An improved method for determining the inversion layer mobility of electrons in trench MOSFETs

For the first time trench sidewall effective electron mobility (/spl mu//sub eff/) values were determined by using the split capacitance-voltage (CV) method for a large range of transversal effective field (E/sub eff/) from 0.1 up to 1.4 MV/cm. The influences of crystal orientation, doping concentration and, for the first time, temperature were investigated. In conclusion, the results show that (1) the split CV method is an accurate method for determining /spl mu//sub eff/(E/sub eff/) data in trench MOSFETs, (2) the {100} /spl mu//sub eff/ data approach published data of planar MOSFETs for high E/sub eff/ and (3) the mobility behavior can be explained with generally accepted scattering models for the entire range of E/sub eff/. The results are important for the optimization of trench power devices

Doped SbTe phase change material in memory cells

Phase Change Random Access Memory (PCRAM) is investigated as replacement for Flash. The memory concept is based on switching a chalcogenide from the crystalline (low ohmic) to the amorphous (high ohmic) state and vice versa. Basically two memory cell concepts exist: the Ovonic Unified Memory (OUM) and the line cell. Switching to the high ohmic or low ohmic state is done using Joule heating. A relatively short (~ns) electrical pulse with large amplitude is used to heat the crystalline phase to melt and quench into the amorphous state (RESET). A pulse with smaller amplitude heats the amorphous region above its crystallization temperature (lower than the melting temperature) and the material returns into the crystalline state (SET). In the OUM cell this will be at the electrode-phase change material contact, whereas for the line cell this will be at the position where the current density is the highest

Contact resistance of TiW to phase change material in the amorphous and crystalline states

Electrical characterisation of metal to Phase Change Material (PCM) contacts is necessary for optimum power transfer during switching of a Phase Change Random Access Memory (PCRAM) cell. In this article, titanium tungsten (Ti0.3W0.7) to two phase change materials; doped-Sb2Te and Ge2Sb2Te5 are characterised using Circular Transfer Length Method (CTLM) structures. A metal lift off process with a maximum process temperature of 120�°C allows processing of these CTLM structures below the crystallization temperature of PCM used. The specific contact resistance for TiW-PCM contacts with PCM in amorphous (high resistive) and crystalline (low resistive) phases is extracted from these CTLM measurements

Scaling properties of doped Sb2Te phase change line cells

For phase change random access memory applications, the scaling perspective of the 3 main programming parameters is essential. The programming time will largely determine the obtainable data rate. The required programming current will largely determine the transistor size and hence the obtainable memory density. Finally, the programming voltage should preferably not exceed the transistor driving voltage. In this paper, the scaling perspective for these 3 main programming parameters is investigated for doped Sb2Te PCRAM line cells

Evidence of the thermo-electric Thomson effect and influence on the program conditions and cell optimization in phase-change memory cells

We present physical and electrical evidence of the Thomson thermo-electric effect in line-type phase-change memory cells. This causes a shift of the molten zone during RESET programming towards the anode contact, and as a consequence the phase change material (PCM) design at the contact area has a significant influence on the program conditions. First statistical studies showed a reduction of minimum Reset currents by ~5% and Set voltages by ~28% when PCM extensions around the anode are used instead of fine line contacts. This Thomson effect remains important with further cell scaling