Font Size: 

This study highlights the difference in the sidewall morphology of n+-typepolysilicon films from two popular microelectromechanical systems (MEMS)processes and its effect on fracture and fatigue properties. Atomic force andtransmission electron microscopy show that thick silicon oxides (20 ± 5 nm) arefound in PolyMUMPs films, caused by galvanic corrosion from the presence ofgold on the chip, whereas in SUMMiT films a much thinner (3.5 ± 1.0 nm) nativeoxide was observed. These thicker oxide layers, in combination with differencesin sidewall roughness (14 ± 5 nm for PolyMUMPs and 10 ± 2 nm for SUMMiT),have a significant effect on the fracture and fatigue properties of polysiliconstructures; this is shown by measuring fracture strength (3.8 ± 0.3 GPa forPolyMUMPs and 4.8 ± 0.2 GPa for SUMMiT) and stress-lifetime high-cyclicfatigue curves