Integration Design and Process of 3-D Heterogeneous 6T SRAM with Double Layer Transferred Ge/2Si CFET and IGZO Pass Gates for 42% Reduced Cell Size

In this work, we propose an advanced 3-D heterogeneous 6T SRAM with a newly designed hetero-integration method. CFET inverters and IGZO pass gates are vertically stacked within a 2T footprint area. The Low-Temperature Hetero-Layers Bonding Technique (LT-HBT) process is utilized successfully to fabricate single crystalline heterogeneous Double Layer Transferred (DLT) Ge/2Si CFET-OI on an 8-inch full wafer. Furthermore, an IGZO nFET is deposited and treated as a pass gate (PG) to realize a 6T SRAM operation. The hetero-integration of IGZO PG and self-align DLT Ge/2Si CFET inverters showed improved Read Static Noise Margin (RSNM) and stand-by leakage power. The state-of-the-art 3-D heterogeneous 6T SRAM leads to 42% area reduction.