Ville Antero Saanila

Diffusion Barrier Deposition on a Copper Surface by Atomic Layer Deposition

Diffusion barrier materials, TiN and WN, were deposited by atomic layer deposition (ALD). The chlorine concentration of the TiN film was as low as 1.2 at.-%, and resistivity was below 200 μΩ cm. Ultra high aspect ratio (AR=85) trenches were used to assess step coverage. Tungsten nitride film, deposited from WF 6 and ammonia, was found to have high resistivity, although the residue content was low. The barrier deposition compatibility was studied using the copper surface exposed on the bottom of vias in the copper dual-damascene structure. The deposition on copper of both TiN and WN was found to be very challenging.

Reduction of Copper Oxide Film to Elemental Copper

The reduction of copper oxide film was studied as a process step in the manufacturing of elemental copper film via copper oxide film. Alcohols, carboxylic acids, and aldehydes were tested as reducing agents. The copper oxide film was exposed to reducing agents below 400°C using nitrogen as a carrier gas. The reduction efficiency was studied by characterizing the oxide residues with ion beam analysis and measuring the electrical resistance of the films. Thermodynamic calculations were compared with the observations. Most of the reducing agents performed well and copper oxide film as thick as 300-400 nm was completely reduced to elemental copper.

Atomic layer deposition of WxN/TiN and WNxCy/TiN nanolaminates

Abstract Diffusion barrier materials, such as TiN, W x N, WN x C y and their nanolaminates were deposited by atomic layer deposition method. TiN film exhibited excellent properties, but W x N film exhibited high resistivity despite the low residue concentration. Both TiN and W x N films suffered from serious incompatibility with the copper metal. WN x C y film was deposited by introducing triethylboron as a reducing agent for tungsten. Excellent film properties were obtained, including very good compatibility with the copper metal, evident as strong adhesion and no pitting on the copper surface. Nanolaminate barrier stacks of W x N/TiN and WN x C y /TiN were successfully deposited. TiN deposition did not cause copper pitting when thin WN x C y film was deposited underneath.