Integration considerations for 193 nm photoresists

Introduction of 193 nm lithography to production insists that we consider interactions of the resist materials with the etch processes that will be used. The photoresist must not only image well, but also deliver pattern transfer fidelity in the substrate etch. In this paper we will propose a view of the required photoresist thickness for lithographic performance down to 100 nm. Historically, there has been adequate pattern transfer when the resist thickness was three times the gate electrode thickness. This relationship can be maintained, even for 193 nm resists with reduced etch resistance. We will demonstrate sufficient etch resistance of both alicyclic and acrylic 193 nm resists to high density etch systems similar to those that will be used for production. One must also consider that photochemical reactions occur during the etch process. This paper will show deprotection of the polymer and non-linear etch rates in the etch process. We will also describe the interactions of several resist chemistries and varied main gas species.