This paper reports our effort to develop amorphous hydrogenated silicon carbide (a-SiC:H) films specifically designed
for MEMS-based microbridges using methane and silane as the precursor gases. In our work, the a-SiC:H films were
deposited in a simple, commercial PECVD system at a fixed temperature of 300°C. Films with thicknesses from 100 nm
to 1000 nm, a typical range for many MEMS applications, were deposited. Deposition parameters such as deposition
pressure and methane-to-silane ratio were varied in order to obtain films with suitable residual stresses. Average residual
stress in the as-deposited films selected for device fabrication was found by wafer curvature measurements to be -658 ±
22 MPa, which could be converted to 177 ± 40 MPa after thermal annealing at 450°C, making them suitable for
micromachined bridges, membranes and other anchored structures. Bulk micromachined membranes were constructed to
determine the Young's modulus of the annealed films, which was found to be 205 ± 6 GPa. Chemical inertness was
tested in aggressive solutions such as KOH and HF. Prototype microbridge actuators were fabricated using a simple
surface micromachining process to assess the potential of the a-SiC:H films as structural layers for MEMS applications.
Micro-and nanoelectromechanical systems (MEMS and NEMS) enable the development of smart products and systems by augmenting the computational ability of microelectronics with perception and control capabilities of micro/nanosensors and micro/nanoactuators. Silicon carbide (SiC) is well known for its excellent properties, making it an outstanding candidate as a structural material for MEMS and NEMS. This paper reviews some of the more significant accomplishments by our group in developing the 3C- polytype of SiC for MEMS and NEMS. Forming the cornerstone of this effort are two key thin film deposition systems that are used to deposit single crystalline and polycrystalline 3C-SiC films for bulk and surface micromachined devices. This paper presents an overview of these two deposition systems, their applicability in MEMS, as well as specific devices that have been fabricated using films from these reactors.
This paper reports our effort to study the failure mechanisms and high temperature behavior of Ni wire bonds. Ultrasonic wire bonding was used to bond 25 micrometers -diameter Ni wire to 7500 angstrom thick Ni pads deposited on 3C-SiC substrates. A series of high temperature experiments which include electrical characterization, annealing tests, and in situ pull test were conducted to test the reliability of the wire bonds at temperatures up to 550 degrees C. In situ pull test were also performed on samples prepared by thermosonic wire bonding. Scanning electron microscope was used to investigate the formation of brittle cracks on the heel of the bonds, to compare the feet of new and used wedges, and to examine the surface texture of wire bonds exposed to high temperatures.
Conference Committee Involvement (2)
MEMS/MOEMS Components and Their Applications V Special Focus Topics: Transducers at the Micro-Nano Interface
21 January 2008 | San Jose, California, United States
MEMS/MOEMS Components and Their Applications IV Special Focus Topics: Transducers at the Micro-Nano Interface
22 January 2007 | San Jose, California, United States
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