PROCEEDINGS ARTICLE | April 5, 2007
Proc. SPIE. 6518, Metrology, Inspection, and Process Control for Microlithography XXI
KEYWORDS: Metrology, Polarization, Sensors, Silicon, Atomic force microscopy, Scanning electron microscopy, Scatterometry, Photomasks, Critical dimension metrology, Scatter measurement
Measurement and control of edge profiles and edge angles is increasingly important in advanced lithography. Especially
for critical dimension metrology a sophisticated multi-dimensional shape metrology is highly beneficial. Different types
of dimensional metrology instrumentation are in use today for edge profile and edge angle measurement. While
destructive cross section SEM measurements often serve as reference, AFM and optical scatterometry systems are
commonly used for day-to-day or in-line control. Due to the limitations of these metrology systems (AFM: slow,
scatterometry: only integral measurements of periodic structures), the evaluation and modelling of top down SEM
images is increasingly considered, too.
At the PTB both SEM and AFM as well as optical scatterometry are applied for edge angle and/or edge profile
metrology, supported by optical transmission microscopy. At the PTB we have realised a new DUV hybrid scatterometer
for measurements over the full range of 6025 format masks which combines essential elements of a reflectometer, an
ellipsometer, and a diffractometer. In addition to scatterometric measurements this set-up allows to measure the complete
Müller-matrix including transmission, polarisation and depolarisation. This new set-up will be presented in detail.
Finally we study the possibilities of evaluating high resolution top down SEM images to determine edge angles. The
potential of edge angle evaluation using these new analysis procedures will be discussed. We present an overview of the
PTB measurement capabilities with an emphasis on newly developed metrology methods and systems.
