Nano-Electro-Mechanical vibrating body FET resonator for high frequency integrated oscillators

This paper reports on the vibrating-body field effect transistor (VB-FET) readout strategy for high frequency (>100MHz) NEM resonators, enabling direct transmission measurements and demonstrating true potential for integrated circuit co-fabrication and co-design. A VB-FET has been fabricated based on electron beam lithography in a topology that bears full resemblance with a suspended Fin-FET, with two lateral independent gates. Fig. 1 shows a topview SEM image of the investigated structure. Enhancement-mode fully-depleted transistors are integrated in the center of clamped-clamped beams with channel lengths varying from 1 to 1.5 μm. The channel width is 200 nm, dictated by the suspended silicon layer thickness. The air gap separating the gate from the channel is 105 nm and forms the lateral gate insulator, together with 27 nm thick gate thermal oxides of the movable channel and the gate sides. A perspective 3D view including, for simplicity, only one of the side gates of the VB-FET is depicted in Fig. 2.