The first DRAM-Patent was granted on June 4, 1968. DRAM’s 55th anniversary is an ideal opportunity to review its evolution and take a look at its future. It took a couple of years from the filing of the patent to the first DRAM memory which was introduced in October 1970 with the Intel 1103 that had a capacity of 1024 bits * 1 (bus width). But once it took off, DRAM evolved continuously and more and more rapidly.
Let’s look at the progress of DRAM since its first introduction:
- Capacity has reached up to 32 Gb, which means an improvement by a factor of 32 million.
- The cell (1 transistor and 1 capacitor) stayed the same, but technology moved from 8µm process to sub-20nm. Leading manufacturers recently unveiled the fifth generation 10nm-class DRAM that the three leading manufacturers refer to as “1b” generation.
- This improvement in patterning was combined with architectural changes. For the DRAM cell, the move from 8F2 to 6 F2 (F= minimum feature size) was the most important for a long time as it arranged capacitors and transistors in a 3-dimensional structure.
- Performance increased tremendously. Burst rate (data access) has improved by a factor of 100 from 60ns 1979 to 0,06 ns in future DDR6. Overall bandwidth scaled with 4800 MT/s today and up to 8800 MT/s tomorrow (MegaTransfers/sec, data transfer rate).
- High bandwidth memories provide significant progress based on a standardized stacked memory technology, that provides wide channels for data, both within the stack and between the memory and logic. At the same time, power consumption was reduced significantly (e.g. 15% from one generation to the next), although the principle of refreshing the charge in capacitors has remained.
While DRAM technology continues to scale and improve in performance, new technologies try to challenge its position in the sector of memories with fast access time.
- Emerging Memories currently under development are Magneto-resistive, Phase-change, Thermochemical RRAM, CBRAM, Charge-based RRAM, and Ferroelectric RAM. Except for the ferroelectric memories all are resistance based, a change in resistance is used for storage of information.
- NEO Semiconductor published a 3D X-DRAM: It is a first-of-its-kind 3D NAND-like DRAM cell array structure based on capacitor-less floating body cell technology, see more details here.
- 3D DRAM is in intensive discussion as in this approach, word lines and bit lines are stacked, but the capacitor is shifted to the side, extending in a horizontal direction.
The evolution from 2D to 3D architecture has boosted the development of NAND Flash and if 3D architectures can be realized in DRAM, it will improve speed significantly.
However, traditional DRAM technology that is based on 1 transistor and 1 capacitor still provides excellent endurance at low costs and thus it will remain the workhorse in many areas of computing. Nevertheless, new types of memory may be introduced in the future that even might drive a change in memory hierarchy.
While DRAM continues its progress in cost and performance, the know-how of the technologies used and the testing of devices to ensure their fit to customer needs will be crucial. This is the strength of Memphis. As a specialist memory distributor with over 18 different memory manufacturers, its experts know memory and can advise on the memory that is best suited for a specific application. Memphis even configures DRAM modules specifically for customer applications if no matching product is available. Reach out!
