Phase change memory (PCM) is an advanced type of non-volatile memory technology or computer storage recently sold in a computer system as a storage-class memory.
It is faster than the Flash Memory popularly used and stores data by changing the physical state of the material used in the memory cell.
Phase-change memory uses the special property of a material called chalcogenide glass which is composed of elements from the chalcogen group (such as sulfur, selenium, and tellurium) and shifts through the passing of current that generates heat when it travels through a cell into two stable phases, crystalline and amorphous.
Although this physics-related device has been widely studied since its discovery in the 1960s, there are still several open and unanswered questions relating to its electrical, thermal, and structural dynamics as well as its characterisation
In this article, I will be sharing what the current understanding is about PCM devices while considering several factors, including the advantages and limitations.
Phase-Change Memory as a form of RRAM
RRAM stands for Resistive Random Access Memory. It is a non-volatile memory technology type that stores data by changing the physical state of the resistance of a material.
A non-volatile memory is one that retains data even when the power supply has been removed. This makes them suitable for use in storage devices, embedded systems, and advanced computing technologies.
The fundamental principle behind the working of RRAM involves the use of a “resistive switching material,”. This material consists of metal oxides or chalcogenides, and these chalcogenides change their resistance according to the applied voltage.
The said resistance can be adjusted between two distinct states, representing binary values; “0” and “1” in a digital data storage system.
RRAM operates based on two resistive states, which are the High Resistance State (HRS) and Low Resistance State (LRS) states. The HRS is represented with the binary value “0” while the LRS is represented with the binary value “1”.
Electric current flows more freely through a material in a High Resistance State than it does in a Low Resistance state.
When sufficient voltage or current pulse is applied to the RRAM, it causes the material to undergo a physical change, forming or dissolving conductive paths (filaments) within the resistive material.
This results in a switch between the HRS and LRS. The filaments formed in this process store the data and determine the resistance state of the cell.
RRAM’s promising characteristic is what makes it qualified enough to be researched and developed for various applications, including phase-change memory devices.
Advantages of Phase-Change Memory
Here are some of the key benefits that phase-change memory technology offers over traditional memory technologies like DRAM (Dynamic Random-Access Memory).
Non-Volatility
PCM’s non-volatility makes it possible for it to retain data even when power is removed from it.
This gives it an advantage over other memory technologies that are volatile and require constant power to maintain data integrity.
The non-volatile nature of PCM makes it suitable for use in applications such as solid-state drives (SSDs) where persistent data storage is required, which requires fast and persistent data storage.
Faster Read and Write Operations
Phase-change memory offers relatively speedy read and write operations compared to other flash memory devices by changing the physical state of the memory cells, which, in turn, provides quicker access times and reduces delay.
High Endurance
PCM can endure a high number of read and write cycles without degrading its performance compared to other flash memory devices.
PCM can withstand a large number of write cycles before degradation occurs. This factor makes PCM ideal for applications where memory longevity is required.
Lower Power Consumption
PCM consumes less power compared to other traditional memory technologies.
The lower write energy requirements and high programming voltages it employs make it much more energy-efficient.
Scalability
PCM can be scaled down to smaller feature sizes as it has the capability for high-density memory solutions on a small chip.
This allows PCM to have an increased storage capacity and gives room for performance improvements in future PCM implementations.
Disadvantages of Phase-Change Memory
Despite all these advantages listed above, phase-change memory is still very much an emerging technology and still has a number of challenges to overcome.
Endurance Limit
Although PCM has higher endurance compared to other flash memory technologies, frequent and intensive write operations could lead to an equally rapid reduction in the lifespan of the memory.
It has a finite number of write cycles it can make before it starts to degrade. When it reaches its limit, it can cause reduced write endurance and increased error rates.
Higher Cost
PCM is expensive and has a higher cost compared to its traditional memory technologies counterparts. This can be a significant barrier to its popularity and influence in the marketplace
It has been quite difficult for it to scale down to smaller feature sizes for consumer devices while maintaining a low cost.
Lower Density
While PCM has the potential for high-density memory solutions, its memory cell size is larger compared to other flash memory technologies, which limits its storage density.
What this means is that PCM may not be the best option to consider when looking for a high-capacity storage device.
Temperature Sensitivity
While PCM is more temperature-resistant compared to other memory technologies, its switching performance and reliability can still be influenced by temperature fluctuations.
This error can potentially cause data corruption, and this is why it is necessary to consider temperature management, especially in extreme conditions.
Despite these disadvantages, however, phase change memory still offers a certain degree of success, an exciting area of research and development, and a substantial investment to major suppliers.
These further benefits and promises lead to more improvements and wider adoption of it.
Phase-change memory (PCM) is a type of non-volatile memory technology that has the potential to offer several incomparable benefits over traditional memory technology devices.
Despite the fact that widespread commercial adoption has been relatively slow because of the price and other factors, it is still expected to become one of the future standard semiconductor memory formats.
There is a high possibility of PCM gaining ground as the most known memory format in the market once perfected.
