Monday, June 18, 2007
Golden Eagle Eyrie (Boise Centre on the Grove)

Development of Metallic Periodic Structures for Surface Plasmon Polariton Sensor

Cory Sparks, Lincoln Bollschweiler, and Wan Kuang. Boise State University, Boise, ID

We present the experimental development of metallic periodic structures for surface plasmon polariton (SPP) sensors. SPPs are surface electromagnetic waves that are spatially confined on the metal surface due to their interaction with electrons. SPP resonance has been widely employed in sensor due to its sensitivity to a small change of dielectric constant at the metal surface. The utilization of periodic structures permits a specifically designed SPP dispersion and makes possible a higher integration density.

Au, Ag, Al and Cr thin-films of varied thicknesses sputter-coated on a fused silica substrate were characterized with a 635-nm diode laser and the reflectance as a function of angle was recorded. These measurements optimized the level of surface plasmon resonance for sensor output.

The periodic structures were created through electron beam lithography (EBL) utilizing a two-layer resist (200 nm PMMA and 300 nm co-polymer) spin-coated on a Si substrate. The development of the process recipe involved a combination of experiments on beam aperture, beam current, magnification, exposure dosage, and the amount of PMMA development time. The adhesion issue for the metallization of sub-micron patterns is solved by two-layer resist lift-off process. It was found that the rate of the metal film deposited into the exposed area varies with the lattice constant.