Superconformal electrodeposition of copper in 500-90 nm features

Superconformal electrodeposition of copper in 500 nm deep trenches ranging from 500 to 90 nm in width has been demonstrated using an acid cupric sulfa te electrolyte containing chloride (Cl). polyethylene glycol (PEG), and 3-m ercapto-1-propanesulfonate (MPSA). In contrast, similar experiments using e ither an additive-free electrolyte, or an electrolyte containing the binary combinations Cl-PEG. Cl-MPSA. or simply benzotriazole (BTAH), resulted in the formation of a continuous void within the center of the trench. Void fo rmation in the latter electrolytes is shown to be reduced through the geome trical leveling effect associated with conformal deposition in trenches or vias with sloping sidewalls. The slanted sidewalls also counterbalance the influence of the differential cupric ion concentration that develops within the trenches. Examination of the i-E deposition characteristics of the ele ctrolytes reveals a hysteretic response associated with the Cl-PEG-MPSA ele ctrolyte that can be usefully employed to monitor and explore additive effi cacy and consumption. Likewise, resistivity measurements performed on corre sponding blanket films can be used to quantify the extent of additive incor poration and its influence on microstructural evolution. The films deposite d from the Cl-PEG-MPSA electrolyte exhibit spontaneous recrystallization at room temperature that results in a 23% drop in resistivity with in a few h ours of deposition. (C) 2000 The Electrochemical Society. S0013-4651(00)04- 078-7. All rights reserved.