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

Transcription

1 From the SelectedWorks of Chengjie Zuo May, 2011 Reconfigurable CMOS Oscillator Based on Multifrequency AlN Contour-Mode MEMS Resonators Matteo Rinaldi, University of Pennsylvania Chengjie Zuo, University of Pennsylvania Jan Van der Spiegel, University of Pennsylvania Gianluca Piazza, University of Pennsylvania Available at:

2 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 58, NO. 5, MAY Reconfigurable CMOS Oscillator Based on Multifrequency AlN Contour-Mode MEMS Resonators Matteo Rinaldi, Member, IEEE, Chengjie Zuo, Member, IEEE, Jan Van der Spiegel, Fellow, IEEE, and Gianluca Piazza, Member, IEEE Abstract 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. Index Terms AlN contour-mode resonator (CMR), complementary-metal oxide semiconductor (CMOS)/ microelectromechanical-system (MEMS) oscillator, microelectromechanical systems (MEMSs), piezoelectric resonator, reconfigurable oscillator. I. INTRODUCTION THE DEMAND of high-performance, single-chip, multiband, and reconfigurable radio-frequency (RF) solutions for next-generation wireless communication is steadily growing. A key element for the implementation of an RF transceiver is a stable frequency source, which acts as a reference signal enabling system synchronization and signal modulation. When a single-chip multiband RF solution is pursued, a reconfigurable multifrequency source is highly desired. Single-frequency high-precision sources are implemented by connecting a high-quality-factor Q mechanical resonator Manuscript received October 21, 2010; accepted December 28, Date of publication January 31, 2011; date of current version April 22, This work was supported in part by the National Consortium for Measures and Signatures Intelligence Research and in part by the National Science Foundation. The review of this paper was arranged by Editor A. M. Ionescu. The authors are with the Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA USA ( rinaldim@seas.upenn.edu; czuo@seas.upenn.edu; jan@seas.upenn.edu; piazza@seas.upenn.edu). Color versions of one or more of the figures in this paper are available online at Digital Object Identifier /TED Fig. 1. Schematic representation of a PLL frequency synthesizer. in the feedback network of a self-sustained oscillator circuit. The natural resonance frequency of the mechanical resonator determines the output frequency of the oscillator. Due to the very high Q, quartz-crystal and surface-acoustic-wave (SAW) resonators have been widely and successfully employed as frequency setting elements in high-stability oscillator circuits. However, conventional quartz-crystal and SAW oscillators can only provide a single output frequency (just a relatively small frequency tuning is possible), the value of which is limited to tens of megahertz for quartz crystals and hundreds of megahertz for SAWs. When multiple and higher frequencies of operation are required, as in the case of oscillators for RF transceivers, phase-locked-loop (PLL) frequency synthesizers (see Fig. 1) are typically employed [1]. PLL frequency synthesizers generate high-frequency signals by multiplying the output frequency of a stable and accurate reference (implemented with a crystal or SAW oscillator) by factor N. The introduction of a PLL significantly increases the chip area dedicated to the oscillator and the total power consumption of the system. Furthermore, the frequency multiplication used to achieve the required output frequency increases the phase noise (PN) of the output signal by 20 log(n) [1], [2]. In this perspective, the implementation of a reconfigurable oscillator that employs high Q mechanical elements at all the desired frequencies of operation without the need of a PLL is potentially extremely advantageous. Nevertheless, when a wide range of operating frequencies needs to be covered (a large number of mechanical resonators is needed), quartz-crystal and SAW resonators fail to represent a viable solution because of their limited maximum operating frequencies and large size. Microelectromechanical system (MEMS) resonators have emerged as a promising alternative to bulky and unintegrable quartz-crystal and SAW resonators. Due to their small-form factor, high frequency of operation, and capability to be cointegrated with complementary-metal oxide semiconductor (CMOS) circuits, MEMS resonators represent the best /$ IEEE

