Taking ReRAM cells to the next level

Photo: Nancy Rothstein

Photo: Nancy Rothstein

Australian company 4DS Memory has announced it has successfully developed and tested 40 nanometre (nm) interface switching resistive random access memory (ReRAM) cells.

This milestone is said to represent a digital memory cell size that is smaller than the current large scale volume production sizes of existing non-volatile memory technology, 3D NAND Flash (3D Flash).

Flash memory is the work horse of silicon storage, but with semiconductor manufacturers continuously working to make computer memory chips smaller and smaller, Flash memory has started to run into physical limitations – Flash memory can’t get any smaller without malfunctioning.

“We are proud of achieving this breakthrough development,” says Chief Executive Officer and Managing Director, Dr Guido Arnout. “4DS is an emerging memory technology leader with working Interface Switching ReRAM cells at 40nm, which is significantly smaller than the current volume production scale for 3D Flash memory of between 45nm and 50nm. It also represents the target cell size needed to prove the value of this leading technology to memory makers.”

4DS has been developing its patented Interface Switching ReRAM, also known as Non-Filamentary ReRAM, with Western Digital subsidiary HGST for the past two years under a joint development agreement (JDA). The JDA was renewed in July 2016 for a further 12 months and is focused on optimising scalability and cycling endurance of ReRAM cells for the mobile and cloud gigabyte silicon storage market.

The JDA, which has focused on the functional behaviour of memory cells at a small scale, has resulted in a significant improvement in the scalability of cells from 800nm, when the JDA commenced, to 40nm, achieving the geometries essential for creating long-term storage class memory (SCM).

Approximately US$12 million has been invested in research and development in the past decade representing a low cash burn rate for an emerging memory technology developer.
At the 2016 Flash Memory Summit in August in Santa Clara, California, Western Digital confirmed that 3D ReRAM is its memory technology of choice for SCM.

4DS’ ReRAM cells are constructed using a perovskite material, which has the same crystal structure as the inorganic compound calcium titanium oxide, and allows for the controlled movement of oxygen ions between electrodes. As the cells have no filaments they are inherently scalable and do not have the same physical limitations as Flash or Filamentary ReRAM.

The ability to scale down 4DS’ technology is vital for the creation of stacked ReRAMs into 3D structures, which are essential for mobile and cloud gigabyte SCM. SCM is required for high capacity data storage applications, such as cloud and data storage, which require low energy consumption and high endurance rates.

4DS’ technology is said to have advantages over traditional and other emerging non-volatile memory storage technologies. These advantages include scalability of cells, low power consumption and high endurance levels.

“The Flash memory market is valued at US$40 billion and is based on a 30-year-old memory technology with diminishing capacity to reliably scale down to meet the exponential growth of data demands globally,” says Arnout. “The amount of data created, replicated and consumed worldwide will reach 50 zettabytes in 2020 driving the increasing need for a SCM solution across diverse applications.

“The limitation of traditional data storage creates a multi-billion-dollar market for emerging, next generation memory developers…”

4DS’s near term goal is to meet key endurance performance milestones (terms of which can be found in Section 14.2 of the Prospectus dated 19 October 2015).

In order to validate and demonstrate commercial viability of a particular storage technology, all memory developers follow a specific development process.

During this multi-step process, memory cells are scaled down, then tested for cycling endurance, access speed and data retention – essential characteristics for a functional memory technology. The cell architecture and manufacturing process is continually being optimised to achieve the targeted goals for these metrics.

Through the JDA with HGST, 4DS is able to carry out this validation and demonstration without incurring the expense of fabricating fully functional 3D ReRAM prototypes.