| 초록 |
The dielectric reliability of low-k materials during mechanical deformation has attracted great interest as the demand for thin electronic devices meeting the ever-shrinking form factor of consumer products increases. However, the strong correlation between the dielectric/ electrical and mechanical properties of low k dielectrics limits their use in practical industrial applications. We report the recoverable leakage current and dielectric properties of nanolattice capacitors during compressive stress cycling. Theoretical models and in-situ mechanical experiments based on electrical failure measurements during stress cycling provide insight into the major breakdown mechanisms of low-k capacitors. Electrical failure occurs at almost 50% strain and recovers again at 0% strain, featuring a switch-like binary characteristic, correlated with the transition from beam bending and buckling to collapse. Breakdown strength appears to recover after each cycle, concomitant with nanolattice’s shape recovery. The permanent buckled beam inside the nanolattice reduces the compressive displacement at breakdown upon cycling, represented by the conversion to full-Frankel emission by the Schottky conduction mechanism. Remarkably, our capacitor with 99% porosity, k ∼ 1.09, is operative up to 200 V, whereas devices with 17% porous alumina films breakdown upon biasing based on a percolation model. Similarly with electrical breakdown, the dielectric constant of the capacitor is recoverable with five strain cycles and is stable under 25% compression. These features could provide a pathway to increase resilience of devices that have to function in extreme environments. For example, such reversibility in both electrical and dielectric properties may offer opportunities to rescue data in memory after an electrical and/or mechanical failure without using complicated and expensive restoration processes and facilities. |
