absorption, then absorption efficiency is improved, but device thickness and complexity increase
Solution Approach 1:
The patent changes the optical parameters of the silicon surface by introducing surface plasmon polariton structures with specific grating patterns and metal layer configurations. These structures are designed to resonate at near infrared wavelengths, fundamentally altering how light interacts with the silicon surface without changing the bulk silicon thickness.
Solution Approach 2:
The patent creates a composite structure combining silicon substrate with metal gratings (such as gold, silver, or aluminum) and dielectric layers. This composite surface structure leverages the plasmonic properties of metals and the optical properties of silicon to achieve enhanced near infrared absorption while maintaining thin overall device profile.
2Reliability
If germanium is added to improve near infrared light absorption, then quantum efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent introduces surface plasmon polariton structures as an intermediary mechanism between incident near infrared light and the silicon photodetector. These metallic grating structures act as mediators that couple light into the silicon substrate through plasmonic resonance, eliminating the need for germanium material modification while achieving similar or superior absorption enhancement.
Solution Approach 2:
The patent replaces the material composition approach (adding germanium to silicon) with a surface structure approach (metal gratings and plasmonic structures). This substitution maintains the simplicity of standard silicon manufacturing processes while achieving enhanced near infrared response through optical engineering rather than material engineering.
3Reliability
If surface plasmon polariton structures are added to improve light coupling, then near infrared absorption is improved, but device complexity increases
Solution Approach 1:
The patent divides the surface plasmon polariton structure into discrete, periodic grating elements that can be independently optimized and fabricated using standard photolithography techniques. This segmentation allows the complex optical function to be achieved through simple, repeating geometric patterns rather than continuous complex surfaces.
Solution Approach 2:
The patent designs the surface plasmon polariton structures to serve multiple functions: enhancing near infrared absorption, maintaining visible light rejection, and providing a platform for further optical engineering. The same grating structures that enhance coupling also serve as the basis for subsequent metal layer deposition and pattern formation, reducing overall process complexity.
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
Improves near infrared light absorption by a factor of five or more, maintaining sensor thickness and reducing complexity by using existing manufacturing processes.
Implementation Method 1
The metal grating and aligned embedded grating of each respective infrared light sensor form a surface plasmon polariton structure configured to couple with light at the design-basis infrared wavelength to form a surface plasmon polariton at the light-receiving surface of the respective infrared light sensor
Implementation Method 2
enhancing optical coupling
Data Source
AI summary
A near infrared sensing device includes a near infrared light sensor configured to detect infrared light at least at a design-basis infrared wavelength, and a surface plasmon polariton structure including at least an embedded grating that is embedded in a light-receiving surface of the near infrared light sensor. The surface plasmon polariton structure is configured to couple with light at the design-basis infrared wavelength to form a surface plasmon polariton at the light-receiving surface of the near infrared light sensor. The surface plasmon polariton structure may further include a metal grating disposed on the light-receiving surface of the near infrared light sensor and aligned with the embedded grating. The embedded grating may comprise an embedded metal grating that is embedded in the light-receiving surface of the near infrared light sensor, or trenches formed in the light-receiving surface of the near infrared light sensor and at least partially filled with air.