Bubbler

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A bubbler or bubbler system , sometimes also referred to as a vapor pressure saturator , is part of a system for metal-organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). Its purpose is to convert the organometallic compounds used as starting materials ( precursors ) into a saturated vapor and to guide this into the reaction chamber in a controlled manner with the help of gas bubbles of an inert carrier gas ( argon , nitrogen or hydrogen ).

construction

The structure of the bubbler container corresponds to a gas washing bottle and is used for protected storage of the organometallic in the absence of air ( oxygen , moisture ). The bubbler usually has a supply pipe and an extraction pipe. The supply pipe ends at the bottom just before the floor. An inert gas is introduced into this tube and the liquid chemical bubbles through it. In the case of a solid chemical, it sublimes . The mixture of controlled inert gas and the vaporizing chemical leaves the bubbler through the extraction tube into a downstream reaction vessel. The temperature is controlled by a thermostat so that a defined, constant vapor pressure can be achieved. The supply of the mostly expensive and sensitive chemical is controlled by the regulated flow of inert gas and the temperature of the bubbler, from which the vapor pressure of the chemical results.

The pipeline between the bubbler and the reaction vessel must have a higher temperature than the bubbler, otherwise the precursor condenses in the pipeline and is thus introduced into the reaction vessel as drops in an uncontrolled manner. If this happens with a fixed precursor, the line can become blocked. A disadvantage of these methods of precursor feeding is that the precursor can degrade when heated.

Web links

Individual evidence

  1. ^ Anthony C. Jones, Michael L. Hitchman: Chemical Vapor Deposition: Precursors, Processes and Applications . Royal Society of Chemistry, 2009, ISBN 978-0-85404-465-8 , pp. 18 .