IQE's smooth approach increases carrier mobilities
IQE Silicon Compounds claims that its so-called "UltraSmooth" strained silicon epiwafers improve the performance of CMOS devices below the 100 nm node.
CMOS is a process technology that uses both NMOS and PMOS (negative- and positive-channel metal oxide semiconductor) devices. In recent years a significant improvement to NMOS device performance has resulted from using a strained active layer, but improving PMOS has proved more problematic.
According to IQE, although additional increases in strain should, in theory, improve PMOS device speed, in practice material defects increase and hamper both NMOS and PMOS performance.
IQE s alternative approach has been to develop a very low dislocation density strained silicon surface using what it describes as a "simple, cost-effective, single-stage epitaxial process".
Working with a silicon IC manufacturer, "significant performance enhancements" to both p-type and n-type devices have been demonstrated with strained silicon deposited on a SiGe buffer layer with a 17 percent germanium content, said IQE. Increases in the mobility of carriers in PMOS and NMOS devices were 15 percent and 100 percent, respectively, compared with standard silicon.
IQE claims that these performance enhancements resulting from its proprietary epiwafers have been confirmed by chip manufacturers in Europe, North America and the Far East.
The company also says that it has applied for patents covering all key processes for carrier enhancement through surface roughness reduction on all forms of silicon, including strained silicon-on-insulator.