Sergio Pacheco

Are Diamonds a MEMS' Best Friend?

Next-generation military and civilian communication systems will require technologies capable of handling data/ audio, and video simultaneously while supporting multiple RF systems operating in several different frequency bands from the MHz to the GHz range [1]. RF microelectromechani-cal/nanoelectromechanical (MEMS/NEMS) devices, such as resonators and switches, are attractive to industry as they offer a means by which performance can be greatly improved for wireless applications while at the same time potentially reducing overall size and weight as well as manufacturing costs.

An RCP Packaged Transceiver Chipset for Automotive LRR and SRR Systems in SiGe BiCMOS Technology

We present a transceiver chipset consisting of a four channel receiver (Rx) and a single-channel transmitter (Tx) designed in a 200-GHz SiGe BiCMOS technology. Each Rx channel has a conversion gain of 19 dB with a typical single sideband noise figure of 10 dB at 1-MHz offset. The Tx includes two exclusively-enabled voltage-controlled oscillators on the same die to switch between two bands at 76-77 and 77-81 GHz. The phase noise is -97 dBc/Hz at 1-MHz offset. On-wafer, the output power is 2 × 13 dBm. At 3.3-V supply, the Rx chip draws 240 mA, while the Tx draws 530 mA. The power dissipation for the complete chipset is 2.5 W. The two chips are used as vehicles for a 77-GHz package test. The chips are packaged using the redistribution chip package technology. We compare on-wafer measurements with on-board results. The loss at the RF port due to the transition in the package results to be less than 1 dB at 77 GHz. The results demonstrate an excellent potential of the presented millimeter-wave package concept for millimeter-wave applications.

A novel low-temperature method to fabricate MEMS resonators using PMGI as a sacrificial layer

A method to fabricate microelectromechanical systems (MEMS) clamped?clamped resonators using polymethylglutarimide (PMGI) as a sacrificial release layer has been developed. Control of the critical air-gap dimension between the resonator beam and drive electrode was maintained by varying the sacrificial PMGI thickness, allowing fabrication of devices with resonator-to-electrode gaps as small as 100 nm. The resonator beam was constructed by depositing a low stress, low temperature bi-layer alpha-TaN/SiON (50/2000 nm) film over the PMGI layer, followed by a multi-step etch process. Physical characterization of devices with varying beam lengths was performed via focused ion beam and scanning electron microscopy analyses to verify complete release of the resonator structures. Electrical testing showed a resonant frequency of 11.3 MHz, which agreed well with simulated results. The measured RF characteristics are fitted with a lumped element model that used Youngs modulus and the device quality factor as adjustable parameters. Youngs modulus of the individual components of the TaN/SiON bi-layer was measured and found to be in good agreement with the values used to fit the measured resonance.

Device-Level Vacuum Packaging for RF MEMS

For specific RF applications, where the use of MEMS is highly attractive, cost-effective reliable packaging is one of the primary barriers to commercialization. Many RF MEMS devices require a hermetic or vacuum operation environment. This paper presents a post-CMOS-compatible method for vacuum packaging of RF MEMS devices by growing an encapsulation layer during the device fabrication. The resulting MEMS devices are surrounded by a vacuum cavity and can then be placed in a conventional low-cost circuit package. This is a low-temperature area-efficient device-level encapsulation for MEMS devices. RF MEMS resonators in a fixed-fixed configuration were used as the test bed since their quality factor can be used as a measure of the package quality. The encapsulation process is based on a double-sacrificial-layer surface micromachining technique, which is used to create a cavity under and above the resonator. Polyimide was used as the sacrificial layer, followed by the deposition of a packaging layer with trench cuts, which facilitate the sacrificial layer removal. The trench cuts were then sealed at a low pressure, forming a cavity around the device at the sealant layer deposition pressure. Extensive RF characterization and reliability tests were performed on the packaged resonators.

A fully packaged piezoelectric switch with lowvoltage actuation and electrostatic hold

This paper reports RF characterization of a fully packaged RF MEMS piezoelectric switch. The switch demonstrates better than 0.8 dB insertion loss at 2 GHz and 30 dB isolation up to 10 GHz. The presented device combines a piezoelectric actuation and a low electrostatic hold voltage to improve contact force. Actuation voltages of the switch are 5 V for both piezoelectric actuation and electrostatic hold. This actuation was sufficient to obtain contact resistance lower than 2 ohms. The switch is packaged by wafer-level packaging technology using gap control, AuSn eutectic bonding and post-process Thru-Silicon Vias.

RF MEMS resonator for CMOS back-end-of-line integration

CMOS back-end-of-line (BEOL) compatible MEMS resonators were fabricated via a low-temperature process flow. The exural-mode resonator beams are made of a bi-layer consisting of a thin TaN and thick SiON 1m. DC measurements of pull-down voltage indicate limitations to operating voltages due to electric field breakdown across the bottom electrode to resonator beam gap. The RF response of the resonators shows resonant frequencies in the 11.0-11.6 MHz range with Q values of 2200.

SiGe technology and circuits for automotive radar applications

Recent advancements in SiGe device development enable the realization of 77GHz automotive radar systems using relatively low-cost silicon technology. This paper will discuss technology requirements for the radar design and also present examples of receiver and transmitter circuit implementations.

Piezoelectric PZT Thin Films in the 100nm Range: A Solution for Actuators Embedded in Low Voltage Devices

This paper reports the piezoelectric properties of sputtered and sol gel PZT thin films investigated in a low thickness range (100-250nm). Piezoelectric-elastic bimorphs including very thin PZT films were realized and the maximum reachable deflection at 5V was characterized. The depoling effect experienced by the PZT versus the maximum post process temperature is also discussed which leads to the motivation of developing low thickness range PZT thin films. Elastic-piezoelectric bimorphs were realized and exhibited deflection higher than 5¿m at 5V. Moreover, these bimorphs showed only a 10% decrease of the deflection after 5 billions cycles.

Characterization of low-temperature Ultrananocrystalline/spl trade/ Diamond RF MEMS resonators

For the first time working MEMS resonators have been produced using low-temperature deposited (550/spl deg/ C) Ultrananocrystalline/spl trade/ Diamond (UNCD/spl trade/) films. Using a lumped-element model to fit experimental data, UNCD materials properties such as a Youngs modulus of 710 GPa and an acoustic velocity of 14,243 m/s have been deduced. This is the highest acoustic velocity measured to date for a diamond MEMS structural layer deposited at low temperatures. A 10 MHz resonator shows a DC-tunability of the resonance frequency of 15% between 15 and 25 V and the breakdown voltage behavior shows electrostatic breakdown rather than electro-mechanical pull-down for higher frequency devices. Good resonant frequency reproducibility is observed when cycling the resonators over bias voltages from 15 to 25 V and over RF power levels of -10 to 10 dBm.

Integrated Passive Technology for Wireless Basestation Applications

An integrated passive device (IPD) technology has been developed for wireless basestations applications. The technology features 6-mil GaAs substrates, airbridges for MIM capacitors, thick gold metallization for high Q inductors, and through-wafer vias for ultra-low-loss RF grounding. Extensive EM simulations were used in the evaluation and design of the inductors, capacitors, through-wafer vias, and the bond wires connecting the LDMOS die and the IPD. 900 MHz and 2.7 GHz Class AB LDMOS power amplifiers (PAs) using IPD output impedance matching networks, and a 900 MHz Class F PA using an IPD harmonic termination circuit, have been designed, fabricated, and tested. All systems show excellent RF performances.