What Is Phase-Change Memory?

Phase change memory, referred to as PCM for short, phase change memory uses the difference in conductivity between special materials between crystalline and amorphous states to store data. A phase change memory is generally an information storage device that uses chalcogen compounds to store data using a large difference in conductivity between crystalline and amorphous states.

In recent years, non-volatile storage technology has made some significant progress in many aspects, which has brought new opportunities for the improvement of storage energy efficiency of computer systems. Adapt to the development of computer technology for high storage energy efficiency. Many new NVM technologies represented by phase change memory have attracted widespread attention from researchers at home and abroad due to their high integration and low power consumption. In particular, PCRAM has the potential of being both main memory and external memory because of its non-volatile, byte-addressable characteristics. Under its influence, the boundary between main memory and external memory is gradually becoming Vagueness may even bring major changes to the future storage architecture. Therefore, it is considered to be a promising new type that is most likely to completely replace DRAM.

From the 1950s to the 1960s, Dr. Stanford Ovshinsky began to study the properties of amorphous substances. Amorphous substances are a class of substances that do not exhibit a defined, ordered crystalline structure. In 1968, he discovered that certain glasses had reversible resistivity changes when they changed phases. In 1969, he discovered that the reflectivity of laser light in optical storage media would change in response. In 1970, he co-founded the Energy Conversion Device (ECD) company with his wife, Dr. Iris Ovshinsky, and released

The typical structure of a PCM device consists of a top electrode, a crystalline GST, an / crystalline GST [, a thermal insulator, a resistor (heater), and a bottom electrode.

Phase change memory (PCM) is a non-volatile storage device that uses reversible phase changes in materials to store information. The same substance can exist in states such as solid, liquid, gas, condensate, and plasma, and these states are called phases. Phase change memories work by using special materials with different resistances between different phases.

In the amorphous state,

Phase-change memory materials have the advantages of fast access speed and high reliability. They have wider application space and better development trends than other memories. Electrical storage's flash memory technology, such as the continuous electrical storage DRAM technology used in computer memory and so on. Although people have gradually realized the superiority of the new storage technology, how to apply it in practice varies.

From the current research, we can see that phase change memory can be mainly used to replace computer main memory, hard disk and flash memory:

Phase-change memory access time is short, and it has byte addressability. Its write latency is about 10 times that of DRAM, which makes him show an advantage in the direct execution of firmware code in the design reference, and has been widely used as The replacement of DRAM. The traditional method of DRAM is to lose all the data in the main memory after the computer is powered off. The computer restart needs to read the operating system data from the external memory again, which consumes more time. Some researchers previously used NOR flash memory. As the main memory, it can solve the problem of data loss when the computer is powered off. However, flash memory has the disadvantages of limited erasing and erasing, poor random write performance, and large write latency. Phase change memory or heterogeneous main memory based on phase change memory is used. Methods can better solve the above problems;

The random read and write performance of phase change memory can effectively solve the I / O bottleneck caused by small-granularity random I / O to disk access in large-scale scientific computing. Using phase change memory to replace traditional hard disks has great advantages;

Both flash memory and phase-change memory are new non-volatile memories. They have no mechanical device and can be read and written randomly. However, compared with phase-change memory, the read-write performance of flash memory is slightly insufficient, especially the entire block needs to be erased before writing. Defects caused by flash memory can only replace some functions of the storage system through a series of more complicated technicalization.

There are many other applications of phase change memory, suitable for fixed line and wireless communication equipment, consumer electronics, PC and other embedded applications: for example, embedded systems used in the spacecraft field, smart meters can be used for Its storage framework is further integrated. In addition, according to some shortcomings of phase change memory, further research is needed to improve storage density, reduce cost and improve write resistance, so as to better promote the application and development of phase change memory. ^[2]