Tuning the Material for Good Memory

Identifying the right composition and thickness of hafnium oxide films for RRAM devices

8GB memory then & now: from floppy disks to microSD card (courtesy: image source)

Your handy pen drive is an example of how much information storage has evolved since the era of bulky magnetic hard disks. To make electronic memory even smaller, faster and more power-efficient at the nano-scale, new materials and technologies are being explored. Resistive random access memory (RRAM) is one such technology. RRAM devices often contain novel oxide materials such as aluminium doped hafnium oxide (HfxAl1-xOy). Prof. U. Ganguly’s team did a series of detailed experiments by varying the material thickness and Al concentration in HfxAl1-xOy. At the 2014 Materials Research Society’s Fall Meeting at Boston, USA, they shared their findings on the optimal values for stable RRAM memory devices.

RRAM devices are metal oxide structures that switch between two resistance states - high & low (also known as ‘SET & RESET’ OR ‘0 & 1’). Depending on the oxide material, device structure and fabrication technique, a wide variation is seen in their switching behaviour. Reducing this device variability, especially when fabricating on a large scale, is critical for RRAM technology to succeed. The team at IITBNF examined the effect of material composition and thickness on HfxAl1-xOy RRAM devices that were made using the combinatorial sputter technique. This technique is easily adaptable for large-scale manufacturing and can be used for precise material control.

They found that in both the cases - with and without Al doping, thinner (around 6 nanometers) hafnium oxide films demonstrated a greater difference between high & low resistance states. This translates to better memory windows in RRAM devices. Adding Al to hafnium oxide stabilized the low resistance state. For Al concentrations of 85% and 41%, devices exhibited the most stable SET and RESET behaviour, along with large memory windows. These results suggest that precise control on material composition can reduce variability in HfxAl1-xOy RRAM devices.

-Rajashree Nori

Work funded/supported by: Dept. of Science & Technology (DST) and Dept. of Electronics & Information Technology (DeIT) of Government of India (GoI); Applied Materials Inc.

Published paper: Pankaj Kumbhare, Paritosh Meihar, Senthilkumar Rajarathinam, Shikhar Chouhan, Suhit Pai, Neeraj Panwar and U. Ganguly, “A Comprehensive Study of Effect of Composition on Resistive Switching of HfxAl1-xOy based RRAM devices by Combinatorial Sputtering” MRS Proceedings, 1729, mrsf14-1729-m06-01 (2015).

Last updated on: 20-Jul-2022