Exposure Characteristics of Photoresist Illuminated by Near-field Light

Abstract

We show an application of a scanning near-field optical microscopy (SNOM) to nanofabrication. SNOM can obtain a resolution beyond the diffraction limit by placing a subwavelength aperture in close proximity to a sample. A sharpened and bent optical fiber with a small aperture is used as a near-field optical probe as well as a cantilever of an atomic force microscope (AFM). To improve the optical resolution, the aperture should be placed as close to the sample as possible. In order to decrease the distance between the aperture and the sample, a thin optical fiber probe with low spring constant (-10N/m) is operated in contact mode. Positive photoresist film for g-line (λ=436nm) is exposed by the near-field light from the thin optical fiber probe coupled by a He-Cd laser (λ=442nm) and developed normally. Groove pattern as narrow as 80nm in full width is produced in the photoresist film on a Si wafer. The exposure characteristics of the photoresist illuminated by the near-field light are discussed.