Effect of slurry chemicals on chemical-mechanical planarization of copper.

摘要

An important component of the slurries used in chemical mechanical planarization (CMP) is an appropriately chosen corrosion/dissolution inhibitor, which facilitates selective material removal from protrusions while protecting recessed regions of the surface. The present work demonstrates the utility of two environmentally benign anionic surfactants, sodium dodecyl sulfate (SDS) and ammonium dodecyl sulfate (ADS) as dissolution inhibitors. Using these surfactants in a standard slurry (1 wt% glycine with 5 wt% H2O 2 at pH = 4.0) typically used for Cu CMP, and combining measurements of open circuit potentials and contact angles with those of Cu removal rates, we show that both SDS and ADS suppress chemical dissolution and polish rates of Cu. The dissolution inhibition efficiencies of ADS and SDS measured in these experiments are found to be superior to those of benzotriazole (BTA), a traditional inhibiting agent used for copper CMP.; It has been demonstrated that ADS can also be utilized as an inhibiting agent for the application in electrochemical-mechanical planarization (ECMP) of copper. Using an acidic electrolyte of glycine and H2O 2, and small Cu discs, we show that the corrosion inhibition efficiency of ADS is superior to that of benzotriazole even in ECMP application.; The relation between PE of Cu patterns and complexing agents has been investigated by measuring removal rates and surface topographies from patterns created on blanket Cu films. It has been observed that PE is dependent on the step height and drops significantly beyond a threshold step height that is in the range of 1000 A. Since the same type of polishing pad (IC 1400) was used in all the experiments, it might be the complexing agent that determines this characteristic PE threshold. Also, the huge increase in Cu dissolution rate for the citric acid system with increasing temperature appears to be responsible for the low PE values measured for this system.; The synergetic effect of mixtures of ADS and BTA on Cu planarization has also been demonstrated. A model slurry containing a mixture of 3 mM ADS and 0.5 mM BTA shows much lower dissolution rate of Cu than that containing 10 mM BTA while sustaining similar polish rates of Cu at 2 psi. The planarization efficiency evaluated using the topographies created on Cu film surface (width: ∼ 15mum, depth: ∼ 5000 A) also shows better results while using the mixture of 3mM ADS and 0.5 mM BTA compared to 10 mM BTA. The relation between the copper dissolution rate and planarization efficiency is shown to be inversely logarithmically proportional to each other. The information from potentiostatic polarization, contact angle, UV/VIS spectroscopy and FTIR spectroscopy suggests that the synergetic effect of the mixture of BTA and ADS is due to electrostatic attraction between Cu/Cu-BTA complex and dodecyl sulfate as well as the complexation of Cu-BTA-dodecyl sulfate.