Problem: Each new generation of photomasks
incorporates increasingly sophisticated resolution enhancement
techniques that reduce the correlation between the pattern on the mask
and that on the printed wafer. This presents a challenge for
traditional inspection systems since they can only produce an image of
the mask itself. By emulating the optical system of 193nm lithography
scanners and placing an image sensor in the wafer plane, the Aera2
system inspects the mask under the same optical conditions as when it
is exposed in a stepper to provide “what you see is what you print”
capability.
Solution: The Aera2 system’s aerial
inspection technology also creates an entirely new set of capabilities
that strengthen the link between the mask shop and lithography cell by
ensuring the printability of a mask before delivery. The system
features an optional ‘IntenCD’ application that leverages the aerial
imaging data to create high-precision, high-density CD uniformity maps
of an entire mask. This allows direct measurement of the complete mask
to determine its contribution to wafer CD uniformity. These maps can
reveal subtle manufacturing effects, helping mask makers to fine-tune
the mask manufacturing process.
Applications: Sub-45nm photomask inspection and qualification, including extreme RET masks of all types.
Platform:
When equipped with IntenCD for high-density, high-precision scanning of
the entire reticle, Aera2 can generate maps of CD trends that could
signal manufacturing process problems. Global trends can be resolved
to approximately 1nm. Mapping occurs concurrent with inspection and can
be performed for a range of applications and simultaneously for
multiple feature sizes.
Availability: April 2008 onwards.