Tuesday, August 22, 2017

Woah - Hafnium oxide as gate dielectric scales also in the 2D world

Hafnium oxide high-k dielectrics deposited by atomic layer deposition have been used in DRAM since 2004 (Samsung 90 nm) and 2007 in high performance CMOS logic (Intel 45 nm). Later the DRAM high-k dielectric was replaced by a zirconium oxide based material but for logic hafnium oxide has remained the material of choice for the high-k metal gate stack by toping off the native oxide of silicon with its higher k-value. Hafnium oxide even survived the transition to narrow 3D FinFET devices and is also the main contender for silicon based Nano Wire FETs. However, recent research in alternative 2D channel materials such as graphene, molybdenum disulfide and others has created a totally new situation where hafnium oxide finds it difficult to compete as the material of choice for the gate stack dielectric. 

Until now that is, because just recently some clever researchers at Stanford has presented an new all hafnium channel and dielectric combo using hafnium diselenide and the natural native oxide of that - ta da - hafnium oxide. Apparently the zirconium version is also brought into play but let us see about that...

You can read all about it in this online article published by Stanford, which also leads you to the original scientific references and journal publications.

New ultrathin semiconductor materials exceed some of silicon’s ‘secret’ powers, Stanford engineers find

The next generation of feature-filled and energy-efficient electronics will require computer chips just a few atoms thick. For all its positive attributes, trusty silicon can’t take us to these ultrathin extremes.

Now, electrical engineers at Stanford have identified two semiconductors – hafnium diselenide and zirconium diselenide – that share or even exceed some of silicon’s desirable traits, starting with the fact that all three materials can “rust.”

TEM cross-section of an experimental chip, the bands of black and white reveal alternating layers of hafnium diselenide – an ultrathin semiconductor material – and the hafnium dioxide insulator. (Image credit: Michal Mleczko)