Effect of Multilayer versus Monolayer Dodecanethiol on Selectivity and Pattern Integrity in Area-Selective Atomic Layer Deposition

Abstract

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.

Copper Oxidation Improves Dodecanethiol Blocking Ability in Area‐Selective Atomic Layer Deposition

“…In fact, its surface morphology is much closer to that of a multilayer DDT-coated Cu sample (Figure S3, Supporting Information), which was fabricated by exposing DDT vapor onto a CuO-covered Cu substrate. [30,34] These AFM results correlate well with the interpretation of the XPS results in Figure 1c that a monolayer DDT structure can still be maintained with slight Cu oxidation, whereas a multilayer DDT structure starts to form as the oxidation time increases significantly. XPS high-resolution scans were performed on blanket acetic acid-etched Cu substrates with different oxidation times to better understand how the surface oxidation state of Cu changes during the oxidation and how that affects DDT quality.…”

“…[28] However, previous results have shown that it is challenging to obtain good selectivity in AS-ALD of Al 2 O 3 . [23,29,30] Therefore, developing a more robust alkanethiol SAM inhibitor that is more effective for Al 2 O 3 ALD is essential.In this work, we demonstrate an approach to improve the packing of dodecanethiol (DDT) SAMs by applying an additional oxidation process on acid-etched Cu surfaces prior to DDT deposition. We follow the oxidation process, observing that Cu 2 O forms first followed by CuO, and show that the different oxide compositions at the Cu substrates influence the subsequent DDT formation.…”

“…[28] However, previous results have shown that it is challenging to obtain good selectivity in AS-ALD of Al 2 O 3 . [23,29,30] Therefore, developing a more robust alkanethiol SAM inhibitor that is more effective for Al 2 O 3 ALD is essential.…”

Area-Selective Molecular Layer Deposition of a Silicon Oxycarbide Low-k Dielectric

“…The degradation of the ODPA SAM is attributed to the presence of HCl, a byproduct for the SiOC MLD process (Figure ), which can readily attack the surface CuO x and destroy the ODPA binding to the CuO x . Alternatively, we tested DDT SAMs on Cu pretreated with acetic acid, which may be more suitable because in this system, DDT molecules bind directly to metallic Cu atoms. ,,, Therefore, the degradation of the DDT SAM can be avoided because no etchable oxidized Cu layer exists. After SiOC deposition on both Cu and DDT-Cu, XPS spectra were collected.…”

“…DDT SAMs were deposited on Cu substrates by vapor phase deposition. In order to form a monolayer DDT SAM, the surface oxides on Cu were removed by soaking the Cu substrates in glacial acetic acid for 2 min, as described in our previous reports. , After N 2 drying, Cu substrates were placed in a vacuum chamber with pressure lower than 10 mTorr. A DDT-containing bubbler was preheated to 65 °C.…”