3 1282 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 58, NO. 5, MAY 2011 TABLE I RESONATOR DESIGN PARAMETERS has the advantage of generating multiple stable frequencies by employing high-quality-factor mechanical elements at all operations without the need of a PLL. Fig. 2. Schematic view and micrograph of the reconfigurable CMOS oscillator prototype based on four-different-frequency AlN MEMS CMRs. (Inset) Schematic representation and scanning-electron-microscope picture of one of the CMRs. candidate for the implementation of compact and multifrequency banks of high-quality-factor mechanical elements that can be used for the fabrication of next-generation reconfigurable local oscillators for RF transceivers. Different MEMS resonator technologies based on electrostatic [3] [6] or piezoelectric [7] [9] transduction have been investigated. Among these, the AlN contour-mode resonator (CMR) technology [7] has emerged as one of the most promising solutions in enabling the fabrication of multiple frequencies (100 MHz 10 GHz) and high-performance resonators on the same silicon chip [10] [16]. Due to the piezoelectric transduction, low values of motional resistance (tens of ohms) can be achieved with the AlN CMR technology. This is an important device characteristic for the implementation of high-frequency and low-power-consumption MEMS-based oscillator circuits, and it is not easily achievable with electrostatically transduced resonators, values of the device impedance of which are considerably higher [3]. In addition, the CMR technology has the same advantages of thin-film bulk-acoustic resonators (FBARs) over SAW devices in terms of miniaturization and integratedcircuit integration capabilities. In contrast to the FBAR, the CMR technology enables the fabrication of multiple frequencies of operation on the same silicon chip. This feature is crucial for the implementation of advanced wireless-communication systems, for which single-chip and multiband RF solutions are highly desirable. In this paper, significant progress toward the development of the next-generation single-chip multiband RF transceivers is achieved by demonstrating the first reconfigurable fourfrequency (268, 483, 690, and 785 MHz) CMOS oscillator based on MEMS resonators (see Fig. 2). For the first time, a bank of multifrequency switchable AlN CMRs was simultaneously connected to a single CMOS oscillator circuit that can be configured to selectively operate in four different states with distinct oscillation frequencies. Jitter values as low as a 114-fs root mean square (RMS; integrated 12 khz 20 MHz) and switching times as fast as 20 μs were measured. This first prototype is 30 times smaller than dual-frequency commercially available voltage-controlled SAW oscillators (VCSOs) [17] and II. DESIGN A. Multifrequency AlN CMR Bank A conventional CMR is composed of an AlN film sandwiched between two metal electrodes (see inset of Fig. 2). When an alternating-current (ac) signal is applied across thickness T of the AlN film, a contour extensional mode of vibration is excited through the equivalent d 31 piezoelectric coefficient of AlN. Given the equivalent mass density ρ eq and Young s modulus E eq of the material stack that forms the resonator, the center frequency f 0 of this laterally vibrating mechanical structure is set by period W of the metal electrode patterned on the AlN plate and can be approximately expressed as f 0 = 1 E eq. (1) 2W ρ eq The other two geometrical dimensions, i.e., thickness T and length L, set the equivalent electrical impedance of the resonator [7] and can be designed independently of the desired resonance frequency. The resonance frequencies of the four CMRs of this paper were properly designed to devise a reconfigurable oscillator covering a frequency spectrum approximately from 250 to 800 MHz. Therefore, period W of the metal electrode patterned on the AlN plate was varied between 6 and 15 μm, whereas the other geometrical dimensions n, T, and L (see inset of Fig. 2) were opportunely scaled [11] in order to maintain a low value of the device equivalent electrical impedance (see Tables I and II). In addition, the thickness-field excitation (TFE) [12] and the lateral-field excitation with a floating bottom electrode (LFE-F) [14] were employed to excite a higher order contour extensional mode of vibration in the AlN structures. The LFE-F involves depositing the AlN film (forming the body of the resonator) on the top of a floating electrode, which acts to confine the electric field across the thickness of the device. The employment of such a floating bottom electrode makes the fabrication process easier (via openings to access the bottom electrode are not necessary), but it also causes the value of the electromechanical coupling k 2 t to degrade with the increase in the device resonant frequency for a given film thickness [18], [19]. Therefore, in order to guarantee high values of the electromechanical

