An Experimental Approach for Studying the Creep Behavior of Thin Film/Substrate Interfaces
Abstract
Large shear stresses often develop at the interface between dissimilar materials in microelectronic devices, when they are subjected to thermo-mechanical excursions. These stresses, which typically occur due to thermal expansion mismatch between the adjoining materials, are usually confined near the edges of films. However, for narrow thin film lines, these stresses may exist over a large fraction of the film-substrate interface. When the substrate is subjected to relatively high homologous temperatures, the imposed interfacial shear stress can facilitate diffusionally accommodated interfacial sliding, or interfacial creep. This thesis explores methodologies to measure the kinetics of interfacial creep at model Al thin film/silicon substrate interfaces. A method of sample production which involved diffusion bonding a polished Si substrate to the surface of a thin Al film deposited on a second Si substrate was developed. The resultant sample geometry comprises a Si/Al/Si sandwich, which when loaded edge-wise in compression, allows the Al thin film-Si interfaces to be loaded in shear. By measuring the relative displacements between the two Si substrates, the interfacial displacement rates at varying temperatures and stresses were experimentally determined. In accordance with previous results, the kinetics was given by a diffusional creep law with a threshold stress, and an activation energy representing interfacial diffusion. The activation energy was found to be unusually low, and further experimental and modeling studies are needed to better understand its origin.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2004
- Accession Number
- ADA427441
Entities
People
- Carl L. Parks
Organizations
- Naval Postgraduate School