Research Projects

Air Spacer MOSFET technology

*** THIS PROJECT IS NO LONGER ACTIVE ***

Jemin Park and Chenming Hu

In a 20nm-gate MOSFET with oxide spacer, 77% of the gate charge is due to the gate to plug/diffusion capacitances. Reducing these capacitances will be an increasingly important way to improve the device speed and switching energy/power at 20nm and beyond. Compared to an air-spacer inverter, a conventional nitride-spacer inverter has 82% longer delay and 85% larger switching energy (power consumption). Even a pure-oxide-spacer inverter has 41% longer delay and 48% larger switching energy than the air-spacer inverter. High density memories employ the SAC technology that requires the use of nitride spacers. This significantly raises the gate to plug/diffusion capacitance and increases the delay and switching energy by about 60%. A novel air-spacer SAC device can preserve the 35% area benefit of SAC device while reducing the delay and power by over 75% to levels even better than the non-SAC conventional device. It also reduces the bit-line and word-line capacitances. The result is increased DRAM and SRAM speed, reduced power, and reduced chip size. These air spacer technologies are promising key technology for 20nm generation and beyond.

[1]
M. Togo, A. Tanabe, A.Furukawa, K.Tokunaga, and T. Hashimoto. : ‘A Gate-side Air-gap Structure (GAS) to Reduce the Parasitic Capacitance in MOSFETs’, Symposium on VLSI Tech. Dig., p. 38, 1996.
[2]
TSUPREM4 User Manual, Synopsys, Mountain View, CA.
[3]
SENTAURUS User Manual, Synopsys, Mountain View, CA