Proceedings Article | 16 March 2009
KEYWORDS: Lithography, Data modeling, Calibration, 3D modeling, Photomasks, Optical proximity correction, Photoresist processing, Semiconducting wafers, Photoresist developing, Process modeling
A precise lithographic model has always been a critical component for the technique of Optical Proximity Correction
(OPC) since it was introduced a decade ago [1]. As semiconductor manufacturing moves to 32nm and 22nm technology
nodes with 193nm wafer immersion lithography, the demand for more accurate models is unprecedented to predict
complex imaging phenomena at high numerical aperture (NA) with aggressive illumination conditions necessary for
these nodes. An OPC model may comprise all the physical processing components from mask e-beam writing steps to
final CDSEM measurement of the feature dimensions. In order to provide a precise model, it is desired that every
component involved in the processing physics be accurately modeled using minimum metrology data. In the past years,
much attention has been paid to studying mask 3-D effects, mask writing limitations, laser spectrum profile, lens pupil
polarization/apodization, source shape characterization, stage vibration, and so on. However, relatively fewer studies
have been devoted to modeling of the development process of resist film though it is an essential processing step that
cannot be neglected. Instead, threshold models are commonly used to approximate resist development behavior. While
resist models capable of simulating development path are widely used in many commercial lithography simulators, the
lack of this component in current OPC modeling lies in the fact that direct adoption of those development models into
OPC modeling compromises its capability of full chip simulation. In this work, we have successfully incorporated a
photoresist development model into production OPC modeling software without sacrificing its full chip capability. The
resist film development behavior is simulated in the model to incorporate observed complex resist phenomena such as
surface inhibition, developer mass transport, HMDS poisoning, development contrast, etc. The necessary parameters are
calibrated using metrology data in the same way that current model calibration is done. The method is validated with a
rigorous lithography process simulation tool which is based on physical models to simulate and predict effects during the
resist PEB and development process. Furthermore, an experimental lithographic process was modeled using this new
methodology, showing significant improvement in modeling accuracy in compassion to a traditional model. Layout
correction test has shown that the new model form is equivalent to traditional model forms in terms of correction
convergence and speed.
