A method, system and unit for determining alignment in a layered device
such as a semiconductor device includes providing a first layer having
detectable surface and subsurface material properties and positioning a
patterned photoresist layer over the first layer, patterned photoresist
layer having detectable surface and subsurface material properties. The
layers are imaged with a FIRAT probe to detect the material properties,
and the detectable material properties are compared for mapping an
alignment of the compared detectable material properties. The first layer
may be a substrate or have a previously processed layer formed thereon. A
surface topography may be included over the substrate and an etchable
layer formed over the substrate or first layer. The FIRAT probe may be a
single tip probe or a dual tip probe.