IntroductionA high performance 0.20pm logic technology has been developed with six levels of planarized copper interconnects. 0.15pm transistors (Lg,,,=0.15+0.04pm) are optimized for 1.8V operation to provide high performance with low power-delay products and excellent reliability. Copper has been integrated into the back-end to provide low resistance interconnects. Critical layer pitches for the technology are summarized in Table 1 and enable fabrication of 7.6pm2 6T SRAM cells.Isolation and Transistors CMP planarized shallow trenches with good electrical isolation down to n+/p+ spacings of 0.5pm were fabricated (Fig. 1). Dual gate 0.15pm transistors with 35A physical gate oxides (accumulation t,,=39A measured at Vg=+l .SV) were formed using super steep retrograde channels, shallow extensions and halos, relatively deep source/drain regions and 1 OOnm nitride spacers. CoSi, was selectively formed on the polysilicon gates and source/drain regions with a nominal sheet resistance of 9Wsq. Rapid thermal processing was utilized as much as possible throughout the flow to minimize transient enhanced dopant diffusion.Fig. 2 shows a typical SEM cross-section of a NMOS transistor with a gate length of 0.15pm. Well delineated shallow S/D extensions and the deeper S/D junctions are clearly observed. The saturation drive currents for nominal gate length NMOS and PMOS devices are shown in Fig. 3 . The nominal drive currents are 630pNpm for NMOS and 230pA/ym for PMOS at 1.8V. The off-state leakage currents of these devices are well below the worst case leakage specification of 2nA/pm. The drain induced barrier lowering (DIBL) measured on NMOS and PMOS devices is plotted as a function of Leff in Fig. 4. Good short channel characteristics are maintained down to effective channel lengths of O.1ym. The Vt roll-off for N and P devices in the linear and saturation regions are shown in Fig. 5. The Vt's are 0.44V and -0.46V for Nch and Pch respectively, at a gate length of 0.15pm and the associated subthreshold slopes are less than 90mv/dec. The use of nitrided gate oxides was investigated due to their superior hot carrier reliability. Fig. 6 compares the degradation under hot carrier stress of nitrided oxides to thermal oxides and highlights the improved reliability of NO-annealed oxides. Peak Gms comparable to those from thermal oxides were obtained (Fig. 7). A further advantage afforded by nitrided gate dielectrics is its superior boron blocking properties, Increasing the poly silicon doping in the P+ gate to reduce poly depletion resulted in only a 88mV Vt shift in nitrided oxides (Fig. 8) compared to a 300mV Vt shift in thermal oxides. A significant reduction in the inversion to, is achieved with the higher gate doping, resulting in improved device characteristics. NMOS transistor design focused on minimizing defect enhanced dopant re-distribution such as TED. To this end, the effect of different source/drain implant energies on NMOS transistor performance is shown in Fig. 9. The lower energy implant results in a significantl...

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Though there is an abundant supply of nitrogen in the atmosphere, it cannot be used directly by the biological systems since it has to be combined with the element hydrogen before their incorporation. This process of nitrogen fixation (N 2 -fixation) may be accomplished either chemically or biologically. Between the two elements, biological nitrogen fixation (BNF) is a microbiological process that converts atmospheric di-nitrogen (N 2 ) into plant-usable form. In this review, the genetics and mechanism of nitrogen fixation including genes responsible for it, their types and role in BNF are discussed in detail. Nitrogen fixation in the different agricultural systems using different methods is discussed to understand the actual rather than the potential N 2 -fixation procedure. The mechanism by which the diazotrophic bacteria improve plant growth apart from nitrogen fixation such as inhibition of plant ethylene synthesis, improvement of nutrient uptake, stress tolerance enhancement, solubilization of inorganic phosphate and mineralization of organic phosphate is also discussed. Role of diazotrophic bacteria in the enhancement of nitrogen fixation is also dealt with suitable examples. This mini review attempts to address the importance of diazotrophic bacteria in nitrogen fixation and plant growth improvement.Key words: Biological nitrogen fixation (BNF), Diazotrophic bacteria, Plant growth promotion, N 2 fixing prokaryotes, nif genes Biological nitrogen fixation (BNF) can convert atmospheric di-nitrogen (N2) into plant-usable form, which improves plant growth and yield.

Solvation thermodynamics-based models for predicting liquid-phase nonidealities and fluid-phase equilibria are gaining attention in modern chemical process and product development. Among this class of thermodynamic models, COSMO-RS and COSMO-SAC are two variants used extensively in industry. A key input to these models is the so-called sigma profile, i.e., a histogram of charge density distribution over the molecular surface. Typically, sigma profiles are generated from quantum mechanical calculations with molecular structure and conformation information as inputs to the calculation. We present an alternative approach for generating sigma profiles from experimental fluid-phase equilibrium data, i.e., solubility. Specifically, we incorporate the conceptual segment concept of NRTL-SAC activity coefficient model into sigma profile generation. We generate "apparent" sigma profiles from linear combination of sigma profiles of conceptual segments represented by reference molecules selected for hydrophobic, polar attractive, polar repulsive, and hydrophilic conceptual segments. Conceptual segment numbers of the molecule of interest are identified from regression of available experimental data. We show applicability of this sigma profile generation approach with solubility modeling for four drug molecules: caffeine, aspirin, paracetamol, and lovastatin.

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