A model for AC hot-carrier degradation in n-channel MOSFETs

A recently developed model for AC hot-carrier lifetimes is shown to be valid for typical and worst-case stress waveforms found in CMOS circuits. Three hot-carrier damage mechanisms are incorporated into the model: interface states created at low and medium gate voltages, oxide electron traps created at low gate voltages, and oxide electron traps created at high gate voltages. It is shown that the quasi-static contributions of these three mechanisms fully account for hot-carrier degradation under inverterlike AC stress. No transient effects are required to explain AC stress results, at least for frequencies up to 1 MKz     

Size-exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

We report the successful size-based separations of large, neutral polysaccharides using capillary electrochromatography (CEC). As the polysaccharides possessed little chromophore for photometric detection, two separate approaches were taken. In the first approach, indirect detection was combined with size-exclusion chromatography using a sulfonated polystyrene/divinylbenzene stationary phase. The separations were performed using a 300 A pore size stationary phase under aqueous conditions. Non-size based interactions were minimal using this material, resulting in an effective calibration range of molecular masses 180 to 112 000 g.mol(-1) for pullulans. In the second approach, the polysaccharides were derivatized with phenylisocyanate and were subsequently separated on columns made using a combination of high capacity ion-exchanger and a neutral polystyrene/divinylbenzene material of various pore sizes. The sulfonated ion-exchange phase provided the electroosmotic flow, while the mixed pore size material provided the extended calibration range. The linear range for this primarily nonaqueous system using tetrahydrofuran was determined to be from molecular masses 738 to 404 000 g.mol(-1) of the original, untagged pullulan. This approach overcame the limited solubility issue associated with analysis of some polysaccharides. Analysis of pullulan and amylose samples by CEC correlated well with results obtained by conventional high-performance liquid chromatography (HPLC). The size-exclusion electrochromatographic separations provide an alternative mode for determining the relative molecular weights of polysaccharides with reduced sample and solvent consumption, as well as analysis times.     

A lifetime prediction method for oxide electron trap damage createdduring hot-electron stressing of n-MOS transistors

Electron trap creation under conditions of hot-electron stress (i.e., stress at V_d=V_g) is examined. It is shown that a relationship exists linking lifetime to the injected gate current and drain current, offering a lifetime prediction method for these types of traps. Comparing this type of damage to interface trap (N_it) creation, it is found that larger energies (approximately 1.5 times that for N_it) are required to generate this defect. It is shown that an extrapolation technique can be used to obtain gate currents at working circuit voltages, extending the prediction of lifetimes for oxide trap creation to low voltages     

Photoconductive response time of a multiple quantum well pinmodulator

Excite and probe measurements on a GaAs/AlGaAs multiple quantum well pin modulator using sub-picosecond optical pulses are reported. The quantum confined Stark effect allows measurement of a limiting rise time of 170 ps for establishing crosswell photoconductivity