4 RINALDI et al.: CMOS OSCILLATOR BASED ON ALN CONTOUR-MODE MEMS RESONATORS 1283 Fig. 3. Micrograph and circuit schematic of the multiplexed CMOS oscillator chip (1.05 mm 2 ). The single CMOS Pierce-like oscillator circuit can be connected to up to eight CMRs (four in this paper) by means of an equivalent number of CMOS switches operating in a time-multiplexed mode and addressed by a three-to-eight (two to four in this paper) digital decoder. Fig. 4. Schematic representation of two CMRs (MBVD equivalent circuit), i.e., Res1 and Res2, connected to the CMOS inverting amplifier A by means of two CMOS switches. In order to have V o V x (i.e., no power dissipation in the turned-off resonator), the resonator geometrical capacitance C 0 has to be larger than C p. Although just two resonators are shown in this schematic, four were effectively connected in the prototype presented in this paper. coupling k 2 t at higher operating frequencies, the employment of a conventional TFE, with patterned electrodes on both bottom and top surfaces, is preferable. B. Multiplexed CMOS Oscillator The oscillator circuit topology used in this paper is shown in Fig. 3. The circuit consists of a Pierce oscillator implemented by means of a CMOS inverter biased in its active region. Transistors M1 and M2 form the CMOS inverting amplifier, while transistor M3 acts as a large resistor to provide the biasing of M1 and M2 in the active region. By employing this circuit topology, transconductance g m of the inverting amplifier is made proportional to the supply voltage V S1 [13], which allows optimizing the oscillator performance in terms of power consumption and PN, depending upon the characteristics of the specific MEMS resonator connected in the feedback loop. By adjusting V S1, the ac gain of the inverting amplifier can be set to be equal to or above the critical transconductance g mc needed for the oscillations to start. The four AlN CMRs are simultaneously connected to the Pierce-like oscillator circuit by means of an equivalent number of CMOS switches (see Fig. 3) operating in a time-multiplexed mode. Each switch is composed of a CMOS transmission gate, dimensions of which are designed (by means of circuit simulations performed in Cadence) in order to minimize the power loss and consequently maintain a low value of gain in the amplifier used to sustain the oscillation. In particular, by acting on the W/L ratio of the transmission-gate transistor, the values of on-resistance and the input/output capacitance of the switches can be set in order to minimize the power dissipation. A large W/L ratio reduces the on-resistance of the switches (hence reduces the power loss and eventually improves the PN) but, at the same time, increases the values of their input/output capacitance C p, which, as shown in Fig. 4, needs to be kept smaller than the resonator geometrical capacitance C 0 in order to limit the excessive power dissipation. Since multiple resonators with different values of geometrical capacitance C 0 ( ff) are connected to the multiplexed oscillator, the value of C p needs to be designed to be smaller than the minimum possible values of C 0 (worst Fig. 5. Critical transconductance g mc normalized with respect to the case without switches as a function of the CMOS switch on-resistance R ON and input capacitance C P. The designed value of R ON ( 210 Ω) is compensated by an increase in the amplifier transconductance g mc by at most 2.5 times. case scenario). On the other hand, the design of such a small value of C P is associated with a high value of the switch onresistance R ON, which might negatively affect the performance of the oscillator. In fact, the insertion of the switch on-resistance R ON in the feedback loop of the circuit causes an increase in the required value of the critical transconductance g mc that is necessary for the oscillations to start [12], hence an overall increase in the oscillator power consumption. Therefore, the design space of the CMOS switches is limited by the values of the input capacitance C P, which has