| AVS 54th International Symposium | |
| Nanometer-scale Science and Technology | Friday Sessions |
| Session NS-FrM |
| Session: | Nanolithography and Nanoprocess Technology |
| Presenter: | B. Craver, University of Houston |
| Authors: | B. Craver, University of Houston H. Guo, University of Houston A. Roy, University of Houston J. Strahan, University of Texas J. Reynolds, University of Houston H. Nounu, University of Houston C.G. Willson, University of Texas J.C. Wolfe, University of Houston |
| Correspondent: | Click to Email |
Atom beam lithography (ABL) is a proximity printing technique where a broad beam of energetic neutral atoms floods a stencil mask and transmitted beamlets transfer the mask pattern to resist on a substrate. ABL exposures are equivalent to those formed by ions in every respect (mass, energy, angular distribution, diffraction, scattering within the mask, resist, and wafer) except for the charge of the lithography particles. ABL images, being formed by electrically neutral particles, are completely free of charge-related artifacts that occur, often unpredictably, in ion printing due to ambient electromagnetic fields and the buildup of electrostatic charge on the mask and wafer. In this paper, we describe an integrated toolset for fabricating high density arrays with an arbitrary unit cell by atom beam lithography. The 30-50 keV exposure tool incorporates a high brightness multicusp ion source and a high pressure gas cell to convert helium ions to energetic helium atoms through charge transfer scattering. A mechanical mechanism has been developed for translating the mask image over the wafer with 1 nm precision. Nano-arrays can, thus, be fabricated using a large-area template mask consisting of a silicon membrane with a periodic array of circular openings. The mask image is translated over the wafer to create, simultaneously, an array of identical unit cells, each corresponding to an individual mask opening. Silicon stencil masks, up to 700 nm thick, are fabricated with ~50 nm openings using a magnetically enhanced, molecular bromine plasma. A plasma-deposited coating of poly(methylmethacrylate) protects the silicon membrane from ion implantation damage and thickens the mask to enhance lithographic contrast. The mask can be coated with sputtered gold to shrink the mask openings as needed for the particular application. Pattern shifts during exposure are imperceptible at the nanometer-scale. Linewidths of 25 nm have been achieved and we anticipate reporting sub-20 nm linewidths at the conference. High resolution resists with optimized sensitivity, currently under development, will be reported at the conference. Potential applications in rapid prototyping and imprint lithography template fabrication will be discussed.