Examination Committee

Prof Philip MOK, ECE/HKUST (Chairperson)
Prof Mansun CHAN, ECE/HKUST (Thesis Supervisor)
Prof Andrew POON, ECE/HKUST

Abstract

Phase change memory (PCM) is a promising resistive non-volatile memory for its fast writing and reading speed, highly scalable properties and long endurance. Phase change memory (PCM) formed by Ge2Sb2Te5 (GST) on CMOS compatible vertical carbon nanotube (CNT) filled contact plug is demonstrated in this work. The CNT electrode is developed from the CMOS compactible CNT via technology.

In order to achieve CMOS compatibility, the CNTs were synthesized using Ni/Al/Ni multilayer catalyst at a low temperature (450 ℃). To prepared CNTs for PCM electrode, the CNTs were selectively grown inside the via hole. And dielectric filling and polishing process is done to and fill the gap between the CNTs and enhance the strength of the electrode for PCM application.

Then GST material was integrated with the CNTs filled via to form the PCM cell. Reasonable contact characteristics between the CNTs and GST is achieved without material compatibility problem. Due to the small contact size of the CNT to the phase change material, a significant reduction in programming power is achieved compared to metal contact at the same via size. The temperature simulation result shows that the CNT filled via helps to reduce the programing area. The fabricated PCM on CNT filled via is able to endure more than 104 SET/RESET cycles without observable degradation.

To meet the high demands for high densely packed cross section array for the PCM, it is important is integrate the PCM cell with the selective driving devices. And CNT-PCM integrated on the silicon p-n diode is demonstrated in this thesis.