Roles of Additives in Damascene Copper Electropolishing

Abstract

This study explores how the dissolution of damascene Cu depends on accelerators of organic acids in alcohol-containing H 3 PO 4 electropolishing electrolytes. Four two-additive electrolytes that contain different accelerators, acetic, citric, citrazinic, and benzoic acids, are evaluated. At the bottom of damascene features, an esterification reaction between alcohols and organic acids efficiently forms a highly resistive layer and reduces the acidity of the solution. Accordingly, outside the damascene features, the rate of removal of Cu is dominated by the acidity of electrolytes but, inside the features, it is also determined by the resistance of the viscous layer. For a weak acidic additive, acetic acid, an extremely high additive concentration is introduced to sustain the moderate acidity of the solution to initiate intense esterification. Therefore, acetic-acid-based two-additive electrolytes exhibit excellent Cu planarization capability.

Electropolishing—A Practical Method for Accessing Voids in Metal Films for Analyses

“…Already in the 20th century, many publications released contributed to obtaining a fundamental understanding of its underlying mechanisms [29,30,[32][33][34][35][36][37][38][39]. As of today, recent review publications [40,41] demonstrate that still a lot of research on electropolishing is performed, especially towards the direction of fine tuning process parameters [42] and the chemical composition of the used electrolyte [43,44]; often in the application of specialized industrial manufacturing processes [45][46][47][48][49][50]. Within the present publication, a simple experimental setup for electropolishing single microelectronic chips with a copper metallization is presented and optimized in terms of micro smoothing results.…”

Establishing the patterns in anode behavior of copper in phosphoric acid solutions when adding alcohols

“…Many studies focused on instructions about the favorable impact of adding certain organic compounds (carboxylic acids or their salts, aldehydes, amines, alcohols) on the process of electrochemical polishing of copper in phosphoricacid solutions [7][8][9][10][11][12][13][14][15][16][17]. The most commonly used as additives are the saturated, unsaturated and aromatic alcohols whose introduction reduces the limiting current density, prevents point etching and metal etching.…”

“…For example, the positive effect is observed when adding to phosphoric-acid solutions glycerin and organic acids [11], ethanol, ethylene glycol or glycerol [12], methanol [13,14], which ensures the uniform dissolution of metal at polishing, decreases the number of etching points and reduces the limit anode current. The influence of additives of aromatic alcohols during copper electropolishing in H 3 PO 4 solutions was investigated in [15].…”

“…Thus, the cited studies highlight only specific cases of copper polishing regarding the treatment of products in electronic industry [11,14], the adsorption phenomena when investigating corrosion processes on copper [13,15]. Of interest is the research aimed at establishing the influence of additives of alcohols on the technical indicators of polishing process, such as the relative smoothing of surface unevenness, coefficient of reflectance, specific metal removal.…”

Study of Cu Electrochemical Polishing Mechanism With Observation of Water Acceptor Diffusion

“…This Cu ECP method has several advantages, such as a solution-based process that uses simple equipment, selectivity for the conductive substrate, and causing no mechanical damages. Due to these unique properties, the Cu ECP process can be used in various applications that treat surfaces for cosmetic purposes ( Du and Suni, 2004 ), for substrates for graphene growth ( Zhang et al, 2012 ), for TEM and EBSD samples ( Sun et al, 2005 ; Lapeire et al, 2013 ), and for Cu planarization in semiconductor interconnections ( Chang et al, 2002 ; Chang et al, 2003 ; Padhi et al, 2003 ; Liu et al, 2005 ; Suni and Du, 2005 ; West et al, 2005 ; Liu et al, 2006 ; Liu et al, 2006 ). Despite the many potentials of Cu ECP, its actual mechanisms are still controversial.…”