Sub-150 nm Resolution Lithography with a 248 nm Bilayer Resist Process

Thin film imaging, which includes bilayer resists and top surface imaging, offers tremendous leverage for extending 248nm lithography to 150nm resolution and below. Advantages of such systems include enhanced process latitude, enhanced resolution, improved ability to print high aspect ratios at smaller feature sizes, and minimization of substrate reflectivity notching. In this paper we will describe the performance of a positive-tone 248 nm bilayer resist system consisting of a silicon containing thin imaging layer (270 nm, ~11 wt-% silicon) over a novel crosslinked polymeric underlayer (700-1000) nm). The chemically amplified imaging layer resist is based on a novel dual-functional silicon containing monomer, tris (trimethylsily1)silylethyl methacrylate, which in addition to providing etch resistance, also functions as the acid sensitive functionality. It will be shown that 125nm lithography can be attained with this system using conventional optical processing techniques. The underlayer was found to have a dramatic impact on the bilayer performance. A variety of different underlayer materials were auditioned. This paper will discuss the effect of the underlayer on the bilayer performance and the overall lithographic performance of this system.