No abstract

The advent of ultra-large and giga-scale-integration (ULSJJGSI) has placed considerable emphasis on the development of new gate oxides and interlevel dielectrics capable of meeting strict performance and reliability requirements. The costs and demands associated with ULSI fabrication have in turn fueled the need for costeffective, rapid and accurate in-line characterization techniques for evaluating dielectric quality. The use of noncontact surface photovoltage characterization techniques provides cost-effective rapid feedback on dielectric quality, reducing costs through the reutilization of control wafers and the elimination of processing time. This technology has been applied to characterize most of the relevant C-V parameters, including flatband voltage (Vffi), density of interface traps (D1j, mobile charge density (Q1,,), oxide thickness (T0), oxide resistivity (p0) and total charge (Q0) for gate and interlevel (ILO) oxides. A novel method of measuring tunneling voltage by this technique on various gate oxides (GOX) is discussed. For ILO, PECVD and high density plasma (HDP) dielectrics, surface voltage (Vs) maps are also presented. Measurements of near-surface silicon quality are described, including minority carrier generation lifetime, and examples of their application in diagnosing manufacturing problems.

No abstract

A major hurdle in the gate dielectric scaling using conventionally grown SiO2 has been excessive tunneling that occurs in ultra-thin (<25Å) SiO2. High dielectric constant materials have high concentrations of bulk fixed charge, unacceptable levels of Si-Ta2O5 interface trap states, and low Silicon interface carrier mobilities. Stacked Ta2O5 gate dielectrics have alleviated these issues with significant improvements in leakage, tunneling, charge trapping behavior, and interface substructure. Transistors fabricated using this stacked gate dielectric exhibit excellent sub threshold, saturation, and drive currents. In this study, we have characterized the first SiO2 (8-12Å) layer of the SiO2-Ta2O5 stack by ThermaWave (TWI 5240SE) absolute ellipsometry (AE) using He-Ne (λ= 630nm) laser light source and by corona oxide semiconductor (COS) non-contact techniques. We have also monitored the kinetics of a thin hydrocarbon layer deposition on top of these films that can be removed by simple heat treatments (250°C - 400°C). Electrical thickness (Tox) of these oxides measured by COS indicates this hydrocarbon layer has no impact on Tox. Stacked Ta2O5 was synthesized by metal organic chemical vapor deposition (MOCVD) of a 50-75Å thick Ta2O5 layer at 480°C, 300mTorr followed by an in-situ 550°C UV-03 anneal to densify the Ta2O5 film and grow an additional 5Å SiO2 layer underneath the first grown SiO2 layer resulting in an effective SiO2 thickness of 25-30Å (process 1). We have done exactly the same deposition schedule after chemically removing the first LP grown SiO2 layer resulting in an effective SiO2 thickness of 15-20Å (process 2). Transistors are now fabricated for our sub-0.16μm CMOS technologies. These stacked films indicated excellent charge trapping (Dit, Vfb, Qtot), leakage and tunneling characteristics from COS electrical measurements.

Malgré les efforts déployés par les pays d'Amérique centrale pour lutter contre la dégradation de l'environnement et fortifier leur réseau d'aires protégées, le rôle direct des gouvernements demeure limité du fait que de nombreux terrains importants du point de vue de la conservation sont des terrains privés. Il est donc extrêmement important de mettre à la disposition des propriétaires des mécanismes flexibles et attrayants qui les incitent à gérer leur terrain tout en conservant les ressources naturelles. Grâce à leur flexibilité, les servitudes de conservation peuvent être adaptées aux caractéristiques d'un pays, d'une région ainsi qu'aux besoins spécifiques de chaque propriétaire. Les objectifs de conservation peuvent également être réalisés par le recours à d'autres instruments conventionnels, tels que l'usufruit, le covenant ou l'accord de conservation. Cet article fait le point sur ces divers mécanismes et les problèmes liés à leur mise en œuvre.