PlasmalabSystem100 Oxford Instruments Plasma Technology Installation Data
Installation Data (PECVD - TEOS)
Issue 10: February 11 Page 20 of 24 Printed: 10-Feb-11, 9:07
8. PLC interlock chain
8.1 General description
The interlocks form a continuous 24Vdc chain, which must be complete before the
process gases and RF power supplies are enabled. An output to disable external devices
unless the lid/ hoist is closed is also provided; this is typically used to disable a lid-
mounted endpoint detector laser.
The interlock chain is monitored by the software, but acts independently. It is also
supplemented by machine protection sensors, which operate only via the software.
To enable RF power:
The 600 mbar vacuum switch (‘Vacstat’) must be at low pressure
The process chamber lid must be shut (or its hoist down)
The primary process pump must be running
The primary process pressure gauge (normally a capacitance manometer) must be
on scale
The load lock inter-chamber valve (where fitted) must be closed
Customer-supplied external alarm devices must be in their safe state
The inert gas purge to the primary process pump must be flowing.
To enable process gases:
RF power must be enabled
The gas box lid must be shut
Specific gases can be set in the gas box hardware to be mutually exclusive, so that
they cannot be turned on together.
Machine protections fitted where appropriate:
A nitrogen pressure switch, to detect adequate purge pressure to turbomolecular
pump bearings.
OR:
A nitrogen flow meter, to detect purge gas flow to pump bearings.
Water flow switch(es).
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