Tutorial Speaker

Photomask Blank Technology: Fundamentals and Recent progress

Kentaro Iwamoto (HOYA Corporation)

Biography

Kentaro Iwamoto received his Master’s degree in Engineering from Tokyo University of Agriculture and Technology in 2019. He joined HOYA Corporation in the same year and has since been involved in the development of EUV mask blanks.

Group Leader of the Inspection and Metrology Technology Team.

Abstract

Photomask blanks are film coated glass plates on which all circuit patterns are generated. Quality of the blanks plays a critical role in ensuring accurate pattern formation and stable manufacturing processes. In this session, I will introduce fundamentals and technology trends for two types of photomask blanks.
The first type is a transmissive mask blank (optical mask blank). Optical blanks, consisting of a metal base film as a light shading layer, are used in g-line, i-line, KrF, and ArF exposure tools. This presentation will explore how film deposition technology has developed to achieve high quality mask patterns in optical lithography.
The second type is a reflective mask blank (EUV mask blank). Reflective mask blanks are fundamentally different from optical mask blanks in that they use a reflective multilayer mirror. In addition to this multilayer mirror, EUV blanks have a cap layer for the multilayer, absorber, and backside film. In such a complicated film structure of EUV blanks, various properties should be considered: strict film thickness control, high durability in the mask manufacturing process, a balanced film stack design, and so on. Meeting these requirements while stacking films with sub-nanometer accuracy demands extremely advanced deposition technology, and as a result, only a very limited number of companies in the world can manufacture EUV mask blanks. This presentation will share the key challenges currently being addressed to meet the requirements of next-generation EUV masks.