Characterization of the Electric Breakdowns in Metal-Insulator-Silicon Capacitor Structures with HfO2/Al2O3 Layers for Non-Volatile Memory Applications

The electric breakdown of memory capacitors with atomic layer deposited HfO
2
/Al
2
O
3
nanolaminated stacks was investigated by voltage ramp method and constant voltage stress. Two types of capacitors – with 2.4 and 3.5 nm tunnel SiO
2
layer were investigated, before and after O
2
annealing. Breakdown voltages ~ - 30 V were obtained independently of the thickness of SiO
2
. The O
2
annealing seems to increase the charge to breakdown due to higher current through the capacitors. The effect is more pronounced for structures with 3.5 nm tunnel layer. The results indicate that the electric breakdown is mainly determined by Al
2
O
3
blocking layer and HfO
2
/Al
2
O
3
nanolaminate. The electric breakdown is accompanied by positive charge build-up and generation of interface states at SiO
2
/Si interface. The latter process is subdued in the annealed samples.