Reduced HfO₂ Resistive Memory Variability by Inserting a Thin SnO₂ as Oxygen Stopping Layer

One of the major roadblocks for filamentary type resistive random access memory is variations in both the write voltage and the read resistance. The variation is inevitable because of the stochastic nature of oxygen ion movement inside the metal oxide. In this letter, we show that by inserting a thin SnO₂ layer within the HfO₂ switching layer, these variations can be significantly reduced. The TiN/HfO₂/SnO₂/HfO₂/Pt material stack achieves ~ 10 times smaller standard deviation for the high resistance state( $>100\text{k}\Omega $ ) cycle to cycle distribution compared with the control group without the SnO₂ layer. The tight high resistance state distribution retained after 10⁷ pulse cycling. Incremental RESET pulse measurement indicates that the thin SnO₂ acts as an oxygen stopping layer and thus explains the origin of reduced variability. The concept of an oxygen stopping layer is promising for reducing variability for resistive memory.