CMDT Sputter Deposition Application

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There is a continuous move to smaller feature sizes in VLSI semiconductor processing. Reduced feature size can increase access speed and decrease power requirements. However, there are technical difficulties associated with scaling down the size of features on semiconductor devices. Two major issues are confining metal diffusion to lower levels in smaller areas and maintaining the integrity and conductivity of metal interconnect contacts.

The stoichiometry of some deposited films can be affected by confined feature geometries, such as trenches and steps that are used as contacts to connect different layers of metals. The effects increase as the feature sizes are reduced. Possible malformations of TiN/Ti bilayers include deposition of too little or none of either component, reactions with the substrate or mixing of the layers to produce sub-stoichiometric TiN, and getting an even covering when the topology is rather complicated. Malformed films could also have less desirable electrical properties or degraded value as a diffusion barrier. Both experimental and computational studies are done to improve the quality.

Ref: Auger depth profiles of TiN/Ti films, J. Vacuum Sci.& Tech., B, 12 (3), pp 1394-1401, May/June 1994.

Sputter Deposition onto a Trench

The figure above left is a view of a full-scale molecular dynamics simulation of sputter deposition onto a trench substrate. The figure shows Ti atoms (red) deposited onto a substrate with Ti atoms (grey); the particles are deposited with a variable incident angle (-180,180). Shadowing effects along the vertical walls result from cluster growth at the top of the trench.

Parameters: Substrate: 32600 Ti atoms. Incident Atoms: 4500 Ti atoms with mean a mean energy of 2.0 eV. Substrate temperature is fixed at 300 K and its size is 127x30x250 Angostroms.

The figure above right is a color mapping showing the spatial decomposition of a parallel molecular dynamics simulation using 14 processors. The spatial boundaries are adjusted automatically to maintain uniform loads, reducing processor idle times. In this simulation, loads are based strictly on the number of force evaluations within each spatial region. Fixed particles along the lower boundaries of the trench do not contribute to load, resulting in unequal spatial partitioning as shown.

Parameters: Substrate: 32600 Ti atoms. Incident Atoms: 4500 Ti atoms with mean a mean energy of 2.0 eV. Substrate temperature is fixed at 300 K and its size is 127x30x250 Angostroms.

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Osman Yasar email: yasaro@ornl.gov