Toward Multiple-Bit-Per-Cell Memory Operation with Stable Resistance Levels in Phase Change Nanodevices
IEEE Transactions on Electron Devices, cilt.63, sa.8, ss.3103-3108, 2016 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 63 Sayı: 8
- Basım Tarihi: 2016
- Doi Numarası: 10.1109/ted.2016.2574498
- Dergi Adı: IEEE Transactions on Electron Devices
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Sayfa Sayıları: ss.3103-3108
- Anahtar Kelimeler: Multiple-bit-per-cell memory, phase change memory (PCM), resistance drift
- Boğaziçi Üniversitesi Adresli: Evet
Özet
Resistance drift of the amorphous states of multilevel phase change memory (PCM) cells is currently a great challenge for the commercial implementation of a reliable multiple-bit-per-cell memory technology. This paper reports observation of a stable intermediate state for a multilevel PCM cell that is achieved through nonuniform heating with a square current injection top electrode. Drift coefficient of the intermediate state is an order of magnitude lower than reset and has weaker temperature dependence. Using finite-element simulations and an analytical model for the subthreshold current-voltage characteristics, based on thermally activated hopping of charge carriers across Coulombic donor-like traps, we conclude that the defect density is two orders of magnitude larger in the intermediate state. We attribute the low drift coefficient of the intermediate state to a large number of stable interfacial defects which dominate the electron transport. Current findings give way to a more stable ultrahigh-density PCM device.