Etching mechanisms behind grayscale 3D multi-height structures transfer for optoelectronic devices

Optoelectronic devices for advanced imaging require complex 3D structures. In this study, optical grayscale microlenses and multi-height structures are etched into a cross-linked polymer layer in a Capacitively Coupled Plasma reactor. Etching can cause profile deformation and surface roughness, which may affect device performances. When varying HF plasma power, we observed strong 3D shape modulation. While lateral CD variations could be related to sidewall passivation mechanisms, height loss understanding is more challenging. Etch selectivity is not sufficient to explain this phenomenon, therefore, UV, temperature and opening ratio effects are under investigation. The influence of structure size is also explored.