In this work we present migration phenomenon of throughholes in silicon membranes.The sealing of through-holes in hydrogen ambient at high temperature (1130°C) with various dimensions and annealing time durations was investigated in both singlecrystalline silicon (sc-Si) and poly-crystalline silicon (poly-Si) membranes.The sealing process in silicon was observed as highly dependent on local crystal grain geometry, leading to more distributed, unpredictable migration rates and shape evolutions in poly-Si compared to holes in sc-Si.These findings can be leveraged in fabrication processes that require a balance between silicon migration and deposition.

Filters with various bandwidths at low intermediate frequency (IF) have been demonstrated using aluminum nitride (AlN) microresonator technology. Specifically, at 13 MHz, 6 kHz, and 25 kHz bandwidth filters were implemented using a single resonator topology, and 250 kHz and 500 kHz bandwidth filters were constructed via the parallel lattice topology using four sub-resonators and L-matching networks. The bandwidths of these filters are from 0.046% to 3.8%, and particularly the 500 kHz bandwidth filter at 13 MHz is wider than that of the resonator kt 2 limit (40 kHz). The 100x variations in filter percent bandwidth were realized in a 1700 nm-thick aluminum nitride film on the same wafer through CMOS-compatible fabrication processes. Changes in the filter termination for proper filter matching were implemented in the Agilent Genesys RF and microwave design simulation software using actual measured filter responses with 50 Ω termination. The great flexibility in filter bandwidths and resonant frequencies, as well as other benefits such as size, manufacturing cost, isolation, and insertion loss provided by AlN microresonators will enable next generation multi-band, multi-waveform, and cognitive radios for defense and consumer wireless applications.

Engineers at Sandia National Laboratories have developed a technology that may bring down the cost and improve the efficiency of photovoltaic energy conversion. Here they explain how they manufacture photovoltaic modules containing as many as 100,000 silicon solar cells using conventional IC fabrication and PCB assembly techniques. They also explain how they estimate module efficiency based on the IV characteristics of individual cells and the detection of open and short circuits.

As the radio frequency (RF) spectrum has become more crowded, the need for adaptable RF components, especially filters, has grown. Recently, aluminum nitride (AlN) microresonator filters have been reported. These filters/resonators are small (<;1mm3), have the high quality factors (>1000) desired for steep filter roll-off, can achieve many filters covering a very wide frequency span (kHz to GHz) on a single chip and can be monolithically integrated with CMOS transistors for reconfiguring the filter array. Using AlN microresonator on CMOS technology, miniature, adaptable RF filters based on banks of switched filters have recently been reported.

This chapter includes a review of MEMS resonators for use as frequency references and filters. Basic modeling and transduction techniques for resonators are described with emphasis on capacitive transduction. A brief history of resonator architectures is given, beginning with early devices consisting of linear comb drive actuators and flexural beams to later devices utilizing bulk resonant modes and parallel plate actuation. The underlying causes of frequency instability are described, with emphasis on the dependence of frequency upon temperature. Descriptions are provided for the various energy dissipation mechanisms that are central to determining the quality factors of resonators. The concept of coupled resonators for narrow-band frequency filters is also covered.

Frequency tuning of aluminum nitride (AlN) microresonators has been demonstrated via localized heating (ovenization) of the resonator. Specifically, piezoelectrically driven ~ 100 MHz microresonators were heated by embedded joule heaters in vacuum. Three different designs with three different film stacks were tested, and among the tested devices, thermal resistances as large as 92 K/mW have been demonstrated, which corresponds to 1-mW power consumption to yield a temperature increase of 92°C. To minimize heat loss, the devices were suspended from the substrate by high thermal isolation beam-type supports. The beams exhibit very high thermal resistance not only due to their high length to cross-sectional area ratio but also because they are made of thin-film-deposited polycrystalline aluminum nitride. Film-deposited AlN has been shown to have thermal conductivity much lower than that measured in bulk materials. Thermal time constants for these devices were measured ranging from submilliseconds to 10 ms depending on the design and film stacks, and frequency tunability was measured as high as 2548 parts per million/mW. The availability of a power-efficient frequency tuning method, coupled with all other performance benefits, makes AlN microresonators a promising candidate for the next-generation timing devices and tunable filters for multiband communication systems.

Recently, with the application of micro/nano machining technologies, there have been immense strides in the research of phononic crystals. This paper reviews basics of micro/nano fabricated 2D phononic crystals, and discusses their promising applications, particularly for RF signal processing and thermal conductivity manipulation with several examples of Sandia National Laboratories.

Micromechanical resonators show a discrepancy between the frequency-temperature (f-T) characteristics they have in open-loop and closed-loop measurements, and this discrepancy adversely affects resonator's temperature stability performance. We explain the discrepancy with a model that combines the temperature-dependent quality factor (Q) with the nonlinear amplitude-frequency (A-f) effect; we then experimentally verify the model using two types of double-ended tuning fork resonators. In addition, we present an improved closed-loop system that removes the discrepancy, thus improving the temperature stability.

The dispersive properties of phononic crystals can be utilized to manipulate the phononic impedance of a material and to engineer the frequency-delay response of time domain signal processing circuits. In this paper we study, in both the frequency and time domains, the dispersive properties of phononic crystals formed in thin suspended plates of aluminum nitride.