Bo-Un Yoon

Effect of Polysilicon Wettability on Polishing and Organic Defects during CMP

This study investigated the wettability effect of polysilicon on the polishing performance and organic defect contamination during polysilicon chemical mechanical polishing (CMP). Contact angle measurement was utilized to understand the nature of polysilicon surfaces. An oxidizer, H 2 O 2 , was added to the silica slurry to modify a hydrophobic polysilicon surface to a hydrophilic surface during polishing. The adhesion force was measured between a polymeric pad particle and a poly-Si wafer surface in KOH solution (pH 11) as a function of H 2 O 2 concentration. The adhesion force of the polymeric pad particle on the polysilicon decreased from 14 to 8 nN as the peroxide concentration increased to 10 vol %, at which the surface became hydrophilic. The hydrophilization of the polysilicon surface during polishing drastically reduced the organic contamination on the polysilicon wafers after polishing. The removal rate, frictional force, and pad temperature during CMP, with and without oxidizing the surface, were measured. They all decreased with the increasing concentrations of the oxidizer. The decrease was attributed to the formation of the lubrication layer of the oxide surface due to the oxidation of polysilicon.

Effect of Wettability of Poly Silicon on CMP Behavior

The hydrophobicity of poly Si is reported to introduce different polishing behavior with careful control of post CMP cleaning process. The purpose of this study was to investigate the effect of poly Si wettability on its CMP behavior. The adhesion force of polymeric particle on the poly Si wafer surfaces was measured in the KOH solution (pH 11) as a function of solution A concentration. Adhesion force decreased and saturated as a function of concentration of solution A. The change of surface wettability affects not only the polishing rates but also the level of contamination on wafer because the interactions between particles and substrates are dependent on the wettability of the surface. Also, hydrophobic poly Si surfaces attracted much more pad particles with water marks than hydrophilic

CMP process development for Cu/low-k with Ru liner

As the design rule of BEOL of the device decreases, it becomes difficult to obtain void-free Cu fill with the conventional PVD barrier metal (TaN/Ta). To increase Cu gap-fill performance, CVD liners such as Co and Ru have been extensively developed. Among them, Ru liner has a great potential for the next generation Cu interconnect technology because it can provide Cu reflow process. However, Ru is one of the famous noble metals, which means that Ru CMP becomes a very challenging and key technology in BEOL technology. In this presentation, the characteristics of Cu/low-k CMP with Ru liner will be discussed in terms of planarity, uniformity and defects. Especially, dishing and erosion behavior including the pattern density and pitch dependency on CMP slurry and conditions will be focused. Electric results from successfully integrated Cu interconnects with Ru will be also presented.