The E-Reticle<sup>TM</sup> system was used to assess the electrostatic risks from mask manufacturing equipment
and processes. Test results showed that some mechanical operations of the equipment examined may
cause electrostatic potential differences in a production reticle higher than the ITRS recommended
specifications, which may bring electrostatic risks to the reticle.
E-Reticle<sup>TM</sup> data also indicated that the
processes play an important role in controlling electrostatic potentials in the reticle. The E-Reticle<sup>TM</sup>
system can be used as an in-situ equipment assessment tool, as well as a process optimization device.
E-Reticle<sup>™</sup> system is an electrostatic field test device, which has the form factor of a conventional six
inch quartz production reticle. The E-Reticle was used to assess the ESD damage risks in a mask cleaning
tool. Test results indicate that a reticle may see higher than ITRS recommended electrostatic potential
specifications when mechanical operations and cold DIW rinse start and in progress, hence seeing
increased probability of electrostatic induced damages.
It has recently been reported  that production reticles are subject to progressive CD degradation during use
and intense study is under way to try and identify the causes of it. One damage mechanism which has already
been identified and quantified  is electric field induced migration of chrome (EFM). This can be caused by
electric fields that are more than 100x weaker than those that cause ESD. Such low level electric fields can be
experienced by a reticle during normal handling and processing steps, as well as coming from external
sources during transportation and storage. The field strength of concern is lower than most electrostatic field
meters are designed to measure and it can be difficult or impossible to measure such fields inside the cramped
environment of equipment.
To measure this risk a new sensor device ("E-Reticle") has been developed having the same materials of
construction and form factor as a standard chrome-on-quartz reticle. It allows the electric field that a reticle
would experience during normal use and handling to be measured and recorded. Results from testing of this
device in a semiconductor production facility are reported, showing that certain processes like reticle washing
are inherently hazardous. It also enables identification of problems with electrostatic protection measures
inside equipment, such as unbalanced ionizers or poor load port grounding. The device is shown to be capable
of recording electric fields in the reticle handling environment that are below the recommended maximum
that is being proposed for the 2009 ITRS guidelines.
Electrostatic protection is an issue for all masks, whether during mask production, shipping, storage, handling or
inspection and exposure. Up to now, only manual electrostatic field measurements, or expensive and elaborate analyses
with Canary reticles have given hints about the risks of pattern damage by ESD events.
A new test device is being introduced, which consists of electrostatic field sensors, integrated INSIDE a closed fused
quartz housing which has the outside dimensions of a 6 inch mask.
This device can be handled and used like a normal 6 inch reticle. It can be handled and processed while recording the
electrostatic charges on the chrome patterns created by friction or field induction just as a reticle would "see" during