Oxford Instruments OpAL, System Manual

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Installation Data
Oxford Instruments Plasma Technology OpAL
8. Interlocks
8.1 General description
The interlocks form a continuous 24Vdc chain, which must be complete before the
process gases 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.
ALD process gases will only flow if all heaters are within tolerance. If any one heater is not
in tolerance, the process will not start.
If the precursor cabinet door is opened, compressed air to the ALD valves is turned off
and process gases are turned off.
Supply to the ALD valves is only available when the system is at base pressure.
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 the interlocks:

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

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 including ALD precursors:
 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).
Installation Data
Printed: 7-Aug-09, 8:03
Page 19 of 22 Issue 3: October 08