A Bubbler cylinder is a component of a unit for the

metal organic chemical vapor deposition Metalorganic vapour-phase epitaxy (MOVPE), also known as organometallic vapour-phase epitaxy (OMVPE) or metalorganic chemical vapour deposition (MOCVD), is a chemical vapour deposition method used to produce single- or polycrystalline thin films. ...

(MOCVD). They are devices that are used for conveying electronic grade metalorganic compounds from a

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

solid Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...

precursor into a usable

vapor In physics, a vapor (American English) or vapour (British English and Canadian English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critic ...

Apparatus

The container of the Bubblers is similar to the construction of a gas washing bottle and used for the protected storage of metalorganic compounds to exclude

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

(

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...

). The bubbler has a supply pipe and a sampling tube. The inlet tube ends just before the bottom of the tube. In this tube, an inert gas is introduced, which bubbles through the liquid chemical; a solid chemical will sublime. The mixture of the controlled

inert gas An inert gas is a gas that does not readily undergo chemical reactions with other chemical substances and therefore does not readily form chemical compounds. The noble gases often do not react with many substances and were historically referred to ...

and the vaporized chemical leaves the cylinder into a downstream reaction vessel. The temperature is controlled by a thermostat, so that a defined, constant steam pressure can be achieved. The supply of the often expensive and sensitive chemical is controlled by the regulated flow of inert gas and the temperature of the bubbler, resulting in a given

vapor pressure Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases ...

of the chemical. The tube between the bubbler and the reactor has to have a higher temperature than the bubble, otherwise the precursor would

condense Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...

in the tube and therefore uncontrolled droplets would be passed into the reaction vessel. If this happens with a solid precursor, it could plug the line.

Application

For example, during the production of high brightness

light emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...

gallium Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...

or other group III-V elements are epitaxially deposited onto a single crystal

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...

substrate. The gallium is introduced into the MOVPE reactor chamber via a vapor. This vapor is generated by bubbling an inert carrier gas (such as

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...

) through a cylinder with a dip tube through a metalorganic precursor, such as

trimethylgallium Trimethylgallium, often abbreviated to TMG or TMGa, is the organogallium compound with the formula Ga(CH3)3. It is a colorless, pyrophoric liquid. Unlike trimethylaluminium, TMG adopts a monomeric structure. When examined in detail, the monomeric ...

. The inert carrier gas and the metalorganic vapor is then introduced into the MOVPE (or MOCVD) reactor chamber during the production of high brightness LEDs.

External links

Description of a Bubbler System

Liquid injection system based on Mass Flow Controller
Semiconductor fabrication equipment {{electronics-stub