According to semiconductor analysis firm SemiAnalysis, China's memory maker CXMT has new DRAM chips and fabrication nodes that blatantly violate U.S. export rules. At the recent IEDM conference, China-based ChangXin Memory Technologies (CXMT) introduced its first dynamic random access memory (DRAM) made using its 18nm half-pitch process technology featuring gate-all-around (GAA) transistors.
DRAM makers have been striving to achieve a 4F^2 cell design for years. It is considered a very efficient memory cell layout in DRAM circuits, enabling makers to build high-capacity chips cheaply. The key feature of a 4F^2 cell design is that it occupies an area only four times the square of the minimum feature size of the fabrication technology used, which requires very advanced process technology (and wafer fab tools). Now, CXMT claims that it has managed to fabricate a fully functional 3D DRAM with vertical channel transistors and 4F^2 cell design on a 18nm half-pitch node using fab equipment it currently has.
"We have successfully fabricated the junction-less GAA VCT combined with a hexagonal capacitor to realize a compact 4F^2 DRAM architecture," a description of the fabrication technology by CXMT reads. "It shows the breakthroughs of /on//of>10^9 and SS=62.5 mV/dec. We also elaborated on various key process issues and device parameters and how they impact on performance."
Meanwhile, China export rules imposed last year require U.S. companies and individuals to obtain licenses for selling fab tools and technologies that can be used to produce DRAM chips with a half-pitch of 18nm or less, non-planar transistor logic chips on 14nm/16nm nodes (and smaller), and 3D NAND with 128 layers or more.
Now that CXMT has officially introduced its 18nm DRAMs with GAA transistors, it means that Applied Materials, KLA, Lam Research, and other U.S.-based makers of wafer fab equipment can no longer ship tools to the fab at which CXMT produced these ICs, reports SemiAnalysis. Having successfully secured funds from the government, CXMT is reportedly planning to spend $7 billion on equipment this year, with $3.8 billion going to U.S.-based companies.
A 4F^2 DRAM cell design may not be the most optimal for an 18nm half-pitch process technology, and we can only wonder whether CXMT is indeed going to use this technology for mass production. However, its technological prowess seems to be undisputed.
