Effects of heat dissipation on unipolar resistance switching in Pt∕NiO∕Pt capacitors

Abstract

We fabricated Pt/NiO/Pt capacitor structures with various bottom electrode thicknesses, t BE , and investigated their resistance switching behaviors. The capacitors with t BE ≥ 50 nm exhibited typical unipolar resistance memory switching, while those with t BE ≤ 30 nm showed threshold switching. This interesting phenomenon can be explained in terms of the temperature-dependent stability of conducting filaments. In particular, the thinner t BE makes dissipation of Joule heat less efficient, so the filaments will be at a higher temperature and become less stable. This study demonstrates the importance of heat dissipation in resistance random access memory.Resistance switching phenomena, observed in numerous materials, 1,2 have regained a great deal of attention recently due to their potential application in nonvolatile memory devices called resistance random access memory (RRAM). 3-9 Achieving good scalability is an important issue for meeting the current demands for device miniaturization. 10-12 One of the important scalability issues is reducing the bottom electrode thickness, t BE , to make the etching process easier. 13 Reducing t BE also lowers the device fabrication cost, especially when using expensive electrode materials such as Pt or other noble metals.Many binary transition oxides such as NiO, TiO 2 , and Fe 2 O 3 exhibit unipolar resistance switching. 5-8 Although the mechanism is still somewhat ambiguous, it is widely accepted that unipolar resistance switching is due to the formation and rupture of conducting filamentary paths under external bias. 1,6,[14][15][16][17][18][19] It is also generally assumed that the rupturing process of the conducting filaments may be closely related to Joule heating. [17][18][19] If this is true, we could control Joule heating effects in unipolar resistance switching by changing the thermal properties of the RRAM device structure, which is typically made with metal/oxide/metal. In particular, t BE could significantly affect the thermal heat dissipation process through the bottom electrode.In this letter, we investigated resistance switching behaviors of Pt/NiO/Pt capacitor structures as a function of t BE . We found that capacitors with t BE ≤ 30 nm exhibited volatile resistance switching behaviors called threshold switching. On the other hand, all capacitors with t BE ≥ 50 nm exhibited typical unipolar memory switching behaviors. We explained this interesting t BE dependence in terms of the thermal stability of conducting filamentary paths, which are closely related to heat dissipation through the bottom electrode. This result indicates that thermal heat dissipation through the electrodes is crucial for RRAM, just as it is for phase change random access memory. 20

Intrinsic constrains on thermally-assisted memristive switching

“…The Joule heat generated inside the metallic cylinder escapes both radially into the insulator and axially toward the metallic electrodes that are assumed to be large enough to act as thermal sinks. Note that significant heating of electrodes has been observed in some experiments [3]; however, it is rather an artifact of a particular device structure/experiment and should be avoided for practical reasons. For example, electrode heating would exponentially increase diffusion and electromigration of electrode material and therefore degrade endurance.…”

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

“…It is widely accepted that the current flow along such a narrow pathway results in Joule heating effects. 88,89 This thermal effect accelerates ion migration in VAN films. Lee et al 46 used finite element methods to understand Joule heating effects for ionic motion when ions flow along vertical heterointerfaces in VAN films.…”

Predictability of reset switching voltages in unipolar resistance switching

“…7 Joule heating has been well established to play a very important role in LRS. 1,[8][9][10][11][12][13] As the percolating conducting filament in LRS is metallic, its local resistance value r should be proportional to its local temperature T:…”