Line Edge Roughness Optimization of Photonics Components in Electronics Photonics Heterogeneous Integration

This paper aims at optimizing the line edge roughness (LER) profile for photonics waveguide patterns using 12” immersion lithography. For simplicity of implementation, LER is tuned by varying the illumination source profile and optimizing development recipe without making any chemical changes. The optimized illumination setting and development recipe, delivered improved critical dimension uniformity (CDU) of ≥97% along with LER of ≤5% of waveguide CD. Major improvement in LER is obtained with the change in illumination source profile from high partial coherence (high-σ) annular, conventionally used off-axis illumination to achieve high resolution, to low partial coherence (low-σ) on-axis. The optimized conditions are suitable for heterogeneous integration of low loss photonics components with electronics for developing an opto-electronics system at wafer level.