Vapor Concentration Monitor
The Metal-Organic Chemical Vapor Deposition (MOCVD) process is widely used in the manufacture of LEDs, optical devices and other components. Liquid and solid precursors are delivered to the reaction chamber by controlling the temperature, pressure and the carrier gas flow rate (bubbling method). The in-line IR-300 Series measures and reports the precursor concentration in real time giving the user the following benefits:
A high optical intensity and long-life light source combined with high-speed signal processing enables the IR-300 Series to achieve faster, more repeatable responses to changes in precursor concentration. These features give the user a true understanding of the actual process though real-time inline concentration measurement.
■Experiment flow sheet
■Monitoring of precursor concentration change
Here is an example in which the concentration of the supplied precursor—which changes due to adjustment of the pressure in the bubbler by the back pressure regulator—was monitored in real time.
Non-dispersive Infrared Absorptiometry (NDIR)
The infrared absorptiometry method employed by the IR-300 Series uses the principle of measuring the absorption of gas molecules in infrared light emitted from an infrared light source. A sample output from a sample that has absorbed the gas being measured is compared to a reference output with no absorbance, and the result is converted into a gas concentration. The use of this double beam method enables long-term, stable measurement results to be obtained.
The optical system is made up of a light source, gas cell and double beam detectors. The stability of the double beam detector has been proven over a period of more than 40 years.
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