Polypeptoids: Exploring the Power of Sequence Control in a Photoresist for Extreme-Ultraviolet Lithography

A new type of a positive tone chemically amplified photoresist based on well-defined, sequence-controlled polypeptoids with ten repeat-units are synthesized and their potential for extreme-UV lithography (EUVL) is demonstrated, resulting in line-space patterns of 70 nm pitch. The synthesized samples contain 4-(ethyl) phenol (Eph) and propyne (Ppy) side chains, while their change in solubility upon exposure is induced by the deprotection of 4-(ethyl) phenol side groups. The resist performance is evaluated using deep UV and extreme-UV lithography. While all samples are developable in isopropyl alcohol, the content, and the sequence of hydrophobic alkyne side chains lead to a detectable change in solubility, dissolution rate, and resist performance. Polypeptoids of defined composition and sequence and a length of ten repeat units are prepared and their potential as a new type of photoresist for extreme-UV lithography (EUVL) is demonstrated achieving well defined line/space patterns down to 35 nm half pitch, while the sequence and composition are shown to affect the lithographic performance.image