COVERSTORY
Optimizing temperature control
in PV deposition chambers
Manufacturers seek every incremental improvement to process and outcome at every
step of the manufacturing value chain. There is a need to not only be aware of potential
changes when manufacturing but also to be able to control any fluctuations in
environment or process. Bill Jesswein of thermal experts, Watlow, discusses the
potential improvements that can be obtained from controlling temperature variations
during the deposition process.
T
iny layers of PV materials make up the loops with Watlow MULTICELL heaters. The focus
core electricity-generating structures in of the manufacturer was on modular, scalable
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today’s solar cells. PV manufacturers using thin control systems with centralized communications
film production techniques deposit silicon, copper, interfaces. A programmable logic controller (PLC)
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indium and other materials in thicknesses ranging fitting these criteria was chosen for trial.
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from nanometres to tens of micrometers. To mass
produce these precise structures, manufacturers The system was configured and installed, but as
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utilize vacuum deposition chambers employing testing progressed, production yield from the
temperature controlled radiant heating systems. deposition chamber was disappointing. An
While there are various forms of deposition investigation found that process generated
chambers and processes, PV manufactures with electrical noise disrupted thermocouple signals to
differing approaches are adopting integrated the PLC which resulted in unacceptable
controllers to optimize temperature control in temperature control.
deposition chambers.
Issue I 2010
The manufacturer decided to explore other control Watlow’s EZ-ZONE
High Loop Count and Noise Immunity system options. Keeping with the desire for a integrated multi-loop
One example of the importance of optimized modular, scalable controller with DeviceNet contoller provides full
temperature control is of a photovoltaic communications, the EZ-ZONE RM was selected scalability provinding
manufacturer who was developing a thin film for testing in the application. This solution proved cost and space
deposition process requiring 140 temperature to be immune from the chamber’s electrical noise savings.
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