Macrochannelling: Characterisation of nano-structures by ion beam analysis

High aspect ratio microstructures produced by novel fabrication methods have important applications in micro-electro mechanical machines (MEMS) and photonics. Investigation of the internal structure of sub-micron scale devices is challenging although scanning electron microscopy (SEM) and scanning tunnelling microscopy (STM) are two commonly used techniques for this purpose. These techniques have the disadvantage that important information about sub-surface structure can be difficult to obtain. Especially difficult to analyse are high aspect ratio structures because of the limited reach of the scanning probe into deep wells, or the shallow penetration of the electron beam. Ion beam channelling, with Rutherford backscattering spectrometry (RBS) is already well-established as a technique for providing information about sub-microscopic structure at the atomic level. Based on this method, we are investigating the use of macroscopic ion beam channelling into micro and nano-scale high aspect ratio textured surfaces. We have developed a numerical simulation program that can calculate the RBS spectrum of textured surfaces, as a function of ion beam tilt angle, which can be used to interpret the experimental spectra from a real specimen. In this paper we compare our simulations with control samples.