Method for preparing trisilylamine (TSA) at ultra-low temperature

A method for preparing trisilylamine (TSA) at an ultra-low temperature, comprising the following steps:

• introducing monochlorosilane (MCS) gas into an ultra-low temperature reaction vessel equipped with a mechanical stirrer and at a low temperature ranging from 100° C. to −40° C.;
• adding ammonia in a gaseous bubbling form by mixing and diluting nitrogen and anhydrous ammonia, a liquid dripping form by liquefaction of the anhydrous ammonia, or a solid form in batches by solidification of the anhydrous ammonia;
• subjecting liquefied MCS and ammonia (NH3) to an ultra-low temperature reaction at a molar ratio of 1:(1.2-1.4), 1:1.5, or 1:1.6, to generate an ammonium chloride solid, and removing the solid by filtration;
• reintroducing an obtained mother liquor into the ultra-low temperature reaction vessel, adding the ammonia, and conducting filtration;
• repeating the process not less than 3 times and up to 5 times by reintroducing a newly-obtained mother liquor into the ultra-low temperature reaction vessel, adding the ammonia, and conducting filtration;
• detecting the MCS by on-line gas chromatography (GC), when only a small amount of the MCS remains, conducting filtration with a metal ion-adsorption permeable membrane, and introducing a resulting filtrate directly into a rectification device to conduct purification;
• wherein the ammonia in the gaseous bubbling form by mixing and diluting nitrogen and anhydrous ammonia, the nitrogen has a volume ratio of 10% to 90%.