Roy A. Carruthers

Plasma‐Enhanced Chemical Vapor Deposition of Silicon Dioxide Films Using Tetraethoxysilane and Oxygen: Characterization and Properties of Films

SiO 2 films were deposited in a commercial single wafer parallel plate plasma deposition reactor using tetraethoxysilane as the silicon source. Deposition conditions were varied to produce films with widely differing properties. Electrical, optical, mechanical, and wet-etch-rate characterization were then used to investigate the as-deposited film quality. Moisture uptake was also measured and related to the initial properties. The films were studied in an ongoing investigation of silicon dioxide interlevel dielectric films used in multilevel ultra large scale integrated chip wiring

In situ and Ex situ Measurements of Stress Evolution in the Cobalt-Silicon System

The biaxial stress in Co thin-films has been investigated in situ by measuring changes in substrate curvature that occurred during deposition and annealing.Films of Co, 35 to 500 nm in thickness, were deposited by UHV magnetron sputtering at room temperature on Si (100) and poly-Si substrates.Results show that during Co deposition the bending force increased linearly with film thickness; a signature of constant stress.In addition, the stress evolution during silicide formation was measured under constant heating rate conditions from room temperature up to 700°C. The stress-temperature curve was correlated with Co 2 Si, CoSi, and CoSi 2 phase formation using in situ synchrotron X-ray diffraction measurements.The room temperature stress for the CoSi 2 phase was found to be ∼0.8 GPa (tensile) in the films deposited on Si (100) and ∼1 GPa (tensile) on the films deposited on poly-Si.The higher tensile stress in the poly-Si sample could be a result of Si grain growth during annealing.

Material and Integration Issues for Rare Earth Silicides as Gate and Diffusion Contacts in Advanced CMOS Technologies

In an integration scheme where the nFETs and pFETs of CMOS devices are silicided with different materials (Dual Silicides), rare-earth erbium (Er) and ytterbium (Yb) silicides are potential candidates for contacts to n-Si because of their lower Schottky barrier heights, as compared to more conventional nickel and cobalt silicides. [1-3] Although the lower Schottky barrier across the silicide/n-silicon interface results in reduced contact resistivity, the microstructure can exhibit defects and morphology issues [3-7] which affect device integrity and may contribute to contact resistance degradation. [8] In this study, we compared the material and integration properties of Er and Yb silicides with those of Ni (Pt-alloyed) silicide. Using four point probe, AFM, optical inspection and SEM, we compared the silicides using sheet resistance, surface morphology, defects density and ease of formation in narrow lines. We found that the silicide morphology is affected by several process parameters such as the type of metal deposition process (sputtering vs. evaporated) and the anneal formation temperature. The silicides were also tested for their ability to withstand aggressive processing after their formation. The processes tested included exposure to PECVD plasma, contact hole reactive ion etching and forming-gas annealing. The rare-earth and Ni(Pt) silicides showed similar stability upon processing. Lastly, we quantified the residual metal remaining on dielectric surfaces after silicide processing. Overall, Er silicide showed better performance than Yb silicide. By optimizing various elements of the silicidation process, higher quality silicide films can be achieved for evaluation as suitable nFet contacts.