Lithography with metastable rare gas atoms

Neutral-Atom Lithographic Concept

Lithography with atom-optical control of metastable rare gasatoms.

While one way to build nanostructures with atom optics is to directly deposit atoms, another way is to use atoms to expose a resist. In a recent report [EPG Pub# 647] we show that metastable rare gas atoms can be used to expose a special resist consisting of a self-assembled monolayer of alkanethiolate molecules. Because metastable rare gas atoms have an atomic level structure that allows them to be manipulated with lasers in the same way that chromium or alkali atoms are controlled, our work shows that the advantages of atom optical methods can potentially be extended to a much broader range of materials.

The exposure mechanism arises from the release of internal energy stored in the metastable rare gas atoms when they strike a surface. Though electrically neutral, metastable atoms have internal energy of as much as 20 eV. This energy is trapped inside the atom unless the atom strikes a surface. When the energy is released, it generates secondary electrons that cause chemical bonds to break, altering the solubility of the resist.

Because of their internal energy level structure, metastable rare gas atoms open another possibility for pattern generation that goes beyond focusing with atom lenses. By exposing the atoms to laser light of an appropriate frequency, the metastable state can be quenched, or have its energy released prematurely. Thus, using a pattern made of laser light, metastable atoms can be removed from the beam in certain areas, transferring the pattern to the surface. In this way, light can be used as a mask for matter, instead of matter being used as a mask for light, as it is in optical lithography.

Now that the exposure mechanism has been demonstrated, work continues to try to test the ultimate resolution limits of this process and also investigate other lithographic processes with metastable rare gas atoms.

Microlithography by Using Neutral Metastable Atoms and Self-Assembled Monolayers

Jabez J. McClelland - NIST

Andreas Bard - University of Hanover; Hanover, Germany
John Gillaspy - Atomic Physics Div., NIST

Through the Consortium for Light Force Dynamics:

Steven L. Rolston - University of Maryland

William Phillips - Atomic Physics Div., NIST

Karl Berggren - Physics Dept., Harvard University

Mara Prentiss - Physics Dept., Harvard University

Jim Wilbur - Chemistry Dept., Harvard University

Andreas Helg - Chemistry Dept., Harvard University

George Whitesides - Chemistry Dept., Harvard University

Supported in part under NSF Grant PHY-9312572

Online: May 1996
Last Updated: February 2008

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