G. Larrieu

Formation of platinum-based silicide contacts: Kinetics, stoichiometry, and current drive capabilities

A detailed analysis of the formation of Pt2Si and PtSi silicides is proposed, based on x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrical characterizations. Published kinetics of the Pt2Si and PtSi transformations under ultrahigh vacuum condition are consolidated on the basis of XPS measurements performed during an in situ annealing at a constant heating rate. At room temperature, an incomplete PtxSi reaction is clearly identified by XPS depth profiling. Using rapid thermal annealing at 300, 400, and 500 °C, the sequential Pt–Pt2Si–PtSi reaction chain is found to be completed within 2 min. Outdiffusion of silicon to the top surface is shown to be responsible for the formation of a thin SiO2 capping layer at 500 °C. Pileup of oxygen occurring at the Pt2Si/Pt reaction front is clearly identified as an inhibiting factor of the silicidation mechanism. Another incomplete reaction scheme limited to the unique formation of Pt2Si is exemplified in the case of ultra thin...

Selective etching of Pt with respect to PtSi using a sacrificial low temperature germanidation process

A soft and scalable etching procedure that selectively eliminates Pt without altering PtSi is proposed. The selective etch is based on the low temperature transformation of the excess Pt into a more reactive PtxGey phase that is easily etched in a sulfuric peroxide mixture. The mechanism of PtxGey alloying is detailed based on x-ray diffraction analysis. The innocuousness of the germanidation-based selective etch on the integrity of the PtSi∕Si junction is consolidated by Schottky barrier measurements. This process is expected to facilitate the integration and the scalability of PtSi on ultrathin silicon layers.

Kinetics, stoichiometry, morphology, and current drive capabilities of Ir-based silicides

A detailed study of the formation of iridium silicide obtained by ultrahigh vacuum annealing and atmospheric rapid thermal processing is proposed using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrical characterizations. Using XPS analysis, the stoichiometry of each silicide phase (IrSi, IrSi1.6) is identified. A model based on the variation of the measured intensity of the Ir 4f spectra is used to obtain the kinetic coefficients of reaction of Ir silicidation (EA=2.48eV, D0=9cm2∕s). TEM cross sections indicate that the roughness of the silicide∕silicon interface increases with temperature. Lastly, electrical characteristics are used to identify the optimum annealing temperature to obtain an iridium silicide contact with the lowest Schottky barrier height to holes.

Recent advances in metallic source/drain MOSFETs

This paper reports on advances in metallic source/drain MOSFETs covering material engineering, integration issues such as metal/silicide selective etching and electrical performance in both DC and RF regimes. A soft and scalable etching procedure that selectively eliminates metallic platinum (Pt) without altering the platinum silicide phase (PtSi) is proposed. Strategies of Schottky barrier reduction based on low temperature dopant segregation are exemplified when PtSi is coupled to boron and arsenic. Finally, the integration of p-type boron-segregated contacts in thin-film SOI p-MOSFETs reveals state-of-the-art results both for DC and RF operation.

TEM Study of the Silicidation Process in Pt/Si and Ir/Si Structures

The annealing of Pt/Si and Ir/Si structures (300, 400 and 500°) leads to the formation of platinum or iridium silicides, respectively. However, the silicidation process proceeds in different ways in both structures. In the Pt/Si structure the silicidation process is completed at each temperature. Annealing of the Ir/Si structure at 300 and 400°C causes only a partial reaction and the formation of a very thin amorphous iridium silicide layer at the Ir/Si interface. At 500°C the reaction is completed and forms a crystalline silicide layer, which consists of two phases.