/Wet processing of high aspect ratio nanostructures

Wet processing of high aspect ratio nanostructures

Leuven | More than two weeks ago

Properties of nanoconfined aqueous solutions are different from bulk and must be characterized to develop new chemistries

​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 [1-6]. Evidence was found for water structuring, decreased permittivity, modified chemical equilibria and slower diffusivity in nanoconfined solutions. The observed phenomena are of interest not only for nanoelectronic manufacturing 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 TiN in the RMG 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. As to 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. 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., Solid State Phenom. 282 (2018) 182-189, [5] G. Vereecke et al., Microel. Eng. 239–240 (2021) 111515, [6] G. Vereecke et al., Microel. Eng. (2022).


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


Required language: English

Required background: Engineering Science

Mentor: Guy Vereecke

Manager: For more information or for application, please contact Guy Vereecke (Guy.Vereecke@imec.be)

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