The rate of tungsten nucleation and island growth is characterized on thermal silicon dioxide in the absence of exposed silicon surfaces in a stainless steel cold wall high vacuum differential reactor. Tungsten hexafluoride (0.05–2.50 torr) was found to react with undoped thermal silicon dioxide in the presence of adjacent tungsten areas for temperatures ranging from 240° to 380°C and reaction times from 1.10 to 2h. The silicon dioxide film did not change thickness, but electron spectroscopy for chemical analysis (ESCA) revealed a surface covering of tungsten, oxygen, fluorine, and silicon. Tungsten nucleates rapidly on silicon dioxide in the presence of reactive surfaces and the hydrogen reduction reaction of tungsten hexafluoride. The observed nucleation is autocatalytic and initiated by an intermediate diffusing from areas of tungsten deposition. For a gas flow rate of 160 sccm, tungsten hexafluoride pressure of 0.05 torr, a hydrogen pressure of 0.70 torr, and temperatures ranging from 268° to 348°C, the activation energy for initiation of nucleation is 23–25 kcal mol−1.

Polysilicon buffered LOCOS (PBL) has been widely utilized for advanced isolation applications as moderately low lateral oxide encroachment may be achieved without defect formation. Unfortunately, PBL does not exhibit sufficient field oxide recess to support aggressive device scaling without introduction of processes which are difficult to control. Recently, polysilicon encapsulated local oxidation (PELOX) has been proposed as an easily scaled isolation technique that exhibits LOCOS equivalent recess. The integration of PELOX into an existing PBL 1 Mb DRAM baseline process is described. PE-LOX integrated PBL (PIPBL) is demonstrated to enhance final field oxide recess without increasing encroachment. The improved final field oxide recess is shown to provide increased process margin as evidenced by superior probe yield.

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Transient pressure interference tests have proved to be very effective for determining parameters for reservoir simulation of deep-well, hazardous waste, injection systems. These well systems provide a unique, large-scale laboratory for conducting interference tests in both fractured and non-fractured wells because disposal takes place in single-phase brine aquifers. A number of multi-well systems are described in a variety of geological settings to demonstrate the wide range of systems in which interference testing has been utilized with remarkable success.