In-seon Park

Crystallization behaviour of ALD-Ta2O5 thin films: the application of in-situ TEM

The microstructure of Ta2O5 thin films, deposited onto Si substrates by atomic layer deposition (ALD), was investigated, using in situ transmission electron microscopy (TEM). As-deposited amorphous films crystallize as the orthorhombic phase L-Ta2O5 upon heating at 750°C. Two dominant crystallographic orientations are found, one with (0 0 1) and (1 11 0) planes perpendicular to the substrate, while the other has (0 0 1) planes parallel to the substrate. The grains consist of subgrains which are rotated a few degrees with respect to each other. The kinetics of the crystallization were studied by in-situ TEM heating experiments carried out at nominal temperatures of 790°C, 820°C and 850°C. They reveal that the growth and crystallization activation energies are about 4.2 eV and 6.3 eV, respectively. Tilted subgrains keep forming during growth until they come in contact with neighbouring grains. The crystallization behaviour can be approximated by the Kolmogorov–Johnson–Mehl–Avrami (KJMA or Avrami) equation, giving mode parameters of 2.5, 1.9, and 1.7 at 790°C, 820°C and 850°C, respectively. A small value of mode parameters is attributed to decreasing growth and nucleation rates with time.

A novel Al-reflow process using surface modification by the ECR plasma treatment and its application to the 256 Mbit DRAM

A novel Al-reflow process with the electron cyclotron resonance (ECR) plasma treatment for the modification of underlayers was developed in a vacuum isolated sputtering equipment. The key feature of this technology is the introduction of the in-situ ECR plasma treatment for the modification of the surface characteristics such as surface morphology and stoichiometry of the TiN wetting/barrier layer. High wettability of the Al film was obtained on the ECR-treated TiN surface, producing a conformal Al film on the sidewall of the contact hole before the reflow process. Consequently, complete filling of contact holes with Al was achieved in deep sub-micron contact holes with a high aspect ratio. This study has demonstrated that the Al-reflow process can be extended to the process of the devices of 256 Mbit DRAM generation and beyond.<<ETX>>