Stanford Advisors

All Publications

  • Characterizing Self-Assembled Monolayer Breakdown in Area-Selective Atomic Layer Deposition. Langmuir : the ACS journal of surfaces and colloids Liu, T., Zeng, L., Nardi, K. L., Hausmann, D. M., Bent, S. F. 2021


    To enable area-selective atomic layer deposition (AS-ALD), self-assembled monolayers (SAMs) have been used as the surface inhibitor to block a variety of ALD processes. The integrity of the SAM throughout the ALD process is critical to AS-ALD. Despite the demonstrated effectiveness of inhibition by SAMs, nucleation during ALD eventually occurs on SAM-protected surfaces, but its impact on SAM structures is still not fully understood. In this study, we chose the octadecyltrichlorosilane (ODTS) SAM as a model system to investigate the evolution of crystallinity and structure of SAMs before and after ALD. The breakdown behavior of SAMs when exposed to ZnO and Al2O3 ALD was systematically studied by combining synchrotron X-ray techniques and electron microscopy. We show that the crystallinity and structure of ODTS SAMs grown on Si substrates remain intact until a significant amount of material deposition takes place. In addition, the undesired ALD materials that grow on ODTS SAMs present contrasting morphologies: dispersed nanoparticles for ZnO while relatively continuous film for Al2O3. Lastly, substrate dependency was explored by comparing a Si substrate to single-crystal sapphire. Similar results in the evolution of SAM crystallinity and formation of ALD nuclei on top of SAM are observed in the ODTS-sapphire system. This study provides an in-depth view of the influence of ALD processes on the SAM structure and the nucleation behavior of ALD on SAM-protected surfaces.

    View details for DOI 10.1021/acs.langmuir.1c02211

    View details for PubMedID 34550696

  • Role of Precursor Choice on Area-Selective Atomic Layer Deposition CHEMISTRY OF MATERIALS Oh, I., Sandoval, T. E., Liu, T., Richey, N. E., Bent, S. F. 2021; 33 (11): 3926-3935
  • Area-Selective Molecular Layer Deposition of a Silicon Oxycarbide Low-k Dielectric CHEMISTRY OF MATERIALS Yu, X., Bobb-Semple, D., Oh, I., Liu, T., Closser, R. G., Trevillyan, W., Bent, S. F. 2021; 33 (3): 902–9
  • Area-Selective Atomic Layer Deposition on Chemically Similar Materials: Achieving Selectivity on Oxide/Oxide Patterns CHEMISTRY OF MATERIALS Liu, T., Bent, S. F. 2021; 33 (2): 513–23
  • Effect of Multilayer versus Monolayer Dodecanethiol on Selectivity and Pattern Integrity in Area-Selective Atomic Layer Deposition ACS APPLIED MATERIALS & INTERFACES Liu, T., Nardi, K. L., Draeger, N., Hausmann, D. M., Bent, S. F. 2020; 12 (37): 42226–35


    Monolayer and multilayer dodecanethiols (DDT) can be assembled onto a copper surface from the vapor phase depending on the initial oxidation state of the copper. The ability of the copper-bound dodecanethiolates to block atomic layer deposition (ALD) and the resulting behavior at the interfaces of Cu/SiO2 patterns during area-selective ALD (AS-ALD) are compared between mono- and multilayers. We show that multilayer DDT is ∼7 times more effective at blocking ZnO ALD from diethylzinc and water than is monolayer DDT. Conversely, monolayer DDT exhibits better performance than does multilayer DDT in blocking of Al2O3 ALD from trimethylaluminum and water. Investigation into interfacial effects at the interface between Cu and SiO2 on Cu/SiO2 patterns reveals both a gap at the SiO2 edges and a pitch size-dependent nucleation delay of ZnO ALD on SiO2 regions of multilayer DDT-coated patterns. In contrast, no impact on ZnO ALD is observed on the SiO2 regions of monolayer DDT-coated patterns. We also show that these interfacial effects depend on the ALD chemistry. Whereas an Al2O3 film grows on the TaN diffusion barrier of a DDT-treated Cu/SiO2 pattern, the ZnO film does not. These results indicate that the structure of the DDT layer and the ALD precursor chemistry both play an important role in achieving AS-ALD.

    View details for DOI 10.1021/acsami.0c08873

    View details for Web of Science ID 000572965700129

    View details for PubMedID 32805867

  • Area-Selective Atomic Layer Deposition of Dielectric-on-Dielectric for Cu/Low-k Dielectric Patterns Liu, T., Bent, S. F., Gronheid, R., Sanders, D. P. SPIE-INT SOC OPTICAL ENGINEERING. 2019

    View details for DOI 10.1117/12.2519845

    View details for Web of Science ID 000482084200012

  • Formation and Ripening of Self-Assembled Multilayers from the Vapor-Phase Deposition of Dodecanethiol on Copper Oxide CHEMISTRY OF MATERIALS Bergsman, D. S., Liu, T., Closser, R. G., Nardi, K. L., Draeger, N., Hausmann, D. M., Bent, S. F. 2018; 30 (16): 5694–5703