Improving etchability and imaging performance of EUV mask absorber materials via ion implantation

Abstract

This study presents a novel strategy for enhancing the etching performance of extreme ultraviolet (EUV) mask absorber materials by incorporating an ion implantation process into the mask fabrication. Conventional EUV masks employing tantalum-based absorbers face limitations in imaging performance at sub-5-nm nodes, prompting the exploration of alternative materials with superior optical properties. However, many of these candidates exhibit poor etchability, restricting their practical application. To address this issue, argon ion implantation was applied to the absorber layer to reduce its crystallinity and improve its etching performance. When implemented on a platinum–tungsten alloy—a promising candidate for next-generation EUV mask absorbers—the process induced nanocrystallization within the film, resulting in a noticeable increase in the etching rate. The optical properties of the underlying Mo/Si multilayer mirror remained unaffected by the implantation. Furthermore, the implanted samples exhibited increased sidewall angles in the patterned structures, leading to an improvement in the normalized image log slope, which is a key metric for imaging performance. These results demonstrate that ion implantation is an effective method for overcoming the etching limitations of absorber materials without compromising mask performance.