Sunday, January 15, 2017

Intermolecular enhances ferroelectricity in dopant-free ALD hafnium oxide

In a new paper published in Applied Physics Letters, Intermolecular discusses how it has developed a method for improving the ferroelectric properties of pure ALD hafnium oxide without introducing additional dopants. [Intermolecular, LinkedIn]
Ferroelectric hafnium oxide (HfO2) is being used in development for non-volatile memory applications, In front end by a ferroelectric MIS-FET and in backend by a MIM Capacitor integration. Since HfO2 is a standard material in both DRAM and Logic since 10 years or more the deposition method, tools an precursors for depositing ultra-thin layers by atomic layer deposition (ALD) are available and therefore very attractive choice as compared to more exotic materials (Sr, Ba) or previous PZT based ferroelectrics.

In previous studies, mixing hafnium and zirconium oxide together, doping the HfO2 with other elements, like silicon, aluminum, yttrium, strontium, lanthanum, and gadolinium, have been used to induce ferroelectricity in HfO2.
Now however, Intermolecular present new results (see below) were they by controlling the oxidant dose can promote ferroelectricity in dopant-free ALD hafnium oxide films. They were able to com near to total suppression of the monoclinic phase in sub-10 nm hafnium oxide films and obsreve a remanent polarization of 13.5 μC/cm2 in a 6.9 nm-thick hafnium oxide film. 
This is a similar high-k film thickness that is used in DRAM and embedded DRAM MIM Caps and also about the sam thickness that Globalfoundries, NaMLab and Fraunhofer have reported for their 28 nm FEFET NVM cells.