System Manual
Oxford Instruments Plasma Technology
OpAL
3.12.4
8-line gas pod
The purpose of the gas pod is to feed a mixture of process gases, at specified flow rates,
to the process chamber. Selection of gases and flow rates are determined by the system
controller. A ‘clean gas’ line can be incorporated to feed an etch gas mixture into the
process chamber to remove process residues.
The gas pod, shown in Fig 3-32, comprises a steel case with a folded removable cover. In
the unlikely event that a leak occurs, an extraction collar at the top of the case enables
any leaked gas to be safely removed by a laboratory extraction system. The back panel of
the case is fitted with fixing holes for wall or frame mounting.
The case incorporates stations for up to eight gas lines. The outputs from the gas lines
are fed into a common manifold, which is connected to the process chamber gas line. The
gas output manifold can be split to provide two out puts; one to the process chamber and
the other to another device, e.g. gas ring.
Pneumatically operated shut-off valves in each gas line are driven by associated SMC
valves mounted on the associated gas pod CAN PCB. Each SMC valve is powered by
compressed air and controlled by signals from the system controller.
All gas pod functions are controlled by interlocks, refer to sub-section 3.6.2.2 for details.
A gas pod cover interlock microswitch disables all gas pod functions unless the cover is
correctly fitted.
Two CAN (Controller Area Network) PCBs are fitted, each controlling four gas lines (1 – 4
and 5 – 8).
Each Gas Pod CAN PCB receives signals from the system controller, to control the SMC
valves, and the Mass Flow Controllers (MFC) fitted in the associated gas lines. For a circuit
diagram of the Gas Pod CAN PCB, refer to the electrical drawings in Volume 2 of this
manual.
A ‘clean gas’ line can be fitted in place of gas line 1.
The ‘clean gas’ line flow rate can be set either manually by a variable valve or by an MFC.
Note that the ‘clean gas’ is usually supplied from a cylinder containing the required gas
mixture. An alternative method is to mix separate gases in optional additional gas lines.
WARNING
THE CONNECTION FROM THE GAS POD MANIFOLD TO THE PROCESS
CHAMBER SHOULD NOT INCLUDE ANY SHUT OFF VALVE, UNLESS
THIS HAS BEEN CLEARED WITH OXFORD INSTRUMENTS PLASMA
TECHNOLOGY. A BLOCKAGE HERE COULD CAUSE PROCESS GASES TO
MIX AND CROSS CONTAMINATE IN THE HIGH PRESSURE GAS
DELIVERY PIPEWORK.
Description
Printed: 07 August 2009 07:42
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Issue 1: August 07
Summary of Contents for OpAL
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