Control of Tungsten Protrusion with Surface Active Agent during Tungsten Chemical Mechanical Polishing

Abstract

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.

A review on chemical and mechanical phenomena at the wafer interface during chemical mechanical planarization

“…Although surfactants such as CTAB [106], ammonium dodecyl sulfate [65], and potassium oleate [107] were also investigated as corrosion inhibitors, BTA is the most common corrosion inhibitor used in CMP slurries. In any case, all these inhibitors can complex with metal ions and remain stable on the metal film as undesirable organic residues [108], and it has been very difficult to remove these organic residues during post-CMP cleaning [109,110].…”

Chemical Mechanical Planarization-Related to Contaminants: Their Sources and Characteristics

“…Many cleaning compositions consisting of oxidizers, complexing agents, cleaning agents, and pH adjuster have been developed so far [20,31]. However, there are still several cleaning challenges for the future technology nodes, while considerable progress has been made [57]; (1) improvement of cleaning efficiency, (2) the removal of smaller particles from the films, (3) the prevention of cross-contamination by brush scrubbing, (4) the removal of new-types contaminants-very thin metal flake, (5) wafer backside cleaning, (6) universal cleaning solution, (7) environmentally friendly post-CMP cleaning, (8) TMAH-free cleaning solution.…”

“…STI CMP uniformly polishes the step height of SiO 2 , formed by the gap-filling process, and stops on an underlying Si 3 N 4 film [4][5][6]. MOL CMP processes include the necessary steps to connect the individual transistors by mainly polishing W contact metal/liner and interlayer dielectric (ILD) layer [7,8]. BEOL processes enable the multilevel interconnect network where Cu lines are isolated by the dielectric materials [9].…”

Recent advances and applications of abrasive processes for microelectronics fabrications

“…Therefore, the barrier removal rate calculated with the peak-to-end-point time might result in a lower barrier rate. You et al (2017) proposed a new slurry formulation to avoid W protrusion in WCMP. When the surface active agent increased to 12 mM from 0, W protrusion decreased largely to 3 nm from 18.6 nm.…”

“…Surface roughness and material removal rates (MRRs) are hot topics for CMP in giantlarge-scale integrated circuit (IC) manufacturing (Liu et al, 2018). Dishing/protrusion is reported to be an issue (You et al, 2017). The SiGe-based fin-field-effect-transistor (FINFET) technology is a solution to extending the complementary metaloxide-semiconductor technology, and CMP helps to integrate SiGe into Si-based structures (Yang et al, 2018).…”