Laser Micro-Machining Using Near-Field Nano-Optics

Solid immersion lenses (SIL) facilitate high numerical aperture (NA) and consequent sub-wavelength diffraction limited focusing in near-field optics based systems. Such systems are in commercial and research use for various applications including near-field scanning optical microscopy, ultra-high density magneto-optic data storage and near-field nanolithography. Here, we present a novel nanomanufacturing method using SIL-based near-field optics for laser-induced sub-micron patterning on silicon wafers. The near-field effect of SILs was investigated by using hemispherical BK7 lenses (n=1.5196, NA=0.9237) to superfocus an incident Q-switched, 532nm Nd:YAG laser beam transmitted through a focusing objective. This optical arrangement achieved a laser-processed feature resolution near the diffraction limit in air. Results of experiments that were conducted at various processing conditions to investigate the effects of varying incident laser power (with average pulse power less than 1W), pulse repetition rate, pulse width, number of pulses and size of SIL on processed feature size and resolution are presented.