Spin-on trilayer approaches to high NA 193nm lithography
2007
New challenges face ArF bottom antireflection coatings (BARCs) with the implementation
of high NA lithography and the concurrent increase use of spin-on hard masks. To achieve superior
reflectivity control with high NA at least two semi-transparent ARC layers, with distinct optical
indices, are necessary to effectively lower substrate reflectivity through a full range of incident
angles. To achieve successful pattern transfer, these layers in conjunction with the organic resist,
should be stacked with an alternating elemental composition to amplify vertical resolution during
etch. This will circumvent the inherent low etch resistance of ArF resist and the decreasing film
thicknesses that accompanies increasing NA. Thus, incorporating hard mask properties and
antireflection properties in the same two layer system facilitates pattern transfer as a whole rather
than just enhancing lithography. As with any material expected to exhibit multiple roles there is a
delicate balance between optimizing materials with respect to one of its roles while not impairing its
other roles. We will discuss some of these conflicts and present Si-BARCs and carbon rich
underlayers which aim to balance these conflicts. In this paper we will explore simulations aimed at
finding the best film thicknesses and optical indices, etch rate selectivity, and lithographic
performance of high silicon content and high carbon content BARC materials designed to meet the
demands of both high NA lithography and trilayer processing.
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