Back-End Photonic Structures With Microwave Dopant Activation
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Solution Overview
Problem
The integration of photonic devices into the CMOS process flow at the front-end increases complexity and cost due to additional processing steps and substrate space requirements, and poses challenges in forming active photonic devices after metallization without damaging CMOS circuits.
Innovation Solution
Forming photonic devices at the back-end of the CMOS process flow using low deposition temperature polysilicon, germanium, and silicon-germanium techniques, along with low-temperature microwave annealing for dopant activation, allowing for the integration of photonic devices without compromising the CMOS circuits, and enabling the use of additional materials like silicon nitride for improved photon propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If photonic devices are integrated into the CMOS process flow at the front-end, then photonic devices can be formed on the substrate, but the additional processing steps interfere with the conventional CMOS process flow and increase complexity
Solution Approach 1:
The patent divides the integration process into two distinct segments: front-end CMOS processing and back-end photonic device formation. This segmentation allows each process to be optimized independently, with photonic devices being formed after CMOS circuits are completed, thus avoiding interference with the conventional CMOS process flow while maintaining integration capability
Solution Approach 2:
The patent applies preliminary action by completing all CMOS circuit fabrication steps before initiating photonic device formation. This sequencing ensures that the CMOS process flow remains conventional and unaffected, while photonic devices are subsequently integrated onto the already-fabricated CMOS circuits
2Reliability
If photonic devices are formed with thicker silicon material, then photonic device performance is improved, but valuable substrate space is occupied and CMOS process compatibility is reduced
Solution Approach 1:
The patent applies local quality by providing thicker silicon material specifically where photonic devices are formed, while maintaining standard CMOS thickness elsewhere. This is achieved through selective epitaxial growth or selective deposition techniques that deposit additional silicon layers only in the photonic device regions, thereby improving photonic performance without occupying excessive substrate space or complicating the overall CMOS process
3Manufacturing precision
If high temperature processing is used for photonic device formation, then photonic device quality is improved, but CMOS circuits are damaged
Solution Approach 1:
The patent uses preliminary action by completing all high-temperature CMOS processing steps before forming photonic devices. This ensures that CMOS circuits are already fabricated and protected before any high-temperature photonic processing occurs, eliminating the risk of thermal damage to CMOS circuits while still allowing high-temperature processing for photonic device quality
Solution Approach 2:
The patent introduces an intermediary protective layer or structure between the CMOS circuits and the photonic device formation process. This intermediary protects the sensitive CMOS circuits from high-temperature damage during photonic processing, while still allowing the necessary thermal processing for high-quality photonic device fabrication
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
This approach reduces dopant migration, achieves uniform dopant concentration, and allows for the integration of photonic devices without interfering with the CMOS process, reducing overall complexity and cost while utilizing additional materials for improved performance.
Implementation Method 1
microwave annealing between 200° Celsius to 500° Celsius
Implementation Method 2
PVD
Implementation Method 3
CVD
Data Source
AI summary
The disclosed embodiments relate to an integrated circuit structure and methods of forming them in which photonic devices are formed on the back end of fabricating a CMOS semiconductor structure containing electronic devices. Doped regions associated with the photonic devices are formed using microwave annealing for dopant activation.