VCSEL Arrays With Backside Trench Isolation
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Solution Overview
Problem
Vertical cavity surface emitting lasers (VCSELs) formed on semi-insulating substrates have reduced reliability due to higher defect rates, which affects their quality and electrical isolation, and existing methods for electrical isolation complicate manufacturing and increase parasitic inductance.
Innovation Solution
The implementation of an isolation structure, such as a backside trench etched from the substrate's bottom side, provides horizontal electrical isolation between VCSEL arrays, allowing them to be formed on conductive substrates with reduced defects, enabling series connection and simplified die attachment without wirebonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VCSELs are formed on semi-insulating substrates, then electrical isolation is achieved, but reliability decreases due to higher defect rates
Solution Approach 1:
The patent divides the substrate into isolated regions using trenches that physically separate adjacent VCSEL arrays. This segmentation prevents defect propagation between arrays and allows each array to be electrically isolated while formed on a conductive substrate, thereby improving reliability without sacrificing manufacturing quality.
Solution Approach 2:
The patent introduces an intermediary isolation structure (trench filled with dielectric material or semiconductor layer) between VCSEL arrays. This intermediary element provides electrical isolation and defect containment while allowing the VCSELs to be formed on low-defect conductive substrates, resolving the contradiction between substrate quality and electrical isolation.
2Reliability
If isolation structures are added between VCSEL arrays, then electrical isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements isolation structures by etching trenches from the backside of the substrate, utilizing the vertical dimension rather than adding complex lateral structures. This approach simplifies manufacturing by enabling electrical isolation through a straightforward backside processing step without complicating the front-side VCSEL fabrication.
Solution Approach 2:
The patent performs isolation trench formation and dielectric layer deposition as preliminary steps before final VCSEL fabrication. By establishing the isolation structure early in the manufacturing process, subsequent VCSEL formation can proceed without additional complexity, as the isolation framework is already in place to guide subsequent processing steps.
3Reliability
If isolation structures are added between VCSEL arrays, then electrical isolation is improved, but parasitic inductance increases
Solution Approach 1:
The patent optimizes the electrical parameters of the isolation structure by controlling the dielectric material properties, trench depth, and fill ratio. By adjusting these parameters, the isolation structure achieves effective electrical isolation while minimizing parasitic inductance, allowing high-current VCSEL arrays to operate with reduced electromagnetic interference and inductive effects.
Data Source
AI summary
A device includes a substrate, a first vertical cavity surface emitting laser (VCSEL) array on the substrate, a second VCSEL array on the substrate and adjacent to the first VCSEL array, and an isolation structure between the first VCSEL array and the second VCSEL array. The isolation structure provides electrical isolation between the first VCSEL array and the second VCSEL array.