The large-scale conversion of biomass to alcohol fuels will generate substantial quantities of byproduct lignin. This study examined the use of lignin from exploded wood as an extender for asphalt in paving mixtures. Uniform blends of up to 50% lignin in AC-10 and AC-20 asphalts were achieved by mechanical mixing. The effect of increasing lignin content was to Increase viscosity and to decrease ductility and aging index of the binders. The lignin in asphalt binders were combined with aggregate to prepare molded samples for Marshall tests, which measure the maximum compressive load (stability) and the corresponding deformation (flow). With 6% total binder content in the pavement mixture, stability increased with increasing lignin content of the binder whereas flow was relatively unaffected by lignin level. For binders containing 30% lignin, stability reached a maximum near 6% total binder content. The viscosity and Marshall properties of 30% lignin in AC-10 asphalt were comparable to unmodified AC-20 asphalt.
Tungsten reactive ion etch (RIE) rate and resist selectivity behavior of three unique Freon systems are investigated using optical emission spectroscopy and electron scanning for chemical analysis (ESCA). An oxygen-rich CF3C1/O2 formulation exhibits an etch rate and selectivity to photoresist on the order of two-three times that possible with CF4/O2. An optical emission spectral analogue has led to the discovery that 5-15% CF2C12 added to CF4/O2 or CHFJO2 yields a similar etch rate and selectivity advantage.In recent history, universal advantage has been taken of the relationship between device performance and component miniaturization in the fabrication of VLSI circuitry. Refractory metals and their silicides have been the subject of increasing interest for their ability to serve as process-compatible, low resistivity substitutes in the partial or complete replacement of polysilicon, the formation of modified gate electrodes, or metal interconnects (1). In particular, the chemical and thermal stability of tungsten along with the commercial availability of chemical vapor deposition (CVD) processing equipment make it a suitable polysilicon replacement in the formation of a "polycide" composite or as an exclusive electrode film (2).With the implementation of CVD tungsten comes a need for the development of reliable dry etch processes for the patterning of submicron structures. A worthy tungsten patterning process must create an anisotropic profile with an etch rate selectivity to the lithographic mask in excess of 1:1 and a selectivity to the support substrate normally of at least 3:1. The tungsten etch rate must be of a level consistent with manufacturing throughput considerations.Though there have been numerous investigations into the dry etching of tungsten and the other refractories (3-13) with either fluorinated or chlorinated chemistries, very few have approached tungsten etching using combinations of entities containing chlorine and fluorine (6, 14-16, 22) and fewer still have considered photoresist etch behavior coincidentally with tungsten (4,5,15,22).Most tungsten patterning efforts to date have relied on an inorganic or multilayer mask for dry etch resistance. In order to satisfy submicron lithographic requirements, the masking film thickness must be minimized. However, because organic materials typically have a lower dry etch resistance than tungsten, it is often difficult or impossible for an organic mask to meet both the lithographic and RIE criteria simultaneously. In such instances, an interlevel inorganic film is employed as part of a multilayer nonerodible mask (NEM). As Fig. la illustrates, a thin resist pattern is used to define the lithographic image, which is transferred by RIE to the inorganic mask, which is on the order of a half micron in thickness. The final image transfer to the tungsten is carried out by RIE through the NEM. Singlelayer resist (SLR) processing (Fig. lb) is infinitely preferable, offering economic and processing advantages in addition to a real opportunity for defect redu...
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