PhD defense – Aurélien Lecavelier – 21st march 2013
Very high frequency, mechanically flexible and performance stable integrated electronics based on SOI-CMOS transfer bonding on plastic substrates
The ability to realize flexible circuits integrating sensing, signal processing, and communicating capabilities is of central importance for the development of numerous nomadic applications requiring foldable, stretchable and large area electronics. A large number of these applications currently rely on organic electronics, or integrate high mobility active films on plastic foils to provide higher performance. A key challenge is however the combination of high electrical performance (i.e. millimeter wave, low noise electronics), with the mechanical flexibility required to adapt to curvilinear surfaces, in addition to high stability of these electrical performance upon deformation.
In this work, a solution has been developed, based on thinning and transfer onto plastic foil of high frequency (HF) CMOS devices initially patterned on conventional silicon-on-insulator (SOI) wafers. This transfer process first enables the fabrication of high performance electronics on plastic, with n-MOSFETs featuring characteristic frequencies fT/fmax as high as 150/160GHz in addition to low noise potentialities: NFmin/Ga of 0.57/17.8dB. Secondly, by locating the neutral plane of the flexible system in its active layer, the relative variation of these high frequency figures-of-merit can be limited to 5% even after aggressive bending, demonstrating flexibility, high performance and stability.
Keywords: flexible electronics, SOI, CMOS, MOSFET, neutral plane, stress, strain