A Tertiary Current Distribution Model for the Pulse Plating of Copper into High Aspect Ratio Sub-0.25 μm Trenches

Abstract

Electrodeposition of copper into sub-0.25 m features has been studied theoretically and experimentally. A physically based twodimensional (2D) pseudo-steady state and a one-dimensional (1D) unsteady-state mass-transfer model have been developed to study the effect of important parameters on the step coverage, evolution of copper deposits in damascene features, and deposition rate inside high aspect ratio single and dual damascene features. An analytical model that assumes linear deposition kinetics and a fixed boundary also has been developed and found to be in good agreement with the numerical results of the free boundary models to about 50% filling of the feature. A new criterion, based on the pulse plating parameters, for optimizing the opposing trends in step coverage and the deposition rate is also given. Copper has been deposited into submicron features, by dc and pulse plating, using an alkaline bath. Deposit evolution inside trenches has been studied by performing sequential plating experiments. Copper deposits with good morphology and resistivity were obtained using the alkaline bath. Experimental observations have been compared to the model trends and found to be in good agreement. Pulse plating experiments show that the deposit quality and the step coverage are improved over dc plating. Slanting the sidewalls also improves step coverage as shown by 2D model calculations.

Superconformal Electrodeposition of Silver in Submicrometer Features

“…4a. trench sidewalls, such that the trenches are wider at the top than at the bottom, will enable geometric leveling that will increase the nominal aspect ratio of the features that can be filled robustly. 6,20 Filling of trenches-experiments.-Silver deposition into trenches 0.41 m deep and between approximately 350 and 200 nm in width was examined using the selenium-catalyzed electrolyte. As shown in Fig.…”

Electrochemical Deposition of Buried Contacts in High-Efficiency Crystalline Silicon Photovoltaic Cells

“…Electrochemical Cu deposition offers several unique features for interconnect technology: ͑i͒ With specific organic additives in the Cu electrolyte and careful process control, superconformal filling of high-aspect-ratio vias is facilitated. [4][5][6][7][8] ͑ii͒ Electrodeposited Cu interconnects can show superior electromigration performance as compared to Cu deposited by physical vapor deposition ͑PVD͒ or chemical vapor deposition ͑CVD͒, depending on texture and grain size. 9,10 ͑iii͒ Electrodeposition is a relatively cheap process as compared to processes relying on ͑high͒ vacuum facilities; moreover, the deposition rate obtainable by electrodeposition is generally much higher than that for PVD or CVD.…”

Calculation of the current density distribution of submicron copper electroplating based on uneven adsorption of poly(ethylene glycol)

“…However, as the deposition proceeds, the change of surface geometry due to deposit growth requires the use of the moving boundary algorithm, [14,15]. The change of trench profile during deposition must eventually conflict with the 1-D (high aspect ratio) assumption and a 2-D model would have to be adopted for overall deposition profile prediction [2][3][4][5][6][7][8]. Nevertheless, the major goal of this work is to qualitatively describe how the uneven PEG adsorption on the surface occurs, rather than quantitatively describe the changing deposition profile, so the 2-D model with the moving boundary effect is not necessary.…”

“…To reduce the required experimental work, numerical modeling can identify optimal operational conditions from limited experimental data. Several papers have shown simulation results with acceptable accuracy as compared to experimental observations [1][2][3][4][5][6][7][8].…”