Chengjie Zuo

Super-high-frequency two-port AlN contour-mode resonators for RF applications

This paper reports on the design and experimental verification of a new class of thin-film (250 nm) superhigh- frequency laterally-vibrating piezoelectric microelectromechanical (MEMS) resonators suitable for the fabrication of narrow-band MEMS filters operating at frequencies above 3 GHz. The device dimensions have been opportunely scaled both in the lateral and vertical dimensions to excite a contour-extensional mode of vibration in nanofeatures of an ultra-thin (250 nm) AlN film. In this first demonstration, 2-port resonators vibrating up to 4.5 GHz have been fabricated on the same die and attained electromechanical coupling, kt 2, in excess of 1.5%. These devices are employed to synthesize the highest frequency MEMS filter (3.7 GHz) based on AlN contour-mode resonator technology ever reported.

1.05-GHz CMOS oscillator based on lateral- field-excited piezoelectric AlN contour- mode MEMS resonators

This paper reports on the first demonstration of a 1.05-GHz microelectromechanical (MEMS) oscillator based on lateral-field-excited (LFE) piezoelectric AlN contourmode resonators. The oscillator shows a phase noise level of -81 dBc/Hz at 1-kHz offset frequency and a phase noise floor of -146 dBc/Hz, which satisfies the global system for mobile communications (GSM) requirements for ultra-high frequency (UHF) local oscillators (LO). The circuit was fabricated in the AMI semiconductor (AMIS) 0.5-¿m complementary metaloxide- semiconductor (CMOS) process, with the oscillator core consuming only 3.5 mW DC power. The device overall performance has the best figure-of-merit (FoM) when compared with other gigahertz oscillators that are based on film bulk acoustic resonator (FBAR), surface acoustic wave (SAW), and CMOS on-chip inductor and capacitor (CMOS LC) technologies. A simple 2-mask process was used to fabricate the LFE AlN resonators operating between 843 MHz and 1.64 GHz with simultaneously high Q (up to 2,200) and kt 2 (up to 1.2%). This process further relaxes manufacturing tolerances and improves yield. All these advantages make these devices suitable for post-CMOS integrated on-chip direct gigahertz frequency synthesis in reconfigurable multiband wireless communications.

Reconfigurable CMOS Oscillator Based on Multifrequency AlN Contour-Mode MEMS Resonators

This paper reports on the first demonstration of a reconfigurable complementary-metal-oxide-semiconductor (CMOS) oscillator based on microelectromechanical system (MEMS) resonators operating at four different frequencies (268, 483, 690, and 785 MHz). A bank of multifrequency switchable AlN contour-mode MEMS resonators was connected to a single CMOS oscillator circuit that can be configured to selectively operate in four different states with distinct oscillation frequencies. The phase noise (PN) of the reconfigurable oscillator was measured for each of the four different frequencies of operation, showing values between -94 and - 70 dBc/Hz at a 1-kHz offset and PN floor values as low as -165 dBc/Hz at a 1-MHz offset. Jitter values as low as a 114-fs root mean square (integrated 12 kHz-20 MHz) and switching times as fast as 20 μs were measured. This first prototype represents a miniaturized solution (30 times smaller) over commercially available voltage-controlled surface-acoustic-wave oscillators and potentially has the advantage of generating multiple stable frequencies without the need of cumbersome and power-consuming phase-locked-loop circuits.

Multifrequency Pierce Oscillators Based on Piezoelectric AlN Contour-Mode MEMS Technology

This paper reports on the first demonstration of multifrequency (176-, 222-, 307-, and 482-MHz) oscillators based on the piezoelectric AlN contour-mode microelectromechanical systems technology. All the oscillators show phase noise values between -88 and -68 dBc/Hz at 1-kHz offset frequency from the carriers and phase noise floor values as low as -160 dBc/Hz at 1 MHz offset. The same Pierce circuit design is employed to sustain oscillations at the four different frequencies; on the other hand, the oscillator core consumes 10 mW. The AlN resonators are currently wire bonded to the integrated circuit realized in the AMIS 0.5-¿m 5-V complimentary metal-oxide-semiconductor process. Limits on phase noise and power consumption are discussed and compared with other competing technologies. This paper constitutes a substantial step forward toward the demonstration of a single-chip multifrequency reconfigurable timing solution that can be used in wireless communications and sensing applications.

