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

Abstract

Area-selective deposition (ASD) of low-k materials is desired in back-end-of-line processes for fabricating nanopatterns such as fully self-aligned vias. However, the high temperature and/or aggressive coreactants used in conventional low-k material deposition have limited the application of the organic inhibitors used in ASD. Here, we report a strategy to selectively deposit low-k methylene-bridged silicon oxycarbide (SiOC) thin films on metal/dielectric patterns by combining growth using molecular layer deposition (MLD) and inhibition using self-assembled monolayers (SAMs). By using bis (trichlorosilyl)-methane and water as a precursor and coreactant, respectively, SiOC thin films with a dielectric constant of 3.6–3.8 are deposited at 40 °C and at a growth rate of 1.5 Å/cycle. We demonstrate area-selective MLD of this SiOC material for up to 30 cycles (equiv. 4.5 nm) on SiO2 vs Cu using a dodecanethiol SAM to block growth on Cu, and up to 70 cycles (equiv. 10 nm) on SiO2 vs Al using an octadecylphosphonic acid SAM to block growth on native oxide-covered Al. Positive and negative pattern transfer of SiOC films on a Cu/Al2O3 pattern is exhibited as a proof of concept. Moreover, because the Cu substrates are contaminated by HCl which is generated as a byproduct in the MLD process, we develop a mild post-treatment method using ethanol to remove chlorine residues.

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

“…Notably, we find that the selectivity for both the MLD and CVD PEDOT processes is larger compared to most previous reports of inorganic and organic ASD. 24,25,27,43 Furthermore, noteworthy is the total time required for these processes. For the MLD conditions used in Figure 2a,b, i.e., 30 and 100 MLD cycles, respectively (not optimized for process speed), the total S1).…”

“…In addition to CVD, ASD of polymers has also been studied by MLD, a stepwise sequence for organic film deposition analogous to ALD. Using MLD, − a polyurea layer up to ∼6 nm in thickness was achieved on Si-OH, with minimal growth on copper that was passivated by an octadecylphosphonic acid self-assembled monolayer (SAM) . Surface passivation by SAMs has also been used for ASD of poly- p -xylylene and silicon oxycarbide (SiCO), in both cases enabling ∼5 nm of ASD.…”

“…Using MLD, − a polyurea layer up to ∼6 nm in thickness was achieved on Si-OH, with minimal growth on copper that was passivated by an octadecylphosphonic acid self-assembled monolayer (SAM) . Surface passivation by SAMs has also been used for ASD of poly- p -xylylene and silicon oxycarbide (SiCO), in both cases enabling ∼5 nm of ASD. In another study, selectivity up to ∼17 nm was shown for ASD of polyimide (nylon 6,2) on amorphous carbon (a-C) vs SiO 2 passivated with dimethylamino-trimethylsilane (DMA-TMS) .…”

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

“…[29,45] By combining the results in Figure 6a,b, we can estimate selectivity for Al 2 O 3 deposition under subsaturation condition on low-k over Cu using the following equation [39,46] intentional oxidation, and second, the selectivities in both cases drop off with increasing ALD cycle numbers, as expected. [39,40,47,48] Using S = 0.9 as a threshold for comparing blocking ability, Figure 6c shows that when the oxidation strategy is applied, 40 Å (50 cycles) of Al 2 O 3 can be deposited on Cu/low-k systems while still maintaining the selectivity above 0.9. On the other hand, when DDT is deposited on Cu substrates without intentional oxidation, the DDT can only block 24 Å (30 cycles) of Al 2 O 3 with S = 0.9.…”

Substrate-Dependent Area-Selective Atomic Layer Deposition of Noble Metals from Metal β-Diketonate Precursors

“…As a result, the ALD growth is prevented on the passivated substrate areas while the growth proceeds on the others, and a self-aligned growth of thin-film patterns is therefore achieved. Self-assembled monolayers (SAMs) − with −CH 3 tail groups are commonly used as the surface passivator to prevent the ALD growth. Inert polymers − have also been studied as passivation layers, though to a lesser extent compared to the SAMs.…”