Thesis: DUV-Assisted Athermal Laser Grooving of Low-κ Dielectrics for Advanced Packaging

In cooperation with the Chair of Laser Technology (LLT), the Fraunhofer Institute for Laser Technology (ILT)—Europe’s leading center for contract research and development in the field of laser technology—is offering the opportunity to write a thesis on the topic: »DUV-Assisted Athermal Laser Grooving of Low-κ Dielectrics for Advanced Packaging«. In advanced microelectronic packaging, low-κ dielectrics (e.g. nanoporous SiCO:H) are structured by laser grooving to reduce mechanical stress during chip dicing. State-of-the-art UV ultrashort pulsed lasers at 343 nm operate with high pulse overlap, causing cumulative heating, melt formation in the silicon substrate, delamination, and burr—critical defects when substrates are thinned below 50 µm. The fundamental problem: low-κ materials are largely transparent, so laser energy penetrates through the stack and is absorbed in the substrate rather than the target layer. This thesis explores a novel dual-pulse approach: a femtosecond DUV pulse (257 nm) transiently generates free carriers in a thin near-surface zone of the low-κ material, making it absorbing for a subsequent 515 nm fs-pulse. This enables controlled, substrate-preserving, athermal layer removal—confining energy deposition exactly where it is needed.