April 26, 2005 – Using a selected set of tools and processes, SEMATECH engineers have achieved twin breakthroughs in channel mobility and reliability of high-k/metal gate transistors, putting high-k technology for CMOS within reach at the 45nm technology node.
The SEMATECH advance involves a titanium nitride (TiN) metal gate on a hafnium silicate (HfSiO) dielectric with an equivalent oxide thickness (EOT) of roughly 10 angstroms, with mobility at 90% of the universal mobility curve for silicon dioxide (SiO2), the historic gate dielectric material. These EOT and mobility metrics meet the 45nm technology node specifications listed by the International Technology Roadmap for Semiconductors (ITRS).
The achievement caps a lengthy effort within SEMATECH’s Front End Processes Division, and is part of a program to fully enable the eventual introduction of high-k/metal gate technology in volume manufacturing. The process is not expected to add significant cost to current CMOS product flows.
“SEMATECH’s high-k process represents a significant step in the search for a complete solution to planar CMOS at the 45nm node and beyond,” said Byoung Hun Lee, manager of the Advanced Gate Stack Program. “We are also working to produce a dual metal gate that can work with this process. Plus, these breakthroughs have applications for specialty architectures, such as FinFETs or fully depleted SOI devices.”
In explaining the significance of the SEMATECH process, Lee said that new materials and techniques must be found for transistors as their sizes decrease into the deep sub-100 nm regime. One of the serious challenges the industry faces is developing new gate dielectric materials. For decades, SiO2 was a reliable dielectric, but as transistors have continued to shrink, its reliability is reaching its physical limits, while the technical challenges of using that dielectric are increasing rapidly.
One solution is to use other materials, such as hafnium-based metal oxides, for gate dielectrics. These high-k materials, so-called because of their high dielectric constant (k), can be made much thicker than SiO2 while achieving the same gate capacitance — the ability to turn a gate on and off, allowing it to process data. SEMATECH has aggressively pursued the high-k option for the past eight years, in broad collaboration with several universities and equipment suppliers to identify materials and processes in time to meet member company and industry manufacturing needs.