Microscale inverse acoustic band gap structure in aluminum nitride

This work presents the design and demonstration of a microscale inverse acoustic band gap (IABG) structure in aluminum nitride (AlN) with a frequency stop band for bulk acoustic waves in the very high frequency range. Conversely to conventional microscale acoustic band gaps, the IABG is formed by a two-dimensional periodic array of unit cells consisting of a high acoustic velocity material cylinder surrounded by a low acoustic velocity medium. The periodic arrangement of the IABG array induces scattering of incident acoustic waves and generates a stop band, whose center frequency is primarily determined by the lattice constant of the unit cell and whose bandwidth depends on the cylinder radius, the film thickness, and the size of the tethers that support the cylinder. A wide band gap (>13% of the center frequency) is formed by the IABG even when thin AlN films are used. The experimental response of an IABG structure having a unit cell of 8.6 μm and an AlN film thickness of 2 μm confirms the existence of a...

12E-3 Channel-Select RF MEMS Filters Based on Self-Coupled AlN Contour-Mode Piezoelectric Resonators

This paper reports experimental results on a new class of single-chip multi-frequency channel-select filters based on self-coupled aluminum nitride (AlN) contour-mode piezoelectric resonators. For the first time, two-port AlN contour- mode resonators are connected in series and electrically coupled using their intrinsic capacitance to form multi-frequency (94 -271 MHz), narrow bandwidth (~ .3%), low insertion loss (~4 dB), high off-band rejection (~60 dB) and extremely linear (IIP3-110 dBm) channel-select filters. This novel technology enables multi-frequency, high-performance and small form factor filter arrays and makes a single-chip multi-band RF solution possible in the near future.

Multi-frequency pierce oscillators based on piezoelectric AlN contour-mode MEMS resonators

This paper reports on the first demonstration of multi-frequency (176, 222, 307, and 482 MHz) oscillators based on piezoelectric AlN contour-mode MEMS resonators. All the oscillators show phase noise values between -88 and -68 dBc/Hz at 1 kHz offset and phase noise floors as low as -160 dBc/Hz at 1 MHz offset. The same Pierce circuit design is employed to sustain oscillations at the 4 different frequencies, while the oscillator core consumes at most 10 mW. The AlN resonators are currently wirebonded to the integrated circuit realized in the AMIS 0.5 mum 5 V CMOS process. This work constitutes a substantial step forward towards the demonstration of a single-chip multi-frequency reconfigurable timing solution that could be used in wireless communications and sensing applications.

Dual-Mode Resonator and Switchless Reconfigurable Oscillator Based on Piezoelectric AlN MEMS Technology

For the first time, this work demonstrates a switchless dual-frequency (472 MHz and 1.94 GHz) reconfigurable CMOS oscillator using a single piezoelectric AlN microelectromechanical-systems resonator with coexisting S0 and S1 Lamb-wave modes of vibration. High performance (high quality factor Q and electromechanical coupling factor kt2 for a resonator and low phase noise for an oscillator) has been achieved for both the resonator and oscillator in terms of dual-mode operation. In particular, 1.94-GHz operation has the best phase noise performance at 1-MHz offset when compared with all previously reported CMOS oscillators that work at a similar frequency.

Demonstration of inverse acoustic band gap structures in AlN and integration with piezoelectric contour mode wideband transducers

This paper presents the first design and demonstration of a novel inverse acoustic band gap (IABG) structure in aluminum nitride (AlN) and its direct integration with contour-mode wideband transducers in the Very High Frequency (VHF) range. This design implements an efficient approach to co-fabricate in-plane AlN electro-acoustic transducers with bulk acoustic waves (BAWs) IABG arrays (10×10). The IABG unit cell consists of a cylindrical high acoustic velocity (V) media, which is held by four thin tethers, surrounded by a low acoustic velocity matrix (air). The center media is formed by 2-µm-thick AlN, which is sandwiched by 200-nm-thick top and bottom platinum (Pt) layers. The experimental results indicate that the designed IABG has a stop band from 185 MHz to 240 MHz and is centered at 218 MHz in the Γ-X direction. This demonstration not only confirms the existence of the frequency band gap in the IABG structure, but also opens possibilities for the integration of ABG structures with RF MEMS devices.

AlN contour-mode resonators for narrow-band filters above 3 GHz

This paper reports on the design and experimental verification of a new class of thin-film (250 nm) Super High Frequency (SHF) laterally-vibrating piezoelectric microelectromechanical (MEMS) resonators suitable for the fabrication of narrow-band MEMS filters operating at frequencies above 3 GHz. The device dimensions have been opportunely scaled both in the lateral and vertical dimensions in order to excite a contour-extensional mode of vibration in nano features of an ultra-thin (250 nm) Aluminum Nitride (AlN) film. In this first demonstration two-port resonators vibrating up to 4.5 GHz were fabricated on the same die and attained electromechanical coupling, kt2, in excess of 1.5 %. These devices were employed to synthesize the highest frequency ever reported MEMS filter (3.7 GHz) based on AlN contour-mode resonator (CMR) technology.