Applications of plasma-polymerized methylsilane as a resist and silicon dioxide precursor for 193- and 248-nm lithography

摘要

Abstract: Silicon dioxide is the primary dielectric fabric ofsilicon integrated circuits, and the need to pattern itaccounts for a large percentage of allphotolithographic operations. As shrinking devicedimensions place extreme demands on both lithographyand etching, patterned oxide films are finding yetadditional applications as intermediate `hard masks.'For example, polysilicon gate and metal layers may beetched with greater selectivity and linewidth controlthrough a thin patterned oxide mask, rather thanthrough a thicker photoresist layer (which is used topattern the oxide and removed before pattern transfer).However, any advantages of such schemes must be weighedagainst the costs of increasing process complexity. Werecently reported a new all-dry photolithographicprocess based on the plasma deposition and patterningof organosilicon resists. These materials, as bestexemplified by plasma polymerized methylsilane (PPMS),possess amorphous Si-Si bond backbone structures andundergo efficient photo-oxidation to give glasslikesiloxane network material. Patterns are developed usingchlorine plasma etching to selectively remove unexposedregions, providing a negative tone image. In previouspapers we have demonstrated the use of these materialsin bilevel processes, using oxygen reactive ion etchingto transfer patterns in thin PPMS layers throughunderlying organic planarizing layers. Using 248 nmdeep UV exposure tools, such schemes afford sub-0.25$mu@m design rule capabilities and are well suited fordifficult device topography. Here we describe thediscovery and development of a fundamentally differentapplication unique to PPMS: a new direct approach topatterned silicon dioxide. !7