Photo Material Readiness at the Eve of EUVL HVM

In the last years, the continuous efforts on the development of extreme ultraviolet (EUV) lithography has allowed to push the lithographic performance of the EUV photoresists on the ASML NXE:3300 full field exposure tool and today both chemically amplified (CAR) and metal-oxide (MOR) EUV photoresists have been introduced for patterning imec's 7nm node critical layers. However, the HVM requirement to have a cost-effective high sensitivity photoresist (< 20 mJ/cm2) still remains a big challenge and further efforts are needed to improve the photoresist sensitivity without affecting resolution and patterning quality. In this work, we present the results of the best performing photoresists (both CAR and MOR) at low exposure dose for dense line-space patterns at 32nm pitch, dense contact holes at 36nm pitch and dense pillars at 38nm pitch, reporting the most critical patterning challenges for the investigated structures. Furthermore, we discuss the role of the substrate underneath the EUV photoresist and its impact on the lithographic EUV process setup from both patterning and light-matter interaction standpoint. Finally, we introduce the tone reversal process (TRP) as alternative capability for pillar patterning.