Nonvolatile memory capacitors based on Al2O3 tunneling and HfO2 blocking layers with charge storage in atomic-layer-deposited Pt nanocrystals

The growth of Pt nanocrystals (NCs) on Al2O3 surface via atomic layer deposition (ALD) was investigated deeply. A charge trapping memory using Pt NC as charge trapping layer and amorphous ALD Al2O3/HfO2 as the tunneling/blocking layers was fabricated. Pure metallic Pt NC can be formed at the initial growth stage, following the nucleation incubation model. Electrical measurements of p-Si\Al2O3\Pt NCs\HfO2 show a larger memory window of 6.6 V at the sweeping gate voltage of ±12 V and ∼73% retention property after 105 s. Fowler-Nordheim tunneling serves as the dominant tunneling mechanism at the applied gate voltage of 10 V. Compared to that of 4.0 V with HfO2 blocking layer, control sample with Al2O3 blocking layer shows negligible memory window of 0.3 V at ±10 V, which is attributed to the smaller electric field intensity in the Al2O3 tunneling layer of stacking structures of p-Si\Al2O3\Pt NCs\Al2O3. ALD Pt NCs with a high density of 1.0 × 1012/cm2 provides a potential approach to fabricate large area nanocrystals for future ultrahigh density nonvolatile memory applications.