Dense N over CMOS 6T SRAM cells using 3D Sequential Integration

Stacking N over CMOS devices using 3D Sequential CoolCube™ Integration has been shown promising for the scaling of 6T SRAMs. By transposing one pass-gate and one pull-down NMOS to the top layer, a cell footprint reduction of 27% could be obtained, leading to a 3D vias density over 10 ⁸ /mm ² achievable. In addition, we presented N-type devices fabricated below 630°C yielding quasi-equivalent performances as high temperature ones while fulfilling the PBTI and hot-carrier effects reliability requirements, comforting the viability of N over CMOS approach.