Atmosphere-Regulated Conversion of Perhydropolysilazane (PHPS): Controlling Si-O-N Composition and Unveiling Atomistic Mechanisms

DY Hou and JL Chen and YZ Li and PF Li and ZB Zhang and J Jiang, ACS APPLIED MATERIALS & INTERFACES, 17, 68457-68472 (2025).

DOI: 10.1021/acsami.5c19276

Perhydropolysilazane (PHPS) is an important polymeric precursor for producing silica-related inorganic materials through versatile solution- based processing, and has found broad applications in semiconductor manufacturing and microelectronic encapsulation. However, owing to its complex linear and branched architecture, high sensitivity to H2O and O2, and the inherently amorphous nature of the resulting silica or silicon oxynitride, the conversion mechanism of PHPS to SiO x /SiO x N y remains poorly understood. This knowledge gap significantly hampers the rational design and optimization of this promising methodology for the development of high-performance inorganic functional materials. Here, we developed a new Si/N/O/H ReaxFF parameter set capable of accurately describing the thermal conversion of PHPS under various O2/H2O atmospheres. ReaxFF molecular dynamics (MD) simulations reveal distinct atomistic pathways for O2 and H2O: O2 accelerates Si-O bond formation but promotes the growth of a SiO x surface layer that impedes further O2 diffusion, whereas H2O facilitates NH3 release and Si-N bond cleavage. Coordination analysis shows that Si-N tetrahedra are highly sensitive to the atmosphere, with higher O2 levels favoring Si atoms bonded to four N atoms. These findings demonstrate that the Si-O-N composition of PHPS- derived SiO x /SiO x N y can be tuned by controlling the atmosphere during thermal conversion, offering practical guidance for processing optimization and material performance enhancement.

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