PHOTO : Techno - Soft-mold nanoimprint lithography

Research Topics - PHOTO / Innovative fabrication technological processes / Soft-mold nanoimprint lithography

During our work on periodic structures on glass, we encountered the problem of sub-micronic lithography, on large surface area, on an insulating substrate. This is a generic keylock common to all current works on large surface nanostructured devices. In close coordination with E. Daran of the LAAS Technology Platform (TEAM), and with strong support from the laboratory, we have sought to develop a technological process to solve the difficulties encountered.

In this context, we have developed an original two-step process of nanoimprinting lithography using flexible molds. A first thermal printing step transfers the patterns from a hard silicon mold into a flexible organic polymer mold (commercial Zéonor). A second printing step under UV radiation allows the transfer of the patterns from the flexible mold into a resist formulated in the laboratory. This resist can then be used as an etch mask for the final transfer of the patterns into a dielectric layer. We then adapted this process to the specific problems of resonant gratings. During K. Sharshavina's thesis, we were able to show that this process makes it possible to fabricate resonant grating filters of very high performance and on large surface area in a reproducible way. We then extended this process to the realization of 4" resonant gratings. Within the framework of the work on CRIGFs, we have been able to show that this process is generic, allowing to fabricate devices on glass substrate for the near infrared as well as CRIGFs on GaAs substrate for the medium infrared range.

Our current work aims to quantify the pattern deformations induced by these processes, and to improve the reproducibility and reliability of these technological steps, in particular by working on specific resist formulations and on the methods and techniques used for characterization of the samples at the different steps of the process.


Left: Schematics of a resonant grating on a glass substrate. Right: photograph of such a resonant grating manufactured by nanoimprinting lithography on a 4'' substrate.

Related publications:
S. Pelloquin, S. Augé, K. Sharshavina, J.-B. Doucet, A. Héliot, H. Camon, A. Monmayrant and O. Gauthier-Lafaye, "Soft mold NanoImprint Lithography: a versatile tool for sub-wavelength grating application," Microsystem Technologies (2018).

S. Augé et al., “Mid-infrared cavity resonator integrated grating filters,” Optics Express, vol. 26, no. 21, 2018.

S. Augé. "Lithographie par nanoimpression pour la fabrication de filtres à réseaux résonants en cavité." Micro et nanotechnologies/Microélectronique. Université de Toulouse 3 Paul Sabatier, 2017.

K. Sharshavina, “New concepts of ultra-selective spectral filters for embedded spectroscopy,” UPS Toulouse - Université Toulouse 3 Paul Sabatier, 2016.