Irradiation response of mobile protons in buried SiO/sub 2/ films

Abstract

We have performed current-voltage, capacitancevoltage and electron-paramagnetic-resonance (EPR) characterization of silicon-on-insulator (SOI) samples, subjected to a wide variety of irradiation and anneal treatments. By comparing transport properties and interfacial reaction mechanisms, we provide evidence for an intrinsic difference in the response of mobile protons in these oxides, depending on whether they are generated by irradiation or by & annealing. A radiation effects study of SO1 buried oxides containing annealing induced mobile protons is presented to gain insight into the mechanisms behind these fundamental differences. Electrical characterization shows that, for these devices, the initial interface trap and mobile proton densities are largely unaffected by the irradiation. However, if the irradiation is carried out in the presence of positive bias applied to the top Si, the protons become trapped in shallow levels. These proton traps are activated by the irradiation and are located near the oxide/substrate interface. These results may lead to improved radiation hardness of buried oxides for nonvolatile memory and other applications.

Hydrogen induced positive charge generation in gate oxides

“…The recent work [15][16][17][18][19][20][21][22][23] shows that annealing in forming gas at temperatures of 500°C or above can introduce a large number (ϳ10 12 cm Ϫ2 ) of fixed and/or mobile positive charges in the oxide. The fixed positive charge has characteristics similar to the oxidation-induced fixed charge.…”

“…Mobile charges are so securely imprisoned in the device that it is proposed that they can be used to form nonvolatile memory devices. 18 Recent work [15][16][17][18][19][20][21][22][23] has improved our understanding in H 2 -induced positive charge generation significantly. The work was mainly carried out in the buried oxide fabricated for silicon-on-insulator ͑SOI͒ devices, although it was shown that mobile charges can also be created in some specially processed and thermally grown oxides.…”

A non-volatile MOSFET memory device based on mobile protons in SiO2 thin films

“…The device is based on a stacked Si/SiO#3i structure, subjected to an anneal at -1100 "C in an inert ambient. Mobile protons ((&+) can be generated in the dielectric of such structures by subjecting them to a forming-gas anneal at temperatures >400 "C. The protons are found to be stable, even under field and thermal stressing and irradiation, i.e., they do not easily escape the dielectric or trap electrons [6]. These observations have been confirmed by other workers [7].T here are several reports in the literature of mobile protons in Si02, which have been generated electrically or by: irradiation in specific types of SiOz [8,9].…”

Nonvolatile memory based on mobile protons

“…Additional studies in the literature have shown that protonic memory elements are (1) stable to at least lo6 cycles, with no degradation in window size [lo], (2) tolerant to -1 Mrad(Si0,) unbiased total dose radiation exposure [IO], and (3) resistant to at least 250°C temperature without significant loss of hysteresis [19]. Hence, we conclude that protonic memory elements can potentially serve as the basis for a lowvoltage, radiation-tolerant nonvolatile memory technology.…”

“…To date, the studies of protonic memory elements in the literature have focused on relatively large geometry capacitor and pseudo-MOSFET test structures [9], [10], [15], [19]. When these structures are scaled down to the submicron regime, there is the possibility that the protons may not be as easily confined and controlled as they are in the structures studied to date, e.g., if there are signficant lateral components to the oxide electric fields.…”