Fred Roozeboom

POSITION: PROFESSOR | PLASMA TECHNOLOGY FOR SYSTEM-IN-PACKAGE APPLICATIONS

TNO UNIT: INDUSTRY (HOLST CENTRE)

UNIVERSITY: TU EINDHOVEN (APPLIED PHYSICS / PLASMA & MATERIALS PROCESSING)

TNO LOCATION: HOLST CENTRE, EINDHOVEN – HIGH TECH CAMPUS 21

TEL: +31651375283

Research area

My research activities focus on investigating and developing new functional ultrathin-film materials and plasma-enhanced processes by Atomic Layer Processing, i.e. Deposition (ALD), and Etching (ALE) and cleaning. In addition, in situ microdiagnostics is being developed for application in spatial ALD.

The research is on both conventional (=vacuum-based) and on spatial ALD contributes in particular to the TNO roadmaps on “High Tech Materials” (Nanotechnology) and “High Tech Systems & Materials” (Fab-of-the-Future).

The spatial variant of ALD is attractive to industry because of its potential in the manufacture of atomic-scale and conformal thin films with superior quality, that can be scaled up to large-area, high throughput in the application fields of photovoltaics, displays, etc., including roll-to-roll or sheet-to-sheet systems. Applications can also be in semicon (e.g. Selective-Area ALD) and ALE-based cleaning (e.g. tin cleaning of EUV optics).

The main objectives in the daily research are Selective-Area ALD of oxides (e.g. of SiO₂ on dielectrics vs. metals), and ALE for cleaning.

Recent results

Area-Selective Atomic Layer Deposition | 1

‘ABC’-type area-selective ALD of SiO₂ was developed by pulsing acetylacetone inhibitor (A), bis(diethylamino)silane-precursor (B), and O₂-plasma (C). IR-spectroscopy and DFT calculations showed selective deposition of SiO₂ on GeO₂, SiN_x, SiO₂, and WO₃, in the presence of Al₂O₃, TiO₂, and HfO₂. The area-selectivity stems from the chemoselective adsorption of the inhibitor.

Atomic Layer Etching | 2

Radical-plasma driven ALE was developed for ZnO utilizing alternating acetylacetone (Hacac) and O₂-plasma. In-situ ellipsometry and IR-spectroscopy confirmed self-limiting half-reactions and ~1.3 Å/cycle etching at 100-250 °C. TEM-microscopy on 3D ZnO-covered nanowires before and after etching proved isotropic and damage-free ALE.

Microdiagnostics of (atmospheric) plasmas | 3

Atmospheric-pressure plasma-enhanced spatial ALD of Al₂O₃ and SiO₂ was investigated by using dedicated micro-diagnostics by means of gas-phase Infrared Spectroscopy on the plasma exhaust gas and in situ Optical Emission Spectroscopy.

For Al₂O₃ films grown at 80-200 ^oC from trimethylaluminum, Al(CH₃)₃, and Ar-O₂ plasma we found that the CH₃-ligands are removed during the plasma half-cycle through two reaction pathways: i)-combustion by the O₂-plasma yielding CO₂ and H₂O, and ii)-thermal ALD reactions of H₂O with the CH₃-ligands yielding CH₄.

Similarly, for SiO₂ grown at 100-250 ^oC using bisdiethylaminosilane (BDEAS) and O₂-plasma we propose a reaction mechanism where BDEAS adsorbs on –OH surface sites by exchanging part of its amine-ligands yielding diethylamine (DEA) desorption. The remaining amine-ligands are removed through combustion-like reactions in the O₂-plasma yielding the desorption of H₂O, CO₂, CO and byproducts such as N₂O, NO₂, and CH-containing species. These volatile byproducts, theoretically predicted, can react further by gas-phase reactions in the plasma as indicated by the presence of OH*, CN* and NH*excited fragments.

This work expands the knowledge on atmospheric-pressure PE-s-ALD of Al₂O₃ and SiO₂ and opens up ways to better process control in spatial ALD.

PhD supervision

Maria Mione (Funding source: M2i-FOM/NWO)

Top publications

Mameli, B. Karasulu, M.A. Verheijen, B. Barcones, B. Macco, A.J.M. Mackus, W.M.M. Kessels, F. Roozeboom, “Area-Selective Atomic Layer Deposition of ZnO by Area-Activation using Electron Beam Induced Deposition”, ACS Chem. Mater., vol. 31, pp. 1250−1257, 2019.
Mameli, M.A. Verheijen, A.J.M. Mackus, W.M.M. Kessels, F. Roozeboom, “Isotropic Atomic Layer Etching of ZnO Using Acetylacetone and O2 plasma”, ACS Appl. Mater. Interfaces, vol. 10, pp. 38588−38595, 2018.
A. Mione, R. Engeln, V. Vandalon, W.M.M. Kessels, and F. Roozeboom, “Infrared and Optical Emission Spectroscopic Study on Atmospheric-Pressure Plasma-Enhanced Spatial ALD of Al2O3”, Journal of Applied Physics Letters, vol. 115, 083101, 201