Kuo Chung Hsu

Amorphous RuW Film as a Diffusion Barrier for Advanced Cu Metallization

Barrier properties of 10 nm thick Ru and amorphous Ru 37.2 W 62.8 films as seedless copper diffusion barriers have been investigated. Thermal stability of the barriers was evaluated after annealing at various temperatures. X-ray diffraction (XRD) analyses and sheet resistance measurements suggested that the Ru 37.2 W 62.8 barrier was thermally stable up to 700°C against Cu diffusion, which improved about 150°C over the Ru film. XRD studies and electron diffraction patterns of the Ru 37.2 W 62.8 film showed that it maintained an amorphous-like microstructure after 30 min annealing at 550°C. This film started to recrystallize at about 600°C and developed to a film with Ru and W0 3 grains after a 700°C anneal. The leakage current of the 500°C postannealed Cu/RuW/ porous SiOCH/Si stacked structure provided nearly 2 orders of magnitude superior than that of the Ru sample. The amorphous Ru 37.2 W 62.8 film is an alternative candidate for the Cu direct platable seedless barrier in the advanced copper metallization process.

A 3 nm self-forming InOx diffusion barrier for advanced Cu/porous low-k interconnects

The copper diffusion barrier properties of a 3 nm self-forming InOx layer on a porous ultralow-k (p-ULK) film have been investigated. A 5 at. % In doped Cu film was directly deposited onto porous low-k films by co-sputtering, followed by annealing at various temperatures. Transmission electron microscopy (TEM) images showed that a 3 nm layer was self-formed at the interface between Cu–In and p-ULK films after annealing at 400 °C for 1 h. An EDS line scan on the region near this interface showed obvious accumulation of In at the interface. X-ray photoelectron spectroscopy (XPS) analyses indicated that the self-formed interfacial layer was InOx. The self-forming InOx layer prevented Cu agglomeration on the p-ULK film surface. The XPS atomic depth profiles showed that the self-formed InOx barrier was thermally stable against Cu diffusion to at least 500 °C for 5 h. The sheet resistance of the post 500 °C annealed Cu–In film was comparable to that of a pure Cu film. The Cu–In self-forming barrier approach may be a viable candidate for Cu/p-ULK interconnects.

5 nm Amorphous Boron and Carbon Added Ru Film as a Highly Reliable Cu Diffusion Barrier

The failure mode and Cu barrier properties of a 5 nm thick boron and carbon added Ru (Ru―B―C) film deposited on Si substrate have been investigated. Results from X-ray diffraction (XRD) and Fourier-transformed electron diffraction patterns indicate that the Ru―B―C film is amorphous up to 700°C. Unlike pure Ru film, the Ru in the Ru―B―C film recrystallized at 750°C instead of reacting with Si at the interface to form Ru 2 Si 3 . The sheet resistance and XRD results show that the 5 nm Ru―B―C barrier is thermally stable up to 750°C, whereas the 5 and 10 nm Ru are only stable below 550 and 600°C, respectively.