Fabrication of NiO Resistance Switching Device and Analysis of Its Electric Characteristics
|School||Tianjin University of Technology|
|Course||Microelectronics and Solid State Electronics|
|Keywords||NiO RRAM Conductive Filament Low Power Consumption|
With the development of electronic product, people wish to pursue super portable, low power consumption, high writing/reading speed and high density memory device. While the typical size becomes from 32nm to 22nm, the Flash memory will meet its physical limitation. Because of this, the manufacture calls for a new technology to satisfy the development of the memory. The Resistance Random Access Memory (RRAM) is widely investigated by researchers in the world for its simple structure, perfect performance, low cost and compatibility with modern semi-conductive procedure. In this dissertation, it starts with the problem of the RRAM at present, using PVD through changing oxygen partial pressure, film thickness, the type of the electrode and electrode thickness to investigate the mechanism of the resistance switching and improve the electric performance of the NiO thin film (such as Reset/Set Voltage) with XRD, AFM and Semiconductor Parameter Analysis. The conclusion is as follows:(1) The change of the oxygen partial pressure from 5% to 15% in the procedure has great influence on the crystalline orientation, deposition speed and surface roughness of the films. It is found that the crystalline orientation of the films becomes from (200) to (220), the deposition speed and surface roughness of the films decrease with the increasing of the oxygen partial pressure. But under the 10% oxygen partial pressure, surface roughness of the films are highest, because the intensity of the (200) and (220) crystalline orientation are comparable.(2) The top electrode of Cu has lower power consumption than that of W and Ni etc., because only the electric filed is needed to push Cu ion formed by redox moving in the films to form the conductive filaments. But for the top electrode of W and Ni etc., the heating function fuses the conductive filaments. So it needs more power.(3) It is found that in order to reduce the operation voltage and the power consumption of the device, the thickness of the films could be reduced. And the high/low resistance ratio for Cu/NiO/Pt structure is constant.(4) Influence of the device performance by changing the bottom electrode is investigated. It is found that for a top electrode of Cu, there is little influence of the device performance; for Ni electrode, there is much influence of the device performance: the low resistance of a device could not retain for a thin bottom electrode. The possible reason is that too thin bottom electrode causes the heat unable to dissipate in time and make the conductive filaments unstable.(5) Mechanism of the resistance switching is addressed. For the top electrode of Cu, the move of Cu ions causes the rupture and connection of conductive filaments. And Cu ions could only move certain distance under certain voltage. Typical thickness is addressed. When the thickness of the film is less than typical thickness, set/reset voltage of the device decreases with the reducing of the thickness of a film. The rupture of conductive filaments is attributed to the heat gathering for the W and Ni etc. electrode.