Effect of Organic Precursor and Annealing on Porosity and Dielectric Properties of Alucone Films for Low-k Materials

Abstract

With the growth of artificial intelligence (AI) in recent years, increases in transistordensity and the development of 3D packaging have accelerated computational processing, memory, and transmission speeds. Low-k dielectric material is an essential component in advanced semiconductors to isolate interconnect wires, prevent current leakage, and minimize RC delays. Among various types of dielectrics, hybrid organic-inorganic porous materials are particularly promising because they combine the benefits of low-polarity bonds with a flexible synthesis pathway. In this thesis, porous dielectric materials were synthesized through molecular layer deposition (MLD) using trimethyl-aluminum (TMA) and two different organic precursors: 2-butyne-1,4-diol (BTY) and 2-methylene-1,3-propanediol (MPD) followed by thermal annealing to investigate the relationship between chemical structure and the resulting dielectric constant. Furthermore, utilizing an MLD process offers a flexible method to address scalability challenges in high-volume industrial manufacturing. The MPD alucone was shown to exhibit a decreased and tunable dielectric constant through optimization of the annealing temperature across a wide temperature range of 400°C–600°C, based on ellipsometry modeling of the film using an Effective Medium Approximation (EMA) with porosity greater than 30%. Conversely, BTY alucone was shown to densify after annealing, potentially due to its rigid linear molecule structure compared to the bulkier structure of MPD. These results suggest that synthesizing alucone via MLD combined with post-deposition thermal annealing provides a versatile approach to tailoring thin-film porosity, and tuning dielectric constants, offering a critical material-level strategy for advanced semiconductor interconnect integration at nextgeneration scaling nodes.