BEOL-Compatible Non-Volatile Capacitive Synapse with ALD W-Doped In2O3 Semiconductor Layer

We experimentally demonstrate BEOL-compatible metal- ferroelectric-semiconductor (MFS)-type non-volatile capacitive (nvCAP) synapse with atomic layer deposition (ALD)-grown W-doped $\text{In}_{2}\mathrm{O}_{3}$ (IWO) as the semiconductor layer. For the first time, ALD with in-situ W doping technique is utilized for the $\mathrm{I}{\mathrm{n}_2}\mathrm{O}_{3}$ layer deposition. We propose $W$ doping and overlap area engineering to achieve capacitance on/off ratio of ~24 under non-destructive read scheme $(\mathrm{V}_{\mathrm{r}\mathrm{e}\mathrm{a}\mathrm{d}}=0\mathrm{V})$, a record value among reported BEOL-compatible capacitive synapses. Array-level performance benchmark of the compute-in-memory (CIM) hardware consisting of 3D scaled ALD IWO-based nvCAPs suggests $24.4\times$ figure-of-merit (=TOPS/WxTOPS/mm2) improvement over state-of-the art resistive synapse thanks to dynamic-power only charge-domain computation and 3D BEOL integration.