Optical Integrated Circuit ESD Protection via Segmented Seal Rings
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Solution Overview
Problem
Optical integrated circuits (OICs) are vulnerable to electrostatic discharge (ESD) events due to the limitations of metal-based seal rings, which can compromise electrical isolation and allow electrical charge to pass through, especially when external optical connections are involved.
Innovation Solution
An optical integrated circuit system with an electrically insulating substrate, an optical connection, and an ESD protection structure that is both electrically non-insulating and optically transparent, coupled with an ESD diode and a ground connection to provide effective ESD protection without affecting optical signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal-based seal ring is used to provide ESD protection, then electrical isolation is improved, but optical signal transmission is blocked due to metal opacity
Solution Approach 1:
The seal ring is segmented into multiple portions (first portion, second portion, third portion) with different functional characteristics. The first portion provides ESD protection through electrical coupling to the waveguide, while the second and third portions maintain optical transparency to allow signal transmission. This segmentation resolves the contradiction by distributing different functions across separate segments rather than requiring a single homogeneous structure.
Solution Approach 2:
Different portions of the seal ring are assigned different material properties and functions. The first portion has electrical non-insulating properties for ESD protection, while the second and third portions have optically transparent properties for signal transmission. This local differentiation of quality allows each portion to optimize its specific function without compromising the overall system performance.
2Illumination intensity
If openings are formed in the metal seal ring to allow optical coupling, then optical signal transmission is improved, but electrical isolation is compromised allowing charge to pass through
Solution Approach 1:
Instead of forming openings in a continuous metal seal ring, the seal ring is designed as segmented portions where the first portion provides electrical coupling for ESD protection and the second and third portions provide optical transparency. This segmentation eliminates the need for openings while maintaining both electrical isolation and optical transmission capabilities.
Solution Approach 2:
The first portion of the seal ring acts as an intermediary structure that provides electrical coupling between the waveguide and ground connection, enabling ESD protection without requiring physical openings in the seal ring. This intermediary electrical pathway allows charge to be diverted safely while maintaining the integrity and continuity of the optical signal transmission path.
3Device complexity
If a seal ring is formed exclusively from metal layers, then ESD protection structure is simplified, but complete protection from ESD events is not achieved when external optical connections are present
Solution Approach 1:
The seal ring is constructed as a composite structure with portions made from different materials having different properties. The first portion uses electrically non-insulating material for ESD protection, while the second and third portions use optically transparent materials. This composite approach achieves superior ESD protection effectiveness compared to exclusive metal construction, while maintaining optical signal transmission capability.
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 solution effectively protects OICs from ESD events while maintaining optical signal integrity and allowing for external optical connections, enhancing the overall ESD protection without compromising the optical properties of the waveguides.
Implementation Method 1
the seal ring may be electrically coupled to an ESD diode which may provide a pathway to a ground connection in the presence of high voltage and/or current conditions
Implementation Method 2
the optical coupling may be achieved using adiabatic or evanescent coupling between OIC waveguides and interposer waveguides
Implementation Method 3
The first ESD protection structure is both electrically non-insulating and substantially optically transparent to the optical signal
Data Source
AI summary
An optical integrated circuit device includes a semiconductor substrate and a first waveguide made of a first material and disposed over the semiconductor substrate. The first waveguide includes a parallel region and a tapered region. The optical integrated circuit device further includes a first cladding structure disposed over and surrounding the parallel region of the first waveguide, a first extension made of the first material and disposed over the semiconductor substrate, and an electrostatic discharge (ESD) protection structure electrically coupled to the first extension. The first extension physically contacts the parallel region of the first waveguide. The first extension includes a first portion within the first cladding structure and a second portion outside the first cladding structure.