Additives for Superconformal Gold Feature Filling. Issue 5 (11th May 2021)

• Record Type: Journal Article
• Authors: Josell, D.; Moffat, T. P.
• Is Part Of: Journal of the Electrochemical Society. Volume 168:Issue 5(2021)
• Publication Date: 2021-05-11
• Subjects: gold -- superconformal -- trench -- superfill -- additives; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/abfcd7
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : An overview of the effect of additives on Au electrodeposition from Na3 Au(SO3 )2 based electrolytes is presented with an emphasis on filling of fully metallized recessed surface features such as trenches and vias. The impact of heavy metal additives Tl +, Pb 2+, and Bi 3+ is reviewed and accompanied by a brief survey of the effects of Sb 3+, Te 4+, SeCN −, 3-mercapto-1-propanesulfonic acid (MPS) and polyethyleneimine (PEI) additions. The addition of Tl +, Pb 2+, Bi 3+ or Sb 3+ accelerates the kinetics of Au(SO3 )2 3− reduction to Au, as manifest in hysteretic voltammetry and rising chronoamperometric transients, and yields bright specular deposits. Gold deposition with Pb 2+ addition exhibits superconformal filling in sub-micrometer trenches while Bi 3+ addition induces a more extreme bottom-up filling, but Tl + and Sb 3+ additions yield essentially conformal deposition for the conditions examined. Modest acceleration and hysteresis observed with Te 4+ addition reflect roughening due to limited nucleation, 3D growth and delayed coalescence, rather than catalysis, and are associated with conformal feature filling. Unlike the other additives, SeCN −, MPS and PEI inhibit the deposition kinetics. Breakdown of suppression during deposition in micrometer size trenches is biased toward recessed surfaces where the flux of suppressor is constrained, yielding localized deposition and superconformal filling.