Sub-50 nm nanopatterning of metallic layers by green pulsed laser combined with atomic force microscopy

Abstract

Pulsed-laser assisted nanopatterning of metallic layers on silicon substrates under an atomic force microscope (AFM) tip has been investigated. A 532 nm Nd:YAG pulsed laser with a pulse duration of 7 ns was used. Boron doped silicon tips were used in contact mode. This technique enables the processing of structures with a lateral resolution down to 10 nm on gold and copper layers. Nanopatterns such as pit array and multilines with lateral dimensions between 10 and 50 nm and depths between 2.5 and 21 nm have been created. The experimental results and mechanism of the nanostructure formation are discussed. The created features were characterized by AFM, scanning electron microscope, and Auger electron spectroscopy. The apparent depth of the created pit has been studied as a function of laser intensity or laser pulse numbers. The dependence of nanoprocessing on the geometry parameters of the tip and on the optical and thermal properties of the processed sample has also been investigated. Thermal expansion of the tip, the field enhancement factor underneath the tip, and the sample surface heating were estimated. It is proposed that the field-enhancement mechanism is the dominant reason for this nanoprocessing.