Full integrated process to manufacture RF-MEMS and MMICs on GaN/Si substrate

Abstract

Radio Frequency Micro-Electro-Mechanical System (RF-MEMS) represents a feasible solution to obtain very low power dissipation and insertion loss, very high isolation and linearity switch with respect to “solid state” technologies. In this paper, we demonstrate the full integration of RF-MEMS switches in the GaN-HEMT (Gallium Nitride/High Electron Mobility Transistor) fabrication line to develop RF-MEMS devices and LNA-MMIC (Low Noise Amplifier/Monolithic Microwave Integrated Circuit) prototype simultaneously in the same GaN wafer. In particular, two different coplanar wave (CPW) LNAs and a series of discrete RF-MEMS in ohmic-series and capacitive-shunt configuration have been fabricated. RF-MEMS performances reveal an insertion loss and isolation better than 1 and 15 dB, respectively, in the frequency range 20–50 GHz in the case of pure capacitive shunt switches and in the frequency range 5–35 GHz for the ohmic-series switches. Moreover, the GaN HEMT device shows an Fmax of about 38 GHz and a power density of 6.5 W/mm, while for the best LNA-MMIC we have obtained gain better than 12 dB at 6–10 GHz with a noise figure of circa 4 dB, demonstrating the integration achievability.

Ta2O5Thin Films for Capacitive RF MEMS Switches

“…In the down state, the return loss is better than −0.3 dB in almost all the measured frequency range and a resonant frequency of 23 GHz (isolation of −38 dB) is observed. The obtained results compare favourably with the S-parameters recently measured for shunt capacitive switches fabricated in III-V technology [10]. The value of the resonant frequency was found to reduce from ∼30 GHz to 15 GHz with increasing the bridge length in the range 450-750 μm, in agreement with the increasing of the inductive contribution [1].…”

Polynomial noise modeling of silicon‐based GaN HEMTs

“…This technology, originally optimized on SiC substrates, has been applied on the AlGaN/GaN heterojunction grown on a 4 in HR‐Si (111) substrate, with a resistivity ρ = 7 kΩ · cm, introducing some targeted optimization for the ohmic contact deposition and for the backside process. The latter procedure consists in lapping down to 50 µm the Si substrate thickness by means of an abrasive 9 µm alumina dust, followed by a polishing treatment to make easier the mask alignment for via holes lithography . Such substrate thinning allows to reduce Si contribution to device thermal conductivities, resulting in a junction temperature under the Gate contact (i.e.…”

Reconfigurable RF Circuits and RF‐MEMS

“…radar and radiometric sensors) [18]. An ongoing trend is also with respect to the monolithic integration of RF-MEMS switches within RFIC/MMIC processes as some semiconductor IC foundries (Rockwell, OMMIC, IHP and Selex) have integrated MEMS switches on top of GaAs, SiGe and GaN substrates [25][26][27][28][29][30]. Nowadays, solid-state semiconductor switches are commonly used in such circuits but they are rather narrow band, nonlinear and have relatively high losses, especially at microwave and millimetre-wave frequencies.…”

“…transistors) fabricated on the same GaN wafer [30]. This is also in spite of the acknowledged superior RF properties of such enabling technologies (e.g., in terms of very high power efficiency and low-loss low-power switching) that should make them ideal candidates for use in future intelligent microsystem (IMS) applications.…”