Super-resolution microscopy for semiconductor metrology

Introduction

Super-resolution microscopy has revolutionized imaging by breaking what was believed to be unbreakable: the diffraction limit – which determines what a microscope can resolve. However, many disciplines in science and engineering cannot benefit from super-resolution microscopy, because practically all current super-resolution microscopes require fluorescence, often introduced by labelling – that is chemically modifying – the samples of interest.

Importance of the Semiconductor Industry

The semiconductor industry is the driver of digitization by producing ever smaller integrated circuits for faster computer chips, and has worldwide importance. The critical dimensions of the latest generation of chips are in the nanometer range, enabled by the breakthrough technology of extreme-ultraviolet nanolithography.

Quality Inspection Challenges

An efficient production process requires constant quality inspection of the printed features, either directly on the integrated circuits or on dedicated metrology targets. However, the resolution of current all-optical microscopy-based metrology methods cannot keep pace with the fast development of smaller structures by nanolithography.

High-Harmonic Generation Technique

Within my ERC Starting Grant, I demonstrated that high-harmonic generation – that is the frequency upconversion of laser pulses – can be optically suppressed and spatially confined in semiconductors without the need for labelling. This can be utilized as sub-diffraction emission for super-resolution scanning microscopy.

Development of MICROSEM

I will further develop this technique in MICROSEM in order to reach resolution below 100 nm in a conventional optical microscope operating in the visible and ultraviolet region, without the need for complicated vacuum equipment. This will enable crucial applications for semiconductor wafer metrology.

Future Applications and Collaboration

I will demonstrate new in-device metrology and pave the way for additional advanced at-resolution metrology schemes. To ensure knowledge transfer, I enlisted one of the key players in the semiconductor industry as a collaborator for MICROSEM.