NMOS

Eig. 3. Cross sections of electronics devices used in ICs. (a) NMOS transistor (b) a twin-tub CMOS device on an n-ty e substrate. 

These processes are considerably more complex in actual CMOS fabrication. First, the lower layers of a CMOS stmcture typically have a twin-tub design which includes both PMOS and NMOS devices adjacent to each other (see Fig. 3b). After step 1, a mask is opened such that a wide area is implanted to form the -weU, followed by a similar procedure to create the -weU. Isolation between active areas is commonly provided by local oxidation of sihcon (LOCOS), which creates a thick field oxide. A narrow strip of lightly doped drain (LDD) is formed under the edges of the gate to prevent hot-carrier induced instabiUties. Passivation sidewalls are used as etch resists. A complete sequence of fabrication from wafer to packaged unit is shown in Figure 10. 

Fig. 5. NMOS capacitance voltage characteristics where C is the oxide capacitance, A shows low frequency characteristics, and B shows high frequency characteristics. At low frequencies C approaches C for negative voltages (accumulation) and positive voltages (inversion). In the flat-band (FB) condition there is no voltage difference between the semiconductor s surface and bulk. The threshold voltage, Dp for channel formation is the point where the...

The sampling system consists of a condensate trap, flow-control system, and sample tank (Fig. 25-38). The analytical system consists of two major subsystems an oxidation system for the recovery and conditioning of the condensate-trap contents and an NMO analyzer. The NMO analyzer is a gas chromatograph with backflush capabihty for NMO analysis and is equipped with an oxidation catalyst, a reduction catalyst, and an FID. The system for the recovery and conditioning of the organics captured in the condensate trap consists of a heat source, an oxidation catalyst, a nondispersive infrared (NDIR) analyzer, and an intermediate collec tion vessel. 

LEY - GRIFFITH Oxidation reagent Oxidation ol alcotwls to caitxnyl compounds with a pemjthenate catalyst and N-methylmorpholine - N-oxIde (NMO), In the presence of other functional gmups... 

Conditions (a) 1-5 mol% catalyst, w-CPBA/NMO, -78°C, CH2CI2. (b) 1-5 mol% catalyst, NaOCl, 4-phenylpyridine iV-oxide, 0°C, CH2CI2. (c) 1-5 mol% catalyst, NaOCl, pyridine iV-oxide, 0°C, CH2CI2. (d) Solvent = diethyl ether... 

Unfortunately, a serious problem with the osmium tetroxide reaction is that Os04 is both very expensive and very toxic. As a result, the reaction is usually carried out using only a small, catalytic amount of OsO, in the presence of a stoichiometric amount of a safe and inexpensive co-oxidant such as A -methylmorpholine N-oxide, abbreviated NMO. The initially formed osmate intermediate reacts rapidly with NMO to yield the product diol plus... 

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