Recent innovations in DRAM manufacturing

Recent generations of Dynamic Random Access Memory (DRAM) have seen remarkable changes in both processes and the materials used. In the past five years the industry has gone from the 9x-nm node through the 7x, 6x, and 5x nodes to the 4x node chips starting to come on the market. In retrospect it is little short of amazing that the competing companies have crammed the required ~25 fF into an ever decreasing amount of floorspace; the cell size of the latest 4x-nm DRAM is ~0.0137 μm² - or maybe we should say ~13,700 nm². This has been achieved by the adoption of dual-layer capacitors, high-k dielectrics, and raised source/drains, among other techniques. Chipworks, as a supplier of competitive intelligence to the semiconductor and electronics industries, monitors the evolution of chip technologies as they come into commercial production. Chipworks has obtained parts from the leading edge manufacturers, and performed structural and compositional analyses to examine the features and manufacturing processes of the devices. This paper illustrates some of the different structures of DRAM cells seen in the last few years from some of the leading companies in the sector, ranging from the 9x-nm node to the latest 4x-nm product.