Waveguide Formation Using the Patterned Shallow Trench Isolation of a Bulk-CMOS Die or Wafer through Post-Foundry Processing

Technology

The invention utilizes shallow trench isolation features patterned during in-foundry processing for subsequent waveguide formation via a post-process dielectric deposition. This is accomplished after etching the silicon on the back side of the wafer and then exposing the photonic integration region, where the desired photonic waveguide core dielectric layer is uniformly deposited, and finally depositing a lower cladding dielectric layer on the waveguide cores. This process is entirely CMOS compatible and utilizes standard patterning and etching techniques.     

Problem Addressed

Optical I/O resolves one of the major bottlenecks in inter and intra chip communications. However, creating waveguides for photonic-electronic devices in bulk semiconductor manufacturing process requires complicated post-processing and high-resolution lithography, which is very costly. Alternatively, back-end integrated waveguides are physically distant from the transistor body layer, making integration with silicon photodetectors, etc., difficult. Deposited dielectric layers also reduce the thermal conductance of the entire chip, reducing allowable power dissipation and hindering performance.  

Advantages

• Low-loss, high patterning resolution waveguide within electronics process utilizing bulk starting wafers
• Waveguide in-plane with transistor body layer allows coupling to other electronic/photonic devices 
• Standard CMOS process flowImproved waveguide integration for wavelengths covering 400nm – 1150 nm with arbitrary dielectrics
• Reduced dielectric covering of die or wafer, which increases total allowable power dissipation