Monolithic 3D SRAM-CIM Macro Fabricated with BEOL Gate-All-Around MOSFETs

For the first time, below 400°C-fabricated gate-all-around (GAA) transistor fabrication process was demonstrated with monolithic computing-in-memory (CIM) circuit. Key enablers are plasma-assisted atomic layer etching (PA-ALE), plasma immersion ion implantation (PIII) and far-infrared laser activation (FIR-LA). The 3D stackable single-grained Si GAA MOSFETs thus fabricated exhibit record-high Ion/Ioff ratio (~10⁸) with low Ioff (pFETs<10^–2 nA/μm). Moreover, the stackability of the GAA MOSFETs and the differential output of dual-mode 10T SRAM readout enable 2x throughput in the CIM circuitry.