Impact of Bottom Electrode Integration on OxRAM Arrays Variability

Abstract : HfO$_2$-based OxRAMs with various metal stacks in the inferior VIA of bottom electrode were fabricated. We demonstrated for the first time that the metal stack of TiN PVD (physical vapour deposition), followed by an annealing step decreases the standard error of the forming voltage by 10% compared to the other variants. The related die-to-die and cell-tocell variability is greatly reduced along the wafer diameter and the LRS shows better control of the tail bits at 3$\sigma$ of the distribution. The number of failed operations over 1e4 cycles for 1k cells is reduced by a factor 3, reaching a BER of 8e-5. Finally, correlation of the cell reliability with the bottom via roughness is discussed.