Si O 2 ∕ Si 3 N 4 ∕ Al 2 O 3 stacks for scaled-down memory devices: Effects of interfaces and thermal annealing

Abstract

Effects of interfaces and thermal annealing on the electrical performance of the SiO 2 /Si 3 N 4 /Al 2 O 3 ͑ONA͒ stacks in nonvolatile memory devices were investigated. The results demonstrated the principal role of Si 3 N 4 /Al 2 O 3 and Al 2 O 3 /metal-gate interfaces in controlling charge retention properties of memory cells. Memory devices that employ both electron and hole trappings were fabricated using a controlled oxidation of nitride surface prior to the Al 2 O 3 growth, a high-temperature annealing of the ONA stack in the N 2 +O 2 atmosphere, and a metal gate electrode having a high work function ͑Pt͒. These devices exhibited electrical performance superior to that of their existing SiO 2 /Si 3 N 4 / SiO 2 analogs.

Modeling the charge transport mechanism in amorphous Al2O3 with multiphonon trap ionization effect

“…In addition, it was found that Al 2 O 3 films grown on silicon have lower leakage currents than that of hafnium oxide [4,5] because of the lower trap density in Al 2 O 3 . Al 2 O 3 films were also proposed to be used as blocking layers in flash memory cells [6][7][8][9][10]. To be used as a blocking layer in flash cells, the leakage current must be extremely low in order to maintain charge storage for a 10 year period at elevated temperatures (85°C).…”

The effect of oxygen source on atomic layer deposited Al2O3 as blocking oxide in metal/aluminum oxide/nitride/oxide/silicon memory capacitors

“…In addition, the image reveals the presence of a significant interfacial layer (IL~1 nm thick) formed between the Si 3 N 4 and the Al 2 O 3 layers. The nature and origin of such a layer, which has been reported in the case of as-deposited and annealed ALD-Al 2 O 3 [17,18], have not been still firmly established and could be attributed to different effects like oxygen deficiency near the interface, difference in Si and Al solubility and partial oxidation of the nitride surface upon exposure to air. Similar TEM results were obtained in the case of the TMA/H 2 O sample (not shown here).…”

The electrostatics of Ta2O5 in Si-based metal oxide semiconductor devices

“…46 Our results can further be applied for band structure engineering in such devices, keeping in mind that Al 2 O 3 is a useful blocking layer in NVMs. 25 In summary, the properties of Ta 2 O 5 films were studied electrically, structurally, and chemically. A systematic variation of the position of thin Ta 2 O 5 layers inside Al 2 O 3 -based MOS devices has excluded the existence of significant charges inside the layer and dipoles at the Al 2 O 3 -Ta 2 O 5 interface.…”

“…However, other than its use as a capping layer, Al 2 O 3 is relevant for metal-insulator-metal (MIM) capacitors and for nonvolatile memories. 25 Moreover, Al 2 O 3 is an important dielectric for MOS devices based on highmobility semiconductors such as GaAs, 26 InGaAs, 27,28 and Ge, 29 where it can be used in a bilayer configuration with another dielectric. 30,33 Ta 2 O 5 was among the first candidates in the early days of high-k dielectrics.…”