Tunnel oxide (SiOx) films, about 20 AA in thickness, were grown on (100) and (111) oriented, 10 Omega cm, p-type silicon wafers at a temperature of 250 degrees C, and pressure of 2 atm in dry oxygen ambient. The SiO x films were characterized using AlSiOx/p-Si MIS diodes with semi-transparent metal electrodes, by variable illumination current-voltage technique. The open-circuit voltage, short-circuit current, ideality factor and reverse saturation current were studied as functions of oxidation time and were found to be in accordance with a reduction of the interface state density with the oxide growth. From the experimental n-values the interface state densities were calculated and were found to be of the order of 1012 cm -2 eV-1 for both orientations. The reverse saturation current density obtained was of the order of 10-7 A cm-2 for (111) oriented substrates and 10-8 A cm-2 for the (100) orientation. The order of the oxide fixed charge was computed using deviation in the experimental barrier height from the theoretical barrier height (assuming no fixed charges are present). This was found to be of the order of 1012 cm-2 in both cases.

E. T Paul Benny

J. Majhi

Barrier heights

Silicon wafers

SEMICONDUCTOR DEVICES, MIS

SEMICONDUCTOR DIODES, TUNNEL

Semiconducting silicon

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IIT Madras

Tunnel oxides in AlSiOx/p-Si diodes by high pressure, low temperature oxidation of Si(100) and Si(111)

Semiconductor Science and Technology

Our earlier XPS and UPS studies have shown that etching a silicon surface with 5% HF concentration produces a stable surface with minimum contamination and low density of surface states. This has prompted us to study the I-V and C-V characteristics of MIS diodes fabricated on silicon surfaces treated with 5% HF. Tunnel oxides of approximately 20 angstroms are grown on p-type (100) surfaces by a high-pressure (2 atm) and low-temperature (250 °C) method. Aluminum dots are vacuum evaporated through metal masks onto the oxide to fabricate MIS diodes. For photovoltaic measurements the gate electrode is made semitransparent by reducing its thickness to approximately 120 angstroms. From the variable-illumination current-voltage characteristics it is observed that the ideality factor n = 1.25, density of interface states Dit = 9×1011cm-2 eV-1, effective barrier height Vb = 0.74 V, open-circuit voltage Voc = 0.28 V and density of fixed oxide charges Q0 to approximately 1011 cm-2 of 5% HF treated diodes are lower than those of untreated devices where n = 1.54, Dit = 2×1012 cm-2 eV-1, Vb = 0.78 V, Voc = 0.42 V and Q0 to approximately 1012 cm-2. This is attributed to the removal of the native oxide and passivation of silicon dangling bonds by HF treatment. C-V characteristics of the MIS diodes also confirmed the reduction in barrier height on HF treatment. An increase in negative charges with increasing HF concentration, possibly due to excess of fluorine ions which may be responsible for the reduction in barrier height, is found in the interfacial layer.

Effect of preoxidation treatment on the I-V and C-V characteristics of Si/SiO2/Al MIS diodes

It is shown here that ultrathin oxides can be grown with excellent control by a low temperature, high pressure oxidation process. The I-V characteristics of tunneling metal-insulator-semiconductor diodes fabricated using this process demonstrate that the interface state density can be reduced by an order of magnitude compared with low temperature, atmospheric pressure oxidation. © 1988.

Journal	Semiconductor Science and Technology
ISSN	02681242
Open Access	No