Vacuum desiccators guard for

Semiconductor manufacturiag faciUties are large and expensive. A modem plant doiag 0.5- lm device manufacturiag on 200-mm siUcon wafers may cost > 1 biUion to iastaH. Semiconductor manufacturiag uses a variety of vacuum depositioa processes resultiag ia the semicoaductor chip. Multiple layers of metal give a three-dimensional circuit ia microscopic patterns. The aext geaeratioa of semicoaductor plants are expected to use 300—400-mm wafers at 0.35- im device size and further shrinkage is ia developmeat (16,42—45) (see Integrated circuits).  [c.137]

Conductivity grade benzonitrile (specific conductance 2 x 10" mho) was obtained by treatment with anhydrous AICI3, followed by rapid distn at 40-50° under vacuum. After washing with alkali and drying with CaCl2, the distillate was vac distd several times at 35° before being fractionally crystd several times by partial freezing. It was dried over finely divided activated alumina from which it was withdrawn as required [Van Dyke and Harrison J Am Chem Soc 73 402 7957].  [c.123]

The size of the filtered sample is established by the anticipated bacterial density. An ideal quantity results in the growth of about 50 colifoim colonies and not more than 200colonies of all types. Often it may be difficult to anticipate the number of bacteria in a sample. Two or three volumes of the same sample must be tested. When the portion being filtered is less than 20 ml, a small amount of sterile dilution water is added to the funnel before filtration. This uniformly disperses the bacterial suspension over the entire surface of the filter. The filter-holding assembly is placed on a suction flask. A sterile filter is placed grid side up over the porous plate of the apparatus using sterile forceps. The funnel is then locked in place holding the membrane. Filtration is performed by passing the sample through the filter under partial vacuum. A culture dish is prepared by placing a sterile absorbent pad in the upper half of the dish and pipetting enough enrichment media on top to saturate the pad. M-Endo medium is used for the coliform group and M-FC for fecal coliforms. The filter is then removed from the filtration apparatus and placed directly on the pad in the dish. The cover is replaced and the culture is incubated (for 24 h at 35 C). For fecal coliforms, incubation is performed by placing the culture dishes in watertight plastic bags and submerging them in a water bath at 44.5 C. Coliform density is calculated in terms of coliforms per 100 ml by multiplying the colonies counted by 100 and dividing this value by the milliliters of the sample filtered.  [c.463]

See pages that mention the term Vacuum desiccators guard for : [c.199]   
Textbook on organic chemistry (1974) -- [ c.138 ]