Titanium reaction layer from

If a single metal film is deposited on an oxide, the sheet resistance measurement results can by easily interpreted and converted to the thickness. In practice, however, this is not usually the case. For example, in W CVD, the tungsten is not directly deposited on oxide due to high residual stress and unreliable adhesion. A titanium (Ti) layer must be first deposited as a glue layer. In addition, to prevent the fluorine in the CVD-precursor WFg from directly reacting with Ti (a strong catalytic reaction will occur), a barrier layer of titanium nitride (TiN) must be deposited on top of the Ti. As a result, we have a trilayer film of W on TiN on Ti on oxide, as shown schematically in Fig. 21. This poses some problems in accuracy in the four-point probe measurements. Based on the resistivities in Table VI, the... 

To a stirred solution of tetrabutylammonium iodide (TBAI, 0.2 mmol) in dry dichloromethane (5 mL) at -78 °C was added titanium tetrachloride (1.5 mmol) dropwise. After stirring for two minutes, a mixture of the enone 142 (1 mmol) and p-nitrobenzaldehyde (2 mmol) in dry dichloromethane (5 mL) was added. The reaction mixture was slowly warmed to -30 C and kept at this temperature for 8 h. A saturated aqueous solution of sodium bicarbonate was added, followed by filtration through a celite pad. The organic layer from the filtrate was separated, and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated. The crude product was then purified by column chromatography eluting with hexane ethyl acetate (80 20) to deliver the product 143 as an oil in 85% yield. 

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