THe electrophysical properties of an Al-Si₃N₄-Si structure

Conclusions

• 1. The instability in Si₃N₄ films cannot be ascribed to ion drift but is due to traps of hole type in the film. Two types of traps are observed, which have relaxation times of a few minutes and some days, the concentrations being 10¹⁵–10¹⁶ and 10¹⁷–10¹⁸ cm⁻³, respectively.

• 2. The conductivity of the nitride films in MNS structures is determined mainly by the bulk properties of the films up to fields of 5 · 10⁶ V/cm. The temperature dependence has two sections with activation energies of 0.8 eV (above 50°C) and 0.17 eV (lower temperatures).

• 3. The contact potential between Al and Si separated by a layer of nitride is somewhat different from that for Al-SiO₂-Si, which should be taken into account in calculating surface parameters.

• 4. Al-Si₃N₄-SiO₂-Si structures with 200–300 Å of SiO₂ have high stability in response to electric fields and temperature. The nitride film is then protected from hole injection from the silicon, while the SiO₂ is protected from electron injection from the Si and also from the penetration of ions from the outer surface. The surface charge is 2–3 · 10¹² cm⁻² for the Si-Si₃N₄ interface and 10¹¹–10¹² cm⁻² for the Si-SiO₂ interface.