PIC Optical Deflector Stack Against SiN Ambient Light Degradation
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Solution Overview
Problem
Silicon nitride (SiN) optical components in photonic integrated circuits (PICs) are prone to light-induced degradation (LID) due to exposure to ambient light, which can occur during manufacturing, packaging, and usage, and enclosing the PIC in an ambient light-impervious container is not always feasible.
Innovation Solution
Incorporating multiple optical deflectors with alternating high and low refractive index dielectric layers over the SiN optical components and interconnect layers to deflect harmful ambient light wavelengths, specifically within the range of 380-570 nanometers, thereby protecting the SiN components from damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiN optical components are used in PIC dies, then high frequency light signals can be handled with low propagation losses, but the SiN components degrade when exposed to ambient light (light-induced degradation)
Solution Approach 1:
The patent introduces an optical deflector as an intermediary layer between the ambient light environment and the SiN optical components. This deflector comprises alternating layers of high and low refractive index dielectric materials that actively intercept and redirect harmful ambient light wavelengths (380-780 nm) away from the SiN components, preventing direct exposure and degradation while allowing the SiN components to maintain their low-loss optical signal transmission capabilities
Solution Approach 2:
The optical deflector is positioned and designed to preemptively block ambient light before it can reach the SiN optical components. By placing the deflector over interconnect layers that sit above the SiN components, the system creates a preliminary barrier that deflects harmful wavelengths in advance, preventing the light-induced degradation from occurring in the first place rather than attempting to repair or mitigate damage after exposure
2Object-affected harmful factors
If the PIC die is enclosed in an ambient light-impervious container, then LID protection is provided, but enclosing the die is not possible during packaging and manufacturing processes
Solution Approach 1:
The optical deflector is nested within the existing PIC die structure, specifically positioned over the interconnect layers that already exist above the SiN optical components. This nested integration allows the protective function to be built-in during the semiconductor manufacturing process itself, eliminating the need for external light-tight containers and enabling standard packaging procedures while maintaining continuous protection against ambient light exposure
Solution Approach 2:
The optical deflector serves multiple functions simultaneously: it acts as a protective barrier against ambient light for the SiN components, maintains compatibility with standard packaging processes, and can be integrated into existing manufacturing workflows. The deflector's design allows it to perform its light-deflection function across various manufacturing and operational stages without requiring specialized handling or packaging equipment
3Object-affected harmful factors
If thin-film dielectric stacks are used as band-pass filters or anti-reflection devices, then optical filtering is achieved, but comprehensive protection across the full ambient light spectrum (380-780 nm) is not provided
Solution Approach 1:
The optical deflector employs a composite structure consisting of multiple alternating layers of high refractive index dielectric materials and low refractive index dielectric materials. This composite configuration creates constructive and destructive interference patterns that collectively deflect a broad spectrum of ambient light wavelengths (380-780 nm). The alternating refractive indices enhance the deflection efficiency across different wavelengths, providing comprehensive protection that single-material filters cannot achieve
Solution Approach 2:
The deflector is segmented into multiple discrete alternating layers rather than using a single uniform layer. Each interface between high and low refractive index layers contributes to the overall light-deflection effect. This segmentation into multiple thin layers allows the structure to address different wavelengths within the ambient light spectrum through cumulative interference effects, achieving broader spectral coverage than any single layer could provide
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
The optical deflectors provide comprehensive protection to SiN components by deflecting harmful ambient light, mitigating LID and ensuring the longevity and functionality of PICs, while being compatible with monolithic silicon photonics platforms and processes, thus easy to implement.
Implementation Method 1
at least one optical deflector over the multiple interconnect layers and over the silicon nitride optical component
Implementation Method 2
each optical deflector including a plurality of alternating layers including at least one high refractive index dielectric layer and at least one low refractive index dielectric layer
Data Source
AI summary
A photonic integrated circuit (PIC) die includes a silicon nitride optical component over an active region. Multiple interconnect layers are over the silicon nitride optical component, each of the multiple interconnect layers including a metal interconnect therein. At least one optical deflector is over the multiple interconnect layers and over the silicon nitride optical component. The optical deflector(s) may also include a contact passing therethrough to the interconnect layers, but do not include any other electrical interconnects. Each optical deflector may deflect light within an ambient light range of less than 570 nanometers (nm) to protect the silicon nitride optical component from light-induced degradation.