Size and frequency of defects in silicon MEMS

Mechanical testing of thin films for MEMS has progressed from a developmental stage to a point where validated techniques are used to study the behavior of devices and materials at a very fine scale. Tensile data covering a range of sizes and test techniques have been analyzed to examine the distribution of defects that would be responsible for the observed fracture strengths. For each sample, a critical defect size was calculated based on a published fracture toughness and a half-circular surface crack fracture toughness model. For polysilicon produced using the SUMMiT V process in the period 1998-1999, the calculated mean defect size was 115 nm. For polysilicon produced using the MUMPS process, the calculated mean defect size was 389 nm.