Dual Beam Laser Interferometry
This special "dual beam" or "twin spot" laser interferometer
for in situ rate/ depth measurements for processes using switching between
etch and deposition processes.
It measures the etch depth from the phase shift and polarisation difference
between the two laser beams without the getting synchronisation signals
from the etch tool and extrapolating the actual etch depth from the rate.
|single beam laser interferometry|
|dual beam laser interferometry||Laser Interferometry for Failure Analysis|