Annette Sänger

Chemical vapor deposition of tungsten silicide (WSix) for high aspect ratio applications

Abstract Chemical vapor deposition of tungsten silicide into high aspect ratio trenches has been investigated using a commercial 8-inch Applied Materials Centura single wafer deposition tool. For an in-depth study of both step coverage and stoichiometry, a combined chemistry/topography simulator has been developed. Dichlorosilane reduction of tungsten hexafluoride (WF6) has been identified as a suitable chemistry to fill deep trenches with tungsten disilicide, while for WF6 reduction with silane (SiH4) or disilane (Si2H6) fundamental drawbacks have been identified for extreme aspect ratios. In the process range under study, good agreement is observed between the simulated step coverages and those obtained from scanning electron microscope images. The simulations predict a deposition regime in which both good step coverage and a suitable stoichiometry are achieved inside deep trenches.

Interfaces characteristics between tungsten silicide electrodes and thin dielectrics

Abstract In today’s ULSI technology there is an increasing demand in metal electrodes for storage capacitors and transistors. In this publication we present an investigation of MOS capacitor structures with CVD tungsten silicide (WSi x ) as metal electrode in conjunction with silicon dioxide (SiO 2 ) and oxidized nitride (NO). Bulk silicon and poly silicon were used as second electrode, respectively. Tungsten silicide has been used both as gate electrode and as bottom electrode. For both cases thermal stability up to 780°C with low leakage current has been shown. Band discontinuities between SiO 2 and WSi x were estimated from current–voltage measurements.

Interface analysis of atomic layer deposited-TiN gate electrodes on ultrathin SiO2 layers

As new gate materials become increasingly interesting in conjunction with tunnel oxides, new deposition techniques have to be developed that deposit thin metal layers without degrading the gate dielectric. Recently, atomic layer deposition has been identified as a suitable method to deposit refractory metal alloys with well-defined properties. For the first time, a recently developed automated characterization of capacitance–voltage (C–V) curves is employed to identify challenges during the initiation of a metal atomic layer deposition process. While some problems were eliminated by adapting the deposition process, others will require further process or tool modifications to reduce the nonuniformities observed within each wafer. The temperature dependence of the C–V curves indicates an unintended titanium-rich layer at the interface, which disappears after annealing above 800 °C. A further development of the surface pretreatment and subsequent deposition will be necessary to avoid this phenomenon. In this...