DRAM, or Dynamic Random Access Memory, ruled the memory market for years. But that is changing with the new generation of memory technologies. This is why the market size of these technologies is expected to hit USD 38.34 Billion by 2033.
The major problem with DRAM is that the data is stored in a capacitor in this memory technology. The word “Dynamic” in its name is because the stored information is susceptible to fading unless the charge of the capacitors in DRAM is refreshed periodically.
The new memory technologies, on the other hand, are much faster than DRAM and can keep data even without being refreshed. Let’s explore memory technologies beyond DRAM and examine their various advantages.
Phase-Change Memory (PCM)
The Phase-Change Memory technology, which is also called Phase-Change RAM or PRAM is made up of a material that is either crystalline or amorphous at normal ambient temperatures. The amorphous state comes with high resistance, while the crystalline state has low resistance.
Current is passed through the bit cell and then allowed to cool at different rates to control the resistance. In physics or chemistry, if something has an amorphous structure, it is said to be in a liquid or gaseous state. Similarly, anything having a crystalline structure is said to be in a solid state. The three states, solid, liquid, and gaseous, are also called “Phases.”
This is where the name of Phase-Change Memory comes from because the bit cell used in it switches between the amorphous and crystalline phases. Phase-change memory is generally based on chalcogenide glasses, however, other materials have also been experimented with PCM.
One of the advantages of Phase-Change Memory that makes it stand out is that it can be selected using a 2-terminal diode because the current runs in the same direction regardless of whether the PCM is setting a bit, resetting it, or reading it. Therefore, it does not need a bidirectional device to work.
Magnetoresistive Random Access Memory (MRAM)
Another RAM in the list of next-generation memory ICs is called Magnetoresistive RAM or MRAM. The phenomenon of giant magnetoresistance (GMR) is used in the MRAM technology. The GMR phenomenon has been used since the early 1990s for HDD recording heads.
If, in a multi-layered GMR stack, a set of layers is magnetized, the other layers show low resistance. Similarly, if the magnetization is done in the opposite direction, the resistance of remaining layers increases. There are two ways to create magnetization: either by passing a forward and reverse current through the bit cell or by creating fields around a wire.
The former is used in Toggle Mode MRAM, while the Spin-Tunnel Torque or STT MRAM uses the latter method of magnetization. Several variants of STT MRAM have been produced over the years, including Spin-Orbit Torque or SOT RAM, Processional Spin Torque RAM, and Perpendicular STT RAM.
Up until now, a three-terminal selector has been used in all MRAM devices; however, this might change soon as new research points to the possibility of using two-terminal selectors in MRAM.
Ferroelectric RAM (FRAM)
This new memory technology is superior to DRAM because it does not use iron. Also known as FeRAM, the behavior of the ferroelectric memory technology is similar to that of iron when it is magnetized and demagnetized. Atoms with the FRAM cell are arranged to shift to one end of a molecule when a current is passed in a certain direction.
Similarly, when the current is reversed, the atoms shift to the opposite end. A destructive read mechanism is used in the modern production of FRAMs. This mechanism applies a write voltage to the cell. The movement of atoms determines the flow of the current. When an atom moves from one end of the cell to the other end, the current flows.
However, if the atom is already at the end of the end, which is in an erased state then there is no flow of current. Sometimes, the atom can also move because of the read operation. In such a situation, the atom must be restored to its original location after the read operation is completed.
Research studies have shown that hafnium oxide can also be used to make FRAMs. This material is already being used in semiconductor fabs. This gives Ferroelectric RAMs a decided advantage over DRAM. However, there is a downside with FRAMs as well, that is, they use three-terminal selectors.
Resistive RAM (ReRAM)
Resistive RAM, or ReRAM, is another next-generation memory technology after DRAM. Also known as RRAM and Memristor, any memory that uses a resistive memory element is referred to as ReRAM. This memory technology uses a bit set/reset mechanism that allows atoms to move around within the device by creating or eliminating either metal filaments or oxygen vacancies.
Both forward and reverse currents are used in the process, which makes it easier to use three-terminal selectors instead of two-terminal selectors. However, certain resistive RAMs work efficiently with two-terminal selectors, and a few variants can even use the bit cell itself to perform the selection.
This ability makes such ReRAMs economical to make when they are used in a single plane. And to further reduce the manufacturing cost, they can be constructed in multiple planes as well.
Most of the time, resistive random access memory technologies use new materials for their manufacturing; however, some ReRAM technologies are also capable of using materials that are already being used in chip production.
Conclusion
Although DRAM technology has a simple structure as compared to the newer memory technologies, it falls short in many aspects. The next generation of RAM technologies is bringing in a revolution in the world of memory ICs.
Whether it’s MRAM, FRAM, or PCM, these new technologies come with a number of advantages, such as using two-terminal selectors, which make them a preferable choice over DRAM.
When it comes to a reliable platform from which to purchase memory ICs, there are hardly any options that come close to Partstack, which is the fastest-growing marketplace for buying, selling, and discovering new electronic parts.
