Public defence, Electronic and Digital Systems, MSc Artem Gabrelian

Title of the thesis: Designing In-Plane Piezoelectric MEMS and NEMS: Vertical Sidewall Transducers from Micro- to Nanoscale

Thesis defender: Artem Gabrelian
Opponent: Dr. Marc Sansa, CEA – Leti, France
Custos: Prof. Mervi Paulasto-Kröckel, Aalto University School of Electrical Engineering 

From the screen rotation in smartphones to airbag triggers in cars and the growing network of Internet of Things (IoT) sensors, micro-electro-mechanical systems (MEMS) are foundational to modern electronics. However, as consumers and industries demand devices that do more, use less energy, and operate at faster speeds, the traditional ways of manufacturing these tiny sensors are reaching their limits. This doctoral thesis explores a novel solution to this problem by changing the architecture of these microscopic devices from horizontal, planar designs to vertical ones. By utilizing piezoelectric materials, which convert mechanical motion into electricity and vice versa, on vertical sidewalls, this research successfully scales this technology down to the nanoscale.

Traditionally, the operation frequency and capabilities of these sensors have been limited by the thickness of the flat materials used to build them. By moving to a vertical, in-plane design, this research bypasses those limitations. It allows engineers to control a device's frequency simply by changing its layout during manufacturing, enabling multiple different sensors to operate on a single chip. Furthermore, a vertical design allows for multidimensional movement in a much smaller physical footprint.

Shrinking vertical structures to the nanoscale presents not only novel applications, but also significant manufacturing challenges, as standard techniques used for micro-scale or flat nano-scale devices are not readily applicable to three-dimensional nano-structures. The main result of this study is the successful development of a dedicated nanoscale manufacturing process. The research demonstrates that it is feasible to deposit active piezoelectric films, specifically aluminum nitride, onto vertical sidewalls at the nanoscale. Using this new method, the study successfully built and tested a platform of functional devices, including static switches, highly sensitive mass sensors, and ultra-fast acoustic resonators operating in the gigahertz range.

The findings brought forward by this thesis provide a practical framework for the tech industry and sensor development. The vertical manufacturing process developed here can be applied to create the next generation of smart devices, highly advanced IoT sensors, and ultra-sensitive equipment capable of detecting minute physical masses. Ultimately, the research concludes that vertical, in-plane piezoelectric design is a robust and promising pathway for the future of micro- and nano-electronics, unlocking physical capabilities that are uniquely accessible at the nanoscale.

Key words: MEMS, NEMS, piezoelectric, AlN, sensors, gyroscope, FBAR, ALD, miniaturization

Thesis available for public display 7 days prior to the defence at Aalto University's public display page.

Contact: 
artem.gabrelian@aalto.fi
https://www.linkedin.com/in/artgab