Friday, July 25, 2014

Intro to Direct Liquid Injection (DLI) Vaporizer

DLI vaporizer
Direct Liquid Injection Vaporizer
Conventional vaporizing technologies have many limitations. Vapor draw systems or bubblers are difficult to start and stop, require very close control of temperature and pressure, and are inefficient at generating well controlled vapor mass flow. Flash vaporizers applying heat via hot metal surface, which cause problems with thermal breakdown of liquid precursors. It also can cause liquid buildup on the treatment surface, causing problems in deposition.

It's also very challenging to precisely measure the amount of vapor mass that is actually being delivered from a conventional vaporizer. In applications where precise vapor mass addition is required, a measurement/control device such as vapor mass flow controllers must be used. This significantly increases the cost and complexity of the vapor system.

None of these conventional technologies eliminate the potential for liquid carry-over and its associated complications. A well documented problem are CVD deposition chamber pressure fluctuations which are caused by incomplete vaporization and precursor carry-over from a conventional vaporizer.

A DLI vaporizer uses heated gas instead of a hot metal surface to achieve liquid vaporization. As the liquid enters the heated gas chamber, it is atomized by a carrier gas stream. As the atomized liquid comes into contact with the hot gas, it immediately changes to vapor. The result is chemically pure vapor, free of decomposition byproducts or liquid carry-over. Moreover, a DLI vaporizer allows for multiple liquid inlets and will mix vapors perfectly. The DLI vaporizer accommodates an extraordinarily wide range of liquid properties: extremely low vapor pressures (sub 1 torr), very low flow rates (sub 5 grams per hour), and very high flow rates (more than 15 kg/hr). Unlike bubblers and hot-surface vaporizers,  the DLI vaporizers are extremely efficient at producing vapor from liquid.

DLI vaporization is an extremely high performing method capable of providing reliable and complete vaporization of many high cost and/or difficult fluids. Providing customized atomization and heat exchanger technologies, the DLI vaporizers deliver pure vapor for every application.  The system also includes a Coriolis low flow controller to precisely measure and control the mass liquid flow.

Applications include:

  • Water vaporization for fuel cell stack humidification and many other water addition applications
  • Liquid precursor vaporization for chemical vapor deposition (CVD), metal oxide chemical vapor deposition (MOCVD), and atomic layer deposition (ALD)
  • Depositing thin films for enhanced thermal, optical, or hardness characteristics such as diamond-like carbon coating and glass coating
  • Vaporizing monomers for vacuum polymer film deposition
  • Generating calibration vapor
  • Vaporizing liquid hydrocarbons

For more information on direct injection vaporizers, please contact Belilove Company-Engineers.