Self-Aligned Optical Interposer for Passive PIC Device Registration
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Solution Overview
Problem
The integration of optoelectrical devices, such as lasers, into photonic integrated circuits (PICs) requires precise alignment with optical and electrical features on the substrate, which is challenging and time-consuming, especially when using passive alignment techniques that are compatible with semiconductor and integrated circuit fabrication.
Innovation Solution
The development of self-aligned alignment aids, including alignment pillars and fiducials, formed on an optical interposer structure using a patterned mask layer, which facilitates passive alignment with patterned planar waveguides, enabling efficient integration of optical and optoelectrical devices without active alignment steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive alignment techniques are used for integrating optoelectrical devices into PICs, then manufacturing compatibility with semiconductor fabrication is improved, but alignment precision and efficiency deteriorate
Solution Approach 1:
Alignment features (alignment marks, fiducials, and positioning structures) are formed on the interposer substrate before the optoelectrical devices are mounted. This preliminary formation of alignment references enables passive alignment techniques to achieve precise positioning without requiring active feedback or complex alignment equipment during the mounting process.
Solution Approach 2:
The patent introduces intermediary alignment structures (such as alignment marks, fiducials, and positioning features) that serve as mediators between the interposer substrate and the optoelectrical devices. These intermediary features enable precise alignment through passive mechanical or optical reference systems, resolving the contradiction between manufacturing simplicity and alignment precision.
2Manufacturing precision
If active alignment steps are used to integrate optoelectrical devices, then alignment precision is improved, but manufacturing time and complexity increase
Solution Approach 1:
The alignment system is designed to be self-aligning through the formation of complementary alignment features on both the interposer and the optoelectrical devices. The alignment marks and fiducials are automatically registered during the mounting process without requiring external active alignment equipment or feedback control, thereby reducing manufacturing time while maintaining precision.
Solution Approach 2:
By pre-forming alignment features on the interposer substrate before device mounting, the patent eliminates the need for time-consuming active alignment steps during the integration process. The alignment references are already in place, enabling rapid passive alignment and significantly reducing manufacturing cycle time.
3Manufacturing precision
If multiple alignment features are formed on the interposer, then alignment precision is improved, but device complexity increases
Solution Approach 1:
The alignment system is segmented into multiple independent alignment features (alignment marks, fiducials, and positioning structures) distributed at different locations on the interposer. Each feature performs a specific alignment function, and together they provide comprehensive precise alignment without requiring a single complex alignment mechanism. This segmentation simplifies the overall design by distributing complexity across multiple simple, manufacturable features.
Data Source
AI summary
Structures and methods that provide and maintain precise lateral registration between mounted optical devices and waveguides formed on an optical interposer structure use a methodology in which a same patterned mask layer is utilized to pattern a plurality of alignment features requiring alignment and the waveguide cores to which mounted devices are aligned in the formation of photonic integrated circuits. Subsequent burial and re-exposure of the patterned mask layer in subsequent processing steps maintains the feature registration provided with the use of the self-aligned layer throughout the formation of the optical interposer and the alignment structures provided thereon.