Wai-Kin Wong

6Mhz Bulk-Mode Resonator with Q Values Exceeding One Million

In this paper, we report a 6.3 MHz Lame-mode square resonator with fully differential drive and sense electronics, exhibiting quality factor, Q values exceeding 1 million in ambient pressures as high as 100 Pa. A maximum Q value of 1.6 million was experimentally measured at vacuum pressure of 36 muTorr. It was also experimentally observed that the Q value for the bulk mode resonator was relatively independent for pressures below 100 Pa suggesting that the Q is pressure limited for pressure higher than 100 Pa. This resonator was fabricated using SOIMUMPs process from MEMSCAP.

12.9MHz Lame-Mode Differential SOI Bulk Resonators

In this paper, differentially driven 12.9 MHz square resonators in Lame mode with two different types of anchor - T-anchor and straight beam anchor are presented in an attempt to investigate how the anchor design influences the quality factor, Q values. These square resonators operated in a vacuum pressure of 36 muTorr exhibited Q values of 807,000 and 404,000, respectively. This difference in Q values for the two resonators is probably due to differing energy losses in their respective anchors. These resonators were fabricated using SOIMUMPs process from MEMSCAP.

Phonon-mediated characterization of microelectromechanical resonators

The authors describe an acoustic-phonon technique for dynamic microelectromechanical device characterization. Proof of concept experiments using electrostatic resonators reveal a linear phonon to displacement relationship, with detection gain factors up to 25.2mV∕μm attained for packaged devices. Q values of 21 600 and 465 obtained at operating pressures of 6.0×10−6 and 760Torr, respectively, conform to theoretical estimates. Duffing behavior for nonlinear resonator operation was also characterized as a third order response. As acoustic phonons are well detected on any external location for packaged devices, destructive depackaging for die probing is unnecessary, allowing noninvasive testing and high measurement throughput to be attained.

Characterization of SOI Lamé-mode square resonators

Characterization of Lame-mode square resonators with different straight-beam anchor lengths, structural layer thickness, and number of anchor support reveals that there is likely an optimal range of anchor designs that provide high quality factor (Q) above one million, along with low motional resistance. Shorter anchor length restricts resonator vibrations and motional resistance could be increased by 3.5 times compared to resonators with longer anchor length. Two-anchor support design is able to achieve higher Qpsilas but results in higher motional resistance compared to four-anchor support. When structural thickness is reduced from 25 mum to 10 mum, Q gets degraded but still maintained above one million.

Estimation of the second crossover in insulators using the electrostatic mirror in the scanning electron microscope

A technique for measuring the second secondary emission crossover in insulators was developed. The method utilizes the behavior of an electrostatic mirror formed on insulating samples to estimate the current equilibrium point as well as the mirror potential. Current results show that the value of the second crossover for glass passivation obtained using this method is in general agreement with previous techniques.

Non-Destructive Functionality and Reliability Assessment of Dynamic MEMS using Acoustic Phonon Characterization

This paper introduces a novel technique for dynamic motion characterization of microelectromechanical (MEMS) devices such as resonators, switches, micromirrors, accelerometers and gyroscopes. Due to the favorable generation and transmission of acoustic phonons through solids, characterization of individual MEMS devices for both dies and packaged devices can be attained non- invasively. Hence, this technique can be utilized for high volume wafer and package-level testing in MEMS manufacturing, allowing new test functionalities and cost economies in back-end wafer and package yield screens to be attained.

Novel acoustic techniques for microelectronic failure analysis and characterization

Acoustic/phonon characterization techniques using active sample probing for localized phonon generation such as scanning electron acoustic microscopy (SEAM), scanning photo or laser acoustic microscopy (SPAM/SLAM) and scanning ion acoustic microscopy (SIAM) are recent developments as extensions of acoustic analysis. In addition to the active electron beam probing mode, passive acoustic detection could also be used in cases where intrinsic phonon generation or phonon-mediated relaxation mechanisms occur during device operation as stated in R. Lifshitz (2002). This technique is currently under active research at the National University of Singapore as a means of dynamically characterizing parameters of microelectromechanical (MEMS) devices such as RF microswitches, resonators, accelerometers and gyroscopes.

Factors governing the discharge of electrostatic mirror formations in the scanning electron microscope

Two primary parameters for an automated electrostatic mirror discharge technique are studied, namely the discharge voltage and the discharge current. It was found that using discharge voltages corresponding to the σ>1 region and near the first crossover point of a sample’s total yield curve gave the optimum discharge rate for the technique. Also, using discharge currents larger than the scanning current was shown to improve the rate of discharge. These optimizations ensure the feasibility of this technique as a discharge tool where repeated high and low beam voltage switching in the scanning electron microscope is needed.

Imaging of charging specimens at high beam energies in the SEM

This paper describes a novel method to observe charging specimens at high beam voltages without specimen preparation. It was found that the technique greatly reduces charging artifacts such as raster faults, discharge streaks, astigmatism and defocussing without sacrificing image quality. Images obtained of uncoated specimens are found to be comparable to gold-coated specimens and without charging effects.