Organosulfide Inhibitor Instigated Passivation of Multiple Substrates for Area-Selective Atomic Layer Deposition of HfO₂

With recent advancements in semiconductor technology, continuous efforts are being made to meet the requirements for further reductions in the feature sizes of electronic interconnects in semiconductor devices. Efforts to improve area-selective deposition (ASD) processes have led to researchers manipulating deposition surfaces using surface inhibitors as tools for area-selective atomic layer deposition (AS-ALD). In this study, organosulfide small-molecule inhibitors (SMIs) were utilized for AS-ALD on metal, oxide, and nitride surfaces such as Cu, SiO2, and TiN, respectively. Upon high-temperature exposure, the organosulfide SMI decomposes to assist the adsorption of its fragmentation products on the Cu and SiO2 substrates, thereby simultaneously adsorbing and passivating the two surfaces upon SMI exposure. The surface chemistry and reactivity were explained by calculations using density functional theory with the slab approach and Monte Carlo simulations. Furthermore, the blocking potential of the SMIs was evaluated using atomic layer deposition (ALD) of HfO2. The SMI-covered Cu substrate showed inhibition against ALD growth of HfO2 with a selectivity of approximately 98% over 25 growth cycles compared to the uncovered Cu substrate successfully blocking approximately 3 nm of HfO2 ALD. The SMI-covered SiO2 substrate showed a lowered selectivity compared to the SMI-covered Cu substrate but still, a substantial selectivity was present compared to bare SiO2 and TiN substrates where no blocking was observed. These results agree with the theoretical findings. This possibility to block two important surfaces in semiconductor manufacturing (Cu and SiO2) while leaving a third one (TiN) unblocked for ALD growth is an important step for the future application of ASD in the production of ever smaller semiconductor devices

Area-Selective Atomic Layer Deposition of Al₂O₃ with a Methanesulfonic Acid Inhibitor

Experiment and density functional theory (DFT) are combined to study the selective growth of Al2O3 with methanesulfonic acid (MSA) as a small molecule inhibitor (SMI) for Cu. Two metalorganic aluminum precursors for Al2O3 atomic layer deposition (ALD), trimethylaluminum (TMA) and dimethylaluminum isopropoxide (DMAI), are compared in the presence of Cu, Ru, SiO2, and TiO2 substrates treated with MSA. Water contact angle goniometry results suggest facile uptake of MSA on Cu, compared to more limited chemisorption on Ru, SiO2, and TiO2, a phenomenon further confirmed with Auger electron spectroscopy (AES) elemental mapping. X-ray photoelectron spectroscopy (XPS) shows a reduction process that occurs between MSA and the native oxide of Cu, suggesting a mechanism in which MSA more favorably interacts with metallic over oxidic surfaces such as SiO2 or TiO2. DFT further elucidates this hypothesis by revealing reaction barriers for MSA and SiO2 that are an order of magnitude higher than those for the reaction between MSA and Cu. Selective chemisorption of MSA on Cu, confirmed by XPS and AES, protects the Cu while allowing growth of up to 3.5 nm of Al2O3 with greater than 97% selectivity on SiO2, TiO2, and Ru using DMAI as the aluminum precursor; TMA as a precursor produces much less selective growth of Al2O3. Together, these results indicate that selective adsorption of MSA allows for the inhibition of Al2O3 ALD on Cu substrates. Furthermore, we show that area-selective atomic layer deposition (AS-ALD) is strongly influenced by precursor selection, revealing that process optimization is a key requirement for producing AS-ALD with SMIs