Dramatic SiO2 Thickness Reduction by Reactive Ion Etching of Nanopillars from Si/SiO2/Si layer stacks


Dramatic SiO2 Thickness Reduction by Reactive Ion Etching of Nanopillars from Si/SiO2/Si layer stacks

Heinig, K.-H.; Engelmann, H.-J.; Gharbi, A.; Tiron, R.; Prüfer, T.; von Borany, J.

Abstract :

The transistor pathway predicts an evolution from lateral MOSFETs via FinFETs to vertical nanowire gate-all-around FETs (vNW GAA-FET). Our European project IONS4SET [1] goes a step further: Aiming at low-power electronics, the principle of operation of transistors will be changed from field effects to single electron tunneling via a Si quantum dot (QD) in SiO2. Room temperature (RT) operation of Single Electron Transistors (SETs) requires Si QDs of ~3 nm and tunneling distances of < 1 nm. The SiO2 with the embedded Si QD has to be ~ 5nm thick. To fabricate vNW GAA-SETs, Si nanopillars with ~5nm SiO2 have to be fabricated by Electron Beam Lithography and Reactive Ion Etching (RIE).
Here we report on a dramatic SiO2 thickness reduction in the Si/SiO2/Si layer stack by RIE of nanopillars. It is strongly pillar diameter dependent: In 100 nm pillars the thickness remains almost unchanged, but for < 20nm it shrinks from 8nm to ~3nm as shown by Energy-Filtered Transmission Electron Beam Microscopy (EFTEM). Modeling, computer simulation and dedicated experiments reveal that it is due to a huge number of electric breakdowns during RIE. A breakdown forms a SiOx filament which emits O in SiO2. Each O atom of the SiO2 becomes many times an O interstitial, which in most cases recombines with an O vacancy. Depending on diameter, some O will emanate from the edge of the SiO2 disk leading to the dramatic oxide thinning.
[1] This work has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 688072 (www.ions4set.eu).

Keywords: Nanoelectronics; Ion Irradiation; Single Electron Transistor; Reactive Ion Etching

Related publications

  • Open Access Logo Lecture (Conference)
    European Materials Research Society 2019 Fall Meeting, 16.-19.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-29582
Publ.-Id: 29582