Electrical study of alumina properties as a function of the deposition rate and the layers thickness

p. 514-518

In this work, we have analyzed the electrical properties of different layers of alumina deposited on silicon substrate, depending on several experimental parameters. Then, the rate of deposition and the thickness of these dielectric layers are studied. Insulator layer surfaces were characterized by elastic peak electron spectroscopy (E.P.E.S) and X rays photoelectron spectroscopy (X.P.S). These control methods are necessary because the variation of the stoichiometry and of the electronic structure of alumina  play an important  role in the growth and the stability of the metal overlayers of the MIS structure. Concerning the interface quality, we have observed that a deposition rate equal to 32 nm/h seems to be less convenient than for a smaller one. The great rate deposition induces a number of defects at the insulator /semiconductor interface and in the insulator. The quantities of charges Q_T in the insulator for deposition rates of 1.2 nm/h and 32 nm/h are evaluated to 10¹¹charges per cm² and 4.33´10¹² charges per cm², respectively. The values of the interfacial densities of states N_ss in the midgap for the structures vary between 9.5´10¹¹ eV^-1.cm^-2 and 1.2´10¹³ eV^-1.cm^-2 respectively.