With shrinkage of the minimum feature size to sub-14 nm, protrusion/dishing issues in chemical mechanical planarization (CMP) processes have become increasingly important to address. In this study, we propose an advanced slurry formulation with a surface active agent to prevent W protrusion during the W CMP process. In the presence of surface active agent, blanket removal rates on both W and SiO2 films showed non-Prestonian behavior at a low threshold pressure, which is explained by adsorption characteristics of the surface active agent on the films. To study the effect of the surface active agent on W protrusion, W-patterned wafers were polished at the threshold pressure. As the concentration of the surface active agent increased from 0 to 12 mM, W protrusion from patterns with line/space widths of 0.5 μm/0.5 μm decreased significantly from 186 to 30 Å. The mechanism on the significant decrease in W protrusion behavior in the presence of the surface active agent is discussed.

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The Fenton reaction has been used for the tungsten oxidation under acidic conditions in tungsten chemical mechanical planarization (CMP). However, the narrow working pH window required for ideal reaction limits its application. Herein, we report a simple Fenton-like system via the reaction between copper ion and hydrogen peroxide (H 2 O 2 ) for the tungsten oxidation over a broad pH range. Copper ion was employed as a reactant with H 2 O 2 for the Fenton-like reaction, resulting in high production rates of hydroxyl radicals in the range of acidic to neutral pH, which leads to a high rate of tungsten oxidation. As a result, the Fenton-like reaction between copper ions and H 2 O 2 enables the high removal rates of tungsten films during CMP process in acidic to neutral pH ranges.

Herein, the corrosion behaviors of W metal gates in the presence of H 2 O 2 at the acidic medium were investigated as a function of dipping time, temperature, and H 2 O 2 concentration. We determined the kinetic constants (i.e. k w and k h ) based on the experimental data. The activation energy (E a ) are calculated from the Arrhenius equation. Thermodynamic parameters ( G ‡ , H ‡ , and S ‡ ) for the dissolution were determined based on the Eyring plot. These results investigated in this study will provide researchers the prior information on parameters to control the corrosion behaviors of W metal gates during the chemical mechanical planarization (CMP) process.

We studied the effect of selective adsorption of polyethylene glycol (PEG) on SiO 2 for high removal selectivity of tungsten to SiO 2 in tungsten CMP. The hydrogen bonding between PEG and SiO 2 increased as the solution pH decreased. At pH 3, the maximum adsorption of PEG on SiO 2 occurred due to the low surface charge of SiO 2 (near its isoelectric point). The selective adsorption led to the selective reduction of removal rate of SiO 2 during CMP process. As a result, the removal selectivity increased from 4.5 to 85.5 as the PEG concentration increased from 0 to 9 wt% at pH 3.