Development of an e-beam/i-line stepper intra-level mix and match approach with the photoresist mr-EBL 6000.5 for PIC related structures such as waveguides, ring resonators and coupling structures

In this paper the development of an intra-level mix and match (ILM&M) process, an expression for the exposure of one resist layer with at least two different exposure technologies, for the negative tone resist mr-EBL 6000.5 (micro resist technology, Germany) is demonstrated. Process development is conducted on a layout with photonic integrated circuit (PIC) related waveguides (WG), ring resonators and coupling structures on 150 mm silicon wafers with a 1000 nm SiO₂ layer and a 450 nm low pressure (LP) Si₃N₄ layer on top. In order to match the intended structure dimensions perfectly, the ideal exposure dose has to be determined with an i-line wafer stepper and in parallel with an e-beam lithography (EBL) system. In addition, different post exposure bake (PEB) processes and their influence on resulting structures, which are investigated by means of CD-SEM and profilometer measurements are investigated. It is shown, that regarding pattern fidelity, coupling structures exposed by EBL match the layout design better than those exposed by the i-line stepper. For the purpose of further optimizing the matching of generated coupling structures to the targeted design, different proximity effect correction (PEC) parameter sets are applied. CD-SEM measurements reveal the PEC parameter set which is most suitable for generating the targeted coupling structures. By combining the measurement results of structures exposed with different exposure doses and selecting the best PEC parameter set regarding structure dimensions and pattern fidelity, a processing recipe for an e-beam/i-line stepper ILM&M with the negative tone resist mr-EBL 6000.5 is successfully established.