to be smaller than 95 ff (minimum possible value of C 0 ), and the on-resistance R ON, which should be chosen in such way that the increase in the critical transconductance g mc with respect to the case without switches is minimal (a maximum increase of three times was considered in this paper, as shown in Fig. 5). According to this consideration and given a minimum channel length L equal to 0.6 μm and set by the available CMOS technology, an optimum value for width W of the transistors forming the switches was estimated to be approximately 18 μm by means of circuit simulations performed in Cadence. This design choice corresponds to values of C p of about 40 ff (smaller than the minimum C 0 value) and switch onresistance R ON of about 210 Ω. As shown in Fig. 5, the designed value of R ON has a limited impact on the oscillator

5 1284 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 58, NO. 5, MAY 2011 Fig. 6. Measured admittance and MBVD model fitting of the 690-MHz AlN CMR. TABLE II CMR CHARACTERISTICS performance. In fact, an increase in the value of the amplifier critical transconductance by 2.5 times with respect to the case without switches is sufficient to compensate the additional loss introduced by the switches and sustain oscillations at all the operating frequencies. In order to reduce the number of pads necessary to control the sensor array, the CMOS switches are addressed through a two-to-four digital decoder integrated on chip (see Fig. 3). Each CMR is driven by the oscillator when the corresponding 2-binary digit (bit) address is presented to the decoder. III. EXPERIMENTAL RESULTS The four AlN CMRs were fabricated on a single chip accordingly to what was previously reported in [7], [11], [12], and [14]. The electrical responses of the fabricated devices were characterized in an RF probe station and the admittance curves measured by an Agilent N5230A network analyzer after performing a short open load calibration on a reference substrate (see Fig. 6). The measured electrical responses of the devices were fitted to the modified Butterworth van Dyke (MBVD) equivalent electrical circuit [20] and showed a high mechanical quality factor Q m (reported values include losses exclusively due to the mechanical motional resistance) up to 3900 and electromechanical coupling kt 2 up to 1.53% (see Fig. 6 and Table II). Such high values (> 20) of the device figure of merit (FoM), i.e., kt 2 Q, are of crucial importance for the direct connection of multiple CMRs to the low-power multiplexed oscillator circuit. In fact, the primary power loss in such an oscillator circuit is Fig. 7. Transient response of the reconfigurable oscillator while switching from the 483-MHz output to the 268-MHz output. due to the motional resistance R m of the resonator [12], the value of which is inversely proportional to the device FoM, i.e., k 2 t Q [11]. The Q values of the four devices depend on process variations. The multiplexed CMOS oscillator chip was taped out in the ON Semiconductor 0.5-μm CMOS process. Both the MEMS resonator die and the CMOS chip were attached to a customdesigned printed circuit board, and all the electrical connections were made through wire-bonding (see Fig. 2). The four combinations of the 2-bit address (corresponding to each of the CMRs in the bank) were cyclically provided to the decoder by a data acquisition system so as to sequentially turn on each resonator. Stable oscillation at all the four different frequencies of operation was achieved by applying supply voltages V S1 and V S2 (buffer power supply) as low as 3.3 and 3.0 V, respectively, which translate in a power consumption of 13 mw for the inverting amplifier and 22.5 mw for the buffer. By tuning the supply voltage V S1, stable oscillation at the two lowest operating frequencies can be achieved with lower power consumption (398 μw at 268 MHz and 4 mw at 483 MHz). Despite the use of a 0.5-μm technology, the typical value of the total power consumption (35.5 mw) for the reconfigurable oscillator of this paper is approximately six times lower than the one achieved with commercially available VCSOs [17]. The switching time of the reconfigurable oscillator was measured by monitoring its transient response with an Agilent DSO80804A oscilloscope. Switching times as fast as 20 μs were measured (see Fig. 7), showing the capability to reconfigure the oscillator at rates in the megahertz range. In order to characterize the noise performance of the reconfigurable oscillator prototype, the output of the oscillator was monitored via an Agilent E5052B signal source analyzer. The PN of the reconfigurable oscillator was measured (see Fig. 8) 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. These PN measurements translate in time-domain jitter values as low as a 114-fs RMS (integrated 12 khz 20 MHz; see Table III). The FoM [13] of this reconfigurable AlN CMR oscillator was also calculated for each of the four different frequencies of operation, and the corresponding values are reported in

