Andrew Sparks

Stiction in Low Humidity Environment

The susceptibility of MEMS devices, treated with anti-stiction coatings, to stiction in a low humidity environment has been investigated for the first time. Wafer-level testing with a pull-in/pull-out voltage technique and current compliant source was used to detect stiction on capped and uncapped wafers. Devices capped in dry Nitrogen environment were found to be sticky at both the wafer-level pull-in/pull-out test as well as the packaged part tap test. Although uncapped devices did not show stiction in a room environment using the pull-in/pull-out detection technique, successive drops in pull-out voltage were detected as the conditions of the test control chamber became drier. The ability of the anti-stiction coating to retain charge was analyzed using KLA-Tencor Quantox XP system where the deposited charge decayed in 6 minutes when measured in room air conditions. Successive pull-in/pull-out cycles separated by a delay of 15 seconds showed decay in pull-out voltage of 22mV/cycle. This unprecedented demonstration opens up new opportunities for understanding stiction in MEMS devices and implementing the necessary solutions.