Silanes safety

Most CGA valves are provided with a restricted flow orifice (RFO). The restricted flow orifice is the most important contribution to silane safety. It will reduce an unrestricted orifice to a maximum orifice size ranging from 0.006 inches to 0.015 inches. It is desirable to limit the flow to 30 liters per minute. With silane, some process engineers argue that these orifices clog. At the 1990 Semiconductor Safety Association Conference, a semiconductor manufacturer indicated they recorded 1600 points without a single incident of clogging. The use of die restricted flow orifices with... 

Pyrophoric gases deserve special consideration. Considerable research on storage and use of silane gas has been performed. A summary of some of this research is provided by the Semiconductor Safety Association. ... 

Semiconductor Safety Association. S.SA Journal, vol. 11,. Special issue Silane., Winter 1997. 

Other noteworthy developments are carrier materials, such as Stamypor (DSM) and Accurel (AKZO), for production of concentrates with liquid or low-melting additives and reactants (see Section 1.2.1). The biggest growth area for additive carriers is coming from liquid peroxides and silanes, due to related health and safety issues for shopfloor staff. The NOR HALS stabiliser Tinuvin 123-S (a non-interacting, low-MW liquid) for TPO, PP and some blends is delivered in a solid carrier (Accurel). 

Ring, M. A. et al., AIP Conf. Proc., 1988, 166 (Photovolt. Safety), 175-182 Very pure silane does not immediately explode with oxygen, but the decomposition products may ignite after a delay [1]. Mixtures of silane with 30% oxygen are metastable and potentially explosive under all pressure conditions studied, and... 

After each CVI experiment nitrogen was used to check the change in permeance of the membrane. For several membranes also permeance measurements were performed with He, H2 or CO2. In these cases the corresponding permselectivities could be calculated, which are a better indication of the membrane quality than the change in nitrogen permeance only. Unfortunately this type of measurements was not possible with our silane set-up (see Figure 2) because of safety regulations involved. 

The CVI-experiments with silane as precursor did not show any increase in permselectivity of the membranes. The reaction temperature was in all cases 275°C and several oxygen pressures were tried. In each experiment, however, white powder was obtained on the membrane surface, indicating the decomposition of silane at the surface of the membrane. Reaction conditions could not be chosen in such a way that a highly separative layer was obtained. This was probably related to with the fact that the reactor temperature or the concentration of silane in the precursor gas was too low. Safety regulations, however, prohibited an increase of the silane concentration in the precursor flow. 

The CVI modification of y-alumina membranes with a 0.5 mol-% silane mixture has not resulted in highly selective membranes. This might be due to an insufficiently high reaction temperature or silane concentration. Unfortunately in this work the temperature was limited by the reaction set up and the silane concentration by safety regulations. 

SAFETY PROFILE A poison. Probably an irritant to the eyes, skin, and mucous membranes. A powerful oxidizer. Explosive reaction with benzene (above 50°C), diethyl-aminotrimethyl silane, dimethyl sulfoxide, limonene + tetrafluoroethylene (polymerization), potassium, molten sodium, tetraio-doethylene. Reaction with organic... 

SAFETY PROFILE A very dangerous fire hazard in the form of dust when exposed to heat or flame or by chemical reaction with moisture or acids. In contact with water, silane and hydrogen are evolved. Slighdy explosive in the form of dust when exposed to flame. Will react with water or steam to produce flammable vapors on contact with oxidizing materials, can react vigorously on contact with acid or acid fumes, can emit toxic and flammable fumes. To fight fire, use CO2, dry chemical. See also LITHIUM, SILICON, and POWDERED METALS. 

SAFETY PROFILE Mildly toxic by inhalation. Silanes are irritating to skin, eyes, and mucous membranes. Easily ignited in air. Explosive reaction or ignition on contact with halogens or covalent halides (e.g., bromine, chlorine, carbonyl chloride, antimony pentachloride, tin(TV) chloride). Ignites in oxygen. Can react with oxidizers. 

One-step (Monosil) process, which involves a continuous feeding of liquid silanes during extrusion. The extruder is equipped with a long barrier screw and an injection system. This speeds up production but poses safety problems owing to the volatile and flammable nafure of silanes. 

Chlorosilanes are also converted to siloxanes by reactions not involving hydrolysis. Most are highly exothermic, and appropriate measures for heat dissipation are recommended for safety. Thus chlorosilanes can be converted to siloxanes by reaction with DMSO or with NajCOj or ZnO in suitable solvents such as ethyl acetate or dioxane. Siloxanes can also be obtained by the reaction of alcohols with chlorosilanes, but this is really a kind of hydrolysis in which the water is generated in situ as a by-product of the formation of alkyl chloride from the alcohol and HCl. Siloxanes can of course be prepared from the reaction of HjO with many other kinds of hydrolyzable silanes (e.g., sulfato, iodo, bromo, fluoro, alkoxy, aryloxy, acyloxy, amino, amido, ketoximo) but such intermediates are themselves derived from chlorosilane precursors. Acetoxysilanes undergo thermolysis to yield siloxane bonds. 

Safety issues are particularly important for CVD since many of the source compounds are toxic and disposal of waste products, e.g., HCl, is often problematic. Additional problems can occur if the reactants are pyrophoric (ignite in contact with air). Table 28.4 lists some of the source gases used in CVD and their potential hazards. Silane is widely used in the semiconductor industry and was the cause of a major explosion and fire at a manufacturing plant in Moses Lake, WA. The incident caused a number... 

Some silanes are also hazardous and need to be used with appropriate Health and safety considerations. 

Health and safety Compound contains peroxide Silane requires special handling and storage Special controls and procedures needed for radiation source... 

Solid state films that have been developed to utilize solid polymer electrolytes without requiring safety sealing and additional packaging. Patents claim that organosilicon compounds (U.S. Patent 20070076349) and polyoxy-alkylene-modified silanes (U.S. Patent 20070048621) are suitable with the additions of varying electrolyte salts (and separators if needed) for use as solid film electrolytes. Table 5.3 lists recent patents on electrolytes. 

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