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

Abstract

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., t S=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., t S=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.

Atomic/Molecular Layer Deposition for Designer's Functional Metal–Organic Materials

“…New organic components have also been developed for the purely organic MLD processes; the MLD material library already includes, besides the initially introduced polyimides [ 15,17–22,137–143 ] and polyamides, [ 15,23–28,144–149 ] many other polymers: polyurea, [ 29,30,37,38,51,150–164 ] polythiourea, [ 52 ] polyurethane, [ 165,166 ] polyazomethine, [ 167–172 ] poly(3,4‐ethylenedioxy‐thiophene), [ 173–177 ] polyimide–polyamide, [ 141 ] poly(ethylene terephthalate) (PET), [ 50,178–180 ] and others. [ 31,32,39–44,176,181–200 ] In recent years, the organic precursor library has been rapidly expanding.…”

Three-Dimensional (3D) Device Architectures Enabled by Oxidative Chemical Vapor Deposition (oCVD)

“…The oMLD growth rates are 100-fold slower than oCVD and the resulting oMLD film properties have not yet matched those of oCVD. 7 When carbon-carbon double bonds are present at the surface of the substrate, the oxidant can induce grafting of the oCVD polymer. 2 The covalent chemical bonds which span across the interface improve durability.…”

“…The influence of surface chemistry was used to achieve self-aligned patterns of oCVD PEDOT over lines of silicon dioxide. 7 Between the lines, inhibition of oCVD growth occurred, as the hydrogen-terminated silicon surface reduced the absorbing oxidants.…”

Compatibility between polymethacrylate-based extreme ultraviolet resists and TiO2 area-selective deposition

“…7,8,10 This is typically achieved with chemical vapor deposition (CVD) or atomic and molecular layer deposition (ALD/MLD), the latter of which relies on self-limiting vapor-solid surface reactions to deposit material with nanoscale thickness control. 8,[10][11][12][13] Thus, an area-selective ALD/MLD process is highly controllable in terms of deposited layer thickness and conformality. 13 Combining ASD with EUV lithography could reduce edge placement error, reduce resist thickness requirements, and provide a means to prevent or repair line breaks and decorate defects.…”

“…8,[10][11][12][13] Thus, an area-selective ALD/MLD process is highly controllable in terms of deposited layer thickness and conformality. 13 Combining ASD with EUV lithography could reduce edge placement error, reduce resist thickness requirements, and provide a means to prevent or repair line breaks and decorate defects. [14][15][16] Thus, areaselective ALD shows promise for depositing etch-resistant layers on EUV resists to enable tone inversion or resist hardening to improve pattern resolution, as shown schematically in Fig.…”