System Manual Oxford Instruments Plasma Technology OpAL
WARNING
BEFORE PROCEEDING WITH ANY MAINTENANCE WORK, READ SECTION 1 - HEALTH AND SAFETY.
4) Close the gas bottle outlet valve associated with the gas line to be checked.
5) Pump down t
he system and flow 100% all gases until flow readbacks are zero.
This will require pumping for a few hours.
6) Manually close the gate valve by removing its 24V dc connector plug.
7) Monitor the leak rate on-screen.
6.2.3 Changing the gas bottles
The operator should be aware that certain process parameters may change as the process
gas bottles pressure drops. For example, inert gas bottles which are normally filled to
about 3000 psi, should be changed when the pressure drops below 400 psi. The inlet
pressure should be 25 - 35 psia. Before disconnecting the empty bottle it is advisable to
thoroughly evacuate the gas line (by closing the gas bottle tap and pumping the line via
the MFC). The line should then be filled with dry N
2
if available.
Once the new bottle has been connected, monitor the vacuum integrity of the gas line
before opening the bottle by setting a high flow on the MFC, pumping the line thoroughly
(via the MFC), isolating the process chamber and noting the rate of pressure rise. An
abnormally high value (>2mTorr/minute) may indicate a leak in the gas line or the
regulator to bottle connection.
During normal operation the bottle pressure and line pressure on the cylinder regulator
should be regularly checked for loss of pressure during periods when the gas bottle tap is
turned off (during shut-down periods, overnight or over a weekend). This will indicate a
leak from the gas line or the regulator.
Maintenance
Printed: 14-Jul-10, 8:14 Page 6-5 of 16 Issue 4: July 10
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