Study On Trib-electrochemical Performance Of Substrate Materials Of Copper Interconnect Wafer

The rapid development of information industry requires higher performance ofwafer. Though the integration density and the running speed of chip can be greatlyimproved by introducing low dielectric (k) materials into Cu Damascene interconnectwafer, the global planarization for Cu/low k wafer is a challenge because low k materiallayer subject to high pressure during chemical mechanical planarization (CMP) processcan be easily damaged. The electrochemical mechanical planarization (ECMP) is analternative especially suitable for the planarization of Cu/low k interconnect since it canbe carried out at lower pressure, non-abrasive, and non-oxidant conditions.In this paper, substrates of copper and silicon were studied by thetribo-electrochemical experiments, the planarization electrolytes were optimizedaccording to the passivation characteristics of the materials, and what’s more, goodmaterial removal rate and surface quality were obtained in the simulated ECMP process.For copper, HEDP was selected as complexing agent, the influence of BTAH,chloride ion and polarization potential to Cu passive film’s formation was studied byelectrochemical impedance spectroscopy (EIS), then the best electrolyte formula andpolarization condition was determined. After that, copper ECMP process in thatelectrolyte was optimized through the simulated ECMP tests, which show that thepolarization potential of optimum conditions is the same with the optimum potential forthe passive film’s formation, indicating the passive film is the key to ECMP process. Asfor passive film formation mechanism, study shows that the passivation process beginsfrom a local point, then passivation points increasing in number, then expanding andcovering most of the surface. Finally, the experiments combined both electrochemicaltesting methods and X-ray photoelectron spectroscopy (XPS) analysis confirmed that anappropriate amount of chloride ion would promote the formation of the Cu passive film,as the Cu2O reduction peak increases in cyclic voltammetry, and the atomic percentageof N elements increases in XPS, and no Cu(II) satellite peak appears. The materialremoval caused by either pure mechanical or electrochemical action is small, but ismostly from the synergistic effect of the electrochemical and mechanical action inECMP.At Last, the effects of slurry pH and oxidant concentration on Si corrosion werestudied to optimize the slurry by electrochemical methods, and the effect of thepolarization potential on CMP material removal rate and surface quality was studied.Results show that suiltable anode potential could significantly enhance the materialremoval rate, but the surface quality deterioated to some extent.