Method for fabricating thick silicon nitride waveguides

Background:

Traditional fabrication of thick silicon nitride (SiN) waveguides faces challenges such as high stress in deposited films and difficulties in patterning thick layers without defects. These issues limit the ability to create waveguides with precise thickness control and desirable sidewall profiles, which are critical for optimizing performance in non-linear optics and quantum photonics. As photonics demand increasingly sophisticated waveguide architectures, there is a strong need for a fabrication method that overcomes these challenges while maintaining low optical losses.

Technology Overview:

This invention introduces a method to fabricate thick silicon nitride waveguides by sequentially depositing thin SiN films in multiple layers, each followed by patterning, thermal treatment, and cladding. The thermal steps serve to reduce film stress and improve the material quality, overcoming the limitations typically encountered with thick single-layer SiN films. By carefully controlling the deposition and patterning process at each stage, the technology achieves precise control over the final waveguide thickness and sidewall angles. This rigorous control supports aggressive line and space dimensions that enhance device density and performance. The multi-layer approach enables ultra-low optical loss waveguides due to improved film quality and smooth sidewalls derived from the thermal treatments. This method is particularly well-suited for applications requiring high-precision timing and quantum photonics, where waveguide consistency and optical clarity are paramount. Moreover, the fabrication process is compatible with existing semiconductor manufacturing infrastructure, facilitating integration into current photonic foundry workflows. The overall innovation addresses the trade-offs between thickness, stress, and patterning difficulty, delivering a robust platform for scalable, high-performance photonic devices.

Advantages:

•    Precise control of waveguide thickness and sidewall angles through multi-layer processing.
•    Reduction of film stress leading to enhanced structural integrity and device reliability.
•    Ultra-low optical losses achieved by heat treatments improving material quality and surface smoothness.
•    Compatibility with aggressive line and space dimensions, enabling higher photonic integration density.
•    Designed for integration with standard semiconductor manufacturing processes, aiding scalability.
•    Particularly valuable for advanced optical applications such as non-linear optics, precision timing, and quantum photonics.

Applications:

•    Non-linear optical devices requiring thick SiN waveguides with low loss and precise geometry.
•    Quantum photonics platforms where waveguide uniformity and optical clarity impact device performance.
•    High-precision timing systems benefiting from stable and well-controlled optical pathways.
•    Integrated photonic circuits demanding compact, high-density waveguide architectures.
•    Photonics manufacturing environments looking to improve fabrication yield and device consistency with scalable processes.

Intellectual Property Summary:

US Patent Application Filed

Stage of Development:

TRL 6

Licensing Status:

This technology is available for licensing.