Dong-won Lim

Full Integration of Highly Manufacturable 512Mb PRAM based on 90nm Technology

Fully functional 512Mb PRAM with 0.047mum2 (5.8F2) cell size was successfully fabricated using 90nm diode technology in which the authors developed novel process schemes such as vertical diode as cell switch, self-aligned bottom electrode contact scheme, and line-type Ge2Sb2Te5. The 512Mb PRAM showed excellent electrical properties of sufficiently large on-current and stable phase transition behavior. The reliability of the 512Mb chip was also evaluated as a write-endurance over 1E5 cycles and a data retention time over 10 years at 85degC

Highly Reliable 256Mb PRAM with Advanced Ring Contact Technology and Novel Encapsulating Technology

Advanced ring type technology and encapsulating scheme were developed to fabricate highly manufacturable and reliable 256Mb PRAM. Very uniform BEC area was prepared by the advanced ring type technology in which core dielectrics were optimized for cell contact CMP process. In addition, relatively high set resistance was stabilized from encapsulating Ge2Sb2Te5 (GST) stack with blocking layers, thus giving rise to a wide sensing window. These advanced ring type and encapsulating technologies can provide great potentials of developing high density 512Mb PRAM and beyond

Novel Heat Dissipating Cell Scheme for Improving a Reset Distribution in a 512M Phase-change Random Access Memory (PRAM)

Programming with larger current than optimized one is often preferable to ensure a good resistance distribution of high-resistive reset state in high-density phase-change random access memories because it is very effective to increase the resistance of cells to a target value. In this paper, we firstly report that this larger current writing may conversely degrade the reset distribution by reducing the resistance of normal cells via the partial crystallization of amorphous Ge2Sb2Te5 and this degradation can be suppressed by designing a novel cell structure with a heat dissipating layer.

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.

Full Integration of Highly Reliable Phase Change Memory With Advanced Ring Type Bottom Electrode Contact

ABSTRACT We successfully developed 256Mb Phase Change Random Access Memory (PRAM) based on 0.10μ m-CMOS technologies using ring type contact. The writing current with uniform CD process variation of Bottom Electrode Contact (BEC) was achieved by improving CMP process and developing core dielectric material. Also, the ring type contact scheme provided strong reliability such as the cycling endurance and data retention time for 256 Mb high density PRAM.