Ring Contact Electrode Process for High Density Phase Change Random Access Memory

It is very important to maintain stable cell uniformity for reliable operation and wide sensing margin since the writing current is mainly governed by the bottom electrode contact (BEC) size which is especially sensitive to small process variation. In order to accomplish low writing current with uniform cell distribution, advanced storage module technology using ring type BEC was proposed. Using this, it was possible to achieve flat and uniform BEC, which results in a wide sensing margin and high manufacturability. Finally, we firstly fabricated advanced ring type contact structure and firstly evaluated based on high density 256 Mbytes phase change random access memory (PRAM) with small cell size technologies.