Development of high-performance tri-layer material
2008
As chip size and pattern size continue to shrink, the thickness of photo resist is getting thinner and thinner. One of the
major reasons is to prevent the small resist features from collapse. It's very challenging to get enough etch resistance
from such thin resist thickness. An approach of Si-tri-layer stack which consists of resist, Si ARC (Si contenting
anti-reflection coating), organic underlayer from top to bottom has been adopted by many IC makers in the
manufacturing of 45 nm node. Even higher resist etching selectivity is needed for 32 nm node. Si ARC, of Si content
as high as 43%, provides good etch selectivity. At the same time, tri-layer also provides good control over reflectivity
in high NA immersion lithography. However, there are several well know issues concern Si-rich ARC. Resist
compatibility and shelf life are on top of the list. An aim of our development work was to overcome those issues in
order to produce manufacturing-worthy Si-rich ARC. Several synthesis methods were investigated to form Si-rich ARC
film with different properties. Collapse of resist patterns is used as an indicator of lithographic compatibility.
Lithographic performance was checked by accelerated shelf life tests at high temperature in order to predict the shelf life
at room temperature. It was found that adhesion between resist and Si-rich ARC is improved when contact angle of
Si-rich ARC is increased to more than 60 degree. Certain synthesis methods improve shelf life. After optimization of
film properties and synthesis methods of Si-rich ARC, SHB-A940 series have best litho compatibility and shelf life is six
months at storage temperature below 10°C.
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