Turning Sample Into (Re)Solution—Focused Ion Beam Shaped Solid Immersion Lenses

Abstract

This work is a unique solution for enhancing optical failure analysis and optical signal transmission. Optical failure analysis remains to be a vital part of the analysis process, despite shrinking feature sizes and challenging package technologies. The presented optical signal transmission supports the development of photonic integrated circuits. The key component is a Focused Ion Beam (FIB) process which shapes optical lenses out of the sample material leading to an improvement in lateral resolution and signal transmission. Two cases are shown that demonstrate these improvements. The first case is an optical backside analysis in a spatially confined opening of a package where other Solid Immersion Lens (SIL) systems could not be applied. It offers an improvement in spatial resolution by a factor of 2, down to a FWHM of 387 nm. The second case is a novel application for FIB shaped lenses aiming at photonic integrated circuits. This lens is created out of the isolating frontside and improves the grating coupler efficiency by a factor of 4.1.