Atomic layer deposited silicon dioxide films on nanomechanical silicon nitride resonators

摘要

Thin silicon dioxide films are deposited on nanomechanical resonators using atomic layer deposition (ALD), and their effect on the resonant properties of silicon nitride devices is studied as a function of thickness. We present experimental data and an analytical model for the effect of ALD growth and corroborate the model by studying resonators coated with atomic layer deposited aluminum nitride as well. As thicker films are deposited, device frequency shifts, become nonlinear with thickness, and quality factors drop significantly. Thin silicon dioxide coatings can be deposited on virtually any device surface to support surface chemistries commonly used in biochemical functionalization on glass surfaces. We also demonstrate that the efficiency of silane functionalization improves by 35% when low stress silicon nitride surfaces are coated with only 2.1 nm of atomic layer deposited silicon dioxide. This ALD modification technique should be particularly useful for nanomechanical resonant sensors since a thin, conformal film does not drastically reduce quality factor nor does it add excessive mass that would decrease device sensitivity.