Substrate-Independent Palladium Atomic Layer Deposition

A novel method is presented for the atomic layer deposition (ALD) of palladium on a tetrasulfide self‐assembled monolayer functionalized SiO2 surface. Additionally, a novel reducing agent (glyoxylic acid) was used to remove the organic ligands from the chemisorbed palladium(II) hexafluoroacetylacetonate metallorganic. Glyoxylic acid is an effective reducing agent above 200 °C, which is not optimal for palladium but it is effective enough to show proof‐of‐concept and deposit a Pd “seed” layer. Palladium was also deposited on iridium at 80 °C and 130 °C via a hydrogen process or on the Pd seed layer at 80 °C. The 60 Å Pd film grown on the tetrasulfide self‐assembled monolayer (SAM) showed nearly random texture and higher carbon and fluorine contamination levels compared to the one grown on Ir. The 55 Å film grown on Ir at 80 °C is highly (111) textured with a grain size of ∼60 Å, as shown by reflection high energy electron diffraction (RHEED). The higher contamination levels of the Pd film deposited on the tetrasulfide SAM, as measured by X‐ray photoelectron spectroscopy (XPS), is attributed to the high temperatures needed to deposit the Pd seed layer. The higher deposition temperatures cause more dissociation of the hfac ligand and a higher metallorganic desorption rate. These equate to less Pd being deposited and with higher contamination levels. A novel method is presented which allows the ALD of palladium onto dielectric surfaces. This is achieved by activating the dielectric surface with sulfide terminated silanes followed by the deposition of a palladium seed layer with the sequential pulsing of PdII(hfac)2 and glyoxylic acid above 200 °C; the acid acts as a novel remover to the chemisorbed organic ligand facilitating the deposition of the palladium seed layer. This is followed by palladium ALD with sequential pulsing of PdII(hfac)2 and H2 at a low temperature of 80 °C. The method is suggested to be appropriate to all metals that sublime and can chemisorb on the substrate without decomposition.