In semiconductor manufacturing, new generations of devices have entered the nano-world, with critical dimensions of the order of 10 nm. Many process steps are still performed using aqueous chemistries, e.g. wet etching of materials for patterning and wet cleaning of surfaces. New transistor geometries are vertical, with the generation of 1-D and 2-D nano-confined spaces (Fig. 1). The physico-chemical phenomena affecting the kinetics of chemical reactions in nano-confined volumes are not well understood. The only well-documented mechanism implies variations in concentrations of ions caused by surface charges and the overlap of electrostatic double layers (EDL). Differences in etch rates observed by Okuyama et al.  and Vereecke et al.  could be qualitatively understood within that frame. However, changes in water properties, such as the increase in proton mobility, call for other mechanisms . A recent study performed at imec has shown that chemical equilibria in nanochannels were affected by water structuring . In this project, we investigate the kinetics of chemical reactions in nano-channels/-holes with 1-D/2-D confinement. A first reaction is the etching of SiO2 by dilute HF solutions that still finds many uses in semiconductor manufacturing. The student typically performs the wet etching tests, the data treatment of SEM (scanning electron microscopy) pictures generated by operators in the pilot-line, and a kinetic analysis. Results are compared to etch rates obtained on planar films with film thickness measured by ellipsometry. A second reaction is a click-reaction involving a SAM (self-assembled monolayer) deposited on the structures, which is used in the functionalization of biosensors. Here the kinetics are studied using ATR-FTIR (attenuated total reflection Fourier-transform IR spectroscopy). The method has already been developed and tested on nano-channels. Typically, the student prepares the ATR crystals (polishing), performs the FTIR tests using a home-build liquid cell, as well as the data treatment and interpretation. Kinetic studies are complemented by the determination of the pH and water structuring in the nano-structures by ATR-FTIR and of the surface potential by a streaming technique. The content of the student project will be adapted depending on the progress of our research.  A. Okuyama et al., Solid State Phenom. 219 (2015) 115-118;  G. Vereecke et al., Microelec. Eng. 200 (2018) 56–61;  K. Mawatari et al., Anal. Chem. 86 (2014) 4068-4077;  G. Vereecke et al., Solid State Phenom. 282 (2018) 182-189.
Figure 1. Cartoon of a cross-sections in a FinFET transistor after removal of the dummy gate (not to scale), showing (a) a nano-slit with 1-D confinement, (b) nano-holes with 2-D confinement.
Type of project: Internship, Thesis
Duration: minimum 3 months
Required degree: Master of Engineering Technology, Master of Science, Master of Engineering Science, Master of Bioengineering
Required background: Chemistry/Chemical Engineering, Nanoscience & Nanotechnology
Supervising scientist(s): For further information or for application, please contact: Guy Vereecke (Guy.Vereecke@imec.be)
Allowance only for students from a non-Belgian university