Strategy of emerging alternative devices
The objective of the emerging alternative devices (EMERALD) program is to study multi-gate field-effect transistor (MUGFET) devices for 32nm and 22nm CMOS logic and dynamic random access memory (DRAM) applications. Thanks to the maturity of the project, the activities in 2007 could move from module development towards optimization of device performance for different applications: high performance and low-standby power logic devices, DRAM peri-transistors, electrostatic discharge (ESD), high-voltage devices. Besides, small (ring oscillators, static random access memory (SRAM), NOR, NAND, amplifiers, voltage-controlled oscillator (VCO), low-noise amplifier (LNA) and large (more than 10k transistors) circuit were demonstrated and characterized for circuit speed, density, power dissipation and compatibility with analog, ESD and RF requirements. In parallel to the silicon-on-insulator (SOI) FinFET device architecture a new bulk FinFET route mainly for DRAM applications was initiated.
One of the key challenges for the MuGFET devices is reducing the source and drain resistance and setting the required threshold voltage. This can be done only through work-function (WF) engineering in ultra-thin FiN devices. Both topics were addressed and thoroughly studied. Research on junction formation focused on damage-free extension formation using optimized implantation process or plasma doping and rapid thermal annealing, in the optimization of selective epitaxial growth (SEG) for raised source/drain area and on the optimization of the silicide process for minimal contact resistance and reduced gate-induced drain leakage (GIDL).
The compatibility of different WF engineering techniques developed within CMOSDR department (gate electrode material, implantation, capping, metal thickness) with high topology FinFET architectures was evaluated for high range high voltage threshold - low voltage threshold (HVT-LVT) CMOS process.