The ALD (atomic layer deposition) technique employs a self-limiting mechanism to precisely control the layer-by-layer growth and can produce an extremely conformal and uniform film over a large area. In the process, the reactants are introduced into the reactor in separate pulses for the adsorption of metallorganic precursor. In between the pulses, the surface is purged with a reduction agent such as hydrogen to desorb the ligands leaving pure metal on the surface. Unlike the conventional CVD (chemical vapor deposition) process, the ALD process does not require the uniformity of the gas pressure in the reactor to obtain a uniform film. Also, there is time for the species to be adsorbed in deep vias and trenches for a conformal build-up of the material monolayer by monolayer.

In this work we use the ALD technique to deposit layers of metal such as Cu, Co, Co-Si, W etc for advanced IC circuits and high density magnetic recording applications. We are particularly interested in the interfacial chemistry for ALD.

Several newly developed characterization techniques suitable for analyzing ultra-thin films are being used to characterize the film thickness and density, including high-resolution Rutherford backscattering spectroscopy (with Professor W. Lanford), nuclear reaction analysis (with Professor H. Bakhru, for high-resolution carbon detection in thin films and interfaces), real time fixed angle energy dispersive X-ray reflectivity (developed in our lab), real time van der Pauw resistivity, X-ray fluorescence, and atomic force microscopy as well as variable angle spectroscopic ellipsometry (VASE).

Metallization of ULSI using atomic layer deposition

This project has been funded by RPI and varies industrial partners. Mark Delarosa, a former student in our group (now worked for Intel) initially worked on Co ALD successfully.