Details

Autor(en) / Beteiligte

• Hai, N.T.M.
• Huynh, T.T.M.
• Fluegel, A.
• Arnold, M.
• Mayer, D.
• Reckien, W.
• Bredow, T.
• Broekmann, P.

Titel

Competitive anion/anion interactions on copper surfaces relevant for Damascene electroplating

Ist Teil von

• Electrochimica acta, 2012-05, Vol.70, p.286-295

Ort / Verlag

Kidlington: Elsevier Ltd

Erscheinungsjahr

2012

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The competitive interaction of chloride and SPS (bis-(sodium-sulfopropyl)-disulfide) at Cu(100)/electrolyte model interfaces was studied by means of cyclic voltammetry in combination with in situ STM and DFT. This specific anion/anion interaction is of paramount importance for the suppressor ensemble deactivation in the context of the industrial Cu Damascene process used for the state-of-the-art on-chip metallization. It is the interplay between chemisorbed chloride and SPS which regulates the dissociative SPS adsorption on copper as the key step in the course of the surface-confined MPS (mercaptopropane sulfonic acid) production. The latter species is considered as the actual anti-suppressor (depolarizer) in context of the Cu Damascene process. Under competitive conditions the chloride adsorbs and orders much faster on Cu(100) than the SPS. The resulting c(2×2)-Cl adlayer acts as an effective barrier for the dissociative SPS adsorption, at least under non-reactive conditions. Defect sites within the chloride matrix are identified as crucial pre-requisites for the dissociative SPS adsorption. Defects are generated under reactive conditions during copper dissolution or copper deposition due to rapid anion adsorption/desorption dynamics. As consequence of the SPS dissociation a mixed, defect-rich c(2×2)-Cl–MPS co-adsorption phase forms on Cu(100) where every second chloride species of the pristine c(2×2)-Cl adlayer is displaced by MPS units. This co-adsorption phase reveals an apparent p(2×2) symmetry in the STM experiment since only the sulfonic head groups of the MPS units are imaged while the S and the Cl species chemisorbed on the copper surface remain invisible at the “buried” interface. The relevance of this surface reaction for the Cu Damascene process is discussed in detail.