Oxford Instruments OpAL - General Description; PLC Interlock Chain

System Manual Oxford Instruments Plasma Technology OpAL
Description
Printed: 07 August 2009 07:42 Page 3-21 of 46 Issue 1: August 07
3.6.2 PLC interlock chain
3.6.2.1 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.
No ALD gases or processes will be run if the heaters are not in tolerance.
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
 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.
To enable delivery of ALD gases:
 The 600 mbar vacuum switch (‘Vacstat’) must be at low pressure
 Pressure in chamber at base pressure
 The process chamber lid must be shut (or its hoist down)
 The precursor cabinet door is shut
 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.
Machine protections fitted where appropriate:
 A nitrogen flow meter, to detect purge gas flow to pump bearings.
 Water flow switch/es.
RF enable interlock chain details are given in
Table 3-2; Refer to drawing SE00A26865
(PC2003 int
erface schematic).