Articles you may be interested inTwo-terminal vertical memory cell for cross-point static random access memory applications A three-terminal spin-torque-driven magnetic switch Appl. Phys. Lett. 95, 083506 (2009); 10.1063/1.3216851Correlations between structural and electrical properties of nitrided SiO x thin films used as power metal oxide semiconductor field effect transistor gate dielectric A comparison of ionizing radiation and high field stress effects in n -channel power vertical double-diffused metaloxide-semiconductor field-effect transistors Vertical metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒ have evolved into dominant members in the power transistor family. Reliability issues continue to be a major concern, as economic requirements drive towards miniaturization, and higher power ratings for these devices. The charge pumping method offers a simple, direct and powerful way of assessing interface damage for planar structures. Absence of an independent substrate contact in the vertical power structure implies that conventional charge pumping, which requires a substrate contact as well as three additional contacts to the remaining terminals of the MOSFETs, cannot be applied directly to these devices. In this article, we propose an adaptation of the charge pumping technique that enables its application to three terminal devices, in general. The modified form of charge pumping was applied to assess effects of Fowler-Nordheim stressing on production level U-shaped trench-gated MOSFETs. A good correlation between transfer characteristic measurements and the proposed method has been observed.

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In contrast to submicrometer geometry, metal oxide semiconductor (MOS) devices which feature ultrathin gate oxides, power MOS field effect transistor (FETs) require gate oxides in the thickness regime from 50 to 70 nm. In this experiment, the effect of preoxidation surface treatments and thermal growth conditions on electrical integrity of thick gate oxides is investigated and compared with the effect on thin oxides (<15 nm). It is demonstrated that the response is relatively independent of oxide thickness when the same temperature of oxidation is used to grow thick and thin oxides. However, when thick gate oxides of the same thickness are grown at different temperatures, the effect of metallic contaminants, namely Fe and Al, plays a decisive role in determining oxide characteristics. In the case of metal-free surfaces (HF/HCl last clean) better oxide integrity in terms of both Enormalbd and Qnormalbd is obtained at high temperatures of oxidation (1000 and 1175°C). However, in the case of starting Si surfaces contaminated with metallic impurities (ammonia hydrogen peroxide mixture-last clean), the benefits of using a high temperature of oxidation are seen only in terms of Enormalbd characteristics while Qnormalbd characteristics are significantly deteriorated as compared with oxides grown at 900°C. © 2001 The Electrochemical Society. All rights reserved.

We have examined the impact of trench processing and trench and device cell geometries on the characteristics of a single n-channel U-shaped trench metal-oxide-silicon field-effect transistor (n-UMOSFET) and a device cell comprising several n-UMOSFETs. The geometrical parameters investigated included the trench depth and width, the trench cross-section and the device cell pitch. We have found out that the geometry does not affect the electron mobility in the channel; however, the effects of the geometry on the characteristics of the isolated device or device cell are manifested on the spreading resistance of the drain end. Trench processing, in the form of trench etching, trench cleaning and subsequent gate-oxide growth, is observed to primarily influence the n-UMOSFET's immunity to electrical stress, which is studied using charge pumping current and gate-oxide breakdown measurements. It is shown that the gate-oxide edge adjacent to the drain and the oxide/silicon interface overlapping the drain are the regions most susceptible to degradation by Fowler-Nordheim stress. These observations coupled with results from scanning electron microscopy suggest that the gate-oxide growth non-uniformity as well as its condition at the trench corners are the key factors in determining the n-UMOSFET's reliability.

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