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The system shown in the figure safely delivers liquid chemica to a plasma etch system and eliminates the need for disconnecting gas lines to relieve vapor lock conditions.
English (United States)
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Liquid Source/Hazardous Chemical Gas Box for Plasma Etchers
The system shown in the figure safely delivers liquid chemica to a plasma
etch system and eliminates the need for disconnecting gas lines to relieve vapor
Present plasma etch systems use thermal mass flow controllers as a means
of metering gas flow. These systems can have a vapor lock which requires a
technician to disconnect the line and either pour the liquid out or purge the line
with pressurized gas. This operation can expose personnel to the chemical and
results in equipment down time.
The system shown in the figure is designed to eliminate the possibility of
vapor lock in a mass flow controller by installing a secondary liquid trap or cross
purge system design to clear locked gas lines. The cross purge vacuum system
can also provide a means by which personnel are protected from exposure to the
chemical during cylinder changes.
The normal path from the liquid chemical source through a
plasma system mass flow controller is as follows: CONDITION
VALVING NORMAL OPERATION V2, V3, V4 and V5
OPEN V1, V6 and V7 CLOSED
In the event of a vapor locked mass flow controller, the following valve
settings will purge any condensed vapor in the lines and chambers between the
mass flow controller and the vendor filled liquid cylinder valve, V2. The
condensed vapor is pumped away by a vacuum pump. CONDITION
VALVING VAPOR LOCKED MASS CONTROLLER V1, V2 and V6
CLOSED V3, V4, V5 and V7 OPEN