Bottom Step Coverage Research Articles

Molecular Dynamics Study on Enhanced Cu Coverage of Trench Filling with Low-Index Ta Surfaces

The Cu coverage of trench filling enhanced by different low-index surfaces of tantalum in physical vapor deposition is studied by molecular dynamics simulation with the embedded atom method (EAM) as the interaction potential for the present alloy metal system. The deposition morphologies and bottom step coverage enhancement of trenches with three different aspect ratios are examined. It is found that the Cu adatom on Ta(110) with uniform and low surface diffusion barrier energy and that on Ta(111) with high surface energy lead to the improvement of the surface diffusion of Cu adatoms. The shadowing effect is inhibited on Ta(110) and Ta(111) such that the bottom step coverage of the trench is enhanced markedly at an early stage and the final coverage of trench filling is improved significantly. Also, the texture of deposition on the trench with Ta(110) has a uniform structure owing to the low surface energy, while that with Ta(111) has a nonuniform structure owing to the high surface energy on the sidewall.

Improved Step Coverage of Cu Seed Layers by Magnetic-Field-Assisted Ionized Sputtering

The relationship between the ion flux of self-ionized sputtering and the static magnetic field supplied by DC coils was investigated by ion current measurements. The ion flux was clarified in order to increase the substrate ion current. The additional magnetic field perpendicular to the substrate increases the substrate ion current and decreases the side electron current. The suppression of Cu ion diffusion increases the substrate ion current of self-ionized sputtering and the current distribution depends on the magnetic field configuration. A stronger magnetic field in the region of the wafer edge is necessary to increase the substrate ion current. This condition results in an increase in bottom step coverage and any asymmetry at the wafer edge is also corrected.

Effect of substrate on the step coverage of plasma-enhanced chemical-vapor deposited tetraethylorthosilicate films

Plasma-enhanced chemical-vapor deposition tetraethylorthosilicate (TEOS) films are extensively used as the interlayer dielectric films in multilevel interconnection processes. When TEOS oxide films were deposited on metal patterns three different substrates, titanium nitride (TiN), aluminum (Al), and oxide (SiO2), were used. This study examines the dependence of these substrates on TEOS step coverage. The deposition rates of TEOS oxide revealed that the SiO2 substrate lead to highest TEOS deposition rate during the initial deposition period of 5 s. Then, the TEOS deposition rate of the substrates was nearly the same. The TiN substrate exhibited the highest sidewall step coverage but the sidewall step coverage of the Al substrate deteriorated due to its granular surface. Additionally, different substrates exhibited different coverage of the bottom step. Moreover, the bottom step coverage exceeded the sidewall coverage for all substrates.

Copper Electroplating for Damascene ULSI Interconnects

ABSTRACTCopper was electroplated on sputtered Cu seed layer with Ta diffusion barrier. We achieved enhanced Cu deposition at the bottom of trenches/vias and defect-free filling sub-0.5 μm trenches (down to 0.25 μm width) of high aspect ratio (up to 4:1). Large grains occupying the entire trench were observed. Bottom step coverage of electroplated copper in sub-0.5 μm trenches was estimated to be about 140%, while sidewalls step coverage was about 120%. Via resistance for sub-0.5 μm vias was measured to be below 0.55 Ω. Strong <111> texture, large grains, and low tensile stress were observed in electroplated Cu films and in-laid Cu lines after low temperature anneal.

Characteristics of PECVD grown tungsten nitride films as diffusion barrier layers for ULSI DRAM applications

We have developed tungsten nitride (W-Nitride) films grown by plasma enhanced chemical vapor deposition (PECVD) for barrier material applications in ultra large scale integration DRAM devices. As-deposited W-Nitride films show an amorphous structure, which transforms into crystalline, β-W2N and α-W phases upon annealing at 800°C. The resistivity of the as-deposited films grown at the NH3/WF6 gas flow ratio of 1 is about 160 μω-cm, which decreases to 50 μω-cm after an rapid thermal annealing treatment at 800°C. In the contact holes with the size of 0.35 μm and aspect ratio of 3.5, the bottom step coverage of the tungsten nitride films is about 60%, which is about three times higher than that of collimated-TiN films. We obtained contact resistance and leakage current with the tungsten nitride barrier layer comparable to those with conventional collimated TiN films. The contact resistance and leakage current are stable upon thermal stressing at 450°C up to 48 h.

Improved gap-filling capability of fluorine-doped PECVD silicon oxide thin films

Fluorine-doped plasma-enhanced chemical vapour deposition (PECVD) tetraethylorthosilicate (TEOS) SiO 2 thin film was investigated for improvement in gap-filling capability as an inter-metal dielectric. Both C 2F 6 and triethoxyfluorosilicate (TEFS) were evaluated as fluorine (F) dopants. Both kinds of F-doped films provided significantly better gap-filling capability than undoped films. This was attributed to the good bottom-step coverage and preferential sidewall etching due to the presence of F. However, there was a markedly different relationship between gap-filling capability and F concentration for the two dopant precursors. Finally, it was shown that either C 2F 6 or TEFS doping can extend the gap-filling capability of SiO 2 down to 0.35 μm metal spacing with an aspect ratio of 2.0:1.

Formation of SiN Films by Plazma-Enhanced Chemical Vapor Deposition Using [(CH3)2N]3SiN3

An organic source gas, tris-dimethyl-amino-silyl-azide (TDSA, [(CH3)2N]3SiN3), was newly synthesized and utilized for the deposition of a passivation film of sub-half-micrometer devices. Deposition temperature dependence of the film formed by plasma-enhanced chemical vapor deposition (PECVD) using TDSA was investigated and step coverage of the TDSA film was examined. As a result, it was clarified that hydrocarbon content in the film decreased with increasing deposition temperature. The bottom step coverage of the films formed using TDSA was greatly improved compared to that of the conventional silicon nitride film.