Substrate-friendly precision processing in low-κ multilayer systems through synergetic use of UV nanosecond and NIR femtosecond laser pulses (SYNULAS)

• Applicants: Professor Dr. Heinz Paul Huber; Professor Dr. Constantin Leon Häfner, since 1/2025
• Subject Area: Production Automation and Assembly Technology
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 423531130

Precise laser material processing of thin, transparent low-k dielectrics is essential for the ongoing miniaturization of integrated circuits in the semiconductor industry. This project aims for the damage-free processing of low-k thin films on silicon wafers using laser radiation. By controlling the energy penetration depth through the excitation of free electrons, selective ablation of the thin film is to be enabled, thereby preventing damages such as delamination and cracking. A nanosecond UV laser pulse, kept below the damage threshold, serves to excite free electrons, reducing the energy penetration depth for a subsequent femtosecond IR laser pulse and enabling effective ablation. The direct goal of the project is to develop an experimentally validated numerical model for the damage-free double-pulse removal of low-k thin films. Systematic investigations into the interaction between ns-UV pulses, fs-IR pulses, and the combination of both pulses with the thin film system are planned. The focus is set on a SiCO:H thin film on a silicon substrate, which is later complemented by a 100 nm thick SiNx passivation layer, using commercially available laser systems for potential industrial applications. To achieve the project goals, the ablation dynamics will be thoroughly characterized by a combination of ultra-short pulse pump-probe experiments and numerical simulations that include electron dynamics, laser radiation absorption, and subsequent material heating. The model aims to precisely predict time-dependent observables such as transient optical properties (reflection, absorption, energy penetration depth, transmission) and thermo-mechanical parameters (temperature, density, pressure waves), to comprehensively investigate the ablation criteria. At the end of the project, the experimentally validated model is expected to define a process window that allows for efficient, damage-free removal with double pulses. The research findings will not only enhance quality and efficiency in semiconductor manufacturing but also significantly expand the understanding of the fundamental mechanisms of ultra-short pulse laser processing of low-k dielectrics.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Wolfgang Schulz, until 1/2025