Reading reliability in 1S1R OTS+PCM devices based on Double-Patterned Self-Aligned structure

International audienceThis study investigates the reliability of the reading operation in 1S1R devices based on Ovonic Threshold Switching (OTS) selector and Phase-Change Memory (PCM) co-integrated in a Double-Patterned Self-Aligned (DPSA) structure targeting Crossbar applications. Upon reading, the SET state can face a threshold voltage (Vth) increase of more than 20% dependently on the reading current and on the number of reading operations, which can lead to a soft failure. We separate the contributions to this increase coming respectively from OTS and PCM, finally providing an assessment protocol for the reading reliability. We show how the reading performances allow to determine the maximum Crossbar array size depending on the target voltage Read Window Margin and current Memory Window

Stress Buildup Upon Crystallization of GeTe Thin Films: Curvature Measurements and Modelling

International audiencePhase change materials are attractive materials for non-volatile memories because of their ability to switch reversibly between an amorphous and a crystal phase. The volume change upon crystallization induces mechanical stress that needs to be understood and controlled. In this work, we monitor stress evolution during crystallization in thin GeTe films capped with SiOx, using optical curvature measurements. A 150 MPa tensile stress buildup is measured when the 100 nm thick film crystallizes. Stress evolution is a result of viscosity increase with time and a tentative model is proposed that renders qualitatively the observed features