Passive Anti-Tamper Latching Stress Sensors for Volume Protection

This Small Business Innovation Research Phase I proposal describes a latching anti-tamper (AT) stress sensor (LATSS) for volumetric protection of military systems. LATSS devices are intended to passively detect and remember if a change in some mechanical aspect of the shield enclosing a protected volume has occurred and provide a signal that can be queried to report the change. They are based on spin dependent tunnel (SDT) junctions utilizing magnetostrictive ferromagnetic electrodes. Magnetostrictive SDT junctions provide a unique combination of capabilities for an AT sensor. The hysteretic magnetic behavior of the SDT electrodes provides the capability to record a change in stress without applied power. The magnetoresistance of the SDT junctions permits electrical readout of the orientation of the magnetization of the ferromagnetic sensor electrodes, which is set by magnetostrictive coupling to the substrate strain. SDT devices can be fabricated using standard back end of line semiconductor processes, potentially making LATSS a low cost volumetric AT solution. Because of their small size, several LATSS devices could be combined on the same substrate to produce a cryptokey memory, providing a new class of passive tamper-responsive cryptokey memory. Additionally, SDT materials are intrinsically radiation hard, permitting development of radiation hard LATSS devices.