Controlling Morphology during Pattern Development in Thin Film Photoresists

 

Ronald L. Jones, Eric K. Lin, Joseph L. Lenhart, Christopher L. Soles, Wen-li Wu

Polymers Division, NIST, Gaithersburg, MD

 

Dario L. Goldfarb, Marie Angelopolous

T.J. Watson Research Center, IBM, Yorktown Heights, NY

 

We report on attempts to control surface morphology using current lithographic processes critical to the development of both inorganic and organic nano-structures.  Bilayers of protected (base insoluble) and deprotected (base soluble) model lithographic polymers are examined using atomic force microscopy and neutron reflectivity to characterize the effects of dissolution parameters on the developed surface morphology.  Relative ionic strength of the developer is controlled using parameters such as ionic strength of the developer, composition of the two polymers, and molecular weight.  In all cases, the length scale of the morphology parallel to the interface, which determines the length scale of pattern blur, is unaffected.   In contrast, variations in the interfacial width between protected and deprotected species is shown to directly control surface morphology (see images below).  In addition to providing insight into photoresist dissolution mechanisms, these results are shown to yield a convenient method of controlling surface morphology in photoresists, enhancing pattern resolution.

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