Adherence/Diffusion Barrier Layers for Copper Metallization: Amorphous Carbon:Silicon Polymerized Films
Description: Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This study proposes modified amorphous silicon carbon hydrogen (a-Si:C:H) films as possible diffusion barriers and replacements for SiO2 between metal levels, interlevel dielectric (ILD), or between metal lines (IMD), based upon the diffusion inhibition of previous a-Si:C:H species expected lower dielectric constants, acceptable thermal conductivity. Vinyltrimethylsilane (VTMS) precursor was condensed on a titanium substrate at 90 K and bombarded with electron beams to induce crosslinking and form polymerized a-Si:C:H films. Modifications of the films with hydroxyl and nitrogen was accomplished by dosing the condensed VTMS with water or ammonia before electron bombardment producing a-Si:C:H/OH and a-Si:C:H/N and a-Si:C:H/OH/N polymerized films in expectation of developing films that would inhibit copper diffusion and promote Cu adherence, wetting, on the film surface. X-ray Photoelectron Spectroscopy was used to characterize Cu metallization of these a-Si:C:H films. XPS revealed substantial Cu wetting of a-Si:C:H/OH and a-Si:C:H/OH/N films and some wetting of a-Si:C:H/N films, and similar Cu diffusion inhibition to 800 K by all of the a-:S:C:H films. These findings suggest the possible use of a-Si:C:H films as ILD and IMD materials, with the possibility of further tailoring a-Si:C:H films to meet future device requirements.
Date: May 2004
Creator: Pritchett, Merry