Samsung Electronics ships first 3D `VNAND’ in the world
2013/08/07 By Oh Eun-ji
english.etnews.com 
Figure <3D stacked NAND flash `VNAND’>
Samsung Electronics succeeded in producing the 3D stacked vertical NAND flash memory `VNAND’ for the first time in the world. If we have improved performance and capacity by increasing densities with nano process technology until now, now we are heralding a changeover in the semiconductor production technology toward cell stacking. As the extreme ultraviolet (EUV) lithography, the core equipment of the nano process, is not necessary anymore, densities can be raised while reducing the burden of capital investment.
On August 6, Samsung Electronics announced that it began to mass produce 3D vertical NAND `3D VNAND’ flash memory. This product has the largest capacity in the memory industry, 128Gb. Cell density has been doubled than before, and the write speed is not two times faster. The read speed is slightly improved, and its power consumption is halved as compared to the NAND flash with the same data capacity.
Samsung Electronics applied its own technology, i.e. the 3D cylindrical CTF (Charge Trap Flash) cell structure. In the existing Floating Gate structure, the floating gate for storing electric charges between the control gate for electrons in the transistor and the silicon wafer. CTF reduced cell-to-cell interference by inserting insulators between the control gate and silicon. The transistor looks like a cylinder with the center empty. If these cylindrical cells are stacked in 24 layers, and a vertical hole is made in the middle, and electrodes are formed, data will be stored while electrons will move through the hole.
Pilot production will be used mostly for data centers or servers that require a high level of reliability. The controller technology will be further improved, and applied to the smartphone and smartpad market. It is also forecast that the next-generation eMMC6.0 standard, which has been slowly developed since built-in NAND (eMMC) 5.0, will be quickly commercialized. Choi Jeong-Hyuk, Samsung's senior vice president, said “in 5 years, it will be possible to implement 1 terabit (Tb) with one chip.
Samsung Electronics is planning to begin mass production at line #16 in the Hwaseong Plant, and in the Xian Plant, China next year. Domestic NAND flash lines will be gradually converted to the VNAND process.
?Eye of the news
Mass production of the 3D stacked NAND flash memory is significant in that it overcame the limits in memory densities. Core processes change. If lithography, which draws fine circuits, has been the core of the memory process, now the hole equipment and process technology for making a vertical hole have become important.
This success completely changed the paradigm in semiconductor process technology. Until now, who will first produce the product with circuits drawn on the wafer die of the same size has been the key. From now on, how many layers you can stack on a single die will be the most important. “Now, line width has become meaningless,” said Mr. Choi Jeong-hyeok. “Theoretically, there is no limitation to the number of layers you can stack.”
As processes smaller than 10nano will not be necessary, the EUV lithography, way more expensive than KRW100 billion, is not needed anymore. Immersion lithography, using the existing reliable Argon Fluoride (ArF) 193? light source, is sufficient. Instead, demands for the dry etching equipment for making hundreds of millions of holes and processes will increase. The EUV lithography technology is developed only by Dutch ASML. Dry etching is a technology owned by US-based Advanced Materials, Tokyo Electron, RAM Research and other domestic equipment makers.
In the future, it seems that memory will develop along two paths: next-generation memories replacing DRAM, such as STT-M RAM, and NAND flash stacking technology. The stacking method is not appropriate for volatile DRAM as electrons move from hole to hole with data. Competitors like SK Hynix, Toshiba and Micron are expected to start mass production of 3D NAND earlier than originally planned. Toshiba said it would start mass production at the end of next year, while SK Hynix said it would begin mass production in 2015.
Oh Eun-ji | onz@etnews.com |
