Hyper NA EUV-lithografie: uitdagingen en oplossingen voor beeldvorming en maskerperspectieven

In this PhD project, research will be done to identify if 0.55NA EUV lithography can be further extended to higher numerical apertures, by which, according to the Rayleigh criterium, the ultimate resolution can be pushed further. The student will work in the EUV lithography team at imec in collaboration with the many EUV partners of imec to understand the current state of the art and how moving beyond 0.55NA challenges many assumptions. At NA's much higher than 0.55, new effects will play a role, like polarization, ultimate mask resolution and material interactions. Already at NA 0.55, a small contrast loss is predicted due to the use of unpolarized light in the scanner. Further increasing the NA, will enhance the contrast loss, unless polarization can be controlled. The challenge will be to find ways to control polarization effects to make extreme high NA possible. To find these, solutions in the polarization of the light source, the mask and the resist can be looked for. In addition, the larger incidence angles on mask when the NA increases above 0.55, will further enhance the M3D effects forcing additional mask changes. To enable proper imaging at high incidence angles, new mask architectures, that include changes in the EUV mask multilayer, will have to be tested using rigorous simulations. A lot of the work can be supported by simulations, but with the AttoLab infrastructure at imec, NA's up to 0.84 can be supported experimentally using two-beam interference, EUV reflectometry, and coherent diffractive imaging. Also, mask material and resist properties can be studied. In summary, the student will use simulations and advanced experimental equipment to address extreme high NA EUV lithography challenges, focusing primarily on imaging effects, novel mask and lithography wafer stack (underlayer and photoresist) concepts. Understanding the effects that play and testing innovative solutions to overcome the effects will be the main charter.