Are surfaces of silicon hardmasks adaptive?

Silicon hardmask (Si-HM) materials used in lithography processes play a critical role in transferring patterns to desired substrates. In addition, these materials allow for the tuning of optical properties such as reflectivity and optical distribution for better lithography. Si-HM materials also need to possess good compatibility with photoresists before and after optical exposure, during which the photoresist in the exposed area may change polarity. Therefore, Si-HM materials may benefit from adaptive or amphiphilic capabilities to keep both exposed and unexposed photoresist compatible with the substrate. In this work, we will demonstrate that Si-HM surfaces may be adaptive or amphiphilic through both experiments and computer simulation. Specifically, we will demonstrate that the functional groups (polar and nonpolar) at the Si-HM surface may be switchable, and the surface will be dictated by the environment to which the Si-HM is exposed. Knowing the adaptive capability of Si-HM materials will greatly facilitate the development of better underlayer materials for improved lithography.