Developer soluble organic BARCs for KrF lithography

Abstract

The increasing speed of technology innovation has demanded faster computer chips and forced integrated circuit (IC) manufacturers to create smaller feature sizes on chips to meet this demand. The semiconductor roadmap has slated feature sizes to be reduced to 90nm in 2004 with continuing to decreases in the following years. Until recently, ion implant layers were not considered critical layers, and many fabricators still use 365nm exposure with dyed resists on these layers. However as implant feature sizes decrease to 250nm or smaller and overlay restrictions are tighter, KrF exposure is required for the ion implant photolithography process. Currently dyed KrF resists are limited in their resolution and their ability to control critical dimensions (CD) due to reflectivity of the substrates. A bottom anti-reflective coating (BARC) is desirable to help control substrate reflectivity and improve CD control. Until now the only solutions for using a BARC under KrF resist are inorganic and organic thermoset BARCs. These two solutions require plasma etch to remove them before the implant process. Plasma etch is undesirable in the implant process for two reasons; the first is damage to the underlying substrate and the second is increased cost of processing time to perform the BARC plasma etch. With a developer soluble BARC, the BARC is removed during the development of the photoresist, resulting in a minimal effect on wafer throughput as well as no permanent effects to the underlying substrate. In this paper we will discuss the chemistry behind a novel developer soluble BARC as well as the processing conditions used for testing these materials. We will also show results using these materials with various photoresists.