Wet processing of high aspect ratio nanostructures

More than two weeks ago

explore the impact of nano-confinement on the properties of water and their impact on physical processes and chemical reactions

In semiconductor manufacturing, new generations of devices have entered the nano-world, with critical dimensions of the order of 10 nm. Moreover, new transistor geometries are vertical, with the generation of 1-D and 2-D nano-confined spaces. While many process steps are still performed using aqueous chemistries, e.g. wet etching of materials for patterning and wet cleaning of surfaces. Recent studies have shown that nano-confinement is affecting all the steps in a wet process from wetting to chemical reactions, rinsing and drying [1-5]. Evidences were found for water structuring, decreased permittivity, modified chemical equilibria and slower diffusivity in nanoconfined volumes. The observed phenomena are of interest not only for nanoelectronics but also for nanofluidics.

Current activities encompass the wetting of deep nanocontacts such as in 3D-NAND memories and advanced logic interconnects, the wet etching of silicon oxide in the insulation module of FinFET, the wet etching of SiGe films in the making of Silicon nanosheets for advanced transistors, and the rinsing of deep nanocontacts. ATR- FTIR (attenuated total reflection Fourier-transform IR spectroscopy) has become a major technique to characterize wetting, chemical reactions and rinsing, as well as properties of aqueous solutions such as structuring, permittivity and diffusivity. 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 characterization of water structuring in the nanostructures and the determination of the surface potential by a streaming technique. Progress in the understanding of phenomena are used to propose and test solutions to the confinement effects. For etching tests, the etch rates on planar films are determined by ellipsometry, while cross-section-SEM (scanning electron microscopy) and image analysis are used on structures. Here the composition of etch chemistries are modified with additives to suppress the confinement effects. The student typically performs the wet etching tests, the ellipsometry measurements, the data treatment of the SEM pictures generated by operators in the pilot-line, and a kinetic analysis comparing planar to patterned etch rates, leading to new chemistry proposals. ATR-FTIR can be used to confirm the impact of additives on water structuring, or to pre-select additives for testing.

Several students are welcome to participate into this project. It is open for internship and/or master thesis. The content of the student project will be adapted depending on the progress of our research.

[1] K. Mawatari et al., Anal. Chem. 86 (2014) 4068-4077; [2] A. Okuyama et al., Solid State Phenom. 219 (2015) 115-118; [3] N. Vrancken et al., Langmuir 33 (2016) 3601-3609; [4] G. Vereecke et al., Microelec. Eng. 200 (2018) 56–61; [5] G. Vereecke et al., Solid State Phenom. 282 (2018) 182-189.

Type of project: Internship, Thesis, Combination of internship and thesis

Duration: at least 3 months, preferably 4 or more

Required degree: Master of Engineering Technology, Master of Science, Master of Engineering Science, Master of Bioengineering

Required background: Bioscience Engineering, Chemistry/Chemical Engineering, Nanoscience & Nanotechnology

Supervising scientist(s): For further information or for application, please contact: Guy Vereecke (Guy.Vereecke@imec.be)

Imec allowance will be provided for students studying at a non-Belgian university.

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