Toward The 5nm Technology: Layout Optimization and Performance Benchmark for Logic/SRAMs Using Lateral and Vertical GAA FETs

摘要

In this paper, we present a layout and performance analysis of logic and SRAM circuits for vertical and lateral GAA FETs using 5nm (iN5) design rules. Extreme ultra-violet lithography (EUVL) processes are exploited to print the desired features: 32 nm gate pitch and 24 nm metal pitch. Layout architectures and patterning compromises for enabling the 5nm node will be discussed in details. A distinct standard-cell template for vertical FETs is proposed and elaborated for the first time. To assess electrical performances, a BSIM-CMG model has been developed and calibrated with TCAD simulations, which accounts for the quasi-ballistic transport in the nanowire channel. The results show that the inbound power rail layout construct for vertical devices could achieve the highest density while the interleaving diffusion template can maximize the port accessibility. By using a representative critical path circuit of a generic low power SoCs, it is shown that the VFET-based circuit is 40% more energy efficient than LFET designs at iso-performance. Regarding SRAMs, benefits given by vertical channel orientation in VFETs has reduced the SRAM area by 20%～30% compared to lateral SRAMs. A double exposures with EUV canner is needed to reach a minimum tip-to-tip (T2T) of 16 nm for middle-of-line (MOL) layers. To enable HD SRAMs with two metal layers, a fully self-aligned gate contact for LFETs and 2D routing of the top electrode for VFETs are required. The standby leakage of vertical SRAMs is 4～6X lower than LFET-based SRAMs at iso-performance and iso-area. The minimum operating voltage (Vmin) of vertical SRAMs is 170 mV lower than lateral SRAMs. A high-density SRAM bitcell of 0.014 um2 can be obtained for the iN5 technology node, which fully follows the SRAM scaling trend for the 45nm nodes and beyond.