Characterization of Amorphous Carbon Films for Mask Protection during Ion Beam Bombardment



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The field of lithography is in simplest terms the use of a beam, incident on a mask, to transfer the mask pattern onto the substrate. This process is utilized by every semiconductor company to create the microchips, which make modern life possible. Though photons are the industry standard, atom/ion beam lithography is a specific niche wherein atoms or ions are used to transfer a mask pattern. Although this technique grants excellent flexibility as far as depth of field and diffraction limit, the use of massive particles causes mask damage, limiting commercial applications of the method. To address this problem, we refine a process to coat masks with diamond-like carbon (DLC) to protect them from ion bombardment. This continues the work of Wasson, Hudek, Nounu, and Abichandani, who pioneered deposition techniques to create amorphous carbon films with low initial compressive stress, which remains constant to very high ion doses. In particular, Nounu and Abichandani’s coating technique is repeated but more fully characterized, refined to eliminate the effects of mask charging, and improved with respect to radiation resistance. Further stress measurements are taken, with particular emphasis on in-situ, in vacuum measurements of film response to ion bombardment.



Amorphous carbon, DLC, Carbon films, Polymers, Mask protection, Ion beam, Ion dose, Radiation, Stress, MMA, Methyl methacrylate, CVD, Annealing