A study of charge injection in metal-A120~-SiO2-silicon (MAOS) structures has been made using the capacitance-voltage technique. Thin SiO2 films were grown thermally on the Si substrates, whereas A1203 layers were obtained by pyrolytic deposition from A1Br3 in a NO-forming gas mixture. Independent of the electrode material, negative charge is introduced into the oxide system when a positive voltage is applied to the metal. With A1 electrodes, the oxide also becomes negatively charged under negative bias. Only for large negative voltages will a gradual loss of negative charge occur, leading to a net positive oxide charge. Charge injection under negative bias is not observed on 02 annealed Al_oO3 layers, or on samples with Au electrodes. The results are discussed in terms of a qualitative model.Charge storage in metal-Si~N4-SiO2-silicon (MNOS) structures has attracted considerable interest since the late sixties because of its potential for memory device application. For stressing voltages exceeding a threshold value carriers will, depending on the direction of the electric field, enter or leave traps near the Si3N~-SiO2 interface, thus changing the state of charge of the system, and thereby the threshold voltages of IGFET devices incorporating such double layers as gate insulators (1-7). Particularly for very thin SiO2 layers (<30A), when the charging takes place by direct tunneling through this oxide film into the traps, these processes are quite fast. The field and time dependencies of the charging processes are determined by the trap energies and by the spatial distribution of the traps. These characteristics will depend, in turn, on the method by which the layers were prepared. The somewhat different results obtained in ReL (5) and (6) (logarithmic increase in induced charge with time under electric stress vs. relatively rapid saturation of the charging process) must be related to details of the sample preparation process.The discovery of such charge storage behavior in the MNOS system raises the question of similar effects occurring in sandwich structures with other insulators. Indeed, it has been reported recently that also in MAOS structures (A : A1203) with A1 electrodes the charge can be varied easily in an electric field. However, here both positive and negative voltage stress tends to induce negative oxide charge. The behavior appears to be independent of the method by which the A120~ film was obtained: reactive evaporation of A1 in O2 (8), pyrolysis of trimethyl-A1 in O2 at 450~ (4) or of Al-isopropoxide in O2 at 420~ (9), pyrolysis of A1CI~ in CO.~-H2 at 850~ (10), or of A1Br3 in NO-H2-N2 at 900~ (11). Only for rf sputtered A1203 films does the injection of negative charge under negative bias on the metal appear to be absent (12). Although some authors (8, 10) have not mentioned the occurrence of SiO2 in their insulator system, it appears likely that in all cases a layer of native oxide was present on the silicon wafers used as substrates for A1203 deposition.In the present study we have explored the ...
Measurements were made of I-V and C-V characteristics of metal-Al~O~silicon capacitors in the dark. The A12Os layers were deposited pyrolytically at temperatures between 700 r and 950~ on substrates of both conductivity types; some of the samples were subjected to a final O2 anneal. The observed dependence of the conduction on the electrode material indicates that the process is injection limited and that electrons are the major carriers. From the magnitude of the effective barrier heights and the relatively weak temperature dependence of the currents, it is concluded that in all cases the injection takes place via a trap-assisted tunneling mechanism. The buildup of space charge in the insulator has a pronounced effect on the magnitude of the Conductivity. The same behavior was observed on MAOS capacitors with a purposely grown 2.5 nm SiO2 film.
Die Ladungsinjektion in Metall‐Alpg‐siOz‐Si‐Bauelemente (MAOS) wird durch Kapazitäts/Spannungs‐Methoden bestimmt.
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