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Context/ study Motivation:
Contamination and especially Airbone Molecular Contamination (AMC) is a critical issue for mask material
flow with a severe and fairly unpredictable risk of induced contamination and damages especially for 193 nm
lithography. It is therefore essential to measure, to understand and then try to reduce AMC in mask environment.
Mask material flow was studied in a global approach by a pool of European partners, especially within the frame
of European MEDEA+ project, so called "MUSCLE". This paper deals with results and assessment of mask pod
environment in term of molecular contamination in a first step, then in a second step preliminary studies to
reduce mask pod influence and contamination due to material out gassing.
Approach and techniques:
A specific assessment of environmental / molecular contamination along the supply chain was performed by all
partners. After previous work presented at EMLC 07, further studies were performed on real time
contamination measurement pod at different sites locations (including Mask manufacturing site, blank
manufacturing sites, IC fab). Studies were linked to the main critical issues: cleaning, storage, handling,
materials and processes.
Contamination measurement campaigns were carried out along the mask supply chain using specific Adixen
analyzer in order to monitor in real time organic contaminants (ppb level) in mask pods. Key results would be
presented: VOC, AMC and humidity level on different kinds of mask carriers, impact of basic cleaning on pod
outgassing measurement (VOC, NH3), and process influence on pod contamination...
In a second step, preliminary specific pod conditioning studies for better pod environment were performed based
on Adixen vacuum process. Process influence had been experimentally measured in term of molecular
outgassing from mask pods. Different AMC experimental characterization methods had been carried out leading
to results on a wide range of organic and inorganic contaminants: by inline techniques based on Adixen
humidity, also VOC and organic sensors, together by off-line techniques already used in the extensive previous
mask pods benchmark (TD-GCMS & Ionic Chromatography). Humidity and VOC levels from mask carriers had
shown significant reduction after Adixen pod conditioning process. Focus had been made on optimized vacuum
step (for AMC) after particles carrier cleaning cycle. Based upon these key results new procedures, as well as
guidelines for mask carrier cleaning optimization are proposed to improve pod contamination control.
Summary results/next steps:
This paper reports molecular contamination measurement campaigns performed by a pool of European partners
along the mask supply chain. It allows us to investigate, identify and quantify critical molecular contamination in
mask pod, as well as VOC and humidity, issues depending on locations, uses, and carrier's type. Preliminary
studies highlight initial process solutions for pods conditioning that are being used for short term
industrialization and further industrialized.
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