Inert ambient annealing effect on MANOS capacitor memory characteristics

Abstract

In this work we report on the influence of nitrogen ambient thermal effects on the performance of Pt/Al2O3/Si3N4/SiO2/Si memory capacitors. Two post deposition annealing (PDA) furnace steps were employed, at 850 and 1050 °C both for 15 min. The alumina films were deposited by atomic layer deposition using TMA/H2O at 250 °C. The structural characteristics of the stacks were evaluated by transmission electron microscopy and x-ray reflectivity measurements. The memory performance of the stacks was evaluated by write/erase and erase/write measurements, endurance and retention testing. It was found that in as-deposited state the Al2O3 layer is defective resulting in strong leakage currents, controlled by deep defects states. Thus, this behavior inhibits the memory functionality of the stacks. PDA crystallizes and condenses the Al2O3 transforming the layer from amorphous to polycrystalline. During this transformation the Al2O3 electrical quality improves greatly indicating that a significant number of these deep defects have been removed during annealing. Physical reasoning implies that the most plausible origin of these deep defects is hydrogen. However, the polycrystalline Al2O3 films showed inferior retention characteristics which are attributed to grain boundary related shallow defects. The findings of this work could pave the way for more efficient annealing schemes, in which an important factor is the time interval for hydrogen out-diffusion from the Al2O3 layer.

Metallization-Induced Oxygen Deficiency of γ-Al2O3 Layers

“…Thanks to the well-known chemical stability and superior electronic properties, (poly)­crystalline γ-Al 2 O 3 layers offer an advantageous alternative to the amorphous (a-) alumina films widely applied in a variety of electron devices. For example, the increase in the conduction band (CB) offset at interfaces with semiconductors upon alumina crystallization , allows for better gate insulation of wide-bandgap channel materials such as GaN and SiC. , In particular, polycrystalline γ-Al 2 O 3 films obtained by annealing-induced crystallization of the atomic-layer-deposited (ALD) alumina , are seen as superior intergate insulators in charge trapping (flash) memory cells, eventually allowing for 3D integration, improving the cell performance , as well as promising a high-temperature operation; however, retention properties of the Al 2 O 3 -insulated memory cells appear to critically depend on the oxygen deficiency developed during postdeposition anneal (PDA), mandating application of an oxygen-containing ambient …”

Ultrafast laser interaction with transparent multi-layer SiO2/Si3N4 films

“…The Si 3 N 4 nano-layers act as 'wicks' feeding the surrounding material with photodissociated, ionized nitrogen and silicon. This observation is expected as the band gap of Si 3 N 4 is effectively lower than for SiO 2 (typically around 5 eV for Si 3 N 4 versus 9 eV for SiO 2 ) 43,44 . As Si 3 N 4 has a significantly higher index, the existence of a guided mode in the confined layer is also to be expected in certain cases corresponding to the photonics bandgap formed by the layer structures (Bloch-wave).…”

Sunlight-Activatable ROS Generator for Cell Death Using TiO2/c-Si Microwires

“…First, the band gap and band position of c -Si and TiO 2 were confirmed. The band gap, electron affinity, and phosphorus doping concentration ( n ) of the n-type c- Si were 1.12 eV, 4.05 eV, and 2 × 10 15 cm –3 , respectively. , The location of the Fermi energy level of n-type c- Si can be calculated from eq where ( E f ) n is the Fermi energy level of n-type c -Si, ( E f ) i is the Fermi energy level of intrinsic c -Si, k is the Boltzmann constant, T is the temperature, and n i is the intrinsic carrier concentration. As can be obtained from eq , the Fermi energy level of n-type c- Si is located at an energy level 0.25 eV lower than the conduction band position of c- Si.…”