Data storage on edge devices need robust and increasingly powerful memory chips. Flash has been a proven solution for many years. But new technologies and materials offer the promise of even faster and more durable memories.
Suitable data memories are also needed for processing data on edge devices. But the memory chips must overcome particular challenges when it comes to storing the data on the devices.
First of all, they need to offer a combination of low cost and high performance. In addition, the storage media should be energy-efficient so that they can also be used in battery-powered devices. Edge devices must be able to withstand lower and also higher temperatures than is necessary with typical PC applications. They have to be impervious to vibrations and shocks too when used in mobile devices. Classic hard disk drives (HDD) are too sensitive in this regard – and also too large for most edge applications.
Flash is proven but pushed to its limits
Flash memories, as familiar from USB flash drives for example, have already proven their worth. These are semiconductor memories in which information (bits) is stored in a memory cell in the form of electrical charges. Whilst flash memories are still somewhat more expensive per gigabyte, they do offer considerably faster data processing processes than HDDs. The read/write speeds that can be achieved in a flash memory are four times higher than those with HDDs. Moreover, they offer a higher density. Thus saving space and weight, and are less susceptible to errors owing to the lack of moving parts.
The development of flash memories has focused in recent years on reducing the size of the cells. And therefore increasing the data density. However, a physical limit has already been reached here with the present-day nanometre structures. And the lifetime and reliability of the memories is suffering as a result. 3D-NAND memories represent one solution. These are memories where – in simple terms – the planar memory cells are stacked vertically in multiple layers. Because of the shorter connections between the memory cells, the storage capacity and storage speed can be increased. And the power consumption reduced, too.
“To respond to the impressive demand for higher storage capacity and reliability while lowering cost per bit, 3D-NAND manufacturers implement innovative techniques”, explains Belinda Dube, Cost Analyst at System Plus Consulting. “They change the storage type, the memory cell design and stack more layers with each generation to increase bit density and hence reduce the die size. The technological changes in the cell architecture and modification of the fundamental memory functions add complexity to the manufacturing process. However these techniques do lower the cost per gigabyte.”
Data storage in the future
Even the current 3D-NAND memories are increasingly reaching their limits. However, as applications become more complex, as the flood of data continues to grow and demands intensify rapidly.
“Data-storage technology has reached a scaling limit. We need new concepts in order to store the data volumes we will produce in the future”, explains Peter Zalden, Scientist at the European XFEL. XFEL operates the largest x-ray laser in the world. Together with researchers from the University of Duisburg-Essen, Zalden used this laser to investigate how data storage could become better and more efficient with new phase-change materials.
Phase-change memories store data by changing the aggregate state of the bits between liquid, vitreous and crystalline. An electromagnetic field, heat or light pulses switch back and forth between the phases. These two different states correspond to the 0 and 1 in binary code. Corresponding memories have the potential to be a thousand times faster and significantly more durable than existing flash memory chips and could allow future generations of smartphones to offer a higher storage density and greater energy efficiency.
Another promising technology is based on magnetic memories. Spin is used in this case, which is the intrinsic angular momentum of the particle. “The spin is closely related to magnetism. It can be impacted by magnetic fields”, says Dr. Viktor Sverdlov from the Institute for Microelectronics at the Vienna University of Technology. “In the same way that information can be stored by applying different electrical charge at specific points, information can also be stored by ensuring different spin at specific points.”
In contrast to flash memories, such memories can be written any number of times and allow very short write and read access times. However, these new storage technologies are still too expensive to be used on a mass scale in edge devices.