FlexMEMS-enabled hetero-integration for monolithic FBAR-above-IC oscillators

Abstract

In this work, a monolithic oscillator chip is heterogeneously integrated by a film bulk acoustic resonator (FBAR) and a complementary metal-oxide-semiconductor (CMOS) chip using FlexMEMS technology. In the 3D-stacked integrated chip, the thin-film FBAR sits directly over the CMOS chip, between which a 4 μm-thick SU-8 layer provides a robust adhesion and acoustic reflection cavity. The proposed system-on-chip (SoC) integration features a simple fabrication process, small size, and excellent performance. The oscillator outputs 2.024 GHz oscillations of −13.79 dBm and exhibits phase noises of −63, −120, and −136 dBc/Hz at 1 kHz, 100 kHz, and far-from-carrier offset, respectively. FlexMEMS technology guarantees compact and accurate assembly, process compatibility, and high performance, thereby demonstrating its great potential in SoC hetero-integration applications.

Surface Engineering of Metal–Organic Framework Prepared on Film Bulk Acoustic Resonator for Vapor Detection

“…Device Fabrication and Sorption Film Preparation. The procedure of fabricating FBAR is reported in our previous work 45,46 and briefly described here (Figure S1). First, an air cavity is etched on a single-side polished silicon wafer.…”

Recent Advances in Flexible RF MEMS

“…For example, Shah et al [ 58 ] introduced an elastomer pneumatic switch for RF micro-devices based on PDMS. Compared with being a flexible substrate material, the usual function of PDMS is to act as a stamp in the transfer printing process [ 97 , 98 , 99 , 100 ]. Chao et al [ 65 ] developed an SU-8 micro-machining process for RF MEMS passive preparation.…”

“…The fabrication techniques of flexible RF MEMS devices can be divided into the following three strategies: (1) surface MEMS processing techniques directly fabricated on various flexible substrates [ 47 , 48 , 57 , 66 , 67 , 69 , 70 , 76 , 77 , 78 , 91 , 92 , 93 , 96 , 102 ]; (2) transfer processing techniques of transferring fabricated RF MEMS from rigid substrates to flexible substrates [ 60 , 62 , 63 , 68 , 94 , 97 , 98 , 99 , 100 , 101 ]; and (3) direct printing inkjet printing processing techniques of functional electronic materials [ 53 , 59 , 60 , 61 , 64 , 71 , 72 , 73 ].…”

“…At present, some progress has been made in the research of various functional flexible RF MEMS, mainly in flexible RF MEMS switches , phase shifters [76][77][78], reconfigurable antennas [78][79][80][81][82][83][84][85][86] and phased array antennas [87][88][89][90] based on them, in MEMS resonators [91][92][93][94][95][96][97][98][99][100][101][102][103], frequency selective hyper surfaces [104], etc.…”