Novel Nanomaterials Growth for Low-Power Charge Trapping Nonvolatile Memory Devices

Abstract

Current charge trapping non-volatile memory devices are facing major scaling limitations due to problems such as short channel effects. As a result, the operating voltage of the memory and gate oxide stack are not scaling as desired. The introduction of new materials and structures is therefore imperative. The manipulation of matter at the nanoscale enables the generation of properties in a material that would otherwise be challenging or impossible to realize in the bulk state. In the first part of this dissertation, we demonstrate and explain the growth of zirconia (ZrO2) and zinc-oxide (ZnO) nano-islands using Atomic Layer Deposition (ALD) on different substrate terminations. The electronic, optical and structural characteristics of the islands are presented. The results show that the ZnO nano-islands size which is in the range of the Bohr radius of excitons lead to quantum confinement effects in the ZnO. In addition, a higher charge trapping density is found in the nano-islands than in a continuous layer, this is attributed to the traps created during the stress relaxation in the islands. In addition, the ZrO2 islands are found to have cubic-phase with high-κ of around 35. The use of such high-κ material in the charge trapping layer of the memory increases the injection field. In the second part, memory devices with ZnO and ZrO2 nano-islands charge trapping layer are demonstrated. The memory widow achieved at each programming voltage, the retention and endurance characteristics, and the charge emission mechanisms are discussed. With ZrO2 nano-islands, a large memory window of 4 V at a low programming voltage of 4 V is reported. In addition, the scalability of these memory devices with nano-islands is studied. Finally, alternative materials for the charge trapping layer are presented such as ultra-small ZnO nanoparticles, Si-nanoparticles, and graphene nanoplatelets along with a double layer of high-κ tunnel oxides; in addition, the electrical characterization of these devices is analyzed.

Date of Award	May 2017
Original language	American English
Supervisor	Ammar Nayfeh (Supervisor)