Nanoscale holographic interferometry for strain measurements in electronic devices da Nature di Etienne Snoeck Nanoscale hologr

Nanoscale holographic interferometry for strain measurements in electronic devices

da Nature di Etienne Snoeck

Nanoscale holographic interferometry for strain measurements in electronic devices

Nature 453, 1086 (2008). doi:10.1038/nature07049

Authors: Martin Hÿtch, Florent Houdellier, Florian Hüe
& Etienne Snoeck

Strained silicon is now an integral feature of the latest generation
of transistors and electronic devices because of the associated
enhancement in carrier mobility. Strain is also expected to have an
important role in future devices based on nanowires and in
optoelectronic components. Different strategies have been used to
engineer strain in devices, leading to complex strain distributions in
two and three dimensions. Developing methods of strain measurement at
the nanoscale has therefore been an important objective in recent years
but has proved elusive in practice: none of the existing techniques
combines the necessary spatial resolution, precision and field of view.
For example, Raman spectroscopy or X-ray diffraction techniques can map
strain at the micrometre scale, whereas transmission electron
microscopy allows strain measurement at the nanometre scale but only
over small sample areas. Here we present a technique capable of
bridging this gap and measuring strain to high precision, with
nanometre spatial resolution and for micrometre fields of view. Our
method combines the advantages of moiré techniques with the flexibility
of off-axis electron holography and is also applicable to relatively
thick samples, thus reducing the influence of thin-film relaxation
effects.