Nanopatterned Area-Selective Vapor Deposition of PEDOT on SiO₂ vs Si-H: Improved Selectivity Using Chemical Vapor Deposition vs Molecular Layer Deposition

Area-selective deposition (ASD) of polymers is expected to be useful for self-aligned patterning of nucleation inhibitors, sacrificial layers, and air-gap materials during future bottom-up nanoscale materials fabrication. This work describes a simple, rapid, and effective method to achieve inherent ASD of poly(3,4-ethylenedioxythiophene) (PEDOT) on SiO2 vs hydrogen-terminated silicon (Si-H) substrates via molecular layer deposition (MLD) and chemical vapor deposition (CVD) using 3,4-ethylenedioxythiophene (EDOT) as a reactive monomer and SbCl5 as an oxidant for polymerization. Film thickness measured by spectroscopic ellipsometry indicates the MLD process can obtain ∼35 nm of deposition with a selectivity of 90%, i.e., tS=0.90 ≈ 35 nm, which is better than many other reports of inorganic or organic material ASD. Furthermore, we show that under CVD conditions, the selectivity is further improved, i.e., tS=0.90 ≈ 55.4 nm and that CVD can achieve ASD at an overall rate more than 100 times faster than MLD for the same ASD thickness, allowing 30 nm of ASD to be achieved in less than 10 s of process time. The selective growth of PEDOT on SiO2 vs Si-H is ascribed to the localized reduction of the SbCl5 on the Si-H surface, thereby inhibiting EDOT polymerization in that region. The high selectivity allows us to observe and analyze lateral “mushroom” overgrowth and compare ASD growth rates on blanket vs patterned wafers. Overall, results suggest that CVD may have distinct advantages over MLD or atomic layer deposition (ALD) for other ASD applications.