Most current capacitive RF-MEMS switch technology is based on conventional dielectric materials such as SiO2 and
Si3N4. However, they suffer not only from charging problems but also stiction problems leading to premature failure of
an RF-MEMS switch. Ultrananocrystalline diamond (UNCD(R) (2-5 nm grains) and nanocrystalline diamond (NCD) (10-
100 nm grains) films exhibit one of the highest Young's modulus (~ 980-1100 GPa) and demonstrated MEMS resonators
with the highest quality factor (Q ≥10,000 in air for NCD) today, they also exhibit the lowest force of adhesion among
MEMS/NEMS materials (~10 mJ/m2-close to van der Waals' attractive force for UNCD) demonstrated today. Finally,
UNCD exhibits dielectric properties (fast discharge) superior to those of Si and SiO2, as shown in this paper. Thus,
UNCD and NCD films provide promising platform materials beyond Si for a new generation of important classes of
high-performance MEMS/NEMS devices.
Ultrananocrystalline diamond (UNCD) films are promising for radio frequency micro electro mechanical systems (RF-MEMS) resonators due to the extraordinary physical properties of diamond, such as high Young's modulus, quality factor, and stable surface chemistry. UNCD films used for this study are grown on 150 mm silicon wafers using hot filament chemical vapor deposition (HFCVD) at 680°C. UNCD fixed free (cantilever) resonator structures designed for the resonant frequencies in the kHz range have been fabricated using conventional microfabrication techniques and are wet released. Resonant excitation and ring down measurements in the temperature range of 138 K to 300 K were conducted under ultra high vacuum (UHV) conditions in a custom built UHV AFM stage to determine the temperature dependence of Young's Modulus and dissipation (quality factor) in these UNCD cantilever structures. We measured a temperature coefficient of frequency (TCF) of 121 and 133
ppm/K for the cantilevers of 350 μm and 400 μm length respectively. Young's modulus of the cantilevers increased
by about 3.1% as the temperature was reduced from 300 K to 138 K. This is the first such measurement for UNCD and suggests that the nanostructure plays a significant role in modifying the thermo-mechanical response of the material. The quality factor of these resonators showed a moderate increase as the cantilevers were cooled from 300 K to 138 K. The results suggest that surface and bulk defects significantly contribute to the observed dissipation in
UNCD resonators.
The Grating Light ValveTM (GLVtm) spatial light modulator is a unique and proven CMOS process-compatible optical MEMS device. The modulator employs a dynamically adjustable diffraction grating to manipulate an optical signal. Today, the GLVTM technology is successfully used in high-resolution display and imaging systems, where its high efficiency, large dynamic range, precise analog attenuation, fast switching speed, high reliability, high yield, and the ability to integrate thousands of channels into a single device are fundamental advantages. These same properties make the GLVTM device desirable for optical telecommunication applications. The optical properties, functionality, device design, and CMOS processing of the GLVTM will be presented. Challenges and solutions that arise from adapting the current GLVTM technology to optical telecommunications wavelengths will be discussed. Measured results will be presented that describe GLVTM performance parameters, including insertion loss, dynamic range, polarization dependent loss, and spectral attenuation accuracy.
Film stresses in doubly-supported bi-layer micro-ribbons have been determined by measurement of their resonant vibration frequency. The composite aluminum/silicon-nitride ribbons constitute a programmable diffraction grating in which ribbon stresses play an important role in device behavior. To determine the intrinsic film stresses in each layer, special ribbon arrays were fabricated in which the coverage of aluminum was systematically varied from end toward the center of each ribbon. With increasing aluminum coverage, the ribbons exhibit a characteristic roll-off in resonant frequency which can be used to refine longitudinal film stresses. An analytical expression describing resonant frequency as a function of partial layer coverage is derived. By least-squares fitting this function to the observed roll-off, the film stresses in each layer are determined. It is found that the silicon-nitride stresses are large and tensile (approximately 800 MPa), while those in the aluminum are small and compressive (approximately -100 MPa).; This paper reviews the relevant theory behind the approach, demonstrates its application to wafer- level data and discusses its repeatability and accuracy.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.