6 RINALDI et al.: CMOS OSCILLATOR BASED ON ALN CONTOUR-MODE MEMS RESONATORS 1285 a broad spectrum going from tens of megahertz to a few gigahertz. The use of large arrays of mechanical devices instead of power-hungry and inefficient circuit elements (such as PLLs) could have a transformational impact on the form factor (100-plus CMRs can fit in 2mm 2 ) and power consumption of next-generation reconfigurable multifrequency sources for RF transceivers. ACKNOWLEDGMENT Fig. 8. Measured PN for the four-frequency reconfigurable AlN CMR oscillator. The supply voltage V S1 was tuned for each of the four different operating frequencies in order to achieve optimum PN performances. TABLE III OSCILLATOR PERFORMANCE AT THE FOUR CMR FREQUENCIES Table III. These FoMs are among the best ever reported for similar frequency oscillators based on MEMS technologies [12], [13], [21]. The measured noise performances are comparable with those of commercially available VCSOs (based on two different SAW resonators) [17]. Therefore, this first prototype of the reconfigurable CMR oscillator not only has the advantage of occupying only a fraction (30 times) of the area typically taken by VCSOs but also meets the PN specifications for many different applications where VCSOs are typically used, such as synchronous optical network/synchronous digital hierarchy, optical transport network, 10-Gb Ethernet, and worldwide interoperability for microwave access (WiMax). IV. CONCLUSION In this paper, the first reconfigurable CMOS oscillator based on laterally vibrating MEMS resonators has been experimentally demonstrated. A bank of multifrequency and switchable AlN MEMS CMRs has been connected to a single oscillator circuit that can be configured to selectively operate in four different states with distinct oscillation frequencies (268, 483, 690, and 785 MHz). The PN of the reconfigurable oscillator has been 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. The excellent results demonstrate that it is possible to envision new timing solutions in which large arrays (100 plus) of micromechanical resonators fully integrated with CMOS circuits could be used for frequency synthesis over The authors would like to thank X. Wu for helpful discussions on the multiplexed oscillator circuit design, the Metal Oxide Semiconductor Implementation Service (MOSIS) Educational Program for the integrated-circuit chip fabrication, and the staff at Wolf Nanofabrication Facility, University of Pennsylvania, for their support in the MEMS fabrication. REFERENCES [1] G. B. Razavi, Monolithic Phase-Locked Loops and Clock Recovery Circuits: Theory and Design. Piscataway, NJ: IEEE Press, [2] Vectron International, Hudson, NH. [Online]. 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7 1286 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 58, NO. 5, MAY 2011 contour-mode MEMS resonators, in Proc. IEEE CICC, San Jose, CA, Sep. 2010, pp [17] Vectron International, Hudson, NH. [Online]. Available: vectron.com/products/vcso/vs709.pdf [18] M. Benetti, D. Cannatà, F. Di Pietrantonio, and E. Verona, Guided lamb waves in AlN free strips, in Proc. IEEE Int. Ultrason. Symp., NewYork, Oct. 2007, pp [19] C.-M. Lin, T.-T. Yen, Y.-J. Lai, V. V. Felmetsger, M. A. Hopcroft, J. H. Kuypers, and A. P. Pisano, Temperature-compensated aluminum nitride lamb wave resonators, IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 57, no. 3, pp , Mar [20] J. D. Larson, III, P. D. Bradley, S. Wartenberg, and R. C. Ruby, Modified Butterworth Van Dyke circuit for FBAR resonators and automated measurement system, in Proc. IEEE Ultrason. Symp., Oct. 2000, pp [21] H. M. Lavasani, R. Abdolvand, and F. Ayazi, Low phase-noise UHF thinfilm piezoelectric-on-substrate LBAR oscillators, in Proc. IEEE 21st Int. Conf. MEMS, Jan. 2008, pp Matteo Rinaldi (S 08 M 11) received the first-level (B.S.) and second-level (M.Sc.) Laurea degrees in electronic engineering (with honors) from the