Attoscience and lithography: how to connect them using ab initio.
M. J. van Setten
If you google lithography, you will be directed to various descriptions of the process of printing images on paper using stone. This may seem quite far removed from atto science and ab initio methods. The method however did give birth to what is more correctly called photolithography, the core technique of the presently 1e12$ semiconductor industry.
In the semiconductor industry we talk about technology nodes. At present we are transferring from the 5 to the 3 nm node. Roughly this means that the smallest dimension of the interconnect wires on the next generation of microchips will be around 3 nm. Moving to these dimensions has two main consequences. Firstly, the fraction of atoms in such structures that is not bulk-like anymore starts to dominate. Consequently, many non-ab initio modeling methods start to fail. Secondly, visible, and even moderate UV light, is too ‘big’ to print patterns like this. To solve this the industry is moving to Extreme UV light sources with a photon energy around 92 eV. This light interacts with the so-called photoresist to cause chemical reactions that form the desired pattern. At 92 eV the interaction starts at semi core electrons, starting a new and yet largely unknown chemistry. Understanding this chemistry is pivotal to develop the next generations of semiconductor devices.
Enabling research into this EUV chemistry has been one of the main driving forces of the development of the atto lab at imec. The core of atto lab are two pump probe laser beams, one fixed at 92 and one tunable from 20 to 120. Pulses with a delay of 300 as to 300 ps are available in this setup. Both vibrational and electronic spectroscopy techniques are being installed.
In this seminar I will introduce the features of the atto lab in more detail and discuss computational techniques we are applying to interpret the time resolved spectra. At present the IR and ARPES machineries are in place. Related to core level electronic excitations I will discuss the status of GW for molecular systems.