Periodic Variation of Stress in Sputter Deposited Si/WSi2 Multilayers

TL;DR

This study investigates the stress behavior in sputter-deposited Si/WSi2 multilayers, revealing periodic stress variations, initial tension instead of compression, and the influence of surface rearrangement and sputtering conditions.

Contribution

It introduces a new model for initial tension due to surface rearrangement and highlights the role of Si layers in stress buildup at low Ar pressures.

Findings

Periodic stress variation correlates with multilayer period.

Initial tension observed instead of compression during early growth.

Surface smoothing phenomena linked to WSi2 sputter deposition.

Abstract

A tension increment after sputter deposition of 1 nm of WSi2 onto sputtered Si was observed at low Ar gas pressures. Wafer curvature data on multilayers were found to have a periodic variation corresponding to the multilayer period, and this permitted statistical analyses to improve the sensitivity to small stresses. The observation of tension instead of compression in the initial stage of growth is new and a model invoking surface rearrangement is invoked. The data also bear on an unusual surface smoothing phenomena for sputtered Si surfaces caused by the sputter deposition of WSi2 . We furthermore report that for low Ar pressures the Si layers are the predominant source of built-up stress.