University of Rome Tor Vergata, Rome, Italy, in 2004 and 2007, respectively, and the Ph.D. degree from the University of Pennsylvania, Philadelphia, in He is currently a Postdoctoral Researcher with the Department of Electrical and Systems Engineering, University of Pennsylvania. He has more than 15 referred publications in the aforementioned research areas and also holds two device patent applications in the field of micro/nano mechanical resonant sensors. His research interests primarily include micro/nano electromechanical systems (MEMS/NEMS) devices, micro/nano AlN piezoelectric gravimetric sensors for multiple volatile organic compound detection, nanosensitive layers for enhanced gas-vapor adsorption, super-high-frequency nanoelectromechanical resonators for radiofrequency and sensing applications, MEMS-/NEMS-based oscillator circuits, and MEMS-IC integration and codesign. Dr. Rinaldi is a member of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society and the IEEE Electron Devices Society. He was the recipient of the Best Student Paper Award at the 2009 IEEE European Frequency and Time Forum International Frequency Control Symposium joint conference. Chengjie Zuo (S 07 M 11) received the B.S. degree in electronic information science and technology from the University of Science and Technology of China, Hefei, China, in 2004 and the M.Sc. degree (with honors) in electrical engineering from the Delft University of Technology, Delft, the Netherlands, in He is currently working toward the Ph.D. degree in electrical and systems engineering at the University of Pennsylvania, Philadelphia. His primary research interests are nano/micro electromechanical systems (MEMS), analog and radio-frequency integrated circuits (IC), and MEMS-IC integration and codesign. Mr. Zuo was the recipient of the Best Student Paper Award in the Oscillators, Synthesizers, and Noise group at the 2008 IEEE International Frequency Control Symposium and the IEEE Solid-State Circuits Society Predoctoral Fellowship for Jan Van der Spiegel (S 73 M 79 SM 90 F 02) received the M.S. and Ph.D. degrees in electrical engineering from the University of Leuven, Leuven, Belgium, in 1974 and 1979, respectively. Since 1981, he has been with the University of Pennsylvania, Philadelphia, where he is currently a Professor with the Department of Electrical and Systems Engineering and the Director of the Center for Sensor Technologies. His research interests are in mixed-mode very-large-scale-integration design, biologically based sensors and sensory information processing systems, microsensor technology, and analog-to-digital converters. Dr. Van der Spiegel is the recipient of the IEEE Educational Activities Board Major Educational Innovation Award (2007), the IEEE Third Millennium Medal (2000), the United Parcel Service Foundation Distinguished Education Chair, and the Bicentennial Class of 1940 Term Chair. He is also the recipient of the Christian and Mary Lindback Foundation and S. Reid Warren Awards for Distinguished Teaching. He has served on several IEEE program committees and was the Program Chair of the 2007 International Solid-State Circuit Conference. He has been the chapters chairs coordinator of the IEEE Solid-State Circuits Society (SSCS). He is an elected member of SSCS, a Distinguished Lecturer of the SSCS, and a member of the SSCS membership committee. Gianluca Piazza (S 00 M 05) received the Ph.D. degree from the University of California, Berkeley, where he developed a new class of AlN contourmode vibrating microstructures for radio-frequency (RF) communications. He is a Wilf Family Term Assistant Professor with the Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia. He has more than ten years of experience working with piezoelectric materials. He is the holder of several patents in the field of micromechanical resonators, some of which have recently been successfully transferred to industry. His research interests focus on piezoelectric micro/nano electromechanical systems (MEMS/NEMS) for RF wireless communications, chemical/biological detection, wireless sensor platforms, and all-mechanical computing. He also has a general interest in the areas of micro/nano fabrication techniques and integration of micro/nano devices with state-of-the-art electronics. Dr. Piazza is the recipient the IBM Young Faculty Award in 2006 and the Best Paper Award with his students in Groups 1 and 2 at the IEEE Frequency Control Symposium in 2008 and 2009, respectively.