Researchers from the University of Linköping University received a patent for the technology of improved metalling holes in the production of multi -layer memory, in particular 3D NAND. Thanks to their development, filling holes with the material will occur evenly throughout the depth, which will also increase the density of their location and, therefore, the number of memory cells created around them in each layer of the chip ..
Image source: Linköping University
Scientists clearly explain the relevance and scale of the problem on the example of the highest building in the world-the 828-meter skyscraper of the Burge-Halphus in Dubai. If we take into account that the ratio of the diameter of the hole for metallization in multi-layer memory to its depth is 1: 100 (diameter-100 nm, depth-10,000 nm), then the base of the burgit-halif on a similar scale should be only 8 meters. In practice, it is 191 meter, but the complexity of the task is understandable – it is necessary to fill out an extremely deep hole evenly along the entire length, since in each place of its contact with the next layer a memory cell is created, and marriage is not allowed here.
The easiest way to achieve uniform filling of the openings by the material was to reduce the temperature at the time of its deposition in the steam phase, which could lead to marriage. However, Finnish scientists proposed a different approach: at this (initial) stage they added a heavy neutral gas of xenon on Wednesday. It is reported that the result exceeded expectation. Thanks to Xenon, it was not necessary to reduce the temperature, and its heavy molecules helped to evenly fill the holes with the material to their bottom. This is the obvious potential for a further increase in the density of memory cells.
«We still do not know how it actually works. We believe that gaseous xenon helps to “push” the molecules into the hole. It was the ingenious course of my graduate student Arun Haridas Chulalakkal. He studied some basic formulas of gases and put forward a hypothesis that this should work. Together we conducted a number of experiments to check it, and it really worked, ”said the project manager Henrik Pedersen.
The developers received a patent for their opening in Finland and sold it to one of the local companies, which has already begun to obtain international patents.